Salivary cortisol concentration and its circadian variation were detected by optimizing the ionic concentration of a solution during the immobilization of aptamers on a field-effect transistor biosensor. This was achieved by modifying our previously developed technique of detecting uncharged cortisol using the transformation of negatively charged aptamers by controlling the aptamer spacing. This spacing control was achieved by synthesizing pseudo-cortisol-binding aptamers with a guanine-quadruplex during the immobilization of the aptamers in a highly concentrated solution of K+.

A low-resistance polypyrrole (PPy) film that can achieve high rates (rates of >1C) while suppressing polysulfide dissolution is developed in this study. To achieve high-rate characteristic in a sulfur cathode with high sulfur loading, a three-dimensional (3D) aluminum foam current collector is used and the Li+ concentration of the PPy film is enhanced by a glyme-Li equimolar complex as the polymerization electrolyte. A PPy-sulfur/ketjenblack (S/KB) 3D aluminum foam laminated cell with a sulfur loading of 5 mg cm(-2) is prepared. Consequently, a high discharge capacity of 794 mAh g(-1)-sulfur at 3.0C is achieved using 1 M lithium bis-(trifluoromethylsulfonyl)imide (LiTFSI) with dimethoxyethane (DME) and 1,3-dioxolane (DOL), (DME/DOL = 1/1 vol.) as the electrolyte and Li foil as the anode. In the cycling test, PPy-S/KB 3D Al foam cathode achieved a significant improvement in discharge capacity retention compared to bare S/KB 3D Al foam cathode without PPy coating. Moreover, almost no polysulfide dissolution is confirmed from the ultraviolet-visible spectrum of the electrolyte after the cycle evaluation. Here, we prepare a 3D structure S/KB cathode that can support high rates while suppressing sulfur dissolution by PPy coating, and reveal its potential for lithium-sulfur battery application.

Both the high sulfur loading cathode and less electrolyte are the most important parameters to realize lithium-sulfur batteries with high energy density. A high sulfur loading cathode was achieved by using 3D structured aluminum foam to act as a support structure and current collector. Moreover, the energy density close to 200 Wh kg-1 was successfully obtained by decreasing the electrolyte in the pouch cell. 5 Ah cell was developed by using the six sheets of the cathode in the cell. Recently, a multi-layer pouch-type cell with a high capacity of 5 Ah and a high energy density of 300 Wh kg-1 was successfully developed with technically reoptimized preparation conditions. These results indicate the possibility of the development of a lithium-sulfur battery with discharge capacity and high energy density for commercial use.

Lithium-ion capacitors (LICs) are energy storage devices that bridge the gap between electric double-layer capacitors and lithium-ion batteries (LIBs). A typical LIC cell is composed of a capacitor-type positive electrode and a battery-type negative electrode. The most common negative electrode material, graphite, suffers from low rate capability and cyclability due to the sluggish kinetics of the Li+ intercalation/de-intercalation process. In this work, metal chloride-pillared graphite, which has recently attracted attention as high-rate LIB anodes, is applied as the negative electrode for LICs for the first time to overcome this drawback. It is shown that AlCl3-graphite intercalation compounds (AlCl3-GICs) with a wide interlayer spacing benefit faster Li+ diffusion. The low molecular weight and conversion reaction of the AlCl3 pillar further enhance the specific capacity per mass. An optimized LIC cell composed of an AlCl3-GIC negative electrode and activated carbon as the positive electrode exhibited higher energy and power densities compared to LICs using graphite as the negative electrode, and displayed stable cycling performance with 85% capacity retention after 10 000 charge/discharge cycles. The AlCl3-GICs synthesized in this work displayed improved electrochemical performances and have the potential to replace the graphite electrode in conventional LICs.

Lithium-ion capacitors (LICs) operate by two mechanisms, namely a double-layer mechanism based on a capacitor-like positive electrode and the intercalation mechanism of a battery-like negative electrode. Hence, well-designed reaction kinetics between the positive electrode and negative electrode are essential for optimizing LIC full-cell configurations. In this study, we investigated the influences of fluoroethylene carbonate (FEC) or vinylene carbonate (VC) as electrolyte additives on full-cell performance of LICs. We confirmed that the internal resistance of graphite increased with the use of FEC, which degraded the cyclability of the LIC full-cell. Conversely, LICs consisting of the VC additive had good cyclability over 4000 cycles owing to the solid electrolyte interphase (SEI) containing polymeric species. This detailed investigation into the function of SEI compounds derived from VC additives and their effect on cyclability will provide new insights into optimization of LIC full-cell configurations with appropriate electrolyte additives.

A field effect transistor (FET) biosensor is a promising device for various applications such as medical diagnosis and environmental monitoring. Because characteristics of FET biosensors are directly influenced by the change of gate-insulator surface potential induced by the adsorption of charged molecules, FET biosensors could provide the rapid and label-free biomolecular detection. Recently, mental stress-related diseases, such as integration disorder syndrome and depression, affect people's health, resulting that simple stress monitoring is expected for early stage detection of the disease. Previously, the relation between concentration of stress markers and mental stress has been reported ^[1], and the monitoring of circadian concentration of the markers is found to be important for prediction of the stress condition. Especially, secretory immunoglobulin A (s-IgA), which is an immunity-related molecule present in the human mucus, is one of the candidates to be monitored as a stress marker. However, conventional methods for measuring concentration of s-IgA are restricted in daily use due to complex protocol, time-consuming and expensive equipment.

Nowadays, we have investigated sensitive detection method for various targets by using the FET biosensor ^[2,3]. To achieve improvement of the sensitivity, small receptors have been applied to increase electrical responses owing to the effective use of a charge-recognition region from FET gate surface, Debye length ^[4,5]. In this study, we selected a small plant lectin, jacalin (66 kDa), which specifically binds glycan of hinge region of IgA, as a receptor. Additionally, jacalin was inexpensive compared with antibody due to the purification from jackfruits seeds. From these points, jacalin-immobilized FET biosensor was worth to be investigated to realize a simple, sensitive and low-cost stress monitoring device for stress marker. Thus, we investigated the usefulness of the jacalin as a FET receptor.

The SiO₂ gate insulator of the FET was exposed to O₂ plasma (200 W for 1 min) for introduction of hydroxyl groups reacting with triethoxysilane groups of self-assembled monolayer (SAM). Then, the FET chip was immersed in toluene solvent including 1%(v/w) 3-aminopropyltriethoxysilane in an argon atmosphere (60ºC for 7 min.). Following by the cross-linking by glutaraldehyde, jacalin was immobilized on FET gate surfaces. Finally, ethanolamine capping was performed to prevent the non-specific adsorption of contaminating molecules in analyzed samples, resulting in the fabrication of the jacalin-immobilized FET biosensor. The FET characteristics were measured by sweeping the gate-voltage (V _g) from -2.0 V to 0 V with 0.1 V drain voltage (V _d) in 0.01 × phosphate buffered saline (pH 7.4). Then, the electrical responses (ΔV _g) were analyzed from the FET characteristics before and after the addition of analyte to gate surface.

To evaluate the specificity of jacalin-immobilized FET biosensor, ΔV _g caused by the addition of s-IgA and human serum albumin (HSA) were measured. The FET charactristics was shifted in a positive direction (+53 mV) due to the adsorption of negative-charged s-IgA (Figure 1a), while the responses related with HSA addition were scarcely observed. Thus, specific capture of the s-IgA molecules by the jacalin-immobilized surface was indicated. Moreover, to evaluate the advantage of jacalin, we compared ΔV _g with FET functionalized by antigen binding fragment (Fab), which was obtained by cleaving the anti-s-IgA antibody. An electrical response of Fab-immobilized FET was +24 mV (Figure 1b). The change in ΔV _g values for these two FET sensors using jacalin or Fab could be discussed as follows. Jacalin could capture more s-IgA molecules within Debye length from the gate surface of FET. In addition, the jacalin-immobilized FET responded linearly to s-IgA in a concentration range from 0.1 μg/mL to 100 μg/mL. Finally, sweat samples collected from healthy persons were examined with the developed jacalin-immobilized FET biosensor, and clear responses were obtained. From these results, jacalin was found to be useful as a receptor for FET biosensors to achieve a sensitive, simple and non-invasive detection of s-IgA.

[1] K. Obayashi, Clin. Chim. Acta, 425, 196-201 (2013).

[2] S. Hideshima, M. Kobayashi, T. Wada, S. Kuroiwa, T. Nakanishi, N. Sawamura, T. Asahi, T. Osaka, Chem. Commun., 50, 3476-3479 (2014).

[3] S. Hideshima, K. Fujita, Y. Harada, M. Tsuna, Y. Seto, S. Sekiguchi, S. Kuroiwa, T. Nakanishi, T. Osaka, Sens. Bio-Sens. Res., 7, 90–94 (2016).

[4] S. Cheng, K. Hotani, S. Hideshima, S. Kuroiwa, T. Nakanishi, M. Hashimoto, Y. Mori, T. Osaka, Materials, 7, (4), 2490-2500 (2014).

[5] S. Hideshima, H. Hayashi, H. Hinou, S. Nambuya, S. Kuroiwa, T. Nakanishi, T. Momma, S.-I. Nishimura, Y. Sakoda, T. Osaka, Sci. Rep., 9, 11616 (2019).

Figure 1 V _g-I _d characteristics of (a) jacalin or (b) Fab-immobilized FET biosensor before and after the addition of 100 μg/mL s-IgA.



Figure 1

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The dosage of 5-fluorouracil (5-FU), which is a widely used for cancer medication, is determined based on body surface area, although efficacy largely depends on the liver function of the individual, resulting that only 21% patients are given an optimal dose of 5-FU in these years. The measurement of the 5-FU concentration in the blood enables us to adjust individual dose adjustment. Conventional methods for 5-FU detection such as an enzyme-linked immunosorbent assay (ELISA) and liquid chromatography are not very suitable for clinical applications because they need time-consuming procedure with expensive equipments. Detection of 5-FU using a field effect transistor (FET) biosensor, which enables rapid and simple measurement, is expected to solve such problems. However, FET biosensor, which detects changes in its surface density due to the adsorption of charged molecules, was unable to detect uncharged 5-FU. In this study, a method for the FET biosensing to detect 5-FU exploiting sequential adsorption of 5-FU modified bovine serum albumin (BSA/5-FU) was proposed. By using this method, FET responses caused by the adsorption of negatively charged BSA/5-FU depending on the 5-FU concentration were detected.

The SiO₂ surface of the FET gate insulator was exposed to O₂ plasma to introduce hydroxyl groups. After the exposure, the surface was exposed to 3-aminopropyltriethoixysilane (APTES), followed by the modification of the cross-linker, glutaraldehyde (GA). A single chain variable fragments (ScFv) and antigen binding fragments (Fab) were allowed to react with each activated GA-modified FET. After the immobilization, the residual aldehyde-groups were treated by ethanolamine to suppress the non-specific adsorption. V _g-I _d characteristics were measured before and after dripping of both 5-FU and BSA/5-FU on the ScFv- and Fab-immobilized FET biosensors. Finally, threshold voltage shifts (∆V _g) caused by the adsorption of BSA/5-FU were obtained.

To compare the capture capability of ScFv and Fab, the electrical responses of the FET biosensors functionalized with the two receptors due to the adsorption of BSA/5-FU were measured. The responses of ScFv- and Fab-immobilized FET biosensor caused by dripping of 25 μg/mL BSA/5-FU were +25 mV and +40 mV, respectively. The difference between ΔV _g values for these two FET sensors using ScFv or Fab can be ascribed to the difference of affinity ^[1]. To verify the specificity of Fab-immobilized FET biosensor, ∆V _g was measured when human serum albumin (HSA) was dropped on the FET biosensor, and the ∆V _g was hardly observed. Additionally, the atomic force microscopic (AFM) images on the FET gate surface shows that the size of observed particles matches the size of BSA/5-FU, while the surface morphology and roughness are not significantly changed. These results indicated that Fab-immobilized surface specifically captured BSA/5-FU. To investigate the quantitative detectability of the Fab-immobilized FET biosensor, we measured the FET responses corresponding to the amount of adsorbed BSA/5-FU, which was related with the concentrations of 5-FU. As a result, the magnitude of ∆V _g by dripping of 1000 ng/mL 5-FU and 25 μg/mL BSA/5-FU was reduced to +12 mV compared with the response of 25 µg/mL BSA/5-FU (Figure 1). These results can be attributed to that the adsorbed 5-FU inhibited the adsorption of BSA/5-FU to the Fab-immobilized surface. Therefore, we conclude that the detection of 5-FU using the FET biosensors by applying the charged BSA/5-FU is a promising simple method for monitoring the concentration of 5-FU.

Reference:

[1] Y. Reiter, et al., J. Biol. Chem., 269, 28, 18327-18331 (1994).

Figure 1 V _g-I _d characteristics of Fab-immobilized FET biosensor before and after dripping of (a) 0 ng/mL 5-FU and 25 µg/mL BSA/5-FU or (b) 1000 ng/mL 5-FU and 25 µg/mL BSA/5-FU.



Figure 1

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Introduction

People have felt that their mind controls the body. Advances in immunology and neuroscience are scientifically elucidating this experience. For example, it has been clarified that the mechanism by which changes in the activity of the central nervous system due to stress regulate the immune response through sympathetic nerves. If these latest medical knowledge and electronic advances can be used to provide a simple monitoring system for stress-related substances, it is hoped that it will help prevent mental and physical diseases. Nevertheless, performing a blood draw to detect the stress hormones cortisol and catecholamine has the challenge that the act of drawing blood itself causes stress. Instead, cortisol concentration measurement from saliva has been developed as a non-invasive detection, but catecholamines cannot be detected from saliva. Salivary cortisol concentration measurements have been developed as an alternative non-invasive detection method, but catecholamines are unable to obtain the necessary information from saliva. Salivary α-amylase and chromogranin A (CgA) have also been studied and used in part as alternatives to catecholamines. Secretary immunoglobulin A (s-IgA) in saliva is also a good stress marker that reflects suppression of the immune system by stress. Simultaneous monitoring of the time-dependence of these stress markers of different origins is expected to help elucidate the complex mental stress mechanisms [1].

Sensor module platform

Accurate and inexpensive biomaterial detectors are required for IoT biosensing systems and monitoring over time has not been realized until now. Field-effect transistor (FET) biosensors are small devices that detect various types of biomarkers at low power consumption without disturbing the system under test [2]. The biggest challenge of FET biosensors when used in electronics systems is instability due to current drift. We have succeeded in developing a method that minimizes drift using only the normal silicon fab process. This manufacturing process does not use tantalum pentoxide or other special materials.

Figure 1 shows a picture of a newly developed four element FET sensor chip with extremely low instability. The electronics part of the developed biosensor module consists of this chip and a Bluetooth Low Energy (BLE)-type communication circuit. We selected four types of aptamers as sensor receptors on the gate insulator on the chip [3]. The aptamers can be stored and used at room temperature for a long period of time. They also have the advantages of being reversible to thermal denaturation and can be produced inexpensively and industrially. Finally, as a technique for producing biosensors with less variation, such as commercial physical sensors, we developed a tool for uniformly immobilizing the receptor monolayer in a narrow range of fixed positions on the chip.

Simultaneous detection of multiple stress markers in saliva

When n types of receptors are immobilized on n FET elements, n-1 types of independent signals can be extracted. The effects of non-specifically adsorbed substances and pH in saliva, temperature fluctuation, optical noise, and crosstalk between elements can be eliminated from the original signals of multiple FET elements. Using this technique, we succeeded in obtaining multiple stress marker concentrations such as cortisol, a-amylase, s-IgA, and CgA [4], at the same time just by dropping saliva on the sensor. The signal time constant is less than 1 minute, which indicates that a continuous monitor is realized substantially.

Operability equivalent to physical sensor

Internet of Things (IoT) systems require many low-cost sensors. FET sensor chips manufactured using only the conventional silicon fab process can achieve a low cost of about $1 per chip. However, even with such cheap biosensors, if they are disposable, the cost burden on the user will increase significantly in the long run. As a result, it becomes difficult to secure good customers as fixed users. In addition, disposable chips are not suitable for continuous monitoring required for medically important data. We are developing biosensors that are as easy to operate as conventional physical sensors by introducing reusable cleaning methods and recycled precision cleaning methods.

References

[1] L. Steinman, Annu. Rev. Immunol., 32, 257-281, (2014).

[2] K. Ohashi, T. Osaka, ECS Transactions, 75, 39, 1-9, (2017).

[3] N Kaneko, H Minagawa, J Akitomi, K Ohashi, S Kuroiwa, S Wustoni, S Hideshima, T Osaka, K Horii, I Waga, The 43rd International Symposium on Nucleic Acids Chemistry, 2P-55, (2016).

[4] S. Kuroiwa, R. Takibuchi, A. Matsuzaka, S. Hideshima, N. Kaneko, H. Minagawa, K. Horii, I. Waga, T. Nakanishi, K. Ohashi, T. Momma, T. Osaka, 232nd ECS Meeting, 2115, (2017).



Figure 1

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Lithium sulfide (Li2S) is considered to be a promising cathode material for safer energy storage cells due to its compatibility with Li metal-free anodes. However, challenges remain regarding the insulating nature of Li2S, which leads to poor electrochemical performance, currently making Li2S electrodes far from practical in real-world applications. Herein we present a chemical method to synthesize Li2S nanoflake wrapped carbon material, Ketjenblack (LS@KB) composite, which can be coated on different current collectors without the addition of a binder. The high contact area between KB nanoparticles and Li2S nanoflakes effectively improves the cathode's conductivity, which contributes to a high Li2S weight ratio (83%). In addition, we prove that the well wrapped LS@KB structure enhances the physical confinement of polysulfides, leading to improved cyclability. As a result, the synthesized LS@KB cathode delivers stable cyclability (1000 cycles) with a fading rate of 0.03% per cycle at 0.5 C-rate. This room temperature fabrication strategy conquers the major drawbacks existing in Li2S fabrication, such as high temperature, hazardous gas release, complex and high-cost production process, making it a promising cathode material for light and safe portable electronic devices. (C) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

A solvate ionic liquid (SIL) of highly concentrated 4.0 M lithium nitrate (LiNO3) in a dimethylsulfoxide solution is introduced for lithium-oxygen batteries. As a redox mediator (RM), highly concentrated LiNO3 in the SIL works more effectively than the lower concentrated one to decompose lithium peroxide (Li2O2) on the cathode with an extremely low charging voltage of 3.6 V. In addition, X-ray photoelectron spectroscopy analysis confirms that side products during discharging and charging are markedly restricted in the SIL. The low solubility of Li2O2 intermediate (LiO2) in the SIL may be an important reason for the restriction of side products. (C) The Author(s) 2019. Published by ECS.

Lithium-ion capacitors (LIC) constructed by combining a supercapacitor-like cathode and battery-like anode are expected to bridge a gap between low power density from lithium-ion batteries (LIB) and low energy density from the supercapacitors. In this study, we synthesize the Sn-Ni alloy by electrodeposition in the aqueous solution as an anode for LIC. The lower volume expansion rate of Sn-86 than pure Sn anode can be confirmed by in-operando investigation using an optically transparent cell during the 1st charging process. This is attribute to the co-deposited Ni can act as a buffer matrix to restrain volume expansion. For the full-cell test, the pre-lithiation condition of Sn-Ni was investigated with different depth of discharge levels. As a result, a LIC consisting of activated carbon (AC) cathode and Sn-86 exhibits a good cyclability for 3000 cycles with a capacity retention of 80% and coulombic efficiency of 98% at 3000th cycle. The Sn-Ni//AC LIC shows improved volumetric energy and power density than graphite//AC LIC. This study presents a new possibility of Sn-Ni alloy as an anode for the improved electrochemical performance of LIC. (C) 2019 The Electrochemical Society.

The silicon-based composite prepared by electrodeposition exhibits outstanding electrochemical performances for several thousand cycles because the co-deposited oxygen and carbon could act as buffer materials to reduce internal stress during charge-discharge cycling. However, it is not easy to increase the loading amount of active materials due to low structural stability at a high passing charge over 15 C cm(-2) for electrodeposition, leading the low areal capacity of Si-O-C composite as an anode. In this study, we propose a new way to enhance the structural stability of silicon-based anode by an electrochemical co-deposition technique using tin as supporting material, namely Sn-Si-O-C composite. The co-deposited tin has a whisker-shaped structure, and it prevents the exfoliation of activated material during electrodeposition. Besides, tin whisker can act as an electron pathway, resulting in improved electrochemical performance including high rate performance. The enhanced electrical conductivity is investigated by electrochemical impedance analysis. The improved electrochemical performance of Sn-Si-O-C composite indicates the high potential as an electrode material for high-performance lithium-ion batteries.

In this work, we present a powdered Si-O-C composite, namely pSi-O-C composite, synthesized by electrodeposition harvesting method. This new type of the Si-O-C composite shows impressive results, such as outstanding cyclability with a good discharge capacity of 616 mAh g(-1) which reached 10,000 cycles, and a remarkable coulombic efficiency of 99% at the 10,000th cycle. Furthermore, the pSi-O-C composite demonstrates the highest amounts of loaded silicon compared to different types of Si-O-C composite deposited on a Cu and CNTs/Cu substrate. (C) 2019 Elsevier B.V. All rights reserved.

Pandemic influenza, triggered by the mutation of a highly pathogenic avian influenza virus (IFV), has caused considerable damage to public health. In order to identify such pandemic IFVs, antibodies that specifically recognize viral surface proteins have been widely used. However, since the analysis of a newly discovered virus is time consuming, this delays the availability of suitable detection antibodies, making this approach unsuitable for the early identification of pandemic IFVs. Here we propose a label-free semiconductor-based biosensor functionalized with sialic-acid-containing glycans for the rapid identification of the pandemic IFVs present in biological fluids. Specific glycans are able to recognize wild-type human and avian IFVs, suggesting that they are useful in discovering pandemic IFVs at the early stages of an outbreak. We successfully demonstrated that a dual-channel integrated FET biosensing system, which were modified with 6'-sialyllactose and 3'-sialyllactose for each gate area, can directly and specifically detect human H1N1 and avian H5N1 IFV particles, respectively, present in nasal mucus. Furthermore, to examine the possibility of identifying pandemic IFVs, the signal attributed to the detection of Newcastle disease virus (NDV) particles, which was selected as a prime model of a pandemic IFV, was clearly observed from both sensing gates. Our findings suggest that the proposed glycan-immobilized sensing system could be useful in identifying new pandemic IFVs at the source of an outbreak.

Here we report an 'injection' strategy to introduce transportable Li-ion in the metallic Li free sulfur-graphite (S-G) pouch type full cell, which could alleviate the safety issues from Li dendrites. A novel process with organo-lithium reagent is used to reduce S to Li2S rapidly during assembling the pouch type full cell. The sublimation property of the side product enables the in-situ injection in the pouch type cell, which will not introduce impurities. In addition, this 'injection' strategy avoids the drawbacks from the instability of the Li2S to moisture, which could largely reduce the production cost and improve the practical energy density of the cell. The injected Li2S-G battery shows quite stable cyclability with a capacity of 640 mAh g(-1) at 0.1 C rate. This in-situ 'injection' method provides an effective and practical way to produce Li metal free sulfur Li-ion battery with alleviated safety issues.

Li-ion capacitors (LIC) which bridge the advantages of supercapacitors and Li-ion batteries have attracted a great deal of attention as a promising energy storage device. In this study, we synthesize the Si-O-C by electrodeposition at low levels of electricity below 2.0 C cm(-2) as an anode for LIC. The deposited Si amounts are controlled by charge density during electrodeposition from 0.3 to 1.0 C cm(-2). The material and electrochemical characteristics of Si-O-C fabricated at a charge density of 1.0 C cm(-2) are studied. The LIC consisting of Si-O-C anode shows an encouraging 95% retention of the initial capacity after 1000 cycles. In addition, the LIC shows a capacity retention ratio of 94% at 140 C-rate. This study reveals the potential prospect to use Si-O-C fabricated by electrodeposition as an anode for a high-rate capability for LIC. (C) The Author(s) 2019. Published by ECS.

Herein, we synthesized the structural stabilized Si-O-C composite using carbon nanotubes (CNTs). The SiO-C/CNTs is employed and tested as an anode for lithium-ion batteries (LIBs) assembled with the LiCoO2 cathode. Through the usage of CNTs, it is possible to improve the cyclability and capacity retention ratio by enhanced structural stability. The enhanced electrochemical performance of LiCoO2//Si-O-C full-cell with CNTs indicates the high potential as a way to produce the high-performance LIBs. (C) 2019 Elsevier B.V. All rights reserved.

In order to obtain highly ordered L1(0)-FePt nanoparticles for hard disk drive applications, the L1(0)-phase transformation of chemically synthesized FePt nanoparticles deposited on a naturally oxidized Si substrate was investigated using rapid thermal annealing. The heating and cooling rates during annealing were changed logarithmically with a constant annealing temperature (800 degrees C) and holding time (10 min). Almost completely ordered L1(0)-FePt nanoparticles were confirmed by grazing incidence X-ray diffraction measurements, irrespective of the heating and cooling rates, and the amount of the silicide changed in response to both. Nearly pure L1(0)-FePt was obtained when rapid heating (more than 780 K/min) and rapid cooling (more than 290 K/min) were applied. L1(0)-FePt degraded into Fe3Si and PtSi when the cooling rate was lower than 7.8 K/min. Rapid heating as well as rapid cooling of FePt nanoparticles can provide a facile route for the high-throughput production of L1(0)-FePt-based high-density magnetic recording media. (c) 2019 The Electrochemical Society.

Lithium-ion batteries are required to have high-power density, that is to reduce impedance, for use in electric vehicles. This paper focuses on interfacial resistance between the cathode layer (CL) and the current collector (CC) observed at high frequencies, which is generally attributed to a resistance of surface film like SEI. To investigate the interfacial resistance systematically, different interfaces between the CL and the CC were prepared by controlling the press rate for the cathode preparation, or by introducing a carbon under-coating layer (CUL), followed by electrochemical impedance spectroscopy (EIS). The interfacial resistance between the CL and the CC prepared with an insufficient press rate or without a CUL was extremely high for the entire cathode. From the cathode cross-sectional observation, it was observed that this high interfacial resistance was caused by low contact rate at the interface. Using a pouch-type symmetric cell, EIS revealed that the interfacial resistance is attributed to electric resistance, that is, contact resistance at the interface. Also, the other resistances were attributed to be the ionic resistance of the electrolyte and pores in the cathode, and the charge transfer resistance of the cathode. Furthermore, the effectiveness of the CUL was shown to decrease the cathode impedance.

The usage of Li metal in lithium sulfur (Li-S) battery has largely hampered the application of Li-S battery due to the formation of Li dendrite during cycling. Here, a novel potentiostatic (p-stat) lithiation method was developed to fabricate Li2Sx cathode. The pre-lithiated Li2Sx cathode can be used to pair with the Li metal free anode to make a full cell with better safety. The dissolution of the polysulfide in electrolyte is the main problem in S cathode, which leads to severe active material loss during lithiation process. Normally, the way to alleviate the dissolution of polysulfide is by trapping the polysulfide from diffusing into the electrolyte. In this work, it is innovatively raised the p-stat lithiation method which can suppress the formation of polysulfides. As a result, dissolution of polysulfide species could be kinetically suppressed. The p-stat lithiated Li2Sx cathode exhibits higher capacity performance (around 400 mAh g−1) than the galvanostatic (g-stat) lithiated Li2Sx cathode. The Li metal free full cell assembled by pairing p-stat lithiated Li2Sx cathode with graphite anode shows stable cyclability.

Sulfur (S) Li-ion battery which use the metallic Li free anode is deemed as a promising solution to conquer the hazards originating from Li metal. However, stable cycling performance and low production price of the S Li-ion battery still remain challenging. Here, we propose a S-LixC full cell system by paring a S cathode and a pre-lithiated graphite anode which is cheap and commercially available. It shows stable cycling performance with a capacity around 1300 mAh (g-S)−1 at 0.2 C-rate and 1000 mAh (g-S)−1 at 0.5 C-rate. In addition, 0.1% per cycle capacity fading rate with a capacity retention of 880 mAh (g-S)−1 after 400 cycles at 0.2 C-rate has been achieved. The pre-formed solid electrolyte interphase (SEI) layer on the pre-lithaited graphite anode largely contributes to the high capacity performance. Notably, a 10-times-enlarged scale of S-LixC laminate type full cell has been assembled with high capacity performance (around 1000 mAh (g-S)−1) even after high rate cycling.

Among the recent advancements in lithium-oxygen (Li-O2) chemistries, redox mediators (RMs) have been revealed to play a significant role in decreasing overpotential on charging and in improving cycling performance. However, an intrinsic problem is redox shuttle of RMs, which leads to degraded RM utilization and induces the accumulation of discharge products on the cathode surface
this remains a significant issue in the current battery cell configuration (Li anode/separator/cathode). To address this detrimental problem, herein we propose a novel Li-O2 cell incorporating a freestanding electropolymerized polypyrrole (PPy) film for the restriction of the redox-shuttle phenomenon of lithium iodide (Li anode/separator/PPy film/cathode). In this study, a PPy film, which is prepared through oxidative electropolymerization using an ionic liquid of 1-methyl-1-butylpyrrolidinium mixed with pyrrole and lithium bis(trifluoromethanesulfonyl)imide, is introduced between the cathode and the separator. From the charge-discharge voltage profile, it is confirmed that the PPy film suppresses the diffusion of the oxidized I3- to the Li anode, while allowing Li ion transport. Secondary scanning electron microscope measurements confirm that the chemical reactions between I3- and Li2O2 are facilitated by the presence of the PPy film because I3- remains near the cathode surface during the charging process. As a result, the cycling performance in the Li-O2 cells with PPy film exhibits a cycling life four times as long as that of the Li-O2 cells without PPy film.

Lithium-ion batteries are required to have high-power density, that is to reduce impedance, for use in electric vehicles. This paper focuses on interfacial resistance between the cathode layer (CL) and the current collector (CC) observed at high frequencies, which is generally attributed to a resistance of surface film like SEI. To investigate the interfacial resistance systematically, different interfaces between the CL and the CC were prepared by controlling the press rate for the cathode preparation, or by introducing a carbon under-coating layer (CUL), followed by electrochemical impedance spectroscopy (EIS). The interfacial resistance between the CL and the CC prepared with an insufficient press rate or without a CUL was extremely high for the entire cathode. From the cathode cross-sectional observation, it was observed that this high interfacial resistance was caused by low contact rate at the interface. Using a pouch-type symmetric cell, EIS revealed that the interfacial resistance is attributed to electric resistance, that is, contact resistance at the interface. Also, the other resistances were attributed to be the ionic resistance of the electrolyte and pores in the cathode, and the charge transfer resistance of the cathode. Furthermore, the effectiveness of the CUL was shown to decrease the cathode impedance.

With the objective of finding an avenue for development of magnetic hyperthermia as an effective mesothelioma treatment, the influence of heating by magnetite nanoparticles (MNPs) with a diameter of similar to 40 nm, which were incorporated into cells and then subjected to AC magnetic field, on induction of cell death was investigated in all three histological subtypes of human mesothelioma cells (i.e., epithelioid NCI-H28, sarcomatoid NCI-H2052, and biphasic MSTO-211H cells). Cellular uptake of MNPs was observed in all cell types, but the amount of MNPs incorporated per cell into MSTO-211H cells was smaller than in NCI-H28 and NCI-H2052 cells. On the other hand, cell death induced by cellular uptake of MNPs was observed specifically in MSTO-211H cells. Hence, when cells are heated by intracellular MNPs under AC magnetic field, a high degree of cell mortality in NCI-H28 and NCI-H2052 cells is induced by the temperature increase derived from the high amount of intracellular MNPs, but the combination of intracellular heating and cell-type-specific toxicity of MNPs induced high rates of cell death in MSTO-211H cells even at a lower temperature. Almost all of the heated cells were dead after 24-h incubation at 37 degrees C in all histological subtypes. Additionally, higher mortalities were observed in all three types of mesothelioma cells after MNPs-heating, as compared to the heating with a thermostatic bath. Herein, the significance of cellular uptake of MNPs for effectively inducing cell death in mesothelioma has been demonstrated in vitro. (C) 2017 Elsevier B.V. All rights reserved.

Degradation of lithium-ion battery (LIB) was evaluated by using liquid chromatography-quadruple time of flight mass spectroscopy (LC-QToF/MS). Lab-made LIBs were degraded by storing at their states of charge of 50% at 25 or 60 degrees C for three months. The degradation of the LIB was accelerated at 60 degrees C compared with that at 25 degrees C. The electrochemical impedance spectroscopy analysis suggested that the remarkable degradation occurred for solid electrolyte interphase (SEI): it was implied that on one hand, the composition of the SEI for the LIB degraded at 25 degrees C did not vary, on the other hand, that at 60 degrees C varied. For LC-QToF/MS analysis, although decomposed products derived from the electrolyte solution were detected from the electrolyte in the LIB degraded at both 25 and 60 degrees C, those decomposed products were almost the same. Whereas, the difference between decomposed products at 25 and 60 degrees C was confirmed for the interphases between electrodes and electrolyte. The characteristic decomposed products at 60 degrees C was a product with more than C35 and more than 500 m/z of mass number. This product should be one of the reason of capacity degradation due to the internal resistance increase. Thus, a possibility of LC-QToF/MS was demonstrated. (C) The Electrochemical Society of Japan, All rights reserved.

This work reports a new chemical pre-lithiation method to fabricate lithium sulfide (Li2S) cathode. This pre-lithiation process is taken place simply by dropping the organolithium reagent lithium naphthalenide (Li(+)Naph(-)) on the prepared sulfur cathode. It is the first time realizing the room temperature chemical pre-lithaition reaction attributed by the 3D nanostructured carbon nanotube (CNT) current collector. It is confirmed that the Li2S cathode fabricated at room temperature showing higher capacity and lower hysteresis than the Li2S cathode fabricated at high temperature pre-lithiation. The prelithiated Li2S cathode at room temperature shows stable cycling performance with a 600 mAh g(-1), capacity after 100 cycles at 0.1 C-rate and high capacity of 500 mAh g(-1) at 2 C-rate. This simple on -site prelithiation method at room temperature is demonstrated to be applicable for the in-situ pre-lithiation in a Li metal free battery. (C) 2017 The Authors. Published by Elsevier B.V.

Rapid gas-evaporation method is proposed and developed, which yields Si nanoparticles (SiNPs) in a few seconds at high yields of 20%-60% from inexpensive and safe bulk Si. Such rapid process is realized by heating the Si source to a temperature &gt;= 2000 degrees C, much higher than the melting point of Si (1414 degrees C). The size of SiNPs is controlled at tens to hundreds nanometers simply by the Ar gas pressure during the evaporation process. Self-supporting films are fabricated simply by co-dispersion and filtration of the SiNPs and carbon nanotubes (CNTs) without using binders nor metal foils. The half-cell tests showed the improved performances of the SiNP-CNT composite films as anode when coated with graphitic carbon layer. Their performances are evaluated with various SiNP sizes and Si/CNT ratios systematically. The SiNP-CNT film with a Si/CNT mass ratio of 4 realizes the balanced film-based capacities of 618 mAh/g(film), 230 mAh/cm(3), and 0.644 mAh/cm(2) with a moderate Si-based performance of 863 mAh/g(Si) at the 100th cycle. (C) 2017 Elsevier B.V. All rights reserved.

Electrochemical impedance measurements of lithium ion batteries (LIBs) in energy storage systems (ESS) were performed. Square-current electrochemical impedance spectroscopy (SC-EIS), which is a simple and cost-effective approach to measure impedance, was chosen to investigate a large-scale LIB system. Harmonics calculated by Fourier transform from a square waveform were used to determine the impedance. On the basis of a simple electrochemical reaction involving the ferri/ferro-cyanide redox couple and the LIB, the accuracy of the impedance measurement was found to depend on both the signal-to-noise ratio of the power spectra of the harmonics as well as the attenuation rate of the "measured value of impedance" and the "theoretical spectra value" from Fourier series. The accuracy was improved by adjusting the input waveform to be close to an ideal square waveform from Fourier series. The accuracy was further improved by the combined use of a simple moving average and an overall average. The impedance from a degraded square waveform generated by a cost-effective power controller was able to be determined by increasing the measurement time, which aided averaging. By designing the input signal to be close to an ideal square waveform from Fourier series, kilowatt-class LIB modules/cubicles in an ESS was able to be measured. Moreover, a degraded LIB module in an ESS was able to be detected using EIS, which highlights the utility of this technique for in situ impedance measurements of large-scale LIB systems. (C) 2017 Elsevier Ltd. All rights reserved.

The cycle durability of electrodeposited Si-O-C composite anodes in glyme-based ionic liquid electrolytes, known as Li(G3)TESI or Li(G4)TFSI (triglyme: G3 and tetraglyme: G4), which is one of the most promising electrolytes for sulfur cathode, was improved for use in lithium secondary batteries by using additives, fluoroethylene carbonate (FEC) or vinylene carbonate (VC). We revealed an importance of the activation process and the effects of additives in the Si-O-C composite anode. The capacity of the Si-O-C composite anode decreased with charge-discharge cycles in electrolytes without additives. Meanwhile, although the capacity retention in electrolytes with additives was improved by 10-20%, their initial capacity was smaller than those without additives. To solve the contradiction, an activation process, in which the Si-O-C composite anode was charged and discharged in electrolytes without additives, was introduced before charge-discharge cycles in electrolytes with additives. Owing to the optimized activation process, the initial capacity in electrolytes with additives showed as high as 1100-1300 mAh(-1) as those without additives with better capacity retention. Therefore, the necessity to adequately generate an activation reaction and to form SEI derived from additives for the Si-O-C composite anode to have better charge-discharge performance was demonstrated. (C) 2017 Elsevier Ltd. All rights reserved.

Mid to low frequency impedance for a cathode in a lithium ion battery (LIB), which is affected by lithiumion diffusion into active materials, was investigated. We had earlier suggested that charge-transfer and diffusion impedances are attributed to a particle size distribution for a commercially available LIB, and we designed an equivalent circuit in which two series circuits of charge-transfer resistance and Warburg impedance were connected in parallel. Here, to validate the design of the equivalent circuit, the secondary-particle size distribution of the LiNi1/3Mn1/3Co1/3O2 cathode in a lab-made LIB, in which the secondary-particles were controlled into wide and narrow distribution by sieving, was investigated by electrochemical impedance spectroscopy. The equivalent circuit was designed in which series circuits of charge-transfer resistance and Warburg impedance were connected in parallel. Dependency of impedance response on the number of parallels of the series circuits was evaluated for the cathodes using different secondary-particle size distributions of the active material. Additionally, the tendency of change in the charge-transfer resistance and the limiting capacitance was discussed from the standpoint of secondary-particle size distribution. The results confirm the effectiveness of the designed equivalent circuit which reflects the secondary-particle size distribution of cathode active materials. (C) 2017 Elsevier Ltd. All rights reserved.

Lithium metal free sulfur battery paired by lithium sulfide (Li2S) is a hot point in recent years because of its potential for relatively high capacity and its safety advantage. Due to the insulating nature and high sensitivity to moisture of Li2S, it calls for new way to introduce Li ion into S cathode besides the method of directly using the Li2S powder for the battery pre-lithiation. Herein, we proposed a pre-lithiation method to lithiate the polypyrrole (PPy)/S/Ketjenblack (KB) electrode into PPy/Li2S/KB cathode at room temperature. By this process, the fully lithiated PPy/Li2S/KB cathode showed facilitated charge transfer than the original PPy/S/KB cathode, leading to better cycling performance at high C-rates and disappearance of over potential phenomenon. In this work, the ion-selective PPy layer has been introduced on the cathode surface by an electrodeposition method, which can suppress the polysulfide dissolution from the cathode source. The lithium metal free full battery coupled by the prepared Li2S/KB cathode and graphite anode exhibited excellent cycling performance. Hence, we believe this comprehensive fabrication approach of Li2S cathode will pave a way for the application of new type lithium metal free secondary battery. (C) 2016 Elsevier B.V. All rights reserved.

:With the objective of finding an avenue for development of magnetic hyperthermia as an effective mesothelioma treatment, the influence of heating by magnetite nanoparticles (MNPs) with a diameter of ~40nm, which were incorporated into cells and then subjected to AC magnetic field, on induction of cell death was investigated in all three histological subtypes of human mesothelioma cells (i.e., epithelioid NCI-H28, sarcomatoid NCI-H2052, and biphasic MSTO-211H cells). Cellular uptake of MNPs was observed in all cell types, but the amount of MNPs incorporated per cell into MSTO-211H cells was smaller than in NCI-H28 and NCI-H2052 cells. On the other hand, cell death induced by cellular uptake of MNPs was observed specifically in MSTO-211H cells. Hence, when cells are heated by intracellular MNPs under AC magnetic field, a high degree of cell mortality in NCI-H28 and NCI-H2052 cells is induced by the temperature increase derived from the high amount of intracellular MNPs, but the combination of intracellular heating and cell-type-specific toxicity of MNPs induced high rates of cell death in MSTO-211H cells even at a lower temperature. Almost all of the heated cells were dead after 24-h incubation at 37°C in all histological subtypes. Additionally, higher mortalities were observed in all three types of mesothelioma cells after MNPs-heating, as compared to the heating with a thermostatic bath. Herein, the significance of cellular uptake of MNPs for effectively inducing cell death in mesothelioma has been demonstrated in vitro.

Lithium nitrate (LiNO3) is a potential option for the lithium salt in lithium-oxygen (Li-O-2) batteries because it reduces the charging overpotential on carbon-based cathodes and protects the lithium metal anode from side reactions. However, the cycling stability of an electrolyte containing LiNO3 in the presence of cathode catalysts has not yet been studied. In this paper, we report an improvement in the cycling performance of sigma-MnO2 cathodes in Li-O-2 batteries using LiNO3 in comparison with that of batteries using lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) in DMSO- based electrolytes. A &gt; 50% improvement in cycling performance is obtained from the electrolyte with LiNO3 versus that with LiTFSI. While the charge-discharge voltage profiles of the two electrolytes are identical to each other, the electrolyte containing LiNO3 produces less side products such as C-F group compounds, Li2SO3, and Li2SO4 on the cathode surface. This may be due to the electrochemically stable behavior of LiNO3 and the preventive effect of NO3- on solvent decomposition, which stabilizes reactive species of superoxide radicals in the electrolyte. (C) 2017 The Electrochemical Society. All rights reserved.

To enlarge the areal capacity of Si-O-C composites as an anode for high energy Li secondary batteries, 3D-structured carbon paper is used as a current collector for electrodeposition of Si-O-C composites. For higher surface affinity between organic solvents with carbon paper, surface treatment of carbon paper is carried out using a sulfuric acid-hydrogen peroxide mixture (SPM) solution. The higher deposited Si amounts and areal capacity are obtained by SPM treatment of carbon paper due to its enhanced surface affinity between carbon paper and electrolytes during Si-O-C electrodeposition. In addition, two kinds of organic solvents, propylene carbonate (PC) and ethylene carbonate/diethyl carbonate (EC/DEC), are employed to investigate their suitability for the electrodeposition of Si-O-C composites. As a result, it is confirmed that the Si-O-C composites synthesized by EC/DEC solvents show more stable cycle abilities than in the case of using PC solvents at a high charge current density of 1.0 mA cm(-2). This is due to the exfoliation of carbon paper by PC, resulting in fast capacity fading during charge/discharge cycle. Nevertheless, it is confirmed that the use of carbon paper as a substrate for Si-O-C electrodeposition is an effective way to increase deposited Si amounts and discharge areal capacity. (C) 2017 The Electrochemical Society. All rights reserved.

A high areal capacity lithium-sulfur battery making use of mass produced aluminum metal foam as a current collector was investigated. A sulfur/Ketjenblack (KB) composite was filled and deposited into the aluminum foam current collector via a predetermined filling procedure, resulting in high sulfur loading. The value for this loading was found to be 17.7 mg sulfur/cm(2) by using carboxymethyl cellulose and styrene butadiene rubber (CMC + SBR) as a binder. An operating single-layer pouch-type cell with an S/KB+CMC+SBR on Al foam cathode was created as a result of this synthesis and found to possess an unprecedentedly high areal capacity of 21.9 mAh/cm(2). On the basis of the achieved areal capacity, the energy density of a theoretical lithium-sulfur battery was estimated with the assumption of an electrolyte/sulfur ratio of 2.7 mu L/mg. This was calculated upon 100% of the pore volume in the S/KB-CMC + SBR on Al foam cathodes and polyolefin separator, along with the inclusion of the weights of the tabs for the current lead and pouch film packaging in the case of a seven-layer pouch-type battery. With this calculation, it was determined that the creation of a lithium-sulfur battery with an energy density of greater than 200 Wh/kg is plausible. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.

In this study, we report the preparation of carbon nanotubes (CNTs) anchor layer on a Cu substrate (CNTs/Cu) by using electrophoretic deposition technique. The CNTs anchor layer increases adhesion strength between Si-O-C composites and Cu substrate, as a result, it is possible to improve deposited Si amounts and areal capacity. The electrodeposited Si-O-C composites on CNTs/Cu (Si-O-C/CNTs/Cu) show homogenously coated surface morphology without cracks even large passing charge for electrodeposition of 15 C cm(-2), resulting in 0.21 mg cm(-2) of deposited Si amounts. On the other hand, Si-O-C composites deposited on as-received Cu substrate (Si-O-C/Cu) begin to peel off from substrate at 8 C cm(-2) of passing charge, resulting in 0.13 mg cm(-2) of deposited Si amounts, and decrease down to 0.10 mg cm(-2) at 15 C cm(-2) of passing charge. As a results, the improved Si amounts deposited on CNTs/Cu substrate achieve higher areal capacity, delivering 0.24 mA h cm(-2), which attains increase in 84.6% in comparison to Si-O-C/Cu, which has areal capacity of 0.13 mA g cm(-2) at 8 C cm(-2) of passing charge. Moreover, the Si-O-C/CNTs/Cu shows improved anode performances including discharge capacity and C-rate performance of the Si-O-C composites than Si-O-C/Cu without CNTs anchor layer. (C) 2016 Elsevier B.V. All rights reserved.

The poor electrical conductivity of Si-based anode materials is a critical challenge for the development of high-performance Li secondary batteries. We propose a new approach for enhancing the electrical conductivity of an electrodeposited Si-O-C composite anode via self-incorporation of nano Cu metal (n-Cu) using a facile and inexpensive electrochemical synthetic method. The Si-O-C composite with n-Cu (Cu/Si-O-C composite) shows stable cycle performance with a fairly high specific capacity. Since Cu precursor ions for the electrodeposition of n-Cu are directly dissolved from a Cu substrate used as the current collector for the anode, electrical conducting additives that causes increase in the weight and volume of the electrode are not unnecessarily supplemented. In the synthesis process, the n-Cu metal and Si-O-C composite are electrodeposited simultaneously. The n-Cu/Si-O-C composite anode results in improved electrochemical performance, including enhancement of areal and specific capacity; coulombic efficiency; and rate capability. Electrochemical impedance spectroscopy suggests that such improvements in performance are due to the enhanced electrical conductivity resulting from the conductive network of the incorporated n-Cu. Moreover, the electrical conductive properties of the incorporated n-Cu suppress electrochemical degradation of the n-Cu/Si-O-C composite anode. (C) 2016 Elsevier Ltd. All rights reserved.

Stable charge-discharge cycling behavior for a lithium metal anode in a dimethylsulfoxide (DMSO)-based electrolyte is strongly desired of lithium-oxygen batteries, because the Li anode is rapidly exhausted as a result of side reactions during cycling in the DMSO solution. Herein, we report a novel electrolyte design for enhancing the cycling performance of Li anodes by using a highly concentrated DMSO-based electrolyte with a specific Li salt. Lithium nitrate (LiNO3), which forms an inorganic compound (Li2O) instead of a soluble product (Li2S) on a lithium surface, exhibits a &gt;20% higher coulombic efficiency than lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium perchlorate, regardless of the loading current density. Moreover, the stable cycling of Li anodes in DMSO-based electrolytes depends critically on the salt concentration. The highly concentrated electrolyte 4.0 M LiNO3/DMSO displays enhanced and stable cycling performance comparable to that of carbonate -based electrolytes, which had not previously been achieved. We suppose this enhancement is due to the absence of free DMSO solvent in the electrolyte and the promotion of the desolvation of Li ions on the solid electrolyte interphase surface, both being consequences of the unique structure of the electrolyte. (C) 2015 Elsevier B.V. All rights reserved.

A novel polypyrrole (PPy) film was investigated to determine the optimal conditions for operation in a Li/S battery. The PPy film was prepared by oxidative electropolymerization to improve the Li/S battery performance, as reported in our previous paper. In such a system, the PPy film was coated directly on the S/Ketjenblack cathode to solve the problem of polysulfide dissolution. The optimum PPy film preparation conditions to prevent polysulfide dissolution and to promote Li+ permeability were determined by varying the PPy polymerization bath composition and polymerization potential. As a result, the inclusion of 1.0 M lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) in the polymerization bath (0.1 M pyrrole in 1-methyl-1-butylpyrrolidinium bis(trifluoromethanesulfonyl) imide) was found to be the most important factor for producing a PPy film with a high Li+ transport number (t(Li+) approximate to 1). A polymerization potential of 4.5 V versus Li/Li+ was shown to be optimum for the promotion of Li+ permeability. The mechanism by which the PPy film prevents polysulfide dissolution and increases Li+ permeability is discussed by analyzing the SEM, CV, XPS, and C-13 solid-state NMR data. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/),which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.

Static degradation of LiCoO2 cathodes is a problem that hinders accurate analysis using our developed separable symmetric cell. Therefore, in this study we investigate the static degradation of LiCoO2 cathodes in separable symmetric cells by electrochemical impedance spectroscopy (EIS) and inductively coupled plasma analyses. EIS measurements of LiCoO2 cathodes are conducted in various electrolytes, with different anions and with or without HF and/or Hli O. This allows us to determine the static degradation of LiCoO2 cathodes relative to their increase of charge transfer resistance. The increase of the charge transfer resistance of the LiCoO2 cathodes is attributed to cobalt dissolution from the active material of LiCoO2. Cobalt dissolution from LiCoO2 is revealed to occur even at low potential in the presence of HF, which is generated from LiPF6 and H2O. The results indicate that avoidance of HF generation is important for the analysis of lithium-ion battery electrodes by using the separable cell. These findings reveal the condition to achieve accurate analysis by EIS using the separable cell.

Electrochemical impedance spectroscopy (EIS) using an equivalent circuit is a powerful tool in the diagnosis of lithium-ion batteries (LIBs). However, LIBs have been increasingly used in applications requiring power higher than that used for conventional LIBs for portable electric devices. Considering this demand for LIBs, the ionic resistances in the electrodes, which raise a reaction distribution under high-power operation, are important. This consequently means EIS analysis should include ionic resistances in the electrodes in equivalent circuits. Additionally, the impedance response of LIBs are too complicated to be analyzed in detail because the impedance response consists of overlapping elemental processes such as chemical reactions and ion migration. This paper therefore presents an analysis of impedance responses, which are independently obtained by a micro reference electrode, by using a transmission line model (TLM) that possesses the ability to count the ionic resistances in the electrodes. Similar to the conventional Randles equivalent circuit, the equivalent circuit with TLM could fit the impedance responses simulated by the equivalent circuit with measured responses. This paper discusses the potential of EIS using an equivalent circuit coupled with a TLM for diagnosis of LIBs in power applications. (C) The Author(s) 2015 Published by ECS. All rights reserved.

A facile and scalable method is proposed to prepare microscale Li2S-C composite from Li2SO4 through carbon-thermal reduction, followed by a carbon coating process. Multi-solvent recrystallization was utilized to reduce the particle size of Li2SO4 to 2 mu m. This fine-grain Li2SO4 helps to shorten the particle size of reduction product from 10 mu mto 3 mu m. Using fine Li2SO4 also brings the benefit of greatly reducing the over potential during the initial charge process and increasing the kinetics for Li2S materials. Finally, the microscale Li2S-C composite prepared from fine Li2SO4 enables a stable capacity of 350 mAh g(-1) at 0.2 C, higher than that obtained using a cathode prepared from commercial Li2SO4. (C) 2015 Elsevier Ltd. All rights reserved.

Novel three-dimensional hierarchical heterostructures composed of two-dimensional SnS2 nanoflakes and zero-dimensional SnO2 nanoparticles were fabricated via a one-step hydrothermal method. Size of the heterostructures was ca. 2 mu m in diameter, and individual SnS2 nanoflakes with thickness of ca. 150 nm were connected to central core of the heterostructures. The SnO2 nanoparticles in a diameter of ca. 5 nm uniformly covered entire surface of the SnS2 nanoflakes. Moreover, both of these structures were highly crystalline. Meanwhile, amorphous carbon was formed within the heterostructures. The SnS2/SnO2/C hierarchical heterostructures had a high initial specific reversible capacity of 1065.7 mAh g(-1), stable cycling stability of 638 mAh g(-1) after 30 cycles, and superior rate capability of 550.8 mAh g(-1) at 1C rate. These SnS2/SnO2/C hierarchical heterostructures showed better performance than individual SnS2 and SnO2 nanomaterials, and the performance was even higher than the graphene-SnS2 and graphene-SnO2 nanohybrid materials. This is attributed to a synergistic effect of high surface area, which is provided by the unique SnS2 internal nanoflake layered structures decorated with ultra-fine SnO2 nanoparticles, and an effective beneficial buffer matrix to accommodate the large volume change upon cycling, which is caused by the side-products such as Li2S or Li2O. The SnS2 nanoflake was deduced to play a similar role as graphene material, since both possess 2D conducting layer structures. The uniform carbon dispersion within the structures also stabilizes the structures and improves electrical conductivity of the hierarchical heterostructures. (C) 2015 Elsevier Ltd. All rights reserved.

The effect of the solid electrolyte interphase (SEI) on a Li anode on the charge-discharge cycling performance in 1 M LiTFSI/dimethylsulfoxide electrolyte solution is examined by using charge-discharge cycling. The chemical structure of the surface and interior of the SEI strongly affects the cycling performance of the anode. The observed coulombic efficiency is low (&lt;45%) when organic compounds such as lithium alkyl carbonates and polycarbonate form predominantly on the surface and interior. However, when inorganic compounds such as Li2CO3, Li2O, and LiF form instead, the coulombic efficiency increases to &gt;85%. This enhanced efficiency remains constant regardless of the O-2 content and despite &lt;1000 ppm concentration of the contaminant H2O in the electrolyte. Thus, the lithium surface should be protected by inorganic compounds prior to cycling to prevent it from undergoing side reactions with the electrolyte during cycling in the electrolyte. (C) 2015 Elsevier B.V. All rights reserved.

To realize electrochemical impedance spectroscopy (EIS) using a simple measurement system, application of a square potential/current waveform to the input signals of EIS was investigated. The impedance of a simple redox reaction of [Fe(CN)(6)](4-)/[Fe(CN)(6)](3-) solution was measured by the potentio-EIS using a square waveform as the input signal, which was generated by a potentiostat system without a frequency response analyzer (FRA). A steady impedance response in the frequency range of 40 Hz-3.5 kHz was obtained, and the impedance was obtained by the potentiostat system with an FRA. The errors-the differences between the impedance measured by EIS with a square potential waveform and that of conventional EIS-were sufficiently low to allow impedance analysis. The impedance of a lithium-ion battery (LIB) was measured by galvano-EIS using a square waveform input signal generated by a power controller. A steady impedance response in the frequency range of 5 Hz-2.5 kHz was obtained, and the errors were sufficiently low to allow impedance analysis. It was demonstrated that both square potential-EIS (SP-EIS) and square current-EIS (SC-EIS) have great potential as simple systems for measuring impedance. Moreover, it was demonstrated that SC-EIS has potential as a simple measurement system for analyzing the state of an LIB. Thus, the potential of the SP/SC-EIS methodology was confirmed for electrochemical systems. (C) 2015 Published by Elsevier Ltd.

We report micrometre-thick porous Si-Cu anodes that are rapidly co-deposited on Cu current collectors in 1 mm. This rapid deposition is realized by heating Si and Cu powders to similar to 2000 degrees C and elevating their vapour pressures, while the porous and amorphous anode structure is realized by keeping the substrates at 100 degrees C. The films spontaneously form a 2-4.5-mu m-thick composition gradient that changes from a Cu-rich region at the bottom to a Si-rich region at the top of the film, because of the higher vapour pressure for Cu than Si. A small addition of 5 wt% Cu to the Si source enhances the cycle performance of the film remarkably in a half-cell test, yielding a gravimetric capacity of 1250 mAh g(film)(-1), a volumetric capacity of 1956 mAh cm(film)(-3), and an areal capacity of 0.96 mAh cm(anode)(-2) at the 100th cycle. However, excess addition of Cu causes partial Si crystallization in the films, which results in poorer cycle performance. While further improvement is needed, this rapid vapour deposition method yields Si-Cu films with compositional gradients on Cu current collectors in 1 min using inexpensive and safe Si and Cu powder sources, and is attractive for practical Si-based anode fabrication. (C) 2015 Elsevier B.V. All rights reserved.

The electrodeposited Sn-O-C composite anode cycling with LiClO4 delivered stable cycle performances showing discharge capacity of 473 mA h g Risri with 95% of coulombic efficiency at 100th cycle. However, the anode showed poor cycle performances with LiPF6 delivering discharge capacity of 69 mA h g(-1) of sn at 100th cycle with 70% of coulombic efficiency. Electrochemical investigation performed by cyclic voltammetry and differential capacity plots revealed that the Sn-O-C composite cycling with LiPF86 suffered from retarded phase transition reaction between Li and Sn during charge/discharge process. X-ray photoelectron spectroscopy declared the existence of fluorinated-Sn and LiF. Moreover, energy dispersive X-ray spectroscopy found increase in their amount with repeated cycles. The morphologies of the Sn-O-C composite cycled with LiPF6 showed aggregated particles containing the chemical state of fluorinated-Sn and LiF on its surface. Furthermore, the significant pulverization and aggregation of the active material were observed from the Sn-O-C composite cycled by LiPF6 rather than that of LiClO4, which was probably promoted by the generated HF strongly corroding metallic component. (C) 2014 Elsevier B.V. All rights reserved.

Polyvinylpyrrolidone (PVP) is used with polyethylene oxide (PEO) as a mixed binder for mechanically milled Li2S. PVP demonstrates its advantage in terms of increasing the capacity of Li2S, but boosts the potential barrier at the beginning of the first charge. It is also revealed that PVP retards the charge-transfer kinetics of Li2S. In Li2S-C prepared by mechanical milling, carbon compensates for the electrochemical insulation of the PVP binder and improves the cycle stability. As a result, the Li2S-C-PVP electrode with 60 wt% Li2S content displays a low potential barrier at the onset of charge and a stable capacity of about 460 mAh g(-1) at 0.1 C. (C) 2014 Elsevier B.V. All rights reserved.

In order to solve the problem of polysulfide dissolution into the electrolyte on sulfur-based cathodes, we propose a novel method of modifying the S cathode by coating it with a polypyrrole (PPy) film, which is prepared by oxidative electropolymerization using a solution consisting of, 1-methyl-1-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and pyrrole. The PPy film demonstrates a high Li+ transport number. The film also exhibits a superior ability to inhibit polysulfide dissolution into the electrolyte during the charge discharge cycles. Furthermore, the charge discharge properties of the coated cathode is evaluated using an electrolyte consisting of 1.0 M LiTFSI in a mixture of 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL), which is known to easily dissolve polysulfides. Because of the surface modification with the PPy film, the cathode exhibits excellent specific capacities of 823 and 354 mAh g(-1) at C-rates of 0.1 and 1.0 C, respectively, with high coulombic efficiency. Thus, the strategy of coating the S cathode with PPy is successful in inhibiting the polysulfides dissolution even in electrolytes known to easily dissolve polysulfides, besides allowing high C-rate operation. Further, the modification of the S cathode allows the selection of a suitable electrolyte based on the anode, rather than being limited by the cathode. (C) 2014 Elsevier B.V. All rights reserved.

The electrode surfaces of degraded lithium-ion batteries (LIB) were analyzed by liquid chromatography-quadrupole time of flight mass spectrometry (LC-QTOF/MS). The solid-electrolyte interphase (SET) layer influences the performance of LIBs. Therefore, we conducted a study aimed at clarifying the deterioration mechanism of LIBs by examining the components in the SET before and after degradation due to cycling. We believe that the change in the mass transfer characteristics at the electrode interface influenced by SET deterioration can be clarified via Lc-QTOF/MS, which would allow elucidation of the deterioration mechanism. The analysis results showed that the degradation products contain multiple components, including polymers of carbonate compounds and phosphate esters, which are formed via electrochemical and chemical reactions, resulting in remarkably reduced capacity. The results suggest that LC-QTOF/MS is a valuable technique for the degradation analysis of LIBs. (C) The Author(s) 2015. Published by ECS. All rights reserved.

Nitrogen-doped/undoped thermally reduced graphene oxide (N-rGO) decorated with CoMn2O4 (CMO) nanoparticles were synthesized using a simple one-step hydrothermal method. The activity and stability of this hybrid catalyst were evaluated by preparing air electrodes with both primary and rechargeable zinc-air batteries that consume ambient air. Further, we investigated the relationship between the physical properties and the electrochemical results for hybrid electrodes at various cycles using X-ray diffraction, scanning electron microscopy, galvanodynamic charge-discharging and electrochemical impedance spectroscopy. The structural, morphological and electrocatalytic performances confirm that CMO/N-rGO is a promising material for safe, reliable, and long-lasting air cathodes for both primary and rechargeable zinc-air batteries that consume air under ambient condition.

The effects of a small amount of H2O with and without CO2 in an electrolyte of I M LiPF6/ethylene carbonate and diethyl carbonate on the cycling life of a Li metal anode is investigated in this paper using charge discharge cycling. A low cycling performance, which is less than 55%, is observed with the electrolyte with trace H2O but without CO2; however, when the trace H2O is accompanied by CO2, performance drastically improves and coulombic efficiency reaches a maximum of 88.9%. In the presence of CO2, the cycling performance is found to be strongly affected by the H2O content in the electrolyte, and increases with an increase in H2O content of up to 35 ppm. From an X-ray photoelectron spectroscopy analysis, trace H2O is found to affect the compounds of the solid electrolyte interphase (SEI) on the lithium surface and produces an Li2CO3 and LW layer on the upper part of the SEI, both known to be good passivation layers for preventing side reactions during charge discharge cycling. (c) 2014 Elsevier B.V. All rights reserved.

The nitrogen-doped carbon nanocapsules (NCNCs) were explored as catalyst support for oxygen reduction reaction (ORR) in acid electrolyte. The deposition of Pt particles on NCNCs support was characterized using various physico-chemical techniques, such as scanning electron microscope, transmission electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy. The high resolution transmission electron microscopy reveals that Pt particles are uniformly dispersed onto the NCNCs and particles size of about 2.2 nm was observed. The electrochemical ORR activities of the Pt supported on NCNCs catalysts were studied and compared with a commercial catalyst. Pt/NCNC showed enhanced ORR activity and better stability than a commercial Pt/C catalyst. The enhanced performance of Pt supported NCNCs can be attributed to the better dispersion and utilization of Pt nanoparticles. (C) 2014 Elsevier Ltd. All rights reserved.

In this paper, we report a lithium-ion battery employing a lithium sulfide cathode and a silicon-based anode. The high capacity of the silicon anode and the high efficiency and cycling rate of the lithium sulfide cathode allowed optimal full cell balance. We show in fact that the battery operates with a very stable capacity of about 280 mAh g(-1) at an average voltage of 1.4 V. To the best of our knowledge, this battery is one of the rare examples of lithium-metal-free sulfur battery. Considering the high theoretical capacity of the employed electrodes, we believe that the battery here reported may be of potential interest as high-energy, safe, and low-cost power source for electric vehicles.

A carbon-coated Li2S was prepared through an adsorption and successive annealing process by using poly(vinylpyrrolidone) (PVP) and acetylene black (AB) as carbon source with Li2S powder. The coating layer was composed of amorphous carbon and embedded AB particles. The carbon coating was found to effectively alleviate the dissolution of polysulfide and the discharge capacity at the first 15 cycles was 800 mA h g(-1) with gradual fading afterward.

Symmetric cells were prepared with a newly designed separable cell module, which enabled ca. 70 mm by 70 mm electrode sheets to be used for a pouch type 5 Ah class Li-ion battery (LIB). Impedance analysis of the LIB as a full cell state was successfully performed with electrochemical parameters obtained by an impedance analysis of symmetric cells of anodes and cathodes obtained from the operated Li-ion batteries. While the charge transfer resistance of the cathode was found to increase after reassembling the cells symmetrically, other electrochemical parameters were found not to change when comparing the values obtained for full cells with symmetric cells. Eelectrodes degraded by charge/discharge cycling of the battery were also investigated, and the parameter change caused by the degradation was confirmed. (C) 2014 Elsevier Ltd. All rights reserved.

The impedance behaviors of Si-O-C composite film electrodeposited on Cu microcones-arrayed current collector have been investigated to understand the electrochemical process kinetics that influences the cycling performance when used as a highly-durable anode in a lithium battery. The impedance was measured by using impedance spectroscopy in equilibrium conditions at various depths of discharge and during several hundred charge-discharge cycles. The measured impedance was interpreted with an equivalent circuit composed of solid electrolyte interphase (SEI) film, charge transfer and solid state diffusion. The impedance analysis shows that the change of charge transfer resistance is the main contribution to the total resistance Change during discharge, but an abrupt augmentation of diffusive resistance at high depth of discharge is also observed which cannot be explained very well by the presented model. The impedance evolution of this electrode during charge-discharge cycles suggests that the slow growth of the SEI film as well as the increase of the electrode density are responsible for the capacity fading after long term cycling. (C) 2014 Elsevier B.V. All rights reserved.

Silicon is one of the most promising materials for lithium secondary battery anodes. However, silicon anodes have a critical drawback to their practical application, which is capacity degradation due to pulverization of the active material by the large volume change of silicon during charge-discharge cycles. This paper reviews recent studies on silicon-based anodes that have attempted to overcome this poor cycle durability through structural control such as through thin films, porous structures, core-shell structures, and by alloying with other metals, and by application of proper binders. Among them, binder-free Si-O-C composite films prepared by electrodeposition exhibit outstanding cycle durability. The origin of this excellent durability is discussed in depth from the standpoint of chemical and morphological changes. Consequently, the combination of active materials such as Si and Li2Si2O5 and inactive materials such as L(i)2O, Li2CO3, and organic compounds is suggested to result in outstanding properties as a lithium secondary battery anode.

Electrodeposition was conducted from an organic carbonate solvent via the potentiostatic technique through three consecutive steps in order to synthesise Sn-O-C composite, which delivered a discharge capacity of 596 mA h g of Sn-1 after 50 cycles. However, the composite anode suffered from a significantly low initial discharge capacity, delivering a discharge capacity of 79 mA h g of Sn-1 until the 5th cycle. It was deduced that the improbably low initial capacity was induced by the deposition of Li-rich compounds, which were formed by electrolyte decomposition accompanied by the reduction product of supporting electrolyte salts during the electrodeposition process, on the surface layer. In order to improve the poor initial capacity, we modified the chemical composition of the surface layer by means of implementing the agitation of the electrolyte during the deposition process. This gave rise to varying the diffusion-layer thickness during the deposition process due to the enhancement of convection by movement of the electrolyte itself. As a result, we achieved improvement of the initial discharge capacity, delivering 572 mA h g of Sn-1 at the 1st cycle and 586 mA h g of Sn-1 at the 50th cycle. It was revealed that the surface layer was composed of a decomposition product of the organic carbonate solvent. Furthermore, a smaller particle size of the Sn-O-C composite was obtained via electrolyte agitation, giving rise to homogeneous shell formation on the Sn compound core. Herein, we thoroughly examined the influence of varying diffusion-layer thickness during the deposition process on the properties of the Sn-O-C composites from an electrochemical standpoint.

Sn-O-C composites were electrodeposited using organic carbonate solvents and their electrochemical mechanism was thoroughly investigated to achieve desired anode performances, such as high capacity and cycle durability for lithium secondary batteries. Cyclic voltammetry study clarified the multiple stages of electrochemical mechanism during the Sn-O-C composite deposition process. It was revealed that Sn deposition, decomposition of organic electrolytes, and reaction between Li+ and deposited Sn were consecutively carried out. X-ray photoelectron spectroscopy and field emission scanning electron microscopy were performed to characterize how each stage contributes to the formation of the Sn-O-C composite. The results showed increase in metallic Sn composition and dense coating with fine particle sizes with a higher overpotential stage. Afterward, different Sn-O-C composite anodes were prepared by varying charge quantities passing through each deposition stage and their electrochemical performances as anode materials were investigated. Discharge capacities were obtained from the lowest value of 33 mAh g of Sn-1 to the highest value of 429 mAh g of Sn-1 at the 100th cycle by varying deposition conditions. Consequently, it was suggested that anode performance was significantly influenced by an electrodeposition process consisting of three consecutive stages with different overpotential regions and reactions of Li ion with deposited Sn. (C) 2014 The Electrochemical Society. All rights reserved.

A common understanding of polymer electrolyte fuel cells (PEFCs) is important to promote the development of PEFCs. This understanding is crucial because complicated phenomena such as chemical reactions, ion transport, and gas diffusion occur during the operation of PEFCs. Electrochemical impedance spectroscopy (EIS), which can separate reactions into elementary processes, is a powerful tool for the analysis of PEFCs without requiring disassembly of the cell. In this study, the effect of flooding in the cathode catalyst layer of PEFCs was analyzed by EIS using the transmission line model (TLM) to determine the distribution of catalytic reactions in the primary and secondary pores. The analysis was conducted by varying experimental conditions such as the relative humidity of the gases supplied into the anode and cathode, the flow rate, and the partial pressure of oxygen in the gas mixture supplied to the cathode channel. The EIS analysis suggests that the resistance to the catalytic reaction in the primary pores drastically increased with the current density. The results suggest that the flooding preferentially occurred in the primary pores, resulting in the reduction of active sites by generated water. The EIS method is a powerful tool for developing membrane electrode assemblies (MEAs) with effective porosity and tortuosity for gas diffusion and ionic transportation, and furthermore, it is a useful tool for judging the process of MEA preparation. (C) 2013 Elsevier Ltd. All rights reserved.

The Sn-O-C composite anode for the Li secondary battery was synthesized by electrodeposition using an organic carbonate solvent. The composite of Sn with organic/inorganic compounds was prepared by the simultaneous reaction of the reduction of Sn2+ ions and electrolysis of the mixture of ethylene carbonate and propylene carbonate. The galvanostatic potential transients for the electrodeposition of the Sn-O-C composite indicate that multiple steps of reactions corresponding to the electrochemical reduction of the tin precursor and the decomposition of organic solvents are involved. The morphology, crystalline structure and chemical composition of the as-deposited Sn-O-C composite anode were characterized to elucidate the mechanism of the synthesis of the buffering matrix enduring volume expansion.
The electrochemical behavior of the Sn-O-C composite anode was investigated by cyclic voltammetry and galvanostatical charge/discharged tests. The discharge capacity of 465 mAh (g of Sn)(-1) was obtained at the 100th cycle showing 80% of the capacity retention after the 100th cycle. The discharge capacity was stable after the 50th cycle, where the phase transformation of the Sn element from Sn to Li0.4Sn at the discharged state was found. (C) 2013 Elsevier B.V. All rights reserved.

The structure of the highly durable silicon-based anode prepared by electrodeposition was investigated for volume change and chemical structure. With repeated charge-discharge cycles, the volume change resulting from the anode film thickness decreased, and, after 100 cycles, essentially no difference was observed between the charged and discharged states. The buffering effect of the volume change was considered to be achieved by the formation of Li2O, Li2CO3, and lithium silicates such as Li4SiO4, whose existence were supported by STEM, EELS, and XPS analyses. From the structural analyses, the main reactions related to the capacity of the silicon-based anode were considered to be the formation of LixSi and Li2Si2O5. LixSi and Li2Si2O5 can be delithiated into Si and SiO2, respectively. (C) 2013 Elsevier Ltd. All rights reserved.

Hybrids possessing both oligomeric ethylene oxide chains and Ti-O-P networks were prepared from TiCl4 and organodiphosphonic acid [(HO)(2)OP(C2H4O)(3)C2H4PO(OH)(2)] via a nonhydrolytic sol gel process and subsequently treated with a LiClO4 solution. The P/Ti ratio was fixed at 2 and the ethylene oxide unit/Li+ ratio was changed from 5 to 20. Li+ ions are likely to be solvated by ether oxygen atoms. Li+ ion transport in the hybrids with ionic conductivity values in the 10(-5) S cm(-1) range was observed at ambient temperatures.

The impedance of Li-ion battery using a Li4Ti5O12 (LTO) anode for high-power applications was measured at various depths of discharge and temperatures during charge discharge cycles. The measured impedance was interpreted with an equivalent circuit made up of anode and cathode, in which the cathode component was composed of two particle size factors. The values obtained for equivalent circuit elements by modeling were in good agreement with the results measured by other techniques, and indicated that the capacity fade of this Li-ion battery due to cycling is mainly caused by the increase of interfacial resistance and a decrease in the capacity of the LiCoO2 cathode. These results suggest that the cyclability of this LIB was improved by using an LTO anode, and show the validity of the equivalent circuit for interpreting the causes of capacity fade. (C) 2012 Elsevier B.V. All rights reserved.

Electrodeposition methods were developed for the fabrication of Si composite anodes with nickel micro-nanocones hierarchical structure (MHS) current collectors for Li secondary batteries. This unique structured nickel current collector is electrodeposited in a simple process to create a complex high surface area conductive substrate, as well as to enhance the interfacial strength between active materials and substrate during cyclic lithiation/delithiation. The MHS supported Si composite anode demonstrated outstanding Li+ storage properties with reversible capacity over 800 mAh g(-1) (600 mu Ah cm(-2)) after 100th cycle with superior retention of 99.6% per cycle. The improved performance of nickel MHS supported Si thick films indicate the potential for their application as electrode materials for high performance energy storage. 2012 Elsevier B.V. All rights reserved.

Ac impedance spectra of electrochemical systems are analyzed by considering adequate equivalent circuits, while the differentiation of responses for each elemental step is sometimes difficult. In this study, enlarged impedances were measured by lowering the temperature of a lithium ion battery (LIB) to make the separation of confusing responses easier. The impedance spectra obtained at the temperatures between -20 degrees C and 20 degrees C showed drastic change in sizes with shifting of the characteristic frequency. The analysis of impedance spectra using an equivalent circuit revealed changes in resistance of each component and shifting of the time constant for each elemental step. The frequency domain of impedance response of solid electrolyte interphase (SEI) was found to overlap with that of the inductive component of the outer electric lead at 20 degrees C in our study. The impedance measurement at the low temperatures is considered to be useful for the detection of the SEI and the accurate evaluation of LIB. (C) 2012 Elsevier B.V. All rights reserved.

To analyze impedance response of an electrochemical system, it is important to model the system with an adequate equivalent circuit. In the present work, an equivalent circuit was designed for the analysis of lithium ion batteries with the contributions of a variety of diffusion parameters resulting from the various particle sizes for the cathode and the solid-electrolyte interphase formed on the anode particles, as well as electrochemical reactions and inductive components. Residual errors resulting from the data fitting was investigated for a variety of equivalent circuits used. The electrochemical impedance of the electrodes in commercial lithium ion batteries at various states of charge was analyzed to evaluate the proposed circuit. (C) 2012 Elsevier B.V. All rights reserved.

A highly durable SiOC composite anode was prepared for use in lithium secondary batteries. The SiOC composite was synthesized by electrodeposition of SiCl4. The composite anode delivered a discharge capacity of 1045 mA h per gram of Si at the 2000th cycle and 842 mA h per gram of Si even at the 7200th cycle. The reason for the excellent cyclability was investigated by methods including field emission scanning electron microscopy (FESEM), scanning transmission electron microscopy with an energy dispersive X-ray analyser (STEM-EDX), and X-ray photoelectron spectroscopy (XPS). The results revealed that the excellent cyclability was achieved by the homogeneous dispersion of SiOx and organic/inorganic compounds at the nanometre scale. The structural uniformity of the SiOC composite is believed to have suppressed the crack formation attributable to the stress resulting from the reaction of silicon with lithium during charge-discharge cycles.

The degradation of the commercial Li ion battery was analyzed by electrochemical impedance spectroscopy, where our previous proposed equivalent circuit was applied. The degradation with the cycling was clearly explained by the main parameters of capacitive and resistive components, i.e., it responded until 300 cycles to the decrease in capacitive component, while after 300 to 550 cycles to the increase in resistive component.

A novel SiOC composite anode material for a Li battery was realized by electrochemical co-deposition of Si, C. and O elements. The composite was deposited by reduction of SiCl(4) in a propylene carbonate based solution. After the initiation process by reduction of the composite in a Li(+) containing electrolyte solution, the SiOC composite was found to be about 3.3 mu m in average thickness and the composite performed as a Li battery anode with over 1000 mAh g(-1) of Si for more than 2000 cycles, and moreover have continued for 7000 cycles with gradual degradation. (C) 2011 Elsevier B.V. All rights reserved.

Many efforts have been paid to realize the superior anodes for future Li batteries in either the dry Ar atmosphere or the dry air atmosphere. In this work, in order to clarify the effects of such atmospheres, the most reactive anodes of Li were freshly electrodeposited under the dry Ar or under the dry air condition. The Solid Electrolyte Interface (SEI) formed during the electrodeposition of Li anodes is revealed to have a different chemical composition and protective feature. The Li deposited under the dry air was revealed to have longer cycle life in the electrolyte than that deposited in Ar, even in the electrolyte containing ionic liquid. From the XPS results, the SEI formed in dry air is proved to be different from that formed in Ar gas atmospheres. that is, the SEI formed in dry air consists of Li(2)CO(3) and Li nitride. In order to improve the performance of the anodes, the atmosphere for the initial preparation of the anode/electrolyte interface should be tuned. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.

A novel transmission line (TML) model is proposed for the impedance analysis, which is nondestructive measurement, on degraded cathode catalyst layers in polymer electrolyte fuel cells (PEFCs). The test PEFC consisted of 1.0 mg/cm(2) of Pt-Ru as an anode catalyst, 1.0 mg/cm(2) of Pt as a cathode catalyst, and Nafion 212 as an electrolyte. The model counts the distribution of the oxygen reduction reaction (ORR) at the inside and outside of agglomerates of the carbon supported catalysts. We demonstrated the importance of the distribution of the ORR for achieving excellent agreement between the calculated and experimental data. The change in parameters obtained by impedance analysis with the TML model was verified by destructive tests, such as transmission electron microscopy, field emission scanning electron microscopy, cyclic voltammetry, micro-Fourier transform infrared spectroscopy and nitrogen adsorption-desorption measurements. Variations of the parameters such as the charge transfer resistance, the double layer capacitance, and the ionic resistance inside and outside the agglomerates of the carbon supported catalysts could be explained by multiple considerations of these destructive test results. Impedance analysis with the TML model offers the possibility understanding the state of degraded cathode catalyst layers in membrane electrode assemblies without the need for disassembling PEFCs. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3610988] All rights reserved.

Sulfated zirconia is an inorganic solid superacid having sulfate groups covalently bonded to its surface. In this work, sulfated zirconia is synthesized by a solvent-free method to obtain it in the nanoparticle form. This nanostructured sulfated zirconia has been evaluated in terms of (i) chemical stability to hydrolysis and to hydrogen peroxide by thermogravimetric analysis, and (ii) influences on Pt catalyst activity by cyclic voltammetry using sulfated-zirconia dispersion as a supporting electrolyte solution. The results demonstrate that our sulfated zirconia is stable almost perfectly to hydrolysis but partly decomposed by a Fenton reagent containing hydrogen peroxide and Fe(2+). In addition, we show that oxygen reduction activity of Pt catalyst in a sulfated-zirconia dispersion is comparatively high (specific activity at 0.9 V vs. RHE, i(0.9): ca. 17 mu A cm(-2)) compared to that in a 0.5 M sulfuric acid solution (i(0.9): ca. 15 mu A cm(-2)). Finally, we demonstrate that sulfated zirconia does not influence hydrogen oxidation reaction. These results lead us to conclude that sulfated zirconia is a promising proton conductor for fuel cells. (C) 2010 Published by Elsevier B.V.

Catalyst layers of direct methanol fuel cells (DMFCs) are modified by in situ electropolymerization of m-aminobenzenesulfonic acid. By using electrochemical impedance spectroscopy and porosimetry, this modification is found to add polymer electrolyte into primary pores (&lt;10 nm), where ionic resistance is high for lack of polymer electrolyte (i.e., Nafion), and the additional electrolyte successfully decreases the ionic resistance by 10-15% compared to the plain carbon surface with a slight ion-conductivity (&gt;40 k Omega cm). In view of methanol oxidation characteristics, this modification decreases the resistance by ca. 25% (from 5.1 Omega cm(2) to 3.7 Omega cm(2)) at 0.6V vs. DHE, resulting in the increase in the cell voltage of DMFC test by ca. 20 mV. The clear relation between the performance and the microstructures is concluded to be helpful to understand the performance of fuel cell electrodes in detail. (C) 2009 Elsevier B.V. All rights reserved.

As potential high capacity anode materials for lithium ion batteries, the Sri and Ni-Sn alloy coatings have been investigated by many electrochemical researchers. However, their mechanical properties have not been extensively Studied, despite the fact that such anode films may fail mechanically during service. Thus, in this study nanoindentation and nanowear tests have been performed. Nanoindentation tests reveal that the ability to carry the load dramatically reduces in the Sri coating after one charge-discharge cycle which makes the plastic strain accumulation in the copper Substrate play a greater Contribution to crack formation and propagation in repeated charge-discharge cycling. Upon the nanoindentation analysis, it also shows that the pores formed by lithiation/delithiation can easily collapse at low loads. Furthermore, nanowear tests explore that the damage resistance of the Sn-Ni alloy film significantly improves after one charge-discharge cycle but it decreases in the Sri film after the same charge-discharge cycle; this explains why the degradation rate of the Ni-Sn alloy is slow after the first charge-discharge cycle and why the high capacity is maintained in further cycling. The links between the mechanical characterization and the degradation in charge-discharge cycling are also discussed. (c) 2008 Elsevier Ltd. All rights reserved.

Non-platinum nanoparticles (Pd, Au, PdAu) have been prepared by sonochemical synthesis. The nanoparticle-modified electrodes showed improved catalytic activity for oxygen reduction compared with Pt nanoparticles in alkaline solution even in the presence of methanol.

Direct methanol alkaline fuel cell (DMAFC) using anion exchange membrane (AEM) was operated in passive condition. Cell with AEM exhibits a higher open circuit voltage (OCV) and superior cell performance than those in cell using Nafion. From the concentration dependences of methanol, KOH in fuel and ionomer in anode catalyst layer, it is found that the key factors are to improve the ionic conductivity at the anode and to form a favorable ion conductive path in catalyst layer in order to enhance the cell performance. In addition, by using home-made Pd-Sn/C catalyst as a cathode catalyst on DMAFC, the membrane electrode assembly (MEA) using Pd-Sn/C catalyst as cathode exhibits the higher performance than the usual commercially available Pt/C catalyst in high methanol concentration. Therefore, the Pd-Sn/C catalyst with high tolerance for methanol is expected as the promising oxygen reduction reaction (ORR) catalyst in DMAFC. (C) 2009 Elsevier B.V. All rights reserved.

Carbon-supported Pd-Sn (Pd-Sn/C) catalyst was prepared under ultrasonic irradiation, and its electrocatalytic activity for oxygen reduction reaction (ORR) was evaluated in 0.5M KOH. TEM images showed that the prepared Pd-Sn/C catalyst particles are smaller in average size than carbon-supported Pd (Pd/C) catalyst particles. XRD and XPS results indicated the small particle size and the electronic interaction between Pd and Sn for the Pd-Sn/C catalyst. The Pd-Sn/C catalyst has a higher ORR activity than the Pd/C catalyst in alkaline media. In addition, the Pd-Sn/C catalyst showed a lower Tafel slope and a larger number of electrons transferred for ORR, compared with those of the Pd/C catalyst. These results indicate that Sn influences both the kinetics and the mechanism of ORR. Based on these results, the Pd-Sn/C catalyst prepared by using ultrasonic irradiation can be expected as a promising ORR catalyst in alkaline media. (C) 2009 Elsevier B.V. All rights reserved.

Nanoparticles of Pd-Sn were prepared under various conditions by applying ultrasonic irradiation, and their electrocatalytic activity for oxygen reduction was evaluated in 0.5 M KOH. The average size of Pd-Sn nanoparticles thus prepared was about 3-5 nm. The Pd in Pd-Sn nanoparticles was found to be mostly in the metallic state. The electrocatalytic activity of the Pd-Sn nanoparticles for the oxygen reduction reaction (ORR) is greater than Pt or Pd nanoparticles in alkaline media. The molar ratio of Pd to Sn metal ions in the synthesizing solution, their initial concentrations, the concentration of ethanol, which increases primary hydrogen radicals during sonolysis, and the concentration of citric acid were found to affect the size distribution of the Pd-Sn nanoparticles, and therefore, those factors controlled the electrocatalytic activity for ORR. Particularly, the concentration of citric acid was found to be important for controlling the surface property on Pd-Sn particles to adjust the electrocatalytic activity for ORR. (C) 2009 Elsevier Ltd. All rights reserved.

In this chapter, micro fuel cells fabricated by microelectromechanical system (MEMS) technology and hybrid power sources based on a combination of fuel cells and capacitors are introduced. These systems are new systems toward miniaturization of power sources. Significant efforts in developing micro (sub-watt) and portable (1-20 W) direct methanol fuel cell (DMFC) systems are being made, including developments of small fuel cells, such as micro fuel cells fabricated with MEMS technology. MEMS technology based on the manufacturing technology of semiconductor devices is a powerful tool to realize small devices. Examples reported to realize the DMFC configuration by MEMS technology, the so-called micro direct methanol fuel cells (μDMFCs), are introduced in this chapter. The hybrid power supply system based on fuel cells is an attractive power source; the utilization of fuel cells with the assistance of capacitor has the merit of realizing the power supply having the features of both fuel cell and capacitor, that is, a high power density and a high power output. In order to construct the hybrid power supply system, simulation of power output from the power supply, by varying the properties of capacitor and fuel cell, would be the introductory research. Typical assessments are described in this chapter.

Sulfated zirconia nanoparticles are evaluated as a possible alternative for a solid proton conductor in a fuel-cell catalyst layer. Two methods are applied for the synthesis of the nanoparticles, i.e.: (i) a conventional method treating ZrO(2) particles in sulfuric acid, and (ii) a solvent-free method directly synthesizing sulfated zirconia nanoparticles through the thermal decomposition of a mixture of ZrOCl(2) and (NH(4))(2)SO(4). The nanoparticles synthesized by the solvent-free method have a size of 5-10 nm and an amorphous structure, and moreover their properties are promising in view of the application. In particular, the proton conductivity of the nanoparticles is high enough, i.e. of the 10(-2) S cm(-1) order, to be comparable to that of Nafion. Even though they possibly reduce the activity of Pt catalyst, layers containing sulfated zirconia as a proton conductor prove to be active as catalyst in fuel cell prototypes. Compared with conventional, Nafion-based cells, the maximum power density of the cells using sulfated zirconia is about one third. We believe that improvement in the preparation procedures for catalyst layers and membrane electrode assemblies will improve the cell performance. Therefore sulfated zirconia can be a valid proton conductor for fuel cell application. (C) 2008 Elsevier B.V. All rights reserved.

This paper proposes a novel design for a microfuel cell as an on-chip power source and demonstrates its fabrication and operation to prove the concept. Its simple design is important from the viewpoints of fabrication (e.g., replication), integration, and compatibility with other microdevices. In testing, the prototype cell was able to generate electric power (maximum: ca. 1.4 mu W) on methonal without pumps under both neutral and acidic conditions. As for the size, the electrode part of the call (two cathodes and one anode) is 400 mu m in width and 6 mm in length. The evaluation demonstrated that the proposed design is a promising on-chip power source for miniature devices.

Pd-Co alloy has been recently proposed as a catalyst for the cathode of direct methanol fuel cells with both excellent oxygen reduction activity and methanol tolerance, hence electrodeposition of this alloy is an attractive approach for synthesizing porous metal electrodes with high methanol tolerance in direct methanol fuel cells. In this Study, we electrodeposited two types of Pd-Co films onto Au substrates by applying different Current density (-10 or -200 mA cm(-2)); and then characterized them in terms of morphology, composition, crystal structure, and catalytic activity. Pd-Co deposited at -10 mA cm(-2) was smooth and possessed smaller particles (ca. 10 nm), while that at -200 mA cm-2 was dendritic (or rough) and possessed larger particles (ca. 50 nm). Both the Pd-Co alloys were found to be almost the same Structure, i.e. a solid solution of ca. Pd7Co3 With Pd-skin, and also confirmed to possess comparable activity in oxygoen reduction to Pt (potential difference at 1.0 mu A cm(-2) was 0.05 V). As for methanol tolerance, cell-voltage was not influenced by addition of I mol dm(-3) methanol to the oxidant solution. Our approach provides fundamental technique for synthesizing Pd-Co porous metal electrodes by electrodeposition. (C) 2008 Elsevier Ltd. All rights reserved.

The feasibility of a di-block copolymer, composed of a polyethylene oxide (PEO) chain and a polystyrene (PS) chain covalently bonded, as the gel electrolyte for lithium secondary batteries was investigated. The PEO-PS di-block copolymer gel electrolyte showed a high ionic conductivity of similar to 1 mS/cm at room temperature. Moreover, it retained good mechanical strength within a co-continuous phase separated structure, and it suppressed the dendritic deposition of Li. Indications were that the interface between the electrolyte and the Li metal was chemically stable, as a result of the PEO phase fixed to PS by covalent bonding. In addition, it was indicated that the Li/PEOPS di-block copolymer gel electrolyte/LiFePO4 cell had a high charge-discharge efficiency of similar to 99% during 30 cycles, while maintaining a discharge capacity of 124 mAh/g.

A simple numerical simulation of current flowing through electronic devices was examined for a hybrid power supply system composed of a DMFC and a capacitor connected in parallel. The simulation was investigated by representing a combination of ohmic resistance, charge transfer reaction resistance, mass transfer resistance and double layer capacitance of a DMFC as a simple ideal resistor, based on measured data when DMFC was generating electricity. The simulation result was found to agree with experimental measured current flowing through the DMFC and the capacitor, although a slight disagreement was observed because of the presence of ohmic resistance between circuit components. The simulation of DMFC-capacitor hybrid power supply system indicated the importance of the inner resistance of the capacitor. The hybrid simulation was also applied to a system assumed to consist of mu DMFC and micro electrochemical capacitor (MECC) system. The effect of applying a DC-DC converter to the system was indicated. The simulation allows to predict the degree of improvement required without performing actual fabrication of mu DMFC and MECC.

A mesoporous Sn anode was electrodeposited in the presence of lyotropic liquid crystals made of nonionic surfactants. The introduction of mesoporous structure was effective for the accommodation of volume change of Sn during charge and discharge cycling of Li ions. The discharge capacity of the mesoporous Sn anode at 1 C rate was as high as 425 mA h g(-1) at the 100th cycle, and that was as high as 320 mA It g(-1) at the 100th cycle even though at 5 degrees C rate.

:This paper proposes a novel design for a microfuel cell as an on-chip power source and demonstrates its fabrication and operation to prove the concept. Its simple design is important from the viewpoints of fabrication (e.g., replication), integration, and compatibility with other microdevices. In testing, the prototype cell was able to generate electric power (maximum: ca. 1.4 microW) on methanol without pumps under both neutral and acidic conditions. As for the size, the electrode part of the cell (two cathodes and one anode) is 400 microns in width and 6 mm in length. The evaluation demonstrated that the proposed design is a promising on-chip power source for miniature devices.

A perpendicular mesoporous platinum electrode with a. at surface is successfully synthesized by electrodeposition using titania nanopillars as template, and the electrochemical studies indicate that this material is a promising catalytic electrode for fuel cells because of its high surface area and perpendicular nanopores.

In lithium ion batteries, it has previously been shown that Ni-Sn thin film anodes containing 62 at.% Sn show outstanding electrochemical characteristics, e. g. good capacity and endurance, during charge-discharge cycling. However, their mechanical response, which is likely related to their lifetime in service, has so far received relatively little attention. To address this, nanoindentation and nanowear techniques have been used to characterize the mechanical properties of thin Ni-Sn films electrodeposited on a copper substrate. In situ morphology analysis together with in situ stress measurement has been performed to assess the properties of Ni-Sn thin film anodes during electrochemical cycling. The change in mechanical properties, residual stress and fracture behaviour of the anodes is related to the phase changes which occur during charge-discharge cycling. The correlation between the mechanical properties of the films and their charge-discharge characteristics serves as a useful indicator for optimized design of a Sn-based intermetallic anode film for lithium ion secondary batteries.

A perpendicular mesoporous platinum electrode with a. at surface is successfully synthesized by electrodeposition using titania nanopillars as template, and the electrochemical studies indicate that this material is a promising catalytic electrode for fuel cells because of its high surface area and perpendicular nanopores.

Polyether chains have been successfully grafted onto the interlayer surface of a Dion - Jacobson- type layered perovskite, HLaNb(2)O(7)center dot xH(2)O, by a reaction between an n- decoxy- derivative of HLaNb(2)O(7)center dot xH(2)O and CH(3)(OCH(2)CH(2))(m)OH (1 &lt;= m &lt;= 4). After the reaction, the interlayer distance decreases from 2.73 nm to 1.58 (m = 1), 2.07 (m = 2), 2.28 (m = 3), and 2.69 (m = 4) nm. Solid- state (13)C CP/MAS NMR spectroscopy indicates that the CH(3)(OCH(2)CH(2))(m)O-groups are bound to the interlayer surface of HLaNb(2)O(7)center dot xH(2)O. The n- decoxy groups are completely removed by the reaction with CH(3)(OCH(2)CH(2)) mOH (m = 2 and 3), while a part of the n- decoxy groups remain after the reaction with CH(3)(OCH(2)CH(2))(m)OH (m = 1 and 4). Upon treatment of the CH(3)(OCH(2)CH(2))(m)O-grafted HLaNb(2)O(7)center dot xH(2)O (m = 2 or 3) with a CH(3)(OCH(2)CH(2)) mOH solution of LiClO(4), the interlayer distance decreases further to 1.78 (m = 2) and 2.01 (m = 3) nm. Inductively coupled plasma emission spectrometry reveals the presence of lithium (0.22 (m = 2) and 0.24 (m = 3) per [LaNb(2)O(7)]). The presence of ClO(4)(-) ions is demonstrated by Raman spectroscopy, and the position of the nu(1)(A(1)) band indicates the presence of isolated ClO(4)(-) ions in the interlayer space. After treatment with a LiClO(4) solution, CH(3)(OCH(2)CH(2))(m)O-grafted HLaNb(2)O(7)center dot xH(2)O (m = 2 and 3) exhibits ionic conductivity, and no clear temperature dependence is observed.

Nanostructured Pt particles are directly deposited onto a Ni foam by utilizing displacement plating after a lyotropic liquid crystalline phase including Pt species was prepared within macropores of the Ni foam. The EDS mapping of Pt after deposition corresponds to the macroscopic framework of the Ni foam, indicating the uniform displacement plating of Pt on the surface of the Ni foam. The Pt particles of 150-250 nm in size are formed over the entire area of the surface of the Ni foam. The TEM images prove that the nanoscale rods (width: about 3 nm) are aggregated with each other to form nanoscale porosity. The active area of Pt can be estimated to be ca. 12 m(2)/g by using the cyclic voltammogram in sulfuric acid. Our method realizes one-step production of hierarchical macro-meso type porous electrodes. (c) 2007 Elsevier Ltd. All rights reserved.

Different shapes (nanosphere or nanorod) of gold nanoparticles (Au-NPs) were synthesized with and without ultrasonic irradiation in the presence of citric acid. Spherical-shaped and rod-shaped Au-NPs showed different surface plasmon resonance (SPR) absorption bands. The Au-NRs with different shapes were immobilized on a monolayer of 3-aminopropyltriethoxysilane (APS) coated on an indium-tin oxide (ITO) electrode. The potential dependence of the SPR band of different shaped Au-NPs in an aqueous solution was explored. The SPR band and intensity changes of the Au-NPs were found to depend on the applied potential. The spherical-shaped and rod-shaped Au-NPs showed different SPR absorption behaviors when potential was applied. These behavior changes were interpreted as the result of the potential-induced changes of the local dielectric environment around the nanoparticles due to molecular absorption/desorption and the charging/discharging of the particles. (C) 2007 Elsevier Ltd. All rights reserved.

The stress of the electrodeposited pure Sn and the Ni-62 atom % Sn alloy thin film electrodes during cycling was measured in situ using an optical cantilever method. The results revealed that the Ni-62 atom % Sn alloy electrode with better cycle endurance actually experiences larger stress compared to the pure Sn electrode. Furthermore, the stress-release phenomenon during the open-circuit period has been confirmed for the first time. This paper demonstrates that the cantilever bending method is effective for the in situ study of the stress development, transition, and hence the phenomena taking place within the Sn-based electrodes. (c) 2007 The Electrochemical Society.

An impedance analysis method for the catalyst layers of a direct methanol fuel cell is evaluated through demonstrating analyses and comparison of two types of the catalyst layers. The catalyst layers were prepared with different dispersing solvents: ethyleneglycol dimethyl ether or isopropyl alcohol aqueous solution. Methanol oxidation current of the catalyst layer prepared with the former solvent was more than twice that with the latter. The proposed method was revealed to have the potential for analyzing the difference clearly in terms of parameters, using our transmission-line equivalent circuit for the catalyst layers based on the assumption of primary and secondary pores. The parameters indicate that the main drawback of the catalyst layer prepared with the latter solvent is 85 times larger ionic resistance in the secondary pores. Moreover, precise analyses on the parameters indicate the microstructures of the catalyst layers, which correspond to a model reported previously. We conclude that this method is effective in analyzing the catalyst layer of the fuel cell. (C) 2007 The Electrochemical Society.

Pd-Co was electrodeposited as a rough cathode catalyst for a direct methanol fuel cell fabricated using micro-electromechanical systems technology. Pd-Co was electrodeposited at -10 mA/cm2 for 60 s or -200 mA/cm 2 for 5 s. The deposits were evaluated with respect to microstructures, electrochemical characteristics, and fuel cell performances. As a result, oxygen reduction activity of the sample prepared at -200 mA/cm 2 was higher than that prepared at 10 mA/cm , while the electrochemically active surface areas were almost the same. Microstructures of the former and the latter were observed dendritic and flat, respectively. We conclude that the difference of oxygen reduction activity is attributed to the difference of the microstructure. In addition, we modified the dendritic sample by depositing Pd-Co at -0.75 V vs. Ag/AgCl. The modification increased open circuit potential for oxygen reduction by 30 mV from 0.70 to 0.73 V. ©The Electrochemical Society.

High-efficientcy micro-electrochemical devices are realized by increasing electrode surface areas while maintaining keeping chip size. The use of three dimensional (3-D) electrodes instead of planar electrodes is effective for this purpose. To realize a metal pattern on 3-D structures, spray coating was utilized and the optimum condition for achieving a good photoresist step coverage was determined. A good step coverage of the photoresist was obtained on the obtuse corner formed by the anisotropic wet etching of (100) silicon and even on the vertical corner formed,by deep reactive ion etching (RIE). We applied this method to fabricate a high-performance micro direct methanol fuel cell (mu DMFC). An open circuit voltage of 548 mV and a maximum power density of 0.72 mW/cm(2) were obtained at room temperature with 2 M methanol.

We have developed an excellent process for selective deposition of mesoporous Pt through tailored microfabrication steps via the "Solvent-Evaporation-mediated Direct Physical Casting (SEDPC)" method. The direct observation by high-resolution scanning microscopy (HR-SEM) shows the formation of an ordered mesoporous structure in a very confined area. The cyclic voltammogram of the mesoporous Pt reveals a typical feature of Pt surface. The surface morphology and ordering of the mesostructure strongly depend on the electrodeposition conditions (constant-current and constant-potential depositions). The roughness factors are greatly enhanced as the charge densities in the constant-current deposition are increased. These findings are important for the morphological design of mesoporous metals in a micrometer scale. (c) 2006 NIMS and Elsevier Ltd. All rights reserved.

This paper describes characteristics of passive direct methanol fuel cell (DMFC). especially the effect of the thickness of electrolyte membrane. Cell performances were compared for membrane electrode assemblies (MEAs) made with Nafion 112, 115, and 117. whose typical thicknesses were 51 mu m, 127 mu m, and 183 mu m, respectively. The MEA made with Nafion 112 showed performance inferior to the other MEAs with thicker membranes. It appears, that the mass of methanol permeated to the cathode through Nafion 112 was large, resulting in the loss of a large quantity of fuel, because its thickness was the smallest among the membranes used in this experiment. The observation of fuel level in the reservoir during open circuit stand indicated that most of the fuel was lost by methanol crossover and evaporation due to the rise in cell temperature. Also. the relationship between the concentration of methanol and the electrode potential at open circuit was investigated with a pseudo dynamic hydrogen electrode calibrated against an Ag/AgCl reference electrode. We found that it is essential to overcome the loss of fuel by methanol crossover and evaporation, which decreases the performance of the anode significantly even when the cell is in the stand-by mode.

On the evaluation of catalyst layers in direct methanol fuel cell (DMFC), we applied the proposed electrochemical cell which enabled to evaluate the catalyst layers without an electrolyte solution circumstance. In addition, properties of polymer electrolytes, such as ionic conductivities inside or outside agglomerates of catalystss were evaluated separately by electrochemical impedance spectroscopy with ail analysis using the proposed equivalent circuit. This method also suggested its possibility for evaluating a distribution of the electrolytes in catalyst layers.

Mesoporous intermetallic Pt-Ni alloys with various compositions have been produced by the chemical reduction of two metal (nickel and platinum) salts dissolved in aqueous domains of a lyotropic liquid crystalline (LLC) phase. The mesoporous Pt-Ni alloys are small particles less than 100 nm in size and exhibit high specific surface areas higher than 40 m(2) g(-1). The ordering of the mesostructure decreases with increasing Ni content in the alloys. The high resolution scanning electron microscopic (HR-SEM) images show that the porous nanostructures are indeed formed over the entire area on the external surface of the particles. The lattice parameters of the alloys decrease with the increasing Ni content, implying the incorporation of Ni. The X-ray photoelectron spectroscopic (XPS) data show that Ni atoms in the alloys are thought to be in the zerovalent metallic state (Ni-0). The transmission electron microscopic (TEM) images prove that the lattice fringes assigned to a fcc structure are randomly oriented in the pore walls. The energy-dispersive X-ray spectroscopic (EDS) mapping shows uniform distribution of Ni atoms in the porous matrix. These results indicate the formation of mesoporous intermetallic Pt-Ni alloys.

We have proposed a novel convenient pathway via solvent-evaporation-mediated direct physical casting (SEDPC) for the fabrication of mesoporous metals in a micrometer scale. We have presented the successful deposition of highly ordered mesoporous Pt into micrometer channels prepared by lithography. The direct observation by a high-resolution scanning microscope (HR-SEM) showed the formation of highly ordered 2D-hexagonal (p6mm) mesoporous metals onto such substrates. The cyclic voltammogram of the mesoporous Pt in sulfuric acid revealed a typical feature which can identify the clean Pt surface. Moreover, mesoporous Pt exhibits an effective reduction of dissolved dioxygen molecules. It is proved that mesoporous Pt deposited in a very confined area via the SEDPC method possesses electrocatalytic performance owing to Pt. (c) 2005 Elsevier B.V. All rights reserved.

Two-dimensional hexagonally ordered mesoporous Pt particles are prepared by Pt deposition in the aqueous domains of lyotropic liquid crystals (LLC) by chemical reduction with Zn powders. Interestingly, the framework is composed of connected nanoparticles of about 3 nm in size. Moreover, it is proved that the lattice fringes on the atomic crystallinity are coherently extended across the several nanoparticles in the framework. Such a framework composed of connected nanoparticles with extended crystallinity is uniquely created by using LLC as a soft template, which is not attainable by a traditional approach using mesoporous silica as a hard template. Through the structural identification, the formation mechanism of mesoporous Pt in the presence of LLC is thought to be continuous deposition of Pt nanoparticles from one nanoparticle.

We have reported in our past work that dectrodeposited Sn-Ni alloy with different composition show considerably different performance as anode materials for Li-ion batteries, and the performance was remarkably well (ca. 650mAh g(-1) at 70th cycle) when the composition was controlled to Sn62Ni38, In this work, structural changes during charge discharge cycling of Sn-Ni alloy with different composition were investigated to evaluate their differences in the cycle performance. From the XRD result, Ni3Sn4 phase was the main phase seen in Sn62Ni38, and its reversible reactivity with Li was confirmed. We suggest that this is the key phase for its high capacity and lengthened cycle life. From Sn54Ni46, which showed low capacity, only a metastable phase close to the structure of SnNi was confirmed. The results from Sn84Ni16 indicated the presence of pure Sn and Sn rich metastable phase would lead to relatively fast electrode degradation. (c) 2005 Elsevier B.V. All rights reserved.

In this paper, we discussed the fabrication of micro-channel electrodes for very small DMFC (direct methanol fuel cell), i.e., mu-DMFC, where the channels composed of a current collector and a catalyst layer. The micro-channel electrodes were fabricated on a silicon wafer with a combination of photolithography, chemical etching with potassium hydroxide, spray coating, and electrodeposition method. The catalyst layer formation of Pt and PtRu was achieved by combining pulse electrodeposition with direct current electrodeposition. From these new processes, the mu-DMFC single unit cell was able to be operated for longer time operation compared with that of prototype test cell which was already reported in the previous paper.

This work studied the design, fabrication, and performance evaluation of a novel micro direct methanol fuel cell (mu-DMFC). A mu-DMFC of 0.018 cm(2) active area was prepared using a series of fabrication steps from micromachined silicon wafer including photolithography, deep reactive ion etching, and electron beam deposition. The novelty of this structure is that we have integrated the anodic and cathodic micro-channels arranged in plane onto a single silicon substrate. This architecture eliminates the need for the membrane electrode assembly (MEA) used in traditional polymer electrolyte-based fuel cells. Another original aspect is the successful electroplating of Pt and Pt-Ru catalysts in the microchannels. In addition, quasi-reference electrodes could be built in the prototype cell. The experimental trials were to verify the feasibility of this novel structure on basis of MEMS technology. The fuel and oxidant were supplied to the unit cell at a rate of 10 mu L/min. Preliminary test results were able to confirm that this new concept of mu-DMFC generates electricity. At ambient temperature under atmospheric pressure, the maximum power density was 0.44 mW/cm(2) at 3 mA/cm(2) with Pt anode catalyst, while the maximum power density reached 0.78 mW/cm(2) at 3.6 mA/cm(2) for cell with Pt-Ru anode catalyst.

Nickel particles with a highly ordered mesostructure are prepared by electroless deposition of Ni salts dissolved in aqueous domains of lyotropic liquid crystalline (LLC) media made of a nonionic surfactant (Brij 56) at a high concentration. The mesostructure inside the Ni particles after the electroless deposition has a macroscopic alignment of mesochannels derived from the LLC media which are composed of crystalline domains on a micrometer scale. It is proved that the arrangements of rod-like self-assemblies in the LLC indeed work as a scaffold to direct the grain growth of Ni. This is the first direct evidence of direct physical casting from LLC. (c) 2005 The Electrochemical Society.

A MEMS based micro direct methanol fuel cell (μ DMFC) was realized on the plastic substrate. Hot embossing is utilized to fabricate the polymer micro channels, and spray coating method is applied to fabricate 3-D micro electrodes structure on the polymer substrate. Power generation was conformed with the first prototype μ DMFC device. Copyright © 2005 by the Transducer Research Foundation, Inc.

Nanosized electrodeposited 62 atom % Sn-Ni alloy was tested to highlight the effects of volume changes on the cycling life of the electrode during lithiation and delithiation. X-ray diffraction showed that the Ni3Sn4 was the main phase of the as-deposited alloy. A unique feature of the 62 atom % Sn-Ni is that it exhibited a capacity recovery upon cycling. When cycled galvanostatically, the Sn62Ni38 offers low capacity fade while reversibly incorporating lithium up to 600 mAh/g. At the first charge LiSn alloy phases are formed. This led to volume expansion of the electrode causing the formation of cracks. At the following cycles the Ni3Sn4 phase was restored and preserved over extensive cycling revealing the reversibility of the reaction between Ni3Sn4 and Li+. As to the reasons of the capacity recovery noticed with this alloy, scanning electron microscopy images provided evidence of modifications of the surface condition accompanying a volume change during cycling. The chemical diffusion coefficient (D-Li) value determined from electrochemical impedence spectroscopy measurements during lithium insertion was within 10(-9) to 10(-10) 10 cm(2) S-1. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.1856913] All rights reserved.

Mesostructured Ni and Co particles are formed by metal deposition in the aqueous domains of lyotropic liquid crystals (LLC) using different reducing agents. We have investigated the role of reducing agents in metal deposition for the synthesis of highly-ordered mesoporous metals by electroless deposition. Slow metal deposition accompanied by the autocatalytic reaction of dimethylamineborane ( DMAB), caused by the combination of Ni and DMAB, led to the formation of highly-ordered mesostructured Ni.

This article summarizes our recent studies on the synthesis of highly ordered mesostructured Ni and Ni-Co alloys by electroless deposition method. We propose that a careful control over the nucleation as well as the grain growth by reducing agents can lead to the fort-nation of a highly ordered mesostructure from a lyotropic liquid crystalline phase (LLC). The sophisticated combination of dimethylamineborane (DMAB) and sodium borohydride (SBH) in an electroless plating bath produces highly ordered mesoporous Ni, and this technique can be extended to prepare a series of mesostructured Ni-Co alloys with various compositions. The composition of the alloys can be varied easily by controlling the metal compositions in the plating bath.

High efficient micro electrochemical devices are realized by the increase of the electrode surface areas keeping the chip size. Use of the 3-D electrodes instead of the planar electrodes is quite effective for this purpose. To realize a metal pattern on 3-D structures, spray coating method was utilized and the optimum condition to achieve good step coverage was observed. Good step coverage of photoresist was obtained on the obtuse corner formed by anisotropic wet etching of (100) silicon and even vertical corner formed by deep RIE. We applied this method to fabricate a high performance micro direct methanol fuel cell (mu DMFC). The open circuit voltage of 548mV and the maximum power density of 0.72mW/cm(2)were obtained at room temperature with 2M methanol.

By a contact plating technique using a galvanic reaction between Al and An in the presence of Pt complex, we have for the first time succeeded in the formation of a highly ordered meso-structured Pt film on a An surface by reduction of Pt ions in the presence of lyotropic liquid crystals.

This work studied the design, fabrication, and performance evaluation of a 36 cm(2), passive, air-breathing, room-temperature, direct methanol fuel cell (DMFC). The cell is completely passive with no external pumps or other ancillary devices. It takes oxygen from the surrounding air, and the methanol solution is stored in a built-in reservoir. The fuel cell runs successfully with methanol concentration ranging from 0.5 to 4 M. It produced a power density of 11 mW cm(-2) reached with 4 M methanol at current densities as high as 36 mA cm(-2) and at a voltage of 0.3. (C) 2004 Elsevier B.V. All rights reserved.

In this work, we describe the fabrication of a room temperature operating direct methanol fuel cell (DMFC) device for portable electronic devices and its performance as an electrical power source for portable phone. The cell stack is completely passive without external pumps or other ancillary devices. It takes oxygen from the surrounding air, whereas the methanol solution is stored in a built-in reservoir. We achieved a maximum power as high as 2 W, which is largely commensurate with cell phone requirements. The DMFC coupled to DC-to-DC converter was capable of powering a cell phone. The maximum power consumption for talk mode was of 1.2 W while 1.8 W was withdrawn from the stack when receiving a call.

A design for a novel micro direct methanol fuel cell (mu-DMFC) of 0.018 cm(2) active area is described. The mu-DMFC was prepared using a series of fabrication steps from micro-machined silicon wafer including photolithography, deep reactive ion etching, and electron beam deposition. The novelty of this structure is that we have fabricated the anodic and cathodic micro-channels arranged in plane, dissimilar to the conventional bipolar structure. The first objective of the experimental trials was to verify the feasibility of this novel structure on basis of MEMS technology. Preliminary testing results show that this new concept L-DMFC generates electricity. (C) 2004 Elsevier B.V. All rights reserved.

Highly ordered mesoporous Ni particles have been prepared by electroless deposition using lyotropic liquid crystals as templates. The bath conditions, in particular the kind of the reducing agents, greatly affected the degree of the ordering of mesostructures. By using well chosen appropriate reducing agents and combining those agents, we have succeeded in synthesizing Ni particles with highly ordered mesoporosity.

In this work, the co-continuous polymer blend was synthesized for use as the electrolyte in lithium batteries. Such electrolytes were characterized by a co-continuous morphology consisting of two three-dimensionally interpenetrated polymer networks simply formed by hot-mixing two nonmiscible polymers. A preliminary electrochemical characterization of the gelified co-continuous polymer blend as electrolyte for lithium batteries is also reported. (C) 2004 The Electrochemical Society.

Mesostructured binary Ni - Co alloys with various compositions are prepared for the first time by the electroless deposition of metal salts ( nickel and cobalt) dissolved in aqueous domains of the lyotropic liquid crystalline phases of a non-ionic surfactant ( Brij 56) at high concentrations. Mesostructured alloys with various Ni/Co ratios are easily obtained by changing the composition of the baths, leading to the control of saturation magnetization. The composition of the alloys affects the ordering of the mesostructure; higher Co content lowers the ordering.

We propose a polymer blending method for preparing the PEO (polyethylene oxide)-LiBF4 complex electrolyte for lithium secondary battery applying to the IPN (interpenetrated polymer network) gel electrolyte. The polymer blend mixture of PEO-PS (polystyrene) -LiBF4 was prepared as a film by the hot-pressing method. The resulting IPN film was plasticized with the electrolyte solution of 0.5 M LiBF4/EC (ethylene carbonate) -PC (propylene carbonate) (I : I vol.), in which the formation of PEO-LiBF4 complex was confirmed by the Raman spectroscopy. The basic properties as an electrolyte of Li metal batteries, i.e., ionic conductivity, chemical stability at the polymer gel electrolyte/lithium metal interface, and charge-discharge performance of the Li/(PEO-LiBF4/PS) gel electrolyte/LiCoO2 cell were studied and discussed.

Thin Sn-alloy films containing various Sn/Ni ratios were prepared by electrodeposition and characterized as lithium-ion secondary battery anodes. The initial drop in discharge capacity varied with the Sn content of the sample; i.e., for samples with 54 atom % Sn and 62 atom % Sn, the drop was less than 100 mAh/g, whereas for those with 84 atom % Sn and 92 atom % Sn, the drop exceeded 500 mAh/g. Among these thin films, the 62 atom % Sn film showed the highest reversible capacity of ca. 650 mAh/g at about the 70th cycle, whereas the other samples (54 atom % Sn, 84 atom % Sn, 92 atom % Sn! showed a capacity of 300 mAh/g. (C) 2003 The Electrochemical Society.

The impedance spectrum of prismatic commercial Li-ion batteries is measured at various states of charge before and after the charge-discharge cycles and storage. The measured impedance is interpreted with a previously proposed equivalent circuit made up of anode and cathode in which the cathode component is composed of two particle size factors. The values corresponding to the characteristics of both electrodes are obtained by a fitting technique. The obtained values suggest that the capacity fade of the Li-ion battery due to the cycles is mainly caused by the increase of interfacial resistance of the cathode and a decrease in the anode capacity. These results suggest the validity of the equivalent circuit to interpret the causes of capacity fade. (C) 2003 Elsevier Science B.V. All rights reserved.

We have proposed SnS2 as promising Li-ion battery anode materials in our previous study. Nanoparticles of this material were synthesized by a sonochemical method. In this work, smaller SnS2 particles were obtained by diluting the starting solution of the synthesis, and particles of 30 nm were observed in the Field Emission SEM (FE-SEM) images. From such SnS2 particles, higher discharge capacity of 620 mAh/g and suppressed electrode degradation were observed in charge-discharge experiments. This indicates that the enlargement of the surface area was effective in facilitating the Li-ion diffusion through the active material, in simplifying the electrochemical reaction and in restraining the stress within the electrode, caused during charge and discharge.
The discharge capacity in the 30th cycle was improved from 319 to 404 mAh/g by annealing the sample. It is suggested that this may be due to the change in its structure. (C) 2003 Elsevier Science B.V. All rights reserved.

The shape of electrodeposited nickel microprobes changed from a flat to an oval shape with the addition of propargyl alcohol in a nickel sulfamate bath ; propargyl alcohol is considered to have the function of the shape control. To research the effect of this organic additive on the function of the shape control, several alcohols having different structures, that is, states of carbon to carbon bonding, numbers of hydroxyl groups bonded to the terminal carbon, and numbers of carbons in the molecule, were investigated.<BR>From the result of preparing nickel microprobes electrodeposited from the bath containing the additive, an alcohol with a carbon-to-carbon triple bond and hydroxyl groups was effective to control the shape, and an alcohol without a triple bond did not have the function of shape control.

In order to realize an electrolyte membrane for DMFC having low methanol permeability, suppression of methanol permeability of Nafion by introducing polyaniline (PAn) was attempted. The membrane obtained by the electropolymerization of aniline at Nafion-coated Pt electrode had bi-layered morphology, and it showed lower ionic conductivity and lower methanol permeability compared with those of Nafion, compared to PAn introduced Nafion membrane by the chemical oxidative polymerization of aniline in Nafion. The PAn introduced Nafion by chemical oxidative polymerization showed superior characteristics to Nafion from the viewpoint of conductivity and methanol permeability.

In order to realize an electrolyte membrane for DMFC having low methanol permeability, addition of ionic conductivity by the introduction of polypyrrole into engineering polymers was attempted. By the chemical oxidation of pyrrole monomer inside the polymer matrix, the composite films of polypyrrole (PPy) and engineering plastics were prepared. By the PPy introduction to poly (ethyleneterephthalate) (PET) the ionic conductivity across the film was increased. Methanol permeability was also examined to assess the performance of the film as the DMFC electrolyte. The composite film of PPy/PET, which was formed by pyrrole oxidation, showed better performance of high ionic conductivity and low methanol permeability.

In this work we report the synthesis and characterization of gel-polymer electrolytes based on co-continuous polymer blends. Such blends are characterized by a bicontinuous morphology consisting of two three-dimensionally interpenetrated polymer networks. Go-continuous polymer blends are simply formed by hot-blending two immiscible polymers. The intrinsic advantage of co-continuous polymer blends consists in the possibility of selecting the polymers. One polymer (e.g., polystyrene) imparts the desired mechanical properties and the other polymer [e.g., poly(ethylene oxide)] enables the ionic conductivity via formation of a gel which contains the electrolytic solution. (C) 2001 The Electrochemical Society.

A potentiometric acetylcholine microsensor was fabricated by use of a composite film consisting of polyion complex (PIC), which consisted with acetylcholine esterase (AChE), and the electrochemically inactive poly-1-aminopyrrole (iPAPy). The iPAPy-PIC (AChE) composite film on Pt electrode displayed potential response to acetylcholine concentration owing to pH change during the enzymatic reaction, where the product contains weak acid CH3COOH. The sensitivity of the iPAPy-PIC (AChE) electrode clearly demonstrated higher sensitivity with low detection limit (1 x 10(-6) mol dm(-3)) than that of the iPAPy-PIC (AChE) electrode of detection limit (1 x 10(-5) mol dm(-3)). The mechanism of increasing the sensitivity of iPAPy-PIC (AChE) electrode was discussed the interaction of -NH2 of iPAPy with CH3 COOH, which would accelerate the dissociation of weak acid CH3COOH.

SnS2 powder made by sonochemistry was applied and examined for anode material of Li ion battery. The annealed SnS2 at 400 degreesC showed a higher capacity of 600 mAh g(-1) than the nan-annealed SnS2. The cell with annealed SnS2 anode and LiCoO2 cathode worked well. From the results, SnS2 material was revealed to be one of the candidates of the anode materials for future Li ion batteries. (C) 2001 Elsevier Science B.V. All rights reserved.

This paper describes studies of the interface between Lithium electrodes and solid electrolyte systems using in situ FTIR spectroscopy in a single internal reflectance mode. In this method, the masking effect of the electrolyte matrix components is largely avoided. We studied gel electrolytes based on polyvinylidene difluoride-hexafluoropropylene with cyclic alkyl carbonates as plasticizers, suitable for ambient temperatures, and a solvent free polymer, derivatives of polyethylene oxide (PEO) with a branched structure: poly[ethyleneoxide-2-(2-methoxyethoxy)ethyl glycidyl ether] at elevated temperatures. We found that the surface chemistry of Li electrodes in contact with the gel matrixes is dominated by alkyl carbonate solvent reduction to ROCO2Li surface species. In the case of the PEG-based polymer, the surface reactions of Li electrodes are dominated by salt and trace water reduction. The polymer itself seems to be stable with lithium even at 60 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.

Trend and state of the affairs for Li ion polymer battery were summarized. Also the situation of the research and development for the Li metal battery was introduced. (C) 2001 Elsevier Science B.V. All rights reserved.

SnS2 powder made by sonochemistry was applied and examined for anode material of Li ion battery. The annealed SnS2 at 400 degreesC showed a higher capacity of 600 mAh g(-1) than the nan-annealed SnS2. The cell with annealed SnS2 anode and LiCoO2 cathode worked well. From the results, SnS2 material was revealed to be one of the candidates of the anode materials for future Li ion batteries. (C) 2001 Elsevier Science B.V. All rights reserved.

The effects of organic additives in a Ni sulfamate bath were investigated in order to form microprobes with a high aspect ratio. Results without the usage of additives confirmed that Ni deposits have a low aspect ratio because of in-plain spread. With the addition of propargyl alcohol, however, the form of Ni deposit changes from a flat to an oval shape. The surface morphology improved with the addition of sodium salt of saccharin, but the probe shape was flattened. Finally, the addition of PEG-4000 to a bath containing propargyl alcohol and saccharin produced probes with a fine, smooth surface and a high aspect ratio. Thus, results confirmed that satisfactory probes could be obtained with Ni electrodeposition.

Ac impedance analysis was applied to a commercial Li-ion battery to get an information of the internal states. The impedance spectra obtained with various charge states were evaluated with an equivalent circuit of the Randles type circuits combined the inductance component, where the inductance on was due to the spiral structure of electrode. In the highest frequency region above 5 kHz reflects the inductive component caused by the cell geometry of spiral electrode. In a middle frequency region, there appeared a spread are combined with the impedance response of anode and cathode. The parameters were evaluated and assigned. The information of the electrochemical parameters obtained during the operation of the battery was proved to become a help to understand the failure mechanism of the battery.

For alkaline batteries, it is important to investigate prospective materials with higher energy density and lower cost. We paid attention to the reaction of quinone compounds and investigated the electrochemical properties of these compounds in alkaline solution and discussed the possibility for a negative active material of alkaline secondary batteries. In alkaline solution, most of these materials, e.g. p-benzoquinone, dissolved, while only chloranilic acid (C6Cl2(OH)2O2) did not. We have found that chloranilic acid is the most possible candidate for the negative active materials of alkaline batteries because of its insolubility to alkaline solutions. There were three couples of peaks in cyclic voltammogram (-1.2 to approximately -0.1 V vs. Ag/AgCl) for the electrode of chloranilic acid. With cathodic scan of cyclic voltammogram on -0.8 V vs. Ag/AgCl, the color of solution changed. It seems that this change is caused by the influence of dissolved products, which was formed by electrochemical redox reaction of chloranilic acid around -1.0 V vs. Ag/AgCl. When the charge-discharge test was conducted in the potential range between -0.45 V and -0.8 V, no colored substance was formed in the solution and the discharge capacity reached to approximate 150 mAh g-1 at the first cycle. From these results, on chloranilic acid, it was suggested that there was a possibility of application for a negative active material of alkaline secondary batteries.

Formation of Ni microstructure with high aspect ratio without thicker photoresist was tried by an electrodeposition method. The Ni microprobes thicker than photoresist thickness were electrodeposited on a patterned substrate using thin photoresist patterned with UV radiation. It was-important for preparing Ni microprobe with high aspect ratio to keep the overpotential of patterned cathode higher, and moreover the agitation using a paddle plating cell system was so effective to form uniform microprobes.

The morphology of electrodeposited lithium was observed in the gel electrolyte consisting of the poly(vinylidene fluoride)hexafluoropropylene (PVdF-HFP) copolymer as a host polymer, LiClO4, and the propylene carbonate (PC)/ethylene carbonate (EC) organic solvents. The dendritic deposition was effectively suppressed in the PVdF-HFP gel electrolyte compared to the LiClO4-PC/EC liquid electrolyte or the polyethylene oxide (PEO) based gel electrolyte. Charge-discharge efficiency of the lithium metal anode was higher in the PVdF-HFP gel electrolyte than that in the liquid or the PEO gel electrolyte, and it was enhanced by CO, addition as well as observed in the LiClO4-PC/EC Liquid electrolyte. (C) 1999 Elsevier Science S.A. All rights reserved.

Soft magnetic films for head core materials mainly electrodeposited CoNiFe based films developed by us were introduced. Electrodeposited CoNiFe thin film has high saturation magnetic flux density (B-s) and low coercivity. Magnetic properties except for B-s and corrosion properties of these films were depended on very small amount of inclusion such as S and H elements. The increase in resistivity (rho) on the base of this high B-s CoNiFe thin film was developed by controlling very small amount of C inclusion. Finally, application of the film to new type of magnetic recording head was reported.

The corrosion resistance of soft magnetic films is an important property to be considered in the manufacture of magnetic devices. We investigated the corrosion behavior of the electrodeposited CoNiFe him with desired soft magnetic properties by varying the crystalline structure and the amount of included sulfur. The corrosion property in 2.5% NaCl solution depends largely on the sulfur content and also on the structure of the film. Although the CoNiFe film contains more than 13 atom % Fe, the film of face-centered to body-centered cubic mixed crystals exhibits a high anticorrosion property because of very small grain size with essentially no sulfur inclusion (&lt;0.1 atom %). (C) 1999 The Electrochemical Society. S0013-4651(98)07-027-X. All rights reserved.

An electric double layer capacitor (EDLC) was prepared with an activated carbon powder electrode with poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) based gel electrolyte. Ethylene carbonate (EC) and propylene carbonate (PC) were used as plasticizer and tetraethylammonium tetrafluoroborate (TEABF(4)) was used as the supporting electrolyte. An optimized gel electrolyte of PVdF-HFP/PC/EC/TEABF(4) = 23/31/35/11 mass ratio exhibited high ionic conductivity of 5 x 10(-3) S cm(-1), high electrode capacitance, and good mechanical strength. An electrode consisting of activated carbon (AC) with the gel electrolyte as the binder (AC/PVdF-HFP based gel, 7/3 mass ratio) showed a higher specific capacitance and a lower ion diffusion resistance within the electrode than a carbon electrode, prepared with PVdF-HFP binder without plasticizer. This suggests that an electrode mixed with the gel electrolyte has a lower ion diffusion resistance inside the electrode. The highest specific capacitance of 123 F g(-1) was achieved with an electrode containing AC with a specific surface area of 2500 m(2) g(-1). A coin-type EDLC cell with optimized components showed excellent cycleability exceeding 10(4) cycles with ca. 100% coulombic efficiency achieved when charging and discharging was repeated between 1.0 and 2.5 V at 1.66 mA cm(-2). (C) 1999 The Electrochemical Society. S0013-4651(98)09-016-8. All rights reserved.

The performance of a lithium metal anode was studied in a poly( vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) gel electrolyte. By using the PVdF-HFP gel electrolyte, we obtained a higher coulombic efficiency (ca. 85%) and a more uniform morphology of the lithium metal anode than those obtained with the propylene carbonate liquid or the poly( ethylene oxide) gel system. Additionally, the CO2 addition to the PVdF-HFP gel system improved both the the uniformity in morphology of the lithium anode and the coulombic efficiency further to ca. 95%. (C) 1999 The Electrochemical Society. S1099-0062(98)03-079-X. All rights reserved.

In order to increase the resistivity of electrodeposited high BS CoNiFe thin film, the effect of an organic additive such as diethylenetriamine (DET) added to the plating bath was investigated. The values of ρ and HC, were gradually increased as a function of DET concentration. The desirable soft magnetic CoNiFe thin film with ρ = 25-90 μΩ-cm under the conditions of BS &gt
1.9 T and HC &lt
2.5 Oe was developed as function of carbon in the deposited films. Additionally, the high resistivity CoNiFe thin film with ρ = 130 μΩ-cm was established under the conditions of BS= 1.7 T and HC &lt
6 Oe. © 1999 IEEE.

The energy and power densities of electric double layer capacitor were calculated in order to estimate the possibility of its application to the pulse power supply for an electric vehicle. The model capacitor is composed of a stack of cell unit simply assembled with bipolar module with the physical and electrochemical properties of aqueous or organic electrolytes. The calculation was done with the variations of cell numbers and the roughness of electrode where the roughness is assumed to be the ratio of real surface area to flat surface area. The resultant energy densities of models showed that the capacitor using organic electrolyte had a merit of high energy density caused by the wide potential window of organic electrolyte. The results of power density under the 30 s full discharge suggested that aqueous electrolyte gave high power density to the capacitor while organic electrolyte lower power output because of the high resistance of the electrolyte solution. Moreover, the power densities of capacitors with organic and aqueous electrolytes showed maximum and sharp decline with an increase in cell stacked number due to the increase of capacitor resistance. From the results, it is suggested that the development of new components and cell construction should be demanded for capacitor with organic electrolyte.

The effect on the enhancement of the charge/discharge behavior of electrodeposited lithium metal on various substrates with CO, was investigated in LiClO4/propylene carbonate electrolyte. The lithium cycleability was enhanced with CO2 addition to the electrolyte solution when using nickel and titanium substrates, whereas no apparent enhancement was observed with copper and silver substrates. The results obtained from voltammetry indicated that the reduction of CO2 did not occur on nickel and titanium, but on copper and silver. It is suggested that the enhancement with CO2 addition is effective with the substrates which do not reduce CO2 in the electrolyte before lithium deposition. (C) 1997 Elsevier Science S.A.

Poly(methylmethacrylate) (PMMA)- and poly(acrylonitrile) (PAN)-based gel electrolytes were applied to Li/polypyrrole (PPy) battery and its performance was investigated, These batteries showed excellent performance with 3 V output voltage and 90-100% coulombic efficiency. Using chemically more stable PMMA gel electrolyte, long charge/discharge cycle life more than 8000 cycles at 0.1 mA cm was obtained. (C) 1997 Elsevier Science S.A.

Electrodeposited lithium produced with and without CO2 in LiClO4/propylene carbonate electrolytes was investigated for charge-discharge cycleability, surface morphology, and composition of he surface layer. The addition of CO2 in the electrolyte enhances the cycleability, produces smoother surface morphology, and forms Li2CO3 in the inner region of the surface film. This paper describes experimental results showing those three different effects of CO2 addition, and discusses the interrelation among them.

We tried to prove the merit of electrochemical reductive polymerization (ERP) original character of which is to control polymerization site on the preparation of pi-conjugated polymer film. As the results, an electroactive poly(p-phenylene) film formed by ERP demonstrated a reversible higher redox property and narrower energy band gap in comparison with the film formed by electrochemical oxidative polymerization of biphenyl. So it is efficient to use EPR as the film formation of pi-conjugated polymer film.

An electrochemically deposited composite film of poly(3-substituted thiophen) and insulating nitrile butadiene rubber (NBR) was used as the emission layer of a polymer electroluminescence (EL) device. The composite film on an ITO substrate was uniform, and by using this film current leakage was prevented. The device with the composite film as the EL emission layer shows rectification properties, the emitted color depending on the substituent of thiophen units. By coating with NBR after the electrodeposition of a poly(3-substituted thiophen) film, EL characteristics were improved compared with the device with NBR coating performed before electropolymerization. Moreover, by using electropolymerized poly(3-n-octylthiophen) film as a hole transporting layer, the luminance of an organic EL device with a poly(N-vinylcarbazole) dip-coating layer was remarkably enhanced. The addition of the hole transporting layer reduced the turn-on bias voltage and increased the emission intensity to 700 ed m(-2).

A urea biosensor was developed by immobilizing urease into an electropolymerized electroinactive polypyrrole (PPy) on a platinum electrode. This enzyme-immobilized PPy electrode showed a stable potential response to urea based on the pH response of the electroinactive PPy film electrode. The electropolymerization conditions were optimized, and thus the biosensor showed a Nernstian response with a slope of 31.8 mV decade(-1) over concentration range of 1 x 10(-4)-0.3 mol dm(-3) urea. Copyright (C) 1996 Elsevier Science Ltd

Deposition processes of lithium in solid polymer [poly(ethylene oxide) (PEG)8+LiClO4] and gel [PEO8+propylene carbonate(PC) +LiClO4] electrolytes, as well as in the liquid (PC+LiClO4) one, were observed in situ using an optical microscope and their difference is discussed. It was confirmed that the dendritic growth of lithium, which appeared in the liquid electrolyte, is suppressed in the solid polymer due to the immobility of the electrolyte molecules, although non-uniform coverage of the cathode was observed because of its low conductivity. In contrast, the gel electrolyte possessed advantages of both the liquid and solid electrolytes, resulting in a smooth and uniform deposition in the current density region up to 2.0 mA cm(-2).

Polypyrrole-V2O5 aerogel nanocomposites were made to enhance the conductivity of the aerogel for applications as cathode in rechargeable lithium batteries. By using a low temperature polymerization, a polypyrrole layer was formed on the walls of the pores inside aerogel particles. The resulting nanocomposite retains the fine sponge-like porous structure from aerogel, without any structural change in the V2O5 phase. The composite material showed superior electrochemical properties due to the formation of conductive paths within the aerogel particles.

Double layer capacitance of phenoric-resin based active carbon fiber (ACF) electrode was enhanced by a method of electrochemical treatment in various acidic electrolytes. Oxidic acids, especially perchloric acid solution, showed higher enhancement of the ACF capacitance by the electrochemical treatment. Thus, the capacitor was constructed with using 1.0 mol dnr3 HC1O4 electrolyte solution and ACF electrode oxidized at 1.0 V vs. SCE for 1 h. The capacitor gives charging-discharging characteristics better than that of HzSCh electrolyte system.

Electrochemical oxidation of an active carbon fiber (ACF) electrode showed an enhancement effect of the electrode capacitance. The modification of ACF, however, increased the electrode inner resistance with an increase in the capacitance. Au deposition, the deaeration and the electrochemical reduction (discharge) after the modification showed a decrease in the inner resistance. Thus, the capacitor using the modified ACF electrodes with deaeration, Au deposition and/or discharge treatment showed an enhancement of capacitance with decreasing inner resistance.

By coating an electroactive polypyrrole (PPy) film electrode with a plasticized poly(vinyl chloride) (PVC) membrane containing valinomycin, an all-solid-state potassium-selective electrode was fabricated. The polymerizing conditions of the PPy film were optimized for stable ionic responses. The electrochemical characteristics of these electrode systems were evaluated by an a.c. impedance method with respect to the mechanism of potential drift. The steady-state response over several days, which depended on the electrode configuration, was related to the impedance behavior of the electrode systems.

Electric double layer capacitance of phenolic-resin based active carbon fiber(ACF) electrode was enhanced by an electrochemical oxidation. However, the enhanced capacitance was effectively used as a capacitor only after an electrochemical reduction treatment. The effect of reduction treatment after oxidation of ACF electrode was evaluated by galvanic polarization, ac impedance analysis and constant current charge-discharge in 0.5 mol dm(-3)H(2)SO(4) aqueous solution.
The reduction treatment made the neutral electrode potential of oxidized ACF cathodic, thus during the charging, the ACF of positive electrode worked without the side reaction of gas evolution. AC impedance analysis proved that the capacitance and resistance of oxidized ACF were effectively increased and decreased, respectively, by the reduction treatment. The XPS results of ACF suggested that the surface oxide was removed by the reduction treatment, and the capacitor performance was enhanced by the surface change.

Isotropic high density graphite (HDG) was used as the polarizable electrode of electric double layer capacitors (EDLC) with a solid electrolyte consisting of PEO/LiClO4([EO]/L[i(+)]=8:1) at 80 degrees C or with a gel electrolyte consisting of PEO/PC/LICLO(4) ([EO]/[PC]/[Li+]=8:8:1) at room temperature. The all-solid state capacitor with HDG electrodes works satisfactorily as a EDLC with a relatively high capacitance, as well as the EDLC with gel electrolyte PEO/PC/LiC1O(4). These EDLCs with solid polymer electrolyte PEO/LiClO4 and gel electrolyte PEO/PC/LiClO4 show good charge/discharge behavior when charged to 1.5 V at 80 degrees C and 20 degrees C, respectively.

An electrochemical reaction of a composite film of p-type electroactive polymer with polyanion was investigated. A polypyrrole doped with polystyrenesulfonate was formed by electropolymerization with various polymerization charges, The redox potential of the thin composite film was influenced by the salt concentration of the electrolyte. The charge transfer resistance of the composite film was not influenced by the film thickness,while the limiting low frequency capacitance showed a linear relationship to the film formation charge.

Nafion(R) was introduced into a polypyrrole (PPy) matrix, and the redox performance of the PPy/Nafion electrode was investigated in a poly(ethylene oxide) (PEO)-LiClO4 electrolyte. A rougher interface between polymer cathode and polymer electrolyte is usually needed for an all-solid battery, however, the PPy/Nafion cathode works well regardless of the flat surface of the PPy/Nafion film. When compared to a PPy film doped with ClO4- anions with a similar morphology, the PPy/Nafion film showed better redox performance. The results of ac impedance spectroscopy and potential-step chronoamperometry confirmed that the improvement in the redox reaction of the PPy/Nafion film was due to the enhancement of the ion diffusion rate in the film. Thus, the PPy/Nafion film showed good charging-discharging properties in a rechargeable Li/PEO-LiClO4/(PPy/Nafion) battery.

In a study of the electroluminescence (EL) of porous silicon on an n-type Si wafer using an S2O82- electrolyte solution, the addition of C2H5OH: to the solution was found to enhance the intensity of EL from the porous silicon. The porous silicon structure was classified into two types which were prepared based on whether the anodizing current density for forming the porous n-Si was above or below the saturated photocurrent. A single layer of fine pores was formed galvanostatically with illumination at a current density below the saturated photocurrent density, and a double layer of fine and rough pores was formed under the same conditions but at a current density above the saturated photocurrent density. The electrochemical and enhanced electroluminescent properties of the two types of porous silicon were studied.

All-solid-state potassium-selective electrodes have been constructed on a Pt disk electrode using a double-layer film of polypyrrole/poly(4-styrenesulfonate) (PPy/PSS) composite covered with a plasticized poly(vinyl chloride) (PVC) membrane containing valinomycin. The lower composite layer is formed by electropolymerization of pyrrole in an aqueous solution containing poly(sodium 4-styrenesulfonate), and the upper PVC layer is formed by casting. The double-layer film electrode using this composite shows no overshoot and lower drift of the standard potential than both a single PVC-coated electrode and a double-layer electrode using polypyrrole doped with ClO4-. This is due to both the highly electrochemical activity of the lower PPy/PSS and the cation-exchange ability between the PPy/PSS and the potassium-selective membrane.

The charge-discharge behavior of a lithium metal anode in propylene carbonate (PC) electrolyte containing added CO2 was investigated using in situ ac impedance measurements during galvanostatic cycling. In PC electrolyte with CO2, the anode's cycle life was twice as long and its charge transfer resistance was smaller than in the same electrolyte without CO2. These enhancements are observed only when lithium is electrodeposited in the presence of CO2 on nickel substrate; the enhancement does not occur when lithium is deposited without CO2 and is cycled with CO2. Even large amounts of H2O in the electrolyte during cycling do not adversely affect the cycle life enhancement by CO2. The CO2 enhancement seems to be due to products formed by reaction of lithium with CO2 on the electrodeposited lithium surface.

The charge-discharge behavior of a lithium metal anode in propylene carbonate (PC) electrolyte containing added C02 was investigated using in situ ac impedance measurements during galvanostatic cycling. In PC electrolyte with C02, the anode's cycle life was twice as long and its charge transfer resistance was smaller than in the same electrolyte without C02. These enhancements are observed only when lithium is electrodeposited in the presence of C02 on nickel substrate
the enhancement does not occur when lithium is deposited without C02 and is cycled with C02. Even large amounts of H20 in the electrolyte during cycling do not adversely affect the cycle life enhancement by C02. The C02 enhancement seems to be due to products formed by reaction of lithium with C02 on the electrodeposited lithium surface. © 1995, The Electrochemical Society, Inc. All rights reserved.

An ambient-temperature, all-solid lithium battery was fabricated by combining a poly(acrylonitrile), PAN-based polymer electrolyte with a lithium metal anode and a polypyrrole, PPy, film cathode. The influence of the morphology of the PPy film cathode on the battery performance was investigated. The results show that the electrode morphology does not considerably influence the charge-discharge cycling response and that the solid-state, Li/PPy battery exhibits high coulombic efficiency, approaching 90%. However, at the present time, the battery has a poor shelf life, and work is in progress for overcoming this drawback.

The lithium metal anode electrodeposited on nickel was studied by charge-discharge test coupled with in-situ ac impedance measurement. The test gives information about lithium anode interface and the modified interface of electrodeposited lithium by CO2 is confirmed to enhance the lithium cycleability. Also the CO2 protects the lithium interface in the presence of H2O impurity during cycling test.

The performance of a composite film of polypyrrole (PPy) and poly(4-styrenesulfonate) (PSS) was studied in combination with an organic electrolyte as a possible lithium battery cathode. The composite film had a fairly flat morphology and exhibited electroactivity in organic electrolyte solutions using dimethylsulfoxide and propylene carbonate (PC) solvents. We confirmed that during the redox process the film charge was compensated with cations. A lithium cell consisting of the composite film as a cathode and a LiClO4-PC electrolyte worked as a rechargeable battery. The energy density of the PPy/PSS cathode was calculated to be 220 Wh liter-1 and the average output voltage of the rechargeable cell was 2.9 V.

An all solid-state lithium/polypyrrole (PPy) battery using polyethylene oxide (PEO)-LiClO4 as a solid polymer electrolyte was assembled, and the effects of the morphology of the PPy film and the concentration of LiClO4 on battery performance were investigated. Optimum conditions for the redox properties of PPy films in PEO-LiClO4 at 80-degrees-C were obtained with an LiClO4 concentration of n = 8 - 20 (n=[EO]/[Li]) when using rough PPy film. A Li/PPy battery using PEO-LiClO4 with optimized conditions exhibited high coulombic efficiency, above 90% at 0.1 mA cm-2 at 80-degrees-C. Cyclability of 1400 cycles with high coulombic efficiency was attained.

Insulating and electroinactive polypyrrole (PPy(NaOH)) film can be synthesized by electropolymerization from an NaOH aqueous solution containing pyrrole at a highly positive, potential. The synthesis of this electroinactive PPy(NaOH) was investigated using in situ UV and X-ray photoelectron spectroscopy, and was compared with the irreversible oxidation (''overoxidation'') of electroactive PPy under a highly positive potential. Overoxidation made the PPy inactive. However, the formation of PPy (NaOH) started above 0.5 V vs. Ag/AgCl, and the ''overoxidation'' began simultaneously in the polymerizing solution. Overoxidation with nucleophilic hydroxide ions caused a structural change in the PPy molecule, which destroyed the original pi-conjugated system.

A polyaniline/polypyrrole (PAn/PPy) dual-layer was prepared by electropolymerization of aniline onto a PPy pre-deposited electrode. The electrochemical properties and battery cathode performance were investigated and the correlation between them was discussed. The effect of the properties of PPy underlayer on the electrochemical properties seemed to lessen with an increase in the thickness of PAn upperlayer, however, the cathode performance of the dual-layer was much influenced by the properties of PPy underlayer.

Electrodeposited lithium was evaluated by ac impedance measurement and optical microscopy in two solutions containing LiClO4; a propylene carbonate (PC) solution and a blended solution consisting of PC and 1,2-dimethoxyethane (DME)(volume ratio = 1:1). The ac impedance data were analyzed in the higher frequency region, where the charge-transfer resistance (R(ct)) of Li+ + e- reversible Li can be evaluated. The value of R(ct) was always larger in the PC electrolyte solution than in the PC-DME(1:1) electrolyte solution, and R(ct) depended on the lithium deposition charge. Microscopic observation indicated that lithium deposited more uniformly in PC-DME (1:1) than in PC solution. The results of morphological evaluation of the electrodeposited lithium using optical microscopy corresponded to the variations in the value of R(ct) obtained from ac impedance measurements, showing that the behavior of R(ct) accurately represented the morphological state. The cycleability of the lithium anode was investigated by charge-discharge testing. The cycle efficiency was worse in PC than in PC-DME (1:1) solution; this seems to be related to the morphological properties of the lithium deposits.

On the basis of a metal/insulator/metal (MIM) device using electroinactive polypyrrole (PPy) film as an insulator, an amperometric pH sensor device for a very small test solution (4 μl) was developed using the structure of Au/PPy/Au with a window hole. Electropolymerized thin PPy film formed from alkaline solution is used for the ion-selective membrane. The Au/PPy/Au device with a d.c. voltage supply from 0 to 0.2 V works well as an amperometric pH sensor, that is, the gradient of the Cottrell plot within 10 s corresponds exactly to the pH value. © 1993.

The electrochemically polymerized conductive polymers were evaluated by an ac impedance measurement for use in a Li/polymer battery. The validity and the limit of ac impedance analysis for this case are discussed. © 1993.

Electroactivity of polypyrrole/polystyrenesulfonate composite film obtained from an aqueous solution was examined in various organic electrolytes. The composite film worked like electroinactive film in electrolyte using propylene carbonate or some solvents except in the case of DMF or DMSO electrolytes, however, the film changed from electroinactive to electroactive even in propylene carbonate and some organic electrolytes after an electrochemical potential application to the film while in DMF or DMSO electrolytes.

The electrical conduction mechanism for the indium tin oxide (ITO)/polypyrrole (PPy)/ITO sandwich type of metal-insulator-metal element was investigated, where electroinactive PPy polymerized in aqueous NaOH solution was used as an insulator. The ITO/PPy/Au element demonstrated a non-linear J-V response exactly the same as that of the ITO/PPy/ITO element, indicating that the carriers do not come from the interface but the bulk of an insulator. For the temperature dependence of the J-V responses of the ITO/PPy/ITO element, Poole-Frenkel emission is confirmed to be a dominant conduction mechanism. The activation energy of PPy electropolymerized for 60 min was calculated to be 0.46 eV on the basis of Poole-Frenkel emission. The activation energy and the conductivity of the PPy film were dependent on polymerization time.

Electroactive polyaniline (PAn) films were deposited from PC (propylene carbonate)-EC (ethylene carbonate) and PC-DME (1,2-dimethoxyethane) mixed polymerization solutions containing aniline, CF3COOH, and LiClO4. Higher dielectric constant solvents are necessary to deposit the PAn film where protons, dissociated from the acid, initiate the polymerization of aniline. Various PAn films deposited in the PC, the PC-EC (50 mole percent), and the PC-DME (50 volume percent) solutions were used for the cathode materials of the rechargeable lithium batteries. Charge capacity and discharge ability of the Li/PAn batteries in the PC-LiClO4 electrolyte solution are almost the same, regardless of the polymerization solvents, such as PC almost-equal-to PC-EC greater-than-or-equal-to PC-DME and PC-EC greater-than-or-equal-to PC-DME almost-equal-to PC. The mixed solvent electrolyte solution effect on the Li/PAn (polymerized in the PC solution) batteries becomes much larger such as PC-DME &gt; PC-EC &gt; PC. Moreover, the electrochemical kinetic factors of the PAn films deposited in the various mixed polymerization solutions and also in the different electrolytes were experimentally determined by measuring the ac impedance. The results of the ac impedance analysis of each PAn film correlate well with the battery performances of Li/PAn cells.