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.

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.

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.

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.

<jats:title>Abstract</jats:title><jats:p>High Entropy Alloys (HEAs) are a versatile material with unique properties, tailored for various applications. They enable pH‐sensitive electrocatalytic transformations like hydrogen evolution reaction (HER) and hydrogen oxidation reactions (HOR) in alkaline media. Mesoporous nanostructures with high surface area are preferred for these electrochemical reactions, but designing mesoporous HEA sis challenging. To overcome this challenge, a low‐temperature triblock copolymer‐assisted wet‐chemical approach is developed to produce mesoporous HEA nanospheres composed of PtPdRuMoNi systems with sufficient entropic mixing. Owing to active sites with inherent entropic effect, mesoporous features, and increased accessibility, optimized HEA nanospheres promote strong HER/HOR performance in alkaline medium. At 30 mV nominal overpotential, it exhibits a mass activity of ≈167 (HER) and 151 A g<jats:sub>Pt</jats:sub><jats:sup>−1</jats:sup> (HOR), far exceeding commercial Pt‐C electrocatalysts (34 and 48 A g<jats:sub>Pt</jats:sub><jats:sup>−1</jats:sup>) and many recently reported various alloys. The Mott‐Schottky analysis reveals HEA nanospheres inherit high charge carrier density, positive flat band potential, and smaller charge transfer barrier, resulting in better activity and faster kinetics. This micelle‐assisted synthetic enable the exploration of the compositional and configurational spaces of HEAs at relatively low temperature, while simultaneously facilitating the introduction of mesoporous nanostructures for a wide range of catalytic applications.</jats:p>

Correction to: Nature Communications, published online 13 July 2023 The original version of the Supplementary Information associated with this Article included incorrect Supplementary Datasets. Dataset 1 reported an editorial policy checklist; Dataset 3 reported a general description of Supplementary Figures and Tables contained in the Supplementary Information PDF file; Dataset 4 contained editorial instructions to the authors for the preparation of the final version of the article. Datasets 1, 3, and 4 have been removed in the corrected version of the Article. In addition, the Reporting Summary and the Source Data file were originally published with the wrong titles of Dataset 2 and Dataset 5. The HTML version of the article has been corrected.

Abstract

Electrocatalyst engineering from the atomic to macroscopic level of electrocatalysts is one of the most powerful routes to boost the performance of electrochemical devices. However, multi‐scale structure engineering mainly focuses on the range of atomic‐to‐particle scale such as hierarchical porosity engineering, while catalyst engineering at the macroscopic level, such as the arrangement configuration of nanoparticles, is often overlooked. Here, a 2D carbon polyhedron array with a multi‐scale engineered structure via facile chemical etching, ice‐templating induced self‐assembly, and high‐temperature pyrolysis processes is reported. Controlled phytic acid etching of the carbon precursor introduces homogeneous atomic phosphorous and nitrogen doping, as well as a well‐defined mesoporous structure. Subsequent ice‐templated self‐assembly triggers the formation of a 2D particle array superstructure. The atomic‐level doping gives rise to high intrinsic activity, while the well‐engineered porous structure and particle arrangement addresses the mass transport limitations at the microscopic particle level and macroscopic electrode level. As a result, the as‐prepared electrocatalyst delivers outstanding performance toward oxygen reduction reaction in both acidic and alkaline media, which is better than recently reported state‐of‐the‐art metal‐free electrocatalysts. Molecular dynamics simulation together with extensive characterizations indicate that the performance enhancement originates from multi‐scale structural synergy.

Abstract

Although hollow carbon structures have been extensively studied in recent years, their interior surfaces are not fully utilized due to the lack of fluent porous channels in the closed shell walls. This study presents a tailored design of open‐mouthed particles hollow cobalt/nitrogen‐doped carbon with mesoporous shells (OMH‐Co/NC), which exhibits sufficient accessibility and electroactivity on both the inner and outer surfaces. By leveraging the self‐conglobation effect of metal sulfate in methanol, a raspberry‐structured Zn/Co‐ZIF (R‐Zn/Co‐ZIF) precursor is obtained, which is further carbonized to fabricate the OMH‐Co/NC. In‐depth electrochemical investigations demonstrate that the introduction of open pores can enhance mass transfer and improve the utilization of the inner active sites. Benefiting from its unique structure, the resulting OMH‐Co/NC exhibits exceptional electrocatalytic oxygen reduction performance, achieving a half‐wave potential of 0.865 V and demonstrating excellent durability.

Abstract

Multimetallic alloys (MMAs) with various compositions enrich the materials library with increasing diversity and have received much attention in catalysis applications. However, precisely shaping MMAs in mesoporous nanostructures and mapping the distributions of multiple elements remain big challenge due to the different reduction kinetics of various metal precursors and the complexity of crystal growth. Here we design a one-pot wet-chemical reduction approach to synthesize core–shell motif PtPdRhRuCu mesoporous nanospheres (PtPdRhRuCu MMNs) using a diblock copolymer as the soft template. The PtPdRhRuCu MMNs feature adjustable compositions and exposed porous structures rich in highly entropic alloy sites. The formation processes of the mesoporous structures and the reduction and growth kinetics of different metal precursors of PtPdRhRuCu MMNs are revealed. The PtPdRhRuCu MMNs exhibit robust electrocatalytic hydrogen evolution reaction (HER) activities and low overpotentials of 10, 13, and 28 mV at a current density of 10 mA cm⁻² in alkaline (1.0 M KOH), acidic (0.5 M H₂SO₄), and neutral (1.0 M phosphate buffer solution (PBS)) electrolytes, respectively. The accelerated kinetics of the HER in PtPdRhRuCu MMNs are derived from multiple compositions with synergistic interactions among various metal sites and mesoporous structures with excellent mass/electron transportation characteristics.

Herein we report the rational syntheses of three conjugated microporous polymers (CMPs) through one-pot polycondensation coupling of a boronated triphenylpyridine (TPP-3Bor) with 4,7-bis(5-bromothien-2-yl)benzo[c][1,2,5]thiadiazole (ThZ-2Br), 2,5-dibromothiophene (Th-2Br), and 1,4-dibromobenzene (Bz-2Br), yielding the TPP-ThZ, TPP-Th, and TPP-Bz CMPs, respectively, featuring different thiophene contents, topologies, and molecular structures. Various characterization techniques are used to investigate the structural properties of these TPP-based CMPs, revealing their spherical morphologies, tunable pore volumes, and high thermal and chemical stabilities. We test the TPP-based CMPs for their use in the dynamic adsorptive reduction of toxic Cr(vi) ions. Among them, the TPP-ThZ CMP possesses the highest adsorption capacity for Cr(vi) (209 mg g−1); this performance is also higher than those of other recently reported adsorbents. Furthermore, our TPP-based CMPs exhibit good reusability for the reduction and adsorption of Cr(vi) ions. Accordingly, these novel thiophene-based CMPs not only function as dynamic materials for the reduction-adsorption of Cr(vi) but also reveal the potential of thiophene linkers in the future design of such Cr(vi) adsorbents.

A uniform nanoframe structure derived from a Prussian blue analogue (PBA) with an internal cavity is successfully synthesized by sonochemical etching. The uniquely structured PBA nanoframes possess a three-dimensional open structure and high surface area, resulting in enhanced electrochemical properties for the oxygen evolution reaction as a model reaction.

Here, we report the synthesis of two-dimensional (2D) layered metal-organic framework (MOF) nanoparticle (NP) superstructures via an ice-templating strategy. MOF NP monolayers and bilayers can be obtained by regulating the concentration of colloidal MOF NPs without any external fields during self-assembly. Adjacent polyhedral MOF NPs are packed and aligned through crystalline facets, resulting in the formation of a quasi-ordered array superstructure. The morphology of the MOF layers is well preserved when subjected to pyrolysis, and the obtained carbon NPs have hollow interiors driven by the outward contraction of MOF precursors during pyrolysis. With the advantages of large surface areas, hierarchical porosity, high exposure of active sites, and fast electron transport of the 2D layered structure, the mono- and bilayered carbon NP superstructures show better oxygen reduction activity than isolated carbon particles in alkaline media. Our work demonstrates that ice-templating is a powerful strategy to fabricate superstructures of various MOFs and their derivatives.

Controlling the morphology, composition, and crystalline phase of mesoporous nonnoble metal catalysts is essential for improving their performance. Herein, well-defined P- and B-codoped NiFe alloy mesoporous nanospheres (NiFeB-P MNs) with an adjustable Ni/Fe ratio and large mesopores (11 nm) are synthesized via soft-template-based chemical reduction and a subsequent phosphine-vapor-based phosphidation process. Earth-abundant NiFe-based materials are considered promising electrocatalysts for the oxygen evolution reaction (OER) because of their low cost and high intrinsic catalytic activity. The resulting NiFeB-P MNs exhibit a low OER overpotential of 252 mV at 10 mA cm(-2), which is significantly smaller than that of B-doped NiFe MNs (274 mV) and commercial RuO2 (269 mV) in alkaline electrolytes. Thus, this work highlights the practicality of designing mesoporous nonnoble metal structures and the importance of incorporating P in metallic-B-based alloys to modify their electronic structure for enhancing their intrinsic activity.

Most commercially available lithium ion battery systems and some of their possible successors, such as lithium (metal)-sulfur batteries, rely on liquid organic electrolytes. Since the electrolyte is in contact with both the negative and the positive electrode, its electrochemical stability window is of high interest. Monitoring the electrolyte decomposition occurring at these electrodes is key to understand the influence of chemical and electrochemical reactions on cell performance and to evaluate aging mechanisms. In the context of lithium-sulfur batteries, information about the analysis of soluble species in the electrolytes-besides the well-known lithium polysulfides-is scarcely available. Here, the irreversible decomposition reactions of typically ether-based electrolytes will be addressed. Gas chromatography in combination with mass spectrometric detection is able to deliver information about volatile organic compounds. Furthermore, it is already used to investigate similar samples, such as electrolytes from other battery types, including lithium ion batteries. The method transfer from these reports and from model experiments with non-target analyses are promising tools to generate knowledge about the system and to build up suitable strategies for lithium-sulfur cell analyses. In the presented work, the aim is to identify aging products emerging in electrolytes regained from cells with sulfur-based cathodes. Higher-molecular polymerization products of ether-based electrolytes used in lithium-sulfur batteries are identified. Furthermore, the reactivity of the lithium polysulfides with carbonate-based solvents is investigated in a worst-case scenario and carbonate sulfur cross-compounds identified for target analyses. None of the target molecules are found in carbonate-based electrolytes regained from operative lithium-titanium sulfide cells, thus hinting at a new aging mechanism in these systems.

A heterostructured porous carbon framework (PCF) composed of reduced graphene oxide (rGO) nanosheets and metal organic framework (MOF)-derived microporous carbon is prepared to investigate its potential use in a lithium-ion battery. As an anode material, the PCF exhibits efficient lithium-ion storage performance with a high reversible specific capacity (771 mA h g(-1) at 50 mA g(-1)), an excellent rate capability (448 mA h g(-1) at 1000 mA g(-1)), and a long lifespan (75% retention after 400 cycles). The in situ transmission electron microscopy (TEM) study demonstrates that its unique three-dimensional (3D) heterostructure can largely tolerate the volume expansion. We envisage that this work may offer a deeper understanding of the importance of tailored design of anode materials for future lithium-ion batteries.

The rational design and fabrication of ordered mesoporous materials with highly exposed surface area are of great significance to address the fundamental challenges in electrochemistry-related applications by providing more active sites and fast ion/gas diffusion channel. In this work, a self-template method is reported to prepare hollow-structured mesoporous carbon (HOMC) nanoplates by depositing resol-F127 micelles onto the surface of metal-organic-framework (MOF) nanoplates, followed by hydrothermal reaction and carbonization. The parameters influencing the morphology and microstructure of the HOMC materials, i.e., the MOF-to-resol-F127 ratio and the concentration of resol-F127 micelles, are systematically investigated. Fe-doped HOMC (Fe/ HOMC) is obtained after carbonization, as a result from adding FeCl3 during the hydrothermal reaction. Benefiting from morphological aspects, such as the nanoplate shape, the hollow structure, and mesoporous walls, the Fe/HOMC exhibits higher electrocatalytic activity and efficiency than the commercial Pt/C during oxygen reduction reaction (ORR). In addition, when compared to traditional Pt/C benchmark, the Fe/HOMC shows a superior durability and tolerance to methanol poisoning while operating for ORR. The assembled Zn-air battery possesses high power densities with excellent cycling stability. The strategy proposed here can provide a new avenue for the design of ordered mesoporous materials with hollow structure for a wide variety of applications.

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.

Lithium-sulfur (Li-S) batteries have attracted particular interest as promising next-generation energy storage devices because of their high theoretical energy density and low cost. The real performance of Li-S batteries is, however, far from achieving the expected values, even when using a porous, highly conductive host of sulfurs to improve their electric conductivity and accommodate their volume changes. The performance restrictions are mainly attributable to the slow reaction kinetics of converting lithium polysulfides species to lithium sulfide and elemental sulfur during the charging and discharging processes, respectively. Recent studies show that single-atom catalysts (SACs) with superior catalytic activity offer an effective strategy for solving this tough issue. The recent advances in utilizing SACs for Li-S batteries, which involve catalyst preparation, battery performance, and mechanistic insights, are summarized here. Modification of the cathodes and separators with SACs helps to absorb polysulfide and promote their conversion kinetics, thus suppressing the notorious "shuttle effect." In addition, the introduction of SACs into Li-S batteries promotes the efficiency of Li stripping/plating and prevents the growth of Li dendrites. Overall, the boost effects of SAC on Li-S batteries performance are noticeable and deserving of more research attention to develop better Li-S batteries.

In this study, the high-rate performance of high sulfur-loaded cathodes have been demonstrated using a novel battery that comprises of a 3 dimensional aluminum foam (current collector), sulfur (active material), acetylene black (conductive additive), and polypyrrole (PPy) coating. Consequently, a stacked laminated cell was prepared, which comprised of two 70 x 70 mm(2) PPy-sulfur/ketjen black sheets (sulfur loading = 4.3 mg/cm(2)), 1 M lithium bis-(trifluoromethylsulfonyl)imide (LiTFSI) with dimethoxyethane (DME) and 1,3-dioxolane (DOL), (DME/DOL = 1/1 vol%), and three Li foils as the cathodes, electrolyte, and anodes, respectively. The 1 M LiTFSI DME/DOL electrolyte, which is suitable for high rate, is applicable because the PPy coating suppresses dissolution of polysulfide into the electrolyte. The discharge capacities were 462 mAh (1075 mAh/g sulfur) at 0.4C (267 mA) and 251 mAh (583 mAh/g-sulfur) at 3.8C (2670 mA). An enhanced conductive path was formed in the cathode by the 3D Al foam and AB, which considerably improved the high-rate performance. This demonstration is particularly significant from the viewpoint of commercializing the high-power output and high-energy-density Li-S batteries for industrial applications such as small mobile device and drone power source. (c) 2020 Elsevier B.V. All rights reserved.

In recent years, due to their structural diversity, adjustability, versatility, and excellent electrochemical properties, organic compounds with nitrogen-containing groups (OCNs) have become some of the most promising organic electrode materials. The nitrogen-containing groups acting as electrochemical active sites include carbon-nitrogen groups, nitrogen-nitrogen groups, nitrogen-oxygen groups in OCNs, and nitrogen-containing groups in covalent organic frameworks. The molecular structure regulation of OCNs with nitrogen-containing groups acting as electrochemical active centers can suppress dissolution in electrolytes, increase electronic conductivity, and improve the kinetics of redox reactions. The kinetics behavior and electrochemical characteristics of OCN electrode materials in alkali metal rechargeable batteries with organic electrolytes are reviewed, and the related relationships between the structure and electrochemical properties of OCNs are the core of this review. Herein, the electrochemical reaction mechanisms and the strategies to improve the electrochemical activity of nitrogen-containing groups in OCNs are clarified, and the conjugate molecular structure of OCNs is shown to be an important direction for improvement. These results will have implications for research on electrode materials and provide more choices for rechargeable batteries. Moreover, this work will guide the study of more efficient OCNs that can be used as electrode materials.

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.

Concave metallic nanocrystals with a high density of low-coordinated atoms on the surface are essential for the realization of unique catalytic properties. Herein, mesoporous palladium nanocrystals (MPNs) that possess various degrees of curvature are successfully synthesized following an approach that relies on a facile polymeric micelle assembly approach. The asprepared MPNs exhibit larger surface areas compared to conventional Pd nanocrystals and their nonporous counterparts. The MPNs display enhanced electrocatalytic activity for ethanol oxidation when compared to state-of-the-art commercial palladium black and conventional palladium nanocubes used as catalysts. Interestingly, as the degree of curvature increases, the surface-area-normalized activity also increases, demonstrating that the curvature of MPNs and the presence of high-index facets are crucial considerations for the design of electrocatalysts.

Lithium-ion capacitors (LICs) have been attracting research interest over the past years as promising electrochemical energy devices because they show higher energy densities than supercapacitors and higher power densities than batteries. In this study, we synthesized an Sn-Ni alloy by electrodeposition and applied it as an anode for LICs. To optimize the full-cell configuration, we controlled the mass balancing between the loading amounts of active materials in the cathode and anode with different mass ratios of 16:1, 8:1, and 4:1. In addition, the Sn-Ni alloy was investigated using electrochemical impedance spectroscopy under different depth of discharge (DOD) levels. The LICs assembled with a mass ratio of 4:1 between the cathode and anode exhibited good cyclability, rate performance, energy, and power density. This study not only improved the cycle performance of LICs full cell by mass balancing, but also revealed the relationship between the electrochemical characteristics of LICs and DOD levels of the Sn-Ni anode.

Lithium sulfur batteries (LSBs) are regarded as promising electrochemical energy storage devices owing to their higher theoretical capacity than commercial cathode materials. Herein, we report a simple method for preparing a modified sulfur/Ketjenblack (S/KB) cathode using polymer composite poly(3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS), which displays ionic and electron conductivity and can suppress polysulfide dissolution during the charge-discharge process. The S/KB + PEDOT:PSS cathode displayed higher electrochemical performance than the S/KB cathode. The effectiveness of suppressing polysulfide dissolution was determined visually and by UV-visible spectroscopy. The findings demonstrate the multi-functionality of PEDOT:PSS as an efficient electron conductive additive for S/KB cathode in high-performance LSBs.

Electrochemical impedance spectroscopy has been widely used to understand the chemistry and physics of battery systems. This review covers electrochemical impedance spectroscopy used for the interpretation of impedance data of lithium-ion batteries (LIBs) from advanced equivalent circuit models to the mathematical model, which is developed by John Newman. In addition, as a method to realize an energy-sustainable society using diagnostics based on the combination of LIBs and electrochemical impedance spectroscopy, on-board diagnostics of battery packs are achieved based on an input signal generated by a power controller in a battery management system instead of the conventionally used frequency response analyzer. The diagnostic system is applicable to energy management systems which are installed in homes, buildings, and communities, accumulating the impedance data on state of health of LIBs. Finally, a future possibility regarding the diagnostics of battery packs coupled with the machine learning of impedance data is introduced.

Tin-nickel (Sn-Ni) alloy is a promising candidate as an anode for the lithium-ion capacitor (LIC) because it is superior in volumetric energy density compared with that of the graphite anode. However, its cycle durability requires improvement, even with a higher utilization ratio of the anode. The effect of lithium salts, LiPF6 and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is investigated for usage in the LIC in severe conditions (utilization ratio of the anode: 20%). The LIC with LiTFSI delivered its initial capacity up to similar to 400 cycles, which is 4 times longer than the LIC with LiPF6. The reason for the capacity decay in the LiPF6 system is attributed to the narrowing of the potential range of the activated carbon cathode due to a widening potential range of the Sn-Ni alloy anode during operation. This widening is attributed to the loss of the active material due to peeling-off from the substrate. However, when LiTFSI is used, no such decay is observed. It is suggested that a polymer-like solid electrolyte interphase derived from TFSI- may suppress the loss of the active material. This finding can encourage the development of an Sn-based anode for LICs in combination with a mild operating condition and electrolyte additives. (C) The Electrochemical Society of Japan, All rights reserved.

A Lithium-ion capacitor (LIC) is composed of an electrochemical capacitor-like cathode and battery-like anode which store charge based on non-faradaic and faradaic processes, respectively. As an anode material for LIC, graphite is widely used because of its physical and electrochemical advantages. In the LIC system, stable cyclability at the high rate conditions is essential for bridging the gap between lithium-ion batteries and supercapacitors. However, there have been reported that the low working potential of graphite (close to 0.05 V vs Li/Li+) causes Li plating on the graphite surface and non-unity coulombic efficiency at high current charge/discharge results in degradation of cycle performance. To overcome this issue, stacked reduced graphene oxide-tin (SrGO-Sn) composite by co-reduction of graphene oxide and Sn2+ are studied in this work. The LIC consisting of SrGO-Sn anode shows good long-term cyclability with a remarkable capacity retention of 85, 77, and 60% at 10,000, 50,000, and 100,000th cycle and coulombic efficiency of 98% after 120,000 cycles. We believe that this study presents a new approach to the design of the high-performance LIC using an alternative to conventional graphite-based anode materials. (c) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

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.

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.

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.

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.

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 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 prelithiated 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.

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.

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 development of lithium-sulfur batteries is associated with many problems. These problems include polysulfide dissolution, the shuttle phenomenon, the low electric and ionic conductivity of S, and the volume change that occurs during charge and discharge. In this review, various elemental techniques for overcoming these problems are summarized from the standpoints of the supporting materials. These techniques include preventing polysulfide dissolution from the cathodes through physical and chemical adsorption on the supporting materials, the use of electrolytes that do not dissolve polysulfides via the coordination of Li+ and solvents, and the use of ion-exchange polymers to permeate Li+ selectively. The following approaches to enable practical applications of S cathodes in future Li-ion batteries are introduced: the utilization of Li-free anode materials, such as C and Si; the use of Li2S cathodes, which are prepared via a pre-lithiation process; and increasing the areal capacity of the S cathode by using a suitable current collector such as Al foam, thus providing a large amount of space for Li+ to migrate and the electron-conductive path. The utilization of an Al foam current collector is one of the promising approaches to creating a cost-effective Li-ion battery owing to the established mass production of Al foam for use in NiMH batteries; such Li-ion battery can achieve an unprecedentedly high areal capacity of 21.9 mAh cm(-2). Owing to the resulting areal capacity, the possibility of developing a lithium-sulfur battery with an energy density greater than 200 Wh kg(-1) has been demonstrated. Consequently, the combination of these approaches, as introduced in this review, would help create a bright, sustainable society.

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.

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.

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.

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.

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.

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.

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.

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.

Electrochemical impedance spectroscopy (EIS) can be utilized to characterize battery features, because it allows the dynamics of each elemental process of the battery reaction to be sensitively and separately determined without destruction of the cell. In addition, EIS is expected to be utilized for premonitory diagnosis of onboard batteries in electric vehicles. Here; an overview of the recent diagnosis technologies for determining the health of commercial lithium-ion batteries (LIB) using EIS is provided. We describe equivalent circuit design techniques while explaining and investigating physical and chemical phenomena for a wide range of measured impedance spectra, which are obtained using commercial LIBs.. Attention is then focused on separation of the frequency responses of each electrode with or without a reference electrode, symmetric cell, and temperature control. Additionally, a square-current EIS (SC-EIS) technique, which we have proposed, is introduced for monitoring of large-scale LIB systems as a promising future technique. (C) 2015 The Electrochemical Society. 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.

Lithium-ion batteries (LIBs) are generally constructed by lithium-including positive electrode materials, such as LiCoO2, and lithium-free negative electrode materials, such as graphite. Recently, lithium-free positive electrode materials, such as sulfur, are gathering great attention from their very high capacities, thereby significantly increasing the energy density of LIBs. Though the lithium-free materials need to be combined with lithium-containing negative electrode materials, the latter has not been well developed yet. In this work, the feasibility of Li-rich Li-Si alloy is examined as a lithium-containing negative electrode material. Li-rich Li-Si alloy is prepared by the melt-solidification of Li and Si metals with the composition of Li21Si5. By repeating delithiation/lithiation cycles, Li-Si particles turn into porous structure, whereas the original particle size remains unchanged. Since Li-Si is free from severe constriction/expansion upon delithiation/lithiation, it shows much better cyclability than Si. The feasibility of the Li-Si alloy is further examined by constructing a full-cell together with a lithium-free positive electrode. Though Li-Si alloy is too active to be mixed with binder polymers, the coating with carbon-black powder by physical mixing is found to prevent the undesirable reactions of Li-Si alloy with binder polymers, and thus enables the construction of a more practical electrochemical cell.

A novel 3D porous Si-O-C/Ni thick film anode is successfully prepared by electrodeposition of porous Ni on Cu substrate and galvanostatical electrodeposition of Si-O-C composite on porous Ni substrate. The 3D porous Si-O-C/Ni thick film is electrochemically activated at a current density of 50 mu A cm(-2) for the first cycle and 200 mu A cm(-2) (0.5 C) for the subsequent cycles, it displays superior electrochemical performance with discharge capacity of 706.3 mAh g(-1) of Si after 100 cycles. The properties of this thick film is analyzed by field emission scanning electron microscopy (FESEM) and scanning transmission electron microscopy with energy dispersive X-ray analyzer (STEM-EDX). The results show that Si-O-C composite not only covers the surface area of porous Ni but also attaches to the highly porous dendritic walls, along with the porous structure of Ni which provides proper accommodation for the volume change of silicon during the lithiation/delithiation processes, are believed to result in the high capacity and excellent cyclability. (C) 2014 Elsevier B.V. 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.

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.

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.

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.

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.

First of all, we express our deepest sympathies for the passing of Professor Su-Moon Park. In the present paper, an electrochemical impedance spectroscopy (EIS), which Professor Su-Moon Park also used frequently for the investigation of electroconducting polymer, is introduced as a recent evaluation tool for a commercially available lithium-ion battery (LIB). The paper surveys how to design equivalent circuits while explaining physical and chemical phenomena in the LIB and how to get more accurate impedance spectra with varying the measuring temperatures. Additionally, a square current EIS (SC-EIS) technique, which we have suggested, is introduced for the larger LIB system as a promising technique for the future.

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 Li 2O, 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. © 2013 Elsevier Ltd. All rights reserved.

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.

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.

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.

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.

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.

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.

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.

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.