Recent progress of surface coating on cathode materials for high-performance lithium-ion batteries

Lithium-ion batteries (LIB) have received substantial attention in the last 10 years,as they offer great promise as power sources that can lead to the electric vehicle (EV) revolution in the next 5 years.Since the cathode serves as a key component in LIB,its properties significantly affect the performance of the whole system.Recently,the cathode surface modification based on coating technique has been widely employed to enhance the electrochemical performances by improving the material conductivity,stabilising the physical structure of materials,as well as preventing the reactions between the electrode and electrolyte.In this work,we reviewed the present of a number of promising cathode materials for Li-ion batteries.After that,we summarized the very recent research progress focusing on the surface coating strategies,mainly including the coating materials,the coating technologies,as well as the corresponding working mechanisms for cathodes.At last,the challenges faced and future guidelines for optimizing cathode materials are discussed.In this study,we propose that the structure of cathode is a crucial factor during the selection of coating materials and technologies.     

锂硫银锗矿固态电解质研究进展

全固态电池因其较高的安全性和能量密度而成为下一代电动汽车和智能电网用储能器件的重点研究方向之一。开发具有高室温锂离子电导率、化学/电化学稳定性优异、对电极材料兼容性优异等特点的固态电解质材料是推动全固态电池发展的重要研究课题之一。硫化物电解质因其相对较高的室温电导率(~10⁻³ S∙cm⁻¹)、较低的电解质/电极固-固界面阻抗等优点而在众多无机固体电解质材料中成为研究热点。本文基于作者多年研究成果和当前国内外发表的相关工作,从电解质的结构、离子传导、合成、综合性能改善及在全固态电池中的应用等方面系统总结了锂硫银锗矿固态电解质材料研究,并分析了该类电解质面临的问题和挑战,最后探讨了其未来可能的研究方向和发展趋势。     

锂离子电池正极材料的第一性原理研究进展

锂离子电池的发展主要依赖于电极材料的突破,解决现有电极材料存在的问题和预测新型未知材料是提高锂离子电池性能的关键,而第一性原理计算的出现能够较好的满足这一需求。本文介绍了第一性原理计算在锂离子电池正极材料研究方面的原理和应用,并对该原理在正极材料的平均嵌锂电压计算,嵌/脱锂机理、结构稳定性研究及新材料预测等方面的应用进行了详细论述,并指出了这一理论计算工具在电池材料设计过程中的重要性和局限性。     

低温等离子体在锂离子电池材料中的应用

综合评述了低温等离子体技术的基本原理、 常用方法及其在锂离子电池材料领域中的研究进展, 重点评述了等离子体技术在锂离子电池正极、 负极、 隔膜及固态电解质等重要组分中的材料制备与表面改性方面的主要研究结果和应用优势, 并对其所面临的挑战和未来的应用方向进行了展望.     

Effect of fullerene coating on silicon thin film anodes for lithium rechargeable batteries

To improve the electrochemical performances of Si thin film anodes for lithium rechargeable batteries, fullerene thin films are prepared by plasma-assisted evaporation methods to be used as coating materials. Analyses via Raman and X-ray photoelectron spectroscopy indicate that amorphous polymeric films originated from fullerene are formed on the surface of the silicon thin film. The electrochemical performance of these fullerene-coated silicon thin film as an anode material for rechargeable lithium batteries has been investigated by cyclic voltammetry, charge/discharge tests, and electrochemical impedance spectroscopy. The fullerene-coated Si thin films demonstrated a high specific capacity of above 3,000 mAh g⁻¹ as well as good capacity retention for 40 cycles. In comparison with bare silicon anodes, the fullerene-coated silicon thin film showed superior and stable cycle performance which can be attributed to the fullerene coating layer which enhances the Li-ion kinetic property at the electrode/electrolyte interface.     

功率型锂/氟化碳一次电池的优化设计研究进展

锂/氟化碳电池作为固态正极中理论比能量较高（2203 Wh/kg）的一种一次电池体系,受到极大的关注,在诸多领域已有应用。本文对高功率锂/氟化碳电池的优化设计的最新研究进展进行了综述,详细讨论了氟化碳材料的前驱体、氟化方法、氟化碳材料表面改性、电极结构设计等因素对电池倍率性能的影响,并对今后功率型锂/氟化碳一次电池的发展方向进行了展望。     

磷酸三甲酯和碳酸亚乙烯酯对锂离子电池的复合作用

应用循环伏安、交流阻抗、扫描电子显微镜和锂离子电池性能检测装置研究了阻燃添加剂磷酸三甲酯(TMP)和成膜添加剂碳酸亚乙烯酯(VC)对锂离子电池的复合作用.结果表明,复合使用TMP和VC不仅能提高电池的安全性而且能改善电池的循环性能,原因可能是在电池首次充放电过程中VC优先还原,还原产物在负极表面聚合形成良好的SEI膜,有效地制约了因TMP在石墨负极表面的分解而造成负极石墨的脱落,同时提高了SEI膜的稳定性.     

基于转化反应机制的锂离子电池电极材料研究进展

基于转化反应机制实现储锂功能的电极材料的研究和开发是提高锂离子电池性能,尤其是其可逆循环容量的重要方法,对于锂离子电池未来的发展有着非常重要的意义。本文综述近年来基于转化反应机制实现储锂功能的锂离子电池电极材料的研究进展,介绍了转化反应机制等新概念,重点讨论了基于转化反应机制实现储锂功能的简单过渡金属化合物电极材料的电...     

Carbon nanofibers decorated with poly(furfuryl alcohol)-derived carbon nanoparticles and tetraethylorthosilicate-derived silica nanoparticles

The present paper introduces a novel method to functionalize nanofiber surfaces with carbon or silica nanoparticles by dip coating. This novel approach holds promise of significant benefits because dip coating of electrospun and carbonized nanofiber mats in poly(furfuryl alcohol) (abbreviated as PFA) is used to increase surface roughness by means of PFA-derived carbon nanoparticles produced at the fiber surface. Also, dip coating in tetraethylorthosilicate (abbreviated as TEOS) is shown to be an effective method for decorating carbon nanofibers with TEOS-derived silica nanoparticles at their surface. Furthermore, dip coating is an inexpensive technique which is easier to implement than the existing methods of nanofiber decoration with silica nanoparticles and results in a higher loading capacity. Carbon nanofiber mats with PFA- or TEOS-decorated surfaces hold promise of becoming the effective electrodes in fuel cells, Li-ion batteries and storage devices.     

Carbon Aerogel Films Synthesized at Ambient Conditions

Carbon aerogels derived from organic sol-gel process and supercritical drying are novel porous materials with interconnect structures and higher electrical conductivity, which are considered to be ideal electrode materials for supercapacitors and rechargeable batteries. The objective of the research was to synthesize carbon aerogel films at ambient conditions. Resorcinol formaldehyde (RF) and carbon aerogel films have been produced with extremely high RC ratio (molar ratio of resorcinol to catalyst) followed by subcritical drying. The structure of the porous films was investigated using electron scanning microscope. The specific surface area was measured by using nitrogen adsorption (BET) and electrical conductivity was measured with four-probe method. It was found that with extremely high RC ratio, the porous structure of RF and carbon aerogel films can be controlled from micro to macro porous at ambient conditions. With respect to the application as electrodes for fuel cells, carbon aerogel films with different porous structures on the two surfaces have been also obtained through optimizing the sol-gel process.     

A New Anode for Lithium‐Ion Batteries Based on Single‐Walled Carbon Nanotubes and Graphene: Improved Performance through a Binary Network Design

Carbon nanomaterials, especially graphene and carbon nanotubes, are considered to be favorable alternatives to graphite‐based anodes in lithium‐ion batteries, owing to their high specific surface area, electrical conductivity, and excellent mechanical flexibility. However, the limited number of storage sites for lithium ions within the sp²‐carbon hexahedrons leads to the low storage capacity. Thus, rational structure design is essential for the preparation of high‐performance carbon‐based anode materials. Herein, we employed flexible single‐walled carbon nanotubes (SWCNTs) with ultrahigh electrical conductivity as a wrapper for 3D graphene foam (GF) by using a facile dip‐coating process to form a binary network structure. This structure, which offered high electrical conductivity, enlarged the electrode/electrolyte contact area, shortened the electron‐/ion‐transport pathways, and allowed for efficient utilization of the active material, which led to improved electrochemical performance. When used as an anode in lithium‐ion batteries, the SWCNT‐GF electrode delivered a specific capacity of 953 mA h g^?1 at a current density of 0.1 A g^?1 and a high reversible capacity of 606 mA h g^?1 after 1000 cycles, with a capacity retention of 90 % over 1000 cycles at 1 A g^?1 and 189 mA h g^?1 after 2200 cycles at 5 A g^?1.     

纳米级锂离子电池正极材料LiFePO4

LiFePO₄以其价格便宜,稳定性好,无毒等优点而倍受关注。但是非纳米LiFePO₄的电子导电率低及扩散系数小限制了其在锂离子电池领域的大规模应用。而纳米电极材料以其特有的优点很好的解决了这些问题。本文主要综述了国内外合成纳米级LiFePO₄ 的不同方法及所得材料的对电化学性能和相关机理,以及纳米LiFePO₄作为锂离子正极材料存在的问题。     

Mechanical degradation of electrode materials within single particle model in Li-ion batteries for electric vehicles

Mechanical degradation of electrode materials, in the form of particle cracking and fragmentation, disintegration, fracturing, and loss in contact between current collectors and the active electrode materials, can affect or deteriorate the performance of Li-ion batteries dramatically and even lead to the battery failure in electric vehicle. This paper firstly built a single particle model (SPM) based upon kinetics of electrochemical reactions. Then the Li-ion concentration, evolution of diffusion induced stresses within the SPM under potentiostatic or galvanostatic operating conditions were analyzed by utilizing a mathematical method. Next, evolution of stresses or strains in the SPM, at the core of relates with mechanical degradation of electrode materials, are elaborated in detail. Finally, surface and morphology of the electrodes dismantled from fresh and degraded cells after galvanostatic charge/discharge cycling have been analyzed to verify the hypothesis aforementioned by observing scanning electron microscopy and analyzing X-ray diffraction.     

Model Ge microstructures as anodes for Li-ion batteries

We examine the properties of microstructured Ge electrodes for Li-ion battery applications. Model-microfabricated single-crystalline Ge electrode structures are used to investigate the effects of Cu coating and partial discharging on cycle life. Results show that the Ge microstructures insert Li more isotropically than do comparable ones comprised of Si. A model Ge microbar electrode with a Cu coating is capable of 95 % coulombic efficiency after 40 cycles when the amount of charge is limited. The microstructured Ge electrode is found to exhibit poor performance at higher delithiation rates (above C/5) relative to microstructured Si electrodes. These results provide an understanding of the effects of electrochemical processes on model-microstructured Ge electrodes which may ultimately aid in the development of advanced anodes for Li-ion batteries.     

Recent Advances in Surface Coatings of Layered Cathode Materials for High-Performance Sodium-Ion Batteries

Layered transition metal oxides (layered materials) have the advantages of simple synthesis methods, high average operating voltages, and good specific capacity, and are therefore promising cathode materials for sodium-ion batteries (SIBs). However, the capacity retention of these materials is poor due to the dissolution of transition metals caused by the detrimental reactions of the electrode with the electrolyte and the rupture of the electrode due to volume expansion during cycling. Studies have discovered that surface modification can effectively improve the aforementioned problems. This paper reviews the effects of different coating materials (e. g., carbon coatings, metal oxide coatings, phosphate coatings, etc.) on the performances of layered cathode materials and analyzes the reasons for the improved performance. In addition, the limitations of different coating materials and coating methods are presented, and future developments are proposed.     

Preparation and surface modification of PVDF-carbon felt composite bipolar plates for vanadium flow battery

The performance of vanadium flow batteries(VFBs) is closely related to the materials used in the bipolar plates. Carbon-based composite bipolar plates are particularly suitable for VFB applications. However,most original preparation methods cannot simultaneously achieve good electrical conductivity and mechanical performance. In this paper, we propose a novel approach to fabricating bipolar plates with carbon plastic materials, including four steps, namely coating a poly(vinylidene fluoride)(PVDF) solution onto carbon felt, solvent evaporation, hot-pressing, and surface modification. The resulting bipolar plates showed high conductivity, good mechanical strength, and corrosion resistance. Surface modification by coating with carbon nanotubes(CNTs) removed the PVDF-rich layer from the surface of the carbon fibers.The high surface area of the CNT withdrew PVDF resin from the carbon fiber surface, and promoted the formation of a conductive network. The flexibility and battery charge-discharge cycle measurements showed that the composite bipolar plates can meet requirements for VFB applications.     

SnS2–graphene nanocomposites as anodes of lithium-ion batteries

SnS₂–graphene nanocomposites are synthesized by a hydrothermal method, and their application as anodes of lithium-ion batteries has been investigated. SnS₂ nanosheets are uniformly coating on the surface of graphene. SnS₂–graphene nanocomposites exhibit high cyclability and capacity. The reversible capacity is 766 mAh/g at 0.2C rate and maintains at 570 mAh/g after 30 cycles. Such a high performance can be attributed to high electron and Li-ion conductivity, large surface area, good mechanical flexibility of graphene nanosheets and the synergetic effect between graphene and SnS₂ nanostructures. The present results indicate that SnS₂–graphene nanocomposites have potential applications in lithium-ion battery anodes.     

锂离子电池用陶瓷聚烯烃复合隔膜

为改善聚烯烃微孔膜的耐热安全性,研究了用于锂离子电池的陶瓷聚烯烃复合隔膜ZrO2/SiO2/PP（聚丙烯）。 复合膜具有高度多孔性和良好液体电解液湿润性。 由于高的毛细吸附作用,通过吸附液态电解液,膜很易传导锂离子。 膜中ZrO2/SiO2的两性特征,将电解液中的酸性HF（氟化氢）消耗掉,而HF作为现在锂离子电池所用电解液中的杂质是不可避免的。 复合膜作为隔膜制备的碳/正极材料锂离子电池不仅具有优良的容量保持性、高温安全性,也显示良好的倍率放电性。     

具有均匀壳层的纳米功能材料：构筑与应用

表面修饰是一种重要的材料处理手段,被广泛应用于催化、光化学、电化学等领域。本文阐述了通过表面均匀包覆构建具有特定功能核壳结构的意义,并分析了构筑均匀包覆层的典型合成方法。同时,针对锂离子电池电极材料这一特定应用对象,综述了进行电极材料表面均匀包覆处理的途径,强调了电极材料核壳结构的构筑对于电极材料表面稳定、电化学性能优化等意义。     

导电高分子的最近进展

因为导电高分子结合了金属与塑料的优点,他们一直受到很大的关注。但是他们的应用受到一些因素的影响,包括他们的电学性质,稳定性和可加工性。近来,导电高分子的性能得到很大的提高。他们在许多领域的重要应用被论证,比如透明电极,可拉伸电极,神经界面,热电转换和能量储存。这篇文章简单综述了导电高分子的电导提高和它们在热电转换,超级电容器和电池的应用。