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(2203Wh/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。     

锂硫电池用多孔碳/硫复合正极材料的研究

锂硫电池具有高的理论比容量和理论能量密度,被认为是当前最有前景的二次电池体系之一。现阶段锂硫电池的研究工作主要集中于高性能硫正极材料的设计与合成。具有优良的导电性、良好的结构稳定性和多孔结构的纳米碳材料,比如活性碳、介孔碳、超小微孔碳、多级结构多孔碳、空心碳球和空心碳纤维,充分满足了锂硫电池正极材料对碳基体的要求。本文综述了近年来多孔碳/硫复合材料作为硫正极的研究进展。总结了以具有不同结构特征的多孔碳基体负载硫组装的锂硫电池的电化学性能,并分析了不同多孔结构对性能的影响。最后在此基础上,从多孔碳/硫复合正极材料的设计和合成的角度,展望了其未来的发展趋势。     

一种有助于稳定锂金属循环的富氟化位点框架结构

锂金属是下一代高能量密度二次电池的理想负极材料,然而它的应用仍然受制于较差的循环稳定性。近期,二维氟化界面被广泛用于改善锂金属负极的成核机制、沉积形貌和循环稳定性。本工作通过将体积缩小化的氟化石墨颗粒与锂离子传导网络结合,获得了一种富氟化位点的三维框架结构。实验结果证明此类三维氟化结构可显著提升锂金属负极在不同电流密度和容量下的循环稳定性,且优于二维氟化界面结构。通过本工作的研究,证明了相较于单纯的二维氟化界面,三维锂离子传导网络和富氟化位点的合理结合可以成为一种改进的界面结构用于锂金属负极保护,为高能量密度锂金属电池的负极保护提供了新的设计思路。     

一种有助于稳定锂金属循环的富氟化位点框架结构（英文）

锂金属是下一代高能量密度二次电池的理想负极材料,然而它的应用仍然受制于较差的循环稳定性。近期,二维氟化界面被广泛用于改善锂金属负极的成核机制、沉积形貌和循环稳定性。本工作通过将体积缩小化的氟化石墨颗粒与锂离子传导网络结合,获得了一种富氟化位点的三维框架结构。实验结果证明此类三维氟化结构可显著提升锂金属负极在不同电流密度和容量下的循环稳定性,且优于二维氟化界面结构。通过本工作的研究,证明了相较于单纯的二维氟化界面,三维锂离子传导网络和富氟化位点的合理结合可以成为一种改进的界面结构用于锂金属负极保护,为高能量密度锂金属电池的负极保护提供了新的设计思路。     

高容量硫/碳复合正极材料

以锂为负极、硫为正极的锂/硫二次电池,由于其较高的理论能量密度(2 600Wh/kg),而成为最具发展潜力的新型高能化学电源体系.但是,硫正极材料存在的活性物质利用率偏低和循环性能较差等缺点制约了锂/硫电池的快速发展.本文主要综述了基于多孔碳材料负载硫来构筑硫/碳复合材料,进而改善硫电极材料电化学性能的研究进展,多孔碳...     

锂硫电池硫碳复合正极材料研究现状及展望

二次锂硫电池被视为最具有发展潜力的下一代高能量密度二次电池之一. 但由于正极硫的电导率低（5×10^-30 S·cm^-1）,且在放电过程中产生的中间体多硫化物易溶于有机电解液,致使锂硫电池活性物质利用率降低,溶解后的多硫化物还会迁移到负极,被还原成不溶物Li2S2/Li2S而沉积于负极锂,使电极结构遭受破坏,造成电池容量大幅衰减,循环性能差,从而限制了进一步的开发应用. 研究表明,以碳作为导电骨架的硫碳复合正极材料能在不同程度上解决上述问题,从而有效提高了锂硫电池的放电容量和循环性能. 本文综述了近年来国内外报道的各种锂硫电池正极材料的研究进展,结合作者课题组的研究,重点探讨了硫碳复合正极材料,并对其今后的发展趋势进行了展望.     

氟化石墨材料的改性及其电化学性能研究

本文以商用氟化石墨为原料,通过水合肼还原的方法对氟化石墨（CF_x）进行改性处理,系统研究了不同水合肼用量对材料电化学性能的影响. 采用XRD、SEM、EDS、XPS、交流阻抗（EIS）和恒流放电测试技术,对改性氟化石墨材料的物相及电化学性能进行了分析研究. 结果表明,采用改性氟化石墨材料制备的锂/氟化碳（Li/CF_x）电池的电压滞后现象得到明显改善,且不同水合肼用量对材料的电化学性能有重要影响. H-CF_x-2（CF_x：C₂H₆O：N₂H₄·H₂O 的比例为1：2：1）材料的综合性能最佳,在0.1C 倍率下,材料的克比容量达到794.5 mAh·g^-1,平台电压为2.53V,电压滞后现象的低波电压为2.37 V.     

非水系锂空气电池碳基正极材料

锂空气电池因其极高的理论能量密度和环境友好等优点,有望成为下一代车用动力电源体系。然而,目前锂空气电池尚存在许多的问题和挑战,就正极而言,空气电极活性低的问题已成为制约锂空气电池技术发展最为重要的问题,因此,开发高性能锂空气电池正极催化剂一直以来都是该领域的重要研究课题。碳基催化剂(正极材料)是目前最具吸引力的锂空气电池正极材料之一,近年来得到了广泛的关注和研究。本文总结和介绍了近年来国内外在多孔碳基材料、石墨烯基材料、掺杂碳材料等碳材料作为锂空气电池正极材料方面的进展,包括本课题组在非水系锂空气电池正极材料方面的研究工作,并对碳基正极材料的发展及其在锂空气电池中的应用前景做了展望。     

氟化石墨的电化学性能研究

对系列氟化石墨及其作为碱性电池正极添加剂的电化学性能进行了研究,考察了氟化石墨作为电极活性材料及用作添加剂时电池的放电行为以及氟化石墨的氟化程度和电极中氟化石墨的含量对电池的放电性能的影响.研究了MnO₂中添加氟化石墨后对电极循环性能的影响,并用XRD比较了几种不同碳材料与氟化石墨的结构特点及MnO₂电极放电前后的状态变化,初步探讨了氟化石墨改善二氧化锰电化学性能的作用机制.     

锂硫二次电池正极研究进展

综述了锂硫电池中硫基正极材料的制备方法、结构特征以及电化学性能. 简述了单质硫正极材料, 重点探讨了有机硫化物、碳/硫复合材料、聚合物/硫复合材料的结构设计、材料制备、反应机理以及充放电特性, 并对其中存在的问题进行了分析, 还介绍了硫化锂正极材料. 最后对硫基正极的进一步发展, 以及锂硫电池的商业化应用进行了展望.     

Property control of new forms of carbon materials by fluorination

Multiwall carbon nanotubes (MWNTs) based on the template carbonization technique were fluorinated in a temperature range 323-473 K by elemental fluorine. The fluorination of the carbon nanotubes results in functionalization and modification of pristine nanotubes with respect to adsorption and electrochemical properties. Selective fluorination of the inner surface of the carbon nanotubes, brings about a decrease in the surface free energy of the inner surface of the tubes and an increase in colombic efficiency of Li/nanotubes rechargeable cells in an aprotic medium. Electrochemical fluoride-ion doping of fullerene C₆₀ thin films (250-450 nm) was carried out in a fluoride-ion conductive solution, MeCN solution of 1 M Et₄NF·4HF. Galvanostatic oxidation yielded C₆₀F_ca.1-3 where fluorine exists as a semi-ionic species in the cavity surrounded by C₆₀ molecules without forming covalent CF bonds     

Coaxial Carbon/MnO2 Hollow Nanofibers as Sulfur Hosts for High‐Performance Lithium‐Sulfur Batteries

Lithium‐sulfur (Li‐S) batteries have recently attracted a large amount of attention as promising candidates for next‐generation high‐power energy storage devices because of their high theoretical capacity and energy density. However, the shuttle effect of polysulfides and poor conductivity of sulfur are still vital issues that constrain their specific capacity and cyclic stability. Here, we design coaxial MnO₂‐graphitic carbon hollow nanofibers as sulfur hosts for high‐performance lithium‐sulfur batteries. The hollow C/MnO₂ coaxial nanofibers are synthesized via electrospinning and carbonization of the carbon nanofibers (CNFs), followed by an in situ redox reaction to grow MnO₂ nanosheets on the surface of CNFs. The inner graphitic carbon layer not only maintains intimate contact with sulfur and outer MnO₂ shell to significantly increase the overall electrical conductivity but also acts as a protective layer to prevent dissolution of polysulfides. The outer MnO₂ nanosheets restrain the shuttle effect greatly through chemisorption and redox reaction. Therefore, the robust S@C/MnO₂ nanofiber cathode delivers an extraordinary rate capability and excellent cycling stability with a capacity decay rate of 0.044 and 0.051 % per cycle after 1000 cycles at 1.0 C and 2.0 C, respectively. Our present work brings forward a new facile and efficient strategy for the functionalization of inorganic metal oxide on graphitic carbons as sulfur hosts for high performance Li‐S batteries.     

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.     

锂金属负极的挑战与改善策略研究进展

锂金属由于其高比容量和低电极电势等优点被认为是下一代高比能量电池体系中最有潜力的负极材料。然而由于锂金属的高活性,锂负极在循环过程中会产生大量的枝晶,导致SEI(solid-electrolyte interphase)破裂,并且枝晶增加了电极与电解液的接触面积,使得副反应进一步增加。此外,脱落的枝晶形成死锂,从而降低电池的充放电库仑效率。并且不可控的锂枝晶持续生长会刺穿隔膜引发电池短路,伴随着电池热失控等安全问题。本综述基于锂负极存在的主要挑战,结合理解锂枝晶的成核生长模型等机理总结并深度分析近些年来在液态和固态电解质体系中改善锂金属负极的主要策略及其作用机理,为促进高比能量锂金属电池的应用提供借鉴参考作用。     

Effect of oxygen-containing functional groups of carbon materials on the performance of Li–O2 batteries

In this communication, we present some new findings on surface oxidized carbon nanotubes (CNTs) when used as cathode of Li–O₂ batteries. It is found that the content of oxygen-containing functional groups has a significant influence on the electrochemical performance of Li–O₂ batteries, by altering the electrical conductivity and density of electrocatalytically active sites of the CNTs and promoting side reactions of the electrolyte. An optimal surface oxygen atomic content of 6.0 at.% on CNTs is found to reach a balance and give the best cycling stability of the Li–O₂ battery under constant capacity and constant current density tests.     

The electrochemistry of activated carbonaceous materials: past, present, and future

Carbonaceous materials are widely used in electrochemistry. All allotropic forms of carbons??graphite, glassy carbon, amorphous carbon, fullerenes, nanotubes, and doped diamond??are used as important electrode materials in all fields of modern electrochemistry. Examples include graphite and amorphous carbons as anode materials in high-energy density rechargeable Li batteries, porous carbon electrodes in sensors and fuel cells, nano-amorphous carbon as a conducting agent in many kinds of composite electrodes (e.g., cathodes based on intercalation inorganic host materials for batteries), glassy carbon and doped diamond as stable robust and high stability electrode materials for all aspects of basic electrochemical studies, and more. Amorphous carbons can be activated to form very high specific surface area (yet stable) electrode materials which can be used for electrostatic energy storage and conversion [electrical double-layer capacitors (EDLC)] and separation techniques based on electro-adsorption, such as water desalination by capacitive de-ionization (CDI). Apart from the many practical aspects of activated carbon electrodes, there are many highly interesting and important basic aspects related to their study, including transport phenomena, molecular sieving behavior, correlation between electrochemical behavior and surface chemistry, and more. In this article, we review several important aspects related to these electrode materials, in a time perspective (past, present, and future), with the emphasis on their importance to EDLC devices and CDI processes.     

Developments in nanostructured LiMPO4 (M = Fe, Co, Ni, Mn) composites based on three dimensional carbon architecture

Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. This review describes recent developments in the synthesis and characterization of composites which consist of lithium metal phosphates (LiMPO(4), M = Fe, Co, Ni, Mn) coated on nanostructured carbon architectures (unordered and ordered carbon nanotubes, amorphous carbon, carbon foams). The major goal of this review is to highlight new progress in using different three dimensional nanostructured carbon architectures as support for the phosphate based cathode materials (e.g.: LiFePO(4), LiCoPO(4)) of high electronic conductivity to develop lithium batteries with high energy density, high rate capability and excellent cycling stability resulting from their huge surface area and short distance for mass and charge transport.     

A novel carbon electrode material for highly improved EDLC performance

Porous materials, developed by grafting functional groups through chemical surface modification with a surfactant, represent an innovative concept in energy storage. This work reports, in detail, the first practical realization of a novel carbon electrode based on grafting of vinyltrimethoxysilane (vtmos) functional group for energy storage in electric double layer capacitor (EDLC). Surface modification with surfactant vtmos enhances the hydrophobisation of activated carbon and the affinity toward propylene carbonate (PC) solvent, which improves the wettability of activated carbon in the electrolyte solution based on PC solvent, resulting in not only a lower resistance to the transport of electrolyte ions within micropores of activated carbon but also more usable surface area for the formation of electric double layer, and accordingly, higher specific capacitance, energy density, and power capability available from the capacitor based on modified carbon. Especially, the effects from surface modification become superior at higher discharge rate, at which much better EDLC performance (i.e., much higher energy density and power capability) has been achieved by the modified carbon, suggesting that the modified carbon is a novel and very promising electrode material of EDLC for large current applications where both high energy density and power capability are required.     

Rutile-TiO2 nanocoating for a high-rate Li4Ti5O12 anode of a lithium-ion battery

Well-defined Li(4)Ti(5)O(12) nanosheets terminated with rutile-TiO(2) at the edges were synthesized by a facile solution-based method and revealed directly at atomic resolution by an advanced spherical aberration imaging technique. The rutile-TiO(2) terminated Li(4)Ti(5)O(12) nanosheets show much improved rate capability and specific capacity compared with pure Li(4)Ti(5)O(12) nanosheets when used as anode materials for lithium ion batteries. The results here give clear evidence of the utility of rutile-TiO(2) as a carbon-free coating layer to improve the kinetics of Li(4)Ti(5)O(12) toward fast lithium insertion/extraction. The carbon-free nanocoating of rutile-TiO(2) is highly effective in improving the electrochemical properties of Li(4)Ti(5)O(12), promising advanced batteries with high volumetric energy density, high surface stability, and long cycle life compared with the commonly used carbon nanocoating in electrode materials.     

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.