改性电解液促进均匀锂沉积的研究进展

随着二次电池的逐渐发展,金属锂为负极的电池体系以其优异的能量密度脱颖而出,但其稳定性和安全性较差的问题亟待解决。电解液作为锂离子在正负极之间传输的载体,决定了锂离子的液相传输过程和迁移速率,同时还会与金属锂负极发生界面反应生成固体电解质界面膜(SEI),电解液的组分变化会极大程度上影响SEI膜的组成和结构。电解液改性能够有效调控金属锂沉积过程,是改善金属锂负极电化学性能的重要途径。本文从电解液对锂离子沉积的影响因素出发,分析了液相传质、SEI膜的形成、电荷转移等基本过程对锂离子沉积的调控机理,总结归纳了溶剂分子、锂盐浓度、添加剂等对金属锂沉积过程的影响,介绍了溶剂混用、复合锂盐、局部高浓度电解液、双功能添加剂等电解液改性促进均匀锂沉积的方法,分析了各种改性方法对实现均匀锂沉积的作用机理,并展望了这些方法的发展趋势。

锂离子电池石墨负极锂沉积研究进展

全面推进交通运输电气化是实现“碳中和”的根本途径,而以电化学能量储存和转化为核心的电池、电容器等储能技术的开发是其中的重要环节。锂离子电池具有储能密度高、充放电效率高、响应速度快、产业链完整等优点,是最近几年发展最快的电化学储能技术。石墨具有导电性好、成本低、循环寿命长、溶胀率低、安全性高等优点,是锂离子电池负极的首选材料。然而石墨负极金属锂的沉积不仅降低电池循环及快充性能,而且带来电池短路甚至爆炸等安全隐患。本综述概述了石墨负极的电化学动力学过程,总结了依托原位技术对锂沉积机理的解析,讨论了锂沉积过程的影响因素以及解决办法。最后提出了本领域今后发展过程中可能面临的挑战及机遇。

研磨及包覆改性石墨抑制金属锂沉积

通过机械研磨和碳包覆两种手段,对人造石墨形貌进行改性,采用SEM、Raman、BET对改性前后石墨形貌、表面结构、比表面积进行表征,同时采用EDS和恒流充放电电化学分析方法对负极极片析锂情况、电池放电容量进行分析,结果表明:碳包覆后样品表面变得光滑,石墨化度未影响,表面无序度增加,减少了金属锂析出;碳包覆前增加机械球磨工艺,使一次颗粒粒度减小,缩短锂离子扩散路径,碳包覆改性引入无序碳结构,两种作用协同效应更有效地抑制点状金属锂沉积的发生,同时提升了电池容量。

新能源汽车动力电池锂沉积现象研究

文章主要研究新能源汽车动力电池在低温以及快充条件下电性能的衰减与伴随产生的锂沉积现象。通过模拟低温快充测试条件,对电池进行充放电处理;再对电芯进行物理拆解,利用扫描电子显微镜、X射线光电子能谱、气相色谱质谱联用仪等材料分析手段对电芯电极片进行锂枝晶的形貌、金属元素价态和气体成分的分析。基于电芯的电性能与材料层级现象之间的关联研究,有助于从机理上理解电池电性能的表现。文章通过优化电池监测的控制条件,发展一种无损检测的技术方案,用于监测动力电池由于产生锂沉积而导致的性能衰减,以及时预警安全隐患来提高电动汽车的安全性。

黑磷-石墨混合物作为锂离子调节器实现稳定的锂沉积

锂金属(Li)负极因其高比容量和低氧化还原电位而被认为是高能量密度锂二次电池最有应用前景的候选材料。然而,锂金属在电池循环过程中的不均匀沉积导致的锂枝晶问题严重阻碍了锂金属负极的实际应用。本文将黑磷-石墨(BP-G)混合物引入作为锂金属负极的人工保护层。具有亲锂性的二维少层黑磷与具有高电子电导的石墨相结合,可以作为离子调节器来调节锂离子的迁移,从而实现均匀稳定的锂沉积。由于锂枝晶的生长受到抑制,锂金属在Li||Cu半电池中的库仑效率在500多个循环中达到>98.5%;在Li||Li对称电池中,极化电压保持在<50 m V,循环寿命达到2000 h以上。此外,带有BP-G锂离子调节器的LiFePO_(4)(LFP)||Li全电池比未修饰的锂金属负极电池具有更高的比容量和更好的循环稳定性。因此,BP-G锂离子调节器的引入被证明是实现可充电锂金属电池稳定锂沉积的有效方法。

三维集流体实现无枝晶锂金属负极

近年来,随着锂空气电池和锂硫电池的快速发展,具有高能量密度的锂金属电池再次受到动力电池研究人员的广泛关注。但是,在电池的循环过程中,锂金属负极存在锂枝晶、体积膨胀以及剧烈的副反应,这会导致电池充放电效率的降低并使得电池存在安全隐患。为了获得稳定的锂金属负极,提出了各种改性策略,例如,电解质添加剂、隔膜改性、人工SEI膜和3D集流体等。其中,集流体的改性直接影响着负极表面结构,并且3D集流体所具有的大的比表面积可以有效地降低局部电流密度,诱导锂的均匀成核与沉积。本文综述了3D集流体改性中具有指导意义的部分研究,旨在为进一步的3D集流体的设计提供参考。

柔性MOF/PVDF隔膜在锂金属电池中的应用

利用简单刮涂的方式将四种不同的金属有机骨架材料(MOF)分别与聚偏二氟乙烯(PVDF)复合制备得到柔性MOF/PVDF多孔隔膜,研究其在锂金属电池中对锂离子传输沉积行为的影响。结果表明,MOF基隔膜很好地引导了锂离子在锂金属负极的沉积,另外,电极的界面电荷传输性质也得到了改善,界面反应动力学有所提升。在0.5C电流密度下,MOF/PVDF隔膜组装的LTO电池在150圈时的放电容量依旧保持在165~170 mAh g^(-1)左右,相较于普通隔膜电池的157.8 mAh g^(-1)有明显的提升。

广西上林矿区沉积型锂矿沉积环境及物源分析

广西贤按煤田晚二叠世合山组地层中锂资源超常富集,具有寻找沉积型锂矿的良好前景。研究表明,赋矿地层中Sr元素含量及Sr/Ba值指示研究区海陆交互相沉积环境;Li主要富集在氧化、弱还原条件下形成的铁质铝土岩和部分黏土岩中。CIA值介于86.3~99.66,表明富锂黏土岩在形成过程中处于温暖潮湿的沉积环境并伴随较为强烈化学风化作用。通过物源分析认为,合山组含矿岩系的物质来源可能主要为中酸性岩浆岩,同时也有夹杂了峨眉山玄武岩火山灰的物质。

LiC_(6)在复合锂负极中的作用、形成和表征

锂金属电池(LMB)被认为是最有前景的下一代储能系统之一。然而,其实际应用存在极大的体积变化和锂枝晶的形成等重大挑战。为了应对这些挑战,引入炭材料的复合锂负极因其优异的化学和电化学稳定性以及在重复循环过程中的优异机械强度引起了极大关注。本文旨在全面概述锂化石墨(LiC_(6))的形成及其在锂沉积和剥离过程中在体相和界面区域的作用。在体相中,LiC_(6)表现出优异的亲锂性能,降低了锂成核的过电位并促进锂的均匀沉积。当在电极-电解质界面引入LiC_(6)时,它通过充当缓冲层来增强电极和电解质之间的接触,从而降低界面阻抗。最后,本文评述了锂碳复合负极发展的前景和挑战。

锂离子电池用先进集流体的应用研究

文章概述了金属箔集流体改性、三维多孔集流体、复合集流体这三种先进集流体,及其在锂离子电池中应用的最新研究成果,为先进集流体的进一步发展和产业化应用提供参考。

高锂利用率锂金属负极及其在锂硫电池中的研究进展

随着社会的进步与环保意识的提高,至2030年,众多老牌汽车厂商都会停止生产内燃机汽车。目前国内外的汽车市场无不对电动汽车或混合动力汽车加大研究投入,高比能量锂离子电池作为新时代汽车储能装置的关键组成部分,一直广受关注。目前锂离子电池负极材料如石墨、硅碳等已经广泛应用于锂离子电池中,但石墨负极低的储锂质量比容量(372 mA•h/g)和硅碳负极巨大的体积膨胀效应一直限制了它们的进一步发展。而正极材料如LiFePO4、LiMO2 (M = Ni、Co、Mn)等虽然也已经投入商用,但低储锂质量比容量(<300 mA•h/g)、安全性、倍率性能等问题也限制着它们的发展。被誉为下一代储能系统最有力候选者的锂硫电池是由有着质量比容量分别为3860 mA•h/g和1675 mA•h/g的锂金属负极和硫正极组成的。然而由于锂金属负极存在着枝晶生长的问题,并且硫正极产生的多硫化物会在电解液中溶解引起穿梭效应,这些都严重影响着锂金属电池锂的利用率及锂硫电池的硫利用率。本综述详细介绍了锂金属电池面临的问题以及锂硫电池目前的研究进展。

锂离子电池的低温性能研究

向电解液中添加碳酸亚乙烯酯(VC),可提高负极界面的导电性与稳定性。在-20℃下放电,电解液中加VC的电池的放电电压平台比不加VC的电池提高约25%。三电极实验结果表明:在低温下由于电池阻抗增大,极化增强,充电过程在负极出现金属锂沉积;金属锂与电解液发生还原反应形成SEI膜,SEI膜的状态与充电电流有关。

锂金属负极材料的改性研究进展

金属锂为负极的Li-S和Li-O_(2)电池因其极高的理论比容量,被认为是极具潜力的下一代可充电电池体系。然而锂金属负极应用过程中发生的安全问题,严重制约了锂金属二次电池的商业化应用。依据锂金属负极面临的挑战,本文分析了锂枝晶的形成机制和生长过程。并以此为基础,从电极的结构和界面的角度综述了目前锂金属负极材料的各种改性方案,对实现无阳极锂金属电池具有重要指导意义。

Preparation and electrochemical lithium storage performance of porous silicon microsphere composite with metal modification and carbon coating

This work adopts a multi⁃step etching⁃heat treatment strategy to prepare porous silicon microsphere com⁃posite with Sb⁃Sn surface modification and carbon coating(pSi/Sb⁃Sn@C),using industrial grade SiAl alloy micro⁃spheres as a precursor.pSi/Sb⁃Sn@C had a 3D structure with bimetallic(Sb⁃Sn)modified porous silicon micro⁃spheres(pSi/Sb⁃Sn)as the core and carbon coating as the shell.Carbon shells can improve the electronic conductivi⁃ty and mechanical stability of porous silicon microspheres,which is beneficial for obtaining a stable solid electrolyte interface(SEI)film.The 3D porous core promotes the diffusion of lithium ions,increases the intercalation/delithia⁃tion active sites,and buffers the volume expansion during the intercalation process.The introduction of active met⁃als(Sb⁃Sn)can improve the conductivity of the composite and contribute to a certain amount of lithium storage ca⁃pacity.Due to its unique composition and microstructure,pSi/Sb⁃Sn@C showed a reversible capacity of 1247.4 mAh·g^(-1) after 300 charge/discharge cycles at a current density of 1.0 A·g^(-1),demonstrating excellent rate lithium storage performance and enhanced electrochemical cycling stability.

功能化固态电解质膜改性锂金属负极的研究进展

对高比能量锂离子电池需求的不断增加激发了锂金属负极的应用研究。锂金属具有高放电比容量(3860 mAh·g^(−1)),低电极电位(−3.04 V),是锂离子电池的理想负极材料。然而,锂金属在循环过程中会形成不稳定的固态电解质(SEI)膜,而且会生成枝晶,枝晶的生长会引发电池短路等安全问题,极大地阻碍了其应用。理想的SEI膜应具有良好的锂离子传导性、表面电子绝缘性和机械强度,可调控锂离子在表面均匀沉积,促进离子传输,抑制枝晶生长,因此构筑功能化SEI膜是解决锂金属负极所面临挑战的一项有效策略。本综述以锂金属枝晶形成和生长的机理为出发点,分析总结SEI膜的构建策略、不同组成SEI膜的结构和功能特性及其对锂金属负极性能的影响,并对锂金属实用化面临的挑战及未来发展方向进行了展望。

Effect of Magnetic Field on Properties of AuPt Particles Magneto- electrodeposited on Carbon Paper

AuPt nano particles are bi-functional catalysts for Oxygen Reduction Reaction （ORR） and Oxygen Evolution Reaction （OER） that were taken place on air electrodes in lithium air batteries. Magnetic field has been applied during electrodeposition for the preparation of AuPt particles. With the increase of the magnetic flux density under constant current density, the grain size decreases from - 1μm to 200nm and the activity of the AuPt catalyst increases. The magnetic field oriented vertical to the electric field has a promotion effect on increasing the catalytic ability of AuPt/carbon electrode. By pulse plating, the grain size decreases to about 100nm. By adjusting parameters of the electric field and the magnetic field, controllable in-situ preparation of AuPt catalyst with various morphology and catalytic activity could be achieved.

Multifunctional interfacial and structural anode for dendrite-free lithium metal-based batteries

Lithium(Li)metal is considered as the candidate for the next generation of Li metal battery(LMB)anodes due to its high capacity and the lowest potential,which is expected to meet the requirements of energy storage devices.Unfortunately,the uncontrollable growth of Li dendrites during the charge/discharge process,as well as the resulting problems of poor cycling stability,low coulomb efficiency and safety risk,has restricted the commercialization of Li anode.Herein,an in-situ interfacial film containing three-dimensional(3D)rod-like micron-structure silver(Ag)is constructed on the surface of the Li metal.Due to the 3D rod-like micron-structure used to homogenize the distribution of current density,achieving uniform nucleation and growth of electrodeposited Li,the produced Li-Ag alloy was employed to restrain the formation of“dead”Li and the in-situ formed LiNO_(3) was utilized to facilitate the stability of solid-electrolyte interface(SEI)film,so the growth of dendritic Li is suppressed via the synergistic effect of structure and surface chemistry regulation.The obtained Li anode can achieve cycling stability at a high current density of 10 mA/cm^(2).This work considers multiaspect factors inducing uniform Li electrodeposition,and provides new insights for the commercialization of LMB.

Single crystal metal-organic framework constructed by vertically self-pillared nanosheets and its derivative for oriented lithium plating

This vertically self‐pillared(VSP)structure extends the application range of traditional porous materials with facile mass/ion transport and enhanced reaction kinetics.Here,we prepare a single crystal metal‐organic framework(MOF),employing the ZIF‐67 structure as a proof of concept,which is constructed by vertically self‐pillared nanosheets(VSP‐MOF).We further converted VSP‐MOF into VSP‐cobalt sulfide(VSP‐CoS2)through a sulfidation process.Catalysis plays an important role in almost all battery technologies;for metallic batteries,lithium anodes exhibit a high theoretical specific capacity,low density,and low redox potential.However,during the half‐cell reaction(Li++e=Li),uncontrolled dendritic Li penetrates the separator and solid electrolyte interphase layer.When employed as a composite scaffold for lithium metal deposition,there are many advantage to using this framework:1)the VSP‐CoS2 substrate provides a high specific surface area to dissipate the ion flux and mass transfer and acts as a pre‐catalyst,2)the catalytic Co center favors the charge transfer process and preferentially binds the Li+with the enhanced electrical fields,and 3)the VSP structure guides the metallic propagation along the nanosheet 2D orientation without the protrusive dendrites.All these features enable the VSP structure in metallic batteries with encouraging performances.

High specific strength MWCNTs/Mg-14Li-1Al composite prepared by electrophoretic deposition, friction stir processing and cold rolling

Multi-wall carbon nanotubes reinforced Mg-14Li-1Al composite(MWCNTs/Mg-14Li-1Al) was prepared by the processes of electrophoretic deposition, friction stir processing, and cold rolling. The microstructure and mechanical properties of the composite were investigated. The results show that, the microhardness of the composite is up to HV 84.4, which is 91.38% higher than that of the as-cast matrix alloy(HV 44.1). The yield strength and ultimate tensile strength of the composite are 259 and 313 MPa, which are 135.45% and 115.86% higher than those of the as-cast matrix alloy, respectively, and a high specific strength of 221.98 k N·m/kg is obtained. In the composite, the MWCNTs serve as nucleation particles during the friction stir processing and cold rolling, causing dynamic recrystallization and grain refinement. Furthermore, MWCNTs hinder the movement of dislocations and transfer the load from the matrix alloy, thus improving the strength.