Formation of Nanostructured MnO/Co/Solid–Electrolyte Interphase Ternary Composites as a Durable Anode Material for Lithium‐Ion Batteries

Nanoporous MnO frameworks with highly dispersed Co nanoparticles were produced from MnCO₃ precursors prepared in a gel matrix. The MnO frameworks that contain 20 mol % Co exhibited excellent cycle performance as an anode material for Li‐ion batteries. The solid–electrolyte interphase (SEI) formed in the frameworks through the electrochemical reaction mediates the active materials, such as MnO, Mn, and Li₂O, during the conversion reaction in the charge–discharge cycle. The Co nanoparticles and SEI provide the electron and Li‐ion conductive networks, respectively. The ternary nanocomposites of the MnO framework, metallic Co nanoparticles, and embedded SEI are categorized as durable anode materials for Li‐ion batteries.     

力曲线用于硅负极材料表面膜的研究

利用原子力显微镜（AFM）力曲线模式来研究锂离子电池硅负极材料在含碳酸亚乙烯酯添加剂（VC）电解质首周循环时固态电解质相表面膜（SEI膜）的三维结构. 测试表明SEI膜具有多层结构,同时得到SEI膜厚度、杨氏模量以及覆盖度在首周循环过程中的变化,采用三维图呈现了硅材料表面膜的分布.     

二氟草酸硼酸钠作为电解液添加剂对石墨负极性能的影响

锂离子电池日益广泛的应用对其性能提出越来越高的要求,而在电解液中加入适当的添加剂能够显著提升电极材料的电化学性能. 本文首次在1 mol·L^-1 LiPF₆/EC + DMC + EMC（体积比1:1:1）的电解液中添加一定量的二氟草酸硼酸钠(NaDFOB),并通过循环伏安（CV）、电化学阻抗图谱（EIS）和扫描电子显微镜（SEM）等分析考察了其对石墨负极材料性能的具体影响. 结果显示,添加NaDFOB的电解液显著提高了石墨材料在常温下的可逆充放电容量和循环性能,同时明显改善了石墨材料的高温循环性能. 其机理在于NaDFOB的阴阳离子同时参与了石墨表面固体电解质界面膜（SEI）的形成,形成高稳定性的电解液/电极界面.     

Constructing Solid Electrolyte Interphase for Aqueous Zinc Batteries

Problems of zinc anode including dendrite and hydrogen evolution seriously degrade the performance of zinc batteries. Solid electrolyte interphase (SEI), which plays a key role in achieving high reversibility of lithium anode in aprotic organic solvent, is also beneficial to performance improvement of zinc anode in aqueous electrolyte. However, various studies about interphase for zinc electrode is quite fragmented, and lack of deep understanding on root causes or general design rules for SEI construction. And water molecules with high reactivity brings serious challenge to the effective SEI construction. Here, we reviewed the brief development history of zinc batteries firstly, then summarized the approaches to construct SEI in aqueous electrolyte. Furthermore, the formation mechanisms behind approaches are systematically analyzed, together with discussion on the SEI components and evaluation on electrochemical performance of zinc anode with various types of SEI. Meanwhile, the challenge between lab and industrialization are also discussed.     

A Flexible Solid Electrolyte Interphase Layer for Long‐Life Lithium Metal Anodes

Lithium (Li) metal is a promising anode material for high‐energy density batteries. However, the unstable and static solid electrolyte interphase (SEI) can be destroyed by the dynamic Li plating/stripping behavior on the Li anode surface, leading to side reactions and Li dendrites growth. Herein, we design a smart Li polyacrylic acid (LiPAA) SEI layer high elasticity to address the dynamic Li plating/stripping processes by self‐adapting interface regulation, which is demonstrated by in situ AFM. With the high binding ability and excellent stability of the LiPAA polymer, the smart SEI can significantly reduce the side reactions and improve battery safety markedly. Stable cycling of 700 h is achieved in the LiPAA‐Li/LiPAA‐Li symmetrical cell. The innovative strategy of self‐adapting SEI design is broadly applicable, providing opportunities for use in Li metal anodes     

电解液组成对中间相石墨微球电化学性能的影响

以2800℃热处理的煤焦油沥青基中间相石墨微球为锂离子二次电池负极材料,考察了中间相石墨微球在不同组成的电解质溶液中的电化学嵌脱锂性能.确定了试样在不同电解液中电极表面生成的SEI膜的化学组成和相对含量,剖析了共溶剂对SEI膜形成反应、膜组成和织构的影响.结果表明,在不同共溶剂的EC基电解液中,电极界面SEI膜形成的电位虽然不同,但SEI膜的化学组成基本相同,负极界面SEI膜的织构是决定电解液与电极材料相容性的关键.     

Studies on the Anode/Electrolyte Interfacein Lithium Ion Batteries

Summary.  Rechargeable lithium ion cells operate at voltages of 3.5–4.5 V, which is far beyond the thermodynamic stability window of the battery electrolyte. Strong electrolyte reduction and anode corrosion has to be anticipated, leading to irreversible loss of electroactive material and electrolyte and thus strongly deteriorating cell performance. To minimize these reactions, anode and electrolyte components have to be combined that induce the electrolyte reduction products to form an effectively protecting film at the anode/electrolyte interface, which hinders further electrolyte decomposition reactions, but acts as membrane for the lithium cations, i.e. behaving as a solid electrolyte interphase (SEI). This paper focuses on important aspects of the SEI. By using key examples, the effects of film forming electrolyte additives and the change of the active anode material from carbons to lithium storage alloys are highlighted. Received May 30, 2000. Accepted June 14, 2000     

Lithium Azide as an Electrolyte Additive for All‐Solid‐State Lithium–Sulfur Batteries

Of the various beyond‐lithium‐ion battery technologies, lithium–sulfur (Li–S) batteries have an appealing theoretical energy density and are being intensely investigated as next‐generation rechargeable lithium‐metal batteries. However, the stability of the lithium‐metal (Li°) anode is among the most urgent challenges that need to be addressed to ensure the long‐term stability of Li–S batteries. Herein, we report lithium azide (LiN₃) as a novel electrolyte additive for all‐solid‐state Li–S batteries (ASSLSBs). It results in the formation of a thin, compact and highly conductive passivation layer on the Li° anode, thereby avoiding dendrite formation, and polysulfide shuttling. It greatly enhances the cycling performance, Coulombic and energy efficiencies of ASSLSBs, outperforming the state‐of‐the‐art additive lithium nitrate (LiNO₃).     

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。     

稳定锂电化学沉积和溶解行为的LiC6异质微结构界面层

本文采用机械辊压方法在金属锂表面通过原位固相反应生成LiC₆异质微结构界面层,并研究了在碳酸酯有机电解液体系下该异质层对锂电化学沉积和溶解行为的影响。通过形貌表征与电化学测试发现,LiC₆异质层能够有效提升锂电化学沉积的可逆性与均匀性,从而抑制枝晶生长及维持沉积/溶解界面的稳定。使用异质层改性金属锂负极的扣式全电池也较纯金属锂负极体系表现出更为优异的循环稳定性。     

Unraveling the stabilization mechanism of solid electrolyte interface on ZnSe by rGO in sodium ion battery

Transition metal selenides have been widely studied as anode materials of sodium ion batteries(SIBs),however,the investigation of solid-electrolyte-interface(SEI)on these materials,which is critical to the electrochemical performance of SIBs,remains at its infancy.Here in this paper,ZnSe@C nanoparticles were prepared from ZIF-8 and the SEI layers on these electrodes with and without reduced graphene oxide(rGO)layers were examined in details by X-ray photoelectron spectroscopies at varied charged/discharged states.It is observed that fast and complicated electrolyte decomposition reactions on ZnSe@C leads to quite thick SEI film and intercalation of solvated sodium ions through such thick SEI film results in slow ion diffusion kinetics and unstable electrode structure.However,the presence of rGO could efficiently suppress the decomposition of electrolyte,thus thin and stable SEI film was formed.ZnSe@C electrodes wrapped by rGO demonstrates enhanced interfacial charge transfer kinetics and high electrochemical performance,a capacity retention of 96.4%,after 1000 cycles at 5 A/g.This study might offer a simple avenue for the designing high performance anode materials through manipulation of SEI film.     

Spatiotemporal Changes of the Solid Electrolyte Interphase in Lithium‐Ion Batteries Detected by Scanning Electrochemical Microscopy

The solid electrolyte interphase (SEI) in lithium‐ion batteries separates the highly reductive lithiated graphite from reducible electrolyte components. It is critical for the performance, durability, and safe operation of batteries. In situ imaging of the SEI is demonstrated using the feedback mode of scanning electrochemical microscopy (SECM) with 2,5‐di‐tert‐butyl‐1,4‐dimethoxy benzene as mediator. The formation of the SEI is indicated by a decrease of the mediator regeneration rate. Prolonged imaging of the same region revealed fluctuation of the passivating properties on time scales between 2 min and 20 h with an inhomogeneous distribution over the sample. The implications of the approach for in situ assessment of local SEI properties on graphite electrodes are discussed with respect to studying the influence of mechanical stress on SEI reliability and the mode of action of electrolyte additives aiming at improving SEI properties.     

Effects of current densities on the formation of LiCoO<Subscript>2</Subscript>/graphite lithium ion battery

The activation characteristics and the effects of current densities on the formation of a separate LiCoO₂ and graphite electrode were investigated and the behavior also was compared with that of the full LiCoO₂/graphite batteries using various electrochemical techniques. The results showed that the formation current densities obviously influenced the electrochemical impedance spectrum of Li/graphite, LiCoO₂/Li, and LiCoO₂/graphite cells. The electrolyte was reduced on the surface of graphite anode between 2.5 and 3.6 V to form a preliminary solid electrolyte interphase (SEI) film of anode during the formation of the LiCoO₂/graphite batteries. The electrolyte was oxidized from 3.95 V vs Li⁺/Li on the surface of LiCoO₂ to form a SEI film of cathode. A highly conducting SEI film could be formed gradually on the surface of graphite anode, whereas the SEI film of LiCoO₂ cathode had high resistance. The LiCoO₂ cathode could be activated completely at the first cycle, while the activation of the graphite anode needed several cycles. The columbic efficiency of the first cycle increased, but that of the second decreased with the increase in the formation current of LiCoO₂/graphite batteries. The formation current influenced the cycling performance of batteries, especially the high-temperature cycling performance. Therefore, the batteries should be activated with proper current densities to ensure an excellent formation of SEI film on the anode surface.     

Highly Stable Lithium Metal Anode Interface via Molecular Layer Deposition Zircone Coatings for Long Life Next‐Generation Battery Systems

Herein, molecular layer deposition is used to form a nanoscale “zircone” protective layer on Li metal to achieve stable and long life Li metal anodes. The zircone‐coated Li metal shows enhanced air stability, electrochemical performance and high rate capability in symmetrical cell testing. Moreover, as a proof of concept, the protected Li anode is used in a next‐generation Li‐O₂ battery system and is shown to extend the lifetime by over 10‐fold compared to the batteries with untreated Li metal. Furthermore, in‐situ synchrotron X‐ray absorption spectroscopy is used for the first time to study an artificial SEI on Li metal, revealing the electrochemical stability and lithiation of the zircone film. This work exemplifies significant progress towards the development and understanding of MLD thin films for high performance next‐generation batteries.     

含FEC电解液的锂离子电池低温性能研究

研究含FEC溶剂电解液(FEC+EMC,EC,PC)的低温性能及其与磷酸铁锂正极或中间相碳微球(MCMB)负极的匹配.该电解液具有较高的低温电导率,FEC可在1.6 V与负极反应成膜,有效地提高负极稳定性.红外测试发现,FEC可抑制其它电解液溶剂在负极成膜过程中的分解,在常温(20℃)和低温(-20℃)下形成的SEI膜阻抗均较低.电化学测试表明,以该电解液装配的锂离子电池(电极)具有较高的低温放电容量和倍率性能.     

锂离子电池中固体电解质界面膜(SEI)研究进展

本文综述了锂离子电池中固体电解质界面膜(SEI膜)的研究进展.在总结SEI膜的形成机理及模型的基础上,讨论了对SEI膜可能的影响因素及其改性方法,以及各种表征技术、特别是原位分析技术在SEI膜研究中的实际应用.指出在今后的研究中,正极表面与电解液间的界面膜,以及引入水溶性粘合剂体系后正负极表面与电解液间的相互作用将成为人们关注的热点。     

Electrolyte Chemistry Enables Simultaneous Stabilization of Potassium Metal and Alloying Anode for Potassium‐Ion Batteries

Alloying anodes are promising high‐capacity electrode materials for K‐ion batteries (KIBs). However, KIBs based on alloying anodes suffer from rapid capacity decay due to the instability of K metal and large volume expansion of alloying anodes. Herein, the effects of salts and solvents on the cycling stability of KIBs based on a typical alloying anode such as amorphous red phosphorus (RP) are investigated, and the potassium bis(fluorosulfonyl)imide (KFSI) salt‐based carbonate electrolyte is versatile to achieve simultaneous stabilization of K metal and RP electrodes for highly stable KIBs. This salt‐solvent complex with a moderate solvation energy can alleviate side reactions between K metal and the electrolyte and facilitate K⁺ ion diffusion/desolvation. Moreover, robust SEI layers that form on K metal and RP electrodes can suppress K dendrite growth and resist RP volume change. This strategy of electrolyte regulation can be applicable to other alloying anodes for high‐performance KIBs.     

Surface analysis of the solid electrolyte interface formed by additives on graphite electrodes in Li‐ion batteries using XPS,FE‐AES,and XHR‐SEM techniques

We investigate the formation and distribution of the solid electrolyte interface (SEI) layer on a graphite anode with two additives [vinylethylene carbonate (VEC) and vinylene carbonate (VC)] in a formation process using XPS, field emission AES, and extreme high‐resolution SEM (XHR‐SEM) techniques, and we studied what factors play an important role in determining the formation of the SEI layer. The VEC‐derived SEI behaviors (morphology, thickness, compound, and balance over electrode position) on a graphite anode largely depend on the elevated temperature. The VC‐derived SEI layer is mostly formed in the initial charging step, showing simple growth (formation) behavior. It is suggested that the properties of the additives are important for SEI bonding configurations at the nanoscale film surface, and to achieve the stable SEI layer, there appears to be an effective formation process for the additive properties. This research highlights the challenges of developing a stable SEI layer with additives in the formation process for electric vehicle batteries and would make a contribution to the understanding of how formation conditions affect an SEI layer with respect to additive properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of Solid Electrolyte Interphase Components on the Reduction of LiFSI over Lithium Metal

The use of a lithium metal anode still presents a challenging chemistry and engineering problem that holds back next generation lithium battery technology. One of the issues facing lithium metal is the presence of the solid electrolyte interphase (SEI) layer that forms on the electrode creating a variety of chemical species that change the properties of the electrode and is closely related to the formation and growth of lithium dendrites. In order to advance the scientific progress of lithium metal more must be understood about the fundamentals of the SEI. One property of the SEI that is particularly critical is the passivating behavior of the different SEI components. This property is critical to the continued formation of SEI and stability of the electrolyte and electrode. Here we report the investigation of the passivation behavior of Li₂O, Li₂CO_3, LiF and LiOH with the lithium salt LiFSI. We used large computational chemistry models that are able to capture the lithium/SEI interface as well as the SEI/electrolyte interface. We determined that LiF and Li₂CO₃ are the most passivating of the SEI layers, followed by LiOH and Li₂O. These results match previous studies of other Li salts and provide further examination of LiFSI reduction.