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。

Progress in Functional Solid Electrolyte Interphases for Boosting Li Metal Anode

The ever-increasing demand for high-energy Li-ion batteries has acted as a powerful stimulus for the development of Li metal as an anode material.Li metal has long been regarded as a“Holy Grail”in Li-ion batteries due to its high discharge capacity(3860 mAh·g^?1)and low electric potential(?3.04 V).However,the formation of unstable solid electrolyte interphases(SEIs)and Li dendrites,as well as the resultant safety issues initiated by catastrophic dendrite growth,have greatly impeded further application.High ion conductivity,surface electron insulation,and favorable mechanical strength are essential properties for an ideal SEI film,which can allow for uniform Li deposition,providing a fast transfer path for Li ions and suppressing Li dendrite growth.Therefore,designing a functional SEI layer is an effective strategy to solve the problems encountered with Li metal anodes.So far,a variety of inorganic,organic,and inorganic/organic hybird SEI layers have been designed and fabricated.Inorganic SEIs are characterized by mechanical strength and ion conductivity;organic SEIs are flexible and have electron insulation properties.Inorganic/organic composite SEIs show favorable ion conductivity derived from the inorganic components,electron insulation properties originating from the organic components,and mechanical strength benefiting from the reinforcing effect between the inorganic and organic components.Oxides,metal sulfides,lithium nitride(Li3N)and its derivates,lithium halide(LiX,X=F,Cl),two-dimensional(2D)layered structure materials,lithium phosphate and“Janus”composite are the representative examples of inorganic SEIs.The design principle of various SEI layers is based on the inhibition of Li dendrite formation and growth.Therefore,it is a prerequisite to better understand the relevant intrinsic mechanisms.Despite past investigations,further studies are still required to fully elucidate the related mechanisms by providing more broadly accepted evidence combined with theoretical calculations and offer reliable guidance for the design of multifunctional SEI layers,boosting the performance of Li metal anodes.In this review,on the basis of the mechanisms underlying Li dendrite formation and growth,strategies for constructing various functional SEI films,highlights in structure and property of the films,and their effects on the performance of Li metal anodes are summarized.Moreover,some challenges encountered with the practical applications of Li metal anodes and the future direction for the development of Li metal anodes are addressed.This review can reveal possible strategies for the commercialization of high-energy,safe and stable Li-ion batteries.