锂金属负极人造保护膜的研究进展

Research Progress on Artificial Protective Films for Lithium Metal Anodes

金属锂因其具有极高的理论容量(3860 mAh·g^(−1))、最低的电极电位(−3.04 V vs.标准氢电极)和低的密度(0.534 g·cm^(−3)),被认为是最具潜力的负极材料。但循环过程中不可控的枝晶生长及不稳定的固体电解质相界面膜所引起的安全隐患和电池库伦效率低等问题严重阻碍了锂金属负极的发展。通过在电极表面构建人造保护膜可以有效调控锂离子沉积行为,因此人造保护膜的构建是一种简单高效抑制锂枝晶生长的策略。本综述将从聚合物保护膜、无机保护膜、有机-无机复合保护膜和合金保护膜总结了人造保护膜的构建方法、抑制锂枝晶生长机理,为促进高比能锂金属电池的商业化应用提供借鉴参考作用。

In the early 1990s,Sony launched the first commercial lithium ion battery(LIB),which achieved great success in energy storage systems.The current commercially used insertion anode,graphite,is approaching its capacity limit(~372 mAh·g^(−1)),and is inadequate to satisfy the ever-increasing energy demand for power grids and large-scale energy storage systems.In order to address this challenge,lithium metal anodes have been the focus of considerable research effort in recent years,and are regarded as the most promising anode materials because of their extremely high theoretical capacity(3860 mAh·g^(−1)),lowest electrode potential(−3.04 V vs.standard hydrogen electrode),and low density(0.534 g·cm^(−3)).For example,the theoretical energy densities of lithium-sulfur batteries and lithium-air batteries are as high as 2567 and 3505 Wh·kg^(−1),respectively.However,the uncontrollable dendrite growth during cycling leads to low coulombic efficiency and puncture of the separator,causing a short circuit or even explosion of the battery,thereby seriously hindering the development of the lithium metal anode.Many solutions have been proposed to inhibit dendrite growth,including the use of electrolyte additives,solid electrolytes,and artificial protective films.During charging and discharging,the solid electrolyte interphase(SEI)plays an important role in lithium metal anodes.However,the infinite volume changes of the electrode during plating/stripping processes result in breakage of the SEI film,which continuously consumes the electrolyte and lithium metal.Designing an artificial interface on the surface of lithium metal anodes has been considered as a simple and efficient strategy to control lithium deposition behavior,and is achieved by precoating a protective layer on the surface of lithium metal.An ideal artificial protective film should possess high ionic conductivity,chemical stability,and excellent mechanical strength,in order to prevent side reactions between lithium metal and the electrolyte and realize dendrite-free lithium metal anodes with a long cycle life and high coulombic efficiencies.In this paper,the research progress on artificial protective films for lithium metal anodes in recent years is reviewed.Further,the structural characteristics and preparation methods of various protective films are introduced in detail,including polymer protective films,inorganic protective films,organic-inorganic composite protective films,and alloy protective films.The mechanisms of various protective films toward the suppression of dendrite growth are summarized.Existing challenges and future research directions are also proposed,which together provide a reference for promoting the use of lithium metal in high-energy batteries.