With funding from the National Natural Science Foundation of China, the my country Association for Science and Technology's Young Talent Support Program, and the Beijing Institute of Technology's Science and Technology Innovation Program, the research group of Special Researcher Huang Jiaqi at the Institute for Frontier Interdisciplinary Sciences, Beijing Institute of Technology, has made new progress in the research of high-safety lithium metal anodes for next-generation high-energy-density lithium metal batteries. Recently, the relevant research results, entitled "Artificial soft–rigid protective layer for endrite-free lithium metal anode," were published online in *Advanced Functional Materials* (impact factor 12.124) on January 8, 2018.
Lithium metal is considered one of the promising high-energy-density anode materials due to its extremely high theoretical specific capacity (3860 mAh g⁻¹) and negative electrode potential (-3.045 V vs. standard hydrogen electrode). However, the practical application of lithium metal electrodes is limited by lithium dendrite growth and low cycle efficiency. Lithium metal is a highly reactive metal, forming a complex solid electrolyte interface with intricate structure and composition when in contact with the electrolyte, making it difficult to maintain interface stability during electrochemical reactions. Therefore, uneven deposition of lithium ions at the interface easily leads to needle-like, dendritic, and moss-like lithium deposits. The growth of lithium dendrites can puncture the separator, causing a short circuit and posing a safety hazard; on the other hand, it increases the contact area between lithium metal and the electrolyte, leading to more side reactions and further reducing the battery's cycle efficiency.
To construct a stable lithium metal/electrolyte interface and regulate uniform lithium deposition, this research group proposed a "rigid-flexible" composite film using inorganic LiF as the rigid component and PVDF-HFP polymer as the flexible component to stabilize the lithium metal-electrolyte interface during electrochemical cycling. The flexible polymer provides flexibility and stretchability to withstand interface fluctuations during lithium metal electrode deposition/dissolution, while the introduction of the rigid component further enhances the mechanical modulus of the modified layer, thereby suppressing lithium dendrite growth and achieving uniform lithium deposition. Introducing this interface modification layer, which simultaneously possesses good deformation properties, high mechanical modulus, and ionic conductivity, into coin cells significantly improved the cycle life and cycle stability of Li-Cu half-cells and Li-Li symmetric cells. In full-cell tests with a lithium iron phosphate cathode, the cycle life of the battery modified with the composite layer increased by 2.5 times.
