In Situ Ion‐Conducting Protective Layer Strategy to Stable Lithium Metal Anode for All‐Solid‐State Sulfide‐Based Lithium Metal Batteries

Abstract Lithium metal is well known to be one of the most promising anodes for all‐solid‐state batteries, due to its ultrahigh capacity (3860 mAh g−1) and the extremely low standard negative electrochemical potential (−3.04 V). However, direct and confined contact of lithium metal with solid‐state electrolytes is still a great obstacle for excellent battery performance, which induces poor interfacial compatibility to further lead to weak lithium ion transport and dendrite formation. In this work, a well‐lithium‐ion‐conducting protective interfacial layer in all‐solid‐state‐Li6PS5Cl‐based lithium metal batteries is in situ established on the surface of polished Li through spin‐coating technique with a mixture of polyacrylonitrile (PAN) and fluoroethylene (FEC) carbonate. Interestingly, it is found there is synergistic effect between PAN and FEC via a solution‐based route. The artificial protective layer (LiPFG) consisting of organic matrix embedded with inorganic Li3N and LiF on the surface of Li regulates the uniform lithium deposition and enhances interface stability and compatibility. Specifically, a high reversible discharge capacity of 125.7 mAh g−1 at 0.1C and a lifetime of over 80 cycles can be achieved for LiZrO3@LiCoO2/Li6PS5Cl/LiPFG@Li full cells. This work inspires ideas for in situ construction of well‐lithium‐ion‐conducting artificial layer by a feasible spin‐coating technique for all solid state lithium metal batteries.