Thermal Decomposition Assisted Construction of Nano‐Li3N Sites Interface Layer Enabling Homogeneous Li Deposition

Lithium (Li) metal is a highly desirable anode for all‐solid‐state lithium‐ion batteries (ASSLBs) due to its high theoretical capacity and being well matched with solid‐state electrolytes. However, the practical applications of Li metal anode are hindered by the uneven Li metal plating/stripping behavior and poor contact between electrolyte and Li anode. Herein, a convenient and efficient strategy to construct the Li3N‐based interlayer between solid poly(ethylene oxide) (PEO) electrolyte and Li anode is proposed by in situ thermal decomposition of 2,2′‐azobisisobutyronitrile (AIBN) additive. The evolved Li3N nanoparticles are capable of combining LiF, cyano derivatives and PEO electrolyte to form a buffer layer of about 0.9 μm during the cell cycle, which can buffer Li+ concentration and homogenize Li deposition. The Li||Li symmetric cells with Li3N‐based interlayer show excellent cycle stability at 0.2 mA cm−2, which is at least 4 times longer cycle life than that of PEO electrolytes without Li3N layer. This work provides a convenient strategy for designing interface engineering between solid‐state polymer electrolyte and Li anode. At the interface: Li3N grown at anode‐electrolyte interface is constructed by in situ thermal decomposition of poly(ethylene oxide) (PEO) based electrolyte containing 2,2’‐azoisisobutyronitrile. The evolved Li3N nanoparticles serve as a buffer layer, exhibiting high ionic conductivity and homogeneous Li deposition behavior for protecting lithium anode of solid‐state batteries.