Efficient nanoarchitectonics of solid-electrolyte-interface for high-performance all-solid-state lithium metal batteries via mild fluorination on polyethylene oxide

Polyethylene oxide (PEO) based polymer electrolytes is promising for all-solid-state lithium metal batteries (ASSLMBs). Solid-electrolyte-interface (SEI) layer formed between polymer electrolytes and lithium metal is crucial to inhibit lithium dendrites growth. Herein, mild fluorination on commercial PEO is engineered as an electrolyte for ASSLMBs, which shows an outstanding cycling stability. During this process, some C-H bonds in PEO chains are substituted with C-F bonds, resulting in the formation of fluorinated PEO (F-PEO) with a low fluorine content of 2.7 at.%. Fluorination alters the regularity of PEO chains, leading to an improved ion conductivity for F-PEO/LiTFSI. An unusual and stable SEI containing relatively high LiF content forms, which can inhibit lithium dendrites growth and boost the battery performance. Li/Li cell with F-PEO/LiTFSI delivers outstanding cycling stability over 2000 h at 0.1 mA cm^-2. When matching with LiFePO₄ cathode, the battery exhibits high capacity of 151.0 mAh g⁻¹ and good cycling stability for 500 cycles (0.05% decay per cycle) at 0.5 C. Even at 1.0 C, the capacity of the battery keeps at 99.8 mAh g⁻¹ after 900 cycles. This facile and low-cost strategy opens an avenue for ASSLMBs towards their commercial applications.