In Situ Formation\nof Stable Dual-Layer Solid Electrolyte\nInterphase for Enhanced Stability and Cycle Life in All-Solid-State\nLithium Metal Batteries

All-solid-state lithium metal batteries have emerged\nas a promising\nsolution to overcoming the energy density and safety challenges associated\nwith conventional lithium-ion batteries. Solid polymer electrolytes,\nparticularly those based on poly(vinylidene fluoride) (PVDF) and dimethylformamide\n(DMF), demonstrate significant potential. However, interfacial side\nreactions between residual DMF solvents and lithium metal present\n substantial challenges. In this study, we investigate the in situ\nformation of solid electrolyte interphase protective layers to mitigate\nthese side reactions. By incorporating F-rich additives, such as fluoroethylene\ncarbonate and lithium difluorophosphate, we successfully establish\na dual-layer inorganic SEI structure characterized by an outer LiF\nlayer and an inner Li<sub>2</sub>O layer. Consequently, our approach\nextends the cycle life of lithium symmetric batteries to 3000 h. Additionally,\nthe Li||LiFePO<sub>4</sub> solid-state battery demonstrates exceptional\nstability, enduring 400 cycles at a 1C rate with an impressive capacity\nretention of 84%. This strategic methodology effectively leverages\nthe benefits of residual solvents, ensuring both enhanced battery\nefficiency and long-term operational stability for PVDF-based all-solid-state\nlithium metal batteries.