Advanced Solid‐State Polymeric Lithium Metal Batteries via Inhibiting Side Reaction of Residual Solvents

Abstract Polyvinylidene fluoride‐co‐hexafluoropropylene (PVDF‐HFP)‐based electrolytes are considered among the most promising candidates for solid‐state electrolytes owing to their high safety performance and superior flexibility. Nonetheless, the interfacial side reactions between the residual N, N‐dimethylformamide (DMF) and Li metal anode have significantly impeded their wide applications in solid‐state Li metal batteries (SLMBs). To address such an issue, a certain amount of fluoroethylene carbonate (FEC) is directly introduced into the PVDF‐HFP‐based electrolyte membrane. As verified, a robust solid electrolyte interphase layer enriched with LiF/Li ₃ N is formed because of the decomposition of FEC, thereby effectively suppressing the unwanted interactions between the leftover DMF and Li metal, and achieving precise regulation of lithium deposition behavior. The optimized electrolyte exhibits high ionic conductivity (0.97 mS cm ⁻¹ ) and significantly enhanced Li⁺ transference number (0.53). The Li symmetric cell with this optimized electrolyte achieves stable cycling for over 1800 h at 0.1 mA cm ⁻² , while the Li || LiFePO ₄ cell retains an impressive 81.4% capacity after 1300 cycles at 2 C. Moreover, the assembled pouch cell maintai stability for 50 cycles at 0.2 C, indicating a good commercial application prospect. This study presents valuable insights for forming a stable and robust electrolyte/Li interface for long‐lifespan and high‐safety SLMBs.