Fluorinate localized solvation PVDF-HFP-based polymer electrolyte producing LiF-rich interface for solid-state lithium metal batteries

Poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP)-based solid polymer electrolytes show great potential for high energy lithium metal batteries, however, the residual solvent and related severe side reactions limit its development. Herein, a PVDF-HFP-based solid polymer electrolyte modified by fluorobenzene (FB) co-solvent is designed to address these problems. The introduced FB with weak solvation interaction regulates the coordination environment and induces anions to enter the solvation structure, generating more contact ion pairs (CIPs) and aggregates (AGGs). In addition, the anions-derived LiF-rich interphases help to improve the interface stability against Li metal. As a result, the FB-PVDF-HFP achieves high ionic conductivity (4.1 × 10 −4 S/cm) and low activation energy (0.125 eV) at room temperature. In addition, Li||Li symmetric cells using FB-PVDF-HFP electrolyte can achieve uniform and dendrite-free lithium deposition/stripping in the long-term cycling over 2300 h. The assembled solid-state Li|FB-PVDF-HFP|LFP full cell shows improved rate performance and cycling performance (600 cycles at 0.5 C and 450 cycles at 3 C) at room temperature. This work verifies the feasibility of fluorinated terminated solid polymer electrolytes on its lithium-ion transport and interfacial stability in lithium metal batteries.