La2O3 Filler's Stabilization of Residual Solvent in Polymer Electrolyte for Advanced Solid‐State Lithium‐Metal Batteries

Abstract

Polymer solid electrolytes (SEs) with high safety and flexibility are ideal for advanced lithium‐metal solid‐state batteries (SSBs). Among various polymer SEs, polyvinylidene fluoride‐co‐hexafluoropropylene (PVDF‐HFP) polymer SEs have gained increased attention for their high dielectric constants, high ionic conductivity, and excellent flexibility. However, severe side reactions at the interface caused by the decomposition of residual DMF solvent significantly reduce the cycle life of PVDF‐HFP‐based SSBs. Herein, La2O3 nanoparticles are used as new inorganic fillers to form a PVDF‐HFP/LiFSI/La2O3‐40% composite polymer electrolyte (PVDF‐HFP/La2O3 CPE). Benefiting from the interaction between La2O3 and N,N‐dimethylformamide (DMF) solvent molecules, the cell cycling stability is greatly improved. In addition, the PVDF‐HFP/LiFSI solid electrolyte (PVDF‐HFP SE) containing 40 wt% La2O3 has the highest ionic conductivity of 1.33 × 10−3 S cm−1 at 25 °C. It also exhibits a higher lithium‐ion transference number of 0.52 and lower polarization. The PVDF‐HFP/La2O3 CPE here ensures high ionic conductivity and stable interface chemistry in SSB, demonstrating a promising application potential.