Solvent-Free Preparation of High-Performance Composite Polymer Electrolytes for Lithium Metal Batteries

The solvent-free preparation of high-performance all-solid-state electrolytes is critical for the commercialization of lithium metal batteries. In this study, the solvent-free approach is proposed to fabricate a high-performance composite polymer electrolyte (FLCP) by densely impregnating the hot-molten polyether (F127)/lithium salt (LITFSI)/crown ether (15-CE-5) composite slurry into the commercialized porous polyethylene (PE) separators. This method effectively eliminates interfacial solvent residues and side reactions in solid electrolytes caused by the traditional solvent-based preparation approaches. The handpicked F127 polymer exhibits good liquidity at an appropriate temperature that greatly simplifies the processing technology. The 15-CE-5 additives with a strong dissociation ability of lithium salts could uniformly dispersed in hot-molten F127 that significantly improves the ionic conductivity and transfer number of the FLCP electrolyte. In addition, based on the reinforcement effect of the PE separator, the FLCP electrolyte also exhibits excellent mechanical performance. Consequently, its symmetric battery exhibits stable operation for over 5000 h and its lithium iron phosphate (LiFePO4)||Li full battery demonstrates exceptional cycle stability after more than 450 cycles at 1 C with a capacity retention rate of 95%. Furthermore, the performance of its flexible battery also validates the outstanding stability and safety in practical applications.