Solvent-Free Process for Blended PVDF-HFP/PEO and LLZTO Composite Solid Electrolytes with Enhanced Mechanical and Electrochemical Properties for Lithium Metal Batteries

All solid-state lithium metal batteries are viewed as a potential next-generation energy storage technology due to their high energy density and better safety performance. The study on solid-state electrolytes (SSE) is of crucial importance for the development of technology in this field. Here, we develop a solvent-free preparation and matrix modification process for all-solid-state composite electrolytes (CSEs) based on the blended PVDF-HFP/PEO polymer matrix, and systematically study the effects of the solvent-free process on their properties. The results show that the solvent-free PVDF-HFP/PEO/10 wt % LLZTO solid-state electrolytes (1:1 mass ratio blended polymer matrix) combine the electrochemical and mechanical advantages of both polymers, thus-prepared electrolytes perform excellent tensile strength and ductility (over 500% strain for polymer matrix as well as 170% strain and 4.78 MPa strength for CSEs), and the ionic conductivity can reach ～6.2 × 10^–4 S·cm^–1 at 80 °C. At the same time, the electrochemical stability and cycle stability of the electrolytes are enhanced due to the optimized process. The discoloration reaction of PVDF-HFP in composite electrolytes is further studied in this work as well. In addition to excellent performance, the simple process based on the solvent-free method also lays the foundation for scale-up production.