LiTa₂PO₈-Based Polymer–Ceramic Electrolyte Paved the Way to High-Performance Solid-State Lithium Metal Batteries

Solid composite electrolytes, leveraging the advantages of both ceramics and polymers, are emerging as a viable alternative to liquid electrolytes in all-solid-state lithium metal batteries. Here, we have developed a polymer–ceramic composite electrolyte with an area-specific resistance of ∼94 Ω cm2 at room temperature (RT) by the solution casting method. A Li-ion conducting LiTa2PO8 ceramic with an RT bulk conductivity of ∼3.2 × 10–4 S cm–1 was synthesized to act as an active filler in a PEO/PVDF-HFP polymer matrix complexed with LiTFSI salt to obtain a polymer–ceramic composite electrolyte. The symmetric lithium cell with the optimized electrolyte exhibited excellent cyclability over 950 cycles at an areal current density of 0.2 mA cm–2. The full cell with LiFePO4 cathode and lithium metal anode delivered a specific capacity of ∼115 mAh g–1 with ∼85% capacity retention after 500 cycles at 1C at RT, making it a viable alternative to be adopted in Li-ion batteries for room temperature applications.