Novel fast lithium-ion conductor LiTa2PO8 enhances the performance of poly(ethylene oxide)-based polymer electrolytes in all-solid-state lithium metal batteries

At present, replacing the liquid electrolyte in a lithium metal battery with a solid electrolyte is considered to be one of the most powerful strategies to avoid potential safety hazards. Composite solid electrolytes (CPEs) have excellent ionic conductivity and flexibility owing to the combination of functional inorganic materials and polymer solid electrolytes (SPEs). Nevertheless, the ionic conductivity of CPEs is still lower than those of commercial liquid electrolytes, so the development of high-performance CPEs has important practical significance. Herein, a novel fast lithium-ion conductor material LiTa₂PO₈ was first filled into poly(ethylene oxide) (PEO)-based SPE, and the optimal ionic conductivity was achieved by filling different concentrations (the ionic conductivity is 4.61 × 10^?4 S/cm with a filling content of 15 wt% at 60 °C). The enhancement in ionic conductivity is due to the improvement of PEO chain movement and the promotion of LiTFSI dissociation by LiTa₂PO₈. In addition, LiTa₂PO₈ also takes the key in enhancing the mechanical strength and thermal stability of CPEs. The assembled LiFePO₄ solid-state lithium metal battery displays better rate performance (the specific capacities are as high as 157.3, 152, 142.6, 105 and 53.1 mAh/g under 0.1, 0.2, 0.5, 1 and 2 C at 60 °C, respectively) and higher cycle performance (the capacity retention rate is 86.5% after 200 cycles at 0.5 C and 60 °C). This research demonstrates the feasibility of LiTa₂PO₈ as a filler to improve the performance of CPEs, which may provide a fresh platform for developing more advanced solid-state electrolytes.