Poly(ethylene oxide) (PEO)-based solid polymer electrolytes are considered promising materials for realizing high-safety and high-energy-density lithium metal batteries. However, the high crystallinity of PEO at room temperature triggers low ionic conductivity and Li+ transference number, critically hindering practical applications in solid-state lithium metal batteries. Herein, we prepared nanosized TiO2 with enriched oxygen vacancies down to 13 nm as fillers by laser irradiation, which can be coated by in situ generated polyacetonitrile, ensuring good dispersibility in PEO. The electrolytes with nanosized TiO2 show a combination of high ionic conductivity, high Li+ transference number, superior electrochemical stability, and enhanced mechanical robustness. Accordingly, the lithium symmetric batteries with nanosized TiO2 composite solid electrolytes exhibit a stable cycling life up to 590 h at 0.25 mA cm-2. The full Li metal batteries paired with a LiFePO4 cathode deliver superior durability for 550 cycles. Moreover, the proof-of-concept pouch cells demonstrate excellent safety performance under various harsh conditions. This work provides a realistic guide in designing novel fillers to achieve stable operation of high-safety and energy-dense solid-state lithium metal batteries.
Keywords: composite solid electrolyte; interfacial compatibility; ionic conductivity; poly(ethylene oxide); pulsed laser irradiation in liquid.