High ionic conductivity,good electrochemical stability,and satisfactory mechanical property are the crucial factors for polymer solid state electrolytes.Herein,fast ion conductor LiAlSiO4 (LASO) is incorporated into polyethylene oxide (PEO)-based solid-state electrolytes (SSEs).The SSEs containing LASO exhibit enhanced mechanical properties performance compared to pristine PEO-LiTFSI electrolyte.A reduced melting transition temperature of 40.57 ℃ is enabled by introducing LASO in to PEO-based SSE,which is beneficial to the motion of PEO chain and makes it possible for working at a moderate environment.Coupling with the enhanced motion of PEO,dissociation of the lithium salt,and conducting channel of LASO,the optimized composite polymer SSE exhibits a high ionic conductivity of 4.68 × 10-4,3.16 × 10-4 and 1.62 × 10-4 S cm-1 at 60,50 and 40 ℃,respectively.The corresponding LiFePO4//Li solid-state battery exhibits high specific capacities of 166,160 and 139 mAh g-1 at 0.2 C under 60,40 and 25 ℃.In addition,it remains 130 nAh g-1 at 4.0 C,and maintains 91.74% after 500 cycles at 1.0 C under 60 ℃.This study provides a simple approach for developing ionic conductor-filled polymer electrolytes in solid-state lithium battery application.