Single‐Ion Conductive Polymer‐Based Composite Electrolytes for High‐Performance Solid‐State Lithium Metal Batteries

Abstract Flexible composite polymer electrolytes (CPEs) with inorganic electrolyte fillers dispersed in polymer electrolytes integrate the merits of the polymer and inorganic electrolytes and have attracted much attention in recent years. In order to increase the electrochemical performance, especially the low lithium (Li ) ‐ion transference number in traditional dual‐ion Li salt‐containing CPEs, single‐ion conductive CPEs are synthesized with a single‐ion polymer conductor (SIPC) as the matrix and Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) particles as the active fillers. The single‐ion conductive CPEs show a high Li‐ion transference number (up to 0.96), high room‐temperature (RT) ionic conductivity (>1.0 × 10 −4 S cm −1 ), wide electrochemical stability window (>5.0 V, vs Li/Li + ), and excellent long‐term cycling stability with Li metal at RT (3200 h). Based on the SIPC‐LLZTO CPE, the solid‐state lithium metal batteries with LiFePO 4 ‐ and LiCoO 2 ‐based cathodes deliver average discharge capacities of 159 mAh g −1 for 600 cycles and 119 mAh g −1 for 200 cycles at RT, respectively. This study sheds light on the design of high‐performance CPEs for next‐generation solid‐state lithium metal batteries.