UV-Cross-Linked Composite Polymer Electrolyte for High-Rate, Ambient Temperature Lithium Batteries

We report an innovative cross-linked composite polymer electrolyte (CPE) based on the garnet-type ceramic super Li + ion conductor, Li 7 La 3 Zr 2 O 12 (LLZO), that is encompassed in a supersoft poly(ethylene oxide)/tetraglyme matrix. UV-induced, facile and solvent-free cross-linking process ensures flexible and self-standing CPEs, which are nonflammable and perfectly shape-retaining under thermal/mechanical stress. The CPEs exhibit high ionic conductivity, exceeding 0.1 mS cm –1 at 20 °C, suitable for ambient and subambient temperature operation. Lab-scale lithium metal polymer cells assembled with LiFePO 4 -based composite cathode and the optimized CPE deliver full capacity at low current rates and outstanding specific discharge capacity of 115 mAh g –1 at 1C rate and ambient temperature. Remarkably, the lithium metal cell can run for hundreds of galvanostatic cycles (>400) with low overpotential, limited fading, and excellent Coulombic efficiency (>99%), which postulates the practical application of the newly developed CPEs as truly solid separating electrolytes in high-power energy storage technologies, assuring safety and performance in a wide range of operating conditions.