A High-Voltage Hybrid Solid Electrolyte Based on Polycaprolactone for High-Performance all-Solid-State Flexible Lithium Batteries

All-solid-state lithium batteries are promising to overcome the safety issues and limited energy density concern of commercial Li-ion batteries (LIBs). In this study, cubic-phase Li1.4Al0.4Ti1.6(PO4)3 (LATP) powders are prepared and filled into biodegradable polycaprolactone (PCL) matrixes to form a flexible PCL–LiClO4–LATP hybrid solid electrolytes (HSEs). Owing to the excellent electrochemical stability of the PCL matrix, the HSEs offer a wide electrochemical potential window of 5 V (vs Li/Li+), an ionic conductivity of 3.64 × 10–5 S cm–1 at 55 °C, and a high Li-ion transference number of 0.58. In addition, the fabricated all-solid-state lithium batteries exhibit an outstanding electrochemical performance with a high initial discharge specific capacity of 136.6 mAh g–1 and a good capacity retention of 75% after 200 cycles at 0.3 C. The superior performance indicates that the HSEs with the PCL as the polymer matrix provide an inspiring approach to develop high-performance flexible and safe all-solid-state lithium batteries.