High-Performance Poly(vinylidene fluoride-hexafluoropropylene)-Based Composite Electrolytes with Excellent Interfacial Compatibility for Room-Temperature All-Solid-State Lithium Metal Batteries

Composite solid-state electrolytes (CSEs) have been developed rapidly in recent years owing to their high electrochemical stability, low cost, and easy processing characteristics. Most CSEs, however, require high temperatures or flammable liquid solvents to exhibit their acceptable electrochemical performance. Room-temperature all-solid-state batteries without liquid electrolytes are still unsatisfactory and under development. Herein, we have prepared a composite solid electrolyte with excellent performance using a polymer electrolyte poly(vinylidene fluoride-hexafluoropropylene) and an inorganic electrolyte Li6.4La3Zr1.4Ta0.6O12. With the assistance of lithium salts and plasticizers, the prepared CSE achieves a high ionic conductivity of 4.05 × 10–4 S·cm–1 at room temperature. The Li/CSE/Li symmetric cell can be stably cycled for more than 1000 h at 0.1 mA/cm2 without short circuits. The all-solid-state lithium metal battery using a LiFePO4 cathode displays a high discharge capacity of 148.1 mAh·g–1 and a capacity retention of 90.21% after 100 cycles. Moreover, the high electrochemical window up to 4.7 V of the CSE makes it suitable for high-voltage service environments. The all-solid-state battery using a lithium nickel-manganate cathode shows a high discharge specific capacity of 197.85 mAh·g–1 with good cycle performance. This work might guide the improvement of future CSEs and the exploration of flexible all-solid-state lithium metal batteries.