Rapid ionic conductivity of ternary composite electrolytes for superior solid-state batteries with high-rate performance and long cycle life operated at room temperature

Solid-state electrolytes (SSEs) are promising alternatives to traditional liquid electrolytes because of their safety issues. However, polymer SSEs have low ionic conductivity and weak mechanical strength, and inorganic SSEs are very brittle and unstable to lithium metal and atmospheric moisture, which restricts their practical applications. To avoid these disadvantages, it is essential to develop polymer–inorganic composite SSEs. In this work, we for the first time construct a solid composite polymer electrolyte of poly(vinylidene fluoride hexafluoropropylene) (PVDF-HFP) blended with Li1.3Al0.3Ti1.7(PO4)3 and flower-like CeO2 particles enriched with oxygen vacancies as inorganic fillers. The composite SSEs exhibit a wide electrochemical window of 5.1 V (vs. Li/Li+) and high ionic conductivity of 1.66 × 10−3 S cm−1 at room temperature. The conductivity enhancement originates from the oxygen vacancies associated with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) for releasing more lithium ions, and CeO2 is also beneficial for the suppression of Li dendrites. The solid-state LiFePO4/SSE/Li cell exhibits superior electrochemical performance at room temperature, the capacity is as high as 166.6 mA h g−1 at 0.1C, and the cell can sustain 83.1 mA h g−1 at 2C after 1000 cycles.