Preparation of new composite electrolytes for solid-state lithium rechargeable batteries by compounding LiTFSI, PVDF-HFP and LLZTO

The addition of Li7La3Zr1.4Ta0.6O12 (LLZTO) particles to polymer electrolytes can reduce the crystallinity of polymer materials, promote the migration of lithium ions, and then improve the ionic conductivity of polymer solid electrolytes. Oxide-polymer composite solid electrolytes with different contents of LLZTO were prepared from Lithium bis(trifluoromethylsulphonyl)imide (LiTFSI), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and LLZTO powder as raw materials. The study has found that the solid electrolyte with 15 wt% LLZTO has higher ionic conductivity and mechanical strength, and has a wider electrochemical window (5.5V). The prepared composite cathode electrode/solid electrolyte/composite anode electrode solid-state lithium ion battery has a charge-discharge specific capacity of 179.56 mAh/g and 146.73 mAh/g for the first cycle, the coulombic efficiency is of 84%, and the discharge capacity retention rate after 30 cycles is above 94%. In addition, the change of impedance before and after the cycle is small, showing good interface stability.