Development of composite solid polymer electrolyte for solid-state lithium battery: Incorporating LLZTO in PVDF-HFP/LiTFSI

Solid-state batteries (SSBs) are regarded as favorable future technology as they promise to deliver high energy density and improved safety. However, despite extensive research efforts, the development of SSBs still fall short of expectations mainly because of suitable solid electrolyte which can provide high ionic conductivity as well as good flexibility to enhance interface contact between electrolyte and electrodes. In this work, we have prepared free-standing, flexible composite solid polymer electrolyte (CSPE) membranes by incorporating LLZTO ceramic particles in PVDF-HFP/LiTFSI based solid polymer electrolyte (SPE). Addition of 20 wt% LLZTO has shown to improve the electrochemical properties of the solid electrolyte such as ionic conductivity (8.2 x 10-4 S cm-1 at 60 degrees C), transference number, electrochemical stability and long-term interface stability with the lithium-metal also showed significant improvement. Furthermore, solid-state LiFePO4/SPE/Li and LiFePO4/CSPE/Li batteries were fabricated, and charge/discharge cycling was performed, where battery with SPE and CSPE exhibited discharge capacity of 119 mA h g-1 and 131 mA h g-1 respectively at 0.1C rate, 60 degrees C.