Optimisation of conductivity of PEO/PVDF-based solid polymer electrolytes in all-solid-state Li-ion batteries

All-solid-state Li-ion batteries, have become increasingly important because of their highly reliable solid electrolyte materials. Flexible solid polyethylene oxide (PEO) based electrolytes have been widely studied. Nevertheless, this material exhibits low lithium-ion conductivity. Herein, we report the optimisation of the composition of PEO/polyvinylidene fluoride (PVDF)-based electrolytes to enhance ionic conductivity. When the weight ratio of lithium bis(trifluoromethane sulphonyl)imide and PEO/PVDF is 1:5 (LiTFSI:PEO/PVDF = 1:5), maximum conductivities are 2.98 × 10−5 S cm−1 at 30°C and 5.56 × 10−4 S cm−1 at 60°C. Furthermore, the all-solid-state battery using this solid electrolyte film, a Li metal anode, and a LiFePO4 cathode delivers initial discharge capacities of 149.6 mAhg−1 (0.1 C, 60°C) and 130.2 mAh g−1 (0.5 C, 60°C). Meanwhile, the solid-state lithium battery also presents good cycling performance and excellent rate capability at 60°C.