High-performance PVDF-HFP based gel polymer electrolyte with a safe solvent in Li metal polymer battery

Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) based gel polymer electrolytes are widely studied owing to their electrochemical stability and high dielectric constant. However, most gel polymer electrolytes show unsatisfied safety and interface compatibility due to excessive absorption of volatile and flammable liquid solvents. Herein, by using a safe solvent (N-methyl-2-pyrrolidone) with higher boiling (203 °C) and flash points (95 °C), we initiatively fabricate a flexible PVDF-HFP based gel polymer electrolyte. The obtained gel polymer electrolyte demonstrates a high ionic conductivity of 7.24 × 10−4 S cm−1, an electrochemical window of 5.2 V, and a high lithium transference number of 0.57. As a result, the synthesized polymer electrolyte exhibits a capacity retention of 70% after 500 cycles at 0.5 C, and a discharge capacity of 86 mAh g−1 even at a high current rate of 10 C for LiFePO4 based Li metal batteries. Moreover, a stable Li plating/stripping for more than 500 h is achieved under 0.1 mAh at both room temperature and 70 °C. Our results indicate that the PVDF-HFP polymer electrolyte is promising for manufacturing safe and high-performance Li metal polymer batteries.