Study of the ion transport properties of succinonitrile plasticized poly(vinylidene fluoride)-based solid polymer electrolytes

Due to the high crystallinity of poly(vinylidene fluoride) (PVDF), the segmental motion is restricted, resulting in low ionic conductivity, which is a barrier to the commercial application of solid-state polymer electrolytes based on PVDF. In this work, a polymeric solid electrolyte material with high ionic conductivity was obtained by plasticizing PVDF with Succinonitrile (SCN). Additionally, a polycationic protective layer was generated in situ on the lithium metal anode surface to inhibit the polymerization reaction of SCN on the lithium metal surface. The experimental results demonstrate that the ionic conductivity of the PVDF electrolyte membrane plasticized SCN (SCN-PVDF) is 4.3 × 10-5 S·cm−1 at room temperature. SCN-PVDF has interconnected lithium-ion 3D network channels. Under a current density of 0.2 mA·cm−2 and an areal capacity of 0.2 mAh·cm−2, the SCN-PVDF electrolyte membrane can last for more than 500 h while maintaining a consistently low polarization potential. At 25℃, the LiFePO4|SCN-PVDF|PDDA-TFSI@Li system exhibits a first-cycle discharge capacity of 163.2 mAh·g−1 at a 0.1C rate, and maintains a capacity retention of 99.8 % after 200 charge/discharge cycles at 0.5C rate.