An in situ-Fabricated Composite Polymer Electrolyte Containing Large-Anion Lithium Salt for All-Solid-State LiFePO4/Li Batteries

In this work, we propose an in situ hydrolytic method to synthesize SiO2 nanoparticles, which are incorporated in poly (ethylene oxide)-based polymer in the presence of lithium salt with a large anion (lithium bis(oxalate)borate). When evaluated as the solid electrolyte for electrochemical performance in lithium batteries, the as-prepared composite polymer electrolyte (CPE) exhibits an exciting ion conductivity of 1.9 mS/cm at 80 degrees C. Moreover, the CPE shows a decent Li+ transference number up to 0.69 and wide electrochemical window of 5.05 V at 60 degrees C. Furthermore, the Li/LiFePO4 cell assembled by the CPE exhibits an impressive capacity of 156.3 mAh/g at 60 degrees C under 0.05 C (1 C=160 mA/g). Considering the aspects mentioned above, the prepared CPE has the potential to be applied in practical high-temperature batteries with a long-term service life. More importantly, the synthetic strategy is favorable for enhancing both physical and electrochemical performance for solid electrolyte and may provide a new strategy for study and fabrication of lithium batteries.