A composite gel polymer electrolyte with high performance based on poly(vinylidene fluoride) and polyborate for lithium ion batteries

A composite membrane based on electrospun poly(vinylidene fluoride) (PVDF) and lithium polyvinyl alcohol oxalate borate (LiPVAOB) exhibiting high safety (self-extinguishing) and good mechanical property is prepared. The ionic conductivity of the as-prepared gel polymer electrolyte from this composite membrane saturated with 1 mol L^-1 LiPF₆ electrolyte at ambient temperature can be up to 0.26 mS cm^-1, higher than that of the corresponding well-used commercial separator (Celgard 2730), 0.21 mS cm ^-1. Moreover, the lithium ion transference in the gel polymer electrolyte at room temperature is 0.58, twice as that in the commercial separator (0.27). Furthermore, the absorbed electrolyte solvent is difficult to evaporate at elevated temperature. Its electrochemical performance is evaluated by using LiFePO₄ cathode. The obtained results suggest that this gel-type composite membrane shows great possibilities for use in large-capacity lithium ion batteries that require high safety. A composite membrane of a single-ion conductor, lithium polyvinyl alcohol oxalate borate (LiPVAOB), with electrospun poly(vinylidene fluoride), exhibits high safety, high conductivity for Li⁺ ions, slow evaporation of liquid electrolytes, and small overpotentials.