A trilayer poly(vinylidene fluoride)/polyborate/poly(vinylidene fluoride) gel polymer electrolyte with good performance for lithium ion batteries

Abstract

A composite membrane based on poly(vinylidene fluoride) (PVDF) and lithium polyacrylic acid oxalate borate (LiPAAOB) exhibiting high safety (self-extinguishing) and good mechanical property was prepared. The ionic conductivity of the gel polymer electrolyte (GPE) by saturating with 1 mol L⁻¹ LiPF₆ electrolyte at ambient temperature can be up to 0.35 mS cm⁻¹, higher than that of the well-used commercial separator (Celgard 2730), 0.21 mS cm⁻¹. The lithium ion transference in the GPE at room temperature is 0.58, twice that in the commercial separator (0.27). Moreover, the GPE presents a true shut-down behavior, which is quite different from the not-real shut-down behaviour of the commercial separators. 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 composite GPE is very attractive to large-capacity battery systems requiring high safety and low cost.