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

摘要

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.