In this study, we prepare a kind of solid polymer electrolyte (SPE) based on N-ethyl-N′-methyl imidazolium tetrafluoroborate (EMIBF4), LiBF4 and poly(vinylidene difluoride-co-hexafluoropropylene) [P(VdF-HFP)] copolymer. The resultant SPE displays high thermal stability above 300°C and high room temperature ionic conductivity near to 10−3 Scm−1. Its electrochemical properties are improved with incorporation of a zwitterionic salt 1-(1-methyl-3-imidazolium)propane-3-sulfonate (MIm3S). When the SPE contains 1.0wt% of the MIm3S, it has a high ionic conductivity of 1.57×10−3 Scm−1 at room temperature, the maximum lithium ions transference number of 0.36 and the minimum apparent activation energy for ions transportation of 30.9kJmol−1. The charge–discharge performance of a Li4Ti5O12/SPE/LiCoO2 cell indicates the potential application of the as-prepared SPE in lithium ion batteries.