Nonflammable polymeric gel electrolyte has been prepared by immobilizing 1M LiBF4/EC+DEC+TEP (55:25:20, v/v/v, EC: ethylene carbonate, DEC: diethyl carbonate and TEP: triethylphosphate) solution in poly(vinylidene fluoride-co-hexafluoro propylene) (PVdF-HFP) where TEP acts as a fire-retardant solvent in the gel electrolyte. The polymeric gel electrolyte has a high value of ionic conductivity of 1.76mScm−1 at 28°C. Thermal safety calorimetry (TSC) experiments show good thermal stability of the gel electrolyte. Cyclic voltammetry and charge/discharge cycling tests were performed on LiMn2O4/gel electrolyte and graphite/gel electrolyte half cells. The gel electrolyte works well for graphite/LiMn2O4 cell although some improvement in the cycleability of the graphite electrode is still needed.