Alkylphosphate-based nonflammable gel electrolyte for LiMn2O4 positive electrode in lithium-ion battery

Polymeric gel containing alkylphosphate has been examined as nonflammable gel electrolyte for LiMn2O4 positive electrode of lithium-ion battery (LIB). The gel was composed of a polymer matrix of poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) and a liquid component consisting of ternary solvent of trimethyl phosphate (TMP) mixed with ethylene carbonate (EC) and diethyl carbonate (DEC) that dissolves lithium salt (LiPF6 or LiBF4). The gel composition of 0.8 M (mol dm−3) LiX (X = PF6 and BF4) dissolved in EC + DEC + TMP (55:25:20) with PVdF-HFP showed excellent nonflammable characteristics and high ionic conductivity of ca. 3.1 mS cm−1 at room temperature (20 °C). The charge–discharge cycling test of LiMn2O4 positive electrode gave good reversibility with high capacitance in the gel electrolyte. With respect to the electrolyte salt, LiBF4 was better than LiPF6 due to its thermal stability during the gel preparation.