New polymerized ionic liquid (PIL) gel electrolyte membranes based on tetraalkylammonium cations for lithium ion batteries

New polymerized ionic liquids (PILs) based on tetraalkylammonium cations with N(CF 3 SO 2 ) 2 − (TFSI − ) anions are synthesized by homopolymerization and anion exchange reaction. Furthermore, a gel polymer electrolyte membrane based on the PILs as polymer host is prepared incorporating a tetraalkylammonium ionic liquid, LiTFSI salt and nano-size SiO 2 . The gel polymer electrolyte membranes show exceptional thermal and electrochemical properties . They are found to be thermally stable up to 336   °C. With the increase of the IL, T g of the PIL-based electrolyte samples decreases obviously. When the IL concentration is 25   wt%, the ionic conductivity of the electrolytes reaches 4.9×10 −4   S   cm −1 at 60   °C. After 130 cycles, the Li/LiFePO 4 battery with the gel polymer electrolyte membranes at 60   °C has discharge capacity of 122   mA   h   g −1 at 0.1 current rates.