Characterization and properties of ternary P(VdF-HFP)-LiTFSI-EMITFSI ionic liquid polymer electrolytes

Gel polymer electrolytes containing 1-ethyl-3-methylimidazolium-bis (trifluoromethyl-sulfnyl)imide (EMITFSI) ionic liquid were prepared for lithium ion batteries by solution casting method. Thermal and electrochemical properties have been determined for the gel polymer electrolytes. Proper addition of EMITFSI to the P(VdF-HFP)-LiTFSI polymer electrolyte improves the ionic conductivity and electrochemical window to 2.11 × 10−3 S cm−1 (30 °C) and 4.6 V. In combination of the prepared ternary P(VdF-HFP)-LiTFSI-EMITFSI ionic liquid polymer electrolytes, Li4Ti5O12 anode exhibited two extra voltage plateaus around 1.1 V and 2.3 V except the typical voltage plateau around 1.6 V by possible side reaction between ionic liquid and polymer. LiFePO4 cathode exhibited high capacity above 140 mA h g−1 and retention of 93.1% due to the suppressed polarization effect caused by enhanced ion transport properties. The high temperature of 80 °C didn't have significant impact on the cycling performance.

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