Li+ conducting polymer electrolyte based on ionic liquid for lithium and lithium-ion batteries

Abstract

Polymer electrolyte (PE), based on PVdF-co-HFP polymer network and MePrPipNTf2+LiNTf2 ionic liquid (MePrPip: N-methyl-N-propylpiperidinium cation, NTf2 is bis(trifluoromethanesulphonyl)imide anion) was prepared. PE contained small amounts of vinylene carbonate. The performance of metallic-lithium and graphite (G) anodes working together with the electrolyte were tested with the use of: electrochemical impedance spectroscopy (EIS), galvanostatic charging/discharging and scanning electron microscopy (SEM). Specific conductance of the membrane was ca. 4mScm−1 at 25°C with activation energy of 14.35kJmol−1. Scanning electron microscopy images showed that the charged/discharged graphite anodes differed in morphology from the pristine material. The surface of graphite flakes was covered with small crystals with a diameter of ca. 1μm (the solid electrolyte interface, SEI). When the graphite anode was soaked with the 1M LiPF6 solution in PC+DMC (propylene carbonate and dimethyl carbonate, respectively), before the G|PE|Li cell assembling, its reversible capacity was ca. 340mAhg−1 (after the 50th cycle).