Ionic liquid-based gel polymer electrolyte for LiMn0.4Fe0.6PO4 cathode prepared by electrospinning technique

Abstract

Two polymer electrolytes (PEs), one consisting of 1 M LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC) (PEEC/DMC) and the other consisting of LiTFSI in room temperature ionic liquid (RTIL), 1-ethyl-3-methyl imidazolium bis(trifluoromethane sulfonyl)imide (EMITFSI) (PEIL), were prepared by using electrospun P(VdF-HFP) membranes. The PEs showed typical impedance spectroscopic responses with high conductivity and good anodic stability. The PEs were applied with carbon coated LiMn0.4Fe0.6PO4 cathode material prepared by sol-gel method. The charge-discharge kinetics of LiMn0.4Fe0.6PO4 cathode cells were studied by electrochemical impedance spectroscopy. The excellent performance with high capacity and good cycle stability was observed for both the cells. The cell comprising of PEIL showed a better performance than the other cell. The cells having PEEC/DMC and PEIL delivered discharge capacities of 150 and 141 mAh g(-1), and 168 and 162 mAh g(-1), respectively, after cycle 1 and 50. The differences in the performance of the PEs originate from the differences in viscosity, ionic conductivity and also from the different levels of interactions of a RTIL and EC/DMC with the polymer. The evaluation of lithium ion diffusion coefficients shows its fast diffusion in both the cases, the trend of which changed with the increase in the number of cycles. (C) 2009 Elsevier Ltd. All rights reserved.