Wang C

Composite gel polymer electrolyte (cGPE) containing a poly (ionic liquid) (PIL) polymer, imidazolium cation-based ionic liquid as a solvent, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as salt, and glass fillers with various concentrations have been developed and tested in lithium batteries. cGPEs with 1 wt% glass filler shows the highest ionic conductivity and lithium-ion transference number with 25 % and 18.18 % improvement compared to gel polymer electrolyte (GPE), respectively. Raman results show that the improvement is due to the improved ion-pair dissociation of LiTFSI, which causes improvement of Li + mobility. Cyclic charge-discharge studies using binder-free LiFePO 4 /C cathode and lithium anode for 100 cycles at various Crates and at a fixed rate of C/2 for 300 cycles show superior performances compared to other cGPEs and GPE. Electrochemical impedance spectroscopy and scanning electron microscopy confirm uniform deposition of reaction products on the cathode surface, which improves the charge-transfer reactions and hence improves cyclic performances for cGPE-1 cells with increasing cycles.

Lithium-sulfur batteries using a lithium anode, sulfur-CNT cathode, and gel polymer electrolyte composed of a poly(ionic liquid), an ionic liquid, and lithium salt are reported. Cyclic charge-discharge studies at various discharge and charge rates for 100 cycles and at a fixed rate for 500 cycles show superior performance for the gel polymer electrolyte (GPE) compared to the ionic liquid electrolyte (ILE) containing batteries. Rapid capacity fading for the first few cycles is observed and its causes are studied using an electrochemical impedance spectroscopy (EIS) approach. EIS reveals a depth-of-discharge dependent impedance growth during the first discharge cycle, that is followed by an interfacial resistance growth between the electrodes and the electrolytes in subsequent cycles.