(684e) Performance of Ternary Ionic Liquid–Lithium Salt Mixtures for Li-O2 Batteries
Identification of stable electrolyte materials which can operate in an oxygen rich atmosphere is a major challenge for the development of the Li-O2 battery. Conceivably, a hydrophobic room temperature ionic liquid (IL) electrolyte, because of its low volatility, can prevent the hydrolysis reaction at the Li anode and drying of the O2 electrode during cycling. Pyrrolidinium IL can create a passivation layer on the Li anode and is stable against highly reactive superoxide O2-. However, it has a high viscosity and low O2 solubility that is detrimental to cell performance. Ternary IL mixtures comprised of both high ionically conductive and less viscous imidazolium (i.e., 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl imide (BMIMTFSI)) and pyrrolidinium (i.e., N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR14TFSI)) based ILs are tested as the electrolyte for Li-O2 batteries. 4:1 (80/20 v/v%) BMIMTFSI : PYR14TFSI based ternary mixtures show excellent cyclability with 330 mAhg-1 over 50 cycles at a current density of 0.1 mA.cm-2, much better than the pure BMIMTFSI, PYR14TFSI and TEGDME electrolytes. The results clearly show the beneficial synergic effect of the two ionic liquids on the electrochemical properties of the mixtures.