The Role of Ionic Liquid in Oxygen Reduction Reaction for Lithium-air Batteries

We have investigated the oxygen reduction reaction (ORR) in the presence of non-aqueous electrolytes in an attempt to overcome the challenges related to lithium-air batteries, such as low reversibility, poor rate capability, and electrode/solvent stability. We have used glassy carbon as the working electrode in electrolytes composed of lithium bis(trifluoromethanesulfonyl)imide and 1,2-dimethoxyethane or N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR₁₄TFSI, ionic liquid). We have employed the kinetic model to treat the electrochemical impedance spectroscopy data. This approach provides the rate constants for each of the elementary steps and allows indirect investigation of the role played by the ionic liquid in the ORR. The ionic liquid shifts the onset potential of the ORR to more positive values. The presence of the large Pyr₁₄⁺ cation increases the rate-determining step by approximately three orders of magnitude as compared to the ether-based electrolyte. This ionic liquid is chemically resistant to degradation reactions and increases the rate of the ORR, which makes it a promising candidate for use in lithium-air batteries.