Aprotic Li–O₂ Battery: Influence of Complexing Agents on Oxygen Reduction in an Aprotic Solvent

Several problems arise at the O 2 (positive) electrode in the Li-air battery, including solvent/electrode decomposition and electrode passivation by insulating Li 2 O 2 . Progress partially depends on exploring the basic electrochemistry of O 2 reduction. Here we describe the effect of complexing-cations on the electrochemical reduction of O 2 in DMSO in the presence and absence of a Li salt. The solubility of alkaline peroxides in DMSO is enhanced by the complexing-cations, consistent with their strong interaction with reduced O 2 . The complexing-cations also increase the rate of the 1-electron O 2 reduction to O 2 •– by up to six-fold ( k ° = 2.4 ×10 –3 to 1.5 × 10 –2 cm s –1 ) whether or not Li + ions are present. In the absence of Li +, the complexing-cations also promote the reduction of O 2 •– to O 2 2– . In the presence of Li + and complexing-cations, and despite the interaction of the reduced O 2 with the latter, SERS confirms that the product is still Li 2 O 2 .