Aprotic Li-O-2 Battery: Influence of Complexing Agents on Oxygen Reduction in an Aprotic Solvent
Résumé
Several problems arise at the O2 (positive) electrode in the Li-air battery, including solvent/electrode decomposition and electrode passivation by insulating Li2O2. Progress partially depends on exploring the basic electrochemistry of O2 reduction. Here we describe the effect of complexing-cations on the electrochemical reduction of O2 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 O2. The complexing-cations also increase the rate of the 1-electron O2 reduction to O2*- 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 O2*- to O22-. In the presence of Li+ and complexing-cations, and despite the interaction of the reduced O2 with the latter, SERS confirms that the product is still Li2O2.