Investigation of the electrocatalytic oxygen reduction and evolution reactions in lithium-oxygen batteries

Oxygen reduction and oxygen evolution reactions were studied on graphite electrodes with different crystal orientations. The kinetics for the redox couple O-2/O-2(center dot-) are very fast, therefore no catalyst seems necessary to assist the charge transfer process. Apparently, the main source of the overpotential for the O-2 reduction reaction is from mass diffusion. Li2O2 becomes soluble in non-aqueous electrolytes in the presence of the tetraethylammonium tetrafluoroborate additive. The soluble B - O-2(2-) ions can be oxidized electro-catalytically. The edge orientation of graphite demonstrates superior catalytic activity for the oxidation over basal orientation. The findings reveal an opportunity for recharging Li-air batteries efficiently and a new strategy of developing the catalyst for oxygen evolution reaction. (c) 2015 Elsevier B.V. All rights reserved.