Study on electrolyte stability and oxygen reduction reaction mechanisms in the presence of manganese oxide catalysts for aprotic lithium-oxygen batteries

The impact of different manganese oxide electrocatalysts on the oxygen reduction reaction (ORR) in aprotic media was investigated. In the absence of a catalyst on pure carbon powder, the ORR was found to proceed partially by O2 dissociation before reduction. The O adatoms generated during this process have been reported previously to promote the decomposition of aprotic electrolytes. The extent to which this mechanism takes place depends strongly on the potential scan rate applied during the cyclic voltammetry measurements. The presence of manganese oxides has different effects on the reaction mechanism: whereas Mn3O4 and Mn5O8 nanoparticles promote chemical O2 dissociation, mesoporous a-Mn2O3 particles suppress this mechanism in favor of the direct reduction of O2, thus forming the desired final product Li2O2. These results lead to a better understanding of the morphological and structural properties, which ideal catalysts for an application in aprotic Li-air batteries should exhibit.