On the Efficacy of Electrocatalysis in Nonaqueous Li-O2 Batteries

Heterogeneous electrocatalysis has become a focal point in rechargeable Li-air battery research to reduce overpotentials in both the oxygen reduction (discharge) and especially oxygen evolution (charge) reactions. In this study, we show that past reports of traditional cathode electrocatalysis in nonaqueous Li-O-2 batteries were indeed true, but that gas evolution related to electrolyte solvent decomposition was the dominant process being catalyzed. In dimethoxyethane, where Li2O2 formation is the dominant product of the electrochemistry, no catalytic activity (compared to pure carbon) is observed using the same (Au, Pt, MnO2) nanoparticles. Nevertheless, the onset potential of oxygen evolution is only slightly higher than the open circuit potential of the cell, indicating conventional oxygen evolution electrocatalysis may be unnecessary.