A Chemically and Electrochemically Bifunctional Mobile Catalyst for Anti-aging Lithium-Oxygen Batteries

Abstract

Aprotic lithium-oxygen batteries (LOBs) have much higher energy density compared to today’s lithium ion batteries. However, highly reactive superoxide, the discharge intermediate of LOBs, triggers side reactions to deteriorate LOB performances. Also, high overpotential is required to oxidize the discharge product Li2O2 during charge due to the non-conductive nature of Li2O2. Herein, we present 4-carboxy-TEMPO as a bifunctional mobile catalyst soluble in LOB electrolytes for improving LOB performances. The roles of 4-carboxy-TEMPO is two-fold: (1) the chemo-catalyst to catalyze superoxide disproportionation reaction for suppressing the superoxide-triggered side reactions; and (2) the redox mediator to oxidize the discharge product Li2O2 in a kinetically effective way for reducing the overpotential during charge. As expected, the use of the mobile catalyst in LOB cells resulted in the 4-fold increase in cycle life from 50 cycles to 200 cycles, significantly reducing the overpotential during charge. Also, the discharge capacity increased 4-fold.