V for batteries: V(acac)3 is used as a bifunctional soluble catalyst for Li–O2 batteries. V(acac)3 integrates with a highly active superoxide intermediate and promotes electron transport in the electrolyte, which effectively improves reaction kinetics and reduces side reactions. The cells with V(acac)3 soluble catalyst exhibited high rate performance, low overpotential, and long cycle life.
Abstract
High donor number (DN) solvents in Li—O2 batteries that dissolve superoxide intermediates in lithium peroxide (Li2O2) formation facilitate high capacities at high rates and avoid early cell death. However, their beneficial characteristics also result in an instability towards highly reactive superoxide intermediates. Furthermore, Li—O2 batteries would deliver a superior energy density, but the multiphase electrochemical reactions are difficult to achieve when operating with only solid catalysts. Herein we demonstrate that vanadium(III) acetylacetonate (V(acac)3) is an efficient soluble catalyst that can address these problems. During discharge, V(acac)3 integrates with the superoxide intermediate, accelerating O2 reduction kinetics and reducing side reactions. During charge, V(acac)3 acts as a redox mediator that permits efficient oxidation of Li2O2. The cells with V(acac)3 exhibit low overpotential, high rate performance, and considerable cycle stability.
