Taxonomy of Antioxidants to Deactivate Reactive Superoxide for Rejuvenating Batteries

Abstract

In lithium batteries employing oxygen electrochemistry as their cathodic process, superoxide radical is recognized as a reactive nucleophile that decomposes electrolytes and therefore deteriorates battery durability. Herein, we categorized the antioxidants employed for deactivating reactive superoxide in batteries into three groups after their working mechanisms were clearly understood and classified. Radical scavengers, as the first group, are sacrificed to provide moieties to neutralize the radical activity of superoxide. The reversible superoxide dismutase mimics (SODm's), distinguished from radical scavengers by their catalytic turnover, were divided into two families in terms of the anti-aging mechanism: electron-mediating SODm (e-SODm) and chemo-catalytic SODm (c-SODm). The redox-active e-SODm family, as the second group, mediates an electron from a superoxide radical to another superoxide, driving oxidation to dioxygen and reduction to peroxide, respectively. The c-SODm family, as the third group, chemically catalyzes superoxide disproportionation reaction, lowering the activation energy of the dismutation between the same radicals.