Unraveling the Key Factors Governing O2 Evolution upon Charging a Reversible LiOH-based Nonaqueous Li-O2 Battery

Abstract

Achieving a highly reversible 4e⁻/O₂ oxygen evolution reaction (OER) is an essential yet highly challenging task for nonaqueous LiOH-based Li-O₂ batteries, as the kinetically sluggish OER tend to entangle with competing parasitic reactions, whose origins unfortunately remain largely elusive. Here we construct a highly reversible LiOH-based Li-O₂ battery using FeCoNi LDH catalysts and tetramethylene sulfone electrolytes. We show that the decomposition of LiOH toward O₂ evolution involves the formation of *OH, *HO₂⁻ and *H₂O₂ species but no ¹O₂. The electrophilic attack of the electrolyte by *OH and the carbon corrosion by LiOH at potentials beyond 3.5 V are primary causes of the irreversibility. We demonstrate that these side reactions can be considerably suppressed by optimizing the solvent | catalyst | electrical conductor interfaces. Our work highlights key strategies for promoting reversible LiOH decomposition via the 4e⁻/O₂ OER, paving the ways towards long-life LiOH-based nonaqueous Li-O₂ batteries.