Unravelling the key factors governing O2 evolution upon charging a reversible LiOH-based nonaqueous Li | |O2 battery

Achieving a reversible four-electron-per-oxygen-molecule oxygen evolution reaction is an essential yet highly challenging task for nonaqueous lithium hydroxide-based Li | |O2 batteries, as the kinetically sluggish oxygen evolution reaction tends to entangle with competing parasitic reactions, whose origins and mitigating strategies remain largely elusive. Here we construct a highly reversible lithium hydroxide-based Li | |O2 battery using iron–cobalt–nickel layered double hydroxide catalysts and tetramethylene sulfone-based electrolytes. Lithium hydroxide decomposition toward oxygen evolution involves key reactive oxygen species of surface-bound hydroxyl and hydroxyl radicals, but no singlet oxygen. These hydroxyl species corrode the electrolyte and carbon support, predominantly accounting for charging irreversibility. While oxidation-resistant solvents and electrical conductors are necessary to reduce hydroxyl-induced side reactions, the synergistic interplay of interfacial water solvation and catalytic surface structures hold the key to steering hydroxyl activity toward the desirable oxygen evolution reaction or by-product formation. This work offers insights into achieving long-life lithium hydroxide-based Li | |O2 batteries. LiOH-based Li | |O2 batteries offer high energy density but suffer from poor reversibility. Here, authors study side-reaction origins and key reactive oxygen species during LiOH decomposition upon charge, and propose holistic strategies to effectively improve the Faradaic efficiency.