Water-Induced Surface Reconstruction of Co3O4 on the (111) Plane for High-Efficiency Li–O2 Batteries in a Hybrid Electrolyte

Abstract

The crystal plane effect of cobalt oxide has attracted much attention in Li–O₂ batteries (LOBs) and other electrocatalytic fields. However, boosting the catalytic activity of a specific plane still faces significant challenges. Herein, a strategy of adding water into the electrolyte is developed to construct a LiOH-based Li–O₂ battery system using the (111) plane-exposed Co₃O₄ as a cathode catalyst. The electrochemical performance shows that on the (111) plane, in the presence of water, the overpotential is largely reduced from 1.5 to 1.0 V and the cycling performance is enhanced. It is confirmed that during the discharge process, water reacts to form LiOH and induce the phase transformation of Co₃O₄ to amorphous CoO_x(OH)_y. At the recharge stage, LiOH is first decomposed and then CoO_x(OH)_y is reduced to Co₃O₄. Compared with pristine (111), the newly formed Co₃O₄ surface exhibits more active sites, which accelerates the following oxygen reduction and oxygen evolution processes. This work not only reveals the reaction mechanism of water-induced reaction on the (111) plane of Co₃O₄ but also provides a new perspective for further design of hybrid Li–O₂ batteries with a low polarization and a longer cycle life.