Manganese cobaltite (MnCoO) is a promising electrode material because of its attractive redox chemistry and excellent charge storage capability. Our previous work demonstrated that the octahedrally-coordinated Mn are prone to react with the hydroxyl ions in alkaline electrolyte upon electrochemical cycling and separates on the surface of spinel to reconstruct into δ-MnO nanosheets irreversibly, thus results in a change of the reaction mechanism with K ion intercalation. However, the low capacity has greatly limited its practical application. Herein, we found that the tetrahedrally-coordinated Co ions were leached when MnCoO was equilibrated in 1 M HCl solution, leading to the formation of layered CoOOH on MnCoO surface which is originated from the covalency competition induced selective breakage of the Co–O bond in Co–O–Co and subsequent rearrangement of free CoO octahedra. The as-formed CoOOH is stable upon cycling in alkaline electrolyte, exhibits conversion reaction mechanism with facile proton diffusion and is free of massive structural evolution, thus enables utilization of the bulk electrode material and realizes enhanced specific capacity as well as facilitated charge transfer and ion diffusion. In general, our work not only offers a feasible approach in deliberate modification of MnCoO's surface structure, but also provides in-depth understanding of its charge storage mechanism, which enable rational design of the spinel oxides with promising charge storage properties.