Role of precursors mixing sequence on the properties of CoMn₂O₄ cathode materials and their application in pseudocapacitor

In this study, the effect of oxygen vacancy in the CoMn₂O₄ on pseudocapacitive characteristics was examined, and two tetragonal CoMn₂O₄ spinel compounds with different oxygen vacancy concentrations and morphologies were synthesized by controlling the mixing sequence of the Co and Mn precursors. The mixing sequence was changed; thus, morphologies were changed from spherical nanoparticles to nanoflakes and oxygen vacancies were increased. Electrochemical studies have revealed that tetragonal CoMn₂O₄ spinels with a higher number of oxygen vacancies exhibit a higher specific capacitance of 1709 F g⁻¹ than those with a lower number of oxygen vacancies, which have a higher specific capacitance of 990 F g⁻¹. Oxygen vacancies create an active site for oxygen ion intercalation. Therefore, oxidation–reduction reactions occur because of the diffusion of oxygen ions at octahedral/tetrahedral crystal edges. The solid-state asymmetric pseudocapacitor exhibits a maximum energy density of 32 Wh-kg⁻¹ and an excellent cyclic stability of nearly 100%.