Optimal geometrical configuration and oxidation state of cobalt cations in spinel oxides to promote the performance of Li-O₂ battery

Co₃O₄ is considered as one of promising cathode catalysts for lithium oxygen (Li-O₂) batteries, which contains both tetrahedral Co²⁺ sites (Co²⁺_Td) and octahedral Co³⁺ sites (Co³⁺_Oh). It is important to reveal the effect of optimal geometric configuration and oxidation state of cobalt ion in Co₃O₄ to improve the performance of Li-O₂ batteries. Herein, through regulating the synthesis process, Co²⁺ and Co³⁺ sites in Co₃O₄ were replaced with Zn and Al atoms to form materials with a unique Co site. The Li-O₂ batteries based on ZnCo₂O₄ showed longer cycle life than that of CoAl₂O₄, suggesting that in Co₃O₄, the Co³⁺_Oh site is a relatively better geometric configuration than Co²⁺_Td site for Li-O₂ batteries. Theoretical calculations revealed that Co³⁺_Oh sites provide higher catalysis activity, regulating the adsorption energy of the intermediate LiO₂ and accelerating the kinetics of the reaction in batteries, which further leads to the change of the morphology of the discharge product and ultimately improves the electrochemical performance of the batteries.