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.