Ordered porous Mn - Co spinel oxide (CoMn₂O₄) with vacancies modulation as efficient electrocatalyst for Li - O₂...

Nonaqueous Li - O₂ battery (LOB) is considered one of the most promising energy storage system due to its ultrahigh theoretical specific capacity (3500 Wh kg^-1). Introducing vacancies in CoMn₂O₄ catalysts is regarded as an effective strategy to enhance the electrochemical performances of LOB. However, the relation between vacancy types in CoMn₂O₄ and catalytic performances in the LOB remains ambiguous. Herein, ordered porous CoMn₂O₄ with oxygen and metal vacancies is obtained via solvothermal reaction followed by temperature-controlled calcination using polystyrene spheres as templates. The increase in treatment temperature reduces the content of oxygen vacancies while increasing that of the metal vacancies. Notably, experimental results and theoretical calculations show that oxygen vacancies in CoMn₂O₄ have a greater influence than metal vacancies in modulating the LiO₂ adsorption during the reaction processes and reducing the overpotential. CoMn₂O₄ synthesized at 500 ℃ (CoMnO-500) with higher oxygen vacancies exhibits stronger adsorption onto the LiO₂, facilitating the formation of film-like Li₂O₂. Therefore, an LOB with the CoMnO-500 catalyst presents the lowest overpotential of 1.2 V and longest cycle lifespan of 286 cycles at a current density of 200 mA g^-1. This study offers insights into the effect of CoMn₂O₄ vacancies on the formation pathway of Li₂O₂ discharge products.