Spin-polarized d-orbital filling in cobalt catalysts boosts solution-mediated Li-O₂ batteries

The sluggish reaction kinetics in current Li-O₂ batteries (LOBs) hinder the efficient nucleation and decomposition of insulating Li₂O₂ on catalyst surfaces. Therefore, developing effective strategies to regulate Li₂O₂ growth and elucidating the catalytic mechanism are essential for unlocking the full potential of LOB technology. Herein, a spin-polarized Co-based catalyst exhibits a significant reversible magnetization change (9.5 emu g^-1) during the oxygen reduction and evolution reactions. The strong overlap between the Co 3d and O 2p orbitals modulates the Co 3d orbital occupancy, enhancing spin-electron filling and thereby facilitating rapid O₂ adsorption and an efficient two-electron transfer process in the initial oxygen reduction reaction step. This optimized electronic structure also promotes the desorption of LiO₂ intermediates, guiding their disproportionation reactions and enabling Li₂O₂ growth via a solution-mediated pathway. Furthermore, the spin-flip effect induced by the internal magnetic field suppresses singlet oxygen (¹O₂) formation, effectively mitigating side reactions. As a result, the LOBs demonstrate a remarkably high specific capacity (18 429.6 mAh g^-1), excellent rate performance and enhanced cycling stability. These findings offer valuable insights into Li₂O₂ nucleation mechanisms on high-performance catalysts and provide new design principles for next-generation LOB technologies.