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

The sluggish reaction kinetics in current Li-O batteries (LOBs) hinder the efficient nucleation and decomposition of insulating LiO on catalyst surfaces. Therefore, developing effective strategies to regulate LiO 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) 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 O adsorption and an efficient two-electron transfer process in the initial oxygen reduction reaction step. This optimized electronic structure also promotes the desorption of LiO intermediates, guiding their disproportionation reactions and enabling LiO growth via a solution-mediated pathway. Furthermore, the spin-flip effect induced by the internal magnetic field suppresses singlet oxygen (O) formation, effectively mitigating side reactions. As a result, the LOBs demonstrate a remarkably high specific capacity (18 429.6 mAh g), excellent rate performance and enhanced cycling stability. These findings offer valuable insights into LiO nucleation mechanisms on high-performance catalysts and provide new design principles for next-generation LOB technologies.