Rapid Cooling Enables High Reversibility in Lithium‐Rich Cathode via Double‐Vacancy Engineering

ABSTRACT Lithium‐rich manganese‐based layered oxides (LRMO) are regarded as promising high‐energy‐density cathode materials that employ both cationic and anionic redox mechanisms. Nevertheless, their practical application is impeded by substantial voltage decay and restricted rate performance, mainly attributable to oxygen release and sluggish Li + diffusion kinetics. In this study, a dual‐vacancy (Li, O) engineering strategy is devised via a rapid cooling process within the LRMO structure. The simultaneous introduction of Li and O vacancies effectively alleviates the kinetic limitations related to slow oxygen diffusion, thus enhancing the reaction kinetics and facilitating the reversible redox activity of oxygen species. Furthermore, these vacancies foster the formation of a disordered surface layer, which acts as a protective barrier by reducing oxygen release and safeguarding the cathode material from electrolyte‐induced degradation. The synergistic effects of chemical defects and reconstructed surface structures contribute to the stabilization of active oxygen species (O 2 /O n− ), thereby suppressing the irreversible oxygen evolution reaction. As a result, the modified material achieves a high capacity of 125.9 mAh g −1 at 5C and retains 96.21% of its capacity after 500 cycles at 3C, significantly outperforming the pristine LRMO. This research presents an effective defect engineering strategy for the development of high‐energy‐density layered oxide cathode materials.