Unraveling and Modulating the Competitive Dynamics in Direct Regeneration of Ni-Rich Cathode Material

Direct regeneration, as a promising technology for recycling spent lithium-ion battery materials, fundamentally involves replenishing missing components in degraded materials to promote structural reconstruction. Current methods to achieve lithium replenishment typically rely on lithium salt conversion at high temperatures. However, the inherent lithium deficiencies in spent cathode materials trigger lattice oxygen loss under thermal conditions, exacerbating structural degradation and hindering further relithiation. The conflicts between relithiation and thermal decomposition are the key to limiting the regeneration effect. Due to insufficient understanding of the competitive mechanisms among the various reactions in direct regeneration, avoiding these conflicts by strategy design remains challenging. Herein, this study elucidates the sequence and dynamic evolution of critical reactions in direct regeneration, identifying a previously unknown prior-relithiation process that occurs at significantly lower temperatures. By promoting this prior-relithiation process, the oxygen vacancy formation energy of spent cathode materials is increased, stabilizing the cathode material structure and mitigating thermal decomposition during direct regeneration. The regeneration effect is therefore significantly improved, achieving a 15% higher capacity recovery rate and significantly enhanced overall electrochemical performance compared to the normal approach. This study deepens the understanding of direct regeneration mechanisms and offers a scientific foundation for developing advanced direct regeneration strategies.