Homogenization enabled efficient regeneration of spent Ni-rich LiNi_<i>x</i>Co_<i>y</i>Mn_{1−<i>x</i>−<i>y</i>}O₂ cathodes

High-Ni LiNi_<i>x</i>Co_<i>y</i>Mn_{1-<i>x</i>-<i>y</i>}O₂ (NCM) oxides with low Co content have emerged as promising candidates for next-generation cathodes due to their high energy density and acceptable manufacturing costs, making them widely adopted in electric mobility applications. However, their limited service life highlights an urgent need for efficient and economical recycling methods. Direct regeneration <i>via</i> relithiation has proven effective for the chemical restoration of degraded cathodes at low cost, but repairing high-Ni NCM cathodes remains challenging due to their degradation mechanisms of intergranular cracking and particle fragmentation. To overcome these challenges, we exploited the weakened interactions along grain boundaries in post-cycled NCM cathodes, achieving morphological reconstruction and size homogenization of degraded Ni-rich NCM through mild ball milling. The resulting NCM nanoparticles expose more facets for Li⁺ diffusion compared with polycrystalline particles, effectively shortening the diffusion pathways during the subsequent relithiation process and enabling efficient regeneration at low temperatures and within short processing durations. This work provides valuable insights into designing effective repairing strategies for mechanically degraded cathodes, advancing the applicability of direct regeneration techniques and fostering the sustainable development of Li-ion batteries.