Regenerating degraded polycrystalline NCM towards high-performance single-crystal NCM622 through tailoring crystal-phase reconstruction

Attracted by ∼100% elements-recovering ratios of NCM, direct regeneration has been regarded as next-generation recycling manner. Owing to complex failure issues, diverse phase-kinds and Ni/Co/Mn element-ratios, crystal-phase reconstruction is vital for obtaining batch stability of physical-chemical properties. However, limited by sluggish element-diffusion, the as-regenerated sample always displays uneven element distribution with poor electrochemical properties. Herein, supported by the mechanical dissociation with semi-liquid assisting strategy, degraded polycrystalline NCM is successfully regenerated towards high-performance single-crystal NCM622. Ultra-uniform particle precursor with large viscosity (∼96.27 Pa·s) is obtained with the exposing of in-depth defects, bringing about the increasing of reaction areas and ion-diffusion paths. Meanwhile, the as-regenerated sample displays highly ordered layered structure with minimal cation mixing (1.6%) and uniform element distribution. Moreover, the established robust TM-O network with the high-frequency E_g and A_1 g vibrations effectively improved the energy barrier for TM ion migration and oxygen vacancy formation. They deliver a capacity of 177.2 mAh g⁻¹ at 0.1 C and remarkable cyclability (93.56% retention after 100 cycles at 1 C). Even at 5.0 C, the capacity could remain about 147.8 mAh g⁻¹. Besides, degraded NCM712 and NCM95 could be also transformed towards NCM622. Given this, this work is expected to provide large-scale crystal-phase reconstruction strategies for regenerating single-crystal NCM622, illustrating the in-depth phase transformation mechanisms.