Regeneration of Single-Crystal with Repaired of the (003) Crystal Plane from Degraded Polycrystalline Ternary Cathode.

Abstract

The direct regeneration of spent polycrystalline cathode materials into highly stable single-crystal counterparts heralds a transformative shift in the recycling of spent lithium-ion batteries (S-LIBs). However, current direct recycling approaches, reliant on molten salt-mediated single-crystal transformation, remain constrained by operational complexity and a fragmented mechanistic understanding of defect repair on the (003) crystal plane. Herein, we unveil a streamlined one-step regeneration strategy leveraging the LiNO₃-LiOH·H₂O-Li₂CO₃ system, enabling the conversion of polycrystalline S-NCM523 to single-crystal R-NCM523 while simultaneously reconstructing (003) crystal plane. DFT and in situ analyses demonstrate that CO₃ ² ^-, NO₃ ^-, and OH^- preferentially adsorb at the 3a sites within the lithium (Li) layer of the (003) plane. Their oxygen atoms hybridize with Li's 2s orbitals and TM's 3d orbitals, effectively suppressing rock-salt phase formation via Li vacancy filling and Oxygen vacancy repair. A Two-step sintering protocol drives particle single-crystallization and active lithium replenishment. The resultant R-NCM523 cathode significantly suppresses H2-H3 phase transitions, delivering an initial half-cell capacity of 165.80 mAh/g and retaining 81.0% of its discharge capacity after 1000 full-cell cycles. This precursor-free strategy achieves a molten salt recovery rate exceeding 90%, providing an industrially viable pathway for efficient, low-energy S-LIB regeneration.