Upcycling Degraded LiNi_0.5Co_0.2Mn_0.3O₂ to Highly Stable Single-Crystalline Cathode Materials through Molten Salt-Assisted Reconstruction

The rapid decommissioning of lithium-ion batteries (LIBs) has spurred the development of green recycling strategies that can restore degraded cathode materials. Direct regeneration is particularly challenging for spent LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) due to severe lithium deficiency and structural collapse. Here, we report an efficient molten salt-assisted reconstruction strategy to transform degraded NCM523 to highly stable single-crystalline cathode materials for LIBs. A LiOH-LiNO 3 eutectic system with 0.5 mol % Al 2 O 3 additive was used to regenerate degraded NCM523 during heat treatment. The inorganic molten salts create a liquid phase environment and speed up the reaction kinetics, which can simultaneously achieve stoichiometric lithium compensation and the formation of single-crystalline Al-doped NCM523 cathodes. The Al-doped NCM523 sample delivers a discharge capacity of 151.8 mAh g –1 at 0.2C and maintains 96.2 mAh g –1 at 5C, significantly outperforming the undoped counterpart (84.6 mAh g –1 ). After 200 cycles at 1C, it retains 89.4% of its initial capacity. In situ X-ray diffraction confirms that Al 3+ doping suppresses lattice distortion, while density functional theory (DFT) calculations indicate that Al 3+ preferentially substitutes Co sites, strengthening Al–O bonding and enhancing oxygen framework stability. This work offers an effective and scalable route for the high-value regeneration of spent LIB cathodes.