Low-Temperature Direct Regeneration of Spent Nickel-Rich NMC via Aqueous Relithiation

The growing demand and resource scarcity of lithium-ion batteries (LIBs) have led to increasing importance in the recycling of spent batteries. Direct recycling of cathode materials is gaining popularity compared with pyrometallurgical and hydrometallurgical processes for its environmental benignity and low energy consumption. Herein, spent nickel-rich LiNi_0.83Mn_0.05Co_0.12O₂ (S-NMC) was successfully regenerated using a simple but effective low-temperature aqueous relithiation process at 90 °C. Lithium hydroxide and sodium thiosulfate were employed as the lithium source and reducing agent, to promote lithium reinsertion and restore the layered structure. The regenerated NMC exhibits a significantly enhanced specific capacity of 180 mAh g^-1 at C/20 and delivers cycling stability comparable to pristine NMC. Our findings highlight the potential of low temperature aqueous relithiation as a sustainable and scalable route for direct recycling of spent cathodes, addressing key limitations of conventional recycling methods in the circular economy of LIBs.