A Universal Molten Salt Method for Direct Upcycling of Spent Ni‐rich Cathode towards Single‐crystalline Li‐rich Cathode

With ever‐increasing pursuit for high‐value output in recycling spent lithium‐ion batteries (LIBs), traditional recycling methods of cathodes tend to be obsolete because of the complicated procedures. Herein, we first upcycle spent polycrystal LiNi_0.88Co_0.095Al_0.025O₂ (S‐NCA) to high value‐added single‐crystalline and Li‐rich cathode materials through a simple but feasible LiOH‐Na₂SO₄ eutectic molten salt strategy. The in situ X‐ray diffraction technique and a series of paratactic experiments record the evolution process of upcycling and prove that excessive Li occupies the transition metal (TM) layers. Beneficial from the single‐crystalline and Li‐rich nature, the regenerated NCA (R‐NCA) exhibits remarkably enhanced electrochemical performances in terms of long‐term cyclability, high‐rate performance and low polarization. This approach can also be successfully extended to other cathode materials e.g., LiNi_xCo_yMn_zO₂ (NCM) and mixed spent NCAs with varied degree of Li loss.