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 LiNi0.88Co0.095Al0.025O2 (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., LiNixCoyMnzO2 (NCM) and mixed spent NCAs with varied degree of Li loss.