Direct upcycling of mixed Ni-lean polycrystals to single-crystal Ni-rich cathode materials

With the widespread adoption of Li-ion batteries (LIBs), recycling of these devices has attracted much attention. The direct recycling of LIBs is the most efficient method for manufacturing sustainability because it aims to regenerate specific cathode materials back to their original performance without the chemical decomposition of secondary particles. However, the recovered cathode material composition may be considered outdated or obsolete. Meanwhile, traditional direct recycling requires additional sorting and separating steps for mixed cathode streams. Here, our new direct upcycling process uses a one-step molten salt method to convert spent polycrystalline Ni-lean cathodes into single-crystal Ni-rich cathodes, which could be applied to mixed cathode streams without additional sorting and separating steps. The obtained upcycled cathode materials exhibit improved capacity and stability beyond that of commercial materials. Thus, this methodology demonstrates a pathway toward the sustainable development of LIBs.