Direct Upcycling of NMC Mixtures in Molten Salts

The effective management of end-of-life (EoL) lithium-ion batteries (LIBs) is increasingly vital to their widespread adoption. To maximize the value of spent cathodes, direct recycling and upcycling have emerged as promising strategies by restoring cathodes to their pristine states through the revitalization of degraded structure and compositions. Notably, nickel-manganese-cobalt-oxide (NMC) cathodes are anticipated to dominate the market soon, underscoring the necessity for efficient direct recycling and upcycling methods for spent NMCs. Our group has previously developed the "reciprocal ternary molten salts" (RTMS) system specifically for these processes. This system consists of molten salts incorporating two cation species and two anion species (Li⁺, Na⁺ || Cl^-, NO₃^-), offering a wide working temperature range and an oxygen-rich environment conducive to the lithiation of EoL-NMC batteries. Despite significant advancements using this method, further improvements are still necessary. In this study, we employed ball milling to refine particle size and promote the integration of lithium or nickel into the NMC structure, resulting in a well-defined layered configuration. The duration of ball milling and the initial material amount play crucial roles in influencing the performance of the recycled materials. This approach not only enhances electrochemical performance but also provides insights into the growth and phase transition mechanisms, ultimately leading to improved efficiency in recycling and upcycling practices for EoL LIBs.