Insights into the Role of Fluoride Impurities in Direct Regeneration of Ni-Rich Layered Cathodes

Battery recycling via direct regeneration has emerged as a next-generation strategy to simultaneously address environmental pollution and resource waste issues caused by end-of-life lithium-ion batteries. While previous research on direct regeneration has mainly focused on materials or repair processes, it has overlooked the impact of lithium fluoride (LiF) impurities, which can significantly degrade the electrochemical performance of regenerated materials. Through combined experimental characterization and computational simulations, we have experimentally confirmed the ubiquitous presence of LiF on spent LiNi0.82Co0.12Mn0.06O2 cathodes and elucidated its formation mechanism via first-principles calculations. To address this challenge, we developed a direct recycling strategy combining an acid-wash pretreatment with a high-temperature regeneration process. The acid wash effectively eliminates residual lithium fluoride impurities, thereby enhancing the lithium-ion transport dynamics. The solid-sintering regeneration simultaneously achieves lithium replenishment along with structural restoration, including microcrack restoration and phase transformation from rock salt to a layered structure. The purified regenerated LiNi0.82Co0.12Mn0.06O2 cathodes produced through our strategy demonstrate an initial discharge capacity of 197.37 mAh·g–1 with a 7.2% enhancement compared to their nonpurified counterparts. Remarkably, the purified regenerated LiNi0.82Co0.12Mn0.06O2 cathodes exhibit a superior rate capability and cycling stability. This work not only uncovers the formation mechanism of lithium fluoride and its critical role in degrading the performance of regenerated batteries but also offers an effective strategy for the practical direct recycling of spent Ni-rich cathodes.