Effects of Different Impurities on the Properties of Recovered Cathode Materials by Hydrometallurgical Recycling

The escalating demand for lithium-ion batteries necessitates sustainable recycling strategies to limit the cost and mitigate environmental impact. The cathode, a critical component of spent lithium-ion batteries, can be effectively regenerated through hydrometallurgical recycling. This process introduces three categories of impurities: cationic, anionic, and solid impurities, from various battery components. Cation impurities, including Al³⁺, Cu²⁺, Fe^2+/3+, originate from cathode/anode current collector and cell cases, respectively. These cations adversely affect morphology and tap density of cathode materials since they can react with OH^- and influence the nucleation of precursors. However, these cations can merge into the lattice of cathode materials. With a small amount of substitution, they can inhibit cation mixing and improve the electrochemical performance of recovered cathode materials. As for anion impurities, there are S^-, F^-, and PO₄^3- and they are sourced from electrode materials and electrolyte. These anions have less effects on the morphology of recovered cathode materials, but some of them can cause holes inside particles, which can improve the electrochemical performance. Solid impurities, mainly neutral insoluble substances, contain carbon from anode and conductive agents. Carbon impurities can affect the nucleation of precursors and form holes inside particles. This study provides a systematic exploration of how these common impurities affect the morphology, tap density, phase, cation mixing, and electrochemical performance of recovered cathode materials, which can offer valuable insights into the role of impurities in recycling processes, aiding researchers in refining recovery techniques for optimal performance of recycled cathodes.