Effect of Impurities on Direct Recycling of Spent LiNi<sub><i>x</i></sub>Co<sub><i>y</i></sub>Mn<sub><i>z</i></sub>O<sub>2</sub> Cathode Material for Lithium-Ion Batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 42107003.
- Also identified by DOI 10.1021/acsnano.5c22606 and PMC identifier 13218363.
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Abstract
Direct recycling is a promising approach for valorizing spent lithium-ion batteries, yet the effect of impurities on cathode regeneration has been insufficiently explored. Herein, an end-of-life LiNi<sub>0.6</sub>Co<sub>0.2</sub>Mn<sub>0.2</sub>O<sub>2</sub> (NCM622) pouch cell is used as a model system to systematically investigate the behavior of impurities and the outcomes for regeneration, using XPS, SRD, and XAS techniques. The analysis identifies AlPO<sub>4</sub>, AlF<sub>3</sub>, Li<sub>3</sub>PO<sub>4</sub>, LiF, Li<sub><i>x</i></sub>PF<sub><i>y</i></sub>O<sub>4</sub>, and Li<sub>2</sub>CO<sub>3</sub> as the main impurities in the spent powder, along with Al-inclusion limited to a surface near region. Among these, Al- and F-containing species are found to significantly affect the regeneration process, inducing further Al- and F-inclusion in the regenerated material, while PO<sub>4</sub><sup>3-</sup> species exhibit a minimal structural impact. In-depth structural analysis reveals that F-inclusion proceeds via substitution of lattice oxygen, causing increased structural disorder. Al-inclusion most likely involves epitaxial crystal growth promoted by excess lithium salts, resulting in structural asymmetry at elevated inclusion levels. Electrochemical evaluation shows that low-level impurity inclusion has a negligible effect on initial capacity. Yet, impurity accumulation, potentially amplified over repeated recycling, markedly compromises capacity recovery and structural integrity. This work clarifies impurity-induced effects during regeneration and highlights the importance of impurity control for enabling sustainable and effective direct recycling.