Unintended Consequences of Salt-water over-discharge : Copper Dissolution and Its Detrimental Effects on LiFePO4 Direct recycling

초록

Salt-water discharging is widely employed to ensure the safe dismantling of lithium-ion batteries by removing residual charges. However, excessive discharge during this process can induce copper dissolution from the current collector. The dissolved copper can redeposit onto the surface of LiFePO₄ (LFP) cathodes, leading to chemical contamination that may adversely affect the structural integrity and electrochemical performance of LFP during direct recycling. Despite its practical relevance, the impact of Salt-water overdischarge-induced copper contamination on LFP direct recycling and the corresponding mitigation strategies have not been systematically investigated. In this study, we investigate copper dissolution and surface contamination phenomena in LFP cathodes subjected to Salt-water overdischarge and evaluate the effect of washing processes on the performance of direct recycling. Copper species deposited on the LFP surface after Salt-water discharging were effectively removed through washing treatment. In contrast, unwashed samples exhibited altered surface chemical compositions and degraded recycling performance due to residual copper contamination. Washed LFP cathodes demonstrated significantly improved structural stability and electrochemical properties, indicating enhanced suitability for direct recycling processes. These results reveal that Salt-water discharging, while intended as a safety measure, can introduce unintended detrimental effects on LFP direct recycling. This study highlights the critical role of washing processes in mitigating copper contamination and provides practical guidelines for achieving high-quality direct recycling of LFP cathode materials.