Selective leaching and magnetic separation for efficient recovery of lithium and iron phosphate from Aluminum-Contaminated cathode materials of spent LiFePO4 batteries

Abstract

The recovery and reuse of resources from spent lithium-ion batteries present significant potential for sustainable development and environmental protection. However, challenges remain, particularly in addressing complex issues such as the removal of aluminum (Al) impurities. This paper introduces an efficient and selective process for leaching lithium (Li) from LiFePO₄ cathode material powder, even in the presence of hard-to-remove Al impurities. First, the LiFePO₄ cathode material was separated from damaged Al foil current collectors using an environmentally friendly water stripping method, resulting in the active material powder containing Al impurities. In the subsequent process, a small amount of H₃PO₄ was used as a leaching agent, H₂O₂ as an oxidant, and the cathode material was subjected to mechanical activation by ball milling. After continuous optimization of all conditions, an efficient leaching of 99.5 % Li was achieved, with almost all (>99 %) Fe and Al impurities separated as precipitates. Li in the leachate was precipitated as Li₂CO₃ by adding Na₂CO₃ at 95 °C, achieving a purity of 99.2 %. A magnetic separation scheme is presented to successfully separate FePO₄ from Al-containing impurities in the leaching residue. After five magnetic separation cycles, the purity of FePO₄ exceeded 98.5 %. Additionally, the mechanisms of the entire reaction system were investigated using characterization methods such as laser particle size analysis, XPS, and XRD. A comprehensive economic evaluation of the entire system confirms its feasibility. This eco-friendly selective separation process shows strong potential for industrial applications and makes a valuable contribution to sustainable development.