Synergic Mechanisms on Carbon and Sulfur during the Selective Recovery of Valuable Metals from Spent Lithium-Ion Batteries

Abstract

Recycling of spent lithium-ion batteries (LIBs) has attracted ever-growing attention owing to the scarcity of critical metals and potential environmental risk. Sulfation roasting, as traditional technology, is considered uneconomical and not environmentally friendly due to tremendous consumption of energy and emission of waste gases such as SO₂ or SO₃. Hereby, a novel and cleaner sulfation roasting—a water leaching process is proposed to recover valuable metals from spent LiCoO₂ (LCO) batteries. It is found that sulfur can be recirculated thoroughly in the form of SO₄²– without the emission of SOₓ during the sulfation roasting process. Besides, the addition of graphite can promote the conversion of LiCoO₂ under relatively milder conditions than those of traditional sulfation roasting. To further understand the conversion mechanism of LCO, the effects of various parameters including roasting temperature, roasting time, the mass ratio of carbon, and the molar ratio of H₂SO₄ during the recovery of Li and Co were investigated. Approximately, 92% of the global Li can be recovered as Li₂CO₃ with a purity as high as 99.76%, and almost 100% of Co can be recovered in the form of CoSO₄ by sulfuric acid leaching. This work proposes a practicable and promising strategy for recycling valuable metals from spent LCO batteries. Meanwhile, the synergic mechanisms on carbon and sulfur for enhancing the selectivity of metal extraction are revealed.