Selective lithium recovery and regeneration of ternary cathode from spent lithium-ion batteries: Mixed HCl-H2SO4 leaching-spray pyrolysis approach

The recycling of spent lithium-ion batteries (LIBs) is crucial for environmental protection and resource sustainability. However, the economic recovery of spent LIBs remains challenging due to low Li recovery efficiency and the need for multiple separation operations. Here, we propose a process involving mixed HCl-H2SO4 leaching-spray pyrolysis for recycling spent ternary LIBs, achieving both selective Li recovery and the preparation of a ternary oxide precursor. Specifically, the process transforms spent ternary cathode (LiNixCoyMnzO2, NCM) powder into Li2SO4 solution and ternary oxide, which can be directly used for synthesizing battery-grade Li2CO3 and NCM cathode, respectively. Notably, SO42− selectively precipitates with Li+ to form thermostable Li2SO4 during the spray pyrolysis, which substantially improves the Li recovery efficiency by inhibiting Li evaporation and intercalation. Besides, SO2 emissions are avoided by controlling the molar ratio of Li+/SO42− (≥2:1). The mechanism of the preferential formation of Li2SO4 is interpreted from its reverse solubility variation with temperature. During the recycling of spent NCM811, 96.5% of Li is selectively recovered, and the regenerated NCM811 exhibits excellent cycling stability with a capacity retention of 81.7% after 300 cycles at 1 C. This work offers a simple and robust process for the recycling of spent NCM cathodes.