Selective lithium extraction from spent LiNi0.5Co0.2Mn0.3O2/graphite mixed black powders and regeneration of single-crystal cathodes

Abstract

Selective recovery of specific elements from spent lithium-ion batteries is essential for the sustainable development of finite resources. An approach to selectively extract lithium from the spent mixed black powder and regenerate single-crystal cathodes was proposed in this work. Firstly, (NH₄)₂SO₄ was utilized to convert some of the spent LiNi_0.5Co_0.2Mn_0.3O₂(S-NCM523) in the mixed black powders to sulfates with different thermodynamic stability. With the further increase in temperature, the transition metal sulfates continued reaction with residual NCM523 (r-NCM523) generated water-soluble phase Li₂SO₄ and water-insoluble slag phase Ni-Co-Mn-O/graphite. It was worth mentioning that the graphite in the black powder reduced the Gibbs free energy of the sulfate roasting reaction under air atmosphere, which helped to reduce energy consumption. Then, 95.73 % of the Li was recovered by water-leaching, which was further converted into battery-grade Li₂CO₃. The precursor Ni_0.5Co_0.2Mn_0.3(OH)₂ was obtained by co-precipitation after acid leaching and filtration of the slag phase to remove residual graphite. Finally, the regeneration single-crystal NCM523 (RSC-NCM523) exhibited stable cycling performance compared with commercial single-crystal NCM523 (CSC-NCM523), which had an initial discharge specific capacity of 151.2 mAh g⁻¹ at 1C and the capacity retention rate of 92.20 % after 100 cycles.