An acid-free process for the selective recovery of lithium from spent ternary lithium-ion batteries
摘要
With the dramatic accumulation of the end-of-life lithium-ion batteries, their recycling is attracting extensive attention worldwide. To address the problem of low lithium recovery in the current typical hydrometallurgy recovery process, this research uses sodium bisulfate as an auxiliary roasting reagent to extract lithium from spent lithium-ion batteries through sulphation roasting, which can enhance the lithium recovery rate significantly. A systematic study of the sulphation roasting process and the mechanisms was carried out with experiments, thermodynamic calculations, and characterization of the roasted sample phases. The results showed that at a roasting temperature of 600 °C, NaHSO4·H2O/spent LiNixCoyMnzO2 cathode powders (S-NCM) mass ratio of 1.2, and roasting time of 60 min, 95% selective dissolution of lithium was acquired, while the leaching rates of Ni, Co, and Mn were confined under 1%. During roasting, the NCM layered structure collapses and the lithium is transformed into the LiNaSO4 phase, while the transition metals transform into Ni6MnO8 and MnCo2O4 phases. The removal of impurity ions from the lithium-rich leaching solution and the generation of Li2CO3 were achieved by a combination of thermodynamic calculations and experiments.