Recovery of valuable metals and modification of cathode materials from spent lithium-ion batteries

Improper disposal of used lithium-ion batteries will cause serious environmental pollution and waste of resources. A closed-loop recycling process based on hydrothermal leaching and co-doping is developed to recycle valuable metals by regenerating cathode material from spent lithium-ion batteries. Valuable metals in scrapped cathode material are efficiently leached out by hydrothermal leaching with a lower concentration of H2SO4 solution. In this work, 93.11% of Ni, 92.84% of Co and 90.18% of Mn can be leached out under the optimal hydrothermal leaching condition (0.5 M H2SO4, 0.1 M Na2SO3, 20 g/L, 120 degrees C and 8 h). The Na-F co-doped materials Li1-xNaxNi0.6Co0.2Mn0.2O2-xFx (x = 0, 0.02, 0.04, 0.06) regenerated by co-precipitation are studied in this paper. The micro substitution of Na for Li can compensate for the effect of fluorine doping on capacity reduction. Na-F co-doping can stabilize the crystal structure, reduce the cation mixing degree and enhance the electrochemical performance. The material with a doping amount of 0.02 exhibits the best crystal structure, the lowest degree of cation mixing, the lowest electrochemical polarization and the minimal resistance, playing the highest discharge capacity (176.37 mAh g(-1)) with the highest capacity retention (93.07%) at 0.2 C after 100 cycles. (C) 2021 Elsevier B.V. All rights reserved.