Sustainable and selective recovery of lithium from spent lithium-ion batteries based on hydrogen reduction: Theoretical analysis and phase transformation

The reduction of cathode materials is one of the keys for almost all of the recycling technologies of spent lithium-ion batteries. Different from the traditional reduction leaching and carbothermic reduction, a new promising process based on hydrogen reduction was studied theoretically in this study. The reduction thermodynamics was analyzed and phase transformation was characterized. It is found that the lithium ions in LiCoO2 and LiNi1/3Co1/3Mn1/3O2 can be converted to soluble LiOH in hydrogen atmosphere, just at a low reduction temperature of 450 °C. Meanwhile, the high valence transition metals in the cathode powders were reduced to their low valence states, which are beneficial to the subsequent acid leaching process. Due to the core–shell and porous structures of reduction particles and high solubility, the LiOH in the reduction products can be leached into water easily. The leaching rates achieve 98.03% and 99.36%, and the lithium concentrations reach up to 23.6 and 23.9 g/L for LiCoO2 and LiNi1/3Co1/3Mn1/3O2, respectively. This method is simple and no harmful substances are produced in the reduction process. Therefore, the recovery technology based on hydrogen reduction-water leaching is environmentally friendly and has a great applied prospect for the industrial production.