Electrochemical properties of nickel manganese cobalt oxide cathode material obtained during battery recycling: Original scientific paper

Recycling spent batteries, particularly lithium-ion batteries, is becoming a global priority. Among the various recycling approaches, hydrometallurgy is one of the most useful methods. Among the many chemical compositions of cathode materials, ternary layered oxides warrant particular attention in recycling technology, making them more suitable candidates than other cathode materials. During hydrometallurgical leaching, various carboxylic acids are employed as solvents; however, oxalic acid deserves special con­sideration due to its high selectivity for lithium extraction. Nickel, cobalt, and manganese oxalates are practically insoluble in water and exist as the corresponding crystal hydrates. When a solution of transition metal sulphates, derived from cathode powder, is treated with a mixture of oxalic acid, the lithium remains in solution as a mixture of lithium sulphate and oxalate, while the transition metals are converted into their corresponding oxalates. In this process, a significant increase in the mass of the precipitate is observed, corresponding to the formation of oxalates. Thus, oxalic acid enables selective extraction of lithium from the “black mass” of lithium-ion batteries based on layered transition metal oxides. Moreover, the resulting mixture of transition metal oxalates, after minor compositional adjustments, can be directly reused for the resynthesis of ternary layered oxides. This paper presents methods for the hydrometallurgical processing of NCM523 (lithium nickel-cobalt-manganese oxide with a 5:2:3 molar ratio of Ni:Co:Mn) cathode material and its subsequent re-synthesis using transition metal and lithium oxalates. The physicochemical characteristics and electrochemical properties of the regenerated NCM523 electrodes are evaluated from the perspective of their potential reuse in rechargeable power sources.