Regeneration of LiNi_1/3Co_1/3Mn_1/3O₂Cathode Active Materials from End-of-Life Lithium-Ion Batteries through Ascorbic Acid Leaching and Oxalic Acid Coprecipitation Processes

One of the emerging issues in solving the electronic waste problem is to address the growing amount of end-of-life Li-ion battery (LIB) waste. In this work, the regeneration of LiNi1/3Co1/3Mn1/3O2 (NCM 111) cathode active materials from end-of-life LIBs was successfully carried out via an easy, fast, and environmentally friendly recycling process that comprised three main stages, i.e., ascorbic acid leaching, oxalate coprecipitation process, and heat treatment. Ascorbic acid was able to leach Li, Ni, Co, and Mn ions from the spent NCM 111 cathode material with a relatively high leaching efficiency up to 90%. The following oxalic acid coprecipitation method has effectively recovered the transition metal ions in the leachate in the form of the metal oxalates MC2O4·2H2O (M = Ni, Mn, and Co), as confirmed by the result of X-ray diffraction characterization. The quantitative analysis of metal ions using X-ray fluorescence revealed that the ratio of Ni, Co, and Mn in the precipitate was approximately 1:1:1, with a slightly lower amount of Mn. Regeneration of NCM 111 via the heat treatment of metal oxalates at temperatures of 800–950 °C successfully reproduced the material (R-NCM) with an R3m hexagonal-layered structure, which could be reemployed as the cathode in LIBs. Charge–discharge characterization of the as-fabricated LIB at 2.5–4.3 V revealed that the battery with the R-NCM cathode synthesized at 900 °C exhibited a slightly higher initial specific discharge capacity (164.9 mAh/g at 0.2 C) than that of commercial NCM (157.4 mAh/g at 0.2 C). Moreover, the Li-ion battery also showed a very stable performance with a capacity retention of 91.3% after 100 cycles at 0.2 C.