Improved hydrometallurgical extraction of valuable metals from spent lithium-ion batteries via a closed-loop process

Abstract

The increasing market size of high-energy storage systems due to the booming of not only portable electronic devices but also electrical vehicles and renewable energy sources has promoted battery technologies, resulting in many spent lithium-ion batteries (LIBs). This study focuses on proposing a closed-loop process to recycle the full valuable metals from spent LiNi1/3Co1/3Mn1/3O2 material. Reduction roasting and hydrometallurgy were combined and used for de-agglomeration of cathode composites and enhanced recycling of valuable metals. Experimental results showed the cathode material was reduced to Ni, Co, Li2CO3, and MnO under microwave carbothermic reduction, and lithium carbonate was directly recovered after dissolved in water with a high yield of 99%. Afterward, transition metals (Ni, Co, Mn) enriched residues can be dissolved in fumaric acid with leaching efficiencies of more than 96% under optimized leaching conditions, and finally recovered as single compounds by step-wise addition of chemicals. The mechanism of the nonthermal effect of microwave on the leaching of metals was analyzed by kinetic studies, and the decreased Ea values for metals demonstrate that microwave treatment is beneficial for metals leaching through decreasing their apparent energies. Besides, the characterization results of X-ray diffraction and scanning electron microscope indicate the destruction of the layered crystal structure and an increased liberation degree after microwave treatment, which is also beneficial for the enhancement of metals leaching. Therefore, the microwave reductive-assisted process is found in a green and effective industrial process to recycle valuable metals from spent LIBs.