Green recovery of Li, Ni, and Mn from spent xLi2MnO3·(1-x)LiMO2 cathode materials: Experimental study and mechanism analysis

Abstract

Recycling of spent lithium-ion batteries (LIBs) cathode materials has become a hot research area owing to limited resources, environmental problems, and strong global demand for LIBs raw materials. However, among multiple types of spent LIBs cathode materials, the recycling of spent xLi2MnO3·(1-x)LiMO2 cathode materials has not been studied and remains challenging. Herein, a green and efficient process has been developed for the simultaneous recovery of Li, Ni, and Mn from spent xLi2MnO3·(1-x)LiMO2 cathode materials by an ammonium sulfate roasting method. At optimal conditions of the roasting temperature of 450 °C, the (NH4)2SO4-to-spent xLi2MnO3·(1-x)LiMO2 mass ratio of 3:1, and the roasting time of 24 min, the spent xLi2MnO3·(1-x)LiMO2 phase was completely destroyed and converted into water-soluble metal-ammine-sulfates and metal-sulfates, resulting in that 99.41% Li, 98.67% Ni, and 98.61% Mn were rapidly extracted. Furthermore, possible conversion mechanisms and the kinetics for the roasting process were both investigated in detail, combined thermodynamics, DSC-TG, macro–micro scale analyses and DFT calculations. Finally, Mn as high-purity MnSO4 products with a purity of 99.98%, and Li and Ni as Li2SO4-NiSO4 mixture products, were efficiently recovered via (NH4)2SO3 precipitation, oxidation leaching, extraction and stripping, and evaporative crystallization. Compared with other current recovery process, this work shows better economic and environmental benefits, while maintaining the considerable Li, Ni, and Mn extraction yields, which is expected for the recycling of spent xLi2MnO3·(1-x)LiMO2 cathode materials in the future.