Strengthening Valuable Metal Recovery from Spent Lithium-Ion Batteries by Environmentally Friendly Reductive Thermal Treatment and Electrochemical Leaching

Abstract

The traditional acid leaching method for recycling valuable metals from the cathode material of spent lithium-ion batteries (LIBs) has encountered the problems of high consumption of H2SO4 and reducing agents. In this study, a novel process has been developed to strengthen valuable metal recovery from spent lithium-ion batteries by reductive thermal treatment and electrochemical leaching. With the help of reductive thermal treatment under the conditions of R = 1600 °C and 120 min, the layered structure of the cathode material LiNi1/3Co1/3Mn1/3O2 is reduced to a mixture of Li2CO3, NiO, Co3O4, Mn2O3, and MnO2 due to the oxygen releasing from the framework. The destruction of the layered crystal structure reduces the difficulty of leaching valuable metals. 90.59% Ni, 90.53% Co, 66.40% Mn, and 100% Li were leached under the optimal conditions of 20 mL/g liquid–solid ratio, 1.5 M H2SO4, 0.8 A, and 150 min at room temperature. Comparing the processes of reductive thermal treatment with acid leaching and direct electrochemical leaching of spent cathode material under the same leaching conditions, the proposed approach can achieve the highest metal recovery and economic benefits. It can be implemented at room temperature, decreases the application of reducing agent and sulfuric acid, and makes full use of spent graphite, resulting in a greener recycling process for recovering valuable metals from spent LIBs.