Recycling of waste carbon residue from spent lithium-ion batteries via constant-pressure acid leaching
Xiangdong Zhu, Jin Xiao, Qiuyun Mao, Zhen-hua ZHANG, Lei Tang, Qifan Zhong
Abstract
Waste carbon residue (WCR) was efficiently detoxicated and regenerated to high-purity graphite (PGC) used in lithium-ion batteries through the constant-pressure acid leaching technique. The leaching conditions were optimized by the combination of orthogonal and single-factor experiments. Results show that PGC with 99.5% purity is regenerated at temperature of 60 °C, initial acid concentration of 12%, leaching time of 180 min, and liquid-to-solid ratio of 25:1, satisfying the requirements of commercial graphite. Meanwhile, the sodium hydroxide precipitation process was designed to recover valuable components from leachate efficiently. Ni, Co, Mn, and Al recoveries reach 96.92%, 87.5%, 97.83%, and 92.17%, respectively, at pH=11. Moreover, the co-product NaF can be recovered with purity over 99% via evaporative crystallization. The loss rate of fluorine is less than 0.5%, thereby eliminating the pollution risk of fluorine to the environment. The proposed process shows considerable environmental and economic benefits.