Synergistic strengthening mechanisms of mechanical activation-microwave reduction for selective lithium extraction from spent lithium batteries

Chao Liu; Jie Long; Wei Luo; Hongwei Liu; Yingying Gao; Zicong Wan; Xuegang Wang

doi:10.1016/j.wasman.2022.11.009

Synergistic strengthening mechanisms of mechanical activation-microwave reduction for selective lithium extraction from spent lithium batteries

Waste Manag. 2023 Jan 1:155:281-291. doi: 10.1016/j.wasman.2022.11.009. Epub 2022 Nov 17.

Authors

Chao Liu¹, Jie Long¹, Wei Luo¹, Hongwei Liu¹, Yingying Gao¹, Zicong Wan¹, Xuegang Wang²

Affiliations

¹ School of Water Resources and Environmental Engineering, East China University of Technology, Nanchang 330013, Jiangxi, China; State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, Jiangxi, China.
² School of Water Resources and Environmental Engineering, East China University of Technology, Nanchang 330013, Jiangxi, China; State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, Jiangxi, China. Electronic address: wangxuegang@ecut.edu.cn.

PMID: 36403412
DOI: 10.1016/j.wasman.2022.11.009

Abstract

Carbothermal reduction of cathode materials is an effective method to selectively extract lithium carbonate, both mechanical activation and microwave heating can enhance thermal reduction of mixed electrode materials. However, the mechanism of enhanced lithium extraction has not been fully revealed. This study attempts to uncover the synergistic strengthening mechanisms of mechanical activation-microwave reduction from the aspects of material structure, dielectric properties, reduction kinetics and lithium recovery rate. Mechanical activation induces amorphization and structural defects. The enhanced dielectric properties of materials and the induced hotspots/arc plasmas are also responsible for the enhancement of the reduction reaction. The average dissociation activation energy in the activated sample is 18.0 kJ·mol^-1, which is 20.3 kJ·mol^-1 lower than that of unactivated sample. The model-free method reveals that the carbothermic reduction process can be divided into three stages: (I) initial stage (α < 0.4(0.6)): the activation energy gradually decreases with the formation of strong microwave acceptor-reduction products; (II) transitional stage (0.4(0.6) < α < 0.7): the increase in mass transfer resistance leads to gradual increase in activation energy. Mechanical activation shortens the transitional reaction stage; (III) later reaction stage (α > 0.7), the decrease in activation energy may be attributed to the enhanced microwave absorption and CO reduction. The model-fitting method reveals that after mechanical activation, the reaction kinetic changes from reaction-order model to Ginstling-Brounshtein diffusion model. The optimized lithium extraction process parameters were: activation 300 rpm for 1.5 h, reduction temperature 550 °C. The research results can provide theoretical support for the enhanced extraction of cathode materials.

Keywords: Carbothermal reduction; Mechanical activation; Microwave; Spent lithium-ion batteries; Strengthening mechanism.