A sodium salt-assisted roasting approach followed by leaching for recovering spent LiFePO4 batteries

Beilei Zhang; Xin Qu; Xiang Chen; Dongxu Liu; Zhuqing Zhao; Hongwei Xie; Dihua Wang; Huayi Yin

doi:10.1016/j.jhazmat.2021.127586

A sodium salt-assisted roasting approach followed by leaching for recovering spent LiFePO₄ batteries

J Hazard Mater. 2022 Feb 15;424(Pt C):127586. doi: 10.1016/j.jhazmat.2021.127586. Epub 2021 Oct 27.

Authors

Beilei Zhang¹, Xin Qu¹, Xiang Chen¹, Dongxu Liu¹, Zhuqing Zhao¹, Hongwei Xie¹, Dihua Wang², Huayi Yin³

Affiliations

¹ Key Laboratory for Ecological Metallurgy of Multimetallic Mineral of Ministry of Education, School of Metallurgy, Northeastern University, Shenyang 110819, PR China.
² School of Resource and Environmental Science, Wuhan University, Wuhan 430072, PR China.
³ Key Laboratory for Ecological Metallurgy of Multimetallic Mineral of Ministry of Education, School of Metallurgy, Northeastern University, Shenyang 110819, PR China,; School of Resource and Environmental Science, Wuhan University, Wuhan 430072, PR China. Electronic address: yinhy@smm.neu.edu.cn.

PMID: 34808449
DOI: 10.1016/j.jhazmat.2021.127586

Abstract

Mild-temperature (<1000 °C) carbothermic reduction has been proven as an effective way to recover Li and transition metals by converting lithium transition metal oxides to transition metals/alloys and Li₂CO₃. However, LiFePO₄ cannot be reduced by carbon because of its thermodynamically stable olivine structure. Herein, LiFePO₄ is converted to Fe and lithium salts by carbon with the assistance of Na₂CO₃ that acts as an activating agent to break down the chemical bonds of LiFePO₄ and thereby enable the carbothermic reduction. Using Na₂CO₃ as the activating agent, LiFePO₄ was reduced to Fe, NaLi₂PO₄, and LiNa₅(PO₄)₂ which can be separated by magnetic separation with a Li recovery rate of 99.2%. Using NaOH as the activating agent, LiFePO₄ was oxidized to Fe₃O₄, NaLi₂PO₄ and LiNa₅(PO₄)₂ at 600 °C, and the roasted products can be separated by magnetic separation process with a Li recovery rate of 92.7%. Various sodium salts were tested to screen proper salts for the reduction process, and a 400-g scale roasting-separation process has been demonstrated. Overall, the salt-assisted roasting is a promising way to recycle spent LiFePO₄ batteries without using strong mineral acids and shows great potential for the industrial-scale implementation.

Keywords: Carbothermic reduction; Recovery; Roasting; Sodium salts; Spent LiFePO(4).