Transformation and migration mechanism of fluorine-containing pollutants in the pyrolysis process of spent lithium-ion battery

Hanlin Huang; Chunwei Liu; Zhi Sun

doi:10.1016/j.jhazmat.2022.128974

Transformation and migration mechanism of fluorine-containing pollutants in the pyrolysis process of spent lithium-ion battery

J Hazard Mater. 2022 Aug 5:435:128974. doi: 10.1016/j.jhazmat.2022.128974. Epub 2022 Apr 20.

Authors

Hanlin Huang¹, Chunwei Liu², Zhi Sun²

Affiliations

¹ National Engineering Research Center of green recycling for strategic metal resources, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China; School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing 101407, China; National Basic Public Science Data Center, Institute of Process Engineering, Beijing 100190, China.
² National Engineering Research Center of green recycling for strategic metal resources, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China; School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing 101407, China; National Basic Public Science Data Center, Institute of Process Engineering, Beijing 100190, China. Electronic address: sunzhi@ipe.ac.cn.

PMID: 35472550
DOI: 10.1016/j.jhazmat.2022.128974

Abstract

Pyrolysis is an effective method to remove organics (e.g. electrolytes and binders) from spent lithium-ion battery (LIB). In this study, the co-pyrolysis characteristics of fluorine-containing substances and active materials from LIB were investigated using thermogravimetric-differential scanning calorimetry (TG-DSC), infrared spectroscopy (IR), and mass spectrometry (MS) analysis. Associated with the pyrolysis, active materials adsorb the residues of electrolyte on the surface and into the pores (20-200 °C), while polyvinylidene fluoride (PVDF) forms a liquid film to cover the local surface of active materials (400-500 °C). These interactions prevent deep removal of organics, leaving fluorine-containing contaminants in active materials. The barrier effect of PVDF liquid mesophase on the removal of organics with secondary liquidous phase formation during pyrolysis was confirmed by in situ optical observation. The migration behavior of fluorine element during the pyrolysis of black mass (BM) from spent LIB was also investigated. With pyrolysis temperature increasing from 100 °C to 600 °C, the dissociable fluorine content in pyrolyzed BM increased from 1.4 wt% to 3.7 wt%. The fluorine-containing contaminants in BM cannot be removed completely by simply increasing pyrolysis temperature. This study provides a better understanding on the transformation of fluorine-containing pollutants during the pyrolysis of BM.

Keywords: Fluorine-containing pollutants; Pyrolysis; Recycling; Spent lithium-ion battery.