Hazardous electrolyte releasement and transformation mechanism during water protected spent lithium-ion batteries...

Wet-crushing with aqueous media protection is considered safer and more efficient than common inert-gas protected dry-crushing in preprocessing spent lithium-ion batteries (LIBs). However, it is also accompanied with the releasement and transformation of hazardous electrolyte, while the mechanisms and pollution impact yet remain unknown. Based on a self-built wet-crushing system, this topic was systematically investigated here. It was found that water might provide efficient cooling to the hazardous electrolyte, while dissolution was a major electrolyte migration pathway. Consequently, nearly 90 % lithium hexafluorophosphate (LiPF₆) could be dissolved with little decomposition in 4 min, and no fluorine and phosphorus was found emitting as gas. Electrolyte organics also suffered rapid dissolution, but emission via thermal gasification, or re-emission from water via evaporation and saturation existed. Fluorine and so forth may precipitate back to the solids. Water temperature and dissolved electrolyte content were found to be the major influencing factor for the above migration and transformations, and solubility can be used as reference. Suggestions about the future wet-crushing process design with hazardous electrolyte control were proposed. Corresponding treatment strategies for exhausted gas and electrolyte enriched circulating water were discussed. These findings and suggestions would help the improvement and implementation of wet-crushing technique.