Implementation of a sub-and supercritical carbon dioxide process for the selective recycling of the electrolyte from spent Li-ion battery

Abstract

The electrolyte in spent Li-ion batteries is prone to cause a high risk of hazardous emissions (HF, etc.) in the state-of-the-art recycling processes. It is the main source of fire risks and represents a significant burden for the recyclers due to the safety. Still, extended research to fully recycle the electrolyte without its destruction at elevated temperature is scarce. This study focuses on the electrolyte extraction from spent LiBs using sub- and supercritical carbon dioxide to fill this gap. The effects of the critical process parameters, pressure (60–120 bar), temperature (15–55 °C) and extraction time (1–50 min) from spent pouch cells were investigated. The results showed that the CO2 density, which is related to pressure and temperature, is significant for the recovery of the non-polar electrolyte solvents. The most important outcome is that dimethyl carbonate, and ethyl methyl carbonate were fully selectively extracted at the studied conditions, whereas the polar ethylene carbonate was extracted only in trace amounts. As results indicated, LiPF6 did not decompose in the proposed process whereby the toxic-gas emissions were dramatically minimized compared to the state-of-the-art recycling processes.

Keywords

• Lithium-ion battery
• Electrolyte
• Recycling process
• Supercritical carbon dioxide extraction
• Spectroscopy analysis
• Exhaust-gas emission characterization