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Supercritical CO2 Extraction: A safer and more efficient recycling process

10/10/2024

When it comes to recycling lithium-ion batteries (LiBs), safety and efficiency are paramount. Classified as hazardous waste under EU legislation, spent LiBs pose significant risks, primarily due to their state-of-the-art (SoA) non-aqueous electrolytes. This complex mixture, which includes conductive salts dissolved in organic solvents and additives, is flammable, volatile, and toxic. By their very nature, the uncontrolled release of these components can harm the environment and endanger workers in recycling plants. Additionally, electrolyte residues in LiB waste streams represent a financial burden for the recycling industry since they are still classified as hazardous waste. Therefore, safely recovering the electrolyte is crucial for developing a secure recycling process.

One promising alternative to traditional methods like vacuum vaporization is supercritical carbon dioxide (ScCO₂) extraction. The easily adjustable properties and excellent mass-transfer characteristics of ScCO₂ make it potentially ideal for selectively extracting electrolyte components from LiB waste, resulting in purified extraction products. Previous research has demonstrated that non-polar electrolyte solvents like dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) can be extracted using low-density CO₂.

Recent results reported by the research team at University of Chalmers (CHA)have shown that by gradually increasing pressure and temperature conditions, more polar electrolyte components such as ethylene carbonate (EC),  and propylene carbonate (PC) can also be successfully extracted. However, selective extraction of solvents remains a challenge, requiring further thermodynamic and kinetic data to optimise the process.

Modelling the extraction behaviour allows the designing of an optimised extraction process that achieves high purity solvents. This high purity enables the recycling industry to either resell the solvents for other uses or even reuse them in battery production, making the process more sustainable and economically viable.

Discover the scientific publication