Advancing circular battery recycling by systematically screening novel deep eutectic solvents for sustainable metal recovery

Abstract

The need to conserve resources and recycle spent lithium-ion batteries (LIBs) has become more urgent due to their increasing use in portable electronics and electric vehicles. This study proposes a unique approach involving computational screening and experimental validation to develop deep eutectic solvents (DESs) for recycling LIB cathodes. Using the conductor-like screening model for real solvents (COSMO-RS), 675 potential combinations of DESs were analyzed to identify the best DES constituents for the extraction of lithium and cobalt. Based on the screening results, eight promising DESs were synthesized from green and biocompatible materials such as glycine, betaine, carnitine, vitamin C, and citric acid. The synthesized DESs were evaluated for their potential to cause metal leaching from lithium cobalt oxide (LCO) cathodes. The combination of tetrabutylammonium chloride and vitamin C (TVW), as well as glycine and vitamin C (GVW), achieved almost complete recovery (>99 % Li, >98 % Co) in only 2 h at a temperature of 80 °C. The DESs have proven their reusability in seven successful recycling runs, enabling the selective recovery of high-purity lithium and cobalt oxalates. The environmental and economic impact of the DES-based process was evaluated, and its potential as a sustainable and cost-effective solution for large-scale LIB recycling was highlighted. This computational-experimental framework facilitates the discovery of environmentally friendly solvents. The methodology follows the principles of green chemistry and engineering while providing practical solutions for resource conservation and sustainable transformation. This will contribute to the development of recycling technologies and the circular economy in the fast-growing energy storage sector.