To drive the transition to a climate-neutral economy, industry will need a sustainable and secure supply of key technology metals, which are essential for large-scale renewable energy production and storage as well as the electrification of mobility. Lithium-ion batteries (LIBs) play an increasingly important role for various energy storage systems. The current and future LIB technologies will require materials that are predicted to have a high supply risk in the future. In light of this, recycling has been put forward as a key strategy next to primary mining and critical raw material substitution.

Great efforts are currently being made to develop smart and sustainable processes for recycling LIB materials from end-of life batteries and production scrap. Lithium nickel manganese cobalt oxide (NMC) and lithium cobalt oxide (LCO) are two common LIB electrode materials. Deep eutectic solvents (DESs) are considered as green solvents in recycling of LIB materials due to their biodegradability and low toxicity combined with good leachability of metal oxides.

In this work, a new process for recycling and direct re-synthesis of NMC111 and LCO is presented. The process is based on leaching using a sustainable DES. Water is used as cosolvent to tune the properties of the DES. Leaching kinetics and mechanisms are determined. The chosen DES shows excellent leaching ability and fast leaching rate at low temperature compared with those DESs reported in the literature. After the leaching step, a new approach is applied to recover the metals from the DES leachate. This approach shows an overall high recovery efficiency and the solid product proves to be a good precursor for direct re-synthesis of new electrode materials. To conclude, this work presents a novel, green, effective and closed-loop metal recovery strategy for recycling LIB materials.