Lithium-ion batteries (LIBs) are widely used in various applications due to their high energy density. As electric mobility advances and large quantities of batteries are needed, it is anticipated that a significant stock of end-of-life (EOL) batteries will accumulate within the next decade [1]. The accumulation of this growing stock represents major environmental and economic challenges. Traditional methods of producing new batteries by extracting non-renewable raw materials are unsustainable in the long term. Recycling EOL batteries appears to be a potential solution to minimize environmental impacts and reduce dependency on primary resources, particularly regarding active materials.
Several recycling processes exist, most of which are focused on Black Masses obtained from mechanical and physico-chemical treatment of spent batteries. Large-scale industrial processes primarily employ pyrometallurgical and hydrometallurgical methods, which recover metal alloys and metallic salts, respectively. However, these methods can be expensive due to high required temperatures or the use of huge quantities of chemicals and water.
In contrast, direct recycling is more studied at the lab scale. This approach aims to regenerate degraded materials without their complete degradation, addressing compositional, electrochemical, structural, and morphological deficiencies in EOL materials. Direct recycling has the potential to reduce energy consumption, waste, and production costs [2].
Among existing positive active materials, nickel-, manganese-, and cobalt-based materials hold significant importance for battery recycling. Our research focuses on direct recycling of NMC-based materials through developing a low-temperature hydrothermal process for cathode chemical relithiation, considering the presence of carbon with degraded active NMC.
The proposed relithiation process includes reducing calcination temperatures while partially preserving carbon additives. Different sources of NMC positive materials have been investigated, from scrap to Black Mass, compared with commercial NMC, within chemical or electrochemical delithiation. The obtained results suggest the possibility of relithiating at lower temperatures, thereby conserving the carbon initially present in the cathode.

[1] Chen, M. et al. Recycling End-of-Life Electric Vehicle Lithium-Ion Batteries. Joule vol. 3 2622–2646
[2] Wu, J. et al. Direct recovery: A sustainable recycling technology for spent lithium-ion battery. Energy Storage Materials vol. 54 120–134