Recycling of lithium-ion batteries (LIBs) helps conserve natural resources and minimizes the need for extracting and refining raw materials. There are various methods industrially available for the recycling of LIBs, including pyrometallurgy and hydrometallurgy or combinations of both. Pyrometallurgy is a well-established method, but the achievable recycling rate is limited as the process is focused on the recovery of specific valuable elements. Hydrometallurgy promises higher recycling rates, but nonetheless requires the resynthesis of the functional materials. A more favorable approach is direct recycling, particularly in terms of the potential material recovery rate. The aim of direct recycling is to preserve the structure of the functional materials, particularly that of the cathode active materials (CAM). Furthermore, direct recycling may be based on aqueous processes.
One of the key steps of an aqueous-based direct recycling process is the regeneration of the CAM. It is well known that Ni-rich layered oxide cathode materials with low Co content and high specific capacity, such as NCM811 (LiNi0.8Co0.1Mn0.1O2), are extremely sensitive to water and moisture. Thus, a regeneration step is necessary to repair degradation which occurred both during the use-phase of the LIB, or due to the water-based recycling process. In particular, the replacement of lost lithium inventory is necessary. This work will present the regeneration of NCM811 (LiNi0.8Co0.1Mn0.1O2) via a hydrothermal process. The active material was subjected to a centrifuge process to model the fractionation step of a direct recycling process. Various parameters such as thermal pre-treatment, thermal post-treatment, heating rate, time, and different concentration of lithium source were studied to investigate their impact on the regeneration process. Furthermore, the electrochemical data obtained for the regenerated cathode material will be presented.