Influence of Flow-Gas Composition on Reaction Products of Thermally Treated NMC Battery Black Mass

Abstract

The recycling of lithium-ion batteries (LIBs) is becoming increasingly important regarding the expansion of electromobility and aspects of raw material supply. Pre-treatment and liberation are crucial for a sufficient recovery of all relevant materials from LIBs. Organic removal and phase transformations by thermal pre-treatment are beneficial in many respects. This study deals with the influence of flow-gas composition on reaction products and water-based lithium recovery after thermal treatment. Therefore, a spent NMC black mass was thermally treated at 610 °C in a moved bed batch reactor under an N2 atmosphere and mixtures of N2 with 2.5% and 5% O2. Since the phase transformation of the lithium content to Li2CO3 is targeted for water leaching, a treatment under a CO2 atmosphere was studied as well. The resulting off-gas was analyzed by FTIR, and the black mass was characterized by XRD. Afterward, water washing of the black mass was carried out for selective lithium recovery. The gained lithium product was analyzed for the purity and phases present. The addition of O2 resulted in reduced reduction reactions of lithium metal oxides and lower Li-yields in the water leaching compared to the other two atmospheres. In the case of CO2, the formation of Li2CO3 is favored compared to LiF, but the Li-yield of 56% is comparable to N2 treatment.