NCM계 폐리튬이온 배터리에서 회수한 Black Mass의 수소환원 거동

초록

NCM(LiNixCoyMnzO2)-based Li-ion batteries (LIBs) for electric vehicles contain critical metals, such as Li, Ni, Co, and Mn. The black mass recovered from spent LIBs contains a large amount of carbon. Therefore, it is necessary to recover valuable metals from spent LIBs to prevent resource depletion. In this study, we investigated the reduction behavior of cathode materials when a black mass was heated in a H2 atmosphere. When the black mass was heated up to 1,100 °C in a H2 atmosphere, emission of a large amount of CO led to rapid weight loss from approximately 780 °C by the Boudouard reaction. During the isothermal reaction in a H2 atmosphere, the weight loss rate and final weight loss of the sample increased with the reaction temperature. Significant amounts of CO were emitted in the region of rapid weight loss. Above 400 °C, NiO was reduced to Ni; above 890 °C, MnO was reduced, and a MnNi3 phase was observed. Li2CO3 was produced at temperatures above 300 °C although the reaction occurred in a hydrogen atmosphere. When the reduced black mass was treated with water, Li and Al were detected in the leaching residue. The product recovered from the water leaching solution contained LiAl2(OH)7·(H2O)2 together with Li2CO3. When the reduction temperature was above 400°C, the Li recovery ratio was approximately 90 % regardless of the temperature. To improve the Li recovery ratio, it is necessary to control the production of complex hydroxides of Li and Al.

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