Temperature-concentration complementary chemical looping hydrogen reduction of LiCoO2: A comprehensive study on reduction characteristics and mechanisms

With the rapid increase in the number of spent lithium-ion batteries, it is necessary to develop an efficient, environmentally friendly recycling technology for large-scale applications. This study proposes a chemical looping hydrogen reduction technique based on the complementary effects of temperature and hydrogen concentration for recovering valuable metals from spent lithium-ion batteries (LIBs). Through experimental characterization and thermodynamic calculations, the reduction characteristics and mechanisms of LiCoO2 under different conditions were systematically analyzed, revealing the complementary role of temperature and hydrogen concentration in the reduction process. The results demonstrate that chemical looping hydrogen reduction is an effective new approach for the recovery of LIBs cathode materials, exhibiting complementary characteristics between temperature and hydrogen concentration. By adjusting temperature and hydrogen concentration, the orderly reduction of LiCoO2 can be achieved. Under conditions of 800 degrees C, 3 % H2, and a reduction time of 120 min, LiCoO2 was fully converted into Li2O, Co, and H2O, achieving a 100 % conversion rate. Experimental and mechanistic analyses show that the reduction process of LiCoO2 involves the stepwise desorption of oxygen, with LiCoO2 first reduced to CoO, followed by further reduction to metallic Co. At high temperatures, LiOH is not formed, and Li2O is directly produced. Kinetic analysis indicates that increasing LiCoO2 conversion rate and lowering hydrogen concentration lead to higher activation energy. These findings provide new insights for optimizing the chemical looping hydrogen reduction process of LiCoO2, contributing to the development of efficient recycling technologies for lithium-ion batteries.