Recycling Of Cobalt, Lithium And Carbon From Crushing-separating Spent Lithiun Batteries

Lithium-ion batteries(LIBs) are widely used in fields of mobile electronic equipment, electric vehicles and energy storage. However, large quantities of spent LIBs are coming into discarding period due to their limited life-cycle and endless requirement for new products. Spent LIBs contain valuable metals like lithium and cobalt whose contents in spent LIBs are much higher than that in concentrate mineral. The present studies on recycling of spent LIBs focused on hydrometallurgical process which generated large quantity of chemical reagent with high concentration. Treatment of wastewater after hydrometallurgical process became a serious threat and cost more. In order to meet the demand of the circular economy, new efficient environmental friendly technology for recycling metals from spent LIBs needs to be developed. Therefore, this paper puts forward the method of anaerobic roasting recovery of electrode materials from spent LIBs, namely reducing cathode materials(LiCoO2) by anode materials(graphite) without additional reducing agent.First of all, pretreatment including discharging and dismantling were launched on LIBs to enrichment electrode materials. Contaminants of metals, non-metals and volatile organic compounds(VOC) were detected and improving measures were put forward. Secondly, the feasibility of reduction reaction between graphite and LiCoO2 at high temperature were studied,including thermodynamics analysis and simultaneous thermogravimetry analysis. Then simulation experiments were carried out in nitrogen atmosphere tube furnace using mixed materials of LiCoO2 and graphite, parameters of raw material ratio, heating temperature and holding time were studied with the detection methods of X-ray diffraction, inductively coupled plasma and total carbon analyzer on characterization of products.The results indicated that suitable conditions for roasting to reduce LiCoO2 at high temperature were mixed materials with chemical amount n(LiCoO2): n(C) =4:3 in a nitrogen atmosphere heating at 850 ℃ for 30 min, the reaction equation was 4LiCoO2+ 3C = 2Li2CO3+ 4Co + CO2. Finally, the roasted product was separated and gathered by wet magnetic separation method, the cobalt content of magnetic solid was 97.68%, the carbon content of non-magnetic solid was 84.86%, and lithium concentration of aqueous solution was 337.4mg/L which was much higher than that of cobalt(0.2046mg/L) in aqueous. The whole recovery efficiency of cobalt and lithium was 90.07% and 93.61%, respectively.The results of this study identify that roasting in nitrogen atmosphere could realize the recycling of cobalt from spent LIB, and the new process simplified the recycling process, lessened secondary pollution. This study put forward new ideas, theoretical and experimental basis for the environmental friendly recycling of spent LIBs.