Reduction Behavior of Black Mass Recovered from NCM-based Spent Lithium-ion Batteries by CO Gas

초록

The cathode active materials of lithium-ion batteries (LIBs) contain critical metals including Ni,Co, Mn, and Li. Since these metals are only produced in a few countries, it is necessary to recover them fromspent lithium-ion batteries. The concentrated electrode materials of lithium-ion batteries are referred to asblack mass (B/M), which contains a large amount of carbon used as the anode material, along with metaloxides used in the cathode. In this study, the effect of roasting temperature in an Ar+CO gas atmosphere onthe reduction behavior of NCM (LiNixCoyMn1-x-yO2)-based black mass powder and the recovery of Li wasinvestigated. In the thermogravimetric analysis, the CO2 concentration increased sharply from about 430 oCto a maximum value and then decreased, during which a weight gain due to the formation of Li2CO3 was alsoobserved. Above approximately 700 oC, the concentration of CO increased due to the reaction of CO2 with theC in the B/M due to the Boudouard reaction. In the isothermal roasting in an Ar+CO 50 vol.% atmosphere,the weight of the sample decreased significantly above 696 oC, and the final weight loss amount also increasedwith increasing temperature. Most of the significant weight loss is thought to be due to the Boudouardreaction. Li2CO3 was generated regardless of temperature. Above 696 oC, most of the Ni and Co oxides werereduced to metals, and above 900 oC, some of the MnO was also reduced and is thought to have been dissolvedin the Ni-Co alloy. At temperatures above 696 oC, where the NiO was fully reduced, the recoveries rate oflithium was approximately 90 % with no significant difference.

키워드