The recovery of valuable metals from spent ternary lithium-ion batteries by repurposing the pyrolysis gas

Abstract

To establish a recycling process for spent lithium-ion batteries (LIBs) suitable for industrialization, minimizing energy consumption and simplifying the recycling process are critical. Herein, we propose a roasting reduction method to recover valuable metals from spent LIBs by repurposing the pyrolysis gas of the LIBs. The pyrolysis gas serves as a reducing agent, while the carbon-based materials in the LIBs (graphite, electrolytes, separators, and binders) act as a carbon resource during the roasting process. The results show that the spent LiNi_0.65Co_0.15Mn_0.2O₂ (LNCM) cell can be completely reduced to Li, Ni, Co, Mn, or their respective compounds using pyrolysis gas at 550 °C. Through a combined environmentally friendly process of water leaching and citric acid leaching, 91.62% of Li, 98.71% of Ni, 99.46% of Co, and 98.51% of Mn are recovered from the roasted products. These recovery efficiencies are higher than that of carbothermal reduction using carbon-based materials in an inert atmosphere. The synergistic effect between the reductive gases in the pyrolysis gas and the carbon resource is a key factor enabling the reduction process of LNCM at lower temperatures compared to conventional carbothermic reduction under an oxygen-free atmosphere. Therefore, the recycling method based on the in situ reduction-leaching of LIBs is environmentally friendly, economical, and has promising applications in industrial scale-up.