Study on the influence mechanism of carbothermal reduction and selective leaching of valuable metals in spent lithium batteries

Abstract BACKGROUND Exploring an innovative method for precious metal recovery from spent batteries, our study combines hydrometallurgy and pyrometallurgy, focusing on pivotal carbothermal reduction. This crucial phase enhances the leachability of metals by significantly reducing their valence. To evaluate the effect of novel carbon materials on this reduction process, our study synthesized two types of nanoporous carbons, Al‐PCP‐800 and ZIF‐8‐800, found in electrode materials. Their carbothermal reduction efficacy was compared to activated carbon using thermogravimetric analysis. RESULTS The experimental findings revealed that ZIF‐8‐800 exhibits superior reducibility, initiating and reaching peak weight loss rate at a lower temperature of 692.01°C with a peak of 32.27%/°C. Under the optimized conditions—roasting temperature of 750°C, time of 3 hours, carbon content of 20%, 2.75 M H 3 PO 4 concentration, 40°C leaching temperature, a liquid‐to‐solid ratio of 6 mL·g ‐1 , and leaching time of 10 minutes—the leaching efficiency of Li and Mn reached 100%, indicating complete extraction with ZIF‐8‐800. However, Co and Ni leaching with ZIF‐8‐800 was low (3.22%, 2.06%). Al‐PCP‐800 showed slightly less efficiency for Li and Mn, but higher for Co and Ni. Activated carbon led to incomplete Li and Mn extraction, with higher Co and Ni leaching, diminishing the process's selectivity. CONCLUSION The study confirms that the carbon material in carbothermal reduction significantly impacts metal leaching efficiency and selectivity. ZIF‐8‐800 was the most effective for Li and Mn leaching, outperforming Al‐PCP‐800 and activated carbon in selectivity. This underscores ZIF‐8‐800's potential to improve metal recovery from spent batteries. This article is protected by copyright. All rights reserved.