The efficiency of scrap Cu and Al current collector materials as reductants in LIB waste leaching

Abstract

This current study addresses the role of copper and aluminum - typical major components of current collector scrap from battery manufacturing plants - in the leaching of pre-treated LiCoO2-rich battery waste concentrate at industrially relevant process conditions (T = 60 °C, [H2SO4] = 2 M, S/L = 200 g/L). An empirical model has been constructed which demonstrates that the effects of both copper and aluminum are significant. Both elements have independent and linear impacts on cobalt extraction and acid consumption. The model predicts that either 11 g of copper (0.75 Cu/Co, mol/mol), 4.8 g of aluminum (0.7 Al/Co, mol/mol) or a combination of both are required for full cobalt extraction from 100 g of sieved industrial battery waste concentrate. Aluminum was shown to influence cobalt leaching although it was less effective (47%) when compared to copper (66%) in terms of current efficiency due to associated side reactions, such as excess H2 formation. Aluminum has several possible reaction routes for LiCoO2 reduction; in parallel or in series via H2 formation, Cu2+ cementation and/or Fe3+ reduction, whereas copper acts solely through Fe3+ reduction. These results indicate that by using copper scrap, in preference to the more typical hydrogen peroxide, the CO2 footprint of the battery leaching stage could be decreased by at least 500 kg of CO2 per ton of recycled cobalt. In contrast, the use of aluminum, although promising, is less attractive due to the challenges related to its removal during subsequent solution purification.