Current collectors as reducing agent to dissolve active materials of positive electrodes from Li-ion battery wastes

This study evaluates the electrochemical effect of mineral, organic and metallic reducing agents to promote LiNi1/3Mn1/3Co1/3O2 (NMC) dissolution in acidic media. The main aim is to compare the reactivity of metallic current collectors (Cu and Al) to more conventional reducing agents such as organic acids and hydrogen peroxide. In a more applied perspective, this work points out the economic interest to use current collectors as an alternative chemical reagent for an efficient NMC dissolution as they are inherently present in the fraction treated by an hydrometallurgical approach. It demonstrates that galvanic interactions are suitable to leach the transition metal oxides from spent LIBs without heating and emission unlike carboxylic acid solutions, allowing the development of low ecological footprint processes. In a more fundamental framework, the results obtained clear several parts of the dissolution NMC mechanism. A fast first step is controlled by the solution pH with a low influence of redox reactions on the kinetic. A slower second stage is subjected to the electrochemical processes with a surface-controlled dissolution.