The interference of copper, iron and aluminum with hydrogen peroxide and its effects on reductive leaching of LiNi1/3Mn1/3Co1/3O2

Copper and iron are known to be effective alternative reducing agents to H2O2 in Li-ion battery leaching. The aim of this work is to study the effect of added H2O2 on its overconsumption to the side reactions such as oxidation of copper, iron, and aluminum in leaching of NMC 111 active material. The interactions between the reducing agents separately were first investigated (T = 30 degrees C, [H2SO4] = 2 M, t = 120 min). Elemental copper was found to be a less efficient reducing agent (78%) compared to aluminum (100%) in terms of Fe3+ reduced to Fe2+. Nevertheless, copper exhibited much higher rate of iron reduction than aluminum. Additionally, aqueous copper ions were found to cement on aluminum surface and redissolve in the presence of iron, thus acting as the metallic reducing agent. In contrast, in the presence of H2O2 ferrous iron and copper were rapidly oxidized resulting in the consumption of all reducing agents. These effects were confirmed also during the leaching of NMC (T = 30 degrees C, [H2SO4] = 1.5 M, t = 120 min), which demonstrated that the leaching efficiency markedly decreased (similar to 63%) in the presence of H2O2 and Cu when compared to H2O2 alone (similar to 78%). Furthermore, results from NMC leaching showed that when copper-iron reductant or H2O2 were added separately, a much higher leaching efficiency was achieved (similar to 66% and similar to 78%, respectively) in contrast to being added together (similar to 58%).

Automated summary

The study investigated the effectiveness of copper and iron as alternative reducing agents in the leaching of lithium-ion batteries, and the impact of added H2O2. It was found that aluminum was more efficient than copper in reducing Fe3+ to Fe2+, although copper exhibited a faster rate of iron reduction. The presence of H2O2 led to rapid oxidation of ferrous iron and copper, depleting all reducing agents.