Electrochemical Redox-Mediated Dissolution of Alkaline Residues via In Situ H2O2Generation: Case Study of Ni, Co, and Mn Recovery from Spent NMC Cathodes

Electrochemical redox-mediated leaching of metals from spent residues such as end-of-life (EoL) batteries is a single-step, energy- and material-efficient alternative to recover energy-critical metals such as Ni, Mn, and Co, in a significant departure from conventional multistep, reagent-intensive hydrometallurgical routes. Concurrent generation of H2O2 as a reducing agent using an indium single-atom catalyst supported on oxidized carbon black (In-CB(O) SAC) electrocatalyst and leaching of Ni, Co, and Mn from spent NMC cathodes resulted in total Ni, Co, and Mn extraction efficiencies (including dissolved and electrodeposited metals) of 82.9%, 74.5%, and 82.1%, respectively. In this electrochemical approach, ∼230 mM (∼2.3% v/v) H2O2 is generated at 45–50% current efficiency in 0.5 M H2SO4. Addressing competing electrochemical processes, including transition-metal electrodeposition, hydrogen evolution, transition-metal-mediated H2O2 decomposition, and electrochemical H2O2 reduction to water, is anticipated to further enhance metal extraction efficiencies. External addition of H2O2 is effective in enabling near-complete Ni, Co, and Mn extraction efficiencies of 99.1%, 99.3%, and 100.0% with 3% v/v H2O2 and only 1 M H2SO4, significantly reducing acid demand compared to conventional methods. However, a comparison of the economic and environmental impacts showed that while external H2O2 addition provides stronger near-term economic performance under current laboratory operating conditions, in situ H2O2 generation offers lower modeled material costs and greenhouse gas emissions and has the potential to become economically superior through continued improvements in electrode durability and metal extraction efficiency. Importantly, the in situ H2O2 generation strategy eliminates the need for external H2O2 addition, lowers chemical consumption, and demonstrates the feasibility of a tunable electrochemical hydrometallurgy platform. Collectively, these results demonstrate the proof-of-concept feasibility of electrochemical redox-mediated recovery of critical metals from spent lithium-ion batteries (LIBs) and provide a basis for further process development.