Recovering Nickel‐Based Materials from Spent NiMH Batteries for Electrochemical Applications

AbstractIn this work, we explored the recovering possibilities of nickel‐based products from the cathode materials of spent nickel‐metal hydride (NiMH) batteries collected from car repair centers in Mongolia. Specifically, nickel‐based by‐products such as metallic nickel, Ni microparticles, nickel oxide, nickel chloride, and betta‐phase (β) nickel hydroxide powders are successfully produced. X‐ray diffraction patterns suggested that all samples show high crystallinity and phase purity. Ni microparticles were recovered using a chemical reduction method from a leachate solution prepared by dissolving the cathode of the spent NiMH battery in hydrochloric acid. Notably, β‐Ni(OH)₂ displayed two redox peaks in KOH electrolyte solution, suggesting that it has excellent electrochemical potential and can be reused for the fabrication of new NiMH batteries. To validate the electrochemical performances, we examined the catalytic activity of nickel microparticles as a catalyst for the degradation of Congo red (CR) dye and oxygen evolution reaction (OER). The reduction reaction rate of CR dye in the presence of a nickel catalyst was 2.17×10−3 s−1, significantly higher than the control experiment without a nickel catalyst. These results provide possible solutions for developing sustainable battery systems by recovering different nickel‐based products from spent NiMH batteries.