Scalable complete conversion of MgCo2O4 by mechanochemistry for high-performance supercapacitors†

MgCo₂O₄, a cobalt-based binary oxide, has garnered increasing attention as a promising active material for supercapacitor electrodes due to its enhanced conductivity and high theoretical capacitance. In this study, a novel mechanochemical approach was developed to convert stoichiometric MgO and Co₂O₃ into MgCo₂O₄. This innovative synthesis involved a one-step ball milling process that integrates two reaction steps. Initially, MgO reacted with water to form Mg(OH)₂, followed by migration of Mg ions from Mg(OH)₂ into the Co₂O₃ lattice to generate MgCo₂O₄. The milling parameters were optimized to enhance the conversion efficiency of MgCo₂O₄ through X-ray diffraction analysis. Complete conversion of MgCo₂O₄ was achieved with a single batch production capacity of 100 g, using a ratio of water volume to reactant weight of 2.0 mL g⁻¹, a ball-to-powder ratio of 10 : 1, a revolution speed of 350 rpm, and a milling time of 80 hours. The synthesis mechanism was elucidated using X-ray photoelectron spectroscopy. The synthesized MgCo₂O₄ particles exhibited a small particle size of 117.8 nm and a high specific surface area of 63.3 m² g⁻¹. Based on these properties, the electrode exhibited a notable specific charge of 266.3 C g⁻¹ at 0.1 A g⁻¹, highlighting its potential as an excellent active material for supercapacitor electrodes. This study demonstrates a facile, green, cost-effective, and scalable production method for MgCo₂O₄, promoting its application in electrochemical energy storage.