Rapid microwave-assisted synthesis of MnCo₂O₄ nanoflakes as a cathode for battery-supercapacitor hybrid

This study reports a rapid and scalable synthesis of MnCo₂O₄ nanoflakes using a microwave-assisted synthesis technique. The material was physicochemically (XRD, XPS, Nitrogen adsorption, FTIR, FESEM, and EDX) and electrochemically (CV, GCD, and EIS) characterized for evaluating its chemical, surface, and electrochemical properties. The supercapacitive charge storage property of the electrode was tested in 3 M KOH and 3 M LiOH, and battery-type electrolyte ion intercalation was the cause of the charge storage. A maximum specific capacitance of 268 C g⁻¹ was obtained for the MnCo₂O₄ electrode in 3 M KOH at a current density of 0.5 A g⁻¹. It was determined that 3 M KOH enhanced the capacitance of the MnCo₂O₄ electrode owing to the lower electrode resistance (1.2 Ω) and charge transfer resistance value (0.13 Ω). The MnCo₂O₄ nanoflake electrode delivered superior cycling stability of ∼96% after 10,000 charge-discharge cycles in 3 M KOH, proving its practical utility. A battery-supercapacitor hybrid (BSH) was fabricated using MnCo₂O₄ nanoflakes as cathode and commercial AC as an anode. The BSH device delivered a maximum energy density of 38.9 Wh kg⁻¹ at a power density of 4.91 kW kg⁻¹ and retained ∼98% of its initial capacitance after 5000 charge-discharge cycles.