Facile synthesis of spinel nickel–manganese cobaltite nanoparticles with high rate capability and excellent cycling performance for supercapacitor electrodes

Nickel- and manganese-based spinel compounds have emerged as important candidates for electrochemical energy storage. In this study, a spinel nickel–manganese cobaltite (s-NMC) material was synthesized by facile hydrothermal/calcination route and the material exhibited remarkable pseudocapacitive behavior performance. The synthesized s-NMC material had a specific capacitance of 418.3 F g⁻¹ at a scan rate of 10 mV s⁻¹ (216.2 F g⁻¹ at a current density of 1 A g⁻¹) and retained 95% of its specific capacitance after 5000 charge–discharge cycles at a current density of 2 A g⁻¹. These excellent electrochemical properties are attributed to the simultaneous presence of three transition metals in the s-NMC material. The asymmetric supercapacitor device using s-NMC delivered a maximum specific energy density of 16.58 Wh kg⁻¹ at a specific power density of 825 W kg⁻¹ and maintains of ∼97% specific capacitance after 2000 cycles at a current density of 2 A g⁻¹. This study highlights that the diversification of transition metals in spinel-based metal oxides is an effective approach to enhance the electrochemical performances in resulting compound materials. Graphical abstract: [Figure not available: see fulltext.]