Facile and large-scale chemical synthesis of highly porous secondary submicron/micron-sized NiCo2O4 materials for high-performance aqueous hybrid AC-NiCo2O4 electrochemical capacitors

•A facile and scalable chemical synthesis strategy is proposed.•The NiCo2O4 materials display a high surface area and porosity.•The NiCo2O4 electrode shows a high specific capacitance and rate capability.•The AC-NiCo2O4 capacitor exhibits a high Ragone behavior and high cycling stability. Highly porous nickel cobaltite (NiCo2O4) materials have been synthesized via a facile and scalable chemical synthesis route. The obtained NiCo2O4 material displays a typical secondary submicron/micron-sized (0.1–2μm) agglomerate morphology, exhibiting large surface area (190.1m2g−1) and high porosity (1.136cm3g−1). The fabricated NiCo2O4 electrode shows high specific capacitance (351Fg−1 at 1Ag−1) and high-rate capability (82.1% capacitance retention at 8Ag−1), which is superior to many reported NiCo2O4 materials. Further, the assembled AC-NiCo2O4 aqueous hybrid capacitor exhibits high power and energy densities (2805Wkg−1, 6.8Whkg−1 at 8Ag−1) and high cycling stability (15% loss after 5000 cycles at 1.5Ag−1). The high-performance of the NiCo2O4 materials is attributed to their large surface area and highly porous structure which contribute to rich surface electroactive sites and easy ions transport pathways for facile electrochemical reactions.