Facile and large-scale chemical synthesis of highly porous secondary submicron/micron-sized NiCo_2O_4 materials for high-performance aqueous hybrid AC-NiCo_2O_4 electrochemical capacitors

摘要

Highly porous nickel cobaltite (NiCo_2O_4) materials have been synthesized via a facile and scalable chemical synthesis route. The obtained NiCo_2O_4 material displays a typical secondary submicron/micron-sized (0.1-2 μm) agglomerate morphology, exhibiting large surface area (190.1 m~2 g~(-1)) and high porosity (1.136 cm~3 g~(-1)). The fabricated NiCo_2O_4 electrode shows high specific capacitance (351 Fg~(-1) at 1 Ag~(-1)) and high-rate capability (82.1% capacitance retention at 8 Ag~(-1)), which is superior to many reported NiCo_2O_4 materials. Further, the assembled AC-NiCo_2O_4 aqueous hybrid capacitor exhibits high power and energy densities (2805 W kg~(-1), 6.8 Wh kg~(-1) at 8 A g~(-1)) and high cycling stability (15% loss after 5000 cycles at 1.5 A g~(-1)). The high-performance of the NiCo_2O_4 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.