Formation of Carbon-Incorporated NiO@Co3O4 Nanostructures via a Direct Calcination Method and Their Application as Battery-Type Electrodes for Hybrid Supercapacitors.

Nickel and cobalt oxides are promising electrode materials for supercapacitors, but their poor conductivity and sluggish kinetics seriously hinder their application. Herein, a simple one-step calcination method was proposed to prepare carbon-incorporated NiO@Co3O4 (denoted as CNC) using a NiCo Prussian blue analogue (NiCo-PBA) as a precursor. The effect of calcination temperature on the electrochemical behavior of CNC was investigated. Benefiting from the relatively large specific surface area and porous structure characteristics, when used as an electrode for supercapacitors, the CNC obtained at 400 °C shows the typical features of a battery-type electrode, with a good specific capacitance of 208.5 F g-1 at 1 A g-1 and a rate capability of 70.8% at 30 A g-1. The hybrid supercapacitor (HSC) constructed with the optimum CNC electrode can provide a high energy density of 32.6 Wh kg-1 at the corresponding power density of 750.0 W kg-1 and an excellent cycling stability of 87.1% over 5000 cycles. This study provides a simple calcination method for preparing MOF-derived high-conductivity mixed metal oxide electrode materials for supercapacitors.