Mesoporous 3D NiCo₂O₄/MWCNT nanocomposite aerogels prepared by a supercritical CO₂ drying method for high performance hybrid supercapacitor electrodes

A facile sol-gel route is developed to build mesoporous 3D NiCo₂O₄/MWCNT nanocomposite aerogels. The crystal structure, surface morphology and electrochemical performance of the aerogel composites are investigated by X-ray diffraction (XRD), Field-emission scanning electrochemical spectroscopy (FE-SEM) and electrochemical measurements. The effects of MWCNT concentration on the capacitance performance of MWCNT/NiCo₂O₄ aerogels are studied. It is found that the NiCo₂O₄/MWCNT nanocomposite aerogels with MWCNTs ∼ 2.1 wt% reach the maximum specific capacitance of up to 1010 F g⁻¹ at a discharge current density of 0.1 A g⁻¹ with excellent cyclic stability. Further, these materials are applied for solid-state asymmetric supercapacitors and show higher areal capacitance value (471.8 mF cm⁻²) at a current density of 5 mA cm⁻² with good cycle stability and glowing red LED for 3mins. The superior electrochemical performance is due to the mesoporous structure and well-connected metal nanoparticles with MWCNT in the nanocomposite aerogels, which can provide more active sites to enhance the electrochemical performance of the device.