Preparation of ZnCo2O4 nanoflowers on a 3D carbon nanotube/nitrogen-doped graphene film and its electrochemical capacitance

Abstract

Homogeneous ZnCo₂O₄ nanoflowers have been synthesized on a 3D layered structure of carbon nanotubes/nitrogen-doped graphene (NGN/CNTs) film by a hydrothermal process and subsequent calcination method. The ZnCo₂O₄ nanoflowers have an average diameter of 4 μm, and are composed of petals less than 100 nanometers. The as-synthesized ZnCo₂O₄/NGN/CNT film can be directly used as a flexible electrode with a high specific capacitance of 1802 F g⁻¹ at 1 A g⁻¹ and excellent cycling stability (almost 0% fade after 4000 sustaining charge/discharge at 10 A g⁻¹). These results suggest that the obtained electrode has a promising application prospect in flexible energy conversion/storage devices. In addition, a binder-free asymmetric supercapacitor has been synthesized with the ZnCo₂O₄/NGN/CNT film as the positive electrode and the NGN/CNT film as the negative electrode. This demonstrates superior energy density (≈37.19 W h kg⁻¹ at 750 W kg⁻¹) and power density (≈14.992 kW kg⁻¹ at 14.16 W h kg⁻¹).