High-performance flexible asymmetric supercapacitors based on Hy-NiCoS/CNTs composites on porous graphene films

Abstract

This research focused on the synthesized NiCoS/CNT composites by a hydrothermal method using thiourea and then drop-cast on laser-induced graphene (LIG) with porous structures for an active electrode of flexible asymmetric supercapacitors. Surface topography, cross-sectional outline, chemical structure and properties, and electrical properties of LIG, NiCoS, and Hy-NiCoS materials were measured and analyzed. In the two-electrode device, the Hy-NiCoS electrode has a high areal capacitance of 817 mF/cm2 under 0.5 mA/cm2 current density and a low internal resistance of 5.19 Ω. Furthermore, the prepared flexible asymmetric supercapacitors (Hy-NiCoS/AC) demonstrated excellent energy density of 0.017 mWh/cm2, power density of 3.2 mW/cm2, and areal capacitance of 85 mF/cm2 under 0.5 mA/cm2 current density. When the bending angles were 0°, 45°, and 90°, the areal capacitances of the prepared flexible asymmetric supercapacitors were 77.7, 75.0, and 70.8 mF/cm2, respectively. There is no obvious capacitance decay even at a large bending angle of 90°, which means that the asymmetric supercapacitor has excellent flexibility and stability. Based on the flexible asymmetric supercapacitors with excellent electrochemical performance, the proposed supercapacitors can be widely used in wearable electronic devices and healthcare products.