In situ generation of CoS1.097 nanoparticles on S/N co-doped graphene/carbonized foam for mechanically tough and flexible all solid-state supercapacitors

Abstract

The development of flexible electrochemical devices with high-density electrochemical capacitive energy storage and high mechanical strength remains the main obstacle for practical applications. Here, we designed and generated a S/N co-doped graphene based electrode (CoS_1.097/GF electrode) with well-distributed CoS_1.097 nanoparticles (NPs), which were anchored directly in/on porous carbonized melamine foam by a squeeze-dip-coating and sulfidation process. The CoS_1.097/GF electrode shows desired conductivity, cycling stability and high ion-accessible surface area, leading to an ultrahigh specific capacitance of 4476 F g⁻¹ at a current density of 1 A g⁻¹ and a favourable rate capability of 87.1% at 10 A g⁻¹. Furthermore, a high-strength and flexible CoS_1.097/GF/KOH/PVA composite film electrode was prepared using KOH/polyvinyl alcohol (KOH/PVA) as a gel electrolyte, and a flexible CoS_1.097/GF||GF asymmetric electrochemical capacitor (a-EC) device was produced with a high energy density of 33.2 W h kg⁻¹ at a power density of 374.7 W kg⁻¹, where the KOH/PVA gel works as a solid-state electrolyte and separator. We observed 95.6% capacitance retention after 10 000 cycles within the potential window of 0–1.5 V. Notably, we confirmed that the CoS_1.097/GF||GF a-EC device performed at large bending angles (from 0° to 180°), and was able to be twisted into various shapes, indicating its potential for application in wearable and portable electronic devices.