Unraveling supercapacitive cobalt manganese sulfide nanoflakes: a standalone binder-free electrode material for a solid-state prototype device

Abstract

An electrode material for asymmetric supercapacitor (ASC) applications, that promises the best performance in electrode and device assemblies, is of utmost importance and attracts industries for scaling up. However, it is often challenging to deliver competitive performance for most electrode materials due to weak ion-diffusion kinetics, limited reactive sites, low surface area, and structural deterioration that occur upon continuous charge–discharge cycling. Here, a 2D bimetallic chalcogenide—cobalt manganese sulfide (CoMn₂S₄) nanoflakes—was designed based on density functional theory (DFT) calculations optimized for best performance. The material could work as a binder-free standalone electrode material for ASC devices, as demonstrated by making a prototype device. It exhibited a high gravimetric capacitance of 2548.3 F g⁻¹ and an areal capacitance of 3.822 F cm⁻² at 20 mA cm⁻². The fabricated solid-state supercapacitor device using this material achieved a high power density of 9.443 W cm⁻² and high energy density of 151 mWh cm⁻². The device exhibited remarkable cyclic stability of 86% after 1000 switchings and could power a DC motor and LEDs, thus opening new avenues for advanced supercapacitor technology for applications in electronic appliances.