Unraveling Supercapacitive Cobalt Manganese Sulfide Nanoflakes: A Standalone Binder-free Electrode Material for Solid State Prototype Device

Abstract

An electrode material, for asymmetric supercapacitor (ASC) applications, that promises the best performance in both forms, namely 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, a low surface area, and structural deterioration that occurs upon continuous charge-discharge cycling. Here, a 2D bimetallic chalcogenide, cobalt manganese sulfide (CoMn2S4) nanoflakes, has been designed based on the density functional theory (DFT) calculations optimized for best performance. The material has the capability of working as a binder-free standalone electrode material for ASC devices, as has been demonstrated by making a prototype device. It exhibited a high gravimetric capacitance of 2548.3 F/g and an areal capacitance of 3.822 F/cm² at 20 mA/cm². The fabricated solid-state supercapacitor device using this material achieved a high power density of 9.443 W/cm² and a high energy density of 151 mWh/cm². Additionally, the device exhibits remarkable cyclic stability of 86% after 1000 switchings and can power a DC motor and LEDs, thus opening new avenues to the pinnacle of advanced supercapacitor technology for application in electronic appliances.