Enhancing redox kinetics by electron orbital modulation for high-performance aqueous energy storage

Abstract

The energy density of supercapacitors can be improved through rapid surface reconstruction of electrode materials in an alkaline medium. Transition metal sulfides (TMSs), including Co9S8, are widely used as energy storage electrode materials owing to their excellent structural characteristics. However, systematic research dealing with the enhancement of Co9S8 reconstruction ability induced by Se doping has not well been investigated. Herein, an electron orbital modulation strategy was developed to promote the reconfiguration capability of Co9S8 by substitution of the Se element. The theoretical simulation and experimental characterization confirmed the successful introduction of the Se element, resulting in more polarized charge distribution in Co9S8 and better charge transfer ability. The improved adsorption capacity of OH− also enhanced the intensity of surface reactions, as well as effectively increased the refactoring rate. The optimized Co9S5.1Se2.9 exhibited a specific capacitance of 1788.1 F g−1 at 1 A g−1. The assembled flexible asymmetric supercapacitor delivered a maximum energy density of 54.9 Wh kg−1. Overall, the proposed strategy can effectively be used to construct high energy density electrode materials with optimized reconstruction of dynamic rates through effective modulation of electron orbitals.