S doping induced phase transition of CoMoO4 and decorated on KCu7S4 for high specific capacitance supercapacitor electrode material

Abstract

Due to the importance of electrode materials for supercapacitors, modified transition metal compounds are better suited to their needs. Compounding and ion doping are two effective modification pathways to optimize the structure of electrode materials and enhance the ion migration kinetics, and thus improve the electrochemical performance of transition metal compounds. In this paper, KCu7S4@S-CoMoO4 (S doping) was prepared by a two-step hydrothermal method. The S doping would cause the phase transition of CoMoO4 and enhance crystallinity. Additionally, the possible substituted oxygen position of S atom was simulated by density functional theory (DFT). Electrochemical characterization showed that the specific capacitance of KCu7S4@S-CoMoO4 prepared under optimal condition was as high as 2866.77 F/g at a current density of 0.5 A/g. The assembled KCu7S4@S-CoMoO4//AC hybrid supercapacitor exhibits the maximum energy density of 132.71 Wh/kg in liquid system condition and the specific capacitance maintained 80.9% of the initial capacitance after 3500 charge/discharge cycles. This work provides ideas for designing materials with high electrochemical performance.