Construction of crystalline/amorphous heterostructures to enhance the supercapacitor performance of a high-entropy sulfide

Abstract

High-entropy materials show promising potential as electrode materials for supercapacitors (SCs) due to their high-entropy effect. Currently, most research focuses on high-entropy materials made from a single substance, while studies on high-entropy composite materials are limited, presenting a promising area for future investigation. In this study, hollow sphere high-entropy sulfides (HESs) of (FeCoNiCuZn)S₂ were prepared from metal nitrates and glycerol by solvothermal and sulfurization methods. Next, a layer of NiCoB (NCB) was constructed on the surface of HESs by chemical precipitation method, resulting in x-NCB@HES heterostructures with various NCB contents. When the NCB content was 0.1 (x = 0.1), the heterostructure exhibited the best electrochemical performance. The 0.1-NCB@HES composite demonstrated a specific capacitance of 1239.1 F·g⁻¹ in a 3 M aqueous KOH solution, surpassing the capacitance of HES at 512.67 F·g⁻¹ and that of NCB at 995.78 F·g⁻¹. After 8000 cycles, the capacity of 0.1-NCB@HES remained at 78.11 % of the initial capacitance. Kinetic studies revealed that capacitance control governs energy storage in NCB@HES. When using 0.1-NCB@HES as the positive electrode and activated carbon (AC) as the negative electrode, the assembled 0.1-NCB@HES//AC asymmetric SC could provide a specific capacitance of 192.53 F·g⁻¹, with an energy density of 60.16 Wh·kg⁻¹ at a power density of 749.91 W·kg⁻¹. This study provides an effective method to enhance the electrochemical performance of high-entropy transition metal sulfides.