Cu-Based Ternary Heterostructures for High-Performance Asymmetric Supercapacitors

In view of cost, electrical conductivity, and environmental friendliness, copper-based heterostructures are suitable alternatives to toxic ruthenium-based materials in a variety of applications, such as catalysis, biological imaging, energy conversion, and storage. The primary hindrances limiting energy-storage performance are heterostructures with irregular sizes, shapes, and compositions. Here, we introduce a three-step strategy to synthesize CuS2@Cu7Se4@NC hollow heterostructures, starting from Cu2O nanocubes and proceeding through two anion exchanges and a carbon coating step. Taking advantage of the electrical synergistic effect and hollow structures, the as-synthesized CuS2@Cu7Se4@NC hollow heterostructures exhibit an excellent electrochemical performance when utilized as a supercapacitor electrode, achieving a high specific capacitance of 660 F g–1 at 1 A g–1 with a good rate capability and excellent cycling stability (retaining 72.6% of its initial capacitance after 4000 charge–discharge cycles). By coupling with commercially activated carbon (AC), an asymmetric supercapacitor device was constructed (CuS2@Cu7Se4@NC//AC) using KOH-PVA as an electrolyte, which delivers an elevated energy density at a power density of 599.7 W kg–1 and reasonable cycling stability (77.6% retention, 4000 cycles at 10 A g–1), suggesting a wide range of potential uses for the CuS2@Cu7Se4@NC electrode in supercapacitors and associated energy applications.