Achieving a High Areal Capacity with a Binder-Free Copper Molybdate Nanocone Array-Based Positive Electrode for Hybrid Supercapacitors

Herein, we develop a binder-free copper molybdate nanocone array with a prism-like morphology on nickel foam (Cu 3 Mo 2 O 9 NCAs/Ni foam) using a single-step hydrothermal method. With an optimal growth time (10 h) under hydrothermal conditions, the prism-like Cu 3 Mo 2 O 9 NCAs are uniformly decorated on Ni foam with good adhesion and crystallinity. The prepared Cu 3 Mo 2 O 9 NCAs/Ni foam has been directly used as a binder-free electrode to examine its suitability as a positive electrode in hybrid supercapacitors. In an aqueous 1 M KOH electrolyte, the binder-free Cu 3 Mo 2 O 9 NCAs/Ni foam showed battery-type behavior with a high areal capacity of 449.5 μAh cm –2 at a discharge current density of 2 mA cm –2 and also exhibited a good cycling stability. In addition, the pouch-type hybrid supercapacitor is assembled using the prism-like Cu 3 Mo 2 O 9 NCAs/Ni foam as a positive electrode and the activated carbon as a negative electrode in a 1 M KOH electrolyte. The hybrid supercapacitor achieves a maximum cell potential of 1.6 V with superior energy storage properties, including a high areal capacitance of 609.7 mF cm –2 at 3.5 mA cm –2, a high areal energy (0.21 mWh cm –2 ), and a high power density (2.73 mW cm –2 ). The obtained results suggest that the facilely synthesized Cu 3 Mo 2 O 9 NCAs/Ni foam electrode has great potential in high-performance energy storage devices.