A novel fluffy nanostructured 3D network of Ni(C7H4O5) for supercapacitors

Supercapacitors have raised considerable research interest in recent years due to their extensive potential application in next-generation energy storage. It is always of great importance to develop new electrode materials for supercapacitors so far. In this research, nickel gallate complex (Ni(C7H4O5)) nanostructures are successfully grown on nickel foam by a facile hydrothermal route, which can be directly used as the electrodes for supercapacitors. X-ray diffraction patterns show that the sample is amorphous. The scanning electron microscopy images reveal that the products consist of novel fluffy 3D network with a mass of fibers. The electrochemical measurements demonstrate that the prepared Ni(C7H4O5) electrode possesses the specific capacitance of 3.688 F cm−2 (1229.3 F g−1) at a current density of 9 mA cm−2 (3 A g−1). It presents an excellent cycling stability with a capacitance retention of 87.9% after 5000 cycles even at a very high current density of 40 mA cm−2. An asymmetric supercapacitor device is assembled using the Ni(C7H4O5) sample as positive electrode and activated carbon as negative one. A high gravimetric capacitance of 71.4 F g−1 at a current density of 0.5 A g−1 can be achieved. The fabricated device delivers the highest energy density of 23.8 W h kg−1 at a power density of 388.2 W kg−1 with a voltage window of 1.55 V. This strategy should be extended to other organometallic compounds for supercapacitors.