Hydrothermal synthesis of vanadium doped nickel sulfide nanoflower for high-performance supercapacitor

With the tremendous demand for high energy and power operation in energy storage devices, supercapacitors (SCs) have demonstrated to be one of the most viable devices for electrical energy conversion and storage applications due to their superior capacity than conventional capacitors and higher power density than batteries. However, the insufficient capacitance of the anode materials severely impedes the development of SCs. Due to their astonishing theoretical capacitance, nickel sulfides have aroused immense attention for the next generation of supercapacitors. But its inability to satisfy the anticipated capacitance values and insufficient structural durability severely hinder the application of capacitive energy storage. Herein, doping vanadium into nickel sulfide (V-Ni3S2, denoted as VNS) was grown on the surface of nickel foam by a one-step hydrothermal method using nickel foam as a nickel source. The results showed that Ni3S2 doped uniformly with valence-rich vanadium remarkably enhanced the redox reaction. Integrating two-dimensional nanosheets into three-dimensional nanoflower morphology not only expands the number of active sites but also enhances the stability of the structure. The VNS electrode with clearly defined ion diffusion channels and affluent redox activity centers significantly enhances the reversible capacitance and the stabilized longevity (2072 F g−1 at 1 A g−1, capacitance retention of 86.4% after 10,000 cycles). Furthermore, using the VNS and activated carbon as cathode and anode electrodes, respectively, the fabricated hybrid supercapacitor delivers an excellent energy density of 81.33 Wh kg−1 at a power density of 160 W kg−1 and agelong cycling durability (capacitance retention of 82.2% after 10,000 cycles). These strategies enlighten the electrochemical properties of various metal sulfide materials employed in energy storage devices.