Sulfur source-inspired synthesis of β-NiS with high specific capacity and tunable morphologies for hybrid supercapacitor

A novel β-NiS active material with tunable morphologies is synthesized through a facile one-step hydrothermal approach by choosing a special substance 2-mercaptopropionic acid as sulfur source. It is found that the introduced sulfur source has a great influence on phase structure and morphology of nickel sulfides. Benefiting from the selection of an excellent sulfur source, pure β-NiS was obtained and the morphology modification from microsphere to microflower and then to urchin-like structure was successfully achieved. More remarkably, the products at all morphologies indicate excellent energy storage capability, among which a highest specific capacity of 313.1 mAh g−1 is attained. In addition, the fabricated asymmetric supercapacitor indicates an attractive energy density of 49 W h kg−1 at a power density of 399 kW kg−1 and a good capacitance retention rate of 98 % after 5000 cycles. Our work opens another avenue for phase-controlled synthesis of pure nickel sulfide with tunable morphologies for various applications.