In situ growth of novel nickel diselenide nanoarrays with high specific capacity as the electrode material of flexible hybrid supercapacitors

Novel nickel diselenide (NiSe2) nanoarrays supported on Ni foams are successfully synthesized by an in situ hydrothermal process. Structural characterizations show that the as-obtained NiSe2 nanoarrays belong to the cubic phase and present the white beech mushroom-like appearance, i.e., the stem diameter about 50–70 nm, the length about 500 nm, and the diameter of the umbrella cover about 50 nm. Controlled experiment results show that the typical mushroom-like NiSe2 nanoarrays can deliver a high specific capacity, low resistance and better cycling stability due to the intrinsic physical properties, and special structural features. More importantly, mushroom-like NiSe2 nanoarrays are further assembled into flexible hybrid supercapacitors with commercial activated carbon as the counter electrodes. This hybrid energy-storage device has 33 Wh kg−1 energy density and 90.3% capacity retention. Meanwhile, it also shows a remarkable mechanical flexibility and high commercial value. Therefore, this work not only proves that the NiSe2 nanoarrays are competitive supercapacitor electrode materials, but also provides a new candidate for flexible, smart, and portable electronic devices.