3D porous nickel nanosheet arrays as an advanced electrode material for high energy hybrid supercapacitors

Abstract

3D porous nickel nanosheet arrays (Ni-NSAs@Ni foam) are prepared by a facile hydrothermal process followed by an annealing treatment. The synthesized Ni-NSAs@Ni foam offered a mesoporous nano structure. First, Ni(OH)2 nanosheet arrays on Ni foam are synthesized by a hydrothermal process. Then, the Ni(OH)2 nanosheet arrays are transformed to Ni-NSAs@Ni foam via horizontal furnace tube. The Ni-NSAs@Ni foam electrode shows a high areal capacitance 4683.6 mF cm−2 at a current density of 1 mA cm−2, a capacitance retention of 80.8% at 10 mA cm−2, low internal resistance Rs~0.75 Ω and a retention ratio of 95.8% after 20,000 charge/discharge cycles. The capacitance of Ni-NSAs@Ni foam is much higher than that of the Ni(OH)2 nanosheet arrays. The outstanding electrochemical characteristic performances of the Ni-NSAs@Ni foam can be ascribed to the 3D porous nano structures of Ni-NSAs@Ni foam, which can offer short diffusion routes for charge carriers (electrons and ions), large active areas between the interface of the electrode/electrolyte and the low internal resistance between grown Ni-NSAs@Ni foam and the conductive current collector. Its hybrid supercapacitor device is assembled by using the Ni-NSAs@Ni foam as the positive electrode and activated carbon AC@Ni foam as the negative electrode. The hybrid supercapacitor device reaches an ultra-high energy density of 141.04 Wh kg−1 and a power density of 226.14 W kg−1 at 1 mA cm−2. The remarkable pseudocapacitive performance of Ni-NSAs@Ni foam electrode shows its great potential in applications of energy storage and conversion devices.