Fabrication of porous nickel (hydr)oxide film with rational pore size distribution on nickel foam by induction heating deposition for high-performance supercapacitors

A room-temperature thermal substrate process, induction heating deposition was introduced to fabricate a layer of porous nickel-based compounds on nickel foam as supercapacitor electrode materials. The as-prepared film was composed of sheet-like NiO, Ni2O3, NiOOH and 3Ni(OH)2·2H2O (α-Ni(OH)2). It possessed a hierarchical 3D-interconnected porous nanostructure with reasonable pore size distribution, among which nickel foam provided macropores, the produced 3D-interconnected sheet supplied mesopores ranging from 8 nm to 80 nm at a peak of 14 nm, while smaller mesopores with a size of about 2.5 nm were directly fomed on the sheet-like crystals. This unique pore nanostructure of the nickel (hydr)oxide compounds, desipte its specific area of only 48 m2 g−1, could not only facilitate the diffusion of electrolyte into the electrode material surface, but also offer more active sites for the electrochemical redox reactions. Thus, the film delivered a very high areal capacitance of 4.5 and 3.2 F cm−2 at 6 and 30 mA cm−2 corresponding to 2250 and 1600 F g−1 at 3 and 15 A g−1, as well as an excellent rate capability (71.1% capacitance retention from 6 to 30 mA cm−2) and good cycling stability (77.7% capacitance retention after 2000 cycles).