A one-step and binder-free method to fabricate hierarchical nickel-based supercapacitor electrodes with excellent performance

Research is currently being carried out in the search for alternative electrode materials to replace the expensive and toxic RuO₂-based electrode. As a typical example, nickel oxide or hydroxide has been widely studied but the results are far from satisfactory. Here, using a facile one-step anodization method, a hierarchical nickel compound (HNC) film with an interconnecting 3D nanoflake structure is obtained, providing large electrochemically active surface area and interconnecting nanoscale pore channels for ion transport. The HNC electrode demonstrates significantly improved capacitance, 70 times higher than the reported NiO-TiO₂ nanotube array electrode with similar thickness. The charge/discharge kinetics are also superior, showing only a 24% capacitance reduction when the scan rate is increased by 50 times, as compared with the typical 70% capacitance reduction for pseudocapacitor electrodes under the same conditions. HNC exhibits an extraordinary excellent cycle life; capacitance increases to 115% after 4500 test cycles. Furthermore, because HNC is in intimate contact with the current collector, it is not necessary to use conducting agents or binders, which reduces the electrode weight and facilitates the electrode preparation process. The method is low cost, facile, scalable, additive free, and is promising for fabricating supercapacitor electrode with excellent performance. A hierarchical nickel compound (HNC) film is prepared using a facile, one-step, and binder-free method. The HNC demonstrates both large capacitance and superior rate capability. The capacitance reduction is only 24%, even when the scan rate is increased by 50 times. The HNC also exhibits an excellent cycle life.