PDDA catalyzed growth of Ni-HCF@MWCNT on Ni foam for high-performance battery-type electrode for asymmetric supercapacitor

poly(dimethyldiallylammonium chloride) (PDDA), a well-known polyelectrolyte, was discovered to effectively catalyze the reaction between Ni foam and K3Fe(CN)6 to produce nickel hexacyanoferrate (Ni-HCF). The construction of binder-free Ni-HCF/multiwalled carbon nanotube (MWCNT) on Ni foam was achieved with a facile one-step hydrothermal route. With Ni foam as the current collector and the nickel source, Ni-HCF@MWCNT composite was synthesized on Ni foam by heating Ni foam in the MWCNT suspension, which was prepared by dispersing pristine MWCNT in the solution of PDDA and K3Fe(CN)6. The produced Ni-HCF@MWCNT/Ni foam electrode presents a 3D hierarchical structure. The electrochemical performances of Ni-HCF@MWCNT/Ni foam, investigated with cyclic voltammetry (CV), galvanostatic charge/discharge technique (GCD) and electrochemcial impedance spectroscopy (EIS), exhibit highly reversible redox reactions during the charge/discharge process, low internal resistance and charge transfer resistance, high areal capacitance and long-term cycling stability. The asymmetric supercapacitor device (ASC), assembled with Ni-HCF/MWCNT/Ni foam and activated carbon (AC), demonstrated wide potential window, high energy density and good rate capability and ultra-long cycling life.