Mesoporous Ni-Zn-Fe layered double hydroxide as an efficient binder-free electrode active material for high-performance supercapacitors

Developing new, cost-effective and high-specific-capacitance electroactive materials is the main focus of current energy storage research. Herein, we report on successful one-step fabrication of binder-free nickel-zinc-iron layered double hydroxide (Ni-Zn-Fe LDH) using the successive ionic layer adsorption and reaction (SILAR) method. Energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), N2 adsorption/desorption, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques are employed to characterize the as-prepared Ni-Zn-Fe LDH. The electrochemical performance of Ni-Zn-Fe LDH is executed by cyclic voltammetry (CV), galvanostatic charging/discharging (GCD) and electrochemical impedance spectroscopy (EIS) in 6 M KOH electrolyte. Ni-Zn-Fe LDH demonstrates high specific capacitance (1452.3 F/g) at 5 mV/s and excellent cycling stability. This can be attributed to its high specific surface area (119.79 m2/g) and mesoporous structure with a pore size of ~3.69 nm, that allow for the electrolyte ions to get in contact with the electroactive material surface to a great extent. High energy density (14.9 Wh/kg), high power density (1077.6 W/kg) and outstanding cycling stability (~95% capacitance retention after 1000 GCD cycles at 1.5 A/g) are obtained from the assembled asymmetric device (AC // Ni-Zn-Fe LDH). All these features make the proposed Ni-Zn-Fe LDH material a promising candidate for supercapacitor applications.