An investigation of ultrathin nickel-iron layered double hydroxide nanosheets grown on nickel foam for high-performance supercapacitor electrodes

Layered double hydroxide materials with sheet-like morphologies (i.e., LDH nanosheets) have been proposed to use in supercapacitors. However, the practical application of LDH nanosheets has been inhibited by the notorious inter-particle aggregation and poor charge transport between active materials and current collectors. In this work, 3D nickel-iron layered double hydroxide (NiFe-LDH) nanosheet films with porous nanostructures were synthesized using a hydrothermal method. The ultrathin nanosheets are homogeneously and vertically aligned on the surface of Ni foam. The pseudocapacitors assembled using NiFe-LDH nanosheets exhibit a superior specific capacitance of 2708 F g(-1) at 5 A g(-1), higher than the previously reported LDHs. The effect of growth concentration and Ni/Fe mole ratio on the electrochemical properties was also investigated. Asymmetric supercapacitors with the NiFe-LDH nanosheets film as the positive electrode and active carbon as the negative electrode display a high energy density of 52 Wh kg(-1) at an average power density of 800 W kg(-1). When two aqueous asymmetric supercapacitors were assembled in series and charged for only 1 min, the stored energy was capable of powering two green light-emitting-diodes for more than 5 min, indicating the great potential of these 3D NiFe-LDH nanosheets for high-performance energy storage. (C) 2017 Elsevier B.V. All rights reserved.