Facile construction of MgCo2O4@CoFe layered double hydroxide core-shell nanocomposites on nickel foam for high-performance asymmetric supercapacitors

Abstract

In this work, hierarchical MgCo2O4@CoFe layered double hydroxide (LDH) core-shell nanowire arrays on Ni foam (NF) are synthesized by facile hydrothermal and calcination methods. MgCo2O4/NF has been first synthesized via a hydrothermal reaction and annealing treatment and then utilized to prepare MgCo2O4@CoFe-LDH/NF core-shell nanocomposites via the second hydrothermal reaction. It is found that the MgCo2O4@CoFe-LDH/NF core-shell nanocomposite prepared from 3 h hydrothermal reaction (MC@CF-LDH-3) exhibits an excellent specific capacitance of 903.15 C g−1 (2007 F g−1) at the current density of 1 A g−1. Moreover, a high capacitance retention (80.2% maintained after 5000 cycles) and a low internal resistance (Rs) (0.75 Ω) can be acquired. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) is assembled using MgCo2O4@CoFe-LDH/NF-3 as the positive electrode and activated carbon (AC) as the negative electrode. The as-fabricated MgCo2O4@CoFe-LDH/NF-3//AC ASC shows a high energy density of 60.82 Wh kg−1 at 725 W kg−1. Meanwhile, the MgCo2O4@CoFe-LDH/NF-3//AC ASC device possesses an excellent cycling stability of 93.6% retention of the initial capacitance after 5000 cycles and two ASC devices connected in series can light up a LED bulb for 8 min. Our results manifest that this hierarchical MgCo2O4@CoFe-LDH composite has huge potential application in energy storage devices.