Multilayered and hierarchical structured NiCo double hydroxide nanosheets generated on porous MgCo2O4 nanowire arrays for high performance supercapacitors

Abstract In this work, MgCo2O4@NiCo layered double hydroxide (LDH) hierarchical structure nanocomposites on Ni foam (NF) are synthesized by facile hydrothermal and calcination methods. MgCo2O4/NF is synthesized first via a hydrothermal reaction and annealing treatment and then utilized to prepare MgCo2O4@NiCo-LDH/NF hierarchical structure nanocomposites via the second hydrothermal process. It is found that the MgCo2O4@NiCo-LDH/NF nanocomposite prepared from 9 h hydrothermal reaction (MC@NC-LDH-2) exhibits an excellent specific capacitance of 5701.2 F g-1 at the current density of 1 A g-1. Moreover, a high capacitance retention (83.7% maintained after 5000 cycles) and a low internal resistance (Rs) (0.783 Ω) can be achieved. Furthermore, a quasi-solid state asymmetric supercapacitor (ASC) is assembled using MgCo2O4@NiCo-LDH/NF-2 as positive electrode and activated carbon (AC) as negative electrode. The as-fabricated MgCo2O4@NiCo-LDH/NF-2//AC ASC shows a high energy density of 89.79 Wh kg-1 at 800 W kg-1. Meanwhile, the MgCo2O4@NiCo-LDH/NF-2//AC ASC device possesses an excellent cycling stability of 89.03% retention of the initial capacitance after 5000 cycles and two ASC devices connected in series can light up a LED bulb for 15 min. Our results manifest that these hierarchical MgCo2O4@NiCo-LDH composites could envision huge potential application in energy storage devices.