Self-Supported Co3O4@Mo-Co3O4 Needle-like Nanosheet Heterostructured Architectures of Battery-Type Electrodes for High-Performance Asymmetric Supercapacitors

Abstract

Herein, this report uses Co₃O₄ nanoneedles to decorate Mo-Co₃O₄ nanosheets over Ni foam, which were fabricated by the hydrothermal route, in order to create a supercapacitor material which is compared with its counterparts. The surface morphology of the developed material was investigated through scanning electron microscopy and the structural properties were evaluated using XRD. The charging storage activities of the electrode materials were evaluated mainly by cyclic voltammetry and galvanostatic charge-discharge investigations. In comparison to binary metal oxides, the specific capacities for the composite Co₃O₄@Mo-Co₃O₄ nanosheets and Co₃O₄ nano-needles were calculated to be 814, and 615 C g^-1 at a current density of 1 A g^-1, respectively. The electrode of the composite Co₃O₄@Mo-Co₃O₄ nanosheets displayed superior stability during 4000 cycles, with a capacity of around 90%. The asymmetric Co₃O₄@Mo-Co₃O₄//AC device achieved a maximum specific energy of 51.35 Wh Kg^-1 and power density of 790 W kg^-1. The Co₃O₄@Mo-Co₃O₄//AC device capacity decreased by only 12.1% after 4000 long GCD cycles, which is considerably higher than that of similar electrodes. All these results reveal that the Co₃O₄@Mo-Co₃O₄ nanocomposite is a very promising electrode material and a stabled supercapacitor.

Keywords: Co3O4@Mo-Co3O4 nanocomposite; binder free electrode; energy storage; hydrothermal; supercapacitor.

Figure 1

Schematic of Co₃O₄@Mo-Co₃O₄ needle-like nanosheets, synthesized by hydrothermal method.

Figure 2

(a,b) XRD pattern and Raman spectra of Co₃O₄ and Co₃O₄@Mo-Co₃O₄ needle-like nanosheet heterostructure, (c) XPS survey spectra of Co₃O₄@Mo-Co₃O₄, (d) deconvoluted high-resolution spectra of Mo3d, (e) deconvoluted high-resolution spectra of Co2p, and (f) deconvoluted high-resolution spectra of O1s.

Figure 3

(a–f) FE-SEM images of Co₃O₄@Mo-Co₃O₄ needle-like nanosheet heterostructure at different magnifications, (g) EDS spectra: inset mapping image of Co₃O₄@Mo-Co₃O₄, (h) elemental map of Mo, (i) elemental map of Co, and (j) elemental map of O.

Figure 4

(a,b) TEM images at different magnifications, (c) high-resolution TEM image of Co₃O₄@Mo-Co₃O₄ needle-like nanosheet heterostructure: inset SAED pattern.

Figure 5

(a,b) Comparison plots of CV at 10 mV/s scan rate and GCD at 1 A/g current density for Co₃O₄ and the Co₃O₄@Mo-Co₃O₄ heterostructure, (c,d) CV curves at scan rates of 10–30 mV/s, (e,f) GCD curves at current densities of 1–10 A/g, (g) calculated specific capacity values from GCD curves, (h) Nyquist plot of Co₃O₄ and the Co₃O₄@Mo-Co₃O₄ heterostructure_, (i) capacitance retention over 4000 GCD cycles; inset: ten consecutive GCD cycles.

Figure 6

(a) Schematic of ASC device, (b) CV curves for different voltage windows at an 80-mV/s scan rate, (c) GCD curves for different voltage windows at a current density of 3 A/g (d,e) CV curves at scan rates of 50–100 mV/s and GCD curves at current densities of 1–10 A/g, (f) calculated specific capacitance values, (g) Power density vs. energy density plot, (h) Nyquist plot of before and after 4000 GCD cycles, (i) capacitance retention over 4000 GCD cycles; inset: ten consecutive GCD cycles of Co₃O₄@Mo-Co₃O₄//AC ASC device.