The
development of asymmetric supercapacitors requires the design
of electrode construction and the utilization of new electroactive
materials. In this regard, an effective strategy is the loading of
active materials on an integrated 3D porous graphene-based substrate
such as graphene foam (GF). Herein, we successfully designed and fabricated
a novel ternary binder-free nanocomposite consisting of polypyrrole,
Fe–Co sulfide, and reduced graphene oxide on a nickel foam
electrode (PPy/FeCoS-rGO/NF) via a facile, cost-effective, and powerful
electrodeposition method for application in high-performance asymmetric
supercapacitors. The monolithic 3D porous graphene foam (GF) obtained
by the facile immersion method not only improves uniform growth of
the FeCoS ultrathin porous nanosheet and conductive PPy film but also
significantly boosts the mechanical stability, rate capability, and
energy storage capacity. The results revealed that FeCoS interconnected
nanosheets coated with a highly conductive PPy layer via the electrodeposition
method are well decorated on the wrinkled surface of the graphene
foam backbones. The PPy/FeCoS-rGO/NF exhibits excellent electrochemical
performance with a high specific capacitance of 3178 F/g at 2 A/g
and a good rate capability. The excellent electrochemical performance
can be ascribed to the high surface area, superior electronic conductivity,
low contact resistance between the PPy/FeCoS-rGO active layer and
Ni foam current collector, short diffusion pathway for electrolyte
ions, fast electron transfer, and effective utilization of active
material during Faradaic charge-storage processes. Benefiting from
their superior properties, a hybrid asymmetric supercapacitor is assembled
by employing PPy/FeCoS-rGO/NF as the positive electrode and nickel
foam coated with reduced graphene oxide (rGO/NF) as the negative electrode.
Assembling the PPy/FeCoS-rGO//rGO device exhibits a high specific
capacitance of 94 F/g at 1 A/g and an energy density of 28.3 Wh kg–1 at a power density of 810 W kg–1. Moreover, the asymmetric supercapacitor device shows an outstanding
cycling performance with 97.5% capacitance retention after 2500 cycles.
The obtained results demonstrate the PPy/FeCoS-rGO/NF electrode can
be used as a promising electrode material for asymmetric supercapacitor
applications.
Flexible and lightweight fiber-shaped micro-supercapacitors have attracted tremendous attentions in the next-generation portable electronic devices, due to their high flexibility, tiny volume, and wearability. Herein, we successfully fabricated a ternary...
Miniaturization of electronic devices
with portable, flexible and
wearable characteristics created a great demand for high-performance
microscale energy storage devices with lightweight and flexible properties.
Among the energy storage devices, wire-shaped supercapacitors (WSSCs)
have recently received tremendous attention due to their tiny volume,
wearability, high flexibility and potential applications in the next-generation
portable/wearable electronic devices. Herein, we successfully fabricated
a porous dendritic Ni–Cu film on Cu wire substrate (CWE) for
fabrication of high-performance wire-type supercapacitors. The porous
structure with dendritic morphology provides a high surface area,
short ion diffusion pathway and low contact resistance between electroactive
materials and metal wire electrode. The Ni(OH)2 electroactive
material is then deposited on Ni–Cu/CWE. The fabricated Ni(OH)2/Ni–Cu/CWE exhibits excellent electrochemical performances
with high areal (volumetric and length) specific capacitance of 12.2
F cm–2 (1220.89 F cm–3, 1.53 F
cm–1), respectively at a current density of 4 mA
cm–2, and an excellent cycle stability (100% even
after 3500 cycles). A novel fiber-shaped flexible asymmetric micro–supercapacitor
(ASC) based on Ni(OH)2/Ni–Cu/CW as positive electrode
and reduced graphene oxide/carbon fiber (RGO/CF) as the binder free
negative electrode was assembled. This device can be operated reversibly
in the voltage range of 0–1.6 V and exhibited a maximum areal
and volumetric energy (E
A = 195 μWh
cm–2, E
V = 15.04 mWh
cm–3) and power (P
A =
7643 μW cm–2, P
V = 588 mW cm–3) densities. In addition, the ASC
device also exhibits an excellent cycling stability with 95.7% capacitance
retention after 5000 cycles and good mechanical stability, which is
checked by bending of the whole device at various angles. These promising
results indicated the great potential of our fabricated device for
portable, flexible and wearable applications.
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