Abstract
Graphene has been widely used in the active material, conductive agent, binder or current collector for supercapacitors, due to its large specific surface area, high conductivity, and electron mobility. However, works simultaneously employing graphene as conductive agent and current collector were rarely reported. Here, we report improved activated carbon (AC) electrodes (AC@G@NiF/G) simultaneously combining chemical vapor deposition (CVD) graphene-modified nickel foams (NiF/Gs) current collectors and high quality few-layer graphene conductive additive instead of carbon black (CB). The synergistic effect of NiF/Gs and graphene additive makes the performances of AC@G@NiF/G electrodes superior to those of electrodes with CB or with nickel foam current collectors. The performances of AC@G@NiF/G electrodes show that for the few-layer graphene addition exists an optimum value around 5 wt %, rather than a larger addition of graphene, works out better. A symmetric supercapacitor assembled by AC@G@NiF/G electrodes exhibits excellent cycling stability. We attribute improved performances to graphene-enhanced conductivity of electrode materials and NiF/Gs with 3D graphene conductive network and lower oxidation, largely improving the electrical contact between active materials and current collectors.
Highlights
IntroductionWith the increasing requirement of energy storage devices in the modern technology society, supercapacitors have drawn great attention due to the higher power density, quicker charge and discharge rate, and longer cycle life compared with traditional lithium-ion batteries [1,2,3,4]
Materials 2018, 11, 799 is the potential range, illustrates that energy density is closely related to the specific capacitance and potential range [8,9,10,11]
We demonstrated a kind of performance-enhanced electrodes of supercapacitors involved in nickel foam (NiF)/G current collectors and graphene as the conductive additive
Summary
With the increasing requirement of energy storage devices in the modern technology society, supercapacitors have drawn great attention due to the higher power density, quicker charge and discharge rate, and longer cycle life compared with traditional lithium-ion batteries [1,2,3,4]. The formula E = 12 CV2 , where E is the energy density, C is the mass specific capacitance, and V. Materials 2018, 11, 799 is the potential range, illustrates that energy density is closely related to the specific capacitance and potential range [8,9,10,11]. As a result, improving specific capacitance or potential range is the fundamental approach to achieve higher energy density. Most researches concentrate on selecting appropriate active materials and electrolytes to get higher specific capacitances and broader working voltages. Carbon materials (graphene, carbon nanotube, AC et al.) with high conductivity, nanostructure transition metal oxide (MnO2 , Co3 O4 , NiX Mn1-X O et al.) with high capacitance and their composites are the most famous active materials being studied [12,13,14,15,16,17]
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