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![(a) Zeta potential of graphene nanoplatelets and binder as a function of pH and (b) electrophoretic mobility of graphene and binder as a function of pH both measured at supporting electrolyte concentration of [KCl] = 1 mM.](profile/Olivier-Hubert-3/publication/355977951/figure/fig5/AS:1088411934957570@1636509035337/a-Zeta-potential-of-graphene-nanoplatelets-and-binder-as-a-function-of-pH-and-b.png)
(a) Zeta potential of graphene nanoplatelets and binder as a function of pH and (b) electrophoretic mobility of graphene and binder as a function of pH both measured at supporting electrolyte concentration of [KCl] = 1 mM.
Source publication
Structural supercapacitors can both carry load and store electrical energy. An approach to build such devices is to modify carbon fibre surfaces to increase their specific surface area and to embed them into a structural electrolyte. We present a way to coat carbon fibres with graphene nanoplatelets by electrophoretic deposition in water. The effec...
Contexts in source publication
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... m t is the total mass of the sample {coating + coated carbon fibres + uncoated carbon fibres}, l t the total length and l nc the uncoated length of fibres (see ESI Fig. S5 for ...
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... graphene used was easily suspended in water without the need for any surfactant. Graphene suspensions with a pH between 7 and 11 appeared stable (clear black suspensions) over more than 3h (ESI Fig. S6). Fig. 5a shows the ζ-potential as a function of pH of graphene and binder. ζ = f(pH) of graphene confirmed the presence of Brønsted acid surface oxides with a ζ plateau of 35 mV and an i.e.p., where ζ = 0, of 4.2. Similar results for graphene were reported in the literature before [41]. A suspension is usually considered stable when |ζ| > 25 mV ...
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... an average ζ = 48 mV, which was likely caused by the presence of an anionic surfactant used for its synthesis. The measured electrophoretic mobility, from which ζ was calculated, gives the ability of a suspended particle to move in an applied electrical field. During EPD the higher the electrophoretic mobility the faster the coating will form. Fig. 5b shows μ = f(pH) for graphene, binder and a 9:1 (graphene:binder weight ratio) mixture. The addition of binder to the graphene suspension increased its electrophoretic mobility for pH < 8 but had very little effect on suspensions at higher pH. The electrophoretic mobility of a suspension that had been used for deposition was analysed ...
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Citations
... Although Hubert et al. have recently developed a structural supercapacitor without a separator that gives an increase in specific capacitance, its mechanical strength was not improved that much. 31 In our early work, fabrication of a supercapacitor device was performed using the a vacuum-assisted resin transfer molding process, which is considered an easy, cost-effective, and ecofriendly process. 32 However, the vacuum bag and resin transfer media often leave some imprint on the device surface, which results in an unusual surface finish. ...
Fibre reinforced polymer plays an important role in many fields, especially in aviation and civil industries where lightweight design is a crucial factor. Over the past two decades, there has been extensive research on the development of multifunctional fibre reinforced composite structures which can fulfil several secondary functions besides its structural role. As a result, structural energy storage composites have been developing rapidly which can sustain electrochemical energy storage as well as structural load-bearing. Among the many structural energy storage composites, struc-tural supercapacitor composites (structural supercapacitors) have attracted the atten-tion of many researchers. This article provides an up-to-date review on the development of structural supercapacitors, which can be integrated into structural fibre reinforced polymeric components. Specifically, an outline is given of the development of carbon fibre fabric based structural supercapacitors, with the focus on various surface activations for performance improvement. Moreover, the recent development in critical components of structural supercapacitors, such as solid electrolytes and separators, is also highlighted. The limitations and challenges for the development of structural supercapacitors are also incorporated. Lastly, the novel fabrication processes and designs for future development are critically discussed. This article will help engineering and scientific communities to gain concise knowledge of structural supercapacitors.
Supercapacitors based on carbon fiber reinforced polymer (CFRPs) were studied and the influence of surface treatment on mechanical and electrochemical properties was explored. Electrodes were prepared by deposition of graphene nanoplatelets (GNPs) combined with different binders (PVDF and PVA) onto the surface of a carbon fiber fabric. A significant decrease in the Interlaminar Shear Strength (ILSS) is observed when comparing the solid polymer electrolyte to the structural resin (around 50 %). Moreover, the addition of any binder promotes a decrease in the ILSS due to lower interfacial properties (around 20 % when compared to the GNP-coated condition). Electrochemical impedance spectroscopy (EIS) analysis proves that the structural capacitor can be fitted with an equivalent circuit consisting of R-CPE series elements. An increase of the bulk resistance was observed when using a binder (29.7 and 22.7 kΩ) when compared to the GNP-only-coated (10.2 kΩ). For this reason, the structural supercapacitor with the best properties was the GNP-only-coated one with a specific capacitance and coulombic efficiency, calculated by Galvanostatic charge-discharge (GCD), of 5.2 mF/g, showing also high stability of electrochemical properties over time. Energy storage capability was successfully demonstrated by a proof of concept consisting of powering a LED after a short charge time of the device.
Load bearing/energy storage integrated devices (LEIDs) allow using structural parts to store energy, and thus become a promising solution to boost the overall energy density of mobile energy storage systems, such as electric cars and drones. Herein, with a new high-strength solid electrolyte, we prepare a practical high-performance load-bearing/energy storage integrated electrochemical capacitors with excellent mechanical strength (flexural modulus: 18.1 GPa, flexural strength: 160.0 MPa) and high energy storage ability (specific capacitance: 32.4 mF cm ⁻² , energy density: 0.13 Wh m ⁻² , maximum power density: 1.3 W m ⁻² ). We design and compare two basic types of multilayered structures for LEID, which significantly enhance the practical bearing ability and working flexibility of the device. Besides, we also demonstrate the excellent processability of the LEID, by forming them into curved shapes, and secondarily machining and assembling them into complex structures without affecting their energy storage ability.
The safety concern arising from flammable liquid electrolytes used in batteries and supercapacitors drives technological advances in solid polymer electrolytes (SPEs) in which flammable organic solvents are absent. However, there is always a trade-off between the ionic conductivity and mechanical properties of SPEs due to the lack of interaction between the ionic liquid and polymer resin. The inadequate understanding of SPEs also limits their future exploitation and applications. Herein, we provide a complete approach to develop a new SPE, consisting of a cation (monomer), anion and hardener from ions–monomers using molecular dynamics (MD) simulations. The results show that the strong solid–liquid interactions between the SPE and graphene electrode lead to a very small gap of ∼5.5 Å between the components of SPE and electrode, resulting in a structured solid-to-liquid interface, which can potentially improve energy storage performance. The results also indicated the critical role of the mobility of free-standing anions in the SPE network to achieve high ionic conductivity for applications requiring fast charge/discharge. In addition, the formations of hardener-depleted regions and cation–anion-poor/rich regions near the uncharged/charged electrode surfaces were observed at the molecular level, providing insights for rationally designing the SPEs to overcome the boundaries for further breakthroughs in energy storage technology.
Carbon fiber is an ideal candidate for preparing electrode of structural supercapacitors, while its low specific surface area is a vital factor which restricts energy storage performance. In this study, MnOOH nanowires (MnOOH‐NWs) are in‐situ deposited onto the woven carbon fiber fabric (WCF) surface through an effective one‐step hydrothermal treatment to prepare MnOOH‐NWs modified WCF (MnOOH‐NWs@WCF) structural supercapacitor with appreciable electrochemical performance. The areal capacitance of MnOOH‐NWs@WCF structural supercapacitor reaches 77.1 mF/cm2, which is two orders of magnitude higher than that made from neat WCF electrode. The increase in areal capacitance is primarily due to the presence of conductive networks and abundant ion storage sites constructed by the MnOOH‐NWs. Meanwhile, flexural strength and modulus of the MnOOH‐NWs@WCF structural supercapacitor are 30.3 MPa and 1.8 GPa, respectively. Interestingly, the resultant structural supercapacitor also enables electromagnetic interference (EMI) shielding based on the conductive networks constructed by the WCF and MnOOH‐NWs, and the maximum EMI‐shielding effectiveness (EMI‐SE) is 59.1 dB. Consequently, a highly integrated multi‐functional structural supercapacitor is developed, which cannot only be applied as energy storage module and load bearing component but can also be adopted to protect electronic devices from the electromagnetic pollution. A multi‐functional structural supercapacitor based on MnOOH‐NWs@WCF electrodes exhibits outstandingelectrochemical properties, desirable mechanical and excellent EMI‐shielding performance.
Nowadays, the energy storage systems based on lithium-ion batteries, fuel cells (FCs) and super capacitors (SCs) are playing a key role in several applications such as power generation, electric vehicles, computers, house-hold, wireless charging and industrial drives systems. Moreover, lithium-ion batteries and FCs are superior in terms of high energy density (ED) as compared to the SCs. But, the down-side associated with them is the low power density (PD). On the other hand, this high PD feature is essential for the enhancement of dynamic performance of the system. Therefore, the SCs are well utilized due to their dominant features such as high specific power, rapid charging-discharging rate and superior cycling life. Hence, this paper mainly focuses on the advancements of various types of SCs along with their performance improvement methods. The important properties and selection of the electrode and electrolyte materials are described in detail. The commercially available SCs are enumerated with much more emphasis on their Figure of Merits (FOMs). Furthermore, the prominent role of SCs is highlighted with respect to the aforementioned applications. Finally, the future challenges associated with the SCs are presented. This review paper gives insightness for the design engineers and researchers in order to fill the research gaps associated with the SCs.
