Structural Supercapacitors Research Articles

A Novel Ternary Pseudocapacitive Electrode with Synergistic Contributions

AbstractTernary electrodes represent an exciting strategy to substantially enhance the performance of supercapacitors beyond what binary electrodes offer. However, the interplays among ternary constituents and their possible synergies remain poorly understood. This study investigates a ternary electrode design, wherein ferric oxyhydroxide (FeOOH) and magnesium dioxide (MnO2) are co‐deposited onto carbon nanotube (CNT) mats. The results reveal that the ternary electrode demonstrates a 33.3% reduction in internal resistance and a 59% increase in areal capacitance compared to its binary MnO2/CNT counterpart. Furthermore, the ternary electrode achieves a 25% increase in capacitance compared to the combined capacitances of separate MnO2/CNT and FeOOH/CNT electrodes. These findings demonstrate that combining FeOOH and MnO2 can synergistically enhance electrical conductivity and pseudocapacitance beyond their binary counterparts. This design yields a surface capacitance exceeding 3500 mF cm−2 at an active material loading up to 15 mg cm−2. By pairing with a binary FeOOH/CNT electrode, the resulting asymmetric supercapacitor exhibits an operational voltage window to 1.6 V. To demonstrate the potential of the new design, ternary electrodes are integrated into wearable and structural supercapacitors. The new synergistic ternary electrode approach provides a promising avenue for enhancing energy storage capacitance and expanding the scope of energy storage structure applications.

Scalable electrochemical grafting of anthraquinone for fabrication of multifunctional carbon fibers

Carbon fiber electrodes were prepared by grafting anthraquinone molecules via a scalable electrochemical approach which simultaneously increased interfacial and electrochemical capacitance properties. In this work, anthraquinone diazonium salts were synthesized and grafted onto carbon fiber tows at various concentrations. These modified fibers were subsequently evaluated mechanically and electrochemically to analyze their suitability in structural supercapacitors. Compared to control fibers, the grafted anthraquinone groups resulted in a 30% increase in interfacial shear strength (IFSS) and 6.6× increase in specific capacitance. Industry application was also a focus thus carbon fibers were also modified with in-situ generated diazonium salts to determine the applicability to an in-line industrial process. Specifically, potentiostatic functionalization of fibers with in-situ generated diazonium salts AQ-1 and AQ-2, showed 3× and 4.3× increase in specific capacitance, respectively, relative to unmodified carbon fiber (CF). We expect that implementing a scalable method to introduce a conductive and electrochemically active covalently bound surface chemistry layer onto carbon fiber exhibits a higher specific capacitance than carbon fiber grafted with most other small molecules reported in literature. This will open new avenues for manufacturing multifunctional and high-performance fibers with tailored properties for specific/targeted applications.

Polymer/cement composite electrolyte with high strength and high ionic conductivity for structural supercapacitors

All-solid-state structural supercapacitors (ASSC) based on polymer/cement electrolytes (PCE) are promising energy storage devices in buildings due to the tremendous demand for zero-energy buildings. However, the challenge of PCE remains in well balancing the mechanical properties and ionic conductivity. Herein, an integrated electro-mechanical PCE introducing PAM (20 wt%, synthesized by in-situ polymerization) and PAM (5 wt%, commercial) simultaneously largely improves the ionic conductivity (68.54 mS/cm) and mechanical properties (47.96 MPa). Surprisingly, PAM (20% wt%, in-situ polymerization synthesis) and PAM (5% wt%, commercial) were introduced simultaneously to modify PCE, which not only had a synergistic effect on compressive strength but also had a synergistic effect on ionic conductivity. Moreover, an assembled ASSC based on 20-AM-5-PAM PCE exhibits excellent performance with an areal energy density of 25.17 μWh/cm2 at a power density of 50 μW/cm2 and ～96% capacitance retention after 5000 cycles. These results demonstrate the great potential for the application of 20-AM-5-PAM PCE in high-strength and large-volume building structure energy storage devices.

Epoxy-based multifunctional solid polymer electrolytes for structural batteries and supercapacitors. a short review.

The potential applications of epoxy-based solid polymer electrolytes are continually expanding because of their versatile characteristics. These characteristics include mechanical rigidity, nonvolatility, nonflammability, and electrochemical stability. However, it is worth noting that pure epoxy-based solid polymer electrolytes inherently exhibit lower ion transport capabilities when compared to traditional liquid electrolytes. Striking a balance between high mechanical integrity and superior ionic conductivity at room temperature poses a significant challenge. In light of this challenge, this review is dedicated to elucidating the fundamental concepts of epoxy-based solid polymer electrolytes. It will explore various preparation techniques, the incorporation of different nanomaterials into epoxy-based solid polymer electrolytes, and an evaluation of their multifunctional properties. This comprehensive evaluation will cover both mechanical and electrical properties with a specific focus on their potential applications in batteries and structural supercapacitors.

Regulating fast cationic redox for high areal-energy-density structural supercapacitors

Structural supercapacitor (SSC) with cement-based materials as electrolytes shows great potential in the construction field due to their high strength and low cost. However, current SSC usually suffer from low areal capacitance and energy density, especially under a specific mechanical strength, limiting their feasibility of a practical application. Herein, a new type of SSC using cement-polyacrylamide (PAM)-Mn(NO3)2 as a redox electrolyte is proposed to realize high areal capacitance and energy density at high mechanical strength. The results show that introducing PAM and Mn2+ largely improves the ionic conductivity and mechanical properties of the cement-based structural electrolyte, both of which are beneficial to high areal capacitance and energy density. Compared with the pure cement electrolyte, the high ionic conductivity, compressive strength, and flexural strength of the redox structural electrolyte (containing PAM and 4 wt% Mn2+) is increased by 91.52 %, 25.80 %, and 60.79 %, respectively. As a proof-concept-application, the areal energy density (0.038 mWh/cm2, at 1 mA/cm2) of the SSC prepared by the redox structural electrolyte is 9 times higher than that of the pure one (0.004 mWh/cm2). Moreover, there is a slight increase in its electrochemical performance even under a pressure of 200 g.

Multifunctionality Analysis of Structural Supercapacitors— A Review

Structural supercapacitors (SSCs) are multifunctional energy storage composites (MESCs) that combine the mechanical properties of fiber-reinforced polymers and the electrochemical performance of supercapacitors to reduce the overall mass in lightweight applications with electrical energy consumption. These novel MESCs have huge potentials, and their properties have improved dramatically since their introduction in the early 2000’s. However, the current properties of SSCs are not sufficient for complete energy supply of electrically driven devices. To overcome this drawback, the aim of the current study is to identify key areas for enhancement of the multifunctional performance of SSCs. Critical modification paths for the SSC constituents are systematically analyzed. Special focus is given to the improvement of carbon fiber-based electrodes, the selection of structural electrolytes and the implementation of separators for the development of more efficient SSCs. Finally, current SSCs are compared in terms of their multifunctionality including material combinations and modifications.

Direct Synthesis of MOF-74 Materials on Carbon Fiber Electrodes for Structural Supercapacitors.

The use of fossil fuels has contributed significantly to environmental pollution and climate change. For this reason, the development of alternative energy storage devices is key to solving some of these problems. The development of lightweight structures can significantly reduce the devices' weight, thereby reducing energy consumption and emissions. Combining lightweight structures with alternative energy storage technologies can further improve efficiency and performance, leading to a cleaner and more sustainable system. In this work, for the first time, MOF-74 materials with different divalent metal ions have been synthesized directly on carbon fiber, one of the most widely used materials for the preparation of electrodes for supercapacitors with structural properties. Different techniques, such as nitrogen adsorption-desorption isotherms, cyclic voltammetry or galvanostatic charge-discharge, among others, were used to evaluate the influence of the metal cation on the electrochemical capacitance behavior of the modified electrodes. The Co-MOF-74 material was selected as the best modification of the carbon fibers for their use as electrodes for the fabrication of structural supercapacitors. The good electrochemical performance shown after the incorporation of MOF materials on carbon fibers provides a viable method for the development of carbon fiber electrodes, opening a great variety of alternatives.

3D porous cementitious electrolytes with “stream-reservoir” ionic channels for high multifunctional performance structural supercapacitors

Structural supercapacitors (SSCs) have attracted extensive attention due to load bearing/energy storage in zero energy buildings (ZEBs).

From stress to charge: investigating the piezoelectric response of solvate ionic liquid in structural energy storage composites.

Solvate ionic liquids (SILs) are a class of ionic liquids where the liquid-state salt is chelated by a coordinating solvent, and of interest due to their advantageous properties such as low vapour pressure and superb thermal and chemical stability for energy storage applications. The electromechanical and piezoelectric effect were studied in lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solvated by triethylene glycol dimethyl ether (triglyme, G3), forming [Li-G3]TFSI. These effects were also investigated in full solid polymer electrolyte (SPE) used in energy storage devices, consisting of [Li-G3]TFSI paired with an epoxy-based resin system. The SIL's electromechanical response was first established in isolation, as well as within the SPE. Experimental data demonstrates the effect of a major part of the SPE contributing to the electrical potential generation during application of force and subsequent pressurisation as well as depressurisation, underlined by a direct piezoelectric effect. SPE response to applied load is explored after the recent discovery of liquid-to-crystalline phase transition following pressurisation in pure ionic liquids. This finding has the potential to ameliorate the performance of energy storage composites via additional effects of charging such a device by subjecting it to stress, leading to increased efficiency. Results to date show a bulk potential difference across the SIL of up to 150 mV, while the SPE potential response is scaled down due to a significantly lower volume of SIL at the interface (∼30 mV). Nevertheless, such findings can still significantly affect the performance of carbon fibre (CF)-based structural supercapacitors and batteries that are able to store and release electrical energy whilst simultaneously contributing to load-bearing performance.

Multifunctional energy storage polymer composites: The role of nanoparticles in the performance of structural supercapacitors

Multifunctional energy storage polymer composites: The role of nanoparticles in the performance of structural supercapacitors

A superior electrolyte composite with high conductivity and strength based on alkali-activated slag and polyacrylamide for structural supercapacitor

In the time to come, structural supercapacitors have broad prospects in large-scale and construction structure energy storage. But the contradiction between ionic conductivity and mechanical performances of structural electrolytes still exists. Here, a novel polyacrylamide/alkali-activated slag (PAM/AAS) structural electrolyte composite is reported to attain a balance of high ionic conductivity and qualified compressive strength. The prepared PAM/AAS composite structural electrolytes show optimal properties with ionic conductivity of 55.01 mS/cm and compressive strength of 44.5 MPa in the dry state and 36.9 MPa after soaked in aqueous solution of 2 M KOH. Structural supercapacitor assembled with rGO electrodes has high mass specific capacitance of 285.35 F/g at 1 mA/cm2, energy density of 2.48 Wh/kg and power density of 59.54 W/kg, and favorable cycle life. The results of PAM/AAS composite structural electrolytes are superior to those in latest researches, attesting its vast application potential in construction structure energy storage.

Complex Materials with Stochastic Structural Patterns: Spiky Colloids with Enhanced Charge Storage Capacity.

Self-assembled materials with complex nanoscale and mesoscale architectureattract considerable attention in energy and sustainability technologies. Their high performance can be attributed to high surface area, quantum effects, and hierarchical organization. Delineation of these contributions is, however, difficult because complex materials display stochastic structural patterns combining both order and disorder, which is difficult to be consistently reproduced yet being important for materials' functionality. Their compositional variability make systematic studies even harder. Here, a model system of FeSe2 "hedgehog" particles (HPs) was selected to gain insight into the mechanisms of charge storage n complex nanostructured materials common for batteries and supercapacitors. Specifically, HPs represent self-assembled biomimetic nanomaterials with a medium level of complexity; they display an organizational pattern of spiky colloids with considerable disorder yet non-random; this patternt is consistently reproduced from particle to particle. . It was found that HPs can accommodate ≈70× greater charge density than spheroidal nano- and microparticles. Besides expanded surface area, the enhanced charge storage capacity was enabled by improved hole transport and reversible atomic conformations of FeSe2 layers in the blade-like spikes associated with the rotatory motion of the Se atoms around Fe center. The dispersibility of HPs also enables their easy integration into energy storage devices. HPs quadruple stored electrochemical energy and double the storage modulus of structural supercapacitors.

High areal capacitance nickel-cobalt transition metal hydroxide/reduced graphene for structural supercapacitors

Structural supercapacitors (SSCs) as a kind of multifunctional energy storage device, show great potential in zero building energy consumption. Herein, SSCs with cement-based material as electrolytes and layered double hydroxides (LDH) as electrodes were prepared. The electrochemical performance of redox electrodes prepared by different methods was studied. The results show that T-3-rGO/NiCo-LDH prepared by the two-step hydrothermal method exhibits the best performance. Then different asymmetric SSCs with T-3-rGO/NiCo-LDH as positive electrode and rGO as negative electrode were fabricated successfully. Just as we expected, the thinner the thickness of the structural electrolyte is, the higher the areal capacitance. Therefore, the SSCs-1 cm2–0.2 cm prototype device exhibits the best performance, with a high areal capacitance of 255.94 mF/cm2, a high energy density of 79.98 μWh/cm2 at 2 mA/cm2 together with power density of 1500 μW/cm2. On this basis, the SSCs-20.25 cm2–0.2 cm was prepared, which exhibits a high energy density (40.32 μWh/cm2 at 5 mA/cm2) at a power density of 3750 μW/cm2. More importantly, the large-size electrode can carry more active substances, thus storing more electrical energy. Hence, the SSCs show great practical application potential in reducing carbon emissions in the field of large-volume buildings.

Structural energy storage system using electrospun carbon nanofibers with carbon nanotubes

AbstractIn the present study, carbon nanofibers containing multi‐walled carbon nanotubes (MWCNTs) were fabricated and employed as electrodes for structural supercapacitors. Carbon nanofibers were utilized as the electrode material in structural supercapacitors to increase the specific surface area. Electrospun polyacrylonitrile (PAN) nanofibers underwent conversion to carbon nanofibers through stabilization and carbonization processes aided by thermal treatment. The specific surface area of the electrospun carbon nanofiber electrodes was further increased approximately 118 times (1946.9 m2/g) using an activation process in comparison with that of non‐activated carbon nanofibers (16.43 m2/g). Multifunctional supercapacitors were fabricated by employing electrospun carbon nanofibers and a vacuum resin infusion technique. The specific capacitance of activated carbon nanofibers (ACNF) and ACNF‐MWCNT exhibited significant improvement (14.87 and 48.25 mF/cm2, respectively) compared to non‐activated carbon nanofibers (CNF‐MWCNT: 1.71 mF/cm2). This improvement was attributed to the reduction in equivalent series resistance and the increase of the surface area of the nanofiber electrodes. Additionally, the carbon nanofiber electrodes contributed to an increased interlaminar fracture toughness of structural supercapacitors, acting akin to “Velcro” between fabric interfaces. This work serves as a “proof of concept” for a straightforward and efficient method to manufacture electrodes for structural supercapacitors based on the electrospinning technique.Highlights Fabrication of carbon nanofibers containing MWCNTs using electrospinning. The carbon nanofiber as an electrode for structural supercapacitors. Simple and effective method. Dramatically improving specific capacitance of the supercapacitors.

Manufacture and characterisation of a structural supercapacitor demonstrator

Structural power composites, a class of multifunctional materials, may facilitate lightweighting and accelerate widespread electrification of sustainable transportation. In the example considered in this paper, structural power composite fuselage components could provide power to open aircraft doors in an emergency and thus reduce or eliminate the mass and volume needed for supercapacitors currently mounted on the doors. To demonstrate this concept, an 80 cm long multifunctional composite C-section beam was designed and manufactured, which powered the opening and closing of a desktop-scale composite aircraft door. Twelve structural supercapacitor cells were made, each 30 cm × 15 cm × 0.5 mm, and two stacks of four cells were integrated into the web of the beam by interleaving and encasing them with low-temperature-cure woven carbon fibre/epoxy prepreg. This article culminates by considering the engineering challenges that need to be addressed to realise structural power composite components, particularly in an aerospace context.

Ti3C2Tx MXene coated carbon fibre electrodes for high performance structural supercapacitors

MXenes, while excellent for electrical energy storage, face challenges in translating their nanoscale properties to macroscale structures. To address this, MXene-coated carbon fibers (CF) were developed as electrode materials for structural supercapacitor composites. CF surface chemistry was tailored using aryl diazonium salts (–NO2, –NH2, -SH, –COOH) to optimize MXene adhesion. Electrodes were characterized for surface chemistry, morphology, and properties including electrochemical, mechanical, and interfacial aspects. Electrodes developed from MXene coated on CF functionalized with a poly(o-phenyelenediamine) coating exhibited a specific capacitance of 157 F/g−1 at 5 mV s−1, a ∼725-fold improvement in capacitance compared to pristine unfunctionalized CF, with minimal to no compromise in the underlying strength and stiffness of the CF. The MXene coating also improved the interfacial adhesion of the electrode to an epoxy-based resin by 54 %. The process was scaled up to functionalize and coat woven CF mats and were used to fabricate a structural supercapacitor device. The device exhibited a specific capacitance of 908 mF/g−1 at 0.5 mA g−1, representing a remarkable ∼42-fold improvement compared to the control. This lightweight multifunctional supercapacitor composite holds great potential in aerospace, automotive, and renewable energy storage sectors, addressing global challenges tied to fossil fuel combustion and associated environmental and socio-economic issues.

Enhanced all-solid-state structural supercapacitor performance of rGO/N1C1M-S3’ nanosheets with high areal capacitance

All-solid-state structural supercapacitors (ASSCs), as a kind of multifunctional energy storage devices, show great application potential in the field of building. However, the inability to achieve high energy density is a major bottleneck in the application of ASSCs. Herein, a novel 3D nanosheet material is designed by a facile method, aiming to boost areal-energy-density for ASSCs. By doping of S (Na2S·9 H2O) on the rGO/N1C1M nanosheet (rGO/N1C1M-S3’), we achieved an extremely areal capacitance of 9407.62 mF/cm2 at 5 mA/cm2, which is much higher than 4421.33 mF/cm2 (rGO/N1C1M). Definitely, this is the best performance reported so far for rGO/NCM electrode. An asymmetric ASSCs (1 cm × 1 cm×0.2 cm) prototype device exhibits excellent performance, with a high areal capacitance of 242.82 mF/cm2, a high areal-energy-density of 0.076 mWh/cm2 at 3 mA/cm2. As a proof-concept-application. the ASSCs was enlarged to 4.5 cm × 4.5 cm × 0.2 cm, three ASSCs connected in series can light up a green light emitting diode indicator about ～1066 s, and can still work normally under the pressure of 500 g. The demonstration of employing rGO/N1C1M-S3’ electrode opens up new opportunities to fabricate high performance ASSCs for structure energy storage in building.

(Invited) Rapid, Large Area Preparation of Few-Layer Graphene Films Using Xenon Flash Lamp Pyrolysis for High-Performance Structural Micro-Supercapacitors

Graphene offers excellent electrical conductivity and very high surface area, which holds great promise for energy storage applications including supercapacitors. Current preparation methods for graphene require relatively long processing times, extremely high temperatures within controlled atmospheres, and/or involve multi-step reactions that present challenges for high throughput fabrication of graphene-based energy storage devices. We report a novel photothermal route to large-scale production of graphene within milliseconds using a commercially available polymers (polybenzoxazine, polyacrylonitrile and polyaniline) and a high intensity xenon flash lamp on various substrates, including carbon fibers, at ambient conditions. The xenon flash lamp provides large-area illumination and a wide emission band (300 nm –1100 nm) that was used to convert the polymeric material directly into few layer graphene upon millisecond exposures. The precursor material is heated to extremely high temperatures in a fraction of a second – a duration that is much shorter than the timescale for thermal equilibrium. This enabled the conversion of the polymeric material into few layer graphene in air and at room temperature, and without thermally damaging the substrate. Conversion to few-layer graphene was strongly dependent on pulse energy and the local temperature which was controlled via pulse power modulation. The obtained graphene composites at optimized conditions exhibited excellent conductivity (0.1 ohm-cm) with ID/IG ratio of 0.3 (Figure 1a). Particularly, graphene derived from polyaniline resulted in the formation of macroporous network (Figure 1b) with good adhesion to the carbon fiber, all of which facilitate the transport of ions through the material. The fabricated supercapacitor devices exhibited a very high areal capacitance of 200 mF/cm2 at 10 mV/s with retention of more than 70% of their capacitance, even at scan rates up to 100 mV/s. Moreover, mechanically, and structurally stable graphene derived from polyaniline on carbon fiber was utilized for the preparation of structural energy storage devices. We assembled symmetric structural supercapacitor comprised of carbonaceous material (carbon fiber and few-layer graphene) and polymer gel electrolyte. This resulted in the preparation of large area device (40 cm2) as shown in the Figure 1c with the capacitance exceeding 2000 mF and almost complete retention of capacitance after 5000 cycles.The preparation of high-quality graphene via photothermal pyrolysis of polymer is amenable to high throughput processing, enabling large-scale production of high performance structural electrochemical energy storage devices. Figure 1

Sulfonated hypercrosslinked polymer enhanced structural composite supercapacitors

Structural supercapacitors are multifunctional devices able to bear mechanical load while storing electrical energy. Carbon fibres can be used as a bifunctional component within structural supercapacitors, acting both as current collector and mechanical reinforcement. A promising route to such devices is to increase the surface area of carbon fibres, which can be achieved by the deposition of active materials, and embed them into a structural electrolyte. A highly sulfonated, high porosity hypercrosslinked polymer was deposited onto carbon fibres by electrophoretic deposition from an aqueous suspension. We investigated the effect of polymer and binder concentration in the deposition suspension on the electrochemical properties of the coated carbon fibre electrodes. Multifunctional structural composite supercapacitors had a fibre volume fraction of only 21% and possessed a tensile strength and Young's modulus of 495 MPa and 49 GPa, respectively. A specific capacitance of 1.2 F/g was reached, comparable to graphene coated carbon fibre electrodes. At room temperature and ambient humidity an energy density of 39 mWh/kg and a power density of 15 W/kg were measured. We demonstrate that moisture plays a major role in the energy storage mechanism in these SCs.

Structural pseudocapacitors with reinforced interfaces to increase multifunctional efficiency.

Structural supercapacitors hold promise to expand the energy capacity of a system by integrating load-bearing and energy-storage functions in a multifunctional structure, resulting in weight savings and safety improvements. Here, we develop strategies based on interfacial engineering to advance multifunctional efficiency. The structural electrodes were reinforced by coating carbon-fiber weaves with a uniquely stable conjugated redox polymer and reduced graphene oxide that raised pseudocapacitive capacitance and tensile strength. The solid polymer electrolyte was tuned to a gradient configuration, where it facilitated high ionic conductivity at the electrode-electrolyte interfaces and transitioned to a composition with high mechanical strength in the bulk for load support. The gradient design enabled the multilayer structural supercapacitors to reach state-of-the-art performance matching the level of monofunctional supercapacitors. In situ electrochemical-mechanical measurements established the device durability under mechanical loads. The structural supercapacitor was made into the hull of a model boat to demonstrate its multifunctionality.