Fibrous Supercapacitors Research Articles

One-Step Wet-Spinning of High-Energy Density Coaxial Fibrous Supercapacitors Based on In Situ Carbon-Modified Nitrogen-Doped MXene Nanosheets.

Fibrous supercapacitors (SCs) are emerging promising power sources for flexible/wearable electronics and have attracted an extensive amount of attention from researchers. However, the low energy density has always hindered their further development. Here, a coaxial fibrous SC (CFSC) was fabricated by one-step wet-spinning combined with an electrodeposition strategy. Benefiting from the large surface area and abundant pore structure of carbon-modified nitrogen-doped MXene nanosheets (NS), as well as the high conductivity of silver (Ag) NS, the electrolyte ion/electron transport paths are significantly improved. Furthermore, the distributed GO in the P(VDF-HFP) separator could form a high-speed continuous ion transport channel, thus enhancing the ionic conductivity. At a power density of 40-200 μW cm-2, the CFSC shows a high energy density of 0.7-3.39 μWh cm-2. The as-prepared CFSC also maintains an excellent capacitance retention rate of 90.3% even after 15 000 charge-discharge cycles. This work provides a general strategy for manufacturing high-performance, flexible, and wearable SCs.

Electrochemically exfoliated graphene oxide enhanced hybrid fibers with high rate performance for fibrous supercapacitors

In this study, a composite graphene fiber was created using electrochemically exfoliated graphene oxide (EGO) and chemically oxidized graphene oxide (GO) through a simple wet spinning process. The incorporation of EGO sheets in the fiber forms a highly conductive network, significantly enhancing its conductivity. The optimized EGO/GO fiber exhibits both high areal capacitance (532 mF cm−2) and volumetric capacitance (103 F cm−3). Moreover, the EGO/GO composite fiber demonstrates superior capacitance retention and increased fiber length compared to the GO fiber. A solid-state device was also constructed by the optimized EGO/GO fiber using PVA/H2SO4 gel electrolyte which demonstrates excellent flexibility. And the as prepared solid-state fiber shaped supercapacitor demonstrates an areal capacitance of 246 mF cm−2 at a current density of 0.69 mA cm−2, while maintains 185 mF cm−2 at a current density of 34.7 mA cm−2 showcasing excellent rate performance.

Three-Dimensionally Conducting Network in Graphene-Based Composite Fibers toward Enhanced Electrochemical and Toughness Performance in Fibrous Supercapacitors

As one of the most promising energy storage devices, graphene-based fibrous supercapacitors (FSSCs) are attracting intensive attention. However, the conflict between specific capacitance and intrinsic brittleness of pure graphene fibers hinders their practical applications. Herein, we develop a strategy to fabricate graphene-based ternary composite CNT/MXene/graphene (CMG) fiber electrodes with high toughness and high electrical and electrochemical performance. These resulting properties are attributed to the three-dimensional cross-linked conducting network within graphene sheets through covalent bonding and π–π interaction among acidified carbon nanotubes, graphene sheets, and MXene, which greatly contributes to the enhanced tensile strength, toughness, and electrical transport in the CMG fiber. The CMG fiber with the optimized mass ratio of different components shows a high toughness of ∼1.7 MJ m–3 and an electrical conductivity of 420 S cm–1, which is 4- and 2-fold that of reduced graphene oxide fiber, respectively. The assembled FSSC based on the optimized CMG fiber exhibits an areal capacitance of 237 mF cm–2 and a good rate performance of 85%.

Surface Functionalization of Carbon Fiber for High-Performance Fibrous Supercapacitor

Surface Functionalization of Carbon Fiber for High-Performance Fibrous Supercapacitor

Reversible faradaic reactions involving redox mediators and oxygen-containing groups on carbon fiber electrode for high-performance flexible fibrous supercapacitors

Flexible fibrous supercapacitors (FFS) are taking account of as the energy storage devices for wearable electronics owing to their high power density, high safety, long cycle life, and simple manufacturing process. Nevertheless, FFSs have the disadvantage of low specific capacitance that results from the electrochemical characteristics of the electrical double layer on the carbon fiber electrode. In this study, for the first time, an FFS comprising surface-activated carbon fibers as an electrode/current collector and a redox additive gel polymer electrolyte (FFS-SARE) was fabricated for use as a wearable energy storage device. The FFS-SARE showed outstanding electrochemical performance, namely, high specific capacitances of 891 and 399 mF cm−2 at current densities of 70.0 and 400 μA cm−2, respectively, and remarkable ultrafast cycling stability over 5000 cycles with 92% capacitance retention at a current density of 400.0 μA cm−2. Moreover, they exhibited mechanical flexibility and had high feasibility, and they showed good energy storage performance that renders them suitable for use in wearable electronic textiles.

Highly Reliable Yarn-Type Supercapacitor Using Conductive Silk Yarns with Multilayered Active Materials

ABSTRACT The fibrous supercapacitor is a promising candidate for wearable energy-storage systems due to excellent mechanical reliability under deformation. In this study, a mechanically reliable fibrous supercapacitor with high volumetric power density and energy density was developed using fiber electrodes composed of multilayered active materials coated on silk yarns. The conductive silk yarn electrodes are fabricated via a sequential dip-coating process of silver nanowires, multi-walled carbon nanotubes (MWCNT, three to seven walls), and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The composite-coated silk yarn electrodes were stable under cyclic bending as well as under washing in water. Due to the synergetic effect of the three conducting materials, an excellent electrochemical performance was obtained resulting in high volumetric energy and power densities of 8–13 mWh cm−3 and 8–19 W cm−3, respectively. A yarn-type supercapacitor was demonstrated by integrating composite-coated silk yarn electrodes with a hydrogel electrolyte, showing a promising stability as evidenced by the retention of over 94% and 93% of the specific capacitance after 90-degree bending and stretching.

Surface Engineering of Carbon via Coupled Porosity Tuning and Heteroatom‐Doping for High‐Performance Flexible Fibrous Supercapacitors (Adv. Funct. Mater. 48/2021)

Flexible Fibrous Supercapacitors In article number 2104256, Geon-Hyoung An, Young-Geun Lee, and Jaeyeon Lee report the surface engineering of carbon via coupled porosity tuning and heteroatom-doping for high-performance flexible fibrous supercapacitors. The optimized fibrous supercapacitors exhibit excellent electrochemical performance and good mechanical properties and remarkable safety in practical application, thus demonstrating its feasibility for use in wearable electronic textiles.

High-Performance Coaxial Asymmetry Fibrous Supercapacitors with a Poly(vinyl alcohol)-Montmorillonite Separator.

Fibrous supercapacitors have garnered great interest from researchers because of their large electrode/electrolyte interface area, short ion transport path, and high flexibility. However, obtaining a thin gel electrolyte interlayer with a high ion transport rate and uniform thickness is still challenging. Here, we proposed an efficient wet-spinning technique to fabricate uniform polyvinyl-montmorillonite tubular layers for the preparation of a high-performance coaxial asymmetry fibrous supercapacitor (AFSC). The coaxial AFSC shows ultrahigh energy densities in the range of 2.86-4.04 μW h cm-2 at power densities of 0.16-1.61 mW cm-2 while maintaining a long cycling life (94% retention even after 20 000 cycles). After charging at a constant voltage of 2.4 V for 30 s, the flexible watchband which is composed of three series-connected AFSCs could power a commercial electronic watch for more than 2 min. This work provides a universal strategy to fabricate high-performance and wearable energy storage devices.

EGaIn Fiber Enabled Highly Flexible Supercapacitors.

Attributed to their soft and stretchable feature, flexible supercapacitors have attracted increasing attention in areas of soft electronics, wearable devices, and energy storage systems. However, it is a challenge to manufacture all-soft supercapacitors with highly flexible properties and excellent electrochemical performance. Here, an EGaIn-based fibrous supercapacitor, which is composed of two paralleled stretchable fibers, is designed and demonstrated first with flexible and stretchable properties. EGaIn coated on the surface of polyurethane (PU)@polymethacrylate (PMA) fibers can serve as a current collector. The prepared supercapacitor is measured with an areal specific capacitance of 26.71 mF·cm–2 by mixing Fe3O4 microparticles with EGaIn. This value can increase up to 61.34 mF·cm–2 after vacuum pumping, the mechanism of which is further revealed to be related with the coarser surface and airhole formation on the fibers. The supercapacitor maintains an excellent electrochemical performance when stretched to 120% strain and exhibits a long cycling life through a charge–discharge cycle of over 1000 times. Finally, the supercapacitors are adopted to light the LED, demonstrating that those supercapacitors can work successfully. All these characteristics indicate the huge potential of EGaIn-based supercapacitors in the field of flexible electronics and wearable devices.

High performance stretchable fibrous supercapacitors and flexible strain sensors based on CNTs/MXene-TPU hybrid fibers

In order to improve the practicability of fibrous supercapacitors, stretchability is a significant characteristic for the devices, which puts forward high requirements for electrode materials. In this work, highly stretchable and conductive CNTs/MXene-TPU hybrid fiber electrodes with porous structure were prepared by wet spinning technique. The mechanical and electrical properties of the fiber electrodes remained stable during the tensile process when the amount of CNTs/MXene is 10 wt%. Meanwhile, the electrodes also showed a high volumetric specific capacitance of 3.9 F cm−3 even at the scan rate of 1 V s−1. The all-solid-state fibrous supercapacitors based on CNTs/MXene-TPU fiber electrodes also exhibited superior electrochemical performance and can be stretched by more than 50% strain. The specific capacitance of the devices changed with the tensile strain and reached 3.1 F cm−3 while the stain was 50%. Based on these characteristics, the fibrous supercapacitors were further applied to flexible strain sensors, which can convert action signals to electrochemical signals rapidly. The stretchable fibrous supercapacitor can be used not only for energy storage, but also as a strain sensor to monitor human movements, making it very promising for the next generation smart textiles.

Surface Engineering of Carbon via Coupled Porosity Tuning and Heteroatom‐Doping for High‐Performance Flexible Fibrous Supercapacitors

AbstractFlexible fibrous supercapacitors (FFS) are considered the next‐generation wearable energy storage devices because they provide reliable safety, eco‐friendliness, and high power density. In particular, the FFS is desirable for application to wearable electronics because it can overcome disadvantages of the lithium‐ion battery (LIB), such as the hazard of explosion and the complex manufacturing process. Nevertheless, the practical application of the FFS continues to be inhibited by the poor energy storage performance due to the limited specific surface area, poor electrical properties, and low wettability of the carbon fiber electrode. Herein, for the first time, the surface engineering of an FFS using nitrogen and fluorine codoped mesoporous carbon fibers (FFS‐NFMCF) is described, and the synergistic effect of porosity tuning and heteroatom codoping upon the electrochemical performance is demonstrated. The resultant supercapacitor shows a high specific capacitance of 243.9 mF cm−2 at a current density of 10.0 µA cm−2 and good ultrafast cycling stability with capacitance retention of 91.3% for up to 10 000 cycles at a current density of 250.0 µA cm−2. More interestingly, the FFS‐NFMCF exhibits good mechanical properties and remarkable safety in practical application, thus demonstrating its feasibility for use in wearable electronic textiles.

High specific capacitance cotton fiber electrode enhanced with PPy and MXene by in situ hybrid polymerization

Fiber electrodes are the main functional elements of flexible and textile-based storage devices. This study proposes a Polypyrrole (PPy) and MXene composite, grown on cotton fiber, as a high capacitance electrode. Pyrrole (Py) and MXene are processed and deposited along with an in-situ polymerization. The mass and areal capacitance of the assembled (PPy/MXene)@Cotton electrode respectively reach to 506.6 F g−1, at current density of 1 A g−1 and 455.9 mF cm−2 at scan rate of 0.9 mA cm−2. These values outperform the PPy@Cotton fiber electrode, around 45.8% and 119% respectively. As-prepared fiber electrodes with mechanical strength of 107.3 MPa and conductivity of 60.8 S/m, offer intriguing application prospects in the field of weaving and flexible fibrous supercapacitors.

Electrochemical Behavior of Fibrous Supercapacitor According to the Design of Gel-Electrolyte

Electronic textiles promise to provide an intelligent platform to enlarge the scope of wearable electronic applications. Therefore, the combination of flexible energy storage devies into wearable systems is a key for operating these electronic textiles during bending, knotting, and rolling. Nonetheless, the application of fibrous supercapacitors consisting of a gel-electrolyte and carbon fiber electrode is still obstructed by low capacitance, low rate-performance, and poor cycling stability owing to the inefficient interface between the gel-electrolyte and electrode. Here, a fibrous supercapacitor is obtained using an optimized gelelectrolyte that improves the ionic diffusion capability. The optimized fibrous supercapacitor shows a superior electrochemical performance, including high specific capacitance of 41 mF cm−2 at current density of 2.0 μA cm−2, high-rate performance with 17 mF cm−2 at a current density of 15.0 μA cm−2, and outstanding cycling stability (88% after 3,000 cycles at a current density of 200.0 μA cm−2). The excellent energy storage performance is mainly attributed to the optimzied interface between the gelelectrolyte and electrode material, leading to an improved ionic diffusion capability.

3D printing coaxial fiber electrodes towards boosting ultralong cycle life of fibrous supercapacitors

Fiber-shaped asymmetric supercapacitors (FASCs) with high electrochemical performance have become an important component of modern wearable fiber-shaped electronic devices. However, terrible cycling stability restricts their further development in energy storage fields. The most common strategy is to coat the carbon layer on the surface of the electrode materials, whereas the carbon layer is prone to peel off during bending process, which decrease the cyclic stability of the electrodes or devices. To overcome this challenge, the coaxial fiber electrodes have been achieved via 3D printing direct ink writing (DIW) technology and the FASC device has the excellent electrochemical cycle performance owing to the compact architectures of the positive and negative electrode. Benefited from the suitable charge match of two electrodes and the uniformity of carbon layer coated on the surface of electrodes, the as-fabricated FASC device embraces high areal capacitance of 318.82 mF cm-2, superior areal energy density of 143.15 μWh cm-2, and excellent long-term cycling performance with capacitance retention of 98.63% after 12,000 cycles.

N-doped reduced graphene oxide (rGO) wrapped carbon microfibers as binder-free electrodes for flexible fibre supercapacitors and sodium-ion batteries

In this study, N-doped reduced graphene oxide (rGO) wrapped carbon micro fibres (CFs) were synthesized by one-step high temperature pyrolysis method. Free-standing binder-free electrodes of N-doped rGO on CF were fabricated to apply in extended flexible fibrous supercapacitors and sodium-ion batteries (NIBs). The results showed that the attachment of N-doped graphene onto CF led to high electrochemical capacitance properties. The micro-fibre electrodes showed high performance supercapacitor behaviour of 18.7 F cm−3 at a current density of 1 A cm−3 as a flexible solid-state energy storage device. In parallel with the supercapacitance properties, the micro-fibre electrode shows impressive electrochemical performances when evaluated as anode for NIB, delivering a reversible capacity of 400 mAh/g with capacity retention approaching 100% after 100 cycles. The excellent performances are attributed to defects induced by N-doping along with large surface area of hierarchical porous architecture that can facilitate the storage and diffusion of Na+ and prevent the restacking of rGO during cycling. Thus, these N-doped rGO fibrous materials have substantial promise for fabricating extended flexible cable electronics and NIBs with superior strength and performance.

Interface-engineered electrode and electrolyte for the improved energy-storing performance and stable mechanical flexibility of fibrous supercapacitors

Flexible fiber-based electronic textiles are considered to provide a future intelligent platform with a potential to expand the scope of electronic applications in wearable technology. In this respect, energy storge devices consisting of flexible fibers are a feature for the efficient powering and operation of wearable electronic textiles in the bent, knotted, and rolled states. Nevertheless, the application of fibrous supercapacitors consisting of a carbon fiber electrode and gel-electrolyte remains hindered not only by an unreliable mechanical flexibility, but also by low capacitance, poor rate-performance, and low cyclic stability due to the inefficient interface between the electrode and electrolyte. Herein, for the first time, a fibrous supercapacitor with a densely packed gel-electrolyte in the core region is obtained by an aging process that significantly increases the number of electrochemical active sites and enhances the ionic diffusion capability, leading to the improved rate performance. This strategy results in an excellent electrochemical performance, including a high energy density of 1.1 and 0.74 μWh cm−2 at a power density of 1.3 and 15.0 μW cm−2, which are superior than the previously-reported fibrous supercapacitors. These results highlight the potential of the fibrous supercapacitor for application in electronic textiles.

Carbon dots modified Ti3C2Tx-based fibrous supercapacitor with photo-enhanced capacitance

The energy crisis has always been a widely concerned problem. It is an urgent need for green and renewable energy technologies to achieve sustainable development, and the photo-assisted charging energy storage devices provide a new way to realize the sustainable utilization of solar energy. Here, we fabricated a photo-assisted charging fibrous supercapacitor (NM2P1) with Ti3C2Tx-based hybrid fibre modified by nitrogen-doped carbon dots (NCDs). The NM2P1 fibre provides a volumetric capacitance of 1,445 F·cm−3 (630 F·g−1) at 10 A·cm−3 under photo-assisted charging, which increases by 35.9% than that of dark condition (1,063 F·cm−3/464 F·g−1). Furthermore, the NM2P1 fibrous supercapacitor device shows that the maximum volumetric energy density and volumetric power density are 18.75 mWh·cm−3 and 8,382 mW·cm−3. Notably, the transient photovoltage (TPV) test was used to further confirm that NCDs as a photosensitizer enhance the light absorption capacity and faster charge transfer kinetics of NM2P1 fibre. This work directly exploits solar energy to improve the overall performance of supercapacitor, which opens up opportunities for the utilization of renewable energy and the development of photosensitive energy equipment.

Fe2O3 nanowire arrays on Ni-coated yarns as excellent electrodes for high performance wearable yarn-supercapacitor

Fibrous supercapacitors with high energy/power densities are important energy supply systems for smart wearable devices. Kinds of yarn-cathodes were fabricated, however, high performance anode materials have not been developed to match with the reported cathodes. Additionally, the (volumetric/area) capacitance of yarn-supercapacitors are often limited by less active material deposition, as the yarn is not resistant to high temperature, and the metal conductive-layer is not corrosion resistant. So, a high mass-loading anode with high volumetric performance has not been fabricated. In this study, we report a novel kind of Fe2O3 nanowires arrays on Ni-coated textiles anodes to solve this problem. The nickel layer deposited on the low-cost polyester yarn was applied as high-conductivity current collector, and vertically aligned Fe2O3 nanowires grown on the nickel layer with high mass loading were used as high performance active materials (Fe2O3//Ni//Yarn). It is worth noting that the Fe2O3//Ni//Yarn-based anodes exhibit a high specific capacitance of 54.2 F cm−3 at a scan rate of 10 mv s−1, furthermore, a symmetrical all-solid-state yarn-supercapacitor based on the above electrodes show a capacitance of 969 mF cm−3 at 10 mv s−1. This work provide a good choice of yarn-anodes to match with the reported high performance cathodes for further yarn-supercapacitor designs.

High Volumetric Energy Density Asymmetric Fibrous Supercapacitors with Coaxial Structure Based on Graphene/MnO2 Hybrid Fibers

AbstractIn order to improve the performance of the fibrous supercapacitors to be more suitable for practical application, we prepared graphene/MnO2 hybrid fibers by doping MnO2 nanorods into graphene fibers through a simple wet spinning method, in which MnO2 act as the pseudocapacitive materials. This hybrid fiber electrode shows a wide potential window of −0.2–1 V and a high volume specific capacitance of 473 F cm−3. Based on these hybrid fibers, we fabricated asymmetric fibrous supercapacitors with coaxial structure. In the coaxial device, the internal electrode is graphene/MnO2 hybrid fiber, while the external electrode is graphene coated by dip coating method. The volume specific capacitance and the volumetric energy density of the coaxial device reaches up to 24 F cm−3 and 8.44 mWh cm−3, respectively, 200 % higher than these of the twisting device. The coaxial structure had not only decreased the charge transfer resistance between the two electrodes, but also increased the volume utilization rate of the devices. Therefore, this type of high volumetric energy density asymmetric fibrous supercapacitors has a wide range of applications in portable and flexible electronics and intelligent fabrics.

Surface-engineered flexible fibrous supercapacitor electrode for improved electrochemical performance

Electronic textiles consisting of flexible and smart fibers have the potential to provide an intelligent platform for significantly expanding the future scope of wearable electronic applications. Thus, the integration of wearable electrochemical energy storage systems into the flexible platform is a key feature for efficiently powering and operating these future electronic textiles during bending, knotting, folding, and rolling. The present paper describes a flexible smart fibrous supercapacitor consisting of surface-engineered carbon fibers functioning as both the electrode and the current collector. In addition, the gel-electrolyte is used for an ion transfer and an electrode separation. The developed supercapacitor exhibits a robust energy storage performance superior to that of previously-reported fiber-based supercapacitors, with a high energy density of 3.5–2.0 μWh cm−2 and a power density ranging from 4 to 30 μW cm−2. These results are strongly attributed to the oxygen-containing functional groups on the carbon surface that provide the pseudocapacitive redox reaction and improved wettability. Furthermore, the fabricated supercapacitor shows outstanding mechanical flexibility and excellent thermal stability with minor capacitance degradation, thus demonstrating its promising applicability to electronic textiles.