Fiber Supercapacitors Research Articles

Space-confined assembly of all-carbon hybrid fibers for capacitive energy storage: realizing a built-to-order concept for micro-supercapacitors

Customized hybrid carbon fiber supercapacitors with energy across two orders and power across four orders of magnitude.

Fabricating Continuous Supercapacitor Fibers with High Performances by Integrating All Building Materials and Steps into One Process.

Supercapacitor fibers are rapidly produced in minutes by an integrated one-step fabrication process. This method is simple and efficient for large production. A variety of pseudocapacitive active materials including graphene oxide, metal oxide, and conducting polymers can be incorporated. The resulting all-solid-state supercapacitor fibers show remarkable energy-storage capabilities with both high power and energy densities.

Shape memory fiber supercapacitors

Smart energy storage materials, which not only store electrochemical energy but also exhibit sensitivity to environmental stimuli, can provide novel multi-functionalities. Here, we report a smart shape memory fiber supercapacitor constituted with a highly stretchable shape memory polymer nanocomposite fiber substrate, multi-walled carbon nanotubes (MWCNT) conductive layer and pesudocapacitive polyaniline layer. Using layer by layer (LBL) technology, we first produce a densely packed MWCNT layer that serves as a well-developed conductive current collector network. Then polyaniline, as an active material, was deposited on the surface of the MWCNT layer to further promote the energy storage capability of the fibers. After the infiltration of a polyvinyl alchohol (PVA) based polymer electrolyte into the porous MWCNT and PANI layer, conductivity of ∼50S/cm and stretchability of more than 400% are obtained. The resultant shape memory polymer supercapacitors (SMPFSCs) not only possess shape memory properties, but also exhibit outstanding energy storage performance, with the best pseudo-capacitance exceeding ∼427F/cm3. Such design strategies can also be extended to other polymer substrates, and could open the door to smart (multi-functional) supercapacitor technologies.

Flexible Fiber Supercapacitor Using Biowaste‐Derived Porous Carbon

AbstractThe front cover artwork is provided by Dr. S. T. Senthilkumar and Dr. R. Kalai Selvan, Bharathiar University (Tamil Nadu, India). The image shows the conversion of dead leaves into porous carbons and their application in a fiber supercapacitor for wearable electronics. Read the full text of the Article at 10.1002/celc.201500090.

Transforming Pristine Carbon Fiber Tows into High Performance Solid-State Fiber Supercapacitors.

A facile activation strategy can transform pristine carbon fiber tows into high-performance fiber electrodes with a specific capacitance of 14.2 F cm(-3) . The knottable fiber supercapacitor shows an energy density of 0.35 mW h cm(-3) , an ultrahigh power density of 3000 mW cm(-3) , and a remarkable capacitance retention of 68%, when the scan rate increases from 10 to 1000 mV s(-1) .

Scalable non-liquid-crystal spinning of locally aligned graphene fibers for high-performance wearable supercapacitors

One-dimensional graphene fibers have attracted increasing interests due to their extraordinary mechanical strength, electrical conductivity and flexibility compared with two-dimensional graphene films/papers and three-dimensional foams/hydrogels/aerogels. Here, we developed a scalable non-liquid-crystal spinning process for the production of continuous graphene fibers with tailored structure for high-performance wearable supercapacitors. These fibers possessed surfaces with bark-like fine microstructure and different shaped cross-sections with locally aligned dense pores, depending on the jet stretch ratio (R) during spinning. Owing to this unique structure facilitating the access to, and diffusion of electrolyte ions, the specific capacitance reached 279Fg−1 (340Fcm−3) at a current density of 0.2Ag−1 (0.244Acm−3) in 1M H2SO4 when R=1.0. A flexible solid-state fiber supercapacitor assembled from these fibers showed a specific capacitance and energy density of 226Fcm−3 and 7.03mWhcm−3 at 0.244Acm−3, respectively. We further demonstrated the proof-of-concept of wearable energy-storage by sewing three solid-state yarn supercapacitors in series into a textile, which was able to power a light-emitting diode for more than 5min after being charged. This non-liquid-crystal spinning strategy could be extended to the assembly of other two-dimensional nanomaterials into macroscopic fibers for applications in micro-devices, wearable electronics and smart textile.

Flexible Fiber Supercapacitor Using Biowaste‐Derived Porous Carbon

AbstractA flexible fiber supercapacitor (SC) was fabricated by using porous carbon as the electrode material and polyvinylalcohol–H3PO4 as the gel‐polymer electrolyte. The porous carbon was derived from dead Ficus religiosa leaves through a single‐step carbonization method and characterized by using BET surface area and TEM analysis as well as XRD, Raman, and FTIR techniques. The fabricated fiber SC works up to 0.8 V and delivers a gravimetric (length) capacitance of 3.4 F g−1 (4.2 mF cm−1) at 1 mA. In addition, it exhibits a maximum gravimetric (length) energy density of 311 mWh kg−1 (37.3×10−8 Wh cm−1) at a power density of 58 W kg−1 (70.3 μW cm−1) with a capacitance retention of 88 % over 4000 cycles.

CuCo2O4 Nanowires Grown on a Ni Wire for High‐Performance, Flexible Fiber Supercapacitors

AbstractFlexible/stretchable supercapacitors for energy harvesting and storage are being extensively studied to meet the demand of specific environments. We successfully fabricated a flexible fiber supercapacitor through a simple and rapid single‐step hydrothermal method, growing CuCo2O4 nanostructures on Ni wires to be used as fiber electrodes. Electrochemical investigations demonstrate that the electrode material can be used in a supercapacitor to give a remarkable performance. The high‐rate specific capacitance of the fiber‐shaped supercapacitor reached 11.09 F g−1 at a current of 2 mA and outstanding cycling stability with about 93.5 % retention at 4 mA after 4000 charge/discharge cycles. Furthermore, the flexible fiber supercapacitor does not show any apparent degradation in the bending test, illustrating its potential to be used in portable and wearable energy‐storage devices.

Stretchable, weavable coiled carbon nanotube/MnO2/polymer fiber solid-state supercapacitors.

Fiber and yarn supercapacitors that are elastomerically deformable without performance loss are sought for such applications as power sources for wearable electronics, micro-devices, and implantable medical devices. Previously reported yarn and fiber supercapacitors are expensive to fabricate, difficult to upscale, or non-stretchable, which limits possible use. The elastomeric electrodes of the present solid-state supercapacitors are made by using giant inserted twist to coil a nylon sewing thread that is helically wrapped with a carbon nanotube sheet, and then electrochemically depositing pseudocapacitive MnO2 nanofibers. These solid-state supercapacitors decrease capacitance by less than 15% when reversibly stretched by 150% in the fiber direction, and largely retain capacitance while being cyclically stretched during charge and discharge. The maximum linear and areal capacitances (based on active materials) and areal energy storage and power densities (based on overall supercapacitor dimensions) are high (5.4 mF/cm, 40.9 mF/cm2, 2.6 μWh/cm2 and 66.9 μW/cm2, respectively), despite the engineered superelasticity of the fiber supercapacitor. Retention of supercapacitor performance during large strain (50%) elastic deformation is demonstrated for supercapacitors incorporated into the wristband of a glove.

Fabrication and characterization of smart fabric using energy storage fibres

Fibre supercapacitors were designed and manufactured using a dip-coating method. Their electrochemical properties were characterized using a VersaSTAT 3 workstation. Chinese ink with a fine dispersion of carbon and binder was coated as the electrode material. The specific capacitance per unit length of a copper fibre supercapacitor with the length of 41 cm reached 34.5 mF/cm. When this fibre supercapacitor was bent on rods with a diameter of 10.5 cm, the specific capacitance per length was 93% of the original value (without bending). It showed that these fibre supercapacitors have good flexibility and energy storage capacity. Furthermore, the fibre supercapacitor in the fabric showed the same capacitance before and after weaving.

Emergence of fiber supercapacitors

Supercapacitors (SCs) are energy storage devices which have high power density and long cycle life. Conventional SCs have two-dimensional planar structures. As a new family of SCs, fiber SCs utilize one-dimensional cylindrically shaped fibers as electrodes. They have attracted significant interest since 2011 and have shown great application potential either as micro-scale devices to complement or even replace micro-batteries in miniaturized electronics and microelectromechanical systems or as macro-scale devices for wearable electronics or smart textiles. This tutorial review provides an essential introduction to this new field. We first introduce the basics of performance evaluation for fiber SCs as a foundation to understand different research approaches and the diverse performance metrics reported in the literature. Next, we summarize the current state-of-the-art progress in structure design and electrode fabrication of fiber SCs. This is followed by a discussion on the integration of multiple fiber SCs and the combination with other energy harvesting or storage devices. Last, we present our perspectives on the future development of fiber SCs and highlight key technical challenges with the hope of stimulating further research progress.

Graphene-based single fiber supercapacitor with a coaxial structure.

A novel all graphene coaxial fiber supercapacitor (GCS) was fabricated, consisting of a continuously wet-spun core graphene fiber and facilely dip-coated graphene sheath. GCS is flexible, lightweight and strong, and is also accompanied by a high specific capacitance of 205 mF cm(-2) (182 F g(-1)) and high energy density of 17.5 μW h cm(-2) (15.5 W h kg(-1)). The energy density was further improved to 104 μW h cm(-2), when an organic ion liquid electrolyte was used.

Advances and prospects of fiber supercapacitors

Being light weight, flexible, weavable and foldable, fiber supercapacitors play an important role in wearable energy storage devices.

Constructing optimized wire electrodes for fiber supercapacitors

Fiber electronic devices are commonly built on fibrous substrates with the advantages for the direct use as weavable and embedded device units or integrated textile modules. In this work, Mn2O3 cube-arrays/carbon wire electrodes were designed for a new kind of fiber supercapacitors. To realize micro-devices with well-optimized performance, different electrode structures were designed and fabricated including the straight, bent, and coiled fiber supercapacitors (S-FSC, B-FSC, and C-FSC), among which the C-FSC showed the optimized and best performance. Our work confirmed that the performance of micro-devices can be well tuned by simply tailoring the device architectures.

Spinning fabrication of graphene/polypyrrole composite fibers for all-solid-state, flexible fibriform supercapacitors

We have developed a facile and straightforward approach for the continuous fabrication of graphene/polypyrrole (G/PPy) composite fibers via a wet-spinning strategy. The diameter of G/PPy fibers can be well-controlled in the range of about 15–80 μm. Furthermore, the fiber possesses high conductivity and mechanical flexibility, thus offering significant advantages as flexible, lightweight electrodes for an efficient fiber-based electrochemical supercapacitor. The all-solid-state fiber supercapacitor with H2SO4–polyvinyl alcohol (H2SO4–PVA) gel electrolyte has been demonstrated, which could be woven into a textile for wearable electronics.

Flexible coaxial-type fiber supercapacitor based on NiCo2O4 nanosheets electrodes

Fiber electronic devices show advantages for the direct use as wearable and embedded device units or integrated textile modules. We successfully developed a coaxial-type flexible fiber supercapacitor by using NiCo2O4 nanosheets grown on Ni wire as the fiber electrodes. The volume capacitance of the fiber-shaped supercapacitor reached 10.3F/cm3 at a current of 0.08mA and outstanding cycling stability. An energy density of 1.44mWhcm−3 and a power density of up to 17Wcm−3 were also obtained for the fiber supercapacitor, which are almost 48-fold higher than the previous values. Furthermore, the coaxial-type fiber supercapacitor does not show any apparent degradation in the bending test, illustrating the promise for use as electrodes for portable and wearable energy storage.

Core-Spun Carbon Nanotube Yarn Supercapacitors for Wearable Electronic Textiles

Linear (fiber or yarn) supercapacitors have demonstrated remarkable cyclic electrochemical performance as power source for wearable electronic textiles. The challenges are, first, to scale up the linear supercapacitors to a length that is suitable for textile manufacturing while their electrochemical performance is maintained or preferably further improved and, second, to develop practical, continuous production technology for these linear supercapacitors. Here, we present a core/sheath structured carbon nanotube yarn architecture and a method for one-step continuous spinning of the core/sheath yarn that can be made into long linear supercapacitors. In the core/sheath structured yarn, the carbon nanotubes form a thin surface layer around a highly conductive metal filament core, which serves as current collector so that charges produced on the active materials along the length of the supercapacitor are transported efficiently, resulting in significant improvement in electrochemical performance and scale up of the supercapacitor length. The long, strong, and flexible threadlike supercapacitor is suitable for production of large-size fabrics for wearable electronic applications.

Gamma-Irradiated Carbon Nanotube Yarn As Substrate for High-Performance Fiber Supercapacitors

As an electrical double layer capacitor, dry-spun carbon nanotube yarn possesses relatively low specific capacitance. This can be significantly increased as a result of the pseudocapacitance of functional groups on the carbon nanotubes developed by oxidation using a gamma irradiation treatment in the presence of air. When coated with high-performance polyaniline nanowires, the gamma-irradiated carbon nanotube yarn acts as a high-strength reinforcement and a high-efficiency current collector in two-ply yarn supercapacitors for transporting charges generated along the long electrodes. The resulting supercapacitors demonstrate excellent electrochemical performance, cycle stability, and resistance to folding-unfolding that are required in wearable electronic textiles.

All-in-one graphene fiber supercapacitor.

A flexible all-in-one single fiber supercapacitor has been fabricated through region-specific reduction of graphene oxide (GO) fiber by laser irradiation, and thus reduced GO layers as electrodes and GO as the separator are integrated into one single fiber. This in-fiber supercapacitor with high mechanical flexibility and high performance could be woven into the textile for wearable electronics and beyond.

Flexible planar/fiber-architectured supercapacitors for wearable energy storage

With the emergence of flexible/stretchable electronic devices, flexible supercapacitors (SCs) have attracted widespread interest in developing lightweight, thin, elastic and efficient portable/wearable energy storage devices that show promising applications in hybrid electric vehicles, uninterruptible power supplies and “smart textiles”. Along with a brief description on the general information about flexible SCs, this feature article focuses on recent advances in flexible SCs including the planar-structured flexible SCs and the new-type fiber SCs as well as fiber integrated/hybrid energy systems containing fiber SCs. The construction of efficient active materials on flexible substrates (e.g. plastics, papers, fabrics/textiles, fibrous substrates, etc.) and feasible strategies to achieve high-performance flexible SCs are highlighted. Perspectives on the research trends of flexible SCs toward practical applications are proposed.