Fiber Supercapacitors Research Articles

Continuous Fabrication of Ti3C2Tx MXene-Based Braided Coaxial Zinc-Ion Hybrid Supercapacitors with Improved Performance

HighlightsTi3C2Tx MXene-based coaxial zinc-ion hybrid fiber supercapacitors (FSCs) were fabricated with braided structure, which can be prepared continuously and present excellent flexibility and ultrastability.A sports watch driven by the watch belts which weaved uses the obtained zinc-ion hybrid FSC and LED arrays lighted by the FSCs under embedding into textiles, demonstrating the great potential application in smart wearable textiles.Zinc-ion hybrid fiber supercapacitors (FSCs) are promising energy storages for wearable electronics owing to their high energy density, good flexibility, and weavability. However, it is still a critical challenge to optimize the structure of the designed FSC to improve energy density and realize the continuous fabrication of super-long FSCs. Herein, we propose a braided coaxial zinc-ion hybrid FSC with several meters of Ti3C2Tx MXene cathode as core electrodes, and shell zinc fiber anode was braided on the surface of the Ti3C2Tx MXene fibers across the solid electrolytes. According to the simulated results using ANSYS Maxwell software, the braided structures revealed a higher capacitance compared to the spring-like structures. The resulting FSCs exhibited a high areal capacitance of 214 mF cm–2, the energy density of 42.8 μWh cm−2 at 5 mV s−1, and excellent cycling stability with 83.58% capacity retention after 5000 cycles. The coaxial FSC was tied several kinds of knots, proving a shape-controllable fiber energy storage. Furthermore, the knitted FSC showed superior stability and weavability, which can be woven into watch belts or embedded into textiles to power smart watches and LED arrays for a few days.

Highly flexible and high energy density fiber supercapacitors based upon spiral silk composite membranes encapsulation

Fiber supercapacitors (FSCs) have attracted great interest recently as promising energy storage devices for wearable electronics. As an important factor for wearable electronics, FSCs require high flexibility and energy density. The current encapsulation methods would dramatically increase the overall diameter of FSCs, reduce the flexibility and knittability/weavability. Herein, a new encapsulating strategy that gives rise to fine FSCs with an overall diameter of ≈1mm is proposed. In particular, the ultra-thin, soft and sufficient mechanical strength of the silk composite membranes are used as an encapsulating material for the first time. This endows FSCs with significant flexibility. Meanwhile, FSCs with higher electrochemical performance have been obtained through a tight spiral-winding encapsulating strategy. This gives rise to the 28% enhancement of electrochemical performance of the FSCs encapsulated using silk composite membranes than that FSCs encapsulated using the traditional plastic tube. Specifically, the corresponding asymmetric FSCs encapsulated with silk composite membranes exhibit excellent performances with respect to a high energy density (12.9 mWh cm−3 at 80 mW cm−3), remarkable bending stability (≈97.1% capacitance retention for 1000 bending cycles), superior to most state-of-the-art supercapacitors. Moreover, the energy storage device woven with 12 FSCs can easily drive a watch and 65 light-emitting diodes. This work demonstrates a new encapsulating design strategy in which the encapsulated FSCs can improve their electrochemical performance without sacrificing flexibility and weavability. In addition, the transparent and skin-friendly silk composite membranes expand the advantages of FSCs in wearable energy storage applications.

High voltage output/energy density flexible asymmetric fiber supercapacitors based on a tree-like topology

Fiber supercapacitors have attracted significant attention because of the relevance for textile electronics. However, the key challenge is to achieve high output voltage and performance of fiber supercapacitors while maintaining the high flexibility of the fibers. Here, we present a fiber supercapacitor, based on an overlaid tree topology configuration, by braiding sub-fiber supercapacitor units in an asymmetrical series connection. The tree-like topology-based asymmetric fiber supercapacitors (TTAFSCs) achieve a high energy density (0.022 Wh cm −3 at a power density of 0.444 W cm −3 ) with an extendable high voltage output (>9.6 V) while maintaining outstanding mechanical properties (>1,000 bending cycles, capable of loading an object of ∼200 g). TTAFSCs of ∼8 cm in length are capable of lighting light-emitting diodes, driving a watch, and powering a display, even in a bent and twisted state. TTAFSCs based on bionic design principles are proposed TTAFSCs have high voltage output/energy density and notable mechanical properties A strategy for preparing coaxial fiber supercapacitors is developed Based on bionic design principles, Shao et al. fabricate tree-like topology-based asymmetric fiber supercapacitors. The fiber supercapacitors are designed to have high output voltage and high energy density and maintain useful mechanical properties.

Hybrid fibers assembled from MoSe2/graphene heterostructures endow improved supercapacitive performance

Fiber supercapacitors (FSCs) that fulfill the necessities of high power/energy density, flexibility, robustness, and wearing comfort are prospective power sources for portable/wearable electronics. The efforts in this field remain to exploit high performance fibrous materials with combined advantages of suitable mechanical properties, high electrical conductivity, and enhanced specific capacitance. Herein, for the first time, we incorporate expanded molybdenum diselenides (MoSe2) into graphene fibers via the assistance of ethylenediamine. The presence of MoSe2 enables the as-fabricated hybrid fiber a 2.2-fold enhancement in volumetric capacitance (148.6 F cm−3) as well as good rate performance. The assembled FSC provides a capacitance of 22.8 F cm−3, an energy density of 1.2 mWh cm−3, and a maximum power density of 314.0 mW cm−3 in addition to excellent cycle stability. Notably, the flexible and mechanically steady FSCs display excellent processability under well-controlled conditions, including weaving into the fabric, and their electrochemical properties maintain unchanged under various bending angles. Furthermore, the FSCs are connected to steadily power LED lamp, illustrating the promising possibility as future wearable energy storage devices.

Fiber supercapacitor using epoxy-based gel polymer electrolyte with high ionic conductivity and mechanical flexibility

Recently, flexible energy storage devices have become an important issue for the smart textile market and flexible electric devices. Among them, fiber supercapacitors are one of the most promising candidates due to their light weight and mechanical flexibility. Traditional liquid electrolytes for fiber supercapacitors exhibit critical problems such as leakage when the device is deformed. On the other hand, solid electrolytes have a trade-off relationship between mechanical property for flexibility and ionic conductivity. Therefore, gel polymer electrolytes (GPEs) have attracted attention because of their sufficient ionic conductivity and high flexibility for maintaining their structure under bending, stretching, or twisting. However, liquid electrolytes in GPEs have a safety issue caused by narrow window voltage and flammability. Electrolytes with narrow window voltages could not provide the appropriate capacitance. To overcome this problem, ionic liquids that featured high electrochemical and thermal stability are used for GPEs. However, GPEs with ionic liquid have limited flexibility and ionic conductivity. In this work, we report a GPE comprising an ionic liquid and polyethylene oxide-abundant epoxy. The epoxy is synthesized from the crosslinking reaction between the amine with three-block copolymer and bisphenol A diglycidyl ether. The ionic conductivity of the fabricated GPE increased 2.0 × 10−3 S cm−1 at room temperature with increasing contents of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI). Further, EMImTFSI gives an improvement of flexibility up to 107%. A fiber supercapacitor using developed GPE shows excellent electrochemical performance approaching using liquid electrolyte. In short, our result demonstrates that the GPE is a promising candidate for various applications involving multidirectional deformation such as fiber-type electric and flexible devices.

RGO–CMC fiber supercapacitors with core-sheath structure manufactured by coaxial extrusion printing

Fiber-shaped supercapacitors are attractive as an energy storage unit due to their excellent flexibility. However, fabricating robust fibers with large yields remains a challenge. In this work, we prepare flexible core-sheath fibers via coaxial extrusion printing. Carboxymethylcellulose sodium salt (CMC) slurry with controlled rheological properties is extruded from the outer channel, while the graphene oxide (GO) slurry is extruded from the inner channel simultaneously. The followed freeze-drying process protects GO sheets from agglomeration, providing more efficient chemical reduction. The reduced GO (rGO) sheets are separated and expanded to fill in the CMC sheath, which eliminates the delamination between the CMC sheath and rGO core. We study the influences of the freeze-drying process on the fiber microstructures, and explore the slurry design, fiber quality, reduction condition, and electrochemical performance. The fabrication method allows scalable manufacturing of the core-sheath electrodes and fiber-shaped supercapacitors with more efficient conductive networks.

Graphene Fiber-Based Wearable Supercapacitors: Recent Advances in Design, Construction, and Application.

Fiber-based supercapacitors (FSCs) that display small volume, robust weavability, high power density, and long-term stability, have urgently become the indispensable power supplies in smart wearable industries. Graphene fiber is regarded as an ideal FSCs electrode due to its remarkable natures of anisotropic framework, adjustable layer spacing, porous structures, large specific-surface-area, processable electroactivity, and high electronical and mechanical properties. This review, mainly focuses on the graphene fiber-based supercapacitors (GFSCs), with respect to fiber preparation, micro-nanostructure modulation, supercapacitor construction, performance optimization, and wearable applications. Various fiber fabrication strategies, including wet-spinning, dry-spinning, film conversion, confined hydrothermal self-assembly, and microfluidic-spinning are presented for fiber's structure manipulation and large-scale production. Advanced nanostructures and electroactivity with various building principles, such as oriented alignment, porous network, hierarchical, and heterogeneous skeleton, engineered active-sites, and mechanical regulation are discussed for boosting charge transfer, and ionic kinetic diffusion and storage. Especially, the optimizing approaches for regular unit alignment, enhanced interlayer interactions, modulated structural nano-architecture are presented to deliver high capacitance and energy density. Moreover, the flexibility and stretchability of graphene fiber, together with wearable applications of power supply are highlighted. Finally, a short summary, current challenges and future perspectives for designing high energy density GFSCs are proposed.

Weldable and flexible graphene ribbon@Ni fibers with ultrahigh length capacitance for all-solid-state supercapacitors

Carbon-based fiber supercapacitors hold great potential in portable electronics. However, those fiber-based electrodes often suffer from low length capacitance and poor rate performance due to low electrical conductivity and sluggish ion diffusion kinetics. And the poor weldability hinders the design of complex circuits. Herein, we report a simple strategy to prepare weldable and flexible graphene ribbon@Ni fiber (GR-Ni-5) with fast ion/electron transfer capabilities for fiber-shaped supercapacitors via the immersion-drying process and followed by thermal treatment. As a result, the GR-Ni-5 exhibits an ultrahigh length capacitance of 73.8 mF·cm−1 at 2 mV·s−1, remarkable rate performance (26.8 mF·cm−1, 200 mV·s−1), and ultrahigh capacitance retention of 80% with the length of the electrode from 1.0 to 10.0 cm. Moreover, the assembled all-solid-state symmetric supercapacitor using GR-Ni-5 fibers as the electrodes and polyvinyl alcohol (PVA)/KOH gel as electrolyte can deliver remarkable electrochemistry properties, as well as good flexibility, and remarkable weldability which are beneficial for miniaturization and application.

Integrated fiber electrodes based on marine polysaccharide for ultrahigh-energy-density flexible supercapacitors

Fiber-shaped supercapacitors with excellent electrochemical performance and high flexibility have attracted particular attention to meet the ever-growing need of portable and wearable electronics. Herein, we developed an integrated fiber electrode of alginate/PEDOT:PSS@polypyrrole based on marine polysaccharide for constructing high-energy symmetrical fiber-shaped supercapacitors. The swelling of alginate insures definite growth of thin polypyrrole layer in the surface region of alginate/PEDOT:PSS, introducing additional pseudocapacitance through faradaic reaction and thus improving charge transport. The composite fiber exhibits ultrahigh volumetric and areal capacity (567.6 F cm−3 and 1002.4 mF cm−2), which is superior to most of the previous reports. Owing to ultrahigh capacity of the fiber electrodes and their sufficient contact with gel electrolyte, the as-fabricated fiber supercapacitor exhibits large specific capacitance of 246.4 mF cm−2, high energy density of 21 μW h cm−2, and excellent flexibility (97% of initial values after 180° bending). These mechanical and electrochemical properties make the fiber supercapacitor a promising energy storage device for next-generation portable and wearable electronics.

A top-down cutting method for construction of high-performance fiber-shaped quasi-solid-state asymmetric supercapacitors

Fiber-shaped asymmetric supercapacitors (FSASCs) have great potential as a future wearable energy storage system because of good weavability, a wide operating voltage window, and high energy density. Conventional bottom-up construction methods for fiber supercapacitors are time-consuming or highly costly. This work proposes a novel facile top-down cutting method to construct FSASCs. FSASCs with desired sizes can be rapidly constructed and easily scaled up by cutting a thin-film supercapacitor into fiber-shaped devices. Serial and parallel FSASCs free of external wire connection were assembled by cutting stacked film supercapacitors and multiplying the cutting width, respectively. Besides, the as-prepared FSASCs exhibit superior comprehensive electrochemical performance, including a high volumetric capacitance of 14.7 F/cm3, a high energy density of 93.5 μWh/cm2, and excellent flexibility. The cutting method with advantages of high simplicity, low cost, and high efficiency may be a general construction method for fiber-shaped energy storage devices.

Full‐Temperature All‐Solid‐State Ti3C2Tx/Aramid Fiber Supercapacitor with Optimal Balance of Capacitive Performance and Flexibility

AbstractFull‐temperature all‐solid‐state flexible symmetrical fiber supercapacitors (FSCs) are assembled by using montmorillonite flake/polyvinyl alcohol organic hydrogel (F‐MMT/PVA OHGE) as the electrolyte and separator and Ti3C2Tx/ANF‐5% (T/A‐5) fiber as the electrode, in which T/A‐5 fiber is prepared by using delaminated Ti3C2Tx nanosheets as assembled units and 5% of aramid nanofiber (ANF) as the functional additive using a wet spinning method in a coagulated bath with 0.5 m FeCl2 solution. The T/A‐5 hybrid fiber exhibits a specific capacity of 807 F cm−3 in 3 m H2SO4 electrolyte, a superior mechanical strength of 104 MPa, and a high conductivity of 1025 S cm−1. The assembled F‐MMT/PVA OHGE T/A‐5 FSC not only shows a specific capacitance of 295 F cm−3 and a capacitance retention of 91% at a current density of 5 A cm−3 after 10 000 charging/discharging cycles, but also a maximum volumetric energy density of 26.2 mWh cm−3. Meanwhile, the assembled device displays good flexibility and excellent capacitance in a wide temperature range of −40 to 80 °C, the electrochemical performance of the FSC is maintained under varying degrees of bending. This study provides an effective strategy for designing and assembling of full‐temperature all‐solid‐state symmetrical flexible FSCs with the optimal balance of capacitive performance and flexibility.

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.

Cold-Resistant Nitrogen/Sulfur Dual-Doped Graphene Fiber Supercapacitors with Solar-Thermal Energy Conversion Effect.

Although graphene fiber-based supercapacitors are promising for wearable electronic devices, the low energy density of electrodes and poor cold resistance of aqueous electrolytes limit their wide application in cold environments. Herein, porous nitrogen/sulfur dual-doped graphene fibers (NS-GFs) are synthesized by hydrothermal self-assembly followed by thermal annealing, exhibiting an excellent capacitive performance of 401 F cm-3 at 400 mA cm-3 because of the synergistic effect of heteroatom dual-doping. The assembled symmetric all-solid-state supercapacitor with polyvinyl alcohol/H2 SO4 /graphene oxide gel electrolyte exhibits a high capacitance of 221 F cm-3 and a high energy density of 7.7 mWh cm-3 at 80 mA cm-3 . Interestingly, solar-thermal energy conversion of the electrolyte with 0.1 wt % graphene oxide extends the operating temperature range of the supercapacitor to 0 °C. Furthermore, the photocatalysis effect of the dual-doped heteroatoms increases the capacitance of NS-GFs. At an ambient temperature of 0 °C, the capacitance increases from 0 to 182 F cm-3 under 1 sun irradiation because of the excellent solar light absorption and efficient solar-thermal energy conversion of graphene oxide, preventing the aqueous electrolyte from freezing. The flexible supercapacitor exhibits a long cycle life, good bending resistance, reliable scalability, and ability to power visual electronics, showing great potential for outdoor electronics in cold environments.

High Voltage Output/Energy Density Flexible Asymmetric Fiber Supercapacitors Based on Tree-Like Topology

Fiber supercapacitors have attracted significant attention owing to the relevancy in textile electronics. However, the key challenge is to achieve a high output voltage and performance in fiber supercapacitors, while maintaining the high flexibility as fibers. Here, we present a particular type of fiber supercapacitors, based on an overlaid tree topological configuration, by braiding sub-fiber supercapacitor units in an asymmetrical series connection. The tree-like topology-based asymmetric fiber supercapacitors (TTAFSCs) simultaneously achieved a high energy density (22 mWh cm-3 at a power density of 444 mW cm-3) and voltage output, while maintaining outstanding mechanical properties (>1000 bending cycles, capable of loading an object of ~200 g). By continuous braiding of a 6-unit TTAFSC (28 cm length), we were able to achieve a tunable output voltage as high as 9.6 V, which is superior to that achieved by most state-of-the-art fiber supercapacitors. Furthermore, TTAFSCs of ~8 cm long are capable of lightening light-emitting diodes, driving a watch, and powering a display, even at the bent and twisted state. The design of TTAFSCs and fabrication technology acquired represent a genuine breakthrough in textile electronics.

ZnCl2 regulated flax-based porous carbon fibers for supercapacitors with good cycling stability

We systemically control the specific surface area and pore structure of flax-based carbon fibers by impregnating with zinc chloride (ZnCl2) solution. The results show that ZnCl2 affects the microstructure and the specific capacitance.

Laser-assisted fabrication of flexible monofilament fiber supercapacitors

A laser-assisted method for the fabrication of a flexible fiber supercapacitor (SC) and serially connected SCs within a seamless monofilament unit.

Reduced graphene oxide/g-C3N4 modified carbon fibers for high performance fiber supercapacitors

The increasing demand for high performance portable electronic devices has promoted the research of flexible energy storage devices, and various devices have been suggested and investigated.

High-performance wearable supercapacitors based on PANI/N-CNT@CNT fiber with a designed hierarchical core-sheath structure

A hierarchical core-sheath structured PANI/N-CNT@CNT fiber is designed to modify the rate capability and cycling stability of flexible fiber supercapacitors.

The Jahn-Teller Effect for Amorphization of Molybdenum Trioxide towards High-Performance Fiber Supercapacitor

Amorphous pseudocapacitive nanomaterials are highly desired in energy storage applications for their disordered crystal structures, fast electrochemical dynamics, and outstanding cyclic stability, yet hardly achievable using the state-of-the-art synthetic strategies. Herein, for the first time, high capacitive fiber electrodes embedded with nanosized amorphous molybdenum trioxide (A-MoO3-x) featuring an average particle diameter of ~20 nm and rich oxygen vacancies are obtained via a top-down method using α-MoO3 bulk belts as the precursors. The Jahn-Teller distortion in MoO6 octahedra due to the doubly degenerate ground state of Mo5+, which can be continuously strengthened by oxygen vacancies, triggers the phase transformation of α-MoO3 bulk belts (up to 30 μm long and 500 nm wide). The optimized fibrous electrode exhibits among the highest volumetric performance with a specific capacitance (CV) of 921.5 F cm−3 under 0.3 A cm−3, endowing the fiber-based weaveable supercapacitor superior CV and EV (energy density) of 107.0 F cm−3 and 9.5 mWh cm−3, respectively, together with excellent cyclic stability, mechanical robustness, and rate capability. This work demonstrates a promising strategy for synthesizing nanosized amorphous materials in a scalable, cost-effective, and controllable manner.

Triaxial Carbon Nanotube/Conducting Polymer Wet-Spun Fibers Supercapacitors for Wearable Electronics.

The ubiquity of wearables, coupled with the increasing demand for power, presents a unique opportunity for nanostructured fiber-based mobile energy storage systems. When designing wearable electronic textiles, there is a need for mechanically flexible, low-cost and light-weight components. To meet this demand, we have developed an all-in-one fiber supercapacitor with a total thickness of less than 100 μm using a novel facile coaxial wet-spinning approach followed by a fiber wrapping step. The formed triaxial fiber nanostructure consisted of an inner poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) core coated with an ionically conducting chitosan sheath, subsequently wrapped with a carbon nanotube (CNT) fiber. The resulting supercapacitor is highly flexible, delivers a maximum energy density 5.83 Wh kg−1 and an extremely high power of 1399 W kg−1 along with remarkable cyclic stability and specific capacitance. This asymmetric all-in-one fiber supercapacitor may pave the way to a future generation of wearable energy storage devices.