Fiber-shaped Supercapacitors Research Articles

Multilayer Core-Sheath Wires with Cus Nanosheet Arrays and Pedot Sheaths for High-Performance Fiber-Shaped Asymmetric Supercapacitors

Multilayer Core-Sheath Wires with Cus Nanosheet Arrays and Pedot Sheaths for High-Performance Fiber-Shaped Asymmetric Supercapacitors

All-pseudocapacitive coordination towards flexible asymmetric fiber-shaped supercapacitors with ultrahigh energy and power density

An asymmetric fiber-shaped supercapacitor with excellent flexibility, ultra-high energy and power density is developed, demonstrating great practical importance.

Regulating zinc electroplating chemistry to achieve high energy coaxial fiber Zn ion supercapacitor for self-powered textile-based monitoring system

Coaxial fiber-shaped Zn-ion hybrid supercapacitors (CFZHSCs) with high power/energy density, long cycle life, splendid mechanical stability, and high safety are promising electrochemical energy storage devices for flexible and wearable electronics. However, the poor electrochemical performance of Zn anode severely restricts their practical application. To address this challenge, a highly reversible fiber-shaped Zn anode with controlled deposition morphology is developed based on theoretical calculation guided design of highly zincophilic 3D metal-organic-frameworks derived carbon with N- and OH-containing functional groups (N,O-MOFC) scaffold, by regulating electroplating chemistry of the initial nucleation and crystal growth time of zinc metal. Benefitting from fast ion diffusion ability of the hierarchically nanostructured 3D Zn/N,O-MOFC anode on the carbon nanotube fiber (CNTF), the assembled CFZHSCs device achieves a large volumetric specific capacitance of 128.06 F cm−3 and a high volumetric energy density of 57.63 mWh cm−3, surpassing the state-of-the-art FZHSCs device. More impressively, the efficient rechargeable capability of the fiber-shaped Zn anode also enables an adequately stable CFZHSCs device with the capacitance retention of 99.20% after 10,000 charge/discharge cycles and remarkable mechanical flexibility. As a conceptual demonstration of system integration, the as-fabricated CFZHSCs device is integrated with triboelectric nanogenerator (TENG) yarn to achieve the self-powered textile-based monitoring systems to stably detect temperature variation.

Enhancing ions/electrons dual transport in rGO/PEDOT:PSS fiber for high-performance supercapacitor

Enhancing the specific capacitance and rate performance of graphene based fiber-shaped supercapacitors (FSSCs) is critical to achieving advanced energy storage devices with desired performance. Here, hierarchically porous reduced graphene oxide/poly (3,4-ethylenedioxythiophene):poly (4-styrenesulfonate) (rGO/PEDOT:PSS) hybrid fiber was constructed by co-assembling confined growth and acid treatment strategy. The rationally designed hybrid fiber addressed the issues of excellent conductivity and abundant porous channels for fast electrons transfer and rapid ions diffusion. As indicated, highly-oxidized small-sized GO precursor was utilized to endow rGO fiber with abundant ions diffusion channels and ions adsorption interfaces for double-layer capacitance, as well as ample oxygen functional groups for additional pseudocapacitance. The incorporation of acid-treated PEDOT:PSS also prevents the stacking of rGO sheets, improves the electrical conductivity and provides partial capacitance. Attributed to the synergy, the obtained hybrid fiber exhibits remarkably improved performance in FSSC with volumetric/areal specific capacitance of 226.5 F cm−3/279.3 mF cm−2 at 0.5 A cm−3 and rate performance of 74.7% capacitance retention at 50 A cm−3, which is much superior to the counterpart of previously-reported FSSC devices. Meanwhile, the resultant FSSC device also exhibits superb electrochemical stability (91%, 10000 cycles), holding a great application prospect in wearable electronics.

A General Equivalent Electrical Circuit Model for the characterization of MXene/graphene oxide hybrid-fiber supercapacitors by electrochemical impedance spectroscopy – Impact of fiber length

Performance engineering of electrochemical energy-storage devices such as Supercapacitors (SCs) requires updated modeling capable of characterizing their electrical output in unique device geometries. In this work, an Equivalent Electrical Circuit (EEC) is developed to fit the impedance data of pseudo-capacitive and electrostatic fiber-shaped supercapacitors (FSCs). The model is applied for the interpretation of impedance data measured on FSCs made of reduced Graphene Oxide (rGO) and MXene in the case of pseudo-capacitors and pure carbon in the case of Electrical Double-Layer Capacitors (EDLCs) as active electrode materials, and polyvinylalcohol (PVA) gel infiltrated with sulfuric acid as the electrolyte and separator. The FSC charge storage behavior is modeled using a Transmission Line Model (TLM) including a finite Warburg impedance for pseudo-capacitance, and a Constant-Phase Element (CPE) for the electrostatic contribution. The high frequency part of the Nyquist plots is characterized by a 45° straight line and the use of a TLM clearly improves the fit quality compared to a Randles circuit usually used for pseudo-capacitor modeling. The difference between the two ciruits becomes more visible as the length of the SC yarns increases, which is consistent with the observed increase in internal resistance with fiber length evidenced with the TLM. Furthermore, the fitting results indicate that the internal resistance of the TLM predominantly corresponds to the electrical resistance of the fiber, i.e. the electron conductive phase of the electrode, instead of the electrolyte ionic resistance in usual SCs. Finally, the low frequency part of the spectra is correctly modeled by a CPE without any leakage resistance, showing that self-discharge is not a significant issue for the electrostatic contribution, at least in the frequency range tested.

Turning industrial waste-flax noil into regenerated cellulose fiber electrodes for eco-friendly supercapacitors

Sustainable conversion of wastes into eco-friendly wearable energy storage materials is of uppermost priority when facing the rapid development of human society. Although some attempts have successfully developed wastes into activated carbon electrodes, the high energy consumption of the production process and the powder form greatly restrict their application in eco-friendly wearable supercapacitors. Here, industrial waste-flax noil was conversed into fiber-shaped supercapacitors (FSSCs) via wet spinning and in situ deposition of polypyrrole (PPy). The regenerated cellulose fibers (RCFs) collected from the ethyl alcohol coagulation bath possessed excellent tensile behaviors and multi-groove surfaces, encouraging the subsequent textile processing and ions activities. After PPy deposition, the obtained fiber electrodes yielded high specific capacitance (510.7 F g-1 at 0.5 A g-1) and excellent coulombic efficiency (99.3% at 10 A g-1). More importantly, the assembled FSSCs delivered remarkable electrochemical performances and could power the LED. The green strategy proposed in this work provides a new consideration for converting wastes into practical eco-friendly wearable devices.

Facile Fabrication of Polyaniline/Graphene Composite Fibers as Electrodes for Fiber-Shaped Supercapacitors

Graphene fiber-based supercapacitors are known as the potential energy resources for wearable/flexible electronics. However, increasing their specific capacitance and energy density remains a significant challenge. This paper indicates a double layer capacitance of the graphene nanosheets accompanied by pseudocapacitive behavior of the polyaniline to prepare composite fibers with high capacitive response. The polyaniline/graphene composite fibers (PANI/GFs) were synthesized by the self-assembled strategy and chemical reduction by HI. The wrinkle architecture of graphene nanosheets and uniform dispersion of the polyaniline are beneficial to increase the internal electroactive sites and provide a stable structure for the composite fibers. The constructed fiber-shaped supercapacitors with solid-state electrolyte deliver an excellent areal specific capacitance of 370.2 mF cm−2 and an outstanding areal energy density of 12.9 μW h cm−2. The current work reveals the attractive potential of the as-synthesized composite fibers for constructing fiber-shaped supercapacitors with distinguished electrochemical performance, which can be applied in future flexible electronics.

Surface Modification of Commercial Cotton Yarn as Electrode for Construction of Flexible Fiber-Shaped Supercapacitor

In this study, we report on the rational design and facile preparation of a cotton-reduced graphene oxide-silver nanoparticle (cotton-RGO-AgNP) hybrid fiber as an electrode for the building of a flexible fiber-shaped supercapacitor (FSSC). It was adequately characterized and found to possess a well-defined core−shell structure with cotton yarn as a core and a porous RGO-AgNP coating as a shell. Thanks to the unique morphological features and low electrical resistance (only 2.3 Ω·cm−1), it displayed attractive supercapacitive properties. When evaluated in a three-electrode setup, this FSSC electrode delivered the highest linear and volumetric specific capacitance of up to ca. 12.09 mF·cm−1 and ca. 9.67 F·cm−3 with a satisfactory rate capability as well as a decent cycling stability. On the other hand, an individual parallel symmetric FSSC cell constructed by this composite fiber fulfilled the largest linear and volumetric specific capacitance of ca. 1.67 mF·cm−1 and ca. 0.67 F·cm−3 and offered the maximum energy density, as high as ca. 93.1 μWh·cm−3, which outperformed a great number of graphene- and textile yarn-based FSSCs. Impressively, bending deformation brought about quite a limited effect on its electrochemical behaviors and almost no capacitance degradation took place during the consecutive charge/discharge test for over 10,000 cycles. Consequently, these remarkable performances suggest that the currently developed cotton-RGO-AgNP fiber has considerable application potential in flexible, portable and wearable electronics.

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.

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.

Interfacial Control of NiCoP@NiCoP Core-Shell Nanoflake Arrays as Advanced Cathodes for Ultrahigh-Energy-Density Fiber-Shaped Asymmetric Supercapacitors.

Efficient improvement of the energy density and overall electrochemical performance of fiber-shaped asymmetric supercapacitors (FASCs) for practical applications in portable and wearable electronics requires highly electrochemically active materials and a rational design. Herein, two-step phosphorization (TSP) processes are performed to directly grow 3D well-aligned NiCoP@NiCoP (NCP@NCP TSP) nanoflake arrays (NFAs) on carbon nanotube fibers (CNTFs). Profiting from the metallic characteristics and excellent electrochemical performance of NiCoP and the hierarchical design of the core-shell heterostructure, the NCP@NCP TSP NFAs/CNTF hybrid electrode exhibits significantly improved electrochemical performance. The as-fabricated NCP@NCP TSP NFAs/CNTF electrode possesses an ultrahigh areal capacitance of 10035mFcm-2 at a current density of 1mAcm-2 , with excellent rate capability and cycling stability. Furthermore, an FASC device with a maximum operating voltage of 1.6V is assembled by adopting NCP@NCP TSP NFAs/CNTF as a positive electrode, hierarchical TiN@VN core-shell heterostructure nanowire arrays (NWAs)/CNTF as negative electrode, and KOH-PVA as a gel electrolyte. The FASC device exhibits a high areal capacitance of 430.4mFcm-2 and an ultrahigh energy density of 51.02mWhcm-3 . Thus, the rationally designed NiCoP@NiCoP electrode is a promising candidate for incorporation into next-generation wearable and portable energy-storage devices.

Microfluidic Spinning of Core–Shell α-MnO2@graphene Fibers with Porous Network Structure for All-Solid-State Flexible Supercapacitors

Fiber-shaped supercapacitors are desirable candidates for flexible and wearable energy storage devices; however, the ultralow capacitance and intricate fabrication process of electrode materials significantly limits their performances. We exploited a steerable method to generate core–shell α-MnO2/graphene fibers (MnGFs), where the sheath of α-MnO2 with porous network structures were grown in situ intertwined on the core of graphene fiber in a microfluidic-spinning strategy. The as-obtained MnGFs exhibited outstanding mechanical flexibility and could be curled over a teflon rod for continuous production. Furthermore, the fiber-shaped supercapacitors (MGSCs) manufactured with MnGFs were successfullu assembled and exhibited good voluminal specific capacitance (136.7 F cm−3), prominent cyclic stability (91.6% retention over 10000 cycles), and high energy density (3.9 mWh cm−3). This advantageous performance was achieved by MnGFs with porous network structures, leading to the rich ion pseudo-capacitance and numerous electron transport channels. The as-prepared MGSCs could be easily adopted to power 5 light-emitting diodes after completel charging. We believe that our microfluidic spinning strategy can provide a new-style structural design method for efficient electrode materials and promote the progress of wearable electronic products.

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.

Flexible fiber-shaped supercapacitors based on graphene/polyaniline hybrid fibers with high energy density and capacitance

Fiber-shaped supercapacitors (FSCs) are promising energy storage devices for portable and wearable electronics due to their miniaturized size, flexibility, and knittability. Despite the significant progress in this area, it is still a challenge to develop large capacitance and high energy density FSCs for practical applications. In this work, a hybrid fiber composed of reduced graphene oxide and polyaniline nanoparticles (r-PANI-GOF) is synthesized via in situ synthesis of polyaniline nanoparticles both on the surface and inside of graphene fibers. The areal specific capacitance of a single r-PANI-GOF electrode is as large as 1755 mF cm−2 in the three-electrode system. The r-PANI-GOF hybrid fibers were also used as electrodes for making an all-solid-state FSCs. This whole device has a specific areal capacitance of up to 481 mF cm−2 and a high areal energy density of 42.76 μWh cm−2. The hybrid fiber electrodes with a high capacitance, and excellent flexibility may become new candidates for the development of fiber-shaped high-performance energy storage devices.

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.

Hierarchical porous carbon fiber for fiber-shaped supercapacitor

Fiber-shaped supercapacitor has drawn more attention for wearable electronic devices. We prepared hierarchical porous carbon fiber (HPCF) successively by phase-separable wet-spinning of polyacrylonitrile, preoxidation and carbonization with tension to use for the fiber-shaped electrode. The added tension during preoxidation and carbonization and the elevated temperature of carbonization improve the order carbon structure and the graphitization degree, endowed HPCF with high strength of 326.95 MPa. Thus, the all solid-state fiber-shaped supercapacitor is assembled without breakage. In addition, the hierarchical porous structure of HPCF with specific surface area of 276.0 m2 g[Formula: see text] contributes a high specific capacitance of 158 F g[Formula: see text]. The novel porous carbon fiber in this work exhibits the appropriate potential for wearable applications.

Activated carbon fiber yarns with birnessite-type MnO2 and oxygen-functional groups for high-performance flexible asymmetric supercapacitors

Carbon fiber yarn (CFY) is deemed to be an ideal fiber flexible substrate because of its excellent mechanical flexibility, conductivity, and low-cost. In this study, positive electrode was prepared by hydrothermal process to form a birnessite-type MnO2 interconnected 3D nanostructure loading on the carbon fiber yarn (MnO2@CFY). Using an acid-etching process, the oxygen-containing functional groups successfully introduce to the surface of carbon fiber yarn (OCFY) as the negative electrode. The asymmetric all-solid-state flexible fiber-shaped supercapacitor (AFFSC) based on as-prepared MnO2@CFY and OCFY delivers an excellent volumetric energy density of 11.05 mWh cm−3 at a volumetric power density of 100.32 mW cm−3, maintaining 95.33% capacitance retention after 5000 bending cycles.

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.

Hybrid Polyaniline/Liquid Crystalline CNT Fiber Composite for Ultimate Flexible Supercapacitors

CNT fibers (CNTFs) are excellent platforms for fiber-shaped supercapacitors, offering both high electric conductivity and mechanical resilience. Here, we propose a polyaniline (PANI)/CNTF composite...

Sword/scabbard-shaped asymmetric all-solid-state supercapacitors based on PPy-MWCNTs-silk and hollow graphene tube for wearable applications

Fiber-shaped supercapacitors (FSSCs) have attracted increasing attention for wearable electronics. Herein, an asymmetrical fiber-shaped supercapacitor, AFSSCs-ICS, with an innovative encapsulated core-sheath architecture has been successfully constructed for the first time. The sword-scabbard inspired AFSSCs-ICS was fabricated by simply inserting a ‘sword’ positive electrode, PPy-MWCNTs-silk, into one tubular graphene ‘scabbard’ negative electrode with H2SO4/PVA gel as electrolyte. Notably, our newly designed PPy-MWCNTs-silk electrode had an ultrahigh length specific capacitance of 15.3 mF cm−1 (corresponding to high areal or volumetric capacitance of 676.9 mF cm−2 or 376.3 F cm−3), representing one of the highest levels among the fabric yarn derived electrodes, while the hollow graphene tube depicted a superior linear capacitance of 19.1 mF cm−1, which could match well with that of the PPy-MWCNTs-silk electrode. Benefiting from the innovative yet rational structure, and ideally balanced charges, the AFSSCs-ICS had an extended operating potential of 1.6 V, and an outstanding length specific capacitance of 2.3 mF cm−1 with a very admirable energy density of 0.8 μWh cm−1, dramatically surpassing numerous reported FSSCs. Moreover, the AFSSCs-ICS device also afforded superb electrochemical and mechanical stabilities with retentions of 81% after 3000 charging-discharging cycles and 95–105% under bending degrees from 0 to 150°. This study may pave a new way for constructing coaxial fiber-shaped energy source unit for next-generation wearable and portable miniaturized electronics.