Wire-shaped Supercapacitors Research Articles

A Flexible One‐dimensional Woven Supercapacitor for Low‐power Smart Electronic Textiles

Flexible energy storage devices are attracting a great attention nowadays in the rapidly growing area of implantable/wearable electronics. This bloom has generated great demands on flexible wire‐shaped supercapacitors (WSC) as power sources in wearable electronic systems that can offer tunable sizes, shapes, and versatile designs. Herein, a flexible WSC is fabricated using MgMn2O4 nanofibers (MMO‐NFs) over a flexible carbon yarn substrate via the electrophoretic deposition method in the first report. The binder‐free deposition of highly porous and one‐dimensionally aligned MMO‐NFs over carbon yarn offers excellent ionic/charge transport into the fabricated device. The assembled WSC device at 0.1 mA/cm current rate shows capacitances of 386 mF/cm2 and 45.5 mF/cm. A capacitance retention of 88% for a WSC device after 10,000 cycles indicates its good cyclability. Further, the WSC exhibits good flexibility, retaining 94% of capacitance at 0.5 mA/cm after 2000 bending cycles. Furthermore, the flexible WSC device shows power and energy density of 744 μW/cm and 14.2 μWh/cm, respectively. Additionally, WSC devices demonstrate their practical energy storage capabilities in a video that shows three similar devices being knitted into a wearable glove and glowing a red light‐emitting diode (LED) for more than five minutes in various bending positions.

Wire-shaped, all-solid-state, high-performance flexible asymmetric supercapacitors based on (Mn,Fe) oxides/reduced graphene oxide/oxidized carbon nanotube fiber hybrid electrodes

Wire-shaped flexible supercapacitors (FSCs) have attracted tremendous attention due to their tiny volume, lightweight, high flexibility, and wearability. In the present study, we report the MnO2- or Fe2O3-loaded three-dimensional (3D) nanostructure networks of reduced graphene oxide (rGO) composite on oxidized CNT (denoted as the OCNTF/3D-rGO/MnO2 and OCNTF/3D-rGO/Fe2O3) fibers as the cathode and anode, respectively, for the fabrication of a high-performance, wire-shaped, all-solid-state, flexible asymmetric supercapacitor (FASC). To this end, the 3D-rGO/OCNTF hierarchical structure was electrochemically fabricated, followed by further pulse electrodeposition of MnO2 and Fe2O3, respectively, into the 3D porous graphene networks and the insides of the OCNTF. As such, they were restricted to nano-sized particles and linked by the graphene and the OCNTF. The OCNTF/3D-rGO/MnO2 as the cathode was assembled with the OCNTF/3D-rGO/Fe2O3 as the anode with the carboxymethyl cellulose sodium (CMC)-Na2SO4 gel electrolyte, producing a wire-shaped, all-solid-state FASC that achieved a high specific capacitance of 59.2 F·cm−3 (171 mF·cm−2) and an exceptional energy density of 26.7 mWh·cm−3. The FASC device also showed good flexibility and cyclability, promising to advance power sources for wearable electronics.

Design and synthesis of NiCo2O4 wire-shaped electrode based on nickel wire with porous foam structure for wire-shaped hybrid supercapacitors

The wire-shaped supercapacitors (SCs) have been widely concerned in wearable electronic devices because of their portability. However, it is still a challenge to prepare wire-like current collectors and high-performance active materials for wire-shaped SCs. Herein, we designed a nickel wire with a three-dimensional porous foam structure, which can be used as the wire-like current collector for loading active materials. And then self-supporting NiCo2O4 nanosheet arrays were electrodeposited into the as-prepared nickel wire without any binder. Moreover, the wire-shaped NiCo2O4@Ni electrode shows excellent electrochemical performance with specific capacitance of 1396.4 F g−1, high rate performance and good cycling stability maintaining capacitance retention of 84.3% after 5000 charge/discharge cycles. In addition, the NiCo2O4@Ni//N-RGO@Ni wire-shaped SCs device has a high specific energy of 25.0 Wh kg−1. Therefore, nickel wire with a three-dimensional porous foam structure can be used as a promising wire-like current collector, and self-supporting NiCo2O4 nanosheet arrays have great potential in wire-shaped supercapacitor devices. This work may provide a new solution for the design of wire-shaped current collectors and electrodes.

Tunable all-solid-state wire-shaped high power device based on carbon nanotubes yarn

Energy storage devices integrated into textiles have emerged as a significant strategy for electronic applications. In this context, in the present paper novel flexible devices were developed, in which the control of both the electrode characteristics and the solid-electrolyte properties allows to build all-solid-state wire-shaped supercapacitors that can be integrated and waved. The proposed device was assembled using modified CNT yarns as electrodes and a blend of ionic liquid, Li salt and poly(ethylene glycol) acrylate to fabricate the solid-polymeric electrolyte. Excellent performance in terms of both electrochemical parameters and stability were obtained. These achievements are possible thanks to the coupling of asymmetric CNT yarns, following an optimization of the activation procedure together with the improvement of the polymeric electrolyte. The results show a capacitance as high as 1.8 mF/cm, energy density of 1.3 μWh/cm and a capacitance retention higher than 100% over 1200 cycles.

Surface modified Ni wire supported flexible asymmetric supercapacitor of Mn3O4// PEDOT-PSS-MWCNT and its solar charging for self-powered Cu-doped ZnO nanorods-based UV photodetector

Recently, wire-shaped supercapacitors (WSCs) with the benefits of being flexible, lightweight, and wearable, have attracted great attention as portable and wearable power sources, though still, they face critical challenges of inadequate energy density and electrochemical stability under mechanical deformations. Therefore, we report the fabrication of the asymmetric WSC constituting surface-modified Ni wire as current collectors, PVA-KOH electrolyte, and hydrothermally grown Mn3O4 nanoflakes and dip-coated PEDOT: PSS-MWCNT nanocomposites as positive and negative electrode active materials, respectively. Owing to surface modification of Ni wire and active materials with approximate mass matching, mesoporous nanostructured surface morphology, and improved surface areas, the twisted asymmetric WSC exhibits excellent volumetric capacitance of 7.55 F/cm3, 2.69 mWh/cm3 energy density, and 95 mW/cm3 power density at 25 μA with a 1.6 V voltage window. In addition, considering the recent trend of developing multi-functional self-powered systems integrating energy harvesters, storage entities, and functional components, ultraviolet photodetector (UV PD) in metal-semiconductor-metal (MSM) configuration was fabricated by hydrothermal growth of Cu-doped ZnO nanorods onto interdigitated electrode printed glass substrate, and hence for the first time a self-powered UV-light detection system with a fast response and high on/off ratio were successfully demonstrated by connecting solar-charged parallel asymmetric WSCs and UV PD.

Chemical reduction-induced fabrication of graphene hybrid fibers for energy-dense wire-shaped supercapacitors

The emerging one-dimensional wire-shaped supercapacitors (SCs) with structural advantages of low mass/volume structural advantages hold great interests in wearable electronic engineering. Although graphene fiber (GF) has full of vigor and tremendous potentiality as promising linear electrode for wire-shaped SCs, simultaneously achieving its facile fabrication process and satisfactory electrochemical performance still remains challenging to date. Herein, two novel types of graphene hybrid fibers, namely ferroferric oxide dots (FODs)@GF and N-doped carbon polyhedrons (NCPs)@GF, have been proposed via a simple and efficient chemical reduction-induced fabrication. Synergistically coupling the electroactive units (FODs and NCPs) with conductive graphene nanosheets endows the fiber-shaped architecture with boosted electrochemical activity, high flexibility and structural integrity. The resultant [email protected] and [email protected] hybrid fibers as linear electrodes both exhibit excellent electrochemical behaviors, including large volumetric specific capacitance, good rate capability, as well as favorable electrochemical kinetics in ionic liquid electrolyte. Based on such two linear electrodes and ionogel electrolyte, a high-performance wire-shaped SC is effectively assembled with ultrahigh volumetric energy density (26.9 mW·h·cm−3), volumetric power density (4900 mW·cm−3) and strong durability over 10,000 cycles under straight/bending states. Furthermore, the assembled wire-shaped SC with excellent flexibility and weavability acts as efficient energy storage device for the application in wearable electronics.

An efficient chemical reduction-induced assembly of Fe3O4@graphene fiber for wire-shaped supercapacitors with ultrahigh volumetric energy density

An efficient chemical reduction-induced assembly of Fe3O4@graphene fiber for wire-shaped supercapacitors with ultrahigh volumetric energy density

Carbon Nanotube Fibers Decorated with MnO2 for Wire-Shaped Supercapacitor.

Fibers made from CNTs (CNT fibers) have the potential to form high-strength, lightweight materials with superior electrical conductivity. CNT fibers have attracted great attention in relation to various applications, in particular as conductive electrodes in energy applications, such as capacitors, lithium-ion batteries, and solar cells. Among these, wire-shaped supercapacitors demonstrate various advantages for use in lightweight and wearable electronics. However, making electrodes with uniform structures and desirable electrochemical performances still remains a challenge. In this study, dry-spun CNT fibers from CNT carpets were homogeneously loaded with MnO2 nanoflakes through the treatment of KMnO4. These functionalized fibers were systematically characterized in terms of their morphology, surface and mechanical properties, and electrochemical performance. The resulting MnO2–CNT fiber electrode showed high specific capacitance (231.3 F/g) in a Na2SO4 electrolyte, 23 times higher than the specific capacitance of the bare CNT fibers. The symmetric wire-shaped supercapacitor composed of CNT–MnO2 fiber electrodes and a PVA/H3PO4 electrolyte possesses an energy density of 86 nWh/cm and good cycling performance. Combined with its light weight and high flexibility, this CNT-based wire-shaped supercapacitor shows promise for applications in flexible and wearable energy storage devices.

Layer-by-Layer Assembly of Reduced Graphene Oxide and MXene Nanosheets for Wire-Shaped Flexible Supercapacitors.

As the demand for wearable electronic devices increases, interest in small, light, and deformable energy storage devices follows suit. Among these devices, wire-shaped supercapacitors (WSCs) are considered key components of wearable technology due to their geometric similarity to woven fiber. One potential method for creating WSC devices is the layer-by-layer (LbL) assembly technique, which is a "bottom-up" method for electrode fabrication. WSCs require conformal and adhesive coatings of the functional material to the wire-shaped substrate, which is difficult to obtain with other processing techniques such as vacuum filtration or spray-coating. However, the LbL assembly technique produces conformal and robust coatings that can be deposited onto a variety of substrates and shapes, including wires. In this study, we report WSCs made using the LbL assembly of alternating layers of positively charged reduced graphene oxide functionalized with poly(diallyldimethylammonium chloride) and negatively charged Ti3C2Tx MXene nanosheets conformally deposited on activated carbon yarns. In this construct, the added LbL film enhances capacitance, energy density, and power density by 240, 227, and 109%, respectively, relative to the uncoated activated carbon yarn, yielding high specific and volumetric capacitances (237 F g-1, 2193 F cm-3). In addition, the WSC possesses good mechanical stability, retaining 90% of its initial capacity after 200 bending cycles. This study demonstrates that LbL coatings on carbon yarns are promising as linear energy storage devices for fibrous electronics.

Microfluidic-architected core–shell flower-like δ-MnO2@graphene fibers for high energy-storage wearable supercapacitors

Wire-shaped supercapacitor is an ideal candidate for wearable energy-storage devices in future. However, complex preparation process and poor capacitance of electrode materials seriously limit practical applications. Herein, we investigated a controllable method to synthesize core–shell MnO2/graphene fibers (MnGFs), where sheath flower-like δ-MnO2 were in situ growth wrapped on graphene core via microfluidic-spinning techniques. The MnGFs possess excellent mechanical flexibility and can be repeatedly bent without damage. Moreover, a flexible wire-shaped supercapacitors (MGSCs) assembled by MnGFs is successfully manufactured and display high capacitance (164.2 F cm−3), prominent energy density (4.3 mWh cm−3), and brilliant cycling stability (93.6% retention over 10,000 cycles). These comprehensive properties of MGSCs are obtained from MnGFs with porous and well-aligned core–sheath structure, resulting in abundant electron transport channels and rich ion pseudo-capacitance. Based on these achievements, the synthesized MGSCs can be employed to light up LEDs and electronic timers. This microfluidic strategy offers an extended design approach of electrochemically active electrode materials and guides the development of wearable fiber-shaped energy storage devices.

Unlocking the Future with Flexible, Wire-Shaped Supercapacitors

Unlocking the Future with Flexible, Wire-Shaped Supercapacitors

A novel flexible wire-shaped supercapacitor with enhanced electrochemical performance based on hierarchical Co(OH)2@Ni(OH)2 decorated porous dendritic Ni film/Ni wire

Wire-shaped supercapacitors, a new class of energy storage devices, have recently received enormous attention advantages of miniature size, lightweight and high flexibility. However, most of the reported wire-shaped supercapacitors are still suffered from low specific capacitance and limited energy densities as well as the relatively poor electrochemical performance. In this research, Co(OH)2@Ni(OH)2 nanosheets were successfully synthesized on the 3D-Ni film-coated Ni wire (NW) by electrochemical methods. The electrochemical tests of Co(OH)2@Ni(OH)2/3D-Ni/NW electrode confirmed the outstanding supercapacitive behavior of nanostructures with excellent cycling stability. This behavior could be attributed to 3D network structure of Ni film and the nanosheets which allow facile electrolyte and electrons transportation. Detailed electrochemical characterization shows that the Co(OH)2@Ni(OH)2/3D-Ni/NW exhibits a high specific capacitance of 355.2 C g–1 at current density of 1 Ag–1 and excellent cycle performance (80.0% retention after 3000 CD cycles). Also, the maximum energy density of 27.24 W h kg–1 at the power density of 234.99 W kg–1 was measured. The obtained results reveal that the Co(OH)2@Ni(OH)2 core-shell can be a promising electroactive material for supercapacitors. This unique supercapacitor opens up a new path in the development of fiber-shaped energy storage apparatuses.

Knitting Controllable Oxygen-Functionalized Carbon Fiber for Ultrahigh Capacitance Wire-Shaped Supercapacitors.

Wire-shaped supercapacitors (WSCs) are promising in wearable electronics but still face critical challenges of limited energy density. Nanostructured materials are dominant in high-performance active materials for improving energy density but are generally limited to wire-shaped electrodes (WSEs) with low mass loading (<0.5 mg cm-1) because of sluggish ionic kinetics in thicker electrodes. To address this problem, we report here the treatment of microstructured carbon fiber (CF) via a surface engineering strategy, which adopts controllable oxygen (O) functional groups on the CF surface with both highly redox-active sites and fast electron/ion transport. By combining a knitting method, we demonstrate that a WSE with high mass loading (∼6.1 mg cm-1) can operate at ultrahigh capacitance (435.1 mF cm-1, 1539.7 mF cm-2, and 68.4 mF cm-3), exceeding that of most of the reported WSEs. An assembled WSC delivers up to 195.3 mF cm-1 and 33 μW h cm-1, surpassing the best carbon symmetric supercapacitor known, and even conducting polymers and metal oxide asymmetric devices. Thus, this work provides a viable method for a high-mass WSE and will stimulate the development of WSCs toward practical applications.

Flexible wire-shaped symmetric supercapacitors with Zn–Co layered double hydroxide nanosheets grown on Ag-coated cotton wire

Flexible wire-shaped supercapacitors have attracted wide interest due to the increasing demand for portable and wearable electronics. Due to the complex functioning atmosphere of wearable electronics, their mechanical stability and electrochemical stability under different bending states are required. In this work, the self-made Ag-coated cotton wire was adopted as the collector and zinc–cobalt layered double hydroxide nanosheets were successfully electrodeposited on this wire (Ag-CW@ZnCo-LDH) by a facile chronopotentiometry with a constant current of 0.02A. Ag-CW@ZnCo-LDH electrode displayed a high specific capacitance of 1732.4 F g−1 at 1 A g−1 and 61.7% of capacitance retention after 2000 cycles at 10 A g−1. Flexible wire-shaped symmetric supercapacitor was fabricated by two same Ag-CW@ZnCo-LDH electrodes, which exhibited a working potential window of 1.2 V. The as-assembled WSSC showed a good electrochemical performance with specific capacitance of 16.3 F g−1 and energy density of 1.33 Wh kg−1 at power density of 1224 W kg−1. In addition, its CV curves barely deviated at all bending angles, manifesting the outstanding mechanical stability and great potential for practical application.

Alternately Dipping Method to Prepare Graphene Fiber Electrodes for Ultra-high-Capacitance Fiber Supercapacitors.

SummaryFlexible fiber supercapacitors are promising candidate for power supply of wearable electronics. Fabrication of high-performance fibers is in progress yet challenging. The currently available graphene fibers made from wet-spinning or electro-deposition technologies are far away from practical applications due to their unsatisfactory capacitance. Here we report a facile alternately dipping (AD) method to coat graphene on wire-like substrates. The excellent mechanical properties of the substrate with greatly diverse choices can be carried over to the fiber supercapacitors. Under such guideline, the graphene fiber with a titanium core made by our AD method (AD:Ti@RGO) shows an ultra-high specific capacitance of up to 1,722.1 mF cm−2, which is ∼1,000 times that of wet-spinning- and electro-deposition-fabricated neat graphene fibers and presents the highest specific capacitance to date. With excellent mechanical properties and striking electrochemical performances, the AD:Ti@RGO-based supercapacitors light the path to the next-generation technologies for wearable devices.

Wet-spinning assembly and in situ electrodeposition of carbon nanotube-based composite fibers for high energy density wire-shaped asymmetric supercapacitor

Wire-shaped supercapacitors (WSC) have attracted tremendous attention for powering portable electronic devices. However, previously reported WSC suffered from a complicated fabrication process and high cost. The objective of this study is to develop a facile and scalable process for the fabrication of high energy density WSC. We coupled the wet-spinning assembly with an in situ electrodeposition technique to prepare carbon nanotube (CNT)-based composite fibers. The charge balance between the electrodes was realized by controlling the deposition time of the pseudocapacitive materials. A wire-shaped asymmetric supercapacitor (WASC) was fabricated by twisting MnO2/CNT fiber cathode and PPy/CNT fiber anode with LiCl/PVA electrolyte. The flexible MnO2/CNT//PPy/CNT WASC operated in a broadened voltage range of 0–1.8 V exhibited a high capacitance of 17.5F cm−3 (10.7F g−1). In addition, it delivered a maximum energy and power densities of 7.88 mWh cm−3 (4.82 Wh kg−1) and 2.26 W cm−3 (1382 W kg−1), respectively. The WASC device demonstrated satisfactory cycling stability with 86% capacitance retention, and its Coulombic efficiency remained at 96% after 5000 charge–discharge cycles. The contributions of the diffusion-controlled insertion and the surface capacitive effect were theoretically quantified to investigate the energy storage mechanism. The fabrication approaches hold potential for the construction of cost-effective and high-performance WSC.

Wire-Shaped 3D-Hybrid Supercapacitors as Substitutes for Batteries

HighlightsThe flexible 3D porous structure with a large surface area provides pathways for rapid ion/electron transport and ion diffusion as well as numerous electroactive sites.The wire-shaped supercapacitor exhibits a high energy density of 153.3 Wh kg−1 and a power density of 8810 W kg−1.The hybrid device demonstrates excellent durability under various mechanical deformations.

Constructing novel fiber electrodes with porous nickel yarns for all-solid-state flexible wire-shaped supercapacitors

A novel scalable MnO2/rGO@PNY fiber electrode is developed for the fabrication of high performance all-solid-state flexible wire-shaped supercapacitors.

Hydrophilically engineered polyacrylonitrile nanofiber aerogel as a soft template for large mass loading of mesoporous poly(3,4-ethylenedioxythiophene) network on a bare metal wire for high-rate wire-shaped supercapacitors

Wire-shaped solid-state supercapacitors (WSSCs) receive ever-growing interest for developing electronic textile. How to achieve a high active mass loading with a suitable mesoporous structure and strong adhesion on a bare metal wire are a severe challenge faced by the development of practical WSSCs, which must meet requirements such as high energy and power densities, fast rate capability, as well as flexibility and stability. Here, a new strategy to synthesize the wire-shaped electrode with excellent electrochemical and mechanical performances is reported using a soft aerogel template in a facile dip coating process. Hydrophilically engineered polyacrylonitrile nanofibers by adding glycerol were electrospun on a Ti metal wire to form the sacrificial aerogel template with a huge void volume, in which poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solution was dip coated to achieve a large mass loading. The capillary effect in the subsequent natural drying process, slow dissolution of the template in a solvent, and PSS etching, together lead to a mesoporous PEDOT thick coating network formed on the metal wire with a high conductivity, strong mechanical strength and intimate interface adhesion. The resulted WSSCs based on Ti/PEDOT electrodes, exhibited a fairly wide potential window, large specific capacitance, ultrahigh rate capability and energy/power densities.

An all-solid-state fiber-type supercapacitor based on hierarchical Ni/NiO@CoNi-layered double hydroxide core-shell nanoarrays

Wire-shaped supercapacitors (WSSCs) with high flexibility, tiny volume and high power density are promising candidates for flexible and wearable devices. However, the practical application of WSSCs is still restricted by their low energy density and poor cycling stability. Herein, we report the design and preparation of well-aligned Ni/NiO@CoNi layered double hydroxide (LDH) arrays via a three-step procedure for high performance WSSCs, which consists of NiO nanobelt core and CoNi-LDH nanoplate shell on Ni wire current collector. The obtained hierarchical Ni/NiO@CoNi-LDH electrode exhibits a high specific areal capacitance (1.63 F cm−2 at 2.5 A cm−2), a good rate performance (retention of 90.7% when the current density increases from 2.5 to 20 A cm−2) and an excellent cycling stability (capacitance retention of 97.6% after 1000 cycles). The Ni/NiO@CoNi-LDH electrode was further assembled with Ni/active carbon electrode to construct an all-solid-state WSSC, which can deliver superior energy and power output. When the power density increases from 150 to 900 mW cm−3, the energy density of the device varies from 6.98 to 6.02 mWh cm−3. This new type of supercapacitor deserves a broad application in next-generation wearable and portable electronic products.