Wire-shaped Supercapacitor Research Articles

Study and Characterization of Solid State, Flexible, Wire-Shaped Supercapacitor for Textile Energy Storage Purpose

Flexible and lightweight energy storage devices have become increasingly important for the development of wearable and portable electronics. In this work, we present a novel wire-shape supercapacitor based on carbon nanotube (CNT) yarns and an ionic liquid based polymer electrolyte. The combination of these materials offers high surface area, high conductivity and excellent flexibility, making them a promising candidate for flexible energy storage.The CNT yarns were characterized in a three-electrode configuration by means of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) either in water-based electrolytes and polymer electrolytes. The polymer electrolytes were prepared by mixing polymers with ionic liquid, which was characterized by thermal analysis and electrochemical measurements.The wire-shape supercapacitor was assembled by coating two CNT yarns with the polymer electrolyte and twisting them together. The devices exhibited high specific capacitance for a waterless system, additionally, they maintained their performance even under extreme deformation: the flexibility of the devices were tested by bending at different angles .Overall, this work highlights the advantages of using CNT yarns and ionic liquid polymer electrolytes for the development of flexible and high-performance supercapacitors. The wire-shape design of the device offers additional advantages for integration into wearable or flexible electronics, providing a promising path towards the development of highly efficient and adaptable energy storage systems.

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.

A Solid-State Wire-Shaped Supercapacitor Based on Nylon/Ag/Polypyrrole and Nylon/Ag/MnO2 Electrodes.

In this work, a novel wire-shaped supercapacitor based on nylon yarn with a high specific capacitance and energy density was developed by designing an asymmetric configuration and integrating pseudocapacitive materials for both electrodes. The nylon/Ag/MnO2 yarn was prepared as a positive electrode by electrochemically depositing MnO2 on a silver-paste-coated nylon yarn. Additionally, PPy was prepared on nylon/Ag yarn by chemical polymerization firstly to enlarge the surface roughness of nylon/Ag, and then the PPy could be easily coated on the chemically polymerized nylon/Ag/PPy by electrochemical polymerization to obtain a nylon/Ag/PPy yarn-shaped negative electrode. The wire-shaped asymmetric supercapacitor (WASC) was fabricated by assembling the nylon/Ag/MnO2 electrode, nylon/Ag/PPy electrode and PAANa/Na2SO4 gel electrolyte. This WASC showed a wide potential window of 1.6 V and a high energy density varying from 13.9 to 4.2 μWh cm-2 with the corresponding power density changing from 290 to 2902 μW cm-2. Meanwhile, because of the high flexibility of the nylon substrate and superior adhesion of active materials, the WASC showed a good electrochemical performance stability under different bending conditions, suggesting its good flexibility. The promising performance of this novel WASC is of great potential for wearable/portable devices in the future.

RETRACTED ARTICLE: Polydopamine-modified MWCNT/graphene oxide hybrid 3D carbon nano-structure for flexible symmetric supercapacitor electrodes

The nanocarbon-based three-dimensional carbon nano-structure was prepared from the combination of one-dimensional multi-walled carbon nanotubes (MWCNTs) and two-dimensional graphene oxide by a simple hydrothermal method. The MWCNT/graphene hybrid hydrogel (CGOH) was used as electrode, and it exhibited higher specific capacitance (193.3 F g−1) compared to graphene oxide hydrogel (62.5 F g−1) due to the increase of electrical conductivity. Further enhancement of the capacitance was studied in this work by utilizing polydopamine (PDA) coating on the CGOH surface and heat treatment at 600 °C under argon gas condition for 2 h (PDA-CGOH-600). The specific capacitance of the PDA-CGOH-600 (217.4 F g−1) was enhanced by 12.5% compared to the CGOH. Using these hybrids, the flexible symmetric supercapacitor (FSS) devices were prepared with a solid polymer electrolyte (polyvinyl alcohol/sulfuric acid). The charge/discharge tests of FSS device confirmed that the highest capacitance of the FSS based on PDA-CGOH-600 because of the nitrogen-doping effect and the graphitic carbon formation. Furthermore, FSS device can be applied in the wire-shaped supercapacitor and good parameters of the energy storage device were achieved, such as specific capacitance of 50 mF cm−2, stability during 3000 times of charge/discharge, as well as stretchability and bending ability.

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.

All-solid-state wire-shaped asymmetric supercapacitor based on binder-free CuO nanowires on copper wire and PPy on carbon fiber electrodes

Abstract A wire-shaped asymmetric supercapacitor based on CuO and polypyrrole (PPy) is developed in this work. The fiber-shaped positive electrode composed of CuO nanowires (CuO NWs) on Cu wire (Cu wire/CuO NWs) is successfully prepared via anodization of copper wire followed by thermal treatment. Meanwhile, conductive polymer PPy is grown on carbon fiber bundle (CF/PPy) by electrodeposition as a negative electrode. Subsequently, an all-solid-state wire-shaped asymmetric supercapacitor is assembled with Cu wire/CuO NWs, CF/PPy and PVA-KOH gel electrolyte. Benefiting from the efficient pseudocapacitive properties of the binder-free positive electrode with CuO nanowires directly grown on the copper wire surface and the negative electrode with PPy tightly covered on the carbon fibers, the all-solid-state wire-shaped asymmetric supercapacitor assembled exhibits a high energy density (9.31 μWh cm−2) and specific capacitance (39.67 mF cm−2, 24.91 mF cm−1). Moreover, this device also shows an excellent stability of electrochemical performance at different bending conditions, demonstrating its potential to serve as a flexible power source for portable/wearable electronics.

NiCo2O4/RGO Hybrid Nanostructures on Surface-Modified Ni Core for Flexible Wire-Shaped Supercapacitor.

In this work, we report surface-modified nickel (Ni) wire/NiCo2O4/reduced graphene oxide (Ni/NCO/RGO) electrodes fabricated by a combination of facile solvothermal and hydrothermal deposition methods for wire-shaped supercapacitor application. The effect of Ni wire etching on the microstructural, surface morphological and electrochemical properties of Ni/NCO/RGO electrodes was investigated in detail. On account of the improved hybrid nanostructure and the synergistic effect between spinel-NiCo2O4 hollow microspheres and RGO nanoflakes, the electrode obtained from Ni wire etched for 10 min, i.e., Ni10/NCO/RGO exhibits the lowest initial equivalent resistance (1.68 Ω), and displays a good rate capability with a volumetric capacitance (2.64 F/cm3) and areal capacitance (25.3 mF/cm2). Additionally, the volumetric specific capacitance calculated by considering only active material volume was found to be as high as 253 F/cm3. It is revealed that the diffusion-controlled process related to faradaic volume processes (battery type) contributed significantly to the surface-controlled process of the Ni10/NCO/RGO electrode compared to other electrodes that led to the optimum electrochemical performance. Furthermore, the wire-shaped supercapacitor (WSC) was fabricated by assembling two optimum electrodes in-twisted structure with gel electrolyte and the device exhibited 10 μWh/cm3 (54 mWh/kg) energy density and 4.95 mW/cm3 (27 W/kg) power density at 200 μA. Finally, the repeatability, flexibility, and scalability of WSCs were successfully demonstrated at various device lengths and bending angles.

A novel wire-shaped supercapacitor based on MnO2 nanoflakes and carbon nanotubes with high performance synthesized by sacrificial template method

With the growing demand of wearable and portable electronic devices, design and development of flexible energy storage devices are essential and urgent. In this study, MnO2//PVA-KOH//carbon nanotubes based wire-shaped supercapacitor with high performance is fabricated, in which copper wire is used as current collector in inner electrode to overcome poor electrical conductivity of MnO2. As outer electrode, carbon nanotubes are obtained by an in-situ chemical vapor deposition (CVD) method, in which cobalt-based catalyst particles are evenly distributed over the surface of SiO2. Finally, etching removal of SiO2 and filling of gel electrolyte are carried out simultaneously by hydrothermal method. The wire-shaped supercapacitor exhibits a good capacitive performance (0.99 F cm−3 or 1.98 F cm−2), a high energy density (0.16 mWh cm−3) at a power density of 37 mV cm−3, and long-term cycling stability (90.38% of capacitance retention at 0.15 A cm−3 after 4000 cycles) with excellent flexibility. Therefore, excellent performance of wire-shaped supercapacitor indicates its broad application prospects in the field of portable and wearable energy storage devices.

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.

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.

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.

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.

Wearable Wire-Shaped Symmetric Supercapacitors Based on Activated Carbon-Coated Graphite Fibers.

With the advantages of being lightweight, flexible, and wearable, wire-shaped supercapacitors have received tremendous attention in wearable and portable power sources in recent years. Considering the demands for large-scale applications, it is necessary to explore a facile and convenient preparation approach for wire-shaped supercapacitors. Herein, we reported a simple approach to fabricate wire-shaped electrodes by a dipping method, which possessed a nitric acid-activated graphite fiber core and an activated carbon-coating layer structure. Parallel and symmetric all-solid-state wire-shaped supercapacitors (PWSCs) based on the electrodes were fabricated. The as-fabricated PWSC showed high energy density (6.60 W h/kg, 8.08 mW h/cm, and 1 mV/s) and power density (253 mW/kg, 0.31 mW/cm, and 100 mV/s) and excellent flexibility. Furthermore, this wire-shaped supercapacitor may bring broader application prospects for energy storage devices in future wearable electronic areas.

Wire-Shaped Supercapacitors with Organic Electrolytes Fabricated via Layer-by-Layer Assembly.

A wire-shaped supercapacitor (WSS) has structural advantages of high flexibility and ease of incorporation into conventional textile substrates. In this work, we report a thin reproducible WSS fabricated via layer-by-layer (LbL) assembly of multiwalled carbon nanotubes (MWCNTs), combined with an organic electrolyte of propylene carbonate (PC)-acetonitrile (ACN)-lithium perchlorate (LiClO4)-poly(methyl methacrylate) (PMMA) that extends the voltage window to 1.6 V. The MWCNTs were uniformly deposited on a curved surface of a thin Au wire using an LbL assembly technique, resulting in linearly increased areal capacitance of the fabricated WSS. Vanadium oxide was coated on the LbL-assembled MWCNT electrode to induce pseudocapacitance, hence enhancing the overall capacitance of the fabricated WSS. Both the cyclic stability of the WSS and the viscosity of the electrolyte could be optimized by controlling the mixing ratio of PC to ACN. As a result, the fabricated WSS exhibits an areal capacitance of 5.23 mF cm-2 at 0.2 mA cm-2, an energy density of 1.86 μ W h cm-2, and a power density of 8.5 mW cm-2, in addition to a high cyclic stability with a 94% capacitance retention after 10 000 galvanostatic charge-discharge cycles. This work demonstrates a great potential of the fabricated scalable WSS in the application to high-performance textile electronics as an integrated energy storage device.

Superelastic wire-shaped supercapacitor sustaining 850% tensile strain based on carbon nanotube@graphene fiber

Stretchable and flexible supercapacitors are highly desired due to their many potential applications in wearable devices. However, it is challenging to fabricate supercapacitors that can withstand large tensile strain while maintaining high performance. Herein, we report an ultra-stretchable wire-shaped supercapacitor based on carbon nanotube@graphene@MnO2 fibers wound around a superelastic core fiber. The supercapacitor can sustain tensile strain up to 850%, which is the highest value reported for this type of device to date, while maintaining stable electrochemical performance. The energy density of the supercapacitor is 3.37 mWh·cm–3 at a power density of 54.0 mW·cm–3. The results show that 82% of the specific capacitance is retained after 1,000 stretch–release cycles with strains of 700%, demonstrating the superior durability of the elastic supercapacitor and showcasing its potential application in ultra-stretchable flexible electronics.

(Invited) Carbon Nanomaterials for Flexible and Stretchable Devices

The development of flexible electronics and equipment attracts significant interests in recent years. It is of great importance to develop flexible and wearable energy storage devices for wearable and portable devices. Carbon nanomaterials have large surface area, good conductivity and excellent mechanical and chemical stability, enabling their applications in high performance energy conversion and energy storage devices. In this talk, I will present fiber-shaped ultra-stretchable and flexible supercapacitor made of carbon nanotube fibers, film-shaped stretchable supercapacitors and flexible Zn-air batteries using stretchable graphitized natural fabrics as electrodes. The ultra-stretchable wire-shaped supercapacitor was made by winding two carbon nanotube@graphene@MnO2 fibers around a superelastic core fiber. The supercapacitor can sustain tensile strain up to 850%, which is hitherto the highest value, while keeping stable electrochemical performance. We further demonstrated that there devices can be assembled with carbon-based flexible sensors into wearable smart systems. These strategy paves new ways for the fabrication of high performance wearable energy storage devices and flexible electronics.

High loading carbon nanotubes deposited onto porous nickel yarns by solution imbibition as flexible wire-shaped supercapacitor electrodes

The deposition of active materials directly onto metal wires is a general strategy to prepare wire-shaped electrodes for flexible and wearable energy storage devices. However, it is still a critical challenge to coat active materials onto the aimed metal wires because of their smooth surface and small specific surface area. In this work, high porous nickel yarns (PNYs) was fabricated using commercial nylon yarns as templates through step-wise electroless plating, electroplating and calcination processes. The PNYs are composed of multiplied fibers with hollow tubular structure of 5–10µm in diameter, allowing the imbibition of carbon nanotubes (CNTs) solution by a facile capillary action process. The prepared CNTs/PNY electrodes showed a typical electrochemical double layer capacitive performance and the constructed all-solid flexible wire-shaped symmetric supercapacitors provided a specific capacitance of 4.67F/cm3 with good cycling stability at a current density of 0.6A/cm3.

A Wire-Shaped Supercapacitor in Micrometer Size Based on Fe3O4 Nanosheet Arrays on Fe Wire

One-dimensional (1D, wire- and fiber-shaped) supercapacitors have recently attracted interest due to their roll-up, micrometer size and potential applications in portable or wearable electronics. Herein, a 1D wire-shaped electrode was developed based on Fe3O4 nanosheet arrays connected on the Fe wire, which was prepared via oxidation of Fe wire in 0.1 M KCl solution (pH 3) with O2-rich environment under 70 °C. The obtained Fe3O4 nanosheet arrays displayed a high specific capacitance (20.8 mF cm−1 at 10 mV s−1) and long cycling lifespan (91.7% retention after 2500 cycles). The excellent performance may attribute to the connected nanosheet structure with abundant open spaces and the intimate contact between the Fe3O4 and iron substrate. In addition, a wire-shaped asymmetric supercapacitor was fabricated and had excellent capacitive properties with a high energy density (9 µWh cm−2) at power density of 532.7 µW cm−2 and remarkable long-term cycling performance (99% capacitance retention after 2000 cycles). Considering low cost and earth-abundant electrode material, as well as outstanding electrochemical properties, the assembled supercapacitor will possess enormous potential for practical applications in portable electronic device.

Ultrahigh-rate wire-shaped supercapacitor based on graphene fiber

The emerging wire-shaped supercapacitors (WSSs) have motivated tremendous research interests in energy storage devices. However, challenges still exist in the pursuit of high-rate performance WSS. Here, a graphene fiber made from chemical vapor deposition grown laminated graphene sheet is adopted to form a WSS which exhibits an exceptional rate capability with a relaxation time constant of 1.4 ms, smallest among WSSs reported to date. Furthermore, the resulting WSS can be charged-discharged at a high scan rate of 100 V s−1 while maintaining good capacitive behavior. When the scan rate increased by 5000 times, from 20 mV s−1 to 100 V s−1, the graphene fiber based WSS maintains 38.6% of its original capacitance. After 10,000 galvanostatic charge-discharge cycles, the specific capacitance retains over 105%, demonstrating a long cycle stability.