Fiber Supercapacitors Research Articles

Achieving superior high-life-stability and stable structure for flexible fiber electrodes inspired by Bamboo rice dumpling

MnO2 is widely recognized as promising pseudocapacitive materials to address the issue of low energy density in fiber supercapacitors. However, it severely suffers from poor cycling stability caused by structure damages. Inspired by Chinese bamboo rice dumplings, herein we demonstrate the strategy of building conductive polymer Poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires around the MnO2 nanoparticles to address the issue. Benefiting from the tight winding of PEDOT nanowires, the flexible fiber electrode achieves a stable structure and an extraordinary cycle stability. Density functional theory calculations further reveals that the charge redistribution of MnO2/PEDOT interface and Fe3+ doping during polymerization in PEDOT improve the conductivity, facilitate ion adsorption, inhibit the hydrogen evolution reaction, and expand the voltage window. Accordingly, the fiber-shaped supercapacitor based on this electrode exhibits a high cycle lifespan of 86% after 22,000 cycles with capacitance (23.5 F cm−3), energy density (8.32 mWh cm−3), power density (8000 mW cm−3) and voltage window of 1.6 V. Furthermore, it can withstand various angles of bending without losing capacity. Our study provides a pathway to construct MnO2 with a stable structure and cycling life, and could be further used for developing other materials with unstable structure in flexible electronic devices.

Diversified constructions and electrochemical cycling stability of metal oxide fiber supercapacitors

Rapid development of electronic technology put forward high requirements for sustainable energy storage systems, and fiber supercapacitors have been considered as one of the prospective research fields. Herein, five metal oxides of Al2O3, Fe2O3, MoO2, NiO and ZnO are chosen as electrochemical active materials to prepare fiber electrodes as well as parallel fiber supercapacitors, respectively. According to the test results, ZnO fiber supercapacitor exhibits the optimal electrochemical performance among them, achieving 1.19 μF·cm−1 at the current density of 0.25 μA·cm−1. In addition, the electrochemical performance of parallel and twisted ZnO fiber supercapacitors are compared systematically so as to illustrate the effect of device structures on their electrochemical performance, and the twisted ZnO fiber supercapacitor shows higher capacitance retention and energy density than the parallel fiber device. Furthermore, the electrochemical cycling stability of parallel as well as twisted ZnO fiber supercapacitors are studied after 10,000 galvanostatic charge–discharge cycles, and parallel ZnO fiber supercapacitor presents better cycle stability owing to the simpler device structure. This work would provide effective evidence for the design and development of high-performance metal oxide-based fiber supercapacitors in the future.

High‐Energy‐Density Graphene Hybrid Flexible Fiber Supercapacitors

AbstractGraphene fiber‐based supercapacitors (GFSCs) as flexible energy‐storage devices have achieved much in the wearable electronics. However, the GFSCs still suffer insufficient energy density, and of which desirable balance between mechanical and electrochemical properties has not been realized. Herein, we developed AgI and conductive polymer assisted co‐enhancement strategy to prepare the high‐performance GFSCs with super‐high energy density, favorable mechanical properties, and superior electrochemical properties. The conductive binder polymer, poly(3,4‐ethylenedioxythiophene) (PEDOT) was introduced into the GO spinning solution to enhance RGO fiber strength, conductivity, and electrochemical performance by forming a strong interface with GO in the spinning solution. On the other hand, the synergistic effect of micro‐ and nano‐scale AgI grown on the fiber surface and aqueous gel electrolyte widen the potential window of the GFSC to 1.6 V, which is much higher than that of reported GFSCs, and resulting in a significantly increased energy density. At 0.1 A cm−3, the volumetric capacitance and energy density of the fabricated GFSCs are as high as 166.6 F cm−3 and 29.65 mWh cm−3, respectively. The high strength and flexibility of the hybrid fibers endowed the GFSCs with ∼100 % capacitance retention when bent to 180°. This work opens a new way to design and fabricate high‐performance GFSCs.

Temperature-dependent pseudocapacitive behaviors of polyaniline-based all-solid-state fiber supercapacitors

The work temperatures have a crucial influence on the performance of supercapacitors. However, temperature effects on pseudocapacitive behaviors are rarely studied for flexible high-performance fiber supercapacitors. Herein, we systematically investigated the electrochemical responses of all-solid-state fiber-based supercapacitors composed of carbon nanotube fiber (CNF) electrodes decorated with porous carbon nanotubes (CNTs)/polyaniline (PANI) and gel electrolyte at various ambient temperatures between −5 °C and 55 °C. The results show that the capacitance of the supercapacitor first enhances with the rising temperature under 40 °C and declines at 55 °C. The internal resistance presents a gradual downward trend and the self-discharge behavior accelerates at high operating temperatures. CNTs/PANI-modified flexible fiber supercapacitors are also far from unsatisfactory for cycling stability tests in a high-temperature environment. After experiencing 5000 charge–discharge cycles at 55 °C, the capacitance retains only 43.86 %, far below the counterpart at low temperatures. This study provides a fundamental comprehension of the temperature dependence of pseudocapacitive behaviors of PANI-based fiber supercapacitors.

Electrostatic Interfacial Cross-Linking and Structurally Oriented Fiber Constructed by Surface-Modified 2D MXene for High-Performance Flexible Pseudocapacitive Storage.

Fiber supercapacitors are promising power supplies suitable for wearable electronics, but the internally insufficient cross-linking and random structure of fiber electrodes restrict their performance. This study describes how interfacial cross-linking and oriented structure can fabricate an MXene fiber with high flexibility and electrochemical performance. The continuous and highly oriented macroscopic fibers were constructed by 2D MXene sheets via a liquid-crystalline wet-spinning assembly. The oxyanion-enriched terminations of surface-modified MXene in situ could reinforce the interfacial cross-linking by electrostatic interactions while mediating the sheet-to-sheet lamellar structure within the fiber. The resultant MXene fiber exhibits high electrical conductivity (3545 S cm-1) and mechanical strength (205.5 MPa) and high pseudocapacitance charge storage capability up to 1570.5 F cm-3. Notably, the assembled fiber supercapacitor delivers an energy density of 77.6 mWh cm-3 at 401.9 mW cm-3, exceptional flexibility and stability exhibiting ∼99.5% capacitance retention under mechanical deformation, and can be integrated into commercial textiles to power microelectronic devices. This work provides insight into the fabrication of an advanced MXene fiber and the development of high-performance flexible fiber supercapacitors.

Optimized electron/ion transport by constructing radially oriented channels in MXene hybrid fiber electrodes for high-performance supercapacitors at low temperatures

High-performance all-solid-state fiber supercapacitors assembled with MXene/RGO/PEDOT:PSS hybrid fiber electrodes with radially oriented channels and an anti-freezing electrolyte exhibit excellent capacitance retention at ultralow temperatures.

Reliable coaxial wet spinning strategy to fabricate flexible MnO2-based fiber supercapacitors

With the rapid development of electronic technique, wearable energy conversion and storage devices are facing huge challenges. Particularly, fiber supercapacitors have advantages of small size, light weight, high flexibility, fast charge/discharge process, high power density, long cycle life and wide operating temperature, showing considerable application prospect in the smart wearable field. This work proposes a strategy to fabricate MnO2, MnO2/PANI and MnO2/GN fiber electrodes via coaxial wet spinning technology, in which the electrochemical active materials could be wrapped into CMC layer perfectly, ensuring the structure stability of fiber electrodes effectively. And a series of MnO2-based parallel fiber supercapacitors are further assembled. After optimization of mixing ratios, the MnO2/PANI fiber supercapacitor with mixing-ratio of 1:1 exhibits specific capacitance of 0.68 μF·cm−1 at 0.25 μA·cm−1, and the MnO2/GN fiber supercapacitor with mixing-ratio of 9:1 presents 1.23 μF·cm−1at the same current density, which are both higher than that of pure MnO2 fiber supercapacitor (0.59 μF·cm−1), proving significant enhancement of electrochemical performance due to the introduced PANI or GN. Therefore, this work provides a reliable guidance for design and application of wearable fiber supercapacitors.

Review of Recent Advances of Supercapacitors Energy Storage Systems

This paper presents a review of the recent advances of the supercapacitors energy storage systems. The recent development of the supercapacitors devices is presented and discussed. The need for highly dependable backup and emergency power is fueling growth in the energy storage and power transmission industries. One of the most advanced types of energy storage devices is the supercapacitor. At the electrode-electrolyte interface, these supercapacitors can store electrical charge in an electric double layer. Different materials are considered for creating the supercapacitors, such as graphene, carbon black, and charcoal. This paper focuses on the electrode material, rare earth and their composites-based electrode materials for supercapacitors, atomic layer deposition in the development of transition-metal-oxide and conducting polymer-based fibers for supercapacitors, and atomic layer deposition in the development of transition-metal-oxide and conducting polymer-based fibers for supercapacitors.

Tailoring molecular interaction in heteronetwork polymer electrolytes for stretchable, high-voltage fiber supercapacitors

Mechanically and electrochemically stable all-solid-state supercapacitors are of great interest in the field of wearable and portable electronic devices. However, when conventional liquid or gel electrolytes are used in supercapacitors, their discontinuous functions appear in harsh external environments. Here, we prepare freeze-tolerant heteronetwork nanohybrid polymer electrolytes (NPEs), composed of hydrophilic poly(lithium acrylate) (PLiA) containing mobile lithium countercations and mechanically robust silica nanoparticles (SNs) serving as stress buffers, via sol–gel reaction and radical polymerization. The combination of PLiA and SN provides NPE (PLiA-SN) with high room temperature ionic conductivity (up to σDC ∼ 10-1 S/cm), which not only remains 100% even after 700% elongation, but also exhibits high ionic conductivity at low temperatures (σDC = 4×10-3 S/cm at 0 °C). This is because Li+ binds strongly to water, thereby preventing water evaporation and crystallization, as revealed by density functional theory (DFT) calculations. The cross-linking of SNs with PLiA chains also gives the resultant NPE superelasticity and self-healing property. The optimized NPE is assembled with metal–organic framework derived carbon (MDC)-coated carbon nanotube yarn (MDC@CNTY) hybrid electrodes, possessing both high charge storage capability and superior mechanical properties, to fabricate high-performance all-solid-state fiber supercapacitors (FSCs). The assembled FSC delivers a high specific capacitance of 51 F/g, high power (6 kW/kg, 27 mW/cm2, 1202 μW/cm) and energy (44 Wh/kg, 0.2 mWh/cm2, 9 μWh/cm) densities, as well as a wide operating voltage window as high as 2.5 V. Moreover, the electrochemical performance of the FSC is maintained under different stretching strains, various degrees of bending, and cutting/healing cycles, and still retains ∼ 92% capacity even at a low temperature (-10 °C), demonstrating excellent mechanical, thermal, and electrochemical stability. This work provides an effective strategy for designing energy storage devices that are sufficiently stretchable, bendable, and reliable for use in extreme environments.

Carbon Nanotube Fiber-Based Wearable Supercapacitors—A Review on Recent Advances

As wearable electronic devices are becoming an integral part of modern life, there is a vast demand for safe and efficient energy storage devices to power them. While the research and development of microbatteries and supercapacitors (SCs) have significantly progressed, the latter has attracted much attention due to their excellent power density, longevity, and safety. Furthermore, SCs with a 1D fiber shape are preferred because of their ease of integration into today’s smart garments and other wearable devices. Fiber supercapacitors based on carbon nanotubes (CNT) are promising candidates with a unique 1D structure, high electrical and thermal conductivity, outstanding flexibility, excellent mechanical strength, and low gravimetric density. This review aims to serve as a comprehensive publication presenting the fundamentals and recent developments on CNT-fiber-based SCs. The first section gives a general overview of the supercapacitor types based on the charge storage mechanisms and electrode configuration, followed by the various fiber fabrication methods. The next section explores the different strategies used to enhance the electrochemical performance of these SCs, followed by a broad study on their stretchability and multifunctionality. Finally, the review presents the current performance and scalability challenges affecting the CNT-based SCs, highlighting their prospects.

Graphene-Based Fiber Supercapacitors

Graphene-Based Fiber Supercapacitors

Coaxial fabrication of Ni-Co layered double hydroxide into 3D carbon nanotube networks for high-performance flexible fiber supercapacitors

Asymmetric fiber-shaped supercapacitors (FSCs), especially those using pseudocapacitive materials, have been considered one of the most promising candidates for high-performance electrochemical devices. Herein, we design a flexible, asymmetric FSC consisting of carbon fiber (CF) as the substrate, multiple and alternate Ni-Co layered double hydroxide/mono-dispersed carbon nanotube (CNT) coaxial layers ([Ni-Co LDH-x/CNT-y]@CF) as the positive electrode materials and tremella-derived activated [email protected] (TDC-z@CF) as the negative electrode material. The 3D Ni-Co LDH/mono-dispersed CNT networks enable the high mass loading of active materials, fast electron transfer, efficient ion diffusion, and mechanical stress release. TDC-z possesses large surface areas with hierarchical porous structures, thus demonstrating high capacitive performance. Based on that, the resulting FSC achieves a remarkable energy density of 26.20 Wh kg−1, a power density of 7569.23 W kg−1, and a superior cycling stability of 112.5% over 5000 cycles at a current density of 5 A g−1. Several supercapacitors connected in series can also drive a portable LED device for over 10 min. Furthermore, the assembled device also exhibits excellent mechanical stability under various deformation conditions. These appealing properties make our FSCs an attractive candidate for powering wearable and flexible electronic devices.

Flexible carbon nanofiber yarn electrodes for self-standing fiber supercapacitors

In this study, polyacrylonitrile (PAN) nanofiber yarns were obtained by twisting the nanofiber mat strips produced in the electrospinning device. On the drum collector, the nanofibers are produced in such a way that the diameter change can be controlled. Through stabilization and carbonization processes, PAN nanofiber yarns were converted to carbon nanofiber (CNF) yarns. The stabilization process stabilized the yarn structure, which was previously unstable, due to thermal treatments. The obtained CNF yarn had a diameter of approximately 360 μm and an average nanofiber diameter of 123 ± 20 nm. On a three-electrode system, the electrochemical performance of CNF yarn in 1 m H2SO4 electrolyte was determined using cyclic voltammetry and galvanostatic charge/discharge test methods. The specific capacitance of the CNF yarn electrode was determined to be 145 F/g at a current density of 0.2 A/g. Up to 500 charge/discharge cycles, the specific capacitance increased by approximately 20% and remained constant thereafter. Due to their superior properties such as high surface area, lightweight, and flexibility, CNF yarn electrodes can be used in a wide variety of electronic applications, including energy harvesting, energy storage (supercapacitors, batteries, etc.), and sensors.

Epitaxial nanofiber separator enabling folding-resistant coaxial fiber-supercapacitor module

Mechanically strengthened fiber-supercapacitors (FSCs) are urgently needed in wearable electronics to adapt frequent severe deformations. However, current bendable FSCs using gel electrolyte as separator are easily short-circuited under harsh folding due to the limited stretchability of gel polymer. Herein, a folding-resistant coaxial FSC, for the first time, was fabricated through in-situ electrospinning polyacrylonitrile (PAN) nanofibers as separator on fiber electrode, thus effectively avoiding the short-circuit risk under highly localized stretching, compressing and folding. Moreover, such “epitaxial growth” ultrathin (∼ 1 µm) PAN separator possesses high porosity, favorable strength and seamless contact with fiber electrode, enabling fast ion transport and decreased internal resistance of FSCs. Coupled with robust polyaniline/carbon nanotube (PANI/CNT) composite as model electrodes, our fabricated coaxial symmetric FSC exhibits outstanding structural folding-resistance without electrochemical failure. Amazingly, such in-situ encapsulated separator technique makes it easier to assemble multi-layer PANI/CNT electrode in series or parallel. As-assembled coaxial integrated series or parallel device keeps almost same volume as single device, but delivers higher output voltage or capacitance; and simultaneously remains excellent foldable property, showing great practical potential.

Activated carbon fibers derived from natural cattail fibers for supercapacitors

Activated carbon fibers derived from natural cattail fibers for supercapacitors

Hierarchical NiCo2S4/PANI/CNT nanostructures grown on graphene polyamide blend fiber as effective electrode for supercapacitors

Fiber-supercapacitors (FSCs) hold great promise in smart wearable energy textiles due to the advantages of security, excellent deformability and unique integration structure. However, the integration of electroactive materials into economically viable textile fibers to produce FSCs with high energy density and mechanical flexibility remains a huge challenge. Herein, we fabricated NiCo2S4/PANI/CNTs hierarchical nanostructures on graphene polyamide blend fiber (GPAF) as effective cathodes for FSCs. The prepared composite fiber electrode exhibited a specific capacity of 1290 mF cm-2 when the current density was 2 mA cm-2, which was benefitted from the delocalized conjugated system of PANI nanolayer and the unique nanostructure of NiCo2S4/PANI. Subsequently, the constructed asymmetrical fiber-supercapacitor (AFSC) delivered energy density up to 83.3 μWh cm-2 when the power density was 420 μW cm-2. In addition, the AFSC also exhibited satisfactory cycling stability, maintaining 80.13% of the initial capacity after 5000 cycles. This work provides new ideas to promote the further development and practical applications of flexible fiber-supercapacitors and accelerate the development process of wearable energy textiles.

Highly Performed Fiber‐Based Supercapacitor in a Conjugation of Mesoporous MXene

AbstractWith the continuous demands for wearable electronics, the embeddable power sources have drawn attention to develop advanced electrode materials and feasible manufacture procedures. Fiber‐based flexible energy storage devices have the potential to be practically integrated by utilizing the high‐performance materials with precisely constructed structures. Herein, a novel approach is presented to achieve an outstanding fiber‐based supercapacitor by simultaneous wet‐spinning of mesoporous MXene (Ti3C2Tx) nanoflakes. The volumetric capacitance of the porous fiber is enhanced up to ≈145% when the content of mesoporous MXene reaches 15 wt%. The symmetric all‐solid‐state fiber supercapacitor shows an extraordinary capability of 821.5 F cm–3 at a current density of 0.5 A cm–3, which reflects an enormous improvement to that of a nonporous MXene fiber‐based supercapacitor. The measured energy density is 8.9 mWh cm–3 at a power density of 401 mW cm–3, which also indicates the effective synergy of the constructed pathways for ions and electrons. This work demonstrates the feasibility of scalable production of fiber‐based electrode materials with porous MXene for powering wearable applications.

Hierarchical layered nickel–iron double hydroxide/carbon nanotube fiber electrode for constructing asymmetric fiber supercapacitor

A flexible fiber supercapacitor assembled using well-matched Ni–Fe LDH@CNTF and RuO2@CNTF fiber electrodes exhibited favorable energy and power combinations, providing a promising solution to the demands for power sources for flexible electronics.

Hierarchical Layered Ni-Fe Double Hydroxide/Cnt Fiber Electrode for Constructing Asymmetric Fiber Supercapacitor

Hierarchical Layered Ni-Fe Double Hydroxide/Cnt Fiber Electrode for Constructing Asymmetric Fiber Supercapacitor

Co-Axial Fabrication of Ni-Co Layered Double Hydroxide into 3d Carbon Nanotube Networks for High-Performance Flexible Fiber Supercapacitors

Co-Axial Fabrication of Ni-Co Layered Double Hydroxide into 3d Carbon Nanotube Networks for High-Performance Flexible Fiber Supercapacitors