Electrode Materials For Flexible Supercapacitors Research Articles

Facile Synthesis of Ag-Doped Urchin-like MnO2 on Carbon Cloth for Supercapacitors.

Based on MnO2/carbon cloth (CC) composite materials, an Ag-doped MnO2 nanowire, self-assembled, urchin-like structure was synthesized in situ on the surface of CC using a simple method, and a novel and efficient flexible electrode material for supercapacitors was developed. The morphology, structure, elemental distribution, and pore distribution of the material were analyzed using SEM, TEM, XRD, XPS, and BET. The electrochemical performance was tested using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). In the three-electrode system, GCD testing showed that the specific capacitance of the material reached 520.8 F/g at 0.5 A/g. After 2000 cycles at a current density of 1 A/g, the capacitance retention rate was 90.6%, demonstrating its enormous potential in the application of supercapacitor electrode materials.

Conductive polymer electrode materials with excellent mechanical and electrochemical properties for flexible supercapacitor

Flexible supercapacitors can be applied in the field of wearable devices, which currently received much attention. As pseudocapacitive electrode material for flexible supercapacitors, PEDOT has been extensively investigated especially to improve the mechanical strength and flexibility of the electrode material, but most methods will disrupt its electrochemical performance. In this study, we designed and prepared a novel alveolate copolymer based on PEDOT by electrochemical polymerization, introducing a certain proportion of carbamate groups as side chains to form a cross-linked structure through hydrogen bonding. This copolymer has excellent flexibility due to intermolecular hydrogen bonding, and outstanding electrochemical performance, especially rate performance and cycling stability, because of the ion channel of copolymer which satisfy the rapid migration of ions. Flexible supercapacitor based on this copolymer electrode material still have 96.1 % capacity retention at high current densities (0.2 mA/cm2) compared to low current density (0.025 mA/cm2). The specific capacity retained 85 % of its initial capacity after 20,000 cycles, especially with almost no loss in capacity even after 1000 bending cycles. This alveolate copolymer with hydrogen bonding cross-linking structure provides a choice for obtaining flexible supercapacitors with excellent mechanical and electrochemical performance, which could be utilized as wearable energy storage devices.

Electropolymerization of 5-amino-2-naphthalenesulfonic acid and their application as the electrode material for supercapacitors

Electropolymerization is a powerful tool in constructing conducting polymers that can be utilized as the electrode materials for flexible supercapacitors. The 5-amino-2-naphthalenesulfonic acid is electropolymerized at anodic potential on carbon cloth from aqueous perchloric acid solutions. The poly(5-amino-2-naphthalenesulfonic acid) coated carbon cloth electrodes (PANS/CC) are characterized, and are used as the electrode material for supercapacitors. The PANS/CC-40 exhibits the optimum charge storage performance, with the specific capacity of 85.5 mAh g−1 at 1 A g−1 charge-discharge current density in 1 M H2SO4. Specific capacities of 44.8 and 38.5 mAh g−1 are achieved for the PNAS/CC-40 in 1 M ZnSO4 and 1 M (NH4)2SO4, respectively, at 1 A g−1. Kinetic analyses show that the PNAS/CC-40 is a battery-type electrode material, and the surface-controlled processes contribute over 80 % of the stored charge. Evidences of cation (de)intercalation accompanying with the redox of amine/imine groups are given. A symmetric supercapacitor is assembled using two PNAS/CC-40 and the PVA/H2SO4 gel electrolyte, and it can deliver the energy density of 1.1 Wh kg−1 and the power density of 136.9 W kg−1 at 1 A g−1. The capacity retention of the symmetric supercapacitor is 88 % after 10,000 cycles at 5 A g−1.

A dual-template strategy assisted synthesis of porous coal-based carbon nanofibers for supercapacitors

The electrospun carbon nanofibers (ECNFs) with the advantages of facile preparation method, excellent electrical conductivity and ease compounding are expected to be excellent electrode materials for supercapacitors. However, the tiny specific surface area and low specific capacitance prevent the further development of carbon nanofibers. In this work, the porous coal-based carbon nanofibers (PCCNFs-2) are fabricated via a facile dual-template method, which can be directly employed as a flexible electrode material for supercapacitors without the addition of any conductive agents and binders. As a result, the flexible self-supporting electrode (PCCNFs-2) achieves a specific capacitance of 262.0 F g−1 at a current density of 1 A g−1, excellent rate performance (81.0 % capacitance retention at a current density of 20 A g−1) and excellent cycling stability (after 10,000 cycles, 124 % capacity retention at 2 A g−1). Furthermore, the aqueous symmetrical supercapacitors (SCs) assembled with melamine foam as the storage electrolyte at an operating voltage of 1.2 V achieved an energy density of 18.5 Wh kg−1 at a power density of 150.5 W kg−1. The effective construction of this porous carbon nanofiber assures the structural integrity and achieves excellent electrochemical performance of the electrode material, which develops a new strategy for efficient utilization of porous coal-based carbon nanofibers in supercapacitors.

Fabrication of Flexible Supercapacitor Electrode Materials by Chemical Oxidation of Iron-Based Amorphous Ribbons.

A flexible electrode constructed from Fe-based amorphous ribbons decorated with nanostructured iron oxides, representing the novelty of this research, was successfully achieved in one-step via a chemical oxidation method, using a low concentration of NaOH solution. The growth of metal oxides on a conductive substrate, which forms some metal/oxide structure, has been demonstrated to be an efficient method for increasing the charge transfer efficiency. Through the control and variation of synthetic parameters, different structures and morphologies of iron oxide were obtained, including hexagonal structures with a hollow ball shape and rhombohedral structures with rhombus-like shapes. Structural and morphological characterization methods such as X-ray diffraction and SEM morphology were used on the as-synthesized composite materials. The supercapacitor properties of the as-developed amorphous ribbons decorated with Fe2O3 nanoparticles were investigated by cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy. The flexible supercapacitor negative electrode demonstrates a specific capacitance of 5.96 F g-1 for the 0.2 M NaOH treated sample and 8.94 Fg-1 for the 0.4 M NaOH treated sample. The 0.2 M treated negative electrodes deliver 0.48 Wh/kg at a power density of 20.11 W/kg, and the 0.4 M treated electrode delivers 0.61 Wh/kg at a power density of 20.85 W/kg. The above results show that these flexible electrodes are adequate for integration in supercapacitor devices, for example, as negative electrodes.

Investigation of molar concentration and its effects in escalated charge storage mechanism on cobalt oxide nanoparticles

In the wake of recent developments, supercapacitors are actively being employed as a superior energy storage material and are being regarded as a viable alternative to traditional battery technology. Its high-power density and quick charging and discharging capabilities have increased their allure. Transition metal oxides have gained much interest as electrode materials for flexible supercapacitors; due to their high specific capacitance, as a result, multifunctional cobalt oxide is one of the most versatile and crucial materials for advances in energy storage. This work suggested utilising a facilitated hydrothermal approach to create cobalt oxide nanoparticles at various molarities. The physicochemical properties of the synthesised products were explored using X-ray diffraction, FT-IR, UV–Visible, SEM, and a charge storage potential was significantly investigated. The formation of single-phased cobalt oxide nanoparticles is revealed by functional investigation, with the estimated crystallite size increasing proportionally to the concentration of cobalt ions. Significantly, the crystalline parameters of cobalt oxide are greatly influenced by the molar ratio changes. Morphological studies strikingly demonstrated the porous-like morphology of particle dispersion over the samples. The electrochemical study found an intrinsic pseudo capacitance with a maximum specific capacitance of 378.61 Fg−1. Duringinvestigations, the cobalt oxide demonstrates an efficient charge storage ability, implying that the cost-effective synthesised cobalt oxide's considerable capacitance capability complies with and supports the energy storage demands.

MXene/AC Composite Membranes as an Electrode Material for Flexible Supercapacitors with Excellent Properties

MXene/AC Composite Membranes as an Electrode Material for Flexible Supercapacitors with Excellent Properties

One-step electrodeposition preparation of NiCoSe2@carbon cloth as a flexible supercapacitor electrode material

Regular nanoarrays are ideal structures for supercapacitors; however, they often require multiple operations during their preparation.

MXene (Ti3C2Tx)/cellulose nanofiber/polyaniline film as a highly conductive and flexible electrode material for supercapacitors

In recent years, supercapacitors based on cellulose nanofiber (CNF) films have received considerable attention for their excellent flexibility, lightweight, and unique structure. In this study, MXene (Ti3C2Tx) /CNF/polyaniline (PANI) hybrid films with good conductivity and flexibility were prepared by a convenient vacuum filtration method. Combined with PANI, MXene creates an open structure with high conductivity, which facilitates ion and electron transport among the materials and provides the composite with high electrochemical activity. The MXene/CNF/PANI electrode presents a high areal specific capacitance of 2935 mF cm−2 at the current density of 1 mA cm−2, excellent cycling stability with high capacitance retention of 94 % after 2000 cycles at 10 mA cm−2 and high electrical conductivity (634.4 S∙cm−1). As a further application of this film, it is used as a free-standing electrode to fabricate a quasi-solid-state supercapacitor with high performance, which has an ultra-thin thickness of 0.344 mm, a significantly high areal specific capacitance (522 mF cm−2) at 5 mA cm−2, a high areal energy density of 94.7 μWh∙cm−2 and a high areal power density of 573 μW∙cm−2. This work shows the great potential of the developed high-performance and flexible cellulose-based composites for fabricating electrodes as well as supercapacitors.

Hierarchical porous nitrogen-doped carbon nanosheets derived from zinc-based bioMOF as flexible supercapacitor electrode

We propose an efficient and flexible supercapacitor electrode material based on hierarchically structured nitrogen-doped graphene-like carbon nanosheets (H-NCNs) with accordion-like shape. H-NCNs were obtained by pyrolyzing zinc-based biometal–organic frameworks (Zn-bioMOFs) and using urea as nitrogen source at high temperature (800 °C) under nitrogen atmosphere, and Zn-bioMOFs were synthesized using biomass molecules, i.e., curcumin. Inheriting from the features of Zn-bioMOF, H-NCNs showed hierarchical structures and unique accordion-like morphology. By changing the urea dosage, the nitrogen-doping degree and porosity of H-NCNs were regulated, optimizing the supercapacitive performance. H-NCNs-8 prepared with Zn-bioMOF/urea mass ratio of 1:8 exhibited high specific capacitance and superior rate capability (293 F g−1 at 0.25 A g−1 and 188 F g−1 at 50 A g−1). The H-NCNs-assembled symmetric supercapacitor offered long cycle life of over 40,000 cycles at 2 A/g and high energy density of 17.6 Wh kg−1 at 250 W kg−1, outperforming most carbon nanomaterial-related ones. Accordingly, the proposed flexible interdigital solid microsupercapacitor demonstrated high areal capacitance, high areal energy densities, and long cycle stability. The present work can provide promising application prospects of MOFs in the field of supercapacitors and flexible electronics.

Graphene-based composites for supercapacitors

Smart devices that are portable and wearable have advanced significantly over the years. Further research on compatible storage devices with tiny, light and flexible properties is required to make wearable electronic devices more versatile, lightweight, smart, and commercially viable. Because of their advantages of having a high-power density, long cycle longevity, superior mechanical strength, good safety, and ease of assembly, supercapacitors have sparked a great deal of interest. Nevertheless, if the conventional supercapacitor is distorted by an external force, the power storage qualities would be significantly diminished or perhaps even eliminated. The primary component of capacitors is the electrode material, hence it is essential to produce extremely flexible electrode materials with superior energy-storage capabilities. This study introduces the supercapacitor energy storage theory and the current state of graphene applications in flexible supercapacitors. Additionally, a succinct summary of the research on pseudo, double-layer, and asymmetric capacitors is provided. Future progress and the difficulties that flexible supercapacitor electrode materials still confront are explored.

Fabrication of Textile-Based Flexible Supercapacitor with a Textile Dye on Polyaniline-Based Composite Electrode for Enhanced Energy Storage

Polyaniline (PANI) is a promising conductive polymer for use in energy storage applications. Here, a one-step hydrothermal method of PANI polymerization on carbon felt electrode was synthesized using an azo dye, a bisulfonated dichloro anionic dye molecule to enhance an efficient textile-based flexible supercapacitor electrode material for energy storage applications. The electrode material synthesized at concentration of 2 mM AY17 exhibits 814.1 F g-1 at the scan rate of 5 mV s-1 with multiwall carbon nanotubes (MWCNTs). Due to electrostatic interaction with the polymer, the presence of high electronegativity Cl atoms in the dye molecule significantly improves the PANI structure's electron donor/acceptor properties. A symmetric supercapacitor exhibits an energy density of 11.7 W h kg−1 at a power density of 300 W kg−1, and it is 4.5 W h kg−1 at 1800 W kg−1 in 3.0 M KCl aqueous electrolyte. The capacitance retention performance value of the symmetric supercapacitor exhibited 81.76% after 2500 cycles.

Highly conductive and flexible porous carbon nanofibers cloth for high-performance supercapacitor

Porous carbon nanofibers combine the superiorities such as good electrical conductivity, intrinsic and structural flexibility, as well as potential mass production, rendering it an important material for flexible and wearable electronics. Nonetheless, the influence of porous carbon nanofiber's nanostructure on electrochemical performances and mechanical flexibility remains an important open question in the design of high-performance and flexible supercapacitors. To address this matter, herein, we report a systematic study to fabricate the porous carbon nanofibers cloth with both high electrical conductivity and flexibility. Our results indicate that the stress concentration during the bending of porous carbon nanofibers can be efficiently relieved through reducing the size of graphite microcrystals and introducing pores between graphite microcrystals, resulting in good flexibility. Meanwhile, the fabricated porous carbon nanofiber achieves high electrical conductivity (Max. 1600 S/m), which can be directly used as flexible supercapacitor electrode material without introducing a conductive agent and binder. Finally, the flexible supercapacitor electrode based on this porous carbon nanofiber exhibits a high specific capacitance of 184 F/g at a current density of 0.5 A/g. Our win-win strategy provides new insight into the fabrication of flexible porous carbon nanofiber materials, showing great application prospects in the field of flexible supercapacitors.

Grape‐clustered polyaniline grafted with carbon nanotube woven film as a flexible electrode material for supercapacitors

AbstractThe continuously reinforced carbon nanotube woven film (CNWF) prepared via the floating catalytic chemical vapor deposition (FCCVD) was modified by mixed acid and vinyltrimethoxysilane (VTMS) respectively to obtain carbon nanotube woven film (CNWF@VTMS) grafted with CH2CH group. A series of novel self‐supporting composite electrode materials (CNWF@VTMS/PANI) for supercapacitors were then prepared by in‐situ chemical oxidative polymerization of aniline in the presence of the CNWF@VTMS film substrate as a conductive network framework. The results showed that CNWF@VTMS/PANI14 flexible electrode with grape‐clustered structure exhibited the highest specific capacitance of 531.3 F/g and the highest energy density of 26.5 Wh/kg at the current density of 1 A/g. It could maintain 75.1% of the initial value at a high current density of 10 A/g. The excellent electrochemical cycle and the structural stability have been confirmed on the condition of the higher capacitance retention of 96.6% after 2000 times of galvanostatic charge/discharge, and the almost unchanged electrochemical performances after 300 times of bending and twisting. Meanwhile, the stronger interfacial bonding between CNWF and PANI endowed a higher tensile strength of 129.2 MPa. In this article, CNWF@VTMS/PANI14 composite electrode could be a potential application in the field of deformable supercapacitors.

Recent Development of Polyaniline/graphene Composite Electrodes for Flexible Supercapacitor Devices

AbstractFlexible supercapacitors are attracting interest in wearable technologies as they can withstand mechanical deformations while delivering their energy storage function. Among frequently investigated electrode materials for flexible supercapacitors, polyaniline/graphene composites are favorable due to their synergistic properties that assure excellent specific capacitance, cycling stability, and high rate capability. This review highlights recent strategies to advance structural designs and synthesis methods of polyaniline/graphene electrodes for flexible supercapacitors. Firstly, the general mechanism and feature of the flexible supercapacitor will be discussed, followed by current challenges that focus on two key aspects, structural design and synthesis of the electrode. Next, by sorting the composites based on their morphological dimensionalities (i. e., one‐, two‐, and three‐dimensional), and focusing the discussion on the two key aspects, we evaluate recent and effective strategies to develop flexible supercapacitors with polyaniline/graphene composite electrode. Finally, future perspectives are given for broader applications of the flexible supercapacitors.

High Capacitive Antimonene/CNT/PANI Free‐Standing Electrodes for Flexible Supercapacitor Engaged with Self‐Healing Function

In virtue of the high electrochemical activity and inherent flexibility, polyaniline (PANI) is an ideal electrode material for flexible supercapacitors (SCs). However, in practical applications, the inevitable agglomeration of PANI leads to low capacitance, poor rate performance, and cycling stability. Here, antimonene (Sb) nanosheets with ultrathin thickness, excellent mechanical strength, and flexibility are introduced into the carbon nanotube (CNT) framework for PANI electrodeposition via simple vacuum filtration, which enables the continuous and uniform growth of PANI. The resultant free-standing Sb/CNT/PANI electrode can thus exhibit a high specific capacitance of 578.57Fg-1 together with a high rate capability. Besides, thanks to the introduction of Sb nanosheets, the agglomeration of PANI during the electrodeposition is improved, which correspondingly alleviates the structural deterioration of PANI during repeated charge/discharge. Thus, the flexible SC assembled by Sb/CNT/PANI electrodes demonstrates both an impressive specific capacitance of 416Fg-1 and outstanding cycling stability over 12000 cycles. Moreover, this SC device can have a practical self-healing function by employing self-healable polyurethane. The facile strategy reported herein sheds light on the design of high-performance flexible SCs, catering to the needs of portable and wearable electronics.

Fluorinated Transition Metal Carbides for Flexible Supercapacitors

The mixed, hexagonal, layered carbides and nitrides known as the MAX phases are utilized in diverse electrochemical devices, in similar ways as graphite is used. Fluorinated graphite shows significantly improved electrochemical energy storage performance when compared to graphite, and while the carbides MAX phases are extensively studied, fluorine-doped MAX phases are yet to be examined. Herein, a series of fluorinated MAX phase materials suitable as a viable electrode material for flexible supercapacitors (FSCs) were prepared by using a fluorination route. The insertion of fluorine as a heteroatom into the MAX phase structures leads to a significant improvement of their structural, wettability, and electrochemical properties. Various electrochemical and morphological characterizations were performed to investigate the influence of various metal (M) elements (e.g., Ti, Ta, V, Cr, and Mo) on the fluorinated MAX phase electrodes. Moreover, the electrochemical outcomes demonstrate that the fluorinated materials effectively increase the capacitance and power density of the electrodes, and the fundamental concepts are established. As a proof concept, supremely FSCs were utilized as a portable power source for powering a digital timer.

Metal-organic framework-derived walnut-like hierarchical Co-O-nanosheets as an advanced binder-free electrode material for flexible supercapacitor

Cobalt-based nanostructured are favorite pseudocapacitive electrode materials for supercapacitors (SCs) due to the low cost and high theoretical capacitance. However, their unsatisfied electrochemical stability severely limits them for practical applications. In this work, metal-organic framework (MOF) derived cobalt oxide (Co-O) hierarchical walnut-like nanosheets supported on carbon fiber cloth (CFC) (denoted as Co-O-NSs@CFC) as a binder-free electrode material was synthesized via scalable and facile hydrothermal method. Results exhibited that the Co-O-NSs@CFC showed crystalline and porous features with high surface area and can be utilized as cathode material for high-performance supercapacitors. The Co-O-NSs@CFC demonstrated excellent charge storage performance with balanced capacitive/diffusion-type charge storage (54% capacitive at 1 mV/s) and achieved 842 F/g (421 C/g) at 1 A/g with outstanding cycling stability of 96.4% till 10,000 cycles. Furthermore, a flexible asymmetric SC was assembled using activated carbon as anode and Co-O-NSs@CFC as a cathode with PVA/KOH as electrolyte (denoted as f-Co-O-NSs@CFC||AC). The f-Co-O-NSs@CFC||AC delivers a high specific capacitance of 178 F/g at 1.5 A/g, excellent energy density of 55.7 Wh/kg at a power density of 1125.9 W/kg with outstanding capacitance retention of 94.5% after 5000 cycles with stable flexible performance. This work shows a remarkable electrochemical performance that could offer high-energy-density electrode materials for flexible SCs.

Facile Synthesis and Characterization of the Mn-MOF Electrode Material for Flexible Supercapacitors

Abstract Metal-organic frameworks (MOFs) due to their porosity and well-defined structures are considered to be very promising electrode materials for the construction of high-performance supercapacitor (SC). In this paper, manganese-based metal-organic framework (Mn-MOF) were prepared on the surface of carbon cloth (CC) by a facile hydrothermal method. The morphology and structure of the electrode material were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Its electrochemical studies show that the Mn-MOF electrode materials exhibit lower charge transfer resistance, the excellent specific capacitance of 433.5 mF/cm2 in 1.0 M Na2SO4 aqueous solution at the current density of 0.8 mA/cm2. It is noteworthy that the flexible electrode have excellent cycle stability and 105% capacitance retention even after 5000 cycles at a current density of 5 mA/cm2. The excellent electrochemical performance of Mn-MOF/CC flexible electrode materials can be attributed to its three-dimensional porous structure.

Conductive PEDOT:PSS/cellulose nanofibril paper electrodes for flexible supercapacitors with superior areal capacitance and cycling stability

PEDOT:PSS has been widely used as the electrode materials for supercapacitors. However, processing PEDOT:PSS bulk films with good flexibility and mechanical stability is still challenging. The present study is aimed at providing a facile and low-cost strategy for the preparation of mechanically strong and conductive PEDOT:PSS based bulk films by using Cellulose nanofibrils (CNF) as building blocks. PEDOT:PSS/CNF suspension was firstly prepared via a simple in situ polymerization process. Afterwards, flexible and conductive PEDOT:PSS/CNF nanopaper (PEDOT:PSS/CNP) were prepared from the PEDOT:PSS/CNF suspension by vacuum filtration and Dimethyl sulfoxide (DMSO) post-treatment. Results showed that the optimized PEDOT:PSS/CNP exhibited excellent flexibility, high tensile strength (72 MPa), and high electrical conductivity (66.67 S/cm). Finally, a symmetric supercapacitor was assembled using the PEDOT:PSS/CNP as electrodes. The assembled supercapacitor could deliver the maximum areal specific capacitance of 854.4 mF cm−2 (corresponding to 122.1F cm−3) at 5 mV/s and offer the highest areal energy density of 30.86 μWh cm−2 (corresponding to 4.41 mWh cm−3), which are among the highest values reported for PEDOT:PSS based supercapacitors. More importantly, the assembled supercapacitor showed remarkable cycling stability with the capacitance retention of 95.8% after 10,000 charge/discharge cycles. Considering the good mechanical properties and excellent electrochemical performance, the PEDOT:PSS/CNP could be a promising electrode material for flexible supercapacitors.