Flexible Electrode For High-performance Supercapacitors Research Articles

Boosting gravimetric and volumetric energy density via engineering macroporous MXene films for supercapacitors

The new family of 2D MXene materials has garnered considerable interest for future energy storage. However, the sluggish ionic kinetics within the compact and dense MXene films are still the fundamental limitation to their electrochemical performance. Here, flexible and free-standing macroporous MXene thin films were fabricated by a facile strategy of incorporating polystyrene (PS) microspheres of various sizes as soft sacrificial templates, followed by calcination. The obtained material possesses high macroporosity with three-dimensional interconnected porous channels to promote electron transport within the electrode and to facilitate electrolyte accessibility without significantly affecting the density of the MXene films. Through appropriate engineering design and optimization, the modified macroporous MXene films could not only achieve a high gravimetric capacitance of 506 F g−1 and a volumetric value of 759 F cm−3 at a current density of 0.5 A g−1, but also delivers a satisfactory gravimetric capacitance of 380 F g−1 under a high current density of 20 A g−1. Furthermore, the assembled symmetric supercapacitor demonstrates a gravimetric energy density of 9.65 Wh kg−1 and a volumetric energy density of 15.1 Wh L−1 at a power density of 67.5 W L−1, illustrating its great potential as a flexible electrode for high-performance supercapacitors.

Free-Standing and Heteroatoms-Doped Carbon Nanofiber Networks as a Binder-Free Flexible Electrode for High-Performance Supercapacitors.

Flexible and heteroatoms-doped (N, O and P) activated carbon nanofiber networks (ACFNs) have been successfully prepared with a mixture of polyamic acid (PAA) and poly(diaryloxyphosphazene) (PDPP) as a solution through electrospinning, followed by a heat post-treatment. The resultant heteroatoms-doped ACFNs can be used as binder-free electrodes for high-performance flexible supercapacitors (SCs) due to lightweight, three-dimensional open-pore structure and good mechanical strength. Despite its surface area being lower than 130.6 m2·g−1, the heteroatoms-doped ACFNs exhibited a high heteroatoms (N, O and P) content of 17.9%, resulting in a highly specific capacitance of 182 F·g−1 at a current density of 1 A·g−1 in 6 M KOH electrolyte in a two-electrode cell and an excellent rate capability of 74.7% of its initial capacitance from 1 A·g−1 to 10 A·g−1 under the mass loading of 1.5 mg·cm−2. The electrical double-layer (EDL) capacitance and pseudocapacitance can be easily decoupled in the heteroatoms-doped mesoporous ACFNs. SCs device based on heteroatoms-doped ACFNs exhibited a high energy density of 6.3 W·h·kg−1 with a power density of 250 W·kg−1, as well as excellent cycling stability with 88% capacitance retention after 10,000 charge–discharge cycles. The excellent electrochemical performance was attributed to the mesoporous structure of ACFNs and pseudocapacitive heteroatoms.

MXene-Bonded Activated Carbon as a Flexible Electrode for High-Performance Supercapacitors

We report a strategy to employ two-dimensional Ti3C2Tx MXene as a flexible, conductive, and electrochemically active binder for one-step fabrication of MXene-bonded activated carbon as a flexible electrode for supercapacitors in an organic electrolyte. In this electrode, the activated carbon particles are encapsulated between the MXene layers, eliminating the need for insulative polymer binders. MXene plays a multifunctional role in the electrode, including as a binder, a flexible backbone, a conductive additive, and an additional active material. The synergetic effect of MXene and activated carbon constructs a three-dimensional conductive network and enlarges the distance between the MXene layers, greatly enhancing the electrode capacitance and rate capability. As a result, the flexible MXene-bonded activated carbon electrode exhibits a high capacitance of 126 F g–1 at 0.1 A g–1 and a retention of 57.9% at 100 A g–1 in an organic electrolyte, which is required for developing high-performance, flexible su...

Flexible Fe3O4@Carbon Nanofibers Hierarchically Assembled with MnO2 Particles for High-Performance Supercapacitor Electrodes

Increasing use of wearable electronic devices have resulted in enhanced demand for highly flexible supercapacitor electrodes with superior electrochemical performance. In this study, flexible composite membranes with electrosprayed MnO2 particles uniformly anchored on Fe3O4 doped electrospun carbon nanofibers (Fe3O4@CNFMn) have been prepared as flexible electrodes for high-performance supercapacitors. The interconnected porous beaded structure ensures free movement of electrolyte within the composite membranes, therefore, the developed supercapacitor electrodes not only offer high specific capacitance of ~306 F/g, but also exhibit good capacitance retention of ~85% after 2000 cycles, which certify that the synthesized electrodes offer high and stable electrochemical performance. Additionally, the supercapacitors fabricated from our developed electrodes well maintain their performance under flexural stress and exhibit a very minute change in specific capacitance even up to 180° bending angle. The developed electrode fabrication strategy integrating electrospinning and electrospray techniques paves new insights into the development of potential functional nanofibrous materials for light weight and flexible wearable supercapacitors.

Electrodeposited NiSe2 on carbon fiber cloth as a flexible electrode for high-performance supercapacitors

A flexible electrode of nickel diselenide/carbon fiber cloth (NiSe2/CFC) is fabricated at room temperature by a simple and efficient electrodeposition method. Owing to NiSe2 character of nanostructure and high conductivity, the as-synthesized electrodes possess perfect pseudocapacitive property with high specific capacitance and excellent rate capability. In three-electrode system, the electrode specific capacitance of the NiSe2/CFC electrode varies from 1058 F g–1 to 996.3 F g–1 at 2 A g–1 to 10 A g–1 respectively, which shows great rate capability. Moreover, the NiSe2 electrode is assembled with an active carbon (AC) electrode to form an asymmetric supercapacitor with an extended potential window of 1.6 V. The asymmetric supercapacitor possesses an excellent energy density 32.7 Wh kg–1 with a power density 800 W kg–1 at the current density of 1 A g–1. The nanosheet array on carbon fiber cloth with high flexibility, specific capacitance and rate capacitance render the NiSe2 to be regarded as the promising material for the high performance superconductor.

Facile fabrication of ultrathin hybrid membrane for highly flexible supercapacitors via in-situ phase separation of polyethersulfone

Abstract In this article, a facile method based on in-situ phase-separation was developed for the fabrication of ultrathin hybrid membranes for highly flexible supercapacitors. The structures and morphologies of the prepared electrodes were characterized by scanning electron microscopy (SEM), Fourier-transformed infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) measurements; and the electrochemical behaviors were examined in 2 M KOH solution. SEM and FTIR characterizations reveal that activated carbon was imbedded into the polymer membrane of polyethersulfone to form a uniform and flexible hybrid membrane. When the thin polymer-carbon membrane (PCM) was used as an electrode material for supercapacitor, a high specific capacitance of 169.4 Fg −1 was obtained at a current density of 0.5 Ag −1 along with good long-term cycle life of 94.6% capacity retention after 2000 charging-discharging cycles. Benefiting from these merits, the as-fabricated PCM//PCM cell shows an excellent electrochemical property. These results suggest a promising route towards the fabrication of highly flexible electrodes for high-performance supercapacitors.

Designing binder-free, flexible electrodes for high-performance supercapacitors based on pristine carbon nano-onions and their composite with CuO nanoparticles

Binder-free flexible CNO–CuO composite electrodes delivering an energy density of 58.33 W h kg−1 at less than 1 $.

Assembly of porous NiO nanowires on carbon cloth as a flexible electrode for high-performance supercapacitors

Porous NiO nanowire layers were deposited on conductive carbon cloth and are used as flexible electrodes for high performance supercapacitors.

Potentiostatically synthesized flexible polypyrrole/multi-wall carbon nanotube/cotton fabric electrodes for supercapacitors

A polypyrrole (PPy)/multi-walled carbon nanotube (MWCNT)/cotton flexible electrode for high-performance supercapacitors was fabricated by a facile two-step method, including MWCNT-coated cotton prepared by a facile “dip and dry” method and then subjected to the electro-deposition of PPy by a potentiostatic deposition technique. The effects of deposition potential, time, and molar ratio of p-toluenesulfonic acid to pyrrole (Py) on the properties of textile electrodes were studied. The sheet resistances and surface morphologies of the as-prepared composite fabrics obtained under different conditions were investigated by means of a four-point probe method and field-emission scanning electron microscope and the electrochemical performances of the PPy/MWCNT/cotton electrodes were evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy measurements. These composite fabrics exhibited outstanding flexibility, high conductivity, with sheet resistance of 6.0 ± 0.4 Ω sq−1, a cauliflower structure with small holes on the surface favoring the contact between the electrode active material, a specific capacitance of 535 F g−1 (maintaining 97.8 % after 100 cycles), and a fitting value of charge-transfer resistance of 13.9 Ω cm−2, which offers great promise in wearable energy storage device applications because of their low-cost and high-performance features.

Nickel oxide grown on carbon nanotubes/carbon fiber paper by electrodeposition as flexible electrode for high-performance supercapacitors

Carbon nanotubes (CNTs) grown on the carbon fiber paper (CFP) via chemical vapor deposition system is used as flexible substrate. NiO nanoparticles are electrodeposited onto CNTs/CFP flexible substrate by electrochemical deposition technique, which is used as a flexible electrode for supercapacitors. The NiO@CNTs/CFP electrode displays specific capacitance as high as 1317 F g−1 at a current density of 1.2 A g−1, which can preserve a capacitance retention of 90.6 % with a high current density of 9.6 A g−1. After 3000 cycles, the composite electrode can retain 90 % of initial capacitance, showing good cyclability. Meanwhile, the 3D porous nanostructure of NiO@CNTs/CFP electrode can offer a great opportunity to fabricate a high-performance flexible binder-free supercapacitor electrode, in which all of the materials could take part in the charge-storage process with their surface in direct contact with the electrolyte.

Flexible free-standing 3D porous N-doped graphene–carbon nanotube hybrid paper for high-performance supercapacitors

Free-standing 3D porous N-doped graphene–CNT hybrid paper has been synthesized, which can be used as flexible electrodes for high-performance supercapacitors.