High-performance Flexible Supercapacitors Research Articles

High performance flexible supercapacitor based on metal-organic-framework derived CoSe2 nanosheets on carbon nanotube film

The manufacture of high-performance wearable supercapacitors (SCs) requires a new class of flexible electrodes with both high conductivity and high mechanical stability. Herein, we report a simple and efficient strategy to design novel CoSe2 two-dimensional nanosheets on carbon nanotube (CNT) films derived from Co-based Metal-Organic Frameworks (MOFs) via an in situ approach. The density functional theory (DFT) simulations show the higher conductivity of the CoSe2/CNT electrode than the Co3O4/CNT electrode. Due to the synergistic properties of self-supported two-dimensional CoSe2 nanosheets and the high pathway of one-dimensional (1D) CNTs, the nanocomposite electrode provides efficient transmission and short paths for electron/ion diffusion. A flexible asymmetric SC (ASC) assembled from the CoSe2 nanosheet positive electrode and FeSe2 nanorod negative electrode delivers high areal energy density of 0.25 mW h cm−2, superior mechanical stability and long lifespan. In addition, the flexible ASC device can power the CoSe2//CNT-based photodetector to generate fast and stable responses to light irradiation with different wavelengths, indicating the excellent practical application performance of flexible ASCs.

Enhanced pseudocapacitive performance of MoS2 by introduction of both N-GQDs and HCNT for flexible supercapacitors

In this work, we report a strategy for enhancing the pseudocapacitive performance of MoS2 materials by the introduction of nitrogen-doped graphene quantum dots (N-GQDs) and helical carbon tubes (HCNT). By a simple hydrothermal process, the hybrid composite (MoS2, N-GQDs and HCNT) were coated on the carbon cloth (CC) without any binders, which can be directly used as advanced electrode material for high-performance solid-state flexible supercapacitors. In this hybrid structure, N-GQDs are inserted between the layers of MoS2 nanosheets, which induce and expose more active sites for pseudocapacitance contributions in MoS2 electrode materials. Meanwhile, HCNT acts as electrically conducting bridge for enhancing the electrical conductivity of MoS2 nanosheets and speeding up transport of electronic. As results, the hybrid composite (MoS2, N-GQDs and HCNT) show higher capacitive performance than pure MoS2. The specific capacitance of hybrid composite is high up to 3360 mF cm−2. Further, the assembled solid-state flexible supercapacitor shows high specific capacitance of 1893 mF cm−2, outstanding cycle life (capacitance retention of 86% after 2500 cycles), good mechanical stability and great flexibility. Our work provides a reference for the preparation of MoS2 composites with high supercapacitive performance.

Nacre-inspired composite films with high mechanical strength constructed from MXenes and wood-inspired hydrothermal cellulose-based nanofibers for high performance flexible supercapacitors.

Two dimensional MXenes with fascinating characteristics of high electrical conductivity, high density and electroactivity show promising applications in various fields. However, the direct applications of MXenes have been limited due to their inferior mechanical properties and easy restacking. Herein, a kind of nacre-like composite film constructed with Ti3C2Tx, cellulose nanofiber (HCNF) and sodium lignosulfonate (Lig) obtained through the hydrothermal process, named Ti3C2Tx/HCNF@Lig, has been successfully synthesized. The hydrothermal cellulose nanofiber (HCNF) film shows an enhanced mechanical strength (114 MPa) compared to that of the CNF film (95 MPa). Wood-inspired HCNF@Lig composite films present an enhanced mechanical tensile strength of up to 133 MPa. Nacre-like deformable Ti3C2Tx/HCNF@Lig(3@1) composite films exhibit high conductivity (up to 1.75 × 105 S m-1) and mechanical properties (up to 258 MPa). The electrodes of Ti3C2Tx/HCNF@Lig(3@1)97/3 composite film assembled flexible solid-state supercapacitors possess an excellent volumetric specific capacitance of 748.96 F cm-3. The corresponding deformable supercapacitors show an excellent energy density of 16.2 W h L-1 and outstanding electrochemical cycling stability. The as-prepared nacre-like Ti3C2Tx/HCNF@Lig composite films with high mechanical properties and electrochemical performance are expected to be practically applied in flexible/wearable energy storage devices.

Realizing high performance flexible supercapacitors by electrode modification.

It is well known that the structure of an electrode material seriously affects its electrochemical performance. In this study, we prepare hybrid structured NiCo2S4@PPy nanoarchitectures by a hydrothermal method and subsequent electrodeposition process. The specific capacitance of the obtained sample is 1733.23 C g−1 at 1 A g−1. The assembled asymmetric device presents an energy density of 59.59 W h kg−1 at 1404.04 W kg−1. The excellent electrochemical performance can be attributed to the synergistic effect between the high theoretical specific capacitance of the NiCo2S4 sheets and the superior cycling stability of the PPy film. The device also shows an outstanding mechanical flexibility at different bending angles.

Flexible free-standing Ni-Mn oxide antenna decorated CNT/nanofiber membrane for high-volumetric capacitance supercapacitors.

There is growing demand for lightweight flexible supercapacitors with high electrochemical performance for wearable and portable electronics. Here, we spun nanoparticles of nickel-manganese oxides along with carbon nanotubes into carbon nanofibers and engineered a 3D networked Ni-Mn oxides/CNT@CNF free-standing membrane for flexible supercapacitor applications. The electrospinning process controlled the nanoparticle aggregation while subsequent heat treatment generates nanochannels in the fibres, resulting in a very porous tubular nanocomposite structure. The preparation process also enabled good interfacial contact between the nanoparticles and the conductive carbon network. The resulting Ni-Mn oxides/CNT@CNF membrane displays high mass loading (Ni-Mn oxides) of 855 mg cm-3 and low CNT incorporation of ∼0.4%. The outstanding porous structure, synergy of the carbon with Ni-Mn oxides, and fast and facile faradaic reactions on the electrode were responsible for the superior volumetric capacitance of 250 F cm-3 at 1 A cm-3, energy density as high as 22 mW h cm-3 and an excellent power density of 12 W cm-3. Despite the low CNT loading, the hybrid electrode exhibits excellent cycling performance with capacitance retention of 96.4% after 10 000 cycles evidencing a well-preserved Ni-manganese oxide nanostructure throughout the cycling. The resulting outstanding electrochemical performances of the Ni-Mn oxides/CNT@CNF synergic system offer new insights into effective utilization of transition metal oxides for establishing high-performance flexible supercapacitors within a confined volume.

MoS2/cellulose paper coupled with SnS2 quantum dots as 2D/0D electrode for high-performance flexible supercapacitor

The effective incorporation of novel and highly conductive hybrid functional nanomaterials onto flexible and porous substrates is extremely desirable to develop flexible supercapacitors.

Thermal effect on the pseudocapacitive behavior of high-performance flexible supercapacitors based on polypyrrole-decorated carbon cloth electrodes

The electrochemical performance of flexible CC/PPy supercapacitors was systematically investigated at various surrounding temperatures.

Highly Efficient Polyaniline Trapping and Covalent Grafting within a Three-Dimensional Porous Graphene Oxide/Helical Carbon Nanotube Skeleton for High-Performance Flexible Supercapacitors

Optimizing the electrode structure to achieve efficient material utilization is crucial for high-capacity wearable energy storage devices. Here, a strategy of embedding and covalently grafting poly...

Design and fabrication of high performance flexible supercapacitor with polypyrrole@carbon fiber yarn electrode and redox active dopants

The flexible fiber-shaped electrodes that polypyrrole (PPy) and hydroquinone (HQ) derivatives coated on the surface of carbon fiber yarn (CFY) were synthesized by a simple one-step electrosynthesis. Besides, the effects of the size and structure of the HQ derivatives on the electrochemical performance of the doped PPy@CFY electrodes were analyzed. The study suggested that sodium lignosulfonate doped PPy@CFY (LS-PPy@CFY) exhibited a high specific capacitance of 245.89 F cm−3 at 0.26 A cm−3. The all-solid-state flexible fiber-shaped supercapacitor (AFFSC) based on two parallel LS-PPy@CFY electrodes showed a high specific capacitance of 50.08 F cm−3 and an excellent energy density of 4.45 mW h cm−3. Moreover, the AFFSC achieved prominent cyclic stability, maintaining 92.7% capacitance retention after 25,000 cycles, as well as excellent flexibility and mechanical stability which kept 89% capacitance retention after 5000 bending cycles. In addition, the AFFSC also exhibited good voltage and current scalability and potentiality in its practical application.

Amorphous MoS nanoparticles grown on cobalt-iron-based needle-like array for high-performance flexible asymmetric supercapacitor

Although flexible supercapacitors have important applications, the development of high-performance flexible supercapacitors still remains a critical challenge owing to the low ion diffusion rate, poor electro-conductivity, and limited active defect sites. Herein, we report the first amorphous MoSx nanoparticles grown on crystalline FeCo-based nanoneedles ([email protected]) via an ethylene glycol-induced strategy. The [email protected] electrode presents an unprecedented specific capacitance of 1956 F g−1 at 1 A g−1 and over 91.1% of capacitance retention even after 6000 cycles because of the unique morphology, the rich defect sites, the high carrier concentration. The [email protected]//AC asymmetric supercapacitor delivers an ultrahigh specific capacitance of 282 F g−1 at 1 A g−1 and an excellent energy density of 88.09 Wh kg−1 along with a power density of 750 W kg−1. And the self-assembled flexible all-solid-state supercapacitor device can be easily bent and twisted with negligible electrochemical properties attenuation.

MXene-Based Flexible Supercapacitors: Influence of an Organic Ionic Conductor Electrolyte on the Performance.

Owing to the rise of miniaturized wearable electronic devices in the last decade, significant demands have arisen to obtain high-performance flexible supercapacitors (FSCs). Recently, a lot of research has been focused on developing smart components of FSCs and integrating them into new device configurations. In this work, FSCs based on a Ti3C2 nanosheet (NS) and an organic ionic conductor (OIC)-induced hydrogel as the electrode and the electrolyte, respectively, were used. The FSCs fabricated have three different configurations (sandwich, twisted fiber, and interdigitated) and a comparative study of their electrochemical performance was investigated in terms of cycle stability, bending stability, power density, and energy density. Finally, the experimental validation of practical application was conducted, which suggested excellent electrochemical stability of Ti3C2 NS FSCs for driven commercial electronic gadgets. This study presents mechanically robust, lightweight, high-performance FSCs, which can be assembled in different configurations for powering wearable electronic devices.

A high performance flexible solid-state asymmetric supercapacitor based on composite of reduced graphene oxide@dysprosium sulfide nanosheets and manganese oxide nanospheres

The reduced graphene oxide@dysprosium sulfide (rGO@Dy2S3) composite and MnO2 films are synthesized using successive ionic layer adsorption and reaction and from chemical bath deposition methods, respectively. Addition of rGO in Dy2S3 film enhances specific surface area from 40 to 78 m2g-1. Using these films flexible solid-state symmetric; rGO@Dy2S3//Dy2S3@rGO and asymmetric; MnO2//Dy2S3@rGO supercapacitor devices are fabricated. The solid-state asymmetric supercapacitor device exhibits specific energy of 41 Wh kg−1 at specific power 1330 W kg−1. The stability of asymmetric supercapacitor is 86% after 5000 cycles and flexibility of 82% at the bending angle 165°. This work highlights the first time use of rGO@Dy2S3 composite thin film material to fabricate symmetric and asymmetric supercapacitor devices and also demonstrates the superior performance of asymmetric device than symmetric one.

Hierarchical self-supporting sugar gourd-shape MOF-derived NiCo2O4 hollow nanocages@SiC nanowires for high-performance flexible hybrid supercapacitors

Rational construction of hierarchical electrode materials has been a research hotspot in the field of energy storage. In this work, metal–organic framework (MOF) derived hollow NiCo2O4 nanocages (NCs) were strung by interwoven SiC nanowires (NWs) network on carbon cloth (CC), forming a unique sugar gourd-like core–shell architecture, which were fabricated via a multi-step process containing of chemical vapor deposition, solution reaction of MOF templates, ion exchanging/etching and subsequent heat treatment. Benefiting from the unique structural advantages, such as hierarchical porous structure with abundant active sites for electrochemical reactions and interwoven conductive networks for electron transport, the formed core-shelled CC/SiCNWs@NiCo2O4NCs as a binder supercapacitor electrode exhibits excellent electrochemical performance with a large specific capacitance (1377.6F g−1 at a current density of 1 A g−1), good rate capability (68.8% capacitance retention at 20 A g−1) and excellent cycling stability (88.3% capacitance retention after 6000 cycles). Furthermore, the hybrid supercapacitor based on CC/SiCNWs@NiCo2O4NCs and activated carbon, not only delivers a high energy density of 46.58 Wh kg−1 at the power density of 800 W kg−1, but also possesses good flexibility with high capacitance retention, exhibiting the application potential in the field of flexible energy storage. More importantly, our work gives a new thinking for structural design of SiCNWs-based and MOF-based electrode materials for high-performance flexible energy storage.

In Situ Growth of 2D Ultrathin NiCo2 O4 Nanosheet Arrays on Ni Foam for High Performance and Flexible Solid-State Supercapacitors.

In order to further overcome the shortage of electrodes with additive/binder and modulate the structure of NiCo2 O4 for supercapacitors, ultrathin NiCo2 O4 nanosheet arrays have been in situ grown on Ni foam by optimizing hydrothermal reactions based on crystal growth dynamics. The structure of ultrathin NiCo2 O4 nanosheet arrays can expose more active sites, provide abundant diffusion channels and buffer the stress caused by phase transition during charge-discharge process of supercapacitors. The optimized hydrothermal reactions can provide more ordered crystal orientations by keeping nanosheets on Ni foam completely coming from in situ growth, which will decrease the inner resistance of ultrathin NiCo2 O4 nanosheets and improve the efficiency and kinetics of electrons transfer. By the virtue of such remarkable features, the electrochemical results confirm the rationality of structural modulation and crystal orientations optimization with a drastically enhanced specific capacitance of 2017.8 F g-1 , admirable rate performance of 93.2% and outstanding stability retention of 90.9% after cycling 5000 times. More impressively, the assembled flexible solid-state asymmetric supercapacitor (ASC) shows superior energy density, power density, and high stability. The modification strategy in this paper may throw light on the rational design of new generation advanced electrode materials for high-performance flexible supercapacitors.

Facile co-deposition of the carbon nanotube@MnO2 heterostructure for high-performance flexible supercapacitors

Herein, a facile co-deposition method is developed to synthesize carbon nanotube (CNT)@MnO2 heterostructures grown on carbon fibre paper (CFP) and flexible carbon fibre cloth (CFC) (denoted as CNT@MnO2/CFP and CNT@MnO2/CFC, respectively). A three-dimensional (3D) interconnected CNT network of highly conductive, ultrathin CNT@MnO2 heterostructure nanosheets with a nanoporous structure and with epitaxial growth of MnO2 on the CNTs achieves excellent capacitance performance for flexible MnO2-based supercapacitor materials. The CNT@MnO2/CFP fabricated in an electrolyte with CNT content of 0.5 g L−1 (0.5-CNT@MnO2/CFP) obtains mass, area and volume specific capacitance values of 393.0 F g−1, 585.0 mF cm−2 and 29.3 F cm−3, respectively, at a charge-discharge rate of 0.25 A g−1. A flexible asymmetric supercapacitor device was successfully assembled which possesses a high energy density of 27.8 Wh kg−1 at a high power density of 250 W kg−1 (0.75 mA cm−2) and a high capacitance retention of 84% after 10,000 performs at a charge-discharge rate of 15 mA cm−2 (5 A g−1). Our work confirmed that this structure can effectively improving the utilization and specific capacitance of MnO2, and the simplicity of the fabrication and the environmentally friendly characteristics of the deposition liquid make this approach suitable for practical production.

Wool textile-derived nitrogen-doped porous carbon cloth for a binder-free electrode material for high-performance flexible solid-state supercapacitors

With the rapid development of portable electronics and wearable devices, flexible solid-state supercapacitor (SC) has recently stimulated wide research interest. Herein, we one-step prepared a nitrogen-doped porous carbon cloth material by directly carbonizing a biomass wool textile without any chemical or physical activation. The obtained wool-derived nitrogen-doped porous carbon cloth (WNPCC) has a microporous structure with a high specific surface area of ~ 500 m2 g−1, as well as superior mechanical property that can be arbitrarily folded. As an electrode material without adding conductive agent and binder, greatly improved electrochemical performance is achieved by the WNPCC in comparison with the commercial carbon cloth and reported flexible SC electrodes. The area specific capacitance of the optimized WNPCC in three-electrode tests is 1012 mF cm−2 (1 mA cm−2), and meanwhile, an excellent durability at 90° bent state is proved. The PVA/H2SO4-based SC shows energy density of 76.6 µWh cm−2 at a power density of 0.60 mW cm−2 and retains 55 µWh cm−2 even at a high power density of 6.73 mW cm−2 with a wide voltage window of 1.4 V. More importantly, the specific capacitance value does not evidently decline when bending the SC device to various degrees in 2000 runs. This work provides a facile route to prepare flexible electrode material using sustainable biomass precursor, which not only is directly used as electrode for all-solid-state SCs, but also can act as the flexible conductive supporter for battery or electrocatalysis applications.

Synthesis of a Three-Dimensional Interconnected Oxygen-, Boron-, Nitrogen-, and Phosphorus Tetratomic-Doped Porous Carbon Network as Electrode Material for the Construction of a Superior Flexible Supercapacitor.

To construct a high-performance next-generation carbon-based flexible supercapacitor, high porosity, large mass density, and high flexibility are three significant challenging goals. However, one side always affects another. Herein, high-density tetratomic-doped porous composite carbon derived from sustainable biomaterials is achieved via two-step processes of carbonization and acid-washing treatment. The assembled carbon-based electrodes are highly doped with various heteroatoms (B, O, N, and P) for 33.59 atom %, resulting in abundant porosity, high densities, high pseudocapacitive contribution for 84.5%, and superior volumetric capacitive performance. The fabricated flexible electrode exhibits high flexibility, high mass loading (316 mg cm-3), and remarkable tensile strength (44.6 MPa). Generally, the volumetric performance is key and a significant parameter to appraise the electrochemical characteristics of flexible supercapacitors within a limited space. The aqueous symmetric supercapacitor demonstrates a high volumetric energy density and an excellent power density of 2.08 mWh cm-3 and 498.4 mW cm-3, respectively, along with 99.6% capacitance retention after 20 000 cycles, making it competitive to even some pseudocapacitors.

Preparation and properties of polypyrrole/polyamide 6 nanocomposite film with core-shell architecture for the high-performance flexible supercapacitor

Herein, the flexible and highly conductive polypyrrole/polyamide 6 (PPy/PA 6) nanocomposite film with unique core-shell architecture has been prepared via a facile chemical oxidative polymerization method. By optimizing the parameters included feed ratio, ferric ions concentration and reaction time, the PPy coating was observed to in-situ growth on the electrospun PA 6 nanofiber surface, leading to a thick shell layer and maximum conductivity of 78.2 S cm−1. Furthermore, the all-solid-state symmetric supercapacitor is assembled, exhibiting high specific capacitance (760 mF cm−2), power density (11 W m−2), energy density (0.68 Wh m−2) and cycling stability. Thus, considering the ideal flexible characteristics and excellent electrochemical performance, the fabricated nanocomposite film shows great potential applications in the wearable electronic system especially for high-performance supercapacitor.

Setaria Viridis-Inspired Electrode with Polyaniline Decorated on Porous Heteroatom-Doped Carbon Nanofibers for Flexible Supercapacitors.

Carbon nanofibers are promising as primary electrode materials for supercapacitors on account of high specific surface area, lightweight, superior physicochemical stability, rich resource, and renewability. However, constructing porous and flexible carbon electrode materials with high capacitance for practical applications remains challenging. Here, heteroatom-decorated hierarchical porous carbon nanofiber composites containing phosphazene [N3P3(p-OC6H4-p-CHO)6, HAPCP], polymethyl methacrylate (PMMA), and graphene oxide (GO) are prepared through one-step electrospinning and subsequent thermal treatment. The alternant phosphorus-nitrogen structure links to the carbon backbones to improve flexibility and electrochemical performance. Inspired by a biomimetic Setaria viridis-like structure, the polyaniline (PANI)-decorated porous hybrid electrodes are prepared. The PANI@GO/PMMA/HAPCP/PAN carbon nanofibers (400P@0.1GPHCNFs) covered by PANI nanofibers as a novel free-standing flexible electrode exhibit an excellent electrochemical performance of 680.8 F g-1 at 0.5 A g-1 with a good capacitance retention of 93.5% after 3000 cycles. Moreover, the symmetric flexible all-solid-state supercapacitor assembled by the novel and delicate electrodes exhibits a high energy density of 27.70 W h kg-1 (at a power density of 231.08 W kg-1) and favorable cycling stability (84.50% retention of the capacitance after 1000 charge-discharge cycles), which indicates that the 400P@0.1GPHCNFs have great potential as a high-performance flexible supercapacitor electrode.

Melt Spinning of Low-Cost Activated Carbon Fiber with a Tunable Pore Structure for High-Performance Flexible Supercapacitors

Activated carbon fibers are emerging as one of the most promising electrode for flexible supercapacitors, as they are highly conductive, lightweight, and flexible. However, the high preparation cos...