Flexible Supercapacitor Electrodes Research Articles

Flexible ultracapacitor device fabricated with an organic electrode material- naphthalene diimide nitrile/reduced graphene oxide

In this work, we have demonstrated a high-performance flexible supercapacitor electrode based on reduced graphene oxide (rGO) and naphthalene diimide nitrile (NDI-CN) composite. The rGO/NDI-CN composite was prepared by a simple approach. This composite was well characterized using various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) etc. Besides, the π -π stacking of NDI-CN on rGO surface was confirmed using UV–vis and FTIR techniques. As fabricated rGO/NDI-CN composite was examined as an electrode material for the supercapacitor applications. The rGO/NDI-CN electrode has delivered an excellent specific capacitance (Csp) of 336 F g−1 at 0.5 A g−1current density. The fabricated supercapacitor (SC) displays robustness with 80 % capacitance retention over 10,000 cycles at higher current density of 10 A g−1. To further explore the real-world application of electrode materials, the corresponding flexible supercapacitor was designed and examined. The flexible device exhibited an energy density of 9.54μWh cm−2 at a power density of 0.3 mWcm−2. These results confirmed that the rGO/NDI-CN electrode material has good potential as an energy storage device. Furthermore, the facile construction and fabrication of flexible device displayed operation of LED when fully charged. The assembled flexible supercapacitor device could be bent and twisted, signifying the potential to be used in practical applications in various high-performance electrochemical devices.

Self-supporting electrode for flexible supercapacitors: NiCo-layered double hydroxide derived from metal organic frameworks wrapped on graphene/polyaniline nanotubes@cotton cloth

Nowadays, constructing hetero-structure materials is an efficacious procedure to uplift the electrochemical performance of layered double hydroxide (LDH) materials. The logical design of such elegant nanostructures is still challenging. Herein, NiCo-LDH nanosheets derived from Co-ZIF grown on graphene/polyaniline nanotube (G/PANI-NT)@cotton cloth (CC) was synthesized by a facile and novel two-step strategy for supercapacitors. Such hetero-structures give a 30.63 m2 g−1 surface area and more subjected electrochemical active sites. The supercapacitor performance results exhibit that the NiCo-LDH/G/PANI-NT@CC electrode has the best supercapacitor performance when it is used as a pseudocapacitor. By the ratio of Ni/Co = 2:1 in the precursor solution, the electrode shows an areal specific capacitance of 88.15 mF cm−2 at a current density of 0.075 mA cm−2. The electrochemical performance of the electrodes was perused using a redox-additive electrolyte. The electrochemical performance of the NiCo-LDH/G/PANI-NT@CC electrode was amended using K2S2O8 in a 3 M KOH solution. Considerably, the areal specific capacitance of NiCo-LDH/G/PANI-NT@CC (181.17 mF cm−2) increased to 431.30 mF cm−2, by changing the K2S2O8 concentration in KOH solution at a current density of 0.075 mA cm−2. Long-term stability test demonstrates that 84.05 % of the original capacitance remains after 10,000 cycles at the current density of 0.2 mA cm−2. The results indicate that NiCo-LDH/G/PANI-NT@CC will be an appropriate candidate for high-performance supercapacitors. The NiCo-LDH/G/PANI-NT@CC//NiCo-LDH/G/PANI-NT@CC flexible solid-state supercapacitor was assembled with the PVA/KOH gel electrolyte.

Wet oxidative functionalization of carbon nanotube cloth to boost its performance as a flexible supercapacitor electrode

Electrochemical recharging behavior of a binder-free flexible carbon nanotube cloth (CNTC) material in respect to aqueous supercapacitor applications is reported. To provide high enough pseudocapacitance, the surface of CNTC was exposed to wet oxidative functionalization by a KMnO4 treatment in an acidic medium. We report the effect of a KMnO4 to CNT molar ratio on capacitance, electrical resistivity and specific surface area of the CNTC material. The change in the composition of oxygen-containing interfacial functional groups attached to the carbon surface is also investigated by X-ray photoelectron spectroscopy and temperature-programmed desorption methods. For the most oxidized CNTC sample the capacitance of ca. 71 F g−1 (29 µF cm−2BET) in 0.5 M H2SO4 (slightly decreasing with a scan rate up to 100 mV s−1) with the retention of ca. 99% during 30,000 recharging cycles as well as specific resistivity of ca. 31 µΩ m are achieved. Finally, two flexible symmetric supercapacitor prototypes based on a 38% H2SO4 solution and operating at 1.3 or 1.5 V were assembled from the freestanding and graphite foil supported functionalized CNTC electrodes, respectively. For the former device, the volumetric capacitance of ca. 22 F cm−3, power density of ca. 10 kW l−1 and energy density of ca. 3 Wh l−1 (per total volume of both electrodes) are demonstrated. The issues of the long-term stability and self-discharge behavior of assembled prototypes are also considered. Reported results allow us to consider the functionalized CNTC material as a promising electrode material for flexible aqueous supercapacitors.

Deposition of ZIF-67 and polypyrrole on current collector knitted from carbon nanotube-wrapped polymer yarns as a high-performance electrode for flexible supercapacitors

Polymeric fiber fabrics with inherent mechanical flexibility, lightweight and porous textile structure are highly attractive as an ideal substrate for building flexible electrodes. However, their insulating nature limits their direct application as current collector. Here, we designed and fabricated a flexible conductive fabric from polymer yarns. This was achieved through wrapping polymer yarns with a carbon nanotube (CNT) cylinder, which was continuously prepared from a floating catalyst chemical vapor deposition process, and a subsequent knitting process. The derived CNT-wrapped polymer yarn fabric (CPYF) could directly serve as current collector/substrate to load zeolitic imidazolate framework-67 (ZIF-67) and polypyrrole (PPy) through in-situ growth and chemical polymerization. The resultant CPYF-ZIF-67-PPy displayed a maximum areal capacitance of 2308.8 mF cm−2 at 0.5 mA cm−2. Moreover, the assembled supercapacitor achieved a maximum areal energy density of 112 μW h cm−2 at the power density of 201.5 μW cm−2. Meanwhile, the device demonstrated an extraordinary flexibility with stable electrochemical properties after 5000 cycles of bending and 1000 cycles of stretching. This work therefore offers a new strategy that can be used to develop flexible conductive fabric for flexible supercapacitors.

Coffee waste-derived porous carbon based flexible supercapacitors

Nitrogen doped porous activated carbon was synthesized from coffee waste for flexible supercapacitor applications. Nitrogen of 8.0 at% was doped, and specific capacitance of 139F g−1 at 0.5 A/g with specific energy of 12.5 Wh kg−1 and specific power of 202 W kg−1 was obtained for flexible supercapacitors. Eventually, high specific capacitance retention (90.5 %) as well as high coulombic efficiency (84.5 %) after 5,000 cycles with reliable flexibility were shown. The results demonstrated that the synthesized nitrogen-doped coffee waste derived carbon electrode could be used for the flexible supercapacitor electrodes.

Copper oxide stabilized oxy-functionalized boron nitride‑carbon nanotube nanohybrid: An ultra-stable electrode for flexible asymmetric supercapacitor device in ionic electrolyte

This work explores the smart combination of functionalized boron nitride (mK-BN) and carbon nanotube (CNT), stabilized with copper oxide (CuO), as a highly stable, flexible supercapacitor electrode in low-cost viable ionic electrolyte. Oxy-surface modified boron nitride (BN) was introduced to induce supplementary acceptor and donor energy levels for charge transport. Incorporation of CNT facilitated the charge storage through EDLC mechanism and also reduced internal resistance. In three-electrode analysis, CuO/mK-BN/CNT nanohybrid exhibited specific capacitance (Csp) of 425 F/g in aqueous KCl. An asymmetric supercapacitor (ASC) device using CuO/mK-BN/CNT as cathode achieved a Csp of 80 F/g and 36 Wh/kg energy density with ⁓88 % stability after 25,000 charging-discharging cycles in organic electrolyte. To further boost the capacitive performance, energy density, and rate capability of the ASC device, a low-cost, solvent free, and viable ionic electrolyte [(NEt3H)+(HSO4)−] was introduced. In ionic electrolyte, device showed a maximum Csp of 132 F/g with an enhanced energy density of 59.4 W h/kg. ASC devices in ionic electrolyte also exhibited superior volumetric energy density of 1.410 mW h/cm3 and excellent electrochemical performances after connecting two cells in parallel or in series combination implying the capability of the device to produce different required capacitance and potential for practical application. Finally, a flexible ASC device with the ionic electrolyte was also tested. This work established that with the smart combination of additional energy level induced functionalized BN, conducting nanotubes, and pseudocapacitive CuO, a highly stable, flexible asymmetric supercapacitor device can be fabricated with high energy density.

Liquid Metal-Templated Tin-Doped Tellurium Films for Flexible Asymmetric Pseudocapacitors.

Liquid metals can be surface activated to generate a controlled galvanic potential by immersing them in aqueous solutions. This creates energized liquid-liquid interfaces that can promote interfacial chemical reactions. Here we utilize this interfacial phenomenon of liquid metals to deposit thin films of tin-doped tellurium onto rigid and flexible substrates. This is accomplished by exposing liquid metals to a precursor solution of Sn2+ and HTeO2+ ions. The ability to paint liquid metals onto substrates enables us to fabricate supercapacitor electrodes of liquid metal films with an intimately connected surface layer of tin-doped tellurium. The tin-doped tellurium exhibits a pseudocapacitive behavior in 1.0 M Na2SO4 electrolyte and records a specific capacitance of 184.06 F·g-1 (5.74 mF·cm-2) at a scan rate of 10 mV·s-1. Flexible supercapacitor electrodes are also fabricated by painting liquid metals onto polypropylene sheets and subsequently depositing tin-doped tellurium thin films. These flexible electrodes show outstanding mechanical stability even when experiencing a complete 180° bend as well as exhibit high power and energy densities of 160 W·cm-3 and 31 mWh·cm-3, respectively. Overall, this study demonstrates the attractive features of liquid metals in creating energy storage devices and exemplifies their use as media for synthesizing electrochemically active materials.

MXene/carboxymethylcellulose-polyaniline (Ti3C2Tx/CMC-PANI) film as flexible electrode for high-performance asymmetric supercapacitors

Two-dimensional (2D) MXene (Ti3C2Tx) materials have received widespread attention as potential electrodes for supercapacitors due to their solution processability, metallic conductivity and excellent energy storage properties. Unfortunately, the self-stacking and interlayer interactions of Ti3C2Tx flakes cause them to acquire poor electrochemical characteristics. Herein, the interwoven carboxymethylcellulose-polyaniline (CMC-PANI) composites were prepared by in-situ polymerization of aniline on the surface of CMC, which was subsequently used as the intercalators to expand the layer spacing of Ti3C2Tx nanosheets via a facile self-assembly process. The interwoven CMC-PANI bridges horizontal Ti3C2Tx nanosheets to construct interconnected conductive and ion channels, making the internal structure of the Ti3C2Tx/CMC-PANI (TCP) film more uniformly and orderly, thereby achieving a high mechanical strength (≈ 35.6 MPa). Meanwhile, the TCP film exhibits a maximum area specific capacitance of 1161.4 mF cm−2 (812.9 mC cm−2) at 1 mA cm−2, and a superior rate performance (maintains 58.4% of the initial value at 50 mA cm−2). Moreover, the fabricated asymmetric supercapacitor (ASC) device presents a high area energy density of 158.7 µW h cm−2 at a power density of 700.1 µW cm−2 and good cycle stability (retention of 89.6% after 15,000 charging/discharging cycles). This rational design balancing flexibility and electrochemical performance provides a broadened idea to solve the inherent defects of MXene and further develop high performance energy storage devices.

Titanium carbide@Poly (3,4-propylenedioxythiophene) composite as electrode for asymmetric flexible supercapacitors

In this paper, the composite of Ti3C2Tx and poly (3,4-propylenedioxythiophene) (PProDOT) is prepared via a simple in-situ chemical oxidative polymerization. The optimum ratio of Ti3C2Tx@PProDOT composite with an outstanding capacitance of 462 C g−1 (462 F g−1) at 1 A g−1 is obtained by adjusting the mass ratio of Ti3C2Tx and ProDOT. The asymmetric flexible supercapacitor with Ti3C2Tx@PProDOT (1:10)//AC exhibits the gravimetric capacity of 238 C g−1 at 1 A g−1, and the retention of initial capacity remains at 79.6% after 10,000 cycles. Meanwhile, the asymmetrical supercapacitor displays an energy density of 48.6 Wh kg−1 at a power density of 729.6 W kg−1. The improvement of these properties stems from that the PProDOT effectively inhibits the stacking of Ti3C2Tx sheets, which is advantageous to shortening the transport path of ions and promoting electron transport as well as the rapid redox reactions. Therefore, these characteristics enhance the electrochemical performance of composites.

Redox-active conjugated microporous anthraquinonylamine-based polymer network grafted with activated graphene toward high-performance flexible asymmetric supercapacitor electrodes

Conjugated microporous polymer (CMP) networks with multi-dimensional structure and excellent physicochemical stability with tunable porosity are receiving increased interest. Herein, we report a composite of anthraquinonylamine-based CMP network and activated graphene (CMAP@AG hybrid) via facile Buchwald-Hartwig coupling. The hybrid composites are made via chemical grafting of CMAP onto AG samples prepared with varied activation treatment times. The grafting of CMAP with AG provides a good hybrid morphology, and its structural properties are tuned by controlling the activation step of AG since both porosity and flake size of the AG sample depend on the etching conditions. The optimized CMAP@AG hybrid exhibits a large surface area of 498 m2 g−1 and low sheet resistance of 278 Ω sq−1, and it can be directly used as an electrode material for supercapacitors. The CMAP@AG hybrid electrode shows a three-electrode specific capacitance of 751 F g−1 at a current density of 1 A g−1 with a good rate capability. A quasi-solid-state CMAP@AG//AG asymmetric supercapacitor (ASC) displays a high energy density of 76.6 Wh kg−1, a power density of 27,634 W kg−1, and good cycle stability with mechanical flexibility. These investigations offer insight into a rational design of CMP-based activated graphene composite for energy storage devices.

Cactus-like NiCo2O4@Nickel-plated fabric nano-flowers as flexible free-standing supercapacitor electrode

Binary transition-metal oxides have caused wide public concern for energy storage as a result of its higher electrical conduction and electrochemical activity compared to single metal oxides in the past few years. However, its practical applications are severely limited by poor specific capacitance and cycling stability. Recently, an effective strategy for enhancing the electrochemical performance of supercapacitors has been demonstrated by proper structural design and optimization of material. Herein, cactus-like NiCo2O4@NPF nano-flower flexible supercapacitor electrodes assembled from 1D NiCo2O4 nanoneedles on 2D hollow metal networks by simple hydrothermal and calcination treatment. The unique nano-flower structure can construct multi-dimensional channels, which facilitate the transport of electrons and ions and significantly enhances the reaction kinetics at the interface between the electrolyte and the active materials. The NiCo2O4@NPF-1 electrode displays an outstanding electrochemical energy storage performance and the specific capacitance is 1106 F g−1 at 1 A g−1. Besides, the composite electrode exhibits a distinguished rate capability (633 F g−1 at 50 A g−1) and favorable cyclability (capacity retention of 92.2% after 2000 cycles). These exceptional results recommend that as-assembled NiCo2O4@NPF nano-flower hybrid material could be a hopeful contender for multifunctional flexible supercapacitor electrodes.

Flexible supercapacitor electrodes based on modified binary metal phosphites on three dimensional graphene sponge

In this paper, two flexible graphene-based materials were prepared by electrochemically depositing FeCoP and FeZnP on graphene sponges (GS) as self-standing electrodes for high-performance electrochemical capacitors. The structural and morphological properties of FeCoP/GS and FeZnP/GS electrodes were characterized using different spectroscopic techniques. As a result, the FeCoP/GS and FeZnP/GS electrodes demonstrated a high specific capacitance of 2100 and 1100 F/g at 1.0 A/g, great cycling stability after 10,000 cycles maintaining 80 % and 74 % of its initial capacitance, respectively, which showed better performance than GS electrode. Moreover, two asymmetric supercapacitors were fabricated with FeCoP/GS and FeZnP/GS electrodes and GS; FeCoP/GS//GS and FeZnP/GS//GS circuits displayed a specific capacitance of 1100 and 780 F/g at 1.0 A/g and an outstanding energy density of 185 and 98 Wh/kg at a high power density of 5.6 and 3.8 kW/kg, respectively. Therefore, the as-fabricated electrodes hold great potential in the field of energy storage.

Morphology modulation of NiCo2S4 arrays in-situ growth on carbon cloth for high performance flexible supercapacitor electrode

NiCo2S4 has been extensively researched as a promising pseudocapacitor material. In this work, NiCo2S4 with three different morphologies (nanoneedles, nanosheets and hexahedrons) were synthesized in-situ grown on the surface of carbon cloth by two-step hydrothermal method with adding different dosage of NH4F. The NH4F plays a key role in controlling the morphology of NiCo2S4 and the mechanisms for the effects of different dosage of NH4F on the morphology of NiCo2S4 are proposed. The electrochemical results show that NiCo2S4 nanosheets delivers the best performance with specific capacitance of 2.98 F cm−2 at 1 mA cm−2 and good cycling stability (82% retention at 20 mA cm−2 after 1000 cycles). In addition, the flexible supercapacitor fabricated with NiCo2S4 nanosheet and activated carbon possesses an energy density of 21.4 Wh kg−1 at a power density of 662.98 W kg−1. All these results indicate that NiCo2S4 nanosheet is an ideal potential electrode material for supercapacitors.

Surface Structure Construction of Fibers in a Conductive Metal–Organic Framework/Metal/Cotton Electrode for Flexible Textile Supercapacitors

Surface Structure Construction of Fibers in a Conductive Metal–Organic Framework/Metal/Cotton Electrode for Flexible Textile Supercapacitors

Binder-free polypyrrole/fluorinated graphene nanocomposite hydrogel as a novel electrode material for highly efficient supercapacitors

Nowadays, many scientific communities and researchers are disparate towards the development of new and advanced energy storage/conversion devices to fulfill the increasing energy demands. Supercapacitors have considered as attractive energy storage devices because of their tremendous features. But their low conductivity creates a barrier to their practical applications, which is a consequence of the presence of binder in the formation of electrode material. Herein, a binder-free flexible supercapacitor electrode based on polypyrrole/fluorinated graphene (PFG) nanocomposite hydrogel on carbon cloth has been designed using in-situ oxidative polymerization. The resultant composite hydrogel possessed excellent electrochemical performance with a high specific capacitance of 1372 F/g in 1 M H2SO4 at a current density of 0.5 A/g. The maximum specific energy and specific power were estimated to be 20.13 Wh/kg and 176 W/kg, respectively. The outstanding electrochemical performance may be attributed to the combined effect of polypyrrole, fluorinated graphene as well as porous morphology of hydrogel. The resultant flexible and binder-free supercapacitor electrode with outstanding electrochemical performance will play a significant role in the field of wearable electronics, touch screens, electronic papers and roll up displays.

Construction of vacancies-enriched CuS/Fe2O3 with nano-heterojunctions as negative electrode for flexible solid-state supercapacitor

The application of supercapacitor is often restricted by unsatisfactory performance of negative electrodes and limited voltage window. Herein, the CuS/Fe 2 O 3 nano-heterojunction with O and S vacancies is constructed by calcination and selective sulfurization, and applied as negative electrode for asymmetric supercapacitor devices. Compared with bare Fe 2 O 3 and CuS, the heterojunction and defect endow the hybrid with improved conductivity, exposed full electrochemical active sites and enhanced charge transfer. Density functional theory (DFT) calculations suggest that the electronic interface reconstruction between CuS and Fe 2 O 3 optimizes the electronic structure and accelerates the electron transport. Therefore, the heterostructured CuS/Fe 2 O 3 exhibits superior supercapacitor negative performance with high capacitance (921 F g -1 at 1 A g -1 ) and good rate capability. After assembling an asymmetric solid-state supercapacitor (CuS/Fe 2 O 3 //MnO 2 ASC) in a PVA/KOH gel, the device shows a high energy density of 56.6 Wh kg -1 at the power density of 900 W kg -1 . In addition, employing polyvinyl alcohol/sodium alginate (PVA/SA/KOH) gel as the electrolyte, a flexible solid-state supercapacitor (CuS/Fe 2 O 3 //MnO 2 SSC) provides 27.8 Wh kg -1 at 900 W kg -1 . This work designs and fabricates defect-rich heterojunction between metal sulfide and oxide and provides insights into developing high-performance electrode materials for supercapacitors. Vacancy-enriched CuS/Fe 2 O 3 nanoparticles take the advantage of CuS and Fe 2 O 3 to increase its conductivity and expand the potential window, and exhibit excellent negative electrode performance for flexible solid-state supercapacitor. • CuS/Fe 2 O 3 was formed via simple calcination and selective sulfurization. • The composite exhibited an oxygen and sulfur vacancies-rich nano heterostructure. • The hybrid presented increased conductivity and electrochemical active sites. • Compared with CuS and Fe 2 O 3 , the composite showed enhanced specific capacitance. • Flexible solid-state supercapacitor showed excellent energy density.

MXene/Graphdiyne nanotube composite films for Free-Standing and flexible Solid-State supercapacitor

MXene with excellent flexibility, metallic conductivity, and ultra-high capacitance, makes a promising electrode for flexible supercapacitor. But the serious restacking phenomenon between MXene layers undesirably limits the ion transport kinetics and substantially reduces ion storage sites, badly restricting the rate capability and storage capacity of supercapacitor. Here, we constructed a free-standing, flexible, structurally 3D-interconnected and hydronium ion penetrable MXene/Graphdiyne nanotube (MG) composite film by employing graphdiyne nanotubes (GDY-NTs) with inherent in-plane pores for horizontal-vertical intercalation among MXene layers. Benefiting from the above synergistic effect, this composite film presents a greatly-improved capacitance of 337.4 F g−1 (337.4 C g−1) and an obviously-enhanced rate capability of 73 %-remaining at 100 mV s−1, which is much better than those of the pure Ti3C2Tx films (230.8 F g−1, 55 %-remaining). Based on it, we developed an asymmetric solid-state flexible supercapacitor with a high energy density of 19.7 Wh kg−1 at the power density of 750 W kg−1 and a capacitance retention of 88.2 % after 10 000 cycles at 8 A g−1. Evidently, this work provides a new route to solve the restacking issue of MXene for high-performance flexible supercapacitor.

CuS/polyaniline nanoarray electrodes for application in high-performance flexible supercapacitors

It is imperative to design and fabricate a high-performance free-standing electrode to meet the demand for flexible energy-storage devices with the development of wearable and portable electronics. CuS is an impressive candidate as an ideal pseudo-capacitance material due to its high theoretical capacity, easy preparation and wide source of raw materials. However, the low conductivity of CuS limits its application. Herein, polyaniline (PANI) was coated on CuS @ functional carbon cloth (fCC) to address the inherent defects of CuS using a facile polymerization procedure. Nano-scale PANI arrays with excellent conductivity grown on super-hydrophilic fCC provide a superior electroactive surface and facilitate electron transfer and electrolyte diffusion, which enhance the electrochemical performance of free-standing electrode. The as-prepared PANI/CuS@fCC electrode exhibits outstanding areal capacitance of 2167.2 mF cm−2 at 0.5 mA cm−2, impressive capacitance retention rate (89.2 %) after 5000 cycles at 5 mA cm−2, and satisfactory mechanical properties and flexibility. The assembled symmetrical supercapacitor also exhibits significant rate capacity with a specific capacitance of 816.4 mF cm−2, a high energy density of 0.268 mW h cm−2 at 0.5 mW cm−2and stable cycle performance with a capacitance retention rate exceeding 98 %. This study provides an effective strategy to fabricate advanced and flexible supercapacitor electrode.

Polyaniline grown on poly(vinyl alcohol)/ionic liquid composite film as electrodes for flexible and self-healable solid-state polymer supercapacitors

Flexible solid-state supercapacitors are considered as one kind of competitive energy storage devices due to the excellent flexibility and high specific capacitance. It attracts considerable attention in recent years. In this paper, binder-free polymer electrodes with outstanding electrochemical performance and mechanical properties were fabricated using poly (vinyl alcohol)/ionic liquid (PVA/IL) composite films as the substrates for the in-suit polymerization of aniline. Scanning electron microscope, cyclic voltammetry, galvanostatic charge-discharge, and tensile test were applied to study the effect of IL content on the structure and properties of the polymer electrodes polyaniline/poly(vinyl alcohol)/ionic liquid (PANI/PVA/IL). The electrode PANI/PVA/IL-1.0 has the optimal comprehensive performance. The specific capacitance and conductivity were 266.6 mF cm −2 and 6.49 S m −1 at 1 mA cm −2 . The tensile strength and elongation at break could reach 1.27 MPa and 509.19%, respectively. PANI/PVA/IL-1.0 was used to assemble the symmetrical polymer supercapacitor with polymer gel electrolyte (PVA/H 2 SO 4 /IL). The area specific capacitance was 251.2 mF cm −2 at 1 mA cm −2 with the capacitance retention of 77.2% after 1000 charge-discharge cycles. Moreover, the solid-state polymer supercapacitor could keep excellent electrochemical performance even under different bending angles or after self-healing, which provides potential applications in electronic encapsulation, flexible energy-storage devices, and high stretchable electric devices etc. The polyaniline/poly(vinyl alcohol)/ionic liquid based electrodes exhibit outstanding electrical and mechanical performance, which endows the solid-state polymer supercapacitors excellent specific capacitance, flexibility and self-healing. • Flexible and self-healable supercapacitors were fabricated using poly(vinyl alcohol)-ionic liquid as substrates. • High tensile strength at break of the polymer indicated its outstanding flexibility due to the presence of ionic liquid. • The fabricated solid-state polymer supercapacitor has good specific capacitance, flexibility and self-healing function.

Three-dimensional tree-like (Ni,Co)Se2/Ni(OH)2 hybrid electrode for flexible supercapacitors

The rational design of hierarchical nanostructure consisting of multiple components with remarkable electrochemical performance is regarded as a significant technique for fabricating high-performance energy storage devices. Herein, self-supported tree-like (Ni,Co)Se2/Ni(OH)2 heterogeneous nanoarrays on carbon cloth (CC) used as electrode materials of supercapacitors (SCs) are designed and synthesized by a multi-step approach. The (Ni,Co)Se2 core can boost electron transport due to excellent conductivity, and the shell layer of Ni(OH)2 nanoflakes improves the surface area. Profiting from the cooperative effects of two active materials and core-shell architecture, the tree-like (Ni,Co)Se2/Ni(OH)2 composite delivers a superior capacity, outstanding rate capability and still retain 151.3 mAh g−1 after 3000 charge/discharge cycles. Meanwhile, the flexible hybrid supercapacitor (HSC) fabricated by the (Ni,Co)Se2/Ni(OH)2 and activated carbon (AC) also manifests a satisfied energy density of 0.79 mWh cm−2 under 1.35 mW cm−2. Therefore, it can be considered that the as-prepared hierarchical (Ni,Co)Se2/Ni(OH)2 nanoarrays are promising candidate for HSC devices in energy storage and conversion.