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The rising Internet-of-Things industry has generated considerable interest in self-sustainable multimodal flexible wearable electronics. However, it remains challenging to fabricate various functional modules for self-sustainable flexible electronics using a single process and material. In this study, monodispersed lignin sulfonate-reduced graphene oxide nanosheets were transformed into 3D self-assembled porous carbon microcapsules (LRCMCs) through ethanol-assisted spray-drying and carbonization. Due to their well-developed porous structure, good conductivity and dispersibility in specific solvents, the resulting LRCMCs could serve as a versatile platform for fabricating various patterned flexible sensors and supercapacitors on flexible Ecoflex substrates through simple solvent drop-casting and transfer printing technology. Results indicated that the sensitivity and detection range of LRCMCs-based flexible strain sensors could be effectively tailored through patterned designs. Therein, the straight-line patterned flexible sensor exhibited an extremely high gauge factor (GF) of ∼219, wide detection range (0–225 %), excellent mechanical durability, and cyclic stability (3000 cycles) for human physiological and physical activities detection. Moreover, a flexible LRCMCs-based humidity sensor was constructed, which could quantitatively measure ambient humidity and monitor human perspiration behavior. For achieving the self-sustainability of multimodal flexible electronics, a flexible supercapacitor was also fabricated using LRCMCs as electrode materials to provide sufficient energy density and driving voltage. [Display omitted] • LRCMCs were prepared by ethanol-assisted spray drying and carbonization method. • Patterned flexible devices were fabricated by drop-casting and transfer printing. • LRCMCs-based strain and humidity sensors show excellent sensing performance. • LRCMCs-based supercapacitor can serve as energy devices to power wearable devices. [ABSTRACT FROM AUTHOR]

Cellulose composite nanopaper is extensively employed in flexible energy storage systems owing to their light weight, good flexibility and high specific surface area. Nevertheless, achieving flexible and ultrathin nanopaper supercapacitors with excellent electrochemical performance remains a challenge. Herein, surface cationization of bacterial cellulose (BC) nanofibers was conducted using 2,3-epoxypropyltrimethylammonium chloride (EPTMAC). Anion-doped polypyrrole (PPy) was incorporated onto the surface of the cationic bacterial cellulose (BCE) nanofibers by an interfacial electrostatic self-assembly process. The obtained PPy@BCE electrode exhibited excellent electrochemical performance, including an areal capacitance of 3988 mF cm−2 at 1.0 mA cm−2 and a capacitance retention of 97 % after 10,000 cycles. A laminated paper-forming strategy was adopted to design and fabricate all-in-one integrated flexible supercapacitors (IFSCs) using PPy@BCE nanopaper as electrodes and BC nanopaper as a separator. The IFSCs showed superior areal capacitance (3669 mF cm−2 at 1 mA cm−2), high energy density (193.7 μWh cm−2 at a power density of 827.3 μW cm−2), and outstanding mechanical flexibility (with no significant capacitance attenuation after repeatedly bending for 1000 times). The present strategy paves a way for the large-scale production of paper-based energy storage devices. [ABSTRACT FROM AUTHOR]

Graphene fiber-based supercapacitors are known as the potential energy resources for wearable/flexible electronics. However, increasing their specific capacitance and energy density remains a significant challenge. This paper indicates a double layer capacitance of the graphene nanosheets accompanied by pseudocapacitive behavior of the polyaniline to prepare composite fibers with high capacitive response. The polyaniline/graphene composite fibers (PANI/GFs) were synthesized by the self-assembled strategy and chemical reduction by HI. The wrinkle architecture of graphene nanosheets and uniform dispersion of the polyaniline are beneficial to increase the internal electroactive sites and provide a stable structure for the composite fibers. The constructed fiber-shaped supercapacitors with solid-state electrolyte deliver an excellent areal specific capacitance of 370.2 mF cm−2 and an outstanding areal energy density of 12.9 μW h cm−2. The current work reveals the attractive potential of the as-synthesized composite fibers for constructing fiber-shaped supercapacitors with distinguished electrochemical performance, which can be applied in future flexible electronics.

Abstract Energy autonomy is critical for wearable and portable systems and to this end storage devices with high‐energy density are needed. This work presents high‐energy density flexible supercapacitors (SCs), showing three times the energy density than similar type of SCs reported in the literature. The graphene–graphite polyurethane (GPU) composite based SCs have maximum energy and power densities of 10.22 µWh cm−2 and 11.15 mW cm−2, respectively, at a current density of 10 mA cm−2 and operating voltage of 2.25 V (considering the IR drop). The significant gain in the performance of SCs is due to excellent electroactive surface per unit area (surface roughness 97.6 nm) of GPU composite and high electrical conductivity (0.318 S cm−1). The fabricated SCs show stable response for more than 15 000 charging/discharging cycles at current densities of 10 mA cm−2 and operating voltage of 2.5 V (without considering the IR drop). The developed SCs are tested as energy storage devices for wide applications, namely: a) solar‐powered energy‐packs to operate 84 light‐emitting diodes (LEDs) for more than a minute and to drive the actuators of a prosthetic limb; b) powering high‐torque motors; and c) wristband for wearable sensors.

Molybdenum sulfide (MoS 2 ) is a promising electrode material for supercapacitors; however, its limited Mo/S edge sites and intrinsic inert basal plane give rise to sluggish active electronic states, thus constraining its electrochemical performance. Here we propose a hierarchical confinement strategy to develop ethylene molecule (EG)-intercalated Co-doped sulfur-deficient MoS 2 (Co-EG/S V -MoS 2 ) for efficient and durable K-ion storage. Theoretical analyses suggest that the intercalation-confined EG and lattice-confined Co can enhance the interfacial K-ion storage capacity while reducing the K-ion diffusion barrier. Experimentally, the intercalated EG molecules with mildly reducing properties induced the creation of sulfur vacancies, expanded the interlayer spacing, regulated the 2H-1T phase transition, and strengthened the structural grafting between layers, thereby facilitating ion diffusion and ensuring structural durability. Moreover, the Co dopants occupying the initial Mo sites initiated charge transfer, thus activating the basal plane. Consequently, the optimized Co-EG/S V -MoS 2 electrode exhibited a substantially improved electrochemical performance. Flexible supercapacitors assembled with Co-EG/S V -MoS 2 delivered a notable areal energy density of 0.51 mW h cm -2 at 0.84 mW cm -2 with good flexibility. Furthermore, supercapacitor devices were integrated with a strain sensor to create a self-powered system capable of real-time detection of human joint motion.

Polyaniline (PANI) has been regarded as a promising electrode material for energy storage devices. However, unsatisfactory cycling stability seriously restricts its practical application. Herein, the nitrogen-doped porous graphene (NPG) film-supported vertically aligned polyaniline nanocones (NPG@PANI) flexible cathodes were synthesized by electrochemical polymerization. The as-prepared NPG@PANI displays unique porous morphology and strong π-π stacking interaction, which facilitates charge transportation and suppresses the dissolution as well as relieves volume changes of PANI during charging-discharging process. Moreover, a novel quasi-solid-state polymer electrolyte (QPE) of porous acrylate rubber/tetraethylammonium tetrafluoroborate-acetonitrile (p ACM/Et 4 NBF 4 -AN) with enhanced ionic conductivity was prepared to match with π-conjugated polymer electrodes, which helps to restrain the dissolution and the structure degradation of electrodes. To enhance the energy density, the organic asymmetric flexible supercapacitor (o AFSC) was assembled by NPG@PANI cathode, NPG supported-poly(1,5-diaminoanthraquinone) (NPG@PDAA) anode and p ACM/Et 4 NBF 4 -AN QPE. The as-assembled o AFSC shows high energy density (6.18 mWh cm−3), good rate capability and superior cycling stability (88.7% capacitance retention after 10000 cycles). [ABSTRACT FROM AUTHOR]

Polyaniline materials are widely utilized as electrodes for supercapacitors because of low cost, facile synthesis, high mechanical flexibility and theoretical high specific capacitance. However, the poor cycle stability and low rate capability restrict their practical applications. Integration of polyaniline with carbon materials is an effective strategy to solve the aforementioned limitations. In this review, polyaniline electrode materials, especially in the forms of different nanostructures, are firstly summarized to demonstrate the general merits of polyaniline-carbon composites for supercapacitors. Subsequent emphasis focuses on the rational design of the composites with various carbon materials, including activated carbon, porous carbon, carbon nanotubes, carbon fibers, graphene or their hybrids. The importance of the compositions, desired architectures and synergistic interactions on the enhanced electrochemical properties is emphasized. In particular, the research trends in the configurational design of unconventional devices, such as flexible, stretchable, compressible and asymmetric supercapacitors with excellent performance at different states (bending, stretching, compressing and/or folding). The review ends with a summary and discusses the perspectives and challenging issues regarding the rational design of flexible supercapacitors in future studies, along with the current outlook for the integrated electronic devices. • Polyaniline electrodes with different nanostructures are summarized. • Influence factors on the performance of PANI-carbon electrodes are emphasized. • The configurational design of unconventional devices is highlighted. [ABSTRACT FROM AUTHOR]

Abstract As promising electrode materials for supercapacitors, manganese oxides still have big challenges such as the low material utilization and poor ionic/electronic conductivity. Reducing particle sizes through nanotechnology has been used to improve material conductivity and electrochemical active sites at materials/electrolyte interfaces. Nevertheless, the extremely small particle size may result in physical and/or chemical instability, mass loss and subsequent capacitance attenuation. Understanding this trade-off effect of electrode materials size with their electrochemical properties is critical to fabricate high-performance supercapacitors. In this work, we prepare homogenous and size-tunable MnO particles (with mean diameters of 80, 41, 20, 15 and 9 nm) on carbon cloth via a facile gel-like film assisted method. It is found that the medium-size nanoparticle (20 nm) displays the best performance instead of the smallest one. These observations are different from the traditional view about material size-property relationship. Instead this work provides a new insight referring to both the size-dependent solubility and ionic/electronic transport. Beneficial from the good flexibility and high conductivity/stability of carbon cloth, the optimized MnO/carbon cloth electrode demonstrates extraordinary performance in symmetric solid-state supercapacitors with energy densities of 86 and 70 Wh kg−1 at the power densities of 450 W kg−1 and 9 kW kg−1, respectively. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Thermally-treated and acid-etched method is utilized to obtain flexible carbon fiber cloth. • N/O-enriched carbon fibers exhibit high surface area and large pore volume. • N- and O-rich functional groups can generate high pseudocapacitance. • The electrode based on N/O-enriched carbon fibers cloth shows prominent area-capacitance and flexibility. Abstract The fast development of portable devices has greatly stimulated the demand for flexible supercapacitors (FSCs). The key to assembling FSCs lies in the development of electrodes with high-performance and good flexibility. In this work, oxygeneous groups modified nitrogen-doped carbon fibers cloth (ONCC) was obtained through annealing the pre-oxidized polyacrylonitrile cloth (PPC), followed by a facile oxidation process using a mixture of concentrated sulfuric acid and concentrated nitric acid. By changing annealing temperature, the nitrogen content can be controlled in the obtained ONCC. It was found that the PPC annealed at 950 °C followed by acid etching for 60 min could deliver the excellent areal and gravimetric specific capacitance of 1385 mF cm−2 and 294.7 F g−1 at the current density of 1 mA cm−2, outstanding rate performance and superb cycling stability. Furthermore, the assembled FSC delivered a high energy density of 19.8 μWh cm−2 (4.03 Wh kg−1) at a power density of 50.1 μW cm−2 (10.2 W kg−1) and good flexibility under different bending conditions. This work provides a facile and efficient route to prepare high-performance carbon fiber based electrode materials in large scale for flexible all-solid-state energy storage devices. [ABSTRACT FROM AUTHOR]

In this study, freestanding paper-like composite films were fabricated using a simple, but scalable and efficient, approach: an environmentally friendly freeze-and-thaw process giving a porous fibrous matrix of cellulose and functionalized carbon nanotubes (f-CNTs), followed by in situ chemical polymerization for the incorporation of polypyrrole (PPy). A homogeneous porous fibrous matrix was formed as a result of strong hydrogen bonding between the f-CNTs and the regenerated cellulose; this material served as an excellent template for the uniform coating of PPy. The structural, morphological, thermal, and electrochemical properties of the as-prepared PPy/f-CNT/cellulose composite films were investigated to evaluate their potential for use as flexible, lightweight, and inexpensive freestanding electrode materials within flexible supercapacitors. The unique microstructure—with high electrical conductivity, good wettability, and a porous architecture—provided large interfacial areas for the storage/release of charge carriers and for the facile diffusion of electrolyte ions in the prepared composite electrodes. With these attributes, the freestanding electrode having the optimal PPy loading exhibited not only an excellent areal capacitance (2147 mF cm−2 at a current density of 1 mA cm−2) but also a good rate capability and an outstanding cycling stability. Moreover, the flexibility, environmental friendliness, and biodegradability of the PPy/f-CNT/cellulose composite films suggest that they will be suitable for use as green and sustainable electrode materials within flexible supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract High-performance electrode materials consisting of intertwined caterpillar-like NiFe layered double hydroxide bridges coated on reduced graphene oxide modified Ni foam (NiFe LDHs/rGO/NF) were prepared via a facile two-step electrodeposition method. First, rGO was electrochemically coated onto NF at a constant potential of −1.2 V vs. SCE for 600 s. Then NiFe LDHs of different Ni to Fe ratios were electrodeposited onto the formed rGO/NF electrodes at −1.2 V vs. SCE for 10 s. Under optimized conditions, NiFe LDHs/rGO/NF composites displayed a high specific capacitance of 1462.5 F g−1 at a current density of 5 A g−1 and retained about 64.7% of the original capacitance after 2000 cycles. Furthermore, a flexible asymmetric supercapacitor was prepared using NiFe LDHs/rGO/NF as the cathode and mesoporous carbon (MC) coated on NF as the anode. The supercapacitor exhibited an energy density of 17.71 Wh kg−1 at a power density of 348.49 W kg−1. All of these findings suggest that the new electrodes developed in this work hold a potential application prospect in flexible energy storage devices. [ABSTRACT FROM AUTHOR]

Flexible supercapacitors (FSCs) with a high areal capacitance are essential for future wearable energy-storage devices due to the limitation of available area on the surface of the human body (< 2 m2). To achieve the performance with high areal capacitance, the surface structure of electrodes should be designed carefully. In this paper, a hierarchical composite electrode based on coaxial-nanostructured polypyrrole (PPy) and multiwall carbon nanotube (MWCNT) was electrochemical co-deposited on the surface of the MWCNT-coated cotton fabric (MCF) by a facile pulse potential method. The pulse potential co-deposition conditions-lower potential (EL), the number of cycles (NC) and EL duration time (tL)-played crucial roles in the uniform distribution of MWCNT within PPy/MWCNT composites, thickness of PPy shell and porous morphology. The three-dimension porous networks of PPy/MWCNT/MCF electrodes not only enhanced the efficiency of faradaic redox reactions but also facilitated the accessibility of the electrolyte to electrode surface, accordingly presenting an ultrahigh areal specific capacitance of 5.05 F cm−2 (0.001 V s−1) and unexceptionable cycling stability of 129.20% specific capacitance retention (1000 cycles, 0.02 V s−1). This work provides a new route to develop FSCs electrodes and shows a promising application in wearable energy-storage technology. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) are recently attracting more and more interests as supercapacitor electrode materials. However, their low conductivity largely thwarts their capacitance performance. Herein, fabric electrodes for flexible supercapacitors were successfully fabricated by depositing polypyrrole (PPy) nanotubes and Zr-based MOF (UiO-66) particles on cotton fabrics. The PPy nanotubes could serve as conductive connectors to bridge the UIO-66 particles due to their superior conductivity with one-dimensional structure. The conductivity of the PPy@UIO-66@cotton fabric electrode was increased to 14.29 S cm−1. A specific capacitance of 565 F g−1 at a current density of 0.8 mA cm−2 was obtained for the PPy@UIO-66@cotton fabric electrode. In addition, the proposed fabric electrode exhibited good cycling stability with capacitance retention of 90% after 500 charge–discharge cycles and excellent rate capability. This study confirmed the combination of MOFs and PPy nanotubes has great application prospect in fabric-based flexible supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract Electrochemical charge injection (ECI) is proved a powerful technique to maximize the available widen potential range of aqueous electrolyte. In this report, reduced graphene oxide/polymer dots (rGO/PDs) nanocomposites are prepared and tested as electrode materials for flexible supercapacitors. The weight ratio of GO/PDs plays an important role in the electrochemical performance of rGO/PDs nanocomposites. Through the ECI technique, a 1.7-V output potential can be delivered by rGO/PDs-based flexible supercapacitors operating with 1 mol L−1 Na 2 SO 4 aqueous electrolyte. A specific energy of 7.1 W h kg−1 with corresponding specific power of 85 W kg−1 can be achieved for a typical flexible supercapacitor, which exhibits a capacitance retention of 90.6% after 5000 cycles at 0.5 A g−1. Highlights • Electrochemical charge injection (CEI) is used in assembling flexible supercapacitor. • A 1.7-V output potential is achieved by performing CEI on aqueous supercapacitors. • Flexible aqueous supercapacitors with specific energy of 7.1 W h kg−1 are achieved. • Flexible supercapacitors with CEI exhibit good cycling performance at 0.5 A g−1. [ABSTRACT FROM AUTHOR]

Film electrodes assembled with MXene have attracted excellent attention for applications in flexible energy storage systems. However, the poor mechanical performance and restricted capacitive surface are limiting factors for the development of high-performance MXene-based supercapacitor. Herein, a MXene-based film electrode with the remarkable integration of mechanical and capacitive properties was provided by using aramid nanofibers/reduced graphene oxide (ANFs/rGO) as reinforcing filler, which achieved 7- and 17-times improvements in tensile strength and toughness, respectively, compared with pure MXene film. Due to the careful regulation of the lamellar structure by introducing ANFs/rGO, the composite film electrode showed a superb volumetric capacitance of 349.2 F cm−3 at a current density of 1 A cm−3. Moreover, a solid-state supercapacitor based on the composite film delivered a maximum energy density of 15.5 mWh cm−3 at a power density of 0.47 W cm−3. The optimal structure-function relationship realized in this work validates the feasibility of optimizing MXene film electrode by ANFs/rGO. [Display omitted] • A film electrode based on MXene, ANFs and rGO was fabricated by a facile vacuum-assisted filtration technique. • The extraordinary mechanical properties set our MXene/ANFs/rGO films among the most strong and stiff MXene composites. • The strengthening and toughening mechanisms of MXene/ANFs/rGO film electrode are investigated in detail. • The ANFs/rGO endows the electrode with a well-order layered nanostructure to enhanced electrochemical properties. [ABSTRACT FROM AUTHOR]

In order to solve the problems of high cost and high brittleness of commercial carbon fiber paper, a low-cost mass production method of carbon fiber paper for flexible super capacitor was proposed. The dispersant CMC-Na is utilized to achieve uniform dispersion of chopped carbon fiber in a water system through ultrasonic dispersion. Sheath-core composite (PE/PET) fiber not only enhances the tensile strength of CFP but also consolidates the electrode network structure formed based on carbon fiber structure. The CFP-3 electrode, impregnated with 3 % AC phenolic resin, exhibits excellent mechanical and electrochemical properties. SEM images reveal that AC is deposited on each carbon fiber and that the CFP-3 electrode retains its three-dimensional structure (with a porosity of 71.2 %), providing an effective permeation path for electrons (with an electrical conductivity of 0.871 S m−1). The CFP-3 electrode can restore its original shape after folding and bending without damage. Electrochemical tests demonstrate that the CFP-3 electrode has a high areal capacitance of 507.2 mF cm−2 at a current density of 0.5 mA cm−2. At a current density of 10 mA cm−2, the capacitance retention rate of the CFP-3 electrode is 96.1 % after 5000 charge-discharge cycles, owing to the well-interconnected structure of the carbon fiber paper. Furthermore, when used as a direct electrode, CFP exhibits excellent stability. Most notably, the cost of producing the CFP-3 electrode (0.0314 m2) is only $0.195, significantly lower than that of commercial products, excluding equipment, utilities, and labor costs. This research provides valuable insights for the low-cost, large-scale production of paper-based flexible supercapacitors. [Display omitted] • Carbon fiber, PE/PET fiber, AC, CMC-Na and ultrasonic dispersion were prepared by traditional wet-mold papermaking method. • The cost of producing each CFP-3 electrode (0.0314 m2) is only $0.195, excluding equipment, utilities, and labor costs. • The areal capacitance of the CFP-3 electrode can reach 507.2 mF cm-2 at 0.5 mF cm-2 and retains 98.2% after 5000 cycles. [ABSTRACT FROM AUTHOR]

Transition metal carbonitrides (MXene) with two-dimensional layered structures are a recent research topic in the field of supercapacitors. However, because MXene can easily self-stack, its capacitance performance is affected. To this end, one-dimensional cellulose nanofibers (CNF) and carboxylic single-walled carbon nanotubes (SWCNT) were used to intercalate MXene to obtain well-dispersed MXene/SWCNT/CNF aqueous suspensions and their hybrid hydrogels, and to obtain hybrid aerogels through supercritical drying. CNF gives aerogel excellent porosity, a high specific surface area (301.03 m2 g−1), good electrolyte infiltration, and gentle mechanical flexibility, while SWCNT imparts high conductivity to aerogel film. We assembled a symmetrical all-solid-state flexible supercapacitor and interdigitated micro-supercapacitors using an aerogel film as a flexible electrode. The area specific capacity of the above electrode reaches 746.68 mF cm−2 and 244.50 mF cm−2, respectively. This study provides a fabrication method of polymer–inorganic hybrid nanocomposite aerogel film electrodes for flexible supercapacitors. The prepared Ti 3 C 2 T x /SWCNT/CNF aerogel film electrode has good structure and electrochemical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of polymer-based devices has attracted much attention due to their miniaturization, flexibility, lightweight and sustainable power sources with high efficiency in the field of wearable/portable electronics, and energy system. In this work, we proposed a polyvinylidene fluoride (PVDF)-based composite matrix for both energy harvesting and energy storage applications. The physicochemical characterizations, such as X-ray diffraction, laser Raman, and field-emission scanning electron microscopy (FE-SEM) analyses, were performed for the electrospun PVDF/sodium niobate and PVDF/reduced graphene oxide composite film. The electrospun PVDF/sodium niobate nanofibrous mat has been utilized for the energy harvester which shows an open circuit voltage of 40 V (peak to peak) at an applied compressive force of 40 N. The PVDF/reduced graphene oxide composite film acts as the electrode for the symmetric supercapacitor (SSC) device fabrication and investigated for their supercapacitive properties. Finally, the self-charging system has been assembled using PVDF/sodium niobate (energy harvester), and PVDF/reduced graphene oxide SSC (energy storage) and the self-charging capability is investigated. The proposed self-charging system can create a pathway for the all-polymer based composite high-performance self-charging system.

MXene is a highly latent capacity electrode material for supercapacitors, but its capacity limits its development. Herein, we have constructed an independently cross-linked three-dimensional (3D) Ti 3 C 2 T X MXene film (Zn-A-MXene) with a hydroxylation surface through a zinc ion (Zn 2+ ) and NaOH. The alkalization of NaOH is used to replace the -F functional group that is not conducive to electrochemical reactions and cross-link the MXene nanosheets through the electrostatic interaction of zinc ions. The synergistic effect can greatly improve the effective area of the electrode, the accessibility of the electrolyte, and the specific capacitance. The 3D Zn-A-MXene films exhibit an extremely high capacity (465.1 F g -1 at 1 A g -1 ). The all-solid-state flexible supercapacitor assembled using a 3D Zn-A-MXene thin film also has a high energy density of 9.55 Wh kg at a power density of 603.16 W kg. After 5000 cycles, the flexible supercapacitor still has 81.25% of its initial capacity, demonstrating good cycling stability. This work furnishes the innovative idea for constructing high-capacity MXene flexible supercapacitors.

Textile electrode materials have attracted intense attention in the flexible supercapacitor field due to their flexibility, light weight, hierarchical porosity and mechanical robustness. However, their electrochemical performance is not good due to the low conductivity, ineffective ion diffusion and small electroactive surface area. In this study, a three-dimensional (3D) textile electrode material was constructed by utilizing ZIF-8 (Zeolitic Imidazolate Framework), metal oxides, conductive polymers and graphene sheets. The polyaniline/ZnO/ZIF-8/graphene/polyester textile electrode exhibited good electrochemical performance with a high areal capacitance of 1.378 F/cm 2 at 1 mA/cm 2 and high stability under different mechanical deformations. A flexible all-solid-state symmetric supercapacitor device was further fabricated, which can provide a high energy density of 235 μWh/cm 3 at a power density of 1542 μW/cm 3 . [ABSTRACT FROM AUTHOR]

Abstract Carbon fiber-based flexible supercapacitors have attracted wide attention due to their excellent properties. In this paper, a novel high performance flexible supercapacitor is reported. The carbon fibers surface-grown with helical carbon nanotubes (CF-HCNTs) are prepared using chemical vapor deposition and then combined with PANI by in-situ polymerization to form a 3D porous structure. The carbon fibers surface-grown with helical carbon nanotubes and polyaniline (CF-HCNTs-PANI) flexible supercapacitor electrodes exhibit a high capacitance of 660 F/g at a current density of 1 A/g with good cycling stability (90.4% capacitance retention after 1000 charge/discharge cycles) and low interfacial charge-transfer resistance of 0.5 Ω. These excellent electrochemical performances are attributed to faradic pseudocapacity, large surface area, 3D porous structure of the CF-HCNTs-PANI electrodes and unique multi-scale fibrous materials. Furthermore, the all-solid-state CF-HCNTs-PANI flexible supercapacitor shows a good specific capacitance of 439 F/g at a current density of 0.05 A/g and has excellent deformation stability. Its electrochemical performance does not cause obvious effect after bending and twisting (95.4% capacitance retention after 500 bending/recovery cycles and near no change after twisting). The CF-HCNTs-PANI electrode with the unique nanostructure will play an important role in the preparation of flexible supercapacitors. Highlights • Carbon fibers surface-grown with helical carbon nanotubes and polyaniline electrode has been successfully synthesized. • CF-HCNTs-PANI electrodes possess good electrochemical properties and high flexibility. • All-solid-state flexible supercapacitors show good specific capacitance and excellent deformation stability [ABSTRACT FROM AUTHOR]

Abstract Potassium-pre-intercalated δ-phase MnO 2 is uniformly grown on carbon nanofibers for the positive electrode of asymmetric supercapacitors. An electrospun CNF is chemically activated with KOH at 800 °C for the negative electrode, showing ideal capacitive behavior. The crystallinity of MnO 2 is significantly reduced by the pre-intercalation of K ions into its layered structure. This textural characteristic is beneficial to the K+ diffusion into/out the interlayer structure, leading to effective utilization of the electroactive material of K x MnO 2. This unique composite electrode provides both ideal pseudo-capacitive behavior from K x MnO 2 and excellent electric conductivity from the CNF network, exhibiting a fairly high specific capacitance value of 279 F g-1 at 1 A g−1 with ca. 82.3% capacitance retention from 1 to 32 A g−1. A flexible ASC consisting of the positive K x MnO 2 @CNF electrode, a paper separator, and the negative ACNF electrode is successfully assembled. This cell shows superior ASC performances: a high cell voltage between 0 and 2 V, excellent capacitance retention (10,000 cycles with 10% decay), and simultaneously reaching high specific energy and power of 21.1 Wh kg−1 and 9.5 kW kg−1. The charge storage behavior of this cell without bending and with a bending angle of 90° shows no apparent difference, demonstrating its potential in the next-generation flexible energy storage devices. Highlights • K-preintercalation favors the K+ diffusion into the interlayer structure of δ-MnO 2. • K-preintercalation enhances the pseudocapacitance utilization of δ-MnO 2. • K-preintercalated δ-MnO 2 is uniformly grown on CNF with ideal behavior for flexible ASCs. • This ASC shows excellent cell capacitance retention and flexibility. [ABSTRACT FROM AUTHOR]

Abstract: A facile and low‐cost strategy has been developed to prepare a highly porous polyaniline/carbon nanotube/polyvinyl chloride film (PANI‐CNTs‐PVC) as an electrode for flexible supercapacitors with the improved performance. The flexible porous film was fabricated via introducing Zn nanopowder into the composition of PANI‐CNTs‐PVC film and then leaching of Zn from the obtained film in an acidic solution. A maximum areal capacitance of 298 mF cm−2 with 86.5 % retention after 5000 cycles at a current density of 0.6 mA cm−2 is achieved for the porous flexible PANI‐CNTs‐PVC film. The capacity is considerably larger than that of the non‐porous flexible PANI‐CNTs‐PVC film prepared without Zn introduction process (90 mF cm−2 with 87 % retention after 5000 cycles). The excellent electrochemical performance of the porous PANI‐CNTs‐PVC film compared to non‐porous PANI‐CNTs‐PVC film is due to the porous 3D network structure and its high hydrophilic property which help to transport electrolyte to the inner region of the composite and facilitate the charge‐transfer between the film and electrolyte. Furthermore, an all‐solid‐state symmetric supercapacitor fabricated from two porous flexible PANI‐CNTs‐PVC films with solid‐state PVA/H2SO4 gel as electrolyte displayed superior flexibility and high electrochemical activity. [ABSTRACT FROM AUTHOR]

Poly (3,4 ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS), among the most used conductive polymers, shows properties easily modulating by adding fillers as Graphene Oxide (GO). Recently, PEDOT-based polymers have been used with encouraging results as electrodes for flexible supercapacitors. We have already developed a green ternary nanocomposite based on PEDOT:PSS doped with GO and glucose (GGO-PEDOT) with a specific capacitance of 16 F/g, indicating how this nanocomposite is potentially suitable to be used as an electrode material for a supercapacitor. In this work, a free-standing nanocomposite film was realized by drop casting the solution in a proper silicone mould, followed by peeling and thermal annealing. Specific analyses, such as thermogravimetric, colorimetric and contact angle measurements, have been performed aiming at assessing the stability of the thermal and of the surface properties, even in severe moisture and UV aging conditions. Finally, The capacitive performance of PEDOT:PSS and of GGO-PEDOT was investigated by means of cyclic voltammetry (CV), in the pristine conditions and under UV aging. The deposited GGO-PEDOT film showed a good conductive behaviour and stability under UV treatment of 4 h. [ABSTRACT FROM AUTHOR]

Abstract: The pursuit of new categories of active materials as electrodes of supercapacitors remains a great challenge. Herein, for the first time, elemental boron as a superior electrode material of supercapacitors is reported, which exhibits significantly high capacitances and excellent rate performance in all alkaline, neutral, and acidic electrolytes. Notably, boron nanowire‐carbon fiber cloth (BNWs‐CFC) electrodes achieve a capacitance up to 42.8 mF cm−2 at a scan rate of 5 mV s−1 and 60.2 mF cm−2 at a current density of 0.2 mA cm−2 in the acidic electrolyte. Moreover, in all these three kinds of electrolytes, BNWs‐CFC electrodes demonstrate a decent cycling stability with >80% capacitance retention after 8000 charging/discharging cycles. The Dominating energy storage mechanism of BNWs in the different electrolytes is analyzed by looking into the kinetics of the electrochemical process. Subsequently, the BNWs‐CFC electrode is used to fabricate a flexible solid‐state supercapacitor, which reveals a specific capacitance up to 22.73 mF cm−2 and good mechanical performance after 1000 bending cycles. This study opens a new avenue to explore elemental boron‐based new nanomaterials for the application of energy storage with superior electrochemical performance. [ABSTRACT FROM AUTHOR]

Abstract: Flexible electrodes made of cotton textile, polypyrrole (PPy) and multi-walled carbon nanotubes (MWCNT) composites were synthesized via a facile in situ chemical deposition method. This method involves a series of successive steps by immersing the cotton fabric in various MWCNT suspensions; adding monomers and p-toluene sulfonic acid (TsOH) as dopant under ultrasonic condition; and then initiating the polymerization by drop-in the oxidant. The fabricated electrodes exhibited a specific capacitance of 597 F g−1 with good cycle stability (maintaining 96.8% after 1000 cycles). Symmetric all-solid-state supercapacitors based on cotton/PPy/MWCNT electrodes and poly(vinyl alcohol) (PVA)/H3PO4 gel electrolytes were fabricated and tested. The electrochemical measurements showed that assembled supercapacitors had a specific capacitance of 206.8 F g−1 at a current density of 1 mA cm−2. The supercapacitors were flexible enough to bend and twist with constant capacitance performance and exhibit 72% capacitance retention after 400 charge-discharge cycles.Graphical Abstract: [ABSTRACT FROM AUTHOR]

In this study, we fabricate solid-state flexible micro-supercapacitors (MSCs) with reduced graphene oxide-carbon nanotube (rGO-CNT) composite electrodes and investigate the electrochemical characteristics by comparing with those of an MSC with rGO electrodes. Regarding the resistance-capacitance time constant and IR drop, the addition of CNTs into the rGO electrodes shows a significant effect owing to both the decrease in the resistance and the increase in the permeability of the electrolytes. Compared to the rGO MSCs, the rGO-CNT MSCs show an excellent areal capacitance of 2.6 mF/cm 2 , a smaller IR drop of 11 mV, a lower RC time constant of 6 ms, and faster charging/discharging rates with a high scan rate ability up to 100 V/s. The mechanical stability of the flexible rGO-CNT MSCs is verified by 1000 bending cycles. In addition, the electrochemical characteristics of the flexible rGO-CNT MSCs are maintained regardless of the MSC array type. [ABSTRACT FROM AUTHOR]

Abstract: Flexible supercapacitors have potential for wearable energy storage due to their high energy/power densities and long operating lifetimes. High electrochemical performance with robust mechanical properties is highly desired for flexible supercapacitor electrodes. Usually, the mechanical properties are improved by choosing high flexible textile substrates but at the much expense of electrochemical performance due to the nonideal contact between conductive materials and textile substrates. Herein, the authors present an efficient, scalable, and general strategy for the simultaneous fabrication of high‐performance textile electrodes and yarn electrodes. It is interesting to find that the conformal reduced graphene oxide (RGO) layer is uniformly and successively painted on the surface of SnCl2 modified polyester fibers (M‐PEF) via a repeated “dyeing and drying” strategy. The large‐area textile electrodes and ultralong yarn electrodes are fabricated by using RGO/M‐PEF as substrate with subsequent deposition of polypyrrole. This work provides new opportunities for developing high flexible textile electrodes and yarn electrodes with further increased electrochemical performance and scalable production. [ABSTRACT FROM AUTHOR]

Abstract: Flexible fiber‐based supercapacitor (FSC) with excellent electrochemical performance and high tensile strength and modulus is strongly desired for some special circumstances, such as load‐bearing, abrasion resistant, and anticutting fabrics. Here, a series of ultrahigh‐strength fiber electrodes are prepared for flexible FSCs based on ultrahigh molecular weight polyethylene fibers, on which the polydopamine, Ag, and poly (3,4‐ethylene dioxythiophene): poly(styrenesulfonate) are deposited in sequence. The modified fiber‐based electrode exhibits superhigh strength up to 3.72 GPa, which is the highest among fiber‐based electrodes reported to date. In addition, FSCs fabricated with the optimized fiber electrode shows a specific areal capacity as high as 563 mF cm−2 at 0.17 mA cm−2, which corresponds to a high areal energy density of ≈50.1 µWh cm−2 at a power density of ≈124 µW cm−2. The specific areal capacity only decrease 8% after 1000 times bending test, indicating the outstanding bending performance of this composite fiber electrode. Furthermore, several FSCs can be connected in series or in parallel to get higher working voltage or higher capacity respectively, which demonstrates its potential for broad applications in flexible devices. [ABSTRACT FROM AUTHOR]

Abstract: Limited by 2D geometric morphology and low bulk packing density, developing graphene‐based flexible/compressible supercapacitors with high specific capacitances (gravimetric/volumetric/areal), especially at high rates, is an outstanding challenge. Here, a strategy for the synthesis of free‐standing graphene ribbon films (GRFs) for high‐performance flexible and compressible supercapacitors through blade‐coating of interconnected graphene oxide ribbons and a subsequent thermal treatment process is reported. With an ultrahigh mass loading of 21 mg cm−2, large ion‐accessible surface area, efficient electron and ion transport pathways as well as high packing density, the compressed multilayer‐folded GRF films (F‐GRF) exhibit ultrahigh areal capacitance of 6.7 F cm−2 at 5 mA cm−2, high gravimetric/volumetric capacitances (318 F g−1, 293 F cm−3), and high rate performance (3.9 F cm−2 at 105 mA cm−2), as well as excellent cycling stability (109% of capacitance retention after 40 000 cycles). Furthermore, the assembled F‐GRF symmetric supercapacitor with compressible and flexible characteristics, can deliver an ultrahigh areal energy density of 0.52 mWh cm−2 in aqueous electrolyte, almost two times higher than the values obtained from symmetric supercapacitors with comparable dimensions. [ABSTRACT FROM AUTHOR]

Mechanically robust graphene papers with both high gravimetric and volumetric capacitances are desired for high-performance energy storages. However, it’s still a challenge to tailor the structure of graphene papers in order to meet this requirement. In this work, a kind of chemical-reduction-tailored mechanically-robust reduced graphene oxide/carbon nanotube hybrid paper has been reported for high-performance electrochemical capacitive energy storages. Gallic acid (GA), as an excellent reducing agent, was used to reduce graphene oxide. Through vacuum filtration of gallic acid reduced graphene oxide (GA-rGO) and carboxylic multiwalled carbon nanotubes (MWCNTs) aqueous suspensions, mechanically robust GA-rGO/MWCNTs hybrid papers were obtained. The resultant hybrid papers showed high gravimetric capacitance of 337.6 F g −1 (0.5 A g −1 ) and volumetric capacitance of 151.2 F cm −3 (0.25 A cm −3 ). In addition, the assembled symmetric device based on the hybrid papers exhibited high gravimetric capacitance of 291.6 F g −1 (0.5 A g −1 ) and volumetric capacitance of 136.6 F cm −3 (0.25 A cm −3 ). Meanwhile, it exhibited excellent rate capability and cycling stability. Above all, this chemical reduction tailoring technique and the resultant high-performance GA-rGO/MWCNTs hybrid papers give an insight for designing high-performance electrodes and hold a great potential in the field of energy storages. [ABSTRACT FROM AUTHOR]

Cellulose nanofibril (CNF) and graphene (GR) powder were added into polylactic acid (PLA)/polypyrrole (PPy) composite films via a low-cost, eco-friendly, low-temperature, and in-situ polymerization synthesis, which obtain novel flexible and conductive polylacticacid-cellulose nanofibril-graphene/polypyrrole (PLA-CNF-GR/PPy) composite films. The CNF was embedded in the PLA matrix to enhance the mechanical properties. Remarkably, when a few GR (1%) powder was added, the tensile strength of composite films increased by 5.6%, respectively, compared with pure PLA-CNF, and increased by 17.6% compared with the PLA. The GR and CNF had a positive influence on mechanical properties of composite films. In addition, the PLA-CNF-GR/PPy composite films exhibited many unique properties when GR powder was introduced, including high thermal stability, and especially electrical conductivity. The electrical conductivity of the PLA-CNF-GR/PPy composite films increased from 0.12 to 1.06S/cm as the content of GR powder increased from 0 to 10%. The PLA-CNF-GR-10/PPy also demonstrated excellent flexible stability, only 7.5% deviation after over 100 bending cycles. Furthermore, we designed and found that the exploration of a flexible solid-state supercapacitor assembled with PLA-CNF-GR-10/PPy composite electrodes had a capacitance of 30F/g at a current density of 0.5A/g. Although it was not quite as prominent as the capacitance, it provided an innovative means for preparing the conductive composite films. Based on these advantages the PLA-CNF-GR/PPy could be considered as sensors, flexible electrodes, and flexible displays. It also opens a new field of potential applications of biodegradable materials. In the current study, the flexible and conductive PLA-CNF-GR/PPy composite films were developed. The electrical conductivity of composite films was increased by adding the GR powder. Meanwhile, PLA-CNF-GR/PPy composite films had a variety of functions, including flexibility, thermotolerance, durability, and electrochemical performance. [ABSTRACT FROM AUTHOR]

The combination of polyaniline (PANI)-coated molybdenum disulfide (MoS 2 ) and activated carbon cloth (CC) is proposed on the basis of a facial hydrothermal and in situ polymerization. The flexible composite of CC/MoS 2 /PANI with a three-dimensional sandwich structure displays remarkable electrochemical performance, in terms of the highest specific capacitance of 972 F g −1 with a current density of 1 A g −1 , compared to CC/MoS 2 (425 F g −1 ) and CC/PANI (440 F g −1 ), good rate performance, low internal resistance, and more importantly, a long cycling life and notable electrochemical stability with retention of the initial specific capacitance at 87% after 5000 cycles (a large current density of 10 A g −1 ). The flexible self-assembled supercapacitors (FSCs) can display good electrochemical performance with the specific capacitance of 193.3 F g −1 , as well as outstanding mechanical flexibility. Furthermore, the performance of this flexible device was obviously decreased under various bending states. The present composite design concept opens a new path for the discovery of efficient electrode materials with three-dimensional sandwich structures. [ABSTRACT FROM AUTHOR]

In this work, a flexible and porous WO 3 /grapheme/polyester (WO 3 /G/PT) textile electrode was successfully prepared by in situ growing WO 3 on the fiber surface inside G/PT composite fabrics. The unique electrode structure facilitates to enhance the energy storage performance because the 3D conductive network constructed by the G/PT increase the electron transportation rate, nanotructured WO 3 exposed enhanced electrochemically active surface area and the hierarchically porous structure improved the electrolyte ion diffusion rate. The optimized WO 3 /G/PT textile electrode exhibited good electrochemical performance with a high areal capacitance of 308.2 mF cm −2 at a scan rate of 2 mV s −1 and excellent cycling stability. A flexible asymmetric supercapacitor (ASC) device was further fabricated by using the WO 3 /G/PT electrode and G/PT electrode, which exhibited a good specific capacitance of 167.6 mF cm −3 and high energy density of 60 μWh cm −3 at the power density of 2320 μW cm −3 . [ABSTRACT FROM AUTHOR]

Nanowires (NWs) have attracted considerable scientific interest in fabricating high-performance electronic and optical devices. In particular, highly ordered NWs could exhibit unique properties such as good intrinsic electrical conductivity and fast electron transportation. In this work, freestanding films from ultralong manganese dioxide/polyaniline (MNW/PANI) coaxial NWs (ca. 200 μm) with a highly ordered structure have been fabricated at the oil/water interface and then used as flexible electrodes. The ultralong MNW/PANI coaxial NWs with highly ordered orientation provide a longer and continuous electron transportation pathway in the electrode compared to disordered NWs, which could greatly reduce the inter-junction resistance between NWs in a film to achieve a high capacitance. The electrodes based on ordered NWs show a much lower contact resistance (10.8 Ω cm−2) compared with the randomly oriented ones (96.5 Ω cm−2). The thin film supercapacitor (TFSC) based on well-ordered MNW/PANI NWs possesses mechanical flexibility, a high specific capacitance of 64.54 mF cm−2 (corresponding to 121.77 F g−1 at a mass loading density of 0.53 mg cm−2), a high energy/powder density (44.80 mWh cm−3, 580 mW cm−3), as well as good cycle stability with high capacitance retention (98 %) after 2000 cycles. [ABSTRACT FROM AUTHOR]

In situ growth of Cu 2+1 O/Cu 2 (CO 3)(OH) 2 /Co(OH) 2 on carbon cloth (CC) is achieved via a facile wet chemical oxidation strategy combined with hydrothermal method, and the self-supported Cu 2+1 O/Cu 2 (CO 3)(OH) 2 /Co(OH) 2 displays a unique multi-dimensional hybrid structure. Cu 2+1 O (CuO with excess metal defects) electroless plated on the surface of CC can not only retain the nanostructures of Cu 2 (CO 3)(OH) 2 and Co(OH) 2 , but also act as the buffer layer to ease volumetric expansion of the materials during the repeated charge/discharge process. When the CC@Cu 2+1 O/Cu 2 (CO 3)(OH) 2 /Co(OH) 2 is used in flexible supercapacitors, it exhibits significantly enhanced areal specific capacitance (624.5 mF cm 2 at 0.5 mA cm 2), rate capability (86.6 %), cyclic stability (100.3 % retention after 1500 cycles) and coulombic efficiency (99.3 % retention after 1500 cycles) due to the synergistic effect of Cu 2+1 O buffer layer, two-dimensional (2D) Co(OH) 2 nanosheets and three-dimensional (3D) Cu 2 (CO 3)(OH) 2 nanoblocks. [Display omitted] • In situ growth of Cu 2+1 O/Cu 2 (CO 3)(OH) 2 /Co(OH) 2 on carbon cloth is facilely achieved. • Both 2D Co(OH) 2 and 3D Cu 2 (CO 3)(OH) 2 play crucial roles in the enhanced performance. • The Cu 2+1 O acts as the buffer layer to ease volumetric expansion of the materials. • The Cu 2+1 O can retain the nanostructures of 3D Cu 2 (CO 3)(OH) 2 and 2D Co(OH) 2. • The material exhibits higher areal specific capacitance than other similar materials. [ABSTRACT FROM AUTHOR]

In this study, Cu x S nanoplates are in-situ synthesized on the surface of copper wire (CW) as active materials (CW@Cu x S) for supercapacitor electrodes, in which CW and Na 2 S are respectively used as copper and sulphur sources. The CW@Cu x S electrode exhibits high specific capacitance up to 3.06 F cm−3, good cycling stability with nearly 80% capacitance retention after 5000 cycles, small charge transfer resistance, and low equivalent series resistance. In addition, the CW@Cu x S electrode shows excellent flexibility applied to one-dimensional supercapacitors, as indicated by the relative stability of the specific capacitance in different bending states. • Cu x S nanoplates have good contact with copper wire due to its in situ synthesis. • Copper wire were used as growth substrate for Cu x S as well as copper source. • The high specific capacitance of copper@Cu x S electrode was up to 3.06 F cm−3. • Reuse of waste copper wires is conducive to the disposal of copper-based cables. [ABSTRACT FROM AUTHOR]

Ti-doped FeOOH quantum dots (QD) decorated on graphene (GN) sheets are designed and fabricated by a facile and scalable synthesis route. Importantly, the Ti-doped FeOOH QD/GN are successfully dispersed within bacterial cellulose (BC) substrate as bending anode with large loading mass for flexible supercapacitor. By virtue of its favorable architecture, this composite electrode exhibits a remarkable areal capacitance of 3322 mF cm−2 at 2 mA cm−2, outstanding cycle performance (94.7% capacitance retention after 6000 cycles), and excellent mechanical strength (68.7 MPa). To push the energy density of flexible supercapacitors, the optimized asymmetric supercapacitor using Mn3O4/GN/BC as positive electrode and Ti-doped FeOOH QD/GN/BC as negative electrode can be cycled reversibly in the operating voltage range of 0-1.8 V and displays ultrahigh areal energy density of 0.541 mWh cm−2, ultrahigh volumetric energy density of 9.02 mWh cm−3, reasonable cycling performance (9.4% decay in specific capacitance after 5000 cycles), and good capacitive retention at bending state. [ABSTRACT FROM AUTHOR]

The demand for portable electronic devices is driving the development of flexible supercapacitor, while current devices still need to improve the performance for practical applications. Here, we report a cost-efficient flexible three-dimensional-Ni (3D-Ni) electrode for a flexible supercapacitor with excellent energy density and power density. The meso-porous 3D-Ni electrode provides a large number of active sites to store charges and good accessibility to the ions in polymer electrolytes, leading to excellent capacitance, high energy density, as well as high power density. The Ni(OH) 2 /3D-Ni positive electrode showed an outstanding specific capacitance of ~3400 F/g at 10 A/g and retained 80% of the initial capacitance at 200 A/g. The negative MnO 2 /3D-Ni electrode exhibited a specific capacitance of 1250 F/g at 10 A/g and excellent capacitance retention of 82% at 200 A/g. The Ni(OH) 2 /3D-Ni//MnO 2 /3D-Ni hybrid supercapacitor delivered an excellent energy density of 75 Wh/kg and a high power density of 5.3 kW/kg, and these values did not change under bending conditions. The 3D-Ni electrode introduced here represents a new type of ideal electrode that can be easily applied to various flexible/wearable electronic device with excellent performance. [ABSTRACT FROM AUTHOR]

The holothurian-like γ-MnS/carbon nanotube (CNT) nanocomposites are successfully fabricated through a facile two-step hydrothermal method. The γ-MnS@CNT hybrid nanocomposite is an attractive electrode material for supercapacitors as it exhibits excellent electrochemical performance with a high specific capacitance of 641.9 F g−1 and cyclic stability of 94.6 % retention after 3000 cycles at a current density of 0.5 A g−1, which are superior to those of CNTs and pure γ-MnS nanoparticles. Furthermore, the as-fabricated all-solid-state supercapacitor reveals remarkable specific capacitance of 263.5 F g−1, high capacitance retention, and a high energy density of 36.6 Wh kg−1 at a power density of 0.5 kW kg−1. The device maintains its supercapacitor performance well, even under bending or twisting states, indicating the excellent mechanical stability and flexibility of the device. The impressive results demonstrate the great opportunity for practical application of this metal sulfide-based composite in high-performance, flexible energy storage devices and wearable electronics. [ABSTRACT FROM AUTHOR]

This paper describes the construction of flexible symmetric and asymmetric supercapacitors made of carbon cloth, polyaniline and carbon nanotubes. The electrode materials (nanostructures of polyaniline-carbon nanotubes, PANI-CNT) were supported on carbon cloth acting as current collector. PANI-CNT nanostructures were synthesized through an oxidative polymerization process in the monomer (aniline) acid solution with the presence of a surfactant and the addition of multi-walled CNT. The CNT were used with and without pretreatment. The cells electrolyte was H 2 SO 4 0.5 M and the selected potential range was 1 V. In order to test their behavior, the different cells configurations were evaluated by electrochemical techniques. Polyaniline nanostructures and polyaniline-carbon nanotubes nanocomposites were used to make the negative and/or positive electrodes of the cell. The cathode in the asymmetric supercapacitors was always carbon cloth/carbon black. The behavior of the arrayed supercapacitors was evaluated by cyclic voltammetry, between 0.0 and 1.0 V at different scan rates (10–100 mVs −1 ), as well as with galvanostatic charge/discharge runs at current densities between 0.3 and 6.7 mAcm −2 . At a constant current density of 0.3 mA cm −2 , a specific capacitance value of 1275 Fg −1 was obtained for a symmetric assembly using both electrodes prepared with polyaniline and carbon nanotubes nanocomposites. When the set was asymmetric, being the positive electrode made of polyaniline and carbon nanotubes nanocomposites, the specific capacitance value was 1566 Fg −1 . For the latter array, the specific power and energy density values were 125 Wkg −1 and 217 Whkg −1 at 0.25 Ag −1 , and 2502 Wkg −1 and 71 Whkg −1 at 5.0 Ag −1 . These results suggest a good energy transfer capacity. Moreover, symmetric and asymmetric supercapacitors demonstrated a high stability over 1000 cycles obtaining a capacitance retention of more than 85%. [ABSTRACT FROM AUTHOR]

Abstracts A novel heterogenous Co 3 O 4 -nanocube/Co(OH) 2 -nanosheet hybrid is prepared by a controllable facile one-pot hydrothermal reaction. The resulting Co 3 O 4 nanocubes are highly uniform in morphology, and are distributed uniformly on the individual Co(OH) 2 nanosheets. Such unique nanostructural features show significant advantages for applications as flexible supercapacitor electrodes in terms of enhanced durability and capacitance. The as-prepared electrode has offered a large capacitance of 1164 F g −1 at 1.2 A g −1 . When being paired with activated carbon, the resulting flexible all-solid-state device exhibited a maximum energy density of 9.4 mWh cm −3 . It is worthwhile noting that this as-assembled device showed little capacitance decay after over 5000 cycles with 97.4% retention of its original specific capacitance. Such a high performance outperforms most metal oxides-based electrodes and shows the advantages of the hybrid strategy, which shed light on exploring robust and cheap electrode materials for high-performance flexible supercapacitors. [ABSTRACT FROM AUTHOR]

A liquid-air interfacial assembly is used to produce a flexible substrate-supported graphene film, which does not need the tedious substrate-transfer procedure that is generally required for many other film-making methods. The graphene film is used as the active working electrode in its planar configuration and an acidic polymer gel is used as the electrolyte, which leads to a flexible planar graphene film supercapacitor with a large areal specific capacitance of 773 µF cm−2 and superior retention performance. In order to demonstrate the versatile application of interfacial assembly in obtaining graphene-based hybrid film electrodes, graphene-manganese oxide and graphene-polyaniline hybrid films are assembled and used to construct planar film supercapacitors with areal specific capacitance of 963 and 2561 µF cm−2, respectively. Compared with the graphene film supercapacitor, the graphene-manganese oxide film supercapacitor, with neutral gel electrolyte, shows no apparent increase of specific capacitance, which is probably due to the larger electrolyte ions and hence the slower ion diffusion rate. Overall, the interfacial assembly is a universal technique for the fabrication of flexible, planar graphene-based film supercapacitors, and this report demonstrates that such supercapacitors are promising as an advanced power system in wearable electronics. [ABSTRACT FROM AUTHOR]

We present the fabrication and electrical response of a flexible prototype supercapacitor based on activated carbon electrodes obtained from bamboo ( Guadua angustifolia Kunth) as precursor. The supercapacitor prototype was fabricated by using a multilayer configuration method; activated carbon electrodes were impregnated with 0.5 M H2SO4 as electrolyte and filter paper was used as separator. Carbon activation was performed by using NaOH and KOH solutions. Activated carbon electrodes were characterized by adsorption isotherms, cyclic voltammetry, and SEM techniques. Electrical response was found by using charge-discharge curves. Through adsorption isotherms analysis, we found a surface area of 408 and 309 m2 g−1 for the activated carbon with NaOH and KOH, respectively. From the electrical characterization analysis of the supercapacitor device, we obtained 0.92 F for the maximum capacitance value by using 0.5 V as fixed value in the bias voltage. Also, we proposed an equivalent electrical circuit for the supercapacitor prototype. This capacitance value is comparable with the capacitance values exhibited by rigid commercial supercapacitor, such as Dinacap and capacitor Capattery Gold, among others. Finally, these results suggest that the activated carbon from bamboo can be used in flexible electronic applications. [ABSTRACT FROM AUTHOR]