ABSTRACT: Attributed to their soft and stretchable feature, flexible supercapacitors have attracted increasing attention in areas of soft electronics, wearable devices, and energy storage systems. However, it is a challenge to manufacture all-soft supercapacitors with highly flexible properties and excellent electrochemical performance. Here, an EGaIn-based fibrous supercapacitor, which is composed of two paralleled stretchable fibers, is designed and demonstrated first with flexible and stretchable properties. EGaIn coated on the surface of polyurethane (PU)@polymethacrylate (PMA) fibers can serve as a current collector. The prepared supercapacitor is measured with an areal specific capacitance of 26.71 mF·cm-2 by mixing Fe3O4 microparticles with EGaIn. This value can increase up to 61.34 mF·cm-2 after vacuum pumping, the mechanism of which is further revealed to be related with the coarser surface and airhole formation on the fibers. The supercapacitor maintains an excellent electrochemical performance when stretched to 120% strain and exhibits a long cycling life through a charge-discharge cycle of over 1000 times. Finally, the supercapacitors are adopted to light the LED, demonstrating that those supercapacitors can work successfully. All these characteristics indicate the huge potential of EGaIn-based supercapacitors in the field of flexible electronics and wearable devices.
Project description:Fiber-type supercapacitors (FSC) have attracted much attention as efficient energy storage devices for soft electronics. This study proposes the synthesis of polypyrrole (PPy) on carbon fiber (CF) using electropolymerization as the energy storage electrode for FSC. Effects of the electrolyte, applied current, and time of electropolymerization for synthesizing PPy on CF are investigated. The configuration of the electrochemical system is also studied to better understand the electropolymerization of PPy. The highest specific capacitance (CM) of 308.2 F/g are obtained for the PPy electrode prepared using 0.5 M pyrrole and 0.3 M NaClO4 as the electrolyte at 40 mA for 20 min. The FSC assembled with PPy electrodes and the polyvinyl alcohol/H3PO4 gel electrolyte shows a CM value of 30 F/g and the energy density of 5.87 Wh/kg at the power density of 60.0 W/kg. Excellent cycling stability with CM retention of 70% and Coulombic efficiency higher than 98% in 3000 times charge/discharge process, and the good bending capability with CM retention of 153% and 148%, respectively, under the bending angle of 180° and the bending times of 600 are achieved. This work gives deeper understanding of electropolymerization and provides recipes for fabricating an efficient PPy electrode for soft energy storage devices.
Project description:The polymerization of pyrrole in the frozen state with the presence of organic dyes (methyl orange (MO) and Acid Blue 25 (AB)) has proven to produce polypyrrole (PPy) nanostructures. Herein, we explore the electrochemical properties of PPy prepared under frozen-state conditions (-24 °C) with and without the presence of organic dyes. The electroactivity of PPy prepared with MO and AB significantly increased in all electrolytic media with a capacitance higher than this of the PPy prepared at room temperature. The highest capacitance (1914 F g-1) was obtained for PPy-MO in 0.2 M HCl solution. The impedance spectra of PPy showed a decrease in charge transfer resistance when the dyes were present. This indicates a conductivity increase of PPy. Improved electrochemical stability was observed for PPy, PPy-MO, and PPy-AB prepared at -24 °C, wherein a steady gain of capacitance was maintained during 5000 potential cycling. In addition, a PPy-based supercapacitor device was fabricated to demonstrate the energy storage characteristics of PPy, where it showed good capacitive behavior and stability. Overall, frozen-state polymerized PPy posed an impressive capacitive performance for flexible supercapacitors.
Project description:A flexible and free-standing 3D reduced graphene oxide@polypyrrole-polyethylene glycol (RGO@PPy-PEG) foam was developed for wearable supercapacitors. The device was fabricated sequentially, beginning with the electrodeposition of PPy in the presence of a PEG-borate on a sacrificial Ni foam template, followed by a subsequent GO wrapping and chemical reduction process. The 3D RGO@PPy-PEG foam electrode showed excellent electrochemical properties with a large specific capacitance of 415 F g-1 and excellent long-term stability (96% capacitance retention after 8000 charge-discharge cycles) in a three electrode configuration. An assembled (two-electrode configuration) symmetric supercapacitor using RGO@PPy-PEG electrodes exhibited a remarkable specific capacitance of 1019 mF cm-2 at 2 mV s-1 and 95% capacitance retention over 4000 cycles. The device exhibits extraordinary mechanical flexibility and showed negligable capacitance loss during or after 1000 bending cycles, highlighting its great potential in wearable energy devices.
Project description:A solid-state flexible supercapacitor (SC) based on organic-inorganic composite structure was fabricated through an "in situ growth for conductive wrapping" and an electrode material of polypyrrole (PPy)-MnO2 nanoflakes-carbon fiber (CF) hybrid structure was obtained. The conductive organic material of PPy greatly improved the electrochemical performance of the device. With a high specific capacitance of 69.3?F cm(-3) at a discharge current density of 0.1?A cm(-3) and an energy density of 6.16 × 10(-3)?Wh cm(-3) at a power density of 0.04?W cm(-3), the device can drive a commercial liquid crystal display (LCD) after being charged. The organic-inorganic composite active materials have enormous potential in energy management and the "in situ growth for conductive wrapping" method might be generalized to open up new strategies for designing next-generation energy storage devices.
Project description:Flexible fiber electrodes are critical for high-performance fiber and wearable electronics. In this work, we presented a highly conductive all-polymer fiber electrode by vapor copolymerization of 2,5-dibromo-3,4-vinyldioxythiophene (DBEDOT) and 2,5-diiodo-3,4-vinyldioxythiophene (DIEDOT) monomers on commonly used polyester threads (PETs) at a temperature as low as 80 °C. The poly(3,4-ethylenedioxythiophene) (PEDOT)-coated PET threads maintain excellent flexibility and show conductivity of 7.93 S cm-1, nearly four times higher than that reported previously via homopolymerization of DBEDOT monomer. A MnO2 active layer was embedded into the PEDOT double layers, and the flexible fiber composite electrode showed a high linear specific capacitance of 157 mF cm-1 and improved stability, retaining 86.5% capacitance after 5000 cycles. Fiber-shaped solid-state supercapacitors (FSSCs) based on the composite electrodes were assembled, and they displayed superior electrochemical performance. This work provides a new approach to realize high-performance and stable wearable electronics.
Project description:Flexible batteries and supercapacitors (SCs) are expected to play a crucial role in energy storage and management in portable electronic devices. In addition, use of materials based on renewable resources would allow for more affordable and sustainable gadgets. In this context, eggshell membranes (ESMs) represent a promising functional platform for production of high-performance electronic components. In this work, we use ESMs for preparing flexible SCs through the incorporation of carbon nanotubes and subsequent in situ polymerization of polypyrrole, producing a highly conductive nanostructure characterized by a porous surface that exhibits both faradic and nonfaradic mechanisms for charge storage. We have found that by controlling the conducting polymer/carbon derivative relative concentration, one can maximize the corresponding capacitance to attain values up to the order 564.5 mF/cm2 (areal capacitance), 24.8 F/cm3 (volumetric capacitance), and 357.9 F/g (gravimetric capacitance). These bioinspired flexible devices exhibit a capacitance retention of 60% after 4000 cycles of charge/discharge and present negligible aging even after 500 bending repetitions (at a density of current 5 mA/cm2). The successful use of ESM-based electrodes in association with carbon derivatives/conducting polymers confirm that the exploit of biological materials offers a promising perspective for the development of new ecofriendly electronic devices.
Project description:Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m(3)) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects.
Project description:Mechanically robust, flexible, and electrically conductive textiles are highly suitable for use in wearable electronic applications. In this study, highly conductive and flexible graphene/Ag hybrid fibers were prepared and used as electrodes for planar and fiber-type transistors. The graphene/Ag hybrid fibers were fabricated by the wet-spinning/drawing of giant graphene oxide and subsequent functionalization with Ag nanoparticles. The graphene/Ag hybrid fibers exhibited record-high electrical conductivity of up to 15,800 S cm(-1). As the graphene/Ag hybrid fibers can be easily cut and placed onto flexible substrates by simply gluing or stitching, ion gel-gated planar transistors were fabricated by using the hybrid fibers as source, drain, and gate electrodes. Finally, fiber-type transistors were constructed by embedding the graphene/Ag hybrid fiber electrodes onto conventional polyurethane monofilaments, which exhibited excellent flexibility (highly bendable and rollable properties), high electrical performance (μh = 15.6 cm(2) V(-1) s(-1), Ion/Ioff > 10(4)), and outstanding device performance stability (stable after 1,000 cycles of bending tests and being exposed for 30 days to ambient conditions). We believe that our simple methods for the fabrication of graphene/Ag hybrid fiber electrodes for use in fiber-type transistors can potentially be applied to the development all-organic wearable devices.
Project description:Carbon nanotubes (CNTs) have been considered as promising electrode materials for energy storage devices, especially flexible electronics owing to their excellent electrical, physicochemical and mechanical properties. However, the severe aggregation between CNTs significantly reduces the electrochemically active surface areas and thus degrades the electrochemical properties. In this study, we demonstrate a facile layer-by-layer strategy toward preparing a CNT/hollow carbon nanocage (HCNC) hybrid film. Through electrochemically removing the impurities in CNT films and optimizing the concentrations of HCNC, the hybrid film exhibits a high specific capacitance of 183.7 F g-1 at 10 mV s-1 and good cycling stability of 85% retention after 5000 cycles at 1 A g-1. Our study provides potential scale-up synthesis of free-standing CNT electrode materials for high-performance supercapacitors.
Project description:A high-quality porous CoNi2S4 nanoplates array was in situ synthesized on carbon fibers (CFs) by a hydrothermal method via a CoNi-layered double hydroxide (LDH) precursor transformation process. The CoNi2S4@CFs electrode exhibits largely enhanced supercapacitor performance with a specific capacitance of 1724 F/g at 1 A/g, in comparison with that of the CoNi-LDH (1302 F/g) precursor. Furthermore, the CoNi2S4@CF electrode shows an extremely high rate capability with capacity retention of 79% under a charge density of 60 A/g, whereas the retention rate of CoNi-LDH@CFs is only ∼34%. The abundant pore structure, improved electrical conductivity, and lower internal resistances of CoNi2S4@CFs (1.0 Ω) compared to those of CoNi-LDH@CFs (9.5 Ω) are responsible for the enhancement of energy storage performance. By using the CoNi2S4 nanoplate array as the positive electrode, an all-solid-state asymmetric fiber-shaped supercapacitor was further obtained, which exhibits outstanding flexible, foldable, and wearable capability. In view of the component tunability for LDH materials, the hydroxide precursor transformation method with merits of mild conditions and easy operation can be extended to the synthesis of a variety of metal sulfides for broad applications in electronic devices.