electrochemical properties, and light weight has attracted widespread attention from academic and industrial fields. [1][2][3][4][5][6][7][8] Among numerous flexible energy storage devices, flexible supercapacitors are often regarded as the optimal candidate on account of their high power density, ultralong cycling stability, and fast charge and discharge capacity. [9][10][11][12] Recently, substantial effort has been devoted to endow flexible supercapacitors with more efficiency, more stability, and low cost in order to develop fully flexible electronics. [13][14][15] High energy density and good mechanical durability are the major difficulties in design and fabrication of flexible supercapacitors. Generally, the common flexible supercapacitors exhibit a multilayer laminated configuration, which are fabricated by placing a gel electrolyte layer between two flexible electrodes. [16][17][18][19] Compared with the common flexible supercapacitors with laminated structure, the major components of the all-inone flexible supercapacitors including two electrodes, separator, electrolyte, and current collectors are integrated on the same substrate. [20,21] This integrated design cannot noly reduce the contact resistance of the interface but also increase the mechanical durability including compression stability and stretching and/or twisting reliability.To date, a series of integrated flexible supercapacitors have been reported. Guo et al. reported healable supercapacitors with all-in-one configuration by in situ polymerization and deposition of single-walled carbon nanotube (SWCNT) and polyaniline (PANI) onto the two sides of the healable hydrogel electrolyte separator. [17] Wang et al. integrated the electrode-electrolyte-electrode component in a free-standing poly(vinyl alcohol) chemical hydrogel film to fabricate an all-in-one supercapacitor. [22] Gao et al. designed an all-in-one asymmetric supercapacitor with high volumetric energy density by electrodeposition of metallic oxide onto each side of the carbon nanotube (CNT) modified porous polyamide nanofiber film. [23] Shao et al. fabricated a tunable integrated flexible supercapacitor using three dimensional reduced graphene oxide/graphene oxide/reduced graphene oxide (3D rGO/GO/rGO) foam via the laser direct writing technology. [24] These all-in-one supercapacitors can avoid unstable physical connection, which is of great important for Compared with laminated structure supercapacitors, all-in-one supercapacitors can reduce the contact resistance of the interface and avoid displacement/delamination of the multilayer structure under deformation, which suggests a highly promising energy-storage device. However, simplifying the assembly process to achieve high voltage output, balance mechanical stability and electrochemical performance is still a serious challenge. Here, an all-inone flexible supercapacitor (AFSC) is designed based on melamine foam and polypyrrole by one-step polymerization method. It exhibits a high volumetric specific capacitance of 2.86 F cm −3 , vol...
Abstract:In this paper, a solvent vapor-induced phase separation (SVIPS) technique was used to create a porous structure in polyvinylidene fluoride/Multi-walled carbon nanotube (PVDF/MWNTs) composites with the aim of increasing the electrical conductivity through the incorporation of MWNTs while retaining a low thermal conductivity. By using the dimethylformamide/acetone mixture, porous networks could be generated in the PVDF/MWNTs composites upon the rapid volatilization of acetone. The electrical conductivity was gradually enhanced by the addition of MWNTs. At the same time, the thermal conductivity of the PVDF film could be retained at 0.1546 W·m −1 ·K −1 due to the porous structure being even by loaded with a high content of MWNTs (i.e., 15 wt.%). Thus, the Seebeck coefficient, power factor and figure of merit (ZT) were subsequently improved with maximum values of 324.45 µV/K, 1.679 µW·m −1 ·K −2 , and 3.3 × 10 −3 , respectively. The microstructures, thermal properties, and thermoelectric properties of the porous PVDF/MWNTs composites were studied. It was found that the enhancement of thermoelectric properties would be attributed to the oxidation of MWNTs and the porous structure of the composites. The decrease of thermal conductivity and the increase of Seebeck coefficient were induced by the phonon scattering and energy-filtering effect. The proposed method was found to be facile and effective in creating a positive effect on the thermoelectric properties of composites.
A flexible all‐solid‐state yarn supercapacitor (YSC) based on metal–inorganic–organic ternary hybrid structure is fabricated by assembling polypyrrole@manganese oxide nanosheets@stainless steel yarn (PMS) yarn electrode of core/sheath/sheath configuration. The PMS yarn electrode combines the advantages of each component and shows excellent electrochemical performance, mechanical flexibility, and flame retardance owing to its unique structure and synergistic effect. The as‐fabricated YSC exhibits a high areal specific capacitance of 181 mF cm−2, areal energy density of 16.1 µWh cm−2, and areal power density of 10.3 mW cm−2. Moreover, the device possesses desirable voltage/current scalability and outstanding mechanical stability, which maintains 95.8% capacitance retention after 1000 bending cycles. As a demonstration, four YSCs are connected in series and then charged for 10 s to drive a light‐emitting diode (LED) digital watch. The outstanding overall performance of the YSC indicates that it is an ideal flexible power source for safe wearable electronics.
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