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1.
Types I and II solid state redox supercapacitors have been constructed using polypyrrole (pPy) and poly (3-methyl thiophene) (pMeT) conducting polymer electrodes with lithium ion conducting polymer electrolyte poly(ethylene oxide) (PEO)-LiCF3SO3 plasticised with poly (ethylene glycol) (PEG). The performance of the capacitors has been characterised by a.c. impedance, linear sweep voltammetry, galvanostatic charge-discharge methods and long term cycling tests. The asymmetric type II capacitors with p-doped pPy and pMeT electrodes give a capacitance value ∼ 2 mF cm−2 (equivalent to 18 Fg−1 of the total mass of the electrodes) and can be charged up to the voltage of 1.7 V. The symmetric type 1 capacitors of the configuration pPy | polymer electrolyte | pPy and pMeT | polymer electrolyte | pMeT show comparable values of capacitance but they are limited to the working voltage of <1.0 V. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997  相似文献   

2.
The manganese oxide/multi-walled carbon nanotube (MnO2/MWNT) composite and the manganese oxide/acetylene black (MnO2/AB) composite were prepared by translating potassium permanganate into MnO2 which formed the above composite with residual carbon material using the redox deposition method and carbon as a reducer. The products were characterized by X-ray diffraction, Fourier transform infrared, and scanning electron microscope. Electrochemical properties of both the MnO2/MWNT and MnO2/AB electrodes were studied by using cyclic voltammetry, electrochemical impedance measurement, and galvanostatic charge/discharge tests. The results show that the MnO2/MWNT electrode has better electrochemical capacitance performance than the MnO2/AB electrode. The charge–discharge test showed the specific capacitance of 182.3 F·g−1 for the MnO2/MWNT electrode, and the specific capacitance of 127.2 F·g−1 for the MnO2/AB electrode had obtained, within potential range of 0–1 V at a charge/discharge current density of 200 mA·g−1 in 0.5 mol·L−1 potassium sulfate electrolyte solution in the first cycle. The specific capacitance of both the MnO2/MWNT and MnO2/AB electrodes were 141.2 F·g−1 and 78.5 F·g−1 after 1,200 cycles, respectively. The MnO2/MWNT electrode has better cycling performance. The effect of different morphologies was investigated for both MnO2/MWNT and MnO2/AB composites.  相似文献   

3.
S. A. Hashmi  H. M. Updahyaya 《Ionics》2002,8(3-4):272-277
Redox supercapacitors using electrochemically synthesised MnO2-polypyrrole composite electrodes have been fabricated with different electrolytes, namely polymer electrolyte film (polyvinyl alcohol, PVA-H3PO4 aqueous blend), aprotic liquid electrolyte (LiClO4-propylene carbonate, PC) and polymeric gel electrolyte [poly methyl methacrylate, (PMMA)-Ethylene carbonate (EC)-Propylene carbonate (PC)-NaClO4]. The capacitors have been characterised using galvanostatic charge-discharge methods. The cell with aqueous PVA-H3PO4 shows non-capacitive behaviour owing to some reversible chemical reaction of MnO2 with water while the MnO2-polypyrrole composite is found to be a suitable electrode material for redox supercapacitors with aprotic (non-aqueous) electrolytes. The solid state supercapacitor based on MnO2-polypyrrole composite electrodes with gel electrolyte gives stable values of capacitance of 10.0–18.0 mF cm−2 for different discharge current densities.  相似文献   

4.
Carbon nanomaterials with remarkable capacitance are highly notable. Although electronic double‐layer capacitors exhibit high power density, their low energy density blocks the practical utility of these carbon materials. Herein, a type of porous‐carbon nanoarchitecture with significant capacitive performance is successfully synthesized using a ZnO template and KOH activation. Benefiting from its excellent conductivity, ultrahigh surface area, and porous architecture, the as‐prepared porous carbon delivers a high capacitance of 245.4 mF cm?2 at a current density of 2 mA cm?2 with impressive rate performance. Moreover, it shows superior cycling durability with more than 99% capacitance retention after 10 000 cycles. A cost‐effective, eco‐friendly, and promising strategy is proposed for the large‐scale preparation of porous‐carbon nanomaterial electrodes.  相似文献   

5.
Amrita Jain  S. K. Tripathi 《Ionics》2013,19(3):549-557
Electrochemical capacitors, based on the double-layer capacitance of high specific surface area carbon materials, are attracting major fundamental and technological interest as highly reversible, electrical-charge storage and delivery devices, capable of being operated at high power densities. In the present paper, studies have been carried out on nanocomposite gel polymer electrolyte comprising poly(vinylidene fluoride-co-hexafluoropropylene)-propylene carbonate-magnesium perchlorate-nanofumed silica with a view to use them as electrolyte in electrochemical double-layer capacitors (EDLCs) based on chemically treated activated charcoal as electrodes. The optimized composition of nanogel polymer electrolyte exhibits high room-temperature ionic conductivity of 5.4?×?10?3 S cm?1 with good mechanical and dimensional stability which is suitable for their application as electrolyte in EDLCs. Detailed chemical and microstructural characterization of chemically treated and untreated activated charcoal was conducted using scanning electron microscopy and Brunauer–Emmett–Teller (BET). BET studies reveal that the effective surface area of treated activated charcoal powder (1,515 m2 g?1) increases by more than double-fold compared with untreated one (721 m2 g?1). Performance characteristics of EDLCs have been tested using cyclic voltammetry, impedance spectroscopy, prolonged cyclic test, and charge–discharge techniques. Analysis shows that the treated activated charcoal electrodes have almost five times more capacitance values as compared with the untreated one. The maximum capacitance of 324 mF cm?2, equivalent to single electrode specific capacitance of 216 F?g?1 was achieved. It corresponds to an energy density of 20 Wh kg?1 and a power density of 2.2 kW kg?1.  相似文献   

6.
Ion conducting polymeric gel electrolytes, based on poly vinylidine fluoride-co-hexafluropropylene (PVdF-HFP)-ethylene carbonate (EC)-propylene carbonate (PC)-salts, LiClO4, NaClO4 and (C2H5)4NClO4 (TEAClO4), have been used in the fabrication of solid state electrical double layer capacitors (EDLCs) with activated charcoal powder electrodes. Comparative studies of different capacitor cells with different gel electrolytes have been carried out using a.c. impedance analysis, linear sweep-reversal voltammetry and galvanostatic charge-discharge techniques. The large values of overall capacitance of 50–100 mFcm−2 (equivalent to single electrode specific capacitance 50–77 Fg−1 of carbon) have been achieved. This corresponds to the energy density 1.6–2.7 Whkg−1. The values of the capacitance have been found to be almost stable up to 5000 voltammetric cycles. The comparative studies of different capacitor cells indicate that the charging processes and hence the coulombic efficiencies are highly affected by the size of the ions, accumulated at the interfaces of EDLCs.  相似文献   

7.
A solvent-free mechanochemical route for the preparation of poly(2,5-dimethoxyaniline) hydrochloride nanostructures is developed and reported in the article. High conductivity, good crystallinity, and nanostructured morphology are observed for the prepared polymer. This polymeric powder is utilized as a cathode material in hybrid supercapacitor and its electrochemical performance is evaluated and discussed in this short report. The maximum specific capacitance of the poly(2,5-dimethoxyaniline) hydrochloride/activated carbon hybrid supercapacitor is found to be 125 F g−1 at 1 mA cm−2 current density. The cell delivers a specific energy as high as 50 Wh kg−1 at a specific power of 97 W kg−1 and also exhibits an excellent cycle performance with more than 99% coulombic efficiency and the maintenance of 85% of its initial capacitance after 1,000 cycles.  相似文献   

8.
S. Shkerin  S. Primdal  M. Mogensen 《Ionics》2003,9(1-2):140-150
Gold electrodes with known contact geometries were studied using impedance spectroscopy. From these data it was possible to determine the specific polarisation conductivity per unit length of three-phase boundary (TPB). The values were found to be (3÷22)×10−4 S·cm−1 dependent on the electrode history in pure oxygen at 977 °C and 2×10−6 S·cm−1 at 977 °C in “pure” hydrogen (PO2=10−20 atm at 1001 °C). The results are compared with previous data obtained for platinum electrodes.  相似文献   

9.
Composites based on commercially available carbon cloth Busofit T-040 and conductive polymer polyaniline are fabricated using the electrochemical polymerization of aniline on the surface of carbon-cloth fibers. The sequence of technological operations for obtaining the composite is optimized; the procedure of preliminary modification of the carbon-cloth surface by electrochemical etching is worked out; and the capacitive characteristics of the obtained composites for use as flexible supercapacitor electrodes are studied. It is found that the introduction of polyaniline into the composition of composite electrode structures leads to an increase in the capacitance by 2–2.5 times compared to the initial carbon cloth due to the pseudocapacitance of polyaniline while maintaining a high electrical conductivity and efficiency. For a composite based on etched carbon cloth, the specific capacitance is 267 F/g (8.9 F/cm2 per unit of the geometric surface of the electrode) with a charge efficiency of 97–99%. The specific surface area of the composite, determined by the BET method, is 548 m2/g.  相似文献   

10.
Indium oxide films doped with tin (ITO-films) have been hf-sputtered from an 80 at-%In2O3/20 at-%SnO2 target onto glass substrates. The sputter atmosphere contained mainly argon (10−2Torr) with addition of oxygen (0≦p O 2≦2·10−2Torr). The sputtered films aren-conductors. The conductivity and density of charge carriers depend on the oxygen content of the sputter gas. They could be varied by two orders of magnitude. In air or in oxygen atmosphere the films oxidize at the surface and for a certain depth beneath the surface, thus decreasing the conductivity. The Hall mobility of the sputtered films is smaller (≈10 cm2V−1 s−1) than one observes at ITO films produced by CVD sparaying or other methods. The conductivity of as sputtered films approached maximum values of about 1000Ώ−1cm−1.  相似文献   

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