J Power Sources 2009 186 216 Mathematical Supercap (original) (raw)
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A B S T R A C T Asymmetric supercapacitors (ASCs) are routinely fabricated using battery-type electrode materials as a positive electrode and electrochemical double layer materials as a negative electrode; the mass-loading in the electrodes is determined by assuming both to be capacitive charge storage materials. This protocol is erroneous as the cyclic voltammograms and galvanostatic charge-discharge curves of the resulting devices showed dissimilarity in the stored charges of the two electrodes and battery-type behaviors, respectively. Herein, we show by employing two choices of battery-type electrodes as positive electrodes and commercial activated carbon as negative electrode in 3 M LiOH electrolyte that equal mass loading in both electrodes leads to supercapacitive charge storage. The positive electrode to negative electrode mass ratio is varied from 0.75 to 1.5 in a mass interval of 0.25 which includes a mass ratio of the conventional method. The electrochemical studies of the fabricated ASCs show that the charge storage capabilities depend on the electrode mass. Electrochemical impedance spectroscopy studies show that the equal mass ratio has low series and charge transfer resistances and wider frequency dispersion of capacitance.
Asymmetric and symmetric supercapacitors based on polypyrrole and activated carbon electrodes
Synthetic Metals
Supercapacitors were prepared using either two polypyrrole (PPy) composite electrodes or one PPy composite and one activated carbon electrode. The PPy composite electrodes were either freestanding paper-like sheets or PPy films printed on graphite ink coated aluminium/PET laminate substrates, using Cladophora algae derived cellulose as the substrate or binder, respectively. The specific capacitance of the PPy electrodes was found to be about 200 F/g depending on the manufacturing method, yielding supercapacitors with capacitances between 0.45 and 3.8 F and energy efficiencies of over 90%. For an asymmetric device with activated carbon positive electrode and PPy negative electrode a capacitance loss of 5% was seen after 14300 cycles.
Journal of Solid State Electrochemistry, 2014
r o l y t e o f s o d i u m bis(trifluoromethanesulfonyl)imide (NaTFSI)-polyethylene oxide (PEO) in an organic solvent mixture has been prepared and examined for supercapacitor applications by using activated carbon electrodes. The solvent was a mixture of propylene carbonate, dimethyl carbonate, and ethylene carbonate at equal molar ratio, and also, a propylene carbonate-based gel was used for a comparison. The polymer-salt interaction was viewed by infrared spectral study. The cells have been characterized in a two-electrode type using linear sweep voltammetry, cyclic voltammetry, galvanostatic cycling, and impedance techniques at 22°C. The voltammograms evidence symmetry and reversibility of the cells. The ternary gel has shown better electrochemical performances. Moreover, the cell operative potential window was found to be stable at 2.5 V with high specific capacitance and also a good efficiency at low charge rate. The typical obtained specific capacitance, real power, and energy density values are 24 F g −1 , 0.52 kW kg −1 , and 18.7 Wh kg −1 , respectively, which may be viewable for a compact capacitor.
Asymmetric supercapacitor devices based on dendritic conducting polymer and activated carbon
Electrochimica Acta, 2017
Dendritic conducting polymers(CPs) are a novel class of porous pseudocapacitive electrode materials assembled with the combination of highly reversible redox active triphenylamine(TPA) and thiophene, 3-methylthiophene, selenophene and thieno[3,2-b]thiophen moieties. Due to the unique combination of three dimensional conducting network, fast redox reversible reactions, porous morphology, high thermal and electrochemical stability have fetched these pseudocapacitive polymers to exhibit high specific capacitance and emerged as an ideal candidate for energy storage devices. The electrochemical performance of as-prepared polymers showed specific capacitance of 278, 257, 246 and 315 Fg-1 for poly tris[4-(2-thienyl)phenyl]amine (P1), poly tris(4-(3-methylthiophene-2yl)phenyl)amine (P2), poly tris(4-(selenophen-2-yl)phenyl)amine (P3) and poly tris(4-thieno[3,2-b]thiophen-2-yl) phenyl)amine (P4) respectively with low internal resistance. An insertion of selenophene and thieno(3,2-b)thiophene linkers in TPA block showed enhanced electrochemical performance than the thiophene-TPA pair. Furthermore, asymmetric supercapacitors were assembled with the polymer as cathode and activated carbon as an anode and the detailed electrochemical characterizations has been investigated. This research may shed light on designing new redox active psuedocapacitors and other electrochemical devices.
Journal of The Electrochemical Society, 2005
The scale-up from a small single cell to a larger stack prototype of a solid-state electrochemical supercapacitor based on polymer electrolyte and activated carbon is demonstrated. The prototype is composed of five single cells stacked in series, has a nominal capacitance of 1.5 F, and a maximum voltage of 5 V. The electrodes of the prototype were prepared using high-surface-area carbon material ͑Norit A Supra Eur͒ and Nafion ionomer. Nafion was used as the electrolyte membrane separator between the electrodes of each single cell and as the binder/ion conductor in the electrodes. The fabricated prototype showed a higher series resistance compared to that estimated in our previous study of a small size single supercapacitor. However, the prototype achieved a specific capacitance of 114 F/g ͑referred to the weight of active carbon materials for a single electrode͒, which is comparable to the specific capacitance of the previously reported 4 cm 2 single-cell supercapacitor. Moreover, an appreciable power density of 1.4 kW/L and a RC-time constant of 0.3 s have been calculated for the device.
Journal of Power Sources, 2006
We have studied some supercapacitor cell assemblies based on high surface area nickel and nickel oxide materials. Both symmetric and asymmetric configurations consisting of nickel and nickel oxide with activated carbon as a negative electrode have been investigated. A single electrode specific capacitance value of 473 F g -1 of nickel is obtained for the porous nickel. We have used cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chargedischarge profile analysis to characterize the supercapacitor cell assemblies. Based on the analysis of impedance data in terms of complex capacitance and complex power, the relaxation time constant (τ 0 ) was calculated for different supercapacitor cell assemblies. The quick response time (of the order of milliseconds) with fast energy delivery at relatively high power suggests that these materials can find applications in short time pulse devices. A coulombic efficiency of 0.93 to 0.99 is obtained for the supercapacitor cell assemblies studied in this work. The measured equivalent series resistance (ESR) value is relatively high due to the contribution from the resistance offered by the pores and the contact resistance arising from the cell fabrication method. Although the specific capacitance values are relatively less, the cell exhibits a fast response time, which is a desirable property in certain specialized applications. .in (V. Lakshminarayanan)
Design of Activated Carbon/Activated Carbon Asymmetric Capacitors
Supercapacitors are energy storage devices that offer a high power density and a low energy density in comparison with batteries. Their limited energy density can be overcome by using asymmetric configuration in mass electrodes, where each electrode works within their maximum available potential window, rendering the maximum voltage output of the system. Such asymmetric capacitors are optimized using the capacitance and the potential stability limits of the electrodes, with the reliability of the design largely depending on the accuracy and the approach taken for the electrochemical characterization. Therefore, the performance could be lower than expected and even the system could break down, if a well thought out procedure is not followed. In this work, a procedure for the development of asymmetric supercapacitors based on activated carbons is detailed. Three activated carbon materials with different textural properties and surface chemistry have been systematically characterized in neutral aqueous electrolyte. The asymmetric configuration of the masses of both electrodes in the supercapacitor has allowed to cover a higher potential window, resulting in an increase of the energy density of the three devices studied when compared with the symmetric systems, and an improved cycle life.
2018 7th International Conference on Computer and Communication Engineering (ICCCE), 2018
A simple RC equivalent circuit model often used to represents a supercapacitor. The model is far from accurately model the behavior of the device. A 2cm by 2 cm supercapacitor prototype based on Activated carbon as the active electrode material and NaOH as the electrolyte was fabricated. This prototype was characterized using Cyclic Voltammetry and Galvanostatic Charge Discharge to get the supercapacitor working potential window, capacitance and internal resistance. The device works up to 0.7V with capacitance of up to 1.6F and internal resistance as low as 190 Ohm was found for the prototype. Several equivalent circuit model of a supercapacitor was simulated to produce similar response of the prototype. Multiple Branch Parallel RC circuit response profile fit the experimental profile the best.
Hybrid Supercapacitors Based on Activated Carbons and Conducting Polymers
Journal of The Electrochemical Society, 2001
A new concept of hybrid supercapacitors has been designed with a conductive polymer as the positive electrode and activated carbon as the negative electrode. The chosen polymer was poly͑4-fluorophenyl-3-thiophene͒ or P-4-FPT, whose good doping properties are well known. Several activated carbons were tested, and the results reported here were obtained with carbons from Spectracorp ͑BP25 and YP17͒. The mass ratio of active materials was calculated to obtain the maximum cell voltage ͑3 V͒. The system studied in our laboratory was 4 cm 2 test cells which reached 48 Wh/kg of maximum energy associated with 9 kW/kg of maximum power ͑considering the mass of the active materials͒. Industrial prismatic prototypes were then assembled, containing 60 cm 2 electrodes. These prototypes reached a maximum energy of 7.5 Wh/kg ͑total mass͒, and a maximum power of 250 W/kg.