Improving the symmetry of asymmetric supercapacitors using battery-type positive electrodes and activated carbon negative electrodes by mass and charge balance (original) (raw)
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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.
Asymmetric Supercapacitor Electrodes and Devices
Advanced materials (Deerfield Beach, Fla.), 2017
The world is recently witnessing an explosive development of novel electronic and optoelectronic devices that demand more-reliable power sources that combine higher energy density and longer-term durability. Supercapacitors have become one of the most promising energy-storage systems, as they present multifold advantages of high power density, fast charging-discharging, and long cyclic stability. However, the intrinsically low energy density inherent to traditional supercapacitors severely limits their widespread applications, triggering researchers to explore new types of supercapacitors with improved performance. Asymmetric supercapacitors (ASCs) assembled using two dissimilar electrode materials offer a distinct advantage of wide operational voltage window, and thereby significantly enhance the energy density. Recent progress made in the field of ASCs is critically reviewed, with the main focus on an extensive survey of the materials developed for ASC electrodes, as well as cover...
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.
Fabrication of Asymmetric Supercapacitor Using Aqueous and Polymer Electrolytes for Energy Storage
The International Conference on Electrical Engineering
Supercapacitors represent an attractive alternative for portable electronics and automotive applications due to their high capacitance, specific power and extended life. In fact, the growing demand of portable systems and hybrid electric vehicles, memory protection in CMOS, logic circuit, VCRs, CD players, PCs, UPS in security alarm systems, remote sensing, smoke detectors, etc. require high power in short-term pulses. So, in the last 20 years, supercapacitors have been required for the development of large and small devices driven by electrical power. In this paper, asymmetric supercapacitors with high energy density were successfully fabricated using graphene as negative electrode and polyaniline as positive electrode. The weight of active material was 5.6 mg. The surface topography was characterized by scanning electron microscopy (SEM). The electrochemical properties of the composite were evaluated by cyclic voltammetry (CV), charge-discharge measurements and electrical impedance spectroscopy (EIS). The separator was a filter paper soaked in aqueous potassium hydroxide (6M).This enhances both the specific capacitance to 620.76 F/g at scan rate of 1 mV/s and the energy density to 86.22Wh/kg. Another low leakage supercapacitor was fabricated using polyvinyl alcohol (PVA) separator and 6 mole potassium hydroxide salt with specific capacitance of 220.35 F/g at scan rate of 1 mV/s.
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)
Scientific reports, 2015
Amongst the materials being investigated for supercapacitor electrodes, carbon based materials are most investigated. However, pure carbon materials suffer from inherent physical processes which limit the maximum specific energy and power that can be achieved in an energy storage device. Therefore, use of carbon-based composites with suitable nano-materials is attaining prominence. The synergistic effect between the pseudocapacitive nanomaterials (high specific energy) and carbon (high specific power) is expected to deliver the desired improvements. We report the fabrication of high capacitance asymmetric supercapacitor based on electrodes of composites of SnO2 and V2O5 with multiwall carbon nanotubes and neutral 0.5 M Li2SO4 aqueous electrolyte. The advantages of the fabricated asymmetric supercapacitors are compared with the results published in the literature. The widened operating voltage window is due to the higher over-potential of electrolyte decomposition and a large differe...
Advance Materials for aqueous supercapacitors in the asymmetric design.pdf
Supercapacitors have been recognized as one of the promising energy storage devices in the future energy technology. In this perspective, rapid progress is made in the development of fundamental and applied aspects of supercapacitors. Various techniques have been developed specifically to estimate the specific capacitance. Numerous efforts have been made in the literature to increase the specific capacitance of electrode materials. Recently, researchers pay more attention on designing supercapacitors of asymmetric type with extending cell voltage and dissimilar materials with complementary working potentials. Researchers try to increase the specific energy of asymmetric supercapacitors (ASCs). Conversely, it is still a challenge to find a suitable operation conditions for ASCs in various designs, especially for the one with battery type electrode. In this review, we describe our recent research works and other reports on the preparation of various nanostructured electrode materials and the performances of both symmetric and asymmetric supercapacitors. Finally, we demonstrate effects of charge balance on the capacitive performances of ASCs which consist of one electrode material of the battery type and one capacitive material. We also demonstrate how to evaluate the charge capacities of both positive and negative electrode materials for this ASC application.
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.
Electrochemical Properties of Asymmetric Supercapacitors in Potassium Hydroxide Electrolyte
Advanced Materials Research, 2012
Three kinds of activated carbons were prepared from Taixi anthracite by NaOH activation. As-obtained activated carbons were adopted as electrode materials to construct asymmetric and symmetric supercapacitors. The electrochemical properties of as-constructed supercapacitors in aqueous electrolyte (3.0M KOH) were investigated. Results show that the asymmetric supercapacitor assembled with activated carbon of a higher specific surface area (SBET) as the positive electrode exhibits better ion diffusion behavior and higher cell gravimetric specific capacitance (Cg). This is different from the case in non-aqueous system, mainly because pseudo-capacitance rather than double-layer capacitance has a more important effect on Cg in the aqueous electrolyte. Namely, the wettability and pseudo-capacitance of activated carbons decrease with increasing mass ratio of NaOH to anthracite, which is more prominent for activated carbons used as negative electrode materials.