Highly Concentrated Aqueous Electrolyte With a Large Stable Potential Window for Electrochemical Double-Layer Capacitors

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Guoqing Zhang ◽  
Yongqing Zhao ◽  
Binbin Jin ◽  
Peng Zhang ◽  
Shuying Kong
Keyword(s):  
Aqueous Electrolyte ◽  
Electrochemical Impedance ◽  
Discharge Rate ◽  
Saturated Calomel Electrode ◽  
Electrochemical Capacitor ◽  
Superior Performance ◽  
Operating Voltage ◽  
Galvanostatic Discharge ◽  
Electrochemical Double Layer Capacitors ◽  
Electrochemical Double Layer

Abstract An active carbon (AC)/AC electrochemical capacitor, taking advantage of a high-concentrated lithium trifluoromethane sulfonate (LiTFS) or lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) aqueous electrolyte, was demonstrated with an extended operating voltage of 2.5 V, which is the largest value till now for aqueous carbon-based capacitors. The AC electrode is entirely capacitive in these two electrolytes and the stable potential window of the single AC electrode can reach −1.2 to 1.2 V versus the saturated calomel electrode (SCE). The performance of the AC-based capacitor is evaluated in two- and three-electrode cells using a combination of electrochemical impedance (EIS), cyclic voltammetry (CV), galvanostatic discharge-charge, and self-discharge (SD, i.e., leakage current) measurements. At 0.5-mA cm−2 charge-discharge rate, the AC/AC capacitor presents 5.5 wh kg−1 and 4.5 wh kg−1 energy density for 20 m LiTFS and LiTFSI electrolyte, respectively. The results suggest that a thorough utilization of such lithium salt aqueous electrolytes with widening electrochemical stable potential window will no doubt lead to further development of electrochemical capacitors toward superior performance.

An Experimental Research on Electrochemical Impedance Spectra of New High-Specific Energy EDLC

2011 ◽  
Vol 675-677 ◽  
pp. 65-68 ◽  
Author(s):  
Zi Lei Liang ◽  
Chong Kuan Cheng ◽  
Ji Bo Liu ◽  
Guo Min Mi
Keyword(s):  
Specific Energy ◽  
Electrochemical Impedance ◽  
Discharge Process ◽  
Electrochemical Impedance Spectra ◽  
Charge Voltage ◽  
Electrochemical Double Layer Capacitors ◽  
Complex Capacitance ◽  
Electrochemical Double Layer ◽  
High Specific Energy ◽  
Double Layer Capacitors

The real times Electrochemical Impedance Spectroscopy (EIS) analysis which corresponds to the charge and discharge process was reported in order to evaluate the relationships between impedance and potential for new high specific energy electrochemical double-layer capacitors (EDLC). Also the Niquist plots were presented and the impedance of the EDLC was discussed in terms of complex capacitance. It was found that the high frequency impedance changed with its potential in charging or discharging process, the medium frequency impedance Rct belonged to the resistance of ions diffusion into micro pore or the inner of electrode material decreased with increasing charge voltage and had a certain capacitance of about 1F.

scholarly journals Carbon-Based Fibrous EDLC Capacitors and Supercapacitors

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
C. Lekakou ◽  
O. Moudam ◽  
F. Markoulidis ◽  
T. Andrews ◽  
J. F. Watts ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Carbon Fibre ◽  
Woven Fabric ◽  
Superior Performance ◽  
Multiwall Carbon Nanotube ◽  
Electrochemical Double Layer Capacitors ◽  
Electrochemical Double Layer ◽  
Improved Performance ◽  
Multiwall Carbon ◽  
Carbon Based

This paper investigates electrochemical double-layer capacitors (EDLCs) including two alternative types of carbon-based fibrous electrodes, a carbon fibre woven fabric (CWF) and a multiwall carbon nanotube (CNT) electrode, as well as hybrid CWF-CNT electrodes. Two types of separator membranes were also considered. An organic gel electrolyte PEO-LiCIO4-EC-THF was used to maintain a high working voltage. The capacitor cells were tested in cyclic voltammetry, charge-discharge, and impedance tests. The best separator was a glass fibre-fine pore filter. The carbon woven fabric electrode and the corresponding supercapacitor exhibited superior performance per unit area, whereas the multiwall carbon nanotube electrode and corresponding supercapacitor demonstrated excellent specific properties. The hybrid CWF-CNT electrodes did not show a combined improved performance due to the lack of carbon nanotube penetration into the carbon fibre fabric.

Cobalt Sulfide-Graphene (CoSG) Composite based Electrochemical Double Layer Capacitors

2015 ◽  
Vol 1786 ◽  
pp. 19-30 ◽  
Author(s):  
R Ramachandran ◽  
Grace A Nirmala ◽  
Chittur K Subramaniam
Keyword(s):  
Double Layer ◽  
Polyvinylidene Fluoride ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Cobalt Sulfide ◽  
Composite Electrodes ◽  
Electrode Structure ◽  
Electrochemical Double Layer Capacitors ◽  
Electrochemical Double Layer ◽  
Double Layer Capacitors

ABSTRACTElectrochemical Double Layer Capacitors, EDLC, using Cobalt sulfide- Graphene (CoSG) composite electrodes, were fabricated and the storage process was studied. CoSG composite was prepared by a simple chemical route. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Field Emission Scanning Electron microscopy (FESEM) were used to characterized the as prepared composites which indicated formation of Co S phase. Solutions of perfluorosulfonic acid and Polyvinylidene Fluoride (PVDF) were used as electrode binding material. The storage capacitance of the composites were studied in 1M KCl and 6M KOH electrolytes using standard electrochemical techniques like cyclic voltammetry, CV, electrochemical impedance spectroscopy, EIS, and discharge profiles. The capacitance was estimated for various binder concentrations for both the electrolytes. The concentration of perflurosulfonic acid binder of 0.8 wt% and PVDF of 0.04 wt% showed optimized specific capacitances of 657.8 F/gm and 1418.8 F/g, respectively. Some of the problems in storage density in activated carbon, like varying micro or meso pores, poor ion mobility due to varying pore distribution, low electrical conductivity, can be overcome by using Graphene and composites of Graphene. Graphene in various structural nomenclatures have been used by different groups for charge storage. Optimization of the electrode structure in terms of blend percentage, binder content and interface character in the frequency and time domain provides insights to the double layer interface structure.

Defect Engineered Multi-Walled Carbon Nanotube arrays as Electrochemical Double Layer Capacitors

2013 ◽  
Vol 1542 ◽  
Author(s):  
Rajaram Narayanan ◽  
Mark Hoefer ◽  
Prabhakar R. Bandaru
Keyword(s):  
Carbon Nanotube ◽  
Double Layer ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Argon Plasma ◽  
Plasma Irradiation ◽  
Multi Walled Carbon Nanotube ◽  
Electrochemical Double Layer Capacitors ◽  
Electrochemical Double Layer ◽  
Double Layer Capacitors

ABSTRACTThe efficacy of vertically aligned defect engineered multi-walled carbon nanotube (MWCNT) arrays as electrochemical double layer capacitors (EDLCs) was investigated using standard electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). We report a ∼ 200% improvement in specific double layer capacitance of MWCNT arrays by extrinsically introducing defects using argon plasma irradiation. The capacitance-voltage characteristics of argon irradiated MWCNTs provide insights into the nature of the defects and their influence on the specific capacitance (capacitance/area).

scholarly journals A rational experimental approach to identify correctly the working voltage window of aqueous-based supercapacitors

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Willian G. Nunes ◽  
Bruno G. A. Freitas ◽  
Renato M. Beraldo ◽  
Rubens Maciel Filho ◽  
Leonardo M. Da Silva ◽  
...  
Keyword(s):  
Water Splitting ◽  
Electrochemical Impedance ◽  
Electrochemical Capacitor ◽  
Cell Voltage ◽  
Operating Voltage ◽  
Electrochemical Characteristics ◽  
Scientific Practices ◽  
Multiwalled Carbon ◽  
Faradaic Current ◽  
Complementary Techniques

Abstract It is common to find in the literature different values for the working voltage window (WVW) range for aqueous-based supercapacitors. In many cases, even with the best intentions of the widening the operating voltage window, the measured current using the cyclic voltammetry (CV) technique includes a significant contribution from the irreversible Faradaic reactions involved in the water-splitting process, masked by fast scan rates. Sometimes even using low scan rates is hard to determine precisely the correct WVW of the aqueous-based electrochemical capacitor. In this sense, we discuss here the best practices to determine the WVW for capacitive current in an absence of water splitting using complementary techniques such as CV, chronoamperometry (CA), and the electrochemical impedance spectroscopy (EIS). To accomplish this end, we prepare and present a model system composed of multiwalled carbon nanotubes buckypaper electrodes housed in the symmetric coin cell and soaked with an aqueous-based electrolyte. The system electrochemical characteristics are carefully evaluated during the progressive enlargement of the cell voltage window. The presence of residual Faradaic current is verified in the transients from the CA study, as well as the impedance changes revealed by EIS as a function of the applied voltage, is discussed. We verify that an apparent voltage window of 2.0 V determined using the CV technique is drastically decreased to 1.2 V after a close inspection of the CA findings used to discriminate the presence of a parasitic Faradaic process. Some orientations are presented to instigate the establishment in the literature of some good scientific practices concerned with the reliable characterization of supercapacitors.

scholarly journals The Capacitive Behaviors of Manganese Dioxide Thin-Film Electrochemical Capacitor Prototypes

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Suh Cem Pang ◽  
Boon Hong Wee ◽  
Suk Fun Chin
Keyword(s):  
Thin Film ◽  
Surface Morphology ◽  
Manganese Dioxide ◽  
Aqueous Electrolyte ◽  
Electrochemical Impedance ◽  
Electrochemical Capacitor ◽  
Pulsed Power ◽  
Power Sources ◽  
Thin Film Electrodes ◽  
Load Leveling

We have documented the fabrication of manganese dioxide (MnO2) thin-film electrochemical capacitor (EC) prototypes with dual-planar electrode configuration. These EC prototypes exhibited good capacitive behaviors in mild Na2SO4aqueous electrolyte. Enhanced capacitive behaviors of EC prototypes were observed upon prolonged voltammetric cycling which could be associated with microstructural transformation of MnO2thin-film electrodes from densely packed plate-like to irregular petal-like surface morphology. Effects of voltammetric scan rates, prolonged voltammetric cycling, electrolyte composition, and electrolyte concentration on the surface morphology of MnO2thin-film electrodes, and associated capacitive behaviors of MnO2thin-film EC prototypes were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge (GCD) techniques. Results of both CV and EIS indicated that thin-film MnO2EC prototypes exhibited the highest specific capacitance of 327 F/g in 0.2 M Na2SO4aqueous electrolyte. Being environmentally benign and cheap, MnO2thin-film electrochemical capacitors have high potential utility as pulsed power sources, as well as load-leveling functions in various consumer electronic devices.

scholarly journals SYNTHESIS AND CHARACTERIZATION OF CHITOSAN/SODIUM ALGINATE BLEND MEMBRANE FOR APPLICATION IN AN ELECTROCHEMICAL CAPACITOR

2020 ◽  
Vol XXV ◽  
pp. 174-191
Author(s):  
Krzysztof Nowacki ◽  
Maciej Galiński ◽  
Izabela Stępniak
Keyword(s):  
Solid Electrolyte ◽  
Sodium Alginate ◽  
Polyelectrolyte Complex ◽  
Electrochemical Impedance ◽  
Electrochemical Capacitor ◽  
Double Layer Capacitor ◽  
Formation Method ◽  
Electrochemical Double Layer ◽  
Stepwise Formation

In this work, we report a stepwise formation method of a chitosan/sodium alginate polyelectrolyte complex (CS/SA PEC) membrane. The proposed method aiming at the utilization of the ultrasonic treatment of chitosan and sodium alginate solution allowed us to obtain a highly homogeneous hybrid membrane for electrochemical usage. The CS/SA PEC membrane saturated in a 2 M Li2SO4 aqueous solution was used in electrochemical double layer capacitor (EDLC) cell to study its applicability as quasi-solid electrolyte. Electrochemical characteristic of EDLC cells was determined by electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge/discharge methods. The results show that the EDLC cell with CS/SA PEC quasi-solid electrolyte exhibit a comparable specific capacitance (102 F g-1 for 0–0.8 V) to CS reference (100 F g-1 for 0–0.8 V) and commercial separator (99 F g-1 for 0–0.8 V) cells. Thus, the CS/SA PEC membrane can be considered as an alternative modification for chitosanbased materials of electrochemical purpose.

A Study on Oxidized Glassy Carbon sheets for Bipolar Supercapacitor Electrodes

1999 ◽  
Vol 575 ◽  
Author(s):  
A. Braun ◽  
M. Bärtsch ◽  
F. Geiger ◽  
B. Schnyder ◽  
R. Kötz ◽  
...  
Keyword(s):  
Double Layer ◽  
Glassy Carbon ◽  
Gas Adsorption ◽  
Electrochemical Impedance ◽  
High Energy ◽  
Active Film ◽  
X Ray Scattering ◽  
Electrochemical Double Layer Capacitors ◽  
Electrochemical Double Layer ◽  
Double Layer Capacitors

ABSTRACTElectrochemical Double Layer Capacitors (EDLC) for high energy and power density applications, based on glassy carbon (GO) electrodes, are being developed in our laboratory. In the context of this project, GC sheets were oxidized and investigated with Small Angle X-ray Scattering (SAXS), Electrochemical Impedance Spectroscopy (EIS) and Nitrogen Gas Adsorption (BET). During oxidation an active film with open pores is built on the surface of the GC. Upon oxidation, the internal volumetric surface area of the active film decreases, whereas the volumetric electrochemical double layer capacitance increases. We show that this effect is correlated with the opening, the growth and the coalescence of the pores.

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