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Andrea Balducci - One of the best experts on this subject based on the ideXlab platform.
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anodic dissolution of al current collectors in unconventional solvents for high voltage Electrochemical Double Layer capacitors
Chemsuschem, 2017Co-Authors: Jakob Krummacher, Larshenning Hes, Andrea BalducciAbstract:This study investigated the anodic dissolution of Al current collectors in unconventional electrolytes for high voltage Electrochemical Double-Layer capacitors (EDLCs) containing adiponitrile (ADN), 3-cyanopropionic acid methyl ester (CPAME), 2-methyl-glutaronitrile (2-MGN) as solvent, and tetraethylammonium tetrafluoroborate (Et4 NBF4 ) and tetraethylammonium bis(trifluoromethanesulfonyl)imide (Et4 NTFSI) as conductive salts. To have a comparison with the state-of-the-art electrolytes, the same salts were also used in combination with acetonitrile (ACN). The chemical-physical properties of the electrolytes were investigated. Furthermore, their impact on the anodic dissolution of Al was analyzed in detail as well as the influence of this process on the performance of high voltage EDLCs. The results of this study indicated that in the case of Et4 NBF4 -based electrolytes, the use of an alternative solvent is very beneficial for the realization of stable devices. When Et4 NTFSI is used, the reduced solubility of the complex Al(TFSI)3 appears to be the key for the realization of advanced electrolytes.
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the use of binary mixtures of 1 butyl 1 methylpyrrolidinium bis trifluoromethyl sulfonyl imide and aliphatic nitrile solvents as electrolyte for supercapacitors
Electrochimica Acta, 2016Co-Authors: Christoph Schutter, Stefano Passerini, Alex R Neale, Patrick Wilde, Peter Goodrich, Christopher Hardacre, Johan Jacquemin, Andrea BalducciAbstract:Abstract The development of high voltage electrolytes is one of the key aspects for increasing both energy and power density of Electrochemical Double Layer capacitors (EDLCs). The usage of blends of ionic liquids and organic solvents has been considered as a feasible strategy since these electrolytes combine high usable voltages and good transport properties at the same time. In this work, the ionic liquid 1-butyl-1-methylpyrrolidinium bis{(trifluoromethyl)sulfonyl}imide ([Pyrr14][TFSI]) was mixed with two nitrile-based organic solvents, namely butyronitrile and adiponitrile, and the resulting blends were investigated regarding their usage in Electrochemical Double Layer capacitors. Both blends have a high Electrochemical stability, which was confirmed by prolonged float tests at 3.2 V, as well as, good transport properties. In fact, the butyronitrile blend reaches a conductivity of 17.14 mS·cm−1 and a viscosity of 2.46 mPa·s at 20 °C, which is better than the state-of-the-art electrolyte (1 mol·dm−3 of tetraethylammonium tetrafluoroborate in propylene carbonate).
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an ether functionalised cyclic sulfonium based ionic liquid as an electrolyte for Electrochemical Double Layer capacitors
Journal of Power Sources, 2016Co-Authors: Alex R Neale, Stefano Passerini, Andrea Balducci, Christoph Schutter, Peter Goodrich, Christopher Hardacre, Sinead Murphy, Johan JacqueminAbstract:A novel cyclic sulfonium cation-based ionic liquid (IL) with an ether-group appendage and the bis{(trifluoromethyl)sulfonyl}imide anion was synthesised and developed for Electrochemical Double Layer capacitor (EDLC) testing. The synthesis and chemical-physical characterisation of the ether-group containing IL is reported in parallel with a similarly sized alkyl-functionalised sulfonium IL. Results of the chemical-physical measurements demonstrate how important transport properties, i.e. viscosity and conductivity, can be promoted through the introduction of the ether-functionality without impeding thermal, chemical or Electrochemical stability of the IL. Although the apparent transport properties are improved relative to the alkyl-functionalised analogue, the ether-functionalised sulfonium cation-based IL exhibits moderately high viscosity, and poorer conductivity, when compared to traditional EDLC electrolytes based on organic solvents (propylene carbonate and acetonitrile). Electrochemical testing of the ether-functionalised sulfonium IL was conducted using activated carbon composite electrodes to inspect the performance of the IL as a solvent-free electrolyte for EDLC application. Good cycling stability was achieved over the studied range and the performance was comparable to other solvent-free, IL-based EDLC systems. Nevertheless, limitations of the attainable performance are primarily the result of sluggish transport properties and a restricted operative voltage of the IL, thus highlighting key aspects of this field which require further attention.
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electrolytes for high voltage Electrochemical Double Layer capacitors a perspective article
Journal of Power Sources, 2016Co-Authors: Andrea BalducciAbstract:Abstract The development of innovative electrolyte components is nowadays considered one of the most important aspects for the realization of high energy Electrochemical Double capacitors (EDLCs). Consequently, in the last years many investigations have been dedicated towards new solvents, new salts and ionic liquids able to replace the current electrolytes. This perspective article aims to supply a critical analysis about the results obtained so far on the development of new electrolytes for high energy EDLCs and to outline the advantages as well as the limits related to the use of these innovative components. Furthermore, this article aims to give indications about the strategies could be used in the future for a further development of advanced electrolytes.
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a new conducting salt for high voltage propylene carbonate based Electrochemical Double Layer capacitors
Electrochimica Acta, 2013Co-Authors: Sebastian Pohlmann, Andrea BalducciAbstract:Abstract In this paper we report about the use of N -butyl- N -methylpyrrolidinium tetrafluoroborate (PYR 14 BF 4 ) as a new conducting salt for propylene carbonate (PC)-based Electrochemical Double Layer capacitors. The electrolyte 2.3 M PYR 14 BF 4 in PC displays conductivity and viscosity values comparable with those of conventional PC-based electrolytes and allows the realization of EDLCs with an operative voltage of 3.2 V. These high voltage EDLCs display higher energy and power compared to conventional EDLCs. Moreover, thanks to the Electrochemical stability of the electrolyte, these EDLCs display high cycling stability at 3.2 V as confirmed by charge–discharge experiments as well as float voltage tests.
Andreas Stein - One of the best experts on this subject based on the ideXlab platform.
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ionic liquids as electrolytes for Electrochemical Double Layer capacitors structures that optimize specific energy
ACS Applied Materials & Interfaces, 2016Co-Authors: Maral P S Mousavi, Benjamin E Wilson, Sadra Kashefolgheta, Evan L Anderson, Philippe Buhlmann, Andreas SteinAbstract:Key parameters that influence the specific energy of Electrochemical Double-Layer capacitors (EDLCs) are the Double-Layer capacitance and the operating potential of the cell. The operating potential of the cell is generally limited by the Electrochemical window of the electrolyte solution, that is, the range of applied voltages within which the electrolyte or solvent is not reduced or oxidized. Ionic liquids are of interest as electrolytes for EDLCs because they offer relatively wide potential windows. Here, we provide a systematic study of the influence of the physical properties of ionic liquid electrolytes on the Electrochemical stability and Electrochemical performance (Double-Layer capacitance, specific energy) of EDLCs that employ a mesoporous carbon model electrode with uniform, highly interconnected mesopores (3DOm carbon). Several ionic liquids with structurally diverse anions (tetrafluoroborate, trifluoromethanesulfonate, trifluoromethanesulfonimide) and cations (imidazolium, ammonium, pyridiniu...
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utilizing ionic liquids for controlled n doping in hard templated mesoporous carbon electrodes for high performance Electrochemical Double Layer capacitors
Journal of Power Sources, 2015Co-Authors: Benjamin E Wilson, William H Smyrl, Keegan Buffington, Stephen G Rudisill, Andreas SteinAbstract:Abstract The specific energy of Electrochemical Double-Layer capacitors (EDLCs) can be increased by design of the pore architecture to provide large interfaces between electrodes and electrolyte and efficient access to these surfaces. Colloidal-crystal templated carbon electrodes with interconnected, uniform mesopores have demonstrated high capacitances at fast charge/discharge rates in EDLCs used with ionic liquid electrolytes. Here we aim to enhance capacitive performance further through nitrogen doping, by combining a phenol-formaldehyde precursor with the ionic liquid (IL) 1-ethyl-3-methylimidazolium dicyanoamide (EMI-DCA) as the nitrogen source. The IL content in this precursor affects the resistance, structural integrity, and specific capacitance of the porous electrodes. With an IL content up to 50 wt%, the electrode resistance is reduced while the bicontinuous mesoporous structure of the resulting carbon is preserved. The specific capacitance of an electrode prepared with 50% IL in the precursor increases over 40% at 10 A g −1 compared to mesoporous carbons prepared using only the phenol-formaldehyde resol. With an ionic liquid electrolyte, the maximum specific capacitance is 237 F g −1 at 0.1 A g −1 , and a specific capacitance of at least 195 F g −1 is maintained after 1000 cycles at 1 A g −1 . A higher IL content in the precursor results in reduced structural order and capacitive performance.
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three dimensionally ordered mesoporous 3dom carbon materials as electrodes for Electrochemical Double Layer capacitors with ionic liquid electrolytes
Chemistry of Materials, 2013Co-Authors: J P Phillips, Philippe Buhlmann, Aijie Han, William H Smyrl, Andreas SteinAbstract:Compared to rechargeable batteries, Electrochemical Double-Layer capacitors (EDLCs) are normally considered to be higher power but lower electrical energy density charge storage devices. To increase the energy density, one can enlarge the interfacial area between electrodes and electrolyte through the introduction of nanopores and employ electrolytes that are stable over wider voltage ranges, such as ionic liquids. However, due to the relatively high viscosity of ionic liquids and large ion sizes, these measures can result in diminished power performance. Here, we describe the synthesis of carbon electrodes that overcome these limitations and simultaneously provide high specific energies and high specific powers in EDLCs using the ionic liquid EMI-TFSI as an electrolyte. A colloidal crystal templating method was optimized to synthesize three-dimensionally ordered mesoporous (3DOm) carbons with well-defined geometry, three-dimensionally interconnected pore structure and tunable pore size in the range from ...
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Three-Dimensionally Ordered Mesoporous (3DOm) Carbon Materials as Electrodes for Electrochemical Double-Layer Capacitors with Ionic Liquid Electrolytes
2013Co-Authors: John Phillips, William H Smyrl, Aijie Han, Philippe Bühlmann, Andreas SteinAbstract:Compared to rechargeable batteries, Electrochemical Double-Layer capacitors (EDLCs) are normally considered to be higher power but lower electrical energy density charge storage devices. To increase the energy density, one can enlarge the interfacial area between electrodes and electrolyte through the introduction of nanopores and employ electrolytes that are stable over wider voltage ranges, such as ionic liquids. However, due to the relatively high viscosity of ionic liquids and large ion sizes, these measures can result in diminished power performance. Here, we describe the synthesis of carbon electrodes that overcome these limitations and simultaneously provide high specific energies and high specific powers in EDLCs using the ionic liquid EMI-TFSI as an electrolyte. A colloidal crystal templating method was optimized to synthesize three-dimensionally ordered mesoporous (3DOm) carbons with well-defined geometry, three-dimensionally interconnected pore structure and tunable pore size in the range from 8 to 40 nm. To achieve precise control over the pore sizes in the carbon products, parameters were established for direct syntheses or seed growth of monodisperse silica nanospheres with specific sizes, using l-lysine-assisted hydrolysis of silicon alkoxide precursors. Porous carbons were then templated from these materials using phenol–formaldehyde (PF) or resorcinol–formaldehyde (RF) precursors. The pore structures of the nanoporous carbon products were characterized in detail, and the materials were tested as electrodes for EDLCs. Optimal pore sizes were identified that provided a large interface between the electrode and the electrolyte while maintaining good ion transport through the relatively viscous electrolyte. 3DOm PF-carbons with pore diameters in the 21–29 nm range exhibited similar high specific capacitance values (146–178 F g–1 at 0.5 A g–1, with respect to the mass of carbon in a single electrode) as typical large-scale activated-carbon-based EDLCs but showed significantly better high-rate performance (80–123 F g–1 at 25 A g–1), a result of the more accessible pore space in which ion diffusion was less restricted
Christoph Schutter - One of the best experts on this subject based on the ideXlab platform.
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the use of binary mixtures of 1 butyl 1 methylpyrrolidinium bis trifluoromethyl sulfonyl imide and aliphatic nitrile solvents as electrolyte for supercapacitors
Electrochimica Acta, 2016Co-Authors: Christoph Schutter, Stefano Passerini, Alex R Neale, Patrick Wilde, Peter Goodrich, Christopher Hardacre, Johan Jacquemin, Andrea BalducciAbstract:Abstract The development of high voltage electrolytes is one of the key aspects for increasing both energy and power density of Electrochemical Double Layer capacitors (EDLCs). The usage of blends of ionic liquids and organic solvents has been considered as a feasible strategy since these electrolytes combine high usable voltages and good transport properties at the same time. In this work, the ionic liquid 1-butyl-1-methylpyrrolidinium bis{(trifluoromethyl)sulfonyl}imide ([Pyrr14][TFSI]) was mixed with two nitrile-based organic solvents, namely butyronitrile and adiponitrile, and the resulting blends were investigated regarding their usage in Electrochemical Double Layer capacitors. Both blends have a high Electrochemical stability, which was confirmed by prolonged float tests at 3.2 V, as well as, good transport properties. In fact, the butyronitrile blend reaches a conductivity of 17.14 mS·cm−1 and a viscosity of 2.46 mPa·s at 20 °C, which is better than the state-of-the-art electrolyte (1 mol·dm−3 of tetraethylammonium tetrafluoroborate in propylene carbonate).
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a 4 farad high energy Electrochemical Double Layer capacitor prototype operating at 3 2 v ies prototype
Journal of Power Sources, 2016Co-Authors: Alberto Varzi, Christoph Schutter, Jakob Krummacher, Rinaldo Raccichini, Christian Wolff, Guktae Kim, S Rosler, B Blumenroder, T Schubert, Stefano PasseriniAbstract:Abstract In this manuscript we report about the realization and testing of a high-voltage Electrochemical Double Layer capacitor (EDLC) prototype (IES prototype), which has been assembled using innovative electrode and electrolyte components. The IES prototype displays a nominal capacitance of 4 F, a maximum voltage of 3.2 V and its maximal energy and power are in the order of 37 Wh kg −1 and 65 kW kg −1 , respectively. Furthermore, it also displays good cycling stability, high capacitance retention after 80 h float test and acceptable self-discharge. Taking into account substantial improvements of the cell design and assembly procedure, the performance of the IES prototype indicates that the components utilized in this device might be suitable alternatives to the state-of-the-art materials used in high energy EDLCs.
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an ether functionalised cyclic sulfonium based ionic liquid as an electrolyte for Electrochemical Double Layer capacitors
Journal of Power Sources, 2016Co-Authors: Alex R Neale, Stefano Passerini, Andrea Balducci, Christoph Schutter, Peter Goodrich, Christopher Hardacre, Sinead Murphy, Johan JacqueminAbstract:A novel cyclic sulfonium cation-based ionic liquid (IL) with an ether-group appendage and the bis{(trifluoromethyl)sulfonyl}imide anion was synthesised and developed for Electrochemical Double Layer capacitor (EDLC) testing. The synthesis and chemical-physical characterisation of the ether-group containing IL is reported in parallel with a similarly sized alkyl-functionalised sulfonium IL. Results of the chemical-physical measurements demonstrate how important transport properties, i.e. viscosity and conductivity, can be promoted through the introduction of the ether-functionality without impeding thermal, chemical or Electrochemical stability of the IL. Although the apparent transport properties are improved relative to the alkyl-functionalised analogue, the ether-functionalised sulfonium cation-based IL exhibits moderately high viscosity, and poorer conductivity, when compared to traditional EDLC electrolytes based on organic solvents (propylene carbonate and acetonitrile). Electrochemical testing of the ether-functionalised sulfonium IL was conducted using activated carbon composite electrodes to inspect the performance of the IL as a solvent-free electrolyte for EDLC application. Good cycling stability was achieved over the studied range and the performance was comparable to other solvent-free, IL-based EDLC systems. Nevertheless, limitations of the attainable performance are primarily the result of sluggish transport properties and a restricted operative voltage of the IL, thus highlighting key aspects of this field which require further attention.
Stefano Passerini - One of the best experts on this subject based on the ideXlab platform.
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the use of binary mixtures of 1 butyl 1 methylpyrrolidinium bis trifluoromethyl sulfonyl imide and aliphatic nitrile solvents as electrolyte for supercapacitors
Electrochimica Acta, 2016Co-Authors: Christoph Schutter, Stefano Passerini, Alex R Neale, Patrick Wilde, Peter Goodrich, Christopher Hardacre, Johan Jacquemin, Andrea BalducciAbstract:Abstract The development of high voltage electrolytes is one of the key aspects for increasing both energy and power density of Electrochemical Double Layer capacitors (EDLCs). The usage of blends of ionic liquids and organic solvents has been considered as a feasible strategy since these electrolytes combine high usable voltages and good transport properties at the same time. In this work, the ionic liquid 1-butyl-1-methylpyrrolidinium bis{(trifluoromethyl)sulfonyl}imide ([Pyrr14][TFSI]) was mixed with two nitrile-based organic solvents, namely butyronitrile and adiponitrile, and the resulting blends were investigated regarding their usage in Electrochemical Double Layer capacitors. Both blends have a high Electrochemical stability, which was confirmed by prolonged float tests at 3.2 V, as well as, good transport properties. In fact, the butyronitrile blend reaches a conductivity of 17.14 mS·cm−1 and a viscosity of 2.46 mPa·s at 20 °C, which is better than the state-of-the-art electrolyte (1 mol·dm−3 of tetraethylammonium tetrafluoroborate in propylene carbonate).
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a 4 farad high energy Electrochemical Double Layer capacitor prototype operating at 3 2 v ies prototype
Journal of Power Sources, 2016Co-Authors: Alberto Varzi, Christoph Schutter, Jakob Krummacher, Rinaldo Raccichini, Christian Wolff, Guktae Kim, S Rosler, B Blumenroder, T Schubert, Stefano PasseriniAbstract:Abstract In this manuscript we report about the realization and testing of a high-voltage Electrochemical Double Layer capacitor (EDLC) prototype (IES prototype), which has been assembled using innovative electrode and electrolyte components. The IES prototype displays a nominal capacitance of 4 F, a maximum voltage of 3.2 V and its maximal energy and power are in the order of 37 Wh kg −1 and 65 kW kg −1 , respectively. Furthermore, it also displays good cycling stability, high capacitance retention after 80 h float test and acceptable self-discharge. Taking into account substantial improvements of the cell design and assembly procedure, the performance of the IES prototype indicates that the components utilized in this device might be suitable alternatives to the state-of-the-art materials used in high energy EDLCs.
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an ether functionalised cyclic sulfonium based ionic liquid as an electrolyte for Electrochemical Double Layer capacitors
Journal of Power Sources, 2016Co-Authors: Alex R Neale, Stefano Passerini, Andrea Balducci, Christoph Schutter, Peter Goodrich, Christopher Hardacre, Sinead Murphy, Johan JacqueminAbstract:A novel cyclic sulfonium cation-based ionic liquid (IL) with an ether-group appendage and the bis{(trifluoromethyl)sulfonyl}imide anion was synthesised and developed for Electrochemical Double Layer capacitor (EDLC) testing. The synthesis and chemical-physical characterisation of the ether-group containing IL is reported in parallel with a similarly sized alkyl-functionalised sulfonium IL. Results of the chemical-physical measurements demonstrate how important transport properties, i.e. viscosity and conductivity, can be promoted through the introduction of the ether-functionality without impeding thermal, chemical or Electrochemical stability of the IL. Although the apparent transport properties are improved relative to the alkyl-functionalised analogue, the ether-functionalised sulfonium cation-based IL exhibits moderately high viscosity, and poorer conductivity, when compared to traditional EDLC electrolytes based on organic solvents (propylene carbonate and acetonitrile). Electrochemical testing of the ether-functionalised sulfonium IL was conducted using activated carbon composite electrodes to inspect the performance of the IL as a solvent-free electrolyte for EDLC application. Good cycling stability was achieved over the studied range and the performance was comparable to other solvent-free, IL-based EDLC systems. Nevertheless, limitations of the attainable performance are primarily the result of sluggish transport properties and a restricted operative voltage of the IL, thus highlighting key aspects of this field which require further attention.
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Electrochemical Double Layer capacitor and lithium ion capacitor based on carbon black
Journal of Power Sources, 2011Co-Authors: A. Krause, Pavel A Kossyrev, Miodrag Oljaca, Stefano Passerini, Martin Winter, Andrea BalducciAbstract:Abstract In this paper we report the physical investigation and the Electrochemical performance of the carbon black SC3 from Cabot Corporation. The SC3 carbon black was investigated in terms of BET surface area, pore size distribution, resistivity and morphology. Composite electrodes containing SC3 as active material were prepared and used for the realization of Electrochemical Double Layer capacitor (EDLC) and lithium-ion capacitor (LIC). In EDLC, at 5 mA cm−2 charge–discharge currents, the carbon black displays a specific capacity of 40 mAh g−1 and a specific capacitance of 115 F g−1. It also displays a very good cycling stability for over 50,000 cycles and excellent performance retention at currents up to 50 mA cm−2. The performance retention at high currents outstandingly differentiates this carbon black from a few commercially available EDLC-grade activated carbons. Because of the high specific capacity of SC3, the carbon black electrodes were also used in combination with LiFePO4 electrodes in LIC. The results of this study indicate that SC3 carbon black is an interesting carbonaceous candidate for the realization of LIC.
R Kotz - One of the best experts on this subject based on the ideXlab platform.
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a reliable determination method of stability limits for Electrochemical Double Layer capacitors
Electrochimica Acta, 2013Co-Authors: D Weingarth, Alexander Wokaun, Heeju Noh, A Foelskeschmitz, R KotzAbstract:Abstract A reliable method for the determination of regions of Electrochemical stability of electrolytes for Electrochemical Double Layer capacitors (EDLC) by means of potential window opening measurements is presented. For this purpose, a new evaluation method for the anodic and cathodic potential limits of Electrochemical systems utilizing high surface area carbon electrodes is suggested. A change of 5% in the faradaic current contribution within a potential step of 1 V to the overall current is proposed as new stability criterion. The results of seven ionic liquids (IL) and three standard electrolytes dissolved in acetonitrile (AN) or propylene carbonate (PC) at RT are presented. For two electrolytes a temperature dependent study is conducted. The feasibility of the new criterion is verified by full cell constant voltage aging experiments. The IL [EMIM][BF 4 ] displays a maximum cell voltage of 3.5 V at RT, which is, compared to standard electrolytes, an increase of about 0.5 V.
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cycle versus voltage hold which is the better stability test for Electrochemical Double Layer capacitors
Journal of Power Sources, 2013Co-Authors: D Weingarth, A Foelskeschmitz, R KotzAbstract:The stability of Electrochemical Double Layer capacitors (EDLC) utilizing an ionic liquid and tetraethylammoninium tetrafluoroborate (TEABF4) in acetonitrile electrolyte was tested by cycling and by constant voltage hold tests. It turned out that possible degradation of the EDLC is visible in the voltage hold test after a time period which is typically much shorter if compared to the cycle tests. A constant capacitance during several thousands of cycles does not necessarily indicate stability. For capacitor cells using a carbon black as active material and an ionic liquid as electrolyte constant capacitance could be demonstrated over 12,000 cycles between 0 V and 3.75 V. Clear ageing was observed, however, during the voltage hold test at 3.75 V after 300 h. For a maximum voltage of 3.5 V both the cycle and the voltage hold test indicated stable performance over 12,000 cycles or 500 h, respectively. For capacitors using an activated carbon as active material and standard electrolyte TEABF4 in acetonitrile both tests clearly demonstrated degradation for a maximum cell voltage of 3.5 V. The evolution of capacitance loss observed for the voltage hold test at 3.25 V is in good agreement with the degradation observed at 3.5 V for the voltage hold test.
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cycle versus voltage hold which is the better stability test for Electrochemical Double Layer capacitors
Journal of Power Sources, 2013Co-Authors: D Weingarth, A Foelskeschmitz, R KotzAbstract:The stability of Electrochemical Double Layer capacitors (EDLC) utilizing an ionic liquid and tetraethylammoninium tetrafluoroborate (TEABF4) in acetonitrile electrolyte was tested by cycling and by constant voltage hold tests. It turned out that possible degradation of the EDLC is visible in the voltage hold test after a time period which is typically much shorter if compared to the cycle tests. A constant capacitance during several thousands of cycles does not necessarily indicate stability. For capacitor cells using a carbon black as active material and an ionic liquid as electrolyte constant capacitance could be demonstrated over 12,000 cycles between 0 V and 3.75 V. Clear ageing was observed, however, during the voltage hold test at 3.75 V after 300 h. For a maximum voltage of 3.5 V both the cycle and the voltage hold test indicated stable performance over 12,000 cycles or 500 h, respectively. For capacitors using an activated carbon as active material and standard electrolyte TEABF4 in acetonitrile both tests clearly demonstrated degradation for a maximum cell voltage of 3.5 V. The evolution of capacitance loss observed for the voltage hold test at 3.25 V is in good agreement with the degradation observed at 3.5 V for the voltage hold test.
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aging of Electrochemical Double Layer capacitors with acetonitrile based electrolyte at elevated voltages
Electrochimica Acta, 2010Co-Authors: Patrick Ruch, R Kotz, Dario Cericola, A Foelskeschmitz, Alexander WokaunAbstract:Abstract Laboratory-scale Electrochemical capacitor cells with bound activated carbon electrodes and acetonitrile-based electrolyte were aged at various elevated constant cell voltages between 2.75 V and 4.0 V. During the constant voltage tests, the cell capacitance as well as the capacitance and resistance of each electrode was determined. Following each aging experiment, the cells were analyzed by means of Electrochemical impedance spectroscopy, and the individual electrodes were characterized by gas adsorption and X-ray photoelectron spectroscopy. At cell voltages above 3.0 V, the positive electrode ages much faster than the negative. Both the capacitance loss and resistance increase of the cell could be totally attributed to the positive electrode. At cell voltages above 3.5 V also the negative electrode aged significantly. X-ray photoelectron spectroscopy indicated the presence of degradation products on the electrode surface with a much thicker Layer on the positive electrode. Simultaneously, a significant decrease in electrode porosity could be detected by gas adsorption.
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a comparison of the aging of Electrochemical Double Layer capacitors with acetonitrile and propylene carbonate based electrolytes at elevated voltages
Electrochimica Acta, 2010Co-Authors: Patrick Ruch, R Kotz, Dario Cericola, Annette Foelske, Alexander WokaunAbstract:Abstract The aging behavior of Electrochemical Double Layer capacitors (EDLCs) based on activated carbon electrodes bound with poly(tetrafluoroethylene) (PTFE) was tested in electrolyte solutions based on acetonitrile (AN) and propylene carbonate (PC) at a constant elevated cell voltage of 3.5 V. The aging was quantified in terms of capacitance loss and resistance increase for the full cell and the individual electrodes. It is shown that the enhanced aging rate of symmetric EDLCs in either solvent at elevated voltages is dominated by the aging of a single electrode, and that the polarity of this limiting electrode depends directly on the solvent. In AN, the positive electrode ages much more rapidly than the negative, while in PC the negative electrode exhibits faster aging than the positive. After aging, the electrodes were investigated by nitrogen adsorption and X-ray photoelectron spectroscopy, revealing significant modifications of the electrode surface and providing clear evidence for the deposition of electrolyte degradation products on the electrodes.