Design of aqueous redox-enhanced electrochemical capacitors with high specific energies and slow self-discharge

Chun, Sang‐Eun; Evanko, Brian; Wang, Xingfeng; Vonlanthen, David; Ji, Xiulei; Stucky, Galen D.; Boettcher, Shannon W.

doi:10.1038/ncomms8818

Cited by 313 publications

(236 citation statements)

References 69 publications

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“…Reproduced with permission. [81] , which were nearly eight times higher than that of the one without KI/ VOSO 4 . Thanks to the GPEs as electrolyte membrane, glassy paper separator, and Nafion 117 membrane could be left out for cost reduction in a comparison to Frackowiak's work.…”

Section: Redox-active Gpes For Supercapacitorsmentioning

confidence: 85%

“…Additional Faradaic oxidation/reduction reactions of the redox couple contribute pseudocapacitance to the overall capacitance of supercapacitors (Figure 2a). [81] In this case, the capacitances are not only contributed by electrode materials but also contributed from the electrolytes. To date, various redox-active mediators contain organic molecules like hydroquinone (HQ), [82,83] methylene blue (MB), [84] indigo carmine, [85] p-phenylenediamine (PPD), [86] m-phenylenediamine, [87] lignosulfonates, [88] and ionic redox active species like KI, [89,90] VOSO 4 , [91] Na 2 MO 4 , [92] and CuCl 2 [93] have been extensively studied.…”

Section: Redox-active Gpesmentioning

confidence: 99%

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Gel Polymer Electrolytes for Electrochemical Energy Storage

Cheng

Pan

Zhao

et al. 2017

Advanced Energy Materials

718

554

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storage devices with adjustable shapes and high flexibility, which is promising for the burgeoning portable and wearable electronics. [7][8][9] Furthermore, the flexibility and elasticity of GPEs are also prone to tolerate the volume change of electrode materials and the dendrites of lithium metal during charge and discharge processes. [10][11][12][13] As a consequence, GPEs have become one of the most desirable alternatives among various electrolytes for the electrochemical energy storage devices, and significant progress has been made in lithium-ion batteries (LIBs), supercapacitors (SCs), lithium-oxygen (Li-O 2 ) batteries as well as the other kinds of electrochemical energy storage devices, such as sodium-ion batteries, lithium-sulfur batteries, fuel cells, and zinc-air batteries. [14][15][16] In order to meet the requirements of wearable devices for flexibility and deformability, more special GPEs with tough, [17] stretchable, [18] and compressible [19] functionalities have been also developed.Typically, a polymeric framework is adopted in GPEs as host material, providing high mechanical integrity. Several criteria for a good polymer host lie in: [20][21][22] (i) fast segmental motion of polymer chain; (ii) special groups promoting the dissolution of salts; (iii) low glass transition temperature (T g ); (iv) high molecular weight; (v) wide electrochemical window; (vi) high degradation temperature. Within the framework, the salts in the GPEs serve as the sources of the charge carriers, which are generally required to have large anions and low dissociation energy for easier dissociating-induced free/mobile ions. According to the types of electrolytes, there are four categories of GPEs based on proton, [23] alkaline, [24] conducting salts, and ionic liquids (ILs). [25] The criteria for an appropriate electrolyte include: [26][27][28] (i) good dissociation without forming ion pairs or ion aggregation; (ii) high thermal, chemical, and electrochemical stability; (iii) high ionic conductivity. In order to dissolve both the polymer hosts and electrolytic salts, the organic/ aqueous solvents are introduced to provide the medium for ionic conduction. A good solvent should simultaneously have high dielectric constant (ɛ > 15), donor number for more dissociation of ion and chemical and electrochemical stability. Organic solvents normally include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dimethyl formamide (DMF), dimethyl sulphoxide, ethyl methyl carbonate, and tetrahydrofuran.To prepare a high-performance GPE, it is essential to select the species of host polymer, solvent, and electrolytic salt, and then blend them by solution or melt processes, such as casting With the booming development of flexible and wearable electronics, their safety issues and operation stabilities have attracted worldwide attentions. Compared with traditional liquid electrolytes, gel polymer electrolytes (GPEs) are preferred due to their higher safety and adaptability to the design of ...

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Section: Redox-active Gpes For Supercapacitorsmentioning

confidence: 85%

Section: Redox-active Gpesmentioning

confidence: 99%

Gel Polymer Electrolytes for Electrochemical Energy Storage

Cheng

Pan

Zhao

et al. 2017

Advanced Energy Materials

718

554

View full text Add to dashboard Cite

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“…As already demonstrated in the literature, SD depends on parameters such as temperature, maximum cell potential reached and hold time at this value, and the charge/discharge history [20,23]. To date, the majority of studies were focused on SD dependence with the kind of aqueous electrolyte , in absence [6,[24][25][26][27] or presence of certain surfactants [26,27] or redox couple (redox-active electrolyte) [28], and type of separator [24,29].…”

Section: H2so4mentioning

confidence: 99%

Self-discharge of AC/AC electrochemical capacitors in salt aqueous electrolyte

García‐Cruz

Ratajczak

Iniesta

et al. 2016

Electrochimica Acta

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Please cite this article as: L.García-Cruz, P.Ratajczak, J.Iniesta, V.Montiel, F.Béguin, Self-discharge of AC/AC electrochemical capacitors in salt aqueous electrolyte, Electrochimica Acta http://dx.doi.org/10. 1016/j.electacta.2016.03.159 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThe self-discharge (SD) of electrochemical capacitors based on activated carbon electrodes (AC/AC capacitors) in aqueous lithium sulfate was examined after applying a three-hour cell potential hold at Ui values from 1.0 to 1.6 V. The leakage current measured during the potentiostatic period as well as the amplitude of self-discharge increased with Ui; the cell potential drop was approximately doubled by 10°C increase of temperature. The potential decay of both negative and positive electrodes was explored separately, by introducing a reference electrode and it was found that the negative electrode contributes essentially to the capacitor self-discharge. A diffusion controlled mechanism was found at Ui ≤ 1.4 V and Ui ≤ 1.2 V for the positive and negative electrodes, respectively. At higher Ui of 1.6 V, both electrodes display an activation controlled mechanism due to water oxidation and subsequent carbon oxidation at the positive electrode and water or oxygen reduction at the negative electrode.

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“…Furthermore, the preparation process for the redox-mediated electrolyte is rather straightforward as controlled amounts of redox-active species are added directly into the supporting electrolyte. [14][15][16][17] To date, small organic redox-active species such as hydroquinone, 18 p-phenylenediamine, 19 p-nitroaniline, 20 methylene blue, 21 indigo carmine 22 etc. have been reported to show remarkable improvements in capacitance of nearly 5-7 fold as compared to that in a pure supporting electrolyte.…”

Section: Introductionmentioning

confidence: 99%

Indole-based conjugated macromolecules as a redox-mediated electrolyte for an ultrahigh power supercapacitor

Xiong

Lee

Chen

et al. 2017

Energy Environ. Sci.

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aBalancing energy density and power density has been a critical challenge since the inception of supercapacitors. Introducing redox-active additives in the supporting electrolyte has been shown to increase the energy density, however the power density and cycling stability are severely hampered in the process. Herein, an extensively conjugated indole-based macromolecule consisting of 5,6-dihydroxyindole/5,6-quinoneindole motifs, prepared by electrochemical polymerization of dopamine under acidic conditions, was employed as a redox-active additive. By utilizing the conjugation effect, the HOMO-LUMO gap (HLG) of the extensively conjugated indole-based macromolecule was reduced to ca. 2.08 eV, which enhanced the electronic transfer kinetics, in turn improving the power density and reversibility of redox reactions. When coupled with a porous honeycomb-like carbon (PHC) electrode, the assembled supercapacitor delivered an excellent rate performance with a high specific capacitance of 205 F g À1 at 1000 A g À1 . This work reports one of the highest power densities recorded at 153 kW kg À1 for redox-mediated electrolyte systems with a respectable energy density of 8.8 W h kg À1.In addition to an excellent cycling stability of 97.1% capacitance retention after 20 000 charge/discharge cycles, the conjugation degree has to be considered when engineering the redox-active electrolyte so as to improve the power density and stability. Broader contextPortable and reliable energy storage devices (ESDs) have become gradually integrated into technological advancements. Supercapacitors have gained significant recognition as important ESDs due to their high power density arising from fast physical ion adsorption based on the electric double layer (EDL) principle. However, the fast EDL principle is dependent on the electrode surface area which ironically is responsible for poor energy density. Thus, such a limitation has resulted in a research interest shift towards pseudocapacitive capacitors as additional pseudocapacitance can be achieved from the Faradaic reaction. One strategy to incorporate pseudocapacitance is via the addition of small redox species into the supporting electrolyte (resulting in 5-7 times energy density enhancement). However, the use of small redox species typically leads to a poor power density and poor cycling stability which renders such energy density enhancement insignificant. In this work, a supercapacitor based on a novel indole-based conjugated macromolecule redox-mediated electrolyte is reported to achieve one of the highest power densities in redox mediated electrolyte supercapacitor research, while excellent cycling stability was simultaneously attained in this system.

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Design of aqueous redox-enhanced electrochemical capacitors with high specific energies and slow self-discharge

Cited by 313 publications

References 69 publications

Gel Polymer Electrolytes for Electrochemical Energy Storage

Gel Polymer Electrolytes for Electrochemical Energy Storage

Self-discharge of AC/AC electrochemical capacitors in salt aqueous electrolyte

Indole-based conjugated macromolecules as a redox-mediated electrolyte for an ultrahigh power supercapacitor

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