Incorporating Ionic Liquid Electrolytes into Polymer Gels for Solid-State Ultracapacitors

Li, Wen; Henry, Kent; Turchi, Craig; Pellegrino, John

doi:10.1149/1.2869202

Cited by 130 publications

(93 citation statements)

References 21 publications

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“…For instance, the room-temperature performance of polymer gel electrolyte-based supercapacitors has been improved by mixing ionic liquids in polymer matrices. [43]. A maximum specific capacitance of 33 F g −1 at a current density of 4 A g −1 was observed at 200°C for supercapacitors based on free-standing TPU/clay/RTIL electrolyte.…”

Section: Il-containing Polymer Gel Electrolytesmentioning

confidence: 90%

Influence of Temperature on Supercapacitor Performance

Xiong

Kundu

Fisher

2015

Thermal Effects in Supercapacitors

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Because of the negligible faradic reactions in double-layer capacitors, heat generated during charge/discharge processes derives mostly from Joule heating, which is determined by internal resistance (or equivalent series resistance, ESR). However, heat generated in pseudo-capacitors derives from both Joule heating and exothermic/ endothermic Faradic reactions. Thus, understanding how temperature affects capacitance and ESR is essential to predict supercapacitor performance under different operating conditions. The general techniques (e.g., CV, constant current-charge/ discharge and EIS) to evaluate capacitance and ESR have been discussed in Sect. 2.4.Many factors contribute to ESR in a supercapacitor: (i) interfacial resistance (contact resistance) between the electrode and the current collectors; (ii) electronic resistance of the electrode material; (iii) resistance of ions migrating through the electrode pores; (v) electrolyte resistance, and (vi) resistance of ions migrating through the separator [2,3]. Consequently, ESR depends on the active area and porosity of electrodes, ionic conductivity of the electrolyte, and physical properties of the separator (e.g., porosity, thickness and tortuosity). Notably, electrolyte resistance is only part of ESR. ESR depends on many factors (e.g., electrode structure, materials, electrolytes, fabrication and temperature). ESR is suggested to be inversely proportional to σ within certain ranges [4], but this relation can be violated. For instance, ESR is more dominated by the carbon electrode resistance and the interface resistance at the current collector than electrolyte resistance, as indicated by a much smaller activation energy of ACN-based supercapacitors than that of the electrolyte [5]. Capacitance is a function of surface area and volume of the electrodes, and ionic conductivity of electrolytes, which strongly depends on temperature variations.The operating temperature strongly influences the properties of electrolytes (e.g., viscosity, solubility of the salt in solvents, ionic conductivity, and thermal stability), leading to dramatic changes of capacitance and ESR, particularly at extreme temperatures (ultra-low and ultra-high temperatures). Consequently, the influence of

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Section: Il-containing Polymer Gel Electrolytesmentioning

confidence: 90%

Influence of Temperature on Supercapacitor Performance

Xiong

Kundu

Fisher

2015

Thermal Effects in Supercapacitors

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“…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.…”

mentioning

confidence: 99%

Gel Polymer Electrolytes for Electrochemical Energy Storage

Cheng

Pan

Zhao

et al. 2017

Advanced Energy Materials

757

562

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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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“…However, its toxicity, low flash point (≈5°C), narrow temperature range (caused by a low boiling point of 80°C) and flammability leads to safety concerns, impeding its large-scale application in supercapacitors for automotive, electronics and back-up systems, and various peak power generation systems. Capacitors with such electrolytes may also explode under certain circumstances (e.g., car accidents) [32]. In fact, some countries such as Japan do not allow the use of ACN in supercapacitors.…”

Section: Thermal Stability Of Organic Electrolytesmentioning

confidence: 99%

“…The ionic conductivity of such gel electrolytes is generally greater than 10 −3 S cm −1 at room temperature. However, these organic solvents are volatile and flammable at high temperatures [32,95]. Table 3.4 lists the flash point (the lowest temperature at which an object can vaporize to form an ignitable mixture in air) of different liquid plasticizers.…”

Section: Thermal Stability Of Polymer Gel Electrolytesmentioning

confidence: 99%

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Influence of Temperature on Supercapacitor Components

Xiong

Kundu

Fisher

2015

Thermal Effects in Supercapacitors

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Among the major thermophysical properties of electrolytes, thermal stability and ionic conductivity are the most two crucial properties in determining the thermal performance of supercapacitors. The former determines the usable temperature range of supercapacitor devices, and the latter dictates the electrochemical performance at different temperatures. This section generally introduces the relationships among the critical thermophysical properties of electrolytes, followed by a discussion of the thermal stability and ionic conductivity of different common electrolytes.

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Incorporating Ionic Liquid Electrolytes into Polymer Gels for Solid-State Ultracapacitors

Cited by 130 publications

References 21 publications

Influence of Temperature on Supercapacitor Performance

Influence of Temperature on Supercapacitor Performance

Gel Polymer Electrolytes for Electrochemical Energy Storage

Influence of Temperature on Supercapacitor Components

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