High voltage electrochemical double layer capacitor containing mixtures of ionic liquids and organic carbonate as electrolytes

Krause, A.; Balducci, Andrea

doi:10.1016/j.elecom.2011.05.010

Cited by 150 publications

(93 citation statements)

References 14 publications

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“…In these devices, the operating voltage is a crucial parameter, which impacts both the power and energy densities 10 . Many groups have therefore tried to develop ionic liquids with large electrochemical windows 11,12 . The other target properties are a low viscosity, in order to decrease the charge/discharge time, down to very low temperatures 13 , and the capacitance at the ionic liquid/electrode interface.…”

mentioning

confidence: 99%

Computer simulations of ionic liquids at electrochemical interfaces

Merlet¹,

Rotenberg²,

Madden³

et al. 2013

Phys. Chem. Chem. Phys.

155

188

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Ionic liquids are widely used as electrolytes in electrochemical devices. In this context, many experimental and theoretical approaches have been recently developed for characterizing their interface with electrodes. In this perspective article, we review the most recent advances in the field of computer simulations (mainly molecular dynamics). A methodology for simulating electrodes at constant electrical potential is presented. Several types of electrode geometries have been investigated by many groups, in order to model planar, corrugated and porous materials and we summarize the results obtained in terms of the structure of the liquids. This structure governs the quantity of charge which can be stored at the surface of the electrode for a given applied potential, which is the relevant quantity for the highly topical use of ionic liquids in supercapacitors (also known as electrochemical double-layer capacitors). A key feature, which was also shown by atomic force microscopy and surface force apparatus experiments, is the formation of a layered structure for all ionic liquids at the surface of planar electrodes. This organization cannot take place inside nanoporous electrodes, which results in a much better performance for the latter in supercapacitors. The agreement between simulations and electrochemical experiments remains qualitative only though, and we outline future directions which should enhance the predictive power of computer simulations. In the longer term, atomistic simulations will also be applied to the case of electron transfer reactions at the interface, enabling the application to a broader area of problems in electrochemistry, and the few recent works in this field are also commented upon.

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mentioning

confidence: 99%

Computer simulations of ionic liquids at electrochemical interfaces

Merlet¹,

Rotenberg²,

Madden³

et al. 2013

Phys. Chem. Chem. Phys.

155

188

View full text Add to dashboard Cite

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“…Na-ion, Mg-ion and metal-air batteries) for the development of potentially safer devices. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Furthermore, the high (electro)chemical stabilities and non-volatilities exhibited by many IL structures provides interesting electrolyte media for electrochemical gas sensors (e.g. for O 2 , [16][17][18][19] CO 2 ,20,21 NO 2 22 ) where traditional solvents are prone to evaporation leading to device failure, and also for electromechanical actuator, [23][24][25] and electrodeposition applications.…”

mentioning

confidence: 99%

“…The mutual solubility between many ILs and common nonaqueous electrochemical solvents enable the consideration of a wide range of formulations in a given mixture with the prospect of balancing the desired properties. As such, investigating the application of IL/molecular solvent blends as electrolytes for Li-ion batteries, [1][2][3][4] Naion batteries, 13 Li-O 2 chemistry, [32][33][34] and EDLCs, [7][8][9][10] has continually revealed material benefits relating to electrolyte stability and device safety.…”

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confidence: 99%

Physical and Electrochemical Investigations into Blended Electrolytes Containing a Glyme Solvent and Two Bis{(trifluoromethyl)sulfonyl}imide-Based Ionic Liquids

Neale

Goodrich

Hughes

et al. 2017

J. Electrochem. Soc.

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In this paper, we report on thermophysical and electrochemical investigations of a series of molecular solvent/ionic liquid (IL) binary mixture electrolytes. Tetraethylene glycol dimethyl ether (TEGDME) is utilized as the molecular solvent component in separate mixtures with two bis{(trifluoromethyl)sulfonyl}imide anion based ILs paired with similarly sized cyclic and acyclic alkylammonium cations; 1-butyl-1-methylpyrrolidinium bis{(trifluoromethyl)sulfonyl}imide, [Pyrr 14 ] [TFSI], or N-butyl-N,N-dimethyl-N-ethylammonium bis{(trifluoromethyl)sulfonyl}imide, [N 1124 ] [TFSI]. The blending of ILs with select molecular solvents is an important strategy for the improvement of the typically sluggish transport capabilities of these interesting electrolytic solvents. Bulk volumetric and transport properties are reported as a function of temperature and binary mixture formulation; demonstrating the capacity for enhancing desired properties of the IL. Micro-disk electrode voltammetry and chronoamperometry in O 2 -saturated binary mixture electrolytes was used to assess the effect of formulation on the solubility and diffusivity of the dissolved gas. In addition, further investigations of the behavior of the O 2 redox couple at a GC macro-disk electrode are discussed. The exploration of ionic liquids (ILs) as alternatives to conventional molecular solvents in electrolyte formulations is continually growing for a variety of electrochemical applications. These low melting organic salts can be tailored to exhibit a variety of properties, including hydrophobicity and thermal, chemical, and electrochemical stability, which make them attractive candidate electrolyte solvents. Composed solely of ionic components, ILs consequently possess intrinsic electrolytic conductivity and are additionally non-volatile. These properties have encouraged the use of ILs as (complete or partial) substitutions of the volatile components of commercial Li-ion batteries, electrochemical double layer capacitors (EDLCs), and other prospective battery technologies (e.g. Na-ion, Mg-ion and metal-air batteries) for the development of potentially safer devices.1-15 Furthermore, the high (electro)chemical stabilities and non-volatilities exhibited by many IL structures provides interesting electrolyte media for electrochemical gas sensors (e.g. for O 2 , 16-19 CO 2 , 20,21 NO 2 22 ) where traditional solvents are prone to evaporation leading to device failure, and also for electromechanical actuator, 23-25 and electrodeposition applications. [26][27][28] Nevertheless, while the properties of ILs are dependent on the virtually unlimited combinations of different cation and anion structures, the attractive features are generally coupled with sluggish transport properties relative to conventional electrolytes based on either aqueous or organic solvents. In turn, electrochemical devices constructed with neat IL electrolytes are likely to suffer transport limitations on useable current rates for the given application, for example restricting power capabiliti...

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“…However, these two quantities vary in opposite ways in concentrated electrolytes, 63 so that the optimum will necessarily be a trade-off between these quantities. [64][65] Other limitations such as the operating temperature or the long-term stability may also be taken into account. It is worth noting that several ionic liquids may be combined, 66 which increases further the number of potential electrolytes.…”

Section: Discussionmentioning

confidence: 99%

“…Nevertheless, from the above observations, an extension to the EWCC model, developed by Huang et al, [63][64] was suggested by the authors. 56 This new model was termed the 'electric multiple chargelayer capacitor' (EMLC) and was used to understand the capacitive behaviour of CNT EDLCs with RTIL electrolytes.…”

Section: Capacitance Enhancement Of [Emim] + [Tfsi]mentioning

confidence: 99%

Molecular modelling of carbon/ionic liquid interfaces for electric double – layer capacitors

Burt¹

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Electric double-layer capacitors (EDLCs) are important energy storage devices that have high potential for use in existing and emerging markets such as electric vehicles, portable electronic devices, and smart grid management. This is due to their high power density and long lifetime, which are a result of their simple ion adsorption mechanism for charge storage. A significant and ongoing effort is being made to improve the energy density of ELDCs, so that they financially compete with batteries. EDLC improvement has mainly been facilitated through the investigation and discovery of novel solid and liquid materials.This topic was studied with the motivation of investigating charge storage mechanisms in EDLCs with configurations where traditional models are not appropriate to describe the phenomena observed in the literature. Significantly, in small pores anomalous results challenged the traditional beliefs of the electric double layer (EDL) and the accessibility of ions to sub-nanometre micropores.Highly dense RTIL electrolyte, which are non-dilute, and can also be solvent free, also can't be described by traditional models and display complex phenomena such as charge over-screening.This thesis evaluates molecular and charge storage mechanisms at solid-liquid interfaces of room temperature ionic-liquid (RTIL) electrolytes and porous carbon electrodes. Changes in charge storage mechanisms with the addition of an aprotic solvent, acetonitrile (ACN,) to the RTIL, was also investigated in simple slit-pores, and complex carbon electrode structures. The contact angle of RTIL drops was also investigated under a variety of conditions. The methodology of molecular dynamics (MD) simulation was chosen for this thesis as it offers unique benefits to approach the problem of understanding molecular phenomena in ELDCs. MD simulation was selected as it is possible to systematically control variables of interest to a high level of accuracy. In this way, theoretical structures, or models derived from real materials, can be analysed. Significantly, analysis of charge storage mechanisms occurring within small pores, or with dense electrolytes, can be completed with relative ease, unlike with experiments which require difficult or expensive in situ experimental techniques.The analysis began with studying simple slit-pore electrodes to provide a framework for comparison with more complex electrode materials. The charge storage mechanism was tested under a variety of conditions. Most interestingly, capacitance was found to have a moderate dependence on the amount of ACN in the electrolyte, which contrasts with previously noted behaviour at flat walls. Additionally, solid-like behaviour was observed for the bulk electrolyte in certain systems.iii We present the first results for a MD simulation of the RTIL EMIMBF 4 in model CDC electrodes at a potential of 1 V, with systematic addition of ACN to the electrolyte. Our simulations showed that the mechanism of charge storage is different between the positive and negative electrode,...

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High voltage electrochemical double layer capacitor containing mixtures of ionic liquids and organic carbonate as electrolytes

Cited by 150 publications

References 14 publications

Computer simulations of ionic liquids at electrochemical interfaces

Computer simulations of ionic liquids at electrochemical interfaces

Physical and Electrochemical Investigations into Blended Electrolytes Containing a Glyme Solvent and Two Bis{(trifluoromethyl)sulfonyl}imide-Based Ionic Liquids

Molecular modelling of carbon/ionic liquid interfaces for electric double – layer capacitors

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