Supercapacitors electrolytes

Storage batteries/supercapacitors/electrolytic capacitors/fuel cells... 

Ruch, P. W., M. Hahn, F. Rosciano et al. 2007. In situ X-ray diffraction of the intercalation of (C2H5)4N+ and BF4 into graphite from acetonitrile and propylene carbonate based supercapacitor electrolytes. Electrochimica Acta 53 1074-1082. 

Foelske-Schmitz, A., P. W. Ruch, and R. Kotz. 2010. Ion intercalation into HOPG in supercapacitor electrolyte—An X-ray photoelectron spectroscopy study. Journal of Electron Spectroscopy and Related Phenomena 182 57-62. 

Vali, R., A. Laheaar, A. Janes, and E. Lust. 2014. Characteristics of non-aqueous quaternary solvent mixture and Na-salts based supercapacitor electrolytes in a wide temperature range. Electrochimica Acta 121 294-300. 

Rennie, A. J. R., N. Sanchez-Ramirez, R. M. Torresi, and P. J. Hall. 2013. Ether-bond-containing ionic liquids as supercapacitor electrolytes. Journal of Physical Chemistry Letters 4 2970-2974. 

Ruiz, V., T. Huynh, S. R. Sivakkumar, and A. G. Pandolfo. 2012. Ionic liquid-solvent mixtures as supercapacitor electrolytes for extreme temperature operation. RSC Advances 2 5591-5598. 

Shirshova, N., A. Bismarck, S. Carreyette et al. 2013. Structural supercapacitor electrolytes based on bicontinuous ionic liquid-epoxy resin systems. Journal of Materials Chemistry A 1 15300-15309. 

Describes a variety of electrochemical supercapacitor electrolytes and their properties, compositions, and systems... 

It is important to choose an electrolyte with a wide electrochemically stable range. For a solvent, the selection seems difficult due to its intrinsic electrochemical stability. For example, for an aqueous solution, the electrochemical disassociation window of water is around 1.23 V at room temperature. If water is used as a supercapacitor electrolyte solvent, the maximum cell voltage will be around 1.23 V if acetonitrile is the solvent, the electrode potential window is around 2.0 V with an ion liquid, the electrode potential window can be as high as 4.0 V. Therefore, different solvents have different potential windows. Table 2.2 lists several common solvents and their potential windows for supercapacitors. 

The supercapacitors described in the literature have an overall specific capacity of about 1 to 5 F/g (i.e., when allowing for the weight of the two electrodes, the leads, the electrolytes, and aU peripheral components). In them, electric energy can be accumulated with a density of 1 to 5 Wh/kg (which is one to two orders of mag-nimde less than in batteries). 

It was seen above that different types of electrochemical supercapacitors exhibit specific capacities many orders of magnitude higher than the film and electrolytic capacitors known before. It must be added at once, however, that the behavior of supercapacitors differs appreciably from that of ideal film capacitors. In contrast to... 

In the last paper, A. Lewandowski et al. of Poland, examines the role of ionic liquids as new electrolytes for carbon-based supercapacitors. Although not directly addressing the role of new carbon materials (the area of major focus of this book), this interesting theoretical work seeks to optimize electrolyte media, which is in contact with carbon electrodes. 

In supercapacitors, apart from the electrostatic attraction of ions in the electrode/electrolyte interface, which is strongly affected by the electrochemically available surface area, pseudocapacitance effects connected with faradaic reactions take place. Pseudocapacitance may be realized through carbon modification by conducting polymers [4-7], transition metal oxides [8-10] and special doping via the presence of heteroatoms, e.g. oxygen and/or nitrogen [11, 12]. 

Lee HY, Goodenough JB. Supercapacitor Behaviour with KC1 Electrolyte. Journal of Solid State Chem. 1999 144 220-3. 

Fig. 12.3 Fabrication of the nanocomposite paper units for battery, (a) Schematic of the battery assembled by using nanocomposite film units. The nanocomposite unit comprises LiPF6 electrolyte and multiwalled carbon nanotube (MWNT) embedded inside cellulose paper. A thin extra layer of cellulose covers the top of the MWNT array. Ti/Au thin film deposited on the exposed MWNT acts as a current collector. In the battery, a thin Li electrode film is added onto the nanocomposite, (b) Cross-sectional SEM image of the nanocomposite paper showing MWNT protruding from the cel-lulose-RTIL ([bmlm] [Cl]) thin films (scale bar, 2pm). The schematic displays the partial exposure of MWNT. A supercapacitor is prepared by putting two sheets of nanocomposite paper together at the cellulose exposed side and using the MWNTs on the external surfaces as electrodes, (c) Photographs of the nanocomposite units demonstrating mechanical flexibility. Flat sheet (top), partially rolled (middle), and completely rolled up inside a capillary (bottom) are shown (See Color Plates)...

Fig. 11.8 (a) Galvanostatic charge-discharge curve of the supercapacitor using G/CNTs (10 1) as the active material at constant current densities of 100, 250, 500, and 1000 mAg-1 using 30wt% KOH electrolyte, (b) Specific capacitance of 3D hybrid G/CNTs (10 1) measured at different current densities. Reprinted with permission from [88]. 

Figure 2. Representation of (A, top) an electrochemical capacitor (supercapacitor), illustrating the energy storage in the electric double layers at the electrode—electrolyte interfaces, and (B, bottom) a fuel cell showing the continuous supply of reactants (hydrogen at the anode and oxygen at the cathode) and redox reactions in the cell.

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