Electrical double layer characteristics of nanoporous carbon derived from titanium carbide

Ionic liquid-based polymer gel electrolytes for symmetrical solid-state electrical double layer capacitor operated at different operating voltages

“…Therefore the cation and anions of magnesium salt and [bdmim] BF 4 can fit well in the pores of the electrode materials. [67][68][69]. This behavior is in agreement with the work of Ania et al [70] and Largeot et al [71].…”

Lithium-ion capacitors using carbide-derived carbon as the positive electrode – A comparison of cells with graphite and Li4Ti5O12 as the negative electrode

“…Therefore, the pores of CDC are easily adopted to match the size of the electrolyte ions and to achieve the most effective usage of the carbon surface for adsorbing the electrical charges from the electrolyte. For example, in common organic electrolytes (e.g., NR 4 þ BF 4 À in non-aqueous solvent), the nanoporous CDC with a pore size of~0.8 nm has revealed an excellent capacity of both, cations (NR 4 þ ) and anions (BF 4 À ), providing a capacitance of as high as 81 F cm À3 and 93 F cm À3 at negative and positive potential values, respectively [7]. Another effective approach to increase the energy density is to increase the operating voltage of the EDLC.…”

The effects of cell assembly compression on the performance of carbon electrochemical double-layer capacitor electrodes

“…Therefore, different sized pores in a porous electrode will have different time constants, which can be correlated to electrolyte ion access times, as elaborated by LozanoCastello [17] and others [7,14,24]. The implication is that not all of the accessible surface area of a porous electrode can be accessed within the same time frame and the maximum capacitance will depend upon the density of the charging current or modulating frequency [4,9,12].…”

“…However, it would be very difficult to assess what effect the changes in the porosity of the carbon electrodes will have on the performance of the supercapacitor based on the results of the porosimetry analyses alone, since that analysis uses an adsorbate gas as a means to determine accessibility. It is well known that a certain portion of the surface area of a porous material, as determined by porosimetry, will be less accessible in an electrochemical environment since electrolyte ions, and their associated solvation spheres, cannot be expected to access all of the same surfaces that an adsorbate gas can [9,17,24]. A more in depth understanding of the electrochemical accessibility of these altered materials can be achieved by evaluating the results of the EIS analyses.…”

“…(5) can be interpreted as a reflection of the potential double layer than can form on those surface areas that are accessible at that analysis frequency. Therefore, the reciprocal of the frequency corresponds to the time allowed for the electrolyte ions to access any particular surface, and so with an increase in the access time (or decrease in frequency), ions can reach those surfaces that are less accessible to form a double layer [24,26]. So as access time increases, more of the surface area of the electrode is being accessed, and the most difficult surface areas to access correspond to the smallest pores in a porous material.…”