Frequency dependence of conductivity of ethylene carbonate based electrolyte for Li-ion battery

Abstract

Specific cell arrangement corresponding to four probe pouch cell with two reversible current and two indifferent potential electrodes is applied to study the existence of frequency dependence on conductivity of a medium between two potential electrodes, i.e., separator impregnated with electrolyte. It is established that frequency dependence of conductivity for carbonate-based electrolyte solution does exist. Series resistance is found to be in a good agreement by specific value with that reported earlier. Low frequency limit of impedance spectra is a few decimal orders higher than that of series resistance. Both low-and high-frequency resistances increase with the interelectrode distance in agreement with Ohm law.

Effect of ethylene carbonate concentration on the conductivity of carbonate-based electrolytes with LiPF6 for Li-ion batteries

“…It should be mentioned that the viscosity of an electrolyte controls the mobility of ions, while the dielectric constant determines the dissociation degree of the electrolyte salt. It is clear that the values of series resistance for the electrolytes correlate with the specific conductivities, as we described previously [1].…”

“…1 Impedance spectra measured between the reference electrodes of a four-probe cell using an auxiliary channel of Solartron equipment at 25°C (a); enlarged spectra of (a) in a lowresistance region (b) seems to be due to the variation in the dielectric constant of the electrolyte solution. The value of the resistance in this region is about one order of magnitude higher than observed earlier for a three-component electrolyte using the same cell geometry [1]. However, the direct current resistance of the cell sharply decreased in the concentration range 40-50 vol.% of EC in the electrolyte.…”

“…Four-probe pouch-type cells were used for EIS measurements [1]. A symmetrical sandwich-type arrangement of a lithium foil electrode (100 μm, Cyprus Foote Mineral Co., USA; electrode area, 40×27 mm) attached to a Ni current collector with polyethylene separators (25 μm NR520) and Ni indifferent electrodes were pressed between two Teflon plates and sealed hermetically in a pouch foil under vacuum condition.…”

“…Two parallel spectra were recorded simultaneously during EIS measurements [1]. The main channel of the Solartron instrument recorded a spectrum for Li/Li cell.…”

“…A proper treatment of EIS results requires deep insight into the intrinsic properties of the cell components. In our previous study [1], a fourprobe model cell was applied for the study of the frequency dependence of the resistance of a separator impregnated with electrolyte between two indifferent electrodes. We demonstrated that there is a frequency dispersion for organic carbonate-based electrolytes.…”