Institute of Molecule and Crystal Physics, Ufa Federal Research Centre of the Russian Academy of Sciences, Prospekt Oktyabrya 151, Ufa, Russia, 450075.
Phys Rev E. 2019 Dec;100(6-1):062601. doi: 10.1103/PhysRevE.100.062601.
We present the analysis of the impedance spectra for a binary electrolyte confined between blocking electrodes with dielectric layers. An expression for the impedance is derived from Poisson-Nernst-Planck equations in the linear approximation taking into account the voltage drop on the dielectric layer. The analysis shows that characteristic features of the frequency dependence of the impedance are determined by the ratio of the Debye length and the effective thickness of the dielectric layer. The impact of the dielectric layer is especially strong in the case of high concentrated electrolytes, where the Debye length is small and thus comparable to the effective thickness of the dielectric layer. To verify the model, measurements of the impedance spectra and transient currents in a liquid crystal 4-n-pentyl-4^{'}-cyanobiphenyl (5CB) confined between polymer-coated electrodes in cells of different thicknesses are performed. The estimates for the diffusion coefficient and ion concentration in 5CB obtained from the analysis of the impedance spectra and the transient currents are consistent and agree with previously reported data. We demonstrate that calculations of the ion parameters from the impedance spectra without taking into account the dielectric layer contribution lead in most cases to incorrect results. Application of the model to analyze violations of the low-frequency impedance scaling and contradictions in the estimates of the ion parameters recently found in some ionic electrolytes are discussed.
我们提出了在具有介电层的阻塞电极之间限制的二元电解质的阻抗谱分析。从泊松-纳斯特-普朗克方程出发，在考虑介电层上电压降的线性近似下，推导出了阻抗的表达式。分析表明，阻抗频率依赖的特征取决于德拜长度与介电层有效厚度的比值。在高浓度电解质的情况下，介电层的影响尤其强烈，此时德拜长度较小，因此与介电层的有效厚度相当。为了验证该模型，在不同厚度的池中，对聚合物涂层电极之间限制的液晶 4-正戊基-4^{'}-氰基联苯（5CB）的阻抗谱和瞬态电流进行了测量。从阻抗谱和瞬态电流分析中获得的 5CB 中扩散系数和离子浓度的估计值是一致的，并且与之前报道的数据相符。我们证明，在不考虑介电层贡献的情况下，从阻抗谱计算离子参数，在大多数情况下会导致错误的结果。我们还讨论了将该模型应用于分析最近在一些离子电解质中发现的低频阻抗标度违反和离子参数估计的矛盾。
