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Journal of Electrochemistry ›› 2021, Vol. 27 ›› Issue (5): 467-497.  doi: 10.13208/j.electrochem.201126

Special Issue: “表界面分析”专题文章 “电化学研究方法”专题文章

• Review & Article • Previous Articles     Next Articles

Fundamentals of Electrochemical Impedance Spectroscopy for Macrohomogeneous Porous Electrodes

Xiang Li1, Qiu-An Huang1,2,*(), Wei-Heng Li2, Yu-Xuan Bai1,2, Jia Wang1,2, Yang Liu2, Yu-Feng Zhao2, Juan Wang1,*(), Jiu-Jun Zhang2,*()   

  1. 1. Shanxi Key Laboratory of Nanomaterials and Nanotechnology, Xi’an University of Architecture and Technology, Xi’an 710055, Shaanxi,China
    2. Institute for Sustainable Energy, Shanghai University, Shanghai 200444, China
  • Received:2020-11-26 Revised:2020-12-25 Online:2021-10-28 Published:2021-02-09
  • Contact: Qiu-An Huang,Juan Wang,Jiu-Jun Zhang E-mail:hqahqahqa@163.com;juanwang168@gmail.com;jiujun.zhang@i.shu.edu.cn

Abstract:

Electrochemical impedance spectroscopy (EIS) can be used to diagnose charge transfer reactions and mass transport in porous electrodes. The charge transfer reactions include interfacial charge accumulation and charge conduction as well as electrochemical reaction. In this paper, the complex phasor method is developed under the macrohomogeneous assumption to build an impedance model of porous electrodes for clarifying several vague expressions in the traditional approaches. The following researches are carried out: (1) Identifying characteristic parameters for the porous electrodes, including electrode electronic conductivity σ1, electrolyte ionic conductivity σ2, interface charge transfer conductivity gct, unit area interface capacitance C, solid phase diffusion coefficient D, rate constant k, electrode thickness d, characteristic hole depth Lp and unit volume surface area Sc ; (2) elucidating characteristic output parameters for the impedance spectroscopic response, including field diffusion constant K, characteristic frequencies ω0, ω1, ω2, ω3, and ωmax for interface conduction reaction, finite field diffusion, redox reaction, pore diffusion and minimum characteristic pore size, respectively. In addition, the transition frequencies fk1 and fk2 from conduction to diffusion area and from diffusion to saturation area are also defined and studied respectively; (3) defining the parameters X and Z, herein, X = σ1,Z = dSc, Lp , C, gct , D, k,which are responsible for the evolution trend of the characteristic parameters for impedance spectroscopic response, the competition effects of X and Z parameters coupled in charge transfer reaction are analyzed; (4) Further analyzing the competition effects of X and Z parameters coupled in the charge transfer reaction, the diverging frequencies fXZ and fXZ are phenomenologically defined. The locations of fXZ and fXZ can indicate the depth and breadth of the charge transfer reaction affected by the parameters X and Z. The non-existence of fXZ and fXZ indicates that the parameter X or Z can affect the charge transfer reaction over the whole frequency range. With the help of characteristic frequency and diverging frequency, the effects of electrode kinetic and microstructure parameters on the charge transfer reaction in porous electrodes are studied; on the other hand, the shape change and trend evolution of the impedance responses for porous electrodes are analyzed. The research results in this paper should be able to provide theoretical basis for system simulation and system identification of impedance spectroscopy, technical support for competitive analysis of charge transfer reaction in porous electrodes, and diagnostic tool for optimal design of electrochemical energy storage system.

Key words: porous electrode, charge transfer reaction, electrochemical impedance spectroscopy, characteristic frequencies, diverging frequencies