Electrochemical Impedance Spectroscopy
Jianbo Zhang, Shangshang Wang, Kei Ono
Abstract
The multi-scale, multi-physics nature of lithium-ion battery (LIB) calls for the combined utilization of multiple characterization techniques, in situ or ex situ, electrochemical or non-electrochemical, to explore the complex structures and processes inside the cell. As a non-destructive frequency domain method, electrochemical impedance spectroscopy (EIS) is one of the most popular lab techniques due to its unique capability in differentiating bulk and interfacial processes such as migration, charge transfer, diffusion, and intercalation processes, via perturbing the test object with small-amplitude AC signal spanning wide frequency ranges. The ever-increasing application of EIS attests to the power of this technique. Meanwhile, it also signifies the need to urge the new practitioners to follow the good practice and to avoid the common pitfalls. This chapter gives an introduction to the essence of EIS method and an in-depth exposition of its application in LIB. It is stressed that EIS study is a multi-stage, iterative processes with multi-loops of verification and validation, and that models should be selected or developed based on the purpose of the study, and preferably based on the cell construction and expected physical processes before the inspection of the spectrum. Tables of basic circuit elements and typical equivalent electric circuit models for electrochemical energy systems, including their representation in Nyquist and Bode plots and characteristic frequencies, are provided for easy access and comparison. The characterization of LIB using EIS in the sequence of measurement, features, models, interpretation, and validation, are elaborated. A compact list of exemplary experimental EIS works in major phases of LIB lifetime is compiled, from which messages on the nature of EIS and good-practice guidelines are drawn and discussed.