Electrochemical impedance spectroscopy (EIS) can be utilized to characterize battery features, because it allows the dynamics of each elemental process of the battery reaction to be sensitively and separately determined without destruction of the cell. In addition, EIS is expected to be utilized for premonitory diagnosis of onboard batteries in electric vehicles. Here, an overview of the recent diagnosis technologies for determining the health of commercial lithium-ion batteries (LIB) using EIS is provided. We describe equivalent circuit design techniques while explaining and investigating physical and chemical phenomena for a wide range of measured impedance spectra, which are obtained using commercial LIBs. Attention is then focused on separation of the frequency responses of each electrode with or without a reference electrode, symmetric cell, and temperature control. Additionally, a square-current EIS (SC-EIS) technique, which we have proposed, is introduced for monitoring of large-scale LIB systems as a promising future technique.The importance of electrochemical impedance spectroscopy (EIS) has grown in accordance with its expanding fields of application, and the number of papers in this field has increased accordingly, as shown in Figure 1. Now, EIS is one of the main subjects of electrochemistry reviews 1 and textbooks. 2,3 Prior to the early 1990s, a number of important papers that contributed greatly to the development of this field were published, and the timeline of the refinement of EIS has been well summarized by Orazem and Tribollet. 4 Nernst's approach towards utilizing EIS in dielectrics 4 pioneered notable contributions such as the application of EIS to diffusion by Warburg, 5 which was based on research on the fundamental electrochemical reaction. Further, Dolin and Ershler 6 interpreted the impedance response to the electrochemical reaction as a parameter of an equivalent circuit (EC). Many researchers have since demonstrated a relationship between electrochemical processes and the impedance response, for example, in the Randles EC comprising charge transfer resistance, double-layer capacitance and diffusion, 7 the transmission line model (TLM) for porous electrodes, 8,9 and the constant phase element (CPE), 10-12 for electrodes with distributed surface reactivity, surface inhomogeneity, roughness or fractal geometry, electrode porosity.In addition, as regards lithium-ion battery (LIB) development, important reports have been published regarding the relationship between EIS and materials research. Specifically, EIS allows the dynamics of each elemental process of the battery reaction to be sensitively and separately analyzed without destruction of the cell. The basic LIB design consists of an anode, a cathode, an electrolyte, and a separator. For examples on anodes for lithium batteries, the resistances of the charge transfer and solid electrolyte interphase (SEI), and the activation energies of the system (carbonaceous materials, 13-17 grown solid-electrolyte interphase (SEI), 18 silicon nano...
