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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...

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The degradation of the commercial Li ion battery was analyzed by electrochemical impedance spectroscopy, where our previous proposed equivalent circuit was applied. The degradation with the cycling was clearly explained by the main parameters of capacitive and resistive components, i.e., it responded until 300 cycles to the decrease in capacitive component, while after 300 to 550 cycles to the increase in resistive component.A detection of the state of the degradation of batteries is one of the most important issues for energy storage systems. Electrochemical impedance spectroscopy (EIS) is the most effective method of nondestructive investigation for batteries. To detect the degradation using the EIS, efforts have been made by various groups. 14 We already proposed an equivalent circuit for a wide range of impedance spectra. 5 The equivalent circuit was newly redesigned for the analysis of the lithium ion battery (LIB) with consideration of the contributions of a variety of diffusion parameters resulting from the various particle sizes for the cathode and the solid-electrolyte interphase (SEI) formed on the anode particles, as well as electrochemical reactions and inductive components. 6 In addition, the sensitive assessment of residual errors resulting from the data fitting demonstrated the validity of the proposed circuit including the SEI component. The electrochemical impedance of the electrodes in a commercial LIB at various states of charge was analyzed to evaluate the proposed circuit.In this study, we focused on an analysis using the impedance fitting technique on the basis of our previously proposed equivalent circuit for the degradation or the capacity fading of LIB with the chargedischarge cycling.A commercially available prismatic LIB (Panasonic Corporation) with a nominal capacity of 850 mA h for cellular phones was used in this work. Active materials of anode and cathode were graphite and lithium cobaltite (LiCoO 2 ), respectively. The LIB was subjected to electrochemical tests at room temperature. The battery was charged and discharged with a constant current constant voltage (CCCV) protocol between 2.75 and 4.

Electrochemical impedance spectroscopy (EIS) using an equivalent circuit is a powerful tool in the diagnosis of lithium-ion batteries (LIBs). However, LIBs have been increasingly used in applications requiring power higher than that used for conventional LIBs for portable electric devices. Considering this demand for LIBs, the ionic resistances in the electrodes, which raise a reaction distribution under high-power operation, are important. This consequently means EIS analysis should include ionic resistances in the electrodes in equivalent circuits. Additionally, the impedance response of LIBs are too complicated to be analyzed in detail because the impedance response consists of overlapping elemental processes such as chemical reactions and ion migration. This paper therefore presents an analysis of impedance responses, which are independently obtained by a micro reference electrode, by using a transmission line model (TLM) that possesses the ability to count the ionic resistances in the electrodes. Similar to the conventional Randles equivalent circuit, the equivalent circuit with TLM could fit the impedance responses simulated by the equivalent circuit with measured responses. This paper discusses the potential of EIS using an equivalent circuit coupled with a TLM for diagnosis of LIBs in power applications.

The electrode surfaces of degraded lithium-ion batteries (LIB) were analyzed by liquid chromatography-quadrupole time of flight mass spectrometry (LC-QTOF/MS). The solid-electrolyte interphase (SEI) layer influences the performance of LIBs. Therefore, we conducted a study aimed at clarifying the deterioration mechanism of LIBs by examining the components in the SEI before and after degradation due to cycling. We believe that the change in the mass transfer characteristics at the electrode interface influenced by SEI deterioration can be clarified via LC-QTOF/MS, which would allow elucidation of the deterioration mechanism. The analysis results showed that the degradation products contain multiple components, including polymers of carbonate compounds and phosphate esters, which are formed via electrochemical and chemical reactions, resulting in remarkably reduced capacity. Since the invention of lithium-ion batteries (LIB), many research groups have actively conducted research on improving the battery performance.1-7 Excellent properties, including high capacity and high energy density, have been achieved owing to the work conducted so far. As a result, LIBs are not only used as power sources for mobile devices such as phones and personal computers, but are also used as power sources in electric vehicles, aviation, etc., as well as large-scale stationary power sources for smart grids. [8][9][10] Owing to the remarkable expansion in their applications, it is necessary that LIBs are highly durable and safe in various environments; as a result, durability tests for LIBs have been conducted under diverse settings. In addition, the battery deterioration mechanisms in various cases have been widely studied. 11-13To accurately understand the deterioration mechanism, it is necessary to utilize precise mass spectrometry techniques to determine the structure and composition of materials present at the electrode interface, including the electrode surface layer (i.e., solid electrolyte interface or SEI). By conducting a proper structural analysis, the deterioration mechanism can be discussed in terms of the exact reactions occurring at the interface. The chief analytical techniques that are used to structurally analyze the SEI layer include X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and nuclear magnetic resonance spectroscopy (NMR). 14-21All of these techniques enable the estimation of the skeletal structures of the compounds present in the SEI. However, since the structural formula obtained by these techniques is not supported by precise mass information, the exact reactions governing the deterioration mechanism cannot be deduced from these techniques. On the other hand, the use of precise mass spectrometry for analyzing the electrode interface, including the SEI layer, may allow accurate elucidation of the degradation behavior at the electrode interface by distinguishing between the degradation components and the components of the intrinsic SEI layer. Further, methods for suppr...