Diagnostics of Functional Layers of All-Solid-State Thin-Film Lithium-Ion Batteries

This chapter of monograph considers the method of Electrochemical Impedance Spectroscopy (EIS) and its application within a structural approach to the study of the charge and mass transfer phenomena in the SSLIB functional layers. The feature of the EIS method is that its understanding requires knowledge of the fundamentals of physical and chemical kinetics, electrical engineering, the theory of a complex variable, mathematical modeling and circuitry. Here this information is given only to the extent that is necessary for a consistent representation of the material without omissions or references to additional information sources. Another feature of the EIS method is that its theory operates by idealized elements with lumped parameters simulating processes that are distributed by definition. Therefore, the chapter pays special attention to the derivation of mathematical expressions for such elements and the transition from the impedance of distributed systems to the impedance of elements with lumped parameters. Here the most common elements of electrochemical systems, such as the Warburg element, the final-length diffusion element, the Gerischer element and the constant phase element are considered. For each of the elements under consideration, the formulation of the boundary value problem and the main stages of its solution are provided. Examples of Nyquist diagrams calculating for structural models of various electrochemical systems are given as well as their interpretation. The final part of chapter is devoted to briefly discussing the most common impedance measurement methods.