Electrochemical impedance spectroscopy (EIS) is a powerful and non-destructive characterization technique widely used in the electrochemical research field. It can measure many macroscopic properties such as internal resistance, capacitance, and diffusivity by fitting the obtained impedance with equivalent circuits. Each of the acquired quantities reflects an electrochemical mechanism, e.g, charge-transfer reaction, double layer formation, and mass transport, taking place in the electrode. However, the obtained quantity is a total value for the whole electrode. The underlying connections between the macroscopic properties, intrinsic material parameters, and electrode microstructures are not well understood. This dissertation focuses on building a modeling framework to simulate EIS processes with given electrode microstructures and intrinsic material parameters. With this simulation tool, we provide a digital bridge between battery electrode material properties, electrode microstructures, and their corresponding EIS impedance. Capacitance of an electrochemical device originates from double layer formation in the electrolyte. However, there is a huge spatial discrepancy between the dimensions of double layer and electrode particles (or interparticle space). Thus, smoothed boundary method and adaptive mesh refinement are used to handle the scale discrepancy and the complex geometries of electrode particles in solving the Nernst-Planck-Poisson equations in simulating the double layer formation under voltage loading.The obtained double-layer capacitance is incorporated into multiphysics electrochemical simulations. Cathode electrode made of Nickel-Manganese-Cobalt (NMC111) oxide, is examined with this simulation tool. As a solid solution material, lithium transport in the NMC111 electrode particles is described by Fick's law. EIS curves for various conditions, including different states of charge, electrolyte salt concentration, electrode microstructures, are extracted from the simulations and analyzed. The simulations properly reflect the relationships between particle exchange current density, reactive surface area, and the total resistance of the electrode.Anodes made of graphite, a phase-transforming material upon lithiation/delithiation, are also examined using the simulation tool. The Cahn-Hilliard equation is employed to model the phase transformation processes in the particles. EIS simulations are conducted on single-phase and multi-phase graphite. For single-phase or core-shell phase-distributed graphite particles, the simulated EIS curves exhibit a typical semicircle with a Warburg part. Interestingly, if phase boundaries intersect particle surfaces, a low frequency inductive loop appears on the EIS curve. Lastly, the simulation tool is applied to simulate EIS processes of a full-cell battery of both cathode and anode microstructures. On each electrode, the total current is comprised of capacitance and reaction currents. It is observed that, depending on the loading frequency, the ratio of capacitance-to-reaction current on the two electrodes can be significantly different. The simulation tool allows us to examine the details of electrochemical processes during EIS measurements.

In this book, a new procedure to analyze lithium-ion cells is introduced. The cells are disassembled to analyze their components in experimental cell housings. Then, Electrochemical Impedance Spectroscopy, time domain measurements and the Distribution function of Relaxation Times are applied to obtain a deep understanding of the relevant loss processes. This procedure yields a notable surplus of information about the electrode contributions to the overall internal resistance of the cell.

In this book, a new procedure to analyze lithium-ion cells is introduced. The cells are disassembled to analyze their components in experimental cell housings. Then, Electrochemical Impedance Spectroscopy, time domain measurements and the Distribution function of Relaxation Times are applied to obtain a deep understanding of the relevant loss processes. This procedure yields a notable surplus of information about the electrode contributions to the overall internal resistance of the cell. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.

The Essential Reference for the Field, Featuring Protocols, Analysis, Fundamentals, and the Latest Advances Impedance Spectroscopy: Theory, Experiment, and Applications provides a comprehensive reference for graduate students, researchers, and engineers working in electrochemistry, physical chemistry, and physics. Covering both fundamentals concepts and practical applications, this unique reference provides a level of understanding that allows immediate use of impedance spectroscopy methods. Step-by-step experiment protocols with analysis guidance lend immediate relevance to general principles, while extensive figures and equations aid in the understanding of complex concepts. Detailed discussion includes the best measurement methods and identifying sources of error, and theoretical considerations for modeling, equivalent circuits, and equations in the complex domain are provided for most subjects under investigation. Written by a team of expert contributors, this book provides a clear understanding of impedance spectroscopy in general as well as the essential skills needed to use it in specific applications. Extensively updated to reflect the field’s latest advances, this new Third Edition: Incorporates the latest research, and provides coverage of new areas in which impedance spectroscopy is gaining importance Discusses the application of impedance spectroscopy to viscoelastic rubbery materials and biological systems Explores impedance spectroscopy applications in electrochemistry, semiconductors, solid electrolytes, corrosion, solid state devices, and electrochemical power sources Examines both the theoretical and practical aspects, and discusses when impedance spectroscopy is and is not the appropriate solution to an analysis problem Researchers and engineers will find value in the immediate practicality, while students will appreciate the hands-on approach to impedance spectroscopy methods. Retaining the reputation it has gained over years as a primary reference, Impedance Spectroscopy: Theory, Experiment, and Applications once again present a comprehensive reference reflecting the current state of the field.