Tutorials

*Impedance Spectroscopy in Solid State Ionics, from basics to applications*

Instructors:

- Prof. Bernard Boukamp (University of Twente, The Neatherlands) - original instructor;
- Dr. Dino Klotz (Technion, Israel) - additional instructor.

Schedule

Sunday, 18 June; 8:00 - 11:15 in **Room A5**, **Hall 7 of "Padova Fiere"**

Tutorial Description

Electrochemical Impedance Spectroscopy (EIS) has become an important tool in Solid State Ionics for studying mass and charge transport in electrochemical systems. It is not only of importance for fundamental research, but also for characterizing batteries, fuel cells, sensors, etc. This tutorial contains **two lectures**: the first one addresses the basic principles of EIS, while the second one deals with more advanced applications of EIS. **The two lectures are followed by an ‘EIS clinic’**, where all kinds of impedance problems from the participants can be discussed with both lecturers.

** The first lecture** presents the mathematical fundamentals of EIS for a basic understanding of the method. The use of the various graphical representations is discussed and illustrated with the frequency dispersion of simple systems. The use of ‘Equivalent Circuits’ and how to build a ‘Circuit description Code’ is shown. The relation of the general components, R, C, L, with actual processes in solid state ionics is discussed. The special diffusion related transfer functions are derived starting from Fick’s laws. Real examples will be used to visualize these special relations. The presentation and interpretation of the ubiquitous ‘Constant Phase Element’ is also discussed. A short introduction to measurement methods is included.

** The second lecture** presents more advanced methods in EIS. Proper analysis starts with a data validation procedure. It is shown how the Kramers-Kronig relations can be used to check data for systematic errors and the noise level. De-convolution of EIS spectra is an important step to find a ‘viable’ Equivalent Circuit and corresponding starting values for the adjustable parameters in the consecutive fit procedure. The Complex Nonlinear Least Squares approach (CNLS-fit) will be briefly outlined and alternative fitting methods are discussed. The transformation of impedances into a Distribution Function of Relaxation Times (DFRT) is not a new concept, but has received renewed attention over the last years. A brief guide on this method will indicate the applicability and limitations of DFRT-analysis. Finally the transformation of time-domain measurements into the frequency domain is presented and also applied to non-electrochemical systems.

** In the ‘EIS clinic’**, following the two lectures, impedance related problems from participants will be analyzed and discussed. Participants are invited to send in their problems (

Duration: two lectures of about 50 minutes each, followed by an interactive *‘EIS clinic’* (*ca.* 1 to 1.5 h). Total with 10 minute intermissions 3 – 3.5 hours.

Registration: 150 Euros.

Tutorial Topics:

- Introduction to the basics of impedance spectroscopy;
- Derivation of various diffusion relations;
- Principle of the Circuit Description Code;
- Aspects of symmetrical and three-electrode measurements;
- Data validation with Kramers-Kronig;
- Interpretation of complex impedance spectra using de-convolution methods;
- Complex Nonlinear Least Squares analysis;
- Transformation to a Distribution of Relaxation Times (DRT);
- Time to Frequency transformations
- Illustration of analysis with many examples.

Dr. Bernard Boukamp obtained his PhD in 1974 at the University of Utrecht (Netherlands). He then joined the group of Prof. R.A. Huggins at Stanford. Here he was involved in the development of electrochemical impedance spectroscopy (EIS) for solid state ionics. In 1980 he went to the University of Groningen and in 1984 to the University of Twente where he developed the data analysis program ‘Equivalent Circuit’. He has (co-) authored many publications dealing with EIS. He has presented many tutorials on this subject. He initiated and organized the first Tutorial Workshop at the SSI-17 conference (Toronto, 2009) and has participated in the organization of successful tutorial workshops at the subsequent SSI conferences.

Dr. Dino Klotz received his PhD from the Karlsruhe Institute of Technology (KIT) in 2012. Since then he has been using impedance techniques to characterize solid oxide fuel cells and lithium ion batteries. He was a post-doc at the University of Tokyo, before he joined Avner Rothschild’s group at the Technion in 2015, where he now investigates the dynamic relations between light intensity, photocurrent and photovoltage on hematite photoanodes for solar water splitting. He is particularly interested in developing new methods for a comprehensive characterization of photoelectrochemical devices.