Electrochemical Impedance Spectroscopy

What? Why?

Welcome to my beginner’s guide to Electrochemical Impedance Spectroscopy (EIS). If you're reading this, you perhaps already know that EIS is an electrochemical analysis technique, which finds a lot of application in studying batteries (and fuel cells, and many other systems). It’s a technique I've used since beginning my PhD in 2008, and taught it regularly for many years: I taught the lab part of this topic at the Southampton Electrochemistry Summer School for 3 years during this time, and while at Uppsala University I put together a number of lectures on EIS which I also taught at workshops in Germany, Malaysia and Turkey.

I put these pages together, based on my lectures, because although I think there are some good resources for learning the theory out there, I don’t think there are many that are at a nice accessible level for, say, battery scientists – who often have a stronger background in materials chemistry than they do in electrochemistry. Nor do I think that there are many that cover the practical aspects of EIS well enough – there’s very little help out there for people who get the basic idea of EIS but are struggling to fit their data or aren’t sure how to set up their experiments. If you're looking to get a handle on EIS but aren't sure where to start, these pages are, hopefully, for you.

The pages that follow include basic explanations starting from the beginning, along with some simulation web apps and some exercises where you can get a feel for working with impedance data. You can get started by following the links below. I'm always open to discuss ideas for expanding these pages further, so if you have some suggestions for future additions or changes, I’d be very happy to hear from you:


Words of caution/encouragement

First off, I want to say that although I’ve been a user of impedance spectroscopy since 2008, on an applied level (battery characterisation) it still confuses the hell out of me on a regular basis. Learning the theory is one thing, but in-depth analysis, especially when it comes to equivalent circuit fitting, is hard – it requires a healthy degree of intuition, and usually needs very carefully designed experiments to get meaningful results… but sometimes it’s just a pain. I'd dare to suggest that a large proportion - maybe even a majority - of the people in the battery field who have done some impedance spectroscopy work in peer-reviewed publications do not really understand what they’re doing with it.

But, don’t be discouraged(!). It’s not easy to learn, but in writing this I’ve done my best to keep the level as accessible as possible, to give examples, some little apps where you can do simulations to see how changing parameters in a model system changes things, and many more, to try and give you the best chance to build up that level of intuition.

I used to finish my lectures with “Matt’s top tips for impedance spectroscopy”, to try to restore some of the enthusiasm and confidence I’ve just stolen from my poor students, and here they are:

Matt's top tips for impedance spectroscopy

* An example is ZView (Scribner Associates). Older versions (e.g. 3.2) allow you to do simulations as well as equivalent circuit fitting of data. Perhaps Google can help you out…

Bonus content

Thank you for reading!

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