Hybrid EIS
Each year, we have new and returning users looking to measure impedance of an electrochemical interface. As you explore the use of standard modes of EIS, we suggest you consider Hybrid EIS. With it, you can set a constant AC voltage in mVrms while still operating under galvanostatic control. This allows you to avoid setting an improper (possibly unsafe!) DC voltage for low impedance devices like batteries. With Hybrid EIS, you set a DC current instead of a DC voltage like you would for Potentiostatic EIS.
But do keep in mind that Hybrid EIS is also useful in freely corroding systems where DC current must be zero, while still maintaining a small AC voltage (≤10mVrms). It’s one of the best ways to ensure that your EIS testing remains “non-destructive” as you periodically monitor the impedance of a corroding coupon over time.
Hybrid EIS is a useful alternative to Potentiostatic EIS under conditions or for devices which make Potentiostatic EIS difficult to perform. The experimental parameters and some of the limitations are indicated and a comparison test shows minimal differences between the two methods for an 18650 battery.
For details on setup parameters and some tips on how to use hybrid EIS, check out our technical note .