An Electrochemical Impedance Spectroscopy Measurement Method based on Multi-frequency Injection

Electrochemical impedance spectroscopy (EIS) is a perturbative method that characterizes the dynamics of an electrochemical process. It is an effective method to evaluate the health status of batteries. The traditional measuring method of EIS is usually injecting an external excitation current to the battery and measuring the response voltage. Then the inpedance of battery can be calculated. However the test frequency band requirements for the EIS of lithium battery is usually from 1mHz to 1kHz. It will take a lot of time to complete the measurement with traditional frequency sweep method. This paper provided a new measuring meathod based on multifrequency excitation. Firstly, an EIS measurement platform was built based on Pico data acquisition card. Next, the frequency selection rules of multi frequency excitation waveform was studied and an example of selecting 5 frequency points per 10 octave was given. Finally, the measurement results of battey EIS under multi frequency excitation were verified. The experimental results show that the electrochemical system of lithium battery has good response characteristics under multi frequency excitation. The measurement results of EIS are basically consistent with that of single frequency excitation.