Wideband Measurement Approach for EIS of Lithium-Ion Batteries Using Low-Frequency Concentrated Disturbance

Precise and rapid measurement for electrochemical impedance spectroscopy (EIS) is conducive to the working state monitoring and fault diagnosis of lithium-ion batteries (LIBs). Although using a wideband signal can effectively reduce measurement time, it will deteriorate the measurement precision due to the insufficient signal-to-noise ratio. Considering this issue, this article proposes a wideband measurement approach using low-frequency concentrated disturbance for the EIS of LIBs. This approach can obtain high measurement accuracy and a wide measurement bandwidth under a small current disturbance. Besides, it effectively reduces the measurement time. First, LIBs are stimulated by a low-frequency concentrated binary sequence signal to enhance measurement precision in a low-frequency region. Then, in the entire frequency region, an accurate EIS can be obtained by a fast Morlet wavelet transform and covariance-based impedance calculation. Finally, the effectiveness of the proposed approach is verified on a buck-boost converter-based EIS measurement platform, and comparative analyses with literature methods are conducted. The experimental results illustrate that the maximum normalized root square error of the two types of LIBs at different state-of-charge is 0.37% under the response voltage amplitude of less than 10 mV. Moreover, this approach is approximately 20 times faster than commercial electrochemical workstations in measurement time.