Rapid detection of dynamic electrochemical impedance spectroscopy of batteries based on sampling function excitation

Abstract

The dynamic electrochemical impedance spectra of a battery are more reflective of its real state under charging and discharging conditions than its static impedance spectra. However, the traditional sinusoidal sweep excitation signal greatly impedes the acquisition of low-frequency impedance and barely meets the “stability” test conditions under dynamic conditions during the charging and discharging of batteries. Thus, the low-frequency data of the current DEIS do not have reference value. This paper proposes a DEIS accelerated test method with the sampling function (Sa(t) signal) as the excitation signal, which utilizes the rectangular window spectral characteristics of the Sa(t) signal with uniform energy distribution over a wide frequency range, and realizes the acceleration of low-frequency impedance test under the premise of guaranteeing the test accuracy. To satisfy the requirements of rapid impedance spectroscopy in a frequency band from 1 kHz to 0.05 Hz, we propose a novel excitation signal by combining a sinusoidal sweep signal and two signals with different parameters Sa(t). Measurements of A123's 26,650 battery under 0.6C discharge conditions show that the DEIS of the battery from 1 kHz to 0.05 Hz can be obtained in 95 s. The test speed of low-frequency impedance has been improved by 92.13 % compared with the traditional frequency sweep method, the modulus error is less than 0.32 mΩ, and the phase error is less than 1.87°. This method solves the problem of the traditional swept excitation not being able to realize DEIS measurement because of the low efficiency of the low-frequency impedance test.