Research On Measurement Methods Of Electrochemical Impedance Spectroscopy Of Lithium-Ion Battery

With the development of large-scale integration of electronic products, as the core energy source, the health status of battery is increasingly becoming the keypoint of system operation. Study result found that EIS of battery reprents its health status. Therefore, rapid and accurate measurement fo the battery's EIS has great significance in life prediction and health management of battery.This paper has studied on the EIS measurement of battery from frequency domain and time domain.Firstly, a intergated virtual frequency sweep signal generator is used instead of traditional signal genetrator under the conventional principle fo frequency sweep on the LabVIEW platfrom. Modular waveform detect function is used to obatin the amplitude and phase of responsing signal instead of traditional correlation or multipliers.Secondly, in order to solve the problem of long time-consuming in frequency-sweeping, this paper has studied a measurement method based on all-phase FFT, the stimulus signal used is componented by multiple frequencies of sinusoidal signal, the data is processed by all-phase FFT. Comparing with the traditional FFT, all-phase FFT is better in spectrum leakge-preventing and phase invariance, the result is much more accurate and measurement time has been reduced.Finally, another measurement method which is based on the Laplace transform analytic function has been studied. With given transient current step excitation to get time domain of system, and the analytical function expression form of time domain response is obatined by half logarithmic. Then the analytic funtcion is Laplace transformed to get impedance expression in frequency domain. This one has further reduced the measurement time and improved accuracy of result.To verify the measurement methods described above all, two kinds of equivalent circuits are designed, and experiment result is compared with theoretical value and result obatined by CS impedance tester, the validity of the algorithm has been proved. Finally, it is used in the measurement of lithium-ion battery EISAnalysis of the three measurement results showed that they are more simple from the software and hardware point of view to implement, as methods described in this article abandoned the traditional signal generators, multipliers, and other related circuit, they are much possible to be embedded. Frequence-sweeping method is much longer in time consuming, especially in low frequencies. Method based on time domain can shorten measurement time greatly, and the Laplace transform of analytic function is better Method based on the Laplace transform of analytic function is more accurate, because in this method, discrete signal acquisitied is transformed into analytic funciton and been studied, and therefore its impedance is continuous and uniform. Above all, measurement method based on the Laplace transform can test rapidly and accurately, and it is easy to be embedded in both hardware and software to meet the rapid test on battery performance.