Lithium battery AC impedance spectrum online synchronous test method and device

Abstract

The invention provides a lithium battery AC impedance spectrum online synchronous test method and device. The method is characterized by obtaining a current discrete sampling sequence and a voltage discrete sampling sequence through current excitation signals and voltage response signals of a lithium battery; then, calculating a cross-correlation function of the current discrete sampling sequence and the voltage discrete sampling sequence through a Wiener-Hopf equation, and serving the cross-correlation function as a time domain impulse response function of the lithium battery; then, carrying out Fourier transform on the time domain impulse response function to obtain frequency response of the lithium battery; and adjusting the order of a signal generator to obtain lithium battery AC impedance spectrum in different frequency bands. The method and device can realize synchronous test of a plurality of AC frequency impedance of the lithium battery; frequency response of the lithium battery can be obtained through the impulse response function; the required priori knowledge is less; identification can also be carried out very well under the condition that noise and signal-to-noise ratio are rather small; the correlation function can be obtained through the Wiener-Hopf equation; and the device and method have higher anti-jamming capability.

Description

technical field [0001] The invention relates to a testing technology for the AC impedance spectrum of a lithium battery, in particular to an online synchronous testing method and device for the AC impedance spectrum of the lithium battery. Background technique [0002] AC impedance technology is an electrochemical measurement and analysis technology that reflects the internal characteristics of the battery. The performance difference and aging state of the battery can be clearly distinguished in the AC impedance spectrum in different frequency domains. This technology is used for the mechanism analysis of battery materials. It can also be used to analyze the state and characteristics of the battery and establish an equivalent circuit model of the battery impedance. Therefore, it is of great significance to obtain the AC impedance spectrum of the lithium battery accurately and quickly. [0003] Currently commonly used impedance spectrum mainly includes the following testing m...

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Problems solved by technology

However, due to the drift at low frequencies, it is difficult to achieve high accuracy below 1 Hz; at high frequencies, due to input noise, the Lissajous figure will be distorted, and the required equipment is huge and not convenient enough, so it is suitable for laboratories. for rough measurements

[0006] (3) Frequency response analyzer, the basic principle of the frequency response analyzer is to give the sinusoidal excitation signal and its 90° phase-shifted synchronous signal, after multiplying the response signal with the 90° phase-shifted synchronous signal of the sinusoidal excitation signal, Then integrate separately, so as to directly obtain the real part and imaginary part of the impedance at this frequency; in order to achieve higher accuracy, the integral filter requires a long measurement time, especially when the low frequency is studied, the measurement time is significantly increased

[0007] At present, several commonly used test methods are carried out after the battery has been left for several hours, and the battery is completely static, and the method of frequency scanning is used during the test, which can only be tested point by point, and the time is old and cannot be in a certain state. Obtaining the impedance at different frequencies is still a time-sharing single-frequency measurement method in essence, that is, the physical quantity corresponding to each frequency point is measured at different times, and the time required for frequency-by-frequency scanning measurement from low frequency to high frequency relatively long

However, due to the continuous and dynamic changes of the battery due to the influence of external factors, the AC impedance measurement results based on the time-division single-frequency method cannot accurately reflect the impedance spectrum information at a specific moment, and it is an offline measurement

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