Health Assessment of Lithium-ion Batteries Based on Characteristic Frequency Impedance

With the widespread use of lithium batteries, accurate estimation of the health status of lithium batteries is very important for battery safety management. In order to accurately estimate the health status of lithium batteries and provide strategies for battery management systems, this paper conducted electrochemical impedance spectroscopy tests on lithium batteries with different states of charge and health in a wide temperature range, and analyzed the lithium battery distribution of relaxation time. A method for estimating the state of health of lithium batteries based on electrochemical impedance spectroscopy was proposed within the operating temperature range of the battery. The test results show that the polarization processes S1 and S2 in the low frequency region are not affected by the state of charge of the lithium battery. However, at different temperatures, the polarization processes S1 and S2 are significantly affected by the state of health, and can effectively characterize the state of battery health. After that, a polarization resistance estimation method based on the relaxation time distribution was proposed to screen out the characteristic frequencies that can effectively characterize the health of the battery, and established a lithium battery health estimation model including the influence of temperature. Finally, the verification experiment shows that the battery health state estimation model established in the article can control the health state estimation error within 2.5%. It can be proved that the distribution of relaxation time method can realize the screening of the characteristic frequencies of batteries, and electrochemical impedance spectroscopy can be used to estimate the state of battery health and improve the level of battery safety.