On-line Estimation Method for Internal Temperature of Lithium-ion Battery Based on Electrochemical Impedance Spectroscopy

The electrochemical reaction in lithium ion power battery is easily affected by temperature, which results in the variation of battery output power and capacity. In order to accurately predict the internal temperature of the battery and provide the basis for the battery management strategy, this paper measured and studied the lithium-ion batteries with different State of Charge (SOC) in a wide temperature range based on the electrochemical impedance spectrum, so as to propose an online estimation method of the internal temperature of the battery based on the electrochemical impedance spectrum. The experimental results show that the imaginary part of the impedance spectrum is not affected by SOC in the range of frequency 10-1000Hz within the range of normal operating temperature of lithium battery (5–55 °C). At the same time, it is sensitive to temperature change and can be used as the characteristic parameter of temperature evaluation. After that, 10Hz is selected as the excitation frequency of the estimation of the internal temperature of the battery, and the internal relationship between the imaginary part value of the battery impedance spectrum and the internal temperature is explored to effectively establish the internal temperature evaluation model of the lithium-ion battery. Finally, the test results show that the temperature evaluation model established in this paper can control the temperature evaluation error within 1.5°C. In this paper, it is proved that the imaginary part of impedance spectrum has a good characterization ability for the battery temperature, which can provide reference for the battery temperature control strategy and improve the temperature rise in the battery working process.