Study On Thermal Performance And Modeling Of Lithium-ion Battery During Charging&Discharging

With the lithium-ion battery gradually applied to high-power military equipment,electric vehicles and power storage and other fields,high-power and high-energy lithium-ion batteries cause more attention.However,with the use of high-energy density batteries,the battery thermal stability problem is even more prominent.Therefore,it is possible to provide a theoretical basis for the research of thermal management system and the guarantee of life cycle safety.In this paper,lithium carbonate battery as the object of study,the thermal performance of the battery is analyzed.Firstly,the entropy thermal coefficient and open circuit voltage are measured and the source of the performance data of the power battery is described,which provide the data support for the thermal performance analysis of the power battery.Secondly,the effects of charge and discharge rate and ambient temperature on the thermal performance(thermal efficiency)of the battery were analyzed.The entropy thermal coefficient of the battery before and after the cycle was analyzed.Finally,the reversible heat generation rate and irreversible heat production rate of the battery during the cycle are investigated.The relationship between the heat loss rate and the heat loss rate during the cycle is analyzed.The results show that the reversible heat production rate varies little with the magnification,but the irreversible heat production rate increases with the increase of the discharge rate.At the same time,the degree of irreversible heat production is more sensitive to the temperature than the reversible heat production rate.The change of the entropy thermal coefficient of the battery with the change of the lithium state of the negative electrode proves that the structure of the electrode material does not change obviously.The reversible heat and irreversible heat loss rate increase with the number of cycles.According to the electrochemical and thermal control equations,the mathematical model was established.After the parameters of the model were calibrated,the test of the 18650 battery running at 50% SOC was carried out under the condition of US06.The simulation results are compared with the experimental results.The results show that the simulated voltage curve and the total heat output are in good agreement with the experimental results if the parameters of the electrochemical model are suitable at room temperature.That can be used to help the battery thermal management system to develop thermal management strategies.