부산대학교 도서관

Lithium-ion cells are popular choice for battery packs in Electric vehicles (EV) and renewable energy grid storage system due to their high energy density and specific power. However, temperature has crucial effect on performance, life and safety. In the present study, to understand the thermal behavior of Lithium-ion cells during constant discharge, a one-dimensional thermal model is developed using MATLAB. The model employs the transient heat conduction equation with internal volumetric heat generation, to estimate the spatial and temporal distribution of temperature within the cylindrical cell. The model is validated using available test data for transient discharge rate and was found to be in good agreement with the published data (with a maximum difference of less than 0.5 °C for 0.5C to 1C discharge rates). The model is employed to analyze the thermal behavior of the cell by investigating its response to various discharge rates ranging from 0.5C to 2C, as well as different coolant inlet velocities. It is observed that (a) Natural convection (heat transfer coefficient of $5 W/ m^{2}K$) with operating temperature of 25 °C enable safe operation for discharge rate of less than 0.5C-rate, b) With increase in discharge rate, temperature of cell rises significantly ($T_{max}$ is 32.6 °C for 0.5C and 52.8 °C for 2C), c) Forced convection with 1 m/s and 25 °C kept cell maximum temperature less than 40 ° C and temperature difference within the cell is found to be less than 3 ° C for 1C discharge rate and d) Maximum temperature of the cell reduces with increase in velocity, but results in increased pumping power.