Measurement of thermophysical parameters and thermal modeling of 21,700 cylindrical battery

There is temperature unevenness inside the operating battery, and the internal temperature distribution of the battery has gradually attracted attention. To establish a thermal model of the 21,700 cylindrical battery that can reflect the internal temperature distribution, thermophysical parameters including anisotropic thermal conductivity and specific heat capacity are tested through experiments. The thermal model includes the heat generation part and heat transfer part. Thermophysical parameters are essential for the heat transfer part. Hybrid pulse power characterization (HPPC) tests are carried out to obtain battery internal resistance, and the entropy coefficient of the battery is also obtained by tests. Internal resistance and entropy coefficient data are used as inputs for the battery heat generation part. The core temperature and surface temperature of the operating battery are measured by the thermocouple embedded inside the battery and the thermocouple pasted on the battery surface. The calculated core and surface temperatures from the battery thermal model are both in good agreement with the measured temperature results. The maximum core temperature of 2C discharging battery is about 60 °C and the maximum temperature difference inside the 21,700 battery reaches 3 °C. The established simulation model can be used for extended research work. When heat dissipation is enhanced by increasing the convection heat transfer coefficient, the overall temperature of the battery decreases but the temperature non-uniformity inside the battery is aggravated.