Research on Heat Generation Measurement for Lithium-Ion Battery Using Isothermal Calorimeter

Isothermal calorimeter is one of the most applicable instruments to measure the heat generation of batteries. In most commercial isothermal calorimeters, battery temperature or its surface temperature is usually controlled. However, such control leads to the calibration factor of isothermal calorimeter varying with batteries and installation methods. This study proposes an improved thermal model to analyze the theory of battery isothermal calorimeter with power compensation method. The innovative finding reveals that when the adapter's temperature is controlled, the calibration factor of isothermal calorimeter approaches one and is independent of heat transfer resistances. In contrast, when the battery temperature is controlled, the calibration factor is less than one and is directly related to the heat transfer resistances. As heat transfer resistances in the calibration process differ from those in the actual battery measurement process, more accurate results can be achieved if the adapter's temperature is controlled. This study also presents the measurement results of a commercial LiNi1/3Co1/3Mn1/3O2/graphite battery under the two different conditions of temperature control. Based on the differential equation when the adapter's temperature is controlled, the real heat flux of the battery is calculated, and the dynamic response characteristic of heat flux is greatly improved.