Dynamic Heat Generation of LiNi0.5Co0.2Mn0.3O2 Half Cell Under Cycling Based on an In Situ Micro-calorimetry

To further understand the thermal properties of lithium ion batteries, in situ measurement and calculation of the heat generation under operating condition are conducted. In this work, a novel micro-calorimeter with high accuracy is applied to study the heat flow of the LiNi0.5Co0.2Mn0.3O2/Li half cell. The dynamic heat generation and corresponding electrochemical data are detected out under isothermal environment from 30 degrees C to 70 degrees C with different current rates (0.2, 0.4, 0.6, 0.8 and 1.0 C) and electrode thicknesses (400, 200 and 100 mu m). In addition, heat generation rate is calculated based on the measurement of entropy coefficient and internal resistance. It is found that the heat generation rises with the increase of thickness and current rate, due to concentration polarization and electrochemical polarization, respectively. The lithiation process is more sensitive to changes in current rate than delithiation. Appropriately increasing the temperature can improve the activity of material and reduce the energy consumption of the battery. Besides, the contribution of reversible heat to the overall heat generation should be taken into account especially at a lower current rate (< 0.5 C). The detailed analysis of heat generation and electrochemical performance can provide accurate data for thermal management systems.