Side plate-based cell-to-pack LiNi_0.5Co_0.2Mn_0.3O₂ lithium battery module design with internal temperature acquisition and precise thermal modeling

Cell-to-pack (CTP) NCM lithium battery cell has been widely applied in electric vehicles (EVs). However, severe heat generation issue significantly affects its safety and wide application. To analyze and solve the severe heat generation issue of large capacity CTP NCM523 (LiNi_0.5Co_0.2Mn_0.3O₂) lithium battery cell, internal temperature detection is carried out through thermocouple insertion, the peak temperature value of the internal rolled cell is proved to be about 2°C and 5°C higher than the temperature value of the external surface under 1/3 C and 1 C discharging, respectively. The relationship between the temperature rising trend and the internal resistance during the charging and discharging has also been found: with a lower state of charge level, the heat generation rate increases, and the peak temperature value occurs at the end of discharging process. Furthermore, a precise battery cell model considering the thermo-physical properties' difference of the battery casing and the internal rolled cell is proposed based on the internal temperature measurement in simulation and numerical calculation, closer to the real heat generation and conduction condition. Finally, the thermal performance of a side plate-based battery thermal management system is investigated through numerical calculation and simulation, the maximum temperature and temperature SD of the battery module under 1 C discharging for 3454 seconds are proved to be decreased by 0.7 K without any supplementary energy cost and coolant devices. Besides, the temperature uniformity of the battery module can be reduced to 0.51°C through the design. Internal temperature of a large capacity LiNi_0.5Co_0.2Mn_0.3O₂ Li-ion battery cell is acquired and analyzed. Precise simulation model is constructed to analyze the heat generation and transfer considering the battery casing and the internal roll. Side plate based battery module is proposed to decrease the temperature rise by 0.7°C without supplementary energy cost coolant devices. Temperature SD of the large capacity Li-ion battery module can be decreased within 0.51°C through the design.