Thermal Runaway Analysis And Extrusion Simulation Of NCM Lithium-ion Battery

Square shaped 37 Ah NCM lithium-ion batteries were studied in this paper.Based on the research of intrinsic thermal characteristics for lithium ion battery,the thermal runaway behavior of battery was studied.Firstly,the conformity assessment of the lithium-ion battery was studied through the discharge capacity at room temperature,HPPC and EIS was tested to select a better consistency of the cell battery.Then,the EV+ARC equipment for the thermal experiments on the cell,including heating dissipation,heat generation and thermal runaway,were applied to study the thermal characteristics of the cell.In addition,we discussed the temperature change of different parts of the cell during the thermal runaway process and the effects of different charge states when thermal runaway occurred.We compared the difference of the thermal runaway cure between NCM and LiFePO₄ lithium-ion batteries.Finally,for a variety of trigger methods of the battery thermal runaway in the electric vehicle safety accident,we selected extrusion,which is a common one,to study its influence on the thermal runaway behavior.Finally,we simulated the mechanical model of the cell under extrusion conditions by the finite element software and sampling of temperature,voltage and the load of the cell.The main results are drawn as follows:?1?The discharge capacity of the battery was 37.6 Ah at room temperature and the consistency of the sample was qualified after HPPC and EIS test.The state of charge had a direct effect on changes in internal resistance and AC impedance.By the Extended Volume Accelerating Rate Calorimeter,specific heat capacity of the cell battery was measured.Its value was 1286.78 J kg^-1 K^-1.The electrochemical measurement was combined to calculate the heat production and power during the process of charging and discharging.As a result,a direct cognition of its basic thermal characteristics was obtained.?2?In the EV+ARC test results revealed that the overall temperature changing trend at all parts of the battery was consistent with the theoretical curve.However,the temperature at the negative electrode and center of the side was higher.Higher state of charge caused more intense thermal runaway.The thermal runaway temperature of NCM battery was higher than LiFePO₄ battery due to its higher specific energy.Our study reveals that it's necessary to make strict requirements for the thermal safety problem of NCM lithium-ion battery.?3?During the extrusion process,thermal runaway was occurred due to the structural damage.More structural damage caused more intense reaction.The simulation results were in good agreement with the experimental data.When the battery load reached 200 kN,the thermal runaway occurs.Our study is instructive for the structural design and the spatial distribution of the battery system.