Simulation Research On Thermal Runaway Problem Of Ternary Lithium Battery Based On COMSOL

Environmental degradation and energy scarcity have become pressing issues facing the world today.The development of technology in the field of new energy is highly anticipated.Lithium-ion batteries are closely watched by the electric vehicle industry for their excellent performance and are evolving rapidly,but vehicle safety accidents due to battery failure are also increasing day by day.Through a large number of accidents to analyze the causes,it was found that the battery thermal runaway was the source of the accident.Lithium-ion batteries activate different reactions under thermal abuse,releasing large amounts of heat,which can trigger thermal runaway if not dissipated in time.The composite phase change material has good heat absorption performance and can play a good role in temperature control and heat dissipation when applied to the battery module.In this paper,the electrochemical-thermal coupling model of a single cell is established by combining the exothermic mechanism of the electrochemical reaction inside the cell,and the electrochemical behavior under charging and discharging is studied in this way.Based on the above basic model,the module of heat generation by side reactions inside the battery is added,the hot box simulation model and the pinning heat abuse model of single cell are established,and the sequence of side reactions occurring and the exothermic power under different high temperature environments and different charge states,pinning diameter and pinning speed are explored respectively,and the influence law of the above factors on the temperature change and distribution of thermal runaway is obtained.The single cell is formed into a group and the thermal management module of the composite phase change material is added,the thermal runaway model of the battery module is established,the influence of the thickness of the phase change material on the heat dissipation of the battery is discussed,and the compression density of the composite phase change material and the influence law of its constituent-expanded graphite mass fraction on the overall material thermal conductivity are further analyzed.Simulation results show that different ambient temperatures trigger different side reactions,and that the partial side reaction heat release varies significantly.charge state and needling speed and the rate of temperature rise in a linear relationship,the two have the opposite effect,the felting needle diameter increases within a certain range will exacerbate the thermal runaway,beyond which the temperature falls instead.The composite phase change material plays an active role in battery module heat dissipation,which can achieve thermal runaway retardation or even blocking between adjacent cells by increasing its thickness,and then the optimal range of thickness is derived by combining the volume share of the battery,meanwhile,the module heat dissipation effect is more obvious by increasing the compression density and increasing the thermal conductivity,changing the mass fraction of expanded graphite,the enthalpy of phase change and thermal conductivity change in opposite law,and the two are in competition with each other,and the optimal solution of expanded graphite mass fraction is obtained after balancing the heat storage and thermal storage speed.The above influencing factors and data can help the design of the battery module heat sink system.