Research On Performance Of Power Battery Compound Thermal Management System

New energy vehicle is an important solution to environmental pollution and energy shortages.Countries around the world are constantly promoting the transformation of traditional fuel vehicles to new energy vehicles.Among them,electric vehicles are currently the most widely promoted new energy vehicles for industrialization and have received widespread attention.As the "heart" of the entire electric vehicle,the power battery has a vital influence on the performance of the electric vehicle.In recent years,frequent fires and explosions of new energy vehicles caused by thermal runaway of power batteries have restricted the promotion and application of electric vehicles.As the most widely used power battery,lithium-ion battery has a high energy density and has a huge safety hazard.When a lithium-ion battery is subjected to external abuse conditions,it is easy to trigger the occurrence of an internal chain reaction,generate a lot of heat,and then enter the thermal runaway state.Based on it,a thermalelectric-chemical multi-field coupling heat generation model of lithium-ion batteries is established in this paper,and the heat generation of lithium-ion batteries at 1C,2C,and3 C discharge rates is studied through a combination of simulation and experiment.The thermal abuse is used to trigger the lithium-ion thermal runaway state,and the changes in the electro-chemical and thermal characteristics of the lithium-ion battery during thermal runaway are analyzed.In addition,a good thermal management system can effectively improve the performance of the lithium-ion battery and ensure the thermal safety of the lithium-ion battery.Therefore,based on the heat-generating characteristics of lithium-ion batteries obtained above,a composite thermal management system including heat pipes,thermally conductive silica gel,phase change materials,and microchannel liquid cooling plates is established in this paper.The velocity uniformity coefficient,friction resistance coefficient,and thermal characteristic parameters are used as evaluation indicators to optimize the design of the inlet flow rate of the thermal management system to obtain the optimal inlet flow rate of the thermal management system.Based on this,the thermal management capability of the established thermal management system under different operating conditions of the lithium-ion battery is analyzed.The research results show that as the discharge rate of lithium-ion batteries increases,the corresponding temperature rise and temperature difference also increase;The established thermal management system can keep the temperature and temperature difference of the lithium-ion battery module during 3C discharge within an appropriate range;The established thermal management system can heat lithium-ion battery modules in different low-temperature environments to a suitable working temperature within 400s;When the WLTC operating conditions are used for testing,the maximum temperature and maximum temperature difference of the lithium-ion battery modules are 298 K,3.5K respectively;The established thermal management system cannot prevent the lithium-ion battery module under thermal abuse conditions from entering the thermal runaway state,but it will delay the time for it to enter thermal runaway.