| Under the background of environmental pollution and petroleum energy dependence during the use of conventional fuel vehicles,the development of new-energy vehicles is an inevitable trend for the automotive industry.In recent years,the rapid development of electric vehicles has put forward higher requirements for the energy density and safety performance of lithium batteries as power sources.Not only are solid-state batteries with high safety and high specific energy becoming an important direction for the development of next-generation batteries,but also effective thermal management system,accurate temperature prediction,and monitoring of equilibria during battery pack discharging are also extremely important.Therefore,it is necessary to study the underlying parameters of the batteries with different material systems,build a higher-accuracy cell/module temperature prediction model,and explore the effectiveness of different thermal management methods and the impact on the equilibria of the battery pack.It can provide a basic basis for building a safe and effective battery thermal management system(BTMS).In this paper,three kinds of batteries with different material systems--semi-solid ternary lithium-iron battery(NCM-S),liquid ternary battery(NCM-L)and lithium-iron phosphate(LFP)are taken as the research objects,and the following work is carried out:First by the hybrid pulse power characteristic experiment(HPPC),entropy coefficient test,open circuit voltage(OCV)test,tab test,electrochemical impedance spectroscopy(EIS)test,the cells temperature rise test and structural parameter measurement to obtain the characteristic data of each cell;then,the experimental results are analyzed,the thermal characteristics with different batteries and the reasons are compared,and the input parameters needed to establish the dynamic thermal model of each cell are obtained;Secondly,based on the experimental results,the battery body thermal model is established to form a dynamic cell thermal model together with the tab thermal model established by the tab identification method.And the accuracy of the model is verified through experiments to ensure the model’s prediction accuracy.Then,a BTMS based on micro-groove plate heat pipe(MPHP)coupled with forced air cooling was designed,which was composed of power battery module,heat pipes,runners and fans.The thermal management experiments were carried out on relatively bad working conditions in a targeted manner,and the temperature rise of three kinds of BTMS by wind speed is briefly analyzed.Based on these,by analyzing the thermal characteristics of different parts of the MPHP,a segmented thermal resistance network model of the MPHP is established.Secondly,based on Kirchhoff’s current and voltage law,a multi-stage series-parallel relationship module is established.The current distribution model is coupled with the dynamic cell thermal model,and a threedimensional thermo-electric coupling model based on MPHP suitable for three BTMSs is established.By comparing with the experimental results,the reliability and accuracy of the model were proved.Finally,the three-dimensional thermal-electrical coupling model established above was further applied to the three cells connected in parallel and four in series(3P4S)BTMS with a more complicated series-parallel relationship.The effects of different thermal management methods(changing cooling air speed,changing cooling air temperature and changing cooling air speed and temperature simultaneously)on the thermal equilibrium and electrical equilibrium of BTMSs with three different material systems were studied by numerical analysis. |
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