动力电池热-电-流多物理场耦合机理研究及多尺度数值模拟

From existing scientific documents, the study about energy management and battery life estimation of power batteries for electric vehicles was mainly based on electrochemical characteristics of battery plates to create models and analyze, which was difficult for researchers to describe them accurately and analyze them quantitatively. This project aims to determine boundary conditions of power batteries and create a battery energy model by analyzing the charging and discharging tests data of power batteries and the demonstration running tests data of electric vehicles; start from the assumption that power batteries would follow basic working theories of electric field under all conditions and establish an electric field model of power batteries, which includes a potential model, an electric field strength model and a current density model, based on basic working principles of power batteries, considering mechatronics boundary conditions and electric field physical characteristics of battery plates; apply the analyzing method of first principle combined with parameter identifying method into studying about the coupling mechanism of multi-physical fields including thermal field, electric field and flow field, and establish coupling mathematical models in multi-scales of battery electrode, battery monomer and battery pack based on multi-physical-fields coupling theories and numerical simulation method; analyze the power battery life attntuation theory and battery performance degradation law to create an evaluation theory and an estimation model about battery life about testing cells; provide a theoretical basis to help analyze mechanical vibration fatigue on electrochemical reaction layer of battery plate and electric field changing law after partly loss to improve batteries' cycle life and working performance ultimately.

在已有文献中，电动车辆动力电池系统能量管理与寿命研究，主要根据电池极板的电化学特性进行建模分析，难于精确描述和定量分析。本项目拟通过分析电池充放电试验数据和电动车辆示范运行工况实测数据，确定动力电池模型边界条件，建立动力电池能量模型；根据动力电池基本工作原理，由电池在工况下必须满足电场基本理论的假设出发，结合电池极板机电边界条件，建立包含电势模型、电场强度模型和电流密度模型的动力电池电场模型；基于多物理场耦合基本理论和数值模拟方法，运用第一性原理和参数辨识法相结合的分析方法，研究电池热场-电场-流场下多物理场耦合机理，建立电池极板、电池单体和电池组多尺度下耦合模型；分析动力电池寿命衰减理论和性能退化规律，形成试验电池对象的总体寿命评价理论和寿命估计模型；最终为分析电池极板电化学反应涂层内机械振动疲劳和部分脱落后的电场变化规律，为提高电池整体循环寿命和使用性能提供理论依据。

锂离子动力电池因其比能量高、循环寿命长、环境污染小等优点已成为电动汽车的主流动力源，而有效地热管理是动力电池安全稳定运行必不可少的条件。本项目从理论仿真和实验测试两个方面，对锂离子动力电池单体电池以及电池组在不同放电条件的温升情况进行研究。旨在研究动力电池热-电-流多物理场情况下的耦合机理，建立电池极板、电池单体和电池组多尺度下耦合模型；探索锂离子动力电池组散热结构的设计方法用以提升电池组温度均一性。.本项目的主要研究内容及重要结果如下：.(1) 根据锂离子动力电池传热以及散热特性，建立了锂离子动力电池热模型，计算锂离子动力电池的热物性参数；根据Bernadi提出的电池生热理论建立了锂离子动力电池的生热速率模型。.(2) 针对锂离子动力电池内部电化学与热能相互影响的特点，通过参数实时传递的方式，实现了一维电化学与三维热模型的耦合计算。结果表明温度会影响电压平台以及活性物质利用率，而电化学反应对温度的影响主要体现在小倍率放电时。.(3) 研究了放电过程中电化学反应速率和传质过程。放电过程中，电化学反应速率在在电极的不同位置存在差异，会形成电化学极化。传质速率的差异会造成扩散极化，正负电极均存在固相扩散极化和液相扩散极化，极化程度随放电过程深入而加大。探索了电极活性物质颗粒粒径以及电极厚度对扩散的影响。揭示了放电倍率、冷却条件对电池单体温度场分布的影响。.(4) 以场协同原理为理论基础，通过仿真计算，提出指导电动汽车动力舱出风口模式的选择，并通过不同环境温度和放电倍率时热流场分析进行验证；同时，还研究电池组不同位置对电动汽车动力舱自然进风散热性能的影响。.项目的完成为提高动力电池使用寿命和使用性能提供理论依据，对锂离子动力电池生产具有重要的指导意义和应用价值。