电动汽车动力电池热管理系统基础科学问题研究

The lithium-ion power battery plays a cruial role in developing of electric vehicles. However, excessive high or low temperature and uneven temperature distribution are disadvantages for the performance and safety of the batteries, leading to explosion in some extremely serious conditions. A compact thermal management system, which has integrated a novel loop heat pipe and phase change material , is proposed based on the optimal operation and safety temperature of lithium-ion battery. The main focused scientific issues of this project are listed as following: (1) the coupled effect for Lithium ion intercalation, deintercalate and electrolyte flow and the influence of this effect on heat generation quantity, battery temperature and performance. (2) the theoretical design model for ultra-thin loop heat pipe and some key factors that affect the starting performance and heat transfer limit. (3) the design theory of phase change materials with high thermal conductivity and latent heat, and the thermodynamics properties of phase change materials at microscopic and mesoscopic scale level..By combining the theoretical, experimental and numerical research methods, a coupled model for battery heat generation and its transfer is proposed to reveal the heat generation mechanism, temperature distribution and performance degradation mechanism. The theoretical model for the design of ultra-thin loop heat pipe is proposed to identify the coupled heat and mass transfer characteristics in vapor-liquid/solid-liquid phase under conditions with unsteady heat sources. Some effective design methods and heat transfer enhancement approaches for phase change materials based on alkanes are proposed. The present work is expected to provide guidelines for thermal management system design and performane improvement for power battery.

锂离子动力电池是发展电动汽车的关键。电池温度过高或过低以及分布的不均衡都不利于其性能的正常发挥和安全性，严重时甚至导致爆炸。本项目针对锂离子电池最佳工作和安全温度，提出基于环路热管耦合相变材料的紧凑型热管理系统。拟将开展如下基础科学问题研究: (1) 锂离子的嵌入、脱嵌及电解液流动的耦合作用对产热量、电池温度及其性能的影响规律。(2) 超薄型环路热管启动及传热极限的影响因素、影响规律及其设计理论模型。(3)基于烷烃的高导热高潜热相变材料的设计理论与微介观热力学特性表征。 . 通过理论、实验和数值模拟结合的研究方法，提出电池产热传热的耦合模型，揭示动力电池产热机理、温度分布及性能衰退规律；提出超薄型环路热管的设计理论模型，阐明非恒定热源条件下，汽-液/固-液相变耦合的热质传递规律；提出基于烷烃的相变材料设计与强化传热的有效方法。研究成果可为动力电池温控系统设计和性能提升提供指导。

围绕电动汽车动力电池热管理系统基础科学问题，提出环路热管/相变材料耦合系统，开展深入系统的实验研究、理论分析与数值模拟。建立了锂电池孔隙尺度物质输运模型，揭示了离子在正极和负极材料表面的非均匀嵌入与脱嵌过程引起的离子与电势的非均匀分布规律，根据锂电池多孔电极内过电势分布特征，进一步获得锂电池的产热规律。系统研究了温度对锂离子电池基本性能和寿命衰减的影响，揭示了电池内部热质传递的温度效应及其对宏观性能衰退的影响机制。成功制备相变调温胶囊材料和热致柔性复合材料，建立了有效导热预测模型，获得了不同温度区间的相变演化过程和传热特性，拓展与丰富了复合相变材料的设计理论。阐明了超薄型环路热管热输送特性，揭示了小深宽比微小通道内受限气泡的特性行为及其对管内流动沸腾过程的影响，明晰了超薄型环路热管的启动响应、运行温度、热阻等工作特性，并建立不同流型的等效换热系数的预测模型。建立基于相变材料/热管耦合的电池热管理系统，实现了在不同工况下的优异散热和均温性能，揭示了热流在固液相变和热管导热竞争作用下的温控模块热流分配规律，实现温控模块的长时间稳定运行。研究结果丰富和发展了相关学科知识，并为电动汽车动力电池热管理设计奠定了坚实的理论基础。