锂离子动力电池碰撞失效机理和表征模拟研究

Crash safety of lithium-ion traction batteries is an important part in the entire electric vehicle safety. At present the capability of predicting impact failure of lithium-ion batteries has not yet been well developed, forming a barrier in the CAE design for crash safety of electric vehicles. Generating applicable crash models and impact injury tolerance of batteries will help not only the structural optimization and design for protection, but also the on-board system improvement for diagnosing and managing battery safety. The present study focuses on the failure mechanism, characterization and modeling of lithium-ion traction batteries under impact loading. (1) Through designing and conducting the impact tests of battery cells and modules based on typical crash scenarios of full vehicles, the characteristics of impact response and the regularities of internal short circuit of batteries are analyzed. (2) The dynamic tests of battery component materials are carried out, and the key issues in material characterization, such as the dynamic mechanical behaviors of each component material and the homogenized dynamic mechanical behaviors of jellyroll, are sophisticatedly solved. (3) By building a detailed heterogeneous finite element model of battery cells, the simulations of battery cell crash scenarios are conducted. Based on testing and simulation results, the characteristics of the injury evolvement inside battery cell during the impact are revealed. (4) By building a finite element model of modules based on homogenization simplification of the jellyroll in the battery cell, the simulations of battery module crash scenarios are conducted. Correlation between the measureable mechanical variables, the battery module deformation and cell injuries, and the internal short circuit during the impact is revealed. The impact injury tolerance of battery modules is established which is adaptable to protective structural designs.

锂离子动力电池碰撞安全是电动汽车安全性的重要环节，目前电动汽车碰撞安全设计中亟待突破的一个技术瓶颈是锂离子动力电池碰撞失效预测。开发电池碰撞仿真模型，建立电池碰撞损伤容限，既有助于电池碰撞保护结构的优化设计，也有助于完善车载电池安全管理系统。本项目以碰撞载荷作用下的锂离子动力电池失效机理和表征模拟为研究核心，（1）基于整车典型碰撞工况设计并开展电池单体和模块碰撞实验研究，分析电池碰撞响应特征和内短路规律；（2）开展电池组分材料动态测试，解决电池组分材料动态力学行为表征和卷芯均质化等效表征等关键问题；（3）构建电池单体的多组分非均质精细模型，开展电池单体碰撞模拟，结合实验观测分析，揭示电池单体碰撞内部损伤演化规律；（4）构建基于均质化的电池单体和模块模型，开展电池模块碰撞模拟，揭示碰撞工况中可监测力学参量、电池变形损伤与内短路的内在联系，建立适用于碰撞保护设计的电池模块碰撞损伤容限。

本项目针对电动汽车用锂离子动力电池的碰撞安全性问题，开展了组分材料、电池单体到电池模组多个层级的变形响应测试表征和建模分析工作。针对关键组分材料的力学特性和失效行为进行了细化表征，建立了动力电池碰撞挤压失效预测模型开发的数据基础；构建了高精度的电池单体精细模型，达到了电池挤压损伤失效的准确预测；基于测试和仿真生成了全面的多工况碰撞结果数据，基于机器学习方法开发了高效率的电池碰撞失效预测工具；揭示了电池挤压过程内部损伤产生和演化机制以及相对应的宏观特征，不同电池构型挤压响应的SOC相关性及其力学机理，电池挤压的动态强化效应及其力学机理，为复杂机械加载下电池变形容限的建立奠定了坚实基础；在电池模组层级上分析了碰撞载荷下的组件相互作用和方向性差异，提出了有效的电池模组碰撞保护结构设计。本项目以材料与结构力学性能分析为重点，结合研究对象的电化学与热学属性开展多物理场分析，获得了较为丰富的研究结果，为电动汽车动力电池系统的安全性设计开发提供了理论基础和技术支撑。