高比能量锂离子电池性能衰减机制、寿命预测及耐久性管理技术基础

The life decay problems have been the critical factor restricted the applications of the high-energy lithium-ion batteries (LIBs). Currently, empirical formula fitting based onexperimental data is mainly employed as the life prediction method of LIBs. However, study on thecorrelation between the battery performance decay and the electrochemical characteristics variation of electrode is rarely reported. This project takes into account from the performance decay mechanisms of coin-type battery and commercial unit cell to the durability management of battery system. Based on themicroscopic properties such as compositional and structural changes of electrode materials and electrode/electrolyte interface, and macroscopic characteristics such as capacity and resistance, combined with in situ/ex situ measurement, we study the performance decay mechanism of LIBs; the influence of single stress to commercial batteries; the coupling mechanisms of each single stress and the corresponding relationship between internal electrochemical reactions and the change of battery external characteristics during the battery capacity degradation process. Based on the researches above, we put forward battery cell accelerated lifetime testing methods, battery lifetime prediction methods based on the fusion of battery aging state identification and data-driven methods. Then we explore the evolution rules of the inconsistencies among battery cells in the different grouping patterns and establish the battery system lifetime prediction model. By studying optimizing and control methods of battery system thermal field, we put forward the charge/discharge-thermal field coordinated control strategy, eventually realizing the aim of durability optimizing management of the battery system.

高比能量锂离子电池的寿命衰减问题已成为其应用的重要制约因素，目前锂离子电池寿命预测方法主要是基于实验数据的经验公式拟合，而对于电池性能衰减与材料电化学特性变化规律的相关性研究尚浅。本项目按照原理电池和商用电池单体性能衰减机制到电池系统耐久性管理的研究思路，从电极材料和界面的组成结构变化等微观属性与电池容量、阻抗演变规律等宏观属性的角度出发，采用原位和异位观测相结合的测试手段，研究高比能量三元锂离子电池性能衰减机理，研究单应力对商用电池寿命的影响及各应力的耦合机制，研究电池衰减过程中电化学反应过程与外特性参数变化之间的对应关系，提出电池单体加速寿命试验方法、老化状态识别-数据驱动融合的寿命预测方法；探索不同成组方式下各电池单体间的作用机制及不一致性变化规律，建立电池系统寿命预测模型，研究电池系统热场优化控制方法，提出充放电-热场协同优化控制策略，最终实现电池系统耐久性优化管理的目标。

为缓解环境危机，新能源车辆已被列入我国七大战略新兴产业，是“中国制造 2025 ”的重要组成部分。高性能锂离子动力电池作为新能源车辆的关键技术，其寿命衰减问题已成为其应用的重要制约因素。本项目采用原位和异位观测相结合的测试手段，从材料基础科学问题出发，研究了锂离子电池用不同体系高容量电极材料的容量衰减机理，提出正负极活性材料损失和锂离子损失对电池容量衰退的影响；进而研究了商用锂离子电池在温度、倍率和SOC区间等应力下的衰退机理，提出了电池健康状态多指标表征参数体系，建立了电池寿命衰减模型，并基于分区间循环建立了电池寿命快速评估方法；基于电池寿命测试以及特征参数演变规律，提出了老化状态识别-数据驱动融合的寿命预测方法，以可用能量为依据提出了锂离子电池系统性能衰减规律、健康状态估计和寿命预测方法；研究了电池的产热特性，基于电池电学模型和热学模型，建立了简化的频域热电耦合模型，提出电池一致性控制方法和均衡策略。最后，综合考虑电池系统衰减规律和寿命模型，提出电池耐久性充放电管理策略，搭建了广义电池管理系统，为高比能量锂离子电池安全稳定运行提供了夯实的理论依据和保证。

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