高比能锂离子电池多因素耦合老化机理解析与衰退建模研究

The battery energy density needs to be increased to develop the new energy vehicles. And the durability of high energy density lithium ion batteries is the key problem and needs to be studied. This project intends to focus on the aging mechanism of the high energy density lithium ion batteries with Nickel–rich cathode and Si-C anode materials by doing battery accelerated life experiments, analyzing the battery anode and cathode aging mechanisms and the aging coupling mechanism, studying a novel in-situ battery aging mechanism analysis method, and establishing battery capacity fade models for the battery design and management optimization. Firstly, based on the battery reconstruction technology with particular anode and cathode materials, the battery aging tests under different working conditions could be designed to research the aging phenomena of the high energy density lithium ion batteries, and the side reactions inside the battery could be analyzed. Secondly, the influence mechanism of the battery external characteristic from internal material parameters could be studied and novel in-situ mechanism analysis methods could be proposed. Then the aging mechanisms related to the anode and cathode and the aging coupling mechanism under different working conditions could be explored. Finally, based on the battery multi-factor coupled degradation mechanism and the electrochemical mechanism, the distribution of the potential, temperature and stress inside the batteries could be analyzed. And the battery side reaction model and battery model could be developed. And the model order reduction methods like the Taylor approximation method could be used to build the battery life degradation reduced order mechanism model. The findings would enrich the theoretical understanding of high energy density battery aging mechanisms, and are expected to provide theoretical guidance for the design of the cells and battery systems, and the management of the cells for the purpose of improve the battery life.

发展电动汽车需要开发高比能电池，而高比能电池的耐久性是核心挑战，亟需研究探索。本项目拟针对基于高镍正极和硅碳负极的高比能电池耐久性问题，通过电池加速寿命试验，揭示电池内部正负极老化机理及其耦合机制，提出电池老化机理原位解析方法，建立电池寿命衰减模型，为电池优化设计与管理奠定基础。首先，开展基于重构电池技术的加速寿命试验，探索不同工况下的电池老化规律，分析电池内部副反应情况。其次，研究电池内部材料特征对外特性的影响机制，开发电池原位机理解析方法，揭示高比能电池不同工况下电池内部正负极老化机理及其耦合机制。最后，根据电池多因素耦合衰减机制与电化学机理，分析电池内部电势、温度、应力分布，建立电池副反应模型与电池模型，并采用泰勒近似等模型降维方法，综合建立多因素耦合作用下的电池衰减降维机理模型。研究成果将丰富高比能锂离子电池老化机理的理论认识，同时可从理论上指导单体设计、系统集成，优化电池管理。

本项目针对行业快速发展过程中的高比能电池设计与管理相关需求，开展了高比能锂离子电池寿命多因素耦合老化机理解析与建模研究，面向车用高比能量锂离子电池，合理设计电池加速寿命实验，探索电池在不同工况下的复杂非线性衰减规律，研究不破坏电池的老化机理原位解析方法，揭示电池内部正负极老化机理及其相互耦合机制，综合建立电池寿命衰减模型，为电池的优化设计与优化管理奠定了一定的理论基础，主要研究内容和进展包括以下四个方面：.(1)从电池设计角度出发，基于电池老化机理和寿命衰减模型，仿真分析不同电池关键参数如正负极活性材料厚度、孔隙率、颗粒大小、电池尺寸等对电池寿命及其他关键特性参数如能量密度、功率密度的影响，从而通过多目标优化算法获得电池最优设计参数，从源头提高电池的寿命。.(2)从电池SOH估计角度出发，考虑到电池的性能如可用能量、可用功率会随着电池的衰减而减小，采用原位解析方法分析电池老化机理，并基于电池寿命衰减模型估计电池的健康状态SOH，并作为重要的估计参数输入给控制系统，从而合理使用电池，防止出现电池滥用和安全性事故。.(3)从电池充放电优化管理的角度出发，针对不同的使用工况对电池未来的寿命影响，基于不同工况下的老化机理及相应电池寿命衰减模型，预估不同工况对电池内部造成的损伤大小，权衡电池的寿命与整车的性能，实现电池充放电优化管理。.(4)从电池剩余寿命预测的角度出发，在电池实车使用、二手车评估和梯次利用等情况下估计电池的剩余寿命，为电池残值评估提供基础，考虑到电池的非线性衰减特征，常规的外推方法无法准确预测电池的剩余寿命情况，本项目基于不同工况和不同衰减状态下电池内部的主要老化机理及相应的寿命衰减模型，实现对电池剩余寿命的可靠预测。.