【摘要】 锂离子电池工作过程中产生的扩散诱导应力和热应力，会导致电池内部发生多种形式的力学损伤，进而导致电池容量减少和寿命缩短，准确获取锂离子电池应力分布和演变情况对研究电池老化机制至关重要。因此亟须研究一种能够获取锂离子电池工作过程中内部应力分布及演化的方法，以揭示应力对其寿命的影响，进一步提高设计和优化的效率。该文首先研究锂离子电池电化学、热、力的多物理场耦合机制，建立锂离子电池电化学-热-应力三维耦合模型；其次搭建锂离子电池充放电实验平台并测试不同倍率下电池的表面温度和表面压力，验证了所建模型的有效性；最后通过验证后的模型分析了电池在不同倍率恒流充电过程中内部应力分布及演化规律。该模型可以有效获取锂离子电池在运行过程中的应力分布情况，有助于电池失效机理研究，为电池的优化设计和应用提供参考。更多还原

【Abstract】 Lithium-ion battery charging and discharging is a complex process involving coupled electrochemical, mechanical, and thermal fields. During this process, diffusion-induced stress and thermal stress generated internally can lead to mechanical damage, such as electrode material fragmentation, detachment, and failure. Understanding the distribution and evolution of internal stress in lithium-ion batteries is crucial for studying the factors influencing battery stress, optimizing battery design, reducing internal stress, and extending battery lifespan. However, current experimental studies on stress have limitations, measurements based on optical principles are complex and expensive, and external stress sensors cannot directly obtain the full-field stress distribution inside the battery. Furthermore, research on stress models within lithium-ion batteries focuses on diffusion-induced stress at the cell level, often neglecting thermal stress from heat expansion. This paper establishes a three-dimensional electrochemical-thermal-mechanical coupling model for lithium-ion batteries combined with experiment and simulation. The stress distribution inside the battery is investigated. Firstly, a pseudo-two-dimensional electrochemical model is used for lithium-ion batteries, integrating the expansion and contraction effects caused by lithium-ion concentration variations and thermal expansion effects from temperature changes. The electrochemical-thermal-mechanical coupling model is established. Secondly, a charging and discharging test platform is constructed to measure the battery’s voltage, temperature, and surface pressure under different charging and discharging rates. The accuracy of the model is validated by comparing experimental and calculated results. Finally, this paper analyzes the battery’s electrochemical, thermal, and mechanical performance during constant-current charging. The distribution patterns of electrochemical,temperature, and stress fields are explored. Simulation and experimental results indicate that during constant-current charging of lithium-ion batteries,due to expansion, the surface pressure gradually increases and reaches its maximum at the end of charging as the state of charge(SOC) increases. As the charging rate increases, the rise in surface pressure accelerates, but SOC reduces at the end of constant-current charging because of polarization effects. The maximum surface pressure at the end of constant-current charging decreases with the increasing rate. The total stress inside the lithium-ion battery is the combination of diffusion-induced stress and thermal stress, with thermal stress being smaller in magnitude than diffusion-induced stress. Since heat generation increases, thermal stress is slightly greater than diffusion-induced stress and increases with the charging and discharging rate. Due to polarization effects and different mechanical parameters, there is non-uniform diffusion-induced stress within the battery. Larger diffusion-induced stress is generated in the positive and negative electrode active layers, with more pronounced non-uniform stress observed in the negative electrode active layer. It can be predicted that with increasing cycles,non-uniform stress and deformation will lead to uneven aging. This model provides theoretical guidance for designing internal structural parameters, selecting battery operating environments, and alleviating internal or non-uniform internal stress to extend battery lifespan.更多还原