锂离子电池极片辊压微观结构演化与过程建模

Microstructure evolution and process modeling for calendering of lithium-ion battery electrode

为阐明锂离子电池极片辊压过程微观结构演化与宏观变形力学量化行为,通过分析变形区内极片涂层和集流体形貌特征。结果表明:辊压方向上活性颗粒密实度显著增加,将辊压对极片涂层的影响总结为碳胶相压缩、活性颗粒破碎及融合为二次颗粒。集流体整体未发生减薄,由于石墨硬度小,负极铜箔表面高度起伏均在600 nm以内,正极部分活性颗粒嵌入表面,最小涂层厚度时,正极部分活性颗粒嵌入表面的深度为2μm。同时,将活性涂层压缩简化为平面变形问题,利用微分单元法和压缩变形本构模型,将变形区分成若干个微元并进行受力分析,依此推导变形区压力分布及轧制力计算公式,构建单位轧制力与涂层厚度、压实密度的关系模型,该模型可为实施AGC厚度精确控制及工艺优化提供理论基础。

For clarifying the microstructure evolution and macroscopic deformation mechanical quantitative behavior of lithium-ion battery electrode during calendering process,the morphological characteristics of electrode coating and current collector in the deformation zone were analyzed.The results show that the denseness of active particles significantly increase in the calendering direction,and the effect of calendering on electrode coating is summarized as carbon-PVDF compression,active particle fragmentation and fusion into secondary particles.The overall current collector has not been thinned.Due to the small hardness of graphite,the surface height of the copper foil fluctuates within 600 nm,and some of the active particles of the cathode electrode are embedded in the surface,with an embedding depth of 2μm at the minimum thickness.Meanwhile,the coating compression is reduced to a plane deformation,and the deformation zone is distinguished into several microelements and force analysis by using the differential unit method and the compression deformation intrinsic model.Based on this,the calculation formulas of pressure distribution and rolling force were derived,and the relationship model between unit rolling force and coating thickness and compaction density is constructed,which can provide the theoretical basis for the implementation of accurate control of AGC thickness and process optimization.