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总览 评价 宋亦诚 * ， 李宗赞 （ 上海大学理学院，上海 200444； ） 摘要： 本文采用相场方法研究LiFePO4薄膜电极各向异性锂化变形对贫锂相-富锂相的相分离结构以及应力的影响。首先将多物理场的能量进行耦合，然后通过变分原理获得锂离子扩散运动的控制方
宋亦诚*， 李宗赞
（
上海大学理学院，上海 200444； ）
摘要：
本文采用相场方法研究LiFePO4薄膜电极各向异性锂化变形对贫锂相-富锂相的相分离结构以及应力的影响。首先将多物理场的能量进行耦合，然后通过变分原理获得锂离子扩散运动的控制方程，最终计算LiFePO4晶格沿薄膜电极不同方向排列时相分离结构中的锂离子浓度和应力。研究发现，当LiFePO4电极的最大锂化变形方向处于薄膜平面内且与相界面平行时，电极具有较大的应力和应变能，对相分离结构具有明显的抑制作用；而当最大锂化变形方向沿薄膜厚度方向且与相界面垂直时，电极内应力和应变能较小，对相分离的抑制作用较弱。因此，各向异性锂化变形对于相分离结构中的锂离子浓度和应力分布具有重要影响。在电极结构设计中，需要充分考虑并利用各向异性锂化变形来减小电极内的充放电应力，保证电极的循环寿命。
关键词：
固体力学；锂离子电池；锂化；各向异性；相分离
SONG Yicheng*， LI Zongzan
（
School of Science, Shanghai University, Shanghai 200444； ）
Abstract：
This paper aims to explore the impacts of anisotropic lithiation induced deformation on the phase separation and stress in LiFePO4 film electrodes. Multiphysics were coupled via energies, the governing equation of the diffusion of lithium ions was obtained with the variation theory, and finally the distributions of lithium concentration and stress were calculated with respect to different alignments of LiFePO4 lattice. It was found that aligning the direction of maximum lithiation deformation of LiFePO4 lattice along with the film plane and parallel to the phase boundary leads to higher stresses and strain energy, which significantly suppresses the phase separation structure, whereas the suppression is much less significant when the direction of maximum lithiation deformation is along the thickness of film and vertical to the phase boundary due to lower stress and strain energy. Therefore, the anisotropic lithiation induced deformation, which is important to the distribution of lithium ion concentration and stress, should be considered in the designing of an electrode to reduce the stress in charge and discharge and ensure the cycle life of electrodes.
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