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各向异性锂化变形对LiFePO4电极相分离及应力的影响

发表时间:2014-08-15  浏览量:1642  下载量:660
全部作者: 宋亦诚,李宗赞
作者单位: 上海大学理学院
摘 要: 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
Title: Impacts of anisotropic lithiation induced deformation on the phase separation and stress in LiFePO4 electrode
Author: SONG Yicheng, LI Zongzan
Organization: College of Sciences, Shanghai University
Abstract: This paper aims to explore the impacts of anisotropic lithiation induced deformation on the phase separation and stress of Li-poor and Li-rich phases in LiFePO4 film electrodes by phase field method. Multiphysics were coupled via energies, the governing equation of the diffusion of lithium ions was obtained with the variation theory, and finally the concentration of lithium ions and stress in phase separation structure 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 led to higher stress and strain energy, which significantly suppressed the phase separation structure, whereas the suppression was much less significant when the direction of maximum lithiation deformation was 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 was important to the lithium ion concentration and distribution of 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.
Key words: solid mechanics; lithium ion battery; lithiation; anisotropic; phase separation
发表期数: 2014年8月第15期
引用格式: 宋亦诚,李宗赞. 各向异性锂化变形对LiFePO4电极相分离及应力的影响[J]. 中国科技论文在线精品论文,2014,7(15):1494-1500.
 
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