硅基薄膜电极充放电过程应力演化解析解研究

Analytical Solution of Stress Evolution in Silicon-Based Thin Film Electrode during Charging and Discharging

为了研究硅电极在充放电过程中的应力演化,在忽略弹性变形的情况下提出了一个考虑粘塑性的简化力学模型,分别导出了出现相分离和不出现相分离时薄膜电极内应力场的解析解,该模型的计算结果与现有的实验结果相吻合.计算结果表明,当存在相分离时,电极中的应力取决于薄膜电极的厚度和充电速率的乘积;在未出现相分离现象时,应力仅取决于充电速率.这个解析形式的力学模型对于锂离子电池电极材料的设计有着重要的指导意义.

A simplified mechanical model considering the viscoplasticity is proposed to study the stress evolution of the thin film electrode with ignorance of the elastic deformation.Analytical solutions for the stress field of thin film electrode with and without phase transformations are derived.The results of this model are in good accord with the existing experimental results.The stress depends on the product of the height of the film electrode and the charging rate when there is a phase transformation,while only depends on the charging rate in the absence of phase transformation.This work provides an important analytical solution for the design of silicon thin film electrode to be used in LIBs.