双相多孔锂离子电池液/固界面的声反射与声透射

采用传递矩阵法,同步联立改进的Biot理论,对含液固界面的双相多孔锂离子电池的超声反射与透射系数进行理论求解。考虑锂离子的摇摆特性对电极力学性能的影响,计算了对应状态下液/固界面的双相多孔锂离子电池声反射及透射系数的角度谱与频率谱。同时,构建了不同荷电状态时含单元锂离子电池的频域仿真模型,以萃取对应的超声反射及透射角度谱及频率谱,并与理论计算结果对比吻合良好。随后,以多单元锂离子电池为例,在不同的荷电状态下,分析了反射与透射系数随斜入射角度、入射波频率的变化关系,并分别指出了其角度谱及频率谱特征点随荷电状态的变化特征,为锂离子电池运行状态的超声无损测量提供了理论基础。

Acoustic reflection and transmission at the interface between two-phase porous lithium-ion battery and liquid media

Based on the combination of transfer matrix method and Biot theory, the acoustic wave reflection and transmission coefficients was theoretically calculated at the liquid/solid interfaces between two-phase porous lithium-ion battery and liquid media. Meanwhile, the influence of the swing characteristics of lithium-ion on the mechanical properties of electrode was considered, and the theoretical prediction of electrode density and elastic modulus under different states of charge is realized. The angle spectrum and frequency spectrum of reflection and transmission coefficients for corresponding state lithium-ion battery can be obtained by the proposed method. Then, a frequency domain simulation model of the multi-layered porous lithium-ion battery was established, and the reflection and transmission coefficients obtained by finite element method for lithium-ion battery are consistent with those results by the proposed approach. For the case of multi-cell lithium-ion battery, the relationship between reflection/transmission coefficients, oblique incident angle or frequency under different azimuth angles are analyzed. The shift law of the characteristic point curves in the angle spectrum and frequency spectrum with the change of the state of charge of the lithium-ion battery is analyzed. It provides a theoretical basis for the ultrasonic measurement of the state of charge of lithium-ion batteries.