Theoretical Analysis of Ultrasonic Reflection/Trasmission Characteristics of Lithium-Ion Battery

The internal state information of lithium-ion batteries, such as lithium-plating, state of charge, etc., which can be reflected by the internal structure of the battery and its mechanical properties. During the battery charging process, the Young's modulus, density and porosity of the internal electrode materials will change. Ultrasonic non-destructive testing can be used to characterize the internal state of the battery and obtain the relationship between wave propagation information and internal state. This study describes in detail the reflection/transmission characteristics of ultrasound in lithium-ion batteries. Based on the working principle of lithium-ion battery, the porosity in the electrode of the lithium-ion battery is considered by Biot theory, and the reflection/transmission coefficient of the single cell is solved by the the transfer matrix method. As the thickness of the lithium plating layer increases, the angle spectrum and the frequency spectrum show regular movement, which makes it possible to further characterize the thickness of the lithium plating layer. The results obtained by the finite element simulation are highly consistent with the theoretical calculation method, which further verifies the feasibility of the method.