关键词: 锂离子电池, 隔膜, 流固耦合, 应变率, 孔隙度, 渗透率

Abstract:

Separator is an important component of lithium-ion batteries, whose property is crucial to the battery performance. Mechanical loading, intercalation/deintercalation of lithium ions on the electrode, and temperature can cause the deformation of battery components, which then compresses the soft separator. The response of a porous medium separator under compression is determined by the viscoelastic behavior of the polymer skeleton and the poroelastic behavior due to the electrolyte in the pores. A axisymmetric mathematical model capable of describing the fluid-structure coupling effect of the separator under compression at different strain rates is established in this paper. The model also introduces dynamic properties of porosity and permeability, and is solved by numerical simulation software. The numerical results in this work are closer to the experimental data than the numerical results in the literature. It is found that the poroelastic effect of the separator leads to the inhomogeneous distribution of porosity and permeability. The model is also used to analyze the permeability, geometry, Young's modulus, Poisson's ratio, fluid bulk modulus, and viscosity of the separator and discuss their effects on the poroelastic behavior of the separator during compression. The findings in this study are of benefit to obtain in-depth understanding of the poroelastic behavior of the separator. Meanwhile, they can also provide theoretical basis for optimization of separator materials and geometrical parameters.

Key words: lithium-ion battery, separator, fluid-structure coupling, strain rate, porosity, permeability