Study on Mechanical Behavior of Lithium Ion Battery Using Multi-scale Analysis

Abstract

Multi-scale analysis was conducted to predict mechanical behavior of lithium ion battery (LIB). Firstly, a finite element analysis approach is proposed to predict the fluid-structure interaction behavior of active materials for lithium-ion batteries (LIBs), which are mainly composed of the graphite powder. Porous matrix of the graphite powder saturated with fluid electrolyte is considered as a representative volume element (RVE) model. 3 different RVE models are proposed to consider the uncertainty of the powder shape and the porosity. Elastic modulus and poisson’s ratio from RVE solutions are compared with poroelastic analyses results based on the microstructure and the interaction between the fluid and the graphite powder matrix. Secondly, all components of the jellyroll in LIB such as electric current collector, active materials and separator were fully modeled in a RVE with micrometer scale. From the LIB jellyroll RVE analyses, elastic modulus for each direction was numerically calculated and compared with analytic solution. The results of elastic properties for the jellyroll were applied to the homogenized cell in the module RVE with millimeter scale. From this multi-scale module RVE, elastic modulus for each direction of LIB module was calculated and compared with analytical solution and two different models with all the jellyroll components were fully described. Finally, Vibration characteristics of lithium ion batteries (LIBs) for an electric vehicle were investigated. To represent the transversely-isotropic properties of LIBs, four numerical models (fully described LIB module and 3 types of homogenized module) were suggested. Modal analyses were conducted for the suggested models, and the results were verified by analytic solutions. Various parametric studies were conducted to quantify how design parameters of the LIB components affect the natural frequencies of the LIB module. Results indicate that the suggested multi-scale analysis method is an exact and efficient method to calculate the natural frequencies and mode shapes of LIB modules.