We report on an experimental and numerical study of deformation in cell/string/module of a lithium ion battery under mechanical loading. We performed compression tests on individual components of the battery cell, such as anode, cathode and separator, and used the results to calibrate the specific material models for these components. Indentations tests were performed on individual battery cells and on a stack of 3 cells. During the indentation test, load, voltage and temperature of the cell were measured. We also studied the evolution of deformation in various components of the cell in order to understand the mechanisms of failure in separator, which could result in an electrical short and thermal runaway of the battery.  

A finite element model (FEM) in which several layers are fully resolved and the remaining components are homogenized was developed for different cell combinations. In FEM maximum strain criterion in separator was used for element deletion and failure at short circuit.. We demonstrate the advantages of this approach by comparing the load-displacement curve and the nature of deformation obtained from simulations to those obtained from experiments.