Homogenized mechanical properties for the jellyroll of cylindrical Lithium-ion cells

A hybrid experimental/analytical approach was developed for extracting the average mechanical properties of cylindrical Li-ion cells. By using the principle of virtual work, and estimating the load transfer mechanism inside the cell, the stress-strain relation for the jellyroll was calculated for the case where the cell was crushed between two flat plates. The procedure was illustrated on an example of a commercial 18650 cell. A finite element model of the cell was then developed using the crushable foam material in LS Dyna. The model calibrated with this method closely predicts kinematic of the cell during two different load cases used for validation. These cases include local crush by a hemispherical punch and indentation by a rigid rod. The load and displacement during deformation, as well as onset of electric short circuit observed from experiments were closely predicted from simulations. It was found that the resistance of the cell comes primarily from the jellyroll. Additional analytical calculations showed that the shell casing and the end-caps provide little contribution to the overall crash resistance of the cell in the loading cases studied in this paper.