Influence of electrolyte presence on the vibration behavior of a Li-ion pouch cell and on the mechanical characteristics of its incorporated Al2O3 -coated polyolefin separator

Quality improvement of battery crash simulation models is essential for realistic mechanically induced shortcircuit prediction in modern electric vehicles, where the battery is part of the load path. In this paper, the electrolyte influence on the mechanical behavior of a commercial pouch cell and its incorporated Al2O3
-coated separator is investigated. To mechanically characterize the separator, both compression and tensile tests were performed. Modal analyses were performed to determine the damping behavior and dynamic stiffness of a
normally conditioned cell (wet) and a cell without electrolyte (dry). In the tensile tests, a slight anisotropy and an increase in stiffness, triggered by higher test speeds, were observed. The wet specimens soaked in substitute
electrolyte mixture showed longer elongation to failure with a stiffer response than the dry specimens under tensile loading. In the compression tests, exactly the opposite mechanical response of wet and dry specimens was measured. From the modal analyses, a stiffening of the dry cell could be determined. Based on the component tests, a finite element model of the separator was developed in LS-DYNA, enabling prediction of the deformation behavior of the separator under mechanical loads — this can be further used in high-fidelity
cell simulation models