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Li-ion batteries (LIB) are used in many applications because of their high-power/energy density, long life cycling, and low self-discharge rate. The use of LIB continues to grow every day, and the necessity for proper safety standards grows as well. A key aspect for safe utilization of LIB is determining their safety and remaining useful life (RUL). Battery

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Summary Homogenization and finding the constitutive model of jellyroll in cylindrical lithium‐ion batteries can be challenging because of their form factor. Taking samples out of the original jellyroll wounding or compressing cell assembly in its cylindrical coordinates are two possibilities for measuring the homogenized lateral strength of the cell. However, the former causes loss of accuracy due to changing constraints and electrolyte environment, and the latter requires complex fixtures that are not readily available or even practical to manufacture. Various approaches have been suggested by researchers to circumvent the above difficulties and allow the extraction of hardening curves. However, the precision of those approaches diminishes when the cells are under global compression vs local punch deformations. In this study, an updated homogenization method is established, using a lateral compression test on the jellyroll. The homogenization method is based on the assumption that the circular cross‐section of the jellyroll under compression is deformed in an elliptical shape. Then the principle of virtual work is used to extract the hardening curve. To validate the above characterization model, isotropic and anisotropic finite element models were developed using crushable foam and modified honeycomb material models from the LS‐DYNA library. Four sets of cell‐level experiments were performed on cylindrical batteries using custom‐designed fixtures, including flat lateral compression, rod indentation, hemispherical punch, and three‐point bending. The voltage and surface temperature of the batteries were measured to capture the onset of short circuit during the tests. Comparison of the simulation results confirmed that the proposed homogenization method and the FE models can predict the behavior of cylindrical lithium‐ion batteries with much higher accuracy compared to the currently available methods presented in the literature.

This study details a framework for an iterative process which is utilized to optimize lithium-ion battery (LIB) pack design. This is accomplished through the homogenization of the lithium-ion cells and modules, the finite element simulation of these homogenized parts, and submodeling. This process enables the user to identify key structures and materials to be modified to optimize performance while keeping simulation time per iteration to a minimum. These iterations can be used to accurately estimate the force and strain values at various points including the lithium-ion cells and can be used to determine failure locations. The study demonstrates this through the examination of an electric bus lithium-ion battery pack as it is processed through the aforementioned steps and iterations to arrive at a conclusion that enabled the author to select appropriate fasteners and optimize for lithium-ion battery integrity in the event of a side impact with a pole on the bus chassis and battery assembly. The steps outlined in the study could be expanded to include an array of different loading scenarios and to include additional levels of homogenization/submodeling such as jellyroll components.

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Li‐ion batteries are widely used in electric vehicles (EVs) propulsion. Therefore, ensuring their safety under mechanical abuse and accidental loads is a major challenge for the industry. To get a better understanding of the battery behavior in such cases, material calibration and computational modeling of the battery cells are essential. This paper aims to develop a universal homogenized model for an 18,650 cell that can predict cell behavior under both axial and lateral loading cases as well as three‐point bending. Previous homogenized models presented in the literature have covered one or two of these cases, but none have been validated in all these three major loading scenarios. To achieve this, precise shell casing and jellyroll material calibrations were performed. The features included in this universal model are (I) uncoupled calibration of axial and lateral properties for the cylindrical jellyroll from experiments performed in these two loading directions and employment of an anisotropic crushable foam model to simulate these features, (II) using Hill's anisotropic yield criteria and modified Mohr–Coulomb fracture criteria for the shell casing. The universal model developed here was able to predict the response of the cell in all lateral, axial, and bending loading scenarios. A comparison of this model with the previously developed isotropic models shows the special advantage of the new model in cases of axial loading and bending. However, for lateral compression cases, even the isotropic model provides a very close prediction. The experiments used for this study were all performed on fresh discharged cells under quasi‐static loading.