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• A space-efficient protective method for battery pack is proposed. • Resin material offers high bearing capacity while foam improves energy absorption. • The protecting mechanisms of various matrix materials are revealed. • Stiffness balance between foam and battery for better protecting effect is unlocked. Mechanical protection of battery packs is challenging due to the limited available space. While filling packing gaps with protective structures is practical and space-efficient, there is a lack of reference for selecting proper matrix materials for the structures. To address this issue, we conducted compression tests on cylindrical battery packs embedded into 3D-printed thin-walled resin, foam, and polyurethane structures. A comprehensive comparison was made among battery packs protected by various materials, as well as the non-protected one, to evaluate their protecting performance including deformation nonuniformity, failure rate, and failure thresholds under various loading conditions. Results showed that the resin- and foam-protected battery packs experienced less damage under similar load level and similar crushing energy, respectively. The underlying mechanisms were further investigated by combining tests and simulations. It is revealed that the stiffness of filling material greatly influences the protective effect, which results in the different distributions of both stress and strain energy in the battery pack. The stiffness balance between the foam and the batteries to achieve better protecting effect was also unlocked under varying crushing energies. Our findings shed light on the space-efficient protection of battery packs under crash. [ABSTRACT FROM AUTHOR]

For this study, lithium-ion pouch cells undergo quasi-static and dynamic tests and are analyzed by interdisciplinary characterization methods. These methods reveal different behaviors of the cells under mechanical-electrochemical coupled failure. The study demonstrates that the inertia effect of a cell's multilayer structure dominates the failure under dynamic loading rather than the strain rate effect of the cell's components. This finding unlocks the underlying mechanism of localized fractures near the impacted surface and counterintuitive premature failures with less critical force under dynamic loading conditions. In addition to instant failure with inflection points in force/voltage curves, this study observes an interesting delayed failure behavior without evident short-term signs in both dynamic and quasi-static tests with different mechanisms. This challenges the validity of using macroscopic inflection points in mechanical tests as indicators for failure prediction and could explain the postponed spontaneous combustion of a cell after mechanical abuse accidents. The cell's capacity and internal resistance after dynamic and quasi-static tests are also assessed. Finally, an experimental evaluation outline is proposed for lithium-ion cells under mechanical abuse. This work sheds light on the understanding of dynamic failure mechanisms and safety evaluation methods for lithium-ion cells. • Failure/degradation of Li-ion cells induced by mechanical abuse is investigated. • Structural inertia effect dominates dynamic failure rather than strain rate effect. • Macro inflection points in mechanical tests may not fully predict cell failure. • Mechanisms of delayed failure are different under dynamic/quasi-static conditions. • Safety-evaluation outline for Li-ion cell mechanical abuse is proposed. [ABSTRACT FROM AUTHOR]