Solid-state batteries, because of
their high energy density, are
promising candidates for long-range electric vehicles and electric
aviation. While the enhanced safety potential of solid-state batteries
has been typically ascribed to the nonflammability of solid electrolytes,
an extensive interrogation of their thermal stability is still required.
In this work, we reveal how the thermal stability in sulfide-based
solid-state batteries is critically dependent on the interphase interactions
at the solid electrolyte/Li interface, thereby illustrating the drastically
different thermal signature of Li10SnP2S12 when compared with Li3PS4 and Li6PS5Cl. Our study shows that thermal runaway occurs
even for a pristine Li10SnP2S12/Li
interface and is severely exacerbated with cycling, which exhibits
a massive thermal spike at the melting point of Li; this shift in
thermal response uniquely correlates to the Li10SnP2S12 interphase evolution. On the basis of these
distinct thermal signatures, cell-level mechanistic safety maps cognizant
of the Li/interphase interaction, cathode/Li crosstalk, and specific
energy are delineated.
The thermal instability of polymer separators severely threatens the safety characteristics of lithium-ion (Li-ion) batteries. Separators will melt, shrink, vaporize, and collapse under high temperatures, leading to internal short circuits and thermal runaway catastrophes of the cell. Therefore, the amelioration of battery safety challenges benefits from a fundamental understanding of separator behaviors under thermally abusive scenarios. This work investigates the role of separator thermal stability in modulating Li-ion cell safety performance. Three types of separators made of commercially available cellulose, trilayer polypropylene/polyethylene/polypropylene, standard polypropylene, and an in-house modified graphene-polydopamine coated separator are fabricated in custom single layer pouch cells and subjected to accelerating rate calorimeter (ARC) tests to investigate dynamic thermo-electrochemical interactions. The safety hazards of 18650 cylindrical cells assembled with different types of separators are predicted using a verified ARC computational model to compare the effects of separator heat resistance on cell-level thermal runaway risks. This study reveals the thermally robust mechanisms of diverse separator microstructures, indicating how the in-house modified graphene-polydopamine coated separator significantly enhances the safety limits of Li-ion batteries.
There are many welded thin-walled square tube structures in ship structures. At present, researchers are mainly involved in axial compressive ultimate strength of square tubes with large aspect ratios. However, the study of square tubes with small aspect ratios on ultimate strength capacity have seldom been conducted. In order to study the ultimate strength capacity of thin-walled square tubes with small aspect ratio under axial compression, three welded thin-walled square tubes with different slenderness ratios were manufactured and studied in this paper. The ultimate strength of those models under axial compression were obtained experimentally. The experimental results were compared with numerical results performed by ABAQUS. The influence of slenderness ratios on the axial compressive ultimate strength of thin-walled square tubes is analyzed, and a feasible modelling of finite element method is proposed.
While lithium-ion batteries are continually increasing in energy and power density, thermal safety still remains a significant concern. In some thermal abuse scenarios, thermal runaway can be triggered by the exothermic reactions from inter-electrode chemical crosstalk between the cathode and the anode without an internal short circuit. Under these circumstances, the thermal runaway temperature is lower than the separator's thermal shrinkage temperature, implying that the cell's catastrophic thermal runaway occurs without a large-scale short circuit produced by separator failure. These cell failures must be managed such that the neighboring cells in a battery module are not affected, a phenomenon known as thermal runaway propagation. In the present work, we employed a high-resolution cell-level thermal runaway model constructed from the accelerating rate calorimetry data of a commercial Li-ion cell to characterize the cell-to-cell thermal runaway propagation behavior for a basic square arrangement of lithium-ion battery module connected by tabs. We determined safe practices under the effects of different ambient conditions, inter-cell spacing, trigger cell location, and external heating power. Additionally, we have identified the critical pathways for the thermal runaway propagation in the battery module and quantified their statistical distribution in terms of the thermal runaway propagation speed, heat release from exothermic reactions, and heat dissipation to the surroundings. The findings from the study are believed to be of immediate relevance for the safer design of lithium-ion battery packs.
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