<p>As lithium-ion&nbsp;(Li-ion)&nbsp;batteries with high energy density&nbsp;are widely applied to drive the advancement of electric vehicles, disastrous safety events&nbsp;are still one of the critical challenges that need to be addressed. Thermal hazard is a safety concern that may lead to catastrophic failures of Li-ion cells since most electrode chemistries become thermally unstable when exposed to high temperatures. Under thermal abuse conditions, the electrode materials will undergo degradation and self-heating triggered by exothermic side reactions with a significant heat release inside the Li-ion cell. As temperature further increases to a critical point, chain reactions are initiated with substantial exothermic activities, resulting in destructive thermal runaway. Therefore, the safety performances of Li-ion batteries fundamentally depend on thermal stabilities of electrode materials, electrolyte solvents and possible chemical interactions among the various key components. The differential scanning calorimetry (DSC) technique is a powerful tool to explore high-temperature thermal instability at material levels. Several previous studies have characterized the exothermic reactions of different Li-ion cell components by analyzing DSC profiles. However, the effects of interlayer chemical crosstalk between the cathode and anode, when they are in the layered arrangement of a Li-ion cell electrode stack, on heat generation is absent from meticulous investigations. Furthermore, kinetic parameters of heat generation learned from DSC of individual or mixed cell components that are ground, rinsed, dried or otherwise changed from their form when they are within a Li-ion cell electrode stack results in reaction kinetic parameters that fail to capture the effects of electrode composite structure, electrolyte wetting, and the layering of the electrodes and separators in a Li-ion cell. Failing to capture these effects in the heat-generating reaction parameters of full cell thermal runaway models can be a significant inhibitor to current modeling efforts attempting to predict the thermal runaway behaviors of Li-ion batteries accurately. In this study, a DSC analysis is performed on various Li-ion material samples from a commercial cell that are maintained in nearly the same form they are in when in a cell electrode stack. Thermal signature of the wet cathode, wet anode, wet cathode with separator, wet anode with separator, and a stack of cathode-separator-anode-separator (DSC-full cell) are captured. Assignment of reaction peaks to cathode decomposition and phase transition, electrolyte combustion and decomposition, SEI decomposition, anode-binder, and anode-electrolyte interactions are made based on previous literature studies. Calorimetric identification and quantification of heat generation due to chemical crosstalk between cathode and anode is made by comparing the heat signature from the DSC-full cell and a linear addition of the wet cathode and wet anode data. High-resolution kinetic parameters, including reaction heat, activation energy and frequency factor, are computationally estimated for each reaction mechanism based on physics-informed non-linear optimization strategies. A thermal abuse model is built based on the extracted kinetic parameters to simulate the thermal runaway phenomenon at single cell level while providing insights into how the interlayer crosstalk effect significantly impacts the safety characteristics of Li-ion cell chemistries.</p>

Effect of Electrode Crosstalk on Heat Release in Li-Ion Batteries Under Thermal Abuse Scenarios

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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