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This paper presents a novel model for analyzing thermal runaway in Li-ion battery cells with an internal short circuit device implanted in the cell. The model is constructed using Arrhenius formulations for representing the self-heating chemical reactions and the State of Charge. The model accounts for a local short-circuit, which is triggered by the device embedded in the cell windings (jelly roll). The short circuit is modeled by calculating the total available electrical energy and adding an efficiency factor for the conversion of electric energy into thermal energy. The efficiency factor also accounts for the energy vented from the cell. The results show good agreement with the experimental data for two cases -a 0D model and a 3D model of a single cell. Introducing the efficiency factor and simplifying the short-circuit modeling by using an Arrhenius formulation reduces the calculation time and the computational complexity, while providing relevant results about the temperature dynamics. It was found that for an 18650 NCA/graphite cell with a 2.4 Ah capacity, 28% of the electrical energy leaves with the effluent. Lithium-ion batteries are gaining more and more popularity in the field of electric energy storage. 1 This trend is followed by an increase in safety, energy density, and cycle life requirements. The increase in energy density brought a significant contribution to this trend, but it came with a trade-off concerning safety.2,3 When operated under abusive conditions such as overcharging, over-discharging, object penetrations or even operation under high ambient temperatures, etc., Li-ion batteries can undergo internal short circuits between the current collectors or electrodes, leading to thermal runaway. 3 The reactions with electrolyte inside the cell decompose the battery components, generating a significant amount of heat, which, if not properly managed can lead to fires and explosions. 4 To assist the design of thermal management systems in mitigating the effects of thermal runaway, it is important to be able to model thermal runaway and account for the energy contributions in the process.Modeling thermal runaway has been the focus of many researchers, but the authors in Refs. 5,6 brought a substantial contribution to the field. The authors found the activation energies and the enthalpies of the different decomposition reactions for the components in an 18650 LCO (2.6 Ah) Li-ion battery and proposed a model for predicting thermal runaway based on Arrhenius formulations. Papers such as Refs. 7,8 added new decomposition reactions (cathode, electrolyte) and extended the model, from a simplified lumped model to complex 2D and 3D geometries for a single cell. Based on these models, some authors extended the models to simulate the thermal behavior of single battery cells.9 A comprehensive list of references and studies of modeling safety in Li-ion is given in Ref. 3. The activation energies and the enthalpies found by the authors in Refs. 5, 6 are crucial for predicting the energy released during therm...

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This paper presents a mathematical model developed for predicting the temperature-pressure behavior and gas generation inside 18650 LCO/Graphite cells with a DMC (Dimethyl Carbonate) electrolyte. The cell was modeled using oven heating conditions, and the analysis was done at time intervals around the venting event. The paper also presents the thermodynamic property table for DMC, as extracted from different resources and calculated using various assumptions. The model was developed by deriving the energy balance for an unsteady-flow control volume and applying the isentropic flow equations corresponding to the venting of gas. The results show that the model fails to predict the pressure measured experimentally when no gas is generated inside. When adding the gas generation due to pre-venting reactions occurring, the model can predict the pressure profile measured experimentally.

Spatially dependent low-temperature to roomtemperature degradation mechanisms for Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 / Li x C 6 (NMC532/graphite) large format 50Ah Li-ion batteries were investigated. First, highly stressed regions of the cathode/ anode are found to be exacerbated by extreme conditions (i.e., lowtemperature cycling). The severe electrochemical polarization of large 50Ah electrodes at low temperature leads to substantial Li 0 deposition and severe gassing at the regions of high stress (i.e., high curvature, edges, and electrode ripples). A series of analytical techniques (e.g., SEM, XPS, GC-MS, and Raman spectroscopy) found that Li 0 plating (charge) or corrosion (storage) leads to severe gassing and decomposition products (including carbides). The expansion/contraction and extreme polarization during lowtemperature cycling, was found to cause a ripple-type Li 0 deposition on the electrode. Multilocation liquid nitrogen (N 2 ) Raman spectroscopy of electrodes indicates significant quantities of Li 0 deposition reside at ripple peaks (high-stress region) and are found negligible at ripple troughs. Postmortem analysis discovered two failure scenarios that originate from low-temperature cycling, either nonthermal runaway venting or an internally shorted thermal runaway. It was found in the first case (storage) that LiC 6 −Li 0 undergoes severe corrosion and gassing during storage conditions (i.e., no movement, current, and temperature) and proceeds to trigger thermal runaway and ejection of materials (∼2 weeks). The second case (RT cycling after low temperature) resulted in nonthermal runaway overpressurized venting of the cell and release of detectable quantities of flammable/toxic gases (e.g., CO 2 , CO, CH 4 , and C 2 H 2 ). The second event was found to be caused by competing reactions (i.e., Li 0 stripping, Li 0 corrosion, and severe gassing). This study finds that low-temperature Li 0 plating and LiC 6 −Li 0 corrosion results in severe gassing, which exacerbates highly stressed regions (i.e., electrode buckling) and greatly compromises safety of the application via nonthermal runaway venting when cycled (e.g., stripping of Li 0 and gassing) and catastrophic thermal runaway when resting under storage (e.g., larger quantities of Li x C 6 −Li 0 corrosion).