Creating a model of the thermal runaway process is complex as it covers a large number of subject areas.
- trigger
- heat generation
- breakdown
- gas generation
- cell venting
- flame propagation
- particle ejection
- secondary combustion
In order to model this it is important to take a multi-physics and multi-scale approach. Pannala et al [1, 2] published this time versus length plot back in 2015 and it shows an important aspect of this subject.
The following example shows an approach to modelling an LFP cell test in an ARC chamber. This shows the development and calibration of the parameters for a model.
Thermal Runaway Modeling and Calibration of an LFP Battery Cell
Build up of a thermal runaway model of an LFP cell and comparison to an ARC test.
Yuanmao Li et al [3] use a numerical thermal abuse model that integrates ordinary differential equations (ODEs), heat-transfer partial differential equations (PDEs), natural convection in computational fluid dynamics (CFD), and thermal radiation to investigate thermal propagation in a battery pack.
From these results, it seems that the presence of a gap can mitigate the safety crisis by slowing the propagation of thermal runaway, allowing the driver more time to escape the vehicle. However, larger gaps result in smaller energy densities within the battery pack. Therefore, it is necessary to balance the cell-to-cell gap and energy density considerations in the design process.
References
- S. Pannala, J. A. Turner, S. Allu, W. R. Elwasif, S. Kalnaus, S. Simunovic, A. Kumar, J. J. Billings, H. Wang, J. Nanda; Multiscale modeling and characterization for performance and safety of lithium-ion batteries. J. Appl. Phys. 21 August 2015; 118 (7): 072017.
- John Turner, Srikanth Allu, Mark Berrill, Wael Elwasif, Sergiy Kalnaus, Abhishek Kumar, Damien Lebrun-Grandie, Sreekanth Pannala, Srdjan Simunovic, Safer Batteries through Coupled Multiscale Modeling, Procedia Computer Science, Volume 51, 2015, Pages 1168-1177, ISSN 1877-0509
- Yuanmao Li, Guixiong Liu, Zuyu Li, Numerical modeling of thermal runaway in high-energy lithium-ion battery packs induced by multipoint heating, Case Studies in Thermal Engineering, Volume 38, 2022