The thermal runaway of individual lithium-ion cells is a complex process that depends on a multitude of factors [1]. Among these factors, state of charge (SOC) plays a crucial role as it influences the initial temperature and energy released during a thermal runaway and therefore its severity [2]. If a cell enters thermal runaway, the released energy can heat up neighboring cells, potentially leading to thermal propagation within a module or the entire battery system [3]. This can result in catastrophic damage to the system and its surroundings. Therefore, a deep understanding of the complex interplay SOC and both thermal runaway and thermal propagation is needed to enhance our ability to design safer and more reliable battery systems for various applications.
Findings from the literature showed that the reduction of the SOC from 100% to 50% SOC, leads to a delay of the propagation time between two cells and within one cell from front to rear side for NMC cells [3]. Additionally, a simulation study of different inhomogeneous and homogeneous SOC distributions motivates discharging cells in case of failure since lower SOC has the potential to delay or limit thermal propagation [4].
This poster analyzes, the influence of the SOC on thermal propagation while assessing critical safety features. To achieve this, three thermal propagation experiments with different SOC distributions were conducted. Each module comprises three lithium pouch cells, with the first cell subjected to thermal abuse using a heating plate until it enters thermal runaway. The following thermal propagation is evaluated considering the maximum cell temperature and the propagation time, among other things, revealing a significant influence of the SOC on thermal propagation. This study addresses the existing scientific gap by providing and comparing experimental data on thermal propagation for lithium-ion pouch cells with different SOC distributions.
[1] J. Liu et al. “Experimental Study of Thermal Runaway Process of 18650 Lithium-Ion Battery”. In: Materials 10 (2017), 230. doi: https://doi.org/10.3390/ma10030230.
[2] O. Willstand et al. „Impact of different Li-ion cell test conditions on thermal runaway characteristics and gas release measurements“. In: Journal of Energy Storage 68 (2023). doi: https://doi.org/10.1016/j.est.2023.107785
[3] H. Li et al. ”Experimental investigation on the thermal runaway and its propagation in the large format battery module with Li(Ni1/3Co1/3Mn1/3)O2 as cathode“. In: Journal of hazardous materials 375 (2019), S. 241–254. doi: 10.1016/j.jhazmat.2019.03.116.
[4] T. Ying et al. ”Thermal runaway propagation characteristics of lithium-ion batteries with a non-uniform state of charge distribution“. In: Journal of Solid State Electro-chemistry 27.8 (2023), S. 2185–2197. issn: 1432-8488. doi: 10.1007/s10008-023-05496-9.