# Complex Battery Storage Fire Propagation Translational Forensic Study Using Cellular Automata
## 1 Introduction  
Lithium-ion batteries (LIBs) have seen a significant rise in adoption as a key technology for supporting the energy transition and mitigating climate change. They are widely utilized in electric vehicles (EVs) and energy storage systems (ESSs). High-capacity LIB units, ranging from 20-30 kWh for EVs to MWh or even GWh scales for utility storage, have become integral to various large-scale applications. Figure 1 shows the projected LIB global sales growth and the shares between EV and ES usage. A major concern with large-scale LIB installations is the risk of battery fires, with several significant incidents reported globally to date [3; 4; 5; 6]. LIB fires involve the thermal runaway phenomenon, which can result in a unique fire propagation problem (Figure 2). It is recognized widely that LIB fire would require much more water to extinguish than other fossil-fuel-associated fires [7]. Another critical issue associated with LIB fire is that the design of the battery pack can be a predominant factor in fire propagation: LIB batteries are fabricated at the cell level and then packaged at the module level; hence, the packaging technique and design can dictate the propagation of a battery fire. Because LIB technology implementation is occurring at such a rapid pace, the biggest challenge is to bring awareness of battery fire issues and research outcomes to industry applications and the public. Herein, the accelerated transfer of technical knowledge to practitioners, also referred to as translational forensics, is suggested for the LIB technology industry. Translational research in an industry aids in sharing technical knowledge across  
Figure 1: Global LIB demand and supply projections from 2020 to 2030 [1; 2]. Figure 2: Diverse scales of LIB fire: (**a**) Experimental evaluation of battery ignition scenarios; (**b**) thermal imaging of a battery fire test; (**c**) post-combustion charred battery; (**d**) suppression measures during fire events; (**e**) battery fire in a commercial building; and (**f**) energy storage facility fire [8]. all sectors, which the medical field calls a \"bench-to-bedside\" transfer [9; 10]; this can be equally beneficial to the battery fire management field, coined \"cells-to-infrastructure\". [PERSON] et al. [8] first introduced the concept of translational research for LIB fire, described as translational forensics. They proposed some general rules and stages for integrated studies of Li-ion battery hazards (hence, forensic science); these are based on goals for practitioners, research, and education and their connections and outcomes. These are presented in Figure 3.  
Figure 4 further outlines the necessary research endeavors and the knowledge advancement process to produce valuable insights into LIB fire safety. These research endeavors can be cleaved into basic, applied, and advanced measures for research. There is also a potential to introduce hybrid methods that combine different research stages, which could yield greater benefits earlier in the process. For instance, integrating numerical modeling (basic research) with risk assessment (applied research) in a collaborative study may be an effective way to accelerate translational work. There are several examples in system design that involve combining various tasks to create concurrent outcomes. Figure 5 illustrates the diverse steps in translational research and the levels of development regarding battery behavior. These levels should account for varying structural complexities, from individual cells to modules and complete battery racks. The high energy density and chemical composition of LIBs make them susceptible to thermal runaway, which can result in overheating and fires or explosions. Thermal runaway may occur due to overcharging, thermal abuse, physical and structural damage, or manufacturing defects.