# A Review of Experimental and Numerical Studies of Lithium Ion Battery Fires
## 1 Introduction  
The world is currently changing environmentally in a negative direction due to the greenhouse effect that poses a direct threat to humanity. The main contributor to these unfavorable changes is CO\({}_{2}\) emissions from the combustion of fossil fuels accounting for 87% of the human-produced CO\({}_{2}\) emissions [1]. The main contributor is the electricity/heat and transportation industry, which contributes nearly two-thirds of the total CO\({}_{2}\) emissions globally [2]. To reduce future CO\({}_{2}\) emissions, greater emphasis has been placed on ecofriendly energy sources such as solar and wind energy systems. Storage systems are required to supply secure and reliable electricity 24 h a day; lithium-ion batteries (LIBs) are currently at the forefront of energy storage technologies. Lithium-ion batteries offer high energy and power density, are lightweight, and have a long lifespan. LIBs are used in an extensive range of applications which can be categorized into the three main industries--consumer electronics, automotive, and grid storage. Therefore, there is an intense interest in the research and initiatives in this field from both industry and government funding agencies. Fire is a major safety concern with the ever-increasing demand for energy storage devices worldwide. The incidence of reported LIB fires is somewhere in the vicinity of one in one million and one in 10 million units [3]. While the probability of a LIB fire on face value does not fit within the realms of a high-risk item, the hazard arises from the sheer volume of lithium batteries being used globally. In the current climate, the pressure on manufacturers to produce high energy density, high efficiency, long-cycle life batteries with minimal memory effect comes with associatedfire safety risks due to the unique chemical composition properties, higher levels of stored energy, and the flammability of the most electrolytes [4]. In the past five years, there have been a number of fires and explosions involving LIBs which have resulted in both damages to property and injuries to people. When the internal temperature of a LIB increases to approximately 80 \({}^{\circ}\)C the solid-electrolyte interphase (SEI) of the battery may decompose and generate more heat [5; 6; 7]. If this produced heat does not dissipate, the battery temperature will elevate further, thereby accelerating the process of heat release. This process is known as thermal runaway (TR) and can be triggered by internal or external means. The abuse conditions which may lead to the TR and fire in LIBs can fall into three categories [8]: electrical abuse (overcharging/discharging) [9; 10; 11; 12; 13; 14], thermal abuse (overtemperature) [5; 15; 16; 17; 18], and mechanical abuse [19; 20]. Heat release rate (HRR) is considered the most critical parameter when specifying the hazard of fire [21; 22; 23], defined as the rate at which the fire releases energy (power). The state of charge (SOC) of LIBs can influence the onset of TR as well as the magnitude of the HRR as the more energy a battery has stored, the more energetic the exothermic reactions of the principal components will be. As more heat and gas are generated in the reactions, the more likely it is that the propagated heat to surrounding cells initiates a fire and explosion, and results in a catastrophic chain reaction [6]. We will, therefore, review past studies on the effect of SOC on TR onset and HRR magnitude. An integral contributor in the design and virtual prototyping of all things involving fluid (including flame and smoke) is computational fluid dynamics (CFD), which is used in a variety of ways, from complementing experiments to testing and certification of the performance, safety, and reliability of a varied array of systems. CFD has become an important tool in fire safety by helping to determine the expected behavior of fire and smoke in many circumstances where it may be impossible to conduct realistic experiments on complete systems.