An investigation of battery fires in fully electric vehicles and effective suppression systems

Electric vehicles have emerged as a significant alternative to internal combustion engine vehicles in mitigating greenhouse gas emissions and environmental pollution. Their quiet operation, environmentally friendly characteristics, and economic advantages have contributed to a growing global interest. Although electric propulsion systems were among the earliest areas of automotive technology research, limitations in battery capacity and the rapid advancement of internal combustion vehicle technology kept electric vehicles in the background for decades. The decline of fossil fuel reserves and the accumulation of combustion-related pollutants in the atmosphere, which damage the ozone layer and contribute to the greenhouse effect, have reignited interest in electric vehicles. Today, electric vehicles are manufactured in three main categories: battery electric vehicles, hybrid electric vehicles, and fuel cell electric vehicles. Battery electric vehicles operate solely on electric motors powered by battery packs. Hybrid electric vehicles combine electric motors with internal combustion vehicles for dual propulsion, while fuel cell electric vehicles use hydrogen storage systems to generate electricity for electric motors. One of the most critical components driving the development of electric vehicle is the lithium-ion batteries. Lithium ion batteries offer high energy density, long cycle life, and rapid charging capabilities, significantly improving electric vehicle range, performance, and usability. Typically, the anode consists of graphite, the cathode is composed of various metal oxides, and the electrolyte is a carbonate-based ion-conductive liquid. Several chemical variations of lithium ion batteries exist, including Lithium Cobalt Oxide (LCO), Lithium Nickel Manganese Cobalt Oxide (NMC), Lithium Nickel Cobalt Aluminum Oxide (NCA), Lithium Iron Phosphate (LFP), Lithium Titanate Oxide (LTO), Lithium Sulfur Dioxide (Li-SO2), and Lithium Manganese Dioxide (Li-MnO2). Each type exhibits distinct advantages and trade-offs in terms of energy density, safety, cost, and cycle life. For instance, NMC and NCA cells offer high energy density, LFP provides superior safety and durability, LTO delivers exceptional reliability and cycle life even at low temperatures, Li-SO2 offers high theoretical energy density but faces technical limitations, and Li-MnO2 provides a balance between safety and service life but lags behind newer chemistries. These advancements underscore lithium ion battery technology's pivotal role in the future transformation of sustainable transportation. The frequency, risk factors, fire dynamics, and suppression methods associated with electric vehicle and lithium ion battery fires require a multidisciplinary and comprehensive evaluation. Global statistics indicate that reported fire incidence rates in battery electric vehicles and hybrid electric vehicles are generally lower than in internal combustion vehicles; however, this is largely attributable to the relatively low market share of electric vehicles in the global vehicle fleet and may lead to misleading conclusions in absolute risk assessments. As the composition of the vehicle fleet evolves and electric vehicles adoption accelerates, the absolute number of fire incidents is expected to rise, making the risk more pronounced, particularly in urban areas, long-distance transportation, logistics operations, and public transport fleets. Fire department reports have documented cases where electric vehicle fires reignited days or even weeks after initial suppression, and the water volume required to control these fires can be approximately 40 times greater than that needed for internal combustion vehicle fires. Data from the United Kingdom and the New York Fire Department (2019–2024) indicate statistically significant increases in injury and fatality rates from battery-related fires, with 2023 marking the peak year for both metrics. Moreover, incidents in maritime shipping, battery production lines, and recycling facilities highlight the cascading fire risks, toxic gas emissions, and high economic losses associated with such events. While lithium ion batteries form the backbone of portable energy storage systems due to their high energy density, long cycle life, rapid charge/discharge capabilities, and compact form factor, their inherently reactive and flammable chemistry makes them susceptible to safety hazards. Mechanical damage, overcharging, over-discharging, manufacturing defects, or external heat exposure can trigger thermal runaway. During thermal runaway, degradation of the solid electrolyte interphase (SEI) layer, separator melting, and the formation of internal short circuits initiate a chain of exothermic reactions. This process releases oxygen, enabling the battery to sustain combustion independently of ambient oxygen supply, thereby limiting the effectiveness of conventional oxygen-deprivation suppression methods. Additionally, the release of highly toxic gases such as hydrogen fluoride (HF) and phosphoryl fluoride (POF₃) poses further hazards to first responders and the environment. Comparative studies in the literature reveal considerable variability in the effectiveness of fire suppression agents. ABC-type dry chemical powders are unsuitable due to their potential for re-ignition and electrically conductive residues. Water mist offers advantages in delaying termal runaway propagation and cooling, yet it has limited effectiveness in large-capacity battery packs or confined spaces and may in some cases increase toxic gas emissions. The addition of surfactants can enhance water's suppression efficiency by reducing surface tension. CO₂ demonstrates low effectiveness because lithium ion batteries can generate their own oxygen during thermal runaway. Halocarbon agents such as HFC-227ea and C6F12O (NOVEC 1230) can be effective when applied early in enclosed environments but may increase toxic gas emissions. Liquid nitrogen can notably prevent or delay thermal runaway through rapid cooling, though its storage and handling present logistical challenges. Aerosol suppressants may provide initial cooling but fail to prevent re-ignition and may leave corrosive residues. Overall, the complex combustion mechanisms, high re-ignition potential, toxic gas emissions, and operational challenges of lithium ion battery fires indicate that most suppression techniques are insufficient in isolation. Effective intervention requires selecting suppression agents based on vehicle type, battery chemistry, fire scenario, environmental conditions, and operational constraints, coupled with integrated active safety systems (e.g., cooling systems, fire detection, rapid isolation) and passive safety measures (e.g., fire-resistant enclosures, robust battery housing designs). Furthermore, regulatory updates, standardized testing protocols, strengthened international cooperation, and widespread training programs are essential to managing lithium ion battery fire risks effectively. This study investigates fire incidents involving 18650-type Lithium Nickel Manganese Cobalt Oxide (NMC) lithium batteries used in EVs and evaluates the effectiveness of different fire suppression agents under controlled conditions. The flammability characteristics of lithium-based battery components present significant challenges for suppression. The combustion behavior of 18650 NMC cells was analyzed by inducing ignition through overheating within specially designed safety enclosures. The suppression agents tested included water, BIOVERSAL, NOVEC 1230, and a high viscosity liquid substance. Experiments were conducted in two phases: free-burning tests of a single cell and suppression tests under conditions where the heat source was either removed or continuously applied. Performance metrics included combustion and explosion temperatures, ignition delay times, and changes in ambient gas composition (O₂, CO, CO₂). Under heat removal conditions, BIOVERSAL exhibited the highest thermal resistance at approximately 247.6 °C, while water achieved the longest ignition delay of approximately 82 seconds. Under continuous heating, high viscosity liquid susbtance reached the highest explosion temperature (approximately 247 °C) and the longest ignition delay (~75 seconds), making it the most effective agent in this scenario. In contrast, NOVEC 1230 demonstrated the lowest suppression efficiency. These findings indicate that BIOVERSAL is most effective under heat removal conditions, whereas high viscosity liquid substance is superior under continuous heat exposure. The results highlight the critical importance of selecting suppression agents based on the specific operational scenario when addressing lithium ion battery fires.