Development of an automation system using endothermic liquid additive water mist in intervention of lithium-ion battery fires

This thesis investigates the fire safety challenges associated with lithium-ion batteries (LIBs) and evaluates suppression strategies, with a particular emphasis on the use of endothermic liquid additive water mist systems integrated into automated extinguishing frameworks. The research is motivated by the increasing reliance on LIBs in electric vehicles, stationary battery energy storage systems, portable electronics, aviation, and other critical infrastructures. While LIBs provide outstanding energy density, long cycle life, and operational efficiency, they also pose severe hazards under fault conditions. Among the most critical of these is thermal runaway, a self-propagating failure process characterized by uncontrollable heat generation, jet flames, explosions, and the release of toxic gases such as carbon monoxide, hydrogen, hydrogen fluoride, and volatile organic compounds. Documented incidents across different sectors highlight the urgent need for fire protection methods that specifically address the unique risks posed by LIBs. Lithium-ion batteries are widely recognized for their high energy density, long cycle life, and relatively low maintenance requirements. However, their chemical and thermal instability under fault conditions presents severe safety hazards. Failures such as thermal runaway can result in self-accelerating exothermic reactions, jet flames, explosions, and the release of flammable and toxic gases (e.g., CO, H₂, HF, VOCs). Such incidents have been documented in electric vehicles, grid-scale battery energy storage systems (BESS), consumer electronics, and aviation applications. Lithium-ion battery fires differ fundamentally from conventional hydrocarbon or solid-fuel fires. They are marked by rapid flame spread, high heat release rates often reaching several megawatts, violent gas venting, and the production of highly toxic emissions. The propagation of failure within modules or packs is strongly influenced by battery chemistry and design as well as the state of charge. Traditional suppression approaches, while effective in certain contexts, reveal critical shortcomings when applied to LIB hazards. Water can provide strong cooling but fails to eliminate gas emissions. Foams cover surface flames but lack deep cooling penetration. Dry chemical powders achieve rapid flame knockdown yet do not prevent re-ignition. Gaseous agents such as CO₂, FM-200, or Novec 1230 are useful in sealed enclosures but cannot counter thermal runaway jets. Aerosol systems, although compact, still lack extensive validation in large-scale LIB fire scenarios. Given these risks, the research investigates the fundamental fire behavior of lithium-ion cells and evaluates alternative suppression methods. Existing suppression techniques—such as water, foam, dry chemicals, gaseous agents, and aerosols—are analyzed in terms of effectiveness, cooling capacity, re-ignition prevention, and compatibility with sensitive electronics. Among these, water mist emerges as a promising option due to its fine droplet distribution, high heat absorption, and minimal collateral damage. To further improve suppression efficiency, the study introduces F-500 EA (Encapsulating Agent) as an endothermic liquid additive, aiming to enhance cooling, gas suppression, and flame knockdown. The thesis sets out the following main objectives: To systematically analyze the fire risks, failure mechanisms, and gas emissions of different lithium-ion battery types (LFP, NMC, NCA). To experimentally investigate the performance of water mist suppression systems under both portable and automated configurations. To evaluate the influence of endothermic liquid additives (F-500 EA) on suppression efficiency, cooling rate, and gas reduction. To design and prototype an automation-based detection and suppression system that integrates sensors, nozzles, and real-time actuation. To contribute to future fire protection standards and guidelines (e.g., NFPA 855, UL 9540A, IEC 62933, EN 14972) by providing empirical evidence. The research adopts a combined literature review, theoretical modeling, and experimental testing approach. First, the study reviews lithium-ion battery structures (anode, cathode, separator, electrolyte) and identifies their thermal vulnerabilities. The concept of thermal runaway and its stages are explained, along with the quantitative estimation of heat release rates and gas generation volumes. For the experimental part, two types of suppression systems were evaluated: Portable Fire Extinguishing Experiments: Prismatic cells were triggered into thermal runaway using controlled heating and mechanical puncture. The extinguishing performance of plain water mist was compared against F-500 EA-enhanced mist. Parameters such as flame duration, peak temperature, and post-extinguishment gas emissions were recorded. Automated Suppression System Experiments: A novel automation system was designed with integrated fire detection (multi-sensor including CO, H₂, smoke, heat, and infrared sensors) and suppression modules. Different nozzle types, droplet size distributions, spray cone angles, and mass flow rates were analyzed to optimize performance. The DOE (Design of Experiments) methodology was applied to ensure statistical validity, and high-resolution thermal imaging and gas analyzers were used for data collection. The experimental results provide several critical insights: Battery Type Influence: NMC cells exhibited the most violent thermal runaway, with rapid temperature escalation and intense jet flames. LFP cells showed better thermal stability, while NCA cells demonstrated intermediate behavior. Suppression Efficiency: Water mist proved highly effective in cooling and suppressing visible flames, even in jet flame scenarios. However, unmodified water mist could not fully eliminate post-fire gas emissions. Role of Endothermic Additives (F-500 EA): The additive significantly improved cooling efficiency, shortened suppression time, and reduced re-ignition risks. It encapsulated volatile hydrocarbons and diluted combustible gases, though complete gas neutralization was not achieved. Automated System Performance: The prototype automation system detected fire events rapidly and discharged mist effectively, ensuring early-stage fire suppression. The integration of real-time sensors and automatic actuation increased reliability compared to manually operated systems. The thesis contributes to both academic knowledge and practical fire safety engineering. Key contributions include: Providing one of the first experimental validations of endothermic additive water mist systems against lithium-ion battery fires. Demonstrating the importance of battery chemistry-specific suppression strategies (e.g., NMC vs. LFP). Proposing a scalable automation architecture for battery fire detection and suppression, which can be applied in electric vehicles, grid storage containers, and industrial applications. Offering guidance for future revisions of international standards by providing performance data that supports the adoption of alternative extinguishing technologies. The results indicate that while water mist with F-500 EA is highly promising, further research is needed on: (i) toxic gas capture, (ii) large-scale containerized BESS applications, and (iii) long-term material compatibility. Although results are promising, further research is required in several areas. Post-fire toxic gas management, particularly the capture and neutralization of HF and VOCs, remains an open challenge. Large-scale tests in multi-module containerized BESS environments are needed to validate performance at realistic industrial scales. Material compatibility must be evaluated to ensure long-term stability of additives with metals, seals, and electronic components. Finally, cost-benefit analysis is essential to compare the economic feasibility of such systems against more conventional gaseous or foam suppression solutions. In conclusion, this research demonstrates that endothermic additive water mist systems provide a highly effective, sustainable, and technically feasible strategy for mitigating lithium-ion battery fires. Their combined effects of rapid cooling, localized oxygen displacement, and hydrocarbon encapsulation present a clear improvement over traditional suppression methods. Integration into automated fire safety frameworks ensures rapid and reliable response, significantly enhancing resilience of critical infrastructures. The findings contribute not only to the academic literature but also to industrial fire safety practices and international standards development, paving the way toward safer, more sustainable energy storage technologies. This research confirms that endothermic additive water mist systems represent an effective, sustainable, and technically feasible solution for mitigating lithium-ion battery fires. The combination of rapid cooling, oxygen displacement, and hydrocarbon encapsulation provides a significant improvement over conventional suppression method. The integration of such systems into automated architectures enhances fire resilience in critical infrastructures, contributing to safer, more reliable, and more sustainable energy storage technologies.