Lithium batteries are generally divided into lithium metal batteries and lithium-ion batteries. Lithium-ion batteries are increasingly widely used due to their rechargeability and high energy density. However, the safety of lithium-ion batteries is a bottleneck hindering the development of lithium-ion batteries and related industries (such as new energy vehicles). The electrolyte inside a lithium-ion battery is a flammable liquid, and the electrodes are made of flammable materials. Lithium batteries can experience thermal runaway under conditions such as overcharging, short circuits, overheating, puncture, or impact, easily leading to fires or even explosions. Cases of fires caused by batteries in mobile phones, electric bicycles, or electric vehicles are frequent.
Drawing on 20 years of experience in the fire protection industry and extensive exchanges with domestic and international counterparts, the author has been researching fire prevention for lithium-ion batteries in electric bicycles and electric vehicles since 2012. This article shares several fire prevention solutions for lithium-ion batteries.
Introduction to Lithium Battery Fire Prevention Strategies
Lithium battery fire prevention requires establishing multiple lines of defense with strategic depth. In addition to using non-flammable or flame-retardant materials inside the battery to ensure its inherent safety, the first line of defense outside the battery is to prevent various factors that could cause the battery to overheat and catch fire, such as overcharging, short circuits, and impacts. This necessitates a safe design for the electrical system.
When the first line of defense is breached (for example, if the battery management system malfunctions and fails to cut off the charging power in time), the battery temperature rises. Temperature sensors or gas and smoke detectors in the monitoring system should promptly detect the malfunction and issue an alarm to alert staff to address the problem and eliminate potential fire hazards. This is the second line of defense.
When a malfunction is not addressed promptly and the second line of defense is breached, battery combustion (smoldering) becomes unavoidable. At this point, the fire suppression system must confine the combustion to the faulty battery compartment (or enclosure) and isolate adjacent unburned batteries and equipment to prevent the fire from spreading. Because lithium-ion batteries reach extremely high temperatures after thermal runaway, existing non-water-based extinguishing agents such as gases and dry powders cannot quickly lower the battery temperature, resulting in less than ideal extinguishing effects. Therefore, setting the battery fire prevention objective as controlled burn-down is a more realistic and cost-effective solution. This constitutes the third line of defense.
If fire control fails and the fire spreads, posing a serious threat to the safety of people and property, it is necessary to activate the fixed water-based fire extinguishing system installed in the vehicle or wait for the fire department to extinguish the fire.
Generally, the first and second lines of defense are considered by battery manufacturers or electric vehicle manufacturers. As fire protection professionals, we can build a robust third line of defense for our clients, customizing solutions based on the specific model, specifications, and performance of the battery. The components used in these solutions come from all over the world and are not limited to any single type of equipment or material.
Examples of fire protection solutions for lithium batteries
This solution draws on advanced international experience and is simple and easy to implement. The fire-retardant material used is mainly composed of granular minerals, which are non-flammable, non-conductive, non-corrosive, safe, environmentally friendly, extremely lightweight, reliable, and cost-effective. It can be widely used for fire prevention and extinguishing during the production, storage, transportation, and use of lithium batteries. The following video is a recording of the lithium battery fire prevention solution testing process. After a lithium battery burns due to heating or overcharging, under the protection of the fire-retardant particles, no open flame is produced, no explosion occurs, and only white smoke is emitted, thus preventing the fire caused by the lithium battery combustion from spreading.
Fire prevention and extinguishing principles: extinguishing fire by isolating oxygen and suffocating it, and extinguishing fire by absorbing heat and cooling it.
Particle size: 1-4mm; Particle density: 360kg/m³; Dry loose bulk density: 240kg/m³
Fire prevention plan for lithium battery transportation
To ensure effective fire prevention and control, an independent fire extinguishing pipe can be installed inside the battery box (or enclosure). This pipe ruptures upon heating after the battery catches fire, automatically releasing extinguishing gas to put out the fire.
Alternatively, water-based fire extinguishing agents specifically designed for lithium-ion batteries can be used, sprayed through fire extinguishers or fixed fire suppression systems.
