Fire behaviour of batteries. Risks,testing and regulations

The energy transition and decarbonization of transportation and electricity generation systems have led to the widespread deployment of lithium-ion batteries, which have become the dominant technology for electrochemical energy storage. Their success is based on high energy density, good durability, and increasing competitiveness. They are now ubiquitous: electric vehicles, large-capacity stationary systems (BESS), light mobility solutions (scooters, electric bikes), and domestic applications.

However, this widespread use comes with a specific fire and explosion risk linked to the intrinsic characteristics of these batteries: high energy storage capacity, flammable organic electrolytes, and rapid exothermic reactions in the event of failure. Unlike conventional fuels, the degradation kinetics of lithium-ion batteries are characterized by a feared phenomenon known as thermal runaway, which can lead to a massive release of heat, toxic and flammable gases, and rapid propagation from cell to cell.

The consequences of such events are particularly critical in confined environments (parking lots, technical rooms, tunnels), where the accumulation of combustible gases and toxic species (HF, POF ₃ ) can lead to delayed explosions and complicate rescue operations. Recent experience shows that battery fires not only cause significant material losses, but also have a major environmental impact due to the release of fluorinated compounds and metals in smoke and extinguishing effluents.

Faced with these challenges, battery fire safety cannot be limited to requirements inherited from conventional fuels. It requires a thorough understanding of the mechanisms of ignition and propagation, the dynamics of gas and particle emissions, and interactions with the environment. A battery can be understood as a series of layers: cell, module, pack, system, each with its own characteristics and safety barriers that determine the overall fire behavior. Prevention strategies must combine intrinsic approaches (cell and pack design), active devices (multi-sensor detection, thermal management), compartmentalization measures, and intelligent monitoring systems incorporating artificial intelligence.

Furthermore, the regulatory framework is evolving rapidly: IEC, UL, and ISO standards define thermal, mechanical, and electrical abuse tests, but gaps remain, particularly with regard to propagation at the pack level and the characterization of toxic emissions. Regulation (EU) 2023/1542 imposes new requirements on traceability and safety throughout the life cycle, reinforcing the need for a systemic approach covering manufacturing, transport, use, second life, and recycling.

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