Thermal Runaway Protection for eVTOL Battery Packs at High Altitude

eVTOL aircraft operate at high altitudes where low atmospheric pressure alters thermal runaway dynamics. Lithium-ion aviation batteries face increased risks of gas venting and flame propagation under reduced pressure. Effective thermal runaway protection must prevent any fire or toxic gas from reaching the passenger cabin, requiring a multi-layered design that addresses both heat and gas management.

Aerogel insulation forms the first line of defense. With ultra-low thermal conductivity (≈0.015 W/m·K) and lightweight structure, aerogel blankets are placed between battery cells and modules. They delay temperature escalation during a thermal runaway event, providing critical time for other systems to respond. The material’s porosity also allows controlled gas release, preventing dangerous pressure buildup within the pack.

Directed smoke exhaust channels are engineered to exploit the pressure difference between the battery pack interior and the external low-pressure atmosphere. These channels use one-way valves and dedicated vents to route hot gases and particulates away from the cabin, ensuring no toxic fumes enter passenger areas. The exhaust path is optimized for rapid removal, reducing the risk of secondary ignition.

Perfluorohexanone (C6F12O) serves as the primary fire suppression medium. It offers high dielectric strength, low toxicity, and environmental safety. When discharged into the battery pack, it rapidly absorbs heat and chemically interrupts the combustion chain reaction, extinguishing flames without damaging sensitive electronics. Its excellent dispersion properties make it effective even in confined spaces.

The three subsystems work together synergistically: aerogel insulation slows heat propagation, the exhaust system reduces internal pressure and removes combustible gases, and perfluorohexanone quickly suppresses any open fire. This integrated design ensures that thermal runaway remains contained within the battery pack, never threatening the cabin. Rigorous testing under simulated high-altitude conditions validates the design, enabling eVTOL battery packs to meet stringent flame retardant standards for airworthiness certification.