Thermal Runaway Heat Flux Limits in Grid Energy Enclosures
Grid battery enclosures require passive inter-cell thermal barriers to limit conductive heat flux below 120 kW/m² and contain thermal runaway propagation.
Inter-Cell Thermal Barrier
Meaning
Insulating sheet or plate positioned between adjacent electrochemical cells to restrict heat transfer and prevent cascading thermal failure. In battery module assembly, the inter-cell thermal barrier provides a passive safety element designed to withstand extreme temperatures and retard thermal transport. This component governs the delay or prevention of thermal propagation between adjacent cells during localized failure events.
It stops applying if the mechanical structure of the module collapses and allows direct contact or electrical shorting bypass. In many electric vehicle packs, these barriers must also act as electrical insulators to prevent high-voltage arcing between cells during a crash or internal rupture.
Material Selection
Aerogels, mica sheets, and ceramic papers represent the primary choices for high-performance safety applications due to their low thermal conductivity and high melting points. Utilizing an inter-cell thermal barrier composed of these materials minimizes heat conduction during a thermal runaway event. Designers must select materials that maintain their mechanical integrity under severe compressive loads and high heat fluxes.
Mechanical Compression
Cell expansion during normal charge and discharge cycles exerts continuous pressure on the insulating materials within a packed module. The inter-cell thermal barrier must possess sufficient elasticity to absorb these volumetric changes without losing its thermal insulation performance. If the material compresses too much, its thickness decreases and its thermal resistance drops below the required threshold.
Pack Integration
Designing battery packs involves a balance between energy density and safety spacing requirements. Adding a thick inter-cell thermal barrier reduces the volumetric energy density of the pack but increases its resistance to cascading fire. Consequently, the chosen barrier thickness must satisfy safety regulations while maintaining competitive energy storage capacity.