The procurement question
You're a battery pack engineer at a Chinese OEM. The pack roadmap mandates thermal runaway propagation prevention — a single cell venting must NOT cascade into adjacent cells within 30 minutes (the regulatory window for occupant escape). The cell-to-cell space available is 1.5-3 mm. Standard mineral-wool insulation doesn't fit. Polyimide foam decomposes under thermal runaway. What do you specify?
Aerogel felt. Specifically, a thin-section grade engineered for the 1000°C+ peak temperature of a venting Li-ion cell. This post explains the specification logic and walks through MEGEL MG-650-EV qualification.
The physics of thermal runaway propagation
When a Li-ion cell enters thermal runaway, electrolyte decomposition releases gas at >300°C, the cell vents through a designed rupture port, and the cell case reaches 600-800°C within seconds. Adjacent cells in close proximity (1-5 mm) receive intense radiative + conductive heat transfer. If the adjacent cell's temperature reaches the self-heating threshold (~150-180°C for NMC chemistry), it also enters thermal runaway. The cascade can propagate through the entire pack in minutes.
Two physical pathways carry the heat to the next cell:
- Radiative (proportional to T⁴) — dominant at peak temperatures
- Conductive (proportional to ΔT × thermal conductivity / thickness) — dominant after peak passes
Aerogel felt suppresses both pathways:
- Low thermal conductivity at high temperature (0.030 W/m·K at 600°C vs ceramic fibre 0.080 W/m·K, mineral wool 0.060 W/m·K)
- Non-radiative absorber — silica particles scatter rather than re-emit infrared radiation
- Survives thermal runaway temperatures — silicon dioxide melts at 1713°C; the aerogel structure remains intact through 1200-1500°C transient exposure
MEGEL MG-650-EV specification
| Property | MG-650-EV | Why it matters |
|---|---|---|
| Thickness range | 1.5-3 mm | Fits between prismatic / pouch cells |
| Density | 240-280 kg/m³ | Mechanically robust, doesn't compress under cell expansion |
| Thermal conductivity at 25°C | 0.020-0.025 W/m·K | Baseline insulation in normal operation |
| Thermal conductivity at 600°C | 0.030 W/m·K | Active during thermal runaway |
| Service temperature continuous | −40 to 650°C | Normal pack operating window |
| Thermal runaway peak survival | 1000°C+ short-duration | Single-cell venting event |
| Reinforcement | Mica/glass laminate | Mechanical robustness without combustion |
| Hydrophobicity | water uptake <3% | Long-term humidity survival |
| Fire class | UL 9540A passing | Required for North American certification |
| Reinforcement burn-through | Does not occur at 1200°C × 5 min | Critical for cell-to-cell isolation |
The mica/glass laminate is the critical reinforcement choice — standard glass fibre may sinter at peak runaway temperatures, while mica is inert through 1500°C+ peak exposure.
UL 9540A qualification logic
UL 9540A is the standard test method for evaluating thermal runaway fire propagation in battery energy storage systems. The test for a pack-level qualification requires:
- Induce thermal runaway in one cell (typically by overcharge, heating, or mechanical penetration)
- Measure propagation to adjacent cells over a 30+ minute window
- Pass criterion: no propagation to adjacent cells = cell-level passing test
The aerogel barrier sits between the initiating cell and adjacent cells, intercepting the heat flux. For a 1.5 mm aerogel barrier at 0.030 W/m·K thermal conductivity, the temperature drop across the barrier is approximately ΔT × 0.030 / 0.0015 W/m² ÷ heat flux. In practice, this gives 200-400°C drop from runaway cell side (600-800°C) to adjacent cell side (200-400°C) — keeping the adjacent cell below its self-heating threshold for the regulatory 30+ minute window.
Cost vs Aspen Pyrogel HPS
Aspen Pyrogel HPS is the established premium aerogel felt for high-temperature applications. MEGEL MG-650-EV is the engineered equivalent at substantially lower landed cost:
| Property | Pyrogel HPS | MEGEL MG-650-EV |
|---|---|---|
| Thermal cond. at 25°C | 0.018-0.022 W/m·K | 0.020-0.025 W/m·K |
| Service temperature | −40 to 650°C | −40 to 650°C |
| UL 9540A qualification | Available | Available |
| Cost per m² (1.5 mm, FOB Shanghai) | $35-45 | $20-28 |
| Lead time (large volume) | 8-12 weeks | 5-7 weeks |
For an 80 kWh EV battery pack with ~4 m² of inter-cell barrier surface, the material cost savings is $60-80 per pack — meaningful at 100,000-pack annual production scale.
Procurement and lead time
MOQ for evaluation: 50 m² (one roll at 1.5-3 mm thickness). Lead time 5-7 weeks FOB Shanghai. Each shipment includes batch CoA with thermal conductivity at 25 / 200 / 600°C, density, fire class certification, and a UL 9540A passing test report on request. For high-volume contract supply (10,000+ m²/year), contract terms include rolling stock at Shanghai port and locked-in pricing for 6-12 months.
FAQ
Is MG-650-EV qualified for use in North American EV markets?
Yes — UL 9540A passing test results are available on request. The reinforcement, density, and thermal conductivity specifications match the requirements for major North American OEM qualification programs. For specific OEM-listed supplier programs (Tesla, GM, Ford), an additional supplier registration step may be required.
Can the felt be slit and shaped for irregular cell geometries?
Yes. Standard slit width 5-200 mm; shaped die-cut available. For high-volume production, the felt can be supplied as die-cut parts ready for direct cell-pack assembly.
What's the difference between MG-650-EV and MG-650-IP for industrial pipe insulation?
Reinforcement and density. MG-650-EV uses mica/glass laminate at 240-280 kg/m³ for runaway survival. MG-650-IP uses standard glass fibre at 180-220 kg/m³ for lower-cost pipe insulation. Service-temperature ratings overlap, but the MG-650-IP material is not qualified for UL 9540A thermal runaway propagation.
Related
- MEGEL® Silica Aerogel Hub — full 5-form lineup
- Aerogel Powder in Vacuum Insulation Panels — neighboring aerogel application
- Aerogel in Heat-Reflective Roof Coatings — third aerogel application
Talk to our application chemists
Send an inquiry — we reply within 24 hours with COA, MSDS, and a sample plan.
Send an inquiry