Electric vehicle battery safety has become one of the defining engineering challenges of the current decade. As cell energy densities climb past 250–300 Wh/kg and packs push beyond 800V architectures, the margin between normal operation and thermal runaway narrows. For engineers and sourcing teams evaluating thermal barrier materials, aerogel is no longer a laboratory curiosity — it is an increasingly specified component in production EV battery packs. This article looks at what real testing and deployment data actually show, where aerogel fits in the thermal barrier stack, and how to evaluate it against alternatives.
What Thermal Runaway Propagation Actually Means for Pack Design
Thermal runaway in a single lithium-ion cell is difficult to prevent entirely. Internal short circuits caused by manufacturing defects, mechanical damage, or electrode degradation can push a cell past its stability threshold, releasing stored chemical energy as heat that can exceed 700°C. The real engineering problem is not stopping that first cell — it is preventing the failure from propagating to adjacent cells.
When one cell enters thermal runaway, it ejects hot gases, flames, and conductive debris toward neighboring cells. If those neighbors absorb enough heat to cross their own thermal runaway threshold, a cascading failure spreads through the pack. In a dense prismatic or pouch cell layout with minimal inter-cell spacing, propagation can move through an entire module in seconds.
This is where thermal barrier materials come in. Inserted between cells or wrapped around modules, these materials must accomplish several things simultaneously: delay heat transfer to adjacent cells, resist flame and hot gas impingement, maintain mechanical integrity under cell swelling, and do all of this within tight thickness and weight budgets that directly affect pack energy density.
Why Aerogel’s Physical Structure Makes It Effective
Silica aerogel’s thermal insulation performance comes from its nanoporous microstructure, not from any exotic chemistry. The material is typically 90–99% air by volume, with pore diameters in the 2–50 nanometer range. Three heat-transfer mechanisms are suppressed simultaneously:
- Solid conduction is minimized because very little solid silica exists in the cross-section. The tortuous, fractal-like solid network creates an extremely long effective path for conductive heat transfer compared to a dense material.
- Gas-phase convection and conduction are suppressed through the Knudsen effect. When pore diameters are smaller than the mean free path of gas molecules (approximately 70 nm for air at standard conditions), gas molecules collide with pore walls more frequently than with each other. This dramatically reduces the ability of gas to transport heat through the material.
- Radiative heat transfer is scattered and absorbed by the aerogel matrix. For high-temperature applications, opacifiers such as carbon black or titanium dioxide are added to further block infrared radiation.
The result is a material with thermal conductivity in the range of 0.013–0.018 W/m·K at ambient temperature — substantially lower than alternatives like mica sheets (0.5–0.8 W/m·K), ceramic fiber blankets (0.05–0.12 W/m·K), or intumescent coatings. For battery applications, this means aerogel can achieve equivalent thermal delay in a fraction of the thickness, which translates directly into more space for active cell material and higher pack-level energy density.
Key Material Properties for Battery Barrier Specifications
When evaluating aerogel for EV battery thermal barriers, several properties beyond thermal conductivity matter in practice:
Thickness and packing efficiency
Production EV applications typically use aerogel pads in the 1–6 mm thickness range, with 2–3 mm being common for prismatic cell barriers. Every millimeter of inter-cell material reduces the space available for electrodes and electrolyte, so the material’s insulation per unit thickness is the critical figure of merit. Aerogel’s low thermal conductivity means a 2 mm pad can provide thermal delay comparable to 40–80 mm of mica — a difference that directly impacts pack energy density.
Compression behavior
Cells expand and contract during charge-discharge cycles. Pouch cells in particular can swell by several percent over their lifetime. Thermal barrier materials must accommodate this cyclic compression without losing insulating performance or suffering permanent deformation. Aerogel composites (aerogel combined with fiber blankets) offer better compressive recovery than monolithic silica aerogel, which is inherently brittle. Typical compressive strength values for commercial battery-grade aerogel pads range from 0.07 to 0.7 MPa (10–100 psi) depending on formulation and density.
Fire resistance and thermal stability
Silica aerogel is inherently non-combustible — silica does not burn and melts at approximately 1,700°C. Commercial aerogel composites for battery applications typically withstand direct flame exposure at 1,000–1,200°C for 15–30 minutes depending on thickness. This is critical during a thermal runaway event where cell venting can produce sustained flame impingement on adjacent cells. Many commercial products achieve Class A fire ratings and UL 94 V-0 classification.
Electrical insulation
Silica aerogel provides dielectric strength of approximately 10–20 kV/mm, making it an effective electrical insulator between cells — an important secondary function, since conductive debris ejected during thermal runaway could otherwise create short circuits across neighboring cells.
Real-World Deployment: What Is Confirmed
The most clearly documented case of aerogel in a production EV platform is the partnership between Aspen Aerogels (NYSE: ASGN) and General Motors. Aspen announced a multi-year supply agreement with GM in 2022 for aerogel thermal barriers on the Ultium battery platform, which underpins vehicles including the Chevrolet Blazer EV, Cadillac Lyriq, and GMC Hummer EV. This partnership is documented in Aspen’s SEC filings and public press releases from both companies, making it the highest-confidence public example of aerogel in series production EVs.
Beyond GM, the picture becomes less transparent. Industry reporting suggests that several major battery manufacturers — including Samsung SDI and CATL — have evaluated or adopted aerogel barriers for prismatic and pouch cell designs, but specific OEM-level applications are typically covered by nondisclosure agreements. Chinese EV makers including NIO, XPeng, and Li Auto have been reported by trade publications to incorporate aerogel in some models, driven by the mandatory GB 38031-2020 safety standard. However, detailed confirmation of which specific vehicle models and cell formats use aerogel, and at what thickness, is rarely available publicly.
This information asymmetry is important for sourcing teams to understand: the aerogel supply chain for automotive batteries is real and growing, but much of the deployment detail remains proprietary. Verification at the component level often requires teardown analysis or direct engagement with Tier 1 suppliers.
Regulatory Drivers That Are Accelerating Adoption
Three regulatory frameworks are directly relevant to aerogel adoption in EV battery packs:
GB 38031-2020 (China — mandatory)
China’s GB 38031-2020 standard, effective since January 2021, requires that thermal runaway in a single cell shall not cause fire or explosion in the battery pack within five minutes — providing occupant escape time — or that propagation to other cells be prevented entirely. Test methods include initiating thermal runaway via heating, nail penetration, or overcharge. This standard applies to all EVs sold in China, the world’s largest EV market, and is a primary driver of aerogel demand from Chinese battery manufacturers.
UN ECE R100 Revision 3 (EU and international)
The United Nations Economic Commission for Europe Regulation No. 100, Revision 3, introduces thermal propagation test requirements being phased in across the EU from 2023 through 2025. The regulation requires that vehicles provide at least five minutes of warning before a hazardous situation develops outside the battery pack following a thermal runaway event. This aligns with the Chinese approach and is driving European OEMs and battery makers to evaluate enhanced thermal barriers.
SAE J2464 (USA — voluntary)
SAE J2464 provides test procedures for EV battery abuse testing, including mechanical (crush, penetration), thermal (external heating), and electrical (overcharge, short circuit) abuse scenarios. While not a pass-fail mandate, it is widely referenced by US OEMs and provides the test methodology framework that many manufacturers use internally. There is no current US federal requirement equivalent to GB 38031 or ECE R100 for thermal propagation specifically, though NHTSA has been evaluating rulemaking in this area.
The common thread across all three frameworks: regulators are moving from “survive a single-cell event” toward “contain the event and protect occupants.” This regulatory trajectory favors high-performance thermal barriers and is one reason aerogel demand from the automotive sector is growing faster than overall aerogel market growth.
Key Suppliers in the EV Battery Aerogel Space
The supplier landscape for battery-grade aerogel is concentrated but expanding:
- Aspen Aerogels (USA) is the most visible supplier to the automotive sector, with the GM Ultium partnership and reported supply agreements with other major OEMs. Their product lines include thin aerogel blankets specifically engineered for battery thermal barriers.
- JIOS Aerogel (Singapore/South Korea) targets the Asian EV battery market with aerogel blankets and silicone-aerogel composite products. The company has reported collaborations with Asian battery manufacturers.
- Chinese producers including Guangdong Alison (Sino-Aerogel), Nano High-Tech, Huaqing New Material, and several others are competing in the domestic market. China’s mandatory thermal propagation standard has created strong domestic demand that multiple domestic suppliers are addressing.
- Cabot Corporation (USA) supplies aerogel particles (LunaQ, Nanogel product lines) that can be incorporated into composite thermal barrier products, though they serve more as a materials supplier than a finished-product manufacturer for this application.
- European suppliers including Active Aerogels (Portugal), Enersens (France), and Svenska Aerogel (Sweden) are developing or offering products targeting the EV sector, though their automotive market presence is currently smaller than Aspen’s or the major Chinese producers.
Aerogel vs. Alternative Thermal Barrier Materials
Aerogel competes against several established materials in the battery thermal barrier space. Understanding the trade-offs is essential for specifying engineers:
Mica sheets are the most common incumbent. They offer excellent electrical insulation and fire resistance at low cost. However, mica’s thermal conductivity (0.5–0.8 W/m·K) is 30–60 times higher than aerogel’s, meaning equivalent thermal delay requires much greater thickness. Mica is also rigid and brittle, making it harder to accommodate cell swelling and module tolerances.
Ceramic fiber blankets provide moderate thermal insulation (0.05–0.12 W/m·K) and good flexibility, but they are thicker than aerogel for equivalent performance and can shed fibers that create contamination concerns in clean battery assembly environments.
Intumescent coatings expand when heated to form an insulating char layer. They are thin at room temperature and relatively inexpensive, but their activation is irreversible — once triggered, the coating expands permanently. They also provide limited thermal delay compared to aerogel’s continuous insulation.
Phase change materials (PCMs) absorb heat during the solid-to-liquid transition, providing temporary thermal buffering. However, their capacity is finite — once the phase change is complete, thermal protection drops substantially. PCMs are typically used as a complement to passive barriers, not a replacement.
In practice, many pack designs use layered approaches combining these materials. Aerogel is increasingly specified as the primary thermal barrier layer where space is tightest and performance requirements are highest, with mica or ceramic materials used in less space-constrained regions.
Practical Considerations for Engineers and Sourcing Teams
- Specify thermal delay time, not just thermal conductivity. The relevant metric is how many seconds or minutes the barrier material delays peak temperature rise on the protected side of the barrier during a simulated thermal runaway event. This depends on thickness, thermal conductivity, heat capacity, and the specific test protocol.
- Account for compression in service. Request test data for thermal performance under compressive loads representative of your cell format and module design. Aerogel’s thermal conductivity increases modestly under compression, and long-term creep can reduce thickness over the pack’s design life.
- Verify fire resistance under realistic conditions. Standard fire ratings (UL 94, Class A) are a starting point, but battery thermal runaway produces a specific combination of flame, hot gas, and particulate ejecta. Request or conduct testing that simulates actual cell venting conditions, not just a standard flame exposure.
- Evaluate total cost of ownership, not per-kilogram material cost. Aerogel is more expensive per kilogram than mica, but its superior insulation per unit thickness can enable higher pack energy density (more cells in the same volume), which has significant system-level value. The cost comparison should be done at the pack level, not the material level.
- Qualify multiple suppliers. The aerogel supply chain for automotive batteries is still consolidating. Production capacity, quality consistency, and delivery reliability vary significantly between suppliers. For production programs, dual-sourcing is prudent.
Conclusion
Aerogel is transitioning from a high-performance niche material to a mainstream component in EV battery safety systems, driven by tightening thermal propagation regulations and the performance demands of high-energy-density cell designs. The physics are straightforward: nanoporous silica provides thermal insulation per unit thickness that no competing material can match, and this matters when every millimeter of inter-cell space directly reduces pack energy density.
For engineers and sourcing professionals evaluating thermal barrier options, the practical path forward is to specify system-level requirements (thermal delay time, compression resistance, fire endurance), test under realistic conditions, and compare materials on total pack-level impact rather than per-kilogram cost. The confirmed deployment in GM’s Ultium platform and the strong pull from China’s GB 38031 standard suggest that aerogel’s role in battery safety will continue to expand as EV production scales and regulatory requirements tighten globally.
Selected Sources and Further Reading
- Aspen Aerogels — investor presentations and SEC filings documenting GM supply agreement and EV product lines
- GB 38031-2020 — China’s “Electric Vehicles Safety Requirements” standard (mandatory for all EVs sold in China)
- UNECE Regulation No. 100, Revision 3 — thermal propagation requirements for the EU and international markets
- SAE J2464 — “EV and HEV RESS Abuse Testing” standard
- JIOS Aerogel — company publications on aerogel for battery thermal management
Workflow marker: Aerogela Auto Blog Series
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