New Challenges in NEV Battery Safety

As new energy vehicles evolve toward 800V high-voltage platforms and fast-charging technology, battery pack safety protection faces unprecedented challenges. When a single cell undergoes thermal runaway, temperatures can surge above 800°C within seconds. If heat rapidly spreads to adjacent cells, it triggers a chain reaction leading to整车fire. Traditional flame-retardant materials soften and fail at high temperatures, unable to effectively block heat propagation. Flame-retardant fluorosilicone rubber, with its unique ceramifying characteristics, has become the key material to solve this problem.

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What Is Ceramifying Flame-Retardant Fluorosilicone Rubber?

Ceramifying flame-retardant fluorosilicone rubber is a specialty elastomer that transforms into a hard ceramic layer under extreme high temperatures. Its core mechanism: the material maintains rubber flexibility and sealing performance under normal conditions; when exposed to fire or thermal runaway, ceramifying fillers (such as mica, silicates, glass powder) in the formulation react with the siloxane matrix above 600°C to form a dense ceramic protective layer. This ceramic shell has the following key properties:

• Electrical Insulation: Maintains excellent dielectric strength even at 1000°C, preventing high-voltage system short circuits
• Thermal Insulation: The ceramic layer has extremely low thermal conductivity, effectively blocking heat transfer to adjacent components
• Structural Integrity: Does not melt or drip at high temperatures, maintaining physical barrier function
• Low Smoke and Non-Toxic: Low smoke density during combustion, no release of halogens or other toxic gases

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Core Performance Advantages

Wide Temperature Range Capability Flame-retardant fluorosilicone rubber operates across a temperature range of -60°C to 230°C, with short-term resistance up to 250°C. This enables it to meet the full temperature range requirements of NEVs, from winter starts in extremely cold regions to summer fast-charging conditions, maintaining good elasticity and sealing performance at -40°C without低温brittleness-induced battery pack seal failure. Electrolyte Corrosion Resistance NEV battery packs contain lithium salt electrolytes (such as LiPF6/EC-DMC systems). Traditional rubber materials swell and age with prolonged contact. The trifluoropropyl functional groups on the side chains of fluorosilicone rubber impart excellent chemical media resistance, with minimal changes in hardness, tensile strength, and volume after 500 hours of immersion in electrolyte, ensuring long-term reliability of the battery pack sealing system. UL94 V-0 Flame Retardancy Rating By adding halogen-free flame retardant fillers such as aluminum hydroxide (ATH) and magnesium hydroxide (MDH), flame-retardant fluorosilicone rubber can achieve the UL94 V-0 highest flame retardancy rating, self-extinguishing within 10 seconds after flame removal. The group standard T/CWDPA 272-2026 "Active Flame-Retardant Protection Materials for Lithium-Ion Battery Packs" released in July 2026 sets clear technical requirements for flame-retardant performance, promoting industry standardization. Low Compression Set Battery pack seals need to maintain sealing force under long-term compression. Flame-retardant fluorosilicone rubber can control compression set to below 15% (150°C × 72h), ensuring the battery pack remains leak-free throughout its 8-10 year service life.

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Typical Applications in NEV Battery Systems

Battery Pack Housing Seals Flame-retardant fluorosilicone rubber sealing strips and O-rings are used at the mating surfaces of upper and lower battery pack housings, preventing external moisture and dust ingress while blocking flame and high-temperature gas escape during thermal runaway. According to the industry standard HG/T 2196-2026 "Classification System for Automotive Rubber Materials" released in June 2026, battery pack seals must meet stringent temperature resistance, flame retardancy, and media resistance requirements. Inter-Cell Thermal Barrier Pads Flame-retardant fluorosilicone rubber thermal barrier pads placed between cylindrical or prismatic cells effectively block heat transfer to adjacent cells when a single cell undergoes thermal runaway, delaying or preventing thermal propagation. In August 2026, Wacker Chemie showcased its ELASTOSIL CM series ceramifying silicone rubber applications in battery thermal barriers at the Battery Show Detroit, validating the technology's effectiveness in suppressing heat propagation. High-Voltage Connector Insulation Boots 800V high-voltage platforms impose higher requirements on arc resistance and flame retardancy of insulation materials. Flame-retardant fluorosilicone rubber boots provide reliable electrical insulation under normal conditions and maintain dielectric strength after ceramification during fires, preventing secondary accidents from high-voltage system short circuits. Liquid Cooling Line Seals NEV battery thermal management systems widely adopt liquid cooling solutions. Seals at cooling line joints must simultaneously withstand coolant corrosion, high-low temperature cycling, and vibration loads. Flame-retardant fluorosilicone rubber combines sealing reliability with fire safety in this scenario, becoming the mainstream choice.

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Market Trends and Localization Progress

According to an industry research report released in August 2026, the global fluorosilicone compound market is expected to grow from $72.04 million in 2025 to $94.54 million in 2032, with a CAGR of 4.0%. NEVs are the largest incremental market. In 2025, China's NEV passenger car sales reached 16.49 million units with a 54% penetration rate, and fluorosilicone rubber usage per vehicle increased by 30%-50% compared to traditional fuel vehicles. On the supply side, the global fluorosilicone rubber market has long been dominated by US companies Dow and Momentive, and Japan's Shin-Etsu, with the top three manufacturers holding approximately 52% market share. However, domestic companies have accelerated追赶in recent years. Enterprises such as Xinyuan Chemical, Zhejiang Huanxin, Shenzhen Guanheng, and Jiangxi Aluda have achieved规模化production, with some high-end products reaching import substitution levels. In 2026, fluorosilicone rubber was included in the "Catalogue of Industries for Encouraging Foreign Investment (2025 Edition)" as an advanced manufacturing/high-tech material, enjoying tax and land policy incentives. In terms of technological innovation, domestic companies are upgrading from general-purpose products to functionalized and customized solutions. In May 2026, Shengxin Rubber (Anhui) Co., Ltd. filed a patent for "High-Elasticity Fatigue-Resistant Fluorosilicone Rubber Compound," significantly improving dynamic sealing life through a composite anti-fatigue agent formulation. In the same month, Honglin Power filed a patent for "Electrolyte-Resistant Fluorosilicone Rubber High-Voltage Cable Sheathing Material for In-Vehicle Applications," developing a specialized formulation for high-voltage cable protection inside battery packs.

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Selection and Procurement Recommendations

For NEV battery pack applications, the following indicators should be prioritized when selecting flame-retardant fluorosilicone rubber:

• Flame Retardancy Rating: Must achieve UL94 V-0 with third-party test reports
• Electrolyte Resistance: Provide immersion test data in LiPF6/EC-DMC systems
• Compression Set: ≤20% under 150°C × 72h conditions
• Operating Temperature Range: At least -40°C to 150°C
• Compliance Documentation: Provide MSDS, REACH/RoHS reports, and batch factory inspection records

When procuring, prioritize suppliers with in-house compounding capabilities and formulation customization services to ensure material performance matches specific application scenarios. For safety-critical components such as battery pack seals, require suppliers to provide complete material traceability information and third-party test reports, avoiding recycled or blended materials of unknown origin.
IOTA FHTV 3600 Flame-retarded Series Fluorosilicone Rubber