As the global automotive industry accelerates toward electrification, traction batteries—the “heart” of new energy vehicles (NEVs)—have become the focal point of technological competition, with safety, reliability, and thermal management as critical performance pillars. Within battery packs comprising hundreds or even thousands of high-energy cells, engineers must simultaneously prevent electrical short circuits, electrolyte leakage, and thermal runaway while accommodating mechanical vibration, cell swelling, and extreme temperature swings. Traditional rigid materials fall short in this demanding environment. Enter high-performance silicone rubber—a multifunctional material prized for its excellent electrical insulation, wide service temperature range, flame retardancy, and elastic cushioning—now deeply embedded across key subsystems as the indispensable “flexible guardian” of high-energy battery cells.

1. Inter-Cell Fire-Resistant Thermal Barrier: The “Firewall” Against Thermal Runaway

In nickel-rich NMC (e.g., NMC811) or NCA batteries, a single cell undergoing thermal runaway can exceed 800°C within seconds, triggering a catastrophic chain reaction among neighboring cells. To interrupt this propagation, flame-retardant silicone rubber thermal barrier pads are inserted between cells:

Low thermal conductivity (0.1–0.3 W/m·K) achieved via fillers like ceramic powder, mica, or aerogel, significantly delaying heat transfer;

Shore hardness of 30A–60A accommodates typical cell volume expansion (5–10%) during charge/discharge cycles without loss of contact;

Oxygen index >30%, meeting UL 94 V-0 flammability rating—no dripping or toxic fumes at high temperatures;

High dielectric strength (>15 kV/mm) prevents high-voltage arcing between adjacent cells.

Leading automakers such as Tesla and BYD have already deployed these silicone-based thermal barriers at scale in premium EV platforms.

2. Module Sealing & Potting: Defense Against Moisture and Vibration

Battery packs must achieve IP67 or IP68 ingress protection to withstand rain, dust, and road splash. Silicone rubber plays a vital role here:

Housing gaskets: Maintain sealing integrity across –40°C to +150°C thermal cycles with compression set <20%;

BMS potting: Encapsulates battery management system (BMS) circuit boards, shielding them from condensation and salt fog corrosion;

High-voltage connector seals: Ensure insulation safety at fast-charging interfaces under humid conditions.

Unlike polyurethane or epoxy, silicone potting compounds remain flexible under thermal shock, making them ideal for regions with harsh seasonal swings—such as frigid northern winters and humid subtropical summers.

3. Thermally Conductive Structural Adhesives: Bonding with Heat Dissipation

Efficient heat extraction from cells to liquid cooling plates is essential for performance and longevity. Thermally conductive silicone structural adhesives (TCSAs) deliver dual functionality:

Thermal conductivity: 1.5–3.0 W/m·K (enhanced with Al₂O₃ or BN fillers);

Shear strength >1.0 MPa, enabling replacement of mechanical fasteners—reducing weight and assembly complexity;

Moderate elastic modulus mitigates thermo-mechanical stress between dissimilar materials (e.g., aluminum cooling plates, copper busbars, polymer housings).

For instance, CATL’s CTP (Cell-to-Pack) architecture uses silicone-based thermal adhesives to directly bond cells to cooling plates, boosting volumetric efficiency and thermal uniformity.

4. Wire Harness & Sensor Protection

High-voltage harnesses passing through battery pack walls require flexible, durable sealing:

Silicone corrugated tubing or overmolded jackets withstand >1000 V DC;

UV-resistant formulations suit underbody exposure;

Provide strain relief and environmental protection for temperature/pressure sensor leads, ensuring signal fidelity over the vehicle’s lifetime.

5. Future Trends: Toward Intelligence and Integration

Phase-Change Silicone Composites: Embedding paraffin-based PCM (phase change materials) enables passive thermal buffering—absorbing excess heat during overloads;

Self-Sensing Silicone: Integrated with piezoresistive or capacitive elements to monitor strain, temperature, or swelling in real time;

Design for Disassembly: Developing modular, easily separable silicone components to support battery second-life applications and material recycling.

Conclusion

As new energy vehicles approach mass adoption—projected to exceed tens of millions annually—every safe kilometer driven relies on silent protectors hidden within the battery pack. Silicone rubber generates no power, yet it ensures energy is released safely; it participates in no electrochemical reaction, yet it halts catastrophic chain reactions before they spread.

This resilient, silicon-based material embodies the convergence of materials science, thermal engineering, and safety philosophy. In an era where green mobility must also be safe mobility, silicone rubber stands as the unassuming yet essential guardian—soft in form, steadfast in function—securing the final line of defense for the electric future.



High Temperature Resistance Silicone Rubber(350℃) MY HTV 329 series