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Battery safety
How silicones from WACKER improve thermal barriers
In a thermal runaway, the choice of material is crucial. At that moment, the ability to act as a reliable thermal barrier becomes the key factor. Silicones from WACKER provide precisely this barrier.
WACKER’s experience is being used to create silicones for the batteries of tomorrow. One example of this is the ELASTOSIL® CM series. Originally developed at WACKER, it was turned into a market-ready solution in collaboration with ISOVOLTA.
New to the portfolio:
The ELASTOSIL® CM series for flexible thermal barriers
Dr. Martina Schüssler asked a simple but crucial question:
"How can we offer OEMs even lighter materials for heat shields?"
She heads a WACKER team responsible for developing silicones for battery safety and, together, they form the core of our innovation work. For this project, she was looking for a development partner that could complement our silicones expertise. She found the ideal match in ISOVOLTA, an experienced supplier of technical laminates.
The subsequent collaboration followed a well-defined process:
WACKER would supply the silicones know-how, ISOVOLTA the textiles expertise.
And so it was that, by treating a fabric with a product from the ELASTOSIL® CM series, they created a high-performance composite that protects the battery cover and adjacent cells. The material remains thin and pliable, but delivers a protective effect that was previously only possible with significantly heavier heat shields.
When treated with an ELASTOSIL® CM grade, the fabric makes an ideal thermal barrier.
The new thermal barrier offers:
Applications:
Performance confirmed in thermal propagation tests
"The silicone matrix ceramifies under high thermal stress. This creates an electrically and thermally insulating protective layer that makes the barrier much more stable in a thermal runaway."
Why the silicone makes the difference
Silicones from WACKER have a heat-stable, crosslinked structure of Si-O bonds. This structure remains functional even under extreme thermal load. For the joint development with ISOVOLTA, WACKER proposed using a silicone elastomer that was developed specifically for battery applications.
The high-performance silicones from the ELASTOSIL® CM series have been specially developed for a range of carrier substrates.
ELASTOSIL® CM series
The result is a highly effective surface that binds ejected particles. The elastomer increases the mechanical stability of the fabric, enabling it to withstand the particle jet and the high pressure load in the thermal runaway.
"The fabric treated with ELASTOSIL® CM is marketed by ISOVOLTA under the name Thermiga®. Thanks to our extensive fabric and processing expertise and WACKER's high-performance silicones technology, we were able to jointly achieve the outstanding product properties of Thermiga®."
WACKER silicones are the foundation for battery safety solutions
The co-innovation shows how silicones from WACKER enable next-generation battery materials:
WACKER and ISOVOLTA have filed a joint patent application for the new process and material. Proteba GmbH has validated the development through intensive thermal propagation tests and post mortem analyses.
WACKER – Your partner for e-mobility
Dr. Martina Schüssler, Technical Manager & Battery Safety Expert, WACKER
Our global teams support OEMs and Tier 1 suppliers throughout the entire development process: from the initial concept phase through material selection, prototyping and testing to series production.
We combine silicones expertise with know-how in battery architectures and engineering support across the entire value chain.
From busbar coating to cell potting: silicones from WACKER make your product more efficient and safer.
Q&A
What role do thermal barriers play in the event of a thermal runaway?
Silicone-resin-based fiber composites are used as rigid heat shields. They reliably withstand temperatures of up to 1,150 °C.
1. Thermal barriers retain extreme heat
Thermal runaway of a battery cell can generate vent gas temperatures of up to 1,300 – 1,400 °C.
A thermal barrier prevents this heat from breaching adjacent cells or the battery cover.
The better the thermal barrier, the lower the temperature that is still measured on its rear surface. The thermal barrier therefore shields the passenger compartment from the extreme temperatures of a thermal runaway.
2. Thermal barriers prevent flames from spreading
Thermal barriers remain intact even under extreme conditions and prevent
Thus, the barrier helps to ensure that the cell fire is contained to one cell as far as possible.
Silicone-resin-based fiber composites prevent penetration by particles.
3. Thermal barriers stop particles and active material (act as particle barriers)
Particles escaping from the cell at high pressure can trigger short circuits, secondary events or cascades.
In this scenario thermal barriers must act like a mechanical shield and remain stable.
4. Thermal barriers increase the time available for evacuation
All in all, thermal barriers increase the time available for a safe evacuation.
In practice, this means:
Which materials are used as thermal barriers in batteries?
Right picture: Examples of silicone-resin-based fiber composites as heat shields (bottom: carbon fiber, top: glass fiber)
Common materials for thermal barriers include:
What silicone-based thermal barriers are available?
| Type of thermal barrier | Products | Examples |
|---|---|---|
| Rigid barrier | SILRES® silicone resins for | Silicone-resin-based glass-fiber composite Basalt slabs |
| Flexible barrier | ELASTOSIL® CM series | Various substrates |
| Coating | ELASTOSIL® CM series | Coating the inside of the battery cover |
What makes silicones ideal for the thermal insulation of batteries?
Silicones are ideal for insulating batteries because various specialty grades
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