Material Solutions for Battery Pack Thermal Runaway Propagation Mitigation
It is predicted that by the mid-2030s, the electrification of passenger vehicles will attain mass-market dominance. This will be the result of growing environmental concerns, advancements in battery technologies, implementation of stricter emissions regulations and government-issued incentives that aid in accelerating the transition to cleaner transportation options.
Without a doubt, the competition amongst automotive manufacturers to deliver faster charging, improved motor performance, higher capacity and extended driving range is ramping up. However, one drawback to high-powered electric batteries is the issue of thermal runaway. As the automotive landscape evolves, the path ahead demands inventive cooling techniques, intelligent battery safeguards and game-changing materials that make a real impact on thermal safety. Saint-Gobain® Tape Solutions has a versatile range of customizable solutions for thermal runaway propagation mitigation. These solutions help to maintain the balance between innovation and safety.
We are devoting our global expertise in materials, application and manufacturing to tackle this critical issue of battery pack longevity and safety.
Fei Wang, R&D Manager, EV Platform
Customizable Cushioning Pad for Battery Cells
Compression pads or tolerance pads are often meticulously designed to compensate for the dimensional variation of Li-ion batteries. They provide optimum cushioning support to the batteries and tolerate the dimensional change during the battery breathing process. This support includes the reversible breathing (dimensional change) of the cell during its charge and discharge cycle as well as the gradual swelling that occurs throughout the battery lifespan.
Our concept of tunable intercell pads has helped us stay in the race when co-developing solutions with our EV customers for this extremely dynamic market.
Dominique Burgeff, Global Automotive Market Manager, Saint-Gobain Tape Solutions
At Saint-Gobain Tape Solutions, our teams can adapt our compression/tolerance foam to provide different surface properties including tackiness, adhesion, supporting layers or delivery format (such as stack or roll). This adaptability facilitates seamless integration into assembly lines. Our pads are adaptable to different battery types (prismatic vs. pouch) and materials (cathode, anode or electrolyte). The tunable compression curves of these pads along with our robust simulation capabilities ensure we can support specific customer requirements and the needs of diverse battery configurations.
Exploring diverse levels of thermal insulation
Due to our advanced simulation capabilities and agile material development, Tape Solutions can offer products with different tiers of thermal insulation and high-temperature integrity. Providing varying degrees of thermal insulation, we have products such as mica laminates with silicone foams and polyurethane (PU) foams or V-0 rated silicone to ensure and meet specific customer needs.
One example is our Norseal® TRP1000 product, a proprietarily formulated silicone foam with mica surface layers. This product features a flat compression curve during normal usage, meaning that over a long range of compression strains, the stress levels are maintained with a narrow range. The properties of the TRP product help to combine the properties of a compressible pad with thermal runaway protection into one. Dielectric foams engineered with a predictable compression force deflection (CFD) are utilized in place of vulnerable elastomer materials which allows them to deliver consistent return energy over a wide range of compression amounts and temperatures throughout battery pack life. The foam can resist permanent deformation under compressive loads due to its low compression set value. This allows for greater protection on multiple fronts and minimal impact on energy density (Figure 2a). The Norseal TRP Series is designed to keep battery cells under a defined range of protection, capable of serving as compression pads for pouch-cell packs or prismatic hard-shell packs. During a thermal runaway test, the TRP insulation effectively mitigated the propagation of thermal events to neighboring cells (Figure 2b).
TRP1000 offers higher resistance to temperature and flame as well as greater durability for withstanding a thermal event. Early evaluations of TRP1000 boast impressive results such as:
- No self-ignition and measured temperature delta of more than 600°C (1112°F) with five minute exposure to 800°C (1472°F) hot plate
- Material integrity and insulation maintained; measured temperature delta of more than 600°C (1112°F) with six minute exposure to 1000°C (1832°F) direct torch
When it comes to material development, Tape Solutions leverages our global teams for strong material expertise as well as strong simulation and proxy testing capabilities to enable agile product development for customers.
Scalable design
The adaptability and customization of surface properties including tackiness, adhesion or delivery format is vital to meet the evolution of manufacturing demands. Ensuring that products meet precise surface characteristics can enhance assembly processes due to properties such as tacky surfaces or the ability to enable vacuum pick-up processes. The ability to design to scale can ensure efficient automation needs.
Our polyurethane foam products (PU) have high conformability, good compression, resilience and excellent gap filling, cushioning and environmental resistance. Options to receive these products with or without adhesive make them ideal for converting and improving die cuttability and spooling. These are easy-to-apply foams that effectively minimize distortion or corrosion of dissimilar materials by eliminating the contact between them and also protect from mechanical and environmental stresses.
Features such as low liner release, custom finger-lifts and poke-yoke elements are essential for a successful work cell to operate. This is accomplished through our own Saint-Gobain adhesive experts and our growing expertise in conversion. Our conversion solutions are particularly valuable to our customers.
Thomas Veilleux, Technology Leader, Saint-Gobain Tape Solutions
Thermal protection for battery pack, battery management systems, busbar and more
For all the various components within an EV including battery packs, battery management systems (BMS) or busbars, Saint-Gobain offers an array of products to provide thermal protection. We aim to support special design needs (shape, thickness, flexibility, thermal integrity, assembly process) by providing products that offer both high-temperature integrity as well as thermal and electrical insulation. Below are some key products and usages:
- TRP5300 and TRP5200: These products are comprised of ceramifiable silicone rubber, are flexible at room temperature and can turn into ceramic insulation at elevated temperatures. They are ideal for applications such as busbar protection or pack cover protection. Due to low dust and high flexibility, they can be a great alternative to mica.
- CHR® FR1000 Tape: This adhesive tape product is comprised of a special mica substrate and a proprietary fire-resistant adhesive. FR1000 is a robust, thin gauge solution for enhancing thermal protection in certain areas such as solid surfaces, corners that need bending of a substrate or design areas with vulnerable holes.
All of the above listed products undergo extensive tests to ensure their ability to withstand the most challenging demands and conditions. Some of the most common tests that our teams perform include 1000–1500°C torch test or UL94 test. Additionally, various electrical insulation and mechanical tests or the addition of abrasive particulate options are made available per customer requirements.
Protection solutions for other battery pack locations
In a thermal runaway event, products such as gaskets and seals, gap filler pads or fixation tapes cannot be overlooked as vital solutions that also cater to the intricate demands of pack and module design, reinforcing safety and promoting reliability.
Gaskets and seals
Our gaskets and seals offer different levels of protection for the management of hot gasses and heat dispersion. Critical to keeping the rest of the battery pack intact is the flow and venting of these hot gasses. Some key products include:
- ThermaCool® R10404 Series silicone sponge can withstand high temperatures (1000°C torch) for extended periods of time, making them ideal options where exposure to intense hot gasses may occur.
- Norseal F-20 silicone foam can form a hard structure after a fire event and will not become powdery ash. Therefore, it is ideal for applications where continued support of the pack structure may be needed.
- Norseal PS-V0 Series is our UL-94 rated PU foam solution. It provides good fire resistance, balanced with cost efficiency.
- Norseal FS1000 Series is our intumescent PU foam solution. It can expand multiple times and fill in a gap if a fire event should occur.
Thermal interface materials
Our thermally conductive gap fillers work as a heat sink providing a thermal path for heat to flow away from the battery. We can tailor hardness, surface tack and liner of these materials.
- ThermaCool TC2009 are gap filler pads that provide good thermal conductivity under normal usage conditions. In the case of a thermal runaway event, the special formulation of these products enables good thermal insulation from the affected cell.
Fixation tapes
Pressure-sensitive adhesive tapes can be leveraged for their strength, versatility and functionality to address and combat challenges such as flammability issues or adhesion to different surfaces. Our tape products with acrylic, rubber or silicone based technologies are key for protecting against thermal runaway due to their flexibility to work with all cell types and their good flame retardancy such as UL94 V-0 or VTM-0.
Adhesive tapes can support thermal interface materials (TIMs) by bonding to heat sinks or chiller plate materials to aid with battery cell or module cooling. The TIM materials facilitate the transfer of heat between components in EV battery assemblies. Additionally, flame retardant or dielectric tapes can be utilized in applications such as electrical that require high flame resistance. Within electrical insulation both single and double-coated tapes are utilized to protect the sensitive battery components. Rigid materials like aluminium chill plates or metal structures are often protected with single-coated tapes while double coated tapes could add electrical insulation to cell protection by being combined with other materials like compression pads.
Our fixation tapes are comprised of flame-retardant adhesives that allow for the attaching of certain parts and maintain strong adhesion to different surfaces. These tapes feature good flame retardancy such as UL94 V-0 or VTM-0. Some key products include 80HS FR acrylic transfer adhesive tape, EV145 double sided adhesive tape, as well as customizable solutions with different choices of adhesion, tack, thickness and liner options.
Next Steps in EV Advancements
Without a doubt, electrification of transportation is the future, and adoption of EVs is growing fast. For continued success, we cannot stop making progress with battery technology advancements to support these newer modes of transportation. Vital to the actual safety of the battery, vehicle and its passengers is thermal management. Luckily, automotive engineers have a number of different options for securing thermal protection at optimal levels. Continued research and development in thermal protection is our primary objective and our teams have implemented strategies that balance the lifespan, safety and performance of your EV—without compromise. Our dedicated global teams have extensive experience in specialized product development and we are a reliable partner for delivering products to meet the unique and demanding requirements to provide complete EV battery pack protection. To discuss your specific needs, contact us today!
