A Partner for the Automotive Industry:
How WACKER and CFP Composites Are Revolutionizing Fire Protection for Battery Packs
WACKER is working with the automotive industry on innovative fire-protection concepts for the safe operation of electric vehicles. The most recent example: a novel composite material made of carbon fibers and silicone resins for passive fire protection of EV batteries. Simon Price, CEO of UK startup CFP Composites Ltd., and Dr. Christoph Briehn, who heads WACKER’s Fiber Composites Innovation Hub in Burghausen, Germany, explain what the material can do, how it protects against fire and what some of its applications are.
Is it my imagination or do electric vehicles catch fire more often than cars with combustion engines?
Simon Price, CEO of UK startup CFP Composites Ltd.
Price: No, as statistics have shown, electric vehicles don’t actually catch fire more often. Because the technology is new and the media are covering electromobility issues very closely, we’ve seen several reports of fires in EVs recently. Still, the intensity of a battery fire is simply greater than a fire in a car with combustion engine. There’s something else you need to know too: thermal runaway of a lithium-ion battery can happen even without a traffic accident or a collision with other vehicles. Very high or low temperatures, improper charging, deep discharging or short circuits in the battery management system can trigger a battery fire as well. Thermal runaway causes the temperature of a lithium-ion battery to jump to between 1,200 and 2,000 degrees Celsius. It also produces a hot, abrasive stream of particles and releases toxic gases. So, what we need are technical solutions that can keep fires from starting and/or spreading and can protect the surrounding area while allowing vehicle occupants to evacuate safely. As a result, there’s a lot of demand right now for materials that can withstand the extreme conditions of a fire and allow us to build safer batteries.
What materials have been used up to now to provide passive fire protection for lithium-ion batteries?
Dr. Christoph Briehn, Head of Fiber Composites Innovation Hub at WACKER
Briehn: Here we draw a distinction between protection that provides thermal insulation for individual battery cells, for battery modules, which contain multiple cells, and for the entire battery pack, which in turn contains the modules. Given the component geometry in standard battery designs, manufacturers have preferred to use heat-resistant materials in the form of thin sheets or mats, that, while thin, can meet the temperature requirements. Mica sheets are one example of an established system used widely for thermal and electrical insulation, both in various technical applications, as well as in everyday appliances like hair dryers and microwaves. While mica sheets are cost-effective and lightweight, their brittleness greatly limits their use in three-dimensional molding processes. Brittleness is especially a problem when batteries undergo runaway, exposing the brittle mica sheet to a powerful jet of abrasive particles.
Price: Demand and interest are growing for high-performance material solutions that are lightweight and thin enough for use in the tight spaces found in battery packs. There aren’t very many materials that are at all suitable in the temperature range we’re talking about. Our newly developed composite material has come at the right time, in other words. The number of inquiries we’ve received from battery manufacturers and the automotive industry has grown for a good two-and-a-half years now, and there are two reasons for that: increasing energy density is making thermal runaway in lithium-ion batteries more and more relevant, and battery safety is considered one of the most important development issues for automakers and their suppliers right now.
”We’ve managed to develop an incredibly powerful material: our new FR.10 composite is made of carbon fibers and silicone resins. It can be produced in a thickness of down to 1 mm, and it’s very lightweight at just 1.5 kg/m2 for the thinnest product.”
Simon Price, CEO of UK startup CFP Composites Ltd.What are the key features of the new product?
Price: One thing you need to know is that the battery pack is the heaviest component of the car. The last thing manufacturers want is to add even more weight for fire protection. More weight ultimately cuts into range. Plus, a few millimeters between individual battery components are all we have to work with for thermal insulation. But despite those design constraints, we’ve managed to develop an incredibly powerful material: our new FR.10 composite is made of carbon fibers and silicone resins. It can be produced in a thickness of down to 1 mm, and it’s very lightweight at just 1.5 kg/m2 for the thinnest product. Another advantage is that our product doesn’t get brittle and doesn’t expand when exposed to heat. We don’t see any structural change across a very broad range of temperatures. Our production process also opens the door to making more than just flat plates – we can also create 3D geometries, which has many advantages in batteries. Our internal tests clearly demonstrated the fire resistance of the laminates: over a period of 7 hours, a 1,500 °C burner flame could not burn through a 2-mm-thick FR.10 sheet.
Briehn: We were especially pleased that the composite material performed very well in a challenging fire safety test conducted by UL Solutions – the world’s leading independent testing laboratory. At the company’s US electromobility lab in Illinois, scientists subjected our material to the UL2596 test, a method developed in-house for testing battery safety. This involved exposing the 2-mm-thick composite to the hot particle stream produced by thermal runaway. Our material withstood those conditions, with the laminate remaining intact.
How exactly does the material protect against fire?
Price: We assume that the carbon fibers dissipate the heat to the sides, preventing it from quickly burning through the laminate. We’re also seeing evidence that the composite reflects the heat, at least in part.
Briehn: Our composite makes clever use of what carbon fibers and silicone resins do naturally: carbon fibers are very lightweight and provide excellent mechanical strength. Because they adhere well to the fibers, silicone resins produce a strong bond. Also, the resins we use have a high silicon dioxide content with very little fire load. They ceramify at high temperatures and when exposed to fire which additionally reinforces the fire protective properties of the material. Comparable composite materials containing organic binders can’t do that.
What have you appreciated most about your work together?
Price: We’re a small company with a unique product range and an innovative, highly scalable technology. WACKER quickly recognized our potential and was very committed. The chemistry between our two companies was good right from the very start. The WACKER team in Germany supports our product and process development work and assists us with application technology. We’re grateful to have a powerful, globally respected partner like WACKER at our side contributing its incredible expertise. That in turn gives our customers peace of mind – a critical factor, especially when it comes to new technologies. After all, automakers need a reliable supply chain.
Briehn: Our goal, of course, is to reach a wide audience for our materials – in this case silicone resins – and, at the same time, we really appreciate development projects like this. Our work with CFP Composites has been an outstanding success story for us and a good reference project. It demonstrates once again the highly versatile performance and wide range of applications of our silicones as binders for fiber composites, especially in combination with carbon fibers. Collaborating with startups is always a good opportunity for us to gain a foothold in a new field – in this case fire safety for electric vehicles. All of us were on the same page: this is a project where we can contribute our expertise to help shape the next generation of materials for electromobility.
”The resins we use have a high silicon dioxide content with very little fire load. They ceramify at high temperatures and when exposed to fire which additionally reinforces the fire protective properties of the material. Comparable composite materials containing organic binders can’t do that.”
Dr. Christoph Briehn, Head of Fiber Composites Innovation Hub at WACKERWhen will we see your composite in EVs and where else do you see potential applications?
Price: Some of our projects with battery manufacturers and auto industry suppliers are already pretty far along. I anticipate seeing our production start up in late 2023 and our first products incorporated into batteries in 2024. The most important electromobility markets for us outside of Europe are currently the US and India. The issue of fire safety in EVs is making headlines, of course, but you have to remember that other areas are going to be important too: trains, airplanes and ferries are all going to be increasingly powered by electricity going forward. Fire safety is also hugely relevant for the energy storage market and EV charging stations. We’re involved in projects there too.
Briehn: I couldn’t agree more. Battery safety is a relevant issue for more than just the automotive industry and mass transit. We see potential in construction too, where innovative facade systems could also benefit from fire-resistant laminates based on silicone resins.
