Optimising BEV battery design to overcome thermal management and other challenges

The development of advanced BEV technologies is pivotal in the transition towards sustainable energy solutions – and in 2023, US battery electric light vehicle sales exceeded one million units for the first time. However, according to analysts at GlobalData, so-called ‘range anxiety’ is still seen as the Achilles heel holding back BEV sales for the mainstream audience.

Thermal runaway fires are another major concern. Despite the data showing lithium-ion-powered EVs are not necessarily more fire-prone then petrol vehicles, dramatic online footage of car fires has fuelled consumer fears.

Thermal Runaway in BEV: A Guide to its Prevention

Thermal runaway is a serious safety issue in lithium-ion batteries and a growing concern in the electric vehicle (EV) industry.

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Other challenges have emerged. Earlier in the year, a cold snap in the US highlighted issues regarding extreme temperatures for BEVs, when freezing weather negatively impacted range and owners were left stranded while infrastructure thawed out.

On the materials side, the environmental impact of battery production and lack of responsible disposal are also significant considerations that must be addressed to ensure a sustainable lifecycle for BEV technologies.

These key factors not only influence the performance and affordability of EVs but also their acceptance in the broader market. Overcoming these challenges will require innovative approaches and collaborative efforts across the industry to pave the way for a more sustainable and efficient future for BEV technology.

One material – silicone – has been used in manufacturing for over 70 years and already has an excellent track record for its high thermal stability and fire-retardant properties. Can this material help build safer and more efficient EV batteries?

What are the key challenges in battery design?

Alleviating customer concerns through better battery design requires navigating numerous significant obstacles.

Energy density: Increasing the energy density of batteries is vital to improve vehicle range while also reducing weight. This requires advancements in battery chemistry and cell design.

Fast charging: Enabling fast charging capabilities is extremely important for convenience and adoption rates, but it introduces challenges around thermal management and battery degradation.

Safety: Ensuring robust safety features to prevent thermal runaway and mitigate fire risks is a critical priority, especially as battery packs become larger.

Cost-effectiveness: Reducing battery costs through manufacturing efficiencies, material selection and economies of scale is necessary to make BEVs more affordable for mainstream consumers.

Packaging constraints: Integrating the battery pack within the limited space and structural requirements of the vehicle platform requires innovative module and pack designs.

Longevity: Extending the useful life of batteries through thermal management, cell chemistry, and battery management system (BMS) controls is crucial for long-term performance.

Extreme operating conditions: Designing batteries that can withstand harsh environmental conditions like temperature extremes, vibration and moisture, is essential for reliable operation.

Integration with vehicle systems: Seamlessly integrating the battery pack with the vehicle’s electrical, thermal and safety systems is necessary for optimal performance and functionality.

Environmental impact: Minimising the environmental footprint of batteries across their lifecycle, from raw material sourcing to end-of-life recycling, is an important consideration.

Addressing these multifaceted challenges requires close collaboration between battery manufacturers, vehicle OEMs, and materials/technology providers.

How can silicone solutions help with these challenges?

John Albaugh is Market Development Manager, Electric Vehicles, for Elkem Silicones, one of the world’s leading silicone manufacturers. Elkem is a supplier of battery materials and silicone solutions for battery packs (Such as Battery sealing solutions for battery pack). Albaugh says that Elkem approaches necessary performance and safety standards as opportunities.

“We don’t see these challenges as problems,” he says. “We are unique in providing customised support through technical consulting, application development and prototyping.”

Albaugh explains that design engineers come to them with specific problems asking if they have materials that can help. “In terms of material properties, we understand silicones and what they can and can’t do,” says Albaugh. “If there’s a specific data point that we don’t have, we’ll go and characterise that, so the engineers can put it into their model and run simulations. It’s extremely interactive.”

One of the key challenges that Elkem is focussed on is battery thermal runaway protection, which poses a significant safety risk to large lithium-ion batteries, potentially leading to catastrophic failure and fire. Elkem offers specialised battery potting materials, such as RTF 3250 silicone syntactic foam, to mitigate the risks of thermal runaway by insulating battery cells and providing fire resistance.

Silicone oils are thin enough to allow for efficient wetting into tight spaces, delivering tiny glass bubbles within the mix that contain the heat. The viscosity of this product is around 800-1000 centipoise and is typically applied by gravity-filling interstitial spaces between battery cells within a module, ensuring efficient distribution and flow.

Albaugh explains that if a modular design is used, the battery packs will be both electrically and physically isolated into individual modules or groups of cells. This compartmentalisation then contains any thermal runaway events within a single module rather than allowing it to propagate through the entire battery pack. A modular approach also enables the battery management system (BMS) to more easily detect and isolate any problematic cells or modules, shutting them off before thermal runaway can occur.

Silicones have attributes that can help with other BEV challenges too. This includes a low elastic modulus, making them able to accommodate thermal expansion and absorb vibration, without cracking or placing stress on battery components. Silicone is also chemically inert with a high resistance to oxidation, ensuring a long lifetime in applications. Moreover, silicones can withstand temperatures over a wide range (from –80°C to 250°C), ensuring reliable operating performance in extreme conditions.

Environmental impact of battery production and disposal

Another advantage of using silicone is their environmental attributes. Silicone is easier to separate from battery cells and other components due to its non-adhesive bonds, making recycling easier. Additionally, silicones have a much safer material composition. When burned, silicone produces a non-toxic smoke, unlike polyurethanes which release toxic fumes.

“Let’s say, 20 years from now, somebody decides they want to take the battery packs out and separate the cells from the battery potting material. They can physically do that because it doesn’t take a lot of energy to separate the silicone; it’s not an adhesive,” Albaugh says. “Also, Elkem is currently exploring second-life uses for spent silicone materials, such as for use as fillers in other applications.”

As the BEV battery landscape evolves, Albaugh says that Elkem is looking to stay ahead of the curve by developing more efficient materials, including adhesives and coatings, to address evolving design requirements.

By using the latest in innovative materials, such as silicones, the BEV auto sector can move forward with safer, more efficient battery designs.

For more information on developing technologies for BEV applications, download the free paper below.