Thermal barriers

Hayley Everett

How can customised 3D safety components for batteries help to ensure safer electric cars?

Over 100 million electric cars are expected to be on roads worldwide by 2030. To make electromobility more efficient in the future, many manufacturers are looking to achieve higher ranges and shorter charging times, with high-performance batteries being a major priority. In lithium-ion batteries, however, higher energy density increases the risk of thermal runway.

To prevent this from occurring, Freudenberg Sealing Technologies has developed thermal barriers that help to slow down thermal runaway by increasing resistance to propagation. The new 3D thermal barriers can be used at various positions within the battery and have already proven reliable in their initial series productions.

“What is completely new is that the thermal barriers are now also available in customised, flexible 3D geometries, which makes it possible to use them in various positions within the battery and allows for integration of additional components,” says Andrew Espinoza, Global Vice President Technology of the Oil Seals Powertrain & Driveline Division at Freudenberg Sealing Technologies.


Thermal runaway, which is the ignition or explosion of a battery cell caused by a self-reinforcing heating process, is a significant safety problem in electric vehicles (EVs). It can be caused by a multitude of internal and external factors, such as overcharging, excessive discharging, damage or heating of the battery. Thermal runaway releases not only flames and hot gases but also electrically conductive particles. These in turn can cause thermal propagation in adjacent cells and lead to short circuits in the electrical system. Thermal barriers, like those developed by Freudenberg Sealing Technologies, act as protective layers that slow down or even prevent the heat and flames from spreading in the battery.

“We have been working hard in developing plastics and elastomers that can stand up to harsh environments in a battery thermal runaway with temperatures up to 1,200°C,” says Espinoza. “In addition to standing up to these temperatures, we have developed functional components that can maintain shape and seal gases and particulates of a thermal runaway. Working with our components and materials allows module or pack designs to be ready to slow down thermal propagation.”


Beyond existing 2D barriers, such as flat mats and thermal blankets, the 3D variation opens up entirely new possibilities. Customer-specific, 3D geometries can be produced in a variety of high and low volume manufacturing processes, such as injection moulding and continuous extrusion. Profile seals, module separators and covers, including those for busbars, cooling lines or electrical components are a few of the products currently being manufactured. These complex 3D geometries are lightweight and have minimal impact on the battery’s overall weight.

Specifically for these types of applications, Freudenberg Sealing Technologies has developed heat-resistant, electrical and thermal insulating materials. In-house testing of these materials has proved that they can safely withstand temperatures of up to 1,200°C. The compounded polymer’s special composition makes them extremely heat-resistant and also resistant against particle impacts, such as those that occur when cells are vented. The 3D thermal barriers utilise elastomer solutions, whether in solid form or as a foam, as well as plastic components such as Quantix Ultra, which enables complex geometries.

“Our customised, flexible 3D geometries can conform to complex mating geometries, enabling the integration of components or multifunctional components,” Espinoza adds. “3D thermal barriers are typically used for applications like module covers, profiles, module or arc barriers as well as for cooling tubes and terminal covers. Moreover, with our thermal barriers we achieve several values for the customers; flexible material for tolerance compensation and complex installations, rigid thermal plastics for additional structural, multifunctional components and management of thermal runaway gases.”


Espinoza adds: “The 3D thermal barriers and the utilised materials have gone through extensive testing that exceeds the required standards. They have proven their outstanding performance and reliability on bench tests as well as battery system testing. The products meet the highest quality standards, are certified pursuant to UL 94 V-0 and are already being used successfully in initial series production for the automotive industry.”

Freudenberg Sealing Technologies’ innovative 3D thermal barriers therefore help to increase the safety of electric cars and lower the risk of thermal propagation in future battery systems.

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