DuPont develops solution to battery temperatures

The recent launch of large-scale electric vehicle production at Renault's Maubeuge and Douai factories in northern France brought with it the use of a seemingly simple paste that represents a breakthrough in battery heat management.

It is a paste developed by DuPont that diverts heat from higher-density batteries during both charging and vehicle operation. It may look simple, but the polyurethane substance is an innovation in cooling, and the result of a drive in R&D investment by the materials supplier, said Tina Wu, global vice president for advanced solutions at DuPont Mobility & Materials.

"No OEM has more than 10 years of experience making batteries," Wu told Automotive News. "Everyone is learning together. Every OEM has different designs for batteries with different engineering teams and a different approaches.

"Our material helps their design to be successful."

In the first days of EVs, batteries were simply air-cooled. Later vehicles employed water-cooling.

The introduction of a highly engineered interface material is a more sophisticated approach.

The paste—marketed under the name Betatech Thermal Interface Material—is designed to keep battery temperatures as close as possible to 77 F—what Christophe van Herreweghe, DuPont's global strategic marketing director, calls "the sweet spot" for optimal battery performance.

Below that level, the vehicle's driving range will be diminished. Above it, battery life will be degraded.

"By transferring heat or cold from the heat sink to the battery module, or by extracting heat very fast from the module to the heat sink, the temperature can managed," van Herreweghe said. "This is achieved by maintaining terminal connectivity through good contact, with no gap between the battery cell and the cooling plate."

But DuPont had to do more than simply create the substance. It also had to design the process for dispensing it onto battery packs as they move along an assembly line. DuPont worked with equipment suppliers to engineer the application processes to match the automaker's cycle-time requirements.

The pumping systems use twin 200-liter drums of Betatech, dispensing it smoothly, rapidly and with no occurrence of air bubbles, which would result in damage to a battery.

"And after all that, the material has to meet the sustainability requirements of each customer," van Herreweghe said.

"You can have the best material in the world, but if your customer can't get it onto the car, you haven't done anything."