E-Mobility Engineering | January/February 2024 45 Battery coatings | Insight battery structures are often effectively transparent to electromagnetic radiation. That potentially causes interference problems with electronics in the battery such as the battery management system (BMS), general vehicle management and safety systems. “We need to make sure that they are protected from crosstalk that would diminish their effectiveness. So we’ve got a range of coatings and other speciality surface materials that help with electromagnetic shielding,” Collison says. Parker Lord provides battery, cooling plate and enclosure coatings to provide electrical insulation and enhance thermal management, with material options including PET film, powder coating, thermally cured and UV cured coatings, says Eric Dean, global bd manager with Parker Lord’s Engineered Materials Group. The company’s thermally cured JMC700K epoxy resin coating, for example, is routinely used on battery enclosures and cooling plates, while its UV cured Sipiol UV line is also used in these applications and additionally on cells. Both have high thermal conductivity, which enables good heat transfer and helps ensure long-term reliability. “We design our solutions from the resin molecules up and then we formulate them into composite solutions for situations where a single material would not give the right balance of performance. We’re able to get that balance from the formulated composite that makes up the coating,” says Munro. The company has deep expertise in epoxies, for example, and uses them very broadly, he adds. “We formulate those in ways to give exceptional corrosion performance. We’re also able to adapt them to become very strong adhesive materials, or we can adapt them so that they can change their nature when exposed to high temperatures, to become a thermal barrier coating. All of those are based on one chemistry set.” PPG engineers coatings from polyesters, polyurethanes and acrylics, and combinations of them. “We’ve got different tools and approaches that we use to join those polymers together so that they form cross-linked functional coatings. There is a host of approaches to that chemistry that influences whether we end up with a polyurethane or a polyurea at the end of the day,” Munro says. “That allows us to meet a lot of challenges in terms of curing cell provide electrical isolation between cells and other components, but also provide protection from corrosion. The electrical demands on dielectric coatings are growing in-line with battery voltages, which regularly reach 800 V, with many new systems exceeding 1000 V. “With those high voltage systems, we’ve got to make sure that electricity doesn’t do what it likes to do, which is find the path of least resistance. Sometimes that’s just jumping across spaces between components,” says Jacob Collison, global strategic product manager at PPG. Coatings are applied throughout an EV battery pack, from fire protection materials on the lid, anti-corrosion protection inside and out, on cooling plates and pipes, on busbars and in cells. Corrosion protection is also vital on the outside of the pack, he adds. “There are a lot of warranty failures that are associated with corrosion on the battery structure itself. Even if it doesn’t penetrate the casing, it can lead to other electrical failures.” Lithium-ion cells only operate efficiently over a very narrow temperature range, Collison notes, and coatings are part of the thermal management solution, variously moving and blocking heat, and containing battery fires. “There’s a holistic approach to fire management in the industry, and we feel that we can commit as a last line of defence,” he says. “Typically, we’ll try to keep the fire within a module or, with the newest designs, within the pack, to make sure that the fire doesn’t get into the cabin. The best way to compartmentalise a fire is to protect the battery box, and our coatings are able to maintain the integrity of the enclosure under these very extreme, high temperature, highly erosive conditions.” Polymer composite materials increasingly used in vehicle and Left: Coating many prismatic cells starts with pre-treating and patterning their surfaces with a laser to increase the surface area and the surface tension of the aluminium casing (Image courtesy of BMW) Coatings are applied throughout an EV battery pack, from fire protection materials on the lid, anti-corrosion protection inside and out, on cooling plates and pipes, on busbars and in cells. (Image courtesy of PPG Industries)
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