E-Mobility Engineering 016 l Aurora Powertrains eSled dossier l In Conversation: Thomas de Lange l Automated manufacturing focus l Torque sensing insight l Battery Show Europe 2022 report l Sodium batteries insight l User interfaces focus

Sabic discussed the progress in validating the fire-resisting performance of its Stamax fibreglass- filled polypropylene for battery cases, among other advances, according to Venkatakrishnan Umamaheswaran (known as UV). Following the previous show in Stuttgart, we reported that a 2.6 mm- thick sample of Stamax had survived an 1100 °C burner test that blew right through a standard 1.5 mm-thick aluminium battery cover, protecting itself with intumescence and limiting the temperature on the non-exposed side to 85 °C. Since then, UV explained, it has survived a more representative test devised by Underwriters Laboratories (UL). “We now have a lot more validated data from our work with UL, which is coming out with a more homogeneous way of testing,” he said. “Industry currently lacks standardised tests, so each car manufacturer uses its own. “UL has a more realistic test that involves building a module and forcing it into thermal runaway without applying an external flame, so the fire starts as it would in an EV in response to high temperature and pressure. Further, there are various tests for mechanical performance, thermal ageing and fatigue resistance, and Stamax has done well in those.” Sabic’s battery crash protection material, Xenoy HTX, has been validated in crash testing that confirmed that its performance holds up in extremes of temperature after going through high-temperature manufacturing processes. It is a polyester-based resin that is formed into an impact-absorbing honeycomb structure. “The primary concern is that the material must withstand high e-coat oven and paint line temperatures, then maintain its crash performance in very cold temperatures,” UV said. “We highlight the cold temperature impact to -20 °C and e-coat oven Henkel also introduced a new dielectric cell coating material based on acrylate 1K that is designed for rapid application. “Dielectric protection is a pivotal challenge in EV battery pack design to protect cells from short-circuits that can cause cell failure and battery fires,” said Lucas Krahl. “Prismatic cell cans are typically made from aluminium, and require special attention when it comes to dielectric protection, so they are commonly wrapped into thin polymer foils that feature a high dielectric breakdown voltage.” New EV battery design trends, however, lead to a need for structural support and integration of cells into the battery pack or vehicle body. “For this increasing requirement, Henkel’s dielectric coating with excellent interfacial adhesion to prevent shock- induced delamination has advantages over conventional foils,” Krahl said. In large-scale production of battery packs, the coating process from application to cure must take place quickly, he explained. “The important thing here is the coating’s fast curing under ultraviolet light, which takes seconds,” he said. In addition to its speed, UV curing also takes place at room temperature. “Its other key properties are a dielectric strength of more than 40 kV/mm, surface protection and compatibility with structural and thermal adhesives. If you want more from the cell, such as structural strength for the pack, our dielectric coating can provide strong adhesion.” The coating is very thin, measuring less than 100 microns, so a thermal conductivity of around 0.2 W/mK enables highly efficient cooling of the cells. He added that the company is now looking into disruptive application options. “We can apply it using an automated spraying process, but there are also some new printing technologies we are investigating.” Vehicle and battery OEMs are also looking for greater maintainability, and they particularly want to avoid having to scrap otherwise serviceable cells because there is a problem with the coating. “We are investigating laser cleaning so that the coating can be completely stripped and a new one applied,” Krahl said. Henkel is currently working on assembly and testing with customers, and Krahl expects the first of them to start using the new coating in cell production next year. ShowReport | Battery Show Europe 2022 Henkel also showed new thermally conductive adhesives, compression pads and UV-curing dielectric coatings for prismatic cells 50 Winter 2022 | E-Mobility Engineering