48 driven by accelerated adoption of EVs, and many players are at different points on the learning curve, Collison at PPG considers. This has necessitated a shift to large scale manufacturing and the need to learn rapidly as unanticipated problems drive changes to designs. One kind of change this has driven is what Munro calls an “evolution from parts to paints” (most coatings can be thought of as paints, he says). He explains that when some of the challenges were first recognised as such, there were solutions that could be adopted from other industries that had experienced similar problems. However, these tended to involve the addition of extra parts. “Any time you add a part you’re adding complexity”, he notes. “It’s another thing that has to be attached, integrated or managed. So we’ve seen a shift from parts to paints where specialised functional coatings can be directly applied to existing components to manage the problem. “There’s been a move during that time frame to minimise complexity while maximising productivity and sustainability,” he adds. “Instead of trying to solve, say, six different problems with six different paints, the aim has been to solve those six problems with maybe two paints or speciality materials, and to try to drive performance up so we need less to do more.” Collison notes that, today, change in the automotive space is at its fastest since the 1920s and ‘30s. “We have new designs every six to nine months that we’re having to manage. And this is because of the rate at which engineers are finding new development pathways that increase the longevity, power density, drivability and range of the next generation of vehicles. “And modelling has gotten better, to where we have a clear picture of what we need today, but that could be radically different in two years time,” he observes. “So we have to look into the crystal ball a little to understand what we’re going to offer in two, three or five years.” Development challenges In this environment, developing coatings for such demanding requirements presents many challenges. According to Henkel’s Dr Knecht, the principal problems in the realm of electrical protection of key battery components include ensuring the coating’s own ability to be stable at extraordinary high voltages, along with typically challenging lifetime requirements. With coatings that contribute to thermal management, thermal runaway containment and the prevention and mitigation of fire, the challenge is to ensure that they achieve the right thickness, temperature stability and mechanical stability, and resistance to penetration by energetic particles, along with ease of automated application. Getting the thickness right is also important for dielectric coatings, as are selecting and fine tuning the curing technology, such as UV curing of coatings on cell cans. Here, ensuring that the coating adheres strongly to the can through the life of the cell preserves structural integrity, Dr Knecht remarks. “Ultimately, any one of these requirements is probably pretty easy to tackle in isolation,” emphasises Dean at Parker Lord. “What makes the work we do fascinating is finding novel approaches to balancing these properties.” Such balancing acts, he says, include developing sprayable materials with exceptional edge coverage, along with achieving high thermal conductivity and high dielectric insulation in less than 100µ thickness while maintaining compliance with UL 94V0. This is the standard that covers flammability of plastic materials used for parts in a wide variety of devices and appliances, including batteries. At PPG, Munro describes balancing multiple properties as a game of trade-offs. “There’s never going to be something that’s the best in every category. So understanding issues that are specific to the system, the environment and the component is critical. A good example is thermal conductivity and flexibility, which tend to be opposing properties,” he explains. “So the higher your thermal conductivity, the more balancing is required in achieving goals for the bending or impact resistance. This high thermal conductivity is fine if the application is on a cooling plate, which is stiff and rigid, as it helps it shed heat. But if on flexible cooling tubes it could potentially face cracking problems.” One way of tackling this kind of problem is by developing engineered systems using multiple different layers that build upon one another, Munro explains. This may include a corrosion protection coating as a base layer, such as a typical e-coat or pre-treatment with a dielectric coating, perhaps applied as a powder, on top of that, and January/February 2024 | E-Mobility Engineering A simulation of a dielectric coating is sprayed onto a prismatic cell. Such coatings can provide better adhesion to the surface than alternative insulating materials such as PET films (Image courtesy of Henkel)
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