January/February 2024 | E-Mobility Engineering characteristics. We can make things cure at very low temperatures, under ambient conditions,” Munro says. “Also, the way that we design the polymers and link them together, we’re able to make materials that are liquid as they’re applied, but form a solid without requiring any solvent,” he says. This provides advantages in the management of volatile organic compounds (VOCs). “If we’re not putting any solvent in, we’re able to reduce the carbon footprint associated to their production and abatement, allowing us to get to a very low or no VOC emissions, thus avoiding air pollution.” PPG also makes other liquid coatings to which functional groups can be added to make them react to electromagnetic radiation of various wavelengths, triggering the curing process. “We don’t need to heat up a massive oven to get the coating to cure. We’re able to do that very effectively with low-energy light sources that can include ultraviolet, near infrared and others,” he says. Coatings can also be applied as dry powders, which can be sprayed or parts can be put into a cloud of powder, usually with opposite electrostatic charges applied to part and powder to aid adhesion before the cure. Dry powder coating, Munro says, also eliminates solvents and associated VOCs. Both powder and liquid process provide for options to recover excess coatings for reuse. A decade of progress The current period of rapid expansion of e-mobility is still fairly young, and the last decade or so has seen many significant improvements in coatings in both materials and application techniques. Henkel’s Dr. Knecht highlights fireresistant coatings, UV cured dielectric materials, and carbon-based conductive coatings. Fire-resistant coatings can greatly increase the temperature stability of steel and aluminium lids, improving the safety of the pack, he says, adding that coatings have become thinner and are more durable against flame and particle penetration. UV cured dielectric coatings have been developed that can be applied to cells after production. They are designed to adhere strongly to the cells and to provide reliable dielectric protection over their lifetimes. “In contrast with adhesive films, the adhesion is stronger, and in combination with thermal or structural adhesives, these coatings can enable cell-to-pack battery designs,” he says. It is a similar story with electrically conductive coatings used in electrodes. “Carbon coatings for energy storage applications emerged more than 20 years ago and have been continuously improved to work with the latest lithium-ion cell technologies” Dr. Knecht remarks. “They have become thinner, more conductive and have enabled stronger adhesion between the active materials and current collector foils.” With its JMC epoxy product line, Parker Lord’s development focus has been on improving resistance to corrosion and heat, and increasing both dielectric strength and thermal conductivity. “About five years ago, we noticed that the PET films were the weakest link in the stack of battery enclosures in terms of bond strength, and finding an adhesive that could bond to them was difficult,” Eric Dean says. “So we invented Sipiol UV, which could be applied and safely cured in seconds using UV light, offering high dielectric strength, edge coverage, and adhesion. After improving the thermal conductivity, applications like enclosure and cooling plates came next.” Massive change in the industry over the last 10 years has mainly been Insight | Battery coatings 46 Conductive coatings provide an interface between the active materials on electrodes and the current collector foils that increases the efficiency and reliability of the cell (Image courtesy of Henkel) Dielectric coatings provide electrical insulation between cells and adjacent components such as module housings and cooling plates/tubes, an essential and increasingly demanding job as battery voltages head towards 1000V (Image courtesy of Parker Lord)
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