The growing focus on sustainability has led to greater demand for electric vehicles. The main element of electric vehicles is a lithium-ion battery which is a part of the powertrain but will also play a key role in enabling new forms of connectivity and autonomous driving.
Covestro has considerable experience in terms of encapsulating lithium-ion batteries for laptops and other electronic devices. The company has developed various polycarbonate blends that can be used in this segment and these materials are just as suitable for use in the automotive sector for making modules, housing parts, cell holders and crash absorbers for electric car batteries. These materials are strong and dimensionally stable yet lightweight and based on requirements, they can even incorporate a flame retardant.
At the recent Battery Show in Stuttgart, Covestro showcased the current innovations in thermoplastics, and battery components that can provide good impact protection and are made from polyurethane using the pultrusion process.
Dr. Julian Marschweski, expert for electromobility at Covestro explained that the company’s current focus is the development of processes for the efficient mass production of complex plastic parts for batteries. Coverstro’s flame-retardant polycarbonate blends need to be processed into especially thin-walled parts. in order to accommodate as many cells as possible in the battery’s interior.
Coverstro is currently working with adhesive manufacturer Henkel on permanently bonding plastic parts in high-voltage batteries with the help of UV-activated Loctite adhesives. They are testing their new adhesives on injection-molded parts made of the flame-retardant PC+ABS blend Bayblend FR3040 EV. With a thickness of only one millimeter, the new plastic already confirms to the category V-0 of the Underwriters Laboratories’ UL94 flammability rating but it also shows good permeability for UV radiation in the wavelength range above 380 nanometers.
One manner in which the new plastic can be used is for the permanent bond of cylindrical battery cells with the surrounding cell holder. The Loctite adhesives are processed as a single-component system and can be cured using UV light in a time that is less than 15 seconds. Thus, the combination of UV-permeable plastic and fast-curing adhesive facilitates the short cycle times that are needed for the mass production of battery modules and battery packs.
Lithium-ion batteries need to meet special safety requirements in case of an impact. For such a scenario, Covestro has developed a complete concept with different materials, so that battery modules benefit from the maximum protection. The bottom part of the battery case obtains its stability from profiles, which are continually manufactured from continuous glass fibers or carbon fibers and a polyurethane matrix of Baydur PUL using the pultrusion process.
The profiles are strongest in a longitudinal direction and keep battery modules safely in their shape, as documented in standard industry side-impact protection tests. Yet, the components can be manufactured efficiently and cost-effectively, and combined easily with other materials.
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