Trends such as climate and resource protection, as well as growing demand for mobility, are driving the development of alternative drive technologies, including electric vehicles. At the core of the future mobility concept is a powerful lithium battery. It will be part of the powertrain, but it should also enable new situations of connectivity and autonomous driving.
Covestro has many years of experience in lithium batteries for laptops and other electronic devices, and has developed various polycarbonate blends for this purpose. Due to its good performance, this material is also very suitable for manufacturing modules, housing parts, battery holders and crash absorbers for electric vehicle batteries. They are lightweight, rugged, dimensionally stable and, on request, equipped with flame retardants.
At Booth 369 at the Stuttgart Battery Show, the company will showcase its currently developed thermoplastic materials and battery modules made using a highly efficient polyurethane pultrusion process to provide good impact protection.
Efficient mass production
"Our current activity is focused on developing processes for the efficient and large-scale production of complex plastic parts for batteries," explains Dr. Julian Marschweski, Covestro's electric vehicle specialist. "In order to house as many batteries as possible inside our batteries, our flame-retardant polycarbonate blends must be processed into particularly thin parts."
Covestro's current collaboration with adhesive manufacturer Henkel involves permanently bonding plastic parts in high-voltage batteries with UV-activated Loctite® adhesives. Partners are testing injection molded parts made of flame retardant PC ABS blended with BayBlend® FR3040 EV. When the thickness is only one millimeter, the injection molded part has reached the UL94 flammability class V-0 of Underwriters Laboratories, and has good permeability to ultraviolet radiation in a wavelength range above 380 nm.
One possible application scenario is the permanent connection of a cylindrical battery to the surrounding battery holder. The Loctite® adhesive is treated as a one-component system and hardens under ultraviolet light in less than 15 seconds. Therefore, the combination of UV-permeable plastics and fast-curing adhesives enables short cycle times required for large-scale production of battery modules and batteries.
Maximum impact protection
In the event of a collision, lithium batteries must meet special safety requirements. Covestro has developed a complete concept using different materials to provide maximum protection for the battery module in this case. The bottom of the battery box is stabilized by a profile made of continuous glass or carbon fiber and a rigid plastic substrate from Baydur® PUL (continuously manufactured using a pultrusion process).
As documented in standard industrial side impact protection tests, these profiles are strongest in the longitudinal direction and keep the battery module safely in its shape. At the same time, components can be manufactured efficiently and economically, and can be easily combined with other materials.