Adhesive Solutions for Efficient Li-ion Cell Assembly

Automotive electrification continues to develop, with strong lithium-ion (li-ion) battery architectures at the center of discussions about electric vehicles. While battery system designs vary by manufacturer, all automotive battery technologies share common performance targets: longer service life, operational safety, cost efficiency and reliability. In recent collaborations, Henkel and Covestro have developed a solution that effectively secures cylindrical li-ion battery cells within a plastic cell holder. The solution is based on a UV-curing adhesive from Henkel and a UV-transparent polycarbonate blend from Covestro.

Strong consumer pressure to reduce electric vehicle prices has made large-scale and low-cost li-ion battery cell assembly a prerequisite for every automotive OEM. For this reason, Henkel's Loctite AA 3963 battery assembly adhesives and Covestro's UV-transparent polycarbonate blend Bayblend® have been developed for compatibility with high-volume automatic dispensing techniques and offer flexible, fast-curing mechanisms. The acrylic adhesive is formulated for use with cell holders made from a specialized flame-retardant plastic. It provides strong adhesion to the substrate material and offers production flexibility with long working times and short cure cycles.

Efficient and flexible production

Frank Kerstan, Head of Henkel e-Mobility Europe, says "High-volume production operations with short cycle times and process flexibility are critical." "Loctite OEM-approved adhesive designed to secure cylindrical li-ion cells to a carrier is a one-component, optionally cured formulation. After high-speed dispensing, the material's long open time allows for unexpected production interruptions, naturally giving the process adaptability. After all cells are placed in the adhesive and attached to the holder, curing with ultraviolet (UV) light is activated and the process is completed in less than five seconds."

This new technology offers a significant advantage over conventional production, where curing times can range from several minutes to hours, thus requiring additional storage capacity for parts. Cell holders are manufactured from Covestro's PC + ABS blend Bayblend® FR3040 EV. At just one millimeter thickness, the plastic already meets Underwriters Laboratories' UL94 flammability rating of V-0 category, but also exhibits good light transmission in the UV radiation wavelength range above 380 nanometers.

[caption id="attachment_98826" align="aligncenter"] (Photo: Henkel, PR082)[/caption]  

Steven Daelemans, Market Development Manager in the Polycarbonate Segment for E-Mobility at Covestro, said "The material enables us to build dimensionally stable parts required for automated mass assembly. This material combination, together with the fast-curing properties of Loctite adhesives, presents an innovative approach to large-scale cylindrical li-ion battery module production."