As the EV industry continues to mature, reducing costs and streamlining volume production have moved to the forefront of concerns for EV manufacturers and battery makers. Since batteries remain the highest cost element in most EVs, this represents a key opportunity.
This article focuses specifically on how the process of assembling and laminating Current Collector Assemblies for EV batteries can be optimized for more efficient production to both boost production output and reduce battery costs.
Overview of CCS Assembly Methods
As the name implies, the Cell Contacting System (CCS) provides the key linkage to collect power outputs from individual battery cells and to aggregate the electrical current for transmittal to the EV drivetrain.
CSSs typically consist of a set of conducting plates or foils, most often made of copper or aluminum, that are bonded to the individual battery cells and provide a low-resistance pathway to carry the energy to the battery’s external circuits.
As shown below, there are three methods typically used to create CCS designs.
- Plastic Tray – this approach uses molded plastic trays to hold the collector plates. Because of the tolerance limitations of plastic molding processes, these CCSs tend to be larger than lamination approaches and they also do not scale well to handle larger battery packs or cell-to-pack and cell-to-chassis applications that are now emerging.
- Hot Lamination – this approach uses thin conductive foil and insulation layers laminated together. It therefore can provide thinner CCSs and accommodate larger sizes and configurations for cell-to-pack or cell-to-chassis. (Typically used with small cells).
- Cold Lamination – this relatively new approach avoids some of the drawbacks of hot lamination, and uses less energy, therefore reducing cost and environmental impact.
Benefits of Lamination and Tradeoffs of Hot vs Cold
In the past, the plastic tray approach offered the additional advantage of helping to properly position the battery cells to keep them in alignment for welding connections and to provide ongoing positional stability.
However, with most modern EV battery designs and cell-to-pack applications, cell positioning is now accomplished by using foam, glue, or other methods, so the plastic tray is no longer as important for cell positioning.
As a result, many battery makers have turned to lamination processes due to their thinner profile, closer tolerances, and ability to accommodate larger size CCSs.
In both hot and cold lamination processes, the CCSs typically consist of a bottom layer, a top layer, current collectors, the conductive flex circuit, and some sort of adhesive to join the components.
Of course, the integrity of the adhesive and its ability to withstand the rigors of harsh automotive environments are key factors for success with laminated CCSs. This leads to one of the key differences between hot and cold lamination processes.
Hot lamination applies both heat and pressure to cure and set the adhesive layer, whereas cold lamination only uses pressure.
While hot lamination is more costly, involves more production steps, and takes more cycle time than cold lamination, the ultimate test is the quality and appropriate robustness of the end product.
ENNOVI offers all three approaches, plastic tray, hot and cold lamination, to serve the diverse needs of our customers in the EV and battery manufacturing sectors.
However, we are always looking to help customers innovate and reduce costs. So, ENNOVI recently conducted an extensive study with adhesive and foil suppliers to determine the best ways to navigate the various advantages and tradeoffs of standard cold adhesive offerings.
This study, along with extensive testing of a range of cold adhesives in actual CCS assembly, has given ENNOVI a solid foundation from which to offer highly cost-effective and robust cold lamination alternatives.
In addition to the significant benefits from streamlining production cycle times, this extensive knowledge base of pre-qualified foils and proven cold lamination processes also offers major advantages for shortening development cycles and reducing time-to-market.
Summary
The evolution of CCS assembly methodologies has now given EV and battery manufacturers a wider range of choices for the design and manufacture of battery assemblies. However, more choices can sometimes lead to delays on the front end if the tradeoffs are not clear.
This is why ENNOVI’s significant investment in building a broad database of pre-tested foils and methods now provides a major advantage for our customers at the design inception stage and throughout the development and production process.
Instead of having to start from scratch with every new design, ENNOVI’s engineering teams can help customers evaluate proven and thoroughly tested alternatives at the outset to avoid any dead ends or restarts throughout the development cycles.
