Flexible gluing and sealing of battery systems
Oct 28, 2024
The requirements for the production and processing of batteries for electromobility are increasing. The gluing and sealing of cell modules and battery packs play a crucial role here, as the precise application of the adhesives and sealants significantly contributes to the safety and durability of the batteries. New battery types with varying designs and enhanced performance demand more flexible solutions, which Dürr addresses with its versatile application technology.
Batteries, typically installed in the underbody of electric cars, are subject to high loads. Stone impacts, vibrations, and heat generation threaten the sensitive battery cells as much as moisture and dirt. Additionally, these batteries must withstand collisions and resist flames until the vehicle occupants are safe. Bonding and sealing the battery components is therefore intergral to overall safety. The application technology precisely applies adhesives, sealants, and thermal interface materials in a targeted way and with high discharge rates. To handle these materials, which are often abrasive and have a high density, without damaging pumps and dosing units, the technology needs to be exceptionally robust and high quality.
Constantly changing requirements for adhesives and application technology
Another challenge is the rapid development of battery systems themselves. For greater ranges and faster charging times, manufacturers change battery designs with each new vehicle generation. Some eliminate modules entirely (cell-to-pack) to house the battery cells, while others opt for specific module sizes. Each new battery generation changes the requirements for adhesives and thus as a result the application technology changes. Dürr’s extensive experience in the robot-guided application of paints, sealants, and adhesives is advantageous here, as technologies used in body construction, paint shop, and final assembly are also used for gluing and sealing batteries.
We can respond flexibly to new requirements, and time and time again integrate technologies from different areas of the company into the application technology for battery systems.
Sebastian Gries, Senior Manager Sales Automotive Gluing Systems at Dürr Systems AG
The different high-voltage battery systems, also called battery packs, follow a similar structural principle depending on the concept: They usually consist of several modules, which in turn comprise several lithium-ion cells. The separate modules are installed in a trough with a cooling system beneath it. The housing that holds the battery pack together consists of an upper part and the protective underbody.
Application methods: extrusion, spraying, and injection
Various application methods are used to bond and seal the components. Extrusion dispense is used for structural adhesive, which stabilizes the battery body and joins it together. For this, Dürr uses high-precision dosing technology from the EcoShot Meter series to ensure an even and uninterrupted application. Spraying, specifically a two-component spraying method, is used to apply the fire protection paste onto the aluminum upper part of the housing to prevent flames from penetrating in the event of a fire as well as for sealing the screwheads of the cover fixing to avoid any leakage. Dürr’s specially developed dosing technology produces a very even spray pattern. Injection fills cavities, such as those between the cell modules and the cooling system, known as gap filling. Whether extrusion, spraying, or injection, the EcoGun series has the right applicators with matching nozzles for every gluing or sealing process.
Dürr’s modular application system is completed by the EcoRam material supply system and the EcoHVMP4 system controller. The EcoRam barrel pump is available in temperature-controlled, i.e. heated, or non-heated versions and can be configured as a single or double barrel pump station. At the heart of every system layout is the EcoHVMP4 system controller, comprising a modular, expandable control cabinet with standard components for controlling pumps and applicators. This includes Dürr’s proprietary EcoHVC4 process software with numerous analysis tools.
With just one single modular system in which all modules are based on the same technology, we can meet the needs of different application areas and apply a wide variety of materials.
Sebastian Gries, Senior Manager Sales Automotive Gluing Systems at Dürr Systems AG
Gap filling: injection cuts costs and weight
Dürr is a technological pioneer in injection. For example, the EcoShot Meter electric piston dosing system applies just the right amount of thermal interface material to fill the cavities between cooling system and cell modules, using less material than flat application via extrusion. Another method is applying the paste in different patterns directly into the trough before inserting the cell module. The paste is then distributed by pressure. Gap filling uses thermal conductive adhesives (TCAs) or thermal interface materials (TIMs) that dissipate heat during battery charging and significantly impact temperature management. These gap fillers contain abrasive materials that enhance thermal conductivity. Since these fillers are three times as expensive and two to three times denser than normal adhesives, being economical with them is crucial for both cost and weight savings.
Every gram you can save counts when it comes to electric vehicles. So even the smallest saving is worth it.
Sebastian Gries, Senior Manager Sales Automotive Gluing Systems at Dürr Systems AG
USP: Endless dosing
The EcoShot Meter Tandem, combining two dosing systems in one unit, is the only one of its kind in the endless dosing system market for 2-component application. For 1-component application Dürr has developed the EcoMeter SP which is also an endless dosing solution. Unlike a single EcoShot Meter, which requires refilling adhesive or sealant after each process cycle, the tandem version eliminates application interruptions. No refilling time is required. The EcoShot Meter Tandem thus saves not only time, but also investment costs, as only one production or robot cell is needed instead of two or three to meet specified cycle times and application rates. This reduces the system design’s footprint. As well as the EcoShot Meter Tandem for 2-component application, the EcoMeter SP has the same advantages for 1-component application. In addition, its weight is similar to that of a single shotmeter, so that the robot-payload for 1-component endless dosing stays the same.
Another specialty of Dürr is the electric stitch bead application, which is mainly used for the application of structural adhesives. This method applies different volumes in very short time cycle times, creating continuous seams that vary in length and size without interruption.
We are a reliable, competent, and innovative partner when it comes to the application technology for batteries too.
Sebastian Gries, Senior Manager Sales Automotive Gluing Systems at Dürr Systems AG
With its comprehensive application technology for batteries, Dürr’s modular system covers all applications and can be flexibly customized for individual needs. Dürr’s extensive experience in body painting, body construction, and final assembly bonding allows it to transfer proven technologies to battery gluing, effectively responding to new requirements.