Industrial dispensing solutions for EV battery assembly

Cell stack and sidewall bonding are critical processes in the production of EV batteries. You need to securely join the cells while maintaining electrical insulation and allowing cell expansion during charging and discharging. These processes require precision, speed, and flexibility.  Thus, you ensure the production of high-quality batteries. These EV batteries meet the stringent safety and performance standards of the automotive industry.

Challenges in cell and sidewall bonding:
For batteries with prismatic cells, the challenge is to attach the cells to a stack firmly. No heat or force can be applied. The joint must meet the highest demands in terms of application quality, rigidity, and crash behavior. Similar challenges appear when bonding the sidewalls around the cell stack. This is why manufacturers often use two-component (2K) materials for this process. They do not require heat for curing. The application and process quality must be right the first time to ensure a safe bond when using 2K materials.

Our solutions for cell and sidewall bonding:
Atlas Copco’s SCA product line offers dispensing solutions that are highly precise. They avoid air pockets and ensure high process reliability. Depending on the customer's requirements, we offer 1K and 2K applications. 2K applications are often used in cell-to-cell bonding. You do not need external heat for the hardening. The high metering accuracy and mixing quality of our systems allow us to handle even advanced 2K applications with high speed and constant quality.

Batteries for electrical vehicles do not like moisture. Any kind of moisture can affect their performance. Depending on the design of the battery, the inner edges of the tray can also let in moisture.  Manufacturers can apply materials such as MS Polymers to the inner contours and trim edges to seal the battery from moisture ingress and gas leakage.

Challenges in battery tray sealing:
Complex part geometries and position deviations during production can make accessibility and precision difficult. This can also involve high programming effort. Depending on the part contours, different seam geometries may be required to achieve 100 % tightness. 

Our solutions for battery tray sealing: 
According to the geometry in the battery tray, our E-Swirl 2AdX applicator can seamlessly switch between bead and swirl applications. The swirl pattern provides an improved material distribution. This is helpful when sealing. Our E-Swirl convinces you with a flexible application distance and easy programming. This applicator enables a stable process window and quality even with difficult accessibility. Combined with our ISRA VISION robot guidance solution SHAPEMATCH3D, we ensure that position deviations of the battery tray are considered before starting the process. The application starts precisely at the correct position.

Battery cells generate heat during charging and discharging. It's important to control and distribute this thermal energy for safety. Thus, you also maintain long-term battery capacity. Apply a thermal interface material (TIM or gap filler) between the battery tray and the cell modules to prevent overheating. This enables active thermal management of large battery packs. The generated heat is dissipated into appropriate cooling structures.

Challenges in the application of thermal interface material:

Temperature management is an essential task in battery manufacturing. You need to operate high-voltage battery cells within a specific temperature range to preserve their performance and avoid overheating. For this reason, apply a heat-conducting paste. To guarantee full thermal conductivity, a bubble-free result is crucial. This is a challenge as the liquid gap filler material is applied at high volumes. On top of that, the material is also highly abrasive and can wear out the equipment quickly. 

Our solutions: 
Our industrial dispensing solutions offer precise metering technology and system components. They are designed to handle high volumes of abrasive materials at a high productivity level. The material needs to be applied with great precision. With an optimized pattern we avoid air pockets in the application process. Adding visual 3D scanning of the battery tray we determine the exact amount of material needed. This saves expensive material and detects dispensing errors in width, position, and bead continuity immediately without adding cycle time.

In the unlikely event of EV battery cells igniting, there is a risk that they will burn through the battery cover. For example, the latest safety regulations in China specify that a passenger must have at least five minutes to leave the vehicle in case of a fire emergency. One approach is to cover the battery lid with a layer of a liquid-applied fire-resistant material. These are often two-component (1K) materials.

Challenges in fire protection:
The material layer must have a defined thickness on the entire surface of the cover. Gaps and overlaps must be within tight tolerance ranges to avoid issues in downstream production processes. Spray applications of materials like epoxy have many disadvantages. Material particles in the air are a health risk. The alternative is a flat stream application. However, applying 2K materials with flat stream has been difficult up to now.

Our solutions for fire protection applications: 
We have developed a solution to apply 2K materials in a sharp-edged flat stream. Our SCA FlexS.Seal applicator mixes two components with high precision. An additional needle valve at the nozzle ensures that the mixed material is dispensed with the right pressure. We optimized the valve to avoid material residues that could affect quality. Thus, we achieve a fast, accurate, and uniform application on large surfaces with clean beginnings and ends. You reduce health risks, material waste, and masking with no overspray issues.

Harmful gas evaporation and humidity ingress could impact the safety and performance of EV batteries. To prevent this, battery manufacturers require several sealing steps in the assembly process. And all that with quality assurance in mind, even with part deviations and difficult contrast ratios.

Challenges in battery cover sealing:
 When it comes to cover sealing, an uninterrupted bead, precise bead beginnings and ends, and an even bead height are mandatory. At the same time, the seam must be reversible to enable repairs. Due to its permanently elastic properties, hot butyl is well suited for this. However, you need to heat up the material to 160 °C for optimal processing. Visual quality inspection is challenging with black material seals on black-coated surfaces.

Our solutions for battery cover sealing: 
Our Atlas Copco hot meter optimally tempers hot materials for a perfect cover sealing result with clean bead beginnings and ends. The inline 3D vision inspection solution RTVision.3d inspects the width and height. This solution also controls the continuity of the bead during the application as well as the applied volume. It also monitors the distance from the center of the bead to the component edge to check accurate positioning. Thus, we can detect any deviations in real time. Thanks to laser technology we can easily inspect the bead despite challenging color mixes (e.g. black on black).