Tab welding is an important step for batteries to function properly. Any misstep will certainly affect how well and how far the battery can last. It can also hamper a battery’s mechanical strength, and thermal efficiency and even create safety issues.
Which welding method is better mostly depends on the tab thickness and the materials that are being used. Among all, battery tab laser welding stands out for the stability and efficiency it brings.
This informative piece will explore laser welding battery tabs. We will see how it takes shape for different battery types and the benefits it brings. Keep reading to learn more.
What is a Battery Tab?
Battery tabs, also called terminals, are the positive and negative wires that connect the cells and carry electricity. The positive and negative currents are sent to different terminals on the module’s busbar (or collector plate). That is how several modules are linked together to make the battery pack.
Tabs are connected to current collectors, or foils, inside the cell casing. These are made of highly conductive materials like copper and aluminum. They carry positive and negative currents from the electrodes.
Battery tabs come in different shapes and sizes, and all kinds of batteries can use them.
Battery Tab Laser Welding
It can take hundreds or even thousands of welds to connect the cells in a battery pack to the terminals. However, even a 1% failure rate is a major problem when it comes to batteries. Hence, the quality of these connections is very important. And with the preciseness of laser welding, maintaining quality becomes a piece of cake.
Laser welding for battery tabs is a fast process that joins surfaces with a very focused beam of light. Ultrafast-moving X-Y mirrors point and move the laser beam. Because of this, there is a lot of freedom to weld any joint geometry and any custom weld patterns. Such freedom makes this welding process perfect for batteries.
It is also possible to use laser welding to join tabs to busbars and foils to tabs. However, when it comes to battery welding, fiber lasers are the best. They can work with copper, aluminum, steel, nickel, and other different materials. Besides, they are flexible with the thickness of the tab.
Using Lasers for Battery Tab Welding Applications
The most familiar battery types are cylindrical lithium-ion cells of the 18650 size (18 mm x 65 mm), large prismatic cells, and lithium polymer pouch cells. There are different welding rules for each type of cell.
Let’s see how laser welding handles each of these types.
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Cylindrical Batteries
The material of the cylindrical battery can is usually nickel-plated steel, and the tab is made of either nickel or tin-coated copper. Nickel plating is better than tin plating because it is more stable. Tin’s very low boiling point can cause holes in the weld and a lot of spatter.
For the cylindrical cell type, the negative terminal weld is the most important part. This is where the battery tab is welded directly to the can instead of the separate platform on the positive side. The negative terminal’s weld must not go through the can’s thickness (usually about 0.015 inches or 0.3 mm).
How thick the tab can be depends on how thick the can is. As a general rule, the tab should be 50–60% as thick as the can.
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Large Prismatic Batteries
The tabs need to be thick to make sure that these high-capacity battery cells have enough carrying capacity. Terminals and tabs are usually made of aluminum, and 1080 and 1100 are good choices for tab materials. However, the tab connection only has to worry about one cell’s capacity.
Thus, making a through hole for a filet weld or thinning out thick tab material for a lap weld greatly reduces the size of the weld. This lowers the amount of heat going into the can, which is always a problem when welding thicker tabs.
The tab thickness should be reduced to 0.01-0.02 inches to strengthen the weld and protect the battery. Do not use aluminum alloy 6061 because it cracks when it is welded.
However, if this one is already set and can not be changed, use a 4047 pre-form for a third material that will not crack. It will add a lot of silicon to the weld.
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Lithium Polymer Batteries
These battery cells come in pouches and have a thin, rectangular shape. They are becoming more and more popular in consumer electronics.
On these batteries, thin sheets of copper and aluminum foil are laser welded to copper and aluminum tabs to make the terminals. Ultrasonic technology is generally used for this weld. That’s because it has to go through a stack of foil.
However, fiber laser welders are now being used for better weld quality and strength. For this fiber laser job to work, you need to make sure that
(a) The foils are close together.
(b) You are using a pulsed laser so it does not get too hot.
Pros of Using a Laser to Weld Battery Tabs
Laser tab welding is useful in many ways during the production process. Here are some of the benefits:
- Welding battery tabs with lasers enhances process stability, which leads to higher system availability.
- Such welding brings a significant increase in battery production efficiency.
- You do not have to switch tools to get the most flexibility in cell design.
- The overall process requires less space than other welding methods.
- The welding process is virtually maintenance-free.
How to Select the Right Welding Power for the Battery Tab?
Good welding requires the right amount of power to create a stable arc, enough heat to melt the joints, and the best metal transfer. To select the right welding power for the battery tab, follow the steps below:
The welding process is affected by the different ways that materials absorb and conduct energy. Hence, you need to figure out how the tabs are put together. Carefully look at the material to make sure the power setting is right.
Thicker tabs usually need more power. Use the different thicknesses in your battery production to make a power gradient. The design of the joint affects how much welding power is needed. Check the geometry of the joint and make changes to the power settings to account for differences in design.
Conclusion
Laser welding is arguably the best way to weld battery tabs. With lasers, you can make sure the quality of the connections within a battery is top-class. However, different types of batteries will require different styles of laser welding.
Fiber laser machines are the best in business when it comes to battery tab welding. However, finding the right tool might be a tricky task, and failing in this will make you end up with low-performing products.
Do not worry! Fiber Laser Welder is now here with industry-standard fiber laser welding machines. All our equipment, parts, and support only guarantee quality, efficiency, and accuracy. Contact us today for the best laser welders at affordable prices!
