Battery Welding: Less Mystery. More Science.

Over the past few years, the demand for lithium-ion cells has increased. A few reasons for this higher demand is their use in computer electronics, electric vehicle applications, and more recently, their expanding presence in the aerospace industry. As this demand increases, so does the need for a seamless manufacturing process.

EWI, a company that delivers innovative technical solutions in manufacturing processes, recently completed a test of battery tab joining methods to optimize lithium-ion cell manufacturing. To find the right process, they’ve started looking at alternatives to laser, resistance, and ultrasonic welding when those types of welding technologies are not feasible in welding tabs, busbars, and cells.

Recently, EWI conducted an experiment using Sunstone’s Omega PA250i welder to determine if pulse arc welding was a successful alternative for battery tab welding. Below, we’ll review the equipment, processes, and outcomes of this study as well as how the Omega produced superior welds.

Here’s What Was Done

To test their theory, EWI selected a number of different types of battery tabs and welded them to typical 18640 battery cans to see which welded better at different weld energy levels. Each of the selected materials were peel-tested to determine the strength of the weld as well as to measure button-size. The material combinations included:

• Copper to nickel-plated steel.
• Nickel to nickel-plated steel.
• Nickel to aluminum.
• Copper to aluminum.
• Copper to 304L stainless steel.
• Copper to nickel to aluminum.

Here’s What Was Found

After the tests were completed, EWI’s initial conclusions showed:

• Copper to nickel-plated steel: Excellent weldability.
• Nickel to nickel-plated steel: Partial penetration to nickel-plated steel, good weldability.
• Nickel to aluminum: Poor weldability.
• Copper to aluminum: Poor weldability.
• Copper to 304L stainless steel: Excellent weldability.
• Copper to nickel to aluminum: Good weldability, but more process refinement is needed.

Both welds on nickel to nickel-plated steel and copper to nickel-plated steel showed acceptable tensile strength with no weld defects, making them the ideal choice for welds.

While the welding of copper tabs to 304L stainless steel showed that welding was possible, some fusion zone defects were found during the tests. The same results were also found in fusing copper to nickel, hence its poor weldability rating.

Finally, in the fusion of copper to nickel to aluminum, EWI was able to weld the materials together, but it resulted in a number of cracks in the weld, which poses a danger to cell integrity. Further investigation is needed to better study the relationship of the weld current and voltage profiles to weld quality.

Essentially, EWI determined that pulse arc welding shows developing potential for implementation into the manufacturing packs produced with a variety of cell materials, including lithium-ion.

For a more in-depth look at the equipment, process, and results of this study, contact EWI.

A Look at the Omega

The Omega is the perfect welder for copper battery welding. We’ve taken all the great features from our previous copper battery welding and added a new, motorized weld head to give users even more precision, accuracy, and control with every weld. Creating lighter, more efficient battery packs without comprising power is all possible with the Omega.

The Omega also provides:

• 250 joules of energy.
• Complete control of welds with a responsive color touch screen.
• CNC compatibility.
• Import/Export saved welds.
• Lock out mode to prevent production changes.
• Alarms and warnings to alert to potential problems.

What really sets the Omega welder apart is its ability to fuse together two dissimilar metals—like copper to aluminum—with ease, making it the perfect choice for battery tab welding. With solderless connections, clean weld spots, and a small heat-affected zone, no other welder can achieve what Omega can.

To see the Omega PA250i welder in action, contact us by calling or texting +1 801-658-0015 or emailing sales@sunstonewelders.com.