Enhanced performance of EV batteries is a major factor in the steady increase in electric vehicle sales. And better performance stems, in part, from recent developments in laser welding of dissimilar metals which increases efficiency by increasing energy storage, reducing size, and preserving reliability. It’s a fact that welding a less resistive metal to the standard stainless-steel terminal of a lithium ion battery can reduce resistance and improve battery efficiency. Traditional resistance spot welding, however, can’t effectively join highly-conductive dissimilar metals like copper and aluminum because the resultant intermetallic mix is brittle. But lasers CAN do the job with surprising results!
Both CW and pulsed fiber lasers are capable of successful dissimilar metal joining. The key is to utilize high power and very short pulses to join the parts without fusing the metals.
The image below, achieved using a 500W single mode continuous wave fiber laser, shows a cross section of spiral weld joining of aluminum and steel and looks a lot like a multi-staking profile. The actual laser weld profile is highlighted in yellow.
Lower power (70 W) pulsed lasers can be used to join thin dissimilar metals. Pulsed lasers feature small spot sizes using more weld spots to create the same contact area in a weld zone and ensure appropriate weld strength at the material interface. The resulting weld profile closely resembles a staking process. The joint is mostly mechanical, with a transition zone between metals of less than ten microns in width and avoids brittle intermetallic formation. Even though the individual welds are small, the technique produces single-layer shear strengths of around 10 lbs (44 N). In addition to aluminum/steel, potential weld combinations include copper/steel, titanium/steel, copper/titanium, and copper/aluminum.
Expect this advanced laser welding technology to continue to drive electric vehicle efficiencies in both the short and long terms.