Fiber Laser Welding Assists Longer Battery Life for EVs

 Fiber laser welding technology is contributing to lower cost and higher reliability batteries for the latest generation of electric vehicles. Fiber laser welding reliably produces consistently high-quality welds for electric vehicle batteries where aluminum, copper, nickel-coated steel and combinations of these materials are welded together.

 

This article provides an update on the latest laser welding developments as they apply to these newest battery designs, including data to document the quality of laser welds of similar and dissimilar metal combinations.

Automakers are reallocating and prioritizing their research and development budgets toward electrification of vehicles.

By 2025, fewer than half the cars sold will be fully combustion-powered, as gas and diesel give way to hybrid, electric, and fuel-cell drivetrains.

For this to occur, there will be significant investment to make electric vehicles more attractive and affordable for mainstream buyers. These investments will include reducing vehicle cost and increasing vehicle reliability and lifetime of the components, particularly the battery technology that powers electric vehicles.

Following is a review of recent product and process developments related to laser welding of electric vehicle battery components.

 

Diverse Weld Requirements

Discussing "Electric Vehicle Battery Welding" implies a broad subject considering the number of variants. First, there are three main styles of batteries: cylindrical, prismatic and pouch shape. Second, there are a number of materials. There are also several types of welds.

 

Different Materials

The electric current-carrying components inside a lithium-ion battery are made of copper or aluminum alloys, as are the external buss bars that need to be joined to the outside terminals that connect a series of cells. Aluminum alloys (3000 series) and pure copper, which are the main materials, need to be laser welded either in similar or dissimilar configurations to produce electrical contact to the positive and negative outside terminals.

Overlap, butt, and fillet welded joints make the various connections within the battery. The final welding steps in the cell assembly are seam sealing of the aluminum cans, which creates a barrier for the internal electrolyte, and welding of tab material to negative and positive terminals. It also creates the electrical contacts for the pack.

Quality through Process Control

As consumers, we expect batteries for electric vehicles to have a relatively long life, typically a minimum of ten years. This is a standard that automotive companies are targeting with their new battery designs. For this to be accomplished, all components and assemblies must be of even higher reliability than current car batteries.

To achieve a ten-year battery life, welding processes must meet the challenges, whether or not the joints involve the same or dissimilar metals. Factors with laser welding that must be considered in creating highly reliable welds of similar and dissimilar metal combinations include:

 

Physical material properties

● Differences in absorption/reflectivity of the laser beam

● Differences in heat conductivity

 

Metallurgical material properties

● Solubility of material/alloying elements

● Differences in melting temperatures

● Thermal expansion

● Formation of intermetallic phases

 

One of the advantages of modern fiber laser systems is the degree of control of laser parameters that is possible. Laser pulse parameters (pulse duration, peak power, and even the shape—peak power as a function of time—of the pulse) can be controlled on a pulse-by-pulse basis. While simpler systems will call a pre-programmed set of conditions, the “real-time” control that is possible goes above and beyond this providing more control of the process and, as a result, metallurgical weld quality.