Knurled Weld Interfaces for Porosity-Resistant Aluminum Battery Tabs
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Solution Overview
Problem
Laser welding of anodized aluminum battery cell tabs often results in weld porosity due to gas release from the anodized layer, leading to surface contamination and reduced weld quality.
Innovation Solution
A knurling process is applied to create a serration pattern on the tabs' contact surfaces, which provides venting paths for gases to escape during welding, reducing trapped gas bubbles and porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If laser welding is performed on anodized aluminum battery cell tabs, then the tabs achieve strong bonding and electrical conductivity, but gas release from the anodized layer causes weld porosity and surface contamination
Solution Approach 1:
A knurling process is applied to the anodized aluminum tabs before welding to create a serration pattern on the surface. This preliminary action modifies the surface topology to provide gas escape pathways during subsequent welding, preventing gas entrapment and porosity formation while preserving the anodized layer's protective properties
Solution Approach 2:
The knurling process creates a controlled porous/serrated surface structure on the anodized tabs. This engineered surface topology provides channels and voids that allow gas to escape during welding, converting the harmful effect of gas release into a controlled venting mechanism that prevents weld porosity
2Object-generated harmful factors
If the anodized layer is removed to prevent gas release, then weld porosity is reduced, but corrosion resistance and surface protection are compromised
Solution Approach 1:
The knurling process applies localized surface modification only to the welding interface area, creating gas escape pathways precisely where needed during welding. The bulk of the anodized layer remains intact, preserving corrosion resistance and protective properties in non-welding regions
Solution Approach 2:
The surface is preliminarily treated with knurling before welding to create gas venting pathways. This allows the anodized layer to be retained for protection while the knurled surface provides the necessary gas escape routes during the welding process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The knurling process significantly improves weld quality by reducing porosity, enhancing strength, uniformity, and electrical conductivity of the weld joint.
Implementation Method 1
During laser welding, energy from the laser beam penetrates abutting sections of the metal workpieces, heating the workpieces to a sufficiently high temperature so that they melt and coalesce together to form a weld joint
Implementation Method 2
heating the workpieces to a sufficiently high temperature so that they melt and coalesce together
Implementation Method 3
Pressure in the weld region causes the gas to expand and 'gas out' through the molten weld pool created by the laser beam
Implementation Method 4
These knurl patterns may be typified by a predefined arrangement of recessed channels, gaps and protrusions that cooperatively define venting paths for the dissolved gases
Data Source
AI summary
Presented are metalworking systems for joining metallic workpieces, methods for forming and welding such workpieces, and lithium-ion battery pouch cells with anodized aluminum tabs joined via knurling and laser welding. A method for laser welding abutting sections of a workpiece or stackup of workpieces includes receiving, via a workpiece support frame, one or more metallic workpieces each with a surface having applied thereto a treatment layer. This treatment layer releases a gas during welding. A metalworking device forms a knurl pattern into the workpiece surface with the treatment layer. The knurl pattern includes a network of channels, such as one or more series of mutually parallel, rectilinear vent channels, designed to exhaust therethrough the gas released from a welded section of the treatment layer. A laser welding device thereafter welds a joint region of the surface(s) of the one or more metallic workpiece with the knurl pattern.