Composite Battery Substrate with Local Roughness for Tab Welding
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high adhesive force and low contact resistance between the tab and the metal layers, which affect the performance and efficiency of the battery.
Innovation Solution
A composite substrate with a support layer and metal layers having distinct surface roughness ratios, where the first region has a higher roughness for improved adhesion and a second region with lower roughness, combined with selective patterning processes like laser welding, enhances the adhesive force and reduces contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface roughness of the metal layer is increased to improve adhesive force with the tab, then the contact resistance decreases, but the manufacturing complexity increases due to selective patterning requirements
Solution Approach 1:
The metal layer is designed with different surface roughness in different regions: the first region (where the tab is attached) has increased surface roughness to enhance adhesive force, while the second region maintains lower surface roughness. This local differentiation resolves the contradiction by providing high adhesion only where needed, avoiding the complexity of patterning the entire surface.
2Reliability
If the surface roughness of the metal layer is increased to reduce contact resistance, then the electrical connectivity improves, but the manufacturing precision requirements increase
Solution Approach 1:
The invention applies different surface roughness characteristics to different regions of the metal layer. The first region has higher surface roughness to reduce contact resistance and improve electrical connectivity with the tab, while the second region has lower surface roughness. This localized approach reduces the overall manufacturing precision requirements compared to uniformly increasing surface roughness across the entire metal layer.
3Strength
If the surface roughness ratio between first and second regions is optimized for performance, then the adhesive force and contact resistance improve, but the device complexity increases due to multi-region structure
Solution Approach 1:
The metal layer is structured with two distinct regions having different surface roughness: the first region with higher roughness for enhanced adhesion and the second region with lower roughness. This simple two-region structure achieves the desired performance improvement without excessive structural complexity, balancing functionality and manufacturability.
Data Source
AI summary
Disclosed are composite substrates and rechargeable lithium batteries. The composite substrate includes a support layer, a first metal layer on a top surface of the support layer, and a second metal layer on a bottom surface of the support layer. At least one of the first metal layer and the second metal layer includes a first region to which a tab is configured to be attached, and a second region different from the first region. A ratio of surface roughness of the first region to surface roughness of the second region is in a range of about 3.5 to about 7.