Composite Cathode Current Collector for Low-Heat Tab Bonding
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Solution Overview
Problem
The existing lithium secondary batteries experience resistance differences and excessive heat generation at the bonding portion of the cathode current collector and cathode tab due to composition disparities, leading to potential separation and peeling issues.
Innovation Solution
A cathode current collector with multiple metal layers, including a first metal layer and a second metal layer with a different composition, such as aluminum and copper, is designed with specific regions and structures to ensure homogeneous bonding and reduce resistance differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer cathode current collector is used, then the structure is simple and manufacturing is easy, but resistance difference occurs at the bonding portion with cathode tab causing excessive heat generation
Solution Approach 1:
The cathode current collector uses a composite structure with a first metal layer (aluminum) and a second metal layer (copper or aluminum-copper alloy) with different compositions. The first metal layer provides basic conductivity and structural support, while the second metal layer specifically addresses bonding compatibility with copper-based cathode tabs, reducing resistance difference and heat generation at the bonding interface.
Solution Approach 2:
The second metal layer is selectively disposed only on the second region (bonding region) of the first metal layer, not on the entire surface. This local application ensures that the bonding portion has optimized composition for matching the cathode tab, while other regions maintain the properties of the first metal layer, thus resolving the contradiction between structural simplicity and bonding reliability.
2Reliability
If a multi-layer cathode current collector is used, then bonding strength and conductivity uniformity are improved, but manufacturing complexity increases
Solution Approach 1:
The second metal layer is applied only to the second region (bonding region) where it is needed for optimal bonding with the cathode tab, rather than covering the entire current collector. This localized approach enhances bonding strength at the critical interface while minimizing the overall structural complexity and material usage.
Solution Approach 2:
Instead of applying a uniform multi-layer structure across the entire current collector, the invention applies the second metal layer partially only to the bonding region. This partial action achieves the necessary bonding improvement without the excessive complexity of a complete multi-layer structure throughout.
3Reliability
If the second metal layer is disposed on the second region, then resistance difference at bonding portion is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The second metal layer is selectively applied to the second region (bonding region) with specific thickness requirements, while the first region maintains the original first metal layer thickness. This localized differentiation improves conductivity uniformity at the bonding interface while concentrating precision requirements only where needed, rather than across the entire structure.
Data Source
AI summary
A cathode current collector for a lithium secondary battery according to embodiments of the present invention may include a first metal layer which includes a first region and a second region having a thickness smaller than that of the first region, and a second metal layer disposed on the second region of the first metal layer and having a different composition from the first metal layer. Accordingly, when the cathode current collector is coupled with a cathode tab, etc., heat generation due to a difference in resistance at the coupled portion may be prevented.