Gradient Nickel Current Collector Laminate Against Cracking
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Solution Overview
Problem
Laminated bodies composed of multiple metal layers experience cracking and breakage under tensile stress due to the expansion and propagation of cracks, which compromises the durability and integrity of negative electrode current collectors in lithium ion secondary batteries.
Innovation Solution
A laminated body structure featuring a copper-based first metal layer and a nickel-containing second metal layer with varying nickel content along its thickness direction, where the nickel content increases from the interface with the first metal layer to the opposite surface, providing a gradient of elastic modulus to enhance tensile strength and suppress cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a laminated body composed of multiple metal layers is used to increase tensile strength, then durability against loads is improved, but cracks are formed and propagate in the metal layers causing breakage
Solution Approach 1:
The patent applies local quality by creating a gradient nickel content distribution within the second metal layer. The nickel content increases from the interface with the first metal layer toward the outer surface, creating regions with different mechanical properties. This gradient structure allows the inner region to provide strong bonding while the outer region provides crack resistance, resolving the contradiction between tensile strength and crack resistance.
Solution Approach 2:
The patent uses a composite laminated structure consisting of a copper-based first metal layer and a nickel-containing second metal layer with gradient composition. This composite structure combines the advantages of different materials: copper provides ductility and electrical conductivity, while the gradient nickel layer provides both bonding strength and crack resistance, effectively resolving the technical contradiction.
2Reliability
If the nickel content in the second metal layer is increased to suppress cracking, then crack resistance is improved, but the elastic modulus becomes too high causing stress concentration at the interface
Solution Approach 1:
The gradient nickel content distribution creates local quality variations where the inner region (near the interface) has lower nickel content for better bonding, while the outer region has higher nickel content for crack resistance. This resolves the contradiction by allowing different regions to optimize for their specific functions.
Solution Approach 2:
The patent changes the composition parameter (nickel content) gradually through the thickness of the second metal layer. This parameter gradient allows the material properties to transition smoothly, preventing stress concentration while maintaining crack resistance, thus resolving the contradiction between interface bonding and crack suppression.
Data Source
AI summary
A laminated body contains a first metal layer containing copper and a second metal layer containing nickel and laminated directly on the first metal layer. A first surface of the second metal layer is a surface in contact with the first metal layer. A second surface of the second metal layer is a reverse surface of the first surface. A thickness direction of the second metal layer is a direction approximately perpendicular to the first surface and oriented from the first surface toward the second surface. A unit of a content of nickel in the second metal layer is % by mass. The content of nickel in the second metal layer increases along the thickness direction.