Gradient Nickel Current Collector to Prevent Li-Ion Electrode Peeling
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Solution Overview
Problem
Conventional negative electrode current collectors for lithium ion secondary batteries experience peeling of the nickel-containing layer due to differences in hardness and elastic modulus between copper and nickel layers, leading to deformation and potential short-circuiting.
Innovation Solution
A laminated body with a copper layer and a nickel layer where the nickel content decreases along the thickness direction, reducing the elastic modulus gradient and minimizing peeling by aligning the nickel layer's softness with the copper layer's deformation, thereby enhancing tensile strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a second metal layer containing nickel is laminated directly on a first metal layer containing copper, then tensile strength is improved, but peeling occurs between layers due to hardness difference
Solution Approach 1:
The patent applies local quality by creating a gradient in nickel content within the second metal layer. The nickel concentration varies from the interface with the copper layer toward the outer surface, with higher nickel content near the interface to reduce hardness difference and prevent peeling, while maintaining sufficient tensile strength. This localized compositional variation resolves the contradiction between strength and peeling resistance.
Solution Approach 2:
The patent changes the compositional parameter of the second metal layer by controlling the nickel content distribution. Specifically, the nickel content is adjusted to be 70-90 mass% near the copper layer interface and decreases toward the outer surface. This parameter change optimizes both the mechanical strength and the interfacial bonding, preventing peeling while maintaining tensile strength.
2Strength
If nickel content in the second metal layer is increased to improve strength, then tensile strength increases, but the layer becomes harder and more prone to peeling
Solution Approach 1:
The patent implements local quality by concentrating higher nickel content (70-90 mass%) specifically at the interface region with the copper layer, where strength is most needed for bonding. The nickel content then decreases toward the outer surface, reducing overall hardness and peeling tendency. This spatially differentiated composition resolves the contradiction between strength enhancement and peeling prevention.
Solution Approach 2:
The patent creates a composite metal layer structure where the second metal layer contains a gradient composition of nickel and other elements. This composite structure combines the high strength benefits of nickel-rich regions near the interface with the lower hardness and better ductility of nickel-poor regions at the outer surface, thereby achieving both high tensile strength and resistance to peeling.
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 face 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 2 decreases along the thickness direction D.