Ni-Co Alloy Steel Sheet for Low Contact Resistance and Color Stability
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Solution Overview
Problem
Surface-treated steel sheets used in battery containers face issues with contact resistance and color changes due to storage conditions, particularly under high temperature and humidity, which affect their performance and longevity.
Innovation Solution
A surface-treated steel sheet with an alloy layer containing nickel (Ni) and cobalt (Co) is designed, where the alloy layer is structured with alternating high Co concentration regions and alloyed regions within a specific depth range, reducing contact resistance and preventing color changes by controlling the distribution of Co concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the alloy layer contains high Co concentration to reduce contact resistance and enhance high-rate characteristic, then the contact resistance decreases and battery performance improves, but the surface color changes during storage under high temperature and humidity
Solution Approach 1:
The patent applies local quality by creating alternating high Co concentration regions and alloyed regions within the alloy layer. The high Co concentration regions (with Co content of 70-90 mass%) provide low contact resistance and high electrical conductivity, while the alloyed regions (with Co content of 30-70 mass%) provide oxidation resistance and color stability. This spatial differentiation of composition allows each region to perform its specific function optimally.
Solution Approach 2:
The patent creates a composite structure within the alloy layer by combining two distinct compositional regions: high Co concentration regions and alloyed regions. This composite approach allows the material to simultaneously exhibit high electrical conductivity (from Co-rich regions) and high oxidation resistance (from alloyed regions), resolving the contradiction between contact resistance and color stability.
2Reliability
If the alloy layer uses uniform high Co concentration throughout to maximize electrical conductivity, then contact resistance is minimized, but the surface is more susceptible to oxidation and color changes during storage
Solution Approach 1:
The patent applies local quality by creating alternating high Co concentration regions and alloyed regions within the alloy layer. The high Co concentration regions (with Co content of 70-90 mass%) provide low contact resistance and high electrical conductivity, while the alloyed regions (with Co content of 30-70 mass%) provide oxidation resistance and color stability. This spatial differentiation of composition allows each region to perform its specific function optimally.
Solution Approach 2:
The alloyed regions act as intermediary protective zones between the high Co concentration regions and the external environment. These regions with moderate Co content serve as a buffer that protects the highly conductive Co-rich regions from direct exposure to oxidizing conditions, thereby maintaining both electrical conductivity and oxidation resistance.
3Stability of the object's composition
If the alloy layer uses uniform low Co concentration to improve oxidation resistance, then color stability is maintained, but contact resistance increases and high-rate characteristic deteriorates
Solution Approach 1:
The patent applies local quality by creating alternating high Co concentration regions and alloyed regions within the alloy layer. The high Co concentration regions (with Co content of 70-90 mass%) provide low contact resistance and high electrical conductivity, while the alloyed regions (with Co content of 30-70 mass%) provide oxidation resistance and color stability. This spatial differentiation of composition allows each region to perform its specific function optimally.
4Reliability
If the alloy layer thickness is increased to improve corrosion resistance and durability, then protection is enhanced, but manufacturing cost and material usage increase
Solution Approach 1:
The patent applies local quality by creating alternating high Co concentration regions and alloyed regions within the alloy layer. The high Co concentration regions (with Co content of 70-90 mass%) provide low contact resistance and high electrical conductivity, while the alloyed regions (with Co content of 30-70 mass%) provide oxidation resistance and color stability. This spatial differentiation of composition allows each region to perform its specific function optimally.
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 solution achieves low contact resistance and suppresses surface color changes, enhancing the steel sheet's performance and durability for battery applications.
Implementation Method 1
Co is an active metal in comparison to Ni. Therefore, by containing Co in an alloy layer, the contact resistance between the surface-treated steel sheet and a positive electrode material or a negative electrode material decreases.
Implementation Method 2
Surface-treated steel sheets used in battery containers face issues with contact resistance and color changes due to storage conditions, particularly under high temperature and humidity
Data Source
AI summary
The surface-treated steel sheet includes an alloy layer containing Ni and Co. In a case where, in a cross section obtained by cutting the alloy layer in the thickness direction, a range having a width of 2000 nm and extending from the surface of the alloy layer to a depth of 100 nm is partitioned into regions each having a width of 100 nm and a depth of 100 nm, within the range the alloy layer includes a plurality of high Co concentration regions in each of which the ratio of a Co concentration to a sum of the Co concentration and a Ni concentration within the partitioned region is 0.8 or more, and a plurality of alloyed regions in each of which a ratio of the Co concentration to a sum of the Co concentration and the Ni concentration within the partitioned region is less than 0.8.