Cu-Stainless-Cu Collector Foil for Wrinkle-Resistant Battery Anodes
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Solution Overview
Problem
High-capacity batteries using alloy-based materials for negative electrodes face significant stress due to volume changes during charging and discharging, leading to wrinkle-like deformation and plastic deformation of the collector foils, especially when stainless steel with high Ni content is expensive and not feasible.
Innovation Solution
A foil for secondary battery negative electrodes is developed with a core material of martensitic stainless steel containing 0.6-3.0% Ni, exhibiting a two-phase structure of ferrite and martensite phases, sandwiched between Cu layers, providing sufficient proof stress and tensile strength while reducing Ni content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stainless steel with high Ni content is used as core material, then proof stress is sufficient to prevent wrinkle deformation, but manufacturing cost increases significantly
Solution Approach 1:
The invention changes the chemical composition parameters of stainless steel, specifically reducing Ni content from traditional high levels (6.0-28.0% as in PTL 1) to a lower range (0.6-3.0%), while compensating for strength through controlled Cr content (10.5-20.0%) and C content (0.01-1.2%), along with heat treatment to achieve the desired two-phase microstructure
Solution Approach 2:
The invention creates a composite microstructure within the stainless steel by controlling the formation of two phases (ferrite and martensite) through specific composition ratios and heat treatment, where the martensite phase provides strength while the ferrite phase provides ductility, achieving sufficient proof stress without high Ni content
2Ease of manufacture
If stainless steel with low Ni content is used as core material, then manufacturing cost decreases, but proof stress becomes insufficient causing plastic deformation and wrinkle-like deformation
Solution Approach 1:
The invention optimizes multiple composition parameters simultaneously: Ni (0.6-3.0%), Cr (10.5-20.0%), and C (0.01-1.2%), where the increased Cr content compensates for reduced Ni content in providing strength, while controlled C content enables martensite formation through heat treatment to achieve sufficient proof stress at lower cost
Solution Approach 2:
The invention utilizes phase transition during heat treatment to transform the stainless steel microstructure into a two-phase structure of ferrite and martensite, where the martensite phase forms through diffusionless transformation providing high strength, while maintaining overall structural integrity and preventing deformation
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 effectively suppresses wrinkle-like deformation and ensures reliable conductivity and corrosion resistance, enabling the use of high-capacity batteries with alloy-based materials like Si or Sn without the need for high-Ni stainless steel.
Implementation Method 1
a stainless steel layer made of martensitic stainless steel containing Ni of more than 0.6% by mass and 3.0% by mass or less, Cr of 10.5% by mass or more and C of 1.2% by mass or less, and exhibiting a two-phase structure of a ferrite phase and a martensite phase
Implementation Method 2
a first Cu layer made of Cu or a Cu-based alloy, a stainless steel layer made of martensitic stainless steel... and a second Cu layer made of Cu or a Cu-based alloy, which are disposed in this order
Implementation Method 3
a stainless steel layer made of martensitic stainless steel containing Ni of more than 0.6% by mass and 3.0% by mass or less, Cr of 10.5% by mass or more and C of 1.2% by mass or less
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
This foil for a secondary battery negative electrode collector (negative electrode-collecting foil 5b) includes a first Cu layer (51) made of Cu or a Cu-based alloy, a stainless steel layer (52), and a second Cu layer (53) made of Cu or a Cu-based alloy, which are disposed in this order, a total thickness is 200 µm or less, and 0.01% proof stress is 500 MPa or more.