Ni-Plated Steel Foil Current Collector for Fe Leaching Resistance
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Solution Overview
Problem
Nickel-hydrogen secondary batteries experience reduced capacity due to metal ion leaching, particularly iron (Fe) from steel foils used as current collectors, when exposed to the alkaline electrolyte in nickel-hydrogen secondary batteries.
Innovation Solution
The use of an Ni-plated steel foil with a thickness of 5 to 50 μm, a tensile strength of 400 MPa to 1200 MPa, and an Ni plating layer thickness of 0.15 μm or greater on both surfaces, which undergoes specific heat treatment after cold rolling to enhance strength and prevent Fe leaching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steel foil is used as current collector in nickel-hydrogen secondary battery, then cost is reduced and strength is improved, but Fe leaching occurs in alkaline electrolyte causing capacity reduction
Solution Approach 1:
A Ni plating layer is introduced as an intermediary between the steel foil and the alkaline electrolyte. This Ni layer acts as a protective barrier that prevents direct contact between Fe and the electrolyte, thereby suppressing Fe leaching while allowing the steel foil to maintain its structural and electrical functions as current collector.
Solution Approach 2:
The current collector is designed as a composite structure consisting of a steel foil substrate with a Ni plating layer. This composite combines the advantages of steel (low cost, high strength, light weight) with the corrosion resistance of Ni in alkaline environments, effectively preventing Fe leaching while maintaining battery capacity.
2Object-generated harmful factors
If Ni plating layer thickness is increased to suppress Fe leaching, then Fe leaching resistance is improved, but manufacturing cost and device weight increase
Solution Approach 1:
The Ni plating layer thickness is optimized to a specific range (0.15 μm or greater but not excessive) to achieve the minimum required protection against Fe leaching. This parameter optimization ensures sufficient corrosion resistance while minimizing additional weight and manufacturing cost, avoiding over-engineering the plating thickness.
3Weight of moving object
If steel foil thickness is reduced to achieve size and weight reduction, then battery size and weight are reduced, but mechanical strength and rust resistance deteriorate
Solution Approach 1:
The steel foil is designed as a thin composite structure with a Ni plating layer. The Ni layer provides corrosion resistance and protects the thin steel substrate from rust, enabling the use of thinner foils without sacrificing durability. This composite approach allows weight reduction while maintaining mechanical strength and rust resistance.
Solution Approach 2:
The Ni plating layer serves as a protective intermediary that shields the thin steel foil from the corrosive alkaline electrolyte. This protection enables the steel foil to be made thinner without compromising rust resistance, as the Ni layer assumes the corrosion protection function that would otherwise require thicker steel.
4Ease of manufacture
If iron foil is used as current collector, then cost is reduced compared to nickel foam, but electrical resistance increases and rust prevention is poor
Solution Approach 1:
The current collector uses a composite structure of steel foil with Ni plating. This combines the low cost and good electrical conductivity of steel/iron with the excellent rust resistance of Ni, creating a material that is both economical and corrosion-resistant, overcoming the limitations of plain iron foil.
Solution Approach 2:
The Ni plating layer acts as an intermediary protective layer between the iron/steel substrate and the alkaline electrolyte environment. This layer prevents direct corrosion of the iron, providing rust resistance while maintaining the cost-effectiveness and electrical properties of the iron-based substrate.
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 Ni-plated steel foil effectively suppresses Fe leaching, maintaining high strength and elongation, thereby achieving a higher capacity and longer life for nickel-hydrogen secondary batteries.
Implementation Method 1
the Ni-plated steel foil effectively suppresses Fe leaching, maintaining high strength and elongation
Implementation Method 2
by preparing such a steel foil provided with an Ni plating layer for suppressing leaching of the Fe component and applying heat treatment to the steel foil under specific conditions after cold rolling
Data Source
AI summary
A high-strength steel foil for the positive and negative electrode current collectors of nickel-hydrogen secondary batteries which uses a light weight and economical steel foil and which is thin and strong and has excellent rust resistance and resistance to metal ion leaching. Also, a high-strength steel foil for the positive and negative electrode current collectors of nickel-hydrogen secondary batteries which has excellent elongation. The Ni-plated steel foil for hydrogen secondary battery current collectors comprises, by mass %, C: 0.0001 to 0.0200%, Si: 0.0001 to 0.0200%, Mn: 0.005 to 0.300%, P: 0.001 to 0.020%, S: 0.0001 to 0.0100%, Al: 0.0005 to 0.1000%, N: 0.0001 to 0.0040%, one or both of Ti and Nb: 0.800% or less respectively, and a balance of Fe and impurities. The Ni-plated steel foil has an Ni plating layer on both surfaces. The thickness of the Ni plating layer on both surfaces of the Ni-plated steel foil is greater than or equal to 0.15 μm, the thickness of the Ni-plated steel foil is 5 to 50 μm, the tensile strength is over 400 MPa but no greater than 1200 MPa, and the surface defect area percentage is less than or equal to 5.00% for both surfaces of the Ni-plated steel foil.