Zinc-Modified Copper Foil for Battery Current Collectors
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Solution Overview
Problem
Copper foils used as negative electrode current collectors in lithium ion secondary batteries face challenges with maintaining high tensile strength after heat treatment, which can lead to deformation and reduced battery performance due to the expansion and contraction of the negative electrode mixture layer, and existing solutions require rare metals for surface treatment.
Innovation Solution
A copper foil with a specific composition including zinc in the range of 0.02% to 2.7% by mass, an internal layer with copper as the main element and 100 ppm or more of small amount-elements like carbon, sulfur, chlorine, and nitrogen, and a concentrated zinc-layer to form compounds at grain boundaries, enhancing tensile strength and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a copper foil is used as a negative electrode current collector, then it provides good electrical conductivity, but its tensile strength decreases after high-temperature heat treatment, causing deformation and reduced battery performance
Solution Approach 1:
The invention changes the compositional parameters of the copper foil by adding zinc (0.02-2.7% by mass) and controlling the content of small amount elements (C, S, Cl, N) to maintain tensile strength after high-temperature heat treatment. This compositional modification allows the copper foil to withstand heat treatment temperatures while preserving mechanical strength.
Solution Approach 2:
The invention creates a composite structure by combining copper with zinc and small amount elements (C, S, Cl, N) to form a multi-element alloy system. This composite material approach enables the copper foil to maintain high tensile strength after heat treatment, preventing deformation and ensuring stable battery performance.
2Strength
If a copper foil with high tensile strength is used to withstand volume changes, then it prevents deformation, but it requires rare metals for surface treatment which increases cost
Solution Approach 1:
The invention replaces expensive rare metals with zinc, which is a cheaper and more abundant metal. The zinc-containing copper foil achieves the required tensile strength without needing rare metal surface treatments, significantly reducing manufacturing costs while maintaining performance.
Solution Approach 2:
The invention modifies the compositional parameters by adding zinc (0.02-2.7% by mass) and controlling small amount elements to achieve high tensile strength inherently, eliminating the need for costly rare metal surface treatments and simplifying the manufacturing process.
3Reliability
If the negative electrode mixture layer adheres to the current collector surface, then it enables effective lithium storage, but repeated expansion/contraction applies stress causing breaks and reduced cycle durability
Solution Approach 1:
The invention uses a composite copper-zinc alloy with controlled small amount elements to create a current collector with enhanced tensile strength. This composite material can withstand the repeated expansion and contraction stresses from the negative electrode mixture layer during charging and discharging cycles, preventing breaks and maintaining cycle durability.
Solution Approach 2:
The invention optimizes the compositional parameters of the copper foil by adding zinc (0.02-2.7% by mass) and controlling small amount elements (C, S, Cl, N) to achieve the required tensile strength that can withstand mechanical stress from electrode expansion/contraction, ensuring long cycle durability.
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 copper foil maintains high tensile strength and corrosion resistance after high-temperature heat loading, preventing deformation and ensuring stable battery performance without the need for rare metals, thus offering a cost-effective solution for lithium ion secondary batteries and other applications.
Implementation Method 1
the internal layer comprises copper as a main element and includes 100 ppm or more of one or mixture of small amount-elements selected from carbon, sulfur, chlorine and nitrogen, and includes zinc at 10% or more in the total mass of zinc included in the entire copper foil
Implementation Method 2
a compound composed of zinc and one or mixture of elements selected from carbon, sulfur, chlorine and nitrogen precipitates at a grain boundary of copper in the internal layer
Implementation Method 3
In the manufacturing process of a negative electrode material, high-temperature is loaded when a negative electrode mixture layer is provided on the surface of a negative electrode current collector
Data Source
AI summary
An object of the present invention is to provide a copper foil inexpensive and sufficient in tensile strength even after heat treatment. The copper foil includes zinc in a content range of 0.02% by mass to 2.7% by mass in the total mass of the entire copper foil, and if the regions in thicknesses direction from both surfaces of the copper foil where occupies 5% by mass in the total mass of the entire copper foil are referred to as the respective external layers and a region between one external layer and the other external layer is referred to as an internal layer, the internal layer includes copper as a main element and includes 100 ppm or more of one or mixture of small amount-elements selected from carbon, sulfur, chlorine and nitrogen, and includes zinc at 10% or more in the total mass of zinc included in the entire copper foil.