Asymmetric Negative Electrode Roughness for Resistance Welding
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Solution Overview
Problem
The production of secondary batteries is hindered by the challenge of welding negative electrode current collectors to copper foil or copper alloy foil cores with significantly different surface roughness on their front and back surfaces, leading to low yields due to unsuitable welding conditions for either surface.
Innovation Solution
A method is developed to produce secondary batteries by forming negative electrode active material mixture layers on both surfaces of the core, with specific surface roughness differences, and then selectively welding the current collector to the smoother surface, ensuring consistent and high-quality welding by alternating mixture layer-formed regions and core-exposed portions during the rolling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If welding conditions are optimized for the smooth surface of the negative electrode core, then welding quality on the smooth surface is improved, but welding on the rough surface deteriorates leading to low yield
Solution Approach 1:
The invention applies local quality by making the negative electrode core asymmetric with different surface roughness characteristics on each side. The smooth surface is specifically designed and positioned to face the welding electrode during resistance welding, ensuring optimal welding conditions only where needed. This resolves the contradiction by creating a localized smooth welding surface while accepting that the opposite surface remains rough, thereby achieving high welding quality without compromising production yield.
2Manufacturing precision
If welding conditions are optimized for the rough surface of the negative electrode core, then welding quality on the rough surface is improved, but welding on the smooth surface deteriorates leading to low yield
Solution Approach 1:
The invention resolves this contradiction by creating an asymmetric negative electrode core where only the welding-facing surface is smooth. By positioning the smooth surface toward the welding electrode, the invention ensures that welding operations occur on the optimally suited surface, eliminating the need to compromise welding quality for either surface type and maintaining high production yield.
3Ease of manufacture
If asymmetric negative electrode cores with different surface roughness are used, then production costs are reduced, but welding difficulty increases
Solution Approach 1:
The invention applies local quality by creating an asymmetric negative electrode core with a smooth surface specifically at the welding location. This design reduces production costs by utilizing the natural roughness variation in rolled copper foil while concentrating the smooth surface treatment only where needed for welding. The simplification of the welding process is achieved by ensuring the smooth surface is consistently positioned toward the welding electrode through proper winding orientation, thereby reducing welding difficulty despite the asymmetric core structure.
Solution Approach 2:
The invention applies inversion by reversing the conventional approach: instead of making the entire negative electrode core surface smooth (which would increase production cost), the invention accepts the natural asymmetric roughness and strategically positions the smooth surface toward the welding electrode. This inverted thinking resolves the contradiction by making the welding process simpler through proper orientation rather than through comprehensive surface treatment.
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
This approach allows for the production of high-quality secondary batteries with improved yields by ensuring appropriate welding conditions for the smoother surface, reducing production costs and enhancing the battery's quality, even when using inexpensive negative electrode cores with varying surface roughness.
Implementation Method 1
a negative electrode current collector electrically connected to the negative electrode core-exposed portion
Implementation Method 2
the rough surface of the negative electrode core and the smooth surface of the negative electrode core differ from each other in terms of the state of contact between the resistance-welding electrode and the negative electrode core
Data Source
AI summary
Provided is a method for producing a non-aqueous electrolyte secondary battery. A negative electrode core of a negative electrode plate has front and back surfaces each with a surface roughness different from the other Rz. In a wound electrode body, a wound negative electrode core-exposed portion is formed at one end portion in the winding axis direction. In the wound negative electrode core-exposed portion, the surface roughness of the negative electrode core-exposed portion on the outer surface side is lower than the surface roughness on the inner surface side. A negative electrode current collector is placed on the outer surface of the wound negative electrode core-exposed portion and the negative electrode current collector is resistance-welded to the wound negative electrode core-exposed portion.