Secondary Battery Negative Electrode Welding to Minimize Voids
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Solution Overview
Problem
Existing methods for welding a negative electrode core and current collector in secondary batteries often result in voids, leading to unwelded portions and high resistance, particularly with increased layers.
Innovation Solution
A method involving a negative electrode core with specific surface roughness and glossiness, combined with a negative electrode current collector featuring projections, is used to resistance-weld the core stacked portion between two members, ensuring no voids exceed 1.0 mm in length and a nugget diameter of at least 1.6 mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of layers of the negative electrode core is increased, then the battery capacity is improved, but the possibility of generating voids at the welded portion increases
Solution Approach 1:
The invention changes the surface parameters of the negative electrode core by controlling the oxide film thickness (0.5-4 nm) and surface roughness (Ra 0.03-0.3 μm), which improves weldability and reduces void formation even when multiple layers are stacked, thereby maintaining welded portion quality while increasing battery capacity
Solution Approach 2:
The invention applies local quality improvement by forming a specific oxide film and controlling surface roughness only at the welded portion of the negative electrode core, ensuring reliable welding at the contact interface while allowing the rest of the electrode structure to accommodate multiple layers for increased capacity
2Ease of manufacture
If conventional welding methods are used, then the manufacturing process is simple, but voids are generated at the welded portion
Solution Approach 1:
The invention performs preliminary action by pre-forming a specific oxide film and controlling surface roughness of the negative electrode core before the welding process, which ensures high-quality welded portions without requiring complex welding procedures, thus maintaining manufacturing simplicity while improving welded portion quality
3Reliability
If the surface roughness of the negative electrode core is increased, then the weldability is improved, but the surface area for active material deposition decreases
Solution Approach 1:
The invention optimizes the surface roughness parameter to a specific range (Ra 0.03-0.3 μm) that provides sufficient weldability while preserving adequate surface area for active material deposition, achieving a balance between the two competing requirements
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 minimizes voids, achieving a high-strength and low-resistance welded interface between the negative electrode core and current collector, enhancing the battery's performance.
Implementation Method 1
resistance-welding the negative electrode current collector and the core stacked portion in a state where the core stacked portion is sandwiched between the first member and the second member from both sides, and the projection is in contact with the core stacked portion
Data Source
AI summary
A method for producing a secondary battery according to the present invention comprises a step wherein a negative electrode collector, which has a projection having a height of from 0.36 mm to 0.45 mm on at least one of a first member and a second member, said members constituting the negative electrode collector, is resistance-welded with a core multilayer part in such a manner that the core multilayer part is sandwiched between the first member and the second member, while having the projection in contact with the core multilayer part.