Nickel-Plated Iron Can Welding for Corrosion Resistance
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Solution Overview
Problem
The nickel-plated iron outer casing in lithium-ion batteries experiences corrosion and electrolyte leakage due to the fusion of nickel and iron during energy beam welding, leading to reduced nickel concentration in the molten trace exposed on the surface, compromising the battery's corrosion resistance and reliability.
Innovation Solution
A sealed cell design featuring a welding process with a first and second energy beam irradiation step, where the second beam forms a layer with higher nickel concentration on the outside surface, covering the first layer, to enhance corrosion resistance and prevent nickel diffusion, thereby maintaining a stable nickel concentration and improving bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If energy beam welding is used to connect the lead to the nickel-plated iron outer casing can, then the bonding strength is improved and spatter generation is reduced, but the nickel and iron fuse together causing corrosion and electrolyte leakage
Solution Approach 1:
The welding process is segmented into two distinct steps: first welding the lead to the outer casing can, then performing annealing to separate the fused nickel and iron. This segmentation allows achieving strong bonding while preventing corrosion by reversing the fusion effect through controlled thermal treatment.
Solution Approach 2:
The annealing process is performed as a preliminary or subsequent treatment to the welding process. By applying controlled heating after welding, the nickel and iron that fused during welding are separated, preventing corrosion before it can occur during battery operation.
2Ease of manufacture
If the outer casing can is irradiated with energy beams in two steps, then the welding is completed, but the nickel component diffuses over a large area reducing the nickel concentration in the molten trace
Solution Approach 1:
The annealing process is applied as a subsequent treatment to restore nickel concentration. By heating the welded area, nickel diffuses back from surrounding areas to the molten trace region, restoring the protective nickel concentration that was depleted during the two-step welding process.
Solution Approach 2:
The thermal parameters are changed through the annealing process. By controlling temperature, time, and atmosphere during annealing, the nickel concentration in the molten trace is restored to appropriate levels, ensuring corrosion resistance while maintaining the welding structure.
3Ease of manufacture
If resistance welding is used to connect the outer casing can and lead, then the manufacturing process is simple, but spatters are generated causing metal foreign matter contamination
Solution Approach 1:
The mechanical resistance welding process is replaced with energy beam welding (laser or electron beam). This substitution eliminates the high-velocity particle ejection characteristic of resistance welding, preventing spatter generation and metal foreign matter contamination while maintaining strong bonding.
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 method effectively improves the corrosion resistance of the molten trace on the outer casing surface, enhancing the battery's reliability and bonding strength between the lead and the outer casing, while maintaining a stable nickel concentration, thus preventing corrosion and electrolyte leakage.
Implementation Method 1
the battery is provided in which the outer casing can and the lead or a current collecting tab corresponding to the lead are welded by being irradiated with an energy beam such as a laser beam from the outside of the outer casing can
Implementation Method 2
a nickel plated layer at the irradiation portion of the energy beam on the outside surface of the outer casing can and the base metal of the outer casing can are fused so that the nickel and the iron are mixed with each other
Data Source
AI summary
A sealed cell includes a bottomed cylindrical outer casing can. The outer casing can is formed by nickel-plated iron, and a lead connected to one of a positive electrode and a negative electrode, and the outer casing can, are welded by a welding part formed from the outside surface of the outer casing can toward the lead. The welding part is formed by molten traces and has a first layer and a second layer having a higher nickel concentration than the first layer. The first layer is formed from the lead through to the inside of the outer casing can, the second layer is formed so as to adjoin the first layer on the outside surface side of the outer casing can, and the whole of the first layer is covered with the second layer when the welding part is viewed from the outside of the outer casing can.