Battery Case Laser Welding for Stronger Sealing Plate Joints
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Solution Overview
Problem
The joint strength between the case and the sealing plate in electricity storage devices is inadequate, particularly near the start point of laser welding, due to insufficient melting and misalignment during the welding process, which is exacerbated in larger devices.
Innovation Solution
A fabrication method that involves setting the start point of laser welding inward of the periphery of the sealing plate, performing a first step with controlled laser output to gradually increase temperature, and a second step to ensure a deep welding depth over the entire circumference, enhancing joint strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If laser welding is performed starting from the periphery of the sealing plate, then welding coverage is complete, but joint strength is insufficient due to misalignment and insufficient melting at the start point
Solution Approach 1:
The patent applies preliminary action by setting the laser welding start point inward from the periphery of the sealing plate rather than at the edge. This preliminary positioning allows the welding process to begin at a location where proper alignment can be achieved, preventing the misalignment and insufficient melting that occur when starting from the periphery. The inward start point serves as a preparatory measure to ensure optimal welding conditions before reaching the actual joint area.
Solution Approach 2:
The patent applies local quality by differentiating the welding start position from the rest of the welding path. Instead of uniformly starting at the periphery throughout, the start point is specifically positioned inward at a location optimized for alignment and melting. This localized adjustment at the start point improves joint strength without affecting the overall welding coverage, addressing the specific problem area where misalignment occurs.
2Productivity
If laser welding output is high from the beginning, then welding speed is fast, but spatters occur and joint strength is reduced
Solution Approach 1:
The patent applies preliminary action by using a preliminary welding step at reduced laser output before the main welding process. This preliminary step prepares the material by creating initial melting and alignment without the harmful effects of high-power spatters. Only after this preparatory phase does the patent proceed to high-output welding, ensuring that the material is ready to withstand the higher energy input without compromising joint strength.
Solution Approach 2:
The patent applies periodic action by dividing the welding process into distinct phases with different laser output levels. The process alternates between a low-output preliminary welding phase and a high-output main welding phase. This periodic variation in laser power allows the system to benefit from both low-power precision (avoiding spatters) and high-power efficiency (maintaining welding speed), thereby resolving the contradiction between productivity and joint strength.
3Reliability
If welding is performed over the entire circumference of the sealing plate periphery, then sealing coverage is complete, but joint strength remains insufficient due to the start point location
Solution Approach 1:
The patent applies preliminary action by positioning the welding start point inward from the periphery before beginning the circumferential welding process. This preliminary positioning ensures that when the laser reaches the actual joint area, proper alignment and melting have already been established. The inward start point acts as a preparatory measure that enables the subsequent circumferential welding to achieve both complete sealing coverage and high joint strength throughout the entire perimeter.
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 method ensures a deep welding depth and improved joint strength between the case and sealing plate, effectively sealing the device and preventing leakage, especially in larger devices.
Implementation Method 1
performing main welding of laser welding the case and the sealing plate over an entire circumference of a periphery of the sealing plate
Implementation Method 2
a start point of laser welding is set inward of the periphery of the sealing plate
Data Source
AI summary
A method for fabricating an electricity storage device includes a case preparing step, a sealing plate preparing step, an assembly step, and a main welding step. In the case preparing step, a square case including an opening is prepared. In the sealing plate preparing step, a sealing plate to be attached to the opening along an edge of the opening is prepared. In the assembly step, the sealing plate is attached to the opening of the case. In the main welding step, the case and the sealing plate are laser welded over an entire circumference of a periphery of the sealing plate. In the main welding step, a start point of laser welding is set inward of the periphery of the sealing plate.