Cylindrical Battery Cell Spiral Welds to Prevent Overwelding
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Solution Overview
Problem
Existing cylindrical battery cells face issues with overwelding during laser welding, leading to heat damage and leakage of electrolytic solutions, while nanosecond pulse laser welding reduces weldability and increases welding time due to its small spot size.
Innovation Solution
A cylindrical battery cell with a discontinuous spiral weld portion formed using a nanosecond pulse laser, where the weld lines do not overlap, minimizing heat-affected areas and preventing overwelding, and a battery module connecting multiple cells via a busbar or metal plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous wave laser welding or millisecond pulse laser welding is used, then welding speed is improved, but excessive heat is supplied causing gasket damage and electrolytic solution leakage
Solution Approach 1:
The patent applies periodic action by using nanosecond pulse laser welding instead of continuous wave or millisecond pulse laser welding. The nanosecond pulse laser delivers energy in extremely short, periodic pulses that prevent excessive heat accumulation and heat conduction to the gasket, thereby avoiding gasket damage and electrolytic solution leakage while maintaining welding effectiveness.
Solution Approach 2:
The patent changes the temporal parameter of laser energy delivery from continuous or millisecond-scale pulses to nanosecond-scale pulses. This parameter change fundamentally alters the heating mechanism, allowing sufficient energy delivery for welding while preventing heat diffusion to surrounding areas and protecting the gasket from thermal damage.
2Object-affected harmful factors
If nanosecond pulse laser welding is used, then heat damage to gasket is prevented, but spot size is small reducing weldability and increasing welding time
Solution Approach 1:
The patent applies segmentation by dividing the welding process into multiple discrete nanosecond pulses rather than using a single long-duration pulse or continuous welding. This segmentation allows the total welding energy to be delivered in controlled increments, maintaining small spot size for precise heating while accumulating sufficient total energy for complete welding through multiple pulses, thereby reducing overall welding time.
Solution Approach 2:
The patent achieves continuity of useful action by delivering multiple nanosecond pulses in rapid succession, maintaining the welding action continuously without interruption. This approach ensures that the small spot size advantage is fully utilized while the cumulative effect of multiple pulses provides sufficient total energy for complete welding, eliminating the need for long single-duration pulses.
3Device complexity
If straight pattern or circular pattern welding is used with nanosecond pulse laser, then welding path is simple, but weld area is limited and workability is lowered
Solution Approach 1:
The patent applies spheroidality by using spiral welding paths instead of straight or simple circular patterns. The spiral path maximizes the utilization of the small nanosecond laser spot size by continuously varying the welding trajectory, creating an optimized weld pattern that covers the required area more effectively while maintaining the simplicity of automated path execution.
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 solution prevents overwelding, maintains gasket integrity, enhances welding strength, and reduces welding time by creating a wide weld area without overlapping heat-affected zones, ensuring secure electrical connections and improved safety.
Implementation Method 1
a weld portion formed by welding a laser beam along a weld line extending from a central part toward an outer periphery of the electrode terminal in a spiral shape
Implementation Method 2
When the gasket is damaged and deformed, it is difficult to prevent leakage of an electrolytic solution, which is the original function of the gasket, whereby sealing performance of the cylindrical battery cell may be seriously affected and it may be difficult to secure safety of the cylindrical battery cell. Consequently, it is appropriate to use a nanosecond pulse laser, which supplies a relatively small amount of heat to the weld portion.
Data Source
AI summary
A cylindrical battery cell may include a cap assembly loaded on an upper end of a battery case having an electrode assembly received therein; and a crimping portion formed at an end of an upper part of the battery case, the crimping portion bent in a direction toward a center thereof while wrapping an outer periphery of the cap assembly. The crimping portion may be a negative electrode terminal. A top cap, which is a central part of the cap assembly, may be a positive electrode terminal. The cylindrical battery cell may further include a spiral weld portion formed on at least one of the negative electrode terminal and the positive electrode terminal. In one or more aspects, overwelding on the positive electrode terminal and the negative electrode terminal is prevented, whereby safety of the cylindrical battery cell is improved.