Wound Electrode Assembly Fixing Thickness for Better Cell Roundness
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Solution Overview
Problem
The existing power storage cells experience stress concentration due to the lower roundness of the wound electrode assembly, which can lead to mechanical issues when the cylindrical case comes into contact with it.
Innovation Solution
The power storage cell design incorporates a fixing member with a maximum thickness that is either equivalent to or less than the total thickness of the first and second foils, or greater than or equal to the thickness of the second foil, to reduce the level difference and improve roundness, thereby minimizing stress concentration. Additionally, the fixing member's thickness can vary uniformly or have inclination to enhance roundness and reduce level differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a fixing member with large thickness is used to secure the wound electrode assembly, then the fixing strength is improved, but the roundness of the wound electrode assembly deteriorates due to level difference
Solution Approach 1:
The invention changes the thickness parameter of the fixing member to be equal to or less than the total thickness of the first and second foils, thereby reducing the level difference at the end of winding and improving the roundness of the wound electrode assembly while maintaining adequate fixing strength
Solution Approach 2:
The invention applies local quality by making the fixing member's thickness specifically tailored to match the local thickness requirements at the end of winding, rather than using a uniformly large thickness throughout, thus achieving both sufficient fixing and minimal roundness degradation
2Shape
If the fixing member thickness is reduced to improve roundness, then the level difference is reduced, but the fixing strength may be compromised
Solution Approach 1:
The invention optimizes the thickness parameter within a specific range (equal to or less than the total foil thickness) to achieve the best balance between roundness improvement and maintaining sufficient fixing strength
3Ease of manufacture
If the wound electrode assembly has lower roundness, then the manufacturing process is simpler, but stress concentration occurs when contacting the cylindrical case
Solution Approach 1:
The invention changes the thickness parameter of the fixing member to improve roundness, thereby reducing stress concentration between the wound electrode assembly and cylindrical case while maintaining manufacturing feasibility
Solution Approach 2:
The invention applies prior cushioning by pre-adjusting the roundness of the wound electrode assembly through proper fixing member selection, thereby preventing stress concentration from occurring in the first place during operation
Data Source
AI summary
A power storage cell comprises a cell case and a wound electrode assembly. The wound electrode assembly includes a first electrode, a separator, a second electrode, and a fixing member. In a winding direction of the wound electrode assembly, the first electrode has a first end portion. The second electrode has a second end portion. The separator has a third end portion. In the winding direction, the second end portion is positioned within a region spanning from the first end portion to the third end portion. The first end portion consists of the first foil. The second end portion consists of the second foil. The fixing member fixes the wound electrode assembly at the third end portion. The expression “0.9×T2≤Tf≤1.1×(T1+T2)” is satisfied. T1 represents a thickness of the first foil. T2 represents a thickness of the second foil. Tf represents a maximum thickness of the fixing member.