Bidirectional Wound Electrode Assembly for Lithium Battery
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Solution Overview
Problem
Conventional electrode assemblies, such as jelly-roll and stacked/folded types, face issues with stress accumulation, non-uniform gaps, and increased width and snaking when the number of unit cells is increased, leading to performance deterioration and safety concerns.
Innovation Solution
A stacked/folded type electrode assembly is designed with a single separation sheet surrounding unit cells, where cells are wound from both ends of the sheet to form first and second stack parts, with a facing unit cell contacting both, minimizing width increase and preventing snaking by maintaining a consistent gap between electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If unit cells are wound in one direction to form a stacked/folded type electrode assembly, then the structure can accommodate multiple unit cells, but the width of the electrode assembly increases and snaking occurs
Solution Approach 1:
The patent transitions from unidirectional winding to bidirectional winding, utilizing both directions from the center of the separation sheet. This dimensional change in the winding approach allows unit cells to be arranged in a compact configuration that reduces width increase while accommodating a greater number of unit cells
2Quantity of substance
If the number of winds is increased to accommodate more unit cells, then the capacity of the battery increases, but snaking occurs leading to non-uniform gaps between electrodes
Solution Approach 1:
By implementing bidirectional winding from the center separation sheet, the patent distributes the winding stress and gap maintenance across two directions rather than one. This allows for increased number of winds without proportionally increasing snaking, as each direction can be controlled to maintain uniform gaps
Solution Approach 2:
The patent introduces asymmetry by placing a facing unit cell at the center position that is different from the regular unit cells. This central facing unit cell acts as an anchor point that helps maintain uniform gaps during the winding process, preventing snaking even as the number of winds increases
3Quantity of substance
If a long separator sheet is used to surround more unit cells, then more unit cells can be included, but the overall width of the electrode assembly increases
Solution Approach 1:
The patent changes the winding strategy from extending the separator sheet in one direction to utilizing bidirectional winding from the center. This allows the separator sheet to effectively serve more unit cells by folding back on itself, reducing the linear width required while increasing the number of unit cells that can be accommodated
Data Source
AI summary
An electrode assembly includes a plurality of unit cells, each including a positive electrode, a negative electrode, and a separator disposed therebetween, and a single separation sheet disposed between the unit cells while surrounding side surfaces thereof. First and second stack parts of unit cells are wound with the separation sheet from each end of the separation sheet toward the middle of the separation sheet, a facing unit cell has one surface that contacts the first stack part with the separation sheet between the one surface of the facing unit cell and the first stack part and the other surface that contacts the second stack part with the separation sheet between the other surface of the facing unit cell and the second stack part, and the unit cells are stacked such that electrodes having opposite polarities are disposed in contact with each other with the separation sheet therebetween.