Wound Cell Separator Layout to Cut Redundant Winding
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Solution Overview
Problem
Conventional wound-type cells require redundant winding of the separator beyond the current collectors, leading to waste and increased thickness, which reduces energy density and increases production costs.
Innovation Solution
The wound-type cell design features a third winding start end of the separator that extends away from the second winding start end without folding back, reducing the need for redundant winding and avoiding overlap in the thickness direction, thereby minimizing separator usage and cell thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separator is redundantly wound beyond the current collectors to ensure proper coverage, then the reliability of separation is improved, but the loss of substance increases and the thickness of the cell increases
Solution Approach 1:
The separator is pre-assembled with the negative electrode plate to form a negative electrode assembly before winding. The third winding start end of the separator extends beyond the negative current collector in advance, allowing the separator to cover the positive current collector automatically during winding without requiring redundant winding length, thus reducing separator waste while ensuring proper coverage and separation reliability
Solution Approach 2:
The separator's third winding start end extends in the length direction beyond the negative current collector, utilizing the length dimension to ensure coverage of the positive current collector during winding, rather than requiring additional length through folding back in the thickness direction. This dimensional approach reduces both separator waste and cell thickness
2Reliability
If the separator is folded back to extend beyond the current collectors, then the separation coverage is improved, but the thickness of the cell increases
Solution Approach 1:
The separator is pre-configured with its third winding start end extending beyond the negative current collector in the length direction before winding begins. This preliminary arrangement ensures that during the winding process, the separator naturally covers the positive current collector without needing to be folded back, thereby maintaining separation coverage while avoiding increased cell thickness
Solution Approach 2:
Instead of extending the separator beyond the current collectors by folding it back in the thickness direction, the invention extends the third winding start end in the length direction. This dimensional change allows the separator to provide adequate coverage during winding without increasing the cell thickness, thus resolving the contradiction between separation coverage and cell thickness
3Reliability
If redundant separator winding is performed, then the separation reliability is improved, but the energy density of the cell decreases
Solution Approach 1:
The separator is pre-assembled with the negative electrode plate and configured with the third winding start end extending beyond the negative current collector before winding. This preliminary arrangement ensures adequate separation coverage during winding without requiring redundant separator length, thereby reducing the overall cell volume occupied by non-active materials and improving energy density while maintaining separation reliability
Solution Approach 2:
The invention extends the separator's third winding start end in the length direction rather than requiring additional thickness through folding. This dimensional approach reduces the volume fraction of inactive separator material in the cell, thereby improving energy density while ensuring proper separation coverage and reliability
Data Source
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AI summary
The present invention provides a wound-type cell which comprises: a first electrode plate having a first current collector and a first active material layer coated on a surface of the first current collector; a second electrode plate having a second current collector and a second active material layer coated on a surface of the second current collector, and a second winding start end of the second electrode plate is positioned at an inner side of a first winding start end of the first electrode plate in a thickness direction; a separator; a first electrode tab; and a second electrode tab. A third winding start end of the separator is positioned at an outer side of the second winding start end of the second electrode plate in a length direction, extends along a direction away from a second end of the second winding start end and is not folded back.