Tab-Less Cylindrical Electrode Assembly for Safer Current Collection
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Solution Overview
Problem
Conventional cylindrical batteries face issues with current collection efficiency and heat generation due to concentrated current flow in strip-shaped electrode tabs, leading to potential ignition during rapid charging, especially when scaled for electric vehicles. Additionally, the exposure of coated electrode portions during handling can cause internal shorts and reduce energy density.
Innovation Solution
A tab-less cylindrical battery design with uncoated portions at the top and bottom of the jelly-roll electrode assembly, where current collectors are welded to these areas, and a fixing member is optimally positioned to prevent coated portions from exposure during handling, using a minimum folding angle and reduced separator usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If strip-shaped electrode tabs are used for current collection, then the battery structure is simple, but current collection efficiency is poor due to large resistance and heat generation
Solution Approach 1:
The uncoated portion of the electrode is divided into multiple uncoated regions along the winding direction, with current collectors attached to each region. This segmentation distributes the current collection points, reducing resistance and heat generation while maintaining structural simplicity.
Solution Approach 2:
The current collectors are wrapped around the outer circumference of the electrode assembly in the radial direction, creating a three-dimensional current collection network. This dimensional change increases the effective current collection area and improves efficiency without complicating the basic electrode structure.
2Reliability
If the separator winding end is extended to prevent coated portion exposure, then safety is improved, but manufacturing complexity increases
Solution Approach 1:
A fixing member is attached to the separator winding end before the electrode assembly is inserted into the battery housing. This preliminary action secures the separator in place, preventing coated portions from exposing during subsequent handling and assembly operations, thereby maintaining safety without requiring complex separator designs.
3Reliability
If more separator is used to prevent coated portion exposure, then safety is improved, but energy density decreases
Solution Approach 1:
The separator winding end is extended only to the minimum necessary length to prevent coated portion exposure, rather than extending it excessively. This partial action provides adequate safety protection while minimizing the amount of separator material used, thereby preserving energy density.
4Reliability
If the fixing member is positioned closer to the separator end, then coated portion exposure is prevented, but handling difficulty increases
Solution Approach 1:
The fixing member is positioned at a specific location on the separator winding end that optimizes both exposure prevention and handling. By placing it where it provides maximum protective effect without interfering with insertion operations, the local quality of the separator structure is improved for both safety and ease of operation.
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
Improves current collection efficiency, reduces heat generation, enhances safety by preventing internal shorts, and maintains energy density by minimizing separator usage and exposure risks.
Implementation Method 1
the current collector is welded to the uncoated portion to improve the current collecting efficiency
Implementation Method 2
the current collector is welded to the uncoated portion
Data Source
AI summary
An electrode assembly has a structure in which a first electrode, a second electrode, and a separator interposed therebetween are wound. An outermost coated portion is the coated portion of the first electrode. A winding end of the separator extends further from the winding end of the coated portion of the first electrode. A fixing member is attached to the winding end of the separator along the axial direction from a point spaced apart from the axial end of the separator. When the winding end corner of the separator is folded as much as possible with the axial end of the fixing member acting as a folding bias point so that its outer surface faces the outer circumference, the winding end corner of the coated portion of the first electrode is not exposed to the outside. A cylindrical battery may include the electrode assembly. A battery pack may include the cylindrical battery, and vehicle may include the battery pack.