Cylindrical Electrode Assembly Layout for Distributed Current Collection
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Solution Overview
Problem
Cylindrical batteries face issues with current collection efficiency due to concentrated current in strip-shaped electrode tabs, leading to heat generation and ignition risks, especially in large form factors, and poor circularity affects assembly and cooling efficiency in battery packs.
Innovation Solution
The electrode assembly design positions the winding start and end portions of the electrodes optimally to maintain good circularity, with the first electrode's winding start closer to the core and end closer to the outer circumference, and the second electrode's end positioned within a specific angular range relative to the first electrode's start, using segmented uncoated portions for improved current collection.
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 concentrated current causing large resistance and heat generation
Solution Approach 1:
The electrode assembly is divided into multiple wound layers with uncoated portions exposed at different positions along the axial direction. Current collectors are attached to these segmented uncoated portions, distributing current collection points along the length of the electrode assembly rather than concentrating them at a single tab location, thereby reducing resistance and heat generation.
Solution Approach 2:
The invention transitions from two-dimensional tab-based current collection to three-dimensional distributed current collection along the axial direction. Multiple uncoated portions are positioned at different heights, allowing current collectors to attach at multiple locations along the length of the electrode assembly, effectively adding the axial dimension to current collection geometry.
2Quantity of substance
If the form factor of cylindrical battery is increased for electric vehicle application, then energy capacity increases, but heat generation around electrode tab increases causing ignition risk
Solution Approach 1:
The electrode assembly is segmented into multiple uncoated portions along the axial direction, with current collectors attached at distributed locations. This segmentation distributes the heat generation that would otherwise concentrate at a single large tab, reducing peak temperatures and ignition risk in large form factor batteries.
Solution Approach 2:
The invention converts the potentially harmful concentrated current and heat at tabs into beneficial distributed current collection along the axial direction. By strategically positioning uncoated portions and current collectors, the design transforms what would be a heat concentration point into a distributed thermal management solution.
3Reliability
If uncoated portions are positioned at top and bottom for tab-less design, then current collection efficiency improves, but manufacturing complexity increases due to welding processes
Solution Approach 1:
Instead of welding current collectors to bent uncoated portions at top and bottom, the invention segments the electrode assembly into multiple uncoated portions along the axial direction. This allows current collectors to be attached in a simpler manner at multiple locations, reducing manufacturing complexity while maintaining efficient current collection.
4Ease of manufacture
If winding start and end portions are not optimally positioned, then manufacturing is simpler, but circularity of electrode assembly deteriorates affecting assembly and cooling efficiency
Solution Approach 1:
The invention applies preliminary action by pre-positioning the winding start and end portions of electrodes and separators in specific configurations before winding. The separator extends beyond electrode ends, and winding begins at strategically selected positions, ensuring that the final wound assembly achieves good circularity without requiring complex post-processing or adjustment.
Data Source
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AI summary
The present disclosure provides an electrode assembly, a cylindrical battery, a battery pack and a vehicle. The electrode assembly is an electrode assembly in which a first electrode, a second electrode, and a separator interposed therebetween are wound around a winding axis to define a core and an outer circumference, wherein a winding start portion of the first electrode is positioned closer to the core than a winding start portion of the second electrode and extends further in a direction opposite to a winding direction, wherein a winding end portion of the first electrode is positioned closer to the outer circumference than a winding end portion of the second electrode and extends further in the winding direction, and wherein in a cross-section of the electrode assembly perpendicular to the winding axis, the winding end portion of the second electrode is included in a fan-shaped region having a circumferential angle corresponding to an angle of the winding direction between the winding start portion of the first electrode and the winding start portion of the second electrode.