Bent Uncoated Electrode Ends for Cylindrical Battery Current Collection
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Solution Overview
Problem
Conventional cylindrical batteries face issues with current collection efficiency due to high resistance and heat generation at the electrode tab, which can lead to ignition during rapid charging, especially when scaled for electric vehicles.
Innovation Solution
A tab-less cylindrical battery design where the uncoated portions of the electrodes are positioned at the top and bottom and welded to a current collector, reducing resistance by increasing the cross-sectional area of the current path and preventing electrolyte injection blockages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a strip-shaped electrode tab is used to connect the uncoated portion of the electrode, then the battery structure is simple and easy to manufacture, but the current collection efficiency is poor due to large resistance and heat generation
Solution Approach 1:
The electrode is divided into a coated portion and an uncoated portion, with the uncoated portion serving as the current collection area. This segmentation allows the current to be collected over a larger area rather than through a narrow strip-shaped tab, reducing resistance and heat generation while maintaining manufacturing simplicity.
Solution Approach 2:
The current collection is transitioned from a one-dimensional strip-shaped tab to a two-dimensional uncoated portion surface. By utilizing the surface area of the uncoated portion for current collection, the effective cross-sectional area for current flow is increased, thereby reducing resistance and improving current collection efficiency.
2Reliability
If the uncoated portion is bent toward the core to form a bending surface region, then the current collection efficiency is improved, but the separator or active material may be damaged during welding
Solution Approach 1:
The uncoated portion is pre-bent toward the core to form a bending surface region before the welding process. This preliminary bending creates a concentrated area for current collection that improves electrical contact, while the bending is controlled to prevent damage to the separator or active material during subsequent welding operations.
Solution Approach 2:
The bending is applied locally to the uncoated portion rather than the entire electrode structure. This localized bending concentrates the current collection function in a specific region while maintaining the integrity of the separator and active material in other areas, preventing damage during welding.
3Reliability
If the uncoated portion is positioned at the top and bottom of the electrode assembly, then the current collection efficiency is improved, but the electrolyte injection may be blocked
Solution Approach 1:
The uncoated portion is positioned at the top and bottom ends of the wound electrode assembly along the winding axis. This spatial arrangement utilizes the axial dimension for current collection while maintaining radial accessibility for electrolyte injection, allowing both functions to coexist without interference.
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
The design enhances current collection efficiency, reduces internal resistance, and prevents damage to the separator or active material during welding, while maintaining electrolyte injection accessibility.
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
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AI summary
Disclosed is an electrode assembly, a battery, and a battery pack and a vehicle including the same. In the electrode assembly, a first electrode, a second electrode, and a separator interposed therebetween are wound based on an axis to define a core and an outer circumference. The first electrode includes an uncoated portion at a long side end thereof and exposed out of the separator along a winding axis direction of the electrode assembly. A part of the uncoated portion is bent in a radial direction of the electrode assembly to form a bending surface region that includes overlapping layers of the uncoated portion, and in a partial region of the bending surface region, the number of stacked layers of the uncoated portion is to or more in the winding axis direction of the electrode assembly.