Cylindrical Electrode Assembly With Bent Tabs for Low-Resistance Welding
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Solution Overview
Problem
Conventional cylindrical batteries face issues with current collection efficiency due to high resistance and heat generation, particularly during rapid charging, which can lead to ignition when scaled for electric vehicles, and there is a need to prevent damage to the separator or active material layer during welding of current collectors.
Innovation Solution
The electrode assembly design features uncoated portions bent to form a bending surface region with overlapping layers, ensuring secure welding and preventing electrolyte injection blockage, while also improving energy density and reducing resistance by directly welding the bending surface to the current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the uncoated portion is bent to form overlapping layers for welding, then welding strength is improved, but the separator or active material layer may be damaged during welding
Solution Approach 1:
The uncoated portion is bent into overlapping layers before the welding process, creating a prepared welding surface that distributes heat and mechanical stress. This preliminary configuration ensures strong welding while protecting the separator and active material from damage during the subsequent welding operation.
2Device complexity
If current is concentrated in the strip-shaped electrode tab, 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 is bent from a flat strip configuration into a three-dimensional overlapping layer structure. This dimensional transformation increases the effective welding surface area and improves current collection efficiency by distributing current flow across multiple layers, thereby reducing resistance and heat generation while maintaining structural simplicity.
3Area of stationary object
If the uncoated portion is bent toward the core, then the welding surface area is increased, but the cavity in the core may be blocked
Solution Approach 1:
The uncoated portion is bent into overlapping layers at specific locations away from the core cavity, creating localized welding surfaces with increased area. This local configuration enhancement provides adequate welding surface area while maintaining the core cavity's accessibility and volume for electrolyte injection.
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
This design enhances welding strength, prevents damage to the separator or active material layer, maintains electrolyte injection pathways, and reduces internal resistance, resulting in improved energy density and safety for larger cylindrical batteries.
Implementation Method 1
the uncoated portion is bent in a radial direction of the electrode assembly to form a bending surface region... a current collector may be welded to the bending surface region
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 10 or more in the winding axis direction of the electrode assembly.