Segmented Electrode Assembly Tabs for Low-Resistance Cylindrical Cells
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Solution Overview
Problem
Conventional cylindrical battery cells face issues with high resistance, heat generation, and low current-collection efficiency due to the concentration of current in strip-shaped electrode tabs, which can lead to ignition during rapid charging, especially when scaled for electric vehicles. Additionally, the bending of uncoated portions during the manufacturing process can cause irregular distortions, internal short circuits, and blockage of the electrolyte injection path.
Innovation Solution
The electrode assembly design includes a jelly-roll structure with uncoated portions at the ends of the electrode sheets, which are cut and bent to form a larger cross-sectional area for current collection, preventing distortion and ensuring the electrolyte path remains open. This design involves cutting and bending the uncoated portions to increase the welding area and reduce resistance, using ultrasonic cutters to accurately form cut lines and prevent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If strip-shaped electrode tabs are used for current collection, then the battery cell structure is simple and easy to manufacture, but the current collection efficiency is low and resistance is high
Solution Approach 1:
The uncoated portion is divided into multiple segments along the winding direction by forming cut lines, creating multiple forming portions that can be independently bent. This segmentation increases the total surface area of the electrode tab while maintaining the simple strip-shaped structure, thereby improving current collection efficiency without complicating the manufacturing process
Solution Approach 2:
The flat strip-shaped electrode tab is transformed into a three-dimensional structure by bending the forming portions at angled directions. This dimensional change increases the effective surface area of the electrode tab in the radial direction, improving current collection efficiency while maintaining the simplicity of the base strip structure
2Reliability
If the uncoated portion is bent to increase welding area, then the current collection efficiency is improved, but irregular distortions and internal short circuits occur
Solution Approach 1:
By dividing the uncoated portion into multiple forming portions through cut lines, the bending process is distributed across multiple segments. This reduces the distortion and stress concentration that would occur in a single large bend, preventing irregular distortions and internal short circuits while still achieving increased welding area
Solution Approach 2:
Different portions of the electrode tab are given different functions: the forming portions are bent to increase welding area, while the unbent portions maintain the original structure. This local differentiation allows selective bending in controlled areas, improving manufacturing precision by preventing distortions in critical regions
3Quantity of substance
If large-capacity battery cells are designed for electric vehicles, then the energy density is improved, but heat generation increases and ignition risk occurs
Solution Approach 1:
The segmented forming portions create multiple distributed welding points and current collection paths throughout the electrode assembly. This segmentation distributes the current flow and reduces localized heat generation, allowing large-capacity battery cells to achieve high energy density without excessive heat buildup or ignition risk
Solution Approach 2:
By transforming the flat electrode tab into a three-dimensional structure with bent forming portions, the current collection area is expanded in the radial direction. This increases the effective surface area for current collection, reducing electrical resistance and heat generation while maintaining the high capacity needed for electric vehicle applications
4Reliability
If the uncoated portion is bent during manufacturing, then the welding area is increased, but the electrolyte injection path may be blocked
Solution Approach 1:
The uncoated portion is differentially treated: forming portions are bent to increase welding area, while unbent portions are maintained to preserve the electrolyte injection path. This local quality differentiation ensures that the bent sections provide enhanced current collection without blocking the central injection通道
Solution Approach 2:
By segmenting the uncoated portion into forming portions and unbent portions, the bending operation is localized to specific areas. This prevents the formation of a continuous bent structure that would block the electrolyte injection path, while still achieving increased welding area through localized bending
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 solution significantly reduces electrical resistance, minimizes heat generation, and prevents ignition by expanding the current path, while ensuring the electrolyte can be properly injected and the battery cell's performance and capacity are maintained, thus enhancing the safety and efficiency of large-capacity battery cells.
Implementation Method 1
a cutter portion configured to form a cut line in the uncoated portion in an axial direction of the electrode assembly while moving in the axial direction
Data Source
AI summary
Discussed is a cutting device configured to cut at least a portion of an uncoated portion of an electrode assembly that includes an electrode cell body portion in which a separator, and a first electrode sheet and a second electrode sheet are wound in a state of being stacked, and the uncoated portion on which an active material layer is not coated is provided on an end portion of at least one of the first electrode sheet and the second electrode sheet in a width direction thereof. The cutting device can include a cutter portion configured to form a cut line in the uncoated portion, the cut line extending in an axial direction of the electrode assembly, and the cutter portion forming the cut line while moving in the axial direction.