Foil Tab Forming for Uniform Battery Current Collection
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Solution Overview
Problem
Existing cylindrical secondary battery designs limit the current path and increase self-resistance due to limited connections between the electrode assembly and external terminals, and methods to increase tab connections face limitations.
Innovation Solution
A foil tab forming apparatus and method that includes a forming jig and pre-forming jig to bend and press positive and negative electrode uncoated portions of the electrode assembly, allowing uniform formation from the outer circumferential to the winding center portion, using multiple shutter blocks and rotating pressing blocks to facilitate smooth bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single tab structure is used to connect the electrode assembly to external terminals, then the device complexity is reduced, but the current path is limited and self-resistance increases
Solution Approach 1:
The electrode assembly is divided into multiple tabs (positive electrode tabs and negative electrode tabs) extending from different positions along the winding axis. This segmentation allows multiple parallel current paths between the electrode assembly and external terminals, reducing self-resistance and improving current distribution without requiring a single complex connection structure
2Reliability
If multiple tabs are added to increase current collection area, then the current path improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The tab structure utilizes the natural winding geometry of the electrode assembly, with tabs extending dynamically from different positions along the winding axis. This dynamic arrangement allows multiple tabs to be formed from the winding structure itself, increasing current collection area without proportionally increasing manufacturing complexity
Solution Approach 2:
Tabs are arranged along the winding axis (vertical dimension) rather than only at the ends of the wound structure. This dimensional change allows multiple tabs to be distributed throughout the length of the electrode assembly, creating parallel current paths without requiring additional horizontal space or complex lateral arrangements
3Reliability
If the foil tab is bent to increase combining area with current collection plate, then the electrical connection improves, but the manufacturing precision and uniformity become difficult to maintain
Solution Approach 1:
A pre-forming jig is used to pre-bend the foil tabs before the main forming process. This preliminary action prepares the tabs in advance with a preliminary curvature that facilitates the subsequent bending operation, ensuring uniform pre-positioning of all tabs before final forming, thereby maintaining manufacturing precision
Solution Approach 2:
The pre-forming jig acts as an intermediary tool between the raw electrode assembly and the final forming process. It introduces a controlled intermediate state (pre-bending) that makes the subsequent forming operation easier and more uniform, reducing the complexity of achieving precise tab formation across all tabs
4Manufacturing precision
If the forming jig presses the foil tab uniformly across the entire electrode assembly, then the manufacturing precision improves, but the device complexity and process complexity increase
Solution Approach 1:
The forming jig is divided into multiple pressing blocks that can independently press different regions of the electrode assembly. Each pressing block corresponds to a specific region (e.g., outer circumferential region, winding center region), allowing localized and differentiated pressing forces to be applied, achieving uniform tab formation across the entire assembly without requiring a single complex pressing mechanism
Solution Approach 2:
Different pressing blocks are configured with different pressing characteristics suitable for their respective regions. For example, pressing blocks for the outer circumferential region may have different force or geometry compared to those for the winding center region, allowing each region to be formed with optimal local parameters, thereby achieving overall uniformity through localized optimization
Data Source
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AI summary
Provided is a foil tab forming apparatus for forming at least one foil tab of a positive electrode foil tab and a negative electrode foil tab respectively provided at a top portion and a bottom portion of an electrode assembly, the foil tab forming apparatus including: a pre-forming jig configured to bend the foil tab by pressing the foil tab, while moving in a direction from an outer circumferential portion of the electrode assembly to a winding center portion of the electrode assembly; and a forming jig configured to press the foil tab that has been primarily bent by the pre-forming jig, by moving along a direction parallel to a winding axis of the electrode assembly.