Cylindrical Electrode Assembly Cutting for Low-Resistance Current Collection
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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.
Innovation Solution
The electrode assembly design includes uncoated portions at the ends of the jelly-roll type electrode sheets, which are welded to current collector plates, increasing the welding cross-sectional area and reducing resistance, while a cutting and bending process forms a forming portion that covers the gaps between these uncoated areas, enhancing current flow and preventing deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If strip-shaped electrode tabs are used to connect uncoated portions, then the battery cell structure is simple and easy to manufacture, but current is concentrated in the electrode tab causing high resistance, heat generation, and low current-collection efficiency
Solution Approach 1:
The uncoated portion is divided into multiple segments: a first uncoated portion for welding the first current collector plate, a second uncoated portion for welding the second current collector plate, and a third uncoated portion positioned between them. This segmentation distributes current flow paths and reduces current concentration, thereby improving current-collection efficiency while maintaining manufacturing simplicity
Solution Approach 2:
The electrode assembly transitions from a two-dimensional strip-shaped electrode tab connection to a three-dimensional multi-point connection structure. By positioning uncoated portions at different locations (first, second, and third uncoated portions) and connecting them to respective current collector plates, the current flow is distributed across multiple spatial dimensions, reducing resistance and heat generation
2Quantity of substance
If the form factor is increased to apply cylindrical battery cell to electric vehicles, then the energy capacity increases, but a large amount of heat may be generated around the electrode tab during rapid charging causing ignition risk
Solution Approach 1:
The current collection function is segmented across multiple uncoated portions and current collector plates instead of relying on a single electrode tab. This distributes the current flow and reduces heat concentration at any single point, mitigating ignition risk during rapid charging of large-capacity battery cells
Solution Approach 2:
Multiple current collector plates are introduced as intermediary components between the uncoated portions and the external circuit. These intermediaries provide additional heat dissipation surfaces and distribute current flow, reducing the thermal load on any single connection point and preventing heat-induced ignition
3Reliability
If uncoated portions are welded to current collector plates at upper and lower ends, then current collection efficiency is improved, but the welding cross-sectional area is limited causing resistance
Solution Approach 1:
The current collection interface is segmented into multiple welding zones: first uncoated portion welded to first current collector plate, second uncoated portion welded to second current collector plate, and third uncoated portion providing additional welding area. This segmentation increases the total welding cross-sectional area and reduces contact resistance
Solution Approach 2:
The welding interface extends from a single-plane connection to a multi-level three-dimensional structure. By positioning uncoated portions at different axial locations (upper, middle, lower ends) and connecting them to respective current collector plates, the welding cross-sectional area is increased across multiple spatial dimensions, reducing resistance and energy loss
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 reduces the heating amount and the risk of ignition, improves current collection efficiency, and increases the electric capacity of the battery cell without compromising the electrolyte injection process.
Implementation Method 1
a first current collector plate electrically connected to the other one of the first electrode sheet and the second electrode sheet to have a second polarity... increasing the welding cross-sectional area and reducing resistance
Data Source
AI summary
Discussed is a cutting device configured to cut at least a portion of an uncoated portion of an electrode assembly. The cutting device can include a first cutter portion to cut the uncoated portion in an axial direction while moving in the axial direction to form a pair of first cut lines parallel to a diameter direction of the uncoated portion; and a second cutter portion to form a pair of second cut lines in the uncoated portion in a peripheral direction while moving in a radial direction of the electrode assembly to form a pair of cut surface portions on an outer side of the pair of first cut lines of the uncoated portion by connecting each of the pair of second cut lines to corresponding first cut lines and cutting out a portion of the uncoated portion defined by the first cut lines and the second cut lines.