Cylindrical Cell Electrode Assembly for Lower Tab Resistance
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Solution Overview
Problem
Large-capacity cylindrical battery cells experience increased inner resistance and heat generation near the electrode tab during rapid charging, leading to potential fires due to concentrated current and high resistance.
Innovation Solution
The implementation of a jelly roll-type electrode assembly with a combination of tab and tabless structures, where the first electrode has a tab structure with multiple tabs to reduce resistance, and the second electrode employs a tabless structure with uncoated portions that act as wide current paths to minimize resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a strip-shaped electrode tab is used to connect the anode and cathode, then the current collection is simplified, but the resistance increases and heat generation occurs
Solution Approach 1:
The electrode tabs are segmented into multiple separate tabs instead of using a single strip-shaped tab. The anode has multiple anode tabs and the cathode has multiple cathode tabs distributed along the electrode length, which divides the current collection points and reduces concentration of current at single points, thereby reducing resistance and heat generation.
Solution Approach 2:
The electrode tabs extend in the axial direction of the cylindrical cell, utilizing the length dimension of the cell. By positioning tabs at different axial locations and making them extend axially, the current collection is distributed along the length of the cell, effectively increasing the current collection area and reducing resistance without complicating the radial structure.
2Reliability
If the number of electrode tabs is increased to widen current path, then resistance is reduced, but device complexity increases
Solution Approach 1:
Different electrodes have different tab configurations optimized for their specific requirements. The anode uses multiple tabs while the cathode uses a tabless structure with uncoated portions, allowing each electrode to have the optimal current collection design for its characteristics without forcing a uniform complex structure on both.
Solution Approach 2:
Instead of adding more tabs to both electrodes, the invention inverts the approach by using a tabless structure for the cathode where the uncoated portion itself serves as the current collection area. This eliminates the need for separate cathode tabs and simplifies the overall structure while still achieving low resistance.
3Reliability
If a tabless structure with uncoated portions is used for the second electrode, then resistance is reduced through wide current paths, but manufacturing precision requirements increase
Solution Approach 1:
The uncoated portions are prepared in advance during the electrode manufacturing process, before assembly into the cell. By pre-forming the uncoated portions with appropriate dimensions and positions on the electrode sheets, the manufacturing precision is managed at the electrode fabrication stage where it is more controllable, rather than requiring precise positioning during cell assembly.
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 configuration effectively decreases resistance in both electrodes, preventing thermal degradation and improving current collection efficiency while maintaining spatial availability and manufacturing simplicity.
Implementation Method 1
current connects to a cell can lid 63 or a cell can 6 only through an anode tab 23 or a cathode tab 43 provided in one or two points of each of an anode 2 and a cathode 4, at both of the anode 2 and the cathode 4. At this time, the surface area of a current path is narrowed, causing an increase in resistance
Implementation Method 2
current concentrates on the strip-shaped electrode tab coupled with the anode uncoated portion and/or the cathode uncoated portion, causing an increase in resistance, generating large amounts of heat
Data Source
AI summary
An electrode assembly includes an electrode stack having a first electrode, a first separation layer, a second electrode and a second separation layer consecutively stacked, the electrode stack being wound around a winding axis in a winding direction, and a first electrode tab electrically connected to the first electrode, the first electrode tab protruding in an axial direction away from a first end of the first electrode. The second electrode includes a second electrode uncoated portion where an active material is not coated, the second uncoated portion being exposed at a second end of the second electrode in the axial direction, the second uncoated portion being configured to be a second electrode tab. A battery cell including the electrode assembly is also provided.