Jelly-Roll Electrode Assembly Layout to Prevent Separator Damage
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Solution Overview
Problem
Conventional cylindrical batteries face issues with irregular deformation and potential short circuits due to bent exposed parts in the jelly-roll type electrode assembly, leading to ignition or explosion, especially when used in electric vehicles.
Innovation Solution
The electrode assembly design includes first and second electrodes with exposed parts that have bending points set differently in the radial direction, preventing irregular deformation by gradually increasing the length of these parts with each winding turn, and using segments to guide electrical connection without tabs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the exposed parts are bent toward the core part to join the current collecting plate, then the current collection efficiency is improved, but the exposed parts show irregular deformation and may damage the separator causing short circuits
Solution Approach 1:
The exposed part is divided into multiple segments along the winding direction, with each segment bendable independently. This segmentation allows controlled deformation that avoids irregular folding and separator damage while maintaining current collection efficiency.
Solution Approach 2:
Different regions of the exposed part have different properties: the first region has first bending characteristics while the second region has second bending characteristics. This local differentiation enables selective bending behavior that prevents harmful deformation patterns.
2Ease of manufacture
If the length from the end of the current collector to the bending point is constant for all winding turns, then the manufacturing process is simplified, but the stacked exposed parts show irregular deformation
Solution Approach 1:
The length from the end of the current collector to the bending point varies by winding turn, with outer winding turns having longer lengths than inner winding turns. This parameter variation compensates for radial position differences and ensures uniform stacking without irregular deformation.
3Device complexity
If strip-shaped electrode tabs are used to connect positive and negative electrodes, then the electrical connection is simplified, but the current is concentrated causing large resistance and heat generation
Solution Approach 1:
The current collection structure transitions from one-dimensional strip tabs to two-dimensional exposed surfaces. The exposed parts of the current collectors directly serve as current collection areas, increasing the effective cross-sectional area for current flow and reducing resistance and heat generation.
Data Source
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AI summary
An electrode assembly according to an embodiment of the present disclosure comprises: a first electrode; a second electrode; and a separator interposed between the first electrode and the second electrode. The first electrode, the second electrode, and the separator are wound together to form a jelly roll structure. The first electrode includes a first electrode current collector and a first active material part formed by applying an electrode active material to one side or both sides of the first electrode current collector. The second electrode includes a second electrode current collector and a second active material part formed by applying an electrode active material to one side or both sides of the second electrode current collector. A first exposed part to which the electrode active material is not applied in the first electrode current collector extends in a first direction, and a second exposed part to which the electrode active material is not applied in the second electrode current collector extends in a second direction opposite to the first direction. The first exposed part and the second exposed part have a bending point for each winding turn. The length from the end of the first electrode current collector in the second direction to the bending point of the first exposed part gradually increases for each winding turn along the radial direction of the jelly roll structure. The radial direction is a direction directed from a core part to an outer part of the jelly roll structure.