Jelly-Roll Electrode Assembly With Graded Anode Coating Stability
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Solution Overview
Problem
Jelly-roll-type electrode assemblies in secondary batteries face issues with delamination of the negative electrode active material, deformation in shape, and the occurrence of cracks in the current collector due to repeated charging and discharging cycles.
Innovation Solution
The electrode assembly features a negative electrode with a current collector and active material layers stacked on its surfaces, where the first layer at the winding tip has a lower expansion ratio and higher bonding strength than the second layer at the rear end, with the first layer occupying 30% or less of the second layer's stacking area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a jelly-roll-type electrode assembly is used for easy manufacture and high energy density, then manufacturing efficiency and energy density are improved, but delamination of negative electrode active material and deformation occur during charging/discharging cycles
Solution Approach 1:
The patent applies local quality by creating a negative electrode with spatially varying properties: the winding tip region has higher bonding strength and lower expansion ratio to prevent delamination during contraction, while the rear end region has higher expansion ratio to accommodate expansion during charging. This local differentiation resolves the contradiction between manufacturing efficiency and reliability.
Solution Approach 2:
The negative electrode active material layer is segmented into functionally distinct regions: a first region at the winding tip with different properties than a second region at the rear end. This segmentation allows each region to be optimized for its specific mechanical role during charging/discharging cycles, preventing overall electrode failure while maintaining the jelly-roll structure's manufacturing advantages.
2Quantity of substance
If the negative electrode active material layer has high expansion ratio to accommodate charging, then charge capacity is improved, but delamination and deformation occur during expansion/contraction cycles
Solution Approach 1:
Different regions of the negative electrode are assigned different expansion ratios matching their functional requirements. The rear end region with higher charge capacity needs higher expansion ratio, while the winding tip region needs lower expansion ratio and higher bonding strength to maintain structural integrity. This local quality differentiation resolves the contradiction between charge capacity and structural stability.
3Ease of manufacture
If uniform active material layer is applied across the current collector, then manufacturing simplicity is maintained, but delamination occurs at regions with different expansion requirements
Solution Approach 1:
The patent implements local quality by applying different active material compositions to different regions of the current collector. The winding tip region receives material with higher bonding strength and lower expansion ratio, while the rear end region receives material optimized for higher expansion. This regional differentiation prevents delamination while remaining manufacturable through modified coating processes.
Solution Approach 2:
The coating process is segmented to apply different active material formulations to different spatial regions of the current collector. This segmentation allows each region to have optimized properties for its specific mechanical demands, resolving the contradiction between manufacturing simplicity and bonding reliability.
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 reduces deformation of the electrode assembly, prevents cracks and disconnection in the current collector, and enhances the stability of the secondary battery by minimizing delamination of the electrode active material.
Implementation Method 1
the first negative electrode active material layer has a lower expansion ratio than the second negative electrode active material layer
Implementation Method 2
the first negative electrode active material layer has higher bonding strength than the second negative electrode active material layer
Data Source
AI summary
An electrode assembly, in which a positive electrode, a first separator, a negative electrode, and a second separator are wound, in which the negative electrode includes a negative electrode current collector, and a negative electrode active material layer stacked on at least a part of one surface or two opposite surfaces of the negative electrode current collector. The negative electrode active material layer includes a first negative electrode active material layer positioned at a winding tip, and a second negative electrode active material layer positioned at a rear end of the first negative electrode active material layer. The first negative electrode active material layer and the second negative electrode active material layer have different properties.