Coiled Cell With Grooved Membrane Tabs
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Solution Overview
Problem
Traditional wound structure in secondary batteries results in a significant reduction of energy density due to the large proportion of electrode tabs in the overall thickness of the cell, leading to inefficiencies in energy storage.
Innovation Solution
A cell design featuring a flat electrode assembly with electrode tabs embedded in grooves within the membranes, reducing the thickness and improving energy density, while also incorporating a first head section to alleviate membrane curl-up and enhance performance consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional wound structure with electrode tabs welded to bare region is used, then electrode connection is achieved, but cell thickness increases and energy density is reduced
Solution Approach 1:
The electrode tabs are nested within grooves formed in the membrane structure, allowing the tabs to be accommodated within the existing cell thickness rather than adding to it. This nesting approach enables the tabs to be integrated into the membrane without increasing overall cell dimensions, thereby maintaining high energy density.
Solution Approach 2:
The invention transitions from a traditional planar tab arrangement to a three-dimensional groove-based structure. By creating grooves in the membrane and positioning tabs within these grooves, the solution utilizes the vertical dimension to accommodate tabs without increasing the horizontal footprint or overall cell thickness, thus preserving energy density.
2Quantity of substance
If electrode tabs occupy large proportion of cell thickness, then electrode connection is ensured, but active material volume is reduced
Solution Approach 1:
The tabs are nested within grooves in the membrane, allowing them to occupy space that would otherwise be unused. This nesting maximizes the utilization of available volume for active material while ensuring proper tab connection, thereby increasing active material volume without proportionally increasing structural complexity.
Solution Approach 2:
The groove structure is implemented locally only where tabs are required, rather than throughout the entire cell structure. This localized approach maintains simplicity in regions where tabs are not needed while providing the necessary complex structure only at specific locations, thus balancing active material volume with manageable structural complexity.
3Reliability
If membrane is made continuous to protect electrode, then adhesion is improved, but membrane curl-up occurs
Solution Approach 1:
The continuous membrane is segmented by introducing grooves that create localized discontinuities. These grooves allow different regions of the membrane to move independently, accommodating thermal expansion and contraction differences between layers. This segmentation prevents curl-up while maintaining adhesion in the regions between grooves, thus preserving reliability without sacrificing membrane flatness.
Solution Approach 2:
The groove structure changes the physical parameters of the membrane by creating localized variations in thickness and flexibility. These parameter changes allow the membrane to accommodate stress and deformation without curling, while the grooved regions provide controlled flexibility that maintains adhesion between electrode and membrane layers.
Data Source
AI summary
A cell (1) includes a flat electrode assembly formed by superposing and winding respective starting ends of a first electrode sheet (10), a first separator (30), a second electrode sheet (20), and a second separator (40). A first electrode tab (50) and a second electrode tab (60) are both located in grooves of the membranes. Respective starting ends of a second outer membrane (202) and a second inner membrane (203) are both aligned with a starting end of the second current collector (201), and a starting end of a first outer membrane (102) is aligned with a starting end of the first current collector (101). A first head section (106) is provided on a surface of the first current collector (101) facing a center of the cell, and a starting end of the first head section (106) is aligned with the first current collector (101).