Battery Separator Suppression Portions for Crack Prevention
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Solution Overview
Problem
In batteries with flat wound electrode bodies, excessive temperature can cause the separator to shrink, leading to cracks that may result in a short circuit between the positive and negative electrode sheets due to thermal stress, especially at the curved portions of the oval-shaped cross section.
Innovation Solution
Incorporating suppression portions in the edge adjacent portions of the separator, particularly in the curved portions of the flat wound electrode body, to prevent crack formation and growth, these suppression portions can be made of differently oriented polymer resin material or reinforced with resin tape, and are arranged in specific configurations to extend along the winding circumferential direction or in a separated pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the separator is made thin to reduce battery size, then the battery volume is reduced, but the separator becomes more prone to cracking when thermally shrunk
Solution Approach 1:
The patent applies local quality by providing suppression portions at specific locations (edge adjacent portions and curve positioned portions) of the separator rather than uniformly throughout. These localized reinforcement zones prevent cracks at the most vulnerable areas where thermal shrinkage causes maximum stress, allowing the rest of the separator to remain thin for volume reduction.
Solution Approach 2:
The suppression portions are formed by superimposing resin layers with different orientation states on the separator. This creates a composite structure where the base separator provides separation function while the suppression portions with differently oriented polymers provide enhanced crack resistance at critical locations.
2Reliability
If the separator is made thick to prevent cracking, then the battery volume increases, but the battery size becomes larger
Solution Approach 1:
Instead of uniformly thickening the entire separator, the invention applies suppression portions only at the edge adjacent portions and curve positioned portions where cracks are most likely to occur during thermal shrinkage. This localized approach provides necessary crack resistance while keeping the overall separator thickness minimal, thus maintaining compact battery volume.
3Strength
If the separator is uniformly reinforced to prevent cracks, then the separator strength is improved, but the battery weight increases
Solution Approach 1:
The suppression portions are localized to specific areas (edge adjacent portions and curve positioned portions) rather than being uniformly distributed across the entire separator. This means additional resin material and weight are added only where crack prevention is most critical, minimizing the overall weight increase while still providing enhanced strength where needed.
4Volume of stationary object
If the separator shrinks thermally to reduce volume, then the battery becomes more compact, but cracks occur in the separator
Solution Approach 1:
The suppression portions are pre-formed on the separator before it undergoes thermal shrinkage during battery operation. These suppression portions with differently oriented polymers create preliminary resistance against the tensile stresses that develop during thermal shrinkage, preventing cracks from forming even as the separator contracts and the battery becomes more compact.
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
The solution effectively prevents the occurrence and growth of cracks in the separator, thereby avoiding short circuits between the positive and negative electrode sheets even when the battery's internal temperature increases, ensuring reliable operation.
Implementation Method 1
a separator thermally shrinks in a winding circumferential direction
Implementation Method 2
a portion having a different orientation state of polymer constituting the resin material
Data Source
AI summary
A battery includes a flat wound electrode body formed by winding a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween into a flat shape. The separator has an outer edge adjacent portion adjacent to either an outer edge of a positive electrode active material layer or an outer edge of a negative electrode active material layer. In a curve positioned portion disposed at least in a curved portion of the flat wound electrode body, the outer edge adjacent portion has a suppression portion for suppressing the occurrence or development of a crack.