Asymmetric Separator Overhang in Wound Cells for Electrolyte Balance
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Solution Overview
Problem
In longitudinal type power storage cells, there is an imbalance in the distribution of the electrolyte solution due to frequent overflow from the upper end portion, leading to insufficient absorption by the separator sheet, resulting in uneven electrolyte distribution.
Innovation Solution
The separator sheet has a longer protruding length at the upper end portion compared to the lower end portion, acting as a weir to reduce overflow and improve absorption, with a ratio of 1.5 to 5 and a difference of 1 to 5 mm between the protruding lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separator sheet has equal protruding lengths at both end portions, then the structure is simple and symmetric, but electrolyte solution overflows frequently from the upper end portion causing imbalance in distribution
Solution Approach 1:
The separator sheet is designed with asymmetric protruding lengths at its two end portions. The first end portion has a longer protruding length than the second end portion. This asymmetric configuration creates different overflow resistance at each end, preventing electrolyte solution from overflowing at the upper end portion while maintaining simpler structure elsewhere, thus resolving the contradiction between distribution uniformity and structural complexity.
2Loss of substance
If the separator sheet protrudes longer at the upper end portion, then electrolyte solution overflow is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The invention specifies concrete parameter ranges for the protruding lengths: the first protruding length is 1 to 5 mm and the second protruding length is 0.5 to 2 mm, with their difference being 0.5 to 5 mm. By defining these specific parameter ranges, the invention transforms the qualitative requirement of 'longer protrusion' into quantifiable manufacturing specifications, thereby reducing electrolyte loss while controlling manufacturing precision requirements within achievable limits.
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 the imbalance in electrolyte solution distribution by minimizing overflow from the upper end portion, ensuring more even absorption and distribution within the wound electrode assembly.
Implementation Method 1
The separator sheet can suck up the electrolyte solution by capillary action
Data Source
AI summary
A power storage cell includes a cell case, a wound electrode assembly, and an electrolyte solution. The cell case houses the wound electrode assembly and the electrolyte solution. The wound electrode assembly includes a positive electrode sheet, a separator sheet, and a negative electrode sheet. In a winding axis direction, the wound electrode assembly has a first end portion and a second end portion. The first end portion faces a top wall. The second end portion is located opposite to the first end portion. At both the first end portion and the second end portion, the separator sheet extends outward with respect to the negative electrode sheet. At the first end portion, the separator sheet has a first protruding length. At the second end portion, the separator sheet has a second protruding length. The first protruding length is longer than the second protruding length.