Ultra-Fine Fiber Separator for Thin Electrochemical Devices
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Solution Overview
Problem
Conventional electrochemical devices, such as electric double layer capacitors, face issues with thickness reduction while maintaining capacity and preventing leakage current and short circuits when using thin nonwoven fabric separators.
Innovation Solution
A nonwoven fabric separator with an average fiber diameter of 0.1 to 1.0 μm and a thickness of 5 μm or more is used, ensuring a thickness-to-fiber diameter ratio greater than 20, which enhances in-plane uniformity and prevents short circuits by keeping active material particles from entering pinholes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the separator is thinned to reduce device thickness, then the device thickness is reduced, but uniformity deteriorates and leakage current increases
Solution Approach 1:
The patent changes the fiber diameter parameter to an ultra-fine range (0.1 to 1.0 μm) and optimizes the thickness-to-fiber diameter ratio (T/Df) to be at least 20. This parameter transformation allows the separator to achieve both thinness (reducing device thickness) and uniformity (preventing leakage current) by creating a densely packed fiber network that maintains structural integrity even at reduced thickness.
2Length of moving object
If the separator is thinned to reduce device thickness, then the device thickness is reduced, but the risk of short circuit increases due to pinholes
Solution Approach 1:
By transforming the fiber diameter parameter to ultra-fine dimensions (0.1 to 1.0 μm) and controlling the T/Df ratio to be at least 20, the patent creates a separator with sufficiently dense structure that eliminates pinholes. This parameter optimization ensures that even when the separator is thinned to reduce device thickness, the ultra-fine fibers pack densely enough to prevent active material particles from penetrating through, thereby eliminating short circuit risk.
3Ease of manufacture
If conventional nonwoven fabric is used as separator, then manufacturing is easy, but thickness reduction below 20 μm causes uniformity deterioration
Solution Approach 1:
The patent transforms the fiber diameter parameter to an ultra-fine range (0.1 to 1.0 μm), which fundamentally changes the packing behavior of fibers. At this scale, fibers can be densely packed even in thin separators, naturally achieving uniform structure without complex manufacturing controls. This parameter transformation maintains ease of manufacture using conventional nonwoven fabric processes while achieving superior in-plane uniformity that prevents leakage current.
4Length of moving object
If separator thickness is reduced to thin devices, then device thickness is reduced, but separator strength becomes insufficient
Solution Approach 1:
By transforming the fiber diameter to ultra-fine dimensions (0.1 to 1.0 μm) and optimizing the T/Df ratio to be at least 20, the patent creates a separator where numerous ultra-fine fibers densely pack together. This creates a network with high fiber count per unit area, providing sufficient mechanical strength even when the overall separator thickness is reduced. The ultra-fine fibers distribute mechanical stress more effectively across the thin structure.
Data Source
AI summary
In an electrochemical device comprising a multilayer body having a separator and a pair of electrodes disposed so as to hold the separator therebetween, and an electrolyte infiltrated in the multilayer body; the electrodes contain an active material particle; the separator is made of a nonwoven fabric having an average fiber diameter Df of 0.1 to 1.0 μm; T≧5 μm and T/Df≧20, where T is the thickness of the separator; and Dp<T, where Dp is the average particle size of the active material particle.