Fibrous Battery Separator With Controlled Pores for Short-Circuit Prevention
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Solution Overview
Problem
Conventional separators for electrochemical elements, such as those used in lithium ion batteries, face limitations in providing low electric resistance and preventing electric short circuits due to large maximum pore diameters and wide pore diameter distributions, which can lead to direct contact between electrodes and ion permeability inconsistencies.
Innovation Solution
A separator with a fibrous structure comprising a first fibrous layer part where short fibers and/or pulp-like fibers are intertwined, and a second fibrous layer part where some of these fibers penetrate, with a pore diameter distribution satisfying 0 μm < Dmax < 18 μm and 0 μm ≤ (Dmax - Dave) < 13 μm, and a percentage of pulp-like fibers by mass of 10% or more, enhancing strength and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a nonwoven fabric with large maximum pore diameter is used, then ion permeability is improved, but electric short circuit risk increases due to direct contact between electrodes
Solution Approach 1:
The patent employs a porous nonwoven fabric structure with specifically controlled pore diameter distribution (0.01 μm < Dmax < 15 μm and 0 μm ≤ (Dmax - Dave) < 10 μm) to achieve optimal ion permeability while preventing electrode contact. The porous structure allows ion transport necessary for battery operation, while the controlled pore size distribution ensures pores are small enough to prevent direct electrode contact and dendrite penetration.
2Ease of manufacture
If a nonwoven fabric with wide pore diameter distribution is used, then manufacturing is simplified, but ion permeability becomes non-uniform leading to higher electric resistance
Solution Approach 1:
The patent applies parameter changes by strictly controlling the pore diameter distribution parameters (Dmax and Dave) within specific ranges. By defining that 0.01 μm < Dmax < 15 μm and 0 μm ≤ (Dmax - Dave) < 10 μm, the invention transforms the manufacturing process into one that produces uniform ion permeability characteristics. This parameter control ensures consistent electrical resistance and performance across different batches while maintaining manufacturing feasibility.
3Power
If separator thickness is reduced to lower electric resistance, then electric output properties improve, but strength decreases and cracks may form causing short circuits
Solution Approach 1:
The patent utilizes a thin nonwoven fabric separator (with controlled pore structure) that functions as a flexible barrier between electrodes. The thin film structure minimizes ionic resistance and improves electric output, while the specific pore diameter distribution and fiber composition provide sufficient mechanical strength to prevent cracking and maintain integrity during battery operation.
Solution Approach 2:
The separator is constructed as a composite nonwoven fabric combining different fiber types and structures to achieve both thinness and strength. By controlling the pore diameter distribution and using appropriate fiber materials, the separator achieves a composite structure that simultaneously provides low ionic resistance for high power output and adequate mechanical strength to prevent short circuits.
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 proposed separator effectively prevents electric short circuits and maintains low electric resistance by ensuring a narrow pore diameter distribution, high strength, and uniform ion permeability, thereby improving the performance of electrochemical elements.
Implementation Method 1
the ion permeability of respective areas in the separator for an electrochemical element is likely to be non-uniform
Data Source
AI summary
Disclosed herein is a separator for an electrochemical element, comprising a fibrous structure, wherein the fibrous structure has a first fibrous layer part in which short fibers and/or pulp-like fibers are intertwined with each other, and a second fibrous layer part; some of the short fibers and/or the pulp-like fibers constituting the first fibrous layer part penetrates the second fibrous layer part; and a pore diameter distribution of the fibrous structure satisfies the following formula: 0 μm<Dmax<18 μm, and 0 μm≤(Dmax−Dave)<13 μm, wherein Dmax is a maximum pore diameter (μm) of the fibrous structure, and Dave is an average pore diameter (μm) of the fibrous structure.