Separator Tortuosity and Vacancy Control for Battery Resistance
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Solution Overview
Problem
Nonaqueous electrolyte batteries face challenges with high separator resistance, which can lead to internal short circuits and capacity reduction due to self-discharge, while existing solutions either increase resistance or risk internal shorts.
Innovation Solution
A nonaqueous electrolyte battery with a separator made of a fiber-made nonwoven fabric having a tortuosity of 1.8 to 3 and a vacancy of 40% to 60%, utilizing fibers like cellulose or polyester, which enhances lithium ion diffusivity and prevents internal short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the vacancy of the separator is increased to decrease resistance, then the resistance decreases, but the rate of occurrence of internal short circuit increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the tortuosity (1.8 to 3.0) and vacancy (40% to 60%) of the separator to optimize both resistance and safety. This specific parameter range allows the separator to achieve low resistance while preventing internal short circuits through controlled ion transport pathways.
Solution Approach 2:
The patent uses composite materials by combining polyolefin resin with inorganic filler particles (such as alumina, silica, or boehmite). This composite structure reduces resistance through the inorganic filler's high ion conductivity while the polyolefin matrix maintains mechanical strength and short-circuit prevention capabilities.
2Loss of energy
If a nonwoven fabric separator is used to reduce resistance, then resistance decreases, but the strength may be insufficient to prevent internal shorts
Solution Approach 1:
The patent combines polyolefin resin fibers with inorganic filler particles to create a composite nonwoven fabric. The inorganic filler (alumina, silica, or boehmite) provides structural strength and rigidity, while the polyolefin matrix ensures flexibility and bonding. This composite structure simultaneously achieves low resistance and high strength to prevent internal short circuits.
Solution Approach 2:
The patent applies local quality by creating regions with different properties within the separator. The inorganic filler particles are distributed throughout the polyolefin matrix, creating local high-conductivity pathways for ion transport while the polyolefin regions maintain mechanical integrity. This local differentiation allows simultaneous optimization of electrical and mechanical properties.
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 reduces battery resistance, suppresses capacity reduction due to self-discharge, and improves rate performance by increasing the volume for lithium ion movement while maintaining sufficient strength to prevent internal shorts.
Implementation Method 1
enhances lithium ion diffusivity
Implementation Method 2
the resistance of the separators considered so far is still high
Data Source
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AI summary
According to one embodiment, provided is a nonaqueous electrolyte battery that includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte. The separator is disposed between the positive electrode and the negative electrode. The separator includes a fiber-made nonwoven fabric having a tortuosity of 1.8 to 3 and a vacancy of 40% to 60%. The negative electrode has an operating potential of 0.7 V or more with respect to the potential of metallic lithium.