Thin Porous Battery Separator for Low Resistance and Heat Stability
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Solution Overview
Problem
Conventional polyolefin-based microporous membranes used in electrochemical device separators exhibit heat shrinking behavior and increased thickness due to a porous coating layer, leading to degradation of resistance characteristics and low ion conductivity, which inhibits the realization of high-output batteries.
Innovation Solution
A separator with a porous substrate made of polyethylene having a molecular weight of 2,500 g/mol or less and a porosity of 40-70%, featuring an inorganic coating layer with a binder ratio of 99.9:0.1-90:10, which includes inorganic particles and a binder resin, and is designed to have a thickness of 5-14 µm with a resistance of 0.5 ohm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous coating layer is added to the polyolefin-based microporous membrane, then heat shrinkage resistance is improved, but separator thickness increases and resistance characteristics degrade
Solution Approach 1:
The patent removes the binder polymer from the coating layer formulation, extracting the harmful element that causes resistance degradation while retaining the protective function against heat shrinkage through inorganic particles alone
Solution Approach 2:
The patent employs a porous coating layer with controlled porosity to maintain ion conductivity pathways while providing heat shrinkage resistance, allowing ions to pass through the porous structure without significant resistance increase
2Strength
If binder polymer is added to the porous coating layer, then coating integrity is improved, but resistance characteristics degrade
Solution Approach 1:
The patent completely removes or eliminates the binder polymer from the coating layer, using only inorganic particles to form the coating structure, thereby preventing resistance degradation while maintaining coating integrity through particle packing and adhesion mechanisms
Solution Approach 2:
The patent uses inorganic particles with specific surface properties and sizing to provide localized adhesion and structural integrity without requiring organic binder materials that would degrade resistance characteristics
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 separator provides excellent resistance characteristics and ion conductivity, enabling improved output characteristics and safety in electrochemical devices, particularly in high-output applications such as electric vehicles.
Implementation Method 1
the porous substrate has a porosity of 40 - 70%, the porous substrate shows at least two peaks at 130 - 160°C upon the initial temperature-rising in its differential scanning calorimetry (DSC) and wherein the separator has an inorganic coating layer formed on at least one surface of the porous substrate
Implementation Method 2
the porous substrate has a porosity of 40 - 70%
Implementation Method 3
Conventional polyolefin-based microporous membranes used conventionally for separators for electrochemical devices show severe heat shrinking behavior at a temperature of 100°C or more due to their material properties and processing characteristics
Implementation Method 4
the separator provides excellent resistance characteristics and ion conductivity
Data Source
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AI summary
Provided is a separator for an electrochemical device. The separator includes a separator substrate made of a porous polymer material, wherein the separator substrate has a small thickness, excellent resistance characteristics and ion conductivity, and high mechanical strength. When the separator is applied to a battery, it is possible to improve the output characteristics of the battery.