Aromatic Polyamide Separator Film for Capacitors
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Solution Overview
Problem
Current separators for capacitors and batteries face challenges in achieving high heat resistance, low electrical resistance, reduced thickness, and high air permeability, while maintaining affinity with electrolytes, especially under high temperature conditions and during manufacturing processes.
Innovation Solution
A porous aromatic polyamide film is developed, comprising aromatic polyamide and a hydrophilic polymer, with specific composition and structural properties that enhance heat resistance, air permeability, and electrolyte retention, suitable for use as separators in capacitors and batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator consists of a heat-resistant layer on one side or both sides of a microporous film comprising a low melting point resin, then shutdown property is achieved, but inability to resist use in high temperature atmosphere and thermal contraction during abnormal heating occurs
Solution Approach 1:
The invention uses a composite structure consisting of a microporous film (providing shutdown function) and a heat-resistant coating layer (providing high temperature resistance). The coating layer contains aromatic polyamide and hydrophilic polymer in specific ratios, creating a composite material that combines the advantages of both components while eliminating their individual weaknesses.
2Productivity
If the thickness of separator is reduced to provide high output, then low resistance is achieved, but difficulty in maintaining sufficient strength occurs
Solution Approach 1:
The heat-resistant coating layer acts as a reinforcing layer that provides mechanical strength to the thin microporous film substrate. This composite structure enables the separator to maintain sufficient strength even when the overall thickness is reduced to 50 μm or less, allowing high output performance while preventing film breakage.
3Temperature
If nonwoven fabric or paper-like sheet of aromatic polyamide fiber is used as separator, then high heat resistance is achieved, but difficulty in industrially producing uniform sheets with sufficient strength and small thickness occurs
Solution Approach 1:
The invention employs a microporous film as the base structure, which can be manufactured uniformly using established membrane fabrication techniques. The porous structure is then coated with aromatic polyamide and hydrophilic polymer, creating a uniform composite separator that maintains consistent properties across large production scales while achieving both heat resistance and mechanical strength.
4Adaptability or versatility
If plasma treatment is carried out for nonwoven fabrics of aromatic polyamide to improve affinity with electrolyte, then affinity is enhanced, but rapid deterioration in hydrophilicity over time and breakage of molecular chains occur
Solution Approach 1:
Instead of using plasma treatment, the invention changes the chemical composition parameters by incorporating a hydrophilic polymer (such as polyvinyl alcohol, polyacrylonitrile, or carboxymethyl cellulose) in specific ratios (5-50 parts by mass per 100 parts by mass of aromatic polyamide). This compositional modification provides sustained electrolyte affinity without the degradation issues associated with plasma treatment.
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 porous film exhibits excellent heat resistance, low electrical resistance, and high air permeability, ensuring effective performance as separators for capacitors and batteries, even under high temperature conditions, with improved durability and productivity.
Implementation Method 1
a porous aromatic polyamide film comprising aromatic polyamide and a hydrophilic polymer wherein the hydrophilic polymer accounts for 12 to 50 parts by mass per 100 parts by mass of the aromatic polyamide, the Gurley air permeability being 0.5 to 300 seconds/100 ml, and the thermal shrinkage rate being −0.5 to 1.0% at 200° C.
Implementation Method 2
the Gurley air permeability being 0.5 to 300 seconds/100 ml
Data Source
AI summary
A porous film includes aromatic polyamide as a constituent component that has high heat resistance, high air permeability and high affinity to electrolytes. It is a porous aromatic polyamide film including aromatic polyamide and a hydrophilic polymer, wherein the hydrophilic polymer accounts for 12 to 50 parts by mass per 100 parts by mass of the aromatic polyamide, the thickness being 2 to 30 micrometers, the Gurley air permeability being 0.5 to 300 seconds/100 ml, and the thermal shrinkage rate being −0.5 to 1.0% at 200° C.