Polyethylene Resin Composition for Microporous Battery Separators
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Solution Overview
Problem
Current methods for manufacturing polyolefin microporous films, such as those used in battery separators, fail to meet the demands for higher air permeation, mechanical strength, and processability, especially for large-size industrial batteries and electric vehicles.
Innovation Solution
A polyethylene resin composition with specific melt flow rate, molecular weight distribution, density, and cross-fractionation chromatography characteristics is developed, comprising an ethylene homopolymer with a specific blend of components, which enhances the air permeability and mechanical strength of the microporous films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional polyethylene blending methods are used to improve air permeation, then porosity increases, but mechanical strength deteriorates
Solution Approach 1:
The invention changes the molecular weight distribution parameters of polyethylene from conventional broad distributions (Mw/Mn > 10) to a specific narrow distribution (Mw/Mn = 2.0 to 5.0). This parameter change enables simultaneous achievement of high air permeation (porosity 30-80%) and maintained mechanical strength, resolving the traditional trade-off between porosity and strength
Solution Approach 2:
The invention creates a composite resin composition by blending polyethylene with specific molecular weight distribution (Mw/Mn = 2.0 to 5.0) and polypropylene in specific ratios. This composite approach allows the polyethylene component to provide porosity control while the polypropylene component contributes to mechanical strength, achieving both high air permeation and adequate strength
2Productivity
If separator thickness is reduced to improve battery energy density, then productivity increases, but mechanical strength deteriorates
Solution Approach 1:
The invention changes the molecular weight distribution parameter (Mw/Mn = 2.0 to 5.0) of polyethylene to achieve uniform pore structure and controlled crystallinity in thin films. This enables production of separators with thickness of 15 μm or less while maintaining adequate mechanical strength and shutdown function, resolving the contradiction between thinness and strength
3Ease of manufacture
If molecular weight distribution is broadened to improve processability, then ease of manufacture increases, but mechanical strength deteriorates
Solution Approach 1:
The invention optimizes the molecular weight distribution parameter to a specific narrow range (Mw/Mn = 2.0 to 5.0), which provides adequate processability for film formation while simultaneously ensuring high mechanical strength. This specific parameter range avoids the strength deterioration associated with broad distributions while maintaining manufacturability
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 polyethylene resin composition improves the processability and performance of microporous films, providing enhanced air permeability and mechanical strength suitable for high-output batteries, including those for electric vehicles.
Implementation Method 1
a microporous film production method comprising: a micropore formation step of forming micropores in a polyethylene resin composition film
Implementation Method 2
a raw film production step of producing a raw film by stretching and extruding the polyethylene resin composition
Data Source
AI summary
The present disclosure relates to a polyethylene resin composition contains an ethylene homopolymer.