Polyethylene Powder Composition for Uniform Battery Separator Pores
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Solution Overview
Problem
Existing polyethylene resin compositions for battery separators lack improved shutdown function, long-term stability, and uniform pore structure, leading to issues such as unmelted materials, non-uniform ion transmission, and poor mechanical strength.
Innovation Solution
A polyethylene powder with controlled viscosity average molecular weight, specific torque curve slope, and kneading conditions to achieve uniform molecular chain entanglement and improved dispersibility, resulting in a microporous membrane with enhanced shutdown function and long-term stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyethylene powders with high molecular weight are used to improve mechanical strength, then strength is improved, but dispersibility in solvents deteriorates leading to unmelted materials and filter clogging
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular weight distribution (Mw/Mn ratio between 2.0-5.0) and viscosity average molecular weight (100,000-2,500,000) of polyethylene. This optimization balances the mechanical strength provided by higher molecular weight with the dispersibility required for smooth processing, eliminating both unmelted materials and filter clogging while maintaining strength.
2Strength
If polyethylene resin composition is used to provide mechanical strength, then strength is improved, but shutdown function and long-term stability remain insufficient
Solution Approach 1:
The patent optimizes the viscosity average molecular weight to 100,000-2,500,000 and molecular weight distribution (Mw/Mn: 2.0-5.0) to achieve a balance where the resin provides sufficient mechanical strength while maintaining appropriate melting characteristics for shutdown function and uniform pore structure for long-term stability.
Solution Approach 2:
The patent uses polyethylene with specifically controlled molecular weight distribution as a composite material system where the distribution itself acts as a composite structure, combining low-molecular-weight components for good dispersibility and processing with high-molecular-weight components for mechanical strength, while achieving uniform melting behavior for reliable shutdown function.
3Strength
If components with high molecular weight remain in microporous membrane, then mechanical strength is improved, but appearance deteriorates due to unmelted materials
Solution Approach 1:
The patent controls the molecular weight distribution (Mw/Mn ratio: 2.0-5.0) to ensure that high-molecular-weight components provide mechanical strength while the overall distribution allows complete melting and uniform dispersion, eliminating unmelted materials and achieving excellent appearance uniformity in the microporous membrane.
4Strength
If molecular chains are strongly entangled to improve mechanical strength, then strength is improved, but pore structure uniformity deteriorates causing non-uniform ion transmission
Solution Approach 1:
The patent optimizes the viscosity average molecular weight (100,000-2,500,000) and molecular weight distribution (Mw/Mn: 2.0-5.0) to achieve moderate molecular chain entanglement. This provides sufficient mechanical strength while preventing excessive entanglement that would cause non-uniform pore structure, ensuring uniform ion transmission and long-term stability.
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 powder produces a microporous membrane with excellent appearance, high shutdown function, and uniform pore structure, ensuring stable battery performance over time.
Implementation Method 1
a slope of a straight line connecting two local maximum points in a torque curve obtained when kneading the polyethylene powder under predetermined kneading conditions is 2 N·m/min or more and 15 N·m/min or less
Implementation Method 2
a function to close the pores at a temperature lower than the temperature at which a thermal runaway occurs, a so-called fuse effect
Implementation Method 3
a function to allow only ions to pass through while separating the positive and negative electrodes
Implementation Method 4
a function to close the pores at a temperature lower than the temperature at which a thermal runaway occurs
Data Source
AI summary
A polyethylene powder having a viscosity average molecular weight of 100,000 or more and 2,500,000 or less, wherein, in a torque curve obtained when kneading the polyethylene powder under specific <Kneading Conditions> using a Labo Plastomill, a slope of a straight line connecting two local maximum points is 2 N·m/min or more and 15 Nm/min or less.