Microporous Membrane for Battery Separator Safety
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Solution Overview
Problem
Larger-sized lithium-ion batteries face challenges in ensuring safety due to increased Joule heat generation and friction issues during the battery winding process, which complicates current interruption and pin removability, leading to potential safety risks and productivity problems.
Innovation Solution
A microporous membrane comprising copolymerized high density polyethylene with specific molecular weight and α-olefin unit content, combined with high density polyethylene and optionally polypropylene, is developed to achieve a lower fuse temperature and reduced friction, enabling faster current interruption and improved pin removability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene microporous membrane is used as battery separator, then fuse effect is achieved at around 140°C, but current interruption speed is insufficient and pin removability deteriorates in larger-sized batteries
Solution Approach 1:
The patent changes the chemical composition parameters of the polyethylene membrane by incorporating specific additives and copolymers. This modifies the membrane's thermal properties to achieve fuse temperature between 120-140°C while maintaining mechanical integrity, thereby improving current interruption speed without sacrificing fuse effect reliability
Solution Approach 2:
The patent creates a composite microporous membrane structure combining polyethylene base material with functional additives and copolymer components. This composite approach enables simultaneous optimization of fuse characteristics, mechanical strength, and surface friction properties for improved pin removability
2Quantity of substance
If larger-sized batteries are used to increase capacity, then battery capacity is improved, but Joule heat generation increases and safety becomes more difficult to ensure
Solution Approach 1:
The patent modifies the thermal parameters of the separator membrane by adjusting polymer composition and molecular weight distribution. This enables the membrane to maintain structural stability at elevated temperatures while facilitating rapid shutdown, thereby managing Joule heat effects in high-capacity batteries
Solution Approach 2:
The patent converts the thermal energy (Joule heat) that would normally cause safety issues into a beneficial shutdown mechanism. By designing the membrane with specific thermal response characteristics, the heat generated during overcharge triggers controlled membrane melting and pore closure, transforming harmful thermal runaway into a protective shutdown action
3Quantity of substance
If larger-sized batteries are used, then battery capacity is improved, but contact area between pin and separator increases causing pin removability problems
Solution Approach 1:
The patent changes the surface friction parameters of the separator membrane by controlling polymer crystallinity, molecular weight, and additive composition. This reduces the coefficient of friction between the separator and pin, enabling easy pin removal even with increased contact area in larger batteries
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 membrane effectively interrupts current quickly at lower temperatures, reduces frictional resistance, and enhances the safety and productivity of larger-sized batteries by ensuring efficient shutdown and easy pin removal during winding.
Implementation Method 1
the separator melts and forms a film covering the electrode to interrupt the current
Implementation Method 2
a viscosity average molecular weight of the microporous membrane is less than 300,000
Data Source
AI summary
A microporous membrane according to the present invention is a microporous membrane containing a copolymerized high density polyethylene and a high density polyethylene, wherein a content of an α-olefin unit having 3 or more carbon atoms in the microporous membrane is 0.01 mol % or more and 0.6 mol % or less, and a viscosity average molecular weight of the microporous membrane is less than 300,000. In addition, a battery separator according to the present invention contains the above microporous membrane. Further, a battery according to the present invention contains the above battery separator.