Battery Separator Opening Ratio for Winding Core Slippage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing separators for batteries, particularly those with a polypropylene outermost layer, suffer from poor surface slippage properties during the winding process, leading to issues like damage, displacement, and current leakage when removing the winding core, which complicates the production process and reduces productivity and yield.
Innovation Solution
A porous polymer film separator with a specific opening ratio of 89% to 96% on its surface is used, which reduces friction with the winding core and maintains appropriate slippage properties, allowing for smooth removal of the core and preventing damage or displacement, thereby enhancing the reliability and safety of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polypropylene outermost layer is used in the separator, then thermal stability and shutdown property are improved, but surface slippage property deteriorates causing damage and displacement during winding core removal
Solution Approach 1:
The separator employs a multilayer structure where only the intermediate layer is made of polypropylene for thermal stability, while the outermost layers use different materials (polyethylene or copolymer) that provide good surface slippage properties. This local differentiation allows the separator to have both thermal stability from the polypropylene layer and ease of operation from the outer layers without conflict.
Solution Approach 2:
The separator is constructed as a composite multilayer structure combining polypropylene with polyethylene or copolymer layers. This composite approach allows the polypropylene layer to provide thermal stability and shutdown property, while the polyethylene/copolymer outer layers provide the necessary surface slippage property for smooth winding core removal, resolving the contradiction between these two requirements.
2Ease of operation
If polyethylene or fluorocarbon resin layer is added to improve slippage property, then ease of operation is improved, but device complexity increases
Solution Approach 1:
The invention applies the slippage-enhancing resin layer specifically at the outermost surfaces of the separator where it contacts the winding core, rather than throughout the entire separator structure. This localized application provides the necessary slippage property only where needed for easy winding core removal, while keeping the rest of the separator structure relatively simple and maintaining its essential functions.
3Ease of operation
If polypropylene with calcium stearate is used to improve slippage, then ease of operation is improved, but manufacturing precision deteriorates due to film moldability issues
Solution Approach 1:
The invention places the polypropylene layer with calcium stearate specifically in the intermediate layer of the multilayer structure, not in the outermost layers. This localized positioning allows the calcium stearate to provide slippage properties where it contacts the winding core, while the outermost layers use materials that maintain good film moldability and manufacturing precision, thus resolving the contradiction between slippage and manufacturing quality.
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 high opening ratio on the separator surface ensures smooth removal of the winding core, reduces current leakage, and improves the productivity and yield of batteries by maintaining a balance between slippage and friction, thus providing a reliable and safe battery solution.
Implementation Method 1
a porous polymer film having a first surface and a second surface opposite to the first surface, wherein the first surface has openings distributed thereon communicating with pores of the porous polymer film
Implementation Method 2
reduces friction with the winding core and maintains appropriate slippage properties
Data Source
AI summary
A separator for a battery includes a porous polymer film having a first surface and a second surface opposite to the first surface, wherein the first surface has openings distributed thereon communicating with pores of the porous polymer film, and the ratio of the total area of the openings to the area of the first surface is 89% or more and 96% or less. The diameters of the openings may be within the range of 0.8 μm or more and 40 μm or less. A region with a predetermined thickness including at least the first surface of the porous polymer film preferably includes at least one selected from the group consisting of polypropylene, and a copolymer of propylene and another copolymerizable monomer.