Porous Separator Substrate Screening by SEM Pore Distribution
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Solution Overview
Problem
Existing methods for quality control of porous polymer substrates used in separators for secondary batteries are inadequate in detecting defects related to pore size and uniformity, leading to issues like increased air permeation time and non-uniform morphology, which cannot be accurately assessed through conventional measurements.
Innovation Solution
A method using scanning electron microscopy (SEM) to quantify and correct the average pore distribution index (PDI) of porous polymer substrates, classifying them as good or defective based on a corrected PDI value, ensuring uniform pore distribution and improved air permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods (capillary flow porometer) are used to determine pore size, then measurement can be performed, but the measurement varies from site to site and cannot accurately detect defective substrates
Solution Approach 1:
The patent uses image copying technology by capturing SEM images of the porous polymer substrate and creating digital replicas for analysis. This allows multiple measurements from the same image without physical contact or variation, enabling consistent pore size measurement and defective substrate detection through digital image processing rather than repeated physical measurements that vary by site
Solution Approach 2:
The patent replaces the mechanical capillary flow porometer measurement system with an optical imaging system (SEM) combined with image processing. This substitution eliminates the mechanical contact and operator-dependent variations inherent in conventional methods, providing more reliable and consistent pore size measurements through automated image analysis
2Reliability
If physical property determination (air permeation time) is performed on finished separator units, then quality assessment can be made, but defective substrates cannot be detected early and time is lost
Solution Approach 1:
The patent performs preliminary detection of substrate defects using SEM imaging and pore distribution analysis before the substrate is used to manufacture finished separator units. By identifying defective substrates early in the production process through image-based pore size measurement, the method prevents waste of time and resources on subsequent processing of defective materials that would fail final quality tests
Solution Approach 2:
The patent segments the quality control process into two distinct stages: (1) preliminary substrate inspection using SEM imaging to detect pore structure defects before manufacturing, and (2) final product verification on finished separator units. This segmentation allows early detection and elimination of defective substrates, reducing overall detection time and preventing defective products from reaching the final quality assessment stage
3Productivity
If excessive heat is applied during orientation step to improve processing, then processing efficiency increases, but pore size becomes too large and morphology becomes non-uniform
Solution Approach 1:
The patent implements a feedback mechanism by using SEM imaging to measure actual pore sizes and pore distribution in the manufactured substrate. This measurement feedback allows identification of substrates where excessive heat caused non-uniform morphology or oversized pores, enabling process optimization by adjusting heating parameters based on measured outcomes to maintain manufacturing precision while preserving processing efficiency
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
This method allows for early detection of defective substrates, reducing time and cost by identifying defects before forming an organic-inorganic composite porous layer, ensuring consistent air permeability and performance in secondary battery separators.
Implementation Method 1
observing the selected porous polymer substrate with a scanning electron microscope (SEM) to obtain an image of the porous polymer substrate
Data Source
Figure 1a~1b
Figure 1c
Figure 2a~2b
AI summary
Disclosed is a method for pre-detecting a defective porous polymer substrate for a separator, including the steps of: selecting a porous polymer substrate having a plurality of pores to detect whether it is a good product or a defective product; observing the selected porous polymer substrate with a scanning electron microscope (SEM) to obtain an image of the porous polymer substrate; quantifying the average value of pore distribution index (PDI) by using the obtained image of the porous polymer substrate; correcting the quantified average value of pore distribution index to obtain the corrected average value of pore distribution index; determining whether or not the corrected average value of pore distribution index is 60 a.u. (arbitrary unit) or less; and classifying the porous polymer substrate as a good product, when the corrected average value of pore distribution index is determined to be 60 a.u. or less, and classifying the porous polymer substrate as a defective product, when the corrected average value of pore distribution index is determined to be larger than 60 a.u.