Porous Separator Sheet Screening by Shut-Down Temperature
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Solution Overview
Problem
Existing porous polymer substrates used in lithium secondary batteries can undergo heat shrinkage, leading to internal short-circuits due to abnormal increases in air permeability after being coated with an organic/inorganic porous coating layer, despite initially meeting thickness and air permeability standards.
Innovation Solution
A system and method using air permeability-determining and temperature sensors to measure the shut-down temperature of a porous sheet, determining it as defective if the shut-down temperature exceeds a predetermined reference value, before coating, by interposing the sheet between jigs and heating it to track temperature and air permeability changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an organic/inorganic porous coating layer is applied onto the porous polymer substrate to reduce heat shrinkage, then heat resistance is improved, but air permeability increases abnormally causing internal short-circuits
Solution Approach 1:
The invention measures air permeability and thickness of the porous polymer substrate before coating to predict and prevent abnormal air permeability increase after coating. By performing detection beforehand, the system identifies substrates that will cause defects after coating, allowing rejection of defective substrates before the coating process and subsequent battery assembly.
2Manufacturing precision
If conventional detection methods are used to check thickness and air permeability before coating, then basic quality standards are met, but defective substrates causing post-coating air permeability increase are not identified
Solution Approach 1:
The invention replaces conventional post-coating defect detection methods with a pre-coating detection system that uses air permeability and thickness measurements combined with a predictive model. This substitution enables identification of substrates that will develop defects after coating, improving detection accuracy without requiring actual coating and subsequent testing.
3Reliability
If post-coating detection methods are used to identify defective separators, then defective products are detected, but additional tests and electrolytes are required increasing cost and time
Solution Approach 1:
The invention performs all necessary detection measurements (air permeability and thickness) before the coating process, eliminating the need for post-coating tests and electrolyte-based detection methods. This preliminary detection approach simplifies the overall process by identifying defective substrates early, avoiding unnecessary coating steps and subsequent complex testing procedures.
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
Enables accurate and efficient detection of defective porous sheets, reducing the need for additional tests and electrolytes, and ensuring high cost-efficiency by identifying potential defects before coating, thereby preventing abnormal air permeability increases.
Implementation Method 1
a heating unit 140 configured to heat the first jig or the second jig
Implementation Method 2
an air permeability-determining unit 170 configured to determine the air permeability (Gurley value) of the porous sheet
Data Source
AI summary
A system for detecting a defective porous sheet includes a jig having a through-hole, a heating unit, a temperature sensor, a controlling unit, an air permeability-determining unit and a judging unit. In this manner, it is possible to provide a novel system for detecting a porous sheet, which may be a defective separator after being coated with a porous coating layer, beforehand by using the air permeability and shut-down temperature of the porous sheet itself.