Porous Active Separator Coating for Adhesion and Thermal Shrinkage
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Solution Overview
Problem
Existing organic/inorganic composite separators face issues with inorganic particle extraction during assembly and weakened adhesion leading to thermal shrinkage and electric short circuits in electrochemical devices.
Innovation Solution
A composite separator with a porous active layer containing a mixture of inorganic particles and binder polymers, having a peeling force of 5 gf/cm or above and thermal shrinkage of 50% or below at 150°C, uses polymers with different hydrophile properties to enhance adhesion and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the content of inorganic particles in the porous active layer is increased to restrain thermal shrinkage, then thermal stability is improved, but the content of binder polymer is relatively decreased causing weakened adhesion and particle extraction
Solution Approach 1:
The patent changes the chemical composition parameters of the binder polymer, specifically using polymers with carboxyl groups (such as polyacrylic acid, carboxymethyl cellulose, or polyvinyl alcohol) that form strong chemical bonds with inorganic particles. This chemical interaction strengthens adhesion even when inorganic particle content is high, resolving the contradiction between thermal stability and adhesion strength
Solution Approach 2:
The patent creates a composite binder system combining organic polymers with carboxyl groups and inorganic particles, forming a synergistic structure where the carboxyl-containing polymer acts as a bridge between inorganic particles and the substrate. This composite approach allows high inorganic content while maintaining strong adhesion through chemical bonding
2Reliability
If the content of binder polymer is increased to prevent inorganic particle extraction, then adhesion is improved, but the content of inorganic particles is relatively decreased reducing thermal shrinkage restraint
Solution Approach 1:
The patent changes the quality parameter of the binder polymer by selecting specific polymer types with carboxyl functional groups that provide strong chemical bonding capability. This allows using smaller amounts of binder polymer (5-50 parts by weight) while achieving superior adhesion, thus maintaining thermal stability without requiring excessive polymer content
3Stability of the object's composition
If inorganic particles are extracted from the porous active layer during assembly, then manufacturing defects occur, but increasing inorganic particle content strengthens thermal stability
Solution Approach 1:
The patent changes the chemical properties of the binder polymer to include carboxyl groups that form strong chemical bonds with inorganic particles. This chemical bonding prevents particle extraction during assembly operations, ensuring manufacturing precision while maintaining high inorganic particle content for thermal stability
Solution Approach 2:
The patent applies preliminary chemical treatment by selecting binder polymers with carboxyl groups that pre-establish strong bonding with inorganic particles before assembly. This preliminary chemical bonding action prevents particle extraction during subsequent assembly processes, resolving the manufacturing precision issue
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
Prevents inorganic particle extraction and electric short circuits, improving the stability of electrochemical devices by maintaining adhesion and controlling thermal shrinkage.
Implementation Method 1
The inorganic particles in the porous active layer formed on the polyolefin porous substrate act as a kind of spacer that keeps a physical shape of the porous active layer, so the inorganic particles restrain thermal shrinkage of the polyolefin porous substrate when the electrochemical device is overheated
Implementation Method 2
a porous active layer having a peeling force of 5 gf/cm or above
Data Source
Figure 1(a)~1(e)
Figure 2
AI summary
An organic/inorganic composite separator includes (a) a polyolefin porous substrate having pores; and (b) a porous active layer containing a mixture of inorganic particles and a binder polymer, with which at least one surface of the polyolefin porous substrate is coated, wherein the porous active layer has a peeling force of 5 gf/cm or above, and a thermal shrinkage of the separator after being left alone at 150°C. for 1 hour is 50% or below in a machine direction (MD) or in a transverse direction (TD). This organic/inorganic composite separator solves the problem that inorganic particles in the porous active layer formed on the porous substrate are extracted during an assembly process of an electrochemical device, and also it may prevent an electric short circuit between cathode and anode even when the electrochemical device is overheated.