Composite Separator Binder for Thermal Stability and Particle Retention
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Solution Overview
Problem
Existing electrochemical devices, particularly lithium secondary batteries, face safety issues due to thermal shrinkage of polyolefin porous substrates leading to electric short circuits and extraction of inorganic particles during assembly, compromising stability and safety.
Innovation Solution
An organic/inorganic composite separator with a porous coating layer containing inorganic particles and a copolymer binder, where the copolymer includes specific functional groups to enhance adhesion and peeling resistance, maintaining thermal stability and preventing particle extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If inorganic particles are added to the porous coating layer to restrain thermal shrinkage, then thermal stability is improved, but inorganic particles are extracted during assembly process
Solution Approach 1:
The patent uses a composite binder polymer system consisting of both polar and non-polar polymer components. This composite material approach allows the binder to simultaneously provide strong adhesion to inorganic particles (through polar interactions) and maintain cohesive bonding, thereby preventing particle extraction while preserving thermal stability.
Solution Approach 2:
The patent modifies the chemical composition parameters of the binder polymer by incorporating specific polar groups (such as carboxyl, hydroxyl, or amide groups) with controlled content ratios. This parameter change enhances the binder's ability to adhere to inorganic particles through dipole interactions, preventing particle extraction during assembly while maintaining the thermal shrinkage restraint function.
2Strength
If binder polymer content is increased to prevent particle extraction, then adhesion is improved, but thermal shrinkage restraint capability is reduced
Solution Approach 1:
The patent optimizes the chemical composition parameters of the binder polymer by incorporating polar groups (carboxyl, hydroxyl, or amide groups) at specific content ratios (0.1-10 mmol per gram of binder). This parameter optimization enables strong particle adhesion through polar interactions while maintaining sufficient structural integrity for thermal shrinkage restraint, eliminating the need to increase overall binder content.
Solution Approach 2:
The patent enhances the local adhesive quality of the binder polymer by introducing polar functional groups at specific locations within the polymer structure. This localized quality enhancement provides strong bonding to inorganic particles without requiring increased overall binder content, thereby preserving the thermal shrinkage restraint capability.
3Ease of manufacture
If conventional polymer binder is used in porous coating layer, then manufacturing is simple, but inorganic particles are extracted during assembly
Solution Approach 1:
The patent modifies the chemical composition parameters of the binder polymer by incorporating polar functional groups (carboxyl, hydroxyl, or amide groups) at controlled ratios. This compositional parameter change enhances adhesion to inorganic particles through dipole and hydrogen bonding interactions, preventing particle extraction while maintaining the simplicity of the coating fabrication process.
Solution Approach 2:
The patent introduces polar functional groups as intermediary elements between the inorganic particles and the polymer matrix. These polar groups act as mediators that facilitate strong bonding interactions with inorganic particles through dipole and hydrogen bonding, preventing particle extraction during assembly while maintaining manufacturing simplicity.
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 composite separator effectively prevents electric short circuits and particle extraction, enhancing the safety and stability of electrochemical devices by restraining thermal shrinkage and improving battery performance.
Implementation Method 1
a copolymer including a first monomer unit and a second monomer unit, wherein the first monomer unit is a monomer unit having at least one functional group selected from the group consisting of OH, COOH, MAH (maleic anhydride) and SO3H
Implementation Method 2
the inorganic particles 3 in the porous coating layer formed on the porous substrate 1 act as a kind of spacer that keeps a physical shape of the porous coating layer, so the inorganic particles restrain thermal shrinkage of the porous substrate when the electrochemical device is overheated
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An organic/inorganic composite separator includes a porous substrate having a plurality of pores; and a porous coating layer formed on at least one surface of the porous substrate with a plurality of inorganic particles and a binder polymer. The binder polymer is a copolymer including: (a) a first monomer unit having a contact angle to a water drop in the range from o° to 49°; and (b) a second monomer unit having a contact angle to a water drop in the range from 50° to 130°. This organic/inorganic composite separator has excellent thermal stability, so it may restrain an electric short circuit between a cathode and an anode. In addition, the separator may prevent inorganic particles in the porous coating layer from being extracted during an assembling process of an electrochemical device, thereby improving stability of an electrochemical device.