Polyhedral α-Alumina Separator Coating for Heat Shrinkage Control
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Solution Overview
Problem
Existing alumina coatings for secondary battery separators suffer from heat shrinkage issues that impair air permeability and ion movement, leading to safety risks and reduced battery performance.
Innovation Solution
A coating composition comprising nano-sized α-alumina particles with a polyhedral crystal structure, produced through a method involving the mixing of aluminum salts, pH adjustment, fluorine-based mineralization, and calcination, which allows for surface contact and forms larger interstitial spaces, enhancing thermal stability and air permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If spherical alumina particles are used for coating, then air permeability is maintained, but heat shrinkage suppression is weak
Solution Approach 1:
The invention transitions from spherical particles to polyhedral particles with flat surfaces. The polyhedral shape enables face-to-face contact between particles and the separator surface, creating strong mechanical interlocking that suppresses heat shrinkage while maintaining porosity for ion transport.
Solution Approach 2:
The invention changes the contact dimension from point contact (spherical) to surface contact (polyhedral). This dimensional change in contact geometry enhances the mechanical constraint on the separator, preventing thermal contraction while preserving the three-dimensional pore structure for ion movement.
2Reliability
If plate-like alumina particles are used for coating, then heat shrinkage suppression is improved, but ion movement is blocked
Solution Approach 1:
The invention uses polyhedral particles that combine flat contact surfaces for mechanical support with three-dimensional geometry that prevents laminated stacking. Unlike plate-like particles that form layered structures blocking pores, polyhedral particles create an open network structure that maintains ion transport pathways.
Solution Approach 2:
The invention creates a composite coating structure where polyhedral alumina particles form a mechanically robust yet porous network. The unique geometry allows simultaneous achievement of heat shrinkage suppression through surface contact and ion movement through interstitial spaces, resolving the contradiction between mechanical support and mass transport.
3Ease of manufacture
If amorphous alumina particles are used for coating, then manufacturing is simplified, but coating defects increase
Solution Approach 1:
The invention changes the crystalline phase parameter from amorphous to polyhedral α-alumina. This phase transition provides well-defined geometric shapes with flat surfaces that enable uniform surface contact and reduce coating defects, while the synthesis route remains relatively straightforward through controlled crystallization during calcination.
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 polyhedral α-alumina particles effectively suppress thermal contraction and maintain high air permeability, ensuring smooth ion movement and improved battery performance by forming a thin, uniformly dispersed coating layer.
Implementation Method 1
a method of producing the same, the method comprising: (S1) mixing and reacting an aqueous solution comprising one or more aluminum salts with an aqueous solution containing a pH adjusting agent, and filtering and washing the product to obtain pseudo-boehmite
Implementation Method 2
calcining it to obtain a powder of α-alumina particles having a polyhedral crystal structure
Implementation Method 3
mixing the pseudo-boehmite with a fluorine-based mineralizer and ultrapure water, and pulverizing the mixture, followed by filtering and drying; and (S3) filtering and drying the product of step (S2) and then calcining it to obtain a powder of α-alumina particles having a polyhedral crystal structure
Data Source
AI summary
The present invention provides a coating agent including α-alumina particles having a polyhedral crystal structure and having an average particle size (D50) of 100-900 nm. The α-alumina particles are produced in such a way that pseudo-boehmite is mixed with a fluoride-based mineralizer and ultrapure water and pulverized to obtain a powder which is then fired and grown into a polyhedral shape. The polyhedral alumina particles make surface contact and are coated on the surface of a porous polymer substrate, and empty space induced by the interstitial volume between particles is formed larger than that of spherical particles, thereby being capable of achieving excellent air permeability while effectively suppressing thermal contraction of the porous polymer substrate. In addition, due to a nano-level particle size, excellent dispersibility and the formation of a thin coating layer can be achieved.