Boehmite-Coated Battery Separator for Heat Shrinkage and Adhesion
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Solution Overview
Problem
Conventional separators for electrochemical devices, such as lithium secondary batteries, face challenges with heat shrinkage and adhesion to electrodes due to material properties, leading to safety concerns and performance issues.
Innovation Solution
A separator comprising a porous polymer substrate with a porous coating layer containing boehmite particles and a binder polymer, where the boehmite particles have a specific average diameter and surface area, enhancing adhesion and reducing resistance, while also improving heat shrinkage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a porous coating layer with alumina particles is applied to improve heat shrinkage resistance, then thermal stability is improved, but the separator becomes more prone to damage from external foreign materials due to high hardness
Solution Approach 1:
The patent changes the material parameter from alumina to boehmite particles, which have lower hardness while maintaining heat shrinkage resistance. This parameter substitution resolves the contradiction by providing thermal stability without the excessive hardness that causes vulnerability to external damage.
Solution Approach 2:
The patent creates a composite coating layer using boehmite particles combined with a binder polymer. This composite structure provides both thermal stability from the boehmite and protection from external damage through the binder matrix, resolving the contradiction between heat resistance and susceptibility to foreign material damage.
2Quantity of substance
If the separator is made thinner to improve energy density, then energy density is improved, but adhesion to electrodes deteriorates
Solution Approach 1:
The patent employs a porous coating layer with controlled porosity that provides mechanical interlocking with electrode surfaces. This porous structure enables strong adhesion even in thin separators, resolving the contradiction between thin film design for energy density and adhesion strength.
Solution Approach 2:
The binder polymer in the composite coating layer provides adhesive functionality that compensates for the reduced thickness. The composite structure of boehmite particles and binder polymer creates a thin yet strongly adhering coating, resolving the adhesion-thickness contradiction.
3Temperature
If a porous coating layer is applied to improve heat shrinkage characteristics, then heat shrinkage is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent specifies precise parameter ranges for boehmite particles (average diameter 2.0-3.5 μm, specific surface area 4.0-4.5 m2/g) that optimize both heat shrinkage resistance and manufacturability. These controlled parameters simplify the manufacturing process by providing clear specifications while achieving the desired thermal performance.
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 solution provides improved adhesion to electrodes, reduced resistance, and controlled heat shrinkage, enhancing the safety and performance of electrochemical devices by optimizing the properties of the boehmite particles within the specified ranges.
Implementation Method 1
the binder polymer is positioned on at least or a part of the surface of the boehmite particles and connects and fixes the boehmite particles with one another
Implementation Method 2
a polyolefin-based porous substrate used conventionally as a separator for an electrochemical device shows a severe heat shrinking behavior at a temperature of 100° C. or higher due to its material property
Implementation Method 3
a porous coating layer on at least one surface of the porous polymer substrate, wherein the porous coating layer comprises boehmite particles and a binder polymer
Data Source
AI summary
A separator for an electrochemical device, including: a porous polymer substrate having a plurality of pores; and a porous coating layer on at least one surface of the porous polymer substrate, wherein the porous coating layer comprises boehmite particles and a binder polymer, wherein the binder polymer is positioned on at least a part of the surface of the boehmite particles and connects and fixes the boehmite particles with one another. The boehmite particles have an average particle diameter of 2.0 μm to 3.5 μm and a specific surface area of 4.0 m2/g to 4.5 m2/g, and one side of the porous coating layer has a thickness of 2 μm to 10 μm.