Composite Separator Coating That Limits Shrinkage in Lithium Batteries
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Solution Overview
Problem
Lithium batteries face challenges in achieving high energy density and stability due to separator shrinkage and deformation at high temperatures, leading to reduced adhesion force and increased volume, which affects thermal stability and energy density.
Innovation Solution
A composite separator with a porous substrate and a coating layer containing a water-soluble binder, such as polyacrylic acid metal salt with a weight average molecular weight of 300,000 Dalton or more, and inorganic particles with an average particle diameter of 500 nm or more, is developed to enhance thermal stability and adhesion force while reducing volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the coating layer including inorganic particles is increased to improve thermal stability, then thermal stability is improved, but the volume of the separator and lithium battery is increased, decreasing energy density
Solution Approach 1:
The patent changes the particle size parameter of inorganic particles to 500 nm or more, which is larger than conventional sizes. This parameter change allows the coating layer to provide sufficient thermal stability while maintaining a thinner profile, thereby reducing separator volume and improving energy density without sacrificing thermal protection performance
Solution Approach 2:
The patent uses a composite coating layer combining inorganic particles with a polyacrylic acid metal salt binder. This composite structure provides enhanced thermal stability through the inorganic particles while the binder ensures strong adhesion, allowing for a thinner, more efficient coating that improves both thermal stability and energy density
2Reliability
If a coating layer including inorganic particles is placed on the porous substrate to improve thermal stability, then thermal stability is improved, but the adhesion force is reduced due to shrinkage and deformation during charging and discharging
Solution Approach 1:
The patent specifies using inorganic particles with an average particle diameter of 500 nm or more, which reduces stress concentration and minimizes coating layer deformation during battery operation. This parameter optimization maintains strong adhesion force while providing necessary thermal stability
Solution Approach 2:
The patent employs a composite coating layer with polyacrylic acid metal salt binder and inorganic particles. The binder provides flexible adhesion that accommodates substrate deformation during charging/discharging cycles, while the inorganic particles provide thermal stability, thus resolving the contradiction between adhesion force and thermal stability
3Volume of stationary object
If the volume of the separator is reduced to increase energy density, then energy density is improved, but thermal stability and adhesion force are compromised
Solution Approach 1:
By increasing the inorganic particle size to 500 nm or more, the patent achieves high thermal stability with a reduced coating layer thickness. This allows the separator volume to be minimized for high energy density while the enlarged particles provide sufficient thermal protection without requiring a thick coating
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 improves thermal stability, adhesion force, and energy density by suppressing shrinkage and deformation, reducing internal resistance, and minimizing side reactions, thereby enhancing the cyclic characteristics and discharge capacity of lithium batteries.
Implementation Method 1
the coating layer includes a water-soluble binder and inorganic particles... increased adhesion force
Implementation Method 2
the inorganic particles may have an average particle diameter (D50) of 500 nm or more... enhanced thermal stability
Data Source
AI summary
Provided are a composite separator, a lithium battery including the same, and a method of manufacturing the composite separator. The composite separator includes: a porous substrate; and a coating layer on at least one surface of the porous substrate, wherein the coating layer includes a water-soluble binder and inorganic particles, and the water-soluble binder includes a polyacrylic acid metal salt.