Dual-Coated Battery Separator for Heat-Stable Adhesion
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Solution Overview
Problem
Current separators for electrochemical devices, such as lithium secondary batteries, face challenges with reduced adhesive strength when exposed to electrolytes and high temperatures, leading to potential short-circuiting and safety issues due to material shrinkage and binder resin swelling.
Innovation Solution
A separator design featuring a porous polymer substrate with distinct porous coating layers on both sides, where the second binder particles have an average diameter 10 or more times larger than the first binder particles, enhancing both dry and wet adhesive strengths by preventing binder infiltration and maintaining structural integrity under heat and electrolyte exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a porous organic-inorganic coating layer is formed by coating with a mixture of excessive inorganic particles and binder polymers, then heat resistance is improved and shrinkage is inhibited, but binder resin swells when electrolyte is injected, resulting in significant decrease in adhesive strength between separator and electrode
Solution Approach 1:
The patent applies different binder polymer types to different locations: a first binder polymer (polymerizable in organic solvent) is used in the porous polymer substrate and first coating layer, while a second binder polymer (polymerizable in water, different from first binder) is used in the second coating layer. This local differentiation prevents uniform swelling throughout the structure when electrolyte is injected, maintaining adhesive strength while preserving heat resistance.
Solution Approach 2:
The patent creates a composite coating structure with multiple layers containing different binder polymer types and inorganic particles. The first coating layer contains first binder polymer and inorganic particles, while the second coating layer contains second binder polymer (different from first) and inorganic particles. This composite structure with chemically distinct binders prevents catastrophic swelling failure while maintaining thermal stability.
2Stability of the object's composition
If binder polymer is used to connect and fix inorganic particles in the coating layer, then the physical shape is maintained and shrinkage is inhibited, but adhesive strength deteriorates rapidly when exposed to electrolyte and heat
Solution Approach 1:
The patent implements local quality by using different binder polymer chemistries in different locations. The first binder polymer (polymerizable in organic solvent) provides structural stability in the substrate and first coating layer, while the second binder polymer (polymerizable in water, different from first) provides adhesive stability in the second coating layer that contacts the electrolyte, preventing rapid deterioration while maintaining shape.
Solution Approach 2:
The patent changes the chemical parameters of the binder polymer based on location and function. By selecting binder polymers with different polymerization conditions and chemical structures for different layers, the patent optimizes each layer's performance: structural integrity in the substrate and first layer, and electrolyte resistance in the second layer, thereby preventing rapid adhesive strength deterioration.
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 separator exhibits improved dry and wet adhesive strengths, reducing the risk of short-circuiting and enhancing the safety and performance of electrochemical devices by maintaining adhesive properties even after electrode lamination and electrolyte injection.
Implementation Method 1
the inorganic particles in the coating layer serve as a sort of spacer capable of maintaining the physical shape of the separator. As a result, shrinkage of the porous substrate is inhibited when exposed to high temperatures
Implementation Method 2
first binder particles disposed on a part or all of the surface of the first inorganic particles to connect and fix the first inorganic particles to each other
Data Source
AI summary
A separator and an electrochemical device comprising same are provided. The separator includes a porous polymer substrate having a plurality of pores; a first porous coating layer on one surface of the porous polymer substrate; and a second porous coating layer on the other surface of the porous polymer substrate. The first porous coating layer includes a plurality of first inorganic particles and first binder particles on a part or all of the surface of the first inorganic particles to connect and fix the first inorganic particles. The second porous coating layer includes a plurality of second inorganic particles and second binder particles on a part or all of the surface of the second inorganic particles to connect and fix the second inorganic particles. The average particle diameter of the second binder particles is at least 10-fold larger than the average particle diameter of the first binder particles.