Polymer-Binder Separator Coating for Adhesion Without Slurry Thickening
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Solution Overview
Problem
Existing separators for electrochemical devices face challenges in achieving optimal adhesion between the coating layer and the porous polymer substrate, leading to issues with dispersibility of inorganic particles and potential electrical short circuits due to insufficient adhesion and viscosity increases in the coating layer slurry.
Innovation Solution
A separator design featuring a coating layer with a higher concentration of a solution-type first polymer binder adjacent to the porous polymer substrate, combined with a lower solubility second polymer binder in the adhesive layer, enhances adhesion and maintains slurry viscosity, using polyacrylic acid, polyurethane, or similar binders, and inorganic particles like BaTiO3, to improve dispersibility and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a coating layer slurry is applied to improve adhesion between the coating layer and porous polymer substrate, then adhesion is enhanced, but the viscosity of the slurry increases which reduces dispersibility of inorganic particles
Solution Approach 1:
The patent uses a solution-type polymer binder that changes its properties based on the environment. The binder has high solubility in water allowing good dispersibility during coating application, and low solubility in organic solvents providing strong adhesion after drying. This parameter change resolves the contradiction between adhesion and dispersibility.
Solution Approach 2:
The patent creates a composite coating layer combining inorganic particles with a solution-type polymer binder. The composite structure allows the inorganic particles to provide mechanical strength and thermal stability while the polymer binder ensures good adhesion to the porous substrate, resolving the contradiction between adhesion enhancement and particle dispersibility.
2Strength
If a polymer binder is added to the coating layer slurry to improve adhesion, then adhesion between layers is enhanced, but the mechanical properties and safety of the electrochemical device may be compromised
Solution Approach 1:
The patent selects a polymer binder with specific parameters: solution-type with controlled molecular weight and functional groups. The binder's solubility parameters are optimized to provide strong adhesion while maintaining electrochemical stability and mechanical integrity of the device.
Solution Approach 2:
The patent applies the polymer binder specifically at the interface between the coating layer and porous substrate where adhesion is needed, rather than throughout the entire coating. This localized application enhances adhesion while minimizing impact on the overall mechanical properties and safety of the electrochemical device.
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 design improves adhesion between the coating layer and the porous polymer substrate, enhances dispersibility of inorganic particles, and prevents electrical short circuits, while maintaining the mechanical integrity and safety of the electrochemical device.
Implementation Method 1
a polymer binder included in an adhesive layer forming slurry is disposed at an interface of a coating layer and a porous polymer substrate to improve adhesion between the coating layer and the porous polymer substrate
Implementation Method 2
to improve dispersibility of inorganic particles included in a coating layer forming slurry
Data Source
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AI summary
A separator for an electrochemical device includes a porous polymer substrate; a coating layer provided on at least one surface of the porous polymer substrate and including a first polymer binder and inorganic particles; and an adhesive layer provided on the coating layer and including a second polymer binder, in which the first polymer binder is a solution type binder, and a content of the first polymer binder included in a portion of the coating layer adjacent to the porous polymer substrate is greater than a content of the first polymer binder included in another portion facing away from the porous polymer substrate.