Dopamine-Coated Battery Separator for Wet-State Thermal Shrinkage
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Solution Overview
Problem
Existing separators for electrochemical devices experience significant dimensional instability and thermal shrinkage in high temperature wet conditions, particularly in cylinder-type batteries, due to low polymer binder content, which compromises adhesive strength and stability.
Innovation Solution
A separator comprising a porous polymer substrate with a porous coating layer containing a polymer binder and inorganic particles, and a dopamine coating layer with polydopamine and dextrin, where the polymer binder is cross-linked with polydopamine, and the substrate has a three-layer structure of polypropylene, polyethylene, and polypropylene, with a reduced polymer binder content of 5% or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymer binder content is reduced in the porous coating layer, then adhesive strength and dimensional stability in wet state improve, but coating layer integrity and thermal shrinkage resistance worsen
Solution Approach 1:
The patent changes the chemical composition parameters of the coating layer by introducing polydopamine and dextrin as new binding components. This creates a dual-function coating layer where inorganic particles provide thermal stability and the polymer-dextrin matrix provides adhesive strength, resolving the contradiction between low polymer content and high stability.
Solution Approach 2:
The patent creates a composite coating layer structure combining inorganic particles (alumina, silica) with organic components (polymer binder, polydopamine, dextrin). This composite structure allows the inorganic particles to provide thermal shrinkage resistance while the organic matrix maintains adhesive strength, even at reduced polymer binder content.
2Stability of the object's composition
If polymer binder content is reduced to improve wet state stability, then thermal shrinkage resistance improves, but coating layer adhesion to substrate worsens
Solution Approach 1:
The patent introduces dextrin as an intermediary substance between the porous polymer substrate and the inorganic particles. Dextrin acts as a bridging agent that enhances the bonding interface, allowing reduced polymer binder content while maintaining strong adhesion and high-temperature dimensional stability.
3Temperature
If separator is designed for low polymer binder content, then thermal shrinkage rate decreases, but adhesive strength between electrode and separator worsens
Solution Approach 1:
The patent changes the chemical composition by adding polydopamine, which forms strong adhesive bonds with both the substrate and inorganic particles. This allows the separator to achieve low thermal shrinkage rate with minimal traditional polymer binder while maintaining strong adhesive strength through polydopamine's unique binding properties.
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 provides improved dimensional stability with a thermal shrinkage rate of 5% or less in the TD direction under 130°C or higher, preventing electrode exposure and thermal runaway, and maintains adhesive strength and thermal stability, effectively preventing electrode exposure and thermal runaway, and maintains electrode exposure and thermal shrinkage, and maintains electrode exposure and thermal stability, effectively preventing electrode exposure and thermal shrinkage, and maintains electrode, thermal stability, effectively preventing electrode exposure and thermal stability in a wet state.
Implementation Method 1
at least a portion of the acrylic binder may be cross-linked with the polydopamine
Implementation Method 2
a dopamine coating layer on the porous coating layer and comprising polydopamine and dextrin
Data Source
AI summary
Disclosed is a separator for an electrochemical device. The separator includes a porous polymer substrate, a porous coating layer formed on at least one surface of the porous polymer substrate and including a polymer binder and inorganic particles, and a dopamine coating layer formed on the porous coating layer and including polydopamine and dextrin. The separator has reduced thermal shrinkage even in a high temperature wet state.