Multiphase Fluoropolymer Separator Coating for Adhesion and Thermal Stability

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Solution Overview

Problem

Current lithium ion batteries face issues with polyolefin-based separators that shrink and oxidize at high temperatures, leading to short circuits and safety risks due to poor adhesion and susceptibility to electrochemical degradation, while fluoropolymers offer excellent adhesion but are difficult to apply without toxic organic solvents.

Innovation Solution

A multiphase fluoropolymer binder composition with a low-swelling, highly crystalline phase for mechanical strength and a softer, higher swelling phase for adhesion, using an aqueous dispersion to enhance both wet and dry adhesion with low leachables.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polyolefin-based separators are used to prevent short circuits, then separation function is improved, but thermal stability and oxidation resistance deteriorate at high temperatures

Engineering Contradiction:

Improveshort circuit preventionVSAvoidthermal stability

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The invention uses a composite structure consisting of a polyolefin base layer combined with a fluoropolymer coating layer. The polyolefin provides the separation function while the fluoropolymer coating provides thermal stability and oxidation resistance, creating a material that exhibits properties superior to either component alone.

Inventive Principle:

Principle #40Composite materials

2Reliability

If fluoropolymer coating is applied to improve adhesion and electrochemical resistance, then reliability is improved, but manufacturing complexity increases due to difficulty in application

Engineering Contradiction:

Improveadhesion and electrochemical resistanceVSAvoidcoating application

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention changes the physical and chemical parameters of the fluoropolymer coating, specifically using a dispersion formulation with controlled particle size distribution and incorporating adhesion promoters. These parameter changes enable the coating to be applied using standard dip-coating or spray-coating techniques without requiring specialized equipment or processes.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If organic solvents are used in fluoropolymer coating to achieve good adhesion, then adhesion is improved, but environmental harm and safety risks increase

Engineering Contradiction:

ImproveadhesionVSAvoidtoxicity and flammability

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the solvent system from organic solvents to aqueous dispersion medium. This parameter change maintains the adhesion properties through the use of adhesion promoters and optimized dispersion formulation while completely eliminating the toxicity and flammability hazards associated with organic solvents.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If polyolefin separators are used to provide separation, then separation function is improved, but cycle life deteriorates due to oxidation at high voltage

Engineering Contradiction:

Improveseparation functionVSAvoidcycle life

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The invention creates a composite separator where the fluoropolymer coating layer provides oxidation resistance at high voltage, protecting the polyolefin base layer from electrochemical degradation. This composite structure extends the cycle life while maintaining the separation function.

Inventive Principle:

Principle #40Composite materials

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 multiphase fluoropolymer binder provides excellent adhesion and mechanical stability in lithium ion batteries, preventing short circuits and enhancing safety by using an aqueous system that avoids toxic solvents and reduces environmental impact.

Implementation Method 1

The low-swelling phase can be highly crystalline and the high-swelling phase can be softer

Methodology Applied

Scientific EffectCrystallinity: Crystallisation

Implementation Method 2

Each of the fluoropolymer phases contains polymers having at least 10 weight percent, of a common fluoromonomer, making the polymer phases compatible with each other

Methodology Applied

Scientific EffectPolymer compatibility:

Data Source

PatentUS12497503B2Fluoropolymer dispersion for separator coating including multiphase fluoropolymer

Publication Date: 2025.12.16 ARKEMA INC

AI summary

The invention relates to a fluoropolymer coating composition that can be used, for example, in coating electrodes and/or separators in electrochemical devices. The fluoropolymer coating composition preferably contains multiple fluoropolymer phases. The coated electrodes and/or separators have both excellent wet adhesion, excellent dry adhesion, and low leachables. Each of the fluoropolymer phases contains polymers having at least 10 weight percent, of a common fluoromonomer, making the polymer phases compatible with each other, and allowing for the phases to be distributed fairly homogeneously on a macroscopic level throughout the composition and dried coating formed from the composition.