Beta-Phase VDF Copolymer Precipitation for Battery Binder Adhesion

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Solution Overview

Problem

Existing vinylidene fluoride (VDF) polymers and copolymers lack a high proportion of beta phase crystals, which are crucial for applications such as lithium ion batteries, due to their limited beta phase content and particle size, especially when produced through emulsion processes.

Innovation Solution

A precipitation polymerization process is developed to produce VDF polymers with predominantly beta phase crystals, achieving a beta phase intensity ratio greater than 5, high melting point, and raspberry morphology, resulting in polymers with enhanced melt viscosity and peel adhesion, suitable for lithium ion battery components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If emulsion polymerization is used to produce PVDF, then the polymer can be produced with controlled molecular weight, but the beta phase content is insufficient and particle size is limited

Engineering Contradiction:

Improvebeta phase contentVSAvoidparticle size control

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent changes the polymerization parameters by using precipitation polymerization instead of emulsion polymerization, controlling temperature (50-70°C), pressure (280-40,000 kPa), and initiator concentration (2000-10000 ppm) to achieve both high beta phase content (intensity ratio >5) and controlled particle size (50-2500 microns) simultaneously

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent utilizes phase transition during precipitation polymerization where the polymer transitions from dissolved state to precipitated particles, enabling formation of beta phase crystals during the phase change process and achieving desired particle morphology and size distribution

Inventive Principle:

Principle #36Phase transitions

2Strength

If molecular weight is increased to improve melt strength and mechanical properties, then toughness and chemical stress crack resistance improve, but melt viscosity increases making processing difficult

Engineering Contradiction:

Improvemechanical propertiesVSAvoidmelt processability

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent optimizes molecular weight parameters through controlled precipitation polymerization, achieving high molecular weight polymers with solution viscosity ≥7000 cP (at 9 wt% in NMP) while maintaining acceptable melt viscosity (53-150 kPoise at 100 sec⁻¹) for processing

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure within the polymer particles featuring raspberry morphology with primary particles (100-800 nm) aggregated into larger particles (50-2500 microns), providing both high mechanical strength and processability

Inventive Principle:

Principle #40Composite materials

3Length of moving object

If spray drying is used to obtain small particle size (1-30 μm), then particle size is reduced, but beta phase content becomes negligible

Engineering Contradiction:

Improveparticle sizeVSAvoidbeta phase content

Core Design Contradiction:

Length of moving objectVSQuantity of substance

Solution Approach 1:

The patent inverts the conventional approach by first forming beta phase rich particles through precipitation polymerization (50-2500 microns) and then optionally size-reducing them, ensuring beta phase content (intensity ratio >5) is maintained or enhanced even at smaller final particle sizes

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent performs preliminary formation of beta phase crystals during the precipitation polymerization process before any size reduction operations, ensuring the crystalline structure is established and preserved in the final product

Inventive Principle:

Principle #10Preliminary action

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 process yields VDF polymers with improved beta phase content, high melting point, and enhanced mechanical properties, specifically increasing peel adhesion strength by up to 200% compared to conventional emulsion polymerized PVDF, making them suitable for high-performance lithium ion battery applications.

Implementation Method 1

A precipitation polymerization process is developed to produce VDF polymers with predominantly beta phase crystals

Methodology Applied

Scientific EffectPrecipitation polymerization:

Implementation Method 2

PVDF has several crystal phases noted as α, β, γ, δ, and ε phases which can be obtained by different processing methods/conditions

Methodology Applied

Scientific EffectCrystallisation: Crystallisation

Implementation Method 3

Vinylidene fluoride based polymers are semi crystalline polymer containing both crystalline and amorphous regions

Methodology Applied

Scientific EffectPolymerization:

Implementation Method 4

In β-phase crystal, PVDF chains have polarity and stack in parallel formation. Consequently, β-phase crystal has the largest dipolar-moment

Methodology Applied

Scientific EffectDipolar-moment alignment: Polarisation

Implementation Method 5

the present invention provides for particles having an average precipitated particle size of 50 to 2500 microns having primarily beta phase

Methodology Applied

Scientific EffectPrecipitation: Precipitation

Data Source

PatentUS20250002618A1VDF containing (CO) polymer with high molecular-weight using a new precipitation poly merization process

Publication Date: 2025.01.02 ARKEMA INC

AI summary

Disclosed is a vinylidene fluoride (co)polymer having a beta phase intensity ratio of greater than 5 and the polymerization process for making the vinylidene fluoride based polymer or copolymer.