Fluorine Polymer Electrode Binder Adhesion via Functional Groups

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Solution Overview

Problem

Nonaqueous electrolyte secondary batteries face challenges in improving adhesion of fluorine-based polymers to metal current collectors and active materials, especially those with large specific surface areas, which affects cycle life and binding properties.

Innovation Solution

A method involving an electrode mixture with a first fluorine-based polymer having side chains represented by Formula (X—COOH) and a second fluorine-based polymer with hydroxy groups, applied onto a current collector, followed by heat treatment to enhance adhesion through chemical or physical crosslinking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fluorine based polymers are used as electrode binders, then electrochemical stability and chemical resistance are improved, but adhesion to metal current collector and binding capacity between active materials deteriorate

Engineering Contradiction:

Improveelectrochemical stabilityVSAvoidadhesion to metal

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent modifies the chemical structure of fluorine-based polymers by introducing carboxyl groups and hydroxyl groups as functional groups. This parameter change in molecular structure enables the polymer to form strong chemical bonds with metal current collectors and active materials, thereby improving adhesion while maintaining electrochemical stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite binder system by copolymerizing vinylidene fluoride with functional monomers containing carboxyl groups and hydroxyl groups. This composite approach combines the electrochemical stability of fluorine-based polymers with the adhesion properties of functional groups, resolving the contradiction between stability and adhesion.

Inventive Principle:

Principle #40Composite materials

2Reliability

If fluorine based polymers are used as electrode binders, then electrochemical stability is improved, but binding capacity between active materials deteriorates

Engineering Contradiction:

Improveelectrochemical stabilityVSAvoidbinding capacity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent introduces functional groups (carboxyl and hydroxyl groups) into the fluorine-based polymer structure. These functional groups provide additional binding sites that enhance the binding capacity between active materials while preserving the electrochemical stability inherent to fluorine-based polymers.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent develops a composite binder by copolymerizing vinylidene fluoride with functional monomers. This composite structure combines the stability of fluorine-based polymers with the binding capability of functional groups, simultaneously achieving both electrochemical stability and high binding capacity.

Inventive Principle:

Principle #40Composite materials

3Adaptability or versatility

If fluorine based polymers are used as electrode binders, then general binder properties are achieved, but adhesion to active materials with large specific surface area deteriorates

Engineering Contradiction:

Improvegeneral binder propertiesVSAvoidadhesion to large surface area materials

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The patent modifies the polymer structure by incorporating functional groups that can form strong chemical bonds. This parameter change enables the binder to effectively adhere to active materials with large specific surface areas, overcoming the limitation of conventional fluorine-based polymers while maintaining general binder properties.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The functional groups (carboxyl and hydroxyl groups) act as intermediaries between the fluorine-based polymer and active materials with large surface areas. These intermediaries facilitate strong bonding by forming chemical bridges, thereby improving adhesion without compromising the polymer's general binder functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 method significantly improves adhesion between the electrode active material and the current collector, even for materials with large specific surface areas, extending cycle life and binding properties.

Implementation Method 1

a coated film is subjected to heat treatment... improve the adhesion between the current collector and the electrode active material

Methodology Applied

Scientific EffectChemical bonding: Chemical Bonding

Implementation Method 2

a second fluorine-based polymer with hydroxy groups... improve the binding properties between active materials

Methodology Applied

Scientific EffectHydrogen bonding:

Data Source

PatentUS10586988B2Electrode structural body and production method thereof

Publication Date: 2020.03.10 KUREHA CORPORATION

AI summary

In an electrode structural body, a coated film is obtained by applying an electrode mixture including an electrode active material, a first fluorine based polymer, and a solvent and drying the mixture, then formed on the surface of a current collector, the first fluorine based polymer has one or more side chains represented by the following Formula (1), and the coated film is subjected to heat treatment.—X—COOH (1)(In Formula (1), X is an atomic group having a molecular weight of less than 500, the main chain of which is made up of 1 to 20 atoms).