Crosslinked Polyacrylic Acid Binder for Negative Electrode Cyclability

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Solution Overview

Problem

Conventional polymer compounds used as binders for negative electrodes in electrical storage devices, such as rechargeable batteries, face challenges in maintaining cyclability and efficiency when the weight average molecular weight is lowered, and they often require high molecular weight polymers to function effectively.

Innovation Solution

A polymer compound is developed by condensing polyacrylic acid with a multifunctional amine, forming a crosslinked structure that includes acid anhydride and amide/imide bonds, which maintains cyclability even with lower molecular weight polyacrylic acid, and is produced through a method involving heating and preheating of an intermediate composition containing polyacrylic acid and the multifunctional amine.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high molecular weight polyacrylic acid is used as a binder, then cyclability is maintained, but productivity decreases due to difficult processing and higher costs

Engineering Contradiction:

ImprovecyclabilityVSAvoidproductivity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The invention changes the molecular weight parameter of polyacrylic acid from high (conventional) to low (10,000-500,000), which improves productivity and processability while maintaining cyclability through the crosslinked structure formed by condensation with multifunctional amine

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite binder system by condensing polyacrylic acid with multifunctional amine (formula 1), forming a crosslinked polymer compound that combines the benefits of low molecular weight polyacrylic acid (processability) with enhanced structural stability (cyclability)

Inventive Principle:

Principle #40Composite materials

2Productivity

If low molecular weight polyacrylic acid is used, then productivity improves, but cyclability deteriorates

Engineering Contradiction:

ImproveproductivityVSAvoidcyclability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention uses low molecular weight polyacrylic acid (10,000-500,000) as the starting material to improve productivity, then applies chemical modification through condensation with multifunctional amine to restore and enhance cyclability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention performs preliminary condensation reaction between polyacrylic acid and multifunctional amine to form a crosslinked structure before electrode fabrication, which pre-establishes the structural stability needed for good cyclability while using easily processable low molecular weight polyacrylic acid

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If conventional binders are used, then manufacturing is straightforward, but stability against lithium intercalation and deintercalation is insufficient

Engineering Contradiction:

Improveease of manufactureVSAvoidstability against lithium intercalation and deintercalation

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The invention creates a composite binder by condensing polyacrylic acid with multifunctional amine having specific structure (formula 1), forming a crosslinked polymer compound that provides superior stability against lithium intercalation and deintercalation while maintaining ease of manufacture through straightforward mixing and heating processes

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention introduces local crosslinked structures (amide/imide bonds and acid anhydride structures) within the binder matrix, creating regions of enhanced stability against lithium intercalation and deintercalation while maintaining overall binder functionality

Inventive Principle:

Principle #3Local quality

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 polymer compound enhances the properties of electrical storage devices by maintaining cyclability and initial efficiency, allowing for the use of lower molecular weight polyacrylic acid while improving the productivity of negative electrodes and stability against lithium intercalation and deintercalation.

Implementation Method 1

a polymer compound obtained by condensing polyacrylic acid and a multifunctional amine

Methodology Applied

Scientific EffectCondensation reaction:

Implementation Method 2

forming a crosslinked structure that includes acid anhydride and amide/imide bonds

Methodology Applied

Scientific EffectCrosslinking:

Implementation Method 3

produced through a method involving heating and preheating of an intermediate composition

Methodology Applied

Scientific EffectHeating: Heating

Data Source

PatentUS9966607B2High-molecular compound, intermediate composition, negative electrode, electrical storage device, slurry for negative electrode method for producing high-molecular compound, and method for producing negative electrode

Publication Date: 2018.05.08 TOYOTA INDUSTRIES CORP

AI summary

A polymer compound for use as a binder for a negative electrode of an electrical storage device is formed by condensing polyacrylic acid and a multifunctional amine represented by the following formula (1), in which Y represents a straight chain alkyl group having 1 to 4 carbon atoms, a phenylene group, or an oxygen atom, and R1 and R2 each independently represent one or more hydrogen atoms, methyl groups, ethyl groups, trifluoromethyl groups, or methoxy groups.