Non-aqueous Battery Negative Electrode Binder Ratio

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Solution Overview

Problem

The use of polyacrylonitrile as a binder in negative electrodes of non-aqueous electrolyte secondary batteries leads to prolonged drying times and increased risk of electrode cracking when attempting to enhance battery capacity by increasing surface density, resulting in reduced productivity.

Innovation Solution

Incorporating polyvinylidene fluoride and polyacrylonitrile in a specified mass ratio (99.9/0.1 to 95.1/4.9) as a binder in the negative electrode mixture to increase solid content, improve mixing uniformity, and reduce drying time while preventing electrode cracking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If polyacrylonitrile is used as a binder to increase surface density for enhancing battery capacity, then the capacity increases, but the drying time becomes long and productivity falls down

Engineering Contradiction:

Improvesurface densityVSAvoidproductivity

Core Design Contradiction:

Quantity of substanceVSProductivity

Solution Approach 1:

The invention changes the chemical composition parameters of the binder by specifying a polyacrylonitrile content of 1-10% by mass and a polyvinylidene fluoride content of 90-99% by mass. This parameter optimization allows achieving high surface density (high capacity) while maintaining appropriate drying characteristics, thus resolving the contradiction between capacity enhancement and productivity maintenance.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If polyacrylonitrile is used as a binder to increase surface density, then the capacity increases, but the degree of hardening increases and electrode cracking is easily caused

Engineering Contradiction:

Improvesurface densityVSAvoidelectrode cracking resistance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The invention uses a composite binder system combining polyacrylonitrile (1-10% by mass) and polyvinylidene fluoride (90-99% by mass). This composite material approach leverages the adhesive properties of polyacrylonitrile while the polyvinylidene fluoride provides flexibility and cracking resistance, enabling high surface density without electrode failure.

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If the amount of polyacrylonitrile is increased to improve mixing uniformity, then the mixing uniformity improves, but the degree of hardening increases and electrode cracking occurs

Engineering Contradiction:

Improvemixing uniformityVSAvoidelectrode cracking resistance

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The invention optimizes the polyacrylonitrile content parameter to a specific range of 1-10% by mass, which is sufficient to achieve uniform mixing of the electrode slurry but low enough to prevent excessive hardening and electrode cracking. This precise parameter control resolves the contradiction between mixing uniformity and cracking resistance.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8178237B2Non-aqueous electrolyte battery and negative electrode

Publication Date: 2012.05.15 MURATA MFG CO LTD

AI summary

A non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the negative electrode contains a negative electrode mixture containing a binder; and the binder contains polyvinylidene fluoride and polyacrylonitrile, with a mass ratio of polyvinylidene fluoride to polyacrylonitrile ranging from 99.9/0.1 to 95.1/4.9.