Vinylidene Fluoride Binder for Battery Electrode Conductivity

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional binder compositions for non-aqueous electrolyte secondary batteries, particularly those using vinylidene fluoride-based copolymers with acidic functional groups, suffer from inadequate dispersibility of conductive additives, leading to low electrical conductivity of the electrode mixture layer.

Innovation Solution

A binder composition comprising a vinylidene fluoride copolymer with an acidic functional group, where the copolymerization of vinylidene fluoride and a monomer with an acidic functional group results in a polymer with a number average molecular weight ratio less than 1 after adsorption onto alumina, enhancing the dispersibility of conductive additives while maintaining sufficient adhesiveness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a vinylidene fluoride-based copolymer composition with an acidic functional group is used as a binder composition, then the adhesion to the current collector is enhanced, but the dispersibility of the conductive additive becomes insufficient

Engineering Contradiction:

Improveadhesion to current collectorVSAvoiddispersibility of conductive additive

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The invention changes the molecular weight parameter of the vinylidene fluoride copolymer composition by controlling the polymerization yield to not exceed 90%, and specifically controlling the ratio of number average molecular weight before and after alumina adsorption to be 0.75 or less. This parameter optimization enables the binder to achieve both sufficient adhesion to the current collector and good dispersibility of the conductive additive, resolving the technical contradiction between these two properties.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention introduces alumina as an intermediary substance to characterize and control the molecular weight of the vinylidene fluoride copolymer composition. By using alumina adsorption as a mediator to define the molecular weight ratio parameter, the invention establishes a specific criterion (Mn1/Mn2 ≥ 0.75) that ensures the binder composition achieves both strong adhesion and good dispersibility, thus resolving the contradiction between these opposing requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the polymerization yield of vinylidene fluoride copolymer composition exceeds 90%, then the production efficiency is improved, but the dispersibility of conductive additive deteriorates

Engineering Contradiction:

Improveproduction efficiencyVSAvoiddispersibility of conductive additive

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The invention optimizes the polymerization yield parameter by setting it to not exceed 90%, and more specifically by controlling the ratio of number average molecular weight before and after alumina adsorption to be 0.75 or less. This optimized parameter range maintains acceptable production efficiency while significantly improving the dispersibility of conductive additives in the electrode mixture, thus resolving the contradiction between productivity and compositional stability.

Inventive Principle:

Principle #35Parameter changes

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 solution achieves improved dispersibility of conductive additives, reducing volume resistance and enhancing electrical conductivity of the electrode, while maintaining strong adhesion to the current collector.

Implementation Method 1

the vinylidene fluoride copolymer composition has, in a case where the vinylidene fluoride copolymer composition is adsorbed onto alumina, a ratio (Mn2/Mn1) of less than 1, the ratio of a number average molecular weight of the vinylidene fluoride copolymer composition that is not adsorbed onto the alumina after the adsorption (Mn2) to a number average molecular weight of the vinylidene fluoride copolymer composition before the adsorption (Mn1)

Methodology Applied

Scientific EffectAdsorption: Adsorption

Data Source

PatentEP3483962B1Electrode mixture, electrode, non-aqueous electrolyte secondary battery, and electrode mixture production method

Publication Date: 2022.11.16 KUREHA CORPORATION

AI summary

A binder composition that exhibits sufficient adhesion and that achieves the excellent dispersibility of a conductive additive is provided. The binder composition according to an embodiment of the present invention is a binder composition including a vinylidene fluoride copolymer composition containing vinylidene fluoride and a monomer having an acidic functional group; and a ratio (Mn2/Mn1) of a number average molecular weight of the vinylidene fluoride copolymer composition after being adsorbed onto alumina (Mn2) to a number average molecular weight of the vinylidene fluoride copolymer composition before being adsorbed onto alumina (Mn1) being less than 1.