Core-Shell Electrode Binder Composition for Dusting Resistance

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Solution Overview

Problem

Conventional binder compositions for electrochemical device electrodes fail to provide adequate peel strength and dusting resistance, especially when the electrode mixed material layer is densified, leading to reduced performance in electrochemical devices, particularly in applications requiring rapid charging and discharging.

Innovation Solution

A binder composition incorporating a particulate polymer with a core-shell structure and a polymer B, where the shell portion has a specific glass-transition temperature and a cyano group-containing monomer unit, mixed with an organic solvent to achieve enhanced viscosity, improving the adhesion and resistance of the electrode mixed material layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the electrode mixed material layer is densified to increase capacity, then the capacity of the electrochemical device increases, but the peel strength and dusting resistance of the electrode mixed material layer deteriorate

Engineering Contradiction:

ImprovecapacityVSAvoidpeel strength

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The binder composition uses a composite structure combining polyacrylonitrile (providing strong adhesion through cyano groups) with carboxymethyl cellulose (providing structural integrity and flexibility). This composite binder system maintains strong binding capacity even when the electrode mixed material layer is densified, preventing peel strength deterioration while allowing capacity increase through higher basis weight.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If the electrode mixed material layer is densified to increase capacity, then the capacity of the electrochemical device increases, but the dusting resistance of the electrode mixed material layer deteriorates

Engineering Contradiction:

ImprovecapacityVSAvoiddusting resistance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The composite binder system combines polyacrylonitrile's strong molecular adhesion (via cyano group interactions) with carboxymethyl cellulose's cohesive binding properties. This dual-mechanism binding system ensures that electrode active material particles remain firmly attached even in densified structures, preventing dusting during electrode cutting and handling while maintaining high capacity.

Inventive Principle:

Principle #40Composite materials

3Quantity of substance

If conventional binder composition is used in densified electrode mixed material layer, then the basis weight increases, but the rate characteristics of the electrochemical device deteriorate

Engineering Contradiction:

Improvebasis weightVSAvoidrate characteristics

Core Design Contradiction:

Quantity of substanceVSSpeed

Solution Approach 1:

The invention changes the chemical composition parameters of the binder by specifying polyacrylonitrile with 60-90 mass% cyano group-containing monomer units and controlling the binder composition to contain 5-20 mass% polyacrylonitrile and 80-45 mass% carboxymethyl cellulose. This specific parameter combination creates a binder that maintains porosity and ion transport pathways even in densified structures, enabling high basis weight electrodes to retain excellent rate characteristics.

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 proposed binder composition significantly enhances the peel strength and dusting resistance of the electrode mixed material layer, enabling electrochemical devices to exhibit superior rate characteristics even at increased density and basis weight.

Implementation Method 1

a polymer forming the shell portion has a glass-transition temperature of not lower than -50°C and not higher than 20°C

Methodology Applied

Scientific EffectGlass-transition temperature:

Implementation Method 2

a mixture obtained by mixing the polymer B in a concentration of 8 mass% with the organic solvent has a viscosity at a shear rate of 1 s-1

Methodology Applied

Scientific EffectViscosity:

Implementation Method 3

the polymer B includes a cyano group-containing monomer unit in a proportion of 60 mass% or more

Methodology Applied

Scientific EffectMolecular adhesion: Adhesive

Data Source

PatentEP3817109B1Binder composition for electrochemical device electrode, slurry composition for electrochemical device electrode, electrode for electrochemical device, and electrochemical device

Publication Date: 2023.10.04 ZEON CORP

AI summary

Provided is a binder composition for an electrochemical device electrode with which it is possible to form an electrode mixed material layer that has excellent peel strength and dusting resistance and that can cause an electrochemical device to display excellent rate characteristics. The binder composition for an electrochemical device electrode contains a binder and an organic solvent. The binder includes a particulate polymer A and a polymer B. The particulate polymer A has a core-shell structure including a core portion and a shell portion at least partially covering an outer surface of the core portion, and a polymer forming the shell portion has a glass-transition temperature of -50°C to 20°C. A mixture obtained by mixing the polymer B in a concentration of 8 mass% with the organic solvent has a viscosity at a shear rate of 1 s-1 of 100 mPa·s to 10,000 mPa·s.