All-Solid-State Battery Binder Composition for Low Resistance Adhesion

Solution Overview

Problem

Conventional binder compositions for all-solid-state secondary batteries lack sufficient adhesiveness and contribute to high internal resistance, necessitating improvements for better performance.

Innovation Solution

A binder composition comprising a specific copolymer and solvent, with a nitrile group-containing monomer unit, ester solvent, and controlled haze and insoluble fraction, is used to enhance adhesiveness and reduce internal resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional binder compositions (nitrile polymer with xylene or CPME) are used, then the functional layer can be formed, but the adhesiveness with battery materials is insufficient

Engineering Contradiction:

ImproveadhesivenessVSAvoidperformance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the binder by using a copolymer containing both nitrile groups and carboxyl groups, rather than a simple nitrile polymer. The specific parameter changes include: nitrile group content (0.1-4.0 mmol/g), carboxyl group content (0.01-0.5 mmol/g), and molecular weight (10,000-1,000,000). These parameter changes enable simultaneous achievement of good adhesiveness and low internal resistance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite binder structure by combining nitrile group-containing polymer chains with carboxyl group functionalities. This composite approach allows the binder to exhibit dual functionality: nitrile groups provide adhesion to electrode materials while carboxyl groups contribute to ionic conductivity and wetting properties, thereby resolving the contradiction between adhesiveness and performance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If conventional binder compositions are used, then the functional layer can be formed, but the internal resistance is high

Engineering Contradiction:

ImproveperformanceVSAvoidinternal resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters of the binder by using a copolymer containing both nitrile groups and carboxyl groups, rather than a simple nitrile polymer. The specific parameter changes include: nitrile group content (0.1-4.0 mmol/g), carboxyl group content (0.01-0.5 mmol/g), and molecular weight (10,000-1,000,000). These parameter changes enable simultaneous achievement of good adhesiveness and low internal resistance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The carboxyl groups in the binder composition act as intermediaries that improve the interface between the functional layer and battery materials. These carboxyl groups enhance ionic conductivity and wetting properties, facilitating better ion transport and reducing internal resistance at the interface, thereby resolving the high internal resistance issue.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If nitrile polymer with xylene or CPME is used as binder composition, then the slurry can be prepared, but the adhesiveness and internal resistance performance cannot be simultaneously optimized

Engineering Contradiction:

Improveslurry preparationVSAvoidadhesiveness and internal resistance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the binder by using a copolymer containing both nitrile groups and carboxyl groups, rather than a simple nitrile polymer. The specific parameter changes include: nitrile group content (0.1-4.0 mmol/g), carboxyl group content (0.01-0.5 mmol/g), and molecular weight (10,000-1,000,000). These parameter changes enable simultaneous achievement of good adhesiveness and low internal resistance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The carboxyl groups in the binder composition act as intermediaries that improve the interface between the functional layer and battery materials. These carboxyl groups enhance ionic conductivity and wetting properties, facilitating better ion transport and reducing internal resistance at the interface, thereby resolving the high internal resistance issue.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250372652A1Binder composition for all-solid-state secondary battery, slurry composition for all-solid-state secondary battery, functional layer for all-solid-state secondary battery, and all-solid-state secondary battery

Publication Date: 2025.12.04 ZEON CORP

AI summary

Provided is a binder composition for an all-solid-state secondary battery that can reduce internal resistance of an all-solid-state secondary battery while also imparting excellent adhesiveness to a functional layer for an all-solid-state secondary battery. The binder composition for an all-solid-state secondary battery contains a copolymer including a nitrile group-containing monomer unit and a solvent. The solvent includes an ester solvent having a carbon number of 6 or more. Proportional content of the nitrile group-containing monomer unit in the copolymer is 10 mass % to 22 mass % when all repeating units in the copolymer are taken to be 100 mass %. The copolymer has a tetrahydrofuran-insoluble fraction of 0.5 mass % to 3 mass %, and a copolymer solution obtained when the copolymer is dissolved in the solvent such that concentration of the copolymer is 8 mass % has a haze of 30% to 80%.