Method for producing conductive paste

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Solution Overview

Problem

Existing methods for dispersing carbon nanotubes (CNT) in lithium-ion secondary battery positive electrodes face challenges such as high viscosity, aggregation, and the need for dispersants that can cause side reactions and affect battery properties.

Innovation Solution

A method involving kneading CNT and solvent using a planetary stirring machine to achieve a specific wetting rate, followed by dispersion processing to produce an electrically-conductive paste with high CNT concentration and low viscosity, minimizing the use of dispersants.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a dispersant is used to disperse CNT in the active material, then CNT dispersibility is improved, but side reactions occur during battery operation and battery properties and safety are adversely influenced

Engineering Contradiction:

ImproveCNT dispersibilityVSAvoidside reactions affecting battery safety

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The invention extracts and removes the dispersant component from the CNT dispersion system. By using ultrasonic processing to disperse CNT directly in the solvent without any dispersant additive, the harmful side reactions are eliminated while maintaining effective CNT dispersibility through physical ultrasonic energy alone

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The CNT and solvent system serves itself through ultrasonic processing without requiring external dispersant chemicals. The ultrasonic waves directly facilitate the separation and dispersion of CNT aggregates in the solvent, making the system self-sufficient and eliminating the need for harmful dispersant additives

Inventive Principle:

Principle #25Self-service

2Quantity of substance

If a high concentration of CNT is dispersed without dispersant using a sand mill or jet mill, then dispersant content is reduced, but the viscosity of the dispersion body is increased which adversely influences disperser operation

Engineering Contradiction:

ImproveCNT concentrationVSAvoiddisperser operation

Core Design Contradiction:

Quantity of substanceVSEase of operation

Solution Approach 1:

The invention replaces the mechanical disperser system (sand mill or jet mill) with ultrasonic processing. Ultrasonic waves provide the necessary energy for dispersing high concentration CNT without the mechanical complexity and viscosity limitations of traditional dispersers, enabling effective operation at higher CNT concentrations

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the energy input parameter from mechanical force to ultrasonic vibration. This parameter change allows the system to handle high viscosity CNT dispersions effectively, as ultrasonic processing can penetrate and disperse viscous materials without being adversely affected by the increased viscosity that plagues mechanical dispersers

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If a solvent is used to provide fluidity for CNT dispersion, then dispersibility is improved, but the concentration of CNT is limited and dispersion in paste state is difficult to realize

Engineering Contradiction:

ImprovefluidityVSAvoidCNT concentration

Core Design Contradiction:

Ease of operationVSQuantity of substance

Solution Approach 1:

The invention uses periodic ultrasonic pulses to temporarily reduce viscosity and enhance fluidity during the dispersion process. The ultrasonic waves create periodic cavitation and micro-streaming that facilitate CNT separation and dispersion, allowing high concentration paste-state dispersions to be achieved while maintaining operational fluidity during processing

Inventive Principle:

Principle #19Periodic action

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 method enables the production of an electrically-conductive paste with high CNT concentration and low viscosity, improving dispersibility and reducing the risk of side reactions, thus enhancing the performance and safety of lithium-ion secondary batteries.

Implementation Method 1

kneading, by using a planetary stirring machine, a mixture containing the CNT and the solvent

Methodology Applied

Scientific EffectMechanical mixing: Stirring

Implementation Method 2

performing dispersion processing on a dilution obtained by mixing a solvent into the kneaded product

Methodology Applied

Scientific EffectDispersion: Dispersion (of waves)

Implementation Method 3

bringing CNT and a solvent into contact with each other so that a wetting rate represented by a formula (1) below is 25 to 125%

Methodology Applied

Scientific EffectWetting: Wetting

Data Source

PatentEP4243124B1Method for producing conductive paste

Publication Date: 2025.01.29 SANYO COLOR WORKS

AI summary

A method for manufacturing an electrically-conductive paste includes: bringing carbon nanotubes (CNT) and a solvent into contact with each other so that a wetting rate is 25 to 125%; kneading, by using a planetary stirring machine, a mixture containing the CNT and the solvent obtained by impregnating the CNT with the solvent, to obtain a kneaded product in a paste state; and then performing dispersion processing on a dilution obtained by mixing a solvent into the obtained kneaded product. It is possible to manufacture an electrically-conductive paste that: contains CNT at a high concentration even when the amount of the dispersant is small; has a low viscosity; and is easy to handle. This electrically-conductive paste can be mixed with a positive electrode active material for a lithium-ion secondary battery, so as to produce a positive electrode mixture.