KR-20260066522-A - BASIC CARBON NANOTUBE SLUDGE, ITS MANUFACTURING METHOD AND CONDUCTIVE COMPOSITION USING SAME

KR20260066522AKR 20260066522 AKR20260066522 AKR 20260066522AKR-20260066522-A

Abstract

The present invention relates to a basic carbon nanotube sludge, a method for manufacturing the same, and a conductive composition using the same. The present invention provides a basic carbon nanotube sludge in which the carbon nanotubes are debundled by introducing oxygen-based functional groups containing oxygen and hydrogen, and then, under basic conditions, the oxygen-based functional groups are deprotonated and charged with a negative charge, and re-bundling is suppressed by the repulsion between negative charges, thereby having high dispersibility.

Inventors

서선희
김정모
정희진
정승열
이건웅

Assignees

한국전기연구원

Dates

Publication Date: 20260512
Application Date: 20241104

Claims (12)

In carbon nanotube sludge, The above carbon nanotubes are, After debundling by introducing oxygen-based functional groups containing oxygen and hydrogen, the oxygen-based functional groups are deprotonated under basic conditions and become negatively charged, and Basic carbon nanotube sludge characterized by having high dispersibility by suppressing re-bundling through the repulsion between the negative charges.
In Article 1, Basic carbon nanotube sludge characterized in that the oxygen-based functional group is one or more selected from the group consisting of hydroxyl groups and carboxyl groups.
In Article 1, The above basic carbon nanotube sludge is a basic carbon nanotube sludge characterized by having a pH of at least 9.
In Article 1, Basic carbon nanotube sludge characterized in that the above basic carbon nanotube has crystallinity satisfying the following relationship 1: [Relationship 1] 5 ≤ I G /I D ≤ 50 (Note: I G / I D is a value calculated as the ratio of the maximum peak intensity (I G ) measured at 1,580 ± 50 cm⁻¹ in the wavenumber region of the Raman spectrum to the maximum peak intensity (I D ) measured at 1,360 ± 50 cm⁻¹ .)
In Article 1, Basic carbon nanotube sludge characterized in that the oxygen atoms present in the basic carbon nanotubes are at least 20 at%.
In Article 1, Basic carbon nanotube sludge characterized in that the length of the basic carbon nanotubes is 2 to 40 μm.
In Article 1, Basic carbon nanotube sludge characterized in that the carbon nanotubes are one or more selected from the group consisting of single-walled carbon nanotubes and double-walled carbon nanotubes.
A step of preparing a mixture by adding carbon nanotubes to and stirring a solution in which an alkali metal salt is dissolved in a first acid; A step of introducing oxygen-based functional groups containing oxygen and hydrogen into the carbon nanotubes while debundling the carbon nanotubes by applying shear stress while heating the mixture after adding the above mixture to a second acid; A step of neutralizing a mixture containing the debundled carbon nanotubes to obtain an acidic carbon nanotube sludge; and A method for producing basic carbon nanotube sludge, characterized by including the step of washing the acidic carbon nanotube sludge under basic conditions to obtain basic carbon nanotube sludge.
In Article 8, The above basic carbon nanotubes are prepared by introducing the above acidic carbon nanotube sludge into a basic solution with a pH of 10 to 14 and then washing it through mechanical dispersion treatment so that the oxygen-based functional groups are deprotonated and charged with a negative charge, and A method for producing basic carbon nanotube sludge characterized by having high dispersibility by suppressing re-bundling through the repulsion between the negative charges.
In Article 8, The first acid is one or more selected from the group consisting of sulfuric acid, fuming nitric acid, red fuming nitric acid, and phosphoric acid, and A method for producing basic carbon nanotube sludge, characterized in that the second acid is one or more selected from the group consisting of nitric acid, hydrogen peroxide, and hydrochloric acid.
In Article 8, A method for producing basic carbon nanotube sludge, characterized in that the alkali metal salt is one or more selected from the group consisting of nitrate compounds, sulfate compounds, and phosphate compounds containing one or more of the elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).
Comprising a polymer binder and a basic carbon nanotube sludge according to any one of claims 1 to 7, A non-dispersed conductive composition comprising a basic carbon nanotube sludge, characterized in that the sludge is dispersed within the polymer binder without a pre-dispersion process.

Description

Basic carbon nanotube sludge, its manufacturing method, and conductive composition using the same The present invention relates to a basic carbon nanotube sludge, a method for manufacturing the same, and a conductive composition using the same. Carbon nanotubes, discovered by Sumio Iijima in 1991, consist of three neighboring carbon atoms bonded to a single carbon atom to form a honeycomb-shaped hexagon. As the hexagonal structure repeats, they form a tube shape that is rolled into a cylinder, and depending on the number of tubes, they are classified into single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT). Due to their excellent electrical and mechanical properties, thermal stability, and adsorption and transport characteristics, carbon nanotubes are the subject of much research for application in various fields, such as conductive materials for secondary batteries. While multi-walled carbon nanotubes, which offer relatively superior cost competitiveness, can be localized, single-walled and double-walled carbon nanotubes, which possess particularly excellent electrical conductivity, have not yet been localized and remain dependent on imports. Unlike multi-walled carbon nanotubes with a diameter of 4 nm or more, carbon nanotubes with a diameter of 3 nm or less have a flake appearance of several mm in size in the form of highly concentrated bundles after synthesis due to strong van der Waals forces caused by the small diameter and the large aspect ratio according to length/diameter, so the dispersion stability is inevitably low. Therefore, it is important to de-bundle the bundles to weaken the strong van der Waals forces and achieve dispersion of carbon nanotubes in the dispersion medium. Conventional debundling typically utilized physical grinding methods using machines such as probe-type ultrasonic dispersion or high-pressure homogenizers, or chemical oxidation methods that apply strong shear stress while using oxidizing agents. However, while these methods can improve the dispersion stability of carbon nanotubes in a dispersion solution by shortening their length to 0.1 to 3 μm, the inherent sp² hexagonal carbon ring structure of the carbon nanotubes is destroyed during the process, causing the electrical conductivity to drop to less than 100 S/cm. Consequently, a separate post-treatment reduction process is required to restore the structure to the sp² form, and the electrical conductivity does not exceed 1,000 S/cm even after reduction, making it chemically unstable. Even when electrical conductivity is maintained at the level of 1,000 S/cm, the use of a separate dispersant or a low-molecular-weight binder with a molecular weight of 90,000 g/mol or less is required for the uniform dispersion of carbon nanotubes. Additionally, additional dilution and redispersion processes are necessary to maximize dispersibility. Furthermore, if the materials of the dispersant and the conventionally used polymer binder are different, mutual compatibility between the two materials must be ensured; failure to meet this requirement may result in limitations on applications or usage amounts. In this regard, 'low-defect carbon nanotube sludge and method for manufacturing the same (KR 10-2023-0055818 A)' discloses a technology that enables the manufacturing of carbon nanotube sludge without the need for a separate dispersant or a complex dispersion process, while stably maintaining the inherent sp2 hexagonal carbon ring structure of carbon nanotubes. This allows for effective dispersion and composite formation by facilitating penetration between carbon nanotube bundles due to the small molecular size of the dispersant or low-molecular-weight binder. Recently, in applications requiring high energy density such as lithium secondary batteries, electrode binder materials with a high molecular weight of 200,000 g/mol or more are being applied to ensure high viscosity and electrode adhesion for coating properties of the electrode slurry while minimizing the use of binders that do not contribute to lithium storage, and thus the demand for carbon nanotube materials applicable to this is increasing. When carbon nanotubes in low-defect carbon nanotube sludge are combined with a high-viscosity electrode binder for lithium secondary batteries with a molecular weight of 200,000 g/mol or more, there is a problem in that the polymer binder has difficulty penetrating between the carbon nanotube bundles, resulting in re-bundling. Consequently, a limitation is being revealed in that it is difficult to effectively control the localized aggregation of carbon nanotubes within a binder conductive composite in which the binder and carbon nanotubes are combined. Therefore, there is a need for the development of technology for high-concentration, highly crystalline carbon nanotubes that can be directly combined with polymer binders without requiring separate dispersants or low-molec