Single-walled carbon nanotube, processing method thereof, conductive paste and application thereof

Abstract

The embodiment of the invention relates to a single-walled carbon nanotube, a processing method thereof, conductive paste and application thereof. The treatment method of the single-walled carbon nanotube comprises the following steps: carrying out at least one heating and cooling treatment on an initial single-walled carbon nanotube; the heating and cooling treatment comprises the following steps: carrying out heating treatment on the initial single-walled carbon nanotube for a preset time; the preset time is 0.1 s to 5 s; and introducing inert gas to carry out cooling treatment on the initial single-walled carbon nanotube subjected to the heating treatment, so that the initial single-walled carbon nanotube is cooled within 1-10 minutes. Therefore, the diameter of the tube bundle of the single-walled carbon nanotube is reduced, and the conductivity of the single-walled carbon nanotube can be improved at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon nanotubes, and in particular to a single-walled carbon nanotube and a treatment method thereof, a conductive paste and an application thereof. Background Art

[0002] Carbon nanotubes can be regarded as one-dimensional tubular nanomaterials formed by curling graphene. Generally, carbon nanotubes can be divided into single-walled carbon nanotubes and multi-walled carbon nanotubes according to the number of tube walls. Since the carbon atoms in carbon nanotubes adopt SP 2 hybridization, compared with SP 3 hybridization, the S orbital component in SP 2 hybridization is relatively large, making carbon nanotubes have high modulus and high strength. The P electrons of the carbon atoms on the carbon nanotubes form a large-range delocalized π bond. Due to the significant conjugation effect, carbon nanotubes have some special electrical properties. Since carbon nanotubes have excellent electrical conductivity, especially single-walled carbon nanotubes, the conductive paste made of carbon nanotubes is widely used in lithium-ion power batteries. In addition, due to the good mechanical strength of carbon nanotubes and their unique tubular structure, it is also beneficial to enhance the stability of the battery electrode plate.

[0003] However, due to the strong intermolecular force between carbon nanotubes, single-walled carbon nanotubes usually exist in the form of bundles. If the single-walled carbon nanotubes are to exert their maximum performance advantages, it is necessary to fully unbundle the bundles of single-walled carbon nanotubes before use. For example, the unbundled single-walled carbon nanotubes are dispersed in a dispersion solvent to form a conductive paste. At present, the unbundling of single-walled carbon nanotubes mainly uses physical methods such as mechanical peeling or ultrasonic waves to unbundle the bundles of single-walled carbon nanotubes. This method has low efficiency and will cause structural defects in the single-walled carbon nanotubes, resulting in poor electrical conductivity of the single-walled carbon nanotubes. Summary of the Invention

[0004] In view of this, the embodiments of the present application provide a single-walled carbon nanotube and a treatment method thereof, a conductive paste and an application thereof to solve at least one problem in the background art.

[0005] In a first aspect, the embodiments of the present application provide a treatment method for single-walled carbon nanotubes, the method comprising:

[0006] Performing at least one heating and cooling treatment on the initial single-walled carbon nanotubes; the heating and cooling treatment includes:

[0007] Performing a heating treatment on the initial single-walled carbon nanotubes for a preset time; the preset time is 0.1 s - 5 s;

[0008] An inert gas is introduced to cool the initial single-walled carbon nanotubes after heat treatment, so that the initial single-walled carbon nanotubes are cooled within 1 min - 10 min.

[0009] Combined with the first aspect of the present application, in an alternative embodiment, the reaction temperature range of the heat treatment is 800°C - 2000°C; and / or, the temperature range after the cooling treatment is 25°C - 100°C.

[0010] Combined with the first aspect of the present application, in an alternative embodiment, the heat treatment is carried out in a reaction atmosphere containing oxygen.

[0011] Combined with the first aspect of the present application, in an alternative embodiment, the number of times of the heat and cooling treatments is greater than or equal to 3 times.

[0012] Combined with the first aspect of the present application, in an alternative embodiment, the bundle diameter of the initial single-walled carbon nanotubes is greater than 100 nm; the average value of IG / ID in the Raman spectrum of the initial single-walled carbon nanotubes is between 30 and 60.

[0013] In a second aspect, an embodiment of the present application provides a single-walled carbon nanotube, which is prepared by using the steps in the treatment method of the single-walled carbon nanotube in any one of the foregoing embodiments.

[0014] In a third aspect, an embodiment of the present application provides a single-walled carbon nanotube, the bundle diameter of the single-walled carbon nanotube is less than or equal to 100 nm; the average value of IG / ID in the Raman spectrum of the single-walled carbon nanotube is between 50 and 150; the proportion of the single-walled carbon nanotube with IG / ID greater than 100 in the Raman spectrum is 20% - 80%; the proportion of the single-walled carbon nanotube with IG / ID greater than 120 in the Raman spectrum is 5% - 40%; the pore size peak of the micropores in the single-walled carbon nanotube is between 0.5 nm and 1 nm.

[0015] In a fourth aspect, an embodiment of the present application provides a conductive paste, which is prepared by using the single-walled carbon nanotube in any one of the foregoing embodiments.

[0016] Combined with the fourth aspect of the present application, in an alternative embodiment, the bundle diameter range of the single-walled carbon nanotubes in the conductive paste is 1.6 nm - 50 nm; the viscosity range of the conductive paste is 500 cp - 10000 cp.

[0017] In a fifth aspect, an embodiment of the present application provides an application of the conductive paste in any one of the foregoing embodiments in a lithium-ion battery.

[0018] The single-walled carbon nanotubes provided by the embodiments of the present application, their treatment methods, conductive pastes and their applications involve performing at least one heating and cooling treatment on the initial single-walled carbon nanotubes; the heating and cooling treatment includes: performing a heating treatment on the initial single-walled carbon nanotubes for a preset time; the preset time is 0.1 s - 5 s; introducing an inert gas to cool the initial single-walled carbon nanotubes after the heating treatment, so that the initial single-walled carbon nanotubes are cooled within 1 min - 10 min. In this way, by performing a relatively fast heating treatment and a relatively fast cooling treatment on the initial single-walled carbon nanotubes, thermal stress is generated between the bundles of single-walled carbon nanotubes, causing the bundles of single-walled carbon nanotubes to open, and the single-walled carbon nanotubes to be unbundled from the thick bundles into thin bundles. In addition, the heating treatment can repair the defects of the single-walled carbon nanotubes and improve their graphitization degree. Therefore, the embodiments of the present application can reduce the bundle diameter of the single-walled carbon nanotubes while improving the electrical conductivity of the single-walled carbon nanotubes.

[0019] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. Description of the Drawings

[0020] The drawings described herein are used to provide a further understanding of the present application, and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation to the present application. In the drawings:

[0021] Figure 1 It is a schematic flow chart of a method for treating single-walled carbon nanotubes provided by an embodiment of the present application;

[0022] Figure 2 It is a scanning electron microscope image of the single-walled carbon nanotubes obtained in Comparative Example 1;

[0023] Figure 3 It is a scanning electron microscope image of the single-walled carbon nanotubes obtained in Example 1;

[0024] Figure 4 It is a scanning electron microscope image of the single-walled carbon nanotubes obtained in Example 4;

[0025] Figure 5 It is a micropore size distribution curve graph of the single-walled carbon nanotubes in Comparative Example 1 and the single-walled carbon nanotubes obtained in Examples 1 to 4;

[0026] Figure 6 It is a result graph of Raman surface scanning of the single-walled carbon nanotubes in Comparative Example 1 and the single-walled carbon nanotubes obtained in Example 4;

[0027] Figure 7 It is a scanning electron microscope image of the conductive paste in Comparative Application Example 1;

[0028] Figure 8 It is the SEM image of the conductive paste in Application Example 2;

[0029] Figure 9 It is the SEM image of the conductive paste in Application Example 3;

[0030] Figure 10 It is the TEM image of the conductive paste in Comparative Application Example 1;

[0031] Figure 11 It is the TEM image of the conductive paste in Application Example 4;

[0032] Figure 12 It is the bar graph of the bulk resistivity and film resistivity measured in Simulation Examples 1 to 5 and Comparative Simulation Example 1;

[0033] Figure 13 SEM image of the electrode sheet prepared in Comparative Simulation Example 1;

[0034] Figure 14 It is the SEM image of the electrode sheet prepared in Simulation Example 4. Detailed Implementation Modes

[0035] To make the technical solutions and beneficial effects of the present invention more obvious and understandable, the following will be described in detail by combining the attached drawings and listing specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are usually in accordance with conventional experimental conditions. The reagents and raw materials used in the present invention are commercially available unless otherwise specified.

[0036] In the following description, a large number of specific details are given to provide a more thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present application, some technical features known to the art are not described; that is, not all features of the actual embodiments are described here, and the well-known functions and steps are not described in detail.

[0037] The purpose of the terms used herein is only to describe specific embodiments and is not a limitation of the present application. When used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, identify the presence of the described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups. When used herein, the term "and / or" includes any and all combinations of the related listed items.

[0038] To thoroughly understand this application, detailed steps and structures will be presented in the following description to illustrate the technical solution of this application. The preferred embodiments of this application are described in detail below. However, in addition to these detailed descriptions, this application may also have other implementation manners.

[0039] Unless otherwise defined, the technical and scientific terms used in this application have the same meanings as those in the technical and scientific fields to which this application belongs.

[0040] For those not specified with specific technologies or conditions in the following embodiments, they are generally carried out according to the conventional technologies or conditions described in the literature in this field, or according to the conditions described in the product specification and recommended by the manufacturer. The numerical ranges in the following embodiments all include the endpoint values.

[0041] Based on this, the embodiments of this application provide a method for treating single-walled carbon nanotubes. Figure 1 It is a schematic flowchart of a method for treating single-walled carbon nanotubes provided by the embodiments of this application. Please refer to Figure 1 , the embodiments of this application provide a method for treating single-walled carbon nanotubes, including:

[0042] Step S101: Perform at least one heating and cooling treatment on the initial single-walled carbon nanotubes; the heating and cooling treatment includes: performing a heating treatment on the initial single-walled carbon nanotubes for a preset time; the preset time is 0.1 s - 5 s; introducing an inert gas to cool the initial single-walled carbon nanotubes after the heating treatment, so that the initial single-walled carbon nanotubes are cooled within 1 min - 10 min.

[0043] Exemplarily, the heating treatment of the initial single-walled carbon nanotubes can be performed by current heating. Specifically, the initial single-walled carbon nanotubes can be placed in an electric heating reactor, and the power supply voltage is directly applied to the initial single-walled carbon nanotubes. When an electric current flows through, the Joule effect of the current is used to convert electrical energy into heat energy to heat the initial single-walled carbon nanotubes. Since the heat generated by this current heating is generated within the heated object itself, the heating efficiency is very high and the heating speed is very fast. After the heating duration reaches the preset time, the power is cut off to stop heating, and an inert gas, such as nitrogen, argon, or helium, is introduced to quickly cool the initial single-walled carbon nanotubes within 1 min - 10 min. The flow rate of the introduced inert gas can be, for example, 10 L / min - 1000 L / min.

[0044] In the embodiments of the present application, the preset time for heat-treating the initial single-walled carbon nanotubes is 0.1 s - 5 s, and the initial single-walled carbon nanotubes after heat treatment are cooled within 1 min - 10 min. By performing a relatively fast heat treatment and a relatively fast cooling treatment on the initial single-walled carbon nanotubes, thermal stress is generated between the bundles of single-walled carbon nanotubes, causing the bundles of single-walled carbon nanotubes to open, and the single-walled carbon nanotubes to be unbundled from the thick bundles into thin bundles. In addition, the heat treatment can repair the defects of the single-walled carbon nanotubes and improve their graphitization degree. Therefore, the embodiments of the present application can improve the electrical conductivity of the single-walled carbon nanotubes while reducing the bundle diameter of the single-walled carbon nanotubes.

[0045] In some embodiments, the reaction temperature range for the heat treatment of the initial single-walled carbon nanotubes can be 800°C - 2000°C.

[0046] In some embodiments, the temperature range of the initial single-walled carbon nanotubes after the cooling treatment can be 25°C - 100°C.

[0047] It can be understood that the higher the reaction temperature and the lower the temperature after the cooling treatment, the greater the temperature change of the initial single-walled carbon nanotubes within 1 min - 10 min. In this way, thermal stress can be better generated between the bundles of the initial single-walled carbon nanotubes, causing the bundles of the initial single-walled carbon nanotubes to open further, and obtaining single-walled carbon nanotubes with a smaller bundle diameter.

[0048] The heat treatment in the embodiments of the present application can be carried out in an electric heating reactor filled with a reaction atmosphere. The reaction atmosphere can be, for example, an inert atmosphere, air, oxygen, or water vapor, etc. The addition of the reaction atmosphere can better control the environmental parameters in the electric heating reactor, and different reaction atmospheres can be selected according to actual needs.

[0049] In some embodiments, the heat treatment can be carried out in a reaction atmosphere containing oxygen. For example, the heat treatment is carried out in a reaction atmosphere of oxygen or water vapor. In this way, by heating in a reaction atmosphere containing oxygen, a weak oxidation treatment of the single-walled carbon nanotubes is carried out at a relatively high temperature, introducing a small amount of oxygen-containing groups, increasing the oxygen content of the single-walled carbon nanotubes, and thus improving the wettability of the single-walled carbon nanotubes in aqueous solvents. Therefore, in practical applications, for example, when using single-walled carbon nanotubes to prepare conductive slurries, the process feeding of the single-walled carbon nanotubes and the viscosity of the prepared conductive slurries can be improved.

[0050] In some embodiments, the number of heat treatment and cooling treatment can be greater than or equal to 3 times. In this way, after multiple heat treatment and cooling treatment, the single-walled carbon nanotubes can be fully unbundled under the action of thermal stress, and single-walled carbon nanotubes with a smaller bundle diameter can be obtained.

[0051] It can be understood that in the actual process, the specific number of heating and cooling treatments can be selected according to actual needs, for example, in combination with the required product performance, working hours, and energy consumption.

[0052] In some embodiments, the bundle diameter of the initial single-walled carbon nanotubes is greater than 100 nm; the average value of IG / ID in the Raman spectrum of the initial single-walled carbon nanotubes is between 30 and 60.

[0053] It should be noted that in the research of carbon materials such as graphene or carbon nanotubes, Raman spectroscopy can be used to characterize the structural information of carbon materials. The G peak and D peak are both Raman characteristic peaks of the carbon atom crystal. Among them, the G peak reflects the graphitization degree of the carbon material, and the D peak reflects the defects of the carbon material. IG and ID represent the intensities of the G peak and D peak respectively. The larger the IG value, the higher the graphitization degree of the carbon material; the larger the ID value, the more defects the carbon material has. Usually, the value of IG / ID is used to characterize the performance of the carbon material. A larger IG / ID value in the Raman spectrum of single-walled carbon nanotubes indicates a higher graphitization degree of the single-walled carbon nanotubes, fewer defects, and better electrical conductivity of the single-walled carbon nanotubes. On the contrary, it indicates a lower graphitization degree of the single-walled carbon nanotubes, more defects, and poorer electrical conductivity of the single-walled carbon nanotubes.

[0054] In some embodiments, the peak pore diameter of the micropores in the initial single-walled carbon nanotubes is between 0.34 nm and 0.7 nm; the oxygen content of the initial single-walled carbon nanotubes is between 1% and 3%.

[0055] Based on this, the embodiments of the present application further provide a single-walled carbon nanotube, which is prepared by using the steps in the treatment method of the single-walled carbon nanotube in any of the foregoing embodiments.

[0056] Based on this, the embodiments of the present application further provide another single-walled carbon nanotube. The bundle diameter of the single-walled carbon nanotube is less than or equal to 100 nm; the average value of IG / ID in the Raman spectrum of the single-walled carbon nanotube is between 50 and 150; the proportion of the single-walled carbon nanotube with an IG / ID greater than 100 in the Raman spectrum is 20% - 80%; the proportion of the single-walled carbon nanotube with an IG / ID greater than 120 in the Raman spectrum is 5% - 40%; the peak pore diameter of the micropores in the single-walled carbon nanotube is between 0.5 nm and 1 nm.

[0057] In the embodiments of the present application, the bundle diameter of the single-walled carbon nanotubes is less than or equal to 100 nm, and the bundles of single-walled carbon nanotubes are relatively thin. The average value of IG / ID in the Raman spectrum of the single-walled carbon nanotubes is between 50 and 150. Among them, the proportion of IG / ID greater than 100 is 20%-80%, and the proportion of IG / ID greater than 120 is 5%-40%. The degree of graphitization of the single-walled carbon nanotubes is high, the defects are few, and the electrical conductivity is excellent. The pore size peak of the micropores in the single-walled carbon nanotubes is between 0.5 nm and 1 nm, indicating that obvious micropores or cracks are formed between the bundles of single-walled carbon nanotubes, which is beneficial to the dispersion of the single-walled carbon nanotubes when preparing conductive pastes with single-walled carbon nanotubes in subsequent applications.

[0058] In some embodiments, the oxygen content of the single-walled carbon nanotubes is 3%-15%.

[0059] In the embodiments of the present application, the single-walled carbon nanotubes have a relatively high oxygen content, which can improve the wettability of the single-walled carbon nanotubes in aqueous solvents. Thus, in practical applications, for example, when using single-walled carbon nanotubes to prepare conductive pastes, the process feeding of the single-walled carbon nanotubes and the viscosity of the prepared conductive paste can be improved.

[0060] Based on this, the embodiments of the present application also provide a conductive paste prepared by using the single-walled carbon nanotubes in any of the foregoing embodiments.

[0061] In some embodiments, the single-walled carbon nanotubes and a dispersant can be added to a solvent to form a conductive paste. Among them, the mass percentages of the single-walled carbon nanotubes, the dispersant, and the solvent can be 0.2%-10%, 0.1%-20%, and 80%-99.7% respectively.

[0062] Exemplarily, the dispersant can be, for example, one or more of polyvinylpyrrolidone, polyvinyl alcohol, silane coupling agent, polyacrylic acid, carboxymethyl cellulose salt, ethyl cellulose, hydroxypropyl cellulose, chitosan, sodium carboxymethyl cellulose, hydroxypropyl cellulose, or ethyl cellulose, etc. The solvent can be, for example, one or more of water, ethanol, or isopropanol, etc. In actual preparation, the single-walled carbon nanotubes and the dispersant can be dissolved in the solvent and dispersed by using a dispersing device to prepare a conductive paste. The dispersing device can be, for example, one or more of a sand mill, an ultrasonic machine, an emulsifying machine, a colloid mill, a homogenizer, etc.

[0063] In some embodiments, the D50 of the prepared conductive paste can be between 0.1 μm and 90 μm.

[0064] In some embodiments, the bundle diameter range of the single-walled carbon nanotubes in the conductive paste is 1.6 nm - 50 nm; the viscosity range of the conductive paste is 500 cp - 10000 cp.

[0065] In some embodiments, the standard deviation of the diameter of a single bundle of single-walled carbon nanotubes in the conductive paste is 10%-30%.

[0066] The conductive paste in the embodiments of the present application is prepared by using the single-walled carbon nanotubes in any of the foregoing embodiments. Since the diameter of the bundle of single-walled carbon nanotubes in any of the foregoing embodiments is small, when preparing the conductive paste, the single-walled carbon nanotubes are more likely to be dispersed, forming a more uniform and dense conductive network, and the conductive performance of the conductive paste is better. Under the condition of adding a relatively smaller amount of single-walled carbon nanotubes, a conductive paste with better conductive performance can be formed.

[0067] Based on this, the embodiments of the present application further provide an application of a conductive paste as in any of the foregoing embodiments in a lithium-ion battery.

[0068] In some embodiments, the conductive paste in any of the foregoing embodiments can be prepared into an electrode paste and applied in a lithium-ion battery.

[0069] Specifically, for example, the battery negative electrode material, the conductive paste, and the binder can be fully mixed to obtain the electrode paste. Among them, the mass percentages of the battery negative electrode material, the conductive paste, and the binder can be 95%-98%, 0.05%-1%, and 1%-5% respectively. Then, the negative electrode sheet can be prepared from the electrode paste and applied in the lithium-ion battery.

[0070] Exemplarily, the negative electrode material can be, for example, silicon monoxide or silicon, and the binder can be, for example, one or more of styrene-butadiene rubber, polyacrylic acid, and sodium carboxymethyl cellulose.

[0071] In the embodiments of the present disclosure, since the conductive performance of the conductive paste is better, the lithium-ion battery finally prepared by applying the conductive paste has better conductive performance.

[0072] The technical solution of the present application will be further described in multiple embodiments below.

[0073] It should be noted that the initial single-walled carbon nanotubes in the embodiments of the present application are commercially available. Comparative example 1 compared with the embodiments of the present application is the initial single-walled carbon nanotubes. Among them, the average value of IG / ID of the Raman spectrum of the initial single-walled carbon nanotubes in comparative example 1 is 47.07, the pore diameter peak of the micropores in the initial single-walled carbon nanotubes is 0.45 nm, and the oxygen content of the initial single-walled carbon nanotubes is 2.64%.

[0074] Example 1

[0075] Place 10 g of the initial single-walled carbon nanotubes in a heated reactor with an argon reaction atmosphere and heat them by passing an electric current. Set the reaction temperature to 800 °C and the duration to 1 s, then introduce argon for cooling. Among them, the argon flow rate for introduction is 100 L / min and the cooling time is 2 min to complete one heating and cooling treatment. Repeat the above process of heating and cooling treatment. After each cooling treatment, the temperature is 25 °C. After a total of 3 heating and cooling treatments, the treated single-walled carbon nanotubes are obtained.

[0076] Example 2

[0077] Place 10 g of the initial single-walled carbon nanotubes in a heated reactor with a water vapor reaction atmosphere and heat them by passing an electric current. Set the reaction temperature to 1000 °C and the duration to 3 s, then introduce argon for cooling. Among them, the argon flow rate for introduction is 500 L / min and the cooling time is 4 min to complete one heating and cooling treatment. Repeat the above process of heating and cooling treatment. After each cooling treatment, the temperature is 30 °C. After a total of 5 heating and cooling treatments, the treated single-walled carbon nanotubes are obtained.

[0078] Example 3

[0079] Place 10 g of the initial single-walled carbon nanotubes in a heated reactor with an oxygen reaction atmosphere and heat them by passing an electric current. Set the reaction temperature to 1400 °C and the duration to 5 s, then introduce argon for cooling. Among them, the argon flow rate for introduction is 200 L / min and the cooling time is 3 min to complete one heating and cooling treatment. Repeat the above process of heating and cooling treatment. After each cooling treatment, the temperature is 35 °C. After a total of 5 heating and cooling treatments, the treated single-walled carbon nanotubes are obtained.

[0080] Example 4

[0081] Place 10 g of the initial single-walled carbon nanotubes in a heated reactor with a water vapor reaction atmosphere and heat them by passing an electric current. Set the reaction temperature to 1800 °C and the duration to 4 s, then introduce argon for cooling. Among them, the argon flow rate for introduction is 600 L / min and the cooling time is 5 min to complete one heating and cooling treatment. Repeat the above process of heating and cooling treatment. After each cooling treatment, the temperature is 45 °C. After a total of 6 heating and cooling treatments, the treated single-walled carbon nanotubes are obtained.

[0082] Example 5

[0083] Place 10 g of the initial single-walled carbon nanotubes in a heated reactor with a reaction atmosphere of water vapor, heat them by passing an electric current, set the reaction temperature at 2000 °C, and maintain for 2 s. Then, introduce argon for cooling, where the argon flow rate is 700 L / min and the cooling time is 6 min, thus completing one heating and cooling process. Repeat the above heating and cooling process. After each cooling process, the temperature is 30 °C. After a total of 4 heating and cooling processes, the treated single-walled carbon nanotubes are obtained.

[0084] Example 6

[0085] Place 10 g of the initial single-walled carbon nanotubes in a heated reactor with a reaction atmosphere of argon, heat them by passing an electric current, set the reaction temperature at 800 °C, and maintain for 0.1 s. Then, introduce argon for cooling, where the argon flow rate is 500 L / min and the cooling time is 2 min, thus completing one heating and cooling process. Repeat the above heating and cooling process. After each cooling process, the temperature is 25 °C. After a total of 5 heating and cooling processes, the treated single-walled carbon nanotubes are obtained.

[0086] Example 7

[0087] Place 10 g of the initial single-walled carbon nanotubes in a heated reactor with a reaction atmosphere of oxygen, heat them by passing an electric current, set the reaction temperature at 1000 °C, and maintain for 3 s. Then, introduce argon for cooling, where the argon flow rate is 500 L / min and the cooling time is 1 min, thus completing one heating and cooling process. Repeat the above heating and cooling process. After each cooling process, the temperature is 25 °C. After a total of 3 heating and cooling processes, the treated single-walled carbon nanotubes are obtained.

[0088] Example 8

[0089] Place 10 g of the initial single-walled carbon nanotubes in a heated reactor with a reaction atmosphere of oxygen, heat them by passing an electric current, set the reaction temperature at 1500 °C, and maintain for 3 s. Then, introduce argon for cooling, where the argon flow rate is 500 L / min and the cooling time is 10 min, thus completing one heating and cooling process. Repeat the above heating and cooling process. After each cooling process, the temperature is 100 °C. After a total of 3 heating and cooling processes, the treated single-walled carbon nanotubes are obtained.

[0090] Comparative Example 1

[0091] As described above, Comparative Example 1 is a commercially available single-walled carbon nanotube, corresponding to the initial single-walled carbon nanotubes before treatment in the examples of this application.

[0092] Comparative Example 2

[0093] 10 g of initial single-walled carbon nanotubes were placed in a heated reactor with an oxygen reaction atmosphere and heated by electricity. The reaction temperature was set at 1000 °C, and the duration was 3600 s. Then, argon was introduced for cooling, where the argon flow rate was 500 L / min and the cooling time was 60 min, completing one heating and cooling treatment. The above process of heating and cooling treatment was repeated. The temperature after each cooling treatment was 25 °C. After a total of 4 heating and cooling treatments, the treated single-walled carbon nanotubes were obtained.

[0094] To verify the performance of the single-walled carbon nanotubes prepared in the above examples, a detection test was conducted on the performance of the single-walled carbon nanotubes obtained in the above examples and Comparative Example 2. The specific results are as follows:

[0095] (I) Scanning electron microscope morphology

[0096] Figure 2 Figure of the scanning electron microscope of the single-walled carbon nanotubes obtained in Comparative Example 1. Figure 3 Figure of the scanning electron microscope of the single-walled carbon nanotubes obtained in Example 1. Figure 4 Figure of the scanning electron microscope of the single-walled carbon nanotubes obtained in Example 4.

[0097] As Figures 2 to 4 shown, the bundles of single-walled carbon nanotubes in Comparative Example 1 are bonded to each other, and the bundle diameter of the single-walled carbon nanotubes is about 100 nm - 300 nm. The bundles of single-walled carbon nanotubes obtained in Example 1 and Example 4 are opened, changing from thick bundles to thin bundles. As Figure 3 shown, the bundle diameter of the single-walled carbon nanotubes obtained in Example 1 is about 50 nm - 100 nm; as Figure 4 shown, the bundle diameter of the single-walled carbon nanotubes obtained in Example 4 is about 30 nm - 80 nm. Since a higher temperature was used for thermal shock in Example 4, a greater thermal stress was formed, and the bundles of the obtained single-walled carbon nanotubes are finer, and the single-walled carbon nanotubes are more fully debundled.

[0098] (II) Physical property tests

[0099] The pore size peak value of the micropores, the average value of the Raman spectrum IG / ID, the ratio of IG / ID > 100 and the ratio of IG / ID > 120, and the oxygen content of the single-walled carbon nanotubes obtained in Examples 1 to 8 and Comparative Example 2 above were tested. The specific test results are shown in Table 1.

[0100] Table 1

[0101]

[0102] As can be seen from Table 1, the peak pore diameters of the micropores of the single-walled carbon nanotubes obtained in Examples 1 to 8 are all increased compared to the peak pore diameters of the micropores of the single-walled carbon nanotubes in Comparative Example 1 and Comparative Example 2.

[0103] Figure 5 It is a graph of the micropore size distribution of the single-walled carbon nanotubes in Comparative Example 1 and the single-walled carbon nanotubes obtained in Examples 1 to 4.

[0104] Combined with Table 1 and Figure 5 it can be seen that the peak pore diameter of the inter-bundle micropores of the single-walled nanotubes in Comparative Example 1 is 0.45 nm. The peak of the inter-bundle micropore diameter of the single-walled carbon nanotubes obtained in Examples 1 to 4 shifts to the right, that is, the peak pore diameter of the micropores becomes larger. At the same time, the peak intensity of the micropores of the single-walled carbon nanotubes obtained in Examples 1 to 4 also increases. Among them, the peak intensity is the ratio of the derivative of the micropore volume to the derivative of the micropore diameter. The higher the peak intensity, the more micropores there are. Therefore, Figure 5 the results show that the number of micropores in the single-walled carbon nanotubes obtained in Examples 1 to 4 is more. This also shows that under the action of thermal stress, micropores or cracks are formed between the single-walled carbon nanotube bundles obtained in Examples 1 to 4, thus gradually unbundling.

[0105] Figure 6 It is a result diagram of Raman surface scanning of the single-walled carbon nanotubes in the comparative example and the single-walled carbon nanotubes obtained in Example 4.

[0106] Combined with Table 1 and Figure 6 it can be seen that the average value of 50 data of the IG / ID value of the Raman surface scanning of the single-walled carbon nanotubes in Comparative Example 1 is 47.07, and there is no point with IG / ID > 100 in the 50 data. The single-walled carbon nanotubes obtained in Example 4 were repaired at high temperature during the heat treatment. The average value of 50 data of the IG / ID value of the Raman surface scanning is 105.54. The proportion of IG / ID > 100 in the 50 data is 80%, and the proportion of IG / ID > 120 in the 50 data is 41%. The IG / ID values of the single-walled carbon nanotubes obtained in Examples 1 to 8 are all increased compared to the IG / ID values of the single-walled carbon nanotubes in Comparative Examples 1 and 2. That is, the single-walled carbon nanotubes in the examples of the present application have improved electrical conductivity while the bundle diameter is reduced.

[0107] As can be seen from Table 1, the oxygen content of the single-walled carbon nanotubes obtained in Examples 2 to 5, Example 7, and Example 8 is greater than that of the single-walled carbon nanotubes in Comparative Example 1 and the single-walled carbon nanotubes obtained in Examples 1 and 6. Since the reaction atmosphere for the heat treatment in Examples 2, 4, and 5 is water vapor, and the reaction atmosphere for the heat treatment in Examples 3, 7, and 8 is oxygen, by heating in an oxygen-containing reaction atmosphere, weak oxidation treatment of the single-walled carbon nanotubes is carried out at a relatively high temperature to introduce a small amount of oxygen-containing groups, increasing the oxygen content of the single-walled carbon nanotubes, thus improving the wettability of the single-walled carbon nanotubes in aqueous solvents. Therefore, in practical applications, for example, when preparing conductive pastes using single-walled carbon nanotubes, the process feeding of single-walled carbon nanotubes and the viscosity of the prepared conductive paste can be improved.

[0108] The single-walled carbon nanotubes obtained in the above Examples 1 to 8, Comparative Example 1, and Comparative Example 2 were prepared into conductive pastes, and to verify the performance of the prepared conductive pastes, a detection test was carried out on the performance of the prepared conductive pastes. The specific results are as follows:

[0109] Application Example 1

[0110] After premixing 2 g of the single-walled carbon nanotubes obtained in Example 1 above with 3 g of carboxymethyl cellulose in 95 g of pure water, it was pre-dispersed to about D50 = 100 μm using an emulsifier, and then transferred to a high-pressure homogenizer. At a pressure of 50 Mpa, it was homogenized multiple times to reduce its D50 to about 10 μm.

[0111] Application Example 2

[0112] The single-walled carbon nanotubes obtained in Example 2 above were used to prepare a conductive paste, and the preparation method of the conductive paste was the same as that in Application Example 1.

[0113] Application Example 3

[0114] The single-walled carbon nanotubes obtained in Example 3 above were used to prepare a conductive paste, and the preparation method of the conductive paste was the same as that in Application Example 1.

[0115] Application Example 4

[0116] The single-walled carbon nanotubes obtained in Example 4 above were used to prepare a conductive paste, and the preparation method of the conductive paste was the same as that in Application Example 1.

[0117] Application Example 5

[0118] After premixing 2 g of the single-walled carbon nanotubes obtained in Example 5 above with 3 g of carboxymethyl cellulose in 95 g of pure water, the mixture was pre-dispersed to about D50 = 130 μm using an emulsifier, and then transferred to a high-pressure homogenizer. Under a pressure of 50 Mpa, it was homogenized multiple times to reduce its D50 to about 10 μm.

[0119] Application Example 6

[0120] The single-walled carbon nanotubes obtained in Example 6 above were used to prepare a conductive paste, and the preparation method of the conductive paste was the same as that in Application Example 1.

[0121] Application Example 7

[0122] The single-walled carbon nanotubes obtained in Example 7 above were used to prepare a conductive paste, and the preparation method of the conductive paste was the same as that in Application Example 1.

[0123] Application Example 8

[0124] The single-walled carbon nanotubes obtained in Example 8 above were used to prepare a conductive paste, and the preparation method of the conductive paste was the same as that in Application Example 1.

[0125] Comparative Application Example 1

[0126] In Comparative Application Example 1, a conductive paste prepared using the initial single-walled carbon nanotubes in Comparative Example 1 above was used, and the preparation method of the conductive paste was the same as that in Application Example 1.

[0127] Comparative Application Example 2

[0128] In Comparative Application Example 2, a conductive paste prepared using the initial single-walled carbon nanotubes in Comparative Example 2 above was used, and the preparation method of the conductive paste was the same as that in Application Example 1.

[0129] Performance Detection Test of Conductive Paste

[0130] (I) Physical Property Test

[0131] The viscosity of the conductive pastes obtained in Application Examples 1 to 8 and Comparative Application Examples 1 and 2 above, the average value of the bundle diameters of the single-walled carbon nanotubes in the conductive pastes, and the standard deviation of the bundle diameters were tested. The specific test results are shown in Table 2.

[0132] Table 2

[0133]

[0134] As can be seen from Table 2, the D50 of the conductive pastes in Application Examples 1 to 8 and Comparative Application Examples 1 and 2 are relatively close. That is, by dispersing the conductive pastes in different application examples and comparative application examples to similar particle sizes, the other performance parameters between different application examples and comparative application examples are made more comparable.

[0135] As can be seen from Table 2, the average value and standard deviation of the bundle diameters of single-walled carbon nanotubes in the conductive pastes of Application Examples 1 to 8 are both smaller than those in the conductive pastes of Comparative Application Examples 1 and 2.

[0136] This shows that in the conductive pastes prepared from the single-walled carbon nanotubes obtained in the above Examples 1 to 8, the dispersibility and uniformity of the single-walled carbon nanotubes are better.

[0137] This is also because the single-walled carbon nanotubes obtained in Examples 1 to 8 were well deflected during at least one heating and cooling process. As a result, during the preparation of the conductive paste, the deflected single-walled carbon nanotubes are more easily further dispersed to form finer bundles, and thus a more uniform and dense conductive network can be formed, improving the electrical conductivity of the conductive paste.

[0138] It can be understood that when preparing the conductive paste with the single-walled carbon nanotubes obtained in Application Examples 1 to 8, even when the addition amount of the single-walled carbon nanotubes is relatively small, the electrical conductivity of the conductive paste can still be good.

[0139] For the same conductive solid content in the conductive paste, the lower the viscosity of the conductive paste, the more stable the conductive paste itself. If the viscosity of the conductive paste is too high, it will be difficult to transport the conductive paste during downstream application, and the viscosity of the conductive paste will increase to a certain extent due to the transportation environment or long-term storage of the conductive paste, and the storage state is also poor. As can be seen from Table 2, due to the better dispersibility of the deflected single-walled carbon nanotubes, the viscosity of the conductive pastes in Application Examples 1 to 8 is lower than that of the conductive paste in Comparative Application Example 1, that is, the stability of the conductive pastes in Application Examples 1 to 8 is better.

[0140]

[0141] ​The oxygen content of single-walled carbon nanotubes obtained by heat treatment in an oxygen-containing atmosphere such as oxygen and water vapor is higher than that of single-walled carbon nanotubes obtained by heat treatment in an inert atmosphere such as argon. As mentioned in the foregoing examples, this is because during heating in an oxygen-containing reaction atmosphere, the single-walled carbon nanotubes are weakly oxidized at a relatively high temperature, introducing a small amount of oxygen-containing groups, which increases the oxygen content of the single-walled carbon nanotubes. In this way, the wettability of the single-walled carbon nanotubes in aqueous solvents can be improved. Therefore, it can also be seen from the data in Table 2 that the single-walled carbon nanotubes with a high oxygen content obtained in the above examples have better hydrophilicity and are more easily dispersed, and the viscosity of the prepared conductive paste is also relatively low.

[0142] (II) Scanning electron microscope morphology

[0143] Figure 7 It is the scanning electron microscope image of the conductive paste in Comparative Application Example 1; Figure 8 It is the scanning electron microscope image of the conductive paste in Application Example 2; Figure 9 It is the scanning electron microscope image of the conductive paste in Application Example 3.

[0144] From Figures 7 to 9 it can be seen that under the condition of being dispersed to basically the same degree (that is, the particle size D50 of the conductive paste is close), the bundles of single-walled carbon nanotubes in the conductive pastes of Application Example 2 and Application Example 3 are finer than the bundles of single-walled carbon nanotubes in the conductive paste of Comparative Application Example 1, forming a more uniform and dense conductive network.

[0145] (III) Transmission electron microscope morphology

[0146] Figure 10 It is the transmission electron microscope image of the conductive paste in Comparative Application Example 1; Figure 11 It is the transmission electron microscope image of the conductive paste in Application Example 4.

[0147] From Figure 10 and Figure 11 it can be seen that under the condition of being dispersed to basically the same degree (that is, the particle size D50 of the conductive paste is close), the bundle diameter of the single-walled carbon nanotubes in the conductive paste of Comparative Application Example 1 is significantly larger than that of the single-walled carbon nanotubes in the conductive paste of Application Example 4, which is consistent with the results of the above scanning electron microscope morphology.

[0148] The conductive paste in the embodiments of the present application can be applied to lithium-ion batteries. The following is a performance study on the application of the conductive paste to lithium-ion batteries. Specifically, the conductive paste is used to simulate the preparation of electrode sheets, and the bulk resistivity and film resistivity of the electrode sheets are tested.

[0149] Simulation Example 1

[0150] The negative electrode main material silicon dioxide, the conductive paste prepared in the above application example 1 and polyacrylic acid were fully mixed in a mass ratio of 96.7:0.3:3, and then coated on the surface of copper foil and high-temperature resistant polyester film (PET film). The coating wet material thickness was 200 μm. The coating was continued for 1 hour at 100°C. After drying, the volume resistivity and film resistivity were tested using a four-probe resistance tester and a pole piece resistance meter, respectively.

[0151] Simulation Example 2

[0152] The difference from Simulation Example 1 is that the conductive paste used is the conductive paste prepared in Application Example 2, and other preparation conditions are the same.

[0153] Simulation Example 3

[0154] The difference from Simulation Example 1 is that the conductive paste used is the conductive paste prepared in Application Example 3, and other preparation conditions are the same.

[0155] Simulation Example 4

[0156] The difference from Simulation Example 1 is that the conductive paste used is the conductive paste prepared in Application Example 4, and other preparation conditions are the same.

[0157] Simulation Example 5

[0158] The difference from Simulation Example 1 is that the conductive paste used is the conductive paste prepared in Application Example 5, and other preparation conditions are the same.

[0159] Simulation Example 6

[0160] The difference from Simulation Example 1 is that the conductive paste used is the conductive paste prepared in Application Example 6, and other preparation conditions are the same.

[0161] Simulation Example 7

[0162] The difference from Simulation Example 1 is that the conductive paste used is the conductive paste prepared in Application Example 7, and other preparation conditions are the same.

[0163] Simulation Example 8

[0164] The difference from Simulation Example 1 is that the conductive paste used is the conductive paste prepared in Application Example 8, and other preparation conditions are the same.

[0165] Comparative simulation example 1

[0166] The difference from Simulation Example 1 is that the conductive paste used is the conductive paste prepared in Comparative Application Example 1, and other preparation conditions are the same.

[0167] Comparative simulation example 2

[0168] The difference from Simulation Example 1 is that the conductive paste applied is the conductive paste prepared in Comparative Application Example 2 above, and other preparation conditions are the same.

[0169] Table 3 shows the volume resistivity and film resistivity measured in Simulation Examples 1 to 8 and Comparative Simulation Examples 1 and 2.

[0170] Table 3

[0171]

[0172] Figure 12 is a bar chart of the volume resistivity and film resistivity measured in Simulation Examples 1 to 5 and Comparative Simulation Example 1.

[0173] From Table 3 and Figure 12 it can be seen that the values of the volume resistivity and film resistivity measured in Simulation Examples 1 to 8 are all smaller than those in Comparative Simulation Examples 1 and 2. This is because the bundles of single-walled carbon nanotubes after debundling are finer, with better dispersibility and uniformity in the conductive paste, and it is easier to construct a good conductive network under the same addition amount, making the conductivity of the conductive paste better. Therefore, when the conductive paste is applied in a lithium-ion battery, for example, the resistivity of the prepared electrode sheet will be smaller, thus making the performance of the lithium-ion battery better.

[0174] Figure 13 Scanning electron micrograph of the electrode sheet prepared in Comparative Simulation Example 1; Figure 14 is the scanning electron micrograph of the electrode sheet prepared in Simulation Example 4.

[0175] From Figure 13 and Figure 14 it can be seen that single-walled carbon nanotubes are coated on the surface of the electrode sheet. Compared with Comparative Simulation Example 1, the bundles of single-walled carbon nanotubes on the surface of silicon monoxide in the electrode sheet of Simulation Example 4 are finer, so that a better conductive network can be formed, which is beneficial to improving the conductivity of the electrode sheet.

[0176] It should be understood that the above embodiments are all exemplary and do not cover all possible implementation manners included in the claims. Without departing from the scope of the present disclosure, various deformations and changes can also be made on the basis of the above embodiments. Similarly, various technical features of the above embodiments can also be arbitrarily combined to form other embodiments of the present invention that may not be clearly described. Therefore, the above embodiments only represent several implementation manners of the present invention and do not limit the protection scope of the present invention patent.

Claims

1. A method for treating single-walled carbon nanotubes, characterized in that, The method includes: Performing at least one heating and cooling treatment on the initial single-walled carbon nanotubes; the heating and cooling treatment includes: Performing a heating treatment on the initial single-walled carbon nanotubes for a preset time; the preset time is 0.1 s - 5 s; Introducing an inert gas to perform a cooling treatment on the initial single-walled carbon nanotubes after the heating treatment, such that the initial single-walled carbon nanotubes are cooled within 1 min - 10 min.

2. The processing method of single-walled carbon nanotubes according to claim 1, characterized in that The reaction temperature range of the heating treatment is 800 °C - 2000 °C; and / or, the temperature range after the cooling treatment is 25 °C - 100 °C.

3. The method for treating single-walled carbon nanotubes according to claim 1, characterized in that, The heating treatment is performed in a reaction atmosphere containing oxygen.

4. The treatment method of single-walled carbon nanotubes according to claim 1, characterized in that, The number of times of the heating and cooling treatment is greater than or equal to 3 times.

5. The treatment method of single-walled carbon nanotubes according to any one of claims 1 to 4, characterized in that, The tube bundle diameter of the initial single-walled carbon nanotubes is greater than 100 nm; the average value of IG / ID of the Raman spectrum of the initial single-walled carbon nanotubes is between 30 and 60.

6. A single-walled carbon nanotube, characterized in that, Prepared by using the treatment method of single-walled carbon nanotubes according to any one of claims 1 to 5.

7. A single-walled carbon nanotube, characterized in that, The tube bundle diameter of the single-walled carbon nanotubes is less than or equal to 100 nm; the average value of IG / ID of the Raman spectrum of the single-walled carbon nanotubes is between 50 and 150; the proportion of the Raman spectrum of the single-walled carbon nanotubes with IG / ID greater than 100 is 20% - 80%; the proportion of the Raman spectrum of the single-walled carbon nanotubes with IG / ID greater than 120 is 5% - 40%; the pore size peak of the micropores in the single-walled carbon nanotubes is between 0.5 nm and 1 nm.

8. A conductive paste, characterized in that, Prepared by using the single-walled carbon nanotubes according to claim 6 or 7.

9. The conductive paste according to claim 8, wherein The tube bundle diameter range of the single-walled carbon nanotubes in the conductive paste is 1.6 nm - 50 nm; the viscosity range of the conductive paste is 500 cp - 10000 cp.

10. Application of a conductive paste according to claim 8 or 9 in a lithium-ion battery.

Images