CN112086643A - Carbon nano tube and application thereof - Google Patents

Abstract

The invention relates to a carbon nanotube and its application. It can be seen under a high-power transmission electron microscope that the lattice fringes of the carbon layer on the tube wall of the carbon nanotube and the tube axis of the carbon nanotube form an included angle of 5° to 15°. This structure can provide more edge lithium storage sites and shorter lithium ion migration channels, which is beneficial to the improvement of lithium storage performance. The carbon nanotubes are more suitable for use as negative electrode materials of lithium ion batteries, and the flexible thin film electrodes containing the carbon nanotubes have high specific capacity, good rate performance and cycle stability when used as negative electrodes of lithium ion batteries.

Description

A kind of carbon nanotube and its application

technical field

The present invention relates to a carbon nanotube and its application.

Background technique

With the development of flexible and wearable electronic devices, there is an increasingly urgent need for high-efficiency flexible batteries, the key of which is the development of flexible thin-film electrodes. Loading active materials or directly growing active materials on flexible conductive substrates (such as carbon fiber cloth or carbon fiber paper) is an important way to prepare flexible electrodes.

Guanhua Zhang et al. disclosed a carbon fiber cloth flexible electrode with core-shell nanoarrays (High-Performance and Ultra-Stable Lithium-Ion Batteries Based on MOF-DerivedZnO@ZnO Quantum Dots/C Core-Shell Nanorod Arrays on a Carbon Cloth Anode, Advanced Materials, 2015, 27, 2400-2405). Firstly, ZnO nanorod arrays are oriented and grown on a flexible carbon cloth substrate by low-temperature solution deposition reaction, and then the ZnO nanorods are used as templates and zinc sources, 2-methylimidazole as ligand and etchant, and the surface of ZnO nanorods is formed on the surface of ZnO nanorods. The zeolite imidazolate framework material was coated, and finally calcined at 650 °C under high-purity N ₂ to transform the coating layer of the zeolite imidazolate framework material into an amorphous carbon framework and ZnO quantum dots, thereby obtaining ZnO@ ZnO quantum dot/C core-shell structured nanorod arrays. The material has a reversible (delithiation) specific capacity of 1055mAh/g at a current density of 100mA/g, and also has a good rate capability (530mAh/g at a current density of 1000mA/g, has a reversible (delithiation) specific capacity of 530mAh/g and cycling stability (capacity loss is only 11% at 500 mA/g current density for 100 cycles).

Jun Chen et al. disclosed a carbon fiber paper flexible electrode for Li-ion batteries (Carbonnanotube network modified carbon fibre paper for Li-ion batteries, Energy & Environmental Science, 2009, 2, 393–396). The iron compound is impregnated on carbon fiber paper as a catalyst, and ethylene is used as a carbon source, and carbon nanotubes are grown on the carbon fiber paper by a vapor deposition method, thereby preparing a carbon fiber paper flexible electrode. In terms of carbon nanotubes, the reversible (delithiation) specific capacity of the flexible electrode was 546 mAh/g after 50 cycles of cycling.

To sum up, in the existing flexible thin film electrodes, either the preparation process is complicated, or the performance is not ideal, so it is necessary to develop a flexible thin film electrode with a simpler preparation process and better performance.

SUMMARY OF THE INVENTION

One of the objectives of the present invention is to provide a flexible thin film electrode, which has better performance when used as a negative electrode of a lithium ion battery. The second purpose of the present invention is to use cheap heavy oil to prepare the aforementioned flexible thin film electrode. The third object of the present invention is to provide a novel carbon nanotube, which is more suitable for use as a negative electrode material for lithium ion batteries.

Specifically, the present invention includes the following.

1. a preparation method of electrode is characterized in that, with heavy oil as carbon source, with the carbon fiber cloth or carbon fiber paper that has been loaded with nickel-cobalt hydrotalcite as substrate, grow carbon nanotubes on described substrate with vapor deposition method, That is, the electrodes are obtained.

2. according to the preparation method described in 1, it is characterized in that, described substrate is made by the following method: in the liquid phase reaction system immersed in carbon fiber cloth or carbon fiber paper, synthesizing nickel-cobalt hydrotalcite, obtains loaded nickel-cobalt water Carbon fiber cloth or carbon fiber paper of talc, that is, the substrate.

3. according to the preparation method described in 1 or 2, it is characterised in that the substrate is obtained by the following method:

(1) prepare the solution of nickel salt, cobalt salt and quaternary ammonium salt, and the solvent is alcohol, water or a mixture of the two;

(2) Immerse carbon fiber cloth or carbon fiber paper in the solution, and then react at 100°C to 200°C for more than 20 hours to obtain carbon fiber cloth or carbon fiber paper loaded with nickel-cobalt hydrotalcite, that is, the substrate.

4. According to the preparation method described in 3, it is characterized in that, in step (1), taking the quality of the solvent as 1 and in terms of the quality of the cobalt element, the consumption of the cobalt salt is 0.0004～0.0008; The molar ratio of cobalt is 1-2.5:1; the amount of quaternary ammonium salt is such that the molar ratio of quaternary ammonium salt and cobalt is 7.5-10:1.

5. The preparation method according to 3 or 4, wherein the alcohol is methanol, ethanol, isopropanol or ethylene glycol.

6. The preparation method according to any one of 3 to 5, wherein the solvent is a mixture of methanol and water, and the mass ratio of the two is 2 to 6:1.

7. The preparation method according to any one of 3 to 6, wherein the nickel salt is nickel nitrate or nickel chloride; and the cobalt salt is cobalt nitrate or cobalt chloride.

8. The preparation method according to any one of 3 to 7, wherein the quaternary ammonium salt has the structure of R(CH ₃ ) ₃ N ⁺ X ^- , wherein R is a straight-chain alkyl group of C10-C18; Described quaternary ammonium salt is preferably dodecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium bromide. ammonium, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, octadecyltrimethylammonium chloride or octadecyltrimethylammonium bromide.

9. The preparation method according to any one of 3 to 8, characterized in that, in step (2), the reaction time is 20 hours to 30 hours.

10. The preparation method according to any one of 1 to 9, characterized in that, comprising:

(1) the substrate and the heavy oil are respectively placed in the deposition zone and the volatilization zone of the vapor deposition furnace;

(2) the carrier gas is blown from the volatilization zone where the heavy oil is placed to the deposition zone where the substrate is placed; vapor deposition is carried out in the deposition zone; the carrier gas is a mixture of hydrogen and an inert gas;

(3) After the deposition is completed, stop the air blowing in the direction described in (2); drop to room temperature under the protection of the atmosphere.

11. The preparation method according to 10, wherein the temperature of the deposition zone is 900°C to 1200°C, and the temperature of the volatilization zone is 400°C to 800°C.

12. The preparation method according to any one of the foregoing, characterized in that, based on the area of the substrate, the amount of heavy oil used is 0.01 g/cm ² to 0.10 g/cm ² .

13. The preparation method according to any one of the foregoing, characterized in that, the time of vapor deposition is 0.5h to 2h.

14. The preparation method according to any one of the foregoing, wherein the heavy oil is atmospheric residual oil or vacuum residual oil.

15. The preparation method according to any one of the foregoing, wherein the sulfur content of the heavy oil is 0.5 m% to 5 m%, and may be 2 m% to 5 m%.

Electrodes prepared by any one of 16.1 to 15.

17. An electrode, characterized in that it comprises carbon fiber cloth or carbon fiber paper, and carbon nanotubes that grow outward on its fibers; the carbon nanotubes are obtained by catalytic growth of nickel/cobalt; The diameter is 80nm-250nm, the inner diameter is 30nm-100nm, and the length is 5μm-50μm; in terms of the area of the carbon fiber cloth or carbon fiber paper, the loading amount of the carbon nanotubes is 1 mg/cm ² -4 mg/cm ² .

18. A carbon nanotube, characterized in that, as can be seen from a high-power transmission electron microscope, the lattice fringes of the carbon layer of the tube wall of the carbon nanotube and the tube axis of the carbon nanotube form an included angle of 5° to 15°.

19. The carbon nanotube according to 18, characterized in that, the carbon nanotube is made from nickel-cobalt hydrotalcite and heavy oil.

20. An electrode, characterized in that the carbon nanotubes described in 19 are used.

21 . A lithium ion battery, characterized by using the electrode prepared by any one of the methods of claims 1 to 15 , the electrode of claim 17 or the electrode of claim 20 .

The present invention has the following beneficial technical effects: in the flexible thin film electrode of the present invention, the carbon nanotubes are evenly distributed on the carbon fiber cloth or carbon fiber paper, the diameter of the pipe is uniform, and the surface is smooth; when the thin film electrode is used as a negative electrode of a lithium ion battery, it has a high ratio of carbon nanotubes. capacity, good rate performance and cycle stability; in addition, the present invention uses inferior heavy oil as a carbon source, which not only has low cost, but also provides a new way for high value-added utilization of inferior heavy oil.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Description of drawings

FIG. 1 is an XRD pattern of the substrate of Example 1. FIG.

FIG. 2 is a scanning electron microscope photograph of the substrate of Example 1 at a magnification of 5000 times.

FIG. 3 is a scanning electron microscope photograph of the thin film electrode of Example 1 at a magnification of 1000 times.

FIG. 4 is a scanning electron microscope photograph of the thin film electrode of Example 1 at a magnification of 30,000 times.

FIG. 5 is a high-resolution transmission electron microscope photograph of carbon nanotubes on the thin film electrode of Example 1. FIG.

FIG. 6 is an enlarged photograph of the boxed area in FIG. 5 .

FIG. 7 is the test result of the charge-discharge cycle performance of the thin-film electrode of Example 1. FIG. Among them, the abscissa is the cycle number, and the unit is: week; the ordinate is the mass specific capacity, and the unit is: milliampere hour/gram (mAh/g).

FIG. 8 is the test results of the rate performance of the thin film electrode of Example 1 under different current densities. Among them, the abscissa is the cycle number, and the unit is: week; the ordinate is the mass specific capacity, and the unit is: milliampere hour/gram (mAh/g).

FIG. 9 is a scanning electron microscope photograph of the substrate of Example 2 at a magnification of 10,000 times.

FIG. 10 is a scanning electron microscope photo of Example 2 when carbon nanotubes grow out of carbon cloth fibers at a magnification of 5000 times.

FIG. 11 is a scanning electron microscope photo of Example 2 when carbon nanotubes grow out of carbon cloth fibers at a magnification of 30,000 times.

12 is a high-resolution transmission electron microscope photograph of carbon nanotubes grown out of carbon cloth fibers in Example 2.

FIG. 13 is an enlarged high-resolution transmission electron microscope photo of the black frame area in FIG. 12 .

FIG. 14 is the test result of the charge-discharge cycle performance of the thin-film electrode in Example 2. FIG. Among them, the abscissa is the cycle number, and the unit is: week; the ordinate is the mass specific capacity, and the unit is: milliampere hour/gram (mAh/g).

FIG. 15 is the test result of the rate performance of the thin film electrode of Example 2. FIG. Among them, the abscissa is the cycle number, and the unit is: week; the ordinate is the mass specific capacity, and the unit is: milliampere hour/gram (mAh/g).

FIG. 16 is a scanning electron microscope photograph of the substrate of Example 3 at a magnification of 10,000 times.

FIG. 17 is a scanning electron microscope photo of Example 3 when the carbon nanotubes grow out of the carbon cloth fiber at a magnification of 10,000 times.

FIG. 18 is an ordinary through-photograph of Example 3 when the carbon nanotubes grow out of the carbon cloth fiber at a magnification of 50,000 times.

FIG. 19 is a high-resolution transmission electron microscope photograph of carbon nanotubes on the thin film electrode of Example 3. FIG.

FIG. 20 is a high-resolution transmission electron microscope photograph of the enlarged black frame area in FIG. 19 .

FIG. 21 is the test result of the charge-discharge cycle performance of the thin-film electrode of Example 3. FIG. Among them, the abscissa is the cycle number, and the unit is: week; the ordinate is the mass specific capacity, and the unit is: milliampere hour/gram (mAh/g).

FIG. 22 is the test result of the rate performance of the thin film electrode of Example 3. FIG. Among them, the abscissa is the cycle number, and the unit is: week; the ordinate is the mass specific capacity, and the unit is: milliampere hour/gram (mAh/g).

FIG. 23 is a scanning electron microscope photograph of the carbon nanotubes of Comparative Example 1 growing out of the carbon cloth fibers at a magnification of 20,000 times.

FIG. 24 is a scanning electron microscope photo of Comparative Example 1 when carbon nanotubes grow out of carbon cloth fibers at a magnification of 100,000 times.

Detailed ways

The technical terms in the present invention, those defined in the present invention shall be defined according to their definitions, and those not defined shall be understood according to the usual meanings in the art.

In the context of this specification, except where explicitly stated, any matter or matter not mentioned applies directly to those known in the art without any change. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are regarded as part of the original disclosure or original record of the present invention, and should not be It is considered to be new content not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

All the features disclosed in the present invention can be combined arbitrarily, and these combinations should be construed as the contents disclosed or recorded in the present invention, unless those skilled in the art consider that the combination is obviously unreasonable. The numerical points disclosed in this specification not only include the specific disclosed numerical points, but also include the endpoints of each numerical range, and the range of any combination of these numerical points shall be regarded as the disclosed or recorded range of the present invention, regardless of whether or not it is described herein. These value pairs are disclosed one by one.

In the present invention, carbon nanotubes refer to one-dimensional tubular carbon materials with a diameter of several nanometers to several hundreds of nanometers.

(1) Preparation of the substrate

The present invention first provides a method for preparing a substrate, which comprises: synthesizing nickel-cobalt hydrotalcite in a liquid-phase reaction system impregnated with carbon fiber cloth or carbon fiber paper to obtain a carbon fiber cloth or carbon fiber paper loaded with nickel-cobalt hydrotalcite , that is, the base.

According to the present invention, the carbon fiber cloth or carbon fiber paper is not particularly limited, and those carbon fiber cloths known in the art can be used. The main component of carbon fiber cloth and carbon fiber paper is carbon fiber, which is generally pretreated before use to remove impurities.

The present invention provides a specific method for preparing the substrate, including:

(1) prepare the solution of nickel salt, cobalt salt and quaternary ammonium salt, and the solvent is alcohol, water or a mixture of the two;

(2) Immerse carbon fiber cloth or carbon fiber paper in the solution, and then react at 100°C to 200°C for more than 20 hours to obtain carbon fiber cloth or carbon fiber paper loaded with nickel-cobalt hydrotalcite, that is, the substrate.

According to the present invention, in step (1), the mass of the solvent is 1 and the mass of the cobalt element is calculated, the amount of the cobalt salt is 0.0004-0.0008; the amount of the nickel salt is such that the molar ratio of nickel to cobalt is 1-2.5:1 ; The dosage of quaternary ammonium salt makes the molar ratio of quaternary ammonium salt and cobalt to be 7.5 to 10:1.

According to the present invention, generally, the carbon fiber cloth (or carbon fiber paper) can be put into the solution according to the ratio of the area of the carbon fiber cloth (or carbon fiber paper) to the solution volume of 0.2 cm ² /mL to 2.0 cm ² /mL.

According to the present invention, the alcohol is not particularly limited as long as it is suitable for preparing nickel-cobalt hydrotalcite. The alcohol can be methanol, ethanol, isopropanol or ethylene glycol.

According to the present invention, the preferred solvent is a mixture of methanol and water, and the mass ratio of the two is 2-6:1.

According to the present invention, the nickel salt or cobalt salt is not particularly limited as long as it is suitable for preparing nickel-cobalt hydrotalcite. The nickel salt can be nickel nitrate or nickel chloride. The cobalt salt can be cobalt nitrate or cobalt chloride.

According to the present invention, the quaternary ammonium salt is not particularly limited as long as it is suitable for preparing nickel-cobalt hydrotalcite. The quaternary ammonium salt preferably has the structure of R(CH ₃ ) ₃ N ⁺ X ^- , wherein R can be a C10-C18 straight-chain alkyl group. Described quaternary ammonium salt is more preferably dodecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium chloride, tetradecyl trimethyl bromide ammonium chloride, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, octadecyltrimethylammonium chloride or octadecyltrimethylammonium bromide.

According to the present invention, in step (2), the reaction time may be 20 hours to 30 hours.

(2) Preparation of flexible thin film electrodes

The invention provides a method for preparing an electrode. The method uses heavy oil as a carbon source, uses a carbon fiber cloth or carbon fiber paper loaded with nickel-cobalt hydrotalcite as a substrate, and uses a vapor deposition method to grow carbon nanotubes on the substrate, That is, the electrodes are obtained.

According to the present invention, the heavy oil is not particularly limited, and it can be atmospheric residual oil or vacuum residual oil.

According to the present invention, very poor quality heavy oils can be used. For example, the sulfur content of the heavy oil may be 0.5 m% to 5 m%, or 2 m% to 5 m%. For example, the gum content of the heavy oil may be 15 m% to 30 m%, or 20 m% to 25 m%. For example, the asphaltene content of the heavy oil may be 5 m% to 25 m%, or 10 m% to 15 m%.

According to the present invention, the heavy oil is used in an amount of 0.01 g/cm ² to 0.10 g/cm ² based on the area of the substrate.

According to the present invention, the time of vapor deposition is generally 0.5h-2h.

The present invention provides a specific method for preparing the electrode, including:

(1) the substrate and the heavy oil are respectively placed in the deposition zone and the volatilization zone of the vapor deposition furnace;

(2) the carrier gas is blown from the volatilization zone where the heavy oil is placed to the deposition zone where the substrate is placed; vapor deposition is carried out in the deposition zone; the carrier gas is a mixture of hydrogen and an inert gas;

(3) After the deposition is completed, stop the air blowing in the direction described in (2); drop to room temperature under the protection of the atmosphere.

According to the present invention, the temperature of the deposition zone is generally 900°C to 1200°C, and the temperature of the volatilization zone is generally 400°C to 800°C.

In the present invention, the inert gas refers to any gas that has no substantial influence on the reaction process, for example, nitrogen gas or a group 18 gas (such as helium gas or argon gas).

According to the present invention, the volume ratio of hydrogen to inert gas is generally 5:95 to 10:90.

(3) Flexible thin film electrodes

The invention provides an electrode, which comprises carbon fiber cloth or carbon fiber paper, and carbon nanotubes growing out on its fibers; the carbon nanotubes are obtained by catalytic growth of nickel/cobalt; the carbon nanotubes are The outer diameter is 80nm-250nm, the inner diameter is 30nm-120nm, and the length is 5μm-50μm; in terms of the area of the carbon fiber cloth or carbon fiber paper, the loading amount of the carbon nanotubes is 1 mg/cm ² -4 mg/cm ² .

(4) Carbon nanotubes

In the process of preparing the aforementioned electrodes, the inventors unexpectedly obtained a carbon nanotube with a novel structure, which can be seen under a high-magnification transmission electron microscope. The axis of the tube is at an angle of 5° to 15°. This novel structure can provide more edge lithium storage sites and shorter lithium ion migration channels, which is beneficial to the improvement of lithium storage performance.

(5) Lithium-ion battery

The present invention also provides a lithium ion battery using the electrode prepared by any of the foregoing methods or any of the foregoing electrodes.

The following examples further illustrate the present invention, but do not constitute any limitation to the present invention.

Example 1

(1) Preparation of substrate

Dissolve 0.1221g of Ni(NO ₃ ) ₂ ·6H ₂ O, 0.0815g of Co(NO ₃ ) ₂ ·6H ₂ O and 1g of cetyltrimethylammonium bromide in a mixed solvent of 24g of methanol and 6g of water , ultrasonically dispersed to obtain a uniform and transparent solution; transfer the solution to a 100 mL polytetrafluoroethylene-lined reaction kettle; cut out 6 pieces of 2cm × 4cm rectangles from the carbon cloth, put them in acetone, anhydrous ethanol, deionized The water was ultrasonically cleaned for 30min, then placed in the solution of the above reaction kettle, and reacted at 150°C for 24h; after the reaction, the carbon cloth was taken out, washed with deionized water, and dried in an oven at 80°C for 8h. the described base.

It can be seen from FIG. 1 (XRD) and FIG. 2 (SEM) that in the obtained substrate, nickel-cobalt hydrotalcite is uniformly supported on the carbon cloth.

(2) Preparation of electrodes

The substrate obtained in (1) is spread on the alumina magnetic boat, then the above-mentioned magnetic boat is placed in the center position of the deposition zone of the double-temperature zone tube furnace, and 0.5g heavy oil (see Table 1 for properties) is weighed and placed in the double-temperature zone. The central position of the volatilization zone of the zone tube furnace; along the direction from the deposition zone to the volatilization zone, a mixture of hydrogen and argon with a volume percentage of 90% argon was passed in at a flow rate of 50mL/min for 0.5h, and then the deposition was carried out within 200min. The temperature was raised to 1000°C in the zone, and then the hydrogen-argon mixture was adjusted to blow from the volatilization zone to the deposition zone, the flow rate of the hydrogen-argon mixture was 50mL/min, and the heating program of the volatilization zone was started, and the volatilization zone was heated to 600°C within 120min. Then keep the temperature reaction for 60min, after the reaction, adjust the direction of the hydrogen-argon mixture to blow from the deposition zone to the volatilization zone, keep the flow rate of the hydrogen-argon mixture at 50mL/min, and cool the furnace body to room temperature to obtain the electrode. .

It can be seen from Fig. 3 that in the obtained electrode, the carbon nanotubes grow out of the carbon cloth fiber and are evenly distributed on the carbon cloth, and the tube length is about 20 μm.

It can be seen from FIG. 4 that in the obtained electrode, the carbon nanotubes are basically straight carbon nanotubes with uniform diameter and smooth surface.

It can be seen from FIG. 5 that in the obtained electrode, the outer diameter of the carbon nanotubes is about 150 nm and the inner diameter is about 70 nm. It can be seen from Figure 6 (enlarged view of the box area in Figure 5) that in the obtained electrode, the lattice fringes of the carbon layer on the tube wall are obviously inclined with respect to the tube axis (c-axis) direction, and the inclination angle is about 12°.

The obtained electrode was punched into a circular electrode sheet with a diameter of 1 cm by a punching machine, and the amount of active material was weighed to calculate the amount of active material before use. The obtained active material loading amount was 1.51 mg/cm ² . Using the obtained electrode sheet as the positive electrode and the lithium sheet as the negative electrode, a half-cell was assembled with BLE-207 electrolyte (DMC+DEC+DC+LiPF ₆ with a volume ratio of 1:1:1, concentration of 1 mol/L). The half-cell is a CR2032 button battery, which is assembled in the German MBRAUN glove box. The assembly materials are negative electrode shell-lithium sheet-diaphragm-positive electrode sheet-gasket-shrapnel-positive electrode shell, assembled from bottom to top, static Test after 24h. The assembled button battery was tested by Land CT2001A battery test system. When the charge-discharge cut-off voltage range is 0.1-2.5V (vs. Li+/Li) and the current density is 400mA/g, the initial reversible specific capacity is 1506.9mAh /g, the reversible specific capacity retention rate was 91.6% after 100 cycles of cycling (see Figure 7 for the test results).

The obtained electrode was punched into a circular electrode sheet with a diameter of 1 cm by a punching machine, and the amount of active material was weighed to calculate the amount of active material before use. The obtained active material loading amount was 1.23 mg/cm ² . Using the obtained electrode sheet as the positive electrode and the lithium sheet as the negative electrode, a half-cell was assembled with BLE-207 electrolyte (DMC+DEC+DC+LiPF ₆ with a volume ratio of 1:1:1, concentration of 1 mol/L). The half-cell is a CR2032 button battery, which is assembled in the German MBRAUN glove box. The assembly materials are negative electrode shell-lithium sheet-diaphragm-positive electrode sheet-gasket-shrapnel-positive electrode shell, assembled from bottom to top, static Test after 24h. The button battery assembled above was tested by Land CT2001A battery test system. When the charge-discharge cut-off voltage range is 0.1-2.5V (vs. Li+/Li) and the current density is 200mA/g, the reversible specific capacity is 1586.2mAh/g , when the current density increased to 5000mA/g, the reversible specific capacity was 714mAh/g, and the rate performance was excellent (see Figure 8 for the test results).

Table 1 Properties of heavy oil

Example 2

(1) Preparation of substrate

Dissolve 0.1017g of Ni(NO ₃ ) ₂ ·6H ₂ O, 0.1018g of Co(NO ₃ ) ₂ ·6H ₂ O and 1g of cetyltrimethylammonium bromide in a mixed solvent of 25g of methanol and 5g of water , ultrasonically dispersed to obtain a uniform and transparent solution; transfer the solution to a 100 mL polytetrafluoroethylene-lined reaction kettle; cut out two 2cm × 4cm rectangles from the carbon cloth, put them in acetone, anhydrous ethanol, deionized The water was ultrasonically cleaned for 40min, then placed in the solution of the above reaction kettle, and reacted at 180°C for 20h; after the reaction, the carbon cloth was taken out, washed with deionized water, and dried in a 100°C oven for 5h. the described base.

As can be seen from FIG. 9 (SEM), in the obtained substrate, nickel-cobalt hydrotalcite was uniformly supported on the carbon cloth.

(2) Preparation of electrodes

The substrate obtained in (1) is spread on the alumina magnetic boat, then the above-mentioned magnetic boat is placed in the center position of the deposition zone of the double-temperature zone tube furnace, and 1.5g of heavy oil (see Table 1 for properties) is weighed and placed in the double-temperature zone. The central position of the volatilization zone of the zone tube furnace; along the direction from the deposition zone to the volatilization zone, a hydrogen-argon mixture with a volume percentage of 95% argon gas was introduced at a flow rate of 100mL/min for 0.5h, and then the deposition was carried out within 275min. The temperature was raised to 1100°C in the zone, and then the hydrogen-argon mixture was adjusted to blow from the volatilization zone to the deposition zone, the flow rate of the hydrogen-argon mixture was 50mL/min, and the heating program of the volatilization zone was started, and the volatilization zone was heated to 650°C within 130min. Then keep the temperature reaction for 90min, after the reaction, adjust the direction of the hydrogen-argon mixture to blow from the deposition zone to the volatilization zone, keep the flow rate of the hydrogen-argon mixture at 100mL/min, and cool the furnace body to room temperature to obtain the electrode. .

It can be seen from Fig. 10 that in the obtained electrode, carbon nanotubes grow out of the carbon cloth fiber and are evenly distributed on the carbon cloth, and the tube length is about 10 μm.

It can be seen from FIG. 11 that in the obtained electrode, the carbon nanotubes are basically straight carbon nanotubes, with uniform diameter and smooth surface.

It can be seen from FIG. 12 that in the obtained electrode, the outer diameter of the carbon nanotubes is about 200 nm and the inner diameter is about 120 nm. It can be seen from Fig. 13 (enlarged view of the box area in Fig. 12) that in the obtained electrode, the lattice fringes of the carbon layer on the tube wall are obviously inclined with respect to the tube axis (c-axis) direction, and the inclination angle is about 9°.

The obtained electrode was punched into a circular electrode sheet with a diameter of 1 cm by a punching machine, and the amount of active material was weighed to calculate the amount of active material before use. The obtained active material loading amount was 1.38 mg/cm ² . Using the obtained electrode sheet as the positive electrode and the lithium sheet as the negative electrode, a half-cell was assembled with BLE-207 electrolyte (DMC+DEC+DC+LiPF ₆ with a volume ratio of 1:1:1, concentration of 1 mol/L). The half-cell is a CR2032 button battery, which is assembled in the German MBRAUN glove box. The assembly materials are negative electrode shell-lithium sheet-diaphragm-positive electrode sheet-gasket-shrapnel-positive electrode shell, assembled from bottom to top, static Test after 24h. The assembled button battery was tested by Land CT2001A battery test system. When the charge-discharge cut-off voltage range is 0.1-2.5V (vs. Li+/Li) and the current density is 400mA/g, the initial reversible specific capacity is 1263.6mAh /g, the reversible specific capacity retention rate was 83.1% after 100 cycles of cycling (see Figure 14 for the test results).

The obtained electrode was punched into a circular electrode sheet with a diameter of 1 cm by a punching machine, and the amount of active material was weighed to calculate the amount of active material before use. The obtained active material loading amount was 1.23 mg/cm ² . Using the obtained electrode sheet as the positive electrode and the lithium sheet as the negative electrode, a half-cell was assembled with BLE-207 electrolyte (DMC+DEC+DC and LiPF ₆ in a volume ratio of 1:1:1, with a concentration of 1 mol/L). The half-cell is a CR2032 button battery, which is assembled in the German MBRAUN glove box. The assembly materials are negative electrode shell-lithium sheet-diaphragm-positive electrode sheet-gasket-shrapnel-positive electrode shell, assembled from bottom to top, static Test after 24h. The button battery assembled above is used in the Land CT2001A battery test system. When the current density is 200mA/g, the reversible specific capacity is 1134mAh/g, and when the current density increases to 5000mA/g, the reversible specific capacity is 258.2mAh. /g, excellent rate performance (see Figure 15 for the test results).

Example 3

(1) Preparation of substrate

Dissolve 0.1424g of Ni(NO ₃ ) ₂ ·6H ₂ O, 0.0611g of Co(NO ₃ ) ₂ ·6H ₂ O and 1g of cetyltrimethylammonium bromide in a mixed solvent of 20g of methanol and 10g of water , ultrasonically dispersed to obtain a uniform and transparent solution; transfer the solution to a 50mL polytetrafluoroethylene-lined reaction kettle; cut out 4 pieces of 2cm×4cm rectangles from the carbon cloth, put them in acetone, anhydrous ethanol, deionized The water was ultrasonically cleaned for 30 minutes, then placed in the solution of the above reaction kettle, and reacted at 120 °C for 28 hours; after the reaction, the carbon cloth was taken out, washed with deionized water, and dried in a 60 °C oven for 10 hours. the described base.

As can be seen from FIG. 16 (SEM), in the obtained substrate, nickel-cobalt hydrotalcite was uniformly supported on the carbon cloth.

(2) Preparation of electrodes

The base obtained in (1) is spread on the alumina magnetic boat, then the above-mentioned magnetic boat is placed in the center position of the deposition zone of the double-temperature zone tube furnace, and 2g heavy oil is weighed and placed in the volatilization zone of the double-temperature zone tube furnace. Center position; along the direction from the deposition zone to the volatilization zone, a hydrogen-argon mixture with a volume percentage of 92% argon gas was introduced at a flow rate of 80mL/min for 0.5h, and then the deposition zone was heated to 900°C within 300min, and then Adjust the hydrogen-argon mixture to blow from the volatilization zone to the deposition zone, keep the flow rate of the hydrogen-argon mixture at 80mL/min, and start the heating program of the volatilization zone, and heat the volatilization zone to 700°C within 175min, and then maintain the temperature for 30min. After the reaction, the direction of the hydrogen-argon mixture was adjusted to blow from the deposition zone to the volatilization zone, and the flow rate of the hydrogen-argon mixture was kept at 80 mL/min to cool the furnace body to room temperature to obtain the electrode.

It can be seen from FIG. 17 that in the obtained electrode, carbon nanotubes grow out of the carbon cloth fibers and are evenly distributed on the carbon cloth, and the tube length is about 10 μm.

As can be seen from FIG. 18 , in the obtained electrode, the carbon nanotubes are basically straight carbon nanotubes, with uniform diameter and smooth surface.

It can be seen from FIG. 19 that in the obtained electrode, the outer diameter of the carbon nanotubes is about 80 nm and the inner diameter is about 30 nm. It can be seen from Fig. 20 (enlarged view of the box area in Fig. 19) that in the obtained electrode, the lattice fringes of the carbon layer on the tube wall are obviously inclined with respect to the tube axis (c-axis) direction, and the inclination angle is about 10°.

For the obtained electrode, the electrode was punched into a circular electrode sheet with a diameter of 1 cm by a punching machine, and the amount of active material was weighed to calculate the amount of active material before use. The obtained active material loading amount was 1.55 mg/cm ² . Using the obtained electrode sheet as the positive electrode and the lithium sheet as the negative electrode, a half-cell was assembled with BLE-207 electrolyte (DMC+DEC+DC+LiPF ₆ with a volume ratio of 1:1:1, concentration of 1 mol/L). The half-cell is a CR2032 button battery, which is assembled in the German MBRAUN glove box. The assembly materials are negative electrode shell-lithium sheet-diaphragm-positive electrode sheet-gasket-shrapnel-positive electrode shell, assembled from bottom to top, static Test after 24h. The assembled button battery was tested by Land CT2001A battery test system. When the charge-discharge cut-off voltage range is 0.1-2.5V (vs. Li+/Li) and the current density is 400mA/g, the initial reversible specific capacity is 929.4mAh. /g, the reversible specific capacity retention rate was 98.5% after 100 cycles of cycling (see Figure 21 for the test results).

For the obtained electrode, the electrode was punched into a circular electrode sheet with a diameter of 1 cm by a punching machine, and the amount of active material was weighed to calculate the amount of active material before use. The obtained active material loading amount was 1.67 mg/cm ² . Using the obtained electrode sheet as the positive electrode and the lithium sheet as the negative electrode, a half-cell was assembled with BLE-207 electrolyte (DMC+DEC+DC and LiPF ₆ in a volume ratio of 1:1:1, with a concentration of 1 mol/L). The half-cell is a CR2032 button battery, which is assembled in the German MBRAUN glove box. The assembly materials are negative electrode shell-lithium sheet-diaphragm-positive electrode sheet-gasket-shrapnel-positive electrode shell, assembled from bottom to top, static Test after 24h. The assembled button battery was tested by Land CT2001A battery test system. When the charge-discharge cut-off voltage range is 0.1-2.5V (vs. Li+/Li) and the current density is 200mA/g, the reversible specific capacity is 967.5mAh/ g, when the current density increased to 5000mA/g, the reversible specific capacity was 305.6mAh/g, and the rate performance was excellent (see Figure 22 for the test results).

Comparative Example 1

The thin film electrode was prepared according to the method of Example 3, except that methane was used as the carbon source, methane was fed for 0.5 h during the deposition process, and the methane flow rate was 100 mL/min.

Figure 23 shows that when a conventional carbon source is used, the grown carbon nanotubes are spread on the surface of the carbon fiber, and the growth amount is small, and a smooth surface of the carbon fiber can be seen.

It can be seen from Fig. 24 that the grown carbon nanotubes are about 60 nm, and there are many pimple-like amorphous carbons around the tubes.

Claims (10)

1. The carbon nanotube is characterized in that the carbon layer lattice fringes of the tube wall of the carbon nanotube and the tube axial direction of the carbon nanotube form an included angle of 5-15 degrees as seen by a high-power transmission electron microscope.

2. The carbon nanotube of claim 1, wherein the carbon nanotube is made from nickel cobalt hydrotalcite and heavy oil.

3. An electrode comprising the carbon nanotube according to claim 1 or 2.

4. The electrode according to claim 3, comprising carbon fiber cloth or carbon fiber paper, and carbon nanotubes grown outwardly on the fibers thereof; the carbon nano tube is obtained by the catalytic growth of nickel/cobalt; the carbon nano tube has an outer diameter of 80nm to 250nm, an inner diameter of 30nm to 150nm and a length of 5 mu m to 50 mu m; the loading capacity of the carbon nano tube is 1mg/cm calculated by the area of the carbon fiber cloth or the carbon fiber paper²～4mg/cm²。

5. An electrode according to claim 3, wherein the electrode is made by: and growing carbon nanotubes on the substrate by using a gas phase deposition method by using heavy oil as a carbon source and carbon fiber cloth or carbon fiber paper loaded with nickel-cobalt hydrotalcite as a substrate to obtain the electrode.

6. The electrode of claim 5, wherein the substrate is made by a method comprising: in a liquid phase reaction system soaked with carbon fiber cloth or carbon fiber paper, nickel cobalt hydrotalcite is synthesized to obtain the carbon fiber cloth or carbon fiber paper loaded with the nickel cobalt hydrotalcite, namely the substrate.

7. The electrode of claim 5, wherein the substrate is made by a method comprising:

(1) preparing a solution of nickel salt, cobalt salt and quaternary ammonium salt, wherein the solvent is alcohol, water or a mixture of the alcohol and the water;

(2) and (2) soaking carbon fiber cloth or carbon fiber paper into the solution, and then reacting for more than 20 hours at 100-200 ℃ to obtain the carbon fiber cloth or carbon fiber paper loaded with the nickel-cobalt hydrotalcite, namely the substrate.

8. The electrode of claim 7, wherein the nickel salt is nickel nitrate or nickel chloride; the cobalt salt is cobalt nitrate or cobalt chloride.

9. The electrode of claim 7, wherein the quaternary ammonium salt is dodecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium chloride, or octadecyl trimethyl ammonium bromide.

10. A lithium ion battery comprising an electrode according to any one of claims 1 to 9.

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