CN104201006A - Preparation method of carbon nanotube/manganese dioxide hybridization supercapacitor electrode material - Google Patents

Abstract

A method for preparing a carbon cloth/carbon nanotube/manganese dioxide hybrid supercapacitor electrode material, using plasma chemical vapor deposition to grow ordered carbon nanotubes with strong binding force on the carbon cloth, and using hydrothermal In this way, the carbon nanotubes are completely coated with a layer of nanosheet-shaped α-MnO ₂ active material. The hybrid electrode material prepared by the invention has a simple structure, has directional porous channels, is beneficial to the insertion, extraction and diffusion of ions, and makes the electrode material have characteristics such as high capacity and high cycle performance.

Description

Preparation method and application of a carbon nanotube/manganese dioxide hybrid supercapacitor electrode material

technical field

The invention belongs to the field of energy storage materials and devices, and in particular relates to a preparation method and application of a high-performance supercapacitor electrode material composed of flexible carbon cloth, oriented carbon nanotubes and manganese dioxide hybrid composites.

Background technique

Energy storage devices and devices for portable and wearable electronic products put forward requirements for lighter, thinner, smaller, and larger capacity. Among many energy storage methods, supercapacitors have high power density and high energy density. received widespread attention. Supercapacitors are divided into two types: electric double layer capacitors and faraday pseudocapacitors. The electrode materials of electric double layer capacitors are mainly carbon materials, and the electrode materials of pseudocapacitors are transition metal oxides, hydroxides, and conductive polymers. In order to obtain a higher capacity, carbon materials and transition metal oxides are currently combined to take advantage of both, and the preparation of hybrid capacitor electrode materials has become a research hotspot.

Flexible energy storage materials need to take into account both electrical and mechanical flexibility, and carbon cloth as a collector or electrode material is one of the very good choices. In traditional supercapacitors, the electrode material is usually solidified on the collector through a binder, which greatly affects its mechanical energy and rate performance. Therefore, the preparation of self-supporting supercapacitor materials without adding any binders and conductive agents more extensive attention and research.

Carbon nanotubes are one-dimensional tubular nanostructures formed by curling graphene, in which the carbon atoms are bonded in a ^Sp2 hybridization manner, which makes carbon nanotubes have both high mechanical strength and high electrical conductivity. And electrochemical performance, it is an advanced flexible energy storage material. Among many transition metal oxide materials, manganese dioxide has the advantages of high specific capacitance, environmental friendliness, and low price, and has been widely concerned, especially α-MnO2 has a large pore diameter, which is beneficial to some The intercalation and deintercalation of cations (Li+, K+, Na+, etc.) and diffusion in the bulk phase have high capacitance rate performance. However, _MnO2 material has the disadvantage of poor electrical conductivity, which limits its further use as a supercapacitor material. Therefore, using the high conductivity of carbon nanotubes and the high specific capacitance of MnO ₂ , combining carbon nanotubes and MnO 2 materials to make hybrid capacitors is a competitive research direction.

Hu liangbing etc. coated CNT on polyester fiber cloth to form a 3D structure, and then used this as a substrate to electrodeposit MnO2 to wrap around the carbon tube to make a flexible hybrid capacitor (Hu liangbing, etal.Symmetrical mnO ₂ - carbon nanotube-textile nanostructures for wearable pseudocapacitors with high mass loading. Acs Nano. 2011, Vol. 5:8904-8913). Zhoucheng et al. disorderly grown carbon nanotubes on carbon cloth by CVD to make flexible supercapacitors (Zhou cheng, et al. Carbon nanotube network film directly grown on carbon cloth for high-performance solid-state flexible supercapacitors.Nanotechnology.2014 , DOI: 10.1088/0957-4484/25/3/035402). CN 102354612A uses liquid phase solution as carbon source and catalyst source, grows carbon tubes with very high surface density and very high aspect ratio on carbon cloth fibers by CVD, and coats carbon nanotubes by electrodeposition MnO ₂ particles, this kind of carbon tubes are easy to fall due to the high aspect ratio, and the high surface density is not conducive to the electrolyte entering into the carbon tube array and the intercalation and extraction of ions, resulting in poor high-rate charge-discharge performance and cycle performance .

The above technology prepares a disordered carbon nanotube structure or a hybrid structure. This disordered structure and non-hybrid capacitors are not conducive to the insertion and extraction of ions, which affects the capacity and rate performance of the capacitor.

Contents of the invention

In order to overcome the defects of the prior art, one of the purposes of the present invention is to provide a preparation method and application of a carbon nanotube/manganese dioxide hybrid supercapacitor electrode material. The invention adopts the plasma chemical deposition method to directional grow ordered carbon nanotubes with strong binding force on the carbon cloth, and adopts a hydrothermal method to completely coat a layer of nanosheet-like α-MnO _active around the carbon nanotubes. substance. The hybrid electrode material prepared by the invention has a simple structure, has directional porous channels, is beneficial to the insertion, extraction and diffusion of ions, and makes the electrode material have characteristics such as high capacity and high cycle performance.

For reaching above-mentioned object, the present invention adopts following technical scheme:

A preparation method of carbon cloth/carbon nanotube/manganese dioxide hybrid supercapacitor electrode material, comprising the steps of:

(1) Remove organic impurities after removing inorganic impurities from the flexible carbon cloth (CC);

(2) Deposit a layer of Ni film on carbon cloth by physical evaporation (including magnetron sputtering, electron beam evaporation, thermal evaporation, etc.) as a catalyst for growing carbon nanotubes;

(3) Arrange the carbon after removing impurities in step (1) into a carbon nanotube plasma chemical deposition (PECVD) growth furnace, and anneal and spheroidize the Ni film;

(4) Cool down and feed C ₂ H ₄ , start the plasma power supply, generate plasma in the cavity, and carry out orderly growth of carbon nanotubes (CNT);

(5) Arrange the carbon with tubes grown in step (4) gained in the reactor, add potassium permanganate solution and seal it, then react under heating, so that potassium permanganate and the outermost layer of the carbon tubes are amorphous Oxidation-reduction reaction occurs in the carbon layer to generate MnO ₂ sheet structure;

(6) After the reaction is finished, the reaction kettle is cooled rapidly and the reaction kettle is opened, the carbon cloth is taken out, rinsed with deionized water, and then the carbon cloth is baked to obtain the carbon cloth/carbon nanotube/MnO ₂ composite material.

The invention adopts the plasma-enhanced chemical vapor deposition (PECVD) method, an ordered CNT array with strong bonding force between directional growth and carbon cloth fibers on flexible carbon cloth, and the diameter of carbon tubes is 130-150nm, and the length is about 5-6 microns , with good self-supporting strength, a certain gap between the carbon tubes is maintained to facilitate the entry of the electrolyte; and a simple and easy hydrothermal reaction is used to grow and coat a layer of nano-sheet α-MnO ₂ around the carbon tubes The material can form a three-dimensional three-dimensional channel, which is beneficial to the intercalation and extraction of ions, and a hybrid capacitor electrode material with high capacity and excellent cycle performance is prepared.

This ordered hybrid porous structure can greatly increase the contact area between the electrode active material and the electrolyte, and facilitate the exchange of ions, which can significantly improve the capacity and rate performance of flexible capacitors, and can be applied to power materials for flexible devices.

As a preferred technical solution, in the preparation method of the present invention, the method for removing inorganic impurities in step (1) is as follows: soak the flexible carbon cloth with nitric acid solution, and then rinse it with deionized water.

Preferably, the method for removing inorganic impurities is: use flexible carbon cloth (for example 5cm×5cm) with 2-8mol/L, for example 2.3mol/L, 2.9mol/L, 3.5mol/L, 5.0mol/L , 6.5mol/L, 7.8mol/L, etc. nitric acid solution for more than 0.5h, such as 0.8h, 1.2h, 2.0h, 3.5h, etc., preferably 1h, and then rinse with a large amount of deionized water.

Preferably, the method for removing organic impurities is: ultrasonically cleaning the carbon cloth after removing inorganic impurities with acetone and ethanol successively.

Preferably, the method for removing organic impurities is as follows: cleaning the carbon cloth treated by removing inorganic impurities with acetone and ethanol for 3-5 times of ultrasonic cleaning.

As a preferred technical solution, in the preparation method of the present invention, the thickness of the Ni film in step (2) is 5-20nm, such as 7nm, 10nm, 14nm, 18nm, etc., preferably 8-15nm.

As a preferred technical solution for the preparation method of the present invention, the conditions for the annealing and spheroidization described in step (3) are: feed ammonia gas, heat up to 700-800°C, such as 720°C, 760°C, 790°C, etc., and keep for 5 -20min, such as 8min, 12min, 17min, etc.

Preferably, the conditions for the annealing and spheroidization are as follows: 150-250 ccm, preferably 200 ccm of ammonia gas is introduced, the pressure in the growth furnace chamber is 15-25 mbar, preferably 20 mbar, and the temperature is raised to 730-770°C, preferably 750°C, and kept 10-12min.

As a preferred technical solution, in the preparation method of the present invention, the temperature reduction in step (4) is to reduce the temperature to 680-750°C.

Preferably, the C ₂ H ₄ feed rate is 40-80 Sccm, preferably 60 Sccm.

Preferably, the power of the plasma power supply is 50-90W, preferably 70W.

Preferably, the pressure in the growth furnace chamber is the same as the pressure during annealing and spheroidizing.

Preferably, the growth time is 15 min-60 min, preferably 30 min.

As a preferred technical solution, in the preparation method of the present invention, the concentration of the potassium permanganate solution in step (5) is 0.05-0.15 mol/L, preferably 0.1 mol/L.

Preferably, the ratio of the amount of potassium permanganate solution added to the surface area of the carbon cloth is 10-50ml/cm ² , for example 13ml/cm ² , 19ml/cm ² , 26ml/cm ² , 35ml/cm ² , 46ml /cm ² etc., preferably 25ml/cm ² .

Preferably, the heating is performed in an oven.

Preferably, the heating temperature is 150-200°C, preferably 180°C; the reaction time is 15min-40min, preferably 25min.

As a preferred technical solution, in the preparation method of the present invention, the cooling in step (6) uses flowing cold water for rapid cooling, and the reactor is opened after cooling for 2-10 minutes.

Preferably, the baking is carried out on a hot table.

Preferably, the baking temperature is 100-200°C, preferably 150°C; the baking time is 0.5-3h, preferably 1h. Roasting is to remove moisture.

Another object of the present invention is to provide the use of the electrode material prepared by the present invention, which can be applied to portable electronic products or wearable electronic products.

The flexible supercapacitor material provided by the present invention has the characteristics of high capacity and high cyclability, can be used as an energy storage device for flexible wearable electronic products or devices, and can meet people's needs for modern technology products and high-quality green life , to provide technical support for the development of lightweight and flexible energy storage devices with high energy density, high power density and high cycle stability. It can be applied to portable electronic products and wearable electronic products, providing an energy storage method for the development of flexible devices in the future.

Description of drawings

Fig. 1 is a process flow diagram of the present invention;

Fig. 2 is the scanning electron microscope picture of the carbon fiber after cleaning;

Fig. 3 is the scanning electron microscope picture of the carbon tube that grows out;

Fig. 4 is the scanning electron microscope (left) and transmission electron microscope photo (right) of CNT/α-MnO ₂ ;

Fig. 5 is the assembled solid-state flexible supercapacitor;

Fig. 6 is the charge-discharge curve of the supercapacitor assembled in Fig. 5 under different discharge current densities;

Fig. 7 is a cycle performance diagram of the supercapacitor assembled in Fig. 5 at a current density of 7A/g.

Detailed ways

In order to facilitate understanding of the present invention, the present invention enumerates the following examples. Those skilled in the art should understand that the examples are only used to help understand the present invention, and should not be regarded as specific limitations on the present invention.

Fig. 1 is a process flow diagram of the present invention.

Embodiments of the present invention are as follows:

A preparation method of a carbon nanotube/manganese dioxide hybrid supercapacitor electrode material, comprising the steps of:

(1) Remove the organic impurities after removing the inorganic impurities with the flexible carbon cloth;

(2) Depositing a Ni film with a thickness of 5-20nm on the carbon cloth by physical evaporation;

(3) Arrange the carbon after removing impurities in step (1) into a carbon nanotube PECVD growth furnace, and anneal and spheroidize the Ni film;

(4) Lower the temperature to 680-750°C and feed C ₂ H ₄ at a rate of 40-80 Sccm, start the plasma power supply and keep the power at 50-90W, and carry out the orderly growth of carbon nanotubes; The same pressure during fireballing; the growth time is 15min-60min;

(5) Arrange the carbon with tubes grown obtained in step (4) into the reactor, add 0.05-0.15mol/L potassium permanganate solution, seal it, and then heat it to 150-200°C for 15min-40min;

(6) After the reaction is over, cool the reactor with flowing cold water for 2-10 minutes, open the reactor, take out the carbon cloth, rinse it with deionized water, and then bake the carbon cloth on a hot table at a temperature of 100-200°C 0.5-3h, obtain carbon cloth/carbon nanotube/ _MnO Composite material;

The method for removing inorganic impurities in step (1) is: soak the flexible carbon cloth with nitric acid solution, then rinse with deionized water;

The method for removing organic impurities described in step (1) is: the carbon cloth after the treatment of removing inorganic impurities is ultrasonically cleaned successively with acetone and ethanol;

The conditions for annealing and spheroidizing in the step (3) are as follows: ammonia gas is introduced, the temperature is raised to 700-800° C., and kept for 5-20 minutes.

Example 1

(1) Soak a 5cm×5cm flexible carbon cloth with 100 ml of 4mol/L nitric acid solution for 1 hour, then rinse it with a large amount of deionized water to remove inorganic impurities; treat the carbon cloth after nitric acid treatment with acetone and alcohol for 4 Ultrasonic cleaning for the second time to remove organic impurities, the carbon fiber after cleaning is shown in Figure 2;

(2) Deposit a layer of 10nm Ni film on the carbon cloth by electron beam evaporation by physical evaporation, as a catalyst for growing carbon nanotubes;

(3) Arrange the carbon into the carbon nanotube PECVD growth furnace, feed 200ccm of ammonia gas, the pressure is 20mbar, heat up to 750°C, keep for 10min, and anneal and spheroidize the Ni film;

(4) Cool down to 720°C, feed 60Sccm C ₂ H ₄ , start the plasma power supply, keep the power at 70W, generate plasma in the cavity, keep the cavity pressure at 20mbar, and carry out the orderly growth of carbon nanotubes, The growth time is 30 min, and the grown carbon tubes are shown in FIG. 3 .

(5) Arrange the carbon with tube growth into a 250ml reaction kettle, add 200ml of 0.1mol/L potassium permanganate solution and seal it, and quickly place the assembled reaction kettle in an oven heated to 180°C , keep the temperature at 180°C, and the reaction time is 25 minutes, so that potassium permanganate and the amorphous carbon layer of the outermost layer of carbon tubes undergo a redox reaction to form a _MnO2 sheet structure;

(6) Remove the reaction kettle from the oven, immediately cool it with flowing cold water, open the reaction kettle after 5 minutes, take out the carbon cloth, rinse it repeatedly with a large amount of deionized water, and finally place the carbon cloth on a hot stage at 150°C Baking for 1h to remove water, the CC/CNT/MnO ₂ composite material can be obtained.

Figure 4 is the scanning electron micrograph (left) and transmission electron micrograph (right) of α-MnO ₂ , it can be seen that the sheet-like structure MnO ₂ is evenly coated around the carbon nanotubes without lodging, and the manganese dioxide atoms are Arranged in short order.

Using the hybrid composite electrode material prepared in this example as the positive and negative electrodes of the capacitor, using PVA/LiCl as the solid electrolyte, and the ultra-thin filter membrane as the diaphragm, a solid flexible supercapacitor was assembled, as shown in Figure 5. The charge-discharge curves under different discharge current densities are shown in Figure 6. All the curves show linear changes and approximately symmetrical shapes, indicating that the electrode material has good electrochemical reversibility and capacity performance; the device is at 7A/g The cycle performance at the current density is shown in Figure 7. After 5000 cycles, the device still maintains approximately 100% capacity performance, indicating that the material structure has very excellent cycle performance.

Example 2

(1) Soak a 5cm×5cm flexible carbon cloth with 100 ml of 2M nitric acid solution for 2 hours, then rinse it with a large amount of deionized water to remove inorganic impurities; put the carbon cloth treated with nitric acid into acetone and alcohol for 5 times Ultrasonic cleaning to remove organic impurities;

(2) Deposit a layer of 8nm Ni film on the carbon cloth by magnetron sputtering by physical evaporation, as a catalyst for growing carbon nanotubes;

(3) Arrange carbon into a PECVD growth furnace such as carbon nanotubes, feed 250ccm of ammonia gas, pressure 25mbar, heat up to 730°C, keep for 12min, and anneal and spheroidize the Ni film;

(4) Cool down to 680°C, feed 45Sccm of C ₂ H ₄ , start the plasma power supply, keep the power at 50W, generate plasma in the cavity, keep the cavity pressure at 25mbar, and carry out the orderly growth of carbon nanotubes, The growth time is 60min;

(5) Arrange the carbon with tube growth into a 250ml reaction kettle, add 200ml of 0.15mol/L potassium permanganate solution and seal it, and quickly place the assembled reaction kettle in an oven heated to 150°C , keep the temperature reaction for 35min, so that potassium permanganate and the amorphous carbon layer of the outermost layer of the carbon tube undergo a redox reaction to generate a MnO ₂ sheet structure;

(6) Remove the reaction kettle from the oven, immediately cool it with flowing cold water, open the reaction kettle after 10 minutes, take out the carbon cloth, rinse it repeatedly with a large amount of deionized water, and finally place the carbon cloth on a hot stage at 100°C Baking for 3 hours to remove moisture, the CC/CNT/MnO ₂ composite material can be obtained.

Example 3

(1) Soak a 5cm×5cm flexible carbon cloth with 100 ml of 8mol/L nitric acid solution for 0.5 hours, then rinse with a large amount of deionized water to remove inorganic impurities; put the carbon cloth treated with nitric acid into acetone and alcohol successively 3 times ultrasonic cleaning to remove organic impurities;

(2) Deposit a layer of 15nm Ni film on the carbon cloth by thermal evaporation by physical evaporation, as a catalyst for growing carbon nanotubes;

(3) Arrange carbon into a PECVD growth furnace such as carbon nanotubes, feed 150ccm of ammonia gas, pressure 15mbar, heat up to 770°C, keep for 10min, and anneal and spheroidize the Ni film;

(4) Cool down to 740°C, feed 75Sccm C ₂ H ₄ , start the plasma power supply, keep the power at 90W, generate plasma in the cavity, keep the cavity pressure at 15mbar, and carry out the orderly growth of carbon nanotubes, The growth time is 15min;

(5) Arrange the carbon with tubes growing into a 250ml reaction kettle, add 200 milliliters of 0.05M potassium permanganate solution and seal it, and quickly place the assembled reaction kettle in an oven heated to 200°C, keep The temperature reaction is 15 minutes, so that potassium permanganate and the amorphous carbon layer of the outermost layer of the carbon tube undergo a redox reaction to form a _MnO2 sheet structure;

(6) Remove the reaction kettle from the oven, immediately cool it with flowing cold water, open the reaction kettle after 2 minutes, take out the carbon cloth, rinse it repeatedly with a large amount of deionized water, and finally place the carbon cloth on a hot stage at 200°C Carry out baking for 0.5h, remove moisture, and then obtain carbon cloth/carbon nanotube/MnO ₂ composite material.

The electrode materials prepared in Examples 2 and 3 were tested for charge-discharge and cycle performance, and the results comparable to those of the electrode materials prepared in Example 1 were obtained.

The applicant declares that the present invention illustrates the detailed process equipment and process flow of the present invention through the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process equipment and process flow process can be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

Claims (9)

1. A preparation method of carbon cloth/carbon nanotube/manganese dioxide hybrid supercapacitor electrode material, comprising the steps: (1) Remove the organic impurities after removing the inorganic impurities with the flexible carbon cloth; (2) Deposit a Ni film on the carbon cloth by physical evaporation; (3) Arranging the carbon after removal of impurities in step (1) into a carbon nanotube plasma chemical deposition growth furnace, annealing and spheroidizing the Ni film; (4) Cool down and feed C ₂ H ₄ , start the plasma power supply, and carry out orderly growth of carbon nanotubes; (5) Arranging the carbon with tubes grown in step (4) into a reactor, adding potassium permanganate solution and sealing it, then heating it to react; (6) After the reaction is finished, the reaction kettle is cooled rapidly and the reaction kettle is opened, the carbon cloth is taken out, rinsed with deionized water, and then the carbon cloth is baked to obtain the carbon cloth/carbon nanotube/MnO ₂ composite material. 2. preparation method according to claim 1, is characterized in that, the method for removing inorganic impurities in step (1) is: flexible carbon cloth is soaked with nitric acid solution, then rinses with deionized water; Preferably, the method for removing inorganic impurities is: soak the flexible carbon cloth in 2-8mol/L nitric acid solution for more than 0.5h, preferably 1h, and then rinse with a large amount of deionized water. 3. The preparation method according to claim 1 or 2, characterized in that, the method for removing organic impurities described in step (1) is: the carbon cloth after the removal of inorganic impurities is cleaned with acetone and ethanol successively by ultrasonic cleaning; Preferably, the method for removing organic impurities is as follows: cleaning the carbon cloth treated by removing inorganic impurities with acetone and ethanol for 3-5 times of ultrasonic cleaning. 4. The preparation method according to any one of claims 1-3, characterized in that the thickness of the Ni film in step (2) is 5-20 nm, preferably 8-15 nm. 5. The preparation method according to any one of claims 1-4, characterized in that, the conditions for annealing and spheroidizing described in step (3) are: feed ammonia gas, heat up to 700-800°C, keep 5- 20min; Preferably, the conditions for the annealing and spheroidization are as follows: 150-250 ccm, preferably 200 ccm of ammonia gas is introduced, the pressure in the growth furnace chamber is 15-25 mbar, preferably 20 mbar, and the temperature is raised to 730-770°C, preferably 750°C, and kept 10-12min. 6. The preparation method according to any one of claims 1-5, characterized in that, the cooling described in step (4) is cooling to 680-750°C; Preferably, the C ₂ H ₄ feed rate is 40-80 Sccm, preferably 60 Sccm; Preferably, the power of the plasma power supply is 50-90W, preferably 70W; Preferably, the pressure in the growth furnace chamber is the same as the pressure during annealing and spheroidizing; Preferably, the growth time is 15 min-60 min, preferably 30 min. 7. according to the preparation method described in any one of claim 1-6, it is characterized in that, the concentration of potassium permanganate solution described in step (5) is 0.05-0.15mol/L, is preferably 0.1mol/L; Preferably, the ratio of the added amount of the potassium permanganate solution to the surface area of the carbon cloth is 10-50ml/cm ² , preferably 25ml/cm ² ; Preferably, the heating is carried out in an oven; Preferably, the heating temperature is 150-200°C, preferably 180°C; the reaction time is 15min-40min, preferably 25min. 8. according to the preparation method described in any one of claim 1-7, it is characterized in that, cooling described in step (6) uses flowing cold water to carry out rapid cooling, after cooling 2-10min, open reactor; Preferably, the baking is carried out on a hot table; Preferably, the baking temperature is 100-200°C, preferably 150°C; the baking time is 0.5-3h, preferably 1h. 9. The use of the electrode material prepared by the preparation method according to any one of claims 1-8, characterized in that it is applied to portable electronic products or wearable electronic products.