A method for preparing a self-supporting carbon nanotube and graphene hybrid material

Abstract

The application belongs to the field of carbon material preparation, and discloses a preparation method of self-supporting carbon nanotube and graphene hybrid material. The preparation method is as follows: two carbon sources with different carbon contents are added into a mixed solution of ethanol and water to form a suspension; the suspension is sprayed on the surface of a metal sheet, and after drying, the metal sheet is placed in a high-temperature furnace for high-temperature heating in a protective atmosphere; after the high-temperature furnace is cooled, the carbon material is taken off from the metal sheet, and then the carbon material is soaked in an acid solution, and then washed with water and dried to obtain the self-supporting carbon nanotube and graphene hybrid material. The method has the characteristics of simple operation, low cost, good product structure interconnection, and easy controllable macro preparation. The self-supporting carbon nanotube and graphene hybrid material can be used as a positive electrode carrier material of a lithium-sulfur battery.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation, specifically relating to the synthesis of a self-supporting carbon nanotube and graphene hybrid material, and its application as a positive electrode carrier in lithium-sulfur batteries. Background Technology

[0002] One-dimensional carbon nanotubes possess excellent mechanical strength, high specific surface area, and high electrical conductivity; graphene has an even larger specific surface area and higher electron mobility, both showing great potential in energy storage. However, due to van der Waals forces, both exhibit a tendency to aggregate, making it difficult to fully realize their excellent physical properties. By compositing one-dimensional carbon nanotubes and two-dimensional graphene into a three-dimensional structure, self-aggregation and stacking phenomena can be effectively alleviated, thus maintaining their inherent physical properties. Theoretical studies have also demonstrated that covalently bonded carbon nanotube and graphene hybrid materials can extend the high electron mobility properties to three-dimensional structures. Therefore, using carbon nanotube and graphene hybrid materials as positive electrode carriers in lithium-sulfur batteries can effectively improve the slow charge transport problem in battery reactions.

[0003] Currently, the commonly used methods for preparing carbon nanotube and graphene hybrid materials are multi-step chemical vapor deposition (Nat. Commun. 2012, 3, 1225) and self-assembly using one-dimensional carbon nanotubes and graphene oxide units (J. Mater. Chem. A 2015, 3, 18605). Chemical vapor deposition requires sophisticated equipment, leading to high costs; self-assembly methods typically involve multiple process steps such as hydrothermal and freeze-drying, and the resulting products have weak inter-unit bonds, resulting in high contact resistance. Therefore, to address the problems of complex operation, high cost, and insufficient product interconnectivity in the synthesis of carbon nanotube and graphene hybrid materials using existing methods, further optimization of the synthesis methods is needed. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a method for preparing self-supporting carbon nanotube and graphene hybrid materials that is simple to operate, low in cost, produces products with good structural interconnectivity, and is easily and controllably prepared in large quantities. The self-supporting carbon nanotube and graphene hybrid materials can be used as positive electrode carrier materials for lithium-sulfur batteries, effectively solving problems such as insufficient actual capacity and short cycle life in lithium-sulfur batteries. The technical solution adopted in this invention is as follows: a method for preparing self-supporting carbon nanotube and graphene hybrid materials, comprising the following steps:

[0005] (1) Add carbon source A with low carbon content and carbon source B with high carbon content to a mixed solution of ethanol and water, and stir to form a suspension; spray the suspension onto the surface of a metal sheet, and dry it to obtain a metal sheet-attached blocky mixture precursor.

[0006] (2) Place the precursor in a high-temperature furnace, introduce a protective gas, heat it to the reaction temperature A, and keep it at that temperature for a certain period of time; after the high-temperature furnace cools down, remove the carbon material from the metal sheet.

[0007] (3) The carbon material is immersed in an acid solution, then washed with water and dried to obtain a self-supporting carbon nanotube and graphene hybrid material.

[0008] In step (1) above, carbon source A is any one or a combination of more of melamine, dicyandiamide, urea, and carbon nitride. Preferably, melamine and dicyandiamide are selected. More preferably, melamine is selected.

[0009] In step (1) above, carbon source B is any one or a combination of glucose, fructose, sucrose, maltose, and starch. Preferably, glucose is selected.

[0010] In step (1) above, the mass ratio of carbon source A to carbon source B is (10-100):1. Preferably, the mass ratio of carbon source A to carbon source B is 20:1.

[0011] In step (1) above, the metal sheet can be any one of iron, cobalt, or nickel. Preferably, a nickel sheet is selected.

[0012] In step (1) above, the drying temperature is 15-60℃ and the drying time is 1-60h. Preferably, the drying temperature is set to 40℃ and the drying time is 6h.

[0013] In step (2) above, the protective gas is any one or a combination of nitrogen, argon, and helium. Preferably, nitrogen is used as the protective gas to reduce costs.

[0014] In step (2) above, the heating rate is 1-50℃ / min, the reaction temperature A is 800-1400℃, and the holding time is 0.5-6h. Preferably, the heating rate is set to 10℃ / min, the reaction temperature is 1000℃, and the holding time is 2h.

[0015] In step (3) above, the acid is either hydrochloric acid or sulfuric acid, or a combination of both. Preferably, hydrochloric acid is chosen.

[0016] In step (3) above, the concentration of the acid solution is 1-12 mol / L, and the soaking time is 12-72 h. Preferably, the concentration of hydrochloric acid is 6 mol / L, and the soaking time is 60 h.

[0017] The prepared self-supporting carbon nanotube and graphene hybrid material can be used as a positive electrode carrier material for lithium-sulfur batteries.

[0018] Compared with the prior art, the preparation method of the present invention has the following outstanding advantages:

[0019] 1) The operation steps of this invention are simple, the equipment requirements are low, and a low-cost and widely available carbon source is used. In addition, the metal sheet can be reused after grinding and polishing, which greatly reduces the process cost and raw material cost of synthesizing carbon nanotube and graphene hybrid materials.

[0020] 2) The self-supporting carbon nanotube and graphene hybrid material prepared by this invention has a certain mechanical support force, and its macroscopic shape changes with the shape of the metal sheet. By using metal sheets of different shapes, the controllable mass production of self-supporting carbon nanotube and graphene hybrid materials with different macroscopic shapes can be achieved.

[0021] 3) The self-supporting carbon nanotube and graphene hybrid material prepared by this invention exhibits good interconnectivity within its internal structure. Carbon source pyrolysis at high temperature, catalyzed by a metal sheet, leads to in-situ growth of carbon nanotubes and graphene, thereby constructing a three-dimensional network structure with superior interconnectivity.

[0022] 4) The self-supporting carbon nanotube and graphene hybrid material prepared in this invention possesses a three-dimensional cross-linked network that provides rapid electron and ion transport. When used as a cathode support material in lithium-sulfur batteries, the lithium-sulfur batteries exhibit excellent capacity density and cycle stability. The lithium-sulfur battery can achieve a specific capacity of 1020 mAh / g at 0.5C, with a specific capacity retention of 96% after 100 cycles. Furthermore, the self-supporting support eliminates the need for current collectors, conductive agents, and binders, effectively improving the actual energy density of the battery while reducing battery costs and simplifying the manufacturing process. Attached Figure Description

[0023] Figure 1 This is a photograph of the self-supporting carbon nanotube and graphene hybrid material prepared according to Embodiment 1.

[0024] Figure 2 The image shows the X-ray diffraction pattern of the self-supporting carbon nanotube and graphene hybrid material prepared according to Embodiment 1.

[0025] Figure 3 The image shows a scanning electron microscope (SEM) image of the self-supporting carbon nanotube and graphene hybrid material prepared according to Embodiment 1.

[0026] Figure 4 This is a transmission electron microscopy (TEM) image of the self-supporting carbon nanotube and graphene hybrid material prepared according to Embodiment 1.

[0027] Figure 5 The first charge-discharge curve of the assembled lithium-sulfur battery at a rate of 0.5C is shown when the self-supporting carbon nanotube and graphene hybrid material prepared in Implementation Method 1 is used as the positive electrode carrier material of the lithium-sulfur battery.

[0028] Figure 6When the self-supporting carbon nanotube and graphene hybrid material prepared in Implementation Method 1 is used as the positive electrode carrier material of a lithium-sulfur battery, the cycling curve of the assembled lithium-sulfur battery at 0.5C rate within 100 cycles is shown. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to examples, but this is not intended to limit the scope of protection of the invention. Specific implementation method one:

[0031] (1) Add 10g of melamine and 0.5g of glucose to a mixed solution of 10mL of ethanol and 0.5mL of water, and stir to form a suspension; spray the suspension onto the surface of a nickel sheet and dry it at 40℃ for 6h to obtain a nickel sheet-attached blocky mixture precursor; (2) Place the precursor in a high-temperature furnace, introduce nitrogen protective gas, heat to 1000℃ at a heating rate of 10℃ / min, and hold for 2h; after the high-temperature furnace cools down, remove the carbon material from the nickel sheet. (3) Place the carbon material in a 6mol / L hydrochloric acid solution and soak for 60h; wash with deionized water until the solution is neutral, and vacuum dry at 60℃ to obtain a self-supporting carbon nanotube and graphene hybrid material.

[0032] The self-supporting carbon nanotube and graphene hybrid material obtained in Embodiment 1 above macroscopically exhibits a carbon paper structure. Figure 1 Its X-ray diffraction pattern ( Figure 2 The two peaks at 26° and 44° in the image correspond to the (002) and (101) crystal planes of the graphite phase, respectively, and no other impurity diffraction peaks appear, indicating that the surface crystallinity and purity of the hybrid material are good; the scanning electron microscope image ( Figure 3 ) and transmission electron micrographs ( Figure 4 It can be observed that the material obtained in Implementation Method 1 exhibits a hybrid structure composed of cross-linked carbon nanotubes and graphene, with the diameter of the carbon nanotubes ranging from 50 to 100 nm.

[0033] The self-supporting carbon nanotube and graphene hybrid material prepared in Embodiment 1 was sliced ​​and used as a positive electrode carrier material for lithium-sulfur batteries. Figure 5 and Figure 6 As shown, the assembled lithium-sulfur battery has high specific capacity and cycle stability. It can achieve a specific capacity of 1020 mAh / g at 0.5C and a specific capacity of 978 mAh / g after 100 cycles, with a specific capacity retention rate of 96%. Specific implementation methods two and three:

[0035] In step (1) of Embodiment 1, the mass of glucose was changed to 0.25g and 1g respectively, and all other operations were the same as in Embodiment 1. The resulting two self-supporting carbon nanotube and graphene hybrid materials showed that the former had a smaller proportion of graphene structure, while the latter had a larger proportion. Specific implementation methods four and five:

[0037] The heating rate in step (3) of Embodiment 1 was changed to 2℃ / min and 20℃ / min, respectively, while all other operations were the same as in Embodiment 1. The two self-supporting carbon nanotube and graphene hybrid materials obtained had carbon nanotube diameters generally greater than 100nm in the former and less than 50nm in the latter. Specific implementation methods six and seven:

[0039] In step (1) of Embodiment 1, glucose was replaced with sucrose and fructose, respectively, and all other operations were the same as in Embodiment 1. The two self-supporting carbon nanotube graphene hybrid materials obtained exhibit a microscopic hybrid structure composed of cross-linked carbon nanotubes and graphene, with tube diameters ranging from 50 to 100 nm. Specific implementation methods eight and nine:

[0041] In step (2) of Embodiment 1, the metal sheet was replaced with an iron sheet and a cobalt sheet, respectively, while all other operations remained the same as in Embodiment 1. The resulting two self-supporting carbon nanotube-graphene hybrid materials had similar morphological structures to the products obtained in Embodiment 1.

Claims

1. A method for preparing a self-supporting carbon nanotube and graphene hybrid material, characterized in that, The self-supporting carbon nanotube and graphene hybrid material is a self-supporting carbon paper material, microscopically composed of cross-linked carbon nanotubes and graphene, and is prepared according to the following steps: (1) Add low-carbon carbon source A and high-carbon carbon source B to a mixed solution of ethanol and water, stir to form a suspension; spray the suspension onto the surface of a metal sheet, and dry to obtain a metal sheet-attached blocky mixture precursor. (2) Place the precursor in a high-temperature furnace, introduce a protective gas, heat it to the reaction temperature A, and keep it at that temperature for a certain time; after the high-temperature furnace cools down, remove the carbon material from the metal sheet. (3) The carbon material is immersed in an acid solution, then washed with water and dried to obtain a self-supporting carbon nanotube and graphene hybrid material; In step (1), carbon source A is any one or more of melamine, dicyandiamide, urea, and carbon nitride; carbon source B is any one or more of glucose, fructose, sucrose, maltose, and starch; the mass ratio of carbon source A to carbon source B is (10-100):1; the metal sheet is any one of iron sheet, cobalt sheet, and nickel sheet. In step (2), the heating rate is 1-50℃ / min, the reaction temperature A is 800-1400℃, and the holding time is 0.5-6h.

2. The preparation method according to claim 1, characterized in that, In step (1), the drying temperature is 15-60℃ and the drying time is 1-60h.

3. The preparation method according to claim 1, characterized in that, In step (2), the protective gas is any one or a combination of nitrogen, argon, and helium.

4. The preparation method according to claim 1, characterized in that, In step (3), the acid is either hydrochloric acid or sulfuric acid, or a combination of both; the concentration of the acid solution is 1-12 mol / L; and the soaking time is 12-72 h.

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