One-dimensional nano-reactor and its preparation method and application

Abstract

The present invention relates to a method for preparing a one-dimensional nano-reactor, which is characterized by comprising the following steps: mixing a metal source, a carbonitride source, a supplementary carbon source, an alkaline metal salt, and a heteroatom source in a dispersant to obtain a mixed liquid slurry; drying the mixed liquid slurry to obtain a precursor; sintering the precursor to obtain a one-dimensional nano-reactor; the molar ratio of the metal source, the carbonitride source, the supplementary carbon source, the alkaline metal salt, and the heteroatom source is (0.1-99):(5-30):(0-15):(0-10):(0-20). The present invention firstly effectively disperses the materials in the dispersant, and secondly, by matching with a suitable drying method, it ensures that the raw material ratio in the precursor remains unchanged while avoiding solid-liquid chromatography of the materials, which will effectively facilitate the formation of one-dimensional tubes and the uniform distribution of catalyst particles in the tubes. Therefore, through the mutual cooperation among the various steps in the preparation method, especially the regulation of the material ratio, the present invention improves the generation and property stability of the one-dimensional nano-reactor.

Description

Technical Field

[0001] The present invention relates to the field of new chemical energy materials, and particularly relates to a one-dimensional nano-reactor, a preparation method thereof, and an application thereof. Background Art

[0002] A one-dimensional nano-reactor is to wrap nano-catalyst particles in a carbon tube, and the carbon tube can be a carbon nano-sphere tube, a carbon nano-prism tube, a long-range carbon nanotube, etc. The carbon tube can perform electron exchange with the encapsulated nano-catalyst to improve the intrinsic catalytic performance of the nano-catalyst. At the same time, the nano-scale reaction chamber allows the reactants and the catalyst to react for a long time without being affected by the external environment, enhancing the reaction efficiency. The long-range one-dimensional electron and reactant transport path is conducive to ensuring the continuity of the reaction. Therefore, the one-dimensional nano-reactor is a new composite material with new properties that realizes one plus one greater than two by integrating multiple components at the nano-scale.

[0003] One-dimensional nano-reactors play an important role in the development of nanomaterials and nanotechnology. Their unique structure and performance show great application potential in various application fields. One-dimensional nano-reactors are commonly used in the catalytic field (electrocatalysis and photocatalysis), including electrocatalytic reactions such as oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER), and in fields such as photocatalytic water splitting for hydrogen production. Energy storage field: In energy storage devices such as lithium-ion batteries and supercapacitors, one-dimensional nano-reactors are widely used due to their excellent electrical conductivity and high surface area. Sensor field: Due to their sensitive surface properties and directional transport capabilities, one-dimensional nano-reactors are also commonly used in the development of highly sensitive sensors.

[0004] The current production methods of one-dimensional nano-reactors mainly include electrospinning method, template method, sol-gel method, pyrolysis method, hydrothermal method, chemical vapor deposition method (CVD method), etc.; at present, except for the CVD method which has achieved industrial application, other methods have achieved laboratory-level preparation, and there is still a long way to go for large-scale efficient preparation. In particular, the production cost limits its application. For example, in the pyrolysis method, the mass loss of the raw material pyrolysis is 80%-90%, and the final product yield is less than 5% after subsequent treatment, which greatly increases the production cost of the one-dimensional nano-reactor and results in its application only on a small scale; in addition, in the traditional pyrolysis method, the metal particle size is not easy to control, and the carbon tube morphology is uneven, resulting in its inability to effectively exert the excellent performance of the one-dimensional nano-reactor. Summary of the Invention

[0005] Based on this, the object of the present invention is to provide a one-dimensional nano-reactor and a preparation method thereof, by controlling the reaction process and the proportion of reaction raw materials, improving the final product yield, controlling the metal particle size and the carbon tube morphology, so as to realize the low-cost and high-efficiency large-scale production of one-dimensional nano-reactors.

[0006] Part I:

[0007] A method for preparing a one-dimensional nano-reactor according to the present invention comprises the following steps:

[0008] Mix a metal source, a carbonitrogen source, a supplementary carbon source, an alkaline metal salt, and a heteroatom source in a dispersant to obtain a mixed liquid slurry;

[0009] Dry the mixed liquid slurry to obtain a precursor;

[0010] Sinter the precursor to obtain a one-dimensional nano-reactor;

[0011] The molar ratio of the metal source, the carbonitrogen source, the supplementary carbon source, the alkaline metal salt, and the heteroatom source is (0.1 - 99):(5 - 30):(0 - 15):(0 - 10):(0 - 20);

[0012] The metal source includes at least one of nitrates, chlorides, sulfates, sulfates, phosphates, oxides, and hydroxides of iron, manganese, nickel, cobalt, copper, zinc, or aluminum;

[0013] The carbonitrogen source includes at least one of urea, pyridine, polyaniline, cyanamide, dicyandiamide, melamine, and dopamine.

[0014] The supplementary carbon source includes at least one of citric acid, glucose, sucrose, starch, maltose, chitosan, polyvinylpyrrolidone, polyethylene, polypropylene, polyethylene glycol, polyvinyl alcohol, and polystyrene;

[0015] The alkaline metal salt includes at least one of nitrates, chlorides, sulfates, sulfates, phosphates, oxide salts, and hydroxide salts of lithium, sodium, magnesium, potassium, and calcium;

[0016] The heteroatom source is at least one of organic or inorganic salts containing sulfur, phosphorus, selenium, or boron elements;

[0017] The dispersant includes at least one of water, ethanol, and acetone.

[0018] During the preparation process of the one-dimensional nano-reactor by the preparation method of the present invention, sintering the precursor composed of the metal source, the carbonitrogen source, the supplementary carbon source, and the alkaline metal salt can obtain a one-dimensional nano-reactor with excellent performance at one time. Specifically, it includes: first, effective dispersion of the materials by mixing in a dispersant and under a stirring / grinding environment, and secondly, matching with a suitable drying method to ensure that the raw material ratio in the precursor remains unchanged while avoiding solid-liquid chromatography of the materials, which will effectively facilitate the formation of one-dimensional tubes and the uniform distribution of catalyst particles in the tubes. Therefore, through the mutual cooperation of the various steps in the preparation method of the present invention, especially the regulation of the material ratio, the generation and property stability of the one-dimensional nano-reactor are improved.

[0019] The alkaline metal salt added in the present invention is a dehydration catalyst and a molecular template. As a dehydration catalyst, at low temperatures, it catalyzes the dehydration reaction in the carbon precursor, inhibits the formation of tar, promotes carbonization and aromatization, thereby increasing the carbon yield, and is not consumed in this process. At higher temperatures, it can be used as a molecular templating agent to generate micropores. This is because the sufficiently dispersed molten alkaline metal salt will remain inside the carbon material, which can inhibit the shrinkage, deformation and collapse caused by the carbonization and shrinkage of the carbon and nitrogen sources. Finally, the impregnated material is washed with acid / water, and the porosity is released. The through-holes formed by the molten salt and the good thermal conductivity of the molten salt itself ensure the uniformity of heating and enhance the thermal efficiency. Therefore, this is one of the keys to ensuring the stability of the material morphology after large-scale production. Through the above effects, the final pyrolysis mass loss is only 70%, and the yield of the final product can reach more than 10% of the raw material quality, reducing the unutilizable ash content, greatly increasing the yield compared with the traditional pyrolysis method, and greatly reducing the production cost. The carbon and nitrogen sources, supplementary carbon sources and heteroatom sources added in the present invention can affect the mass ratio of elements such as nitrogen, carbon, boron, sulfur, etc. contained in the carbon layer, which can further improve the properties such as the structural stability and electronic conductivity of the material.

[0020] The inventors also found that the dispersion degree of the metal in the raw material and the ratio of the metal source to the supplementary carbon source directly affect the morphology and size of the product. Therefore, by adjusting the ratio of the appropriate metal source to the supplementary carbon source to make the metal dispersed to an appropriate degree, the problems of difficult control of the metal particle size and uneven carbon nanotube morphology in the traditional pyrolysis method are overcome. In addition, the preparation method of the present invention has a simple preparation process, and can directly utilize the production lines, production equipment of materials that have been industrialized, such as lithium iron phosphate, silicon-carbon negative electrodes, etc., and the cost of product conversion is low.

[0021] As a preferred embodiment, the mixing method includes at least one of ball milling, grinding, and stirring; the drying includes at least one of atmospheric drying, spray drying, freeze drying, and fluidized bed drying.

[0022] As a preferred embodiment, the steps of mixing, drying, and sintering are performed at least once, or in combination. Performing the mixing, drying, and sintering in combination, or multiple times, can produce one-dimensional nano-reactors with different morphologies and structures; for components with different raw material compositions and ratios, the process can also be adjusted by performing the mixing, drying, and sintering in combination, or multiple times.

[0023] As a preferred solution, the following steps are further included: drying the mixed liquid slurry to obtain a first precursor, crushing the first precursor and mixing again to obtain a second precursor, and sintering the second precursor to obtain a one-dimensional nano-reactor. This process has simple equipment requirements. The drying process only requires the simplest atmospheric pressure drying and is applicable to the case where large lumps are formed after the first drying. By crushing and mixing again, the morphology of the one-dimensional nano-reactor after sintering can be made more uniform.

[0024] As a preferred solution, the following steps are further included: simultaneously drying and sintering the mixed liquid slurry to obtain a one-dimensional nano-reactor. This process combines the drying and sintering steps and is applicable to the case where the raw material composition is simple and the morphology of the generated one-dimensional nano-reactor is easy to control.

[0025] As a preferred solution, the following steps are further included: mixing the metal source and the supplementary carbon source, drying and then performing a first sintering to obtain a one-dimensional nano-reactor preform; mixing the one-dimensional nano-reactor preform with the carbonitride source, alkaline metal salt, and heteroatom source, drying and then performing a second sintering to obtain a one-dimensional nano-reactor. This process is applicable to the case where the raw material composition is complex and the product is difficult to form in one step. Multiple sinterings can better control the metal particle size, maintain the uniform morphology of the one-dimensional nano-reactor, and reduce the pyrolysis mass loss.

[0026] As a preferred solution, a thickening agent is also added during mixing. The addition amount of the thickening agent is 0.1 - 2 wt% of the dispersant. The thickening agent includes at least one of polytetrafluoroethylene, polyethylene glycol, and hydroxypropyl methylcellulose.

[0027] The functions of the thickening agent mainly include four parts:

[0028] ① Improving the slurry uniformity: The thickening agent helps the particles in the precursor slurry to be evenly distributed, prevents solid substances from precipitating or caking in the slurry, ensures that the component ratios of the materials are consistent before calcination, and thus guarantees the uniformity of the final calcined product.

[0029] ② Enhancing the shape retention ability: Before calcination, the precursor material needs to be shaped. The thickening agent can increase the viscosity of the slurry, enabling it to maintain the required shape and structure before drying and calcination, and preventing the material from collapsing or deforming at high temperatures.

[0030] ③ Controlling the release of moisture and volatile substances: The thickening agent can regulate the moisture content in the slurry, slowly releasing moisture or volatile substances during the calcination process, avoiding cracking or holes caused by the rapid evaporation of moisture, and ensuring a dense material structure after calcination.

[0031] ④ Improve calcination efficiency: By controlling the rheological properties of the slurry, the thickener can optimize the thermal decomposition and reaction process of the precursor material, help the precursor to be more evenly converted into the target material during the calcination process, and improve the purity and performance of the final product.

[0032] As a preferred embodiment, the sintering is carried out in a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, argon, hydrogen, ammonia, and methane; the sintering conditions are: heating at a rate of 0.1 to 10 ° C / min, rising to 300 to 1400 ° C, and keeping warm for 2 to 24 hours. By adding a protective atmosphere, the loss of raw material quality can be greatly reduced, the loss of raw material quality can be reduced to less than 60%, and the final product output can reach more than 20% of the raw material quality. More preferably, the sintering has multiple stage temperatures, illustratively, 600 ° C for 2 hours, then 700 ° C for 4 hours, and finally 900 ° C for 2 hours. This process is determined according to the reaction between the reactants. The purpose of setting the temperature and time is to ensure the completeness of the reaction. The appropriate sintering temperature, sintering time and heating rate during sintering can improve the completion of the reaction, so as to obtain a one-dimensional nanoreactor material with stable properties. If the sintering process is not set reasonably, it may lead to uneven morphology of the product, a large loss of raw materials, etc.

[0033] Second aspect:

[0034] A one-dimensional nanoreactor prepared by the preparation method described in the first aspect is a carbon nanotube, a carbon nanoprism or a long-range carbon nanotube, which is a carbon layer wrapped around metal nanoparticles doped with heteroatoms with a particle size of 2-200nm; the metal nanoparticles include at least one of a metal element, an alloy, a phosphide, a sulfide, a nitride, a carbide, and an oxide; and the heteroatoms include at least one of sulfur, phosphorus, selenium, and boron.

[0035] Charge transfer can occur between metal nanoparticles and heteroatom-doped carbon layers. Furthermore, electrons on the surface of heteroatom-doped carbon layers are transferred to metal nanoparticles, which will help improve the ion transmission rate and conductivity of the carbon layer surface, and at the same time improve the catalytic conversion ability of metal nanoparticles. And its long-range ordered tubular structure can form a well-interconnected structure, ensuring the connectivity between materials. It can be applied to various application fields such as energy storage and catalysis.

[0036] The third aspect:

[0037] An application of the one-dimensional nanoreactor as described in the second aspect in a lithium-sulfur battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the preparation process of a one-dimensional nanoreactor;

[0039] Figure 2 It is the SEM image of the long tubular B, N co-doped Fe3C@CNT prepared in Example 1;

[0040] Figure 3 It is the SEM image of the long tubular B, N co-doped Fe3C@CNT prepared in Example 1;

[0041] Figure 4 It is the TEM image of the long tubular B, N co-doped Fe3C@CNT prepared in Example 1;

[0042] Figure 5 It is the XRD pattern of the long tubular B, N co-doped Fe3C@CNT prepared in Example 1;

[0043] Figure 6 It is the SEM image of the sphere / short tubular B, N co-doped Fe3C@CNT prepared in Example 2;

[0044] Figure 7 It is the TEM image of the sphere / short tubular B, N co-doped Fe3C@CNT prepared in Example 2;

[0045] Figure 8 It is the SEM image of the prismatic tubular B, N co-doped Fe3C@CNT prepared in Example 3;

[0046] Figure 9 It is the TEM image of the prismatic tubular B, N co-doped Fe3C@CNT prepared in Example 3;

[0047] Figure 10 It is the XRD pattern of the B, N co-doped Fe3C@CNT prepared in Examples 4, 5, and 6;

[0048] Figure 11 It is the XRD pattern of the B, N co-doped Mn5C2@CNT prepared in Example 7;

[0049] Figure 12 It is the XRD pattern of the B, N co-doped Co@CNT prepared in Example 8;

[0050] Figure 13 It is the XRD pattern of the pure Fe3C powder and Fe3C-CNT prepared in Comparative Example 1;

[0051] Figure 14 It is the thermogravimetric analysis diagram of the cathode materials prepared in Example 1 and Comparative Example 3;

[0052] Figure 15 It is the lithium-sulfur battery cycle performance diagram of the cathode materials prepared in Example 1 and Comparative Examples 1-2. Detailed implementation manners

[0053] The preparation method of a one-dimensional nano-reactor according to the present invention comprises the following steps:

[0054] As Figure 1 shown, a metal source, a carbonitrogen source, a supplementary carbon source, an alkaline metal salt, and a heteroatom source are added to a dispersant, and a thickener is simultaneously added for mixing to obtain a mixed liquid slurry;

[0055] The mixed liquid slurry is dried to obtain a precursor;

[0056] The precursor is sintered and washed to obtain a one-dimensional nano-reactor;

[0057] The molar ratio of the metal source, the carbonitrogen source, the supplementary carbon source, the alkaline metal salt, and the heteroatom source is (0.1 - 99):(5 - 30):(0 - 15):(0 - 10):(0 - 20);

[0058] The metal source includes at least one of nitrates, chlorides, sulfates, sulfates, phosphates, oxides, and hydroxides of iron, manganese, nickel, cobalt, copper, zinc, or aluminum;

[0059] The carbonitrogen source includes at least one of urea, pyridine, polyaniline, cyanamide, dicyandiamide, melamine, and dopamine.

[0060] The supplementary carbon source includes at least one of citric acid, glucose, sucrose, starch, maltose, chitosan, polyvinylpyrrolidone, polyethylene, polypropylene, polyethylene glycol, polyvinyl alcohol, and polystyrene;

[0061] The alkaline metal salt includes at least one of nitrates, chlorides, sulfates, sulfates, phosphates, oxide salts, and hydroxide salts of lithium, sodium, magnesium, potassium, or calcium;

[0062] The heteroatom source is at least one of organic or inorganic salts containing sulfur, phosphorus, selenium, or boron elements;

[0063] The dispersant includes at least one of water, ethanol, and acetone;

[0064] The thickener includes at least one of polytetrafluoroethylene, polyethylene glycol, and hydroxypropyl methylcellulose, and the addition amount of the thickener is 0.1 - 2 wt% of the dispersant.

[0065] The mixing, drying, and sintering steps are performed at least once or in combination; the mixing method includes at least one of ball milling, grinding, and stirring; the drying includes at least one of atmospheric drying, spray drying, freeze drying, and fluidized bed drying;

[0066] The conditions for sintering are that the temperature is raised at a rate of 0.1 - 10 °C / min to 300 - 1400 °C and held for 2 - 24 h.

[0067] The one-dimensional nano-reactor is a carbon nano-sphere tube, a carbon nano-prism tube or a long-range carbon nanotube with a carbon layer wrapping metal nano-particles doped with heteroatoms and having a particle size of 2-200 nm; the metal nano-particles include at least one of elemental metals, alloys, phosphides, sulfides, nitrides, carbides, and oxides; the heteroatoms include at least one of sulfur, phosphorus, selenium, and boron.

[0068] Testing of the lithium-sulfur battery cathode material:

[0069] Weigh sulfur powder and the one-dimensional nano-reactor material according to a mass ratio of 7:3, perform sufficient mixing, and heat to 155 °C to melt sulfur in a reaction kettle for 12 h to obtain a cathode material of sulfur-loaded one-dimensional nano-reactor material.

[0070] Take the obtained sulfur-loaded one-dimensional nano-reactor material, carbon black conductive agent (Super P), and polyvinylidene fluoride (PVDF) binder and mix them according to a mass ratio of 8:1:1. Then add an appropriate amount of N-methylpyrrolidone (NMP), grind them into a paste in an agate mortar, apply it on a current collector aluminum foil, then place it in a vacuum drying oven at 60 °C for 8 h of drying, and cut and prepare a pole piece. Then transfer them all to a glove box filled with argon for the assembly of a button battery. The button battery model is CR2032, use a metal lithium sheet as the counter electrode, the separator is a polypropylene microporous membrane Celgard 2400, and the electrolyte is 1 mol / L LiPF6 / EC+DMC+EMC (V / V / V = 1:1:1). Perform electrochemical performance testing on the assembled lithium-sulfur battery on a Neware testing system, and the voltage range is 1.7-2.8 V.

[0071] Example 1

[0072] The preparation process of a long-tubular N, B co-doped Fe3C@CNT one-dimensional nano-reactor described in the present invention includes the following steps:

[0073] Add ferric chloride hexahydrate, melamine, glucose, anhydrous calcium chloride, and boron oxide with a molar ratio of 5:12:2:2.5:1 to ethanol, and add polytetrafluoroethylene. The addition amount of polytetrafluoroethylene is 1 wt% of ethanol. After mixing, place it in a vacuum mixer and stir for 4 h to obtain a mixed liquid slurry; transfer the mixed liquid slurry to a drying oven and dry it at 80 °C for 12 h to obtain a precursor. Place the precursor in a tube rotary furnace, introduce nitrogen, purge for 1 h, then rise to 350 °C at 5 °C / min and hold for 2 h, then rise to 600 °C at 5 °C / min and hold for 4 h, and finally rise to 900 °C at 2.5 °C / min and hold for 2 h. After cooling, obtain long-tubular N, B co-doped Fe3C@CNT one-dimensional nano-reactor powder after cleaning.

[0074] Sulfur powder and long tubular N, B co-doped Fe3C@CNT one-dimensional nanoreactor powder were weighed in a mass ratio of 7:3, mixed thoroughly, and heated to 155°C to melt the sulfur in a reactor for 12 hours to obtain sulfur-loaded long tubular N, B co-doped Fe3C@CNT one-dimensional nanoreactor powder lithium-sulfur battery positive electrode material.

[0075] Figure 2 and Figure 3 The large-field and small-field SEM images of the long tubular N and B co-doped Fe3C@CNT one-dimensional nanoreactor are shown in Figure 2. Figure 2 It can be seen that this is a long-range tubular one-dimensional nanoreactor with a large aspect ratio. Under a wide field of view, it can be seen that it has a dense texture. Figure 3 It can be seen that the one-dimensional nanoreactor has uniform morphology and uniform diameter; Figure 4 This is the TEM image of a long tubular N, B co-doped Fe3C@CNT one-dimensional nanoreactor. It can be seen that the one-dimensional nanoreactor is encapsulated with metal nanoparticles; Figure 5 This is the XRD pattern of the long tubular N and B co-doped Fe3C@CNT one-dimensional nanoreactor, which shows that N and B atoms are successfully doped.

[0076] Example 2

[0077] The preparation process of a spherical tubular N and B co-doped Fe3C@CNT one-dimensional nanoreactor of the present invention comprises the following steps:

[0078] Add ferric chloride hexahydrate, melamine, glucose, anhydrous calcium chloride and boron oxide in a molar ratio of 5:12:3:2.5:1 to ethanol, and add polyethylene glycol, wherein the amount of polyethylene glycol added is 0.5wt% of ethanol, and place the mixture in a vacuum mixer, stir for 4 hours to obtain a mixed liquid slurry; transfer the mixed liquid slurry to a drying oven and dry it at 80°C for 12 hours to obtain a precursor. Place the precursor in a tubular rotary kiln, pass nitrogen, wash for 1 hour, then increase the temperature to 350°C at 5°C / min for two hours, then increase the temperature to 600°C at 5°C / min for 4 hours, and finally increase the temperature to 900°C at 2.5°C / min for 2 hours. After cooling, the spherical tubular N, B co-doped Fe3C@CNT one-dimensional nanoreactor powder is obtained after washing.

[0079] Figure 6 and Figure 7 The SEM and TEM images of the spherical tubular N and B co-doped Fe3C@CNT one-dimensional nanoreactor are shown in Figure 2. Figure 6 It can be seen that this is a long-range one-dimensional nanoreactor shaped like beads. Figure 7 This is the TEM image of the spherical tubular N and B co-doped Fe3C@CNT one-dimensional nanoreactor. It can be seen that the material is also wrapped with metal nanoparticles.

[0080] Example 3

[0081] The preparation process of the prismatic tubular N, B co-doped Fe3C@CNT one-dimensional nano-reactor described in the present invention includes the following steps:

[0082] Add ferric chloride hexahydrate, melamine, glucose, anhydrous calcium chloride, and boron oxide with a molar ratio of 5:12:1:2.5:1 to ethanol, and add hydroxypropyl methylcellulose. The addition amount of hydroxypropyl methylcellulose is 2 wt% of ethanol. After mixing, place it in a vacuum mixer and stir for 4 h to obtain a mixed liquid slurry; transfer the mixed liquid slurry to a drying oven and dry it at 80 °C for 12 h to obtain a precursor. Place the precursor in a tubular rotary furnace, introduce nitrogen, purge for 1 h, then keep it at 350 °C for 2 h at a rate of 5 °C / min, then raise the temperature to 600 °C at a rate of 5 °C / min and keep it for 4 h, and finally raise the temperature to 900 °C at a rate of 2.5 °C / min and keep it for 2 h. After cooling, wash it to obtain the prismatic tubular N, B co-doped Fe3C@CNT one-dimensional nano-reactor powder.

[0083] Figure 8 and Figure 9 are respectively the SEM image and TEM image of the prismatic tubular N, B co-doped Fe3C@CNT one-dimensional nano-reactor. It can be seen through Figure 8 that this is a one-dimensional nano-reactor composed of multiple long-range prismatic tubes. Figure 9 is the TEM image of the spherical tubular N, B co-doped Fe3C@CNT one-dimensional nano-reactor. It can be seen that there are larger particle size metal nanoparticles attached to this material.

[0084] It can be seen from Examples 1-3 that by adjusting the ratio of raw materials, the morphology of the one-dimensional nano-reactor can be controlled.

[0085] Example 4

[0086] The preparation process of the N, B co-doped Fe3C@CNT one-dimensional nano-reactor described in the present invention includes the following steps:

[0087] Dissolve ferric chloride hexahydrate and melamine with a molar ratio of 5:12 evenly in an ethanol solvent, dry the mixed liquid slurry to obtain a first precursor, and then mix it with glucose, anhydrous calcium chloride, and boron oxide with a molar ratio of 1:2.5:1, and add polyvinylpyrrolidone. The addition amount of polyvinylpyrrolidone is 0.5 wt% of ethanol. Polyvinylpyrrolidone can also be used for further dispersion and fixation of catalyst particles and providing a carbon source. After mixing, place it in a ball mill and dry-mill it into powder to obtain a second precursor.

[0088] Place the precursor in a tube rotary furnace, introduce nitrogen gas, and purge for 1 h. Then, raise the temperature to 350 °C at a rate of 5 °C / min and hold for 2 h, then raise the temperature to 600 °C at a rate of 5 °C / min and hold for 4 h, and finally raise the temperature to 900 °C at a rate of 2.5 °C / min and hold for 2 h. After cooling, wash to obtain the N, B co-doped Fe3C@CNT one-dimensional nano-reactor powder.

[0089] Figure 10 There is an XRD pattern of the N, B co-doped Fe3C@CNT one-dimensional nano-reactor in Example 4, indicating the successful synthesis of N, B co-doped Fe3C@CNT.

[0090] Example 5

[0091] The preparation process of the N, B co-doped Fe3C@CNT one-dimensional nano-reactor described in the present invention includes the following steps:

[0092] Add ferric chloride hexahydrate, melamine, glucose, anhydrous calcium chloride, and boron oxide with a molar ratio of 5:12:2:2.5:1 to ethanol. After mixing, place it in a vacuum mixer and stir for 4 h to obtain a mixed liquid slurry. Place the mixed liquid slurry directly in a tube rotary furnace, introduce nitrogen gas, and purge for 1 h. Then, raise the temperature to 350 °C at a rate of 5 °C / min and hold for 2 h, then raise the temperature to 600 °C at a rate of 5 °C / min and hold for 4 h, and finally raise the temperature to 900 °C at a rate of 2.5 °C / min and hold for 2 h. After cooling, wash to obtain the long tubular N, B co-doped Fe3C@CNT one-dimensional nano-reactor powder.

[0093] Figure 10 There is an XRD pattern of the N, B co-doped Fe3C@CNT one-dimensional nano-reactor in Example 5, indicating the successful synthesis of N, B co-doped Fe3C@CNT.

[0094] Example 6

[0095] The preparation process of the N, B co-doped Fe3C@CNT one-dimensional nano-reactor described in the present invention includes the following steps:

[0096] Ferric chloride hexahydrate, melamine, glucose, anhydrous calcium chloride, and boron oxide with a molar ratio of 5:12:3:2.5:1 were added to ethanol. After mixing, it was placed in a vacuum blender and stirred for 4 h to obtain a mixed liquid slurry. The mixed liquid slurry was transferred to a drying oven and dried at 80 °C for 12 h to obtain a precursor. The precursor was placed in a tubular rotary furnace, nitrogen was introduced, and the gas was washed for 1 h. Subsequently, it was heated to 350 °C at a rate of 5 °C / min and held for 2 h, and then taken out after cooling, which was the precursor after the first heat treatment. The precursor after the first heat treatment was placed in a tubular rotary furnace, nitrogen was introduced again, and the gas was washed for 1 h. It was heated to 600 °C at a rate of 5 °C / min and held for 4 h, and finally heated to 900 °C at a rate of 2.5 °C / min and held for 2 h. After cooling, N, B co-doped Fe3C@CNT one-dimensional nano-reactor powder was obtained after washing.

[0097] Figure 10 There is an XRD pattern of the N, B co-doped Fe3C@CNT one-dimensional nano-reactor in Example 6, indicating that the N, B co-doped Fe3C@CNT was successfully synthesized.

[0098] It can be seen from Examples 4 - 6 that the target product can be obtained by adjusting the process.

[0099] Example 7

[0100] The preparation process of a long tubular N, B co-doped Mn5C2@CNT one-dimensional nano-reactor according to the present invention includes the following steps:

[0101] Manganese chloride tetrahydrate, melamine, glucose, anhydrous calcium chloride, and boron oxide with a molar ratio of 6:12:2:2.5:1 were added to ethanol. After mixing, it was placed in a vacuum blender and stirred for 4 h to obtain a mixed liquid slurry. The mixed liquid slurry was transferred to a drying oven and dried at 80 °C for 12 h to obtain a precursor. The precursor was placed in a tubular rotary furnace, nitrogen was introduced, and the gas was washed for 1 h. Subsequently, it was heated to 350 °C at a rate of 5 °C / min and held for 4 h, then heated to 600 °C at a rate of 5 °C / min and held for 4 h, and finally heated to 900 °C at a rate of 2.5 °C / min and held for 6 h. After cooling, N, B co-doped Mn5C2@CNT one-dimensional nano-reactor powder was obtained after washing.

[0102] Figure 11 There is an XRD pattern of the N, B co-doped Mn5C2@CNT one-dimensional nano-reactor in Example 7, indicating that the N, B co-doped Mn5C2@CNT was successfully synthesized.

[0103] Example 8

[0104] The preparation process of a long tubular N, B co-doped Co@CNT one-dimensional nano-reactor according to the present invention includes the following steps:

[0105] Manganese chloride hexahydrate, melamine, glucose, anhydrous calcium chloride, and boron oxide with a molar ratio of 4:12:2:2.5:1 were added to ethanol. After mixing, the mixture was placed in a vacuum blender and stirred for 4 h to obtain a mixed liquid slurry. The mixed liquid slurry was transferred to an oven and dried at 80 °C for 12 h to obtain a precursor. The precursor was placed in a tubular rotary furnace, nitrogen was introduced, and the gas was washed for 1 h. Subsequently, the temperature was raised to 300 °C at a rate of 10 °C / min and held for 4 h, then the temperature was raised to 600 °C at a rate of 5 °C / min and held for 4 h, and finally the temperature was raised to 900 °C at a rate of 1 °C / min and held for 2 h. After cooling, the N, B co-doped Co@CNT one-dimensional nano-reactor powder was obtained after washing.

[0106] Figure 12 In the XRD pattern of the N, B co-doped Co@CNT one-dimensional nano-reactor in Example 8, it can be seen that the N, B co-doped Co@CNT was successfully synthesized.

[0107] Using a method similar to that of Example 1, a series of one-dimensional nano-reactor materials were also prepared by changing the reaction raw materials and conditions, as shown in the following table:

[0108]

[0109]

[0110] Comparative Example 1

[0111] Ferric chloride hexahydrate, melamine, glucose, and anhydrous calcium chloride with a molar ratio of 5:12:3:2.5 were added to ethanol. After mixing, the mixture was placed in a vacuum blender and stirred for 4 h to obtain a mixed liquid slurry. The mixed liquid slurry was transferred to an oven and dried at 80 °C for 12 h to obtain a precursor. The precursor was placed in a tubular rotary furnace, nitrogen was introduced, and the gas was washed for 1 h. Subsequently, the temperature was raised to 700 °C at a rate of 5 °C / min and held for 1 h. After cooling, the pure Fe3C powder was obtained after washing.

[0112] The Fe3C powder and CNT with a mass fraction ratio of 2:8 were mixed in an ethanol solvent, ultrasonicated for 30 min with an ultrasonic cleaner, and then placed in an oven to evaporate the solvent to obtain the comparative sample Fe3C-CNT.

[0113] Sulfur powder and Fe3C-CNT material were weighed according to a mass ratio of 7:3, thoroughly mixed, and heated to 155 °C to melt sulfur in a reaction kettle for 12 h to obtain the sulfur-loaded Fe3C-CNT-S lithium-sulfur battery cathode material.

[0114] Figure 13 It is the XRD pattern of the pure Fe3C powder and Fe3C-CNT prepared in Comparative Example 1.

[0115] Comparative Example 2

[0116] Weigh sulfur powder and carbon nanotube (CNT) materials according to a mass ratio of 7:3, mix them thoroughly, and heat to 155 °C to melt sulfur in a reaction kettle for 12 h to obtain the CNT-S lithium-sulfur battery cathode material loaded with sulfur.

[0117] Comparative Example 3

[0118] Use the traditional process to fabricate the N, B co-doped Fe3C@CNT one-dimensional nano-reactor for comparison, including the following steps:

[0119] Grind ferric chloride hexahydrate, melamine, and boron oxide with a molar ratio of 5:12:1 to obtain a precursor. Place the precursor in a tubular rotary furnace, pass nitrogen gas, wash for 1 h, then keep warm at 5 °C / min to 350 °C for 4 h, then rise to 600 °C at 5 °C / min and keep warm for 4 h, and finally rise to 900 °C at 2.5 °C / min and keep warm for 6 h. After cooling, wash to obtain the N, B co-doped Fe3C@CNT one-dimensional nano-reactor powder.

[0120] Figure 14 It is the thermogravimetric analysis of Comparative Example 3 and Example 1. It can be seen that Example 1 has a higher raw material utilization rate through the improvement of the formula and process.

[0121] Effect test

[0122] Respectively take the sulfur-loaded cathode materials obtained in Example 1 and Comparative Examples 1-2, carbon black conductive agent (Super P), and polyvinylidene fluoride (PVDF) binder, mix them according to a mass ratio of 8:1:1, then add an appropriate amount of N-methylpyrrolidone (NMP), grind to a paste in an agate mortar, smear it on the current collector aluminum foil, then place it in a 60 °C vacuum drying oven for 8 h, and cut to prepare the electrode sheet. Then transfer them all to a glove box filled with argon for the assembly of button batteries. The button battery model is CR2032, use a lithium metal sheet as the counter electrode, the separator is a polypropylene microporous membrane Celgard 2400, and the electrolyte is 1 mol / L LiPF6 / EC+DMC+EMC (V / V / V = 1:1:1). Test the electrochemical performance of the assembled lithium-sulfur battery on a Neware test system, and the voltage range is 1.7-2.8 V.

[0123] Figure 15 It is the cycle performance diagram of the lithium-sulfur battery with the cathode materials prepared in Example 1, Comparative Example 1, and CNT. It can be seen from the figure that the cathode material prepared in Example 1 has a capacity retention rate of 70.2% after 500 cycles at a 1C rate; the cathode material prepared in Comparative Example 1 has only a capacity retention rate of 57.5% after 500 cycles at a 1C rate; while the untreated CNT (Comparative Example 2) has a capacity retention rate decay to 32.3% after 500 cycles at a 1C rate.

[0124] The above-described embodiments merely represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. For those of ordinary skill in the art, without departing from the concept of the present invention, several variations and improvements can still be made, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing a one-dimensional nano-reactor, characterized in that, The following steps are involved: Mixing a metal source, a carbon and nitrogen source, a supplemental carbon source, an alkaline metal salt, and a heteroatom source in a dispersant to obtain a mixed liquid slurry; Drying the mixed liquid slurry to obtain a precursor; Sintering the precursor to obtain a one-dimensional nanoreactor; The molar ratio of the metal source, carbon and nitrogen source, supplementary carbon source, alkaline metal salt, and heteroatom source is (0.1-99): (5-30): (0-15): (0-10): (0-20); The metal source includes at least one of nitrates, chlorides, sulfates, phosphates, oxides, and hydroxides of iron, manganese, nickel, cobalt, copper, zinc, or aluminum; The carbon and nitrogen source includes at least one of urea, pyridine, polyaniline, cyanamide, dicyandiamide, melamine, and dopamine; The supplementary carbon source comprises at least one of citric acid, glucose, sucrose, starch, maltose, chitosan, polyvinyl pyrrolidone, polyethylene, polypropylene, polyethylene glycol, polyvinyl alcohol, and polystyrene; The alkaline metal salt includes at least one of nitrates, chlorides, sulfates and phosphates of lithium, sodium, magnesium, potassium and calcium; The heteroatom source is at least one of organic or inorganic salts containing sulfur, phosphorus, selenium, and boron; The dispersant includes at least one of water, ethanol and acetone.

2. The preparation method of a one-dimensional nano-reactor according to claim 1, wherein The mixing method includes at least one of ball milling, grinding, and stirring; the drying includes at least one of normal pressure drying, spray drying, freeze drying, and boiling drying.

3. The preparation method of a one-dimensional nano-reactor according to claim 2, characterized in that, The mixing, drying and sintering steps are performed at least once or in combination.

4. The preparation method of a one-dimensional nano-reactor according to claim 3, wherein, The following steps are also included: The mixed liquid slurry is dried to obtain a first precursor, the first precursor is crushed and mixed again to obtain a second precursor, and the second precursor is sintered to obtain a one-dimensional nanoreactor.

5. The preparation method of a one-dimensional nano-reactor according to claim 3, wherein, The following steps are also included: The mixed liquid slurry is dried and sintered simultaneously to obtain a one-dimensional nanoreactor.

6. The preparation method of a one-dimensional nano-reactor according to claim 3, wherein, The following steps are also included: The metal source and the supplementary carbon source are mixed, dried, and then sintered once to obtain a one-dimensional nanoreactor preform; the one-dimensional nanoreactor preform is mixed, dried, and then sintered twice to obtain a one-dimensional nanoreactor.

7. The preparation method of a one-dimensional nano-reactor according to claim 1, characterized in that, A thickener is also added during the mixing, and the amount of the thickener added is 0.1-2wt% of the dispersant. The thickener includes at least one of polytetrafluoroethylene, polyethylene glycol, and hydroxypropyl methylcellulose.

8. The preparation method of a one-dimensional nano-reactor according to claim 1, characterized in that, The sintering is carried out in a protective atmosphere, which includes at least one of nitrogen, argon, hydrogen, ammonia and methane. The sintering conditions are: heating the temperature to 300-1400° C. at a heating rate of 0.1-10° C. / min and keeping the temperature for 2-24 hours.

9. A one-dimensional nano-reactor prepared by the preparation method of the one-dimensional nano-reactor according to any one of claims 1-8, characterized in that, The one-dimensional nanoreactor is a carbon nanotube, a carbon nanoprism or a long-range carbon nanotube, which is composed of a carbon layer wrapping metal nanoparticles doped with heteroatoms with a particle size of 2-200nm; the metal nanoparticles include at least one of a metal element, an alloy, a phosphide, a sulfide, a nitride, a carbide, and an oxide; and the heteroatoms include at least one of sulfur, phosphorus, selenium, and boron.

10. Application of a one-dimensional nano-reactor as described in claim 9 in a lithium-sulfur battery.

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