Nano-cobalt selenide@three-dimensional honeycomb carbon composite material and its preparation and application

Abstract

The present invention discloses a nano-cobalt selenide@three-dimensional honeycomb carbon composite material, its preparation method, and its application in preparing lithium-ion battery negative electrodes. In the nano-cobalt selenide@three-dimensional honeycomb carbon composite material, carbon presents a three-dimensional honeycomb pore structure, and cobalt selenide CoSe grows densely and evenly on the inner surface of the honeycomb pores of the honeycomb carbon in the form of nanoparticles. Preparation method: First, PS pellets are synthesized, and then the PS pellets and a solution containing dissolved Co(NO)2 and PVP are slowly evaporated and dried, followed by calcination under a protective atmosphere, and finally selenization by a vapor phase method to obtain the nano-cobalt selenide@three-dimensional honeycomb carbon composite material. The present invention can significantly improve the specific capacity, cycle performance, and rate performance of cobalt selenide.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a nano-cobalt selenide (CoSe)@three-dimensional honeycomb carbon composite material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have attracted widespread attention due to their high operating voltage, high energy efficiency, long cycle life, and clean and environmentally friendly characteristics. They are currently the most widely used type of energy storage device on the market.

[0003] As a new type of negative electrode material for lithium-ion batteries, metal selenides have the advantages of high theoretical capacity, low potential platform, and relatively high electrochemical activity.

[0004] Compared with metal sulfides, metal selenides have higher electronic conductivity.

[0005] Among metal selenides, CoSe also has the advantages of high capacity and high conductivity. However, the intercalation and deintercalation of lithium ions into CoSe can cause severe volume expansion and contraction, leading to structural collapse and gradual pulverization of the material, which in turn degrades the cycling and rate performance of lithium-ion batteries.

[0006] Therefore, preparing CoSe with stable cycle performance and high reversible capacity is an important technical challenge faced today.

[0007] In order to improve the performance of lithium-ion batteries based on CoSe, some explorations have been carried out.

[0008] The invention patent application with publication number CN114229805A reported a nitrogen-doped porous carbon-coated cobalt diselenide composite material, the invention patent application with publication number CN113666344A reported a transition metal selenide-carbon composite material, the invention patent application with publication number CN109768241A reported a cobalt diselenide / carbon nanomaterial, and the invention patent application with publication number CN114927661A reported a hierarchical hollow superstructure cobalt selenide bird's nest-shaped composite material.

[0009] In general, there is still little exploration of CoSe, and there are not many related academic papers and patented technologies. There is a lack of in-depth understanding and innovative design of CoSe nanostructures and composite structures, so the progress in this field is still very limited. Summary of the Invention

[0010] In response to the deficiencies in the art, the present invention provides a nano-cobalt selenide@three-dimensional honeycomb carbon composite material, which has the characteristics of unique structure, excellent performance and simple synthesis process.

[0011] A nano-cobalt selenide@three-dimensional honeycomb carbon composite material, in which carbon presents a three-dimensional honeycomb pore structure, and cobalt selenide CoSe grows densely and evenly on the inner surface of the honeycomb pores of the honeycomb carbon in the form of nanoparticles.

[0012] In a preferred embodiment, in the nano-cobalt selenide@three-dimensional honeycomb carbon composite material, the particle size of the cobalt selenide nanoparticles is 3-100 nm.

[0013] In a preferred embodiment, the nano-cobalt selenide@three-dimensional honeycomb carbon composite material, the honeycomb carbon is an amorphous material produced by decomposing polyvinylpyrrolidone (PVP), and the honeycomb pore diameter is 50-1000 nm.

[0014] In a preferred embodiment, in the nano-cobalt selenide@three-dimensional honeycomb carbon composite material, the mass percentage of cobalt selenide is 40%-90%, and the rest is carbon.

[0015] The present invention also provides a method for preparing the nano-cobalt selenide@three-dimensional honeycomb carbon composite material, comprising the steps of:

[0016] (1) Deionized water was heated to 60°C under nitrogen deoxygenation and protection, oleic acid and styrene were added, and then heated to 70°C, K2S2O8 aqueous solution was added to initiate polymerization, and the reaction was stirred for 5-35 hours. The reaction was then heated to 80°C and kept warm for 30 minutes, and cooled to obtain a monodispersed PS sphere emulsion.

[0017] (2) adding polyvinyl pyrrolidone to the PS sphere emulsion obtained in step (1), stirring and heating to 50°C, keeping warm for 30 minutes, then adding Co(NO3)2·6H2O, stirring for 5 hours, and drying the obtained mixed solution at 60°C to obtain the precursor Co(NO3)2@PVP@PS spheres;

[0018] (3) heating the precursor Co(NO3)2@PVP@PS ball obtained in step (2) to 470-490°C under an Ar atmosphere and keeping the temperature for 3 hours to obtain a nano-Co3O4@3D honeycomb carbon composite material;

[0019] (4) The nano-Co3O4@3D honeycomb carbon composite material obtained in step (3) is mixed with selenium powder, placed in a quartz tube and vacuum sealed, and then the quartz tube is heated to 580-620°C, kept warm for 30 hours, and cooled to room temperature. The resulting product is placed in a quartz tube furnace again, heated to 500°C under argon protection, kept warm for 0.5 hours, and cooled to room temperature to obtain a nano-cobalt selenide@3D honeycomb carbon composite material.

[0020] The preparation method of the present invention first synthesizes PS pellets, then slowly evaporates and dries the PS pellets and a solution containing dissolved Co(NO3)2 and PVP, then calcines under a protective atmosphere to synthesize a nano-Co3O4@3D honeycomb carbon composite material, and finally selenizes the nano-CoSe@3D honeycomb carbon composite material by a vapor phase method. The main purpose of the second heating in step (4) (i.e., 500°C for 0.5h) is to remove excess selenium to avoid affecting the nano-CoSe@3D honeycomb carbon composite material. The present invention can improve the specific capacity, cycle performance, and rate performance of CoSe.

[0021] In a preferred embodiment, in step (1):

[0022] The usage ratio of deionized water, oleic acid, styrene, and K2S2O8 aqueous solution is 280 mL:200 μL:2-50 mL:10 mL;

[0023] The concentration of the K2S2O8 aqueous solution is 20 mg / mL.

[0024] In a preferred embodiment, in step (2):

[0025] The average molecular weight (MW) of polyvinylpyrrolidone is 58,000;

[0026] The usage ratio of polyvinyl pyrrolidone, PS ball emulsion and Co(NO3)2·6H2O is 0.15g:60mL:0.1-0.6g.

[0027] In a preferred embodiment, in step (4), the mass ratio of the nano-Co3O4@3D honeycomb carbon composite material to the selenium powder is 3:1.

[0028] A preferred preparation method of the nano-cobalt selenide@three-dimensional honeycomb carbon composite material comprises the following steps:

[0029] (1) Add 280 mL of deionized water to a 500 mL three-necked flask, insert a thermometer, a nitrogen inlet tube, and a reflux tube. Heat the solution to 60°C, add 200 μL of oleic acid and 2-50 mL of styrene. Deoxygenate the solution by bubbling nitrogen for 1 hour, then heat the solution to 70°C. Add 10 mL of an aqueous solution containing 200 mg of K₂S₂O₄ to initiate polymerization. Stir the solution continuously for 5-35 hours, then heat to 80°C for 30 minutes, and finally cool to room temperature to obtain a monodisperse polystyrene (PS) sphere emulsion.

[0030] (2) 0.15 g of polyvinylpyrrolidone (PVP, MW58000) was added to 60 mL of PS sphere emulsion, stirred and heated to 50 °C for 30 min, then 0.1-0.6 g of Co(NO3)2·6H2O was added and stirred for 5 h. The resulting mixed solution was dried at 60 °C to form the precursor Co(NO3)2@PVP@PS spheres.

[0031] (3) 200 mg of the precursor was heated to 470-490 °C in an Ar atmosphere and kept warm for 3 h to obtain a nano-Co3O4@3D honeycomb carbon composite material.

[0032] (4) 90 mg of nano-Co3O4@3D honeycomb carbon composite material and 30 mg of selenium powder were mixed and placed in a quartz tube for vacuum sealing. The quartz tube was then placed in a muffle furnace, heated to 580-620°C, kept warm for 30 h, and cooled to room temperature. The product was placed in a quartz tube furnace again and heated to 500°C under argon protection, kept warm for 0.5 h, and cooled to room temperature to obtain a nano-CoSe@3D honeycomb carbon composite material.

[0033] The present invention also provides the use of the nano-cobalt selenide@three-dimensional honeycomb carbon composite material in preparing a negative electrode of a lithium-ion battery.

[0034] In a preferred embodiment, the nano-CoSe@3D honeycomb carbon composite material of the present invention is used to make a lithium-ion battery negative electrode: the nano-CoSe@3D honeycomb carbon composite material, acetylene black conductive agent, and PVDF binder are weighed in a mass ratio of 8:1:1, the PVDF is dissolved in an appropriate amount of N-methylpyrrolidone, and stirred until completely dissolved. The evenly ground active material and acetylene black are then added to the above solution, and stirring is continued to ensure that the slurry is evenly mixed. The slurry is then evenly coated on a circular copper foil (diameter 12mm), dried in a vacuum oven at 100°C, and finally flattened on a tablet press at a pressure of 10MPa to produce an electrode sheet.

[0035] In a glove box filled with high-purity argon, the prepared electrode sheet, lithium sheet, and separator were assembled into a CR2025 button-type lithium-ion battery. The electrolyte was an EC / DMC solution containing 1 mol / L LiPF6. The charge-discharge and cycling performance of the lithium-ion battery was tested using a Xinwei battery testing system.

[0036] The present invention can obtain a nano CoSe@stereoscopic honeycomb carbon composite material with high specific capacity, excellent cycle performance and rate performance.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1) The precursor synthesis process is simple: Co(NO3)2 and PVP are dissolved in a PS sphere emulsion and then dried. Drying the solution achieves three objectives: after drying, the PS spheres form a dense, three-dimensional stack, which prepares the structure for the formation of three-dimensional honeycomb pores. Simultaneously, PVP precipitates from the solution, filling the gaps between the PS spheres and solidifying the dense, three-dimensional stacking structure of the PS spheres, which prepares the material for the formation of three-dimensional honeycomb pores. Simultaneously, Co(NO3)2 also precipitates from the solution and settles at the interface between the PVP and PS spheres, providing a key growth foundation for the in-situ growth of nano-Co3O4 on the inner surface of the three-dimensional honeycomb carbon pores and ultimately for the encapsulation of nano-CoSe within the three-dimensional honeycomb carbon pores. If nano-Co3O4 is added directly to the solution, or if Co(NO3)2 is added but first precipitated with an alkali to form a cobalt oxide precursor, the nano-Co3O4 or cobalt oxide precursor cannot enter the interface between the PVP and PS spheres after the solution dries, and cannot enter the pores of the honeycomb carbon, thus failing to form the composite material structure of the present invention.

[0039] 2) The intermediate product, nano-Co3O4@three-dimensional honeycomb carbon composite material, can be obtained by simple calcination. One calcination can achieve three goals: the PS balls decompose and gasify to produce holes, forming three-dimensional honeycomb macropores; PVP decomposes into an amorphous carbon framework, retaining the macropores produced by the decomposition of the PS balls; Co(NO3)2 decomposes into nano-Co3O4, which adheres to the inner surface of the amorphous carbon macropores. The calcination temperature is very critical. If the temperature is too low, Co(NO3)2 cannot be fully decomposed; if the temperature is too high, carbon will reduce Co3O4 to metallic cobalt. Through vapor phase selenization, vapor phase selenium penetrates into the interior of the honeycomb pores, selenizing Co3O4 into CoSe. By using the synthesis method of the present invention, CoSe can be simply and conveniently encapsulated in each honeycomb carbon pore, maximizing the utilization rate of the honeycomb carbon pores.

[0040] 3) Due to the closed nature of the carbon pores, even if CoSe pulverizes during the charge-discharge cycle, it remains confined within the carbon pores and can still participate in the charge-discharge reaction, ensuring the high cycling stability of CoSe. The separation of CoSe by honeycomb pores effectively prevents the problem of CoSe reaggregation during the charge-discharge process, ensuring the material's high electrochemical activity and high lithium battery performance.

[0041] 4) CoSe is in close contact with the honeycomb carbon, and the three-dimensional honeycomb carbon can effectively improve the conductivity of CoSe, which can significantly improve the rate performance of CoSe. The large pores provide sufficient space to buffer the volume change of CoSe, which helps to improve the stability of CoSe. The liquid electrolyte can penetrate and be stored inside the honeycomb pores, which not only meets the electrochemical reaction requirements of CoSe inside the pores, but also produces an unexpected effect, namely the formation of a polymer colloidal film inside the honeycomb pores. The polymer colloidal film will wrap the CoSe inside the honeycomb pores, thereby improving the cycle performance and reversible capacity of CoSe.

[0042] 5) Compared with the traditional independent carbon hollow spheres that encapsulate electrode materials, the CoSe encapsulated in each honeycomb hole inside the three-dimensional honeycomb carbon realizes a highly integrated and ordered structure. It is the most efficient form of utilization of the hollow structure, which can significantly improve the loose and tight density of the electrode material and plays an important role in improving the volume energy density of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a scanning electron microscope (SEM) photograph of the PS sphere prepared in Example 1;

[0044] Figure 2 This is the SEM image of the precursor Co(NO3)2@PVP@PS sphere prepared in Example 1;

[0045] Figure 3 This is a SEM photo of the nano-Co3O4@3D honeycomb carbon prepared in Example 1;

[0046] Figure 4 TEM image of nano-CoSe@3D honeycomb carbon prepared in Example 1;

[0047] Figure 5 This is the XRD pattern of the nano-CoSe@3D honeycomb carbon prepared in Example 1;

[0048] Figure 6 The nano-CoSe@3D honeycomb carbon prepared in Example 1 was heated to a current density of 2A g -1 Cycling performance;

[0049] Figure 7 This is the rate performance of the nano-CoSe@3D honeycomb carbon prepared in Example 1. DETAILED DESCRIPTION

[0050] The present invention will be further described below in conjunction with the accompanying drawings and specific examples. It should be understood that these examples are intended to illustrate the present invention and are not intended to limit the scope of the invention. The operating methods in the following examples where no specific conditions are specified are generally performed under conventional conditions or as recommended by the manufacturer.

[0051] Example 1

[0052] (1) Add 280 mL of deionized water to a 500 mL three-necked flask, insert a thermometer, a nitrogen inlet tube, and a reflux tube. Heat the solution to 60°C, add 200 μL of oleic acid and 7 mL of styrene. Deoxygenate the solution by bubbling nitrogen for 1 hour, then heat the solution to 70°C. Add 10 mL of an aqueous solution containing 200 mg of K₂S₂O₄ to initiate polymerization. Stir the solution continuously for 10 hours, then heat to 80°C and maintain for 30 minutes. Finally, cool to room temperature to obtain a monodisperse polystyrene (PS) sphere emulsion.

[0053] (2) 0.15 g of polyvinyl pyrrolidone (PVP, MW58000) was added to 60 mL of PS sphere emulsion, stirred and heated to 50 °C for 30 min, then 0.29 g of Co(NO3)2·6H2O was added and stirred for 5 h. The resulting mixed solution was dried at 60 °C to form the precursor Co(NO3)2@PVP@PS spheres.

[0054] (3) 200 mg of the precursor was heated to 480 °C in an Ar atmosphere and kept warm for 3 h to obtain a nano-Co3O4@3D honeycomb carbon composite material.

[0055] (4) 90 mg of nano-Co3O4@3D honeycomb carbon composite material and 30 mg of selenium powder were mixed and placed in a quartz tube for vacuum sealing. The quartz tube was then placed in a muffle furnace, heated to 600°C, kept warm for 30 h, and cooled to room temperature. The product was placed in a quartz tube furnace again and heated to 500°C under argon protection, kept warm for 0.5 h, and cooled to room temperature to obtain a nano-CoSe@3D honeycomb carbon composite material.

[0056] Figure 1 These are synthetic PS spheres with uniform particle size of approximately 200-220nm. The PS spheres have clear outlines, smooth surfaces, and are well dispersed. Figure 1 This is the shape of the PS ball emulsion after slow evaporation. It can be seen that the PS balls are densely packed, showing a good self-assembly effect. Figure 2 This is the SEM image of the Co(NO3)2@PVP@PS ball precursor. It can be seen that the precursor is in the form of a dense three-dimensional deposit, indicating that the three have been successfully mixed together. Figure 3This is an SEM photo of nano-Co3O4@3D honeycomb carbon. After the PS balls decompose, a large number of large pores are formed, which are distributed throughout the surface and interior of the product, showing typical honeycomb features. Many Co3O4 nanoparticles grow on the surface of the honeycomb pores. The Co3O4 is uniform in size and not aggregated. The diameter of the large pores is about 200nm. The structure of the nano-CoSe@3D honeycomb carbon after selenization is no different from that before selenization under the scanning electron microscope. In order to observe it by TEM, the nano-CoSe@3D honeycomb carbon was crushed and dispersed by ultrasonic vibration. The results are as follows Figure 4 As shown in the figure, a large number of CoSe nanoparticles with a particle size of 20-40nm are adhered to the surface of a carbon framework fragment. Thermogravimetric analysis experiments show that the CoSe content is 70.3%, and the rest is carbon.

[0057] Figure 5 This is the XRD pattern of nano-CoSe@3D honeycomb carbon. All diffraction peaks of the product belong to CoSe (JCDPS 89-2004), with no diffraction peaks for Co(NO3)2 or Co3O4 present, indicating complete decomposition of Co(NO3)2 and thorough selenization of Co3O4. There is a broad, weak diffraction peak in the 2θ range of 20-30°, corresponding to PVP-derived amorphous carbon.

[0058] The nano-CoSe@3D honeycomb carbon composite material of the present invention is used to make a lithium-ion battery negative electrode: the nano-CoSe@3D honeycomb carbon composite material, acetylene black conductive agent, and PVDF binder are weighed in a mass ratio of 8:1:1. The PVDF is dissolved in an appropriate amount of N-methylpyrrolidone and stirred until completely dissolved. The evenly ground active material and acetylene black are then added to the solution, and stirring is continued to ensure the slurry is evenly mixed. The slurry is then evenly coated on a circular copper foil (diameter 12 mm), dried in a vacuum oven at 100°C, and finally flattened on a tablet press at a pressure of 10 MPa to produce an electrode sheet.

[0059] In a glove box filled with high-purity argon, the prepared electrode sheet, lithium sheet, and separator were assembled into a CR2025 button-type lithium-ion battery. The electrolyte was an EC / DMC solution containing 1 mol / L LiPF6. The charge-discharge and cycling performance of the lithium-ion battery was tested using a Xinwei battery testing system.

[0060] Figure 6 The nano-CoSe@3D honeycomb carbon composite material prepared in Example 1 was heated to a current density of 2A g -1 The specific capacity of nano-CoSe@3D honeycomb carbon shows a slowly decreasing trend, and the first cycle discharge capacity is 1022mAh g -1 The discharge capacity of the 100th cycle is 778 mAh g -1 , the 200th cycle is 730mAh g-1 , the 250th cycle is 610mAh g -1 The cycling performance of the nano-CoSe@3D honeycomb carbon composite material is better than that of a CoSe2 / C composite material reported in the invention patent application with publication number CN113666344A, which has a discharge capacity of about 150 mAh g after about 170 cycles. -1 , which is better than the discharge capacity of a CoSe2 / C composite material of about 490 mAh g after 50 cycles reported in the invention patent application with publication number CN105428647A. -1 , which is superior to the nitrogen-doped porous carbon-coated cobalt diselenide composite material reported in the invention patent application with publication number CN114229805A at a current density of 0.2A g -1 The discharge capacity after 250 cycles is about 130 mAh g -1 .

[0061] Figure 7 The rate performance of the nano-CoSe@3D honeycomb carbon prepared in Example 1 is shown at current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 10 A g -1 , with average discharge capacities of 1049, 991, 904, 849, 745, 472, and 262 mAh g -1 The rate performance is better than that of a nitrogen-doped porous carbon-coated cobalt diselenide composite material reported in the invention patent application with publication number CN114229805A.

[0062] Example 2

[0063] (1) Add 280 mL of deionized water to a 500 mL three-necked flask, insert a thermometer, a nitrogen inlet tube, and a reflux tube. Heat the solution to 60°C, add 200 μL of oleic acid and 28 mL of styrene. Deoxygenate the solution by bubbling nitrogen for 1 hour, then heat the solution to 70°C. Add 10 mL of an aqueous solution containing 200 mg of K₂S₂O₄ to initiate polymerization. Stir the solution continuously for 28 hours, then heat to 80°C for 30 minutes, and finally cool to room temperature to obtain a monodisperse polystyrene (PS) sphere emulsion.

[0064] The subsequent process is the same as that in Example 1.

[0065] The structure of the product nano-CoSe@3D honeycomb carbon is similar to that of Example 1, with the main difference being that the diameter of the PS sphere is increased to 360-380 nm, and the honeycomb pore diameter of the synthesized 3D honeycomb carbon is changed to about 360 nm.

[0066] Example 3

[0067] (1) Add 280 mL of deionized water to a 500 mL three-necked flask, insert a thermometer, a nitrogen inlet tube, and a reflux tube. Heat the solution to 60°C, add 200 μL of oleic acid and 7 mL of styrene. Deoxygenate the solution by bubbling nitrogen for 1 hour, then heat the solution to 70°C. Add 10 mL of an aqueous solution containing 200 mg of K₂S₂O₄ to initiate polymerization. Stir the solution continuously for 10 hours, then heat to 80°C and maintain for 30 minutes. Finally, cool to room temperature to obtain a monodisperse polystyrene (PS) sphere emulsion.

[0068] (2) 0.15 g of polyvinyl pyrrolidone (PVP, MW58000) was added to 60 mL of PS sphere emulsion, stirred and heated to 50 °C for 30 min, then 0.39 g of Co(NO3)2·6H2O was added and stirred for 5 h. The resulting mixed solution was dried at 60 °C to form the precursor Co(NO3)2@PVP@PS spheres.

[0069] The subsequent process is the same as that in Example 1.

[0070] The structure of the product nano-CoSe@3D honeycomb carbon composite material is similar to that of Example 1, with the main differences being that the mass percentage of CoSe is increased to 75.1%, with the remainder being carbon; and the diameter of CoSe is increased to 25-45 nm.

[0071] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for preparing nano-cobalt selenide@three-dimensional honeycomb carbon composite material, characterized in that: Including steps: (1) Deionized water was heated to 60°C under nitrogen deoxygenation and protection, oleic acid and styrene were added, and then heated to 70°C, K2S2O8 aqueous solution was added to initiate polymerization, and the reaction was stirred for 5-35 hours. The reaction was then heated to 80°C and kept warm for 30 minutes, and cooled to obtain a monodispersed PS sphere emulsion. (2) adding polyvinyl pyrrolidone to the PS sphere emulsion obtained in step (1), stirring and heating to 50°C, keeping warm for 30 minutes, then adding Co(NO3)2·6H2O, stirring for 5 hours, and drying the obtained mixed solution at 60°C to obtain the precursor Co(NO3)2@PVP@PS spheres; (3) heating the precursor Co(NO3)2@PVP@PS ball obtained in step (2) to 470-490°C under an Ar atmosphere and keeping the temperature for 3 hours to obtain a nano-Co3O4@3D honeycomb carbon composite material; (4) mixing the nano-Co3O4@3D honeycomb carbon composite material obtained in step (3) with selenium powder, placing the mixture into a quartz tube for vacuum sealing, then heating the quartz tube to 580-620°C, keeping the temperature for 30 hours, and cooling to room temperature; the resulting product is again placed in a quartz tube furnace, heated to 500°C under argon protection, kept the temperature for 0.5 hours, and cooled to room temperature to obtain a nano-cobalt selenide@3D honeycomb carbon composite material; In the nano-cobalt selenide@three-dimensional honeycomb carbon composite material, the carbon presents a three-dimensional honeycomb pore structure, and the cobalt selenide CoSe grows densely and evenly on the inner surface of the honeycomb pores of the honeycomb carbon in the form of nanoparticles.

2. The preparation method according to claim 1, characterized in that The particle size of the cobalt selenide nanoparticles is 3-100 nm.

3. The preparation method according to claim 1, characterized in that The honeycomb carbon is an amorphous material produced by decomposing polyvinyl pyrrolidone, and the diameter of the honeycomb pores is 50-1000 nm.

4. The preparation method according to claim 1, characterized in that In the nano-cobalt selenide@three-dimensional honeycomb carbon composite material, the mass percentage of cobalt selenide is 40%-90%, and the rest is carbon.

5. The preparation method according to claim 1, characterized in that In step (1): The usage ratio of deionized water, oleic acid, styrene, and K2S2O8 aqueous solution is 280 mL:200 μL:2-50 mL:10 mL; The concentration of the K2S2O8 aqueous solution is 20 mg / mL.

6. The preparation method according to claim 1, characterized in that In step (2): The average molecular weight of polyvinylpyrrolidone is 58,000; The usage ratio of polyvinyl pyrrolidone, PS ball emulsion and Co(NO3)2·6H2O is 0.15g:60mL:0.1-0.6g.

7. The preparation method according to claim 1, characterized in that In step (4), the mass ratio of the nano-Co3O4@3D honeycomb carbon composite material to the selenium powder is 3:1.

Images