A heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite, a preparation method and applications thereof

Abstract

The application provides a kind of heteroatom doped honeycomb carbon covalent coupling cobalt / cobalt telluride heterojunction nanocomposite, preparation method and application, with such characteristics, preparation method includes the following steps: step S1, citrate and nitrogen-containing small molecule are dissolved and mixed, through evaporation, carbonization, etching, obtain heteroatom doped honeycomb carbon;Step S2, heteroatom doped honeycomb carbon is dissolved in mixed solvent and stirred evenly, then the above-mentioned solution stirred evenly is added with organic ligand to react, after reaction, metal organic framework / heteroatom doped honeycomb carbon nanocomposite is obtained;Step S3, metal organic framework / heteroatom doped honeycomb carbon nanocomposite is placed into porcelain boat, is transferred to the downstream of tubular furnace, and tellurium powder is placed in the upstream of tubular furnace, calcination is carried out under inert gas atmosphere, and heteroatom doped honeycomb carbon covalent coupling cobalt / cobalt telluride heterojunction nanocomposite is obtained.

Description

Technical Field

[0001] This invention relates to the field of nanocomposite materials technology, specifically to a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material, its preparation method, and its application. Background Technology

[0002] With the increasing emphasis placed on environmental protection by the country, the development of clean energy is inseparable from environmentally friendly energy storage devices. As we all know, the advent of lithium-ion batteries has brought a lot of convenience to our daily lives, such as the use of micro and small electronic products like mobile phones and laptops.

[0003] However, with the development of technology and the improvement of living standards, lithium-ion batteries, due to their limited energy density, cannot meet people's current needs. Therefore, it is becoming increasingly urgent to develop energy storage devices with higher energy density.

[0004] Lithium-sulfur batteries are considered the most promising next-generation energy storage system due to their high theoretical energy density (2600 Wh / kg), abundant sulfur reserves, low cost, and environmental friendliness. However, the insulating properties of sulfur, slow reaction kinetics, and severe shuttle effect of lithium-sulfur batteries severely limit their commercial application potential. Therefore, developing catalytic materials that can promote the conversion of lithium polysulfides is of great research significance for improving the electrochemical performance of lithium-sulfur batteries.

[0005] Porous carbon with highly exposed active sites is a promising lithium-sulfur battery catalyst because it not only has abundant hierarchical channels and a larger specific surface area, enabling high sulfur loading storage and providing sufficient attachment space for sulfur conversion reactions, but also significantly improves electrode conductivity and enables rapid electron transport.

[0006] However, the currently reported methods for preparing porous carbon are complex and expensive. Therefore, it is very important to develop conductive carbon materials that are simple to synthesize and inexpensive. Among them, metal heterojunction catalysts are considered to be one of the most efficient active sites in lithium-sulfur batteries. However, as more and more metal elements are studied and the research scope becomes wider, it is necessary to explore some effective methods to further improve the catalytic activity of heterojunction catalysts. Summary of the Invention

[0007] This invention was made to solve the above-mentioned problems, and aims to provide a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material, its preparation method and its application, which has important implications for the design of highly catalytically active heterojunction materials and the development of lithium-sulfur batteries.

[0008] This invention provides a method for preparing heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite materials, characterized by the following steps:

[0009] Step S1: Citrate and nitrogen-containing small molecules are dissolved and mixed, and then evaporated, carbonized and etched to obtain heteroatom-doped honeycomb carbon;

[0010] Step S2: Dissolve heteroatom-doped honeycomb carbon in a mixed solvent and stir until homogeneous. Then add organic ligands to the homogeneous solution to carry out the reaction. After the reaction, metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material is obtained.

[0011] Step S3: The metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material is placed in a ceramic boat and transferred to the downstream of a tube furnace. Tellurium powder is placed upstream of the tube furnace, and calcination is carried out in an inert gas atmosphere to obtain a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0012] In step S3, the mass ratio of the metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material to tellurium powder is 1.5 to 2.5.

[0013] In the preparation method of heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material provided by the present invention, it may also have the following feature: wherein, in step S1, the molar ratio of citrate and nitrogen-containing small molecules is 0.5 to 4.0.

[0014] In step S1, the evaporation is carried out by oil bath, water bath or sand bath, and the temperature is 80℃~130℃.

[0015] In step S1, during calcination, the inert gas atmosphere is nitrogen or argon, the temperature is 500℃~900℃, the heating rate is 2℃ / min~10℃ / min, and the calcination time is 0.5h~5h.

[0016] In the preparation method of a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material provided by the present invention, it may also have the following feature: wherein, in step S2, the molar ratio of cobalt salt and organic ligand is 0.1 to 10.0.

[0017] In the preparation method of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material provided by the present invention, it may also have the following characteristics: in step S2, the reaction temperature is 20℃~70℃ and the reaction time is 1h~24h.

[0018] In the preparation method of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material provided by the present invention, it may also have the following characteristics: wherein, in step S3, the preset gas atmosphere is a mixture of nitrogen, argon and H2 / Ar (V% = 5:95%), and during calcination, the temperature is 500℃~900℃, the heating rate is 2℃ / min~15℃ / min, and the calcination time is 0.5h~5h.

[0019] In the preparation method of heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material provided by the present invention, it may also have the following characteristics: wherein the mass ratio of metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material to tellurium powder is 0.067 to 15.000.

[0020] In the preparation method of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material provided by the present invention, it may also have the following characteristics: wherein, in step S3, a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material can be obtained by simultaneously carbonizing and tellurizing the metal-organic framework ( / heteroatom-doped honeycomb carbon nanocomposite material and Te powder in one step, or by first carbonizing the metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material and then tellingurizing it with tellurium powder in two steps.

[0021] The present invention also provides a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material, which is prepared by the above-mentioned preparation method of heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0022] The present invention also provides an application of the above-mentioned heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material as a positive electrode electrocatalyst for lithium-sulfur batteries.

[0023] This invention also provides a method for using the above-mentioned heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material as a positive electrode electrocatalyst for lithium-sulfur batteries, specifically as follows: using a composite material of heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride and S as the cathode, a lithium metal sheet as the negative electrode, and a mixed solution of lithium bis(trifluoromethane) yellow imide and lithium nitrate dissolved in 1,3-dioxolane and ethylene glycol dimethyl ether in a glove box to assemble a coin cell.

[0024] The role and effect of invention

[0025] According to the preparation method of heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterostructure nanocomposite material involved in this invention, the present invention obtains a highly exposed oxygen covalently coupled cobalt / cobalt telluride heterostructure by controllably adjusting the size and distribution of metal-organic framework on nitrogen-doped honeycomb carbon rich in oxygen functional groups, and prepares heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterostructure nanocomposite material. It has universality and can also be applied to heterostructure materials constructed by all other metals (Fe, Ni, Zn) and metal compounds (oxides, sulfides, selenides, phosphides and nitrides).

[0026] The present invention provides a simple and controllable preparation process for heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite materials, with high yield, small material size, abundant active sites, and high catalytic activity, which is conducive to large-scale commercial production. The prepared heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite materials are applied to the cathode of lithium-sulfur batteries, and the sulfur cathode has high catalytic activity, while the lithium-sulfur battery has excellent cycle stability and electrochemical performance.

[0027] This invention reduces the size of the catalyst by confined growth of porous carbon, thereby increasing the exposed area and utilization rate of active sites. In addition, considering the reduction of the resistance between the three-phase heterojunction interfaces, rapid charge transport of the entire catalyst is achieved through the covalent coupling of oxygen. More importantly, the covalent coupling of oxygen atoms can further regulate the electronic configuration of the heterojunction, maximizing the activation of active atoms at the catalytic sites and achieving efficient and controllable catalyst construction. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention;

[0029] Figure 2 This is a schematic diagram showing the dimensions of the cobalt / cobalt telluride heterostructure nanoparticles in Example 1 of the present invention.

[0030] Figure 3 This is a transmission electron microscope image of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention;

[0031] Figure 4 Selected area electron diffraction pattern of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention;

[0032] Figure 5 This is an X-ray diffraction pattern of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention;

[0033] Figure 6 The infrared spectrum of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of this invention;

[0034] Figure 7 The X-ray photoelectron spectrum of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of this invention is shown below.

[0035] Figure 8 The X-ray absorption spectrum (XAFS) of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention includes near-edge absorption structure (XANES), extended edge absorption structure (EXAFS) and wavelet transform analysis results.

[0036] Figure 9 This is a graph showing the electrochemical performance (cyclic voltammetry curves, constant current charge-discharge) test data of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material used as a sulfur cathode in a lithium-sulfur coin cell, as described in Example 1 of the present invention.

[0037] Figure 10 This is a graph showing the electrochemical performance (rate and cycle) test data of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material as a sulfur cathode in a lithium-sulfur battery, as described in Example 1 of the present invention.

[0038] Figure 11 The graph shows a comparison of the first charge-discharge curves of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material used as a sulfur cathode in lithium-sulfur batteries at a current density of 0.1C.

[0039] Figure 12 This is a graph showing the electrochemical performance (cyclic voltammetry curves, constant current charge-discharge) test data of the heteroatomic honeycomb carbon anchored cobalt / cobalt oxide heterostructure nanocomposite material used as a sulfur cathode in a lithium-sulfur coin cell in Comparative Example 1 of the present invention.

[0040] Figure 13 This is a graph showing the electrochemical performance (rate and cycle) test data of the heteroatomic honeycomb carbon-anchored cobalt / cobalt oxide heterostructure nanocomposite material used as a sulfur cathode in a lithium-sulfur coin cell, as described in Comparative Example 1 of the present invention. Detailed Implementation

[0041] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material and its preparation method.

[0042] Example 1

[0043] This embodiment describes a method for preparing a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material, comprising the following steps:

[0044] Step S1 involves dissolving and mixing citrate and nitrogen-containing small molecules, followed by evaporation, carbonization, and etching to obtain heteroatom-doped honeycomb carbon. The specific process is as follows:

[0045] 2.3265g of urea and 20g of sodium citrate were dissolved in 50mL of water and stirred until dissolved. After evaporation at 100℃, a white powder was obtained. The powder was then placed in a tube furnace and carbonized at 800℃ for 2 hours under a nitrogen atmosphere with a heating rate of 5℃ / min. After the tube furnace cooled to room temperature, the carbonized black powder was collected. 4M hydrochloric acid was added to the black powder and stirred continuously for 24 hours. The powder was washed with a large amount of deionized water until neutral and then placed in a vacuum oven and dried at 60℃ for 12 hours.

[0046] Step S2: Dissolve heteroatom-doped honeycomb carbon in a mixed solvent and stir until homogeneous. Then, add organic ligands to the homogeneous solution to carry out the reaction. After the reaction, metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material is obtained. The specific process is as follows.

[0047] 1.0 mmol of cobalt nitrate hexahydrate and 50 mg of heteroatom-doped honeycomb carbon obtained in step S1 were ultrasonically dissolved in 10 mL of methanol. Then, 20 mL of a solution containing 4 mmol of 2-methylimidazole was added. The mixture was stirred at room temperature for 8 h, washed three times with methanol, and dried at 60 °C for 12 h.

[0048] Step S3: The metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material is placed in a ceramic boat and transferred to the downstream of a tube furnace. Tellurium powder is placed upstream of the tube furnace, and calcination is carried out in an inert gas atmosphere to obtain a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material. The specific process is as follows:

[0049] The 50 mg metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material obtained in step S2 was placed in an alumina crucible, transferred to the lower end of a tube furnace, and 25 mg of tellurium powder was placed at the upper end. Under an Ar atmosphere, the heating rate was 2 °C / min, and the mixture was held at 600 °C for 3 h to obtain heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0050] The heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material obtained above is used as a positive electrode electrocatalyst for lithium-sulfur batteries. The specific application method is as follows:

[0051] A coin cell was assembled in a glove box using a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite and S composite material as the cathode, a lithium metal sheet as the anode, Celgard 2500 as the separator, and a 1.0M bis(trifluoromethane)-xanimide lithium and 0.15M lithium nitrate dissolved in a mixed solution of 1,3-dioxolane and ethylene glycol dimethyl ether.

[0052] The preparation process of the cathode (S / CoTe2 / Co-O-NC) is as follows: CoTe2 / Co-O-NC heterojunction material and S are heated to 155℃ for 12 hours using a low-temperature melting method to obtain the S / CoTe2 / Co-O-NC composite material. Then, the S / CoTe2 / Co-O-NC composite material, carbon black (as a conductive agent), and polyvinylidene fluoride (as a binder) are mixed at a mass ratio of 7:2:1. NMP dispersant is added, and the mixture is stirred for 12 hours in a sealed and dry environment. The uniformly stirred slurry is then coated onto aluminum foil and dried in a 60℃ vacuum oven for 12 hours. After drying, it is cut into small round pieces using a 13mm cutting machine for later use.

[0053] Figure 1 These are scanning electron microscope (SEM) images of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention, wherein (a) is a 10K magnification SEM image, (b) is a 50K magnification SEM image, and (c) is an 80K magnification SEM image.

[0054] like Figure 1 As shown, the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterostructure nanocomposite material prepared in this embodiment has a typical honeycomb morphology and a highly exposed cobalt / cobalt telluride heterostructure.

[0055] Figure 2 This is a schematic diagram showing the length of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Embodiment 1 of the present invention.

[0056] like Figure 2 The heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material prepared in this embodiment is shown in which the cobalt / cobalt telluride heterojunction particles grow tightly on the pore walls of the honeycomb carbon, and the particle size is only 31 nanometers.

[0057] Figure 3 These are transmission electron microscope (TEM) images of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention, wherein (a) is a low-magnification TEM image, and (b) and (c) are high-resolution TEM images.

[0058] like Figure 3As shown, the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material prepared in this embodiment has a distinct cobalt / cobalt telluride heterostructure interface, and is uniformly distributed in the form of small particles on the pore walls of the honeycomb carbon. Figure 3 As shown in (c), the lattice spacings of the (200) and (111) planes of Co and CoTe2 are 0.177 and 0.28 nm, respectively.

[0059] Figure 4 This is a selected area electron diffraction pattern of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention.

[0060] like Figure 4 As shown, the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material prepared in this embodiment exhibits diffraction crystal forms of both cobalt and cobalt telluride phases. This is consistent with... Figure 3 (c) The analysis results of the medium and high resolution transmission electron microscopy images are very consistent. The polycrystalline diffraction rings in the images can be labeled as the (111) and (200) crystal planes of Co and the (012), (121) and (111) crystal planes of CoTe2, respectively.

[0061] Figure 5 This is an X-ray diffraction pattern of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention.

[0062] like Figure 5 As shown, the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material prepared in this embodiment has three phase structures: graphite carbon, cobalt, and cobalt telluride. In the figure, the diffraction peaks at 31.9°, 33°, 43.7°, 46.7°, and 49.3° correspond to the (111), (012), (121), (200), and (103) crystal planes of CoTe2 (PDF#74-0245), and the diffraction peaks at 44.2°, 51.5°, and 75.8° correspond to the (111), (200), and (220) crystal planes of metallic cobalt (PDF#15-0806). This means that the CoTe2 / Co junction was successfully formed.

[0063] Figure 6 This is the infrared spectrum of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention.

[0064] like Figure 6 As shown, the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material prepared in this embodiment mainly contains C=O, COOH, CC, CN, and CO-Co functional groups, located at wavenumbers of 1680, 1652, 1573, 1382, and 1250 cm⁻¹, respectively.

[0065] Figure 7 This is the X-ray photoelectron spectrum of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention, wherein... Figure 7 (a) is the full X-ray photoelectron spectrum, (b) is the fine C1s X-ray photoelectron spectrum, (c) is the fine N1s X-ray photoelectron spectrum, (d) is the fine O1s X-ray photoelectron spectrum, (e) is the fine Co 2p X-ray photoelectron spectrum, and (f) is the fine Te 3d X-ray photoelectron spectrum.

[0066] like Figure 7 As shown, the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterostructure nanocomposite material prepared in this embodiment mainly contains five elements: carbon, nitrogen, oxygen, cobalt, and tellurium. Cobalt mainly exists in 0-valent and 2-valent / 3-valent oxidation states, corresponding to elemental cobalt and cobalt telluride phases, respectively.

[0067] Figure 8 The X-ray absorption spectrum (XAFS) of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material in Example 1 of the present invention includes the near-edge absorption structure (XANES, Figure a), the extended edge absorption structure (EXAFS, Figures b and c), and the wavelet transform analysis results (Figures d to f).

[0068] like Figure 8 As shown in Figure a, the Co K-edge X-ray absorption near-edge structure (XANES) spectrum edge energy of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material (CoTe2 / Co-O-NC) lies between that of the Co foil and CoO, indicating that the average valence state of Co is between 0 and +2. From the Fourier transform (FT) k... 3 The weighted Co k-side extended X-ray absorption fine structure (EXAFS) spectrum (Figure b) shows that the peaks and scattering paths of CoTe2 / Co-O-NC are different from those of CoO and Co2O3, further indicating that no metallic Co-O bonds are formed in CoTe2 / Co-O-NC. Furthermore, CoTe2 / Co-O-NC exhibits different peaks and scattering paths at approximately 1.5, 2.2, and 1.5 k-side extensions. The peaks at these locations correspond to Co-O, Co-Co, and Co-Te bond coordination, respectively. Furthermore, the Co-O bond length in CoTe2 / Co-O-NC is shorter than that in CoO, indicating that Co and O are only covalently connected. Quantitatively considering these three backscattering paths, least-squares EXAFS curve fitting analysis (Figure c) was performed, determining the bond distances of Co-O, Co-Te, and Co-Co to be 1.99, 2.52, and 1.52, respectively. Furthermore, we explored the wavelet transform (WT) EXAFS contour plots of CoTe2 / Co-O-NC, proving that CoO species do not exist in CoTe2 / Co-O-NC, as shown in Figure df, and that it has Co-Co coordination characteristics.

[0069] Compared to the Wt contour map of CoO, the Wt contour map of CoTe2 / Co-O-NC shows bands corresponding to Co-Te / Co-Co, but lacks the coordination characteristics of Co-Co in Co foil and CoO. This indicates that CoO species are absent in CoTe2 / Co-O-NC, thus fully demonstrating the covalent coupling between Co and O.

[0070] Figure 9 This is a graph showing the electrochemical performance test data of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material used as a sulfur host in a lithium-sulfur battery, as described in Example 1 of this invention. Figure 9 (a) shows the cyclic voltammetry curve test data, and (b) shows the constant current charge-discharge test data.

[0071] like Figure 9 As shown, the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material, as a catalytic host for sulfur, exhibits strong redox peak currents (CV results show two reduction peaks (Ⅰ and Ⅱ) and one oxidation peak (Ⅲ), corresponding to S8, respectively). 2- →S4 2- S4 2- The reaction processes →Li2S2 / Li2S and Li2S2 / Li2S→S8) and typical charge-discharge plateaus demonstrate the high catalytic conversion performance of heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposites for lithium polysulfides.

[0072] Figure 10 This is a graph showing the electrochemical performance test data of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material used as a sulfur host in a lithium-sulfur battery, as described in Example 1 of this invention. Figure 10 (a) shows the rate data of lithium-sulfur batteries tested at different current densities, and (b) shows the cycle stability graph tested at a current density of 2C.

[0073] like Figure 10As shown, the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material, acting as a catalytic host for sulfur, exhibits excellent rate performance and cycle stability. Figure a shows that the battery maintains good cycle stability at different current densities. Even when the current drops sharply from 3C to 0.1C, the battery continues to operate smoothly with minimal capacity loss, demonstrating excellent electrode structure stability and electrochemical cycle reversibility. Figure b shows the cycle stability of the lithium-sulfur battery at a high current density of 2C for 300 cycles, showing a cycle decay rate of 0.023% per cycle and a coulombic efficiency of nearly 100%. This also indicates that the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material, as a catalytic host for sulfur, possesses excellent catalytic activity for sulfur conversion and can significantly improve the electrochemical performance of lithium-sulfur batteries.

[0074] In summary, the method of heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterostructure nanocomposite material of the present invention can successfully prepare cobalt / cobalt telluride heterostructure nanocomposite material with typical honeycomb morphology and high exposure of oxygen covalently coupled. This composite material has excellent catalytic activity and stability, and can be used as an efficient electrocatalyst for sulfur cathode of lithium-sulfur battery to achieve ultra-high energy density of lithium-sulfur battery, and has very considerable commercial application potential.

[0075] Example 2

[0076] In this embodiment, based on the preparation conditions of Example 1, sodium citrate in step S1 was replaced with ammonium citrate to prepare heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0077] Example 3

[0078] In this embodiment, based on the preparation conditions of Example 1, urea in step S1 was replaced with melamine to prepare heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0079] Example 4

[0080] In this embodiment, based on the preparation conditions of Example 1, the carbonization at 800°C for 2 hours in a nitrogen atmosphere in step S1 was replaced with calcination at 500°C for 5 hours to prepare heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0081] Example 5

[0082] In this embodiment, based on the preparation conditions of Example 1, the heating rate of 5℃ / min in step S1 was replaced with a heating rate of 2℃ / min to prepare heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0083] Example 6

[0084] In this embodiment, based on the preparation conditions of Example 1, 1.0 mmol of cobalt nitrate hexahydrate in step S2 was replaced with 2.0 mmol to prepare heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0085] Example 7

[0086] In this embodiment, based on the preparation conditions of Example 1, the 25 mg of tellurium powder in step S3 was changed to 5 mg to prepare heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0087] Example 8

[0088] In this embodiment, based on the preparation conditions of Example 1, the heating rate in step S3 was 2℃ / min, and the temperature was kept at 600℃ for 3h, and the heating rate was 10℃ / min, and the temperature was kept at 600℃ for 5h, to prepare heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0089] Example 9

[0090] In this embodiment, based on the preparation conditions of Example 1, the heating rate in step S3 was 2℃ / min, and the temperature was kept at 600℃ for 3h, and the heating rate was 5℃ / min, and the temperature was kept at 700℃ for 1h, to prepare heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

[0091] Figure 11 The graph shows the comparison of the first charge-discharge curves of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite materials prepared under the preparation conditions of Examples 2-9, which were used as cathodes of lithium-sulfur batteries. As can be seen from the graph, the specific capacity measured in Examples 2-9 is lower than that measured in Example 1.

[0092] Comparative Example 1

[0093] This comparative example discloses a heteroatomized honeycomb carbon-anchored high-exposure cobalt / cobalt oxide heterostructure nanocomposite material, the preparation method of which is as follows:

[0094] Step S1: Mix 30 mmol sodium citrate and 15 mmol urea and dissolve them in 30 mL of water. Evaporate the solvent at 110 °C in an oil bath. Grind the mixture to obtain a white powder. Place the white powder in a tube furnace under a nitrogen atmosphere and calcine at 800 °C for 1 h. Then, etch with dilute hydrochloric acid to remove excess product. After filtration, washing with water, and drying, obtain heteroatomized honeycomb carbon.

[0095] In step S2, 1.0 mmol of cobalt nitrate hexahydrate and 50 mg of heteroatomized honeycomb carbon obtained in step S1 were ultrasonically dispersed in 20 mL of methanol. Then, 20 mL of methanol solution containing 4.0 mmol of 2-methylimidazole was added. After reacting at room temperature for 6 h, the mixture was centrifuged and washed with methanol to obtain the metal-organic framework / heteroatomized honeycomb carbon nanocomposite material.

[0096] Step S3: The metal-organic framework / heteroatomized honeycomb carbon nanocomposite material obtained in step S2 is placed in a ceramic boat and transferred to a tube furnace. The heating rate is 2℃ / min, and it is calcined at 700℃ for 2h in a nitrogen atmosphere to obtain a heteroatomized honeycomb carbon anchored high-exposure cobalt / cobalt oxide heterostructure nanocomposite material.

[0097] Figure 12 This is a graph showing the electrochemical performance test data of the heteroatomized honeycomb carbon-anchored cobalt / cobalt oxide heterostructure nanocomposite material in Comparative Example 1 of the present invention as a sulfur host in a lithium-sulfur battery. Figure 12 (a) shows the rate data of lithium-sulfur batteries tested at different current densities, and (b) shows the cycle stability graph tested at a current density of 2C.

[0098] Compared with the preparation method and application instructions of a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material, the attached figure shows... Figure 8 (a) shows the cyclic voltammetry curve test data, and (b) shows the constant current charge-discharge test data. Figure 8 As shown in Figure a, peaks I, II, and III correspond to S8, respectively. 2- →S4 2- S4 2- The reaction processes →Li2S2 / Li2S and Li2S2 / Li2S→S8. Compared with the CV test of the S / CoTe2 / Co-O-NC electrode, the peak current of S / Co-CoO / HLNPC is significantly reduced, and the voltage difference between peak II and peak III is also significantly increased. This indicates that the catalytic conversion performance of S / Co-CoO / HLNPC for lithium polysulfides is significantly weakened and is significantly inferior to that of the S / CoTe2 / Co-O-NC electrode. Figure 8 b shows the constant current charge-discharge curve of the S / Co-CoO / HLNPC cathode at a current density of 0.1C. As can be seen from the figure, the charge-discharge specific capacity of the battery is reduced by 536 mAh g-1 compared with that of the S / CoTe2 / Co-O-NC cathode. The polarization of the battery increases and the electrochemical performance is significantly reduced.

[0099] Figure 13 This is a graph showing the electrochemical performance test data of the heteroatomized honeycomb carbon-anchored cobalt / cobalt oxide heterostructure nanocomposite material in Comparative Example 1 of the present invention as a sulfur host in a lithium-sulfur battery. Figure 13(a) shows the rate data of lithium-sulfur batteries tested at different current densities, and (b) shows the cycle stability graph tested at a current density of 2C.

[0100] In Figure a, when S / CoTe2 / Co-O-NC is used as the sulfur cathode in a lithium-sulfur battery, the specific capacities at current densities of 0.1C, 0.2C, 0.3C, 0.5C, 1C, 2C, and 3C are 1468, 1156, 1053, 948, 790, 695, and 597 mAh g, respectively. -1 However, when S / Co-CoO / HLNPC is used as the sulfur cathode in a lithium-sulfur battery, the specific capacities at current densities of 0.1C, 0.2C, 0.3C, 0.5C, 1C, 2C, and 3C are 991, 680, 590, 480, 454, 385, and 111 mAh g, respectively. -1 The S / CoTe2 / Co-O-NC cathode exhibits significantly worse performance than the former. In Figure b, at a current density of 2C, the S / CoTe2 / Co-O-NC cathode shows a capacity decay rate of 0.023% per cycle after 300 cycles, while the S / Co-CoO / HLNPC cathode shows a capacity decay rate of 1.38% per cycle. This indicates that the S / Co-CoO / HLNPC cathode cannot effectively suppress lithium polysulfide shuttle and catalyze lithium polysulfide conversion, and its cycle stability is significantly worse than the former. Therefore, the electrochemical performance of the S / Co-CoO / HLNPC cathode is significantly inferior to that of the S / CoTe2 / Co-O-NC cathode.

[0101] The role and effect of the embodiments

[0102] As demonstrated in Examples 1-9 and Comparative Example 1, the method for preparing a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material according to the present invention provides a simple and efficient way to prepare oxygen covalently coupled high-exposure cobalt / cobalt telluride heterostructure nanocomposite materials. This composite material exhibits a typical honeycomb morphology and highly exposed cobalt / cobalt telluride heterojunction catalytic active sites, making it suitable as a high-performance sulfur cathode catalyst material for lithium-sulfur batteries. It demonstrates excellent performance and good stability, offering significant advantages for the commercial development of lithium-sulfur batteries. Furthermore, the porous structure and numerous, highly efficient active sites of the material of the present invention also offer broad development prospects and application space in other types of energy catalysis and environmental improvement fields such as water pollution control.

[0103] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material, characterized in that, Includes the following steps: Step S1: Citrate and nitrogen-containing small molecules are dissolved and mixed, and then evaporated, carbonized and etched to obtain heteroatom-doped honeycomb carbon; Step S2: Dissolve the cobalt salt and the heteroatom-doped honeycomb carbon in a mixed solvent and stir until homogeneous. Then add an organic ligand to the homogeneous solution to react and obtain a metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material after the reaction. Step S3: The metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material is placed in a ceramic boat and transferred to the downstream of a tube furnace. Tellurium powder is placed upstream of the tube furnace, and calcination is carried out under an inert atmosphere to obtain a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material, denoted as CoTe2 / Co-O-NC. This composite material has a three-phase structure of graphite carbon, cobalt, and cobalt telluride, and also includes CO-Co functional groups. In step S3, the mass ratio of the metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material to tellurium powder is 1.5 to 2.

5.

2. The method for preparing a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material according to claim 1, characterized in that: in, In step S1, the molar ratio of the citrate to the nitrogen-containing small molecule is 0.5 to 4.

0. In step S1, during evaporation, the evaporation method is an oil bath, water bath, or sand bath, and the temperature is 80℃~130℃. In step S1, during carbonization, the inert atmosphere is nitrogen or argon, the temperature is 500℃~900℃, the heating rate is 2℃ / min~10℃ / min, and the calcination time is 0.5h~5h.

3. The method for preparing a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material according to claim 1, characterized in that: in, In step S2, the molar ratio of the cobalt salt to the organic ligand is 0.1 to 10.

0.

4. The method for preparing a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material according to claim 1, characterized in that: in, In step S2, the reaction temperature is 20℃~70℃ and the reaction time is 1h~24h.

5. The method for preparing a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material according to claim 1, characterized in that: in, In step S3, the inert atmosphere is nitrogen, argon, or a H2 / Ar mixed atmosphere with a volume ratio of 5:

95. During calcination, the temperature is 500℃~900℃, the heating rate is 2℃ / min~15℃ / min, and the calcination time is 0.5h~5h.

6. The method for preparing a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material according to claim 1, characterized in that: in, In step S3, a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material is obtained by simultaneously carbonizing and tellurizing the metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material and Te powder in one step, or by first carbonizing the metal-organic framework / heteroatom-doped honeycomb carbon nanocomposite material and then tellingurizing it with tellurium powder in two steps.

7. A heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterostructure nanocomposite material, characterized in that: The nanocomposite material was prepared by the method described in any one of claims 1 to 6, which is a heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material.

8. The application of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material as described in claim 7 as a positive electrode electrocatalyst for lithium-sulfur batteries.

9. The application of the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material according to claim 8 as a positive electrode electrocatalyst for lithium-sulfur batteries, characterized in that, The specific application method is as follows: Using the heteroatom-doped honeycomb carbon covalently coupled cobalt / cobalt telluride heterojunction nanocomposite material and S composite material as the cathode, lithium metal sheet as the anode, and lithium nitrate sheet as the electrolyte, a coin cell is assembled in a glove box.

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