Preparation method of phosphinyl dysprosium complex composite carbon two-dimensional material and application of phosphinyl dysprosium complex composite carbon two-dimensional material in lithium-sulfur battery

Abstract

The invention discloses a preparation method of a phosphinyl dysprosium complex compounded carbon two-dimensional material and application of the phosphinyl dysprosium complex compounded carbon two-dimensional material in a lithium-sulfur battery. The simple formula of the structure of the two-dimensional material is CNT (at) [(dppBO2) DyCl3 (mu-dppBO2) DyCl3 (dppBO2)] n. A two-dimensional material of rare earth complex composite carbon is prepared by selecting a carbon material and a phosphinyl dysprosium complex, an f track in the phosphinyl dysprosium complex can regulate and control an electron transmission path of a catalytic interface, reaction kinetics is enhanced, and the electron conductivity of the two-dimensional material is improved. Meanwhile, the two-dimensional material also has the advantages of good stability, high catalytic activity, excellent discharge performance, good cycle performance and the like, can be used as a polysulfide redox material, and has wide application prospects in the fields of lithium-sulfur batteries, fuel cells, electrochemical sensors and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material preparation, and specifically, to a preparation method of a two-dimensional material of an oxygen-phosphine-based dysprosium complex composite carbon and its application in lithium-sulfur batteries. Background Art

[0002] The redox reaction of polysulfides is of great significance in many fields, such as lithium-sulfur batteries, fuel cells, electrochemical sensors, etc. However, the redox reaction kinetics of polysulfides is slow, which severely restricts the performance of related devices. Therefore, it is of great significance to develop efficient and stable catalysts for the redox reaction of polysulfides. Two-dimensional carbon nanotube materials have excellent electrical conductivity, large specific surface area and rich surface chemical properties, and are ideal catalyst carriers. Rare earth metal complexes, especially dysprosium complexes, have unique electronic structures and coordination abilities, and show good catalytic activity in the redox reaction of polysulfides.

[0003] Lithium-sulfur batteries are regarded as the next-generation high-energy energy storage devices due to their high theoretical specific capacity and energy density. However, the "shuttle effect" of polysulfides leads to the loss of active substances and capacity decay, severely restricting their commercialization. At present, carbon-based materials such as carbon nanotubes (CNT), graphene, etc. can physically adsorb polysulfides, but lack catalytic activity for redox reactions; transition metal compounds can catalyze the conversion of polysulfides, but have poor electrical conductivity and insufficient stability. Rare earth complexes have potential in multi-electron catalysis due to their unique electronic structures and coordination abilities, but the composite of their one-dimensional chain structure with two-dimensional conductive substrates has not been fully studied. Summary of the Invention

[0004] To overcome the above-mentioned defects and deficiencies in the prior art, the present invention provides a preparation method of a two-dimensional material of an oxygen-phosphine-based dysprosium complex composite carbon and its application in lithium-sulfur batteries.

[0005] The first object of the present invention is to provide a dysprosium complex.

[0006] The second object of the present invention is to provide a preparation method of the above-mentioned dysprosium complex.

[0007] The third object of the present invention is to provide the application of the above-mentioned dysprosium complex in the preparation of a polysulfide redox catalyst.

[0008] The fourth object of the present invention is to provide a composite material.

[0009] The fifth object of the present invention is to provide a preparation method of a composite material.

[0010] The sixth object of the present invention is to provide a composite material prepared by the above-mentioned preparation method.

[0011] The seventh object of the present invention is to provide the application of the above composite material in catalyzing the oxidation-reduction of polysulfide.

[0012] The eighth object of the present invention is to provide the application of the above composite material in preparing the electrode of a lithium-sulfur battery.

[0013] The present invention claims the following:

[0014] A dysprosium complex, the structural formula of the dysprosium complex is [(dppBO2)DyCl3(μ-dppBO2)DyCl3(dppBO2)], n wherein dppBO2 is 1,4-butanediylbis(diphenylphosphine oxide);

[0015] The dysprosium complex crystallizes in the trigonal system, belongs to the R-3 space group, and the unit cell parameters are: α = 90°, β = 90°, γ = 120°,

[0016] The preparation method of the above dysprosium complex: reacting the ethanol solution of dppBO2 and DyCl3·6H2O at 130 - 150 °C for 72 - 74 h, and then cooling at a rate of less than 5 °C / h to obtain it.

[0017] Preferably, the dosage ratio of dppBO2, ethanol and DyCl3·6H2O is (0.8 - 1.2) mmol : (3.2 - 4.8) mL : (0.8 - 1.2) mmol.

[0018] More preferably, the dosage ratio of dppBO2, ethanol and DyCl3·6H2O is 1 mmol : 4 mL : 1 mmol.

[0019] More preferably, the reaction temperature is 140 °C.

[0020] More preferably, the reaction time is 72 h.

[0021] More preferably, the cooling rate is 2 °C / h.

[0022] More preferably, the cooling is to cool to 24 - 26 °C.

[0023] The application of the above dysprosium complex in preparing a polysulfide oxidation-reduction catalyst.

[0024] A composite material, the composite material includes the above dysprosium complex and a carbon material, the dysprosium complex is dispersed in the conductive network formed by the carbon material and forms a cross-linked structure;

[0025] The carbon materials include carbon nanotubes, graphite, carbon fibers and graphene.

[0026] A preparation method of a composite material, the preparation method is as follows: after fully mixing the carbon material, dppBO2 and ethanol, add DyCl3·6H2O, and react fully at 130-150 °C for 72-74 h, and then cool down at a rate of less than 5 °C / h to obtain;

[0027] The carbon materials include carbon nanotubes, graphite, carbon fibers and graphene.

[0028] Preferably, the carbon material is carbon nanotubes.

[0029] More preferably, the dosage ratio of the carbon nanotubes, dppBO2, ethanol and DyCl3·6H2O is (28-32) mmol:(0.8-1.2) mmol:(3.2-4.8) mL:(0.8-1.2) mmol.

[0030] Further preferably, the dosage ratio of the carbon nanotubes, dppBO2, ethanol and DyCl3·6H2O is 30 mmol:1 mmol:4 mL:1 mmol.

[0031] More preferably, the reaction temperature is 140 °C.

[0032] More preferably, the reaction time is 72 h.

[0033] More preferably, the cooling rate is 2 °C / h.

[0034] More preferably, the cooling is to cool down to 24-26 °C.

[0035] The composite material prepared by the above preparation method.

[0036] Application of the above composite material in catalyzing polysulfide redox.

[0037] Application of the above composite material in preparing a lithium-sulfur battery electrode.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention discloses a preparation method of an oxygen-phosphine-based dysprosium complex composite carbon two-dimensional material and its application in a lithium-sulfur battery. The structural formula of the two-dimensional material is CNT@[(dppBO2)DyCl3(μ-dppBO2)DyCl3(dppBO2)] n . The present invention selects a carbon material and an oxygen-phosphine-based dysprosium complex [(dppBO2)DyCl3(μ-dppBO2)DyCl3(dppBO2)] nA two-dimensional material of rare earth complex composite carbon was prepared. The f orbitals in the dysprosium oxyphosphine complex can regulate the electron transport path at the catalytic interface, enhance the reaction kinetics, and improve the electron conductivity of the two-dimensional material. At the same time, the two-dimensional material of the present invention also has the advantages of good stability, high catalytic activity, excellent discharge performance, large specific surface area, rich active sites, and good cycling performance. It can be used as a polysulfide redox material to solve the problems of slow polysulfide redox kinetics and shuttle effect through the synergistic effect of one-dimensional chain rare earth complexes and carbon two-dimensional materials, and has broad application prospects in the fields of lithium-sulfur batteries, fuel cells, electrochemical sensors, etc.

[0040] In addition, the preparation method of the two-dimensional material of the dysprosium oxyphosphine complex of the present invention is simple and low-cost. High-yield and high-crystallinity composite functional materials can be prepared through low-temperature solvothermal reaction, which meets the requirements of green chemistry and is suitable for large-scale production. Brief Description of the Drawings

[0041] Figure 1 Single crystal structure diagram of the dysprosium oxyphosphine complex prepared in Example 1; (a): minimum asymmetric unit, (b): unit cell structure diagram, (c): two-dimensional layered stacking diagram of the complex; (d): the central dysprosium ion shows a six-coordinate octahedral configuration. All structure diagrams omit H atoms for simplicity and clarity.

[0042] Figure 2 Infrared spectra of the dysprosium oxyphosphine complex prepared in Example 1 and the composite material prepared in Example 2, where 1 is the dysprosium oxyphosphine complex and 2 is the composite material.

[0043] Figure 3 Raman spectra of the dysprosium oxyphosphine complex prepared in Example 1 and the composite material prepared in Example 2, where 1 is the dysprosium oxyphosphine complex and 2 is the composite material.

[0044] Figure 4 Thermogravimetric curves of the dysprosium oxyphosphine complex prepared in Example 1 and the composite material prepared in Example 2, where 1 is the dysprosium oxyphosphine complex and 2 is the composite material.

[0045] Figure 5 X-ray powder diffraction patterns of the dysprosium oxyphosphine complex prepared in Example 1 and the composite material prepared in Example 2, where 1synthesized is the diffraction spectrum of the dysprosium oxyphosphine complex obtained from single crystal testing, 2synthesized is the diffraction spectrum of the composite material obtained from single crystal testing, and 1simulated is the theoretical diffraction spectrum of the dysprosium oxyphosphine complex simulated based on single crystal testing.

[0046] Figure 6Scanning electron microscope images of the phosphine oxide group dysprosium complex prepared in Example 1 and the composite material prepared in Example 2; (a): The phosphine oxide group dysprosium complex magnified 20,000 times, (b): The phosphine oxide group dysprosium complex magnified 50,000 times, (c): The composite material magnified 20,000 times, (d): The composite material magnified 110,000 times.

[0047] Figure 7 Transmission electron microscope images of the phosphine oxide group dysprosium complex prepared in Example 1 and the composite material prepared in Example 2; (a): Transmission electron microscope image of the phosphine oxide group dysprosium complex, (b): Energy dispersive spectrum image of the phosphine oxide group dysprosium complex in the area scan mode; (c): Transmission electron microscope image of the composite material, (d): Energy dispersive spectrum image of the composite material in the area scan mode.

[0048] Figure 8 X-ray photoelectron spectroscopy images of the phosphine oxide group dysprosium complex prepared in Example 1 and the composite material prepared in Example 2; (a): The phosphine oxide group dysprosium complex, (b): The composite material.

[0049] Figure 9 Comparison of the discharge capacities of pure carbon nanotubes and the composite material prepared in Example 2 at different currents.

[0050] Figure 10 Long cycle performance graph of the electrodes of pure carbon nanotubes and the composite material prepared in Example 2 at a current of 0.5C. Detailed implementation manners

[0051] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0052] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0053] The structural formula of dppBO2 used in the examples is shown in Formula (I), where n = 4, which is dppBO2 in Chinese Patent CN118745199A.

[0054]

[0055] Preparation of the phosphine oxide group dysprosium complex in Example 1

[0056] Weigh 0.0568 g of dppBO2 into a polytetrafluoroethylene reaction kettle, add 4 mL of ethanol, stir for 10 min at 25 °C, then add 0.0545 g of DyCl3·6H2O, continue to stir for 10 min, and then carry out a solvothermal reaction. The reaction conditions are as follows: heat to 140 °C in 5 h and then keep the temperature constant for 72 h, and then cool to 25 °C at a rate of 2 °C / h to obtain colorless block crystals, which are the phosphine oxide-based dysprosium complex [(dppBO2)DyCl3(μ-dppBO2)DyCl3(dppBO2)] n .

[0057] Preparation of the composite material in Example 2

[0058] Weigh 25 mg of carbon nanotubes and 0.0568 g of dppBO2 into a polytetrafluoroethylene reaction kettle, add 4 mL of ethanol, stir for 10 min at 25 °C, then add 0.0545 g of DyCl3·6H2O, continue to stir for 10 min, and then carry out a solvothermal reaction. The reaction conditions are as follows: heat to 140 °C in 5 h and then keep the temperature constant for 72 h, and then cool to 25 °C at a rate of 2 °C / h to obtain colorless block crystals, which are the composite material CNT@[(dppBO2)DyCl3(μ-dppBO2)DyCl3(dppBO2)] n .

[0059] Crystal structure determination and characterization in Example 3

[0060] I. Experimental method

[0061] Select a colorless block single crystal product with a size of 0.095×0.093×0.072 mm 3 (prepared in Example 1) for structure testing. Diffraction is carried out using a Rigaku XtaLAB Synergy R, DW system, HyPix single crystal X-ray diffractometer at a temperature of 298.15 K, and the CuKα ray monochromatized by a graphite monochromator is used as the incident light source to collect diffraction data and process it. All calculations are carried out using the SHELXS-2014 and SHELXL-2014 programs.

[0062] Infrared spectrum testing, Raman spectrum testing, thermogravimetric analysis, scanning electron microscopy detection, and transmission electron microscopy detection are respectively carried out on the phosphine oxide-based dysprosium complex prepared in Example 1 and the composite material prepared in Example 2, and X-ray powder diffraction testing is carried out after placing the phosphine oxide-based dysprosium complex and the composite material in air for 3 months.

[0063] II. Experimental results

[0064] Single crystal structure analysis shows that the phosphine oxide-based dysprosium complex prepared in Example 1 (referred to as Complex 1 in Table 1) belongs to the trigonal system, with the space group R-3 and the unit cell parameters as follows: α = 90°, β = 90°, γ = 120°, The crystallographic data are shown in Table 1.

[0065] Table 1 Crystallographic data and refinement results of the phosphine oxide-based dysprosium complex

[0066]

[0067]

[0068] From Figure 1 (a) - (d) in it, it can be seen that the asymmetric unit of the phosphine oxide-based dysprosium complex prepared in Example 1 includes one Dy III , half of the phosphine oxide ligand, and one coordinated chloride ion, and there is no crystalline solvent in the external environment. The central metal ion dysprosium ion forms a six-coordinate octahedral geometry (O h ) with 3 chlorines and 3 oxygens. Since the 3 oxygen atoms come from different phosphine oxide ligands respectively, a two-dimensional layered structure is formed in the plane extension. The nearest Dy-Dy distance within the molecule is Using Shape software, the CShM value of the central Dy(III) ion is calculated to be 0.93697 (Table 2). The average Dy-O and Dy-Cl bond lengths are and Due to symmetry, the three Dy-O and three Dy-Cl bond lengths are all equal.

[0069] Table 2 CShM value of the central Dy(III) ion of the phosphine oxide-based dysprosium complex (Complex 1)

[0070]

[0071] *HP-6 = hexagon, PPY-6 = pentagonal pyramid, OC-6 = octahedron, TPR-6 = triangular prism, JPPY-6 = Johnson pentagonal pyramid J2.

[0072] The infrared spectra of the phosphine oxide-based dysprosium complex prepared in Example 1 and the composite material prepared in Example 2 are as shown in Figure 2 . It can be seen from Figure 2 that obvious benzene ring characteristic peaks can be observed in the phosphine oxide-based dysprosium complex at 1597 cm -1 . At 900 - 650 cm -1Out-of-plane deformation vibration of C-H on the aromatic ring appears in the region. Compared with the phosphine oxide ligand, the absorption peaks of certain functional groups in the dysprosium phosphine oxide complex and the composite material have undergone obvious red shifts, and the intensities have also changed to a certain extent, indicating that the organic ligand 1,4-butanediylbis(diphenylphosphine oxide) participates in coordination.

[0073] The Raman spectra of the dysprosium phosphine oxide complex prepared in Example 1 and the composite material prepared in Example 2 are as Figure 3 shown. From Figure 3 it can be seen that when the excitation wavelength is 532 nm, the composite material in the middle frequency region shows a disorder peak (disorder), that is, the D peak, of the boundary vibration mode of the hexagonal Brillouin zone induced by disorder at 1341 cm -1 . It originates from the stretching vibrations of C-C bonds and C=C double bonds and is a typical Raman peak in carbon materials such as carbon nanotubes and graphene. An obvious G peak appears at 1582 cm -1 , which is caused by the vibration of sp 2 carbon atoms in the carbon nanotubes and reflects the graphitization characteristics of the carbon nanotubes. The 2D peak appears at about 2686 cm -1 , which is caused by the van der Waals force between the carbon nanotube layers. Compared with pure carbon nanotubes, there is an obvious blue shift, indicating that the dysprosium phosphine oxide complex has an impact on the carbon nanotubes. For the dysprosium phosphine oxide complex, a single peak caused by the double bond of the aromatic molecule can be observed at 1587 cm -1 . The absorption peak of low-frequency C-H appears at 3060 cm -1 , showing an obvious blue shift compared with the ligand, indicating that the intermolecular interaction is enhanced after the formation of the dysprosium phosphine oxide complex.

[0074] The thermogravimetric diagrams of the dysprosium phosphine oxide complex prepared in Example 1 and the composite material prepared in Example 2 are as Figure 4 shown. From Figure 4 it can be seen that both the dysprosium phosphine oxide complex and the composite material have high thermal stability and only start to lose weight and show structural destruction and decomposition phenomena above 350 °C.

[0075] The X-ray powder diffraction test results of the dysprosium phosphine oxide complex prepared in Example 1 and the composite material prepared in Example 2 after being placed in air for 3 months are as Figure 5 shown. From Figure 5 it can be known that the peak positions, peak shapes, and peak intensities of the test peaks and the simulated peaks obtained after single crystal testing are basically the same, indicating that the dysprosium phosphine oxide complex and the composite material of the present invention have good stability, can be stored in an air environment for a long time, and maintain good crystallinity.

[0076] The scanning electron microscope images of the dysprosium phosphine oxide complex prepared in Example 1 and the composite material prepared in Example 2 are as Figure 6As shown. From Figure 6 It can be seen that the phosphine oxide group dysprosium complex presents a layered stacking structure, while the composite material presents a cross-linked structure, and the layered complex is dispersed in the carbon nanotubes.

[0077] The transmission electron microscopy images and energy dispersive spectroscopy images of the phosphine oxide group dysprosium complex prepared in Example 1 and the composite material prepared in Example 2 are as shown in Figure 7 (a)-(b) in, and the X-ray photoelectron spectroscopy images are as shown in Figure 8 (a)-(b) in. The element contents are shown in Table 3. From Figure 8 and Table 3, it can be seen that the phosphine oxide group dysprosium complex is dispersed in the conductive network of the carbon nanotubes, the interface is blurred and the element distribution is continuous, indicating the existence of chemical compatibility. The carbon nanotube network ensures the smooth conduction of electrons, and the phosphine oxide group dysprosium complex provides active centers for adsorbing polysulfide lithium and catalyzing its redox reaction. It can also be confirmed from the energy dispersive spectroscopy images and the element content table (Table 3) in the surface scanning mode that the two-dimensional phosphine oxide group dysprosium complex is successfully compounded in the carbon nanotube network.

[0078] Table 3 Element Contents

[0079]

[0080]

[0081] Comparative Example 1

[0082] I. Experimental Method

[0083] The dysprosium complex was synthesized according to the method of Example 1, except that the reaction temperature was adjusted to below 130 °C.

[0084] II. Experimental Results

[0085] The product is a powdery solid, and the complex crystals did not precipitate.

[0086] Comparative Example 2

[0087] I. Experimental Method

[0088] The dysprosium complex was synthesized according to the method of Example 1, except that the constant temperature reaction time was set to less than 72 h.

[0089] II. Experimental Results

[0090] The product is a powdery solid precipitate or extremely small crystals, and the structure cannot be determined.

[0091] Comparative Example 3

[0092] I. Experimental Method

[0093] The dysprosium complex was synthesized according to the method of Example 1, except that the cooling rate was set to 5 °C / min or higher.

[0094] II. Experimental Results

[0095] The product was a powdery solid, and no complex crystals were precipitated.

[0096] Comparative Example 4

[0097] I. Experimental Method

[0098] The dysprosium complex was synthesized according to the method of Example 1, except that ethanol was replaced by methanol, acetonitrile or water.

[0099] II. Experimental Results

[0100] The product was a powdery solid precipitate or microcrystals, and the structure could not be determined.

[0101] Comparative Example 5

[0102] I. Experimental Method

[0103] The dysprosium complex was synthesized according to the method of Example 1, except that the reaction temperature was adjusted to above 150 °C.

[0104] II. Experimental Results

[0105] The crystal growth rate was too fast and defects were easily formed. The product was an amorphous powdery solid precipitate with large and uneven particle sizes, and the structure could not be determined.

[0106] Comparative Example 6

[0107] I. Experimental Method

[0108] The composite material was synthesized according to the method of Example 2, except that the reaction temperature was adjusted to below 130 °C.

[0109] II. Experimental Results

[0110] The product was a black-doped white powdery solid with large and non-uniform particles.

[0111] Comparative Example 7

[0112] I. Experimental Method

[0113] The composite material was synthesized according to the method of Example 2, except that the reaction time was set to less than 72 h.

[0114] II. Experimental Results

[0115] The product was a black-doped white microcrystalline powdery solid with large and non-uniform particles.

[0116] Comparative Example 8

[0117] 1. Experimental method

[0118] The composite material was synthesized according to the method of Example 2, except that the cooling rate was set to 5 °C / min or more.

[0119] 2. Experimental results

[0120] The product was a black-doped white microcrystalline powdery solid, with large and non-uniform particles.

[0121] Comparative Example 9

[0122] 1. Experimental method

[0123] The composite material was synthesized according to the method of Example 2, except that ethanol was replaced by methanol, acetonitrile or water.

[0124] 2. Experimental results

[0125] The product was a black-doped white powdery solid, without crystallinity.

[0126] Comparative Example 10

[0127] 1. Experimental method

[0128] The composite material was synthesized according to the method of Example 2, except that the reaction temperature was adjusted to above 150 °C.

[0129] 2. Experimental results

[0130] The crystal growth rate was too fast and defects were easily formed. The product was a black amorphous powdery solid precipitate, with relatively large and non-uniform particle sizes.

[0131] Comparing Examples 1-2 with Comparative Examples 1-10, it can be seen that the preparation of the phosphine oxide group dysprosium complex and the composite material of the present invention requires a solvothermal reaction for 72 h at a reaction temperature of 130-150 °C using ethanol as a solvent. At the same time, the cooling rate should be slow, so that the final product can crystallize out with a suitable solubility, thereby obtaining a target product with excellent crystal form and high purity.

[0132] Example 4 Electrochemical test

[0133] Preparation of sulfur-carbon composite material: Take 0.09 g of the composite material CNT@[(dppBO2)DyCl3(μ-dppBO2)DyCl3(dppBO2)] prepared in Example 2 n as a sulfur carrier, mix and grind it with 0.21 g of commercial sublimed sulfur for 50 min, then place it in a reaction kettle and heat it at 155 °C for 12 h to obtain a sulfur-carbon composite material.

[0134] Electrode Preparation: 0.21 g of sulfur-carbon composite material, 0.06 g of conductive carbon black, and 0.03 g of polyvinylidene fluoride (PVDF) were used to prepare a homogeneous slurry by magnetic stirring in N-methylpyrrolidone (NMP) for 12 h. The prepared slurry was evenly coated on aluminum foil and transferred to a vacuum drying oven at 50 °C to dry the solvent, thus obtaining the electrode.

[0135] Using the prepared electrode as the positive electrode and metallic lithium as the negative electrode; LiNO3 and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were dissolved in a solution prepared by mixing 1,3-dioxolane and ethylene glycol dimethyl ether in a volume ratio of 1:1 as the electrolyte, such that the mass fraction of LiNO3 in the electrolyte was 2%, and the concentration of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was 1 mol / L; A commercial Celegard 2400 polymer porous film was used as the separator, and a button cell was assembled in an inert atmosphere glove box.

[0136] Through a Blue-Electric battery test system, in the voltage range of 1.7 - 2.8 V, by changing the input current value, the charge-discharge capacity of the sulfur-carbon composite material at different currents (0.2, 0.5, 1.0, 2.0 C) and the cycle stability at 0.5 C current were tested.

[0137] II. Experimental Results

[0138] Compared with using pure carbon nanotubes as the sulfur carrier material, the composite material prepared in Example 2 as the sulfur carrier can significantly improve its rate performance ( Figure 9 ) and cycle stability ( Figure 10 ). After 350 cycles, the capacity retention rate of pure carbon tubes is less than 30%, while after being compounded with the dysprosium phosphine oxide complex, the capacity retention rate increases by more than 2 times and can reach more than 60%. Compared with the current of pure carbon nanotubes increasing from 0.2 C to 2.0 C, the capacity decreases from 800 mAh / g to about 350 mAh / g. When the current of the composite material prepared in Example 2 is 0.2 C, the capacity is as high as 900 mAh / g, and when the current is increased to 2.0 C, the capacity is 550 mAh / g, and the retention rate can reach 55%.

[0139] Generally speaking, based on the above test results, it can be known that the composite material prepared in the present invention is a carbon nanotube composite two-dimensional dysprosium-based complex composite material, which has good stability and high catalytic activity and can be used as a battery catalytic material. In terms of the preparation method, the raw materials selected in the present invention are rich, simple and easy to operate. High-yield and high-crystallinity samples can be prepared through low-temperature solvothermal method, meeting the development needs of green chemistry. This dysprosium-based complex composite carbon material has high application value in the field of new energy materials.

[0140] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A dysprosium complex, characterized in that, The structural formula of the dysprosium complex is [(dppBO2)DyCl3(μ-dppBO2)DyCl3(dppBO2)] n , where dppBO2 is 1,4-butanediylbis(diphenylphosphine oxide); The dysprosium complex crystallizes in the trigonal system, belonging to the R-3 space group, and the unit cell parameters are as follows: α = 90°, β = 90°, γ = 120°, 2. The preparation method of the dysprosium complex according to claim 1, characterized in that, An ethanol solution of dppBO2 and DyCl3·6H2O are fully reacted at 130 - 150 °C for 72 - 74 h, and then cooled at a rate lower than 5 °C / h to obtain the product.

3. The preparation method according to claim 2, characterized in that, The dosage ratio of dppBO2, ethanol and DyCl3·6H2O is (0.8 - 1.2) mmol : (3.2 - 4.8) mL : (0.8 - 1.2) mmol.

4. Use of the dysprosium complex according to claim 1 in the preparation of a polysulfide redox catalyst.

5. A composite material, characterized in that, The composite material includes the dysprosium complex according to claim 1 and a carbon material. The dysprosium complex is dispersed in the conductive network formed by the carbon material and forms a cross-linked structure. The carbon material includes carbon nanotubes, graphite, carbon fiber and graphene.

6. A preparation method of a composite material, characterized in that, After fully mixing the carbon material, dppBO2 and ethanol, add DyCl3·6H2O, and fully react at 130 - 150 °C for 72 - 74 h, and then cool at a rate lower than 5 °C / h to obtain the product. The carbon material includes carbon nanotubes, graphite, carbon fiber and graphene.

7. The preparation method according to claim 6, characterized in that, The dosage ratio of the carbon material, dppBO2, ethanol and DyCl3·6H2O is (28 - 32) mmol : (0.8 - 1.2) mmol : (3.2 - 4.8) mL : (0.8 - 1.2) mmol.

8. A composite material prepared by the preparation method according to any one of claims 6 - 7.

9. Use of the composite material according to claim 5 and / or the composite material according to claim 8 in catalyzing polysulfide redox.

10. Use of the composite material according to claim 5 and / or the composite material according to claim 8 in the preparation of a lithium-sulfur battery electrode.

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