Preparation method of a multi-layered black phosphorus @ molybdenum selenide @ graphene battery negative electrode material

Abstract

The present invention discloses a method for preparing a multi-layered black phosphorus, molybdenum selenide, and graphene battery anode material. The method involves ultrasonically exfoliating black phosphorus blocks in a pre-prepared hydrazine hydrate aqueous solution. A certain amount of the black phosphorus suspension is then drawn, selenious acid and sodium molybdate are added, and the mixture is stirred for a certain period before undergoing a hydrothermal reaction to form a black phosphorus and molybdenum selenide composite. The prepared black phosphorus, molybdenum selenide, and graphene are then ultrasonically dispersed in anhydrous ethanol, mixed and stirred uniformly, and then reduced with a certain amount of hydrazine hydrate dropwise, thereby obtaining a multi-layered black phosphorus, molybdenum selenide, and graphene composite material. The method utilizes a hydrazine hydrate-pretreated aqueous solution as the stripping solvent, facilitating post-processing while avoiding the use of toxic, hazardous, and expensive organic solvents. The resulting black phosphorus, molybdenum selenide, and graphene material exhibits excellent electrochemical performance, which is of great significance for the development of black phosphorus-based potassium ion anode materials.

Description

Technical Field

[0001] The invention relates to a method for preparing a black phosphorus@molybdenum selenide@graphene battery negative electrode material with a multi-level layered structure, and belongs to the field of potassium ion batteries. Background Art

[0002] Potassium-ion batteries (KIBs) share similar operating principles to lithium-ion batteries. Since Professor Ali Eftekhari reported the use of Prussian blue as a KIB cathode material in 2004, KIBs have gradually attracted the attention of researchers. Currently, KIB research focuses primarily on the development and optimization of cathode and anode materials. However, limited by the limited development of these materials, KIB research remains confined to the early laboratory stage. While some progress has been made, progress is slow. Compared to lithium ions, KIBs have a larger ionic radius. The insertion and extraction of KIBs during charge and discharge causes greater volume expansion, placing higher demands on the stability and structural strength of the anode materials. Several candidate materials, such as graphite, graphene, carbon nanotubes, carbon spheres, and some metal oxides and sulfides, have been investigated as KIB anode materials, and while some progress has been achieved, battery stability, cycle life, energy density, and safety remain pressing challenges.

[0003] There are three main allotropes of phosphorus: white phosphorus, red phosphorus and black phosphorus. White phosphorus is composed of tetrahedral P4 molecules. It has high activity and toxicity, so it is not suitable for use as a battery material. Amorphous red phosphorus has been studied as a negative electrode material for potassium ion batteries, but its conductivity is poor, and the alloy-type potassium storage mechanism has a large volume expansion, resulting in poor cycle life and rate performance. Black phosphorus with a layered orthorhombic crystal structure is the most thermodynamically stable allotrope of phosphorus. Black phosphorus is a good conductor (~300S m -1 ), in a single layer of phosphorus, each phosphorus atom is bonded to three adjacent phosphorus atoms, and the layers are connected by covalent bonds to form a wrinkled honeycomb structure. Compared with graphite, the interlayer channels of black phosphorus are larger. This means that potassium ions In 2017, Professors Md Mokhlesur Rahman, Ying Chen and Alexey M. Glushenkov used in-situ XRD technology to study and found that during the discharge process, P and K alloyed and the final discharge product was KP, with a theoretical capacity of 843 mAh g -1 In 2019, Professor Chunsheng Wang and Professor Nikhil Koratkar used ex-situ XPS and XRD techniques to find that during the discharge process, black phosphorus can form a K4P3 alloy with potassium, with a theoretical capacity of up to 1200 mAh g-1 However, the stability of the material is very poor, and the capacity can only be maintained at ~9% after cycling. Although there have been reports on black phosphorus as anode materials for potassium ion batteries, its cycle stability and rate performance need to be improved. When exposed to electrolytes, the large number of edge atoms on the surface of the layered black phosphorus will be reconstructed, hindering the K + Diffusion on its surface, resulting in low rate capability. In addition, the volume expansion of black phosphorus during the cycle is large (≈300%), which leads to a rapid capacity decay of the material. At the same time, the solid electrolyte membrane (SEI) continues to thicken and is very unstable during the cycle, resulting in poor cycle stability. Currently, the commonly used means of stripping black phosphorus are mainly ultrasonic stripping and electrochemical stripping. Both methods inevitably require the use of a large amount of organic solvents. These organic solvents are expensive and most of them are toxic and harmful, and the subsequent processing is also very difficult. Therefore, it is of great significance to seek a preparation method for black phosphorus-based potassium ion battery negative electrode materials with simple synthesis process, mild reaction conditions, long cycle life and high rate performance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a black phosphorus@molybdenum selenide@graphene battery negative electrode material with a multi-level layered structure. The method avoids the use of expensive and toxic organic solvents. Hydrazine hydrate is pre-treated to reduce oxygen in deionized water, which is used as a stripping agent to ultrasonically strip black phosphorus blocks. Molybdenum selenide nanosheets are then uniformly grown on the surface of the black phosphorus sheets through a hydrothermal reaction. At the same time, the conductivity of the material is further improved by introducing graphene. The present invention protects the exposed edge atoms of black phosphorus through the action of chemical bonds such as CP, PO / P=O, and P-Mo, thereby improving the rate performance and cycle stability of the material. The prepared material can be used in potassium ion batteries, and its electrochemical performance can be significantly improved. This is of great significance to the further development of black phosphorus-based materials in the field of potassium ion batteries.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for preparing a multi-layered black phosphorus@molybdenum selenide@graphene battery negative electrode material is carried out in the following steps:

[0007] S1, deionized water and hydrazine hydrate solution were stirred under a sealed container in a volume ratio of 1:1 for 2 h, and the oxygen in the water was removed by mixing to obtain a hydrazine hydrate aqueous solution;

[0008] S2. The prepared hydrazine hydrate aqueous solution was transferred to a three-necked flask, and under nitrogen protection, black phosphorus blocks were added, wherein the mass volume ratio of the black phosphorus blocks to the hydrazine hydrate aqueous solution was 0.8:400 g / mL, and ultrasonic treatment was performed to obtain stripped black phosphorus;

[0009] S3, centrifuging the peeled black phosphorus to remove the remaining black phosphorus lumps to obtain a black phosphorus suspension;

[0010] S4, adding selenious acid and sodium molybdate to the prepared black phosphorus suspension, stirring to mix them evenly, then performing a hydrothermal reaction, cooling to room temperature, washing with anhydrous ethanol, and then freeze-drying to obtain a black phosphorus@molybdenum selenide complex;

[0011] S5. Ultrasonic dispersion of black phosphorus @ molybdenum selenide and graphene in anhydrous ethanol is performed separately, and the mixture is stirred for 2 h to allow the mixture to mix evenly. Hydrazine hydrate is then added, and the mixture is stirred for 12 h and then washed with anhydrous ethanol. The washed powder is placed in a freeze dryer and freeze-dried to obtain a black phosphorus @ molybdenum selenide @ graphene composite.

[0012] As a limitation of the present invention, in step S2, the ultrasonic power is 720 W and the treatment time is 12 hours.

[0013] As a second limitation of the present invention, in step S3, the centrifugal speed is 2000 rpm and the centrifugal time is 8 min.

[0014] As a third limitation of the present invention, in step S4, the molar ratio of sodium molybdate to selenious acid is 1:2.

[0015] As a fourth limitation of the present invention, in step S4, selenious acid is added and stirred for 12 hours, sodium molybdate is added and stirred for 2 hours, the hydrothermal reaction temperature is 220°C, the time is 24 hours, and the hydrothermal reaction is heated from room temperature to the target temperature at a heating rate of 2°C / min.

[0016] As a fifth limitation of the present invention, in step S4, the freeze-drying temperature is -60°C and the freeze-drying time is 24 hours.

[0017] As a sixth limitation of the present invention, in step S5, the mass ratio of black phosphorus@molybdenum selenide to graphene is 100:(20-80).

[0018] As a seventh limitation of the present invention, in step S5, the mass volume ratio of graphene to hydrazine hydrate is 20:1 mg / mL.

[0019] The present invention has another limitation, that in step S5, the freeze-drying temperature is -60°C and the freeze-drying time is 24 hours.

[0020] Due to the adoption of the above technical solution, the technical advancements achieved by the present invention are:

[0021] 1. The present invention pre-treats the black phosphorus block with hydrazine hydrate to reduce the oxygen in the deionized water, and uses it as a stripping agent to ultrasonically strip the black phosphorus block, thereby avoiding the use of some toxic, harmful and expensive organic solvents. The reaction conditions are mild, the hydrazine hydrate is easy to remove in the later stage, and the preparation process is simple.

[0022] 2. The multi-layered black phosphorus @ molybdenum selenide @ graphene material prepared by the present invention, through the action of P-Mo, allows molybdenum selenide nanosheets to grow uniformly on the surface of black phosphorus sheets during the hydrothermal process. On the one hand, the presence of black phosphorus can prevent the agglomeration of molybdenum selenide nanosheets, and on the other hand, the presence of molybdenum selenide can protect the exposed edge atoms of black phosphorus, thereby improving the material's rate performance and cycle stability.

[0023] 3. The present invention can further improve the conductivity of the material by introducing graphene. At the same time, graphene and black phosphorus are bonded through chemical bonds such as CP and PO / P=O, which synergistically further protect the exposed edge atoms of black phosphorus, thereby improving the electrochemical properties of the material.

[0024] 4. The multi-layered black phosphorus@molybdenum selenide@graphene material of the present invention has long cycle stability and high rate performance, and is used as anode material for potassium ion batteries, and its electrochemical performance is significantly improved.

[0025] The technical solution of the present invention will be further described in detail below in conjunction with the embodiments of the present invention and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a transmission electron microscope image of the multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention;

[0027] Figure 2 This is a scanning electron microscope image of the multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention;

[0028] Figure 3 This is an energy spectrum image of the multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention;

[0029] Figure 4 This is a high-resolution image of the multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention;

[0030] Figure 5 This is the XRD pattern of the black phosphorus@molybdenum selenide@graphene material with a multi-layer structure prepared in Example 2 of the present invention;

[0031] Figure 6 This is a thermogravimetric image of the black phosphorus@molybdenum selenide@graphene material with a multi-layered structure prepared in Example 2 of the present invention;

[0032] Figure 7 This is an XPS graph of the black phosphorus@molybdenum selenide@graphene material with a multi-layered structure prepared in Example 2 of the present invention;

[0033] Figure 8 This is an impedance diagram of a potassium ion battery made of a multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention;

[0034] Figure 9 The multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention is used as a potassium ion battery at 0.5mV·s -1 CV curves measured at a scan rate of ;

[0035] Figure 10 The multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention is used to make potassium ion batteries at 0.05A·g -1 The charge and discharge diagram measured under the current of ;

[0036] Figure 11 The multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention is used to make potassium ion batteries at 0.1A·g -1 Performance diagram after 160 cycles at a current density of ;

[0037] Figure 12 This is a rate performance diagram of a potassium ion battery made of a multi-level layered black phosphorus @ molybdenum selenide @ graphene material prepared in Example 2 of the present invention at different current densities. DETAILED DESCRIPTION

[0038] Unless otherwise specified, the reagents described in the following examples are all commercially available reagents, and the preparation and detection methods are all based on existing methods unless otherwise specified.

[0039] Example 1

[0040] (1) Deionized water and hydrazine hydrate solution were added to 200 mL of deionized water in a volume ratio of 1:1, and the mixture was stirred for 2 h under a sealed state to allow the mixture to mix evenly and remove oxygen from the water to obtain a hydrazine hydrate aqueous solution;

[0041] (2) 400 mL of the prepared hydrazine hydrate aqueous solution was transferred to a three-necked flask, 0.8 g of black phosphorus block was added under nitrogen protection, and ultrasonic treatment was performed at a power of 720 W for 12 h to obtain exfoliated black phosphorus;

[0042] (3) centrifuging the stripped black phosphorus at 2000 rpm for 8 min to remove the remaining black phosphorus lumps and obtain a black phosphorus suspension;

[0043] (4) The black phosphorus suspension was ultrasonicated for 2 h to allow it to be evenly dispersed. Then, 40 mL of the dispersed black phosphorus suspension (containing 60 mg of black phosphorus) was taken, 0.5 mmol of selenious acid was added, and stirred under closed conditions for 12 h until the color of the solution no longer changed. Then, 0.25 mmol of sodium molybdate was added and stirred for 2 h to allow it to mix evenly. Finally, the solution was transferred to a polytetrafluoroethylene stainless steel autoclave (total capacity 100 mL) and maintained at 220 ° C for 24 h with a heating rate of 2 ° C / min. After cooling to room temperature, it was washed with anhydrous ethanol and then freeze-dried at -60 ° C for 24 h to obtain a black phosphorus @ molybdenum selenide complex.

[0044] (5) Take 0.1g of black phosphorus @ molybdenum selenide and ultrasonically treat it for 2h, disperse it in 40mL of anhydrous ethanol to form a black phosphorus @ molybdenum selenide solution, and at the same time, ultrasonically treat 20mg of graphene for 2h and disperse it in 40mL of anhydrous ethanol to form a graphene suspension. Then, add the graphene suspension to its black phosphorus @ molybdenum selenide solution and stir it for 2h to mix it evenly; finally, add 1.0mL of hydrazine hydrate, stir it for 12h, and then wash it with anhydrous ethanol. Then, place the washed powder in a freeze dryer and freeze-dry it at -60℃ for 24h to obtain a black phosphorus @ molybdenum selenide @ graphene composite.

[0045] Example 2

[0046] (1) Deionized water and hydrazine hydrate solution were added to 200 mL of deionized water in a volume ratio of 1:1, and the mixture was stirred for 2 h under a sealed state to allow the mixture to mix evenly and remove oxygen from the water to obtain a hydrazine hydrate aqueous solution;

[0047] (2) 400 mL of the prepared hydrazine hydrate aqueous solution was transferred to a three-necked flask, 0.8 g of black phosphorus block was added under nitrogen protection, and ultrasonic treatment was performed at a power of 720 W for 12 h to obtain exfoliated black phosphorus;

[0048] (3) centrifuging the stripped black phosphorus at 2000 rpm for 8 min to remove the remaining black phosphorus lumps and obtain a black phosphorus suspension;

[0049] (4) The black phosphorus suspension was ultrasonicated for 2 h to allow it to be evenly dispersed. Then, 40 mL of the dispersed black phosphorus suspension (containing 60 mg of black phosphorus) was taken, 1 mmol of selenious acid was added, and stirred under closed conditions for 12 h until the color of the solution no longer changed. Then, 0.5 mmol of sodium molybdate was added and stirred for 2 h to allow it to mix evenly. Finally, the solution was transferred to a polytetrafluoroethylene stainless steel autoclave (total capacity 100 mL) and maintained at 220 ° C for 24 h with a heating rate of 2 ° C / min. After cooling to room temperature, it was washed with anhydrous ethanol and then freeze-dried at -60 ° C for 24 h to obtain a black phosphorus @ molybdenum selenide complex.

[0050] (5) Take 0.1g of black phosphorus @ molybdenum selenide and ultrasonically treat it for 2h, and disperse it in 40mL of anhydrous ethanol. At the same time, ultrasonically treat 40mg of graphene for 2h and disperse it in 40mL of anhydrous ethanol. Then add the graphene suspension to its black phosphorus @ molybdenum selenide solution and stir for 2h to mix them evenly. Finally, add 2.0mL of hydrazine hydrate, stir for 12h, and wash with anhydrous ethanol. Then, place the washed powder in a freeze dryer at -60℃ and freeze-dry for 24h to obtain a black phosphorus @ molybdenum selenide @ graphene composite.

[0051] A series of performance tests were conducted on the product prepared in this example, and the specific results are as follows:

[0052] Figure 1 This is a transmission image of the multi-level layered black phosphorus @ molybdenum selenide @ graphene material prepared in Example 2 of the present invention. It can be clearly seen from the image that molybdenum selenide nanosheets are evenly grown on the exfoliated black phosphorus sheets, with a thin layer of graphene on the outer layer. The material presents a multi-level layered structure.

[0053] Figure 2 This is a scanning electron microscope image of the multi-layered black phosphorus @ molybdenum selenide @ graphene material prepared in Example 2 of the present invention. Molybdenum selenide grows vertically on the surface of the black phosphorus sheet and is evenly distributed, which is consistent with the transmission results.

[0054] Figure 3 This is the energy spectrum of the black phosphorus @ molybdenum selenide @ graphene material with a multi-level layered structure prepared in Example 2 of the present invention. From the figure, it can be seen that the four elements C, P, Mo and Se are evenly distributed in the entire material, proving the presence of C, P, Mo and Se elements in the system.

[0055] Figure 4 This is a high-resolution image of the multi-layered black phosphorus @ molybdenum selenide @ graphene material prepared in Example 2 of the present invention. From the image, it can be seen that molybdenum selenide nanosheets grow vertically on the black phosphorus sheet, with about 4-7 layers of molybdenum selenide. The lattice fringes of molybdenum selenide are Corresponding to the (002) crystal plane of molybdenum selenide; the lattice fringes of black phosphorus are Corresponding to the (111) crystal plane of black phosphorus, it further proves the existence of black phosphorus and molybdenum selenide in the system.

[0056] Figure 5This is the XRD pattern of the multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention. It can be seen from the figure that the obtained black phosphorus@molybdenum selenide@graphene material basically overlaps with the PDF#00-029-0914 of molybdenum selenide and the PDF#98-008-8816 of carbon, proving the presence of molybdenum selenide and graphene in the system. In addition, since the black phosphorus flakes are uniformly coated with molybdenum selenide nanosheets and the outermost layer is coated with graphene, only a few black phosphorus flakes are exposed, and no diffraction peaks of black phosphorus are detected here.

[0057] Figure 6 This is the thermogravimetric diagram of the black phosphorus @ molybdenum selenide @ graphene material with a multi-level layered structure prepared in Example 2 of the present invention. The decrease in mass from room temperature to 300°C corresponds to the evaporation of water in the material, the increase in mass from 300-350°C corresponds to the oxidation of molybdenum selenide, the decrease in mass from 350-450°C corresponds to the sublimation of selenium dioxide, the decrease in mass from 450-600°C corresponds to the sublimation of black phosphorus, and the decrease in mass from 600-700°C corresponds to the oxidation of carbon.

[0058] Figure 7 This is the XPS of the black phosphorus @ molybdenum selenide @ graphene material with a multi-level layered structure prepared in Example 2 of the present invention. In the XPS total spectrum, the presence of C, P, Mo and Se further proves the synthesis of the black phosphorus @ molybdenum selenide @ graphene material, and the presence of CP, P-Mo and PO / P=O bonds proves that the materials are bonded by chemical bonds.

[0059] Figure 8 This is an impedance diagram of the black phosphorus @ molybdenum selenide @ graphene material with a multi-level layered structure prepared in Example 2 of the present invention measured in a potassium ion battery. It can be seen from the figure that the charge transfer resistance Rct of Example 2 is 1638 ohms, showing good conductivity.

[0060] Figure 9 The multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention is used as a potassium ion battery with a power output of 0.5mVs -1 The CV curves were measured at a scan rate of . It can be seen from the figure that the curves have good overlap in the last two circles, indicating that the material has good cycle stability.

[0061] Figure 10 The multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention is used to make potassium ion batteries at 0.05A g -1 The charge and discharge diagram measured at a current of 100 Ω is shown in the figure. From the figure, we can see that the first cycle discharge capacity of the material is 395.7 mAh g -1 , the first coulombic efficiency is 65.0%.

[0062] Figure 11The multi-layered black phosphorus@molybdenum selenide@graphene material prepared in Example 2 of the present invention is used to make potassium ion batteries at 0.1A g -1 The performance diagram after 160 cycles at a current density of 10000 cycles shows that the capacity of the material can still be maintained at 223.2 mAh g after 160 cycles. -1 , the capacity retention rate is 89.9%.

[0063] Figure 12 This is the rate performance diagram of the multi-level layered black phosphorus @ molybdenum selenide @ graphene material obtained in Example 2 of the present invention. It can be seen from the figure that the rate performance of the multi-level layered black phosphorus @ molybdenum selenide @ graphene material obtained in Example 2 is even at 5Ag. -1 At a current density of 126.4 mAh g -1 mass specific capacity.

[0064] Example 3

[0065] (1) Deionized water and hydrazine hydrate solution were added to 200 mL of deionized water in a volume ratio of 1:1, and the mixture was stirred for 2 h under a sealed state to allow the mixture to mix evenly and remove oxygen from the water to obtain a hydrazine hydrate aqueous solution;

[0066] (2) The prepared hydrazine hydrate aqueous solution was transferred to a three-necked flask, 0.8 g of black phosphorus block was added under nitrogen protection, and ultrasonic treatment was performed at a power of 720 W for 12 h to obtain exfoliated black phosphorus;

[0067] (3) centrifuging the stripped black phosphorus at 2000 rpm for 8 min to remove the remaining black phosphorus lumps and obtain a black phosphorus suspension;

[0068] (4) The black phosphorus suspension was ultrasonicated for 2 h to allow it to be evenly dispersed. Then, 40 mL of the dispersed black phosphorus suspension (containing 60 mg of black phosphorus) was taken, 2 mmol of selenious acid was added, and stirred under closed conditions for 12 h until the color of the solution no longer changed. Then, 1.0 mmol of sodium molybdate was added and stirred for 2 h to allow it to mix evenly. Finally, the solution was transferred to a polytetrafluoroethylene stainless steel autoclave (total capacity 100 mL) and maintained at 220 ° C for 24 h with a heating rate of 2 ° C / min. After cooling to room temperature, it was washed with anhydrous ethanol and then freeze-dried at -60 ° C for 24 h to obtain a black phosphorus @ molybdenum selenide complex.

[0069] (5) Take 0.1g of black phosphorus @ molybdenum selenide and ultrasonically treat it for 2h, and disperse it in 40mL of anhydrous ethanol. At the same time, ultrasonically treat 60mg of graphene for 2h and disperse it in 40mL of anhydrous ethanol. Then add the graphene suspension to its black phosphorus @ molybdenum selenide solution and stir for 2h to mix evenly. Finally, add 3.0mL of hydrazine hydrate, stir for 12h, and wash with anhydrous ethanol. Then, place the washed powder in a freeze dryer and freeze-dry at -60℃ for 24h to obtain a black phosphorus @ molybdenum selenide @ graphene composite.

[0070] Example 4

[0071] (1) Deionized water and hydrazine hydrate solution were added to 200 mL of deionized water in a volume ratio of 1:1, and the mixture was stirred for 2 h under a sealed state to allow the mixture to mix evenly and remove oxygen from the water to obtain a hydrazine hydrate aqueous solution;

[0072] (2) The prepared hydrazine hydrate aqueous solution was transferred to a three-necked flask, 0.8 g of black phosphorus block was added under nitrogen protection, and ultrasonic treatment was performed at a power of 720 W for 12 h to obtain exfoliated black phosphorus;

[0073] (3) centrifuging the stripped black phosphorus at 2000 rpm for 8 min to remove the remaining black phosphorus lumps and obtain a black phosphorus suspension;

[0074] (4) The black phosphorus suspension was ultrasonicated for 2 h to allow it to be evenly dispersed. Then, 40 mL of the dispersed black phosphorus suspension (containing 60 mg of black phosphorus) was taken, 2 mmol of selenious acid was added, and stirred under closed conditions for 12 h until the color of the solution no longer changed. Then, 1.0 mmol of sodium molybdate was added and stirred for 2 h to allow it to mix evenly. Finally, the solution was transferred to a polytetrafluoroethylene stainless steel autoclave (total capacity 100 mL) and maintained at 220 ° C for 24 h with a heating rate of 2 ° C / min. After cooling to room temperature, it was washed with anhydrous ethanol and then freeze-dried at -60 ° C for 24 h to obtain a black phosphorus @ molybdenum selenide complex.

[0075] (5) Take 0.1g of black phosphorus @ molybdenum selenide and ultrasonically treat it for 2h, and disperse it in 40mL of anhydrous ethanol. At the same time, 80mg of graphene is ultrasonically treated for 2h and dispersed in 40mL of anhydrous ethanol. Then, the graphene suspension is added to its black phosphorus @ molybdenum selenide solution and stirred for 2h to mix evenly. Finally, 4.0mL of hydrazine hydrate is added, stirred for 12h, and then washed with anhydrous ethanol. The washed powder is then placed in a freeze dryer and freeze-dried at -60℃ for 24h to obtain a black phosphorus @ molybdenum selenide @ graphene composite.

[0076] Performance Testing

[0077] A series of electrochemical performance tests were performed on the products prepared in Examples 1-4 of the present invention, as shown in the table below.

[0078]

[0079]

[0080] In summary, the black phosphorus@molybdenum selenide@graphene material with a multi-level layered structure of the present invention has long cycle stability and high rate performance, and its electrochemical performance is significantly improved when used as a negative electrode material for potassium ion batteries.

[0081] Comparative Example

[0082] Group A: Black phosphorus@molybdenum selenide battery negative electrode materials

[0083] This group of examples prepares a black phosphorus @ molybdenum selenide battery negative electrode material. The specific preparation method is similar to that of Example 2, except that graphene is not introduced into the material, that is, step (5) does not occur, and the product obtained in step (4) is the black phosphorus @ molybdenum selenide battery negative electrode material.

[0084] Group B: Black phosphorus@graphene battery anode materials

[0085] This group of examples prepares a black phosphorus@graphene battery negative electrode material. The specific preparation method is similar to that of Example 2, except that molybdenum selenide is not introduced into the material. The specific process is as follows:

[0086] (1) Deionized water and hydrazine hydrate solution were added to 200 mL of deionized water in a volume ratio of 1:1, and the mixture was stirred for 2 h under a sealed state to allow the mixture to mix evenly and remove oxygen from the water to obtain a hydrazine hydrate aqueous solution;

[0087] (2) 400 mL of the prepared hydrazine hydrate aqueous solution was transferred to a three-necked flask, 0.8 g of black phosphorus block was added under nitrogen protection, and ultrasonic treatment was performed at a power of 720 W for 12 h to obtain exfoliated black phosphorus;

[0088] (3) Take 0.1g of exfoliated black phosphorus and ultrasonically treat it for 2h, then disperse it in 40mL of anhydrous ethanol. At the same time, 40mg of graphene was ultrasonically treated for 2h and dispersed in 40mL of anhydrous ethanol. Then, the graphene suspension was added to its black phosphorus solution and stirred for 2h to mix evenly. Finally, 2.0mL of hydrazine hydrate was added, stirred for 12h, and then washed with anhydrous ethanol. The washed powder was then placed in a freeze dryer and freeze-dried at -60℃ for 24h to obtain a black phosphorus@graphene composite.

[0089] Group C: Black phosphorus battery negative electrode materials

[0090] In this group of examples, a black phosphorus battery negative electrode material is prepared. The specific preparation method is similar to that of Example 2, except that graphene and molybdenum selenide are not introduced into the material, that is, step (4) and step (5) do not occur. After step (3), the material is centrifuged at 8000 rpm and washed with anhydrous ethanol, and then freeze-dried at -60°C for 24 hours. The obtained product is the black phosphorus battery negative electrode material.

[0091] Group D: Molybdenum selenide battery negative electrode materials

[0092] This group of examples prepares a black phosphorus battery negative electrode material. The specific preparation method is similar to that of Example 2, except that black phosphorus and graphene are not introduced into the material. The specific process is as follows: 40 mL of hydrazine hydrate aqueous solution (20 mL of water + 20 mL of hydrazine hydrate) is added to 4 mmol of selenious acid, and stirred under closed conditions for 12 hours until the color of the solution no longer changes. Then, 2.0 mmol of sodium molybdate is added and stirred for 2 hours to allow it to mix evenly. Finally, the solution is transferred to a polytetrafluoroethylene stainless steel autoclave (total capacity 100 mL) and maintained at 220°C for 24 hours with a heating rate of 2°C / min; after cooling to room temperature, it is washed with anhydrous ethanol and then freeze-dried at -60°C for 24 hours to obtain a product that is a molybdenum selenide battery negative electrode material.

[0093] The present invention conducted a series of electrochemical performance tests on the materials prepared in the above comparative examples, and the specific results are shown in the following table.

[0094]

[0095]

[0096] Finally, it should be noted that the above-described embodiments of the present invention are merely examples for the purpose of clarifying the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will readily appreciate that various modifications, readjustments, and substitutions can be made without departing from the scope of the present invention. It is not necessary and impossible to provide an exhaustive list of all embodiments. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of the claims.

Claims

1. A method for preparing a multi-layered black phosphorus @ molybdenum selenide @ graphene battery negative electrode material, characterized in that: Follow the steps below in order: S1, deionized water and hydrazine hydrate solution were stirred under a sealed container in a volume ratio of 1:1 for 2 h, and the oxygen in the water was removed by mixing to obtain a hydrazine hydrate aqueous solution; S2. The prepared hydrazine hydrate aqueous solution was transferred to a three-necked flask, and under nitrogen protection, black phosphorus blocks were added, wherein the mass volume ratio of the black phosphorus blocks to the hydrazine hydrate aqueous solution was 0.8:400 g / mL, and ultrasonic treatment was performed to obtain stripped black phosphorus; S3, centrifuging the peeled black phosphorus to remove the remaining black phosphorus lumps to obtain a black phosphorus suspension; S4, adding selenious acid and sodium molybdate to the prepared black phosphorus suspension, stirring to mix them evenly, then performing a hydrothermal reaction, cooling to room temperature, washing with anhydrous ethanol, and then freeze-drying to obtain a black phosphorus@molybdenum selenide complex; S5. Ultrasonic dispersion of black phosphorus @ molybdenum selenide and graphene in anhydrous ethanol is performed separately, and the mixture is stirred for 2 h to allow the mixture to mix evenly. Hydrazine hydrate is then added, and the mixture is stirred for 12 h and then washed with anhydrous ethanol. The washed powder is placed in a freeze dryer and freeze-dried to obtain a black phosphorus @ molybdenum selenide @ graphene composite.

2. The method for preparing a multi-layered black phosphorus @ molybdenum selenide @ graphene battery negative electrode material according to claim 1, characterized in that: In step S2, the ultrasonic power is 720W and the treatment time is 12 hours.

3. The method for preparing a multi-layered black phosphorus @ molybdenum selenide @ graphene battery negative electrode material according to claim 1, characterized in that: In step S3, the centrifugal speed is 2000 rpm and the centrifugal time is 8 min.

4. The method for preparing a multi-layered black phosphorus @ molybdenum selenide @ graphene battery negative electrode material according to claim 1, characterized in that: In step S4, the molar ratio of sodium molybdate to selenious acid is 1:

2.

5. The method for preparing a multi-layered black phosphorus @ molybdenum selenide @ graphene battery negative electrode material according to claim 1, characterized in that: In step S4, after adding selenious acid, stir for 12 hours, after adding sodium molybdate, stir for 2 hours, the hydrothermal reaction temperature is 220° C., the time is 24 hours, and the hydrothermal reaction is heated from room temperature to the target temperature at a heating rate of 2° C. / min.

6. The method for preparing a multi-layered black phosphorus@molybdenum selenide@graphene battery negative electrode material according to claim 1, characterized in that: In step S4, the freeze-drying temperature is -60°C and the freeze-drying time is 24 hours.

7. The method for preparing a multi-layered black phosphorus@molybdenum selenide@graphene battery negative electrode material according to claim 1, characterized in that: In step S5, the mass ratio of black phosphorus@molybdenum selenide to graphene is 100:(20-80).

8. The method for preparing a multi-layered black phosphorus@molybdenum selenide@graphene battery negative electrode material according to claim 1, characterized in that: In step S5, the mass volume ratio of graphene to hydrazine hydrate is 20:1 mg / mL.

9. The method for preparing a multi-layered black phosphorus@molybdenum selenide@graphene battery negative electrode material according to any one of claims 1 to 8, characterized in that: In step S5, the freeze-drying temperature is -60°C and the freeze-drying time is 24 hours.

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