Bimetal selenide heterostructure and preparation and application thereof

Abstract

The invention relates to a bimetallic selenide heterostructure and preparation and application thereof. The preparation method comprises the following steps: firstly, synthesizing a selenium nanorod as a template and a selenium source, then coating the selenium nanorod with a bimetallic organic framework (MOF), and finally synthesizing a heterostructure in which bimetallic selenide nanoparticles grow on a hollow carbon tube through in-situ pyrolysis. Compared with the prior art, the method has the advantages that the selenium nanorod is ingeniously used as a template and a selenium source of a one-dimensional structure, and various bimetallic selenide heterostructures can be formed by different combinations of metals through flexible matching of the bimetallic MOF. The bimetallic selenide heterostructure is applied to an electrode material of a secondary battery, and shows excellent energy storage performance of high capacity, high rate and long circulation.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and in particular to a bimetallic selenide heterostructure and a preparation and application thereof. Background Art

[0002] With the rapid development of energy technology, the demand for energy supply in modern society is increasing. In order to reduce dependence on fossil fuels, it is urgent to turn to sustainable energy. Rechargeable batteries have attracted much attention due to their advantages such as high energy density and long cycle life. In the past three decades, lithium-ion batteries (LIBs) have been widely used in portable electronic products and are considered to be the most promising power batteries for electric vehicles. The core issue of lithium-ion batteries is to further improve their energy density. The most common anode material for lithium-ion batteries that is widely used in business is graphite, but the relatively low theoretical capacity of graphite limits the further development of lithium-ion batteries.

[0003] Bimetallic selenides have attracted much attention in the field of electrochemical energy storage due to their unique structure and properties. Compared with single metal selenides, bimetallic selenides have higher conductivity, better stability and more excellent electrochemical performance. However, traditional preparation methods of bimetallic selenides usually have problems such as complex steps, high cost and difficult to control product morphology, which limits their promotion and application in practical applications.

[0004] In recent years, heterostructure materials have gradually become a research hotspot because of their built-in electric field formed at the interface, which can effectively promote charge separation and transfer and exhibit excellent electrochemical properties. The energy storage performance of materials can be significantly improved by rationally designing and controlling heterostructures. However, how to achieve efficient synthesis of bimetallic selenides and construct heterostructures with excellent electrochemical properties remains an urgent problem to be solved.

[0005] Chinese patent CN201910976646.6 discloses a method for preparing a sodium ion battery negative electrode material of a bimetallic selenide, which synthesizes a MoSe2@CoSe2@C heterostructure through a simple process to achieve the purpose of enhancing the electrochemical performance of sodium ion batteries. The method first synthesizes MoO3 nanorods, and then grows a layer of Co-MOF nanosheets on the surface of the MoO3 nanorods. After high-temperature selenization and calcination, a core-shell structure with a uniform heterogeneous interface is obtained, which can improve the ion diffusion kinetics and increase the electronic conductivity, thereby improving the electrochemical performance of the battery. Compared with pure MoSe2, SIBs using MoSe2@CoSe2@C heterostructures as negative electrodes show significantly improved specific capacity, excellent cycle stability and rate performance. However, the synthesis of selenides in this patent requires the synthesis of oxides first and then selenization. The method is cumbersome, and the morphology and structure of the oxides need to be regulated first. Summary of the invention

[0006] The purpose of the present invention is to provide a bimetallic selenide heterostructure and its preparation and application in order to solve the problems existing in the prior art. The present invention uses selenium nanorods (Se nanorods) as templates and selenium sources, and coats bimetallic organic frameworks (bimetallic MOFs) on the outside thereof, and synthesizes heterostructures of bimetallic selenide nanoparticles grown on hollow carbon tubes by in-situ pyrolysis. This method cleverly utilizes Se nanorods as templates and selenium sources for one-dimensional structures, and combined with the adjustability of bimetallic MOFs, different combinations of metals can form various bimetallic selenide heterostructures, and finally obtain different bimetallic selenide heterostructures. The heterostructure has a built-in electric field, which can accelerate the transmission of electrons and ions, thereby accelerating the reaction kinetics and significantly improving the energy storage performance of secondary batteries. The bimetallic selenide heterostructure is applied to the electrode material of secondary batteries, showing excellent energy storage performance of high capacity, large rate and long cycle.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for preparing a bimetallic selenide heterostructure, the specific steps are as follows:

[0009] S1. Synthesis of selenium nanorods (Se nanorods):

[0010] Selenium nanorods are obtained by stirring and mixing sodium carboxymethyl cellulose (CMC-Na) solution, NaOH solution, H2SeO3 solution and NaBH4 solution;

[0011] S2, bimetallic organic framework (bimetallic MOF) coated selenium nanorods:

[0012] Selenium nanorods obtained in step S1, polyvinyl pyrrolidone (PVP), two metal salts and 2-methylimidazole are sequentially added to the methanol solution, and the selenium nanorods coated with the bimetallic organic framework are obtained after stirring;

[0013] S3. Synthesis of bimetallic selenide heterostructures:

[0014] The selenium nanorods coated with the bimetallic organic framework obtained in step S2 are placed under the protection of an inert gas and kept at a high temperature to obtain a bimetallic selenide heterostructure.

[0015] Furthermore, in step S1, the volume ratio of the sodium carboxymethyl cellulose (CMC-Na) solution, the NaOH solution, the H2SeO3 solution and the NaBH4 solution is (1-10):1:(1-5):(0.1-0.5).

[0016] Furthermore, in step S1, the concentration of the sodium carboxymethyl cellulose solution is 0.1-2.0 g / L.

[0017] Furthermore, in step S1, the concentration of the NaOH solution is 0.01-2.0M.

[0018] Furthermore, in step S1, the concentration of the H2SeO3 solution is 0.01-2.0M.

[0019] Furthermore, in step S1, the concentration of the NaBH4 solution is 0.01-2.0M.

[0020] Furthermore, in step S1, the molar ratio of the NaOH solution to the H2SeO3 solution is 1:1-1:5.

[0021] Furthermore, in step S1, the steps of synthesizing selenium nanorods are as follows:

[0022] Sodium carboxymethyl cellulose was dissolved in water, and then NaOH solution and H2SeO3 solution were added under stirring. After stirring until the solution was transparent, NaBH4 solution was added dropwise. After stirring for a period of time at room temperature, a brown suspension was obtained. The solid product was collected by centrifugation, washed three times with deionized water and ethanol, and then vacuum dried to obtain selenium nanorods.

[0023] In the above further aspect, the stirring time is 1-6 hours.

[0024] In the above, further, the vacuum drying temperature is 40-90° C., and the drying time is 1-24 hours.

[0025] Further, in step S2, methanol solution: selenium nanorods: polyvinyl pyrrolidone: two metal salts: 2-methylimidazole = 180 mL: (0.2 g to 0.5 g): 1 g: (0.5 g to 5 g): 0.5 g.

[0026] Furthermore, in step S2, the polyvinyl pyrrolidone is PVP-K30.

[0027] The dosage of PVP (K-30) is 1g.

[0028] Further, in step S2, the two metal salts are selected from any one of the following combinations:

[0029] (1)Zn(NO3)2·6H2O and Co(NO3)2·6H2O,

[0030] (2) Zn(NO3)2·6H2O and molybdenum acetate,

[0031] (3) Zn(NO3)2·6H2O and molybdenum nitrate.

[0032] Furthermore, in step S2, the molar ratio of metal elements of the two metal salts is 1:2-1:20.

[0033] Furthermore, in step S2, the mass ratio of 2-methylimidazole to metal salt is 1:1-1:10.

[0034] Furthermore, in step S2, the steps of coating the selenium nanorods with the bimetallic organic framework are as follows:

[0035] The selenium nanorods obtained in step S1 are dispersed in methanol, a certain amount of polyvinyl pyrrolidone is added, and after stirring, methanol solutions of two metal salts are added, and then a methanol solution of 2-methylimidazole is added. After stirring for a period of time, the bimetallic selenide precursor is collected by centrifugation, washed with methanol several times, and vacuum dried to obtain selenium nanorods coated with a bimetallic organic framework.

[0036] In the above further, the concentration of the 2-methylimidazole methanol solution is 0.1-2.0 g / L.

[0037] Furthermore, in the above, the stirring time is 30 minutes to 6 hours.

[0038] In the above, further, the vacuum drying temperature is 40-90° C., and the drying time is 1 to 24 hours.

[0039] Furthermore, in step S3, the insulation temperature is 600-900° C., and the insulation time is 1 to 6 hours.

[0040] Furthermore, in step S3, the inert gas is argon.

[0041] Further, in step S3, the steps of synthesizing the bimetallic selenide heterostructure are as follows:

[0042] The selenium nanorods coated with the bimetallic organic framework obtained in step S2 are heated from room temperature to high temperature at a certain heating rate under the protection of inert gas, and kept at high temperature for a certain period of time, and then naturally cooled to obtain a bimetallic selenide heterostructure.

[0043] Furthermore, in the above, the heating rate is 1-10°C / min.

[0044] The present invention also provides a bimetallic selenide heterostructure. The bimetallic selenide heterostructure obtained by the above preparation method consists of bimetallic selenide nanoparticles and hollow carbon tubes, and the bimetallic selenide nanoparticles are attached to the hollow carbon tubes.

[0045] Furthermore, the diameter of the bimetallic selenide nanoparticles is 5-20 nm.

[0046] Furthermore, the bimetallic selenide nanoparticles are randomly distributed and embedded in the tube wall of the hollow carbon tube.

[0047] In addition, the present invention also provides an application of a bimetallic selenide heterostructure, wherein the bimetallic selenide heterostructure is used to prepare an electrode material for a secondary battery.

[0048] Furthermore, the secondary battery is a lithium-ion battery.

[0049] The bimetallic selenide heterostructure, as a negative electrode material for lithium-ion batteries, exhibits excellent energy storage performance with high capacity, large rate and long cycle.

[0050] Furthermore, the preparation method of the negative electrode material of the lithium ion battery is as follows:

[0051] S1, mixing bimetallic selenide heterostructure, acetylene black and polyvinylidene fluoride (PVDF), adding N-methylpyrrolidone (NMP) as a solvent, and grinding to a uniform black slurry;

[0052] S2, evenly coating the black slurry obtained in step S1 on the copper foil;

[0053] S3, drying the electrode sheet coated in step S2 in a vacuum drying oven to obtain a negative electrode sheet for a lithium-ion battery, and assembling and performing performance testing.

[0054] Furthermore, in step S1, the mass ratio of the bimetallic selenide heterostructure, acetylene black and polyvinylidene fluoride is 6:1:1 to 10:1:1, preferably 8:1:1.

[0055] Furthermore, in step S1, the mass ratio of the bimetallic selenide heterostructure to N-methylpyrrolidone is 1:5.

[0056] Furthermore, in step S2, the coating thickness is 50-200 μm, preferably 100 μm.

[0057] Furthermore, in step S3, the vacuum drying temperature is 60 to 100° C., and the drying time is 6 to 24 hours.

[0058] The technical principles of the present invention are as follows:

[0059] Based on the confinement effect of graphite carbon cages, by injecting the chalcogenide precursor solution into the carbon cage, the chalcogenide grows evenly in the confined space inside the carbon cage, forming a chalcogenide with a short-range ordered structure. This structure can not only improve the structural stability and conductivity of the material, but also effectively alleviate the volume expansion problem of the negative electrode material of the lithium-ion battery during the charging and discharging process, and accelerate the reaction kinetics, thereby improving the overall performance of the battery.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] 1. The present invention studies a preparation method of a novel bimetallic selenide heterostructure and explores its application in secondary batteries. First, Se nanorods with good dispersibility and uniform size are prepared by chemical reduction, and their morphology and size are optimized. Then, a layer of bimetallic organic framework (MOF) is coated by solution method using Se nanorods as templates and selenium sources. Appropriate metal salts and organic ligands are selected, and the molar ratio of metal salts is regulated to prepare Se nanorods coated with bimetallic MOFs of different proportions. Then, the Se nanorods coated with bimetallic MOFs are in situ pyrolyzed under argon protection to convert the bimetallic MOFs into bimetallic selenide nanoparticles, and hollow carbon tubes are formed during the pyrolysis process, and finally a heterostructure in which bimetallic selenide nanoparticles grow on hollow carbon tubes is obtained. Finally, the heterostructure material is used as the negative electrode material of a lithium-ion battery, and the electrochemical performance test is carried out to evaluate its energy storage performance. By studying the electron and ion transport behavior of heterostructure materials in electrochemical reactions, the influence of built-in electric fields on reaction kinetics is explored, and its advantages in improving the energy storage performance of secondary batteries are verified. The research of this invention provides new ideas for the design and preparation of high-performance bimetallic selenide heterostructure materials, and the application of the prepared materials in secondary batteries shows good development prospects and potential.

[0062] 2. Efficient preparation. The present invention uses selenium nanorods as templates and selenium sources, and coats bimetallic MOF on the outside thereof. The heterogeneous structure of bimetallic selenide nanoparticles grown on hollow carbon tubes is synthesized by in-situ pyrolysis, which simplifies the synthesis steps and improves the preparation efficiency.

[0063] 3. Flexible matching: By selecting different metal sources, the composition of bimetallic selenides can be easily adjusted to prepare heterostructure materials with different properties, thus broadening the application range of the materials.

[0064] 4. Excellent performance: The bimetallic selenide heterostructure has a built-in electric field, which can accelerate the transmission of electrons and ions, thereby accelerating the reaction kinetics, significantly improving the energy storage performance of secondary batteries, and showing the advantages of high capacity, large rate and long cycle life.

[0065] 5. Stable structure. Using selenium nanorods as a template for one-dimensional structure helps maintain the structural stability of the material during the electrochemical cycle, reduces capacity decay, and improves the cycle stability and durability of the battery.

[0066] 6. Environmentally friendly: the synthesis process of the present invention is relatively mild, the reaction conditions are easy to control, the impact on the environment is reduced, and the controllability and consistency of the material are improved, which has good industrial application prospects.

[0067] 7. Compared with the prior art, the bimetallic selenide designed in the present invention is to first synthesize Se nanorods, then coat the bimetallic MOF on the Se nanorods, and then pyrolyze to obtain a bimetallic selenide with a hollow nanostructure. Conventional selenide synthesis requires the synthesis of oxides first, and then selenization. The method is cumbersome and requires the morphology and structure of the oxides to be regulated first. In the present invention, the Se nanorods are both templates for making one-dimensional structures and provide a Se source. When coating the bimetallic MOF, the choice of bimetals is flexible, and the ratio is also flexible. The method can flexibly regulate the synthesis of any two metal selenides such as CoSe-ZnSe or MoSe-ZnSe, while ensuring the structure of the hollow nanotube. The bimetallic selenide with a hollow structure prepared by the present invention can effectively alleviate the volume expansion during the charge and discharge process, and has better structural stability than solid nanowires.

[0068] In summary, the present invention has significant advantages in improving the lithium storage performance, conductivity and process simplicity of lithium-ion battery negative electrode materials, and has broad application prospects and market value. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is the SEM photograph of the Se nanorods prepared in Example 1.

[0070] Figure 2 This is the SEM photo of the Se nanorod-coated bimetallic Zn-Co MOF prepared in Example 1.

[0071] Figure 3 This is a TEM image of the ZnSe / CoSe heterostructure prepared in Example 1.

[0072] Figure 4 This is the XRD spectrum of the ZnSe / CoSe heterostructure prepared in Example 1.

[0073] Figure 5 This is a high-resolution TEM image of the ZnSe / CoSe heterostructure prepared in Example 1.

[0074] Figure 6 This is a cycling performance diagram of the ZnSe / CoSe heterostructure prepared in Example 1. DETAILED DESCRIPTION

[0075] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0076] In conjunction with the accompanying drawings, some embodiments of the present invention are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0077] Example 1

[0078] This embodiment provides a method for preparing a bimetallic selenide heterostructure, and the specific steps are as follows:

[0079] (1) Synthesis of selenium nanorods:

[0080] 1 g of sodium carboxymethyl cellulose (CMC-Na) was dissolved in 10 mL of water, and then 10 mL of NaOH solution (1.0 M) and 10 mL of H2SeO3 solution (1.0 M) were added under stirring. When the above solution was stirred until transparent, NaBH4 solution (1.0 mL, 1.0 M) was added dropwise. After stirring at room temperature for 3 hours, the mixed solution became a brown suspension. The solid product was collected by centrifugation, washed three times with deionized water and ethanol, and then vacuum dried at 60 ° C for 12 hours to obtain Se nanorods. As shown in the attached Figure 1 As shown, the SEM image of Se nanorods shows that this method successfully prepared a one-dimensional nanorod structure.

[0081] (2) Synthesis of bimetallic selenide heterostructures:

[0082] 0.3 g of the obtained Se nanorods were dispersed in 90 mL of methanol, 1 g of PVP (K-30) was added, and the mixture was stirred continuously. Then, 0.5 g of Zn (NO3) 2·6H2O and Co (NO3) 2·6H2O were added, and the metal element molar ratio of the two metal salts was controlled to be 1:16, respectively, and stirred for 2 hours. Subsequently, 0.5 g of 2-methylimidazole was weighed and dissolved in 90 mL of methanol, and the above solution was slowly mixed. After stirring for 30 minutes, the precursor (Se nanorods @ Zn-Co MOF) was collected by centrifugation, washed with methanol 2-3 times, and then vacuum dried at 60 ° C for 12 hours.

[0083] (3) Synthesis of bimetallic selenide heterostructures:

[0084] The dried sample was heated from room temperature to 700°C at a heating rate of 5°C / min under argon protection, kept at this temperature for 3 hours, and cooled naturally to obtain a bimetallic selenide heterostructure.

[0085] As attached Figure 2 As shown, the SEM image of Se nanorods coated with bimetallic Zn-Co MOF shows that the outside is coated with MOF.

[0086] As attached Figure 3 As shown, the TEM image of the ZnSe / CoSe heterostructure shows a hollow tubular structure.

[0087] As attached Figure 4 As shown, the XRD pattern of ZnSe / CoSe heterostructures illustrates the existence of two phases of ZnSe and CoSe.

[0088] As attached Figure 5 As shown, the high-resolution TEM image of the ZnSe / CoSe heterostructure shows that this method successfully achieves the growth of the two-phase heterostructure together and the existence of a heterojunction interface.

[0089] In addition, this embodiment also provides an application of a bimetallic selenide heterostructure, wherein the bimetallic selenide heterostructure is used to prepare a negative electrode material for a lithium-ion battery.

[0090] In this embodiment, the preparation method of the negative electrode material of the lithium ion battery is as follows:

[0091] The bimetallic selenide heterostructure prepared above was mixed with acetylene black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, and N-methylpyrrolidone (NMP) was added as a solvent, and ground into a uniform black slurry. The slurry was evenly coated on a copper foil with a coating thickness of 100 μm. The coated electrode sheet was dried in a vacuum drying oven at 80°C for 12 hours to obtain a negative electrode sheet for a lithium-ion battery.

[0092] Battery assembly and performance testing:

[0093] The prepared negative electrode sheet and the metal lithium sheet were assembled into a button cell and a standard electrolyte was used. The charge and discharge performance of the button cell was tested as shown in the attached Figure 6 As shown in the cycling performance diagram of the ZnSe / CoSe heterostructure, the specific capacity remains at 1419 mAh g after 100 cycles at a current density of 0.2 A / g. -1 Therefore, the bimetallic selenide heterostructure prepared by this method has excellent energy storage performance as a lithium-ion anode material, including high capacity, large rate and long cycle stability.

[0094] Example 2

[0095] This embodiment provides a method for preparing a bimetallic selenide heterostructure, and the specific steps are as follows:

[0096] (1) Synthesis of selenium nanorods:

[0097] 1 g of sodium carboxymethyl cellulose (CMC-Na) was dissolved in 30 mL of water, and then 10 mL of NaOH solution (1.0 M) and 10 mL of H2SeO3 solution (1.0 M) were added under stirring. When the above solution was stirred until transparent, NaBH4 solution (1.0 mL, 1.0 M) was added dropwise. After stirring at room temperature for 3 hours, the mixed solution became a brown suspension. The solid product was collected by centrifugation, washed three times with deionized water and ethanol, and then vacuum dried at 60 ° C for 12 hours to obtain Se nanorods.

[0098] (2) Synthesis of bimetallic selenide heterostructures:

[0099] 0.5 g of the obtained Se nanorods were dispersed in 90 mL of methanol, containing 1 g of PVP (K-30), and stirred continuously. Then, 0.5 g of Zn (NO3) 2·6H2O and Co (NO3) 2·6H2O were added, and the molar ratio of the metal elements of the two metal salts was controlled to be 1:4, respectively, and stirred for 2 hours. Subsequently, 0.5 g of 2-methylimidazole was weighed and dissolved in 90 mL of methanol, and the above solution was slowly mixed. After stirring for 30 minutes, the precursor (Se nanorods @ Zn-Co MOF) was collected by centrifugation, washed with methanol 2-3 times, and then vacuum dried at 60 ° C for 12 hours.

[0100] (3) Synthesis of bimetallic selenide heterostructures:

[0101] The dried sample was heated from room temperature to 700°C at a heating rate of 5°C / min under argon protection, kept at this temperature for 3 hours, and cooled naturally to obtain a bimetallic selenide heterostructure.

[0102] In addition, this embodiment also provides an application of a bimetallic selenide heterostructure, wherein the bimetallic selenide heterostructure is used to prepare a negative electrode material for a lithium-ion battery.

[0103] In this embodiment, the preparation method of the negative electrode material of the lithium ion battery is as follows:

[0104] The bimetallic selenide heterostructure prepared above was mixed with acetylene black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, and N-methylpyrrolidone (NMP) was added as a solvent, and ground into a uniform black slurry. The slurry was evenly coated on a copper foil with a coating thickness of 200 μm. The coated electrode sheet was dried in a vacuum drying oven at 80°C for 12 hours to obtain a negative electrode sheet for a lithium-ion battery.

[0105] Battery assembly and performance testing:

[0106] The prepared negative electrode sheet and the metal lithium sheet were assembled into a button cell, and a standard electrolyte was used. The charge and discharge performance of the button cell was tested, and the results showed that the button cell maintained a capacity of 1419 mAh / g after 100 cycles at a current density of 0.2 A / g, and the capacity retention rate was 98.2%. Therefore, the bimetallic selenide heterostructure has excellent energy storage performance as a lithium-ion negative electrode material, including high capacity, high rate and long cycle stability.

[0107] Example 3

[0108] This embodiment provides a method for preparing a bimetallic selenide heterostructure, and the specific steps are as follows:

[0109] (1) Synthesis of selenium nanorods:

[0110] 2 g of sodium carboxymethyl cellulose (CMC-Na) was dissolved in 80 mL of water, and then 10 mL of NaOH solution (1.0 M) and 10 mL of H2SeO3 solution (1.0 M) were added under stirring. When the above solution was stirred until transparent, NaBH4 solution (1.0 mL, 1.0 M) was added dropwise. After stirring at room temperature for 3 hours, the mixed solution became a brown suspension. The solid product was collected by centrifugation, washed three times with deionized water and ethanol, and then vacuum dried at 60 ° C for 12 hours to obtain Se nanorods.

[0111] (2) Synthesis of bimetallic selenide heterostructures:

[0112] 0.2 g of the obtained Se nanorods were dispersed in 90 mL of methanol, containing 1 g of PVP (K-30), and stirred continuously. Then, 0.5 g of Zn (NO3) 2·6H2O and Co (NO3) 2·6H2O were added, and the molar ratio of the metal elements of the two metal salts was controlled to be 1:8, respectively, and stirred for 2 hours. Subsequently, 0.5 g of 2-methylimidazole was weighed and dissolved in 90 mL of methanol, and the above solution was slowly mixed. After stirring for 30 minutes, the precursor (Se nanorods @ Zn-Co MOF) was collected by centrifugation, washed with methanol 2-3 times, and then vacuum dried at 60 ° C for 12 hours.

[0113] (3) Synthesis of bimetallic selenide heterostructures:

[0114] The dried sample was heated from room temperature to 700°C at a heating rate of 5°C / min under argon protection, kept at this temperature for 3 hours, and cooled naturally to obtain a bimetallic selenide heterostructure.

[0115] In addition, this embodiment also provides an application of a bimetallic selenide heterostructure, wherein the bimetallic selenide heterostructure is used to prepare a negative electrode material for a lithium-ion battery.

[0116] In this embodiment, the preparation method of the negative electrode material of the lithium ion battery is as follows:

[0117] The bimetallic selenide heterostructure prepared above was mixed with acetylene black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, and N-methylpyrrolidone (NMP) was added as a solvent, and ground into a uniform black slurry. The slurry was evenly coated on a copper foil with a coating thickness of 150 μm. The coated electrode sheet was dried in a vacuum drying oven at 80°C for 12 hours to obtain a negative electrode sheet for a lithium-ion battery.

[0118] Battery assembly and performance testing:

[0119] The prepared negative electrode sheet and the metal lithium sheet were assembled into a button cell, and a standard electrolyte was used. The charge and discharge performance of the button cell was tested. The bimetallic selenide heterostructure as a lithium ion negative electrode material has excellent energy storage performance, including high capacity, high rate and long cycle stability.

[0120] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a bimetallic selenide heterostructure, characterized in that: The specific steps are as follows: S1. Synthesis of selenium nanorods: The sodium carboxymethyl cellulose solution, the NaOH solution, the H2SeO3 solution and the NaBH4 solution are stirred and mixed to obtain selenium nanorods; S2, bimetallic organic framework coated selenium nanorods: Sequentially adding the selenium nanorods obtained in step S1, polyvinyl pyrrolidone, two metal salts and 2-methylimidazole to the methanol solution, and stirring to obtain the selenium nanorods coated with the bimetallic organic framework; S3. Synthesis of bimetallic selenide heterostructures: The selenium nanorods coated with the bimetallic organic framework obtained in step S2 are placed under the protection of an inert gas and kept at a high temperature to obtain a bimetallic selenide heterostructure.

2. The method for preparing a bimetallic selenide heterostructure according to claim 1, characterized in that: In step S1, the volume ratio of the sodium carboxymethyl cellulose solution, the NaOH solution, the H2SeO3 solution and the NaBH4 solution is (1-10):1:(1-5):(0.1-0.5); The concentration of the sodium carboxymethylcellulose solution is 0.1-2.0 g / L, The concentration of the NaOH solution is 0.01-2.0M, The concentration of the H2SeO3 solution is 0.01-2.0M, The concentration of the NaBH4 solution is 0.01-2.0M.

3. The method for preparing a bimetallic selenide heterostructure according to claim 1, characterized in that: In step S1, the steps of synthesizing selenium nanorods are as follows: Sodium carboxymethyl cellulose was dissolved in water, and then NaOH solution and H2SeO3 solution were added under stirring. After stirring until the solution was transparent, NaBH4 solution was added dropwise. After stirring for a period of time at room temperature, a brown suspension was obtained. The solid product was collected by centrifugation, washed three times with deionized water and ethanol, and then vacuum dried to obtain selenium nanorods.

4. The method for preparing a bimetallic selenide heterostructure according to claim 1, characterized in that: In step S2, methanol solution: selenium nanorods: polyvinyl pyrrolidone: two metal salts: 2-methylimidazole = 180 mL: (0.2 g to 0.5 g): 1 g: (0.5 g to 5 g): 0.5 g; The two metal salts are selected from any one of the following combinations: (1)Zn(NO3)2·6H2O and Co(NO3)2·6H2O, (2) Zn(NO3)2·6H2O and molybdenum acetate, (3) Zn(NO3)2·6H2O and molybdenum nitrate; The molar ratio of metal elements of the two metal salts is 1:2-1:

20.

5. The method for preparing a bimetallic selenide heterostructure according to claim 1, characterized in that: In step S2, the steps of coating the selenium nanorods with the bimetallic organic framework are as follows: The selenium nanorods obtained in step S1 are dispersed in methanol, a certain amount of polyvinyl pyrrolidone is added, and after stirring, methanol solutions of two metal salts are added, and then a methanol solution of 2-methylimidazole is added. After stirring for a period of time, the bimetallic selenide precursor is collected by centrifugation, washed with methanol several times, and vacuum dried to obtain selenium nanorods coated with a bimetallic organic framework.

6. The method for preparing a bimetallic selenide heterostructure according to claim 1, characterized in that: In step S3, the holding temperature is 600-900°C and the holding time is 1-6 hours. The inert gas is argon; In step S3, the steps of synthesizing the bimetallic selenide heterostructure are as follows: The selenium nanorods coated with the bimetallic organic framework obtained in step S2 are heated from room temperature to high temperature at a certain heating rate under the protection of inert gas, and kept at high temperature for a certain period of time, and then naturally cooled to obtain a bimetallic selenide heterostructure.

7. A bimetallic selenide heterostructure, characterized in that: The bimetallic selenide heterostructure obtained by the preparation method described in any one of claims 1 to 6 consists of bimetallic selenide nanoparticles and hollow carbon tubes, and the bimetallic selenide nanoparticles are attached to the hollow carbon tubes.

8. A bimetallic selenide heterostructure according to claim 7, characterized in that: The diameter of the bimetallic selenide nanoparticles is 5-20 nm.

9. An application of a bimetallic selenide heterostructure, characterized in that: The bimetallic selenide heterostructure obtained by the preparation method described in any one of claims 1 to 6 is used to prepare electrode materials for secondary batteries.

10. The use of a bimetallic selenide heterostructure according to claim 9, characterized in that: The secondary battery is a lithium-ion battery, The bimetallic selenide heterostructure is used as a negative electrode material for a lithium-ion battery.

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