Preparation method and application of ZnS-MXene heterostructure

Abstract

The invention discloses a preparation method and application of a ZnS-MXene heterostructure, and belongs to the technical field of nano composite materials and application thereof. And performing in-situ growth of ZnS nanospheres on the surface of the MXene nanosheet through mild water bath heating to obtain the ZnS-MXene heterostructure material. According to the ZnS-MXene prepared by the preparation method disclosed by the invention, the high conductivity characteristic of MXene is reserved, the self-stacking of MXene nanosheets is effectively inhibited, and more active sites for adsorbing and catalyzing the conversion of polysulfide are exposed; meanwhile, the built-in electric field of the heterogeneous interface can further adjust the electronic structure and promote electron / Li < + > migration. When being applied to battery diaphragm modification, the composite material can effectively accelerate sulfur redox reaction, improve the sulfur utilization rate and relieve the shuttle effect.

Description

Technical Field

[0001] The present invention relates to the technical field of nanocomposite materials and their applications, and in particular to a preparation method of a ZnS-MXene heterostructure and its application. Background Art

[0002] With the growing demand for portable electronics, electric vehicles, and smart grids, more diverse energy storage systems are needed to replace traditional lithium-ion batteries. Lithium-sulfur batteries are considered one of the most promising next-generation energy storage systems, however, their further commercial application still faces many problems, such as low sulfur utilization, fast capacity decay, and poor rate performance. Extensive studies have shown that the most important problem is the notorious "shuttle effect".

[0003] In order to suppress the shuttle effect, MXene, as a new type of two-dimensional transition metal carbide / carbonitride material, is introduced into lithium-sulfur batteries as a catalyst to accelerate the adsorption-catalytic conversion reaction of sulfur species due to its good conductivity, two-dimensional structure and rich surface functional groups, especially the ability to interact strongly with polysulfides through Ti-S bonds. However, pure MXene materials have a strong tendency to self-stacking due to their large specific surface area and the action of a large number of hydrogen bonds, and often lack sufficient active sites. Therefore, it is necessary to controllably manipulate the MXene surface to maximize the activity and efficiency of lithium-sulfur batteries. It is reported that MXene-derived heterostructures not only have the characteristics of preventing nanosheet stacking, but also can synergistically utilize the advantages of different materials to better reduce the reaction energy barrier, thereby accelerating redox kinetics. However, the preparation of MXene-derived heterostructures usually involves high-temperature reactions, which can easily lead to MXene oxidation, thereby reducing conductivity and greatly hindering its application. Therefore, how to further enhance its catalytic activity in polysulfide conversion without sacrificing the original properties of MXene remains a challenge. In response to the above problems, the present invention provides a preparation method and application of ZnS-MXene heterostructures. Summary of the invention

[0004] The purpose of the present invention is to provide a preparation method of a ZnS-MXene heterostructure and an application thereof. The prepared ZnS-MXene heterostructure is applied to the diaphragm modification of a lithium-sulfur battery, which can accelerate the sulfur redox reaction, improve the sulfur utilization rate and mitigate the shuttle effect, and improve the long-cycle stability and service life of the lithium-sulfur battery.

[0005] To achieve the above object, the present invention provides a method for preparing a ZnS-MXene heterostructure, comprising the following steps:

[0006] (1) LiF is added to HCl solution and mixed evenly, Ti3AlC2 MAX is added and heated in a water bath and stirred for reaction, and then centrifuged to remove the precipitate to obtain a MXene solution;

[0007] (2) The MXene solution is added to the zinc nitrate aqueous solution and stirred to uniformly adsorb zinc ions on the surface of the MXene nanosheets. Then, concentrated nitric acid, thioacetamide and deionized water are added in sequence. The mixture is refluxed and heated in a low-temperature water bath to react so that zinc sulfide nanospheres nucleate and grow in situ on the surface of the MXene nanosheets. After the reaction is completed, the mixture is cooled, centrifuged and washed, and then vacuum dried to obtain a ZnS-MXene heterostructure.

[0008] Preferably, in step (1), the amount of LiF used is 0.8-1.6 g; the amount of HCl solution used is 10-20 mL, and the concentration is 9 M; and the amount of Ti3AlC2 MAX used is 0.5-1 g.

[0009] Preferably, in step (1), the water bath heating reaction temperature is 32° C. and the reaction time is 48 h.

[0010] Preferably, in step (1), the concentration of the obtained MXene solution is 10 mg / mL.

[0011] Preferably, in step (2), the amount of MXene solution used is 7.5 to 15 mL; the amount of zinc nitrate aqueous solution used is 10 to 20 mL, and the concentration is 30 mg / mL.

[0012] Preferably, in step (2), the amount of concentrated nitric acid used is 25-50 μl, and the concentration is 16 M; the amount of thioacetamide used is 0.9-1.8 g; and the amount of deionized water used is 12.5-25 mL.

[0013] Preferably, in step (2), the temperature of the low-temperature water bath is 60-70° C., and the reflux heating time is 3-4 h.

[0014] Preferably, in step (2), the washing solution is deionized water and isopropanol, and the vacuum drying temperature is 50°C.

[0015] The present invention also provides a ZnS-MXene heterostructure prepared by the above preparation method.

[0016] The present invention also provides the application of the ZnS-MXene heterostructure prepared above in the modification of lithium-sulfur battery separators.

[0017] Therefore, the present invention provides a preparation method of a ZnS-MXene heterostructure and its application, and the specific beneficial effects are as follows:

[0018] (1) The present invention adopts a low-temperature in-situ method to prepare ZnS-MXene heterostructures, which can prevent MXene oxidation and self-stacking, thereby exposing more active sites while retaining its high conductivity, which is conducive to the efficient catalytic conversion of polysulfides. The operation process is simple and easy to obtain, and has good application prospects;

[0019] (2) The ZnS-MXene heterostructure prepared in the present invention has a built-in electric field at the interface, which can enhance the adsorption-catalytic activity and promote the electron / Li + migration, further improving the redox kinetics of sulfur;

[0020] (3) The ZnS-MXene heterostructure membrane modified material obtained in the present invention is applied to lithium-sulfur batteries, has good cycle stability, and can effectively inhibit the shuttle effect.

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a transmission electron microscope (TEM) image of the ZnS-MXene heterostructure material prepared in an embodiment of the present invention;

[0023] Figure 2 This is a scanning electron microscope (SEM) image of the ZnS-MXene heterostructure material prepared in an embodiment of the present invention;

[0024] Figure 3 This is a high magnification scanning electron microscope (SEM) image of the ZnS-MXene heterostructure material prepared in an embodiment of the present invention;

[0025] Figure 4 This is a graph showing the initial capacity of the ZnS-MXene heterostructure material prepared in an embodiment of the present invention for lithium-sulfur batteries at 0.1C;

[0026] Figure 5 This is a charge and discharge cycle diagram of the ZnS-MXene heterostructure material prepared in an embodiment of the present invention used in a lithium-sulfur battery at 0.5C. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Any other changes, modifications, substitutions, combinations, and simplifications made without violating the spirit and principle of the present invention should all be equivalent replacement methods and are included in the protection scope of the present invention. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application, and all belong to the scope of protection of the present invention.

[0028] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0029] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0030] Unless otherwise specified in the present invention, the reagents, instruments, and equipment used are those commonly used by technicians in this field.

[0031] Example

[0032] This embodiment provides a method for preparing a ZnS-MXene heterostructure, which specifically includes the following steps:

[0033] (1) 1.6 g LiF and 20 mL HCl solution (9 M) were mixed evenly, and 1 g Ti3AlC2 MAX was slowly added. The mixture was reacted in a 32 °C water bath under stirring conditions for 48 h. The obtained product was manually peeled off and centrifuged to remove the precipitate to obtain a MXene solution with a concentration of 10 mg / mL.

[0034] (2) Take 7.5 mL of the solution obtained in step (1), add 10 mL of a 30 mg / mL zinc nitrate aqueous solution and stir for 5 min to uniformly adsorb zinc ions on the surface of the MXene nanosheets. Subsequently, 25 μl of concentrated nitric acid (16 M), 0.9 g of thioacetamide and 12.5 mL of deionized water were added in sequence, and refluxed for 3 h in a low-temperature water bath at 70 ° C to allow ZnS nanospheres to nucleate and grow in situ on the surface of the MXene nanosheets. Finally, the resulting product was cooled and washed several times by centrifugation with deionized water and isopropanol, and dried in vacuo at 50 ° C to obtain a ZnS-MXene heterostructure.

[0035] Depend on Figure 1 It can be seen that ZnS nanospheres with an average size of about 300 nm are uniformly grown in situ on the surface of MXene nanosheets to form a ZnS-MXene heterostructure.

[0036] Depend on Figure 2 and Figure 3 It can be seen that the introduction of ZnS inhibits the dense stacking of two-dimensional MXene nanosheets, thereby generating many pores and exposing more active sites.

[0037] The ZnS-MXene heterostructure material prepared in this example was used for diaphragm modification of lithium-sulfur batteries, and button cells were assembled to test the electrochemical properties of the synthesized material.

[0038] (1) Diaphragm preparation: ZnS-MXene heterostructure powder, acetylene black and PVDF were mixed in NMP at a mass ratio of 8:1:1 and magnetically stirred for 12 hours to obtain a mixed slurry. The slurry was evenly coated on a polypropylene diaphragm (Celgard2500) and placed in a vacuum drying oven at 50°C for 12 hours. Finally, the obtained functional diaphragm was punched into a disc with a diameter of 16 mm using a punching machine.

[0039] (2) Preparation of positive electrode: CNTs and sublimed sulfur were mixed in a mass ratio of 1:4 and ground for 30 min, then placed in a sealed vacuum glass tube, and the glass tube containing the powder was heated at 155°C for 12 h. After the glass tube was naturally cooled to room temperature, the obtained product, carbon black and PVDF were mixed in NMP in a mass ratio of 8:1:1, and magnetically stirred for 12 h to obtain a mixed slurry. The above slurry was evenly coated on a carbon-coated aluminum foil, vacuum dried at 60°C for 12 h, and then cut into a circular electrode piece with a diameter of 12 mm (named S-CNT).

[0040] (3) Battery assembly: Button cells are assembled in a glove box, with oxygen and water contents below 0.1ppm. With lithium sheets as the negative electrode, the required electrolyte composition ratios are as follows: the volume ratio of DOL to DME is 1:1, the concentration of LiTFSI is 1M, and the concentration of LiNO3 is 0.1M. The negative electrode shell, positive electrode, electrolyte, diaphragm, electrolyte, lithium sheet, gasket, shrapnel and positive electrode shell are stacked in order, and the corresponding electrochemical tests are performed after being sealed and left to stand for 12 hours.

[0041] like Figure 4 As shown, the discharge capacity at 0.1C is as high as 1230mAhg -1 .like Figure 5 As shown in the graph, the capacity decay rate of each cycle after 500 charge and discharge cycles at a rate of 0.5C is only 0.082%. The experiment shows that the prepared ZnS / Mxene heterostructured membrane modified material has improved sulfur utilization and good cycle stability.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a ZnS-MXene heterostructure, characterized in that: The following steps are involved: (1) LiF is added to HCl solution and mixed evenly, Ti3AlC2 MAX is added and heated in a water bath and stirred for reaction, and then centrifuged to remove the precipitate to obtain a MXene solution; (2) The MXene solution is added to the zinc nitrate aqueous solution and stirred, and then concentrated nitric acid, thioacetamide and deionized water are added in sequence, and refluxed and heated in a low-temperature water bath for reaction. After the reaction is completed, the solution is cooled, centrifuged and washed, and then vacuum dried to obtain a ZnS-MXene heterostructure.

2. The method for preparing a ZnS-MXene heterostructure according to claim 1, characterized in that: In the step (1), the amount of LiF used is 0.8-1.6 g; the amount of HCl solution used is 10-20 mL, and the concentration is 9 M; and the amount of Ti3AlC2 MAX used is 0.5-1 g.

3. The method for preparing a ZnS-MXene heterostructure according to claim 1, characterized in that: In the step (1), the water bath heating reaction temperature is 32° C. and the reaction time is 48 h.

4. The method for preparing a ZnS-MXene heterostructure according to claim 1, characterized in that: In the step (1), the concentration of the obtained MXene solution is 10 mg / mL.

5. The method for preparing a ZnS-MXene heterostructure according to claim 1, characterized in that: In the step (2), the amount of MXene solution used is 7.5 to 15 mL; the amount of zinc nitrate aqueous solution used is 10 to 20 mL, and the concentration is 30 mg / mL.

6. The method for preparing a ZnS-MXene heterostructure according to claim 1, characterized in that: In the step (2), the amount of concentrated nitric acid used is 25-50 μl, and the concentration is 16 M; the amount of thioacetamide used is 0.9-1.8 g; and the amount of deionized water used is 12.5-25 mL.

7. The method for preparing a ZnS-MXene heterostructure according to claim 1, characterized in that: In the step (2), the temperature of the low-temperature water bath is 60-70° C., and the reflux heating time is 3-4 hours.

8. The method for preparing a ZnS-MXene heterostructure according to claim 1, characterized in that: In the step (2), the washing solution is deionized water and isopropanol, and the vacuum drying temperature is 50°C.

9. A ZnS-MXene heterostructure, characterized in that: The ZnS-MXene heterostructure is prepared by the preparation method according to any one of claims 1 to 8.

10. A ZnS-MXene heterostructure according to claim 9, characterized in that: The ZnS-MXene heterostructure is used in separator modification of lithium-sulfur batteries.

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