Preparation Method and Application of a Sugar-Coated Hawthorn Fruit String-Type Copper-Based Metal-Organic Framework Nanocomposite

Abstract

The present invention discloses a preparation method and application of a sugar-coated haws string-type copper-based metal-organic framework nanocomposite, which includes mixing MnO2, Na3C6H5O7·2H2O, PVP and a methanol solution, and ultrasonically homogenizing to obtain intermediate product 1; adding Cu(NO3)2·3H2O to intermediate product 1, ultrasonically stirring and stirring evenly at room temperature to obtain intermediate product 2; adding C9H6O6 to the methanol solution, and stirring at room temperature to obtain intermediate product 3; mixing intermediate product 2 and intermediate product 3, stirring, washing and sedimenting at room temperature to obtain a sugar-coated haws string-type copper-based metal-organic framework nanocomposite. This method realizes the tandem connection of MnO2 nanorods to Cu-BTC for the first time. The prepared copper-based metal-organic framework nanocomposite has higher stability than MnO2, and this method has the advantages of being fast, without high temperature and a large amount of organic solvents, and has potential application value in improving the cycling performance of lithium-sulfur batteries.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of nanomaterials, and particularly relates to a preparation method and application of a sugar-coated haws-shaped copper-based metal-organic framework nanocomposite material. Background Art

[0002] Manganese dioxide (MnO2) is a multifunctional transition metal oxide that has been widely studied. It has the advantages of environmental friendliness, low price, and rich resources, and has excellent physical and chemical properties. As a polar oxide, MnO2 can be used as an internal mediator to anchor long-chain polysulfides in solution and convert long-chain lithium polysulfide into lower-order polysulfides through chemical reactions, which is beneficial to alleviating the "shuttle effect" of lithium-sulfur batteries. At the same time, due to the polymorphic morphology of manganese dioxide, it is often used in fields such as catalysis, ion exchange, molecular sieve adsorption, and biosensors. However, its lack of sufficient stability limits large-scale industrial applications.

[0003] Copper is a variable-valence metal among transition metals and is a non-precious metal and relatively inexpensive, and is widely used in various catalytic reactions. Copper ions themselves have Lewis acidity and strong electrophilic ability, and can effectively bind to electron-rich centers. In the past decade or so, MOFs constructed using copper salts and electron-rich organic ligands have been widely present in people's vision and have also shown their unique excellent properties as heterogeneous catalysts.

[0004] Currently, there are many preparation methods for composites of metal oxide nanomaterials and MOFs, but these preparation methods of composites are all based on relatively stable noble metals and metal oxide nanomaterials. However, due to the instability of such metal oxide materials during conventional hydrothermal and solvothermal synthesis processes, it is still very difficult to composite MOFs with metal oxide nanorods with poor stability. Summary of the Invention

[0005] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a preparation method for a sugar-coated haws-shaped copper-based metal-organic framework nanocomposite material.

[0008] To solve the above technical problems, the present invention provides the following technical solutions: A preparation method of a sugar-coated haws string-shaped copper-based metal-organic framework nanocomposite, comprising,

[0009] Mix MnO2, Na3C6H5O7·2H2O, PVP and a methanol solution, and ultrasonically mix them evenly to obtain intermediate product 1;

[0010] Add Cu(NO3)2·3H2O to intermediate product 1, ultrasonically mix and stir evenly at room temperature to obtain intermediate product 2;

[0011] Add C9H6O6 to a methanol solution, and stir at room temperature to obtain intermediate product 3;

[0012] Mix the intermediate product 2 and intermediate product 3, stir at room temperature, wash and sediment to obtain a sugar-coated haws string-shaped copper-based metal-organic framework nanocomposite.

[0013] As a preferred embodiment of the preparation method of the present invention, wherein: the diameter of the MnO2 nanorods is 40±3 nm.

[0014] As a preferred embodiment of the preparation method of the present invention, wherein: the mass ratio of MnO2, Cu(NO3)2·3H2O and C9H6O6 is 25:946:460.

[0015] As a preferred embodiment of the preparation method of the present invention, wherein: the mass ratio of Na3C6H5O7·2H2O to PVP is 2:1.

[0016] As a preferred embodiment of the preparation method of the present invention, wherein: when mixing MnO2, Na3C6H5O7·2H2O, PVP and a methanol solution, the ratio of MnO2 to the methanol solution is 25 mg:50 mL.

[0017] As a preferred embodiment of the preparation method of the present invention, wherein: when ultrasonically mixing evenly to obtain intermediate product 1, the ultrasonic time is 1-2 h.

[0018] As a preferred embodiment of the preparation method of the present invention, wherein: when adding C9H6O6 to a methanol solution and stirring at room temperature, the room temperature stirring time is 0.5-1 h.

[0019] As a preferred embodiment of the preparation method of the present invention, wherein: when stirring, washing and sedimenting at room temperature, the stirring time is 10-12 h.

[0020] Another object of the present invention is to overcome the deficiencies in the prior art and provide a sugar-coated haws string-shaped copper-based metal-organic framework nanocomposite.

[0021] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of a sugar-coated haws-on-a-stick-shaped copper-based metal-organic framework nanocomposite in the preparation of a lithium-sulfur battery separator.

[0022] Advantages of the present invention:

[0023] (1) The present invention first proposes a preparation method for a "sugar-coated haws-on-a-stick-shaped" copper-based metal-organic framework nanocomposite. This method realizes the tandem connection of MnO2 nanorods to Cu-BTC for the first time. The prepared copper-based metal-organic framework nanocomposite has higher stability than MnO2, and this method has the advantages of being fast, requiring no high temperature, and using a large amount of organic solvents.

[0024] (2) The "sugar-coated haws-on-a-stick-shaped" copper-based metal-organic framework nanocomposite prepared by the present invention realizes the tight combination of metal oxides and MOFs materials. The prepared composite material has potential application value in improving the cycling performance of lithium-sulfur batteries. Description of the drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0026] Figure 1 is the TEM image of the "sugar-coated haws-on-a-stick-shaped" copper-based metal-organic framework nanocomposite prepared in Example 1 of the present invention;

[0027] Figure 2 is the SEM image of the "sugar-coated haws-on-a-stick-shaped" copper-based metal-organic framework nanocomposite prepared in Example 1 of the present invention;

[0028] Figure 3 is the SEM image of the MnO2 nanowires used in the preparation method of the present invention;

[0029] Figure 4 is the SEM image of pure Cu-BTC of the present invention;

[0030] Figure 5 is the SEM image of the copper-based metal-organic framework nanocomposite prepared in Examples 2-5 of the present invention.

[0031] Figure 6 is the cycling performance comparison chart of Test Example 1, Test Example 2 and the comparative example at a current rate of 0.5 C. Detailed implementation manners

[0032] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific embodiments of the present invention in conjunction with the embodiments of the specification.

[0033] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0034] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or alternative embodiments that exclude each other with other embodiments.

[0035] The method for synthesizing MnO2 nanorods in the present invention: 2 mmol of potassium permanganate and 2 mmol of ammonium fluoride are dissolved in 40 ml of deionized water. After ultrasonic mixing for 30 min, 3 mmol of manganese sulfate tetrahydrate is added, and ultrasonic treatment is continued for 30 min. After the solution is mixed evenly, it is poured into the inner liner of a 75 ml reaction kettle, placed in a high-pressure reaction kettle, and heated in an oven at 160 °C for 12 h. After cooling, it is washed with deionized water and dried to obtain the product MnO2 nanorods.

[0036] In the present invention, PVP (polyvinylpyrrolidone) is purchased from Anychem Chemical Reagent Network, and its molecular weight is K15 - K19.

[0037] Example 1 (PVP:Na3C6H5O7·2H2O = 1:2)

[0038] (1) At room temperature, weigh MnO2 (25 mg), Na3C6H5O7·2H2O (200 mg), and PVP (100 mg), pour them into a methanol solution (50 ml), and react under ultrasonic conditions of 100 W for 1 h to obtain Intermediate Product 1;

[0039] (2) Weigh Cu(NO3)2·3H2O (946 mg) and add it to Intermediate Product 1, perform ultrasonic treatment (1 h) at 100 W and stir (0.5 h) at a normal temperature rotation speed of 400 revolutions per minute to obtain Intermediate Product 2;

[0040] (3) Add C9H6O6 (460 mg) to a methanol solution (50 ml) and stir (0.5 h) at a normal temperature rotation speed of 400 revolutions per minute to obtain Intermediate Product 3;

[0041] (4) Blend the intermediate product 2 and intermediate product 3, stir at a normal temperature rotation speed of 400 revolutions per minute for 10 h, add sufficient deionized water for washing and sedimentation, and then centrifuge to separate the solid. After washing the solid, the solid turns dark brown. Dry the solid in an oven at 60 °C overnight for analysis and characterization.

[0042] Example 2 (PVP:Na3C6H5O7·2H2O = 1:1)

[0043] (1) At room temperature, weigh 25 mg of MnO2, 100 mg of Na3C6H5O7·2H2O, and 100 mg of PVP, pour them into 50 ml of methanol solution, and react under 100 W ultrasonic conditions for 1 h to obtain intermediate product 1;

[0044] (2) Weigh 946 mg of Cu(NO3)2·3H2O and add it to intermediate product 1, perform ultrasonic treatment at 100 W for 1 h and stir at a normal temperature rotation speed of 400 revolutions per minute for 0.5 h to obtain intermediate product 2;

[0045] (3) Add 460 mg of C9H6O6 to 50 ml of methanol solution, and stir at a normal temperature rotation speed of 400 revolutions per minute for 0.5 h to obtain intermediate product 3;

[0046] (4) Blend the intermediate product 2 and intermediate product 3, stir at a normal temperature rotation speed of 400 revolutions per minute for 10 h, add sufficient deionized water for washing and sedimentation, and then centrifuge to separate the solid.

[0047] After washing the solid, the solid turns dark brown. Dry the solid in an oven at 60 °C overnight for analysis and characterization.

[0048] Example 3 (PVP:Na3C6H5O7·2H2O = 1:4)

[0049] (1) At room temperature, weigh 25 mg of MnO2, 400 mg of Na3C6H5O7·2H2O, and 100 mg of PVP, pour them into 50 ml of methanol solution, and react under 100 W ultrasonic conditions for 1 h to obtain intermediate product 1;

[0050] (2) Weigh 946 mg of Cu(NO3)2·3H2O and add it to intermediate product 1, perform ultrasonic treatment at 100 W for 1 h and stir at normal temperature for 0.5 h to obtain intermediate product 2;

[0051] (3) Add 460 mg of C9H6O6 to 50 ml of methanol solution, and stir at a normal temperature rotation speed of 400 revolutions per minute for 0.5 h to obtain intermediate product 3;

[0052] (4) Blend the intermediate product 2 and intermediate product 3, stir at a normal temperature rotation speed of 400 revolutions per minute for (10 h), add sufficient deionized water for washing and sedimentation, and then centrifuge to separate the solid. After washing the solid, it turns dark brown. Dry the solid in an oven at 60 °C overnight for analysis and characterization.

[0053] Example 4 (PVP:Na3C6H5O7·2H2O = 2:1)

[0054] (1) At room temperature, weigh out MnO2 (25 mg), Na3C6H5O7·2H2O (100 mg), and PVP (200 mg), pour them into a methanol solution (50 ml), and react under 100 W ultrasonic conditions for 1 h to obtain intermediate product 1;

[0055] (2) Weigh out Cu(NO3)2·3H2O (946 mg) and add it to intermediate product 1, perform ultrasonic treatment at 100 W for (1 h) and stir at normal temperature for (0.5 h) to obtain intermediate product 2;

[0056] (3) Add C9H6O6 (460 mg) to a methanol solution (50 ml), stir at a normal temperature rotation speed of 400 revolutions per minute for (0.5 h) to obtain intermediate product 3;

[0057] (4) Blend the intermediate product 2 and intermediate product 3, stir at a normal temperature rotation speed of 400 revolutions per minute for (10 h), add sufficient deionized water for washing and sedimentation, and then centrifuge to separate the solid. After washing the solid, it turns dark brown. Dry the solid in an oven at 60 °C overnight for analysis and characterization.

[0058] Example 5 (PVP:Na3C6H5O7·2H2O = 4:1)

[0059] (1) At room temperature, weigh out MnO2 (25 mg), Na3C6H5O7·2H2O (100 mg), and PVP (400 mg), pour them into a methanol solution (50 ml), and react under 100 W ultrasonic conditions for 1 h to obtain intermediate product 1;

[0060] (2) Weigh out Cu(NO3)2·3H2O (946 mg) and add it to intermediate product 1, perform ultrasonic treatment at 100 W for (1 h) and stir at a normal temperature rotation speed of 400 revolutions per minute for (0.5 h) to obtain intermediate product 2;

[0061] (3) Add C9H6O6 (460 mg) to a methanol solution (50 ml), stir at a normal temperature rotation speed of 400 revolutions per minute for (0.5 h) to obtain intermediate product 3;

[0062] (4) Blend the intermediate product 2 and intermediate product 3, stir at a normal temperature rotation speed of 400 revolutions per minute for 10 h, add a sufficient amount of deionized water for washing and sedimentation, and then centrifuge to separate the solid. After washing the solid, it turns dark brown. Dry the solid in an oven at 60 °C overnight for analysis and characterization.

[0063] For the TEM image of the "sugar-coated haws on a stick"-type copper-based metal-organic framework nanocomposite prepared in Example 1, see Figure 1 ; for the SEM image of the "sugar-coated haws on a stick"-type copper-based metal-organic framework nanocomposite prepared in Example 1, see Figure 2 , it can be seen that the "sugar-coated haws on a stick"-type copper-based metal-organic framework nanocomposite was successfully prepared;

[0064] For the SEM images of the "sugar-coated haws on a stick"-type copper-based metal-organic framework nanocomposites prepared in Examples 2-5, see Figure 5 , where (a)-(d) correspond to PVP:Na3C3H3O7·2H2O = 1:1, 1:4, 2:1, 4:1 in sequence. It can be seen that compared with Example 1, the composite effect of its product is poor and it is impossible to form the "sugar-coated haws on a stick" with a specific structure

[0065] For the SEM image of the MnO2 nanowires used in the preparation method of the present invention, see Figure 3 ; for the SEM image of pure Cu-BTC, see Figure 4 , it can be seen that neither of them has a specific "sugar-coated haws on a stick" type.

[0066] Among them, the preparation of pure Cu-BTC:

[0067] Dissolve Cu(NO3)2·3H2O (946 mg) in 50 ml of methanol and stir at normal temperature for 0.5 h to disperse it evenly. Add C9H6O6 (460 mg) to the methanol solution (50 ml), stir at normal temperature for 0.5 h, pour the methanol solution containing C9H6O6 into the methanol solution containing Cu(NO3)2·3H2O, continue to stir at 400 revolutions / min at normal temperature for 4 h, centrifuge, and wash and dry with methanol to obtain pure Cu-BTC.

[0068] Application Example 1

[0069] Preparation of a MnO2 / Cu-BTC modified separator for a lithium-sulfur battery by a separator coating method:

[0070] It is prepared by mixing the MnO2 / Cu-BTC composite material prepared in Example 1 and a binder evenly and then coating it on the surface of the separator. The steps are as follows:

[0071] MnO2 / Cu - BTC and PVDF were mixed evenly at a mass ratio of 9:1 (54 mg: 6 mg) and N - methylpyrrolidone (1 mL) was added to obtain a coating slurry.

[0072] The slurry was evenly coated on the surface of Celgard 2400 separator and vacuum - dried at 60 °C for 12 hours to obtain a modified separator, marked as MnO2 / Cu - BTC modified separator, and the coating thickness was 25 μm.

[0073] Test Example 1

[0074] A lithium - sulfur battery was prepared according to the following steps:

[0075] (1) Sulfur and super p were mixed and ball - milled at a mass ratio of 7:3. The ball - milled sulfur / super p was placed in a reaction kettle and heated to 155 °C for 12 hours. The above sulfur / super p composite material and the binder polyvinylidene fluoride (PVDF) were mixed evenly at a mass ratio of 9:1 and N - methylpyrrolidone was added to obtain a coating slurry. The slurry was evenly coated on the surface of aluminum foil and vacuum - dried at 60 °C to obtain the positive electrode of the lithium - sulfur battery.

[0076] (2) The positive electrode material was cut into thin slices with a diameter of 14 mm to make electrode sheets.

[0077] Using metallic lithium as the counter electrode, a CR2032 coin - type battery was made in a glove box filled with argon. The separator used was the MnO2 / Cu - BTC modified separator, and the electrolyte was 1.0 mol·L -1 lithium bis(trifluoromethanesulfonyl)imide dissolved in a mixed solution of 1,3 - dioxolane and dimethoxyethane with a volume ratio of 1:1, and the additive was anhydrous lithium nitrate with a mass fraction of 1 wt%.

[0078] The charge - discharge performance of the sample was tested using a Land CT2001A battery test system, and the charge - discharge cut - off voltage was 1.7 - 2.8 V.

[0079] Test Example 2

[0080] A lithium - sulfur battery was prepared according to the following steps:

[0081] (1) The preparation of the positive electrode of the lithium - sulfur battery was the same as that in Test Example 1.

[0082] (2) The positive electrode material was cut into thin slices with a diameter of 14 mm to make electrode sheets.

[0083] Using metallic lithium as the counter electrode, a CR2032 coin - type battery was made in a glove box filled with argon. The separator used was the MnO2 modified separator, and the electrolyte was 1.0 mol·L -1Lithium bis(trifluoromethanesulfonyl)imide is dissolved in a mixed solution prepared from 1,3-dioxolane and ethylene glycol dimethyl ether with a volume ratio of 1:1, and the additive is anhydrous lithium nitrate with a mass fraction of 1 wt%.

[0084] The test conditions are the same as those in Test Example 1.

[0085] Comparative Example

[0086] A lithium-sulfur battery, in which the MnO2 / Cu-BTC in the second step is replaced with the original separator, and the others are the same as in Test Examples 1 and 2, and it is prepared according to the following steps:

[0087] (1) The preparation of the positive electrode of the lithium-sulfur battery is the same as that in Test Example 1;

[0088] (2) The positive electrode material is cut into a thin sheet with a diameter of 14 mm to make a pole piece;

[0089] Using metallic lithium as the counter electrode, a CR2032 type button battery is made in a glove box filled with argon. The separator is a commercially available battery separator (purchased from Cyber Electrochemical Materials online, model celgard 2400, made in the United States), and the electrolyte is 1.0 mol·L -1 Lithium bis(trifluoromethanesulfonyl)imide is dissolved in a mixed solution prepared from 1,3-dioxolane and ethylene glycol dimethyl ether with a volume ratio of 1:1, and the additive is anhydrous lithium nitrate with a mass fraction of 1 wt%.

[0090] Figure 6 It is a comparative diagram of the cycle performance of Test Example 1, Test Example 2 and the Comparative Example. Under the condition of discharging at a current rate of 0.5 C, after 50 cycles, the discharge specific capacities of the battery with the MnO2 / Cu-BTC modified separator, the battery with the MnO2 modified separator and the battery with the original separator are 779.6 mAh g -1 , 559.5 mAh·g -1 , 553.1 mAh·g -1 . It can be seen that the battery with the MnO2 / Cu-BTC modified separator shows high specific capacity and cycle stability, while the discharge specific capacity of the battery with the original separator decays severely and is low throughout.

[0091] The present invention takes the separator of the lithium-sulfur battery as the research object, and modifies a layer of MnO2 / Cu-BTC composite material on the surface of the commercial battery separator to improve the cycle performance of the lithium-sulfur battery. Among them, Cu in Cu-BTC 2+It has a strong catalytic effect on the conversion of polysulfides. MnO2 has a strong adsorption effect on polysulfides. Therefore, the MnO2 / Cu-BTC composite material inhibits the dissolution of polysulfides, slows down the shuttle effect, and improves the cycling performance of the battery. When this modified separator is used in a lithium-sulfur battery, it exhibits excellent cycling performance, and its preparation method is simple, low-cost, and environmentally friendly, with good prospects for industrial application.

[0092] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the present invention.

Claims

1. A preparation method of a candied fruit string-shaped copper-based metal-organic framework nanocomposite, characterized in that: including, Mix MnO2 nanorods with Na3C6H5O7·2H2O, PVP, and methanol solution, and ultrasonically mix them evenly to obtain Intermediate Product 1. Among them, the mass ratio of Na3C6H5O7·2H2O to PVP is 2:1; Add Cu(NO3)2·3H2O to Intermediate Product 1, ultrasonically mix it, and stir it evenly at room temperature to obtain Intermediate Product 2; Add C9H6O6 to methanol solution and stir it at room temperature to obtain Intermediate Product 3; Mix Intermediate Product 2 and Intermediate Product 3, stir at room temperature, wash and sediment to obtain the sugar-apple-like copper-based metal-organic framework nanocomposite.

2. The preparation method according to claim 1, characterized in that: The diameter of the MnO2 nanorods is 40±3 nm.

3. The preparation method according to claim 1 or 2, characterized in that: The mass ratio of the MnO2 nanorods, Cu(NO3)2·3H2O, and C9H6O6 is 25:946:

460.

4. The preparation method according to claim 1, characterized in that: Mix the MnO2 nanorods with Na3C6H5O7·2H2O, PVP, and methanol solution. Among them, the ratio of MnO2 nanorods to methanol solution is 25 mg:50 mL.

5. The preparation method according to claim 1, characterized in that: Ultrasonically mix evenly to obtain Intermediate Product 1. Among them, the ultrasonic time is 1-2 h.

6. The preparation method according to claim 1, characterized in that: Add C9H6O6 to methanol solution and stir at room temperature. Among them, the room temperature stirring time is 0.5-1 h.

7. The preparation method according to claim 1, characterized in that: Stir at room temperature, wash and sediment. Among them, the stirring time is 10-12 h.

8. The sugar-apple-like copper-based metal-organic framework nanocomposite prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the sugar-apple-like copper-based metal-organic framework nanocomposite according to claim 8 in the preparation of a lithium-sulfur battery separator.

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