Nitrogen-doped graphene composite material and preparation method thereof

Abstract

The invention discloses a nitrogen-doped graphene composite material and a preparation method thereof, and belongs to the technical field of composite materials. The preparation method comprises the following steps: S1, preparing a nitrogen-doped graphene material; s2, dissolving indium nitrate, 2-amino-benzothiazole and the nitrogen-doped graphene material in a DMF (Dimethyl Formamide) aqueous solution, carrying out hydrothermal reaction, cooling to room temperature, washing and freeze-drying to obtain a nitrogen-doped graphene / indium-based MOF (Metal Organic Framework) material; and S3, adding the nitrogen-doped graphene / indium-based MOF material into the lead acetate dispersion liquid, carrying out ultrasonic treatment, stirring and uniformly mixing, dropwise adding a 2g / L sodium hydroxide solution into the mixed liquid in a stirring state until the solution Ph is 8, then carrying out freeze drying, putting a dried sample into a tubular furnace, and calcining in an inert atmosphere to obtain the nitrogen-doped graphene composite material. When the prepared composite material is applied to the negative electrode of the lead-acid battery, the hydrogen evolution side reaction in the charging process of the negative electrode plate can be remarkably reduced, and the electrochemical performance of the battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a nitrogen-doped graphene composite material and its preparation method. Background Technology

[0002] With the depletion of various non-renewable energy sources, the construction of a green, low-carbon, and sustainable energy system has become the main focus of the energy market. Energy storage batteries are an indispensable part of solving the problem of renewable energy power generation consumption. Currently, traditional lead-acid batteries remain the mainstream choice in the rechargeable battery market due to their advantages of low cost, mature technology, and high safety. The main failure mode of lead-acid batteries is irreversible sulfation on the surface of the negative electrode plate. Extensive research has shown that introducing additional carbon materials, such as carbon black, graphite, activated carbon, carbon nanotubes, and graphene, can significantly suppress sulfation, thereby significantly improving battery cycle life. However, while carbon materials suppress sulfation, they also exacerbate the hydrogen evolution side reaction at the negative electrode plate, especially at the end of charging. This not only reduces coulombic efficiency and damages the microstructure of the electrode plate but also accelerates moisture loss. Severe hydrogen evolution side reactions can lead to electrolyte desiccation, causing battery failure and even safety issues.

[0003] Patent CN119695143A discloses a graphene-lead oxide powder composite material, its preparation method, and its application. This patent involves reacting graphite powder, lead nitrate, and ammonium nitrate at 400-500℃ for 2-4 hours. The generated gas is recovered and treated, and the resulting solid is ground to obtain the graphene-lead oxide powder composite material. This invention's graphene-lead oxide powder composite material requires only one reaction step, uses only graphite powder as the raw material (eliminating the need for expensive graphene), has a simple production process, and requires no intermediate operations. As an additive in the negative electrode formulation of lead-acid batteries, it can significantly improve battery capacity and cycle life. However, this mixing method suffers from uneven mixing of carbon materials and metal oxides, failing to achieve the optimal effect of suppressing hydrogen evolution on the battery's negative electrode. Summary of the Invention

[0004] The purpose of this invention is to provide a nitrogen-doped graphene composite material and its preparation method, so as to solve the problem that the simple physical mixing method in the background technology has the problem of uneven mixing of carbon materials and metal oxides, which cannot achieve the best effect of suppressing hydrogen evolution of battery negative electrode plates.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a nitrogen-doped graphene composite material, comprising the following steps:

[0007] S1. Preparation of nitrogen-doped graphene materials;

[0008] S2. Preparation of nitrogen-doped graphene / indium-based MOF materials:

[0009] Indium nitrate, 2-amino-benzothiazole and nitrogen-doped graphene were dissolved in DMF aqueous solution. The mixture was transferred to a reaction vessel and reacted at 120-140℃ for 12-14 h. After cooling to room temperature, the mixture was washed and freeze-dried to obtain nitrogen-doped graphene / indium-based MOF material.

[0010] The ratio of indium nitrate, 2-amino-benzothiazole, nitrogen-doped graphene material, and DMF aqueous solution is 0.2g:0.08-0.12g:0.03g:30-40mL; the volume ratio of DMF to deionized water in the DMF aqueous solution is 1:1.

[0011] S3. Preparation of nitrogen-doped graphene composite materials:

[0012] Nitrogen-doped graphene / indium-based MOF material was added to lead acetate dispersion, sonicated for 30-40 min and stirred until homogeneous. While stirring, 2 g / L sodium hydroxide solution was added dropwise to the mixture until the solution pH = 8. The mixture was then freeze-dried, and the dried sample was placed in a tube furnace and calcined under an inert atmosphere to obtain nitrogen-doped graphene composite material.

[0013] The ratio of nitrogen-doped graphene / indium-based MOF material to lead acetate dispersion is 0.2g:10mL; the concentration of lead acetate dispersion is 20-60g / L; and the mass ratio of lead acetate to polyvinyl alcohol in lead acetate dispersion is 1:(1-3).

[0014] Furthermore, in step S1, the method for preparing nitrogen-doped graphene material is as follows:

[0015] The graphene aqueous solution was ultrasonically mixed evenly, and then thiourea and urea were added to the solution. The mixture was ultrasonically mixed for 30 minutes and then transferred to a high-pressure reactor for hydrothermal reaction. The solution was washed, freeze-dried, and calcined under a nitrogen atmosphere to obtain nitrogen-doped graphene material.

[0016] The ratio of graphene aqueous solution, thiourea, and urea used was 20 mL: 0.4-1 g: 0.1-0.25 g; the concentration of graphene aqueous solution was 2 mg / L; the hydrothermal reaction temperature was 150℃-180℃ and the time was 12 h; the calcination temperature was 200℃-300℃ and the time was 2 h.

[0017] Furthermore, in step S3, the inert atmosphere is any one of nitrogen, argon, or helium.

[0018] Furthermore, in step S3, the calcination temperature is 450-550℃ and the time is 2-3 hours.

[0019] Furthermore, in step S3, the molecular weight of polyvinyl alcohol is 5500-7000.

[0020] Secondly, the present invention provides a nitrogen-doped graphene composite material, which is prepared by any one of the preparation methods described above.

[0021] The beneficial effects of this invention are:

[0022] (1) This invention first prepares nitrogen-doped graphene / indium-based MOF materials. Indium-based MOF materials can further improve the dispersibility of nitrogen-doped graphene and avoid performance degradation caused by agglomeration. After calcination, indium-based MOF materials form In2O3. In2O3 is a metal oxide with a relatively high hydrogen evolution overpotential. This substance can reduce the hydrogen evolution side reaction during the charging process of the negative electrode plate. When used as a negative electrode additive for lead-acid batteries, it can improve the electrochemical performance of the battery. In addition, indium-based MOF materials contain sulfur, which can form sulfur-doped carbon materials after sintering, which helps to further suppress the hydrogen evolution reaction.

[0023] (2) Nitrogen-doped graphene / indium-based MOF materials contain amino groups, which can react with Pb in lead acetate. 2+ Coordination occurs, anchoring metal ions to the material surface and pores through chemical bonding. This coordination effect can effectively suppress Pb. 2+ Agglomeration during subsequent sintering ensures uniform dispersion within the composite material system. As sintering progresses, lead acetate further transforms into lead oxide (PbO), and the uniformly dispersed PbO optimizes the electrochemical environment of the negative electrode, reducing the probability of hydrogen evolution side reactions during charging, thereby improving the performance stability of lead-acid batteries. Furthermore, the porous structure of indium-based MOF materials, compared to nitrogen-doped graphene alone, is more conducive to the dispersion of Pb in lead acetate. 2+ The dispersion.

[0024] (3) In this invention, polyvinyl alcohol is added to the lead acetate dispersion. Polyvinyl alcohol can improve the dispersion uniformity of lead acetate and other mixtures, thereby improving the electrochemical performance of the battery. Attached Figure Description

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] Figure 1 This is a SEM image of the nitrogen-doped graphene composite material obtained in Example 1 of the present invention;

[0027] Figure 2 This is a SEM image of the nitrogen-doped graphene composite material obtained in Example 2 of the present invention;

[0028] Figure 3This is a SEM image of the nitrogen-doped graphene composite material obtained in Example 3 of the present invention. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0030] Example 1

[0031] A method for preparing a nitrogen-doped graphene composite material includes the following steps:

[0032] S1. Preparation of nitrogen-doped graphene materials:

[0033] 20 mL of a 2 mg / L graphene aqueous solution was ultrasonically mixed until homogeneous. Then, 0.4 g of thiourea and 0.1 g of urea were added to the solution and ultrasonically mixed for 30 min. The mixture was then transferred to a high-pressure reactor for hydrothermal reaction at 170 °C for 12 h. After washing and freeze-drying, the material was calcined at 250 °C for 3 h under a nitrogen atmosphere to obtain nitrogen-doped graphene material.

[0034] S2. Preparation of nitrogen-doped graphene / indium-based MOF materials:

[0035] 0.2 g indium nitrate, 0.08 g 2-amino-benzothiazole and 0.03 g nitrogen-doped graphene material were dissolved in 35 mL of DMF aqueous solution. The volume ratio of DMF to deionized water in the DMF aqueous solution was 1:1. The mixture was transferred to a reaction vessel and reacted at 130 °C for 13 h. After cooling to room temperature, the mixture was washed and freeze-dried to obtain nitrogen-doped graphene / indium-based MOF material.

[0036] S3. Preparation of nitrogen-doped graphene composite materials:

[0037] 0.2 g of nitrogen-doped graphene / indium-based MOF material was added to 10 mL of lead acetate dispersion with a concentration of 20 g / L. The lead acetate dispersion also contained 0.2 g of polyvinyl alcohol with a molecular weight of 6000. The mixture was sonicated for 40 min and stirred until homogeneous. While stirring, 2 g / L sodium hydroxide solution was added dropwise to the mixture until the pH of the solution was 8. The mixture was then freeze-dried. The dried sample was placed in a tube furnace and calcined at 500 °C for 3 h under a nitrogen atmosphere to obtain the nitrogen-doped graphene composite material.

[0038] Example 2

[0039] A method for preparing a nitrogen-doped graphene composite material includes the following steps:

[0040] S1. Preparation of nitrogen-doped graphene materials:

[0041] 20 mL of a 2 mg / L graphene aqueous solution was ultrasonically mixed until homogeneous. Then, 0.7 g of thiourea and 0.2 g of urea were added to the solution and ultrasonically mixed for 30 min. The mixture was then transferred to a high-pressure reactor for hydrothermal reaction at 170 °C for 12 h. After washing and freeze-drying, the material was calcined at 250 °C for 3 h under a nitrogen atmosphere to obtain nitrogen-doped graphene material.

[0042] S2. Preparation of nitrogen-doped graphene / indium-based MOF materials:

[0043] 0.2 g indium nitrate, 0.1 g 2-amino-benzothiazole and 0.03 g nitrogen-doped graphene material were dissolved in 35 mL of DMF aqueous solution. The volume ratio of DMF to deionized water in the DMF aqueous solution was 1:1. The mixture was transferred to a reaction vessel and reacted at 130 °C for 13 h. After cooling to room temperature, the mixture was washed and freeze-dried to obtain nitrogen-doped graphene / indium-based MOF material.

[0044] S3. Preparation of nitrogen-doped graphene composite materials:

[0045] 0.2 g of nitrogen-doped graphene / indium-based MOF material was added to 10 mL of lead acetate dispersion with a concentration of 30 g / L. The lead acetate dispersion also contained 0.4 g of polyvinyl alcohol with a molecular weight of 6000. The mixture was sonicated for 40 min and stirred until homogeneous. While stirring, 2 g / L sodium hydroxide solution was added dropwise to the mixture until the pH of the solution was 8. The mixture was then freeze-dried. The dried sample was placed in a tube furnace and calcined at 500 °C for 3 h under a nitrogen atmosphere to obtain the nitrogen-doped graphene composite material.

[0046] Example 3

[0047] A method for preparing a nitrogen-doped graphene composite material includes the following steps:

[0048] S1. Preparation of nitrogen-doped graphene materials:

[0049] 20 mL of a 2 mg / L graphene aqueous solution was ultrasonically mixed until homogeneous. Then, 1 g of thiourea and 0.25 g of urea were added to the solution and ultrasonically mixed for 30 min. The mixture was then transferred to a high-pressure reactor for hydrothermal reaction at 170 °C for 12 h. After washing and freeze-drying, the material was calcined at 250 °C for 3 h under a nitrogen atmosphere to obtain nitrogen-doped graphene material.

[0050] S2. Preparation of nitrogen-doped graphene / indium-based MOF materials:

[0051] 0.2 g indium nitrate, 0.12 g 2-amino-benzothiazole and 0.03 g nitrogen-doped graphene material were dissolved in 35 mL of DMF aqueous solution. The volume ratio of DMF to deionized water in the DMF aqueous solution was 1:1. The mixture was transferred to a reaction vessel and reacted at 130 °C for 13 h. After cooling to room temperature, the mixture was washed and freeze-dried to obtain nitrogen-doped graphene / indium-based MOF material.

[0052] S3. Preparation of nitrogen-doped graphene composite materials:

[0053] 0.2 g of nitrogen-doped graphene / indium-based MOF material was added to 10 mL of lead acetate dispersion with a concentration of 40 g / L. The lead acetate dispersion also contained 0.6 g of polyvinyl alcohol with a molecular weight of 6000. The mixture was sonicated for 40 min and stirred until homogeneous. While stirring, 2 g / L sodium hydroxide solution was added dropwise to the mixture until the pH of the solution was 8. The mixture was then freeze-dried. The dried sample was placed in a tube furnace and calcined at 500 °C for 3 h under a nitrogen atmosphere to obtain the nitrogen-doped graphene composite material.

[0054] Example 4

[0055] The only difference between this embodiment and Example 3 is that the "40 g / L lead acetate dispersion" in Example 3 is replaced with "50 g / L lead acetate dispersion".

[0056] Example 5

[0057] The only difference between this embodiment and Example 3 is that the "40 g / L lead acetate dispersion" in Example 3 is replaced with "60 g / L lead acetate dispersion".

[0058] Comparative Example 1

[0059] The only difference between this comparative example and Example 1 is that the polyvinyl alcohol in step S3 is omitted. The specific steps of S3 are as follows:

[0060] 0.2 g of nitrogen-doped graphene / indium-based MOF material was added to 10 mL of lead acetate dispersion with a concentration of 20 g / L. The mixture was sonicated for 40 min and stirred until homogeneous. While stirring, 2 g / L sodium hydroxide solution was added dropwise to the mixture until the pH of the solution was 8. The mixture was then freeze-dried. The dried sample was placed in a tube furnace and calcined at 500 °C for 3 h under a nitrogen atmosphere to obtain nitrogen-doped graphene composite material.

[0061] Comparative Example 2

[0062] The only difference between this comparative example and Example 1 is that 2-amino-benzothiazole in step S2 is replaced with 2-aminobenzimidazole. The specific steps of S2 are as follows:

[0063] 0.2 g indium nitrate, 0.08 g 2-aminobenzimidazole and 0.03 g nitrogen-doped graphene were dissolved in 35 mL of DMF aqueous solution with a DMF to deionized water volume ratio of 1:1. The mixture was transferred to a reaction vessel and reacted at 130 °C for 13 h. After cooling to room temperature, the mixture was washed and freeze-dried to obtain nitrogen-doped graphene / indium-based MOF material.

[0064] Comparative Example 3

[0065] The only difference between this comparative example and Example 1 is that 2-amino-benzothiazole in step S2 is replaced with 2-methylimidazole. The specific steps of S2 are as follows:

[0066] 0.2 g indium nitrate, 0.08 g 2-methylimidazole and 0.03 g nitrogen-doped graphene were dissolved in 35 mL of DMF aqueous solution with a DMF to deionized water volume ratio of 1:1. The mixture was transferred to a reaction vessel and reacted at 130 °C for 13 h. After cooling to room temperature, the mixture was washed and freeze-dried to obtain nitrogen-doped graphene / indium-based MOF material.

[0067] Comparative Example 4

[0068] The only difference between this comparative example and Example 1 is that the indium-based MOF material is omitted. The specific steps are as follows:

[0069] S1. Preparation of nitrogen-doped graphene materials:

[0070] 20 mL of a 2 mg / L graphene aqueous solution was ultrasonically mixed until homogeneous. Then, 0.4 g of thiourea and 0.1 g of urea were added to the solution and ultrasonically mixed for 30 min. The mixture was then transferred to a high-pressure reactor for hydrothermal reaction at 170 °C for 12 h. After washing and freeze-drying, the material was calcined at 250 °C for 3 h under a nitrogen atmosphere to obtain nitrogen-doped graphene material.

[0071] S2. Preparation of nitrogen-doped graphene composite materials:

[0072] 0.2 g of nitrogen-doped graphene material was added to 10 mL of lead acetate dispersion with a concentration of 20 g / L. The lead acetate dispersion also contained 0.2 g of polyvinyl alcohol with a molecular weight of 6000. The mixture was sonicated for 40 min and stirred until homogeneous. While stirring, 2 g / L sodium hydroxide solution was added dropwise to the mixture until the pH of the solution was 8. The mixture was then freeze-dried. The dried sample was placed in a tube furnace and calcined at 500 °C for 3 h under a nitrogen atmosphere to obtain the nitrogen-doped graphene composite material.

[0073] The composite materials prepared in Examples 1-5 and Comparative Examples 1-4 were used as additives for the negative electrode of lead-acid batteries, with an addition ratio of 5%. The weight of the composite material was counted as the weight of the lead powder, i.e., the total weight of the composite material and the lead powder was used as the base. In addition, 0.06% short fiber, 1% barium sulfate, 0.3% humic acid, 0.5% acetylene black, 0.25% lignin, 10.15% pure water, and a density of 1.4 g / cm³ were added. 3 8% sulfuric acid was added separately and mixed in a paste mixer to make negative electrode lead paste. For the positive electrode, based on the weight of lead powder, 0.1% short fiber, 0.1% stannous sulfate, 0.2% antimony trioxide, 0.1% bismuth trioxide, and 5% red lead were added separately and mixed in a paste mixer to make positive electrode lead paste. All other components were manufactured using the same process to create 2V 20Ah single-cell experimental batteries. The 2-hour capacity and cycle life of the batteries were tested. 2-hour capacity was tested according to GB / T22199.1-2017; cycle life was tested according to GB / T22199.1-2017. The test results are shown in Table 1.

[0074] Table 1

[0075] project 2hr capacity / Ah Cycle life / times Example 1 22.4 472 Example 2 22.7 476 Example 3 23.1 483 Example 4 23.6 489 Example 5 24.0 493 Comparative Example 1 21.3 452 Comparative Example 2 21.5 457 Comparative Example 3 20.4 446 Comparative Example 4 19.8 431

[0076] As can be seen from Table 1, the 2hr capacity and cycle life of the composite materials prepared in Examples 1-5 are higher than those in Comparative Examples 1-4.

[0077] In Comparative Example 1, the polyvinyl alcohol in step S3 was omitted, and the 2-hour capacity and cycle life were lower than those in Example 1. This indicates that polyvinyl alcohol can improve the dispersion uniformity of lead acetate and other mixtures, thereby improving the electrochemical performance of the battery.

[0078] In Comparative Example 2, 2-amino-benzothiazole in step S2 was replaced with 2-amino-benzimidazole. The 2-hr capacity and cycle life were lower than those in Example 1, indicating that the amino group can react with Pb in lead acetate. 2+ Coordination occurs, anchoring metal ions to the material surface and pores through chemical bonding. This coordination effect can effectively suppress Pb. 2+ Agglomeration during subsequent sintering process allows it to be uniformly dispersed within the composite material system.

[0079] In Comparative Example 3, 2-amino-benzothiazole in step S2 was replaced with 2-methylimidazole. The 2hr capacity and cycle life were lower than those in Example 1, indicating that sulfur can form sulfur-doped carbon materials after sintering, which helps to further suppress the hydrogen evolution reaction.

[0080] In Comparative Example 4, indium-based MOF material was omitted. The 2-hour capacity and cycle life decreased significantly compared to Example 1, indicating that indium-based MOF material can further improve the dispersibility of nitrogen-doped graphene and avoid performance degradation caused by agglomeration. After calcination, indium-based MOF material forms In₂O₃. In₂O₃ is a metal oxide with a relatively high hydrogen evolution overpotential. This substance can reduce hydrogen evolution side reactions during the charging process of the negative electrode plate. When used as a negative electrode additive in lead-acid batteries, it can improve the electrochemical performance of the battery.

[0081] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen-doped graphene composite material, characterized in that, Includes the following steps: S1. Preparation of nitrogen-doped graphene materials; S2. Preparation of nitrogen-doped graphene / indium-based MOF materials: Indium nitrate, 2-amino-benzothiazole and nitrogen-doped graphene were dissolved in DMF aqueous solution and reacted at 120-140℃ for 12-14h. After cooling to room temperature, the mixture was washed and freeze-dried to obtain nitrogen-doped graphene / indium-based MOF material. S3. Preparation of nitrogen-doped graphene composite materials: Nitrogen-doped graphene / indium-based MOF material was added to lead acetate dispersion, sonicated for 30-40 min and stirred until homogeneous. While stirring, 2 g / L sodium hydroxide solution was added dropwise to the mixture until the solution pH = 8. Then, the mixture was freeze-dried and calcined under an inert atmosphere to obtain nitrogen-doped graphene composite material.

2. The method for preparing a nitrogen-doped graphene composite material according to claim 1, characterized in that, In step S1, the preparation method of nitrogen-doped graphene material is as follows: The graphene aqueous solution was ultrasonically mixed evenly, and then thiourea and urea were added to the solution. The mixture was ultrasonically mixed for 30 minutes and then transferred to a high-pressure reactor for hydrothermal reaction. The solution was washed, freeze-dried, and calcined under a nitrogen atmosphere to obtain nitrogen-doped graphene material.

3. The method for preparing a nitrogen-doped graphene composite material according to claim 2, characterized in that, The ratio of graphene aqueous solution, thiourea, and urea is 20 mL: 0.4-1 g: 0.1-0.25 g; the concentration of the graphene aqueous solution is 2 mg / L. The hydrothermal reaction was carried out at a temperature of 150℃-180℃ for 12 hours. The calcination temperature is 200℃-300℃, and the time is 2 hours.

4. The method for preparing a nitrogen-doped graphene composite material according to claim 1, characterized in that, In step S2, the ratio of indium nitrate, 2-amino-benzothiazole, nitrogen-doped graphene material, and DMF aqueous solution is 0.2g:0.08-0.12g:0.03g:30-40mL; the volume ratio of DMF to deionized water in the DMF aqueous solution is 1:

1.

5. The method for preparing a nitrogen-doped graphene composite material according to claim 1, characterized in that, In step S3, the ratio of nitrogen-doped graphene / indium-based MOF material to lead acetate dispersion is 0.2 g: 10 mL.

6. The method for preparing a nitrogen-doped graphene composite material according to claim 1, characterized in that, In step S3, the concentration of the lead acetate dispersion is 20-60 g / L; the mass ratio of lead acetate to polyvinyl alcohol in the lead acetate dispersion is 1:(1-3).

7. The method for preparing a nitrogen-doped graphene composite material according to claim 1, characterized in that, In step S3, the inert atmosphere is any one of nitrogen, argon, or helium.

8. The method for preparing a nitrogen-doped graphene composite material according to claim 1, characterized in that, In step S3, the calcination temperature is 450-550℃ and the time is 2-3 hours.

9. The method for preparing a nitrogen-doped graphene composite material according to claim 1, characterized in that, In step S3, the molecular weight of polyvinyl alcohol is 5500-7000.

10. A nitrogen-doped graphene composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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