A method for synthesizing a high-crystallinity hard carbon based on intermolecular hydrogen bonds

Abstract

The application is suitable for the technical field of hard carbon preparation, and provides a synthesis method of high-crystallinity hard carbon based on intermolecular hydrogen bond, which comprises the following steps: dispersing PEA solution in aqueous solution to obtain micellar dispersion liquid; weighing a proper amount of glucose and dissolving the glucose in water to obtain a glucose precursor solution; adding the micellar dispersion liquid into the glucose precursor solution drop by drop to form a complex micellar solution; performing hydrothermal treatment on the complex micellar solution to obtain a pre-carbonization precursor; cleaning the pre-carbonization precursor with water and ethanol alternately, and placing the pre-carbonization precursor in an oven to dry overnight; and placing the dried sample in a crucible to anneal under a nitrogen atmosphere, so that the hard carbon ball with adjustable crystallinity is obtained. The application realizes accurate control of the structure and composition of the precursor at the molecular level, and improves the crystallinity of the hard carbon; by freezing the carbon atom before migration, it is ensured that the carbon atom will not migrate a lot in the subsequent carbonization process, so that the relative order of the carbon structure is ensured.

Description

Technical Field

[0001] This invention belongs to the field of hard carbon preparation technology, and particularly relates to a method for synthesizing highly crystalline hard carbon based on intermolecular hydrogen bonds. Background Technology

[0002] Carbonaceous materials, including graphite, soft carbon, hard carbon, and graphene-related carbons, are all sp. 2 Polycrystalline carbon. Graphite is fully crystalline, and the disorder of the structure gradually increases from soft carbon to hard carbon. Hard carbon materials are named for their mechanical hardness. The key to this "hardness" lies in the solid-phase carbonization of the precursor. Due to the strong cross-linking structure of the initial precursor and the mesophase network during pyrolysis, a fluid state cannot be formed, making the final product difficult to graphitize. Hard carbon materials possess a short-range ordered, few-layer stacked, and oriented disordered microcrystalline structure. This unique microstructure has been theoretically and experimentally proven to synergize with the defects in materials, leading to its wide application in various fields such as catalysis, energy, adsorption, and separation. However, the disorder of the hard carbon structure greatly limits its applications. Adjusting the crystallinity of the hard carbon microstructure is currently a challenge. Effective methods to reduce defects by increasing the carbonization temperature or doping hard carbon materials with soft carbon have been developed, but soft carbon doping often requires cross-linking agents to modify the carbon precursor, making it difficult to achieve the desired effect. On the other hand, hard carbon materials need to be processed at temperatures above 2500°C to obtain a significant increase in crystallinity, but this involves high pyrolysis temperatures that can easily cause environmental pollution. Therefore, developing a new method to obtain highly crystalline hard carbon at low temperatures using simple precursors has become a current research challenge.

[0003] During carbonization, the molten state of the precursor promotes the rearrangement of carbon layers, which is a necessary condition for graphitization. The precursor for preparing hard carbon exists in solid form during pyrolysis; therefore, during the pre-carbonization stage, carbon atoms only migrate to a certain extent, leading to minor atomic rearrangement and ultimately forming a carbon network with high mechanical hardness. The migration of carbon atoms easily causes network interlacing, forming discrete, curved carbon layers, resulting in a reduced degree of graphitization. Therefore, the molecular structure of the precursor is crucial for the carbonization of the mesophase and maintaining the stability of the framework structure during carbonization. Thus, rationally designing the molecular structure of the precursor may be an effective strategy for controlling the crystallinity of hard carbon. Based on the above information, this invention proposes a method for synthesizing highly crystallinity hard carbon based on intermolecular hydrogen bonds. Summary of the Invention

[0004] The purpose of this invention is to provide a method for synthesizing highly crystalline hard carbon based on intermolecular hydrogen bonds, thereby addressing the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for synthesizing highly crystalline hard carbon based on intermolecular hydrogen bonds includes the following steps:

[0007] Step 1: Disperse the PEA solution in an aqueous solution and stir at 600 rpm for 30 min to obtain a micelle dispersion;

[0008] Step 2: Weigh an appropriate amount of glucose and dissolve it in water. Stir at 600 rpm for 30 minutes to obtain a glucose precursor solution.

[0009] Step 3: Add the micelle dispersion obtained in Step 1 dropwise to the glucose precursor solution obtained in Step 2 at a dropping rate of 3 mL / min, and stir at a stirring rate of 600 rpm for more than 30 min to form a composite micelle solution.

[0010] Step 4: Perform solvothermal treatment on the composite micelle solution obtained in Step 3 to obtain the pre-carbonized precursor;

[0011] Step 5: Wash the pre-carbonized precursor obtained in step 4 with water and ethanol alternately, and dry the washed sample in a 60℃ oven for 24 hours.

[0012] Step 6: Place the dried sample into a crucible and anneal it under a nitrogen atmosphere in a tube furnace to obtain hard carbon spheres with adjustable crystallinity.

[0013] Furthermore, in step 4, the heat treatment process specifically involves placing the composite micelle solution obtained in step 3 in an oven at 180°C for 20 hours.

[0014] Furthermore, in step 6, the annealing process is as follows: first, the temperature is increased to 350°C at a heating rate of 2°C / min and held for 3 hours; then, the temperature is increased to 900°C at a heating rate of 5°C / min and held for another 3 hours.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] This method for synthesizing highly crystalline hard carbon based on intermolecular hydrogen bonds achieves precise control over the precursor structure and composition at the molecular level, thereby improving the crystallinity of hard carbon. The method "freezes" carbon atoms before they migrate, ensuring that a large number of carbon atoms do not migrate during subsequent carbonization, thus guaranteeing the relative order of the carbon structure. Attached Figure Description

[0017] Figure 1 The XRD data are for the hard carbon spheres prepared in Examples 1 to 3 of this invention.

[0018] Figure 2 These are the BET data for the hard carbon balls prepared in Examples 1 to 3 of this invention.

[0019] Figure 3 This is a SEM image of the hard carbon spheres prepared in Example 1 of this invention.

[0020] Figure 4 This is a SEM image of the hard carbon spheres prepared in Example 2 of this invention.

[0021] Figure 5 This is a SEM image of the hard carbon spheres prepared in Example 3 of this invention.

[0022] Figure 6 These are the electrochemical data for the hard carbon spheres prepared in Examples 1 to 3 of this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0025] One embodiment of the present invention provides a method for synthesizing highly crystalline hard carbon based on intermolecular hydrogen bonds, comprising the following steps:

[0026] Step 1: Disperse the PEA (polyetheramine) solution in an aqueous solution and stir at 600 rpm for 30 min to obtain a micelle dispersion;

[0027] Step 2: Weigh an appropriate amount of glucose and dissolve it in water. Stir at 600 rpm for 30 minutes to obtain a glucose precursor solution.

[0028] Step 3: Add the micelle dispersion obtained in Step 1 dropwise to the glucose precursor solution obtained in Step 2 at a dropping rate of 3 mL / min, and stir at a stirring rate of 600 rpm for more than 30 min to form a composite micelle solution.

[0029] Step 4: Place the composite micelle solution obtained in Step 3 in an oven at 180℃ for 20 hours to obtain the pre-carbonized precursor (brown sample);

[0030] Step 5: Wash the pre-carbonized precursor obtained in step 4 with water and ethanol alternately, and dry the washed sample in a 60℃ oven for 24 hours.

[0031] Step 6: Place the dried sample into a crucible and anneal it in a tube furnace under a nitrogen atmosphere. First, heat the sample to 350°C at a heating rate of 2°C / min and hold for 3 hours. Then, heat the sample to 900°C at a heating rate of 5°C / min and hold for another 3 hours to obtain hard carbon spheres with adjustable crystallinity.

[0032] In this embodiment of the invention, in addition to glucose, other hydroxyl-rich sugar compounds may be used as raw materials for the reaction.

[0033] Since the intermolecular hydrogen bonds between micelles and carbon precursors can act simultaneously in both precursor synthesis and pre-carbonization processes, the localization of carbon atom migration is ensured, thereby effectively improving the crystallinity of hard carbon materials.

[0034] Example 1: An embodiment of the present invention provides a method for synthesizing highly crystalline hard carbon based on intermolecular hydrogen bonds, comprising the following steps:

[0035] (1) Weigh 0.3g PEA and add it to 8ml of ultrapure water. Stir at 600rpm for 30min to obtain a micelle dispersion.

[0036] (2) Weigh 1g of glucose and add it to 10ml of ultrapure water. Stir at 600rpm for 30min to obtain a homogeneous glucose solution.

[0037] (3) The micelle dispersion from step (1) is added dropwise to the glucose solution obtained in step (2) at a dropping rate of 3 mL / min, and then stirred uniformly at a stirring rate of 600 rpm for 30 min to form a composite micelle solution.

[0038] (4) The composite micelle solution prepared in step (3) is kept in an oven at 180°C for 20 hours to achieve pre-carbonization of the carbon precursor.

[0039] (5) Wash the brown sample obtained by pre-carbonization three times with water and ethanol respectively to remove unreacted intermediates.

[0040] (6) The cleaned sample was dried in an oven at 60℃ for 24 hours.

[0041] (7) Finally, place the dried sample into a crucible and anneal it in a tube furnace under a nitrogen atmosphere. First, heat the sample to 350°C at a heating rate of 2°C / min and hold for 3 hours; then heat the sample to 900°C at a heating rate of 5°C / min and hold for another 3 hours. This will yield PEA-3 hard carbon spheres with controllable crystallinity.

[0042] Example 2: One embodiment of the present invention provides a method for synthesizing highly crystalline hard carbon based on intermolecular hydrogen bonds, comprising the following steps:

[0043] (1) Weigh 0.6g PEA and add it to 8ml of ultrapure water. Stir at 600rpm for 30min to obtain a micelle dispersion.

[0044] (2) Weigh 1g of glucose and add it to 10ml of ultrapure water. Stir at 600rpm for 30min to obtain a homogeneous glucose solution.

[0045] (3) The micelle dispersion from step (1) is added dropwise to the glucose solution obtained in step (2) at a dropping rate of 3 mL / min, and then stirred uniformly at a stirring rate of 600 rpm for 30 min to form a composite micelle solution.

[0046] (4) The composite micelle solution prepared in step (3) is kept in an oven at 180°C for 20 hours to achieve pre-carbonization of the carbon precursor.

[0047] (5) Wash the brown sample obtained by pre-carbonization three times with water and ethanol respectively to remove unreacted intermediates.

[0048] (6) The cleaned sample was dried in an oven at 60℃ for 24 hours.

[0049] (7) Finally, place the dried sample into a crucible and anneal it in a tube furnace under a nitrogen atmosphere. First, heat the sample to 350°C at a heating rate of 2°C / min and hold for 3 hours; then heat the sample to 900°C at a heating rate of 5°C / min and hold for another 3 hours. This will yield PEA-6 hard carbon spheres with controllable crystallinity.

[0050] Example 3: One embodiment of the present invention provides a method for synthesizing highly crystalline hard carbon based on intermolecular hydrogen bonds, comprising the following steps:

[0051] (1) Weigh 0.9g PEA and add it to 8ml of ultrapure water. Stir at 600rpm for 30min to obtain micelle dispersion.

[0052] (2) Weigh 1g of glucose and add it to 10ml of ultrapure water. Stir at 600rpm for 30min to obtain a homogeneous glucose solution.

[0053] (3) The micelle dispersion from step (1) is added dropwise to the glucose solution obtained in step (2) at a dropping rate of 3 mL / min, and then stirred uniformly at a stirring rate of 600 rpm for 30 min to form a composite micelle solution.

[0054] (4) The composite micelle solution prepared in step (3) is kept in an oven at 180°C for 20 hours to achieve pre-carbonization of the carbon precursor.

[0055] (5) Wash the brown sample obtained by pre-carbonization three times with water and ethanol respectively to remove unreacted intermediates.

[0056] (6) The cleaned sample was dried in an oven at 60℃ for 24 hours.

[0057] (7) Finally, place the dried sample into a crucible and anneal it in a tube furnace under a nitrogen atmosphere. First, heat the sample to 350°C at a heating rate of 2°C / min and hold for 3 hours; then heat the sample to 900°C at a heating rate of 5°C / min and hold for 3 hours. This will yield PEA-9 hard carbon spheres with controllable crystallinity.

[0058] In the embodiments of the present invention, the amount of micelle PEA used, in addition to the 0.3g / 0.6g / 0.9g used in Examples 1 to 3, can be adjusted according to the experimenter's needs.

[0059] like Figure 1 The image shows the XRD data of the hard carbon spheres prepared in Examples 1-3. Figure 1 It can be seen that the (002) peak and (100) peak shown in the XRD spectrum of the prepared sample satisfy the two diffraction peaks of carbon materials, and the broad peaks shown indicate that the obtained hard carbon material is amorphous carbon.

[0060] like Figure 2 The image shows the BET data for the hard carbon spheres prepared in Examples 1-3. Figure 2 The BET data of the prepared sample showed that the specific surface area of ​​PEA-3 was 60 m². 2 g -1 The specific surface area of ​​PEA-6 is 14 m². 2 g -1 And the specific surface area of ​​PEA-9 is 4m³. 2 g -1 This confirms that the material synthesized in this invention is a shell-shaped hard carbon sphere.

[0061] like Figure 3 The image shown is a SEM image of the hard carbon spheres prepared in Example 1. Figure 3 It can be seen that its larger wrinkles are due to its larger glucose shell. This indicates that fewer PEA micelles lead to weaker intermolecular hydrogen bonding.

[0062] like Figure 4 The image shown is a SEM image of the hard carbon spheres prepared in Example 2. Figure 4 It can be seen that its moderate wrinkling is due to its medium glucose shell. This indicates that the medium mass of PEA micelles leads to an appropriate amount of intermolecular hydrogen bonding.

[0063] like Figure 5The image shown is a SEM image of the hard carbon spheres prepared in Example 3. Figure 5 It can be seen that its dense wrinkles are due to its relatively thin glucose shell. This indicates that the large number of PEA micelles leads to a high density of intermolecular hydrogen bonding.

[0064] like Figure 6 The figures show the electrochemical data of the hard carbon spheres prepared in Examples 1-3, demonstrating the electrochemical performance of the prepared hard carbon spheres in sodium ion storage. Figure 6 It can be seen that PEA-9 exhibits high carbon crystallinity due to the better fixation effect of molecular hydrogen bonds, thus exhibiting the best sodium storage performance.

[0065] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for synthesizing highly crystalline hard carbon based on intermolecular hydrogen bonds, characterized in that, Includes the following steps: Step 1: Disperse the PEA solution in an aqueous solution and stir at 600 rpm for 30 min to obtain a micelle dispersion; Step 2: Weigh an appropriate amount of glucose and dissolve it in water. Stir at 600 rpm for 30 minutes to obtain a glucose precursor solution. Step 3: Slowly add the micelle dispersion obtained in Step 1 to the glucose precursor solution obtained in Step 2 at a dropping rate of 3 mL / min, and stir at a stirring rate of 600 rpm for more than 30 min to form a composite micelle solution. Step 4: Perform solvothermal treatment on the composite micelle solution obtained in Step 3 to obtain the pre-carbonized precursor; Step 5: Wash the pre-carbonized precursor obtained in step 4 with water and ethanol alternately, and dry the washed sample in a 60℃ oven for 24 hours. Step 6: Place the dried sample into a crucible and anneal it in a tube furnace under a nitrogen atmosphere. First, heat the sample to 350°C at a heating rate of 2°C / min and hold for 3 hours. Then, heat the sample to 900°C at a heating rate of 5°C / min and hold for another 3 hours to obtain hard carbon spheres with adjustable crystallinity.

2. The method for synthesizing highly crystalline hard carbon based on intermolecular hydrogen bonds according to claim 1, characterized in that, In step 4, the heat treatment process specifically involves placing the composite micelle solution obtained in step 3 in an oven at 180°C for 20 hours.

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