Preparation method of layered sulfur-doped carbon composite material

Abstract

The invention provides a preparation method of a layered sulfur-doped carbon composite material, which is applied to a sodium-ion battery material. The preparation method comprises the following steps: dissolving metal nickel ions, 1, 3, 5 trimesic acid, 4-4'dipyridyl and other organic ligands in an ethylene glycol solvent, and preparing a metal organic framework precursor through a hydrothermal method; with the precursor as a template, metal ions are removed through high-temperature calcination and acid pickling, and a layered carbon material is prepared; and mixing and calcining the carbon material and a sulfur source to obtain the layered sulfur-doped carbon sodium battery composite material. And sulfur chains with different lengths are introduced by optimizing and adjusting the ratio of a carbon source to a sulfur source, so that the composite material has excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-ion battery electrode materials, and particularly relates to a preparation method of a layered sulfur-doped carbon composite material. Background Art

[0002] In recent years, fossil energy has conflicted with the goal of green and sustainable development, but energy supply is crucial for human society. Secondary batteries are considered energy storage devices that can be widely applied in environmental protection vehicles, power storage, and power fields. Among them, lithium-ion batteries have been put into practical use due to their advantages such as high energy density, high window voltage, light weight, and no self-discharge. However, with wider applications, the demand for lithium resources conflicts with its abundance on the earth's surface, so the cost of lithium has increased accordingly. At this time, sodium ions, which are in the same group as lithium and have similar chemical properties, make it possible for sodium-ion batteries to replace and supplement lithium-ion batteries. As a key component, the electrode material directly affects the performance of sodium-ion batteries. Developing electrode materials with excellent performance can make the commercialization of sodium-ion batteries possible. Among them, the research on anode materials mainly focuses on intercalation materials based on carbon-based materials, conversion reaction materials based on transition metal oxides / sulfides, and alloy reaction materials.

[0003] Carbon-based materials such as hard carbon, graphene, carbon nanotubes, carbon quantum dots, and some biomass-derived carbons have made significant progress in sodium-ion storage. However, due to the inherent low capacity and conductivity of carbon-based materials, their practical applications have been restricted. Usually, the specific capacity and rate performance of carbon materials can be improved by improving the proportion of pseudocapacitance behavior and diffusion behavior. MOF materials are excellent substrates with adjustable morphology, and the selection of metal ions and organic groups will affect their morphology. Therefore, MOF materials are often used as precursors in material design to increase the specific surface area of materials. A number of studies have shown that introducing heteroatoms into the porous carbon framework is an effective strategy to provide more active sites. Among them, the bonding between sulfur atoms in the carbon framework can expand the interlayer of carbonaceous materials, and more sodium storage sites can be introduced on the basis of increasing the carbon layer spacing.

[0004] It can be seen that reasonably designing the material structure and introducing doping can improve the performance of carbon-based materials in sodium-ion batteries, making it possible for them to be applied in the field of sodium-ion batteries. In the present invention, doping and structure construction are combined. By constructing a MOF precursor, a composite material with a stacked layer structure is obtained. The optimized structure not only facilitates the penetration of the electrolyte but also effectively inhibits the volume expansion of the material during the cycling process. At the same time, the introduction of sulfur atoms increases the carbon layer spacing, and the expanded carbon layer spacing is conducive to the insertion and extraction of sodium ions, thereby making the sodium storage process faster. Combining morphology optimization and composition doping, an anode material for sodium-ion batteries with excellent performance is obtained. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of a layered sulfur-doped carbon composite material in view of the deficiencies of the above-mentioned prior art. The layered structure increases the contact area between the electrode material and the electrolyte, slows down the volume expansion during the sodiation / desodiation process, and the introduction of sulfur doping increases the layer spacing of local graphite carbon, which is beneficial to the insertion and extraction of sodium ions and improves the rate of sodium ion migration.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A layered sulfur-doped carbon composite material is prepared by reacting 1,3,5-benzenetricarboxylic acid and 4,4'-bipyridine organic ligands in an ethylene glycol solvent to form a MOF precursor with controllable morphology. Using this precursor as a template, a layered carbon material is prepared by high-temperature calcination and pickling to remove metal ions, and then the layered sulfur-doped carbon composite material is obtained by mixing and calcining this carbon material with a sulfur source;

[0008] The present invention provides a preparation method of a layered sulfur-doped carbon composite material, which is characterized by including the following steps:

[0009] S1. In an appropriate amount of ethylene glycol solution, a metal nickel salt is mixed with 1,3,5-benzenetricarboxylic acid and 4,4'-bipyridine, and then an appropriate amount of manganese source is added. After stirring evenly, a hydrothermal reaction is carried out. After washing, separating, and drying, a wedge-shaped MOF material of the precursor is obtained;

[0010] S2. The wedge-shaped MOF material of the precursor obtained in S1 is subjected to high-temperature calcination in an argon atmosphere to obtain Ni-Mn-C;

[0011] S3. The Ni-Mn-C obtained in S2 is dissolved in a diluted HCI solution and reacted at a certain temperature for a sufficient time to remove metal ions, obtaining a layered carbon material M-C;

[0012] S4. The M-C obtained in S3 is mixed with an appropriate amount of sulfur source and subjected to high-temperature sulfidation in a tube furnace to finally obtain a layered sulfur-doped carbon material M-SC-S.

[0013] Specifically, in S1, nickel ions are reacted with 1,3,5-benzenetricarboxylic acid and 4,4'-bipyridine organic ligands by a hydrothermal method to form a wedge-shaped MOF precursor, and an appropriate amount of manganese ions is added. The selection of the solvent and the addition of Mn ions have a great influence on the morphology of the wedge-shaped MOF precursor;

[0014] In S2, under the protection of an argon atmosphere, the wedge-shaped MOF precursor is calcined at high temperature to form stacked-layered Ni-Mn-C. At high temperature, organic functional groups hydrogen and crystal water produce Ni-Mn-C, which is dissolved in a hydrochloric acid solution with a certain concentration, and kept at a certain temperature for a sufficient long time to remove metal ions to obtain M-C;

[0015] In S4, M-C is mixed with sulfur powder and calcined at high temperature. At high temperature, sulfur atoms are incorporated into the carbon layer skeleton.

[0016] Furthermore, in S1, the molar ratio of metal nickel ions to manganese ions is 1:0.25 - 1:3, and the molar ratio of all metal ions to 1,3,5-benzenetricarboxylic acid and 4,4'-bipyridine is 1:1:1. The temperature of the hydrothermal reaction is 80°C to 160°C, and the reaction time is 2h to 10h.

[0017] Furthermore, in S1, the metal nickel salt is nickel nitrate.

[0018] Furthermore, in S2, the temperature of the high-temperature calcination is 450°C to 600°C, and the reaction time is 2 to 5h.

[0019] Furthermore, in S3, the concentration of the hydrochloric acid is 1 - 5M, the holding temperature is 140°C to 180°C, and the holding time is 18 - 48h.

[0020] Furthermore, in S4, the sulfur source is sulfur powder, and the mass ratio of M-C to sulfur powder is 1:1. The reaction temperature is 450°C to 600°C, and the reaction time is 2 to 5h.

[0021] The beneficial effects of the present invention are as follows: The present invention prepares a layered manganese-sulfur doped carbon composite material with a structure similar to that of the precursor through a template method. Its special structure is beneficial to slowing down the volume expansion and self-pulverization problems of the electrode material during the charge and discharge process, and can correspondingly improve its cycle stability;

[0022] The introduction of sulfur atoms increases the layer spacing of graphite carbon, which is beneficial to the storage of sodium ions during the cycling process, and reduces the migration resistance of sodium ions. Moreover, the introduction of sulfur atoms increases the defect degree of the carbon layer and introduces more active sites;

[0023] The layered sulfur-doped carbon composite prepared by the present invention has excellent electrochemical performance. It has a discharge specific capacity of 470.8 mAh / g after cycling 100 times at a current density of 0.1 A / g. It still has a discharge specific capacity of 283.3 mAh / g after long cycling 4000 times at a large current density of 10 A / g, and the attenuation rate per cycle is only 0.0048%, reflecting good rate performance and excellent cycle life. Description of the Drawings

[0024] Figure 1XRD pattern of the M-SC-S composite material prepared in Example 1;

[0025] Figure 2 SEM images of the MOF material precursor prepared in Example 1;

[0026] Figure 3 SEM images of the M-SC-S composite material prepared in Example 1;

[0027] Figure 4 Cycling performance graph of the M-SC-S composite material prepared in Example 1 at a current density of 0.1 A / g;

[0028] Figure 5 Cycling performance graph of the M-SC-S composite material prepared in Example 1 at a current density of 10 A / g;

[0029] Figure 6 XRD pattern of the M-C composite material prepared in Comparative Example 1;

[0030] Figure 7 SEM images of the M-SC composite material prepared in Comparative Example 2;

[0031] Figure 8 SEM images of the M-SC-S-1 composite material prepared in Comparative Example 3;

[0032] Figure 9 , Figure 10 Are all comparative graphs of the cycling performance of Example 1 (M-SC-S), Comparative Example 1 (M-C), Comparative Example 2 (M-SC), and Comparative Example 3 (M-SC-S-1) at different current densities. Detailed implementation mode

[0033] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Example 1

[0035] A preparation method of a layered sulfur-doped carbon composite material specifically includes the following steps:

[0036] S1. Dissolve 1 mmol of nickel nitrate, 3 mmol of 1,3,5-benzenetricarboxylic acid, and 3 mmol of 4,4'-bipyridine in an ethylene glycol solution to obtain solution A, and dissolve 2 mmol of manganese chloride in the above solution A; place the mixed solution A in a reaction kettle and heat it to 120 °C for hydrothermal reaction for 4 h; wash the obtained precipitate four times with deionized water and absolute ethanol respectively, and then obtain the MOF precursor after vacuum drying;

[0037] S2. Place the obtained MOF precursor in a tube furnace protected by argon, heat it to 600 °C at a heating rate of 3 °C / min and hold for 3 h to obtain Ni-Mn-C;

[0038] S3. Dissolve Ni-Mn@C in 2 M HCl, ultrasonically disperse it evenly, and then heat it to 150 °C to react fully for 24 h to remove metal ions, obtaining the M-C composite material.

[0039] S4. Mix 80 mg of M-C with 80 mg of S powder, and perform high-temperature calcination in a tube furnace filled with argon at a temperature of 600 °C and hold for 3 h to obtain the M-SC-S composite material.

[0040] Figure 1 XRD pattern of the M-SC-S composite material prepared in Example 1. It can be seen from the XRD pattern that a bulging peak appears near 25°. The peak shape characteristics indicate that the material is a typical amorphous carbon material. The XRD results show that the M-SC-S composite material has been successfully synthesized. Figure 2 ,3 SEM images of the MOF and M-SC-S composite materials prepared in Example 1. It can be seen from the figure that the M-SC-S composite material forms a layered structure composed of nanosheets stacked along one direction, and there are obvious layer voids between the nanosheets.

[0041] Comparative Example 1

[0042] This comparative example provides a preparation method of Comparative Example 1 (M-C), which specifically includes the following steps:

[0043] Prepare Comparative Example 1 according to the first three steps of the example. Figure 6 XRD pattern of the M-C composite material prepared in Comparative Example 1. Its peak shape is similar to that of Example 1, but by comparing the angles where the diffraction peaks are located, it can be seen that the diffraction peak angle of M-C is relatively larger.

[0044] Comparative Example 2

[0045] This comparative example provides a preparation method of the Comparative Example 2 (M-SC) composite material, which specifically includes the following steps:

[0046] S1, S2, S3, and S4 are the same as the steps of Example 1 above and will not be repeated here.

[0047] S5. Calcinate the prepared M-SC-S composite material at 500 °C for 2 h to reduce the sulfur atom content in the carbon layer and break some of the long carbon-sulfur chains to obtain short-chain carbon-sulfur bonds.

[0048] Figure 7SEM image of the M-SC composite material prepared in Comparative Example 2. It can be seen from the figure that after the last calcination step, the morphology of this composite material is generally the same as that of M-SC-S.

[0049] Comparative Example 3

[0050] This comparative example provides a method for preparing a composite material of Comparative Example 3 (M-SC-S-1), which specifically includes the following steps:

[0051] S1, S2, and S3 are the same as those in Step 1 of Example 1 above and will not be elaborated here.

[0052] S4. Mix 80 mg of M-C with 320 mg of S powder, and conduct high-temperature calcination in a tubular furnace filled with argon at a temperature of 600 °C for 3 h to obtain the M-SC-S-1 composite material.

[0053] Figure 8 SEM image of the M-SC-S-1 composite material prepared in Comparative Example 3. It can be seen from the figure that excessive sulfur atoms will damage some of the stacked carbon layers, showing a curling phenomenon;

[0054] Application Example

[0055] Mix the composite materials prepared in Example 1 and Comparative Examples 1-3, a conductive agent (Super P), and carboxymethyl cellulose (CMC) evenly at a mass ratio of 7:2:1, add an appropriate amount of ultrapure water to form a slurry, and coat it on a copper foil using a spatula or a four-sided coater to make a negative electrode sheet. Place the coated copper foil in a drying oven at 80 °C for 12 h, then cut the copper foil coated with the material into small round pieces with a diameter of 12 mm, and assemble them into a button battery (CR2032) in a glove box. Using the prepared composite material as the working electrode and a sodium block as the counter electrode, test its electrochemical performance. Among them, the separator uses Whatman GF / A, and the electrolyte system is a solute of 1 M NaF6 and a solvent of 100% DME.

[0056] Perform electrochemical performance tests on the assembled button batteries. The test instruments used for the electrochemical performance tests are as follows: LANHE-CT2001A multi-channel battery test system produced by Wuhan Blue Electronic Co., Ltd., the standing time is 12 h, the voltage window range is: 0.01 - 3 V, the current density range is: 100 - 10000 mA g-1, and the number of cycles range is: 100 - 10000 times.

[0057] Figure 4 Cycling performance graph of the M-SC-S composite material prepared in Example 1 at a current density of 0.1 A / g. It can be seen from the figure that after 100 cycles, this composite material still maintains a discharge specific capacity as high as 470.8 mAh / g, showing good cycling stability.

[0058] Figure 5 Cycling performance graph of the M-SC-S composite material prepared in Example 1 at a current density of 10 A / g. It can be seen from the graph that the composite material still has a discharge specific capacity of 283.3 mAh / g after 4000 cycles, and the attenuation rate per cycle is only 0.0048%, reflecting good rate performance and excellent cycle life.

[0059] Figure 9 , 10 is the rate performance comparison graph of Example 1 (M-SC-S), Comparative Example 1 (M-C), Comparative Example 2 (M-SC) and Comparative Example 3 (M-SC-S-1) at different current densities. It can be seen that Example 1 with the optimal addition amount of sulfur-doped carbon has the best cycling performance.

[0060] From the above experiments, it can be concluded that appropriate sulfur doping can increase the carbon layer spacing of the composite material to achieve a higher sodium ion migration rate and improve the conductivity; and the special morphology structure helps the contact between the active material and the electrolyte and increases the sodium ion storage sites.

[0061] The above-described embodiments only represent the implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be based on the appended claims.

Claims

1. A method for preparing a layered sulfur-doped carbon composite material, characterized in that: The following steps are involved: S1. In an appropriate amount of ethylene glycol solution, a metal nickel salt is mixed with 1,3,5-trimethylbenzene carboxylic acid and 4-4'-bipyridine, and then an appropriate amount of manganese source is added. After stirring evenly, a hydrothermal reaction is carried out. After washing, separation and drying, a wedge-shaped MOF material of the precursor is obtained; S2, calcining the wedge-shaped MOF material of the precursor obtained in S1 at high temperature under an argon atmosphere to obtain Ni-Mn-C; S3, dissolving the Ni-Mn-C obtained in S2 in a diluted HCl solution, and reacting at a certain temperature for a sufficient time to remove metal ions, thereby obtaining a layered carbon material MC; S4, mixing the MC obtained in S3 with an appropriate amount of a sulfur source, and performing high-temperature sulfurization in a tubular furnace to finally obtain a layered sulfur-doped carbon material M-SC-S.

2. The method for preparing a layered sulfur-doped carbon composite material according to claim 1, characterized in that: In S1, the molar ratio of metal nickel ions to manganese ions is 1:0.25-1:3, and the molar ratio of all metal ions to 1,3,5-trimethylbenzene carboxylic acid and 4-4'-bipyridine is 1:1:

1. The temperature of the hydrothermal reaction is 80 to 160 degrees, and the reaction time is 2 hours to 10 hours.

3. The method for preparing a layered sulfur-doped carbon composite material according to claim 2, characterized in that: In S1, the metal nickel salt is nickel nitrate.

4. The method for preparing a layered sulfur-doped carbon composite material according to claim 1, characterized in that: In S2, the high temperature calcination temperature is 450 to 600 degrees, and the reaction time is 2 to 5 hours.

5. The method for preparing a layered sulfur-doped carbon composite material according to claim 1, characterized in that: In S3, the hydrochloric acid concentration is 1-5M, the insulation temperature is 140-180 degrees, and the insulation time is 18-48 hours.

6. The method for preparing a layered sulfur-doped carbon composite material according to claim 1, characterized in that: In the S4, the sulfur source is sulfur powder, and the mass ratio of MC to sulfur powder is 1:1, the reaction temperature is 450 to 600 degrees, and the reaction time is 2 to 5 hours.

Images