Preparation method, product and application of three-dimensional porous molybdenum carbonitride coated carbon nanomaterial
By preparing three-dimensional porous molybdenum carbonitride@carbon nanomaterials, the problem of polysulfide dissolution and diffusion in lithium-sulfur batteries was solved by utilizing their strong chemical interaction and conductivity, thereby improving the cycle stability and discharge capacity of the batteries.
Patent Information
- Application Number
- CN202511156574.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-19
- Publication Date
- 2025-11-21
AI Technical Summary
The dissolution and diffusion of polysulfides in lithium-sulfur batteries lead to severe polarization and capacity decay. Existing carbon materials have weak interactions with polysulfides, making it difficult to effectively prevent their diffusion in the electrolyte.
By employing three-dimensional porous molybdenum carbonitride@carbon nanomaterials, molybdenum carbide and molybdenum nitride existing in the form of nanocrystals are encapsulated in the carbon nanoframework, forming strong chemical forces that restrict polysulfides on the positive electrode side. Combined with conductivity and rich porous structure, this inhibits the diffusion of polysulfides.
It significantly reduces polarization in lithium-sulfur batteries during charging and discharging, improves discharge capacity and cycle stability, enhances conductivity and physicochemical adsorption of polysulfides, and inhibits polysulfide diffusion.
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Figure CN120998966A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-sulfur battery material preparation technology, and in particular to a method for preparing three-dimensional porous molybdenum carbonitride@carbon nanomaterials, products and applications. Background Technology
[0002] Currently, lithium-sulfur batteries are popular due to their high energy density (2600Wh / kg). -1 Sulfur, as a positive electrode active material, is abundant in nature, inexpensive, and environmentally friendly. However, lithium-sulfur batteries still face many problems, such as poor cycle stability, poor rate performance, and short lifespan. This is mainly attributed to the insulating properties of sulfur / lithium sulfide and the shuttle effect caused by the dissolution of intermediate polysulfides. Recent studies have shown that graphene and other nanostructured carbon materials (such as carbon nanotubes (CNTs), porous carbon, etc.) can solve these problems to some extent. These carbon materials generally have high specific surface area, high conductivity, interconnected ion channels, nanoscale pore structures, and mechanical stability. However, their interaction with polysulfides is weak, making it difficult to prevent the dissolution and diffusion of polysulfides into the electrolyte, resulting in severe polarization and capacity decay.
[0003] Therefore, developing a sulfur-loaded composite material that has a strong interaction with polysulfides is of great research significance. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing three-dimensional porous molybdenum carbonitride@carbon nanomaterials, products and applications, in order to solve the problem of severe polarization and capacity decay caused by the dissolution and diffusion of polysulfides in lithium-sulfur batteries.
[0005] To achieve the above objectives, the following technical solution is adopted:
[0006] The first technical solution of the present invention is a three-dimensional porous molybdenum carbonitride@carbon nanomaterial, comprising molybdenum carbide, molybdenum nitride and carbon; wherein the carbon exists in the form of a carbon nanoframework, the carbon nanoframework is a loose and porous three-dimensional structure, and the molybdenum carbide and molybdenum nitride exist in the form of nanocrystals and are encapsulated in an ultrathin carbon nanoframework.
[0007] As a preferred technical solution, the carbon nanoframework is a three-dimensional porous structure composed of two-dimensional nanosheet structures, and the nanocrystals are encapsulated in the carbon nanoframework. The thickness of the two-dimensional nanosheet structure is 3-8 nm.
[0008] As a preferred technical solution, the size of the nanocrystals does not exceed 10 nm.
[0009] It should be noted that the three-dimensional porous structure carbon / molybdenum nitride@carbon nanomaterial provided by the present application has an ultrathin two-dimensional nanosheet structure, and the nanosheet thickness is 3-8 nm; the three-dimensional porous structure carbon / molybdenum nitride@carbon nanomaterial has three components, namely molybdenum carbide, molybdenum nitride and carbon, the molybdenum carbide and the molybdenum nitride exist in the form of nanocrystals with a size of less than 10 nm, are wrapped in an ultrathin carbon nanoskeleton, and the ultrathin carbon nanoskeleton is a loose and porous three-dimensional structure; a large number of uniformly distributed molybdenum carbide and molybdenum nitride nanocrystals in the three-dimensional porous structure carbon / molybdenum nitride@carbon nanomaterial have a strong chemical force on polysulfides, and can well confine the polysulfides to the positive electrode material side, effectively weakening the "shuttle effect".
[0010] The three-dimensional porous structure carbon / molybdenum nitride@carbon nanomaterial has good electrical conductivity, rich pore structure and high specific surface area, and can be used as a lithium-sulfur battery positive electrode conductive skeleton and sulfur to be compounded, can provide a large number of surfaces and semi-closed internal spaces for the loaded sulfur powder, endow the sulfur positive electrode with good electrical conductivity and physical confinement and physical and chemical adsorption effect on polysulfides, thereby significantly reducing the polarization phenomenon of the lithium-sulfur battery in the charging and discharging process, inhibiting the "shuttle effect", and improving the discharge capacity and cycle stability of the lithium-sulfur battery under high sulfur loading.
[0011] The second technical scheme of the present application is a preparation method of the three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial, which comprises the following steps:
[0012] (1) reacting metal molybdenum powder and hydrogen peroxide solution in ethanol, stirring, adding melamine, stirring, centrifuging, and obtaining molybdenum precursor by drying;
[0013] (2) mixing the molybdenum precursor with urea to obtain a mixture;
[0014] (3) calcining the mixture under NH3 and N2 atmosphere, heating to a target calcination temperature at a set heating rate, and heat preserving to obtain the three-dimensional porous structure carbon / molybdenum nitride@carbon nanomaterial.
[0015] As a preferred technical scheme, in step (1), the amount of metal molybdenum powder is 0.1-0.8 g, the concentration of hydrogen peroxide solution is 25%-35%, the amount of hydrogen peroxide solution is 1-2 ml, and the amount of melamine added is 1-2 g.
[0016] In step (2), the molybdenum precursor and urea are mixed in a mass ratio of 1:8 to 1:1.
[0017] As a preferred technical scheme, in step (3), the set heating rate is 5-15℃ / min -1 ; and the target calcination temperature is 600-700℃.
[0018] The technical scheme three of the present application: a composite sulfur positive electrode material, comprising the three-dimensional porous carbon molybdenum nitride@carbon nanomaterial and sulfur powder as described above.
[0019] The technical scheme four of the present application: a preparation method of the composite sulfur positive electrode material as described above, comprising the following steps:
[0020] The three-dimensional porous carbon / molybdenum nitride and sulfur powder are mixed, and after being fully ground, they are co-heated until the sulfur is diffused to the surface and internal pore structure of the three-dimensional porous carbon / molybdenum nitride@carbon material, and then cooled to room temperature to obtain the composite sulfur positive electrode material.
[0021] The technical scheme five of the present application: the application of the three-dimensional porous carbon molybdenum nitride@carbon nanomaterial as described above as a conductive framework of a lithium-sulfur battery positive electrode.
[0022] The technical scheme six of the present application: the application of the three-dimensional porous carbon molybdenum nitride@carbon nanomaterial as described above as a lithium-sulfur battery separator modification material.
[0023] The present application has the following beneficial effects:
[0024] (1) The three-dimensional porous carbon / molybdenum nitride@carbon composite material with a three-dimensional porous structure is prepared in the present application, and when the three-dimensional porous carbon / molybdenum nitride@carbon composite material is used as a conductive framework of a lithium-sulfur battery sulfur positive electrode, the conductivity of the sulfur positive electrode can be significantly improved; the three-dimensional porous structure provides a large amount of surface and internal space for loading sulfur, thereby improving the loading capacity of sulfur; the large amount of molybdenum carbide and molybdenum nitride nanocrystals uniformly distributed on the surface of the three-dimensional porous carbon / molybdenum nitride@carbon composite material have a strong chemical force with polysulfides, which can well anchor the polysulfides on the surface, inhibit the dissolution and diffusion of the polysulfides in the electrolyte, and improve the cycle stability of the battery.
[0025] (2) When the three-dimensional porous carbon / molybdenum nitride@carbon composite material with a three-dimensional porous structure is loaded on one side of the lithium-sulfur battery separator Celgrad2400 surface (towards the lithium-sulfur battery positive electrode side), the polysulfides can be obviously intercepted from diffusing from the positive electrode to the negative electrode, thereby improving the cycle stability of the battery. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1 The scanning electron microscope image of the three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial prepared in Example 1 is shown in the following figure:
[0027] Figure 2 The transmission electron microscope image of the three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial prepared in Example 1 is shown in the following figure:
[0028] Figure 3A high-resolution transmission electron microscope image of the three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial prepared for Example 1 is shown in Figure 1.
[0029] Figure 4 A scanning electron microscope image of the three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial prepared for Example 2 is shown in Figure 2.
[0030] Figure 5 A discharge specific capacity cycle curve of the coin cell assembled for Example 4 at a current density of 0.1C is shown in Figure 3.
[0031] Figure 6 A discharge specific capacity cycle curve of the coin cell assembled for Example 5 and Comparative Example 1 at a current density of 0.2C is shown in Figure 4.
[0032] Figure 7 A discharge specific capacity cycle curve of the coin cell assembled for Example 6 and Comparative Example 2 at a current density of 0.1C is shown in Figure 5. DETAILED DESCRIPTION
[0033] The present application is herein described, by way of example only, with reference to certain embodiments thereof. It is to be understood that variations and modifications can be effected without departing from the scope of the application. The following examples and embodiments are intended to be representative only.
[0034] The specific embodiments of the present application will be further described in the following detailed description with reference to the accompanying drawings and examples.
[0035] Example 1
[0036] The present application provides a preparation method of a three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial for a lithium sulfur positive electrode material, which is carried out according to the following steps:
[0037] (1) 0.4 g of metallic molybdenum powder and 1.4 mL of 30% hydrogen peroxide solution were reacted in 30 mL of ethanol, stirred for 48 h, 1.6 g of melamine was added, stirred for 24 h, and then centrifuged at a speed of 5000 rpm, and dried at 40°C to obtain a molybdenum precursor;
[0038] (2) The molybdenum precursor obtained in step (1) was mechanically mixed with urea at a mass ratio of 1:5;
[0039] (3) The mixture of the molybdenum precursor and urea particles obtained in step (2) was placed in a crucible and calcined in a tube furnace under a 3-7% NH3 / N2 atmosphere, the calcination temperature was 650°C, and the heating rate was 10°C / min.-1 ; the holding time is 6h, to obtain the three-dimensional porous structure carbon / molybdenum nitride@carbon nanomaterial.
[0040] The scanning electron microscope graph of the three-dimensional porous structure carbon / molybdenum nitride@carbon nanomaterial prepared in Example 1 is shown in Figure 1 , the transmission electron microscope graph is shown in Figure 2 , and the high-resolution transmission electron microscope graph is shown in Figure 3 .
[0041] As can be seen from Figures 1 to 3 , the three-dimensional porous structure carbon / molybdenum nitride@carbon nanocomposite material prepared in this embodiment has a three-dimensional porous structure, and the molybdenum carbide and molybdenum nitride nanocrystals with a size of about 3nm are wrapped in the ultra-thin two-dimensional carbon nanoskeleton.
[0042] Example 2:
[0043] The embodiment of the present application provides a preparation method of a three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial for a lithium sulfur positive electrode material, which is based on steps (1)-(3) provided in Example 1, and in step (3) thereof, the molybdenum precursor and urea are mechanically mixed according to a mass ratio of 1:1, and the other steps are the same as those in Example 1.
[0044] The scanning electron microscope graph of the three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial prepared in Example 2 is shown in Figure 4 , and Figure 4 As can be seen from the above, compared with Example 1, the three-dimensional porous structure carbon / molybdenum nitride@carbon nanocomposite material prepared in this embodiment has a greater distribution density of molybdenum carbide and molybdenum nitride nanocrystals.
[0045] Example 3:
[0046] The embodiment of the present application provides a preparation method of a three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial for a lithium sulfur positive electrode material, which is based on Example 2, and in step (3), calcination is performed in a 5% NH3 / N2 atmosphere in a tube furnace, and the other steps are the same as those in Example 2.
[0047] Example 4:
[0048] The embodiment of the present application provides a preparation method of a composite sulfur positive electrode material, which carries sulfur on the three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial obtained in Example 3, and the specific steps are as follows:
[0049] Step one: preparing a three-dimensional porous carbon / molybdenum nitride@carbon / sulfur composite sulfur positive electrode material.
[0050] Mixing three-dimensional porous carbon / molybdenum nitride with sulfur powder according to a mass ratio of 2:8, after grinding thoroughly, transfer to a round bottom flask and co-heat at 155℃ for 4-8h, promote the sulfur to melt and diffuse into the surface and internal pore structure of the three-dimensional porous carbon / molybdenum nitride@carbon material, cool to room temperature to obtain the composite sulfur cathode material.
[0051] Step two: preparing lithium-sulfur battery cathode electrode sheet, including the following steps (1) and (2).
[0052] (1) Disperse the composite sulfur cathode material in N-methyl pyrrolidone solvent, magnetically stir at room temperature for 24-48h, add polyvinylidene fluoride binder and continue to stir for 12-24h to obtain cathode slurry.
[0053] (2) Take the slurry in step (1) and evenly coat on aluminum foil with a doctor blade, dry in a forced air drying oven at 40℃ for 4h, and then punch to obtain a cathode electrode sheet with a diameter of 1.2cm.
[0054] Step three: assemble lithium-sulfur battery.
[0055] Use the cathode electrode sheet obtained in step two to assemble a coin cell for lithium-sulfur battery performance test, the anode is a metal lithium sheet, the separator is Celgard2400, and the electrolyte is an ether electrolyte; the electrolyte composition is: the electrolyte is lithium bis(trifluoromethanesulfonyl)imide (1mol L -l ), the solvent is 1,3 dioxolane and ethylene glycol dimethyl ether, the volume ratio of the two is 1:3-3:1, the mass fraction of added LiNO3 is 1%, and the amount of the electrolyte is 20-50μL; the charge and discharge voltage window is 1.8-2.6V.
[0056] Figure 5 The discharge specific capacity cycle curve of the coin cell assembled in step three at a current density of 0.1C, the sulfur surface loading of the composite sulfur cathode is 2.9mg cm -2 , as can be seen from the figure, after 5 cycles of 0.05C activation, the discharge specific capacity at 0.1C is 760mAh g -1 , and the discharge specific capacity after 100 cycles is 620mAh g -1 .
[0057] Example 5:
[0058] The difference between this example and specific example 4 is that the sulfur surface loading of the composite sulfur cathode used in step three is 3.1mg cm -2 , and the charge and discharge current density is 0.2C. The others are the same as example 4.
[0059] Comparative example 1:
[0060] The CNT / S composite cathode prepared using carbon nanotubes (CNT) as the conductive framework of the sulfur cathode was prepared according to the method of Example 4, except that the three-dimensional porous carbon / molybdenum nitride in step one was replaced by CNT. The other steps were the same as in Example 5.
[0061] Figure 6 The discharge specific capacity cycle curves of the coin cell assembled in Example 5 and the control group at a current density of 0.2C were obtained, as shown in the figure. After activation at 0.05C, the discharge specific capacity of the control group at 0.2C was almost zero, which was mainly because the sulfur in the cathode electrode sheet had a high surface loading, and a large amount of polysulfide was dissolved and diffused into the electrolyte during the discharge process, which increased the viscosity of the electrolyte and caused severe polarization of the battery. The discharge specific capacity of the composite sulfur cathode prepared using three-dimensional porous carbon / molybdenum nitride@carbon as the conductive framework under the same conditions can reach 700mAh g -1 , and has good cycle stability, indicating that the three-dimensional porous carbon / molybdenum nitride@carbon not only has good conductivity, but also has a strong interaction with polysulfide, inhibiting the "shuttle effect".
[0062] Example 6:
[0063] The application provides an application of the three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial prepared in the above examples as a lithium-sulfur battery separator modification material, specifically a preparation method of a three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial modified separator, which is prepared in the following manner:
[0064] The three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial is dispersed in a N-methylpyrrolidone solvent, and then the obtained dispersion is filtered by a vacuum filtration device on one side of a lithium-sulfur battery separator Celgard 2400, and dried at room temperature for 12 hours. A puncher is used to punch the obtained separator into a round piece with a diameter of 1.4 cm, which is used as a modified separator for lithium-sulfur battery performance testing and is moved into a glove box for standby.
[0065] Assemble a lithium-sulfur battery: use the CNT / S composite cathode prepared using carbon nanotubes (CNT) as the conductive framework of the sulfur cathode as the cathode, and the preparation method is the same as in Comparative Example 1. The separator is the modified separator prepared in Example 6, and the side with the three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial coating faces the positive electrode side when the battery is assembled.
[0066] Comparative Example 2:
[0067] Comparative Example 2 uses the unmodified separator Celgard 2400 as the separator of the lithium-sulfur battery for battery assembly, and the other steps are the same as in Example 6.
[0068] Figure 7Discharge specific capacity cycle curves of lithium-sulfur batteries assembled for Example 6 and Control Example 2, with a sulfur surface loading of 3.3 mg cm for the CNT / S composite cathode -2 As can be seen from the figure, the battery assembled for Example 6 can reach a discharge specific capacity of 900 mAh g at a current density of 0.1 C after 0.05 C activation -1 The above, and good cycle stability in subsequent cycles, while the discharge specific capacity (0.1 C) of Control Example 2 under the same test conditions is almost zero, indicating that the three-dimensional porous carbon / molybdenum nitride@carbon nanomaterial coating in the modified separator can effectively intercept the diffusion of polysulfides to the negative electrode, inhibit the "shuttle effect", and its good electrical conductivity is conducive to the conversion of polysulfides to sulfur or low-sulfur compounds, improving the utilization of sulfur, thereby exhibiting good cycle stability.
[0069] The above embodiments are only used to illustrate the present application, and are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, all equivalent technical solutions also belong to the scope of the present application, and the patent protection scope of the present application should be defined by the claims.
Claims
1. A three-dimensional porous molybdenum carbonitride@carbon nanomaterial, characterized in that, The carbonized molybdenum, the nitrogenated molybdenum and the carbon are included; wherein the carbon exists in the form of carbon nano skeleton, the carbon nano skeleton is a loose porous three-dimensional structure, the carbonized molybdenum and the nitrogenated molybdenum exist in the form of nanocrystals and are wrapped in the ultra-thin carbon nano skeleton.
2. The three-dimensional porous molybdenum carbonitride@carbon nanomaterial of claim 1, wherein, The carbon nano skeleton is a three-dimensional porous structure composed of two-dimensional nanosheet structures, the nanocrystals are wrapped in the carbon nano skeleton, and the thickness of the two-dimensional nanosheet structure is 3-8 nm.
3. The three-dimensional porous molybdenum carbonitride@carbon nanomaterial of claim 2, wherein, The size of the nanocrystals is not more than 10 nm.
4. A method for preparing the three-dimensional porous molybdenum carbonitride@carbon nanomaterial according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: (1) reacting metal molybdenum powder and hydrogen peroxide solution in ethanol, stirring, adding melamine, stirring, centrifuging, and obtaining molybdenum precursor by drying; (2) mixing the molybdenum precursor with urea to obtain a mixture; (3) calcining the mixture under an NH3 and N2 mixed atmosphere, heating to a target calcination temperature at a set heating rate, and holding to obtain a three-dimensional porous structure carbon / nitrogenated molybdenum@carbon nanomaterial.
5. The production method according to claim 4, wherein In step (1), the amount of metal molybdenum powder is 0.1-0.8 g, the concentration of hydrogen peroxide solution is 25%-35%, the amount of hydrogen peroxide solution is 1-2 ml, and the amount of melamine is 1-2 g; the volume fraction of NH3 in the NH3 and N2 mixed atmosphere is 3-50%; In step (2), the molybdenum precursor and urea are mixed in a mass ratio of 1:8-1:
1.
6. The production method according to claim 4, wherein In step (3), the setting temperature increase rate is 5-15°C / min -1 ; the target calcination temperature is 600-700°C.
7. A composite sulfur cathode material, characterized in that, The method comprises the following steps:
8. A method of preparing the composite sulfur cathode material of claim 7, characterized in that, The three-dimensional porous carbon / nitrogenated molybdenum is mixed with sulfur powder, and after being fully ground, the mixture is heated until the sulfur melts and diffuses into the surface and internal pore structure of the three-dimensional porous carbon / nitrogenated molybdenum@carbon material, and the composite sulfur positive electrode material is obtained after cooling to room temperature.
9. Use of the three-dimensional porous carbon / nitrogenated molybdenum@carbon nanomaterial as claimed in any one of claims 1 to 3 as a conductive skeleton of a lithium-sulfur battery positive electrode.
10. Use of the three-dimensional porous carbon / nitrogenated molybdenum@carbon nanomaterial as claimed in any one of claims 1 to 3 as a lithium-sulfur battery separator modification material.