Preparation method of carbon-coated molybdenum carbide, carbon-coated molybdenum carbide and its application

Abstract

This application relates to a preparation method of carbon-coated molybdenum carbide, which comprises the following steps: mixing a phosphomolybdic acid solution and a dopamine solution, performing solid-liquid separation after reaction at a first temperature to obtain a solid; heat-treating the solid at a second temperature in an inert gas atmosphere to obtain the carbon-coated molybdenum carbide. The preparation method of carbon-coated molybdenum carbide provided by the embodiments of this application directly forms a structure with molybdenum atoms as the center and carbon, phosphorus, nitrogen, oxygen, hydrogen and other atoms aggregated around by mixing the phosphomolybdic acid solution and the dopamine solution to obtain a solid; then directly heat-treating the solid to directly form a core-shell structure with molybdenum carbide as the core and a nitrogen, phosphorus and oxygen-doped carbon layer as the shell. The preparation steps are simple, the formed product has high uniformity and good electrochemical performance.

Description

Technical Field

[0001] This application relates to the field of lithium batteries, and particularly to molybdenum carbide composites. Background Art

[0002] As a high-performance energy storage device, rechargeable lithium-ion batteries have developed rapidly in recent years and have been widely used in various portable electronic devices and electric vehicles. With the further increase in the demand for energy storage facilities, higher requirements are put forward for the electricity storage capacity of lithium batteries. Therefore, it is particularly important to develop high-performance lithium-ion battery electrode materials. Graphite-based carbon materials, as the negative electrode materials used in current commercial lithium-ion batteries, have the advantages of good stability and low cost, but also face the problems of low specific capacity and fast cycle decay during use. Therefore, it is necessary to develop other high-performance, low-cost and low-pollution electrode materials to replace traditional commercial graphite electrodes. Carbon materials are considered to be electrode materials with great development potential due to their high conductivity, easy preparation of porous structures with large specific surface areas, and chemical stability. Research shows that by coating metal compounds and introducing heteroatom doping to modify the carbon matrix, the electricity storage capacity of the carbon matrix material can be effectively improved.

[0003] However, carbon coating of metal compounds and then heteroatom doping of the carbon coated on the outer layer often involve very complex preparation steps. The complexity of the preparation steps not only leads to an increase in preparation costs, but also makes the preparation process more susceptible to random factors, resulting in poor morphology uniformity of the product and affecting the electrochemical performance. Summary of the Invention

[0004] The embodiments of this application provide a preparation method of carbon-coated molybdenum carbide, carbon-coated molybdenum carbide and its application, so as to solve the technical problem of the complex preparation steps of carbon coating of metal compounds.

[0005] In a first aspect, the embodiments of this application provide a preparation method of carbon-coated molybdenum carbide, and the preparation method of carbon-coated molybdenum carbide includes the following steps:

[0006] Mix a phosphomolybdic acid solution and a dopamine solution, and after reacting at a first temperature, perform solid-liquid separation to obtain a solid;

[0007] Heat-treat the solid in an inert atmosphere at a second temperature to obtain the carbon-coated molybdenum carbide.

[0008] In some embodiments of this application, both the phosphomolybdic acid solution and the dopamine solution are aqueous solutions.

[0009] In some embodiments of this application, the concentration of the phosphomolybdic acid solution is 1-100 mg / mL; and / or,

[0010] The concentration of the dopamine solution is 1 to 25 mg / L.

[0011] In some embodiments of the present application, when mixing the phosphomolybdic acid solution and the dopamine solution, the mass ratio of the phosphomolybdic acid to the dopamine ranges from 0.5 to 2.0.

[0012] In some embodiments of the present application, the first temperature is 5 to 60 °C.

[0013] In some embodiments of the present application, when reacting at the first temperature, the reaction time is not less than 10 h.

[0014] In some embodiments of the present application, the inert gas is at least one of argon and nitrogen.

[0015] In some embodiments of the present application, the second temperature is 500 to 900 °C; and / or,

[0016] The time of the heat treatment is not less than 2 h.

[0017] In a second aspect, an embodiment of the present application provides a carbon-coated molybdenum carbide, which is prepared by the preparation method of the carbon-coated molybdenum carbide according to any one of the embodiments in the first aspect.

[0018] In a third aspect, an embodiment of the present application provides a lithium battery, and the lithium battery includes the carbon-coated molybdenum carbide according to any one of the embodiments in the second aspect.

[0019] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0020] The preparation method of the carbon-coated molybdenum carbide provided by the embodiment of the present application obtains a solid by mixing a phosphomolybdic acid solution and a dopamine solution, and directly forms a structure with molybdenum atoms as the center and carbon, phosphorus, nitrogen, oxygen, hydrogen and other atoms aggregated around; then directly performs heat treatment on the solid to directly form a core-shell structure with molybdenum carbide as the core and a nitrogen, phosphorus, and oxygen-doped carbon layer as the shell. The preparation steps are simple, the formed product has high uniformity, and the electrochemical performance is good. Description of the Drawings

[0021] The drawings here are incorporated into the description and form a part of this description, showing embodiments consistent with the present application, and are used together with the description to explain the principles of the present application.

[0022] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0023] Figure 1 Scanning electron microscope photos of the solid substance prepared in Example 1 and molybdenum carbide coated with carbon

[0024] Figure 2 Transmission electron microscope photos of molybdenum carbide coated with carbon prepared in Example 1 and element content distribution diagrams

[0025] Figure 3 Energy spectrum analysis diagram and element semi-quantitative diagram of molybdenum carbide coated with carbon prepared in Example 1 under transmission electron microscope

[0026] Figure 4 X-ray photoelectron spectroscopy full element spectrum diagram of molybdenum carbide coated with carbon prepared in Example 1

[0027] Figure 5 XRD diagram of molybdenum carbide coated with carbon prepared in Example 1

[0028] Figure 6 Raman spectrum diagram of molybdenum carbide coated with carbon prepared in Example 1

[0029] Figure 7 Cyclic voltammogram of molybdenum carbide coated with carbon prepared in Example 1

[0030] Figure 8 Galvanostatic charge-discharge curve of molybdenum carbide coated with carbon prepared in Example 1 at a current density of 0.1 A / g

[0031] Figure 9 Galvanostatic charge-discharge curve of molybdenum carbide coated with carbon prepared in Example 1 at a current density of 0.037 A / g

[0032] Figure 10 Rate test and Coulomb efficiency diagram of molybdenum carbide coated with carbon prepared in Example 1 at different current densities from 0.05 to 0.5 A / g

[0033] Figure 11 Scanning electron microscope photos of the solid substance prepared in Example 2 and molybdenum carbide coated with carbon

[0034] Figure 12 Scanning electron microscope photos of the solid substance prepared in Example 3 and molybdenum carbide coated with carbon Detailed implementation manners

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Apparently, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0036] Unless otherwise specifically stated, the terms used in this document should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used in this document have the same meaning as the general understanding of those skilled in the art to which this application belongs. In case of any conflict, this specification shall prevail.

[0037] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in this application can be obtained through market purchases or can be prepared by existing methods.

[0038] There is a technical problem in the existing preparation of carbon-coated metal compounds that the steps are complex.

[0039] The technical solutions provided by the embodiments of this application to solve the above technical problems are generally as follows:

[0040] In a first aspect, the embodiments of this application provide a method for preparing carbon-coated molybdenum carbide. The method for preparing carbon-coated molybdenum carbide includes the following steps:

[0041] S1: Mix a phosphomolybdic acid solution with a dopamine solution, react at a first temperature, and then perform solid-liquid separation to obtain a solid;

[0042] S2: Heat-treat the solid in an inert gas atmosphere at a second temperature to obtain the carbon-coated molybdenum carbide.

[0043] Those skilled in the art can understand that dopamine and phosphomolybdic acid will undergo complex ion exchange, complexation reactions, and polymerization reactions to form a water-insoluble polymer. In this polymer, molybdenum atoms are central atoms with multiple coordination numbers, and atoms such as carbon, phosphorus, nitrogen, oxygen, and hydrogen are coordinated around the molybdenum atoms in the form of groups. After the heat treatment in step S2, most oxygen atoms and hydrogen atoms are removed, forming a core-shell structure with molybdenum carbide as the core and a nitrogen, phosphorus, and oxygen-doped carbon layer as the shell.

[0044] In the existing solutions, when carbon coating is carried out on metal compounds and then heteroatom doping is carried out on the carbon coated on the outer layer, it is often necessary to first prepare a core structure, then coat the core structure, carry out doping during the coating process, and finally treat the coating into a carbon layer through heat treatment. The preparation steps are very complex, and each step in the preparation process will be affected by random factors. Therefore, the complexity of the preparation steps not only leads to an increase in the preparation cost, but also makes the preparation process more susceptible to random factors, resulting in poor morphology uniformity of the product and affecting the electrochemical performance.

[0045] In this application, a solid is obtained by mixing a phosphomolybdic acid solution and a dopamine solution, directly forming a structure centered on molybdenum atoms with carbon, phosphorus, nitrogen, oxygen, hydrogen and other atoms aggregated around; then directly carrying out heat treatment on the solid to directly form a core-shell structure with molybdenum carbide as the core and a carbon layer doped with nitrogen, phosphorus and oxygen as the shell. The preparation steps are simple, the formed product has high uniformity, and the electrochemical performance is good.

[0046] In some embodiments of this application, both the phosphomolybdic acid solution and the dopamine solution are aqueous solutions.

[0047] The synthesis process of this application can be completely carried out in an aqueous solution, which has the advantage of environmental friendliness and does not contain any additives, thus ensuring the high purity of the structure of the obtained product and eliminating the material purification process.

[0048] In some embodiments of this application, the concentration of the phosphomolybdic acid solution is 1-100 mg / mL; and / or,

[0049] The concentration of the dopamine solution is 1-25 mg / L.

[0050] In some embodiments of this application, when mixing the phosphomolybdic acid solution and the dopamine solution, the mass ratio range of the phosphomolybdic acid to the dopamine is 0.5-2.0.

[0051] In some embodiments of this application, the first temperature is 5-60 °C.

[0052] As a preferred solution, the first temperature is 25 °C.

[0053] In some embodiments of this application, when reacting at the first temperature, the reaction time is not less than 10 h.

[0054] As a preferred solution, the reaction time is 24 h.

[0055] Since the reaction includes relatively complex changes such as ion exchange and polymerization reactions, if the reaction time is too short, it is likely to lead to incomplete reactions.

[0056] In some embodiments of this application, the inert gas is at least one of argon and nitrogen.

[0057] In some embodiments of the present application, the second temperature is 500 - 900 °C; and / or,

[0058] The time of the heat treatment is not less than 2 h.

[0059] The beneficial effect of selecting the second temperature within the above temperature range is that it can not only fully carbonize the solid substance, but also not remove too much oxygen and nitrogen doping elements.

[0060] The beneficial effect of the heat treatment time not being less than 2 h is that the carbonization during the heat treatment can be fully carried out.

[0061] As a preferred solution, the second temperature is 700 °C and the time of the heat treatment is 3 h.

[0062] In a second aspect, the embodiments of the present application provide a carbon-coated molybdenum carbide, which is prepared by the preparation method of the carbon-coated molybdenum carbide according to any one of the embodiments in the first aspect. Since the carbon-coated molybdenum carbide is prepared by the preparation method of the carbon-coated molybdenum carbide according to any one of the embodiments in the first aspect, it also has all the beneficial effects possessed by the first aspect, which will not be elaborated here.

[0063] In a third aspect, the embodiments of the present application provide a lithium battery, and the lithium battery includes the carbon-coated molybdenum carbide according to any one of the embodiments in the second aspect. Since the lithium battery includes the carbon-coated molybdenum carbide according to any one of the embodiments in the second aspect, it also has all the beneficial effects possessed by the second aspect, which will not be elaborated here.

[0064] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. For the experimental methods without specific conditions indicated in the following embodiments, they are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0065] Example 1

[0066] The present embodiment provides a preparation method of carbon-coated molybdenum carbide, and the steps are as follows:

[0067] Prepare an aqueous solution of phosphomolybdic acid with a volume of 100 mL and a concentration of 10 mg / mL, denoted as solution A; prepare an aqueous solution of dopamine with a volume of 80 mL and a concentration of 2.5 mg / mL, denoted as solution B. Subsequently, quickly pour solution B into solution A, mix the two solutions, let it stand at room temperature for 24 h, then perform vacuum filtration to achieve solid-liquid separation, and obtain a solid substance after drying, and its form is dark green solid powder.

[0068] Put 100 mg of the above-obtained solid into a tube furnace, introduce nitrogen as an inert gas, heat it to 700 °C at a heating rate of 3 °C / min, hold for 3 h, and after cooling, take out the obtained black solid powder, which is molybdenum carbide coated with carbon.

[0069] Example 2

[0070] This example provides a method for preparing molybdenum carbide coated with carbon, and the steps are as follows:

[0071] Prepare an aqueous solution of phosphomolybdic acid with a volume of 40 mL and a concentration of 1 mg / mL, denoted as solution A; prepare an aqueous solution of dopamine with a volume of 80 mL and a concentration of 1 mg / mL, denoted as solution B. Subsequently, quickly pour solution B into solution A, mix the two solutions, let it stand for 10 h at 5 °C, then perform vacuum filtration to achieve solid-liquid separation, and after drying, obtain a solid, whose form is dark green solid powder.

[0072] Put 100 mg of the above-obtained solid into a tube furnace, introduce nitrogen as an inert gas, heat it to 500 °C at a heating rate of 3 °C / min, hold for 2 h, and after cooling, take out the obtained black solid powder, which is molybdenum carbide coated with carbon.

[0073] Example 3

[0074] This example provides a method for preparing molybdenum carbide coated with carbon, and the steps are as follows:

[0075] Prepare an aqueous solution of phosphomolybdic acid with a volume of 10 mL and a concentration of 100 mg / mL, denoted as solution A; prepare an aqueous solution of dopamine with a volume of 20 mL and a concentration of 25 mg / mL, denoted as solution B. Subsequently, quickly pour solution B into solution A, mix the two solutions, let it stand for 24 h at 60 °C, then perform vacuum filtration to achieve solid-liquid separation, and after drying, obtain a solid, whose form is dark green solid powder.

[0076] Put 100 mg of the above-obtained solid into a tube furnace, introduce nitrogen as an inert gas protection gas, heat it to 900 °C at a heating rate of 3 °C / min, hold for 10 h, and after cooling, take out the obtained black solid powder, which is molybdenum carbide coated with carbon.

[0077] Related experiments and effect data:

[0078] Figure 1 Scanning electron microscope (SEM) photos of the solid prepared in Example 1 and molybdenum carbide coated with carbon. Among them, Figure 1 (a) is the scanning electron microscope photo of the solid prepared in Example 1, Figure 1 (b) is the scanning electron microscope photo of the molybdenum carbide coated with carbon prepared in Example 1. As Figure 1(a) It can be seen that the obtained precursor solid is a spherical nanostructure with relatively uniform size, and the diameter is about 500 nm. The carbon matrix material obtained by subsequent heat treatment is molybdenum carbide coated with carbon, as Figure 1 (b) shows. There is a certain shrinkage in the original spherical structure, which is caused by the destruction of the original structure with dopamine as the organic framework during high-temperature heat treatment. However, the spherical nanostructure of the original precursor is well retained, with a diameter of about 300 nm and relatively uniform size.

[0079] The distribution of each element of the carbon-coated molybdenum carbide prepared in Example 1 was tested by transmission electron microscopy. Please refer to Figure 2 , Figure 2 is the transmission electron microscopy photograph of the carbon-coated molybdenum carbide prepared in Example 1 and the distribution map of the content of each element in the Mapping mode (TEM-Mapping). Among them, the corresponding element is marked in the upper left corner of each element content distribution map. From Figure 2 it can be seen that the above-obtained material structure contains five elements, namely O, N, Mo, C, and P, and each element is evenly distributed in the spherical nanostructure, indicating that the carbon matrix material has been well modified with heteroatoms and the molybdenum carbide nanoparticles are embedded.

[0080] The content of each element of the carbon-coated molybdenum carbide prepared in Example 1 was semi-quantitatively tested by energy spectrum analysis. Please refer to Figure 3 , Figure 3 is the energy spectrum analysis diagram and its element semi-quantitative diagram (TEM-EDS) of the carbon-coated molybdenum carbide prepared in Example 1 under transmission electron microscopy. From this result, it can be seen that the atomic percentage contents of its main elements are C (46.61 at.%), O (5.48 at.%), P (2.95 at.%), and Mo (45.56 at.%) respectively. It should be noted that due to the low content of nitrogen element, its content ratio could not be detected; however, this test is a semi-quantitative test, and its result is an approximate reference value, which is not sufficient to deny the existence of nitrogen element.

[0081] Furthermore, to verify the existence of N element in the above material, the carbon-coated molybdenum carbide prepared in Example 1 was tested by X-ray photoelectron spectroscopy (XPS). Figure 4 is the full spectrum of X-ray photoelectron spectroscopy elements of the carbon-coated molybdenum carbide prepared in Example 1. From this result, it can be seen that the N element exists, and the above result supports the Figure 2 conclusion that the nitrogen element is evenly distributed.

[0082] The phase structure of the carbon-coated molybdenum carbide prepared in Example 1 was analyzed by X-ray diffraction test. Please refer to Figure 5 , Figure 5XRD pattern of the carbon-coated molybdenum carbide obtained in Example 1 shows that the main structure of the obtained carbon-coated molybdenum carbide material is a carbon matrix, and there is an amorphous carbonaceous structure. In addition, there is also a MoC component, which is a metal-organic structure centered on metal Mo formed by the complexation of phosphomolybdic acid and dopamine during the material preparation process. Subsequently, during the high-temperature heat treatment process, this structure is reduced and transformed into MoC.

[0083] To further understand the existence form of carbon elements in the carbon matrix structure of the carbon-coated molybdenum carbide prepared in Example 1, Raman spectroscopy was performed on it. Please refer to Figure 6 , Figure 6 Raman spectrum of the carbon-coated molybdenum carbide prepared in Example 1. As can be seen from the figure, the peaks appearing at wavenumbers of 1300 and 1571 cm -1 correspond to the D-band peak and G-band peak of the carbon material respectively, and the area ratio of the two (ID / IG) is 1:1, indicating that the carbonaceous component of the obtained carbon material has a high degree of graphitization, thus endowing the material with excellent electrical conductivity. At the same time, the relatively high D-band peak also proves the existence of defects in the material, and these defect structures are beneficial to the combination of carbon atoms and lithium ions, thereby further improving the lithium storage capacity of the material. The weak signal peak appearing near 900 cm -1 corresponds to the vibration of Mo-O bonds in the material, indicating that the metal element Mo on the surface of the material is inevitably slightly oxidized when exposed to air.

[0084] By characterizing and analyzing the structure of the carbon-coated molybdenum carbide prepared in Example 1, the application of the carbon-coated molybdenum carbide obtained in Example 1 as an active material in a lithium-ion battery negative electrode material was further tested by cyclic voltammetry. As Figure 7 shown, Figure 7 Cyclic voltammogram of the carbon-coated molybdenum carbide prepared in Example 1. As can be seen from the figure, the reduction peaks appearing near 0.75 V and 1.5 V in the first cycle are caused by the redox of metal Mo. Subsequently, they disappeared after the second cycle test, which is due to the formation of the SEI layer. And the third cycle and the second cycle overlap to a large extent, indicating that the material has good stability.

[0085] Furthermore, the electricity storage performance of the carbon-coated molybdenum carbide prepared in Example 1 as an active material was tested. Therefore, constant current charge-discharge tests were carried out on it under the conditions of current densities of 0.1 A / g and 0.037 A / g (0.1C, C = 372 mAh / g) respectively, and the results are shown in Figure 8 and Figure 9 respectively. As shown by Figure 8It can be seen that when the current density is 0.1 A / g, the charge-discharge specific capacitance value is stable at 160 mAh / g, and the corresponding charge-discharge Coulomb efficiency is about 100%. After 300 charge-discharge cycles, there is no obvious attenuation. The above results indicate that the material has excellent lithium storage capacity and long-life cycle stability. As Figure 9 shown, when the charge-discharge current density is reduced to 0.037 A / g, the charge-discharge specific capacitance value is stable at 170 mAh / g, and the corresponding charge-discharge Coulomb efficiency is about 100%. After 300 charge-discharge cycles, there is no obvious attenuation.

[0086] In addition, the carbon-coated molybdenum carbide prepared in Example 1 was further tested for its electricity storage performance under charge-discharge conditions at different current densities when used as an active material. As Figure 10 shown, Figure 10 is the rate test and Coulomb efficiency diagram of carbon-coated molybdenum carbide at different current densities from 0.05 to 0.5 A / g. When the initial charge-discharge current density is 0.05 A / g, the corresponding specific capacity value is 235 mAh / g. As the charge-discharge current density increases to 0.5 A / g, the obtained specific capacity value is 155 mAh / g. The above results indicate that the obtained material has excellent rate characteristics under different current density conditions. The above electrochemical performance shows that the material prepared by the present invention has practical application prospects.

[0087] Figure 11 and Figure 12 are SEM photos of the final products obtained in Example 2 and Example 3 respectively, Figure 11 and Figure 12 indicating that both Example 2 and Example 3 prepared spherical nanostructures with uniform size and similar morphology. Since the relevant parameters in the preparation processes of Example 2 and Example 3 are different from those of Example 1, this shows that the parameters in the preparation process of this application have a certain flexibility, and the preparation scheme provided by this application has a relatively wide scope of application.

[0088] The various embodiments of this application can exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the description of the range has specifically disclosed all possible sub-ranges and the individual values within that range. For example, it should be considered that the description of the range from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as the individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of what the range is. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0089] In this application, unless otherwise specified, the orientation terms such as "upper" and "lower" specifically refer to the drawing directions in the attached drawings. Additionally, in the description of the specification of this application, the terms "comprising", "including", etc. mean "including but not limited to". Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, the elements defined by the statement "comprising..." do not preclude the presence of additional identical elements in the process, method, article or device comprising the said elements. In this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this document, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, or B exists alone. For the association relationship of more than three associated objects described by "and / or", it means that these three associated objects can exist alone in any one item, or any at least two of them exist simultaneously. For example, for A, and / or B, and / or C, it can represent that any one of A, B, and C exists alone, or any two of them exist simultaneously, or all three of them exist simultaneously. In this document, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one item (piece) below" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, "at least one item (piece) among a, b, or c", or, "at least one item (piece) among a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0090] The above are only specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A preparation method of carbon-coated molybdenum carbide, characterized in that, The preparation method of the carbon-coated molybdenum carbide comprises the following steps: Mix the phosphomolybdic acid solution and the dopamine solution, react at 5 - 60 °C for no less than 10 h, and then perform solid-liquid separation to obtain a solid. The mass ratio range of the phosphomolybdic acid to the dopamine is 0.5 - 2.0; Heat-treat the solid in an inert gas atmosphere at a temperature of 500 - 900 °C for no less than 2 h to obtain the carbon-coated molybdenum carbide. The inert gas is at least one of argon and nitrogen; The concentration of the phosphomolybdic acid solution is 1 - 100 mg / mL, and the concentration of the dopamine solution is 1 - 25 mg / L; The carbon-coated molybdenum carbide has a core-shell structure with molybdenum carbide as the core and a nitrogen, phosphorus, and oxygen-doped carbon layer as the shell.

2. The preparation method of the carbon-coated molybdenum carbide according to claim 1, characterized in that, Both the phosphomolybdic acid solution and the dopamine solution are aqueous solutions.

3. A carbon-coated molybdenum carbide, characterized in that, The carbon-coated molybdenum carbide is prepared by the preparation method of the carbon-coated molybdenum carbide according to any one of claims 1 - 2.

4. A lithium battery, characterized in that, The lithium battery comprises the carbon-coated molybdenum carbide according to claim 3.

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