A molybdenum carbide modified hard carbon solid nanosphere negative electrode material and a preparation method and application thereof

Abstract

The application belongs to the technical field of energy storage batteries, and discloses a molybdenum carbide modified hard carbon solid nanosphere negative material, a preparation method and application thereof, and has the advantages of simple and controllable synthesis mode, and the like. First, a molybdenum modified hard carbon nanosphere precursor is synthesized by using a hydrothermal method, and then the hard carbon solid nanosphere modified by molybdenum carbide is obtained by calcination in an inert gas. The hard carbon nanosphere disperses molybdenum carbide in situ on the surface thereof, has uniform size, has a good solid structure, is beneficial to improving the volume capacity density of the electrode material, and can maintain good electrode material structure stability in the repeated deintercalation / intercalation process of ions, so as to improve the battery rate and cycle performance, and can further exhibit high reversible capacity and long cycle life under a large current density, and has a wide application prospect. The molybdenum carbide modified hard carbon solid nanosphere negative material prepared by the application has excellent electrochemical performance when applied to an alkali metal ion battery electrode, and has the advantages of simple process and mild conditions.

Description

Technical Field

[0001] This invention belongs to the field of energy storage battery technology, and relates to a molybdenum carbide modified hard carbon solid nanosphere anode material, its preparation method and application. Background Technology

[0002] The excessive combustion of fossil fuels has led to excessive carbon dioxide emissions. Adjusting the global energy structure is urgent and cannot be delayed. Research and development of rechargeable batteries play a crucial role in achieving a sustainable energy society. From electric vehicles to large-scale energy storage, rechargeable batteries hold a significant position. Since lithium-ion batteries were approved for use in portable devices and largely commercialized in the 1990s, alkali metal-ion batteries have been considered the preferred energy technology. Hard carbon materials, with their low plateau voltage, large capacity, stable cycle life, wide availability, and simple preparation process, are a promising anode material for alkali metal-ion batteries for commercial applications.

[0003] Hard carbon, also known as non-graphitized carbon, is mainly composed of short-range ordered regions of small-area curved graphene sheets and abundant nanopores formed by microcrystalline regions. Compared to soft carbon, hard carbon has a higher degree of structural disorder, containing numerous pseudo-graphene nanosheets with defect sites and a large number of nanopore structures. In energy storage applications, hard carbon has been widely studied due to its unique structure and cost advantages, and is considered a highly promising anode material for commercializing alkali metal ion batteries. In the extended "adsorption-insertion" ion storage mechanism of hard carbon, researchers believe that the phase with an interlayer spacing d value greater than 0.40 nm is mainly highly disordered carbon. This part of carbon allows alkali metal ions to freely transfer through a "pseudo-adsorption" mechanism, increasing the capacity of the ramp region; the phase with an interlayer spacing d value of 0.36-0.40 nm is an amorphous carbon containing short-range ordered graphene sheets, called pseudo-graphitic carbon. Similar to lithium ion insertion in graphite, the "insertion" of alkali metal ions in the pseudo-graphitic carbon layer makes a significant contribution to the plateau capacity. To prepare hard carbon anode materials suitable for commercial applications, it is essential to develop appropriate strategies to expand the surface area of ​​pseudo-graphite carbon to increase low-potential plateau capacity. However, the practical application of hard carbon faces several challenges. First, the adsorption of alkali metal ions at defect sites and pore surfaces is partially irreversible, and the reaction between the electrode material and the electrolyte to form a solid electrolyte interface film consumes some of the alkali metal ions, both contributing to a lower first-cycle coulombic efficiency. Second, due to its complex structure, the size and ratio of graphite domains and pores are difficult to control precisely. Finally, the lower rate capability and poor cycling performance at high current densities of hard carbon materials reduce the competitiveness of the battery.

[0004] To address the shortcomings of the aforementioned hard carbon materials, this invention modifies them, producing a molybdenum carbide-modified solid hard carbon nanosphere material. Molybdenum carbide is formed by carbon atoms entering the molybdenum lattice. The introduction of carbon atoms alters the electronic structure of the parent molybdenum, particularly modifying the d-band, thus improving electron mobility. The molybdenum carbide-modified solid hard carbon nanosphere material disperses molybdenum carbide in situ on the surface of the hard carbon nanospheres, limiting particle aggregation at high temperatures. This significantly increases the number of electrochemically active sites, enhances ion diffusion, and maintains good structural stability during repeated ion insertion / extraction / deintercalation. Consequently, it improves battery rate capability, reversible capacity at high current densities, and cycle stability. Furthermore, the molybdenum carbide surface exhibits high oxygen adsorption activity and readily oxidizes in air to form an oxide layer. This inert oxide layer hinders direct contact between the active phase and the electrolyte, reducing irreversible alkali metal ion consumption and improving the first-cycle coulombic efficiency. Furthermore, the molybdenum carbide-modified hard carbon solid nanosphere anode material prepared by the hydrothermal method possesses abundant pseudo-graphite domains, which can provide active sites for the migration and storage of alkali metal ions, significantly improving the plateau capacity. Simultaneously, the interfacial stability of the molybdenum carbide-modified hard carbon solid nanosphere anode material is enhanced, and the reaction kinetics are improved, thus exhibiting high reversible plateau capacity, enhanced rate performance, and excellent long cycle life. This invention provides a simple preparation method for molybdenum carbide-modified hard carbon solid nanosphere anode materials. Summary of the Invention

[0005] The purpose of this invention is to provide a molybdenum carbide-modified hard carbon solid nanosphere anode material, its preparation method, and its applications. After synthesis, molybdenum carbide is dispersed in situ on the surface of hard carbon nanospheres, which have a solid structure and excellent electrochemical performance. The process of this invention is easy to implement and control, and the synthesized product has uniform particle size (approximately 500–600 nm in diameter) and good dispersibility. As an anode material for alkali metal ion batteries, it exhibits high reversible capacity, strong rate performance, and excellent long cycle life, showing broad application prospects.

[0006] A method for preparing a molybdenum carbide-modified hard carbon solid nanosphere anode material includes the following steps:

[0007] (1) Dissolve molybdenum salt or molybdenum oxide in a solvent to form a mixed solution;

[0008] (2) Add the alkaline solution to the solution obtained in step (1) and mix well;

[0009] (3) Add the mixed solution obtained in step (2) and the organic matter to the solvent and mix well;

[0010] (4) The mixed solution obtained in step (3) is subjected to a hydrothermal reaction;

[0011] (5) After cleaning and drying the product obtained in step (4), calcining it in an inert atmosphere will yield the molybdenum carbide modified hard carbon solid nanosphere anode material.

[0012] In the preparation method described above, the dissolution temperature in step (1) is 30-90℃, preferably 50-80℃, and the stirring time is 1-24h, preferably 3-12h.

[0013] In the preparation method described above, the alkaline solution in step (2) is an alkaline solution or salt solution with a pH greater than 7, including at least one of sodium bicarbonate solution, potassium carbonate solution, and ammonia water.

[0014] In the preparation method described above, the alkaline solution in step (2) is added dropwise at a rate of 0.05 mL / min to 0.25 mL / min, preferably 0.05 mL / min to 0.15 mL / min, so that the solution can be fully diffused and mixed evenly.

[0015] In the preparation method described above, the volume ratio of the alkaline solution added in step (2) to the solution obtained in step (1) is 1:20 to 1:200, preferably 1:20 to 1:100, so that the pH of the mixed solution is 7 to 8.5, which is weakly alkaline.

[0016] In the preparation method described above, the volume ratio of the mixed solution obtained in step (2) to the solvent in step (3) is 1:10 to 1:500, preferably 1:50 to 1:200.

[0017] The preparation method described herein, wherein the organic matter in step (3) is biomass, resin carbon, carbohydrates or other organic polymers, and further includes at least one of hazelnut shells, glucose, glutamic acid, and phenolic resin; the concentration of the added organic matter is 1 to 100 mg / mL, preferably 1 to 50 mg / mL.

[0018] In the preparation method described above, the hydrothermal temperature in step (4) is 100-250℃, preferably 100-200℃, and the holding time is 4-24h, preferably 6-20h; the calcination process in step (5) is a calcination temperature of 700-1600℃, preferably 900-1500℃, a calcination time of 0.5-6h, preferably 1-4h, and a heating rate of 0.1℃ / min-5℃ / min, preferably 2℃ / min-5℃ / min.

[0019] The present invention also provides a molybdenum carbide-modified hard carbon solid nanosphere anode material prepared by the above method.

[0020] This invention also provides the application of the molybdenum carbide-modified hard carbon solid nanosphere anode material for the preparation of alkali metal ion battery electrodes.

[0021] The method for synthesizing molybdenum carbide-modified hard carbon solid nanosphere anode materials provided by this invention has the following advantages:

[0022] 1. The synthesis process of this invention adopts a hydrothermal method, and the morphology of the synthesized product is controllable and the process is simple.

[0023] 2. The synthesized product of this invention has a unique morphology; it is a solid nanosphere with a high volumetric capacity density.

[0024] 3. The synthesized product of this invention has a uniform particle size distribution, stable structure, abundant pseudo-graphite domains, and stable interfacial properties. When applied to alkali metal ion batteries, it exhibits high reversible plateau capacity, stable cycle performance, and excellent rate performance.

[0025] 4. The product synthesized in this invention disperses molybdenum carbide in situ on the surface of hard carbon nanospheres, which significantly increases the electrochemical active sites of the material and enhances the ion diffusion ability. Furthermore, the oxide layer on the surface of molybdenum carbide hinders the direct contact between the active phase and the electrolyte, thus significantly improving the electrochemical performance of the material. Attached Figure Description

[0026] Figure 1 Scanning electron microscope image of the molybdenum carbide-modified hard carbon solid nanosphere anode material of Example 1;

[0027] Figure 2 The sodium-ion battery prepared from the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 1 exhibits a voltage range of 0.01-3V and a performance of 30-2000 mAg. -1 Rate performance under certain conditions;

[0028] Figure 3 Scanning electron microscope image of the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2;

[0029] Figure 4 Transmission electron microscope image of the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2;

[0030] Figure 5 Example 2: Energy dispersive X-ray spectral distribution of Mo element in the hard carbon solid nanosphere anode material modified with molybdenum carbide;

[0031] Figure 6 XRD pattern of the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2;

[0032] Figure 7 The lithium-ion battery prepared from the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2 exhibits a voltage range of 0.01-3V and a capacity of 30-2000 mAg. -1 Rate performance under certain conditions;

[0033] Figure 8 The sodium-ion battery prepared from the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2 exhibits a voltage range of 0.01-3V and a performance of 30-2000 mAg. -1 Rate performance under certain conditions;

[0034] Figure 9 The sodium-ion battery prepared from the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2 operates within a voltage range of 0.01-3V and has a capacity of 50 mAg. -1 Cyclic performance under low current density conditions;

[0035] Figure 10 The sodium-ion battery prepared from the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2 exhibits a voltage range of 0.01-3V and a capacity of 2000 mAg. -1 Cyclic performance under high current density conditions;

[0036] Figure 11 The potassium-ion battery prepared from the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2 exhibits a voltage range of 0.01-3V and a capacity of 30-2000 mAg. -1 Rate performance under certain conditions;

[0037] Figure 12 Scanning electron microscope image of the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 3;

[0038] Figure 13 The sodium-ion battery prepared from the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 3 exhibits a voltage range of 0.01-3V and a capacity of 30-2000 mAg. -1 Rate performance under certain conditions;

[0039] Figure 14 Scanning electron microscope image of the hard carbon anode material in Comparative Example 1;

[0040] Figure 15 Transmission electron microscope image of the hard carbon anode material in Comparative Example 1;

[0041] Figure 16 Sodium-ion batteries prepared from the hard carbon anode material of Comparative Example 1 and the molybdenum carbide-modified hard carbon solid nanosphere anode material of Example 2 exhibit voltage ranges of 0.01-3V and 30-2000 mAg. -1 Comparison chart of rate performance under different conditions;

[0042] Figure 17 Sodium-ion batteries prepared from the hard carbon anode material of Comparative Example 1 and the molybdenum carbide-modified hard carbon solid nanosphere anode material of Example 2 exhibit performance in the voltage range of 0.01-3V and 50 mAg. -1Comparison of cycling performance under low current density conditions;

[0043] Figure 18 Sodium-ion batteries prepared from the hard carbon anode material of Comparative Example 1 and the molybdenum carbide-modified hard carbon solid nanosphere anode material of Example 2 exhibit a voltage range of 0.01-3V and a capacity of 2000 mAg. -1 Comparison of cycling performance under high current density conditions;

[0044] Figure 19 Scanning electron microscope image of MoO2-CNTs prepared in Comparative Example 2;

[0045] Figure 20 Lithium-ion batteries prepared using the MoO2-CNT material in Comparative Example 2 exhibited good performance in the test voltage range of 1–3 V and current density of 50–20000 mA g. -1 Rate performance at lower speeds. Detailed Implementation

[0046] Example 1:

[0047] 0.36 g of commercial MoO3 was added to 40 ml of distilled water. 25% ammonia solution was added dropwise at a rate of 0.05 mL / min to adjust the pH of the solution to approximately 7.5. The solution was stirred until homogeneous at 80 °C. 0.4 ml of the prepared solution was mixed with 3.15 g of glucose and added to 70 ml of distilled water, then stirred until homogeneous. The solution was transferred to a 100 ml hydrothermal reactor and hydrothermally heated at 180 °C for 12 h. The resulting product was centrifuged and washed with anhydrous ethanol, then dried at 80 °C for 12 h in a constant temperature oven. The resulting powder was calcined in helium at 1300 °C for 3 h to obtain molybdenum carbide-modified hard carbon solid nanosphere anode material, with a heating rate of 5 °C / min.

[0048] The morphology and particle size of the samples were observed using a Nova NanoSEM 230 scanning electron microscope from FEI (USA). It was found that the spherical particle size distribution was uniform and no agglomeration occurred. Figure 1 The prepared molybdenum carbide-modified hard carbon solid nanosphere anode material was uniformly mixed with 80 wt.% of the prepared material, 10 wt.% of conductive acetylene black, and 10 wt.% of sodium carboxymethyl cellulose (CMC) to form a slurry. This slurry was then uniformly coated onto copper foil. After vacuum drying, coin cells were assembled using sodium foil as the counter electrode for rate performance testing. The rate performance test voltage range was 0.01–3V, and the current density was 30–2000 mA g. -1 Its rate performance test results are as follows: Figure 2 As shown.

[0049] Example 2:

[0050] 0.72 g of commercial MoO3 was added to 40 ml of distilled water. 25% ammonia solution was added dropwise at a rate of 0.05 mL / min to adjust the pH of the solution to approximately 7.5. The solution was stirred until homogeneous at 80 °C. 0.4 ml of the prepared solution was mixed with 3.15 g of glucose and added to 70 ml of distilled water, then stirred until homogeneous. The solution was transferred to a 100 ml hydrothermal reactor and hydrothermally heated at 180 °C for 12 h. The resulting product was centrifuged and washed with anhydrous ethanol, then dried at 80 °C for 12 h in a constant temperature oven. The resulting powder was calcined in helium at 1300 °C for 3 h to obtain molybdenum carbide-modified hard carbon solid nanosphere anode material, with a heating rate of 5 °C / min.

[0051] The morphology and particle size of the samples were observed using a Nova NanoSEM 230 scanning electron microscope from FEI (USA). It was found that the spherical particles had a uniform size distribution, with a diameter of approximately 500–600 nm, and no aggregation was observed. Figure 3 The internal structure of the sample was observed using a JEOL JEM-2100F transmission electron microscope (TEM), revealing its unique solid structure, such as... Figure 4 As shown. Energy-dispersive X-ray spectroscopy analysis of the material yielded the surface distribution map of Mo elemental distribution, as shown below. Figure 5 The molybdenum carbide-modified hard carbon solid nanosphere material, by dispersing molybdenum carbide in situ on the surface of hard carbon nanospheres, significantly increases the number of electrochemical active sites, improves reversible capacity, and the oxide layer on the molybdenum carbide surface hinders direct contact between the active phase and the electrolyte, reducing the consumption of irreversible alkali metal ions, thus improving the first-cycle coulombic efficiency and enhancing the electrochemical performance of the material. The samples were analyzed using a Rigaku D / max-2500 X-ray diffractometer (Japan), and the results are as follows: Figure 6 As shown, apart from the two broad carbon peaks (002) and (101), the other diffraction peaks in the figure correspond to the diffraction peaks of Mo2C after comparison and analysis with the PDF card. The prepared molybdenum carbide-modified hard carbon solid nanosphere anode material was mixed evenly with 80 wt.% of the preparation material, 10 wt.% of conductive acetylene black, and 10 wt.% of sodium carboxymethyl cellulose (CMC) to form a slurry, which was then uniformly coated onto copper foil and vacuum dried. Subsequently, a coin cell was assembled using a lithium sheet as the counter electrode for rate performance testing. The rate performance test voltage range was 0.01–3V, and the current density was 30–2000 mA g. -1 Its rate performance test results are as follows: Figure 7 As shown, coin cells were assembled using sodium sheets as the counter electrode, and their electrochemical performance was tested. Rate performance testing was conducted over a voltage range of 0.01–3V and a current density of 30–2000 mA / g. -1 Its rate performance test results are as follows: Figure 8As shown, the prepared molybdenum carbide-modified hard carbon solid nanosphere anode material exhibits a significant rate advantage under both low and high current density conditions. Within the test voltage range of 0.01–3V, even when the current density increases to 2000 mA g, the rate performance remains superior. -1 At that time, the specific capacity of the material can still reach 200 mAh g. -1 The above applies; the cycle performance test voltage range is 0.01–3V, and the current density is 50mA g. -1 Its cycle performance test results are as follows: Figure 9 As shown in the figure, at 50mA g -1 At current density, the first discharge capacity reaches 350mAh g. -1 The initial coulombic efficiency is as high as 82%, and the capacity retention is very high after 100 cycles; the cycle performance test voltage range is 0.01~3V, and the current density is 2000mA g. -1 Its cycle performance test results are as follows: Figure 10 As shown in the figure, at 2000 mA g -1 At the current density, the activated discharge capacity reaches as high as 184.57 mAh g. -1 After 600 cycles, the capacity retention rate reached 99.70%, demonstrating the high reversible capacity and excellent cycle stability of the molybdenum carbide-modified hard carbon solid nanosphere anode material. A coin cell was assembled using a potassium sheet as the counter electrode for rate performance testing. The rate performance test voltage range was 0.01–3V, and the current density was 30–2000 mA g. -1 Its rate performance test results are as follows: Figure 11 As shown.

[0052] Example 3:

[0053] 1.08 g of commercial MoO3 was added to 40 ml of distilled water. 25% ammonia solution was added dropwise at a rate of 0.05 mL / min to adjust the pH of the solution to approximately 7.5. The solution was stirred until homogeneous at 80 °C. 0.4 ml of the prepared solution was mixed with 3.15 g of glucose and added to 70 ml of distilled water, then stirred until homogeneous. The solution was transferred to a 100 ml hydrothermal reactor and hydrothermally heated at 180 °C for 12 h. The resulting product was centrifuged and washed with anhydrous ethanol, then dried at 80 °C for 12 h in a constant temperature oven. The resulting powder was calcined in helium at 1300 °C for 3 h to obtain molybdenum carbide-modified hard carbon solid nanosphere anode material, with a heating rate of 5 °C / min.

[0054] Using a Nova NanoSEM 230 scanning electron microscope from FEI (USA) to observe the morphology and particle size of the samples, it was found that the spherical particle size distribution was uniform and no agglomeration occurred. Figure 12The prepared molybdenum carbide-modified hard carbon solid nanosphere anode material was uniformly mixed with 80 wt.% of the prepared material, 10 wt.% of conductive acetylene black, and 10 wt.% of sodium carboxymethyl cellulose (CMC) to form a slurry. This slurry was then uniformly coated onto copper foil. After vacuum drying, coin cells were assembled using sodium foil as the counter electrode for rate performance testing. The rate performance test voltage range was 0.01–3V, and the current density was 30–2000 mA g. -1 Its rate performance test results are as follows: Figure 13 As shown.

[0055] Comparative Example 1

[0056] Add 25% ammonia solution dropwise to 40 ml of distilled water at a rate of 0.05 mL / min to adjust the pH of the solution to approximately 7.5, and stir until homogeneous at 80°C. Take 0.4 ml of the prepared solution and 3.15 g of glucose, mix them, and add them to 70 ml of distilled water, stirring until homogeneous. Transfer the solution to a 100 ml hydrothermal reactor and hydrothermally heat at 180°C for 12 h. Centrifuge the resulting product and wash it with anhydrous ethanol, then dry it in a constant temperature oven at 80°C for 12 h. Calcine the resulting powder in helium at 1300°C for 3 h to obtain pure hard carbon anode material with glucose as a precursor, with a heating rate of 5°C / min.

[0057] Using a Nova NanoSEM 230 scanning electron microscope from FEI (USA) to observe the morphology and particle size of the samples, it was found that the particle size distribution was uneven and there was a large amount of agglomeration. Figure 14 The internal structure of the sample was observed using a JEOL JEM-2100F transmission electron microscope (TEM), revealing its unique solid structure, such as... Figure 15 As shown. The prepared hard carbon material was mixed evenly with 80 wt.% of the raw material, 10 wt.% of conductive acetylene black, and 10 wt.% of sodium carboxymethyl cellulose (CMC) to form a slurry. This slurry was then uniformly coated onto copper foil. After vacuum drying, coin cells were assembled using a sodium sheet as the counter electrode for electrochemical performance testing. The rate performance test voltage range was 0.01–3V, and the current density was 30–2000 mA g. -1 Its rate performance is comparable to that of the sodium-ion battery made from the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2, in the voltage range of 0.01-3V and 30-2000 mAg. -1 The comparison chart of rate performance under the given conditions is shown below. Figure 16 Cyclic performance testing voltage range is 0.01–3V, current density is 50mA g -1 Its cycle performance is comparable to that of the sodium-ion battery made from the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2, within a voltage range of 0.01-3V and a 50mAg. -1 The comparison graph of cycling performance under the conditions is shown below. Figure 17 Cyclic performance testing voltage range is 0.01–3V, current density is 2000 mA g -1 Its cycle performance is comparable to that of the sodium-ion battery made from the molybdenum carbide-modified hard carbon solid nanosphere anode material in Example 2, within a voltage range of 0.01-3V and a 50mAg. -1 The comparison graph of cycling performance under the conditions is shown below. Figure 18 It can be seen that, in terms of both rate capability and cycle life, the molybdenum carbide-modified hard carbon solid nanosphere anode material performs far better than that of pure hard carbon material, demonstrating the superiority of the molybdenum carbide-modified hard carbon solid nanosphere anode material.

[0058] Comparative Example 2

[0059] Multi-walled carbon nanotube powder was ultrasonically dispersed in anhydrous ethanol for 30 minutes using a magnetic stirrer. After vacuum filtration, the solution was dried at 120°C for 3 hours to remove residual solvent, yielding a binderless carbon nanotube paper electrode with a diameter of 50 mm and a thickness of 50 ± 10 μm. The obtained carbon nanotube paper was transferred to an open atomic layer deposition (OpAL) apparatus, where a molybdenum oxide coating was prepared by cycling using molybdenum hexacarbonyl (Mo(CO)6) as the metal precursor and ozone as the reactant gas. Mo(CO)6 was preheated to 60°C in a bubbler and introduced into the reaction chamber using argon as the carrier gas. One atomic layer cycle consisted of 15 s of Mo(CO)6 addition, 10 s of argon purging, 45 s of ozone addition, and a final 15 s of pumping. The reactor temperature was maintained at 165°C during deposition. The carbon nanotube paper electrode was placed vertically in the reactor to allow effective penetration of the precursor from both sides, thus ensuring the coating covered the entire thickness of the carbon nanotube electrode. After coating preparation, the sample underwent further thermal annealing. MoO2-CNTs were obtained by annealing at 500℃ in an argon atmosphere for 1 hour. All annealing steps were performed at 10℃·min. -1 The heating and cooling rates were carried out at a certain level.

[0060] The morphology of the samples was observed using a JEOL JSM-7500F system with an accelerating voltage of 3kV, such as... Figure 19 Plate-like crystals were observed within a CNT network with a lateral dimension of up to 150 nm and a thickness of approximately 50 nm. For half-cell characterization, a mass loading of 1.3 ± 0.3 mg / cm³ was used. 2A 10mm MoO2-CNT electrode sheet was used as the working electrode, and a lithium metal chip was used as the reference and counter electrode. In the LIC device, MoO2-CNT was used as the negative electrode, AC (YP-80F type, Kuraray, 5% wt% PTFE bond, 100μm thickness) was used as the positive electrode, and a lithium metal chip was used as the observation reference electrode. Battery assembly was performed in an argon-filled glove box. Rate performance testing was conducted at a voltage range of 1–3V and a current density of 50–20000 mA g. -1 Ratio performance such as Figure 20 As can be seen from the figure, molybdenum oxide agglomerates extensively on the CNT surface, forming plate-like crystals. Compared with molybdenum carbide dispersed in situ on the surface of hard carbon nanospheres, the electrochemical active sites are significantly reduced, and the ion diffusion capacity is decreased. This results in a large area of ​​direct contact between the active phase and the electrolyte, making the performance of MoO2-CNT material far inferior to that of the molybdenum carbide-modified hard carbon solid nanosphere anode material in terms of both rate capability and cycle capability.

[0061] Comparative Example 2: Reference Fleischmann, S.; Zeiger, M.; Quade, A.; Kruth, A.; Presser, V. Atomic Layer-Deposited Molybdenum Oxide / Carbon Nanotube Hybrid Electrodes: The Influence of Crystal Structure on Lithium-Ion Capacitor Performance.ACSAppl.Mater.Inter.2018,10,18675–18684.

[0062] This invention has many other embodiments. Those skilled in the art can make corresponding changes and modifications without departing from the spirit and substance of the invention, but such changes and modifications should fall within the protection scope of the claims of this invention.

Claims

1. A method for preparing a molybdenum carbide-modified hard carbon solid nanosphere anode material, characterized in that, Includes the following steps: (1) Dissolve molybdenum salt or molybdenum oxide in deionized water to form a solution; (2) Add the alkaline solution to the solution obtained in step (1) and mix well; (3) Add the mixed solution obtained in step (2) and the organic matter to the solvent and mix well; (4) The mixed solution obtained in step (3) is subjected to a hydrothermal reaction; (5) After cleaning and drying the product obtained in step (4), calcining it in an inert atmosphere will yield the molybdenum carbide modified hard carbon solid nanosphere anode material.

2. The preparation method according to claim 1, characterized in that, Step (1) The dissolution temperature is 30~90 ℃ and the stirring time is 1~24 h.

3. The preparation method according to claim 1, characterized in that, The alkaline solution mentioned in step (2) is an alkaline solution or salt solution with a pH slightly greater than 7, including at least one of sodium bicarbonate solution, potassium carbonate solution, and ammonia water.

4. The preparation method according to claim 1, characterized in that, The alkaline solution in step (2) is added dropwise at a rate of 0.05 mL / min to 0.25 mL / min to ensure that the solution is fully diffused and mixed evenly.

5. The preparation method according to claim 1, characterized in that, The volume ratio of the alkaline solution added in step (2) to the solution obtained in step (1) is 1:20 to 1:200, so that the pH of the mixed solution is 7 to 8.5, which is weakly alkaline.

6. The preparation method according to claim 1, characterized in that, The volume ratio of the mixed solution obtained in step (2) to the solvent in step (3) is 1:10 to 1:

500.

7. The preparation method according to claim 1, characterized in that, The organic matter mentioned in step (3) is biomass, resin carbon, carbohydrates or other organic polymers, and the concentration of the added organic matter is 1~100 mg / mL.

8. The preparation method according to claim 1, characterized in that, The hydrothermal temperature in step (4) is 100~250℃ and the holding time is 4~24 h; the calcination process in step (5) is a calcination temperature of 700~1600℃, a calcination time of 0.5~6 h, and a heating rate of 0.1℃ / min~5℃ / min.

9. A molybdenum carbide-modified hard carbon solid nanosphere anode material, characterized in that, It is prepared by the method described in any one of claims 1-8.

10. The application of the molybdenum carbide-modified hard carbon solid nanosphere anode material according to claim 9, characterized in that, Used to prepare electrodes for alkali metal ion batteries.

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