Preparation method of amorphous MoO2-x (at) C composite material

Abstract

The invention relates to the technical field of amorphous preparation technologies, in particular to a preparation method of an amorphous MoO2-x (at) C composite material, which comprises the following steps: S1, dissolving phosphomolybdic acid in ethanol; dissolving 2-methylimidazole in another part of ethanol, standing the mixed solution, and collecting an obtained Mo-MI precursor through centrifugal operation; s2, dispersing the Mo-MI precursor nanospheres into deionized water, and stirring the Mo-MI precursor nanospheres and the deionized water; dropwise adding a pyrrole (Py) solution, and continuously stirring under an ice-water bath condition; then, through centrifugal treatment, a Mo-MI coated PPy (Mo-MI coated with polypyrrole) precursor is obtained; and S3, placing the dried Mo-MI-coated PPy precursor in a nitrogen environment, and carrying out pyrolysis treatment at 450 DEG C for 2 hours to obtain the amorphous MoO2-x-coated C composite material. The MoO2 prepared by the method disclosed by the invention has the characteristics of an amorphous structure and a core-shell structure, the electronic conductivity of the MoO2 is remarkably enhanced due to the characteristic of the amorphous state, and the migration mode of Li < + > is optimized, so that the rate performance of the material is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of amorphous preparation technology, and in particular to an amorphous MoO 2-x @C Preparation method of composite material. Background Art

[0002] MoO2 is beneficial to Li due to its unique distorted rutile crystal structure. + The embedding and extraction inside the material show a high reversibility of capacity, thus having the potential for industrial application. However, due to the current preparation methods, low conductivity and volume expansion problems during the cycle, MoO2 faces the challenges of poor cycle performance and poor cycle stability when used as an electrode material. These factors jointly restrict the progress of its large-scale application.

[0003] The existing Chinese patent document CN201911410269.6 discloses a method for synthesizing MoO2@C nanofiber flexible film material by electrospinning technology. The method for synthesizing MoO2@C nanofiber flexible film material by electrospinning technology of the present invention is: taking a molybdenum source and dissolving it in a mixed solution of deionized water and ethylene glycol to obtain a solution A after dissolution; adding polyvinyl pyrrolidone (PVP) to solution A to dissolve and obtain a solution B; electrospinning, drying, pre-oxidizing, and sintering the solution B under inert atmosphere conditions to obtain a MoO2@C nanofiber flexible film material.

[0004] The existing Chinese patent document CN201210100507.5 discloses a method for preparing a molybdenum dioxide / carbon composite negative electrode material, and the main steps are as follows: 1) soaking a cotton fiber fabric of a certain size in an ethanol solution of phosphomolybdic acid and stirring; 2) drying and aging the soaked cotton fiber fabric; 3) heat-treating the dried and aged cotton fiber fabric in a mixed atmosphere to obtain a molybdenum dioxide / carbon (MoO2 / C) composite material.

[0005] The above preparation methods all have the disadvantages of complex preparation process, many influencing factors, poor repeatability, etc. The prepared electrode materials have poor effects and are prone to waste of resources. In addition, the above problems only consider the acceleration of Li + diffusion in porous channels and solid / liquid interfaces, but does not promote Li + Rapid migration in the MoO2 crystal structure. Summary of the invention

[0006] The object of the present invention is to provide an amorphous MoO 2-x @C composite material preparation method, the method of the present invention is to prepare amorphous MoO by low temperature rapid annealing 2-x @C. The amorphous properties significantly enhance its electronic conductivity and have a positive impact on Li+ The migration mode of MoO2 was optimized, which greatly improved the rate performance of the material. More importantly, the combination of this amorphous structure and the carbon coating layer provides the necessary volume expansion buffer space for MoO2 during the charge and discharge cycle, effectively enhancing its lithium storage capacity and cycle stability, and extending the cycle life.

[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0008] Amorphous MoO 2-x The preparation method of the @C composite material uses phosphomolybdic acid as a molybdenum source and pyrrole as a carbon source, comprising the following steps:

[0009] S1: dissolving phosphomolybdic acid in ethanol to prepare a phosphomolybdic acid ethanol solution. Subsequently, dissolving 2-methylimidazole in another portion of ethanol to form a 2-methylimidazole ethanol solution, and adding it to the phosphomolybdic acid ethanol solution. Next, the mixed solution is allowed to stand, and the resulting Mo-MI precursor is collected by centrifugation.

[0010] S2: Disperse the Mo-MI precursor (generated by the reaction of phosphomolybdic acid and 2-methylimidazole) nanospheres obtained in step S1 into deionized water and stir. Then, add pyrrole (Py) solution dropwise and continue stirring under ice-water bath conditions. After that, obtain Mo-MI@PPy (polypyrrole-coated Mo-MI) precursor by centrifugation. The precursor is vacuum dried at 60°C for 24 hours.

[0011] S3: The dried Mo-MI@PPy precursor was placed in a nitrogen environment and pyrolyzed at 450 °C for 2 hours to obtain amorphous MoO 2-x @C composite material (0<x<1).

[0012] Furthermore, in step S1, the ratio of phosphomolybdic acid to ethanol is 0.06 mmol:100 mL.

[0013] Furthermore, in step S1, the ratio of 2-methylimidazole to ethanol is 12.0 mml:100 mL.

[0014] Furthermore, the purity of ethanol in step S1 is 99.7%.

[0015] Furthermore, in step S2, the ratio of Mo-MI nanospheres to ionized water is 50 mg:50 mL.

[0016] Furthermore, the amount of pyrrole used in step S2 is 100 μL.

[0017] Furthermore, in step S2, the Mo-MI nanospheres are dispersed in deionized water and stirred for 1 hour, and then 100 μL of pyrrole (Py) solution is added dropwise and stirred in an ice-water bath for 2 hours.

[0018] Beneficial effects of the present invention:

[0019] Amorphous MoO 2-x @C composites show significantly enhanced electronic conductivity, the core reason for which is the disorder of the amorphous structure. This disordered structure breaks the strict band structure in the crystalline material, resulting in the generation of electron localization and the reduction of the band gap, so Li + It can be easily embedded / released in the material. In addition, the carbon coating further improves the conductivity of the material. The carbon material forms a conductive network in the composite material, providing a high-speed channel for electron transmission, thereby greatly improving the conductivity of the entire composite material. This structural electron transmission advantage enables the electrode material to maintain excellent performance under fast charge and discharge conditions.

[0020] Amorphous structure for Li + The migration path of Li + This is partly due to the lack of defects such as grain boundaries and dislocations in amorphous materials, which usually block Li in crystalline materials. + In addition, the presence of the carbon layer not only provides physical protection, but also further reduces the Li + The resistance to migration accelerates the insertion and extraction of lithium ions. + The migration mechanism enables the material to maintain excellent discharge capacity at high rates.

[0021] During the charge and discharge process, Li + The embedding / de-embedding of MoO2 will lead to the volume change of MoO2 materials, and the traditional crystalline structure is prone to structural collapse and pulverization. 2-x @C provides sufficient volume expansion buffer space through the flexible coating of the carbon layer, absorbs the intrinsic stress, and prevents the agglomeration and rupture of the active material particles. This core-shell structure design significantly improves the structural integrity and stability of the material in multiple charge and discharge cycles. The results show that the material can still maintain high capacity after multiple cycles, which means that its cycle life has been effectively extended.

[0022] The use of phosphomolybdic acid and pyrrole as reaction precursors and the low-temperature pyrolysis process not only avoid the environmental burden that may be caused by high temperature and violent reaction conditions, but also ensure the chemical stability of the material. The presence of the carbon layer provides a protective barrier for the active material, avoiding excessive oxidation or dissolution caused by side reactions during the electrochemical reaction, further ensuring the chemical stability and safety of the material. In addition, the selection of chemical reagents and the process flow in the entire synthesis process are in line with the principles of green chemistry, reducing the risk of environmental pollution and improving the sustainability of the process.

[0023] The amorphous MoO provided by the present invention 2-x @C composite materials have shown significant improvements in electrochemical performance, laying a solid foundation for their large-scale application in energy storage devices such as lithium-ion batteries.

[0024] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0026] Figure 1 It is a schematic diagram of the overall process of the present invention;

[0027] Figure 2 The carbon-coated amorphous MoO2 (MoO 2-x @C) Field emission scanning images and high-magnification transmission electron microscopy images; (a) Mo-MI precursor and (b) MoO 2-x SEM image of @C-450. (c) MoO 2-x @C-450 low magnification transmission image. (de)MoO 2-x High magnification transmission electron microscopy images of (gl) MoO@C-450 and (f) MoO2@C. 2-x @STEM element mapping of C-450;

[0028] Figure 3 The carbon-coated amorphous MoO2 (MoO 2-x @C) Electrochemical performance diagram; (a) MoO 2-x @C-450 cyclic voltammetry curve. (b) MoO 2-x Rate performance of MoO2@C-350 / 450 / 550 and MoO2@C. (c) MoO 2-x@C-450 charge and discharge curves at different current densities. (d) MoO 2-x Long cycle performance of MoO2@C-450 and MoO2@C. 2-x @C-450 charge and discharge curves at constant current density. (f) MoO 2-x @C-450 at different scan rates (0.1-1.0mV s -1 ) CV curves under 0.1, 0.2, 0.5, 0.8 and 1.0 mV s -1 When, MoO 2-x @C-450 The percentage of capacitance effect and diffusion effect.

[0029] Figure 4 The carbon-coated amorphous MoO2 (MoO 2-x @C) Electrochemical kinetics and full cell diagram; (a) MoO 2-x Electrochemical impedance spectroscopy of MoO2@C-350 / 450 / 550 and MoO2@C. (b) Warburg factor diagram in low frequency region. (c) MoO 2-x GITT curves of MoO2@C-450 and MoO2@C. (d) 2-x @C-450 and MoO2@C in discharge and charge states Li+ )value. (e)MoO 2-x @C-450 EIS spectra at different cycle times. (f) Full battery (MoO 2-x @C-450||LCO). (g) MoO 2-x @C-450||Rate performance of LCO. (h)MoO 2-x @C-450||Cycling performance of LCO. (i) Capacity-voltage curves of the whole battery at different cycles. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] The amorphous MoO 2-x The preparation method of the @C composite material uses phosphomolybdic acid as a molybdenum source and pyrrole as a carbon source, comprising the following steps:

[0033] S1: 0.06 mmol of phosphomolybdic acid was dissolved in 100 mL of ethanol. Then, 12.0 mml of 2-methylimidazole was dissolved in another 100 mL of ethanol to prepare a solution, which was then added to the phosphomolybdic acid solution. The mixed solution was allowed to stand for 24 hours. Thereafter, the resulting precursor was collected by centrifugation and vacuum dried at 60°C for 24 hours.

[0034] S2: 50 mg of Mo-MI nanospheres were dispersed in 50 mL of deionized water and stirred for 1 hour, and then 100 μL of pyrrole (Py) solution was added dropwise and stirred in an ice-water bath for 2 hours. The solution was centrifuged to obtain the Mo-MI@PPy precursor, which was then vacuum dried at 60 °C for 24 hours.

[0035] S3: The prepared Mo-MI@PPy precursor was pyrolyzed in a nitrogen environment at 450 °C for 2 h to obtain carbon-coated amorphous MoO2 (MoO 2-x @C).

[0036] Example 2

[0037] The amorphous MoO 2-x The preparation method of the @C composite material uses phosphomolybdic acid as a molybdenum source and dopamine hydrochloride as a carbon source, comprising the following steps:

[0038] S1: 0.06 mmol of phosphomolybdic acid was dissolved in 100 mL of ethanol. Then, 12.0 mml of 2-methylimidazole was dissolved in another 100 mL of ethanol to prepare a solution, which was then added to the phosphomolybdic acid solution. The mixed solution was allowed to stand for 24 hours. Thereafter, the resulting precursor was collected by centrifugation and vacuum dried at 60°C for 24 hours.

[0039] S2: Disperse 50 mg Mo-MI nanospheres into 50 mL Tris buffer (10×10 -3 M) and stirred for 1 hour, and then 50 mg of dopamine hydrochloride (PDA) was added to the mixture. After the solution was stirred for 24 hours, the solution was centrifuged to obtain Mo-MI@PDA precursor. The collected material was vacuum dried at 60°C for 24 hours.

[0040] S3: The prepared Mo-MI@PDA precursor was pyrolyzed in a nitrogen environment at 450 °C for 2 h to obtain carbon-coated amorphous MoO2 (denoted as MoO 2-x @PDA).

[0041] Example 3

[0042] The amorphous MoO 2-xThe preparation method of the @C composite material uses phosphomolybdic acid as a molybdenum source and polyacrylonitrile as a carbon source, comprising the following steps:

[0043] S1: 0.06 mmol of phosphomolybdic acid was dissolved in 100 mL of ethanol. Then, 12.0 mml of 2-methylimidazole was dissolved in another 100 mL of ethanol to prepare a solution, which was then added to the phosphomolybdic acid solution. The mixed solution was allowed to stand for 24 hours. Thereafter, the resulting precursor was collected by centrifugation and vacuum dried at 60°C for 24 hours.

[0044] S2: 0.5 g of polyacrylonitrile (PAN) was added to 5.0 mL of N,N-dimethylformamide (DMF). Subsequently, 0.15 g of the prepared Mo-MI precursor was dispersed into the solution and stirred vigorously for 24 h to ensure uniformity. Finally, the homogeneous solution was loaded into a 5 mL syringe and electrospun at 20 kV to form Mo-MI@CNF precursor.

[0045] S3: The prepared Mo-MI@CNF precursor was pyrolyzed in a nitrogen environment at 450 °C for 2 h to obtain carbon-coated amorphous MoO2 (denoted as MoO 2-x @CNF).

[0046] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. Amorphous MoO 2-x @C A method for preparing a composite material, characterized in that: Using phosphomolybdic acid as a molybdenum source and pyrrole as a carbon source, the method comprises the following steps: S1: dissolving phosphomolybdic acid in ethanol to prepare a phosphomolybdic acid ethanol solution. Subsequently, dissolving 2-methylimidazole in another portion of ethanol to form a 2-methylimidazole ethanol solution, and adding it to the phosphomolybdic acid ethanol solution. Next, the mixed solution is allowed to stand, and the resulting Mo-MI precursor is collected by centrifugation. S2: Disperse the Mo-MI precursor nanospheres obtained in step S1 into deionized water and stir. Then, add the pyrrole solution dropwise and continue stirring under ice-water bath conditions. After that, obtain the Mo-MI@PPy precursor by centrifugation. The precursor is vacuum dried at 60°C for 24 hours. S3: The dried Mo-MI@PPy precursor was placed in a nitrogen environment and pyrolyzed at 450 °C for 2 hours to obtain amorphous MoO 2-x @CComposite materials.

2. Amorphous MoO according to claim 1 2-x @C A method for preparing a composite material, characterized in that: In the step S1, the ratio of phosphomolybdic acid to ethanol is 0.06 mmol:100 mL.

3. Amorphous MoO according to claim 1 2-x @C A method for preparing a composite material, characterized in that: In the step S1, the ratio of 2-methylimidazole to ethanol is 12.0 mml:100 mL.

4. The amorphous MoO according to claim 1 2-x @C A method for preparing a composite material, characterized in that: The purity of ethanol in step S1 is 99.7%.

5. The amorphous MoO according to claim 1 2-x @C A method for preparing a composite material, characterized in that: The ratio of Mo-MI nanospheres to ionized water in step S2 is 50 mg:50 mL.

6. The amorphous MoO according to claim 1 2-x @C A method for preparing a composite material, characterized in that: The amount of pyrrole used in step S2 is 100 μL.

7. The amorphous MoO according to claim 1 2-x @C A method for preparing a composite material, characterized in that: In step S2, the Mo-MI nanospheres were dispersed in deionized water and stirred for 1 hour, and then 100 μL of pyrrole solution was added dropwise and stirred in an ice-water bath for 2 hours.

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