A method for preparing a molybdenum-based organic metal framework composite negative electrode material

Abstract

The present invention discloses a platinum-based organic metal framework composite negative electrode material and a preparation method thereof. First, molybdate, copper salt and L-glutamic acid are dissolved in deionized water and stirred to form a molybdenum salt solution. Then, graphene oxide prepared by an improved Hummers method is added to the above solution to form a graphene oxide molybdenum salt dispersion. Thiophene dicarboxylic acid is added to an anhydrous ethanol solvent and stirred evenly, and then added to the above graphene oxide molybdenum salt dispersion for reaction. The precipitate is centrifuged to obtain a platinum-based organic metal framework composite negative electrode material. The present invention uses a one-step method to composite a platinum-based organic metal framework material with graphene oxide. The prepared platinum-based metal framework negative electrode material has good cycle life and high discharge specific capacity. The preparation method is highly controllable, has a simple preparation process, is easy to mass produce, and has good practical application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery material preparation, and in particular to a molybdenum-based organic metal framework composite negative electrode material and a preparation method thereof. Background Art

[0002] New energy storage technology is the most effective solution for alleviating the fossil fuel crisis and maximizing the utilization of renewable energy. Lithium-ion batteries have become a leading energy storage technology due to their high energy density, long lifespan, and lightweight. However, extensive research has demonstrated that the electrochemical performance of lithium-ion batteries depends on the electrode materials used. Therefore, the search for electrode materials with high energy storage capacity and stable cycle life has become a research hotspot.

[0003] Metal-organic frameworks (MOFs) have been used as lithium-ion electrode materials due to their high porosity, tunable pore structure, and high specific surface area. The ultra-high porosity and tunable pore structure of MOFs facilitate interfacial charge transfer. Furthermore, compared to pure organic materials, MOFs exhibit superior thermal stability. Consequently, a growing number of researchers are investigating MOFs as lithium-ion electrode materials. However, like a double-edged sword, MOFs suffer from defects such as poor electronic conductivity, cycling stability, and low energy density, which limit their practical application in lithium-ion battery systems. To address these deficiencies, the synergistic effect of MOFs and graphene oxide has been exploited to enhance the overall performance of MOF-based composite anode materials. The resulting MOF-based composites exhibit significantly improved electrochemical cycling stability and discharge capacity. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a molybdenum-based organic metal framework composite negative electrode material and a preparation method thereof.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a molybdenum-based organic metal framework composite negative electrode material and a preparation method thereof, comprising the following steps:

[0006] Step (1), using the improved Hummers method, oxidizing graphite to obtain graphene oxide; and ultrasonically dispersing the graphene oxide in deionized water to obtain a graphene oxide dispersion;

[0007] Step (2), adding molybdate, copper salt and L-glutamic acid into deionized water in sequence and stirring until completely dissolved to obtain solution A;

[0008] Step (3): adding different masses of graphene oxide dispersions in step (1) to the solution in step (2), and continuing to stir to form solution B.

[0009] Step (4): add thiophenedicarboxylic acid to anhydrous ethanol solvent and stir evenly to form solution C.

[0010] Step (5): Mix solution B and solution C, stir evenly to obtain a black precipitate, centrifuge, wash the precipitate alternately with water and anhydrous ethanol, collect the precipitate, and vacuum dry to obtain a molybdenum-based organic metal framework composite negative electrode material.

[0011] Preferably, in the step (1), the graphene oxide is dispersed by centrifuging the product at 9000 rpm to form a dispersion.

[0012] Preferably, in step (2), the molybdate is one of ammonium tetrathiomolybdate, ammonium molybdate tetrahydrate, and sodium molybdate dihydrate.

[0013] Preferably, in step (2), the copper salt is one of copper sulfate, copper nitrate, and copper acetate, and the copper ion

[0014] The molar ratio of molybdenum to carbon is 1:2 to 4.

[0015] Preferably, in step (2), the mechanical stirring speed is 400 rpm and the stirring time is 0.5 to 3 h.

[0016] Preferably, in step (3), the ratio of the mass of graphene oxide added to the mass of molybdate is 1 to 3:20.

[0017] Preferably, in step (3), the mechanical stirring speed is 400 rpm and the stirring time is 1 to 3 hours.

[0018] Preferably, in step (4), the molar ratio of thiophenedicarboxylic acid to molybdenum atoms is 1:1 to 3.

[0019] Preferably, in step (4), the mechanical stirring speed is 400 rpm and the stirring time is 1 to 3 hours.

[0020] Preferably, in step (5), the mechanical stirring speed is 400 rpm and the stirring time is 9 to 16 hours.

[0021] Preferably, in step (5), the stirring temperature is 20-30°C.

[0022] Preferably, in step (5), the centrifugal speed is 4000 rpm and the centrifugal time is 8 min.

[0023] Preferably, in step (5), the vacuum drying temperature is 80° C. and the drying time is 12 h.

[0024] Beneficial effects: The present invention reports a simple method for synthesizing molybdenum-based organic metal framework composite negative electrode materials at room temperature. The present invention adopts the method of co-precipitation of Mo source and thiophene dicarboxylic acid to synthesize organic metal framework materials. At the same time, graphene oxide is introduced into the skeleton to improve the conductive properties of MOFs composite materials. By utilizing the synergistic effect of MOFs skeleton and graphene oxide, the comprehensive performance of MOFs composite negative electrode materials is improved, and the electrochemical cycle stability and discharge capacity of the obtained MOF-based composite materials are significantly improved. During the preparation process, graphene oxide adopts the improved Hummers method. The graphene oxide obtained by the improved Hummers method has a larger specific surface area and oxygen-containing groups, and is easier to coat on the surface of the molybdenum-based organic metal framework. The preparation method of the present invention is simple, low-cost, and mild reaction conditions, which is conducive to large-scale industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described here are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 These are electron microscope photos of the surface morphology of molybdenum-based organic metal framework composite negative electrode materials provided by some typical embodiments of the present invention;

[0027] Figure 2 This is an electron microscope photograph of the surface morphology of the molybdenum-based organic metal framework composite negative electrode material provided in the comparative example of the present invention;

[0028] Figure 3 Some typical embodiments of the present invention are 0.1mV s -1 Cyclic voltammetry curves at scan rates;

[0029] Figure 4 1. The constant current charge and discharge curves of some typical embodiments of the present invention as negative electrode materials for lithium-ion batteries;

[0030] Figure 5 Graphs showing the charge and discharge cycle performance of some typical embodiments of the present invention as negative electrode materials for lithium-ion batteries. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] Example 1

[0033] This embodiment provides a preparation process of a molybdenum-based organic metal framework composite negative electrode material, which specifically includes the following steps:

[0034] (1) Preparation of graphene oxide dispersion with a solution concentration of 5 mg / mL;

[0035] The improved Hummer method was used to prepare graphene oxide. The graphite oxidation time was appropriately extended. The graphene oxide used to prepare the composite negative electrode material was obtained by centrifugation at a speed of 9000 rpm.

[0036] (2) 0.02 mol sodium molybdate dihydrate, 0.01 mol copper acetate monohydrate, and 0.8 g L-glutamic acid were added to 400 mL deionized water and stirred for 0.5 h to obtain solution A.

[0037] (3) 0.24 g of graphene oxide dispersion was dropped into solution A and stirred at 400 rpm for 1 h to obtain solution B;

[0038] (4) Add 0.02 mol of thiophenedicarboxylic acid to 400 mL of anhydrous ethanol and stir at 400 rpm for 1 h to form solution C.

[0039] (5) Solution B was added to solution C, and after stirring at 20°C and 400 rpm for 9 h, a black precipitate was produced. The mixture was centrifuged at 4000 rpm for 8 min, and the black product was collected and washed alternately with deionized water and anhydrous ethanol for 2-3 times. Finally, the mixture was dried in a vacuum drying oven at 80°C for 12 h to obtain a molybdenum-based organic metal framework composite negative electrode material.

[0040] The scanning electron microscope image of the molybdenum-based organic metal framework composite negative electrode material prepared in the above steps is as follows: Figure 1 As shown in the figure, it can be seen that the composite negative electrode material is in a granular shape and is relatively uniform in size.

[0041] The composite material is used as a negative electrode material for lithium-ion batteries and exhibits a high discharge capacity (the first-cycle discharge capacity at a current of 0.1A / g reaches 1432 mAh / g). After 50 cycles, the capacity remains at 546.4 mAh / g. The electrochemical performance test results are as follows: Figure 3 、 Figure 4 、 Figure 5 shown.

[0042] Example 2

[0043] This embodiment provides a preparation process of a molybdenum-based organic metal framework composite negative electrode material, which specifically includes the following steps:

[0044] (1) Preparation of graphene oxide dispersion with a solution concentration of 5 mg / mL;

[0045] The improved Hummer method was used to prepare graphene oxide. The graphite oxidation time was appropriately extended. The graphene oxide used to prepare the composite negative electrode material was obtained by centrifugation at a speed of 9000 rpm.

[0046] (2) Take 0.03 mol of sodium molybdate dihydrate, 0.01 mol of copper acetate monohydrate, and 0.8 g of L-glutamic acid, add them to 400 mL of deionized water, and stir for 1.5 hours to obtain solution A;

[0047] (3) 0.48 g of graphene oxide dispersion was dropped into solution A and stirred at 400 rpm for 2 h to obtain solution B;

[0048] (4) Add 0.06 mol of thiophenedicarboxylic acid to 400 mL of anhydrous ethanol and stir at 400 rpm for 2 h to form solution C.

[0049] (5) Solution B was added to solution C, and after stirring at 25°C and 400 rpm for 14 h, a black precipitate was produced. The mixture was centrifuged at 4000 rpm for 8 min, and the black product was collected and washed alternately with deionized water and anhydrous ethanol for 2-3 times. Finally, the mixture was dried in a vacuum drying oven at 80°C for 12 h to obtain a molybdenum-based organic metal framework composite negative electrode material.

[0050] The scanning electron microscope image of the molybdenum-based organic metal framework composite negative electrode material prepared in the above steps is as follows: Figure 1 As shown in the figure, it can be seen that the composite negative electrode material is in a granular shape and is relatively uniform in size.

[0051] The composite material is used as a negative electrode material for lithium-ion batteries and exhibits a high discharge capacity (the first-cycle discharge capacity at a current of 0.1A / g reaches 1507.4 mAh / g). After 50 cycles, the capacity remains at 737.3 mAh / g. The electrochemical performance test results are as follows: Figure 3 、 Figure 4 、 Figure 5 shown.

[0052] Example 3

[0053] This embodiment provides a preparation process of a molybdenum-based organic metal framework composite negative electrode material, which specifically includes the following steps:

[0054] (1) Preparation of graphene oxide dispersion with a solution concentration of 5 mg / mL;

[0055] The improved Hummer method was used to prepare graphene oxide. The graphite oxidation time was appropriately extended. The graphene oxide used to prepare the composite negative electrode material was obtained by centrifugation at a speed of 9000 rpm.

[0056] (2) 0.04 mol of sodium molybdate dihydrate, 0.01 mol of copper acetate monohydrate, and 0.8 g of L-glutamic acid were added to 400 mL of deionized water and stirred for 3 h to obtain solution A.

[0057] (3) 0.72 g of graphene oxide dispersion was dropped into solution A and stirred at 400 rpm for 3 h to obtain solution B;

[0058] (4) 0.12 mol of thiophenedicarboxylic acid was added to 400 mL of anhydrous ethanol and stirred at 400 rpm for 3 h to form solution C;

[0059] (5) Solution B was added to solution C, and after stirring at 30°C and 400 rpm for 16 h, a black precipitate was produced. The mixture was centrifuged at 4000 rpm for 8 min, and the black product was collected and washed alternately with deionized water and anhydrous ethanol for 2-3 times. Finally, the mixture was dried in a vacuum drying oven at 80°C for 12 h to obtain a molybdenum-based organic metal framework composite negative electrode material.

[0060] The scanning electron microscope image of the molybdenum-based organic metal framework composite negative electrode material prepared in the above steps is as follows: Figure 1 As shown in the figure, it can be seen that the composite negative electrode material is in a granular shape and is relatively uniform in size.

[0061] The composite material is used as a negative electrode material for lithium-ion batteries and exhibits a high discharge capacity (the first-cycle discharge capacity at a current of 0.1A / g reaches 950.4 mAh / g). After 50 cycles, the capacity remains at 525.4 mAh / g. The electrochemical performance test results are as follows: Figure 3 、 Figure 4 、 Figure 5 shown.

[0062] Example 4

[0063] This embodiment provides a preparation process of a molybdenum-based organic metal framework composite negative electrode material, which specifically includes the following steps:

[0064] (1) Preparation of graphene oxide dispersion with a solution concentration of 5 mg / mL;

[0065] The improved Hummer method was used to prepare graphene oxide. The graphite oxidation time was appropriately extended. The graphene oxide used to prepare the composite negative electrode material was obtained by centrifugation at a speed of 9000 rpm.

[0066] (2) 0.02 mol of ammonium tetrathiomolybdate, 0.01 mol of copper acetate monohydrate, and 0.8 g of L-glutamic acid were added to 400 mL of deionized water and stirred for 0.5 h to obtain solution A.

[0067] (3) 0.24 g of graphene oxide dispersion was dropped into solution A and stirred at 400 rpm for 1 h to obtain solution B;

[0068] (4) Add 0.02 mol of thiophenedicarboxylic acid to 400 mL of anhydrous ethanol and stir at 400 rpm for 1 h to form solution C.

[0069] (5) Solution B was added to solution C, and after stirring at 20°C and 400 rpm for 9 h, a black precipitate was produced. The mixture was centrifuged at 4000 rpm for 8 min, and the black product was collected and washed alternately with deionized water and anhydrous ethanol for 2-3 times. Finally, the mixture was dried in a vacuum drying oven at 80°C for 12 h to obtain a molybdenum-based organic metal framework composite negative electrode material.

[0070] This composite material is used as a negative electrode material for lithium-ion batteries, showing a high discharge specific capacity (the first-cycle specific capacity at a current of 0.1A / g reaches 1135.4 mAh / g) and good cycle performance.

[0071] Example 5

[0072] This embodiment provides a preparation process of a molybdenum-based organic metal framework composite negative electrode material, which specifically includes the following steps:

[0073] (1) Preparation of graphene oxide dispersion with a solution concentration of 5 mg / mL;

[0074] The improved Hummer method was used to prepare graphene oxide. The graphite oxidation time was appropriately extended. The graphene oxide used to prepare the composite negative electrode material was obtained by centrifugation at a speed of 9000 rpm.

[0075] (2) Take 0.006 mol of ammonium molybdate tetrahydrate, 0.01 mol of copper nitrate dihydrate, and 0.8 g of L-glutamic acid, add them to 400 mL of deionized water, and stir for 1 hour to obtain solution A;

[0076] (3) 0.48 g of graphene oxide dispersion was dropped into solution A and stirred at 400 rpm for 2 h to obtain solution B;

[0077] (4) Add 0.06 mol of thiophenedicarboxylic acid to 400 mL of anhydrous ethanol and stir at 400 rpm for 2 h to form solution C.

[0078] (5) Solution B was added to solution C, and after stirring at 20°C and 400 rpm for 9 h, a black precipitate was produced. The mixture was centrifuged at 4000 rpm for 8 min, and the black product was collected and washed alternately with deionized water and anhydrous ethanol for 2-3 times. Finally, the mixture was dried in a vacuum drying oven at 80°C for 12 h to obtain a molybdenum-based organic metal framework composite negative electrode material.

[0079] This composite material is used as a negative electrode material for lithium-ion batteries, showing a high discharge specific capacity (the first-cycle discharge specific capacity at a current of 0.1 A / g reaches 1257.1 mAh / g) and good cycle performance.

[0080] Example 6

[0081] This embodiment illustrates a preparation process of a molybdenum-based organic metal framework composite negative electrode material, which is substantially the same as that of Example 1, except that in step 2, 0.003 mol of ammonium molybdate tetrahydrate replaces sodium molybdate dihydrate.

[0082] The prepared molybdenum-based organic metal framework composite negative electrode material has a surface morphology similar to that in Example 1, and when applied to lithium-ion batteries, it can also obtain a higher specific capacity and better cycle stability.

[0083] Example 7

[0084] This embodiment illustrates a preparation process of a molybdenum-based organic metal framework composite negative electrode material, which is substantially the same as that of Example 1, except that in step 2, 0.01 mol of copper sulfate pentahydrate replaces copper acetate monohydrate.

[0085] The prepared molybdenum-based organic metal framework composite negative electrode material has a surface morphology similar to that in Example 1, and when applied to lithium-ion batteries, it can also obtain a higher specific capacity and better cycle stability.

[0086] Comparative Example 1

[0087] This embodiment provides a preparation process of a molybdenum-based organic metal framework composite negative electrode material, which specifically includes the following steps:

[0088] (1) Preparation of graphene oxide dispersion with a solution concentration of 5 mg / mL;

[0089] The improved Hummer method was used to prepare graphene oxide, and the graphite oxidation time was appropriately extended. The graphene oxide used to prepare the composite negative electrode material was a centrifugal product obtained at a speed of 9000 rpm.

[0090] (2) Take 0.02 mol of sodium molybdate dihydrate and 0.8 g of L-glutamic acid, add them to 400 mL of deionized water, and stir for 0.5 h to obtain solution A;

[0091] (3) 0.5 g of graphene oxide dispersion was dropped into solution A and stirred at 400 rpm for 1 h to obtain solution B;

[0092] (4) Add 0.02 mol of thiophenedicarboxylic acid to 400 mL of anhydrous ethanol and stir at 400 rpm for 1 h to form solution C.

[0093] (5) Solution B was added to solution C, and stirred at 20°C and 400 rpm for 9 h to produce a black precipitate. The solution was centrifuged at 4000 rpm for 8 min, and the black product was collected and washed alternately with deionized water and anhydrous ethanol for 2-3 times. Finally, the solution was dried in a vacuum drying oven at 80°C for 12 h to obtain a molybdenum-based organic metal framework composite negative electrode material.

[0094] The scanning electron microscope image of the molybdenum-based organic metal framework composite negative electrode material prepared in the above steps is as follows: Figure 2 As shown in the figure, it can be seen that the composite negative electrode material is granular.

[0095] This composite material is used as a negative electrode material for lithium-ion batteries and exhibits a high discharge capacity (the first-cycle discharge capacity at a current of 0.1A / g reaches 1110.7 mAh / g). After 50 cycles, the capacity is only 420.9.3 mAh / g. The electrochemical performance test results are as follows: Figure 3 、 Figure 4 、 Figure 5 Compared with other examples, it is shown that copper ions are beneficial to improving the cycle performance of the composite material.

[0096] Comparative Example 2

[0097] This embodiment provides a preparation process of a molybdenum-based organic metal framework composite negative electrode material, which specifically includes the following steps:

[0098] (1) Preparation of graphene oxide dispersion with a solution concentration of 5 mg / mL;

[0099] The improved Hummer method was used to prepare graphene oxide, and the graphite oxidation time was appropriately extended. The graphene oxide used to prepare the composite negative electrode material was obtained by centrifugation at a speed of 9000 rpm.

[0100] (2) Take 0.02 mol of sodium molybdate dihydrate and 0.8 g of L-glutamic acid, add them to 400 mL of deionized water, and stir for 0.5 h to obtain solution A;

[0101] (3) Add 0.02 mol of thiophenedicarboxylic acid to 400 mL of anhydrous ethanol and stir at 400 rpm for 1 h to form solution B.

[0102] (4) Solution B was added to solution C, and after stirring at 20°C and 400 rpm for 9 h, a black precipitate was produced; the solution was centrifuged at 4000 rpm for 8 min, and the green product was collected and washed alternately with deionized water and anhydrous ethanol 2-3 times, and finally dried in a vacuum drying oven at 80°C for 12 h to obtain a molybdenum-based organic metal framework composite negative electrode material.

[0103] The scanning electron microscope image of the molybdenum-based organic metal framework composite negative electrode material prepared in the above steps is as follows: Figure 2 As shown in the figure, it can be seen that without adding graphene oxide, the morphology of the composite material is more seriously united and the uniformity is poor.

[0104] The composite material is used as a negative electrode material for lithium-ion batteries and exhibits a high discharge capacity (the first-cycle discharge capacity at a current of 0.1A / g reaches 1074.3 mAh / g). After 50 cycles, the capacity is only 362.3 mAh / g. The electrochemical performance test results are as follows: Figure 3 、 Figure 4 、 Figure 5 Experiments have shown that graphene oxide can improve the electrochemical performance of composite negative electrode materials.

Claims

1. A method for preparing a molybdenum-based organic metal framework composite negative electrode material, characterized in that: The following steps are involved: Step (1), using the improved Hummers method, oxidizing graphite to obtain graphene oxide; and ultrasonically dispersing the graphene oxide in deionized water, and dispersing the obtained product by centrifugation at 9000 rpm to obtain a graphene oxide dispersion, wherein the solution concentration is 5 mg / mL; Step (2), adding molybdate, copper salt and L-glutamic acid into deionized water in sequence and stirring until completely dissolved to obtain solution A; Step (3), adding different masses of graphene oxide dispersions in step (1) to the solution in step (2), and continuing to stir to form solution B; the ratio of the mass of the graphene oxide dispersion to the molar amount of molybdate is 0.24 g: 0.02 mol, 0.48 g: 0.03 mol or 0.48 g: 0.006 mol; Step (4), adding thiophenedicarboxylic acid to anhydrous ethanol solvent and stirring uniformly to form solution C; Step (5): Mix solution B and solution C, stir evenly to obtain a black precipitate, centrifuge, wash the precipitate alternately with water and anhydrous ethanol, collect the precipitate, and vacuum dry to obtain a molybdenum-based organic metal framework composite negative electrode material.

2. The method for preparing a molybdenum-based organic metal framework composite negative electrode material according to claim 1, wherein: In step (2), the molybdate is one of ammonium tetrathiomolybdate, ammonium molybdate tetrahydrate, and sodium molybdate dihydrate.

3. The method for preparing a molybdenum-based organic metal framework composite negative electrode material according to claim 1, wherein: In step (2): the copper salt is one of copper sulfate, copper nitrate and copper acetate.

4. The method for preparing a molybdenum-based organic metal framework composite negative electrode material according to claim 1, wherein: In step (2): the molar ratio of copper ions to molybdenum atoms is 1:2 to 4.

5. The method for preparing a molybdenum-based organic metal framework composite negative electrode material according to claim 1, wherein: In the step (2), the mechanical stirring speed is 400 rpm and the stirring time is 0.5 to 3 hours.

6. The method for preparing a molybdenum-based organic metal framework composite negative electrode material according to claim 1, wherein: In the step (3), the mechanical stirring speed is 400 rpm and the stirring time is 1 to 3 hours.

7. The method for preparing a molybdenum-based organic metal framework composite negative electrode material according to claim 1, wherein: In the step (4), the molar ratio of thiophenedicarboxylic acid to molybdenum atoms is 1:1 to 3.

8. The method for preparing a molybdenum-based organic metal framework composite negative electrode material according to claim 1, wherein: In the step (4), the mechanical stirring speed is 400 rpm and the stirring time is 1 to 3 hours.

9. The method for preparing a molybdenum-based organic metal framework composite negative electrode material according to claim 1, wherein: In the step (5), the mechanical stirring speed is 400 rpm, the stirring time is 9 to 16 hours, and the stirring temperature is 20 to 30°C.

10. The method for preparing a molybdenum-based organic metal framework composite negative electrode material according to claim 1, wherein: In the step (5), the centrifugal speed is 4000 rpm, the centrifugal time is 8 minutes, the vacuum drying temperature is 80°C, and the drying time is 12 hours.

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