Preparation method of high-performance supercapacitor electrode material

Abstract

The invention provides a preparation method of a high-performance supercapacitor electrode material, and belongs to the field of supercapacitor electrodes, and the method comprises the following steps: firstly synthesizing MoS2 powder through a hydrothermal reaction, then adding the MoS2 powder into a metal organic framework precursor, and after a proper standing time, obtaining a Co3O4 / MoS2 composite material through high-temperature annealing. The composition and performance of the composite material are optimized by regulating and controlling the content of Co3O4. The synergistic effect of Co3O4 and MoS2 significantly improves the electrochemical performance, and effectively overcomes the defects of a single material in the aspect of capacitive performance. The synthesis method is simple and convenient in process and low in material cost, and the composite material shows excellent electrochemical performance and has huge potential in practical application.

Description

Technical Field

[0001] The invention belongs to the technical field of supercapacitors, and in particular relates to a method for preparing a high-performance supercapacitor electrode material. Background Art

[0002] Energy plays an important role in economic development and human life, but the over-exploitation of fossil energy has caused serious environmental problems. In order to cope with the energy and environmental crisis, it is urgent to develop renewable green energy. However, solar energy, wind energy, etc. are limited by natural conditions, and the supply is unstable, which increases transportation costs. Therefore, research on energy storage technology is crucial. Supercapacitors have become a research hotspot in the field of new energy due to their advantages such as high power density, long cycle life, and high safety. However, the low energy density of supercapacitors limits their widespread use in practical applications.

[0003] Electrode materials are the key factors that determine the performance of supercapacitors. Therefore, it is of great significance to develop a new type of supercapacitor material. In recent years, transition metal sulfides, as a graphite-like layered structure material, have attracted widespread attention in the field of supercapacitors due to their adjustable electronic structure, good chemical stability, low cost, and abundant resources. However, due to problems such as low electrical conductivity and easy agglomeration, their effective performance as supercapacitor electrode materials is affected. Therefore, it is necessary to combine with other nanomaterials to construct heterogeneous composite materials. In past studies, many scholars have improved their electrochemical properties by combining them with carbon-based materials, doping them with metal or non-metal elements, or combining them with metal oxides. Although these methods have contributed to improving conductivity and electrochemical properties, the capacitance performance of the composite materials has not met expectations.

[0004] Therefore, a new type of composite material is needed that can effectively improve the conductivity and stability of transition metal sulfides and enhance the electrochemical performance, further breaking through the bottleneck of existing methods. Summary of the invention

[0005] In order to solve the problem of insufficient performance of transition metal sulfides used as supercapacitor electrode materials in the prior art, the present invention proposes a composite strategy based on transition metal oxides (Co3O4, MnO2, Fe2O3, etc.) and transition metal sulfides (MoS2, WS2, TiS2, etc.), by constructing an oxide-sulfide synergistic structure, optimizing the electron transmission path, reducing the charge transfer impedance, and improving the overall electrochemical activity. The excellent redox reaction of the oxide provides an additional pseudocapacitive effect, enhancing the specific capacitance of the material. At the same time, the oxide acts as a skeleton support, inhibits sulfide agglomeration, provides additional electrochemical active sites, and improves the overall energy storage performance. The oxide-sulfide composite strategy of the present invention provides a new idea for the development of high-performance supercapacitor electrode materials, and has broad application prospects in the field of energy storage devices.

[0006] The present invention provides a method for preparing a high-performance supercapacitor material, comprising the following steps:

[0007] (1) adding a molybdenum source and a sulfur source into deionized water in sequence to obtain a precursor solution;

[0008] (2) transferring the precursor solution into a high-pressure reactor to perform a hydrothermal reaction to obtain a black liquid;

[0009] (3) centrifuging and drying the black liquid in sequence to obtain MoS2 powder;

[0010] (4) adding a cobalt source into deionized water and stirring until completely dissolved to obtain solution A;

[0011] (5) adding the organic ligand into deionized water and stirring until completely dissolved to obtain solution B;

[0012] (6) Pour solution A into solution B, mix well, then add the MoS2 powder prepared in step (3), and let stand to react;

[0013] (7) After the reaction is completed, the mixed solution of step (6) is centrifuged and then dried to obtain MOF / MoS2 powder;

[0014] (8) Using a tubular furnace to perform high temperature annealing on the MOF / MoS2 powder to obtain Co3O4 / MoS2 supercapacitor material.

[0015] Preferably, in step (1), the molybdenum source is selected from at least one of ammonium heptamolybdate, molybdenum trioxide, and sodium molybdate, and the sulfur source is selected from at least one of thioacetamide, thiourea, and sodium sulfide, wherein the molar ratio of the molybdenum source to the sulfur source is 1:2.

[0016] Preferably, in step (2), the hydrothermal reaction is carried out in an oven, the hydrothermal reaction temperature is 160-200° C., and the reaction time is 20-30 hours.

[0017] Preferably, in step (3), ethanol and deionized water are used for centrifugation multiple times respectively until the impurities are completely separated and the supernatant appears clear; and the drying method is vacuum drying or freeze drying.

[0018] Preferably, in step (4), the cobalt source is selected from at least one of cobalt nitrate, cobalt chloride and cobalt sulfate, and the concentration of solution A is 0.5-3 mM.

[0019] Preferably, in step (5), the organic ligand is selected from at least one of 2-methylimidazole, benzimidazole and imidazole, and the concentration of solution B is 8-30 mM.

[0020] Preferably, in step (6), after adding MoS2 powder, the Co / Mo ratio in the reaction system is 1:1-1:3, and the static reaction is allowed to stand at room temperature for 2-10 hours.

[0021] Preferably, in step (7), ethanol and deionized water are used for centrifugation several times respectively until the impurities are completely separated and the supernatant appears clear; the drying method is vacuum drying or freeze drying.

[0022] Preferably, in step (8), the annealing temperature is 300-500° C. and the time is 1-3 hours.

[0023] The present invention also provides a high-performance supercapacitor material prepared by the method.

[0024] The present invention also provides application of the high-performance supercapacitor material in a supercapacitor.

[0025] The present invention has the following beneficial effects:

[0026] (1) The present invention compounds Co3O4 and MoS2. The introduction of Co3O4 enables MoS2 to be evenly dispersed on the surface of Co3O4, effectively preventing agglomeration of MoS2 and maintaining a large specific surface area, thereby improving the charge storage capacity of the material.

[0027] (2) The electron transport capacity of Co3O4 itself is better than that of MoS2, which can effectively compensate for the inherent low conductivity of MoS2, making the electron transport path of the entire composite material more continuous and reducing the charge transfer impedance. The layered structure of MoS2 also provides additional storage sites for the reaction of ions in the electrode material, making the material exhibit better ion dynamics during the charge and discharge process.

[0028] (3) The pseudocapacitive properties of Co3O4 can provide additional redox reaction sites and enhance the specific capacitance of the electrode. MoS2 has both pseudocapacitance and double-layer capacitance, and its layered structure helps to improve the charge storage capacity. The synergistic effect of the two can significantly increase the total capacitance. In addition, the appropriate Co3O4 content can also adjust the electronic structure of MoS2 and optimize its interfacial charge transfer process, thereby enhancing the overall electrochemical activity of the material.

[0029] (4) The prior art is to obtain cobalt hydroxide by hydrothermal method and then anneal to obtain cobalt tetroxide; or to directly obtain cobalt tetroxide by hydrothermal reaction. The materials prepared in this way have particle agglomeration, low specific surface area, and are greatly affected by hydrothermal conditions (temperature, pH, precursor concentration), resulting in uneven morphology of the materials and large fluctuations in electrochemical properties, making it difficult to achieve precise control.

[0030] The present invention obtains Co-MOF by static reaction and obtains cobalt oxide by annealing. The advantage of this method is that the metal organic framework (MOF) has the characteristics of large specific surface area, adjustable structure and abundant active sites. The metal oxide obtained by annealing retains and inherits the characteristics of MOF, that is, forming a porous structure, high specific surface area and more active sites, which is conducive to charge storage and ion diffusion; at the same time, it can prevent particle agglomeration and improve the uniform dispersion of the material, thereby improving the cycle stability and electrochemical performance of the electrode; in addition, the conditions are mild, no high temperature and high pressure equipment is required, and it is energy-saving and environmentally friendly.

[0031] (5) The present invention successfully improves the conductivity and capacitance performance through the composite strategy of transition metal sulfides and transition metal oxides, while maintaining the advantages of low cost and easy preparation. This idea provides important inspiration for the design of efficient, stable and low-cost supercapacitor electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 The samples of Examples 1-5 and Comparative Example were scanned at a rate of 5 mV s -1 Cyclic voltammetry curves of the test.

[0034] Figure 2 The sample of Example 2 is 5-200mV s -1 Cyclic voltammetry curves.

[0035] Figure 3 The samples of Examples 1-5 and Comparative Example were subjected to a current density of 1A. -1 Constant current charge and discharge curve tested.

[0036] Figure 4 It is the constant current charge and discharge curve of the sample in Example 2 tested at different current densities.

[0037] Figure 5 It is the specific capacitance of the samples of Examples 1-3 at different current densities.

[0038] Figure 6 It is the electrochemical impedance diagram of Examples 1-5 and the comparative example samples. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] (1) First, add 0.5 mM ammonium molybdate and 7 mM thioacetamide into 60 mL of deionized water in sequence and stir evenly;

[0042] (2) transferring the prepared mixed solution into a high pressure reactor and placing it in an oven at 170° C. for 24 hours for hydrothermal reaction;

[0043] (3) After the hydrothermal reaction is completed, the mixture is centrifuged with ethanol and deionized water and freeze-dried for 24 hours to obtain MoS2 powder;

[0044] (4) Then, 1 mM cobalt nitrate was added to 40 mL of deionized water and stirred evenly to obtain solution A;

[0045] (5) Add 16 mM 2-methylimidazole to 40 mL of deionized water and stir well to obtain solution B;

[0046] (6) Pour solution A into solution B and stir evenly; add 160 mg of MoS2 powder to the mixed solution; let stand at room temperature for 2 hours;

[0047] (7) After the reaction is completed, centrifuge with ethanol and deionized water, and finally dry in a vacuum oven to obtain MOF / MoS2 powder;

[0048] (8) The obtained MOF / MoS2 powder was annealed at 350°C for 2 hours in an air atmosphere of a tube furnace to obtain Co3O4 / MoS2-1 supercapacitor electrode material, wherein the molar ratio of Co3O4 / MoS2 was 1:3.

[0049] Example 2

[0050] The difference between this embodiment and embodiment 1 is that the standing time at room temperature described in step (6) is 4 hours, and the other steps and parameters are the same as those in embodiment 1, thereby obtaining Co3O4 / MoS2-2 supercapacitor electrode material.

[0051] Example 3

[0052] The difference between this embodiment and embodiment 1 is that the standing time at room temperature described in step (6) is 6 hours, and the other steps and parameters are the same as those in embodiment 1, and Co3O4 / MoS2-3 supercapacitor electrode material is obtained.

[0053] Example 4

[0054] (1) First, add 0.5 mM ammonium molybdate and 7 mM thioacetamide into 60 mL of deionized water in sequence and stir evenly;

[0055] (2) transferring the prepared mixed solution into a high pressure reactor and placing it in an oven at 170° C. for 24 hours for hydrothermal reaction;

[0056] (3) After the hydrothermal reaction is completed, the mixture is centrifuged with ethanol and deionized water and freeze-dried for 24 hours to obtain MoS2 powder;

[0057] (4) Then, 0.5 mM cobalt nitrate was added to 40 mL of deionized water and stirred to obtain solution A;

[0058] (5) Add 8 mM 2-methylimidazole to 40 mL of deionized water and stir well to obtain solution B;

[0059] (6) Pour solution A into solution B and stir evenly; add 160 mg of MoS2 powder to the mixed solution and let it stand at room temperature for 4 hours;

[0060] (7) After the reaction is completed, centrifuge with ethanol and deionized water, and finally dry in a vacuum oven to obtain MOF / MoS2 powder;

[0061] (8) The obtained MOF / MoS2 powder was annealed at 350°C for 2 hours in an air atmosphere of a tube furnace to obtain Co3O4 / MoS2-4 supercapacitor electrode material, wherein the molar ratio of Co3O4 / MoS2 was 1:5.

[0062] Example 5

[0063] (1) First, add 0.5 mM ammonium molybdate and 7 mM thioacetamide into 60 mL of deionized water in sequence and stir evenly;

[0064] (2) transferring the prepared mixed solution into a high pressure reactor and placing it in an oven at 170° C. for 24 hours for hydrothermal reaction;

[0065] (3) After the hydrothermal reaction is completed, centrifuge at 9000 r / min, 10 min / time and freeze-dry for 24 hours to obtain MoS2 powder;

[0066] (4) Then, 1.5 mM cobalt nitrate was added to 40 mL of deionized water and stirred to obtain solution A;

[0067] (5) Add 24 mM 2-methylimidazole to 40 mL of deionized water and stir well to obtain solution B;

[0068] (6) Pour solution A into solution B and stir evenly; add 100 mg of MoS2 powder to the mixed solution and let it stand at room temperature for 4 hours;

[0069] (7) After the reaction is completed, centrifuge at 10000 r / min for 5 min / time, and finally dry in a vacuum oven to obtain MOF / MoS2 powder;

[0070] (8) The obtained MOF / MoS2 powder was annealed at 350°C for 2 hours in an air atmosphere of a tube furnace to obtain Co3O4 / MoS2-5 supercapacitor electrode material, wherein the molar ratio of Co3O4 / MoS2 was 1:2.

[0071] The difference between the above-mentioned embodiments 1-3 is that the standing time in step (6) is different. The difference between embodiments 2, 4 and 5 is that the solution ratios in steps (4) and (5) of these three embodiments are different.

[0072] Comparative Example

[0073] (1) First, add 0.5 mM ammonium molybdate and 7 mM thioacetamide into 60 mL of deionized water in sequence and stir evenly;

[0074] (2) transferring the prepared mixed solution into a high pressure reactor and placing it in an oven at 170° C. for 24 hours for hydrothermal reaction;

[0075] (3) After the hydrothermal reaction is completed, the mixture is centrifuged with ethanol and deionized water and freeze-dried for 24 hours to obtain MoS2 powder.

[0076] Electrochemical tests were performed on the samples prepared in Examples 1-5 and the comparative example, and the specific results are as follows:

[0077] Figure 1 (a) shows the CV curves of the samples prepared in Examples 1-3 and the comparative example in the range of 0-0.5 V at a scan rate of 5 mV·s-1, showing the electrochemical properties of the samples obtained after different standing times; Figure 1(b) shows the electrochemical properties of samples obtained by different ratios under the same standing time of Examples 4-5 and Comparative Examples. As can be seen from the figure, each curve has a clear oxidation / reduction peak. Overall, the electrochemical performance of the composite material is significantly improved compared to single MoS2. The Co3O4 content is adjusted by changing the standing time and the precursor ratio. As the standing time and the precursor ratio increase, the Co3O4 content gradually increases, and the electrochemical performance of the composite material shows a trend of first rising and then falling, which indicates that the Co3O4 content is not the more the better. Excessive Co3O4 may cause the material structure to be too dense, limiting the effective transmission of ions and electrons, thereby affecting its electrochemical performance, proving that appropriate Co3O4 content and standing time can optimize the electrochemical performance of the composite material. In contrast, the electrochemical performance of the sample of Example 2 is the best, wherein the molar ratio of Co3O4 / MoS2 is 1:3, and the standing time at room temperature is 4 hours.

[0078] Figure 2 The voltage scan rate for the sample of Example 3 was 5-200 mv s in the voltage range of 0-0.5 V. -1 From the cyclic voltammetry curves at , it can be seen that with the increase of scanning speed, the peak intensity of the redox peak gradually increases, and the shape remains stable, indicating that the sample has good capacitance performance.

[0079] Figure 3 (a) shows the samples prepared in Examples 1-3 and Comparative Examples at 1Ag -1 Constant current charge and discharge curve when Figure 3 (b) shows the samples prepared in Examples 4-5 and Comparative Examples at 1Ag -1 The results show that the charge and discharge time of the composite material is significantly prolonged by combining with cobalt tetroxide, and the electrochemical performance of molybdenum disulfide is significantly improved. According to calculations, the specific capacitances of Examples 1-5 are 690, 977, 630, 328 and 388 F g respectively. -1 , indicating that the composite material has stronger charge storage capacity and more stable electrochemical behavior, and Example 2 is significantly higher than other examples. However, the change in capacitance is consistent with the cyclic voltammetry test results, further proving that appropriate Co3O4 content can improve the performance of the material.

[0080] Figure 4 The constant current charge-discharge curves of the sample in Example 3 were measured at different current densities. -1 At the current density, the specific capacitance of the capacitor is 977.32, 817, 754, 701, 670, 643 and 639 F g respectively. -1 .

[0081] Figure 5The specific capacitance variation diagram of the samples prepared in Examples 1-3 at different current densities shows that as the current density increases, the specific capacitance value gradually decreases. Consistent with the results discussed above, Example 2 exhibits a maximum specific capacitance of 977.32 F g at the same current density. -1 , and the capacitance retention rate is the highest (66%). This result further illustrates the synergistic effect between Co3O4 / MoS2 and further verifies the effectiveness of optimizing the Co3O4 content in improving material performance.

[0082] Figure 6 (a) is the electrochemical impedance diagram of samples prepared in Examples 1-3 and Comparative Examples, Figure 6 (b) is the electrochemical impedance diagram of samples prepared in Examples 4-5 and Comparative Examples. Among them, MoS2 has a higher impedance and poorer conductivity. As the content of Co3O4 increases, the impedance of the Co3O4 / MoS2 composite material gradually decreases, indicating that the introduction of Co3O4 significantly improves the conductivity of the composite material. Overall, the addition of Co3O4 effectively reduces the internal resistance of the composite material and improves its conductivity and electrochemical performance.

[0083] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a high-performance supercapacitor material, characterized in that: The following steps are involved: (1) adding a molybdenum source and a sulfur source into deionized water in sequence to obtain a precursor solution; (2) transferring the precursor solution into a high-pressure reactor to perform a hydrothermal reaction to obtain a black liquid; (3) centrifuging and drying the black liquid in sequence to obtain MoS2 powder; (4) adding a cobalt source into deionized water and stirring until completely dissolved to obtain solution A; (5) adding the organic ligand into deionized water and stirring until completely dissolved to obtain solution B; (6) Pour solution A into solution B, mix well, then add the MoS2 powder prepared in step (3), and let stand to react; (7) After the reaction is completed, the mixed solution of step (6) is centrifuged and then dried to obtain MOF / MoS2 powder; (8) Using a tubular furnace to perform high temperature annealing on the MOF / MoS2 powder to obtain Co3O4 / MoS2 supercapacitor material.

2. The method for preparing a high performance supercapacitor material according to claim 1, characterized in that: In step (1), the molybdenum source is selected from at least one of ammonium heptamolybdate, molybdenum trioxide, and sodium molybdate, and the sulfur source is selected from at least one of thioacetamide, thiourea, and sodium sulfide, wherein the molar ratio of the molybdenum source to the sulfur source is 1:

2.

3. The method for preparing a high performance supercapacitor material according to claim 1, characterized in that: In step (2), the hydrothermal reaction is carried out in an oven, the hydrothermal reaction temperature is 160-200° C., and the reaction time is 20-30 hours.

4. The method for preparing a high performance supercapacitor material according to claim 1, characterized in that: In step (4), the cobalt source is selected from at least one of cobalt nitrate, cobalt chloride and cobalt sulfate, and the concentration of solution A is 0.5-3 mM.

5. The method for preparing a high performance supercapacitor material according to claim 1, characterized in that: In step (5), the organic ligand is selected from at least one of 2-methylimidazole, benzimidazole and imidazole, and the concentration of solution B is 8-30 mM.

6. The method for preparing a high performance supercapacitor material according to claim 1, characterized in that: In step (6), after adding MoS2 powder, the Co / Mo molar ratio in the reaction system is 1:1-1:3, and the static reaction is allowed to stand at room temperature for 2-10 hours.

7. The method for preparing a high performance supercapacitor material according to claim 1, characterized in that: In step (8), the annealing temperature is 300-500° C. and the time is 1-3 hours.

8. A high performance supercapacitor material prepared by the method according to any one of claims 1 to 7.

9. Use of the high performance supercapacitor material according to claim 8 in a supercapacitor.

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