Mnco3 / cnts composite material, preparation method and application thereof

Abstract

The application discloses a MnCO3 / CNTs composite material and a preparation method and application thereof, and is characterized in that: the MnCO3 / CNTs composite material is prepared by using manganese acetate and urea as raw materials and by adopting a one-step solvothermal method to in-situ synthesize MnCO3 on a planar structure composed of carbon nanotube fibers; the MnCO3 nanospheres are orderly grown on the planar structure of the carbon nanotubes to form "leaf" shaped nanosheets; the structure of the nanosheets greatly improves the specific surface area of the MnCO3; the planar structure of the CNTs also improves the stability of the MnCO3 / CNTs composite material, thereby effectively increasing the capacity of the manganese carbonate material, and solving the problems of the manganese carbonate material, such as low conductivity, fast capacity attenuation and poor cycle performance stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery positive electrode material preparation, and more particularly relates to a MnCO3 / CNTs composite material, a preparation method and application thereof. BACKGROUND

[0002] Aqueous zinc ion battery has broad application prospects in large-scale energy storage and distributed energy storage due to its high safety, easy assembly, low cost, environmental friendliness, and high specific capacity of zinc metal negative electrode (820 mAh g -1 ).

[0003] Manganese carbonate (MnCO3) has been applied in lithium ion batteries, potassium ion batteries and supercapacitors due to its advantages of abundant reserves, environmental friendliness and simple synthesis. In CN202211680018.1, a kind of aqueous zinc ion battery electrode material and its preparation method and application, manganese salt and carbon are mixed and ground to obtain a precursor, and microwave reaction is carried out to obtain a manganese-based oxide and carbon composite material of the aqueous zinc ion battery electrode material. The manganese salt includes at least one of manganese acetate and its hydrate, manganese carbonate and its hydrate, or manganese oxalate and its hydrate, and the carbon material is at least one of carbon nanotubes, graphite, conductive carbon black, charcoal, coke, activated carbon and other carbon materials, preferably carbon nanotubes. Although the conductivity is improved by mixing manganese salt and carbon material, the dispersion of carbon in manganese salt is not uniform, and the improvement of stability is limited. Moreover, the inherent low electrical conductivity of MnCO3 material causes serious capacity decay, which limits the application of MnCO3 material in aqueous zinc ion battery, thereby hindering the application of MnCO3 material. SUMMARY

[0004] To overcome the problem that the existing manganese carbonate material is limited in the application in electrochemical energy storage devices due to its low electrical conductivity, fast capacity decay and poor cycle performance stability, the application provides a preparation method of MnCO3 / CNTs composite material.

[0005] Another technical problem solved by the application is to provide the MnCO3 / CNTs composite material and application thereof.

[0006] The application is achieved by the following technical solutions:

[0007] A preparation method of MnCO3 / CNTs composite material, the preparation steps comprising:

[0008] S1. Dissolving manganese acetate and urea in an organic solvent to obtain a mixed solution;

[0009] S2. mixing carbon nanotubes with organic solvent, dispersing and interweaving carbon nanotubes by ultrasonic to obtain carbon nanotube dispersion liquid;

[0010] S3. mixing and stirring the mixed solution in S1 with the carbon nanotube dispersion liquid in S2, then heating to 140-160℃, reacting for 14-18h, and cooling;

[0011] S4. separating the reacted substance in S3 to obtain a precipitate, and washing and drying to obtain MnCO3 / CNTs composite material.

[0012] The present application adopts ultrasonic to disperse and interweave carbon nanotube single fibers to form a planar structure, then uses manganese acetate and urea as raw materials to in-situ synthesize MnCO3 on the planar structure composed of carbon nanotube fibers by one-step solvothermal method, and forms MnCO3 / CNTs nanosheet composite material. In the method, the carbon nanotubes are uniformly doped in the manganese carbonate material, which improves the conductivity and the specific surface area of MnCO3, and effectively increases the capacity and cycle stability of the manganese carbonate material.

[0013] Further, the amount-of-substance ratio of manganese acetate and urea in S1 is 1:5.

[0014] Further, the frequency of the ultrasonic in S2 is 38-42khz, the power is 500-800w, and the ultrasonic time is 15-20min.

[0015] Further, the outer diameter of the carbon nanotubes in S2 is not more than 8nm, and the length is 10-30um.

[0016] Further, the mass of the carbon nanotubes in the dispersion liquid in S3 is 1.5%-3.5% of the mass of manganese acetate in the mixed solution.

[0017] Further, the stirring time in S3 is 20-40min.

[0018] Further, the organic solvent in S2 and S3 includes N,N-dimethylformamide.

[0019] Further, the drying temperature in S4 is 50-80℃.

[0020] A MnCO3 / CNTs composite material prepared by the above method, wherein the MnCO3 / CNTs composite material is in a nanoscale sheet structure, the diameter of the nanosheet is 45-65nm, and the thickness is 25-40nm.

[0021] Further, the MnCO3 / CNTs composite material is applied to water-based zinc ion battery positive electrode material.

[0022] Further, the preparation step of the water-based zinc ion battery positive electrode material comprises: mixing and grinding the MnCO3 / CNTs composite material, acetylene black and the binder PVDF, adding the conductive agent NMP to become a uniform slurry, coating, and drying to obtain the water-based zinc ion battery positive electrode material.

[0023] Further, the ratio of the MnCO3 / CNTs composite material, acetylene black and the binder is 7:2:1.

[0024] Compared with the prior art, the beneficial effects are:

[0025] The application utilizes the advantages of good stability and electrical conductivity of carbon nanotubes, and first arranges the carbon nanotubes into a planar structure through ultrasonic, then forms MnCO3 nanospheres in situ on the carbon nanotubes, the MnCO3 nanospheres grow in order on the planar structure of the carbon nanotubes to form a "leaf" shaped nanosheet, and the MnCO3 / CNTs composite material is obtained, the structure of the MnCO3 / CNTs composite material greatly improves the specific surface area of the MnCO3, and the planar structure of the CNTs also improves the stability of the MnCO3 / CNTs composite material, thereby effectively increasing the capacity of the manganese carbonate material, and solving the problem of poor cycle performance of the existing manganese carbonate material. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The schematic diagram of the method described in Example 1;

[0027] Figure 2 The XRD test curve and the FT-IR test curve of the product prepared in Example 1 and Example 4; wherein (a) is the XRD spectrum, and (b) is the FT-IR spectrum;

[0028] Figure 3 The scanning electron microscope (SEM) image of the product prepared in Example 1 and Example 4;

[0029] Wherein (a, b) are the SEM images of the MnCO3-T synthesized in Example 4, and (c, d) are the SEM images of the MnCO3 / CNTs composite material synthesized in Example 1;

[0030] Figure 4 The TEM characterization test image of the product prepared in Example 1;

[0031] Figure 5 The SEM characterization test image of the product prepared in Example 2;

[0032] Figure 6 The SEM characterization test image of the product prepared in Example 3;

[0033] Figure 7 The electrochemical performance diagram of the product prepared in Example 1 and Example 4;

[0034] wherein (a) is a rate capability comparison chart, (b) is a cycle performance chart at a current density of 0.2 Ag -1 (c) is a long cycle performance chart at a current density of 1.0 Ag -1 . DETAILED DESCRIPTION

[0035] The present application is further explained and illustrated with reference to the following examples, but the particular examples should not be construed to limit the application in any way. Unless otherwise specifically indicated, the methods and materials used in the examples are those commonly used by those skilled in the art. The materials used in the examples are commercially available unless otherwise indicated.

[0036] Example 1

[0037] The present embodiment provides a preparation method of MnCO3 / CNTs composite material, and the preparation steps include:

[0038] S1. 1.7303 g of manganese acetate and 3.003 g of urea were weighed, i.e. the molar ratio of manganese acetate to urea was 1:5, which was added to 20 mL of N,N-dimethylformamide solvent, and stirred and dissolved to obtain a brown mixed solution.

[0039] S2. 0.04 g of multi-walled carbon nanotubes was taken, the inner diameter of the multi-walled carbon nanotubes was 2-5 nm, the outer diameter was not greater than 8 nm, and the length was 10-30 um, which was added to 20 mL of N,N-dimethylformamide solvent and stirred uniformly, and then ultrasonic was performed at a frequency of 40 kHz and a power of 600 W for 20 min, so that the single fibers of the carbon nanotubes were dispersed and interwoven to form a planar structure, and a black carbon nanotube dispersion liquid was obtained.

[0040] S3. The brown mixed solution in S1 and the black carbon nanotube dispersion liquid in S2 were mixed and stirred for 30 min, and then the temperature was raised to 150°C, and reacted for 16 h, and after the reaction was completed, it was naturally cooled to room temperature.

[0041] S4. 20 ml of anhydrous ethanol was added to the precipitated solution after the reaction and stirred for 10 min, and then the solution was centrifuged at 6000 rad / min for 5 min, and the supernatant was poured out to leave a black precipitate, and then the black precipitate was washed with deionized water to remove the organic solvent N,N-dimethylformamide and other impurities in the reaction, and then dried at 60°C for 12 h to obtain a MnCO3 / CNTs composite material.

[0042] Example 2

[0043] The present embodiment provides a preparation method of MnCO3 / CNTs composite material, and the preparation steps include:

[0044] S1. Take 1.7303 g of manganese acetate and 3.003 g of urea, i.e. the molar ratio of manganese acetate to urea is 1:5, and add them to 20 mL of N,N-dimethylformamide solvent, stir and dissolve to obtain a brown mixed solution.

[0045] S2. Take 0.02 g of multi-walled carbon nanotubes with an inner diameter of 2-5 nm, an outer diameter of not more than 8 nm, and a length of 10-30 um, add them to 20 mL of N,N-dimethylformamide solvent and stir uniformly, then perform ultrasonic treatment at a frequency of 40 kHz and a power of 600 W for 20 min to disperse and interweave the single fibers of the carbon nanotubes into a planar structure, and obtain a black carbon nanotube dispersion.

[0046] S3. Mix the brown mixed solution in S1 with the black carbon nanotube dispersion in S2 and stir for 30 min, then heat to 150°C and react for 16 h, and then naturally cool to room temperature after the reaction is complete.

[0047] S4. Add 20 mL of anhydrous ethanol to the precipitated solution after the reaction and stir for 10 min, then centrifuge the solution at 6000 rad / min for 5 min, pour out the supernatant to leave a black precipitate, wash the black precipitate with deionized water to remove the organic solvent N,N-dimethylformamide and other impurities in the reaction, and then dry at 60°C for 12 h to obtain a MnCO3 / CNTs composite material.

[0048] Example 3

[0049] The present embodiment provides a preparation method of a MnCO3 / CNTs composite material, and the preparation steps include:

[0050] S1. Take 1.7303 g of manganese acetate and 3.003 g of urea, i.e. the molar ratio of manganese acetate to urea is 1:5, and add them to 20 mL of N,N-dimethylformamide solvent, stir and dissolve to obtain a brown mixed solution.

[0051] S2. Take 0.06 g of multi-walled carbon nanotubes with an inner diameter of 2-5 nm, an outer diameter of not more than 8 nm, and a length of 10-30 um, add them to 20 mL of N,N-dimethylformamide solvent and stir uniformly, then perform ultrasonic treatment at a frequency of 40 kHz and a power of 600 W for 20 min to disperse and interweave the single fibers of the carbon nanotubes into a planar structure, and obtain a black carbon nanotube dispersion.

[0052] S3. Mix the brown mixed solution in S1 with the black carbon nanotube dispersion in S2 and stir for 30 min, then heat to 150°C and react for 16 h, and then naturally cool to room temperature after the reaction is complete.

[0053] S4. In the precipitated solution after the reaction, add 20 ml of anhydrous ethanol and stir for 10 min, then centrifuge the solution at 6000 rad / min for 5 min, pour out the supernatant to leave the black precipitate, then wash the black precipitate with deionized water to remove the organic solvent N,N-dimethylformamide and other impurities in the reaction, and dry at 60°C for 12 h to obtain the MnCO3 / CNTs composite material.

[0054] Example 4

[0055] The embodiment provides a preparation method of a MnCO3 / CNTs composite material, and the preparation steps comprise:

[0056] S1. Take 1.7303 g of manganese acetate and 3.003 g of urea, i.e. the molar ratio of manganese acetate to urea is 1:5, add them to 20 mL of N,N-dimethylformamide solvent, stir and dissolve to obtain a brown mixed solution.

[0057] S2. Take 0.04 g of multi-walled carbon nanotubes, wherein the inner diameter of the multi-walled carbon nanotubes is 2-5 nm, the outer diameter is not greater than 8 nm, and the length is 10-30 um, add them to 20 mL of N,N-dimethylformamide solvent and stir uniformly, then perform ultrasonic treatment at a frequency of 40 kHz and a power of 500 W for 20 min, so that the single fibers of the carbon nanotubes are dispersed and interwoven to form a planar structure, and a black carbon nanotube dispersion liquid is obtained.

[0058] S3. Mix and stir the brown mixed solution in S1 and the black carbon nanotube dispersion liquid in S2 for 30 min, then heat them to 150°C and react for 16 h, and then naturally cool to room temperature after the reaction.

[0059] S4. In the precipitated solution after the reaction, add 20 ml of anhydrous ethanol and stir for 10 min, then centrifuge the solution at 6000 rad / min for 5 min, pour out the supernatant to leave the black precipitate, then wash the black precipitate with deionized water to remove the organic solvent N,N-dimethylformamide and other impurities in the reaction, and dry at 60°C for 12 h to obtain the MnCO3 / CNTs composite material.

[0060] Example 5

[0061] The embodiment provides a preparation method of a MnCO3 / CNTs composite material, and the preparation steps comprise:

[0062] S1. Take 1.7303 g of manganese acetate and 3.003 g of urea, i.e. the molar ratio of manganese acetate to urea is 1:5, add them to 20 mL of N,N-dimethylformamide solvent, stir and dissolve to obtain a brown mixed solution.

[0063] S2. Take 0.04 g of multi-walled carbon nanotubes with an inner diameter of 2-5 nm, an outer diameter of no more than 8 nm, and a length of 10-30 um, and add it to 20 ml of N,N-dimethylformamide solvent and stir until uniform, then perform ultrasonic dispersion at a frequency of 40 kHz and a power of 800 w for 15 min to disperse and interweave the single fibers of the carbon nanotubes into a planar structure, obtaining a black carbon nanotube dispersion liquid.

[0064] S3. Mix and stir the brown mixed solution in S1 with the black carbon nanotube dispersion liquid in S2 for 30 min, then heat it to 150°C and react for 16 h, and then naturally cool it to room temperature after the reaction is complete.

[0065] S4. Add 20 ml of anhydrous ethanol to the precipitated solution after the reaction and stir for 10 min, then centrifuge the solution at 6000 rad / min for 5 min, pour out the supernatant, and leave the black precipitate, then wash the black precipitate with deionized water to remove the organic solvent N,N-dimethylformamide and other impurities in the reaction mixture, and dry it at 60°C for 12 h to obtain the MnCO3 / CNTs composite material.

[0066] Example 6

[0067] This example provides a method for preparing a MnCO3-T material, which includes the following steps:

[0068] S1. Weigh manganese acetate and urea, with a molar ratio of 1:5, and then add 40 ml of N,N-dimethylformamide, and stir quickly for 30 min until the raw material powder is dissolved, obtaining a brown solution.

[0069] S2. Heat the brown solution to 150°C and react for 16 hours, and then naturally cool it to room temperature after the reaction is complete.

[0070] S3. Add 20 ml of anhydrous ethanol to the precipitated solution after the reaction and stir for 10 min, then centrifuge the solution at 6000 rad / min for 5 min, pour out the supernatant, and leave the brown precipitate.

[0071] S4. Wash the brown precipitate with deionized water to remove the organic solvent N,N-dimethylformamide and other impurities in the reaction mixture, and dry it at 60°C for 12 h to obtain the MnCO3 material.

[0072] Example 7

[0073] This example provides a method for preparing a positive electrode material for aqueous zinc ion batteries, which includes the following steps:

[0074] The MnCO3 material in Example 1 or Example 4, acetylene black and binder PVDF were mixed and ground in a mass ratio of 7:2:1, and after adding the conductive agent NMP to become a uniform slurry, coating, drying to obtain a water-based zinc ion battery positive electrode material.

[0075] The MnCO3 / CNTs composite material and MnCO3-T material prepared in Example 1 and Example 6 were characterized by XRD and FT-IR, and the XRD results are as shown in Figure 2 (a). When CNTs were added to the reaction, the MnCO3 / CNTs composite material had characteristic peaks of crystal faces (012), (104), (202), (116) and (122) near diffraction angles of 24.37°, 31.54°, 45.14°, 51.54° and 60.25°, and matched well with the standard card (PDF #83-1763) of the synthesized MnCO3-T material and MnCO3, proving that the samples synthesized in Example 1 and Example 6 were mainly MnCO3. The FT-IR test is as shown in Figure 2 (b). There is a relatively wide characteristic peak in the 1451cm -1 band, which together with the characteristic peak at 864cm -1 corresponds to the vibration of C-O bond in , and the band at 3444cm -1 corresponds to the stretching vibration of -OH bond. The FT-IR characterization results further prove that the main materials of MnCO3 / CNTs and MnCO3-T samples are MnCO3.

[0076] The MnCO3 / CNTs composite material and MnCO3-T material prepared in Example 1 and Example 6 were characterized by micro-morphology, and the MnCO3 / CNTs composite material was in a nanosheet structure, with a diameter of 45-65nm and a thickness of 25-40nm. As shown in Figure 3 , the MnCO3-T material shown in (a) and (b) is in a granular nanosphere aggregation, and the MnCO3 / CNTs composite material shown in (c) and (d) is in a microstructure with "leaf" shape, which is orderly arranged in the same direction by nanospheres.

[0077] Specifically, from the TEM images in Figure 4 , it can be clearly seen that part of the interwoven carbon nanotube fiber structure is exposed in the upper right of (a). As shown in (b), the lattice spacing is mainly 0.288nm, which corresponds to the (104) crystal face of MnCO3, further verifying that the main body of the MnCO3 / CNTs sample is MnCO3 material.

[0078] from Figure 5 and Figure 6It is found that when 0.02g of double-walled carbon nanotubes are added, nanosheets cannot be formed, while when 0.06g of double-walled carbon nanotubes are added, nanosheets can be formed, but the surface is uneven. Figure 4 As shown in the figure, when 0.04 g of multi-walled carbon nanotubes were added, the surface of the nanosheets was smooth and the structure was the best.

[0079] The electrochemical performance of the positive electrodes prepared using the MnCO3 / CNTs composite material in Example 1 and the MnCO3-T material in Example 6 in Example 7 was tested. The discharge specific capacity test results of the two materials at different current densities are shown in Table 1 below:

[0080] Table 1

[0081]

[0082] As shown in Table 1 and Figure 7 As shown in (a), the MnCO3 / CNTs samples at 0.1, 0.2, 0.3, 0.5 and 1.0 A·g -1 The current densities were 244.7, 215.2, 193.3, 166.2 and 114.8 mAh g -1 The discharge capacity, when the current density returns to 0.1A·g -1 The specific capacity returned to 258.2 mAh g -1 ; MnCO3-T samples at 0.1, 0.2, 0.3, 0.5 and 1.0 A·g -1 The current densities were 167.4, 150.9, 141.8, 125.6 and 94.4 mAh g -1 When the current density returns to 0.1A·g -1 The specific capacity returned to 165.1 mAh g -1 It can be seen that the discharge specific capacity of the MnCO3 / CNTs composite material prepared in the present invention is significantly improved compared with that of pure manganese carbonate.

[0083] like Figure 7 As shown in (b), the MnCO3 / CNTs sample at 0.2A·g -1 The discharge capacity after 100 cycles at a current density of 219.2 mAh g -1 , MnCO3-T sample at 0.2A·g -1 The discharge capacity after 100 cycles at a current density of 157.2 mAh g -1 .

[0084] like Figure 7 As shown in (c), at 1.0A·g -1After 1000 cycles at a current density of 1.5, the MnCO3 / CNTs sample still has a charge capacity of 81.4 mAh g -1 The discharge specific capacity of MnCO3-T material decays to 0 after 600 cycles.

[0085] Therefore, the MnCO3 / CNTs composite material prepared in the present invention has better electrochemical performance as a positive electrode material for aqueous zinc ion batteries.

[0086] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a MnCO3 / CNTs composite material, characterized in that: The preparation steps include: S1. dissolving manganese acetate and urea in an organic solvent to obtain a mixed solution; S2. The carbon nanotubes are uniformly mixed with an organic solvent, and the carbon nanotubes are dispersed and interwoven by ultrasound, wherein the ultrasound frequency is 38 to 42 khz, the power is 500 to 800w, and the ultrasound time is 15 to 20min to obtain a carbon nanotube dispersion; S3. The mixed solution in S1 is mixed with the carbon nanotube dispersion in S2, wherein the mass of the carbon nanotubes in the carbon nanotube dispersion is 1.5% to 3.5% of the mass of manganese acetate in the mixed solution, and then heated to 140 to 160 ° C, reacted for 14 to 18 hours, and cooled; S4. The reacted material in S3 is separated to obtain a precipitate, which is then washed and dried to obtain a MnCO3 / CNTs composite material. The MnCO3 / CNTs composite material is a nano-scale "leaf"-shaped nanosheet with a diameter of 45~65nm and a thickness of 25~40nm.

2. The method for preparing the MnCO3 / CNTs composite material according to claim 1, characterized in that: The molar ratio of manganese acetate to urea in S1 is 1:

5.

3. The method for preparing the MnCO3 / CNTs composite material according to claim 1, characterized in that: The carbon nanotubes in S2 have an outer diameter of no more than 8 nm and a length of 10 to 30 μm.

4. The method for preparing the MnCO3 / CNTs composite material according to claim 1, characterized in that: The stirring time in S3 is 20 to 40 minutes.

5. A MnCO3 / CNTs composite material, characterized in that: Prepared by the method according to any one of claims 1 to 4, the MnCO3 / CNTs composite material is in the form of nano-scale "leaf-shaped" nanosheets with a diameter of 45 to 65 nm and a thickness of 25 to 40 nm.

6. The MnCO3 / CNTs composite material according to claim 5 is used as a positive electrode material for aqueous zinc ion batteries.

7. The use of the MnCO3 / CNTs composite material according to claim 6, characterized in that: The preparation steps of the aqueous zinc ion battery positive electrode material include: mixing and grinding a MnCO3 / CNTs composite material, acetylene black and a binder PVDF, adding a conductive agent NMP to form a uniform slurry, coating, and drying to obtain the aqueous zinc ion battery positive electrode material.

8. The use of the MnCO3 / CNTs composite material according to claim 7, characterized in that: The ratio of the MnCO3 / CNTs composite material, acetylene black and binder is 7:2:1.

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