Preparation method of a self-supporting film and its application in preparing a composite anode of a lithium / sodium ion battery

Abstract

The present invention discloses a preparation method of a self-supporting film and its application in the preparation of a composite anode for lithium / sodium ion batteries, belonging to the technical field of battery anode materials. A composite material containing molybdenum, iron, and MXenes is obtained by mixing a ferric chloride solution, an ammonium molybdate solution, and a Ti3C2 MXenes dispersion. The composite material can be heat-treated at 280-480 °C in a tube furnace under a N2 atmosphere to obtain a composite material containing MoO2, FeMoO4, and MXenes. The composite material has high capacity, good rate performance, and cycle stability as the anode material for lithium / sodium ion batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery anode materials, and particularly relates to a preparation method of a self-supporting film and its application in the preparation of a composite anode for lithium / sodium ion batteries. Background Art

[0002] Among transition metal oxides, oxides of transition metals molybdenum and iron both have excellent pseudocapacitance characteristics. If they are assembled in the same material, more significant pseudocapacitance characteristics will be obtained. Therefore, based on the preparation of composite materials of multiple transition metal compounds, it can have the pseudocapacitance characteristics of multiple transition metal oxides, exert the electrochemical synergistic effect between various transition metal elements, and improve the pseudocapacitance contribution, rate performance, and charge-discharge cycle stability performance of the composite material in electrochemical energy storage.

[0003] Currently, the preparation of multi-metal oxide composite materials mainly uses co-precipitation, hydrothermal, and mechanical mixing methods. Among them, the yield of multi-metal compounds prepared by hydrothermal and co-precipitation methods is relatively low, and the preparation process conditions are harsh; the multi-metal compounds prepared by mechanical mixing method are unevenly distributed, and the interaction force between monomers in the composite material is weak. Therefore, it is necessary to develop new synthesis methods. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a preparation method of a self-supporting film and its application in the preparation of a composite anode for lithium / sodium ion batteries. The rate and cycle stability of the membrane electrode (lithium / sodium ion battery anode) prepared from the self-supporting film are excellent.

[0005] To achieve the above object, the present invention provides a preparation method of a self-supporting film, comprising the following steps:

[0006] (1) Mix a ferric chloride solution, an ammonium molybdate solution, and a Ti3C2 MXenes dispersion liquid, stir, filter, and dry to obtain a composite material containing Mo, Fe, and MXenes;

[0007] (2) Heat-treat the composite material containing molybdenum (Mo), iron (Fe), and MXenes to obtain a composite material containing MoO2, FeMoO4, and MXenes;

[0008] (3) Mix the composite material containing MoO2, FeMoO4, and MXenes, polyacrylonitrile, and dimethylformamide to obtain an electrospinning solution, and perform electrospinning to obtain a self-supporting film of the composite material containing MoO2, FeMoO4, and MXenes.

[0009] Further, in the method for preparing the self-supporting film, in step (1), the method for preparing the ferric chloride solution is as follows: completely dissolve 5.4 g of ferric chloride in 20 g of water to obtain a ferric chloride solution;

[0010] The method for preparing the ammonium molybdate solution is as follows: completely dissolve 10 g of ammonium molybdate in 20 g of water to obtain an ammonium molybdate solution;

[0011] The concentration of the Ti3C2 MXenes dispersion is 5 mg / mL.

[0012] Further, in the method for preparing the self-supporting film, step (1) includes the following steps: completely dissolve 5.4 g of ferric chloride in 20 g of water to obtain an aqueous solution of ferric chloride; completely dissolve 10 g of ammonium molybdate in 20 g of water to obtain an aqueous solution of ammonium molybdate; take 40 mL of a 5 mg / mL dispersion of Ti3C2 MXenes; mix the above three solutions and stir for 48 h, then filter and dry to obtain a composite material containing Mo, Fe, and MXenes.

[0013] Further, in the method for preparing the self-supporting film, in step (2), the heat treatment temperature is 350 - 550 °C, and the heat treatment time is 5.0 h. The heat treatment in step (2) is carried out in a tube furnace under an N2 atmosphere.

[0014] Further, in the method for preparing the self-supporting film, in step (3), the mass ratio of the composite material containing MoO2, FeMoO4, and MXenes to polyacrylonitrile is 1:1; the mass-volume ratio of dimethylformamide to polyacrylonitrile is 17 mL:1 g.

[0015] Further, in the method for preparing the self-supporting film, in step (3), during electrospinning: the voltage is 28 kV, the feeding speed is 18 μL / min, and the temperature is 30 °C.

[0016] A self-supporting film is prepared according to the above preparation method.

[0017] The application of the self-supporting film in preparing a composite negative electrode for a lithium / sodium ion battery.

[0018] When used as a composite negative electrode for a lithium / sodium ion battery, the areal density is 0.8 - 4.0 mg / cm 2 , and the charge-discharge voltage range is 0.01 - 3.0 V vs Or Its charge-discharge current density is 0.1 - 4 A / g.

[0019] A preparation method of a lithium / sodium ion battery composite anode, comprising pre-oxidizing a self-supporting film of a composite material containing MoO2, FeMoO4 and MXenes, and performing heat treatment to obtain the lithium / sodium ion battery composite anode.

[0020] Further, in the preparation method of the lithium / sodium ion battery composite anode, the pre-oxidation is carried out in an air atmosphere, the pre-oxidation temperature is 280 °C, the pre-oxidation time is 4 h, and the heating rate is 10 °C / min.

[0021] Further, in the preparation method of the lithium / sodium ion battery composite anode, the heat treatment temperature is 550 - 750 °C, and the heat treatment time is 4.0 h.

[0022] The present invention uses a thermal conversion method to convert salts containing Fe and Mo and MXenes into a composite material of multiple metal oxides or salts and MXenes; the process is simple, and the interaction between different metal compounds in the obtained composite material is strong, and the morphology and element distribution are uniform. During the electrochemical energy storage process, this composite material can better exert the pseudocapacitance characteristics of multiple transition metal elements and the synergistic electrochemical effect between metal elements. When used as the anode of a lithium / sodium ion battery, the pseudocapacitance characteristics will be more significant.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] (1) The preparation process of the present invention is simple, does not require harsh reaction conditions, has a short preparation time, and has a high uniformity of the composite material containing MoO2, FeMoO4 and MXenes.

[0025] (2) The self-supporting film electrode of the composite material containing MoO2, FeMoO4 and MXenes prepared by the present invention has better pseudocapacitance characteristics, rate performance and charge-discharge cycle stability when used as the anode of a lithium / sodium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0027] Figure 1 It is the SEM image of the composite material MFM containing Mo, Fe and MXenes of Example 1;

[0028] Figure 2 It is the SEM image of the composite material MFM-1 containing MoO2, FeMoO4 and MXenes of Example 2;

[0029] Figure 3SEM image of composite material MFM-2 containing MoO2, FeMoO4 and MXenes for Example 3;

[0030] Figure 4 SEM image of composite material MFM-3 containing MoO2, FeMoO4 and MXenes for Example 4;

[0031] Figure 5 XRD pattern of the composite materials of Examples 1-4;

[0032] Figure 6 SEM image of the self-supporting membrane electrode MFM@CNFs-1 for Example 7;

[0033] Figure 7 SEM image of the self-supporting membrane electrode MFM@CNFs-2 for Example 8;

[0034] Figure 8 SEM image of the self-supporting membrane electrode MFM@CNFs-3 for Example 9;

[0035] Figure 9 XRD pattern of the self-supporting membrane electrodes of Examples 7-9. Detailed implementation manners

[0036] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0037] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0038] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0039] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the description of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of the present invention are obvious to those skilled in the art. The description and examples of the present invention are merely exemplary.

[0040] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0041] The raw materials and reagents used in the present invention are all commercially available products.

[0042] Example 1

[0043] 5.4 g of ferric chloride was completely dissolved in 20 g of water to obtain an aqueous solution of ferric chloride; 10 g of ammonium molybdate was completely dissolved in 20 g of water to obtain an aqueous solution of ammonium molybdate; 40 mL of a 5 mg / mL dispersion of Ti3C2 MXenes was taken; the above three solutions were mixed and stirred for 48 h and then filtered and dried to obtain a composite material containing Mo, Fe and MXenes, denoted as MFM.

[0044] Example 2

[0045] The composite material MFM containing Mo, Fe and MXenes prepared in Example 1 was heat-treated in a tube furnace under a N2 atmosphere at 350 °C for 5.0 h to obtain a composite material containing MoO2, FeMoO4 and MXenes, denoted as MFM-1.

[0046] Example 3

[0047] The composite material MFM containing Mo, Fe and MXenes prepared in Example 1 was heat-treated in a tube furnace under a N2 atmosphere at 450 °C for 5.0 h to obtain a composite material containing MoO2, FeMoO4 and MXenes, denoted as MFM-2.

[0048] Example 4

[0049] The composite material MFM containing Mo, Fe and MXenes prepared in Example 1 was heat-treated in a tube furnace under a N2 atmosphere at 550 °C for 5.0 h to obtain a composite material containing MoO2, FeMoO4 and MXenes, denoted as MFM-3.

[0050] Example 5

[0051] 1.2 g of the composite material MFM-2 containing MoO₂, FeMoO₄ and MXenes prepared in Example 3, 1.2 g of polyacrylonitrile and 40 mL of dimethylformamide were mixed and stirred for 48 h to obtain an electrospinning solution. A self-supporting film of the composite material containing MoO₂, FeMoO₄ and MXenes can be obtained by electrospinning. Electrospinning conditions: voltage 28 kV, feeding speed 18 μL / min -1 , temperature 30 °C, and the areal density of the self-supporting film is 3.1 mg / cm 2 .

[0052] Example 6

[0053] The self-supporting film of the composite material containing MoO₂, FeMoO₄ and MXenes prepared in Example 5 was pre-oxidized at 280 °C for 4 h in an air atmosphere with a heating rate of 10 °C / min to obtain a pre-oxidized self-supporting film of the composite material containing MoO₂, FeMoO₄ and MXenes.

[0054] Example 7

[0055] The pre-oxidized self-supporting film prepared in Example 6 was heat-treated at 550 °C for 4.0 h to obtain a self-supporting film electrode of the composite material containing MoO₂, FeMoO₄ and MXenes, labeled as MFM@CNFs-1, and the areal density of the self-supporting film is 2.3 mg / cm 2 .

[0056] Example 8

[0057] The pre-oxidized self-supporting film prepared in Example 6 was heat-treated at 650 °C for 4.0 h to obtain a self-supporting film electrode of the composite material containing MoO₂, FeMoO₄ and MXenes, labeled as MFM@CNFs-2, and the areal density of the self-supporting film is 2.2 mg / cm 2 .

[0058] Example 9

[0059] The pre-oxidized self-supporting film prepared in Example 6 was heat-treated at 750 °C for 4.0 h to obtain a self-supporting film electrode of the composite material containing MoO₂, FeMoO₄ and MXenes, labeled as MFM@CNFs-3, and the areal density of the self-supporting film is 2.1 mg / cm 2 .

[0060] Performance test

[0061] The constant current charge-discharge performance of the materials and self-supporting membrane electrodes prepared in the above Examples 2-4 and 7-9 as the anode materials of lithium / sodium ion batteries is shown in Table 1. The constant current charge-discharge test process is to test the charge-discharge performance of the electrode at a constant current value. The test can obtain the relationship curve between the potential U and the time t. According to the following formula, the mass specific capacity C can be calculated based on the constant current charge-discharge curve m :

[0062]

[0063] where I (mA) is the discharge current, m (g) is the mass of the electrode active material, and t (h) is the discharge time or charge time.

[0064] In the present invention, a NEWARE BTS-5V type battery charge-discharge test system developed by Neware is used to perform a constant current charge-discharge test on the assembled lithium / sodium ion battery. The charge-discharge voltage range is 0.01-3.0V vs, E Na+ / Na or E Li+ / Li , and its charge-discharge current density is 0.01-4.0 A / g.

[0065] Table 1 Application performance of the materials prepared in Examples 2-4 and 7-9 in the anode of lithium / sodium ion batteries

[0066]

[0067]

[0068] As can be seen from Table 1, compared with the performance of the composite material containing Mn2V2O7 and Na5V 12 O 32 composite material, the self-supporting membrane electrode of the composite material containing Mn2V2O7 and Na5V 12 O 32 composite material has significantly improved rate and cycle stability performance due to better coating effect and the introduction of carbon nanofibers.

[0069] The SEM image of the composite material MFM containing Mo, Fe and MXenes in Example 1 is shown in Figure 1 , and it can be seen from Figure 1 that the composite material containing Mo, Fe and MXenes is a sandwich structure composite material, and the composite material has good uniformity.

[0070] The SEM images of the composite materials containing MoO2, FeMoO4 and MXenes in Examples 2-4 are shown in Figures 2-4 , and it can be seen from Figure 2 , Figure 3 and Figure 4It can be seen that after heat treatment, the composite material containing Mo, Fe, and MXenes is transformed into a rod-shaped composite material. The composite material obtained by heat treatment at 450 °C has better uniformity, and there is a protective film on the material surface.

[0071] The XRD patterns of the composite materials in Examples 1-4 are shown in Figure 5 , and it can be seen from Figure 5 that after heat treatment at 350 °C and 450 °C, the composite material containing Mo, Fe, and MXenes is transformed into MoO2 and FeMoO4. The composite material obtained by heat treatment at 450 °C has higher crystallinity, and the material composition becomes more complex after treatment at 550 °C.

[0072] The SEM images of the self-supporting membrane electrodes in Examples 7-9 are shown in Figures 6-8 , and it can be seen from Figures 6 to 8 that the composite material of MoO2, FeMoO4, and MXenes can be completely coated inside the nanofibers of polyacrylonitrile after electrospinning with polyacrylonitrile, and it is still coated inside the carbon material transformed from polyacrylonitrile after further heat treatment. This fully coated structure can enhance the rate and cycle stability of the material.

[0073] The XRD patterns of the self-supporting membrane electrodes in Examples 7-9 are shown in Figure 9 , and it can be seen from Figure 9 that after electrospinning, the composite material of MoO2, FeMoO4, and MXenes is completely coated inside the carbon nanofibers, so the characteristic diffraction peaks of MoO2 and FeMoO4 are not detected in its XRD pattern.

[0074] Comparative Example 1 (without Mo, Fe, and MXenes)

[0075] Measure 20 mL of DMF (N,N-dimethylformamide) and place it in a beaker. Weigh 1.2 g of polyacrylonitrile and add it to the DMF. After stirring for 48 h, electrospin to prepare a self-supporting membrane of carbon nanofibers without molybdenum, iron, and MXenes on a TTE-1 type electrospinning machine. Electrospinning conditions: voltage 28 kV, feeding speed 18 μL min -1 , temperature 30 °C, and the areal density of the self-supporting membrane is about 4.0 mg / cm 2 .

[0076] Pre-oxidize the above self-supporting membrane in an air atmosphere at a temperature of 280 °C for 4 h with a heating rate of 10 °C / min to obtain a pre-oxidized self-supporting membrane. Then continue to heat-treat the pre-oxidized self-supporting membrane at 750 °C for 4.0 h to obtain a self-supporting membrane electrode, labeled as CNFs. The mass of the self-supporting membrane is about 2.1 mg / cm 2 .

[0077] Comparative Example 2 (without adding Mo and Fe)

[0078] Measure 20 mL of DMF (N,N-dimethylformamide) and place it in a beaker. Weigh 1.2 g of polyacrylonitrile and 1.2 g of MXenes and add them to the DMF. After stirring for 48 h, electrospinning is carried out on a TTE-1 type electrospinning machine to prepare a self-supporting carbon nanofiber membrane without MXenes. Electrospinning conditions: voltage 28 kV, feeding rate 18 μL min -1 , temperature 30 °C, and the areal density of the self-supporting membrane is about 3.5 mg / cm 2 .

[0079] The above self-supporting membrane is pre-oxidized in an air atmosphere at a temperature of 280 °C for 4 h with a heating rate of 10 °C / min to obtain a pre-oxidized self-supporting membrane. Then, the pre-oxidized self-supporting membrane is heat-treated at 750 °C for 4.0 h to obtain a self-supporting membrane electrode, marked as M@CNFs. The mass of the self-supporting membrane is about 2.1 mg / cm 2 .

[0080] The self-supporting membrane electrode prepared in this comparative example is assembled into a battery, and its performance is tested. The performance test is the same as that in Examples 2-4. The results are shown in Table 2. It is found that for the membrane electrode prepared without adding Mo and Fe, when used as the anode of a lithium / sodium ion battery, both the cycle stability and the specific capacity at the same current density decrease significantly.

[0081] Table 2 Application performance of the materials prepared in the comparative example in the anode of lithium / sodium ion batteries

[0082]

[0083] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for preparing a self-supporting membrane, characterized in that, It includes the following steps: (1) Mix ferric chloride solution, ammonium molybdate solution and Ti3C2 MXenes dispersion, stir, filter, and dry to obtain a composite material containing molybdenum, iron and MXenes; (2) Heat-treat the composite material containing molybdenum, iron and MXenes to obtain a composite material containing MoO2, FeMoO4 and MXenes; (3) Mix the composite material containing MoO2, FeMoO4 and MXenes, polyacrylonitrile and dimethylformamide to obtain an electrospinning solution, and perform electrospinning to obtain a self-supporting film.

2. The method for preparing the self-supporting film according to claim 1, wherein, In step (1), the preparation method of ferric chloride solution is: completely dissolve 5.4 g of ferric chloride in 20 g of water to obtain ferric chloride solution; The preparation method of ammonium molybdate solution is: completely dissolve 10 g of ammonium molybdate in 20 g of water to obtain ammonium molybdate solution; The concentration of Ti3C2 MXenes dispersion is 5 mg / mL.

3. The method for preparing the self-supporting film according to claim 1, wherein In step (2), the heat treatment temperature is 350 - 550 °C, and the heat treatment time is 5.0 h.

4. The preparation method of the self-supporting film according to claim 1, wherein In step (3), the mass ratio of the composite material containing MoO2, FeMoO4 and MXenes to polyacrylonitrile is 1:1; the mass-volume ratio of dimethylformamide to polyacrylonitrile is 17 mL:1 g.

5. The method for preparing the self-supporting film according to claim 1, characterized in that, In step (3), during electrospinning: the voltage is 28 kV, the feeding speed is 18 μL / min, and the temperature is 30 °C.

6. A self-supporting film, characterized in that, Prepared according to the preparation method described in any one of claims 1 - 5.

7. Application of the self-supporting film described in claim 6 in the preparation of a composite negative electrode for lithium / sodium ion batteries.

8. A method for preparing a composite anode of a lithium / sodium ion battery, characterized in that, Pre-oxidize and heat-treat the self-supporting film of the composite material containing MoO2, FeMoO4 and MXenes described in claim 6 to obtain a composite negative electrode for lithium / sodium ion batteries.

9. The preparation method of the lithium / sodium ion battery composite negative electrode according to claim 8, characterized in that, The pre-oxidation is carried out in an air atmosphere, the pre-oxidation temperature is 280 °C, the pre-oxidation time is 4 h, and the heating rate is 10 °C / min.

10. The preparation method of the lithium / sodium ion battery composite negative electrode according to claim 8, wherein The heat treatment temperature is 550 - 750 °C, and the heat treatment time is 4.0 h.

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