Zinc / nitrogen co-doped porous hard carbon negative electrode material and preparation method and application thereof

Abstract

The invention discloses a zinc / nitrogen co-doped porous hard carbon negative electrode material and a preparation method and application thereof, and belongs to the field of negative electrode materials. The method comprises the following steps: mixing a hard carbon precursor zinc gluconate with an organic nitrogen source in deionized water, and heating in a water bath to fully react with the zinc gluconate and the organic nitrogen source; taking out and drying after sufficient reaction to obtain intermediate powder; and performing carbonization treatment on the obtained intermediate powder under the protection of an inert atmosphere to obtain the porous hard carbon negative electrode material containing Zn-N doping and closed pores. The existence of a proper amount of Zn atoms and N atoms is beneficial to the transmission of sodium ions on the hard carbon surface and in a graphite-like layer, and meanwhile, the dense closed-pore structure can effectively improve the sodium storage space. The hard carbon negative electrode material disclosed by the invention has relatively wide carbon layer spacing and relatively high defect degree, and also shows excellent electrochemical performance, the initial discharge capacity is 462.13 mAh / g, and the first discharge efficiency is 83.48%. The preparation process has the characteristics of simplicity, rapidness and environmental protection, and is easy to realize large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of anode materials, and particularly relates to a zinc / nitrogen co-doped porous hard carbon anode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous progress of smart grid and electric vehicle technologies, the demand for lithium-ion batteries (LIBs) is increasing significantly. However, due to the limited lithium resources, this growth trend may be restricted, thereby affecting the application expansion of lithium-ion batteries in various fields. Sodium has similar physical and chemical properties to lithium, and the sodium reserves are richer than lithium, so it has great advantages in terms of cost and large-scale application. The problems of low specific capacity, first efficiency, and energy density of hard carbon materials in sodium battery anode materials still restrict the development of sodium-ion batteries.

[0003] In order to create more closed pores in hard carbon, the published patent CN118306967A specifically relates to a preparation method and application of a hard carbon anode material. However, during the implementation of this method, the raw materials need to be treated with acid dissolution and alkali dissolution to obtain a hard carbon precursor, and at the same time, multiple sintering processes are required to prepare a closed pore hard carbon material. The whole process is not only complex in steps but also the waste acid and alkali solutions will pollute the environment. Therefore, it is necessary to optimize the modification strategy to eliminate the use of strong acids and strong bases, so as to prepare a modified hard carbon material with more excellent performance more conveniently, simply, and environmentally friendly. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems of low specific capacity and low first efficiency of hard carbon materials, and to provide a zinc / nitrogen co-doped porous hard carbon anode material, a preparation method thereof, and an application thereof.

[0005] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0006] A preparation method of a zinc / nitrogen co-doped porous hard carbon anode material, the method is: mixing zinc gluconate as a hard carbon precursor with an organic nitrogen source in deionized water, heating in a water bath to allow the two to react fully; after the full reaction, taking out and drying to obtain an intermediate powder; under the protection of an inert atmosphere, carbonizing the obtained intermediate powder to obtain a porous hard carbon anode material containing Zn-N doping and containing closed pores.

[0007] Further, the mass ratio of the zinc gluconate to the organic nitrogen source is 1:4 - 9:1, and the concentration of the organic nitrogen source is 0.050 - 0.100 mol / L. The weight of the zinc gluconate is 0.5 - 5.0 g.

[0008] Further, the organic nitrogen source is at least one of ethylenediaminetetraacetic acid, nitrilotriacetic acid, glycine, and glutamic acid.

[0009] Further, the water bath temperature is 60 - 100 °C, the magnetic stirring speed is 400 - 800 ppm, and the magnetic stirring time is 0.5 - 2 h.

[0010] Further, the heating is carried out in three stages. Specifically, in the first stage, it is heated to 100 - 500 °C at a heating rate of 2 - 10 °C, in the second stage, it is heated to 500 - 1200 °C at a heating rate of 1 - 5 °C, and in the third stage, it is heated to 1200 - 1800 °C at a heating rate of 5 - 10 °C, and after holding for 2 - 6 h, it is naturally cooled.

[0011] A zinc / nitrogen co-doped porous hard carbon negative electrode material prepared by the above preparation method. In the zinc / nitrogen co-doped porous hard carbon material, the carbon layer spacing is 0.380 nm - 0.450 nm, the pore size is 2 - 20 nm, and the degree of defect I D (degree of disorder) / I G (degree of order) is 1.000 - 1.200.

[0012] An application of a zinc / nitrogen co-doped porous hard carbon negative electrode material prepared by the above preparation method in a sodium ion battery.

[0013] The beneficial effects of the present invention compared with the prior art are as follows:

[0014] (1) The presence of an appropriate amount of Zn atoms and N atoms is beneficial to the transport of sodium ions on the surface of hard carbon and in the graphite-like layers. At the same time, the dense closed pore structure can effectively improve the sodium storage space.

[0015] (2) The hard carbon negative electrode material of the present invention has a relatively wide carbon layer spacing and a high degree of defect, and at the same time exhibits excellent electrochemical performance, with an initial discharge capacity of 462.13 mAh / g and a first discharge efficiency of 83.48%.

[0016] (3) The preparation process has the characteristics of simplicity, rapidity, and environmental protection, and is easy to realize large-scale industrial production. Description of the Drawings

[0017] Figure 1 It is the SEM image of the zinc / nitrogen co-doped hard carbon material in Example 1.

[0018] Figure 2 It is the SEM image of the hard carbon material in Comparative Example 1. Detailed Embodiments

[0019] The technical solutions of the present invention will be further described below in conjunction with the drawings and embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered within the protection scope of the present invention.

[0020] In the present invention, by using the chelating agent ethylenediaminetetraacetic acid, which has abundant carboxylic acid functional groups (-COOH) and tertiary amines (-NH-), a certain grasping force is generated on the zinc atoms in the hard carbon material, hindering the formation of ZnO during the normal carbonization process, thereby introducing Zn atoms and N atoms into the system. The zinc / nitrogen doping changes the surface defects and layer spacing of the hard carbon, which is beneficial to accelerating the sodium ion insertion / extraction efficiency; at the same time, a dense closed pore structure is formed, providing more storage sites for sodium ions. This method has the characteristics of simplicity, rapidity, and environmental friendliness, and can prepare a hard carbon material with high capacity and first Coulomb efficiency.

[0021] Example 1

[0022] First, weigh 0.5 g of the organic nitrogen source ethylenediaminetetraacetic acid (hereinafter referred to as EDTA) and add it to a beaker containing deionized water, and add an appropriate amount of ammonia water to completely dissolve it, thereby preparing an EDTA solution with a concentration of 0.086 mol / L. Subsequently, add 4.5 g of zinc gluconate, and under the conditions of a water bath at 80 °C and magnetic stirring at 500 ppm for 1 h, allow it to fully carry out the chelation reaction. Finally, take out the product and carbonize it in an argon-protected atmosphere at 1400 °C. The carbonization conditions are as follows: first, increase the temperature to 200 °C at a heating rate of 5 °C / min, then increase the temperature to 900 °C at a heating rate of 1 °C / min, and finally increase the temperature to 1400 °C at a heating rate of 5 °C / min, with a holding time of 3 h, to obtain a hard carbon material containing closed pores and atomic-level Zn-N doping, named Zn-N-HC-10, as Figure 1 shown.

[0023] Example 2

[0024] First, weigh 1 g of the organic nitrogen source EDTA and add it to a beaker containing deionized water, and add an appropriate amount of ammonia water to completely dissolve it, thereby preparing an EDTA solution with a concentration of 0.172 mol / L. Subsequently, add 4 g of zinc gluconate, and under the conditions of a water bath at 80 °C and magnetic stirring at 500 ppm for 1 h, allow it to fully carry out the chelation reaction. Finally, take out the product and carbonize it in an argon-protected atmosphere at 1400 °C. The carbonization conditions are as follows: first, increase the temperature to 200 °C at a heating rate of 5 °C / min, then increase the temperature to 900 °C at a heating rate of 1 °C / min, and finally increase the temperature to 1400 °C at a heating rate of 5 °C / min, with a holding time of 3 h, to obtain a hard carbon material containing closed pores and atomic-level Zn-N doping, named Zn-N-HC-20.

[0025] Example 3

[0026] First, weigh 2.5 g of the organic nitrogen source EDTA and add it to a beaker containing deionized water. Then add an appropriate amount of ammonia water to completely dissolve it, thus preparing an EDTA solution with a concentration of 0.430 mol / L. Subsequently, add 2.5 g of zinc gluconate and carry out chelation under the conditions of a water bath at 80 °C and magnetic stirring at 500 ppm for 1 h. Finally, take out the product and carbonize it in an argon-protected atmosphere at 1400 °C. The carbonization conditions are as follows: first, increase the temperature to 200 °C at a heating rate of 5 °C / min, then increase the temperature to 900 °C at a heating rate of 1 °C / min, and finally increase the temperature to 1400 °C at a heating rate of 5 °C / min. The holding time is 3 h to obtain a hard carbon material containing closed pores and atomic-level Zn-N doping, named Zn-N-HC-50.

[0027] Example 4

[0028] First, weigh 4 g of the organic nitrogen source EDTA and add it to a beaker containing deionized water. Then add an appropriate amount of ammonia water to completely dissolve it, thus preparing an EDTA solution with a concentration of 0.688 mol / L. Subsequently, add 1 g of zinc gluconate and carry out chelation under the conditions of a water bath at 80 °C and magnetic stirring at 500 ppm for 1 h. Finally, take out the product and carbonize it in an argon-protected atmosphere at 1400 °C. The carbonization conditions are as follows: first, increase the temperature to 200 °C at a heating rate of 5 °C / min, then increase the temperature to 900 °C at a heating rate of 1 °C / min, and finally increase the temperature to 1400 °C at a heating rate of 5 °C / min. The holding time is 3 h to obtain a hard carbon material containing closed pores and atomic-level Zn-N doping, named Zn-N-HC-80.

[0029] Example 5

[0030] The difference from Example 1 is that the organic nitrogen source added in the experimental steps is nitrilotriacetic acid with a mass of 0.5 g, and the addition amount of zinc gluconate is 4.5 g, named Zn-N-HC-10-2.

[0031] Example 6

[0032] The difference from Example 1 is that the organic nitrogen source added in the experimental steps is glycine with a mass of 0.5 g, and the addition amount of zinc gluconate is 4.5 g, named Zn-N-HC-10-3.

[0033] Example 7

[0034] The difference from Example 1 is that the organic nitrogen source added in the experimental steps is glutamic acid with a mass of 0.5 g, and the addition amount of zinc gluconate is 4.5 g, named Zn-N-HC-10-4.

[0035] Comparative Example 1

[0036] It is different from Examples 1-4 in that the amount of the organic nitrogen source EDTA added in the experimental steps is 0, and the amount of zinc gluconate added is 5 g, named HC-0, as Figure 2 shown.

[0037] Product testing

[0038] The hard carbon anode materials, conductive carbon Super-P and binder carboxymethyl cellulose (CMC) prepared in the above examples and comparative examples were mixed and ground according to a mass ratio of 8:1:1, and an appropriate dispersant deionized water was added to finally obtain a delicate, uniform and particle-free electrode paste. Then it was coated on the current collector copper foil, dried in a vacuum drying oven at 80 °C for 12 h, rolled and cut into circular electrode sheets with a diameter of 14 mm using a cutting machine, and finally assembled into a button cell in a glove box filled with argon. A sodium sheet was used as the counter electrode, the electrolyte was a 1 mol / L NaPF6 ether-based electrolyte, the solvent component was dimethyl ether DME, and the separator was a glass fiber separator. The prepared sodium-ion battery was subjected to constant current charge and discharge testing, and the voltage window was set to 0.01-3 V. The performance of the hard carbon materials prepared in the above examples and comparative examples was tested, and at the same time, the prepared sodium-ion battery was subjected to constant current charge and discharge testing (the voltage window was set to 0.01-3 V), and the test results are shown in Table 1.

[0039] Table 1

[0040]

Claims

1. A preparation method of a zinc / nitrogen co-doped porous hard carbon negative electrode material, characterized in that: The method is as follows: Zinc gluconate as the hard carbon precursor and an organic nitrogen source are mixed in deionized water, and then heated in a water bath to allow the two to react fully; after the full reaction, it is taken out and dried to obtain an intermediate powder; the obtained intermediate powder is carbonized under an inert atmosphere to obtain a porous hard carbon anode material.

2. The preparation method of a zinc / nitrogen co-doped porous hard carbon negative electrode material according to claim 1, characterized in that: The mass ratio of the zinc gluconate to the organic nitrogen source is 1:4 to 9:1, and the concentration of the organic nitrogen source is 0.050 - 0.100 mol / L.

3. The preparation method of a zinc / nitrogen co-doped porous hard carbon negative electrode material according to claim 1, characterized in that: The organic nitrogen source is at least one of ethylenediaminetetraacetic acid, nitrilotriacetic acid, glycine, and glutamic acid.

4. The preparation method of a zinc / nitrogen co-doped porous hard carbon negative electrode material according to claim 1, characterized in that: The water bath temperature is 60 - 100 °C, the magnetic stirring speed is 400 - 800 ppm, and the magnetic stirring time is 0.5 - 2 h.

5. The preparation method of a zinc / nitrogen co-doped porous hard carbon negative electrode material according to claim 1, characterized in that: The heating is carried out in three stages. Specifically, in the first stage, it is heated to 100 - 500 °C at a heating rate of 2 - 10 °C, in the second stage, it is heated to 500 - 1200 °C at a heating rate of 1 - 5 °C, and in the third stage, it is heated to 1200 - 1800 °C at a heating rate of 5 - 10 °C, and after holding for 2 - 6 h, it is naturally cooled.

6. A zinc / nitrogen co-doped porous hard carbon anode material prepared by the preparation method according to any one of claims 1 - 5.

7. Application of a zinc / nitrogen co-doped porous hard carbon anode material prepared by the preparation method according to any one of claims 1 - 5 in a sodium ion battery.

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