CN113461015A - Preparation method of nitrogen-doped carbon-coated porous silicon - Google Patents

Preparation method of nitrogen-doped carbon-coated porous silicon Download PDF

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CN113461015A
CN113461015A CN202110750168.4A CN202110750168A CN113461015A CN 113461015 A CN113461015 A CN 113461015A CN 202110750168 A CN202110750168 A CN 202110750168A CN 113461015 A CN113461015 A CN 113461015A
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nitrogen
silicon
porous silicon
doped carbon
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CN113461015B (en
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冯金奎
安永灵
田园
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Shandong University
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    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
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    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The disclosure relates to the technical field of porous silicon preparation, in particular to a preparation method of nitrogen-doped carbon-coated porous silicon, which comprises the following steps: taking silicon-magnesium alloy as a precursor, mixing the silicon-magnesium alloy with carbon nitride, carrying out primary heat treatment under the inert atmosphere or vacuum condition, then continuously heating, and carrying out secondary heat treatment under the inert atmosphere or vacuum condition; or, taking silicon-magnesium alloy as a precursor, mixing the silicon-magnesium alloy with carbon nitride, carrying out heat treatment under the inert atmosphere or vacuum condition, then treating the intermediate product in acid, and drying to obtain the nitrogen-doped carbon-coated porous silicon. The method can effectively improve the binding force between the carbon coating layer and the silicon and improve the electrochemical stability of the porous silicon negative electrode material.

Description

Preparation method of nitrogen-doped carbon-coated porous silicon
Technical Field
The disclosure relates to the technical field of porous silicon preparation, in particular to a preparation method of nitrogen-doped carbon-coated porous silicon.
Background
The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.
When the silicon is used as the lithium ion battery cathode material, the silicon has the advantages of ultrahigh theoretical specific capacity, lower de-intercalation lithium potential, environmental friendliness, rich reserve and the like, and is considered to be very promising to replace the traditional graphite cathode material to be used as the next generation of high-energy-density lithium ion battery cathode material. However, the large volume change of the silicon negative electrode in the repeated lithium deintercalation process is considered to be a main cause of the insufficient cycle life thereof. Its short cycle life has hindered the commercial application of silicon anodes. In addition, the silicon negative electrode has a problem of poor electron conductivity, resulting in poor rate performance.
The problems of the silicon cathode can be better solved by designing a special silicon material structure. In various structures, the porous silicon can effectively buffer the volume change in the circulating process, increase the interface contact, accelerate the ion transmission and obtain better electrochemical performance. In addition, the carbon coating layer can also inhibit the volume change in the lithium extraction process and improve the electronic conductivity of the silicon material, and can further improve the electrochemical performance of the silicon negative electrode.
However, the inventor finds that the traditional method for preparing the carbon coating layer is complex in process, and the bonding force between the carbon coating layer and silicon is poor, so that the carbon coating layer is easy to fall off in the electrochemical cycle reaction process. For example, the prior patent discloses that silicide and carbon source are mixed for heat treatment and acid cleaning to obtain the porous silicon/carbon composite material, but the acid cleaning is needed in the process, the use of acid not only causes environmental pollution, but also easily etches the pore structure and causes the structure collapse; jeong et al use ethylenediamine as a nitrogen-doped carbon source to coat porous silicon, however, in this method, ethylenediamine and porous silicon are directly mixed, refluxed, and then subjected to heat treatment, and thus the production of a carbon coating layer and silicon cannot be performed simultaneously, resulting in weak bonding force between the carbon coating layer and silicon; shi et al use gelatin as a nitrogen-doped carbon source, but this method requires calcium carbonate, acid washing, etc., increases the complexity of preparation and causes problems of acid contamination, and also has difficulty in improving the bonding force between the carbon coating layer and silicon.
Therefore, the development of a method for preparing nitrogen-doped carbon-coated porous silicon, which is green and low in cost and can improve the bonding force between the carbon coating layer and silicon, is of great significance in accelerating the commercialization of silicon.
Disclosure of Invention
Researches show that the existing method for preparing the carbon-coated porous silicon has the problems of serious acid pollution, complex preparation process and difficulty in weakening the bonding force between the carbon coating layer and the silicon.
Specifically, the technical scheme of the present disclosure is as follows:
in a first aspect of the present disclosure, a method for preparing nitrogen-doped carbon-coated porous silicon includes: taking silicon-magnesium alloy as a precursor, mixing the silicon-magnesium alloy with carbon nitride, carrying out heat treatment under the inert atmosphere or vacuum condition, then treating an intermediate product in acid, and drying;
or, taking silicon-magnesium alloy as a precursor, mixing the silicon-magnesium alloy with carbon nitride, carrying out first heat treatment under the inert atmosphere or vacuum condition, then continuously heating, and carrying out second heat treatment under the inert atmosphere or vacuum condition to obtain the nitrogen-doped carbon-coated porous silicon.
In a second aspect of the disclosure, the nitrogen-doped carbon-coated porous silicon material is obtained by the preparation method of the nitrogen-doped carbon-coated porous silicon.
In a third aspect of the present disclosure, a lithium ion battery includes a negative electrode material, an electrolyte, and a positive electrode material, where the negative electrode material is the above nitrogen-doped carbon-coated porous silicon material.
In a fourth aspect of the present disclosure, the nitrogen-doped carbon-coated porous silicon material and/or the lithium ion battery are/is applied to the fields of energy storage devices and electric vehicles.
One or more technical schemes in the disclosure have the following beneficial effects:
(1) the silicon-magnesium alloy is adopted as a precursor, and is mixed with carbon nitride and pyrolyzed, in the pyrolysis process, magnesium in the precursor alloy reacts with the carbon nitride to generate magnesium nitride and nitrogen-doped carbon, a nitrogen-doped carbon coating layer is formed, and the binding force between the carbon coating layer and silicon is greatly improved. In addition, the magnesium nitride is evaporated at a higher temperature, and the nitrogen-doped carbon-coated porous silicon can be obtained.
(2) Researches show that in the process of simultaneously pyrolyzing the silicon-magnesium alloy and the carbon nitride, a two-section calcination method is adopted, and the carbon nitride is calcined and matched through two sections, so that the binding force between the carbon coating layer and the silicon can be improved, the acid washing can be avoided, and the electrochemical performance of the porous silicon is greatly improved.
(3) According to the preparation method, the carbon coating layer with controllable graphitization degree can be prepared by adjusting the synthesis temperature, and the nitrogen-doped carbon coating layer and the silicon are generated simultaneously, so that the binding force between the silicon and the coating layer is strong, which is beneficial to improving the electronic conductivity and buffering the volume change, and the improved electrochemical performance is obtained.
(4) The step of acid washing can be avoided by evaporating the intermediate product, and the silicon with a porous structure can be obtained, so that the volume change in the process of buffering circulation is facilitated, the transmission of ions and the infiltration of electrolyte are promoted, and the good electrochemical performance is obtained.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
Fig. 1 is an XRD pattern of the precursor magnesium silicide alloy in example 1.
Fig. 2 is an XRD pattern of the nitrogen-doped carbon-coated porous silicon material prepared in example 1.
Fig. 3 is a Raman chart of the nitrogen-doped carbon-coated porous silicon material prepared in example 1.
Fig. 4 is an SEM image (3500 times) of the nitrogen-doped carbon-coated porous silicon material prepared in example 1.
Fig. 5 is an SEM image (10000 times) of the nitrogen-doped carbon-coated porous silicon material prepared in example 1.
Fig. 6 is an SEM image (20000 times) of the nitrogen-doped carbon-coated porous silicon material prepared in example 1.
Fig. 7 is a cyclic voltammetry curve of the nitrogen-doped carbon-coated porous silicon material prepared in example 1 as a negative electrode material of a lithium ion battery.
Fig. 8 is a charge and discharge curve of the nitrogen-doped carbon-coated porous silicon material prepared in example 1 as a negative electrode material of a lithium ion battery.
Fig. 9 shows the cycle performance of the nitrogen-doped carbon-coated porous silicon material prepared in example 1 as a negative electrode material of a lithium ion battery.
Detailed Description
The disclosure is further illustrated with reference to specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The reagents or starting materials used in the present invention can be purchased from conventional sources, and unless otherwise specified, the reagents or starting materials used in the present invention can be used in a conventional manner in the art or in accordance with the product specifications. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention. The preferred embodiments and materials described herein are intended to be exemplary only.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, and/or combinations thereof, unless the context clearly indicates otherwise.
At present, the process of preparing the silicon cathode is complex, polluting chemical substances such as acid and the like can be used, the existing preparation method only utilizes the characteristics of the carbon material such as conductivity and the like, the binding force between a carbon coating layer and silicon is not considered, and the prepared carbon-coated porous silicon material has poor stability and is easy to generate the problems of active substance falling, volume expansion and the like in the electrochemical circulation process. Therefore, the disclosure provides a preparation method of nitrogen-doped carbon-coated porous silicon.
In one embodiment of the present disclosure, a method for preparing nitrogen-doped carbon-coated porous silicon includes: taking silicon-magnesium alloy as a precursor, mixing the silicon-magnesium alloy with carbon nitride, carrying out heat treatment under the inert atmosphere or vacuum condition, then treating an intermediate product in acid, and drying;
or, taking silicon-magnesium alloy as a precursor, mixing the silicon-magnesium alloy with carbon nitride, carrying out first heat treatment under the inert atmosphere or vacuum condition, then continuously heating, and carrying out second heat treatment under the inert atmosphere or vacuum condition to obtain the nitrogen-doped carbon-coated porous silicon.
The carbon nitride has a graphite-like layered structure, and rings are connected through terminal N atoms to form an infinitely expanded plane, so that the carbon nitride has excellent physical and chemical properties. The carbon nitride contains abundant nitrogen, and provides enough nitrogen source for obtaining nitrogen-doped carbon. During pyrolysis, due to the unique structure of carbon nitride, the carbon nitride reacts with magnesium to generate magnesium nitride and nitrogen-doped carbon, so that a uniform carbon coating layer can be obtained. Along with the generation and removal of the intermediate product magnesium nitride, the porous silicon is gradually formed, and the nitrogen-doped carbon coating layer and the silicon are generated simultaneously, so that the binding force between the carbon coating layer and the silicon is improved.
Under the inert atmosphere, the temperature of the first heat treatment is 550-950 ℃, and the time is 0.5-5 h; or, under inert atmosphere, the temperature of the second heat treatment is 1100-.
Or, under the vacuum condition, the temperature of the first heat treatment is 500-; or, under the vacuum condition, the temperature of the second heat treatment is 1000-.
In the first heat treatment process, carbon nitride reacts with magnesium in the silicon-magnesium alloy to generate magnesium nitride and nitrogen-doped carbon, and the nitrogen-doped carbon is gradually coated on the surface of the porous silicon. And (4) continuing heating treatment, further enhancing the bonding force between the carbon coating layer and the silicon, evaporating the intermediate product magnesium nitride, and synthesizing the target product nitrogen-doped carbon-coated porous silicon.
Wherein, the inert atmosphere is one or two mixed gases of argon gas/nitrogen gas.
The vacuum condition is that the vacuum degree is less than or equal to 10 Pa.
In one embodiment of the present disclosure, the acid is one or a mixture of two or more of hydrochloric acid, sulfuric acid, acetic acid, oxalic acid, citric acid, phosphoric acid, sulfurous acid, hydrofluoric acid, formic acid, benzoic acid, acetic acid, propionic acid, stearic acid, carbonic acid, hydrosulfuric acid, hypochlorous acid, boric acid, and silicic acid. Impurities such as oxides can be removed by acid washing and more of the pore structure is exposed.
In an embodiment of the present disclosure, the nitrogen-doped carbon-coated porous silicon material obtained by the above method for preparing nitrogen-doped carbon-coated porous silicon has a carbon content of 5 to 30% and a specific surface area of 50 to 200m2 g-1The pore size distribution is 1-100 nm.
In one embodiment of the present disclosure, a lithium ion battery includes a negative electrode material, an electrolyte, and metallic lithium, where the negative electrode material is the above nitrogen-doped carbon-coated porous silicon material;
further, the electrolyte in the electrolyte is one or a mixture of more than two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis (difluoro) sulfonyl imide, lithium bis (trifluoromethyl) sulfonyl imide, lithium difluoro (oxalic) borate and lithium bis (oxalic) borate;
further, the solvent in the electrolyte is one or a mixture of more than two of Ethylene Carbonate (EC), Propylene Carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC) and Methyl Propyl Carbonate (MPC);
in one embodiment of the disclosure, the nitrogen-doped carbon-coated porous silicon material and/or the lithium ion battery are/is applied to the fields of energy storage devices and electric vehicles.
In order to make the technical solutions of the present disclosure more clearly understood by those skilled in the art, the technical solutions of the present disclosure will be described in detail below with reference to specific embodiments.
Example 1
A preparation method of nitrogen-doped carbon-coated porous silicon comprises the steps of uniformly mixing 1.0g of magnesium silicide and 2.5g of carbon nitride powder, placing the mixture in a tubular furnace, introducing argon, carrying out heat treatment at 900 ℃ for 0.5h, continuously raising the temperature, carrying out heat treatment at 1100 ℃ for 0.1h, cooling to room temperature, treating with 2M hydrochloric acid solution for 2h to remove impurities in a product, filtering, washing and drying to obtain the nitrogen-doped carbon-coated porous silicon material.
Assembling the battery:
preparing a negative electrode material: uniformly mixing nitrogen-doped carbon-coated porous silicon, carbon black and PAA in a mass ratio of 6:2:2, adding deionized water, stirring for 12 hours, coating on a copper foil, and drying at 80 ℃ for 15 hours under a vacuum condition to obtain the required negative electrode material.
The electrolyte adopts 1M LiPF6(EC + EDC), the cell was assembled in a glove box with metallic lithium plates as counter and working electrodes.
And (3) performance testing:
cyclic voltammetry testing: the sweeping speed is 0.2mV s-1The voltage interval is 0.01V-3V.
And (3) testing the cyclicity: the current density was 500mA g-1The voltage interval is 0.01V-3V.
Fig. 1 is an XRD pattern of the precursor magnesium silicide alloy in example 1, which has less impurities and higher purity in the precursor magnesium silicide.
Fig. 2 is an XRD pattern of the nitrogen-doped carbon-coated porous silicon material prepared in example 1, and characteristic peaks of silicon and characteristic peaks of carbon were observed as a product, illustrating successful synthesis of the nitrogen-doped carbon-coated porous silicon.
Fig. 3 is a Raman graph of the nitrogen-doped carbon-coated porous silicon material prepared in example 1, in which characteristic peaks of silicon and characteristic peaks of G and D of carbon were observed, illustrating that carbon was successfully coated on the surface of silicon. The nitrogen-doped carbon layer can effectively improve the electronic conductivity of the material, promote the transmission of ions, relieve the volume change in the circulation process and obtain good electrochemical performance.
Fig. 4, 5, and 6 are SEM images (3500 times) of the nitrogen-doped carbon-coated porous silicon material prepared in example 1 at different times, and the obtained product has a typical three-dimensional porous structure, and is beneficial to promoting infiltration between an electrolyte and an electrode material, accelerating ion transport speed, alleviating volume expansion during a cycle process, and obtaining excellent electrochemical performance.
Fig. 7 is a cyclic voltammetry curve of the nitrogen-doped carbon-coated porous silicon material prepared in example 1 as a negative electrode material of a lithium ion battery, which shows typical oxidation peaks and reduction peaks of silicon, and illustrates that the synthesized silicon-based negative electrode has high purity and no other impurities. In addition, the superimposed curves also demonstrate that the obtained silicon-based negative electrode has good cycling performance.
FIG. 8 is a charge-discharge curve of the nitrogen-doped carbon-coated porous silicon material prepared in example 1 as a negative electrode material of a lithium ion battery, wherein the silicon negative electrode has a high specific capacity and a high first-cycle coulombic efficiency, and the reversible capacity reaches 2579mAh g-1The first-week coulombic efficiency is 92.3%, and the superposed curve further proves the excellent cycle performance of the modified silicon negative electrode.
FIG. 9 shows the cycle performance of the nitrogen-doped carbon-coated porous silicon material prepared in example 1 as the negative electrode material of a lithium ion battery, with a capacity of 2180mAh g after 20 cycles-1And shows good cycle performance. This further demonstrates that the bonding force between nitrogen-doped carbon and porous silicon is strong, the coating layer does not fall off from the surface of silicon during the circulation process, the transport of ions can be effectively promoted, the volume change can be buffered, and excellent electrochemical performance can be obtained.
Example 2
A preparation method of nitrogen-doped carbon-coated porous silicon comprises the steps of uniformly mixing 1.0g of magnesium silicide and 2.5g of carbon nitride powder, placing the mixture in a tubular furnace, introducing argon, carrying out heat treatment at 800 ℃ for 2 hours, then continuously raising the temperature, continuously raising the temperature to 1300 ℃ under the condition of argon for treatment for 0.1 hour, cooling to room temperature, treating for 2 hours by using 2M hydrochloric acid solution to remove impurities in a product, filtering, washing and drying to obtain the nitrogen-doped carbon-coated porous silicon material.
Example 3
A preparation method of nitrogen-doped carbon-coated porous silicon comprises the steps of uniformly mixing 1.0g of magnesium silicide and 2.5g of carbon nitride powder, placing the mixture in a tube furnace, carrying out heat treatment at 600 ℃ for 4 hours under a vacuum condition, then continuously raising the temperature, continuously raising the temperature to 1300 ℃ under the vacuum condition for 0.1 hour, cooling to room temperature, treating for 2 hours by using 2M hydrochloric acid solution to remove impurities in a product, filtering, washing and drying to obtain the nitrogen-doped carbon-coated porous silicon material.
Example 4
A preparation method of nitrogen-doped carbon-coated porous silicon comprises the steps of uniformly mixing 1.0g of magnesium silicide and 2.5g of carbon nitride powder, placing the mixture in a tube furnace, carrying out heat treatment at 700 ℃ for 3h under a vacuum condition, then continuously raising the temperature, continuously raising the temperature to 1200 ℃ under an argon condition for 1.0h, cooling to room temperature, treating for 2h by using 2M hydrochloric acid solution to remove impurities in a product, filtering, washing and drying to obtain the nitrogen-doped carbon-coated porous silicon material.
Example 5
A preparation method of nitrogen-doped carbon-coated porous silicon comprises the steps of uniformly mixing 1.0g of magnesium silicide and 2.5g of carbon nitride powder, placing the mixture in a tube furnace, carrying out heat treatment at 500 ℃ for 0.5h under a vacuum condition, then continuously raising the temperature, continuously raising the temperature to 1000 ℃ under the vacuum condition for 0.2h, cooling to room temperature, then treating for 2h with 2M hydrochloric acid solution to remove impurities in a product, filtering, washing and drying to obtain the nitrogen-doped carbon-coated porous silicon material.
Example 6
A preparation method of nitrogen-doped carbon-coated porous silicon comprises the steps of uniformly mixing 1.0g of silicon-aluminum alloy and 2.0g of carbon nitride powder, placing the mixture in a tubular furnace, introducing argon, carrying out heat treatment at 910 ℃ for 1.5h, then continuously raising the temperature, continuously raising the temperature to 1100 ℃ under a vacuum condition for treatment for 0.5h, cooling to room temperature, treating for 2h by using 2M hydrochloric acid solution to remove impurities in a product, filtering, washing and drying to obtain the nitrogen-doped carbon-coated porous silicon material.
Example 7
A preparation method of nitrogen-doped carbon-coated porous silicon comprises the steps of uniformly mixing 1.5g of silicon-zinc alloy and 2.5g of carbon nitride powder, placing the mixture in a tubular furnace, carrying out heat treatment at 600 ℃ for 2.5h under a vacuum condition, then continuously raising the temperature, continuously raising the temperature to 1200 ℃ under the vacuum condition for treatment for 2h, cooling to room temperature, treating for 2h by using 2M hydrochloric acid solution to remove impurities in a product, filtering, washing and drying to obtain the nitrogen-doped carbon-coated porous silicon material.
Example 8
A preparation method of nitrogen-doped carbon-coated porous silicon comprises the steps of uniformly mixing 1.5g of silicon-antimony alloy and 3.0g of carbon nitride powder, placing the mixture in a tubular furnace, carrying out heat treatment at 800 ℃ for 3 hours under a vacuum condition, then continuously raising the temperature, continuously raising the temperature to 1200 ℃ under an argon condition for treatment for 1.0 hour, cooling to room temperature, treating for 2 hours by using 2M hydrochloric acid solution to remove impurities in a product, filtering, washing and drying to obtain the nitrogen-doped carbon-coated porous silicon material.
Example 9
A preparation method of nitrogen-doped carbon-coated porous silicon comprises the steps of uniformly mixing 0.8g of silicon-magnesium alloy and 2.0g of carbon nitride powder, placing the mixture in a tubular furnace, introducing argon, carrying out heat treatment at the temperature of 750 ℃ for 2 hours, cooling to room temperature, treating with 2M hydrochloric acid solution for 20 hours, filtering, washing and drying to obtain the nitrogen-doped carbon-coated porous silicon material.
Example 10
A preparation method of nitrogen-doped carbon-coated porous silicon comprises the steps of uniformly mixing 0.8g of silicon-aluminum alloy and 2.0g of carbon nitride powder, placing the mixture in a tube furnace, introducing argon, carrying out heat treatment at 900 ℃ for 0.5h, cooling to room temperature, treating with 1M sulfuric acid solution for 25h, filtering, washing and drying to obtain the nitrogen-doped carbon-coated porous silicon material.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. A preparation method of nitrogen-doped carbon-coated porous silicon is characterized by comprising the following steps: taking silicon-magnesium alloy as a precursor, mixing the silicon-magnesium alloy with carbon nitride, carrying out heat treatment under the inert atmosphere or vacuum condition, then treating an intermediate product in acid, and drying;
or, taking silicon-magnesium alloy as a precursor, mixing the silicon-magnesium alloy with carbon nitride, carrying out first heat treatment under the inert atmosphere or vacuum condition, then continuously heating, and carrying out second heat treatment under the inert atmosphere or vacuum condition to obtain the nitrogen-doped carbon-coated porous silicon.
2. The method according to claim 1, wherein the acid is one or more selected from hydrochloric acid, sulfuric acid, acetic acid, oxalic acid, citric acid, phosphoric acid, sulfurous acid, hydrofluoric acid, formic acid, benzoic acid, acetic acid, propionic acid, stearic acid, carbonic acid, hydrosulfuric acid, hypochlorous acid, boric acid, and silicic acid.
3. The method as claimed in claim 1, wherein the first heat treatment is performed at 550-950 ℃ for 0.5-5h in an inert atmosphere; or, under inert atmosphere, the temperature of the second heat treatment is 1100-.
4. The method as claimed in claim 1, wherein the first heat treatment is performed at 500-900 ℃ for 0.5-5h under vacuum condition; or, under the vacuum condition, the temperature of the second heat treatment is 1000-.
5. The method according to claim 1, wherein the silicon-magnesium alloy is magnesium silicide.
6. The nitrogen-doped carbon-coated porous silicon material obtained by the preparation method of nitrogen-doped carbon-coated porous silicon according to any one of claims 1 to 5.
7. A lithium ion battery comprises a negative electrode material, an electrolyte and a positive electrode material, and is characterized in that the negative electrode material is the nitrogen-doped carbon-coated porous silicon material of claim 6; further, the electrolyte in the electrolyte is one or a mixture of more than two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis (difluoro) sulfonyl imide, lithium bis (trifluoromethyl) sulfonyl imide, lithium difluoro (oxalic) borate and lithium bis (oxalic) borate; the solvent in the electrolyte is one or a mixture of more than two of Ethylene Carbonate (EC), Propylene Carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC) and Methyl Propyl Carbonate (MPC); the positive electrode material is selected from lithium manganate, lithium cobaltate, lithium iron phosphate, lithium nickel cobalt manganese oxide or lithium nickelate.
8. The nitrogen-doped carbon-coated porous silicon material of claim 6 and/or the lithium ion battery of claim 7 are applied to the fields of energy storage devices and electric vehicles.
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