CN111403744A - Nitrogen-containing silicon oxygen carbon compound composite negative electrode material of lithium ion secondary battery and preparation method - Google Patents

Abstract

The invention discloses a preparation method of a nitrogen-containing silicon oxygen carbon compound composite negative electrode material of a lithium ion secondary battery, which comprises the following steps: stirring and mixing a silica precursor, a carbon source and a nitrogen source in an acidic aqueous solution to form slurry; drying the slurry, roasting at high temperature under protective gas, cooling, crushing and scattering to obtain a carbonized nitrogen-containing porous silicon oxygen carbon compound prepolymer; and blending the obtained nitrogen-containing porous silicon-oxygen carbide precursor and a carbon coating material, and carrying out high-temperature carbonization, cooling, crushing and scattering under protective gas to obtain the uniform and stable coating structure of the nitrogen-containing silicon-oxygen carbide composite negative electrode material of the lithium ion secondary battery. The composite negative electrode material containing the nitrogen-silicon oxygen carbon compound of the lithium ion secondary battery prepared by the preparation method has good negative electrode material conductivity and cycle performance.

Description

Nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material for lithium ion secondary battery and preparation method thereof

technical field

The invention relates to the technical field of lithium ion batteries, in particular to a nitrogen-containing silicon oxygen carbon compound composite negative electrode material and a preparation method for a lithium ion secondary battery.

Background technique

Compared with the traditional lithium ion anode material carbon-based anode material (maximum theoretical specific capacity 372mAh/g), the silicon-based anode material of lithium ion secondary battery has a higher theoretical specific capacity, and the maximum theoretical specific capacity of silicon single-element anode material reaches 4200mAh/g, the maximum theoretical specific capacity of silicon-oxygen negative electrode material has also reached 2100mAh/g, its specific capacity is much larger than that of carbon-based negative electrode material, and has greater commercial value and development prospects.

Compared with carbon-based materials, silicon-based materials have a huge capacity advantage, but their shortcomings are also very obvious. The main shortcomings of silicon-based materials are large cyclic expansion and poor electrical conductivity. Among them, the expansion rate of silicon-based anode materials can reach 300 %, and the silicon-oxygen anode material also has an expansion rate of nearly 200%. Such a high expansion rate makes silicon-based materials as anode materials for lithium-ion secondary batteries easy to pulverize and fall off during the cycle of use, resulting in reduced capacity and service life. The shortening has seriously affected the commercialization of silicon-based anode materials.

As the anode material of lithium ion battery, the expansion rate of silicon-oxygen material is relatively small compared with that of silicon material, the main reason is that oxygen in the silicon-oxygen anode material easily reacts with lithium ions to form stable lithium silicate compounds (Li ₂ O, Li ₄ SiO ₄ ), which can effectively control and relieve the expansion of the silicon-oxygen anode material and improve its cycle performance to a certain extent. Therefore, silicon oxide materials have been widely studied as anode materials for lithium ion secondary batteries.

To this end, we propose a nitrogen-containing silicon-oxygen-carbon composite negative electrode material and a preparation method for lithium-ion secondary batteries.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a nitrogen-containing silicon oxygen carbon compound composite negative electrode material and a preparation method for a lithium ion secondary battery, which have the advantages of improving the conductivity and cycle performance of the negative electrode material.

In order to achieve the above purpose, the present invention provides a preparation method of a nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material for a lithium ion secondary battery. The steps of the preparation method are as follows:

In step (1), the silicon-oxygen precursor, the carbon source and the nitrogen source are stirred and mixed in an acidic aqueous solution to form a slurry;

In step (2), the slurry in step (1) is dried, calcined at high temperature, cooled, crushed and dispersed under a protective gas to obtain a nitrogen-containing porous silicon oxycarbon compound precursor after carbonization. Among them, cooling is natural cooling to room temperature; crushing and dispersing requires the median particle size of material particle size D50 to be 1-20 μm.

In step (3), the nitrogen-containing porous silicon oxycarbide precursor obtained in step (2) is blended with the carbon coating material, and under protective gas, high temperature carbonization, cooling, crushing and dispersing are carried out, that is, a uniform and stable product is prepared. The nitrogen-containing silicon oxycarbon compound composite negative electrode material for the lithium ion secondary battery with the coating structure has a median particle size D50 of 1-80 μm. Wherein, the high temperature baking, cooling and crushing in step (3) are the same as those in step (2).

Preferably, the silicon-oxygen precursor described in step (1) is silicon tetrachloride, ethyl orthosilicate, trimethylhydroxysilane, trimethylmethoxysilane, aminopropyltriethoxysilane, One or more hydrolyzable silicon oxides such as silane coupling agents.

Preferably, the carbon source described in step (1) is one or more carbons with functional groups, such as citric acid, polyacrylic acid, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, polyquaternary ammonium salt, etc. base polymer or compound.

Preferably, the nitrogen source described in step (1) is melamine, polyacrylamide, polyethyleneimine, polyethylene ammonia, acetamide, formamide, p-aminobenzoic acid, amino acid, acrylamide, urea, isocyanate, amino One or more compounds or polymers containing nitrogen and functional groups such as formate.

Preferably, the pH value of the acidic aqueous solution in step (1) is controlled between 1 and 6, and the acidic aqueous solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; Hydrolysis of raw materials and reaction rate.

Preferably, the stirring in step (1) is magnetic stirring, mechanical stirring, ultrasonic mixing or heating stirring, the reaction temperature is controlled at 20-120°C, and the hydrolysis and reaction speed are adjusted by adjusting the reaction temperature.

Preferably, in step (2), the drying of the slurry is to wash the material with pure water and then dry it at 80-120° C. The drying equipment is a vacuum oven or a blast box; the protective gas is nitrogen, argon One or more mixtures of gas, helium, neon or xenon; the high-temperature roasting device is a box furnace, roller kiln, rotary kiln or heating kettle, the temperature is set to 600-1500 ° C, and the roasting time is 5 ~48h. Preferably, the temperature is set to 800-1200°C, and the calcination time is 6-24h. The heating rate is 0.1 to 20°C/min, preferably, 0.5 to 15°C/min.

Preferably, the carbon coating material in step (3) is coal tar, petroleum tar, starch, polyvinyl chloride, glucose, epoxy resin, polystyrene, phenolic resin, urea-formaldehyde resin, polyurethane, polythiophene, polyvinyl chloride, etc. One or more of hydroxyalcohols and the like are mixed and obtained by high temperature treatment. Preferably, one or more of coal tar pitch, petroleum pitch, starch, and glucose are mixed and obtained by high temperature treatment. Coal tar pitch, petroleum pitch, starch, glucose, etc. are in powder form, and the particle size is 10-1000 μm, preferably 100-100 μm. 500μm.

Preferably, the added mass ratio of the nitrogen-containing porous silicon oxycarbide precursor to the carbon coating material is 1:0.05-1:1; more preferably, 1:0.1-1:0.8.

A nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material for a lithium ion secondary battery prepared by the above-mentioned preparation method, comprising a nitrogen-containing silicon-oxygen-carbon compound, and the structure of the nitrogen-containing silicon-oxygen-carbon compound is a carbon-nitrogen compound. The compound is a shell and the silicon-oxygen compound is a core-shell structure, the carbon shell is uniformly coated on the surface of the silicon-oxygen compound, and the nitrogen element is uniformly dispersed in the middle or inside of the carbon shell.

Preferably, the median particle size D50 of the nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material for the lithium ion secondary battery is 1-80 μm, the first reversible capacity is not less than 1580 mAh/g, the first Coulombic efficiency is greater than 76%, and the cycle is 50 The capacity retention rate after one week is greater than 90%, the expansion rate is less than 45%, and the electrical conductivity is greater than 3.5S/m.

Compared with the prior art, the present invention has the following beneficial effects:

1. The structure of the material prepared by the present invention is a core-shell structure with carbon-nitrogen compound as shell and silicon oxide as core; using hydrogen bond or chemical bond effect, carbon-based material and silicon-oxygen precursor are uniformly dispersed in water solvent, Lay the foundation for the in-situ uniform formation of a stable coating layer; the in-situ method is used to generate a uniform and stable nitrogen-containing silicon-oxygen-carbon compound composite anode material, and then modified with a carbon-based coating material to generate a stable and uniform core-shell structure The composite negative electrode material, its electrical conductivity and cycle performance are greatly improved;

2. Using hydrogen bonds or chemical bonds, when introducing nitrogen elements, it can ensure that nitrogen-containing compounds are evenly dispersed in the material, which lays the foundation for uniformly improving the conductivity of the material; the use of carbon coating materials can significantly improve the surface properties of the material, Reduce the specific surface of the material and form a double-layer carbon cladding layer, which significantly improves the electrical conductivity and cycle performance of the material;

3. The preparation method is simple, low in cost and pollution-free.

Description of drawings

1 is a scanning electron microscope spectrum of the nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material for the lithium ion secondary battery prepared in Example 1.

FIG. 2 is the electrical conductivity data curve of Example 1, Example 2 and Comparative Example 1 under different compaction densities.

Detailed ways

In order to make the technical means, creative features, achievement goals and effects realized by the present invention easy to understand, the present invention will be further described below with reference to the specific embodiments.

Example 1

Dissolve tetraethyl orthosilicate in the aqueous solution, the mass ratio of tetraethyl orthosilicate and water is 1:5, add hydrochloric acid to adjust PH=2, water bath heating mechanical stirring mode, the temperature is set to 60 ° C, stirring speed 200rpm, stirring time is 30min, then add citric acid, the molar ratio of tetraethylorthosilicate and citric acid is 1:0.5, the temperature and stirring speed are unchanged, stirring time is 120min, then add melamine, tetraethylorthosilicate The molar ratio of ester to melamine was 1:0.2, the temperature and stirring speed were kept constant, and the stirring time was 120 min. After the reaction was completed, it was dried in an oven at 80°C. The dried material is put into a box furnace for roasting, the roasting temperature is 1000 °C, nitrogen atmosphere is protected, the heating rate is 3 °C/min, and the temperature is kept for 6 hours. The above-mentioned materials are crushed, demagnetized and sieved to obtain a material with a median particle size (D50) of 1 to 80 μm. The above-mentioned materials and phenolic resin are mixed with VC, the mixing speed is 1000rpm, and the time is 3h. Nitrogen-containing silicon oxygen carbon composite negative electrode The mass ratio of the material to the phenolic resin is 1:0.02, and the mixed material is placed in a box furnace for calcination. The finished product of nitrogen-containing silicon oxycarbon composite negative electrode material is pulverized, demagnetized, and sieved to obtain a material with a median particle size (D50) of 1-80 μm, which is a nitrogen-containing silicon oxygen carbon composite negative electrode material for lithium ion secondary batteries. .

Example 2

Dissolve tetraethyl orthosilicate in the aqueous solution, the mass ratio of tetraethyl orthosilicate and water is 1:5, add hydrochloric acid to adjust PH=2, water bath heating mechanical stirring mode, the temperature is set to 60 ° C, stirring speed 200rpm, the stirring time is 30min, then add citric acid, the molar ratio of tetraethyl orthosilicate and citric acid is 1:0.8, the temperature and stirring speed are unchanged, the stirring time is 120min, then add melamine, tetraethylorthosilicate The molar ratio of ester to melamine was 1:0.4, the temperature and stirring speed were kept constant, and the stirring time was 120 min. After the reaction was completed, oven drying was adopted, and the drying temperature was 80 °C. The dried material is put into a box furnace for roasting, the roasting temperature is 1000 °C, nitrogen atmosphere is protected, the heating rate is 3 °C/min, and the temperature is kept for 6 hours. The above-mentioned materials are crushed, demagnetized and sieved to obtain a material with a median particle size (D50) of 1 to 80 μm. The above-mentioned materials and phenolic resin are mixed with VC, the mixing speed is 1000rpm, and the time is 3h. Nitrogen-containing silicon oxygen carbon composite negative electrode The mass ratio of the material to the phenolic resin is 1:0.02, and the mixed material is placed in a box furnace for calcination. The finished product of nitrogen-containing silicon oxycarbon composite negative electrode material is pulverized, demagnetized, and sieved to obtain a material with a median particle size (D50) of 1-80 μm, which is a nitrogen-containing silicon oxygen carbon composite negative electrode material for lithium ion secondary batteries. .

Example 3

Dissolve tetraethyl orthosilicate in the aqueous solution, the mass ratio of tetraethyl orthosilicate and water is 1:5, add hydrochloric acid to adjust PH=2, water bath heating mechanical stirring mode, the temperature is set to 60 ° C, stirring speed 200rpm, the stirring time is 30min, then add citric acid, the molar ratio of tetraethyl orthosilicate and citric acid is 1:1, the temperature and stirring speed are unchanged, the stirring time is 120min, then add melamine, tetraethylorthosilicate The molar ratio of ester to melamine was 1:0.6, the temperature and stirring speed were kept constant, and the stirring time was 120 min. After the reaction was completed, oven drying was adopted, and the drying temperature was 80°C. The dried material is put into a box furnace for roasting, the roasting temperature is 1000 °C, nitrogen atmosphere is protected, the heating rate is 3 °C/min, and the temperature is kept for 6 hours. The above-mentioned materials are crushed, demagnetized and sieved to obtain a material with a median particle size (D50) of 1 to 80 μm. The above-mentioned materials and phenolic resin are mixed with VC, the mixing speed is 1000rpm, and the time is 3h. Nitrogen-containing silicon oxygen carbon composite negative electrode The mass ratio of the material to the phenolic resin is 1:0.02, and the mixed material is placed in a box furnace for calcination. The finished product of nitrogen-containing silicon oxycarbon composite negative electrode material is pulverized, demagnetized, and sieved to obtain a material with a median particle size (D50) of 1-80 μm, which is a nitrogen-containing silicon oxygen carbon composite negative electrode material for lithium ion secondary batteries. .

Example 4

Dissolve silicon tetrachloride in the aqueous solution, the mass ratio of silicon tetrachloride and water is 1:5, add hydrochloric acid to adjust PH=2, water bath heating mechanical stirring mode, temperature is set to 60 ° C, stirring speed 200rpm, stirring time For 30min, then add polyacrylic acid, the molar ratio of silicon tetrachloride and polyacrylic acid is 1:0.5, the temperature and stirring speed are unchanged, and the stirring time is 120min, then add polyacrylamide, silicon tetrachloride and polyacrylamide. The molar ratio was 1:0.2, the temperature and stirring speed were kept unchanged, and the stirring time was 120 min. After the reaction was completed, oven drying was adopted, and the drying temperature was 80°C. The dried material is put into a box furnace for roasting, the roasting temperature is 1000 °C, nitrogen atmosphere is protected, the heating rate is 3 °C/min, and the temperature is kept for 6 hours. The above-mentioned materials are crushed, demagnetized and sieved to obtain a material with a median particle size (D50) of 1 to 80 μm. The above-mentioned materials and phenolic resin are mixed with VC, the mixing speed is 1000rpm, and the time is 3h. Nitrogen-containing silicon oxygen carbon composite negative electrode The mass ratio of the material to the phenolic resin is 1:0.02, and the mixed material is placed in a box furnace for calcination. The finished product of nitrogen-containing silicon oxycarbon composite negative electrode material is pulverized, demagnetized, and sieved to obtain a material with a median particle size (D50) of 1-80 μm, which is a nitrogen-containing silicon oxygen carbon composite negative electrode material for lithium ion secondary batteries. .

Example 5

Dissolve trimethylmethoxysilane in an aqueous solution, the mass ratio of trimethylmethoxysilane to water is 1:5, add hydrochloric acid to adjust PH=2, heat in a water bath with mechanical stirring, and set the temperature to 60°C, The stirring speed is 200rpm, the stirring time is 30min, then polyacrylic acid is added, the molar ratio of trimethylmethoxysilane and polyacrylic acid is 1:0.8, the temperature and stirring speed are unchanged, the stirring time is 120min, and p-aminobenzoic acid is added. , the molar ratio of trimethylmethoxysilicon to p-aminobenzoic acid is 1:0.4, keep the temperature and stirring speed unchanged, and the stirring time is 120min. After the reaction is completed, use oven drying, and the drying temperature is 80 ° C . The dried material is put into a box furnace for roasting, the roasting temperature is 1000 °C, nitrogen atmosphere is protected, the heating rate is 3 °C/min, and the temperature is kept for 6 hours. The above-mentioned materials are crushed, demagnetized and sieved to obtain a material with a median particle size (D50) of 1 to 80 μm. The above-mentioned materials and phenolic resin are mixed with VC, the mixing speed is 1000rpm, and the time is 3h. Nitrogen-containing silicon oxygen carbon composite negative electrode The mass ratio of the material to the phenolic resin is 1:0.02, and the mixed material is placed in a box furnace for calcination. The finished product of nitrogen-containing silicon oxycarbon composite negative electrode material is pulverized, demagnetized, and sieved to obtain a material with a median particle size (D50) of 1-80 μm, which is a nitrogen-containing silicon oxygen carbon composite negative electrode material for lithium ion secondary batteries. .

Example 6

Dissolve aminopropyltriethoxysilane in an aqueous solution, the mass ratio of aminopropyltriethoxysilane to water is 1:5, add hydrochloric acid to adjust PH=2, heat in a water bath with mechanical stirring, and set the temperature to 60 ℃, the stirring speed is 200rpm, the stirring time is 30min, then polyacrylic acid is added, the molar ratio of aminopropyltriethoxysilane and polyacrylic acid is 1:1, the temperature and stirring speed are unchanged, the stirring time is 120min, and then the amino acid is added , the molar ratio of aminopropyltriethoxysilane and amino acid is 1:0.6, keeping the temperature and stirring speed unchanged, stirring time is 120min, after the reaction is completed, adopt oven drying, drying temperature is 80 ℃. The dried material is put into a box furnace for roasting, the roasting temperature is 1000 °C, nitrogen atmosphere is protected, the heating rate is 3 °C/min, and the temperature is kept for 6 hours. The above-mentioned materials are crushed, demagnetized and sieved to obtain a material with a median particle size (D50) of 1 to 80 μm. The above-mentioned materials and phenolic resin are mixed with VC, the mixing speed is 1000rpm, and the time is 3h. Nitrogen-containing silicon oxygen carbon composite negative electrode The mass ratio of the material to the phenolic resin is 1:0.02, and the mixed material is placed in a box furnace for calcination. The finished product of nitrogen-containing silicon oxycarbon composite negative electrode material is pulverized, demagnetized, and sieved to obtain a material with a median particle size (D50) of 1-80 μm, which is a nitrogen-containing silicon oxygen carbon composite negative electrode material for lithium ion secondary batteries. .

Comparative Example 1

The silicon monoxide and phenolic resin are mixed with VC according to the mass ratio of 1:0.04. The mixing speed is 1000rpm and the time is 4h. The mixed materials are placed in a box furnace for roasting, and the roasting temperature is 800℃. , nitrogen atmosphere protection, the heating rate is 3 ℃/min, the temperature is kept for 6 hours, and the silicon oxycarbon composite negative electrode material is obtained after cooling. , that is, the silicon-oxygen-carbon composite negative electrode material for lithium-ion secondary batteries.

Comparative Example 2

Silica, phenolic resin and melamine are mixed with VC according to the mass ratio of 1:0.04:0.02, the mixing speed is 1000rpm, the time is 4h, and the mixed materials are placed in a box furnace for roasting, roasting The temperature is 800 °C, nitrogen atmosphere is protected, the heating rate is 3 °C/min, and the temperature is kept for 6 hours. After cooling, the silicon oxycarbon composite negative electrode material is obtained. The above material is pulverized, demagnetized, and sieved to obtain the median particle size (D50) It is 1-80 μm, which is the silicon-oxygen-carbon composite negative electrode material of lithium ion secondary battery.

The negative electrode materials of Examples 1 to 6 and Comparative Examples 1 to 2 are tested below, and the particle size range and distribution of the materials are tested by using Malvern Laser Particle Size Tester MS3000; Analysis to test the specific surface area of the material; X-ray diffractometer X'Pert Pro, PANalytical was used to test the material structure.

The morphology, particle size, etc. of the samples were observed with a Hitachi S4800 scanning electron microscope; Figure 1 clearly reflects the particle size and surface condition of the material, indicating the modified shape of the material.

The MCP-PD51 powder conductivity test equipment of Japan's Mitsubishi Chemical Corporation was used to test the conductivity of the material; Figure 2 clearly reflects the change of conductivity of different materials and the conductivity of different materials under the same compaction density.

The electrochemical cycle performance was tested by the following method: mix the negative electrode material, conductive agent, and binder in a solvent according to a mass ratio of 92:2:6, control the solid content to 55%, coat the copper foil current collector, and dry to obtain a Negative pole piece; then use conventional positive piece, 1mol/L LiPF6/EC+DMC (V/V=1:1) electrolyte, CeLgard2400 diaphragm, the shell adopts conventional production process to assemble 18650 cylindrical battery, constant current charge at 1C rate Discharge, charge and discharge voltage is limited to 2.75 ~ 4.2V.

The electrochemical test results and expansion rate test results of the negative electrode materials prepared in Examples 1 to 6 and Comparative Example 1 and Comparative Example 2 are shown in Table 1:

Combined with the electrochemical test results and expansion rate tests in Examples 1 to 6, it can be seen from Table 1 that the median particle size D50 of the nitrogen-containing silicon oxygen carbon compound composite negative electrode materials for lithium ion secondary batteries obtained in Examples 1 to 6 is: 1 ~ 80μm, the first reversible capacity is not less than 1580mAh/g, the first Coulombic efficiency is greater than 76%, the capacity retention rate after 50 cycles of cycling is greater than 90%, the expansion rate is less than 45%, and the electrical conductivity is greater than 3.5S/m.

In comparison, Comparative Example 1 and Comparative Example 2 have shortcomings in capacity, cycle performance, expansion rate, and electrical conductivity, respectively. Compared with Comparative Example 1 and Comparative Example 2, the lithium-ion secondary battery nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material prepared by the preparation method of the present invention shows a low expansion rate under the condition that the high capacity remains unchanged, and Excellent guiding performance.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. A preparation method of a nitrogen-containing silicon oxygen carbon compound composite negative electrode material of a lithium ion secondary battery is characterized by comprising the following steps:

stirring and mixing a silica precursor, a carbon source and a nitrogen source in an acidic aqueous solution to form slurry;

drying the slurry obtained in the step (1), roasting at high temperature under protective gas, cooling, crushing and scattering to obtain a carbonized nitrogen-containing porous silicon-oxygen-carbon compound prepolymer;

and (3) blending the nitrogen-containing porous silicon-oxygen carbide precursor obtained in the step (2) with a carbon coating material, and carrying out high-temperature carbonization, cooling, crushing and scattering under protective gas to obtain the uniform and stable coating structure of the nitrogen-containing silicon-oxygen carbide compound composite negative electrode material of the lithium ion secondary battery.

2. The method for preparing the nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material of the lithium ion secondary battery as claimed in claim 1, wherein the silicon-oxygen precursor in the step (1) is one or more hydrolyzable silicon oxides such as silicon tetrachloride, ethyl orthosilicate, trimethylhydroxysilane, trimethylmethoxysilane, aminopropyltriethoxysilane, silane coupling agent, and the like.

3. The method for preparing the nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material of the lithium ion secondary battery according to claim 1, wherein the carbon source in the step (1) is one or more carbon-based polymers or compounds with functional groups, such as citric acid, polyacrylic acid, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, polyquaternary ammonium salt and the like.

4. The method for preparing the nitrogen-containing silicon oxycarbide compound composite anode material for the lithium ion secondary battery according to claim 1, wherein the nitrogen source in the step (1) is one or more compounds or polymers containing nitrogen elements and having functional groups, such as melamine, polyacrylamide, polyethyleneimine, polyvinylamine, acetamide, formamide, p-aminobenzoic acid, amino acid, acrylamide, urea, isocyanate and carbamate.

5. The preparation method of the nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material of the lithium ion secondary battery according to claim 1, wherein the pH value of the acidic aqueous solution in the step (1) is controlled to be 1-6, and the acidic aqueous solution is one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; the hydrolysis and reaction speed of the raw materials are controlled by adjusting the pH value of the acidic aqueous solution; in the step (1), the stirring is magnetic stirring, mechanical stirring, ultrasonic mixing or heating stirring, and the reaction temperature is controlled to be 20-120 ℃.

6. The preparation method of the nitrogen-containing silicon oxygen carbon compound composite anode material for the lithium ion secondary battery according to claim 1, wherein the step (2) of drying the slurry is to dry the material at 80-120 ℃ after washing the material with pure water, and the drying equipment is a vacuum oven or a blast air box; the protective gas is one or more of nitrogen, argon, helium, neon and xenon; the high-temperature roasting device is a box furnace, a roller kiln, a rotary kiln or a heating kettle, the temperature is set to be 600-1500 ℃, and the roasting time is 5-48 hours.

7. The method for preparing the nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material of the lithium ion secondary battery according to claim 1, wherein the carbon coating material in the step (3) is obtained by mixing one or more of coal tar pitch, petroleum pitch, starch, polyvinyl chloride, glucose, epoxy resin, polystyrene, phenolic resin, urea resin, polyurethane, polythiophene, polyhydric alcohols and the like and performing high-temperature treatment.

8. The method for preparing the nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material of the lithium ion secondary battery according to claim 1, wherein the addition mass ratio of the nitrogen-containing porous silicon-oxygen-carbon compound prepolymer to the carbon coating material is 1: 0.05-1: 1.

9. The composite negative electrode material of the nitrogen-containing silicon-oxygen-carbon compound for the lithium ion secondary battery prepared by the preparation method of any one of claims 1 to 8 is characterized by comprising the nitrogen-containing silicon-oxygen-carbon compound, wherein the structure of the nitrogen-containing silicon-oxygen-carbon compound is a core-shell structure with a carbon-nitrogen compound as a shell and a silicon-oxygen compound as a core, the carbon shell is uniformly coated on the surface of the silicon-oxygen compound, and nitrogen elements are uniformly dispersed in the middle or inside of the carbon shell.

10. The nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material for the lithium ion secondary battery as claimed in claim 9, wherein the particle size median diameter D50 of the nitrogen-containing silicon-oxygen-carbon compound composite negative electrode material for the lithium ion secondary battery is 1-80 μm, the first reversible capacity is not less than 1580mAh/g, the first coulombic efficiency is greater than 76%, the capacity retention rate after 50 weeks of circulation is greater than 90%, the expansion rate is less than 45%, and the conductivity is greater than 3.5S/m.

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