CN107482196B - Composite nano material for lithium ion battery and preparation method thereof - Google Patents
Composite nano material for lithium ion battery and preparation method thereof Download PDFInfo
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- H01M4/00—Electrodes
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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- B82—NANOTECHNOLOGY
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- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a composite nano material for a lithium ion battery and a preparation method thereof.
Description
Technical Field
The invention relates to the technical field of electrochemistry, in particular to a composite nano material for a lithium ion battery and a preparation method thereof.
Background
The lithium ion battery has the advantages of high voltage, small volume, light weight, large energy density, good cycle performance, no memory effect and the like, is widely applied to portable mobile electric appliances such as mobile phones, notebook computers and the like, and has wide application prospect in electric bicycles and electric automobiles.
The negative electrode material of the commercial lithium ion battery generally adopts graphite materials (such as graphite microspheres, natural modified graphite, artificial graphite and the like), the graphite materials have better cycle stability, but the capacity of the graphite materials is lower, and the theoretical capacity of the graphite is 372 mAh/g. The new generation of lithium ion batteries put higher demands on the capacity and the cycling stability of electrode materials, and not only the cathode materials are required to have higher electrochemical capacity, but also good cycling stability is required.
Therefore, the search for high capacity anode materials is a very important research direction.
Disclosure of Invention
The invention aims to provide a composite nano material for a lithium ion battery and a preparation method thereof.
In order to achieve the purpose, the invention provides a preparation method of a composite nano material for a lithium ion battery, which comprises the following specific steps:
(1) acidifying a multi-walled carbon nanotube and dispersing the multi-walled carbon nanotube in water to obtain a dispersion liquid of the acidified multi-walled carbon nanotube:
(2) adding an organic carbon source into the dispersion liquid of the acidified multi-walled carbon nanotubes obtained in the step (1), uniformly mixing, and performing ultrasonic dispersion to obtain a dispersion liquid I;
(3) dissolving ethyl orthosilicate in ethanol, adding polyethylene glycol 1000, performing ultrasonic dispersion, adding a urea solution, and stirring to form sol for later use;
(4) sequentially adding tin tetrachloride pentahydrate and the sol obtained in the step (3) into the dispersion liquid I obtained in the step (2), then adding concentrated hydrochloric acid (38 w.t.%), then slowly adding concentrated ammonia water to adjust the pH value to 7-10, reacting at 120-180 ℃ for 2-3 days, washing with water, filtering, drying, and roasting at 420-440 ℃ for 2-3 hours to obtain the silicon dioxide/tin dioxide/multiwalled carbon nanotube composite nanomaterial;
(5) and (4) putting the silicon carbide and the silicon dioxide/tin dioxide/multi-walled carbon nano tube composite nano material obtained in the step (4) into a ball mill for grinding, putting the obtained powder into a tubular furnace for heating and roasting, and then cooling to room temperature along with the furnace to obtain the silicon carbide/tin dioxide/multi-walled carbon nano tube composite nano material.
As one of the preferable technical proposal, the specific method of the step (1) is as follows: stirring and mixing the multi-walled carbon nano-tube and concentrated nitric acid uniformly, reacting for 8-10 hours at 120-130 ℃, carrying out suction filtration and washing on the obtained product to be neutral, carrying out vacuum drying to obtain an acidified multi-walled carbon nano-tube, and then dispersing in water to obtain a dispersion liquid of the acidified multi-walled carbon nano-tube.
As one of the further preferable technical solutions, the mass concentration of the concentrated nitric acid is 65%, and the mass-to-volume ratio of the multi-walled carbon nanotube to the concentrated nitric acid is 1 g: 100mL, the mass concentration of the acidified multi-wall carbon nanotubes in the dispersion liquid of the acidified multi-wall carbon nanotubes is 1 g/L.
As one of the preferable technical solutions, in the step (2), the organic carbon source is a mixture of sucrose and resorcinol, and the mass ratio of the sucrose to the resorcinol is 2: 1, the mixture is added in an amount 1/10 weight of the dispersion of acidified multi-walled carbon nanotubes.
As one of the preferable technical solutions, the mass-to-volume ratio of the tetraethoxysilane, the ethanol, the polyethylene glycol 1000 and the urea solution in the step (3) is 1 g: 10-20 mL: 0.08-0.1 g: 2-3 mL, wherein the concentration of the urea solution is 20-30%.
As one preferable technical scheme, the stirring time in the step (3) is 4-5 hours.
As one of the preferable technical proposal, the mass concentration of the concentrated ammonia water in the step (4) is 25 percent.
As one of the preferable technical schemes, the mass volume ratio of the acidified multi-wall carbon nano tube, the tin tetrachloride pentahydrate, the sol and the concentrated hydrochloric acid contained in the dispersion liquid I in the step (4) is 1 g: 50-60 mL: 40-50 g: 60-70 mL.
As one of the preferable technical solutions, the mass ratio of the silicon carbide to the silicon dioxide/tin dioxide/multiwalled carbon nanotube composite nanomaterial in the step (5) is 1: 0.5: 0.7.
as one of the preferable technical proposal, the silicon carbide in the step (5) is prepared by the following method:
(51) preparing a silicon carbide precursor;
(52) under the protection of helium atmosphere, heating the silicon carbide precursor to 1200-1250 ℃ at a heating rate of 25-30 ℃/min, preserving heat for 2-3 hours, then heating to 1400-1450 ℃ at a heating rate of 5-8 ℃/min, preserving heat for 7-8 hours, and naturally cooling to room temperature to obtain dark green initial-stage silicon carbide;
(53) and (5) adding the initial-stage silicon carbide obtained in the step (52) into a hydrofluoric acid solution with the mass concentration of 35%, removing unreacted silicon dioxide, washing with water, filtering, and drying to obtain the silicon carbide.
As a further preferred embodiment, the specific method of step (51) is: dissolving sucrose in water and ethylene glycol, adding ferric nitrate, stirring to dissolve the sucrose to form a mixed solution, adding tetraethyl silicate and organic silicon at 40-60 ℃ while stirring, adding citric acid, hydrolyzing for 15-20 hours to prepare a carbon-silicon binary sol, then adding the carbon-silicon binary sol into hexamethylenetetramine, keeping the temperature of 40-60 ℃ for gelling, aging the gel for 20-30 hours, and drying at 100-150 ℃ for 12-15 hours to prepare a brown silicon carbide precursor; wherein the mass ratio of sucrose, water, glycol, ferric nitrate, tetraethyl silicate, organic silicon, citric acid and hexamethylenetetramine is 1: 10-20: 8-10: 0.02-0.03: 3: 0.5-0.7: 0.1-0.2: 0.2 to 0.3.
As a further preferable technical scheme, the silicon carbide precursor obtained in the step (51) is firstly ground into 25-40 meshes, and then the treatment in the step (52) is carried out.
As one of the preferable technical proposal, the heating program of the tube furnace in the step (5) is as follows: heating to 300-400 ℃ at a heating rate of 5-8 ℃/min under a helium atmosphere, preserving heat for 2-3 hours, heating to 800-900 ℃ at a heating rate of 12-15 ℃/min, and roasting at a constant temperature for 10-12 hours.
The invention also provides the composite nano material for the lithium ion battery, which is prepared by the preparation method.
The invention has the following beneficial effects:
according to the invention, the multi-walled carbon nanotube is used as a raw material to prepare a silicon dioxide/stannic oxide/multi-walled carbon nanotube composite nanomaterial, and then the silicon carbide is further coated, so that the obtained composite nanomaterial can be used as a lithium ion battery cathode material, and has the advantages of high coulombic efficiency, high capacity, high cycling stability and the like for the first time; the method comprises the following specific steps:
1. the invention first acidifies the multi-walled carbon nano-tube, so that the multi-walled carbon nano-tube can be dispersed in water, and the reaction system is more environment-friendly. The multi-walled carbon nanotube is acidified by concentrated nitric acid, and the multi-walled carbon nanotube is fully acidified after reacting for 8-10 hours at 120-130 ℃, so that the multi-walled carbon nanotube is completely converted into the acidified multi-walled carbon nanotube, and can be uniformly dispersed in water, and the electrical property of the obtained composite nano material is ensured.
2. The organic carbon source is added into the dispersion liquid of the acidified multi-wall carbon nano tube to carry out carbonization, which is more beneficial to the uniform dispersion of the acidified carbon nano tube, and is further beneficial to improving the uniformity of the finally obtained composite nano material, so that the electrical property index is more ideal. The invention further selects the mixture of sucrose and resorcinol as an organic carbon source, and the electric performance index of the composite nano-material prepared by using the mixture as the organic carbon source has obvious advantages through verification.
3. According to the invention, tetraethoxysilane is used as a raw material to prepare sol, the sol and tetrachloroethylene pentahydrate are sequentially added into a dispersion liquid I, and a silicon dioxide/stannic oxide/multi-walled carbon nanotube composite nano material is prepared through hydrothermal reaction and a series of post-treatments, wherein the multi-walled carbon nanotube composite silicon dioxide and stannic oxide can modify the surface of the multi-walled carbon nanotube, the current guide is adjusted, and the conductivity is excellent.
4. The silicon carbide is coated on the surface of the silicon dioxide/stannic oxide/multi-walled carbon nano tube composite nano material, so that the capacity and the cycling stability can be obviously improved.
5. The silicon carbide is prepared by preparing a silicon carbide precursor, rapidly heating the silicon carbide precursor under the protection of helium gas, combining slow heating and two-stage heating treatment to obtain initial silicon carbide, and finally acidifying the initial silicon carbide.
In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below.
Detailed Description
The following is a detailed description of embodiments of the invention, but the invention can be implemented in many different ways, as defined and covered by the claims.
Example 1:
a preparation method of a composite nano material for a lithium ion battery comprises the following specific steps:
(1) acidifying a multi-walled carbon nanotube and dispersing the multi-walled carbon nanotube in water to obtain a dispersion liquid of the acidified multi-walled carbon nanotube:
(2) adding an organic carbon source into the dispersion liquid of the acidified multi-walled carbon nanotubes obtained in the step (1), uniformly mixing, and performing ultrasonic dispersion to obtain a dispersion liquid I;
(3) dissolving ethyl orthosilicate in ethanol, adding polyethylene glycol 1000, performing ultrasonic dispersion, adding a urea solution, and stirring to form sol for later use;
(4) sequentially adding tin tetrachloride pentahydrate and the sol obtained in the step (3) into the dispersion liquid I obtained in the step (2), then adding concentrated hydrochloric acid (38 w.t.%), then slowly adding concentrated ammonia water to adjust the pH value to 7, reacting at 120 ℃ for 2 days, washing with water, filtering, drying, and roasting at 420 ℃ for 2 hours to obtain the silicon dioxide/tin dioxide/multiwalled carbon nanotube composite nanomaterial;
(5) and (4) putting the silicon carbide and the silicon dioxide/tin dioxide/multi-walled carbon nano tube composite nano material obtained in the step (4) into a ball mill for grinding, putting the obtained powder into a tubular furnace for heating and roasting, and then cooling to room temperature along with the furnace to obtain the silicon carbide/tin dioxide/multi-walled carbon nano tube composite nano material.
The specific method of the step (1) is as follows: stirring and mixing the multi-walled carbon nano-tube and concentrated nitric acid uniformly, reacting for 8 hours at 120 ℃, carrying out suction filtration and washing on the obtained product to be neutral, carrying out vacuum drying to obtain an acidified multi-walled carbon nano-tube, and then dispersing in water to obtain a dispersion liquid of the acidified multi-walled carbon nano-tube. The mass concentration of the concentrated nitric acid is 65%, and the mass volume ratio of the multi-walled carbon nano-tube to the concentrated nitric acid is 1 g: 100mL, the mass concentration of the acidified multi-wall carbon nanotubes in the dispersion liquid of the acidified multi-wall carbon nanotubes is 1 g/L.
In the step (2), the organic carbon source is a mixture of sucrose and resorcinol, and the mass ratio of the sucrose to the resorcinol is 2: 1, the mixture is added in an amount 1/10 weight of the dispersion of acidified multi-walled carbon nanotubes.
In the step (3), the mass-to-volume ratio of the ethyl orthosilicate, the ethanol, the polyethylene glycol 1000 and the urea solution is 1 g: 10mL of: 0.08 g: 2mL, wherein the concentration of the urea solution is 20%. The stirring time was 4 hours.
The mass concentration of the concentrated ammonia water in the step (4) is 25 percent. The mass volume ratio of the acidified multiwalled carbon nanotube, the tin tetrachloride pentahydrate, the sol and the concentrated hydrochloric acid contained in the dispersion liquid I is 1 g: 50mL of: 40 g: 60 mL.
In the step (5), the mass ratio of the silicon carbide to the silicon dioxide/stannic oxide/multi-walled carbon nanotube composite nano material is 1: 0.5: 0.7. the silicon carbide is prepared by the following method:
(51) preparing a silicon carbide precursor;
(52) under the protection of helium atmosphere, heating the silicon carbide precursor to 1200 ℃ at the heating rate of 25 ℃/min, preserving heat for 2 hours, then heating to 1400 ℃ at the heating rate of 5 ℃/min, preserving heat for 7 hours, and naturally cooling to room temperature to obtain dark green initial-stage silicon carbide;
(53) and (5) adding the initial-stage silicon carbide obtained in the step (52) into a hydrofluoric acid solution with the mass concentration of 35%, removing unreacted silicon dioxide, washing with water, filtering, and drying to obtain the silicon carbide.
The specific method of the step (51) is as follows: dissolving sucrose in water and ethylene glycol, adding ferric nitrate, stirring to dissolve the sucrose to form a mixed solution, adding tetraethyl silicate and organic silicon at 40 ℃ while stirring, adding citric acid, hydrolyzing for 15 hours to prepare carbon-silicon binary sol, then adding the carbon-silicon binary sol into hexamethylenetetramine, maintaining the temperature at 40 ℃ for gelling, aging the gel for 20 hours, and drying at 100 ℃ for 12 hours to prepare a brown silicon carbide precursor; wherein the mass ratio of sucrose, water, glycol, ferric nitrate, tetraethyl silicate, organic silicon, citric acid and hexamethylenetetramine is 1: 10: 8: 0.02: 3: 0.5: 0.1: 0.2.
and (5) grinding the silicon carbide precursor obtained in the step (51) into 25 meshes, and then carrying out the treatment in the step (52).
The heating program of the tube furnace is as follows: heating to 300 ℃ at a heating rate of 5 ℃/min under a helium atmosphere, preserving heat for 2 hours, heating to 800 ℃ at a heating rate of 12 ℃/min, and then roasting at constant temperature for 10 hours.
The composite nano material for the lithium ion battery is prepared by the preparation method.
Example 2:
a preparation method of a composite nano material for a lithium ion battery comprises the following specific steps:
(1) acidifying a multi-walled carbon nanotube and dispersing the multi-walled carbon nanotube in water to obtain a dispersion liquid of the acidified multi-walled carbon nanotube:
(2) adding an organic carbon source into the dispersion liquid of the acidified multi-walled carbon nanotubes obtained in the step (1), uniformly mixing, and performing ultrasonic dispersion to obtain a dispersion liquid I;
(3) dissolving ethyl orthosilicate in ethanol, adding polyethylene glycol 1000, performing ultrasonic dispersion, adding a urea solution, and stirring to form sol for later use;
(4) sequentially adding tin tetrachloride pentahydrate and the sol obtained in the step (3) into the dispersion liquid I obtained in the step (2), then adding concentrated hydrochloric acid (38 w.t.%), then slowly adding concentrated ammonia water to adjust the pH value to 10, reacting at 180 ℃ for 3 days, washing with water, filtering, drying, and roasting at 440 ℃ for 3 hours to obtain the silicon dioxide/tin dioxide/multiwalled carbon nanotube composite nanomaterial;
(5) and (4) putting the silicon carbide and the silicon dioxide/tin dioxide/multi-walled carbon nano tube composite nano material obtained in the step (4) into a ball mill for grinding, putting the obtained powder into a tubular furnace for heating and roasting, and then cooling to room temperature along with the furnace to obtain the silicon carbide/tin dioxide/multi-walled carbon nano tube composite nano material.
The specific method of the step (1) is as follows: stirring and mixing the multi-walled carbon nano-tube and concentrated nitric acid uniformly, reacting for 10 hours at 130 ℃, carrying out suction filtration and washing on the obtained product to be neutral, carrying out vacuum drying to obtain an acidified multi-walled carbon nano-tube, and then dispersing in water to obtain a dispersion liquid of the acidified multi-walled carbon nano-tube. The mass concentration of the concentrated nitric acid is 65%, and the mass volume ratio of the multi-walled carbon nano-tube to the concentrated nitric acid is 1 g: 100mL, the mass concentration of the acidified multi-wall carbon nanotubes in the dispersion liquid of the acidified multi-wall carbon nanotubes is 1 g/L.
In the step (2), the organic carbon source is a mixture of sucrose and resorcinol, and the mass ratio of the sucrose to the resorcinol is 2: 1, the mixture is added in an amount 1/10 weight of the dispersion of acidified multi-walled carbon nanotubes.
In the step (3), the mass-to-volume ratio of the ethyl orthosilicate, the ethanol, the polyethylene glycol 1000 and the urea solution is 1 g: 20mL of: 0.1 g: 3mL, wherein the concentration of the urea solution is 30 percent. The stirring time was 5 hours.
The mass concentration of the concentrated ammonia water in the step (4) is 25 percent. The mass volume ratio of the acidified multiwalled carbon nanotube, the tin tetrachloride pentahydrate, the sol and the concentrated hydrochloric acid contained in the dispersion liquid I is 1 g: 60mL of: 50 g: 70 mL.
In the step (5), the mass ratio of the silicon carbide to the silicon dioxide/stannic oxide/multi-walled carbon nanotube composite nano material is 1: 0.5: 0.7. the silicon carbide is prepared by the following method:
(51) preparing a silicon carbide precursor;
(52) under the protection of helium atmosphere, heating the silicon carbide precursor to 1250 ℃ at the heating rate of 30 ℃/min, preserving heat for 3 hours, then heating to 1450 ℃ at the heating rate of 8 ℃/min, preserving heat for 8 hours, and naturally cooling to room temperature to obtain dark green initial-stage silicon carbide;
(53) and (5) adding the initial-stage silicon carbide obtained in the step (52) into a hydrofluoric acid solution with the mass concentration of 35%, removing unreacted silicon dioxide, washing with water, filtering, and drying to obtain the silicon carbide.
The specific method of the step (51) is as follows: dissolving sucrose in water and ethylene glycol, adding ferric nitrate, stirring to dissolve the sucrose to form a mixed solution, adding tetraethyl silicate and organic silicon at 60 ℃ while stirring, adding citric acid, hydrolyzing for 20 hours to prepare carbon-silicon binary sol, then adding the carbon-silicon binary sol into hexamethylenetetramine, maintaining the temperature at 60 ℃ for gelling, aging the gel for 30 hours, and drying for 15 hours at 150 ℃ to prepare a brown silicon carbide precursor; wherein the mass ratio of sucrose, water, glycol, ferric nitrate, tetraethyl silicate, organic silicon, citric acid and hexamethylenetetramine is 1: 20: 10: 0.03: 3: 0.7: 0.2: 0.3.
and (5) grinding the silicon carbide precursor obtained in the step (51) into 40 meshes, and then carrying out the treatment in the step (52).
The heating program of the tube furnace is as follows: heating to 400 ℃ at a heating rate of 8 ℃/min under a helium atmosphere, preserving heat for 3 hours, heating to 900 ℃ at a heating rate of 15 ℃/min, and then roasting at constant temperature for 12 hours.
The composite nano material for the lithium ion battery is prepared by the preparation method.
Example 3:
a preparation method of a composite nano material for a lithium ion battery comprises the following specific steps:
(1) acidifying a multi-walled carbon nanotube and dispersing the multi-walled carbon nanotube in water to obtain a dispersion liquid of the acidified multi-walled carbon nanotube:
(2) adding an organic carbon source into the dispersion liquid of the acidified multi-walled carbon nanotubes obtained in the step (1), uniformly mixing, and performing ultrasonic dispersion to obtain a dispersion liquid I;
(3) dissolving ethyl orthosilicate in ethanol, adding polyethylene glycol 1000, performing ultrasonic dispersion, adding a urea solution, and stirring to form sol for later use;
(4) sequentially adding tin tetrachloride pentahydrate and the sol obtained in the step (3) into the dispersion liquid I obtained in the step (2), then adding concentrated hydrochloric acid (38 w.t.%), then slowly adding concentrated ammonia water to adjust the pH value to 7, reacting at 180 ℃ for 2 days, washing with water, filtering, drying, and roasting at 440 ℃ for 2 hours to obtain the silicon dioxide/tin dioxide/multiwalled carbon nanotube composite nanomaterial;
(5) and (4) putting the silicon carbide and the silicon dioxide/tin dioxide/multi-walled carbon nano tube composite nano material obtained in the step (4) into a ball mill for grinding, putting the obtained powder into a tubular furnace for heating and roasting, and then cooling to room temperature along with the furnace to obtain the silicon carbide/tin dioxide/multi-walled carbon nano tube composite nano material.
The specific method of the step (1) is as follows: stirring and mixing the multi-walled carbon nano-tube and concentrated nitric acid uniformly, reacting for 8 hours at 130 ℃, carrying out suction filtration and washing on the obtained product to be neutral, carrying out vacuum drying to obtain an acidified multi-walled carbon nano-tube, and then dispersing in water to obtain a dispersion liquid of the acidified multi-walled carbon nano-tube. The mass concentration of the concentrated nitric acid is 65%, and the mass volume ratio of the multi-walled carbon nano-tube to the concentrated nitric acid is 1 g: 100mL, the mass concentration of the acidified multi-wall carbon nanotubes in the dispersion liquid of the acidified multi-wall carbon nanotubes is 1 g/L.
In the step (2), the organic carbon source is a mixture of sucrose and resorcinol, and the mass ratio of the sucrose to the resorcinol is 2: 1, the mixture is added in an amount 1/10 weight of the dispersion of acidified multi-walled carbon nanotubes.
In the step (3), the mass-to-volume ratio of the ethyl orthosilicate, the ethanol, the polyethylene glycol 1000 and the urea solution is 1 g: 20mL of: 0.08 g: 3mL, wherein the concentration of the urea solution is 20%. The stirring time was 5 hours.
The mass concentration of the concentrated ammonia water in the step (4) is 25 percent. The mass volume ratio of the acidified multiwalled carbon nanotube, the tin tetrachloride pentahydrate, the sol and the concentrated hydrochloric acid contained in the dispersion liquid I is 1 g: 50mL of: 50 g: 60 mL.
In the step (5), the mass ratio of the silicon carbide to the silicon dioxide/stannic oxide/multi-walled carbon nanotube composite nano material is 1: 0.5: 0.7. the silicon carbide is prepared by the following method:
(51) preparing a silicon carbide precursor;
(52) under the protection of helium atmosphere, heating the silicon carbide precursor to 1200 ℃ at the heating rate of 30 ℃/min, preserving heat for 3 hours, then heating to 1450 ℃ at the heating rate of 5 ℃/min, preserving heat for 7 hours, and naturally cooling to room temperature to obtain dark green initial-stage silicon carbide;
(53) and (5) adding the initial-stage silicon carbide obtained in the step (52) into a hydrofluoric acid solution with the mass concentration of 35%, removing unreacted silicon dioxide, washing with water, filtering, and drying to obtain the silicon carbide.
The specific method of the step (51) is as follows: dissolving sucrose in water and ethylene glycol, adding ferric nitrate, stirring to dissolve the sucrose to form a mixed solution, adding tetraethyl silicate and organic silicon at 60 ℃ while stirring, adding citric acid, hydrolyzing for 15 hours to prepare carbon-silicon binary sol, then adding the carbon-silicon binary sol into hexamethylenetetramine, maintaining the temperature at 60 ℃ for gelling, aging the gel for 20 hours, and drying at 150 ℃ for 12 hours to prepare a brown silicon carbide precursor; wherein the mass ratio of sucrose, water, glycol, ferric nitrate, tetraethyl silicate, organic silicon, citric acid and hexamethylenetetramine is 1: 20: 8: 0.03: 3: 0.5: 0.2: 0.2.
and (5) grinding the silicon carbide precursor obtained in the step (51) into 40 meshes, and then carrying out the treatment in the step (52).
The heating program of the tube furnace is as follows: heating to 400 ℃ at a heating rate of 5 ℃/min under a helium atmosphere, preserving heat for 2 hours, heating to 800 ℃ at a heating rate of 15 ℃/min, and then roasting at constant temperature for 12 hours.
The composite nano material for the lithium ion battery is prepared by the preparation method.
Example 4:
a preparation method of a composite nano material for a lithium ion battery comprises the following specific steps:
(1) acidifying a multi-walled carbon nanotube and dispersing the multi-walled carbon nanotube in water to obtain a dispersion liquid of the acidified multi-walled carbon nanotube:
(2) adding an organic carbon source into the dispersion liquid of the acidified multi-walled carbon nanotubes obtained in the step (1), uniformly mixing, and performing ultrasonic dispersion to obtain a dispersion liquid I;
(3) dissolving ethyl orthosilicate in ethanol, adding polyethylene glycol 1000, performing ultrasonic dispersion, adding a urea solution, and stirring to form sol for later use;
(4) sequentially adding tin tetrachloride pentahydrate and the sol obtained in the step (3) into the dispersion liquid I obtained in the step (2), then adding concentrated hydrochloric acid (38 w.t.%), then slowly adding concentrated ammonia water to adjust the pH value to 10, reacting at 120 ℃ for 3 days, washing with water, filtering, drying, and roasting at 420 ℃ for 3 hours to obtain the silicon dioxide/tin dioxide/multiwalled carbon nanotube composite nanomaterial;
(5) and (4) putting the silicon carbide and the silicon dioxide/tin dioxide/multi-walled carbon nano tube composite nano material obtained in the step (4) into a ball mill for grinding, putting the obtained powder into a tubular furnace for heating and roasting, and then cooling to room temperature along with the furnace to obtain the silicon carbide/tin dioxide/multi-walled carbon nano tube composite nano material.
The specific method of the step (1) is as follows: stirring and mixing the multi-walled carbon nano-tube and concentrated nitric acid uniformly, reacting for 10 hours at 120 ℃, carrying out suction filtration and washing on the obtained product to be neutral, carrying out vacuum drying to obtain an acidified multi-walled carbon nano-tube, and then dispersing in water to obtain a dispersion liquid of the acidified multi-walled carbon nano-tube. The mass concentration of the concentrated nitric acid is 65%, and the mass volume ratio of the multi-walled carbon nano-tube to the concentrated nitric acid is 1 g: 100mL, the mass concentration of the acidified multi-wall carbon nanotubes in the dispersion liquid of the acidified multi-wall carbon nanotubes is 1 g/L.
In the step (2), the organic carbon source is a mixture of sucrose and resorcinol, and the mass ratio of the sucrose to the resorcinol is 2: 1, the mixture is added in an amount 1/10 weight of the dispersion of acidified multi-walled carbon nanotubes.
In the step (3), the mass-to-volume ratio of the ethyl orthosilicate, the ethanol, the polyethylene glycol 1000 and the urea solution is 1 g: 10mL of: 0.1 g: 2mL, wherein the concentration of the urea solution is 30 percent. The stirring time was 4 hours.
The mass concentration of the concentrated ammonia water in the step (4) is 25 percent. The mass volume ratio of the acidified multiwalled carbon nanotube, the tin tetrachloride pentahydrate, the sol and the concentrated hydrochloric acid contained in the dispersion liquid I is 1 g: 60mL of: 40 g: 70 mL.
In the step (5), the mass ratio of the silicon carbide to the silicon dioxide/stannic oxide/multi-walled carbon nanotube composite nano material is 1: 0.5: 0.7. the silicon carbide is prepared by the following method:
(51) preparing a silicon carbide precursor;
(52) under the protection of helium atmosphere, heating the silicon carbide precursor to 1250 ℃ at the heating rate of 25 ℃/min, preserving heat for 2 hours, then heating to 1400 ℃ at the heating rate of 8 ℃/min, preserving heat for 8 hours, and naturally cooling to room temperature to obtain dark green initial-stage silicon carbide;
(53) and (5) adding the initial-stage silicon carbide obtained in the step (52) into a hydrofluoric acid solution with the mass concentration of 35%, removing unreacted silicon dioxide, washing with water, filtering, and drying to obtain the silicon carbide.
The specific method of the step (51) is as follows: dissolving sucrose in water and ethylene glycol, adding ferric nitrate, stirring to dissolve the sucrose to form a mixed solution, adding tetraethyl silicate and organic silicon at 40 ℃ while stirring, adding citric acid, hydrolyzing for 20 hours to prepare carbon-silicon binary sol, then adding the carbon-silicon binary sol into hexamethylenetetramine, maintaining the temperature at 40 ℃ for gelling, aging the gel for 30 hours, and drying for 15 hours at 100 ℃ to prepare a brown silicon carbide precursor; wherein the mass ratio of sucrose, water, glycol, ferric nitrate, tetraethyl silicate, organic silicon, citric acid and hexamethylenetetramine is 1: 10: 10: 0.02: 3: 0.7: 0.1: 0.3.
and (5) grinding the silicon carbide precursor obtained in the step (51) into 25 meshes, and then carrying out the treatment in the step (52).
The heating program of the tube furnace is as follows: heating to 300 ℃ at a heating rate of 8 ℃/min under a helium atmosphere, preserving heat for 3 hours, heating to 900 ℃ at a heating rate of 12 ℃/min, and then roasting at constant temperature for 10 hours.
The composite nano material for the lithium ion battery is prepared by the preparation method.
Example 5:
a preparation method of a composite nano material for a lithium ion battery comprises the following specific steps:
(1) acidifying a multi-walled carbon nanotube and dispersing the multi-walled carbon nanotube in water to obtain a dispersion liquid of the acidified multi-walled carbon nanotube:
(2) adding an organic carbon source into the dispersion liquid of the acidified multi-walled carbon nanotubes obtained in the step (1), uniformly mixing, and performing ultrasonic dispersion to obtain a dispersion liquid I;
(3) dissolving ethyl orthosilicate in ethanol, adding polyethylene glycol 1000, performing ultrasonic dispersion, adding a urea solution, and stirring to form sol for later use;
(4) sequentially adding tin tetrachloride pentahydrate and the sol obtained in the step (3) into the dispersion liquid I obtained in the step (2), then adding concentrated hydrochloric acid (38 w.t.%), then slowly adding concentrated ammonia water to adjust the pH value to 8, reacting at 160 ℃ for 2 days, washing with water, filtering, drying, and roasting at 430 ℃ for 2.5 hours to obtain the silicon dioxide/tin dioxide/multiwalled carbon nanotube composite nanomaterial;
(5) and (4) putting the silicon carbide and the silicon dioxide/tin dioxide/multi-walled carbon nano tube composite nano material obtained in the step (4) into a ball mill for grinding, putting the obtained powder into a tubular furnace for heating and roasting, and then cooling to room temperature along with the furnace to obtain the silicon carbide/tin dioxide/multi-walled carbon nano tube composite nano material.
The specific method of the step (1) is as follows: stirring and mixing the multi-walled carbon nano-tube and concentrated nitric acid uniformly, reacting for 9 hours at 125 ℃, carrying out suction filtration and washing on the obtained product to be neutral, carrying out vacuum drying to obtain an acidified multi-walled carbon nano-tube, and then dispersing in water to obtain a dispersion liquid of the acidified multi-walled carbon nano-tube. The mass concentration of the concentrated nitric acid is 65%, and the mass volume ratio of the multi-walled carbon nano-tube to the concentrated nitric acid is 1 g: 100mL, the mass concentration of the acidified multi-wall carbon nanotubes in the dispersion liquid of the acidified multi-wall carbon nanotubes is 1 g/L.
In the step (2), the organic carbon source is a mixture of sucrose and resorcinol, and the mass ratio of the sucrose to the resorcinol is 2: 1, the mixture is added in an amount 1/10 weight of the dispersion of acidified multi-walled carbon nanotubes.
In the step (3), the mass-to-volume ratio of the ethyl orthosilicate, the ethanol, the polyethylene glycol 1000 and the urea solution is 1 g: 15mL of: 0.09 g: 2.5mL, wherein the concentration of the urea solution is 25%. The stirring time was 4.5 hours.
The mass concentration of the concentrated ammonia water in the step (4) is 25 percent. The mass volume ratio of the acidified multiwalled carbon nanotube, the tin tetrachloride pentahydrate, the sol and the concentrated hydrochloric acid contained in the dispersion liquid I is 1 g: 55mL of: 45 g: 65 mL.
In the step (5), the mass ratio of the silicon carbide to the silicon dioxide/stannic oxide/multi-walled carbon nanotube composite nano material is 1: 0.5: 0.7. the silicon carbide is prepared by the following method:
(51) preparing a silicon carbide precursor;
(52) under the protection of helium atmosphere, heating the silicon carbide precursor to 1225 ℃ at a heating rate of 28 ℃/min, preserving heat for 2.5 hours, then heating to 1425 ℃ at a heating rate of 7 ℃/min, preserving heat for 7.5 hours, and naturally cooling to room temperature to obtain dark green initial-stage silicon carbide;
(53) and (5) adding the initial-stage silicon carbide obtained in the step (52) into a hydrofluoric acid solution with the mass concentration of 35%, removing unreacted silicon dioxide, washing with water, filtering, and drying to obtain the silicon carbide.
The specific method of the step (51) is as follows: dissolving sucrose in water and ethylene glycol, adding ferric nitrate, stirring to dissolve the sucrose to form a mixed solution, adding tetraethyl silicate and organic silicon at 50 ℃ while stirring, adding citric acid, hydrolyzing for 18 hours to prepare carbon-silicon binary sol, then adding the carbon-silicon binary sol into hexamethylenetetramine, maintaining the temperature at 50 ℃ for gelling, aging the gel for 25 hours, and drying for 14 hours at 125 ℃ to prepare a brown silicon carbide precursor; wherein the mass ratio of sucrose, water, glycol, ferric nitrate, tetraethyl silicate, organic silicon, citric acid and hexamethylenetetramine is 1: 15: 9: 0.03: 3: 0.6: 0.1: 0.3.
and (5) grinding the silicon carbide precursor obtained in the step (51) into 30 meshes, and then carrying out the treatment in the step (52).
The heating program of the tube furnace is as follows: heating to 350 ℃ at the heating rate of 6 ℃/min under the atmosphere of helium, preserving heat for 2.5 hours, heating to 850 ℃ at the heating rate of 13 ℃/min, and then roasting at constant temperature for 11 hours.
The composite nano material for the lithium ion battery is prepared by the preparation method.
Comparative example 1
A preparation method of a composite nano material for a lithium ion battery comprises the following specific steps:
(1) acidifying a multi-walled carbon nanotube and dispersing the multi-walled carbon nanotube in water to obtain a dispersion liquid of the acidified multi-walled carbon nanotube:
(2) adding an organic carbon source into the dispersion liquid of the acidified multi-walled carbon nanotubes obtained in the step (1), uniformly mixing, and performing ultrasonic dispersion to obtain a dispersion liquid I;
(3) dissolving ethyl orthosilicate in ethanol, adding polyethylene glycol 1000, performing ultrasonic dispersion, adding a urea solution, and stirring to form sol for later use;
(4) sequentially adding tin tetrachloride pentahydrate and the sol obtained in the step (3) into the dispersion liquid I obtained in the step (2), then adding concentrated hydrochloric acid (38 w.t.%), then slowly adding concentrated ammonia water to adjust the pH value to 8, reacting at 160 ℃ for 2 days, washing with water, filtering, drying, and roasting at 430 ℃ for 2.5 hours to obtain the silicon dioxide/tin dioxide/multiwalled carbon nanotube composite nanomaterial;
(5) and (4) putting the silicon carbide and the silicon dioxide/tin dioxide/multi-walled carbon nano tube composite nano material obtained in the step (4) into a ball mill for grinding, putting the obtained powder into a tubular furnace for heating and roasting, and then cooling to room temperature along with the furnace to obtain the silicon carbide/tin dioxide/multi-walled carbon nano tube composite nano material.
The specific method of the step (1) is as follows: stirring and mixing the multi-walled carbon nano-tube and concentrated nitric acid uniformly, reacting for 9 hours at 125 ℃, carrying out suction filtration and washing on the obtained product to be neutral, carrying out vacuum drying to obtain an acidified multi-walled carbon nano-tube, and then dispersing in water to obtain a dispersion liquid of the acidified multi-walled carbon nano-tube. The mass concentration of the concentrated nitric acid is 65%, and the mass volume ratio of the multi-walled carbon nano-tube to the concentrated nitric acid is 1 g: 100mL, the mass concentration of the acidified multi-wall carbon nanotubes in the dispersion liquid of the acidified multi-wall carbon nanotubes is 1 g/L.
In the step (2), the organic carbon source is sucrose, and the addition amount of the organic carbon source is 1/10 of the weight of the dispersion liquid of the acidified multi-wall carbon nano tubes.
In the step (3), the mass-to-volume ratio of the ethyl orthosilicate, the ethanol, the polyethylene glycol 1000 and the urea solution is 1 g: 15mL of: 0.09 g: 2.5mL, wherein the concentration of the urea solution is 25%. The stirring time was 4.5 hours.
The mass concentration of the concentrated ammonia water in the step (4) is 25 percent. The mass volume ratio of the acidified multiwalled carbon nanotube, the tin tetrachloride pentahydrate, the sol and the concentrated hydrochloric acid contained in the dispersion liquid I is 1 g: 55mL of: 45 g: 65 mL.
In the step (5), the mass ratio of the silicon carbide to the silicon dioxide/stannic oxide/multi-walled carbon nanotube composite nano material is 1: 0.5: 0.7. the silicon carbide is prepared by the following method:
(51) preparing a silicon carbide precursor;
(52) under the protection of helium atmosphere, heating the silicon carbide precursor to 1225 ℃ at a heating rate of 28 ℃/min, preserving heat for 2.5 hours, then heating to 1425 ℃ at a heating rate of 7 ℃/min, preserving heat for 7.5 hours, and naturally cooling to room temperature to obtain dark green initial-stage silicon carbide;
(53) and (5) adding the initial-stage silicon carbide obtained in the step (52) into a hydrofluoric acid solution with the mass concentration of 35%, removing unreacted silicon dioxide, washing with water, filtering, and drying to obtain the silicon carbide.
The specific method of the step (51) is as follows: dissolving sucrose in water and ethylene glycol, adding ferric nitrate, stirring to dissolve the sucrose to form a mixed solution, adding tetraethyl silicate and organic silicon at 50 ℃ while stirring, adding citric acid, hydrolyzing for 18 hours to prepare carbon-silicon binary sol, then adding the carbon-silicon binary sol into hexamethylenetetramine, maintaining the temperature at 50 ℃ for gelling, aging the gel for 25 hours, and drying for 14 hours at 125 ℃ to prepare a brown silicon carbide precursor; wherein the mass ratio of sucrose, water, glycol, ferric nitrate, tetraethyl silicate, organic silicon, citric acid and hexamethylenetetramine is 1: 15: 9: 0.03: 3: 0.6: 0.1: 0.3.
and (5) grinding the silicon carbide precursor obtained in the step (51) into 30 meshes, and then carrying out the treatment in the step (52).
The heating program of the tube furnace is as follows: heating to 350 ℃ at the heating rate of 6 ℃/min under the atmosphere of helium, preserving heat for 2.5 hours, heating to 850 ℃ at the heating rate of 13 ℃/min, and then roasting at constant temperature for 11 hours.
The composite nano material for the lithium ion battery is prepared by the preparation method.
Comparative example 2
A preparation method of a composite nano material for a lithium ion battery comprises the following specific steps:
(1) acidifying a multi-walled carbon nanotube and dispersing the multi-walled carbon nanotube in water to obtain a dispersion liquid of the acidified multi-walled carbon nanotube:
(2) adding an organic carbon source into the dispersion liquid of the acidified multi-walled carbon nanotubes obtained in the step (1), uniformly mixing, and performing ultrasonic dispersion to obtain a dispersion liquid I;
(3) dissolving ethyl orthosilicate in ethanol, adding polyethylene glycol 1000, performing ultrasonic dispersion, adding a urea solution, and stirring to form sol for later use;
(4) and (3) sequentially adding tin tetrachloride pentahydrate and the sol obtained in the step (3) into the dispersion liquid I obtained in the step (2), then adding concentrated hydrochloric acid (38 w.t.%), then slowly adding concentrated ammonia water to adjust the pH value to 8, reacting at 160 ℃ for 2 days, washing with water, filtering, drying, and roasting at 430 ℃ for 2.5 hours to obtain the silicon dioxide/tin dioxide/multiwalled carbon nanotube composite nanomaterial.
The specific method of the step (1) is as follows: stirring and mixing the multi-walled carbon nano-tube and concentrated nitric acid uniformly, reacting for 9 hours at 125 ℃, carrying out suction filtration and washing on the obtained product to be neutral, carrying out vacuum drying to obtain an acidified multi-walled carbon nano-tube, and then dispersing in water to obtain a dispersion liquid of the acidified multi-walled carbon nano-tube. The mass concentration of the concentrated nitric acid is 65%, and the mass volume ratio of the multi-walled carbon nano-tube to the concentrated nitric acid is 1 g: 100mL, the mass concentration of the acidified multi-wall carbon nanotubes in the dispersion liquid of the acidified multi-wall carbon nanotubes is 1 g/L.
In the step (2), the organic carbon source is a mixture of sucrose and resorcinol, and the mass ratio of the sucrose to the resorcinol is 2: 1, the mixture is added in an amount 1/10 weight of the dispersion of acidified multi-walled carbon nanotubes.
In the step (3), the mass-to-volume ratio of the ethyl orthosilicate, the ethanol, the polyethylene glycol 1000 and the urea solution is 1 g: 15mL of: 0.09 g: 2.5mL, wherein the concentration of the urea solution is 25%. The stirring time was 4.5 hours.
The mass concentration of the concentrated ammonia water in the step (4) is 25 percent. The mass volume ratio of the acidified multiwalled carbon nanotube, the tin tetrachloride pentahydrate, the sol and the concentrated hydrochloric acid contained in the dispersion liquid I is 1 g: 55mL of: 45 g: 65 mL.
The composite nano material for the lithium ion battery is prepared by the preparation method.
Comparative example 3
A preparation method of a composite nano material for a lithium ion battery comprises the following specific steps:
(1) acidifying a multi-walled carbon nanotube and dispersing the multi-walled carbon nanotube in water to obtain a dispersion liquid of the acidified multi-walled carbon nanotube:
(2) adding an organic carbon source into the dispersion liquid of the acidified multi-walled carbon nanotubes obtained in the step (1), uniformly mixing, and performing ultrasonic dispersion to obtain a dispersion liquid I;
(3) adding tin tetrachloride pentahydrate into the dispersion liquid I obtained in the step (2), then adding concentrated hydrochloric acid (38 w.t.%), then slowly adding concentrated ammonia water to adjust the pH value to 8, reacting for 2 days at 160 ℃, washing with water, filtering, drying, and roasting for 2.5 hours at 430 ℃ to obtain the tin dioxide/multiwalled carbon nanotube composite nanomaterial;
(4) and (4) placing the silicon carbide and the stannic oxide/multi-walled carbon nanotube composite nano material obtained in the step (3) into a ball mill for grinding, placing the obtained powder into a tubular furnace for heating and roasting, and then cooling to room temperature along with the furnace to obtain the composite nano material.
The specific method of the step (1) is as follows: stirring and mixing the multi-walled carbon nano-tube and concentrated nitric acid uniformly, reacting for 9 hours at 125 ℃, carrying out suction filtration and washing on the obtained product to be neutral, carrying out vacuum drying to obtain an acidified multi-walled carbon nano-tube, and then dispersing in water to obtain a dispersion liquid of the acidified multi-walled carbon nano-tube. The mass concentration of the concentrated nitric acid is 65%, and the mass volume ratio of the multi-walled carbon nano-tube to the concentrated nitric acid is 1 g: 100mL, the mass concentration of the acidified multi-wall carbon nanotubes in the dispersion liquid of the acidified multi-wall carbon nanotubes is 1 g/L.
In the step (2), the organic carbon source is a mixture of sucrose and resorcinol, and the mass ratio of the sucrose to the resorcinol is 2: 1, the mixture is added in an amount 1/10 weight of the dispersion of acidified multi-walled carbon nanotubes.
The mass concentration of the concentrated ammonia water in the step (3) is 25 percent. The mass volume ratio of the acidified multiwalled carbon nanotube, the tin tetrachloride pentahydrate and the concentrated hydrochloric acid contained in the dispersion liquid I is 1 g: 55mL of: 65 mL.
In the step (4), the mass ratio of the silicon carbide to the silicon dioxide/stannic oxide/multi-walled carbon nanotube composite nano material is 1: 0.5: 0.7. the silicon carbide is prepared by the following method:
(41) preparing a silicon carbide precursor;
(42) under the protection of helium atmosphere, heating the silicon carbide precursor to 1225 ℃ at a heating rate of 28 ℃/min, preserving heat for 2.5 hours, then heating to 1425 ℃ at a heating rate of 7 ℃/min, preserving heat for 7.5 hours, and naturally cooling to room temperature to obtain dark green initial-stage silicon carbide;
(43) and (5) adding the initial-stage silicon carbide obtained in the step (42) into a hydrofluoric acid solution with the mass concentration of 35%, removing unreacted silicon dioxide, washing with water, filtering, and drying to obtain the silicon carbide.
The specific method of the step (41) is as follows: dissolving sucrose in water and ethylene glycol, adding ferric nitrate, stirring to dissolve the sucrose to form a mixed solution, adding tetraethyl silicate and organic silicon at 50 ℃ while stirring, adding citric acid, hydrolyzing for 18 hours to prepare carbon-silicon binary sol, then adding the carbon-silicon binary sol into hexamethylenetetramine, maintaining the temperature at 50 ℃ for gelling, aging the gel for 25 hours, and drying for 14 hours at 125 ℃ to prepare a brown silicon carbide precursor; wherein the mass ratio of sucrose, water, glycol, ferric nitrate, tetraethyl silicate, organic silicon, citric acid and hexamethylenetetramine is 1: 15: 9: 0.03: 3: 0.6: 0.1: 0.3.
and (4) grinding the silicon carbide precursor obtained in the step (41) into 30 meshes, and then carrying out the treatment in the step (42).
The heating program of the tube furnace is as follows: heating to 350 ℃ at the heating rate of 6 ℃/min under the atmosphere of helium, preserving heat for 2.5 hours, heating to 850 ℃ at the heating rate of 13 ℃/min, and then roasting at constant temperature for 11 hours.
The composite nano material for the lithium ion battery is prepared by the preparation method.
Test examples
The composite nanomaterials obtained in examples 1 to 5 and comparative examples 1 to 3 were subjected to application tests.
Respectively using the composite nano material as a negative electrode, a lithium sheet as a counter electrode, Celgard in America as a diaphragm, and 1mol/L of LiPF6/EC + DMC [ V (EC): v (dmc) ═ 1:1] was used as an electrolyte and assembled into a button cell in a stainless steel glove box filled with argon gas. Constant-current and constant-voltage charge and discharge tests are carried out on a Land-BTL10 (blue electricity) full-automatic battery program-controlled tester, and all electrical performance indexes are shown in Table 1.
TABLE 1 comparison of electrical Properties
As can be seen from Table 1, the composite nanomaterial disclosed by the invention has high initial coulombic efficiency, high capacity and high cycle stability, and is far superior to those of comparative examples 1-3. Comparative example 1 the organic carbon source is sucrose, comparative example 2 omits silicon carbide coating, comparative example 3 omits silicon dioxide compounding, the electrical property index is obviously poor, and the dispersibility of the carbon nano tube, the surface coating of the carbon nano tube and the surface modification of the carbon nano tube are directly related to the electrical property of the obtained composite nano material.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. 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 (2)
1. A preparation method of a composite nano material for a lithium ion battery is characterized by comprising the following specific steps:
(1) acidifying a multi-walled carbon nanotube and dispersing the multi-walled carbon nanotube in water to obtain a dispersion liquid of the acidified multi-walled carbon nanotube:
(2) adding an organic carbon source into the dispersion liquid of the acidified multi-walled carbon nanotubes obtained in the step (1), uniformly mixing, and performing ultrasonic dispersion to obtain a dispersion liquid I;
(3) dissolving ethyl orthosilicate in ethanol, adding polyethylene glycol 1000, performing ultrasonic dispersion, adding a urea solution, and stirring to form sol for later use;
(4) sequentially adding tin tetrachloride pentahydrate and the sol obtained in the step (3) into the dispersion liquid I in the step (2), then adding concentrated hydrochloric acid, slowly adding concentrated ammonia water to adjust the pH to be 7-10, reacting at 120-180 ℃ for 2-3 days, washing with water, filtering, drying, and roasting at 420-440 ℃ for 2-3 hours to obtain the silicon dioxide/tin dioxide/multiwalled carbon nanotube composite nanomaterial;
(5) putting silicon carbide and the silicon dioxide/stannic oxide/multi-walled carbon nanotube composite nano material obtained in the step (4) into a ball mill for grinding, putting the obtained powder into a tubular furnace for heating and roasting, and then cooling to room temperature along with the furnace to obtain the silicon carbide/stannic oxide/multi-walled carbon nanotube composite nano material;
in the step (2), the organic carbon source is a mixture of sucrose and resorcinol, and the mass ratio of the sucrose to the resorcinol is 2: 1, the amount of the mixture added is 1/10 weight of the dispersion of the acidified multi-walled carbon nanotubes;
the silicon carbide in the step (5) is prepared by the following method:
(51) preparing a silicon carbide precursor;
(52) under the protection of helium atmosphere, heating the silicon carbide precursor to 1200-1250 ℃ at a heating rate of 25-30 ℃/min, preserving heat for 2-3 hours, then heating to 1400-1450 ℃ at a heating rate of 5-8 ℃/min, preserving heat for 7-8 hours, and naturally cooling to room temperature to obtain dark green initial-stage silicon carbide;
(53) adding the initial-stage silicon carbide obtained in the step (52) into a hydrofluoric acid solution with the mass concentration of 35%, removing unreacted silicon dioxide, washing with water, filtering, and drying to obtain the silicon carbide;
in the step (3), the mass-to-volume ratio of the ethyl orthosilicate, the ethanol, the polyethylene glycol 1000 and the urea solution is 1 g: 10-20 mL: 0.08-0.1 g: 2-3 mL, wherein the concentration of the urea solution is 20-30%;
the specific method of the step (1) is as follows: uniformly stirring and mixing the multiwalled carbon nanotube and concentrated nitric acid, reacting for 8-10 hours at 120-130 ℃, performing suction filtration and washing on the obtained product to be neutral, performing vacuum drying to obtain an acidified multiwalled carbon nanotube, and dispersing in water to obtain a dispersion liquid of the acidified multiwalled carbon nanotube;
the mass concentration of the concentrated nitric acid is 65%, and the mass volume ratio of the multi-walled carbon nano-tube to the concentrated nitric acid is 1 g: 100mL, wherein the mass concentration of the acidified multi-wall carbon nanotubes in the dispersion liquid of the acidified multi-wall carbon nanotubes is 1 g/L;
the stirring time in the step (3) is 4-5 hours.
2. A composite nanomaterial for a lithium ion battery, which is prepared by the preparation method of claim 1.
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