CN114256454A - Carbon nanotube-carbon nanosheet-germanium composite negative electrode material and preparation method and application thereof - Google Patents

Carbon nanotube-carbon nanosheet-germanium composite negative electrode material and preparation method and application thereof Download PDF

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CN114256454A
CN114256454A CN202111604599.6A CN202111604599A CN114256454A CN 114256454 A CN114256454 A CN 114256454A CN 202111604599 A CN202111604599 A CN 202111604599A CN 114256454 A CN114256454 A CN 114256454A
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germanium
carbon
aqueous solution
carbon nanosheet
solution
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CN114256454B (en
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刘双科
许静
吴文植
郝紫勋
李宇杰
孙巍巍
郑春满
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National University of Defense Technology
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    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/16—Preparation
    • 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
    • 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

Abstract

The invention discloses a carbon nanotube-carbon nanosheet-germanium composite negative electrode material and a preparation method and application thereof. Then uniformly dispersing the three-dimensional porous carbon nano sheet in an aqueous solution containing a surfactant; dissolving germanium oxide in an alkaline aqueous solution, adjusting the solution to be neutral, adding the solution into the mixed solution, ultrasonically stirring and dispersing, adding a borohydride aqueous solution, carrying out water bath, stirring and reacting at constant temperature, and obtaining germanium precursor composite carbon nanosheet powder. And finally, grinding or ball-milling the germanium precursor composite carbon nanosheet powder, melamine, high-boiling-point mineral oil and a cobalt salt solution uniformly to form a muddy mixture, and putting the muddy mixture in an inert atmosphere for carbonization treatment to obtain the carbon nanotube-carbon nanosheet-germanium composite material. The preparation method provided by the invention has the advantages of cheap and easily available raw materials, simple preparation process and capability of realizing mass preparation.

Description

Carbon nanotube-carbon nanosheet-germanium composite negative electrode material and preparation method and application thereof
Technical Field
The invention relates to the technical field of battery materials, in particular to a carbon nanotube-carbon nanosheet-germanium composite negative electrode material and a preparation method and application thereof.
Background
Germanium (Ge) is a group IVA element, and has high theoretical specific capacity (1600 mAh g)-1The theoretical volumetric specific capacity is 8500mAh cm-3) The lithium-intercalation potential is low, and the conductivity is good, so the material is considered to have great potential in replacing graphite cathode to become a cathode material of a lithium ion battery with high specific energy. However, the volume expansion of the germanium negative electrode after lithium insertion can reach 300%, and a large stress can be generated by a large volume expansion effect, so that the germanium negative electrode material is pulverized and fails, and is separated from a current collector, and the capacity is rapidly attenuated. In addition, the volume expansion effect of the germanium negative electrode also causes that a stable solid electrolyte interface (SEI film) is difficult to form on the surface of the germanium negative electrode, and the specific capacity, the stability, the coulombic efficiency and the like of the germanium negative electrode are seriously influenced.
Disclosure of Invention
The invention provides a carbon nanotube-carbon nanosheet-germanium composite negative electrode material, and a preparation method and application thereof, which are used for overcoming the defects of poor electrochemical activity, large volume expansion effect and the like of a germanium negative electrode in the prior art.
In order to achieve the purpose, the invention provides a preparation method of a carbon nanotube-carbon nanosheet-germanium composite negative electrode material, which comprises the following steps:
s1: carrying out ball milling on organic acid sodium salt, carrying out heat treatment under inert atmosphere, cooling, filtering, washing and drying to obtain three-dimensional porous carbon nanosheet powder;
s2: dispersing the three-dimensional porous carbon nanosheet powder in an aqueous solution containing a surfactant to obtain a mixed solution; dissolving germanium oxide in an alkaline aqueous solution, adjusting to be neutral, adding the solution into the mixed solution, ultrasonically stirring and dispersing, adding a borohydride aqueous solution, stirring in a water bath at a constant temperature, washing, filtering and drying the obtained product to obtain germanium precursor composite carbon nanosheet powder;
s3: and mixing the germanium precursor composite carbon nanosheet powder with melamine and mineral oil, adding a cobalt salt solution, grinding or ball-milling and uniformly mixing to form a muddy mixture, and carrying out carbonization treatment under an inert atmosphere to obtain the carbon nanotube-carbon nanosheet-germanium composite negative electrode material.
In order to achieve the purpose, the invention also provides a carbon nanotube-carbon nanosheet-germanium composite anode material prepared by the preparation method; the carbon nano tube-carbon nano sheet-germanium composite cathode material consists of nano germanium, carbon nano sheets and carbon nano tubes and is of a three-dimensional network porous structure; the nano germanium and the carbon nano tube are grown in situ in the three-dimensional pore structure of the carbon nano sheet.
In order to achieve the purpose, the invention also provides an application of the carbon nanotube-carbon nanosheet-germanium composite negative electrode material, and the carbon nanotube-carbon nanosheet-germanium composite negative electrode material prepared by the preparation method or the carbon nanotube-carbon nanosheet-germanium composite negative electrode material is used as a negative electrode of a lithium ion battery.
Compared with the prior art, the invention has the beneficial effects that:
1. the preparation method of the carbon nanotube-carbon nanosheet-germanium composite negative electrode material provided by the invention comprises the following step of firstly, taking organic acid sodium salt as a raw material, and carrying out heat treatment to obtain the three-dimensional porous carbon nanosheet. Then uniformly dispersing the three-dimensional porous carbon nanosheets in an aqueous solution containing a surfactant, wherein the surfactant is helpful for uniformly dispersing the three-dimensional porous carbon in the aqueous solution; dissolving germanium oxide powder in an alkaline aqueous solution, reacting germanium oxide with alkali to form soluble germanate ions, adding the soluble germanate ions into the mixed solution, ultrasonically stirring and dispersing, adding a borohydride aqueous solution, carrying out water bath constant-temperature stirring reaction, reducing germanate into nano germanium, and growing a nano germanium precursor in situ in a limited-domain environment of a three-dimensional porous carbon nanosheet to obtain germanium precursor composite carbon nanosheet powder. And finally, grinding or ball-milling the germanium precursor composite carbon nanosheet powder, melamine, high-boiling-point mineral oil and a cobalt salt solution uniformly to form a muddy mixture, putting the muddy mixture in an inert atmosphere for carbonization treatment, cracking and carbonizing the melamine and the high-boiling-point mineral oil at high temperature, heating the mixture in the inert atmosphere, reducing cobalt ions into metal cobalt, and growing the carbon nanotube in situ under the catalysis of the metal cobalt by using carbon to obtain the carbon nanotube-carbon nanosheet-germanium composite material. The preparation method provided by the invention has the advantages of cheap and easily available raw materials, simple preparation process and capability of realizing mass preparation.
2. The carbon nano tube-carbon nano sheet-germanium composite material provided by the invention is composed of nano germanium, carbon nano sheets and carbon nano tubes, and has a three-dimensional network porous structure, and the nano germanium and the carbon nano tubes both grow in situ in the three-dimensional pore structure of the carbon nano sheets. The in-situ growth of the nano germanium in the three-dimensional porous carbon nanosheet network structure can inhibit the agglomeration of the nano germanium in the high-temperature heat treatment process and inhibit the structural damage caused by volume expansion, thereby improving the electrochemical activity and stability of the germanium cathode. The carbon nano tube and the carbon nano sheet have good conductivity and mechanical property, and are compounded with the nano germanium particles to form a three-dimensional conductive network structure, so that on one hand, the conductivity among the germanium particles is improved, the rate capability is improved, and on the other hand, the volume expansion and contraction effects of the germanium cathode material can be effectively inhibited, so that the stability of a solid electrolyte interface (SEI film) is improved. When the cathode material is used as a cathode material of a lithium ion battery, the electrochemical activity and the cycling stability can be effectively improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a Scanning Electron Microscope (SEM) image of a carbon nanotube-carbon nanosheet-germanium composite in example 1 of the present invention;
fig. 2 is a cycle performance curve diagram of a lithium ion battery assembled by a carbon nanotube-carbon nanosheet-germanium composite material in embodiment 1 of the present invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.
The drugs/reagents used are all commercially available without specific mention.
The invention provides a preparation method of a carbon nanotube-carbon nanosheet-germanium composite negative electrode material, which comprises the following steps of:
s1: and (3) carrying out ball milling on the organic acid sodium salt, carrying out heat treatment under an inert atmosphere, cooling, filtering, washing and drying to obtain the three-dimensional porous carbon nanosheet powder.
Preferably, the organic acid sodium salt is at least one of sodium citrate, sodium ascorbate, sodium succinate and sodium gluconate; the selected organic acid sodium salt can be cracked into sodium carbonate crystals and a coated carbon layer through heat treatment in a high-temperature inert atmosphere, and the sodium carbonate crystals are washed with water to obtain the three-dimensional porous carbon nanosheet structure.
The inert atmosphere is Ar gas and N2Gas, Ar/H2One kind of mixed gas. The sodium salt of the organic acid is cracked to carbon under an inert atmosphere.
Preferably, the rotation speed of the ball milling is 100-500 r/min, and the time is 1-12 h; the proper earth grinding rotation speed and ball milling time are beneficial to refining and uniformity of organic acid sodium salt particles, and uniform three-dimensional porous carbon nanosheets are formed in the subsequent high-temperature heat treatment process.
The temperature of the heat treatment is 500-1000 ℃, and the time is 0.5-12 h, so that the organic acid sodium salt is completely cracked.
S2: dispersing the three-dimensional porous carbon nanosheet powder in an aqueous solution containing a surfactant to obtain a mixed solution; dissolving germanium oxide in an alkaline aqueous solution, adjusting to be neutral, adding the solution into the mixed solution, ultrasonically stirring and dispersing, adding a borohydride aqueous solution, stirring in a water bath at a constant temperature, washing, filtering and drying the obtained product to obtain germanium precursor composite carbon nanosheet powder.
Preferably, the mass fraction of the surfactant in the surfactant-containing aqueous solution is 0.01-1%; the surfactant is at least one of dodecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride and polyvinylpyrrolidone; the proper and proper amount of surfactant is helpful for uniform dispersion of the three-dimensional porous carbon nanosheet in the aqueous solution.
The alkaline aqueous solution is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution; the concentration of sodium hydroxide or potassium hydroxide in the alkaline aqueous solution is 0.5-3 mol/L. The alkaline aqueous solution with appropriate concentration can dissolve germanium oxide to form germanate ions which are adsorbed on the surface of the three-dimensional porous carbon nanosheet.
Preferably, the concentration of germanium oxide in a solution formed by dissolving germanium oxide in an alkaline aqueous solution is 0.01-0.2 mol/L; the mass ratio of the three-dimensional porous carbon nanosheet powder to the germanium oxide is (0.5-5): 12; the method is beneficial to growing fine nano germanium in the limited space of the three-dimensional porous carbon nano sheet.
The concentration of borohydride in the borohydride aqueous solution is 1-5 mol/L, and the borohydride is sodium borohydride or potassium borohydride; the molar ratio of the borohydride to the germanium oxide is (2-5): 1. Adding borohydride with proper concentration to reduce germanate into nano germanium particles.
Preferably, the temperature of the water bath constant-temperature stirring is 40-80 ℃, and the time is 1-12 h. Proper reaction temperature and time are favorable for completely reducing germanic acid radicals in the solution into nano germanium.
S3: and mixing the germanium precursor composite carbon nanosheet powder with melamine and mineral oil, adding a cobalt salt solution, grinding or ball-milling and uniformly mixing to form a muddy mixture, and carrying out carbonization treatment under an inert atmosphere to obtain the carbon nanotube-carbon nanosheet-germanium composite negative electrode material.
Besides carbonization, the mineral oil has certain fluidity, so that the cobalt salt can be dispersed more uniformly.
Preferably, the mass ratio of the germanium precursor composite carbon nanosheet powder to the mineral oil is (0.02-0.2): 1, which is favorable for forming a uniform semi-solid pasty mixture; the mass ratio of the germanium precursor composite carbon nanosheet powder to the melamine is (0.1-0.5): 1; the molar ratio of the cobalt salt to the melamine in the cobalt salt solution is (0.01-0.06): 1; the growth and content of the carbon nano tube are controlled by controlling the proportional relation.
The mineral oil is at least one of paraffin oil, kerosene, diesel oil, lubricating oil and liquid asphalt; the cobalt salt in the cobalt salt solution is one of cobalt nitrate, cobalt chloride, cobalt acetate and cobalt sulfate; the solvent in the cobalt salt solution is one of ethanol, methanol or propanol (which is convenient for solvent evaporation);
the inert atmosphere is Ar gas and N2Gas, Ar/H2One kind of mixed gas.
Preferably, the carbonization treatment temperature is 500-800 ℃ and the time is 1-6 h, so that the melamine and the mineral oil are completely carbonized.
The nano germanium in the carbon nano tube-carbon nano sheet-germanium composite cathode material prepared by the invention is confined in the three-dimensional conductive network structures of the carbon nano sheet and the carbon nano tube, so that the nano germanium is beneficial to inhibiting the agglomeration of the nano germanium in the high-temperature heat treatment process, the conductivity and the structural stability of the germanium composite cathode are improved, the discharge capacity and the rate capability of the germanium composite cathode are obviously improved when the nano germanium is used as the cathode of a lithium ion battery, the preparation method is simple and convenient, the effect is good, and the nano germanium composite cathode material has wide application prospect in the lithium ion battery.
The invention also provides a carbon nano tube-carbon nano sheet-germanium composite negative electrode material prepared by the preparation method; the carbon nano tube-carbon nano sheet-germanium composite cathode material consists of nano germanium, carbon nano sheets and carbon nano tubes and is of a three-dimensional network porous structure; the nano germanium and the carbon nano tube are grown in situ in the three-dimensional pore structure of the carbon nano sheet.
Preferably, the particle size of the nano germanium is 30-100 nm, the pipe diameter of the carbon nano tube is 10-100 nm, and the thickness of the carbon nano sheet is 5-20 nm; the mass fraction of germanium in the carbon nanotube-carbon nanosheet-germanium composite negative electrode material is 30-90 wt%.
The invention also provides an application of the carbon nanotube-carbon nanosheet-germanium composite negative electrode material, and the carbon nanotube-carbon nanosheet-germanium composite negative electrode material prepared by the preparation method or the carbon nanotube-carbon nanosheet-germanium composite negative electrode material is used as a negative electrode of a lithium ion battery.
Example 1
The embodiment provides a carbon nanotube-carbon nanosheet-germanium composite negative electrode material, which consists of nano germanium, carbon nanosheets and carbon nanotubes and is of a three-dimensional network porous structure; the nano germanium and the carbon nano tube are grown in situ in the three-dimensional pore structure of the carbon nano sheet. The grain diameter of the nano germanium is 30-100 nm, the pipe diameter of the carbon nano tube is 10-50 nm, and the thickness of the carbon nano sheet is 5-10 nm.
The invention also provides a preparation method of the carbon nanotube-carbon nanosheet-germanium composite negative electrode material, which comprises the following steps:
(1) and (3) putting 60g of sodium citrate into a planetary ball mill, ball-milling for 3h at 350r/min, putting the ball-milled sodium citrate into a tube furnace, heating to 700 ℃ in the high-purity Ar atmosphere, preserving heat for 2h, cooling, filtering, washing and drying to obtain black three-dimensional porous carbon nanosheet powder.
(2) Dispersing 0.4g of the three-dimensional porous carbon nanosheet powder in 150ml of aqueous solution containing 0.2 wt% of hexadecyl trimethyl ammonium bromide;
dissolving 2.4g of germanium oxide in 60ml of 2mol/L NaOH aqueous solution, dropwise adding hydrochloric acid to adjust the solution to be neutral, adding the solution into the three-dimensional porous carbon nanosheet mixed solution, ultrasonically stirring and dispersing, dissolving 3g of sodium borohydride in 20ml of aqueous solution, adding the aqueous solution into the aqueous solution, carrying out water bath constant-temperature stirring reaction for 3 hours at the temperature of 60 ℃, washing, filtering and drying the obtained product to obtain germanium precursor composite carbon nanosheet powder.
(3) Mixing 1g of germanium precursor composite carbon nanosheet powder with 4g of melamine and 4g of paraffin oil, then adding 2ml of ethanol solution containing 0.4g of cobalt nitrate, continuously grinding uniformly to form a pasty mixture, keeping the temperature at 700 ℃ for 5h under the high-purity Ar atmosphere, and naturally cooling to obtain the black carbon nanotube-carbon nanosheet-germanium composite negative electrode material.
Fig. 1 is an SEM image of the carbon nanotube-carbon nanosheet-germanium composite anode material prepared in this embodiment, and it can be seen that the carbon nanotube-carbon nanosheet-germanium composite anode material prepared in this embodiment is composed of nano germanium, carbon nanosheets and carbon nanotubes, and has a three-dimensional network porous structure; the nano germanium and the carbon nano tube grow in situ in the three-dimensional pore structure of the carbon nano sheet, the particle size of the nano germanium is 30-100 nm, the tube diameter of the carbon nano tube is 10-50 nm, and the thickness of the carbon nano sheet is 5-10 nm.
The carbon nanotube-carbon nanosheet-germanium composite negative electrode material prepared in the embodiment can be used as a negative electrode material of a lithium ion battery, and the carbon nanotube-carbon nanosheet-germanium composite negative electrode material, superconducting carbon and a binder LA133 are mixed according to a mass ratio of 8: 1: 1 dispersed in an aqueous solution (solids content 20%) Stirring for 12h to obtain uniform germanium cathode slurry, coating the slurry on copper foil by using a wire bar scraper coater, drying, and cutting into pole pieces with the diameter of 12mm, wherein the loading amount of germanium on the pole pieces is 1.0-1.5 mg/cm2The pole piece, the lithium cathode and the diaphragm are assembled into a lithium ion battery in a glove box to carry out charge-discharge and cycle performance tests.
Fig. 2 is a cycle performance curve diagram of a lithium ion battery assembled by the carbon nanotube-carbon nanosheet-germanium composite material in this embodiment, and the first discharge capacity of the carbon nanotube-carbon nanosheet-germanium composite negative electrode material is 1834mAh/g and the first charge capacity is 1069mAh/g at a rate of 0.1C, which indicates that the carbon nanotube-carbon nanosheet-germanium composite negative electrode material has excellent electrochemical performance.
Example 2
The embodiment provides a carbon nanotube-carbon nanosheet-germanium composite negative electrode material, which consists of nano germanium, carbon nanosheets and carbon nanotubes and is of a three-dimensional network porous structure; the nano germanium and the carbon nano tube are grown in situ in the three-dimensional pore structure of the carbon nano sheet. The grain diameter of the nano germanium is 30-100 nm, the pipe diameter of the carbon nano tube is 10-100 nm, and the thickness of the carbon nano sheet is 5-20 nm.
The invention also provides a preparation method of the carbon nanotube-carbon nanosheet-germanium composite negative electrode material, which comprises the following steps:
(1) putting 60g of potassium citrate into a planetary ball mill, ball-milling for 3h at 350r/min, putting the ball-milled potassium citrate into a tube furnace, heating to 800 ℃ in the high-purity Ar atmosphere, preserving heat for 2h, cooling, filtering, washing and drying to obtain black three-dimensional porous carbon nanosheet powder;
(2) dispersing 0.2g of the three-dimensional porous carbon nanosheet powder in 150ml of aqueous solution containing 0.4 wt% of hexadecyl trimethyl ammonium bromide, dissolving 2.4g of germanium oxide in 60ml of 2mol/L NaOH aqueous solution, dropwise adding hydrochloric acid to adjust the solution to be neutral, adding the solution into the three-dimensional porous carbon nanosheet mixed solution, ultrasonically stirring and dispersing, dissolving 3g of potassium borohydride in 20ml of aqueous solution, adding the aqueous solution into the aqueous solution, carrying out water bath constant-temperature stirring reaction at 50 ℃ for 4 hours, washing, filtering and drying the obtained product to obtain germanium precursor composite carbon nanosheet powder;
(3) mixing 1g of germanium precursor composite carbon nanosheet powder with 4g of melamine and 2g of paraffin oil, then adding 2ml of ethanol solution containing 0.1g of cobalt nitrate, continuously grinding uniformly to form a pasty mixture, keeping the temperature at 700 ℃ for 6h under the high-purity Ar atmosphere, and naturally cooling to obtain the black carbon nanotube-carbon nanosheet-germanium composite negative electrode material.
Example 3
The embodiment provides a carbon nanotube-carbon nanosheet-germanium composite negative electrode material, which consists of nano germanium, carbon nanosheets and carbon nanotubes and is of a three-dimensional network porous structure; the nano germanium and the carbon nano tube are grown in situ in the three-dimensional pore structure of the carbon nano sheet. The grain diameter of the nano germanium is 30-100 nm, the pipe diameter of the carbon nano tube is 10-100 nm, and the thickness of the carbon nano sheet is 5-20 nm.
The invention also provides a preparation method of the carbon nanotube-carbon nanosheet-germanium composite negative electrode material, which comprises the following steps:
(1) putting 60g of sodium ascorbate into a planetary ball mill, ball-milling for 3h at 350r/min, putting the ball-milled material into a tube furnace, heating to 800 ℃ in the high-purity Ar atmosphere, preserving heat for 4h, cooling, filtering, washing and drying to obtain black three-dimensional porous carbon nanosheet powder;
(2) dispersing 0.1g of the three-dimensional porous carbon nanosheet powder in 150ml of aqueous solution containing 0.1 wt% of hexadecyl trimethyl ammonium bromide, dissolving 2.4g of germanium oxide in 60ml of 1mol/L NaOH aqueous solution, dropwise adding hydrochloric acid to adjust the solution to be neutral, adding the solution into the three-dimensional porous carbon nanosheet mixed solution, ultrasonically stirring and dispersing, dissolving 3g of sodium borohydride in 20ml of aqueous solution, adding the solution into the aqueous solution, carrying out water bath constant-temperature stirring reaction at 60 ℃ for 4 hours, washing, filtering and drying the obtained product to obtain germanium precursor composite carbon nanosheet powder;
(3) mixing 1g of germanium precursor composite carbon nanosheet powder with 4g of melamine and 4g of paraffin oil, then adding 2ml of ethanol solution containing 0.2g of cobalt nitrate, continuously grinding uniformly to form a pasty mixture, keeping the temperature at 800 ℃ for 4h under the high-purity Ar atmosphere, and naturally cooling to obtain the black carbon nanotube-carbon nanosheet-germanium composite negative electrode material.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (10)

1. A preparation method of a carbon nanotube-carbon nanosheet-germanium composite negative electrode material is characterized by comprising the following steps of:
s1: carrying out ball milling on organic acid sodium salt, carrying out heat treatment under inert atmosphere, cooling, filtering, washing and drying to obtain three-dimensional porous carbon nanosheet powder;
s2: dispersing the three-dimensional porous carbon nanosheet powder in an aqueous solution containing a surfactant to obtain a mixed solution; dissolving germanium oxide in an alkaline aqueous solution, adjusting to be neutral, adding the solution into the mixed solution, ultrasonically stirring and dispersing, adding a borohydride aqueous solution, stirring in a water bath at a constant temperature, washing, filtering and drying the obtained product to obtain germanium precursor composite carbon nanosheet powder;
s3: and mixing the germanium precursor composite carbon nanosheet powder with melamine and mineral oil, adding a cobalt salt solution, grinding or ball-milling and uniformly mixing to form a muddy mixture, and carrying out carbonization treatment under an inert atmosphere to obtain the carbon nanotube-carbon nanosheet-germanium composite negative electrode material.
2. The method according to claim 1, wherein in step S1, the organic acid sodium salt is at least one of sodium citrate, sodium ascorbate, sodium succinate, and sodium gluconate; the inert atmosphere is Ar gas and N2Gas, Ar/H2One kind of mixed gas.
3. The preparation method of claim 1, wherein in step S1, the rotation speed of the ball mill is 100 to 500r/min for 1 to 12 hours; the temperature of the heat treatment is 500-1000 ℃, and the time is 0.5-12 h.
4. The method according to claim 1, wherein in step S2, the surfactant in the surfactant-containing aqueous solution is present in an amount of 0.01 to 1% by mass; the surfactant is at least one of dodecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride and polyvinylpyrrolidone;
the alkaline aqueous solution is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution; the concentration of sodium hydroxide or potassium hydroxide in the alkaline aqueous solution is 0.5-3 mol/L.
5. The method according to claim 1, wherein in step S2, the concentration of germanium oxide in the solution obtained by dissolving germanium oxide in an aqueous alkaline solution is 0.01 to 0.2 mol/L; the mass ratio of the three-dimensional porous carbon nanosheet powder to the germanium oxide is (0.5-5): 12;
the concentration of borohydride in the borohydride aqueous solution is 1-5 mol/L, and the borohydride is sodium borohydride or potassium borohydride; the molar ratio of the borohydride to the germanium oxide is (2-5): 1.
6. The preparation method according to claim 1, wherein in step S2, the temperature of the water bath constant temperature stirring is 40-80 ℃ and the time is 1-12 h.
7. The preparation method according to claim 1, wherein in step S3, the mass ratio of the germanium precursor composite carbon nanosheet powder to the mineral oil is (0.02-0.2): 1; the mass ratio of the germanium precursor composite carbon nanosheet powder to the melamine is (0.1-0.5): 1; the molar ratio of the cobalt salt to the melamine in the cobalt salt solution is (0.01-0.06): 1;
the mineral oil is at least one of paraffin oil, kerosene, diesel oil, lubricating oil and liquid asphalt; the cobalt salt in the cobalt salt solution is one of cobalt nitrate, cobalt chloride, cobalt acetate and cobalt sulfate; the solvent in the cobalt salt solution is ethanol;
the inert atmosphere is Ar gas and N2Gas, Ar/H2One kind of mixed gas.
8. The method according to claim 1, wherein the carbonization treatment is performed at 500 to 800 ℃ for 1 to 6 hours in step S3.
9. A carbon nanotube-carbon nanosheet-germanium composite anode material is characterized by being prepared by the preparation method of any one of claims 1 to 8; the carbon nano tube-carbon nano sheet-germanium composite cathode material consists of nano germanium, carbon nano sheets and carbon nano tubes and is of a three-dimensional network porous structure; the nano germanium and the carbon nano tube are grown in situ in the three-dimensional pore structure of the carbon nano sheet.
10. An application of the carbon nanotube-carbon nanosheet-germanium composite negative electrode material is characterized in that the carbon nanotube-carbon nanosheet-germanium composite negative electrode material prepared by the preparation method of any one of claims 1 to 8 or the carbon nanotube-carbon nanosheet-germanium composite negative electrode material of claim 9 is used as a negative electrode of a lithium ion battery.
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