CN114975979B - C/G/CNT-S negative electrode material, preparation method and application - Google Patents

C/G/CNT-S negative electrode material, preparation method and application Download PDF

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CN114975979B
CN114975979B CN202210796544.8A CN202210796544A CN114975979B CN 114975979 B CN114975979 B CN 114975979B CN 202210796544 A CN202210796544 A CN 202210796544A CN 114975979 B CN114975979 B CN 114975979B
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graphene
negative electrode
electrode material
box
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CN114975979A (en
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蔡金明
陈其赞
郝振亮
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Guangdong Morion Nanotech Co Ltd
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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
    • H01M4/36—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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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 provides a C/G/CNT-S negative electrode material, a preparation method and application thereof, and particularly relates to the technical field of lithium ion batteries. The C/G/CNT-S negative electrode material comprises carbon fiber, a sulfur core, a graphene box and a carbon nano tube; the graphene boxes are arranged on the surface of the carbon fiber in an array manner; the sulfur kernel is positioned inside the graphene box; the carbon nano tube is positioned on the surface of the graphene box and is bonded with the graphene box in a C-C bonding mode. The graphene box is used as a buffer space for volume expansion in the sulfur cathode charging and discharging process, compact outer layer protection is provided for sulfur, and sulfur falling is effectively prevented; the graphene box is bonded with the carbon nano tube to form a stable structure, so that the conductivity of the anode material is improved. The integrated C/G/CNT-S anode material perfectly builds a 3D conductive network, improves the conductivity and stability of the whole anode material, and further improves the electrical property.

Description

C/G/CNT-S negative electrode material, preparation method and application
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a C/G/CNT-S negative electrode material, a preparation method and application thereof.
Background
Sulfur has a theoretical capacity of up to 1675mAh/g and is a lithium ion battery negative electrode candidate material with great potential, but sulfur has two major obstacles as a lithium ion negative electrode material: poor conductivity and volume expansion, so the commercial use of sulfur as a lithium ion anode material still requires further improvement.
In improving the conductivity of sulfur, the common practice is to compound with a high-conductivity carbon material to improve the electron conductivity of sulfur, SP 2 The hybridized two-position graphene material and the one-dimensional carbon nanotube material are outstanding in conductivity in the carbon material, and can be used as a modified material for improving the sulfur conductivity; in terms of volume expansion during charge and discharge, the common practice is to constructAnd (3) building a special structure, and reserving enough expansion buffer space.
For the modification design, various modification means such as loading, doping, core-shell structure construction and the like are developed, and large-scale application cannot be realized usually due to factors such as complex process, low efficiency, high cost and the like. The traditional conductive composite carbon material uses reduced graphene oxide or carbon nanotubes to construct a conductive network through physical mixing, sulfur is loaded on the surfaces of the graphene and the carbon nanotubes, the loading strength is weak, and the conductive composite carbon material is used as a negative electrode material, and is easy to fall off after repeated circulation to cause the capacity attenuation of a battery.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide a C/G/CNT-S negative electrode material, which is used for solving the technical problems of poor conductivity, volume expansion and battery capacity attenuation caused by easy falling of sulfur on the surfaces of graphene and carbon nano tubes when sulfur is used as the negative electrode material in the prior art.
The second purpose of the invention is to provide a preparation method of the C/G/CNT-S negative electrode material, so as to solve the technical problems of complex process, low efficiency and high cost of the conductive composite carbon material preparation in the prior art.
In order to solve the technical problems, the invention adopts the following technical scheme:
the first aspect of the invention provides a C/G/CNT-S anode material, which comprises carbon fiber, a sulfur kernel, a graphene box and carbon nanotubes;
the graphene boxes are arranged on the surface of the carbon fiber in an array manner;
the sulfur kernel is positioned inside the graphene box;
the carbon nano tube is positioned on the surface of the graphene box and is bonded with the graphene box in a C-C bonding mode.
The second aspect of the present invention provides a method for preparing a C/G/CNT-S anode material, comprising the steps of:
step A: uniformly mixing soluble salt of transition metal, a catalytic growth source, a chelating agent and a pH value regulator to obtain a first solution;
and (B) step (B): pouring the first solution into a container in which carbon fiber cloth is placed, transferring the container to a reaction kettle for reaction to obtain G@ metal compound;
step C: transferring the G@ metal composite to a single-temperature zone tube furnace, heating up under a protective gas atmosphere, and introducing carbon source gas to grow graphene to obtain a C/G@ metal composite;
step D: the C/G@ metal compound is respectively treated by acid and alkali and then dried, and then treated by CO 2 And N 2 Heat treatment under mixed atmosphere, acid water bath treatment, washing and secondary drying to obtain C/G/CNT;
step E: uniformly scattering sulfur powder on the surface of the C/G/CNT, and preserving heat in an inert atmosphere to obtain the C/G/CNT-S negative electrode material.
Optionally, the soluble salt of a transition metal comprises a soluble salt of nickel.
Preferably, the soluble salt of nickel comprises at least one of nickel nitrate, nickel chloride and nickel sulfate.
Preferably, the catalytic growth source comprises ferric nitrate.
Preferably, the chelating agent comprises 5-sulfosalicylic acid.
Preferably, the pH adjustor comprises at least one of urea, sodium hydroxide, and ammonia.
Optionally, the mole ratio of the soluble salt of the transition metal, the catalytic growth source and the pH adjustor is 4: (0.2-1.5): (0.8-4.5).
Preferably, the chelating agent is added in an amount that is the sum of the moles of the soluble salt of the transition metal and the catalytic growth source.
Alternatively, in step B, the temperature of the reaction is 80 ℃ to 150 ℃.
Preferably, in step B, the reaction time is from 4h to 24h.
Preferably, step B further comprises washing after the reaction and drying again to obtain the metal composite.
Preferably, the temperature of the re-drying is 60 ℃ to 100 ℃.
Optionally, in the step C, the heating rate is 2 ℃/min-5 ℃/min.
Preferably, the temperature after the temperature rise is 900 ℃ to 1100 ℃.
Preferably, the carbon source gas comprises ethylene.
Preferably, the carbon source gas is introduced at a rate of 200ml/min to 500ml/min.
Preferably, the graphene is grown for a period of 10min-30min.
Optionally, in step D, the temperature of the heat treatment is 700 ℃ to 900 ℃.
Preferably, the time of the heat treatment is 0.2h to 1h.
Optionally, in step E, the temperature of the incubation is 130 ℃ to 200 ℃.
Preferably, in the step E, the time of heat preservation is 12-24 hours.
Alternatively, in step E, the acid water bath treatment is performed using HCI solution.
Preferably, the HCI solution has a concentration of 0.5M to 2M.
Preferably, the acid water bath treatment time is 0.5h-2h.
The third aspect of the invention provides the application of the C/G/CNT-S anode material in a lithium ion battery.
Compared with the prior art, the invention has at least the following beneficial effects:
in the C/G/CNT-S negative electrode material provided by the invention, the carbon fiber provides a load substrate for the growth of the graphene box structure, which is beneficial to the growth of the graphene box structure; the graphene box is used as a buffer space for volume expansion in the sulfur cathode charging and discharging process, so that crushing and collapse caused by insufficient volume expansion space of sulfur are prevented; the sulfur is positioned in the graphene box, and the graphene box provides compact outer layer protection for the sulfur, so that the sulfur is effectively prevented from falling off; the graphene box is bonded with the carbon nano tube to form a stable structure, so that the conductivity of the anode material is improved. The integrated C/G/CNT-S anode material perfectly builds a 3D conductive network, improves the conductivity and stability of the whole anode material, and further improves the electrical property.
According to the preparation method of the C/G/CNT-S anode material, the material is obtained through the strategies of template establishment, growth and template etching. The preparation method is continuous in process, high in controllability, capable of accurately regulating and controlling the graphene box-shaped structure, capable of realizing fit coating of sulfur, easy to popularize and beneficial to large-scale industrial production.
The C/G/CNT-S negative electrode material provided by the invention contributes to the extremely high volume specific capacity of the lithium ion battery, so that the volume energy density of the lithium ion battery is greatly improved, and the lithium ion battery is smaller. And the obtained lithium ion battery has high reversible specific capacity and good capacity retention rate, and is suitable for large-scale popularization and use.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a carbon fiber substrate provided for LDHs growth in example 1;
FIG. 2 is a drawing of Fe-doped alpha-Ni (OH) grown on a carbon fiber-supported substrate of example 1 2 An LDHs template of (c);
FIG. 3 is a sample of C-G@FeNi-LDHs grown with graphene of example 1;
FIG. 4 is a sample of C-G-CNTs after etching of LDHs templates in example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. The components of embodiments of the present invention may be arranged and designed in a wide variety of different configurations.
The first aspect of the invention provides a C/G/CNT-S anode material, which comprises carbon fiber, a sulfur kernel, a graphene box and carbon nanotubes;
the graphene boxes are arranged on the surface of the carbon fiber in an array manner;
the sulfur kernel is positioned inside the graphene box;
the carbon nano tube is positioned on the surface of the graphene box and is bonded with the graphene box in a C-C bonding mode.
In the C/G/CNT-S negative electrode material provided by the invention, the carbon fiber provides a load substrate for the growth of the graphene box structure, which is beneficial to the growth of the graphene box structure; the graphene box is used as a buffer space for volume expansion in the sulfur cathode charging and discharging process, so that crushing and collapse caused by insufficient volume expansion space of sulfur are prevented; the sulfur is positioned in the graphene box, and the graphene box provides compact outer layer protection for the sulfur, so that the sulfur is effectively prevented from falling off; the graphene box is bonded with the carbon nano tube to form a stable structure, so that the conductivity of the anode material is improved. The integrated C/G/CNT-S anode material perfectly builds a 3D conductive network, improves the conductivity and stability of the whole anode material, and further improves the electrical property.
The second aspect of the present invention provides a method for preparing a C/G/CNT-S anode material, comprising the steps of:
step A: uniformly mixing soluble salt of transition metal, a catalytic growth source, a chelating agent and a pH value regulator to obtain a first solution;
the soluble salts of transition metals are chosen because graphene generally requires a relatively smooth substrate for growth, preferably in the form of micrometer or submicron sheets of a certain thickness, and the substrate structure cannot be stacked layer by layer to fully utilize its growth area. The soluble salt of the transition metal and the catalytic growth source can generate transition metal double hydroxide under the action of the pH value regulator.
The transition metal double hydroxide generally presents a lamellar structure, the surface is smooth and fine, and lamellar transition metal hydroxide (LDHs) is an ideal substrate for growing box-shaped graphene micro-sheets. The LDHs material is simple to prepare, the metal source can be widely selected, and meanwhile, carbon nano-particles can be obtained on the surface of the LDHs by doping an iron source to obtain a catalytic site for the growth of the CNTs. Since the iron source for the catalytic growth of the CNT tube tends to have a small size, which is difficult to maintain thermal stability under high temperature conditions, the present invention obtains the iron catalytic source for the in-situ catalytic growth of the thermally stable CNT of a small size by doping recombination. Common LDHs are mainly prepared by hydrothermal methods, and samples are generated in a precipitated form, which often makes it difficult to obtain regularly-grown samples.
And (B) step (B): pouring the first solution into a container with carbon fiber cloth, and transferring the container to a reaction kettle for reaction to obtain the G@ metal compound.
In some embodiments of the present invention, the carbon fiber cloth preferably has a thickness of 1 μm to 50 μm, and is pre-treated and reused. During pretreatment, immersing the carbon fiber cloth in a nitric acid solution, pretreating for 0.5-5h at 60-150 ℃, and then washing with deionized water for multiple times until the pH value is neutral. The method aims at removing organic impurities on the surface of the carbon fiber cloth and activating the carbon fiber cloth, so that the carbon fiber cloth has better loading capacity and helps nucleation and vertical growth of LDHs materials. Compared with the traditional substrate-free hydrothermal preparation process, the carbon fiber cloth pretreated by nitric acid can obtain the vertically grown LDHs which are orderly arranged.
G@ metal composite is a micron LDHs vertically grown on the surface array of carbon fiber cloth.
Step C: transferring the G@ metal composite to a single-temperature zone tube furnace, heating in a protective gas atmosphere, and introducing carbon source gas to grow graphene to obtain the C/G@ metal composite.
In some embodiments of the present invention, the shielding gas is typically, but not limited to, nitrogen or argon.
The C/G@ metal complex is a substance with graphene grown on the surface of LDHs.
Step D: the C/G@ metal compound is respectively treated by acid and alkali and then dried, and then treated by CO 2 And N 2 And carrying out heat treatment, acid water bath treatment, washing and secondary drying under the mixed atmosphere to obtain the C/G/CNT.
The C/G@ metal complex is subjected to acid-base treatment for removing alpha-Ni (OH) 2 And (5) a template.
CO 2 And N 2 The heat treatment and the secondary acid-base treatment in the mixed atmosphere are used for generating residual Fe catalytic source by the CNT。
Step E: uniformly scattering sulfur powder on the surface of the C/G/CNT, and preserving heat in an inert atmosphere to obtain the C/G/CNT-S negative electrode material.
The purpose of step E is to allow sulfur to penetrate into the interior of the box-shaped graphene micro-sheet through hot melt diffusion, so that the method has more ideal coating property compared with the traditional load.
According to the preparation method of the C/G/CNT-S anode material, the material is obtained through the strategies of template establishment, growth and template etching. The preparation method is continuous in process, high in controllability, capable of accurately regulating and controlling the graphene box-shaped structure, capable of realizing fit coating of sulfur, easy to popularize and beneficial to large-scale industrial production.
Optionally, the soluble salt of a transition metal comprises a soluble salt of nickel.
Preferably, the soluble salt of nickel comprises at least one of nickel nitrate, nickel chloride and nickel sulfate.
Nickel hydroxide alpha-Ni (OH) 2 The LDHs template which is vertically grown on the surface of the carbon fiber cloth in an array arrangement manner can be obtained through carrying nucleation growth on the surface of the pretreated carbon fiber cloth in a nano sheet structure of a thin layer, and meanwhile, ni is also a good catalytic source for graphene growth.
Preferably, the catalytic growth source comprises ferric nitrate.
As a catalytic growth source, ferric nitrate promotes the in-situ growth of Carbon Nanotubes (CNT), and Fe is doped in the hydroxide alpha-Ni (OH) of nickel 2 Doping is carried out on the graphene/carbon nano tube composite material to obtain a small-size thermally stable CNT catalytic growth source, and an ideal 3D conductive network is built for the subsequent graphene/carbon nano tube composite material.
Preferably, the chelating agent comprises 5-sulfosalicylic acid.
5-sulfosalicylic acid is used as a chelating agent for the growth of LDHs because 5-sulfosalicylic acid can form complexes with transition metal ions and metal ions in the catalytic growth source in aqueous solution.
Preferably, the pH adjustor comprises at least one of urea, sodium hydroxide, and ammonia.
In a preferred embodiment of the invention, the pH adjustor is urea, as urea can hydrolyze under high temperature conditions to produce ammonia, which can provide an alkaline environment for LDHs growth. Meanwhile, as the urea hydrolysis reaction is very slow, the supersaturation degree of LDHs crystallization and precipitation is very low, the nucleation speed of LDHs is slow, the crystallization degree of LDHs materials is improved, the LDHs template with micron/submicron-level large sheet diameter is obtained, and the sheet diameter of the LDHs template is easy to control.
Optionally, the mole ratio of the soluble salt of the transition metal, the catalytic growth source and the pH adjustor is 4: (0.2-1.5): (0.8-4.5).
In some embodiments of the invention, the molar ratio of the soluble salt of the transition metal, the catalytic growth source, and the pH adjuster is typically, but not limited to, 4:0.2:0.8, 4:0.2:4.5, 4:1.5:0.8, 4:1.5:4.5, 4:0.8:0.8, 4:0.8:4.5, 4:0.8:2.5, or 4:0.8:2.5.
In some embodiments of the invention, microstructures of different morphologies can be obtained by adjusting the type and addition ratio of the soluble salts of the transition metals and the catalytic growth source.
Preferably, the chelating agent is added in an amount that is the sum of the moles of the soluble salt of the transition metal and the catalytic growth source.
Alternatively, in step B, the temperature of the reaction is 80 ℃ to 150 ℃.
In some embodiments of the invention, the temperature of the reaction is typically, but not limited to, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, or 150 ℃.
Preferably, in step B, the reaction time is from 4h to 24h.
In some embodiments of the invention, the time of the reaction is typically, but not limited to, 4h, 8h, 12h, 16h, 20h, or 24h.
Preferably, step B further comprises washing after the reaction and drying again to obtain the metal composite.
Preferably, the temperature of the re-drying is 60 ℃ to 100 ℃.
The post-reaction washing is to remove the reaction residues remaining on the surface of the LDHs template. In some embodiments of the present invention, the temperature of the redrying is typically, but not limited to, 60 ℃, 70 ℃,80 ℃, 90 ℃, or 100 ℃.
Optionally, in the step C, the heating rate is 2 ℃/min-5 ℃/min.
In some embodiments of the invention, the rate of temperature increase is typically, but not limited to, 2 ℃/min, 3 ℃/min, 4 ℃/min, or 5 ℃/min.
Preferably, the temperature after the temperature rise is 900 ℃ to 1100 ℃.
In some embodiments of the present invention, the post-warming temperature is typically, but not limited to, 900 ℃, 1000 ℃, or 1100 ℃.
Preferably, the carbon source gas comprises ethylene.
Carbon atoms in the carbon source gas have high solubility in Ni, when graphene grows on a Ni substrate, a large amount of carbon atoms are dissolved in Ni and randomly distributed in Ni at high temperature, and when the temperature is reduced, the carbon atoms are precipitated at the grain boundary of Ni, then nucleate and grow on the surface of hydroxide to form graphene block-shaped areas, and the block-shaped areas are mutually connected with each other along with the extension of the growth time to generate single-layer or multi-layer graphene.
Preferably, the carbon source gas is introduced at a rate of 200ml/min to 500ml/min.
In some embodiments of the invention, the carbon source gas is typically, but not limited to, introduced at a rate of 200ml/min, 300ml/min, 400ml/min, or 400ml/min.
Preferably, the graphene is grown for a period of 10min-30min.
Optionally, in step D, the temperature of the heat treatment is 700 ℃ to 900 ℃.
In some embodiments of the invention, in step D, the temperature of the heat treatment is typically, but not limited to, 700 ℃,800 ℃, or 900 ℃.
Preferably, the time of the heat treatment is 0.2h to 1h.
Optionally, in step E, the temperature of the incubation is 130 ℃ to 200 ℃.
In some embodiments of the invention, in step E, the temperature of the incubation is typically, but not limited to 130 ℃, 170 ℃ or 200 ℃.
Preferably, in the step E, the time of heat preservation is 12-24 hours.
Alternatively, in step E, the acid water bath treatment is performed using HCI solution.
The acid water bath treatment is to dissolve alpha-Ni (OH) 2 And (5) a template.
Preferably, the HCI solution has a concentration of 0.5M to 2M.
Preferably, the acid water bath treatment time is 0.5h-2h.
The third aspect of the invention provides the application of the C/G/CNT-S anode material in a lithium ion battery.
The C/G/CNT-S negative electrode material provided by the invention contributes to the extremely high volume specific capacity of the lithium ion battery, so that the volume energy density of the lithium ion battery is greatly improved, and the lithium ion battery is smaller. And the obtained lithium ion battery has high reversible specific capacity and good capacity retention rate, and is suitable for large-scale popularization and use.
Some embodiments of the present invention will be described in detail below with reference to examples. The following embodiments and features of the embodiments may be combined with each other without conflict.
Example 1
The embodiment provides a C/G/CNT-S negative electrode material, which comprises the following specific steps:
1) Selecting carbon fiber cloth with the thickness of 5 mu m as a load substrate, as shown in fig. 1, firstly, preprocessing the carbon fiber cloth: immersing the carbon fiber cloth in a nitric acid solution, pretreating for 1h at 80 ℃, and then washing with deionized water for multiple times until the pH value is neutral.
2) The soluble salt of transition metal is Ni (NO) 3 ) 2 ·6H 2 O, the catalytic growth source is Fe (NO) 3 ) 3 ·9H 2 The chelating agent is 5-sulfosalicylic acid and the pH value regulator is urea.
3) According to the mole ratio of 4:0.8 ratio Ni (NO) was added to 500ml deionized water containing 20% urea by mass 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 O powder, adding 4.8 mol of 5-sulfosalicylic acid dihydratel, using magnetic stirring at 50 ℃ to stir and dissolve the solute.
4) Cutting a proper amount of the carbon fiber cloth obtained in the step 1) and placing the carbon fiber cloth at the bottom of a polytetrafluoroethylene lining, pouring the solution obtained in the step 3) into the polytetrafluoroethylene lining, transferring the polytetrafluoroethylene lining to a reaction kettle, reacting for 15 hours at 100 ℃, washing the carbon fiber cloth with deionized water and ethanol for multiple times after the reaction is finished, and drying the carbon fiber cloth in an oven at 80 ℃ to obtain the G@FeNi-LDHs material, as shown in figure 2.
5) Transferring the G@FeNi-LDHs obtained in the step 4) into a single temperature zone tube furnace, heating to the growth temperature of 980 ℃ at the heating rate of 5 ℃ per minute under the nitrogen atmosphere, and introducing 300ml/min of C after the temperature is stable 2 H 4 And (3) growing the carbon source gas for 10min, and after the reaction is finished, closing heating to naturally cool the carbon source gas to room temperature in an inert atmosphere to obtain the C/G@FeNi-LDHs material, as shown in figure 3.
6) The C/G@FeNi-LDHs material was treated with a 1M HCI solution at 80℃for 2 hours and a 5M NaOH solution in a water bath for 1 hour, then transferred to an 80℃oven for drying, and then the obtained sample was subjected to a CO gas treatment at a volume ratio of 1:4 2 /N 2 And (3) carrying out heat treatment at 800 ℃ for 30min under the atmosphere, and finally, carrying out water bath treatment in a 1M HCI solution for 1h, and then washing and drying by using deionized water to obtain a purified C/G/CNT sample. Fig. 4 is a sample of C-G-CNTs left on a carbon fiber substrate after etching, and a collapse phenomenon occurs to some extent due to the loss of LDHs template support.
7) Uniformly spraying sulfur powder on the surface of a C/G/CNT sample, preserving heat for 20 hours in an inert atmosphere at 160 ℃, and naturally cooling to room temperature to obtain the C/G/CNT-S negative electrode sample.
Example 2
The present embodiment provides a C/G/CNT-S negative electrode material, which is different from embodiment 1 in that the pH adjustor is NaOH, and the remaining raw materials and steps are the same as those of embodiment 1, and are not described herein.
As can be seen from a scanning electron microscope, the grown LDHs are formed by the nano-sheets with the sheet diameters of about 200-500nm to form the flower-shaped secondary particles, which is attributable to the large quantity of LDHs nucleating during the auxiliary growth of NaOH, the high nucleating speed and difficulty in obtaining the LDHs with large sheet diameters.
Example 3
The present embodiment provides a C/G/CNT-S negative electrode material, which is different from embodiment 1 in that the pH adjustor is ammonia water, and the other raw materials and steps are the same as those of embodiment 1, and are not described herein.
As can be seen from a scanning electron microscope, the grown LDHs are focused on the surface of the carbon fiber cloth by nano sheets with the sheet diameter of about 0.8-1 mu m, and the key factors influencing the size of the LDHs sheets due to the adjustment of the pH value of the solution can be obviously found in comparative examples 1 and 2, and are also the key factors for controlling the growth speed of the LDHs template.
Example 4
The difference between the present embodiment and embodiment 1 is that in step 1), the carbon fiber cloth is not required to be pretreated with nitric acid, and is simply cleaned with absolute ethyl alcohol, and the other raw materials and steps are the same as those in embodiment 1, and are not described herein.
The scanning electron microscope can show that the LDHs has lower load density on the surface of the carbon fiber cloth, and a partial vacuum zone exists on the surface of the carbon fiber cloth, which can be attributed to the activation of the carbon fiber cloth by the pretreatment of nitric acid, enhance the load capacity and facilitate the nucleation and the growth of the LDHs on the surface of the carbon fiber cloth.
Example 5
This example provides a C/G/CNT-S negative electrode material, unlike example 1, in step 3), ni (NO 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 The molar ratio of the O powder is 4:0.2, the sulfosalicylic acid dihydrate is 4.2mol, and the other raw materials and steps are the same as those of the example 1, and are not repeated here.
Example 6
This example provides a C/G/CNT-S negative electrode material, unlike example 1, in step 3), ni (NO 3 ) 2 ·6H 2 O and Fe (NO) 3 ) 3 ·9H 2 The molar ratio of the O powder is 4:1.5, the sulfosalicylic acid dihydrate is 5.5mol, and the other raw materials and steps are the same as those of the example 1, and are not repeated here.
Example 7
The present embodiment provides a method ofThe C/G/CNT-S anode material is different from example 1 in that in the step 2), the soluble salt of the transition metal is CuSO 4 The remaining raw materials and steps are the same as in example 1, and are not described in detail herein.
The result shows that the carbon dissolution capability of Cu is very weak, copper is used as a growth catalytic source, the growth speed of graphene is slow, the number of layers is mostly single, and the stable graphene box is not easy to construct.
Comparative example 1
The comparative example provides a common graphene/sulfur composite anode, which has a simple structure that graphene is composited with sulfur, and the preparation process is the same as that of the sulfur doping process of the embodiment 1, wherein the used graphene is purchased from the sixth element in Changzhou.
Comparative example 2
This comparative example provides a C/G/CNT-S anode material, unlike example 1, in which the catalytic growth source is Co (NO 3 ) 2 ·6H 2 O, the rest of the raw materials and steps are the same as in example 1, and are not described in detail here.
From a scanning electron microscope, the sample only grows graphene on the surface of LDHs, and the built 3D conductive network is not ideal because of no CNT which grows transversely.
Comparative example 3
This comparative example provides a C/G/CNT-S negative electrode material, differing from example 1 in that step 5) has a growth temperature of 900 ℃, and the other steps are the same as example 1. The results show that only a small amount of graphene domains grow on the surface of the LDHs, and do not grow into a coated closed graphene box.
Test example 1
The C/G/CNT-S negative electrode samples obtained in examples 1 to 7 and the general graphene/sulfur composite negative electrode provided in comparative example 1 were directly cut into a wafer (wafer diameter 12 mm) as a negative electrode, and a button half cell was assembled to perform a 0.5C charge-discharge test and a 1C cycle 100-week capacity retention test, and the data obtained by the test are shown in table 1 below.
TABLE 1 charge and discharge test results
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (10)

1. The C/G/CNT-S negative electrode material is characterized by comprising carbon fibers, a sulfur core, a graphene box and carbon nanotubes;
the graphene boxes are arranged on the surface of the carbon fiber in an array manner;
the sulfur kernel is positioned inside the graphene box;
the carbon nano tube is positioned on the surface of the graphene box and is bonded with the graphene box in a C-C bonding mode;
the preparation method of the C/G/CNT-S anode material comprises the following steps:
step A: uniformly mixing soluble salt of transition metal, a catalytic growth source, a chelating agent and a pH value regulator to obtain a first solution;
wherein the soluble salt of a transition metal comprises a soluble salt of nickel; the soluble salt of nickel comprises at least one of nickel nitrate, nickel chloride and nickel sulfate;
the catalytic growth source comprises ferric nitrate;
the chelating agent comprises 5-sulfosalicylic acid;
the pH regulator comprises urea;
the mole ratio of the soluble salt of the transition metal, the catalytic growth source and the pH value regulator is 4: (0.2-1.5): (0.8-4.5), wherein the addition amount of the chelating agent is the sum of the mole numbers of the soluble salt of the transition metal and the catalytic growth source;
and (B) step (B): immersing the carbon fiber cloth in a nitric acid solution, pretreating for 0.5-5 hours at 60-150 ℃, and then washing with deionized water for multiple times until the pH value is neutral to obtain pretreated carbon fiber cloth; pouring the first solution into a container in which the pretreated carbon fiber cloth is placed, transferring the container to a reaction kettle, and reacting for 4-24 hours at 80-150 ℃ to obtain a G@ metal compound, wherein the G@ metal compound is micron layered transition metal double hydroxide vertically grown on the surface array of the pretreated carbon fiber cloth;
step C: transferring the G@ metal compound to a single-temperature-zone tube furnace, heating to 980-1100 ℃ at a heating rate of 2-5 ℃/min under a protective gas atmosphere, and introducing carbon source gas to grow graphene for 10-30 min to obtain a C/G@ metal compound;
wherein the carbon source gas comprises ethylene; the carbon source gas is introduced at a rate of 200ml/min-500ml/min;
step D: the C/G@ metal compound is respectively treated by acid and alkali and then dried, and then treated by CO 2 And N 2 Heat treatment under mixed atmosphere, acid water bath treatment, washing and secondary drying to obtain C/G/CNT;
step E: uniformly scattering sulfur powder on the surface of the C/G/CNT, and preserving heat at 130-200 ℃ in an inert atmosphere to obtain the C/G/CNT-S anode material.
2. The C/G/CNT-S negative electrode material according to claim 1, wherein step B further comprises post-reaction washing and re-drying to obtain a metal composite.
3. The C/G/CNT-S negative electrode material according to claim 2, wherein the re-drying temperature is 60 ℃ to 100 ℃.
4. The C/G/CNT-S negative electrode material according to claim 1, wherein in step D, the temperature of the heat treatment is 700 ℃ to 900 ℃.
5. The C/G/CNT-S negative electrode material according to claim 1, wherein in step D, the time of the heat treatment is 0.2h to 1h.
6. The C/G/CNT-S negative electrode material according to claim 1, wherein in step E, the incubation time is 12h-24h.
7. The C/G/CNT-S negative electrode material according to claim 1, wherein in step E, the acid water bath treatment is performed using HCl solution.
8. The C/G/CNT-S negative electrode material according to claim 7, wherein the HCl solution has a concentration of 0.5M-2M.
9. The C/G/CNT-S negative electrode material according to claim 1, wherein the acid water bath treatment time is 0.5h-2h.
10. Use of the C/G/CNT-S negative electrode material according to any one of claims 1-9 in a lithium ion battery.
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