CN108155350A - A kind of functionalization graphene composite material and its preparation method and application - Google Patents

Abstract

The present invention provides a kind of functionalization graphene composite materials, including graphene nanometer sheet, vertical-growth in the carbon nano pipe array of the graphene nano on piece, and by graphene nanometer sheet polyelectrolyte crosslinked together, by the way that π is pi-conjugated, one or more of chemical bond, hydrogen bond, Van der Waals force active force connect between the graphene nanometer sheet and the polyelectrolyte.The functionalization graphene composite material can be used as lithium battery system cathode protection materials; the effect of artificial SEI films can be functioned similarly to by being coated on the surface of lithium battery system negative electrode active material, improved the cyclical stability of cathode pole piece, extended battery；And the formation of Li dendrite can effectively be avoided by being coated on lithium anode surface, and then the phenomenon that prevent battery short circuit and coulombic efficiency from reducing.The present invention also provides the preparation method and application of the functionalization graphene composite material.

Description

A kind of functionalized graphene composite material and its preparation method and application

technical field

The invention relates to the technical field of lithium batteries, in particular to a functionalized graphene composite material and a preparation method and application thereof.

Background technique

With the research and development of the lithium battery system, people hope to ensure that the battery has a long cycle life and high rate charge and discharge performance while obtaining a leap in battery energy density. Existing metal lithium negative electrodes of lithium batteries and negative electrode active materials of lithium ion batteries are often accompanied by volume expansion of the pole piece after lithium intercalation, resulting in instability of the SEI film on the surface of the material. Due to the repeated generation and rupture of SEI, it will cause a large loss of electrolyte and excessive irreversible capacity loss, which greatly limits the improvement of battery cycle life. Therefore, the research on the protection of the negative electrode of the lithium battery system is very important for the improvement of the battery performance.

At present, some people use highly stable graphene materials to coat the negative electrode active material to improve the stability of the SEI film on the surface of the negative electrode active material and effectively improve the cycle of the electrode sheet. However, for high-expansion lithium-ion battery anode active materials such as silicon, such surface modification cannot satisfy the stability of the material in its highly-expanded state. Therefore, it is necessary to design an artificial SEI protective layer for the negative electrode active material of the lithium battery system with certain elasticity, so as to isolate the direct contact between the negative electrode active material and the electrolyte, and to meet the requirement that the negative electrode active material is still completely intact under the high lithium intercalation expansion state. It is coated in the artificial SEI shell to improve the cycle stability of the material. At the same time, the elastic artificial SEI protective layer should have high electrical conductivity and mechanical stability, so as to avoid excessive internal resistance of the pole piece caused by traditional elastic polymer coating.

Contents of the invention

In view of this, the first aspect of the present invention provides a functionalized graphene composite material, the functionalized graphene composite material coated on the surface of the negative electrode active material of the lithium battery system can play a role similar to an artificial SEI film, and improve the performance of the negative electrode. The cycle stability of the sheet can prolong the service life of the battery; and the coating on the surface of the metal lithium negative electrode can effectively avoid the formation of lithium dendrites, thereby preventing the short circuit of the battery and the decrease of the Coulombic efficiency.

Specifically, in the first aspect, the present invention provides a functionalized graphene composite material, comprising graphene nanosheets, carbon nanotube arrays vertically grown on the graphene nanosheets, and intersecting the graphene nanosheets The polyelectrolytes linked together, the graphene nanosheets and the polyelectrolytes are connected by one or more of π-π conjugation, chemical bonds, hydrogen bonds, and van der Waals forces.

Wherein, the graphene nanosheet and the carbon nanotube array form a graphene/carbon nanotube three-dimensional structure composite, and the mass ratio of the graphene/carbon nanotube three-dimensional structure composite to the polyelectrolyte is 1 -10:1.

The graphene nanosheets are single-layer or multi-layer graphene with a thickness of 5nm-500nm.

The height of the carbon nanotube array is 500nm-4μm.

The polyelectrolyte includes one or more of cationic polyelectrolyte, anionic polyelectrolyte, amphoteric polyelectrolyte and polyelectrolyte complex.

More specifically, the polyelectrolyte includes protein, nucleic acid, gum, modified starch, modified cellulose, polyacrylic acid, sodium polyacrylate, polyacrylamide, polymethacrylic acid, polymaleic anhydride, polymetaphosphoric acid, poly Ethylene oxide, polyvinylamine, polyvinylpyridine, polyvinylpyrrolidone, sodium polystyrenesulfonate, diethylene glycol diacrylate phthalate, polyethylenesulfonic acid, polyethyleneimine, amino acids, natural nucleic acids and poly One or more of dimethyl diallyl ammonium chloride.

The functionalized graphene composite material provided by the first aspect of the present invention has graphene nanosheets as the main body, and carbon nanotube arrays are vertically grown on the surface of the graphene nanosheets, and the graphene nanosheets are elastically cross-linked by polyelectrolyte. The functionalized graphene composite material can be used as the negative electrode protection material of the lithium battery system, and is coated on the surface of the negative electrode active material or the surface of the metal lithium negative electrode. Among them, graphene and carbon nanotubes can provide efficient and fast electron conduction for the electrode as a whole, polyelectrolyte It can provide a transfer channel for Li ⁺ diffusion, and by using the "bridging" effect of polyelectrolyte between graphene nanosheets, the coated negative electrode active material can be expanded even if graphene nanosheets and Relative sliding occurs between the sheets, but they can still be tightly connected into a dense film layer, so that the coated negative electrode active material does not come into contact with the electrolyte, and even if the structure collapses and pulverizes, it is still completely wrapped in the functionalized graphene composite. In the material protection layer, without losing the effective electrical contact with the conductive network, thereby improving the cycle stability of the electrode as a whole.

Second aspect, the present invention provides a kind of preparation method of functionalized graphene composite material, comprises the following steps:

Graphene nanosheets with carbon nanotube arrays grown vertically on the surface are prepared by chemical vapor deposition to obtain a graphene/carbon nanotube three-dimensional structure composite;

The graphene/carbon nanotube three-dimensional structure composite is ultrasonically dispersed in water to obtain a dispersion liquid, and the dispersion liquid is mixed and stirred with a polyelectrolyte aqueous solution for 0.5-3 hours, and then centrifuged and washed, and the obtained precipitate is functionalized graphite vinyl composites.

In the present invention, the preparation process of the graphene/carbon nanotube three-dimensional structure composite is specifically:

Taking the metal catalyst, spraying the metal catalyst evenly on the substrate, placing the substrate in the center of a horizontal quartz tube, and then placing the quartz tube in a tube furnace for heating;

Pass argon and hydrogen into the tube furnace, and after _the temperature in the furnace rises to 500°C-1000°C, introduce reaction gas _C2H4 to react for 10min-100min, so as to vertically grow carbon nanotubes on the substrate array;

The gas flow is changed to argon and heated to 500°C-1000°C, and the reaction gas _CH is introduced into the tube furnace for 10min-100min to generate horizontal graphene nanosheets between vertically grown carbon nanotube arrays, namely Obtain the crude product of graphene/carbon nanotube three-dimensional structure composite;

After the reaction, cool the tube body, take out the crude product, and treat the crude product with 1mol/L-10mol/L HCl aqueous solution at 50°C-150°C for 5h-24h, and then use 1mol/L-10mol/L The HF aqueous solution of L is treated at 50°C-150°C for 5h-24h to obtain the graphene/carbon nanotube three-dimensional structure composite.

Specifically, the metal catalysts include Cu, Al, Fe, Mo, Co, Ni, Ti, V, Cr, Mn, Zn, Ag, Pt, Au, Hg catalysts, and two or more of the above components One or more of the multimetallic catalysts.

The flow rate of the argon gas is 150mL/min, the flow rate of the hydrogen gas is 100-200mL/min, the flow rate of _{the C2H4} is 10-100mL/min; the flow rate of the _CH4 is 100-200mL/min .

In addition, the present invention also provides a lithium battery system negative electrode material, including a negative electrode active material and a functionalized graphene composite material coated on the surface of the negative electrode active material, the lithium battery system negative electrode material has a core-shell structure, the The functionalized graphene composite material is the functionalized graphene composite material according to the first aspect of the present invention, and the lithium battery system negative electrode material is a lithium ion battery negative electrode material or a lithium polymer battery negative electrode material. The functionalized graphene composite material is connected to the negative electrode active material through one or more of π-π conjugation, chemical bond, hydrogen bond, and van der Waals force.

Wherein, the mass ratio of the functionalized graphene composite material to the negative electrode active material is 1:1-100.

The present invention also provides a lithium battery system negative electrode sheet, including a current collector and a negative electrode material loaded on the current collector, the negative electrode material is the above-mentioned lithium battery system negative electrode material of the present invention, and the lithium battery system negative electrode The pole piece is a negative pole piece of a lithium ion battery or a negative pole piece of a lithium polymer battery.

The present invention also provides a lithium metal negative electrode sheet, including a lithium metal sheet and a protective layer arranged on the surface of the lithium metal sheet, the material of the protective layer is the functionalized graphene composite described in the first aspect of the present invention Material.

Wherein, the mass ratio of the functionalized graphene composite material to the lithium metal sheet is 1:1-100.

And the present invention also provides a battery, which comprises the above-mentioned lithium battery system negative electrode sheet or lithium metal negative electrode sheet.

The advantages of the present invention will be partly clarified in the following description, and part of them will be obvious from the description, or can be known through the implementation of the embodiments of the present invention.

Description of drawings

Fig. 1 is the structural representation of the negative electrode material of lithium-ion battery prepared in embodiment 1 of the present invention;

Fig. 2 is the charge-discharge cycle performance test diagram of the lithium-ion button cell prepared in Example 1 of the present invention;

FIG. 3 is a test chart of the charge-discharge cycle performance of the metal lithium battery prepared in Example 2 of the present invention.

Detailed ways

The following descriptions are preferred implementations of the embodiments of the present invention. It should be pointed out that those skilled in the art can make some improvements and modifications without departing from the principles of the embodiments of the present invention. These improvements And retouching are also regarded as the scope of protection of the embodiments of the present invention.

An embodiment of the present invention provides a functionalized graphene composite material, including graphene nanosheets, carbon nanotube arrays vertically grown on the graphene nanosheets, and a polymer crosslinking the graphene nanosheets together. An electrolyte, the graphene nanosheet and the polyelectrolyte are connected by one or more of π-π conjugation, chemical bonds, hydrogen bonds, and van der Waals forces.

The functionalized graphene composite material provided by the embodiment of the present invention mainly uses graphene nanosheets as the main body, and carbon nanotube arrays are grown vertically on the surface of the graphene nanosheets, and the graphene nanosheets are elastically cross-linked by polyelectrolyte. The graphene composite material can be used as the negative electrode protection material of the lithium battery system, coated on the surface of the negative electrode active material of the lithium battery system or coated on the surface of the metal lithium negative electrode. In the functionalized graphene composite structure, graphene nanosheets grown with vertical carbon nanotube arrays are interlaced, which can provide an efficient and fast conductive network for the electrode as a whole, which is helpful to improve the battery rate performance; polyelectrolyte has ion-conducting properties. It can be used as a transfer channel for Li ⁺ to diffuse into the negative electrode active material, ensuring the rapid ion transfer efficiency of the system; at the same time, the polyelectrolyte has film-forming and cohesive properties, and functions as a functionalization between graphene nanosheets and sheets. The "bridge" function between the graphene composite material and the coated negative electrode active material, when the negative electrode active material undergoes lithium intercalation expansion, the relative sliding between the graphene nanosheets and the elastic crosslinking of the polyelectrolyte ensure that the negative electrode The active material is completely wrapped in the functionalized graphene composite film layer and will not be exposed to the electrolyte. Even if the negative active material is pulverized, it will not lose effective electrical contact with the conductive network, thus stabilizing the SEI film, Improve the coulombic efficiency of the pole piece and reduce the irreversible capacity loss. At the same time, graphene nanosheets have strong structural toughness and mechanical strength, which ensures the structural stability of the material during the cycle; when the functionalized graphene composite material is applied to the metal lithium anode protection, the graphene composite material forms The film can improve the uniformity of ion dispersion on the surface of the metal lithium negative electrode, effectively avoid the formation of lithium dendrites, and at the same time, the polyelectrolyte in the structure can also improve the interfacial fusion between the metal lithium and the electrolyte.

In the embodiment of the present invention, the graphene nanosheet and the carbon nanotube array form a graphene/carbon nanotube three-dimensional structure composite, and the mass of the graphene/carbon nanotube three-dimensional structure composite and the polyelectrolyte The ratio is 1-10:1. Further optionally, the mass ratio is 3-6:1.

The graphene nanosheets are single-layer or multi-layer graphene with a thickness of 5nm-500nm. Further optionally, the thickness is 50nm-200nm.

The height of the carbon nanotube array is 500nm-4μm. Further optionally, the height of the array is 1 μm-3 μm.

In the embodiment of the present invention, the polyelectrolyte includes one or more of cationic polyelectrolyte, anionic polyelectrolyte, amphoteric polyelectrolyte and polyelectrolyte complex. Polyelectrolytes can provide fast ion-electron transfer channels through their charged ions. The specific connection method between the polyelectrolyte and the graphene nanosheet depends on the specific structure of the polyelectrolyte. Depending on the structure, it can be connected by one or more of π-π conjugation, chemical bonds, hydrogen bonds, and van der Waals forces.

In the embodiment of the present invention, the polyelectrolyte includes protein, nucleic acid, gum, modified starch, modified cellulose, polyacrylic acid, sodium polyacrylate, polyacrylamide, polymethacrylic acid, polymaleic anhydride, polymetaphosphoric acid , polyethylene oxide, polyvinylamine, polyvinylpyridine, polyvinylpyrrolidone, sodium polystyrenesulfonate, diethylene glycol diacrylate phthalate, polyethylenesulfonic acid, polyethyleneimine, amino acid, natural nucleic acid and one or more of polydimethyldiallylammonium chloride.

The functionalized graphene composite material provided by the embodiment of the present invention is mainly based on graphene nanosheets, and carbon nanotube arrays are vertically grown on the surface of graphene nanosheets, and elastic crosslinking is achieved between graphene nanosheets through polyelectrolyte. The functionalized graphene composite material can be used as the negative electrode protection material of the lithium battery system, coated on the surface of the negative electrode active material or modified on the surface of the metal lithium negative electrode to improve the overall cycle stability of the electrode.

Correspondingly, the embodiment of the present invention also provides a method for preparing a functionalized graphene composite material, comprising the following steps:

S10, using a chemical vapor deposition method to prepare graphene nanosheets with carbon nanotube arrays vertically grown on the surface to obtain a graphene/carbon nanotube three-dimensional structure composite;

S20. Ultrasonic disperse the graphene/carbon nanotube three-dimensional structure compound into water to obtain a dispersion liquid, mix and stir the dispersion liquid with the polyelectrolyte aqueous solution for 0.5-3 hours, then centrifuge and wash, and the resulting precipitate is the function graphene composites.

In the embodiment of the present invention, in step S10, the preparation process of the graphene/carbon nanotube three-dimensional structure composite is specifically:

S11. Take the metal catalyst, spray the metal catalyst evenly on the substrate, place the substrate in the center of a horizontal quartz tube, and then place the quartz tube in a tube furnace for heating;

S12. Introduce argon and hydrogen into the tube furnace, and after _the temperature in the furnace rises to 500°C-1000°C, introduce reaction gas _C2H4 to react for 10min-100min, so as to vertically grow carbon on the substrate nanotube arrays;

S13. Change the gas flow to argon and heat it to 500°C-1000°C, introduce the reaction gas _CH4 into the tube furnace for 10min-100min to generate horizontal graphene nanosheets between the vertically grown carbon nanotube arrays , that is, the crude product of graphene/carbon nanotube three-dimensional structure composite is obtained;

S14. After the reaction is over, cool the tube body, take out the crude product, and treat the crude product with 1mol/L-10mol/L HCl aqueous solution at 50°C-150°C for 5h-24h, and then use 1mol/L- 10mol/L HF aqueous solution is treated at 50°C-150°C for 5h-24h to obtain the graphene/carbon nanotube three-dimensional structure composite.

In the embodiment of the present invention, in step S11, the metal catalyst includes Cu, Al, Fe, Mo, Co, Ni, Ti, V, Cr, Mn, Zn, Ag, Pt, Au, Hg catalyst, and the above two One or more of the multimetallic catalysts composed of one or more components. Alternatively, the substrate may be an alumina ceramic boat or the like.

In the embodiment of the present invention, in step S12, the flow rate of the argon gas is 150mL/min, the flow rate of the hydrogen gas is 100mL/min-200mL/min, and the flow rate of _{the C2H4} is 10mL/min-100mL/min min. Further optionally, the flow rate of the hydrogen is 120mL/min-160mL/min, and the flow rate of the C ₂ H ₄ is 50mL/min-80mL/min. Optionally, after the temperature in the furnace rises to 600°C-900°C, the reaction gas C ₂ H ₄ is introduced.

In the embodiment of the present invention, in step S13, the flow rate of the argon gas is 150 mL/min, and the flow rate of the CH ₄ is 100 mL/min-200 mL/min. Further optionally, the flow rate of the CH ₄ is 120mL/min-160mL/min. Optionally, after heating to 600°C-900°C, the reaction gas CH ₄ is introduced.

In the embodiment of the present invention, in step S20, the mass ratio of the graphene/carbon nanotube three-dimensional structure composite in the dispersion liquid to the polyelectrolyte in the polyelectrolyte aqueous solution is 1-10:1. Further optionally, the mass ratio is 3-6:1. The concentration of the dispersion liquid may be 1 mg/mL-2.5 mg/mL; the concentration of the polyelectrolyte aqueous solution may be 0.05 g/L-0.2 g/L. The washing is carried out with deionized water.

The preparation method of the functionalized graphene composite material provided by the embodiment of the present invention has a simple process and is beneficial to industrial production.

The functionalized graphene composite material provided by the embodiments of the present invention can be used for surface protection of lithium ion batteries and lithium polymer battery powder negative electrode active materials, and is especially suitable for solving the problem of lithium intercalation volume expansion of negative electrode active materials. Correspondingly, an embodiment of the present invention provides a lithium battery system negative electrode material, including a negative electrode active material and a functionalized graphene composite material coated on the surface of the negative electrode active material, and the lithium battery system negative electrode material has a core-shell structure, the functionalized graphene composite material is the functionalized graphene composite material provided above in the embodiment of the present invention, and the lithium battery system negative electrode material is a lithium ion battery negative electrode material or a lithium polymer battery negative electrode material. The functionalized graphene composite material is connected to the negative electrode active material through one or more of π-π conjugation, chemical bond, hydrogen bond, and van der Waals force.

In an embodiment of the present invention, the mass ratio of the functionalized graphene composite material to the negative electrode active material is 1:1-100. Further, the mass ratio is 1:1-25 or 1:30-80.

In the embodiment of the present invention, the functionalized graphene composite material can be modified on the negative electrode active material by one or more methods of liquid phase method, solid phase method, electrochemical method, sputtering method and spray drying method. surface. The specific operating parameters of the above method can be set according to specific conditions.

In the negative electrode material of the lithium battery system provided by the embodiment of the present invention, the functionalized graphene composite material is coated on the surface of the negative electrode active material, and the shell layer formed by the functionalized graphene composite material plays the role of an artificial SEI film on the surface of the negative electrode active material. , using the relative sliding between the high-toughness graphene sheets and the elastic cross-linking effect of the polyelectrolyte layer modified on the surface and edge of the graphene sheets, it can ensure that the core of the negative electrode active material is still completely covered in the functionalized layer after expansion. The interior of the graphene composite shell avoids excessive irreversible capacity loss caused by repeated contact with the electrolyte.

The embodiment of the present invention also provides a lithium battery system negative electrode sheet, including a current collector and a negative electrode material supported on the current collector, the negative electrode material is the lithium battery system negative electrode material provided above in the embodiment of the present invention, so The negative pole piece of the lithium battery system is a negative pole piece of a lithium ion battery or a negative pole piece of a lithium polymer battery.

The functionalized graphene composite material provided by the embodiments of the present invention can also be used for the protection of lithium metal anodes such as metal lithium batteries, lithium-sulfur batteries, and lithium-air batteries that use metal lithium as the anode. Since the surface of the metal lithium electrode has a huge volume expansion during the charging process, and the SEI film naturally formed on the surface is relatively brittle, when the SEI film breaks due to Li expansion, it will cause the growth of lithium dendrites at the defect, resulting in short circuit and lower battery life. Coulombic efficiency. However, coating the above-mentioned functionalized graphene composite material in the embodiment of the present invention on the surface of metal lithium can stabilize the SEI film layer and effectively solve the above problems.

Correspondingly, an embodiment of the present invention provides a lithium metal negative electrode sheet, including a lithium metal sheet and a protective layer disposed on the surface of the lithium metal sheet, the material of the protective layer is the functionalized graphite described above in the embodiment of the present invention vinyl composites. The functionalized graphene composite material is connected to the metal lithium sheet through one or more forces of π-π conjugation, chemical bond, hydrogen bond, and van der Waals force.

In an embodiment of the present invention, the mass ratio of the functionalized graphene composite material to the lithium metal sheet is 1:1-100. Further, the mass ratio is 1:20-50 or 1:50-100.

The lithium metal negative electrode sheet can be prepared in the following manner: the functionalized graphene composite material is dispersed in an NMP organic solvent to obtain a mixed slurry, and then the obtained mixed slurry is coated on the surface of the metal lithium sheet electrode, vacuum 50 Dry overnight at -65°C to obtain.

In addition, an embodiment of the present invention also provides a battery, which includes the above-mentioned lithium battery system negative electrode sheet or lithium metal negative electrode sheet. Wherein, the negative electrode sheet of the lithium battery system is a lithium ion battery or a lithium polymer battery; and the lithium metal negative electrode sheet is a metal lithium battery, a lithium air battery or a lithium sulfur battery. The battery provided by the embodiment of the present invention has good cycle stability.

The embodiments of the present invention will be further described below in several embodiments. Wherein, the embodiments of the present invention are not limited to the following specific embodiments. Within the scope of unchanging master rights, changes can be implemented as appropriate.

Example 1

A preparation method of functionalized graphene composite material, comprising the following steps:

S101: Using metal Fe/Mo as the reaction catalyst for the preparation of graphene/carbon nanotube three-dimensional structure composites by chemical vapor deposition (CVD), evenly spray the Fe/Mo catalyst into the porcelain boat, and place the porcelain boat on the horizontal quartz the center of the tube, heated in a tube furnace;

S102: Introduce Ar (150mL/min) and H ₂ (120mL/min) into the tube furnace. After the temperature rises to 750°C, introduce reaction gas C ₂ H ₄ (60mL/min) and react for 30min to form a vertical aligned carbon nanotube (CNT) arrays;

S103: Change the gas flow to Ar (150mL/min), heat to 950°C, change the reaction gas to CH ₄ (120mL/min), and pass it for 30min to generate horizontal graphene nanosheets between the vertical CNT arrays to obtain graphene / carbon nanotube three-dimensional structure composite crude product;

S104: After the reaction is completed, cool the tube body under the condition of continuous flow of Ar, and treat the crude product of the graphene/carbon nanotube three-dimensional structure composite with HCl (6.0mol/L) aqueous solution at 80°C for 12h, and then use HF to (6.0mol/L) aqueous solution was treated at 80°C for 12h to remove the catalyst component in the product to obtain a graphene/carbon nanotube three-dimensional structure composite (CNT/CNs);

S105: ultrasonically disperse the obtained graphene/carbon nanotube three-dimensional structure composite in 200mL deionized water to form a suspension with a concentration of 1mg/mL; ) aqueous solution was stirred and mixed for 30 minutes; after repeated centrifugation and washing, the supernatant was removed, and the precipitate obtained was the functionalized graphene composite material (CNT/CNs/PSS ternary composite).

Preparation of anode materials for lithium ion batteries

Surface modification of silicon-carbon composite powder materials for lithium-ion batteries using functionalized graphene composite materials: the silicon-carbon composite negative electrode material powder particles and CNT/CNs/PSS were dispersed in deionized water at a mass ratio of 10:1 , after mixing with ultrasound for 2 hours, filter under reduced pressure to remove water, and obtain a filter cake that is a CNT/CNs/PSS-coated silicon-carbon composite, and dry it under vacuum at 60°C overnight to obtain a negative electrode material product for lithium-ion batteries.

FIG. 1 is a schematic structural view of the lithium-ion battery negative electrode material prepared in Example 1 of the present invention. In the figure, 10 is the core of silicon-carbon composite anode material, 20 is the shell of functionalized graphene composite material (CNT/CNs/PSS ternary composite), 201 represents graphene nanosheets, 202 represents carbon nanotubes, and 203 represents polycarbonate electrolyte.

Li-ion battery preparation

Button battery production: the lithium-ion battery negative electrode material prepared above is according to the ratio of negative electrode material: conductive carbon black: styrene-butadiene rubber = 80:10:10, is coated with deionized water as a dispersant after stirring evenly on copper foil The surface of the current collector; after vacuum drying, sliced and weighed, it was assembled into a button battery in the environment of high-purity argon gas in a glove box with a metal lithium sheet as the counter electrode. Among them, the diaphragm is Celgard2400, and the electrolyte is 1M LiPF _6/ EC+PC+DEC+EMC (volume ratio 1:0.3:1:1) solution. The electrochemical test charge and discharge voltage window is 0.02-1.5V, and the environmental test temperature is 25±2°C.

Full battery production: 4.4V high-voltage lithium cobalt oxide is used as the positive electrode material, dispersed in NMP solvent according to the ratio of active material: conductive carbon black: PVDF = 80:10:10 and coated on the surface of aluminum foil, and used as the positive electrode after vacuum drying The above-mentioned silicon-carbon composite pole piece is used as the negative electrode, the electrolyte is 1M LiPF _6/ EC+PC+DEC+EMC (volume ratio 1:0.3:1:1), and the separator is PP/PE/PP three-layer separator ( The thickness is 16 μm), and assembled into a full battery in a glove box; the electrochemical test charge and discharge window of the full battery is 2.75-4.4V, and the environmental test temperature is 25±2°C.

Example 2

A preparation method of functionalized graphene composite material, comprising the following steps:

S201: Use metal Co as the reaction catalyst for the preparation of graphene/carbon nanotube three-dimensional structure composites by CVD, uniformly spray the Co catalyst into the porcelain boat, and place the porcelain boat in the center of the horizontal quartz tube, in the tube furnace heating;

S202: Introduce Ar (150mL/min) and H ₂ (180mL/min) into the tube furnace, and after the temperature rises to 600°C, introduce reaction gas C ₂ H ₄ (80mL/min) for 20min to generate vertically arranged CNT array;

S203: Change the gas flow to Ar (150mL/min) and heat to 1050°C, introduce the reaction gas CH ₄ (150mL/min) for 20min to generate horizontal graphene nanosheets between the vertical CNT arrays;

S204: After the reaction is completed, cool the tube body under the condition of continuous flow of Ar, and treat the crude product of the graphene/carbon nanotube three-dimensional structure composite with HCl (8.0mol/L) aqueous solution at 60°C for 15h, and then use HF to (8.0mol/L) aqueous solution was treated at 60°C for 15h to remove the catalyst component in the product, and a graphene/carbon nanotube three-dimensional structure composite (CNT/CNs) was obtained.

S205: ultrasonically disperse the graphene/carbon nanotube three-dimensional structure composite in 200mL deionized water to form a suspension with a concentration of 2.5mg/mL; Acrylate (PDDA) aqueous solution was stirred and mixed for 60 minutes; then after repeated centrifugation and washing, the supernatant was removed, and the precipitate obtained was the functionalized graphene composite material (CNT/CNs/PDDA ternary composite);

Preparation of lithium metal negative electrode sheet

Use functionalized graphene composite materials to modify the surface of lithium metal negative electrodes in lithium batteries: disperse CNT/CNs/PDDA in NMP organic solvents to obtain a mixed slurry, and coat the resulting mixed slurry on metal lithium batteries by spin coating The surface of the electrode was dried overnight at 60°C in vacuum to obtain a lithium metal negative electrode sheet modified by a functionalized graphene composite material; the mass ratio of the metal lithium sheet to the CNT/CNs/PDDA protective layer was 10:1.

Preparation of lithium metal batteries

α-MnO _The powder is dispersed in NMP solvent according to the ratio of active material: conductive carbon black: styrene-butadiene rubber = 80:10:10, then vacuum-dried after being coated on aluminum foil, sliced and weighed; -MnO ₂ pole piece is used as the positive electrode, the metal lithium plate after the surface modification and protection of the functionalized graphene composite material is used as the negative electrode, and 1M LiPF _6/ EC+PC+DEC+EMC (volume ratio 1:0.3:1:1) is used as the electrolytic Liquid, Celgard2400 is used as a diaphragm to assemble a metal lithium battery; the working voltage of the electrochemical test is 2.75-3.3V, and the ambient test temperature is 25±2°C.

Example 3

A preparation method of functionalized graphene composite material, comprising the following steps:

S301: Metal Cu is used as a reaction catalyst for the preparation of graphene/carbon nanotube three-dimensional structure composites by chemical vapor deposition (CVD). The Cu catalyst is evenly sprayed into the porcelain boat, and the porcelain boat is placed in the center of the horizontal quartz tube. heating in a tube furnace;

S302: Introduce Ar (180mL/min) and H ₂ (120mL/min) into the tube furnace. After the temperature rises to 600°C, introduce reaction gas C ₂ H ₄ (80mL/min) and react for 15 minutes to form a vertical aligned carbon nanotube (CNT) arrays;

S303: Change the gas flow to Ar (100mL/min), heat to 1000°C, change the reaction gas to CH ₄ (150mL/min), and pass it for 20min to generate horizontal graphene nanosheets between the vertical CNT arrays to obtain graphene / carbon nanotube three-dimensional structure composite crude product;

S304: After the reaction, cool the tube body under the condition of continuous flow of Ar, and treat the crude product of graphene/carbon nanotube three-dimensional structure composite with HCl (6.0mol/L) aqueous solution at 80°C for 12h, and then use HF to (6.0mol/L) aqueous solution was treated at 80°C for 12h to remove the catalyst component in the product to obtain a graphene/carbon nanotube three-dimensional structure composite (CNT/CNs);

S305: ultrasonically disperse the graphene/carbon nanotube three-dimensional structure composite obtained above in 200 mL of deionized water to form a suspension with a concentration of 1 mg/mL; then stir and mix with 50 mL of polyethylene sulfonic acid aqueous solution with a concentration of 0.2 g/L for 30 min ; After repeated centrifugation and washing, the supernatant was removed, and the precipitate obtained was the functionalized graphene composite material (CNT/CNs/polyethylenesulfonic acid ternary composite).

Example 4

A preparation method of functionalized graphene composite material, comprising the following steps:

S401: Using metal Al as a reaction catalyst for the preparation of graphene/carbon nanotube three-dimensional structure composites by chemical vapor deposition (CVD), the Al catalyst is evenly sprayed into the porcelain boat, and the porcelain boat is placed in the center of the horizontal quartz tube, heating in a tube furnace;

S402: Introduce Ar (200mL/min) and H ₂ (150mL/min) into the tube furnace. After the temperature rises to 800°C, introduce reaction gas C ₂ H ₄ (50mL/min) and react for 20min to form a vertical aligned carbon nanotube (CNT) arrays;

S403: Change the gas flow to Ar (100mL/min), heat to 800°C, change the reaction gas to CH ₄ (120mL/min), and pass it for 40min to generate horizontal graphene nanosheets between the vertical CNT arrays to obtain graphene / carbon nanotube three-dimensional structure composite crude product;

S404: After the reaction is completed, cool the tube body under the condition of continuous flow of Ar, and treat the crude product of the graphene/carbon nanotube three-dimensional structure composite with HCl (6.0mol/L) aqueous solution at 80°C for 12h, and then use HF to (6.0mol/L) aqueous solution was treated at 80°C for 12h to remove the catalyst component in the product to obtain a graphene/carbon nanotube three-dimensional structure composite (CNT/CNs);

S405: ultrasonically disperse the graphene/carbon nanotube three-dimensional structure composite obtained above in 200 mL of deionized water to form a suspension with a concentration of 1 mg/mL; then stir and mix with 50 mL of polyethyleneimine aqueous solution with a concentration of 0.1 g/L for 30 min ; After repeated centrifugation and washing, the supernatant was removed, and the precipitate obtained was the functionalized graphene composite material (CNT/CNs/polyethyleneimine ternary composite).

Effect example

In order to strongly support the beneficial effects brought by the technical solutions of the embodiments of the present invention, the following performance tests are provided:

The lithium-ion button battery prepared in Example 1 of the present invention was subjected to a charge-discharge cycle performance test at a current density of 0.2C, and the test results are shown in FIG. 2 . The results show that the button battery has excellent cycle performance. This is because the embodiment of the present invention uses a functionalized graphene composite material as a protective material to coat the silicon-carbon composite powder material of a lithium-ion battery, which can effectively inhibit The surface SEI film rupture caused by the huge volume expansion of the silicon anode material during repeated lithium intercalation/delithiation cycles greatly reduces the irreversible capacity loss of the electrode during the cycle and improves the battery cycle life.

The metal lithium battery prepared in Example 2 of the present invention was tested for cycle performance, and the test results are shown in FIG. 3 . After cycling for 100 cycles at a current density of 2C, the battery did not suffer from short circuit phenomenon caused by the growth of lithium dendrites, and the cycle performance was excellent. It shows that the functionalized graphene composite material prepared in the embodiment of the present invention is suitable for the protection of lithium metal negative electrodes, and helps to improve the cycle performance of lithium batteries.

It should be noted that, according to the disclosure and explanation of the above description, those skilled in the art to which the present invention belongs may also make changes and modifications to the above implementation manners. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some equivalent modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (16)

1. a kind of functionalization graphene composite material, which is characterized in that including graphene nanometer sheet, vertical-growth in the graphite Carbon nano pipe array in alkene nanometer sheet and by graphene nanometer sheet polyelectrolyte crosslinked together, the graphite Pass through the effect of one or more of π-pi-conjugated, chemical bond, hydrogen bond, Van der Waals force between alkene nanometer sheet and the polyelectrolyte Power connects.

2. functionalization graphene composite material as described in claim 1, which is characterized in that the graphene nanometer sheet with it is described Carbon nano pipe array forms graphene/carbon nano-tube three-dimensional structure compound, and the graphene/carbon nano-tube three-dimensional structure is compound The mass ratio of object and the polyelectrolyte is 1-10:1.

3. functionalization graphene composite material as described in claim 1, which is characterized in that the graphene nanometer sheet is individual layer Or multi-layer graphene, thickness 5nm-500nm.

4. functionalization graphene composite material as described in claim 1, which is characterized in that the height of the carbon nano pipe array It is 500nm-4 μm.

5. functionalization graphene composite material as described in claim 1, which is characterized in that the polyelectrolyte includes cation It is one or more in type polyelectrolyte, anionic polyelectrolyte, amphoteric polyelectrolyte and polyelectrolyte complex.

6. functionalization graphene composite material as claimed in claim 5, which is characterized in that the polyelectrolyte includes albumen Matter, nucleic acid, natural gum, modified starch, modified cellulose, polyacrylic acid, Sodium Polyacrylate, polyacrylamide, polymethylacrylic acid, Polymaleic anhydride, poly-metaphosphoric acid, polyethylene glycol oxide, polyvinylamine, polyvinyl pyridine, polyvinylpyrrolidone, polystyrene sulphur Sour sodium, phthalic acid diethylene glycol diacrylate, polyvinyl sulfonic acid, polyethyleneimine, amino acid, natural acid and poly- two It is one or more in methyl diallyl ammonium chloride.

7. a kind of preparation method of functionalization graphene composite material, which is characterized in that include the following steps：

Preparing surface vertical-growth using chemical vapour deposition technique has the graphene nanometer sheet of carbon nano pipe array, obtains graphite Alkene/carbon nanotube three-dimensional structure compound；

Dispersion liquid will be obtained in the graphene/carbon nano-tube three-dimensional structure compound ultrasonic disperse to water, by the dispersion liquid It is mixed 0.5-3 hours with polyelectrolyte aqueous solution, then through centrifuging, washing, gained precipitation is that functionalization graphene is answered Condensation material.

8. preparation method as claimed in claim 7, which is characterized in that the graphene/carbon nano-tube three-dimensional structure compound Preparation process be specially：

Metallic catalyst is taken, by the metallic catalyst equably splash to substrate, and the substrate is placed in horizontal quartz Then the quartz ampoule is placed in tube furnace and heats by the center of pipe again；

Argon gas and hydrogen are passed through into the tube furnace, after in-furnace temperature rises to 500 DEG C -1000 DEG C, introduces reaction gas C₂H₄ 10min-100min is reacted, with vertical-growth carbon nano pipe array on the substrate；

Air-flow is become into argon gas and is heated to 500 DEG C -1000 DEG C, reaction gas CH is introduced to the tube furnace₄React 10min- 100min, to generate horizontal graphene nanometer sheet between the carbon nano pipe array of vertical-growth to get to graphene/carbon nanometer Pipe three-dimensional structure compound crude product；

After reaction, tube body is cooled down, takes out the crude product, and by the HCl/water of the crude product 1mol/L-10mol/L 5h-24h is handled at 50 DEG C -150 DEG C of solution, then 5h- is handled at 50 DEG C -150 DEG C of the HF aqueous solutions of 1mol/L-10mol/L For 24 hours, the graphene/carbon nano-tube three-dimensional structure compound is obtained.

9. preparation method as claimed in claim 8, which is characterized in that the metallic catalyst include Cu, Al, Fe, Mo, Co, Ni, Ti, V, Cr, Mn, Zn, Ag, Pt, Au, Hg catalyst and the more metal catalytics being made of above two or two or more components One or more of agent.

10. preparation method as claimed in claim 8, which is characterized in that the flow of the argon gas be 150mL/min, the hydrogen The flow of gas is 100mL/min-200mL/min, the C₂H₄Flow be 10mL/min-100mL/min；The CH₄Flow For 100mL/min-200mL/min.

11. a kind of lithium battery system negative material, which is characterized in that including negative electrode active material and be coated on the negative electrode active The functionalization graphene composite material of material surface, the lithium battery system negative material have nucleocapsid, the functionalization Graphene composite material is claim 1-6 any one of them functionalization graphene composite materials, and the lithium battery system is born Pole material is lithium ion battery negative material or lithium polymer battery negative material.

12. lithium battery system negative material as claimed in claim 11, which is characterized in that the functionalization graphene composite wood The mass ratio of material and the negative electrode active material is 1:1-100.

13. a kind of lithium battery system cathode pole piece, which is characterized in that including collector and be supported on negative on the collector Pole material, the negative material are the lithium battery system negative material described in claim 11 or 12, and the lithium battery system is born Pole pole piece is lithium ion battery negative electrode or lithium polymer battery cathode pole piece.

14. a kind of lithium an- ode pole piece, which is characterized in that including metal lithium sheet and be arranged on the metal lithium sheet surface Protective layer, the material of the protective layer is claim 1-6 any one of them functionalization graphene composite materials.

15. lithium an- ode pole piece as claimed in claim 14, which is characterized in that the functionalization graphene composite material with The mass ratio of the metal lithium sheet is 1:1-100.

16. a kind of battery, which is characterized in that the battery include lithium battery system cathode pole piece as claimed in claim 13 or Lithium an- ode pole piece as claimed in claim 14.