Conductive composite of graphene, method for producing the same, use thereof and lithium-ion battery

Abstract

A graphene conductive composite, its manufacturing method, its use, and a lithium-ion battery are disclosed. The graphene conductive composite comprises graphene nanosheets and a conjugated copolymer, wherein the conjugated copolymer contains alkynyl groups, has a linear structure, and is grafted to the graphene nanosheets. The graphene conductive composite manufacturing method includes the following steps: pretreating graphene nanosheets with 4-bromobenzenediazonium tetrafluoroborate, and forming a conjugated copolymer in the presence of the pretreated graphene nanosheets. The graphene conductive composite of the present invention can be uniformly dispersed in an electrode slurry, reducing the internal resistance of the electrode and improving the electrode's conductivity. Furthermore, the flexible structure derived from the graphene nanosheets can mitigate the volume expansion of silicon-containing negative electrode materials during charging and discharging, thereby improving the structural stability of the silicon-containing negative electrode. When applied to a lithium-ion battery, this can improve the rate capability and cycle stability of the lithium battery.

Description

Detailed Description of the Invention

[0001] [Technical Field] The present disclosure relates to lithium ion batteries, and in particular to conductive composites of graphene, their manufacturing methods and applications, and lithium ion batteries.

[0002] 〔background〕 Graphene has been used as a new type of conductive agent. Graphene has a two-dimensional sheet structure. This two-dimensional sheet structure provides a lower conductivity threshold, significantly reducing internal resistance and improving battery performance at various current rates. The two-dimensional sheet structure also provides high flexibility, which can effectively mitigate the volume expansion associated with charge-discharge cycling and improve battery cycling performance. Therefore, graphene has been widely used as a conductive agent in lithium batteries. For example, CN109824041A discloses a graphene conductive agent for use in lithium batteries and a method for preparing the same. A predetermined amount of graphite, a dispersant, and a solvent are subjected to ball grinding and vibration separation through a sieve to obtain the graphene conductive agent. When used as a cathode additive, the graphene conductive agent can significantly improve the overall performance of lithium cobalt oxide cathode materials. CN108975322A discloses a method for producing graphene slurry, in which expanded graphite is placed in a dispersion medium and subjected to immersion, stirring, and ultrasonic stripping to obtain a graphene slurry. It has been found that conductive graphene slurries produced by subjecting graphite and a solvent to treatment in a ball mill, high pressure, or ultrasonic homogenizer are prone to agglomeration. At the same time, the slurry lacks stability, and the graphene is in the form of thick sheets. Therefore, it is considered to be of low quality. To solve the above problems, CN111509226A discloses graphene with carbon nanotubes formed on its surface. Grafting carbon nanotubes transforms the two-dimensional structure of graphene into a three-dimensional structure, thereby reducing the problems associated with graphene stacking. However, this method has strict requirements for graphene and is complex, making it difficult to apply on an industrial scale.

[0003] Therefore, there remains a need to develop conductive composites of graphene that have excellent dispersion properties, are easy to fabricate, are low cost, and are of high quality.

[0004] Summary of the Invention The present invention aims to solve one or more problems of graphene composites in the prior art, such as uneven dispersion in solvents, tendency to agglomerate, large sheet thickness, etc. Therefore, the present disclosure provides a novel conductive graphene composite, its manufacturing method and application, and a lithium-ion battery including the conductive graphene composite. The conductive graphene composite of the present disclosure is well dispersible in organic solvents, does not easily agglomerate, and has significantly improved conductivity.

[0005] A first aspect of the present disclosure relates to a conductive composite of graphene comprising graphene nanosheets and a conjugated copolymer, wherein the conjugated copolymer contains an alkynyl group, has a linear structure, and is grafted to the graphene nanosheets.

[0006] A second aspect of the present disclosure relates to a method for producing a conductive composite of graphene, comprising graphene nanosheets and a conjugated copolymer, wherein the conjugated copolymer comprises an alkynyl group, has a linear structure, and is grafted to the graphene nanosheets, the method comprising pretreating the graphene nanosheets with 4-bromobenzenediazonium tetrafluoroborate, and forming the conjugated copolymer in the presence of the pretreated graphene nanosheets.

[0007] A third aspect of the present disclosure relates to a conductive composite of graphene produced by the method.

[0008] A fourth aspect of the present disclosure relates to the use of the above-described conductive composite of graphene in a lithium-ion battery.

[0009] A fifth aspect of the present disclosure relates to a lithium-ion battery including a negative electrode including a conductive composite of graphene according to the present disclosure and a silicon-containing negative electrode material, a positive electrode including a lithium-containing positive electrode material, a separator, and an electrolyte.

[0010] The present invention has the following technical advantages: 1. The graphene conductive composite material of the present disclosure comprises a conjugated copolymer grafted onto graphene nanosheets. The grafted conjugated copolymer acts as a "barrier layer" that inhibits the aggregation and accumulation of graphene nanosheets, thereby improving the dispersion of the resulting material in a solvent. At the same time, the conjugated moieties (sites) in the conjugated copolymer are bonded via alkynyl groups. The alkynyl groups open channels for electron transfer, which is advantageous for electron transfer not only within the conjugated copolymer but also between the graphene nanosheets and the conjugated copolymer. Furthermore, the grafted conjugated copolymer also acts as a "conductive brush." ​​The grafted conjugated copolymer not only lowers the conductivity threshold of the graphene nanosheets but also extends the conductive structure of the graphene nanosheets by extending the two-dimensional conductive plane into three-dimensional space. When used in an electrode, all of the above can increase the conductivity of the electrode and reduce its internal resistance. At the same time, the flexible structure associated with the graphene nanosheets can mitigate the volume expansion of silicon-containing negative electrode materials during charge / discharge cycles. Therefore, the flexible structure associated with graphene nanosheets can improve the structural stability of the anode and the overall performance of the anode, and the application of the material to lithium-ion batteries can improve the performance at various current rates and the cycling stability of lithium batteries.

[0011] 2. In the method for producing a conductive graphene composite according to the present disclosure, graphene nanosheets are pretreated with 4-bromobenzenediazonium tetrafluoroborate. Thus, halogen functional groups (bromide, iodide, etc.) are introduced onto the graphene nanosheets. Then, a conjugated copolymer is grafted via a coupling reaction between the halogen and the conjugated copolymer. In this way, the grafted conjugated copolymer is uniformly distributed on the surface of the graphene nanosheets. Furthermore, the conjugated copolymer has a linear structure due to the selection of the monomer.

[0012] 3. The method according to the present disclosure is not limited to the type of graphene nanosheet feedstock, and is simple, making it more suitable for industrial production.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the structure of the conductive composite material of graphene obtained in Example 1, in which A is graphene and B is a conjugated copolymer; Figure 2 shows the infrared spectra of A-1, A-2, and A-3 obtained in Example 1; Figure 3 shows the SEM image of the conductive composite of graphene obtained in Example 1; FIG. 4 shows an SEM image of the graphene nanosheet feedstock included in Example 1; Figure 5 shows the SEM image of A-3 obtained in Example 1; FIG. 6 shows an SEM image (plan view) of the negative electrode according to the present disclosure in Application Example 1; Figure 7 shows an SEM image (plan view) of the control negative electrode in Application Example 2; FIG. 8 shows the cycling performance of the cells obtained in Application Examples 1 and 2 at various current rates.

[0014] Detailed Description It should be understood that the endpoints of the ranges and any values ​​disclosed herein are not limited to the exact range or value, but encompass values ​​close to that range or value. For ranges of values, it is possible to combine the endpoints of each range, the endpoints of each range and the individual points, and the individual points to provide one or more new ranges of values, just as if those ranges of values ​​were specifically disclosed herein.

[0015] Other than in the examples, all numerical values ​​of parameters herein should be understood to be modified in all instances by the term "about," regardless of whether "about" actually appears before the numerical value.

[0016] As used herein, the term "graphene" refers to a group of sp -crystalline silicon nanotubes arranged in a honeycomb structure. 2It refers to a two-dimensional material composed of a single layer of hybridized carbon atoms. Graphene is typically produced by mechanical stripping, oxidation-reduction, or SiC epitaxial growth. Thus, the term "graphene" also includes graphene oxide, reduced graphene oxide, etc.

[0017] As used herein, the term "graphene nanosheet" refers to a layered assembly of graphene and can contain 1 to 10 graphene layers. Therefore, graphene nanosheets include not only low-layer graphene containing 3 to 10 graphene layers, but also monolayer graphene (which can simply be referred to as graphene) and bilayer graphene. When the number of layers is 10 or less, the layered assembly of graphene is generally considered to have properties similar to those of graphene (monolayer graphene). Therefore, it is called a graphene nanosheet. When the number of layers is more than 10, the properties of the layered assembly of graphene are similar to those of graphite. The thickness of a graphene nanosheet is on the nanometer scale, and the other two dimensions are usually larger than the nanometer scale. In one variation, the planar dimensions of a graphene nanosheet are 0.05 to 5.0 μm.

[0018] As used herein, planar dimension refers to the largest radial dimension of a material on the XY plane. In this disclosure, unless otherwise indicated, the planar dimensions of graphene nanosheets may be characterized by scanning electron microscopy or atomic force microscopy.

[0019] One aspect of the present disclosure provides a conductive graphene composite material comprising graphene nanosheets and a conjugated copolymer, wherein the conjugated copolymer contains an alkynyl group, has a linear structure, and is grafted to the graphene nanosheets.

[0020] Graphene conductive composites have a resistance of 50 to 300 m 2 / g, preferably 100 to 250m 2 / g. The graphene conductive composite has a conductivity of 200 to 800 S / cm.

[0021] In one variation, the graphene conductive composite has a Raman spectrum of I D and I G and a D peak and a G peak, each having a peak height of I D / I G is less than 0.50. D / I G may be 0.01 to 0.50, preferably 0.03 to 0.30, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, etc., but is not limited to these.

[0022] Raman spectroscopy is widely used in the analysis of carbon materials. The Raman spectrum of graphene materials can consist of several peaks, mainly G, D, and G'. The G peak is the main characteristic peak of graphene, and the G peak is the sp 2 It is due to the in-plane vibration of hybridized carbon atoms. It can effectively reflect the number of graphene layers in a graphene sample. The D peak is usually regarded as the disorder vibration peak of graphene and is used to characterize structural defects in graphene samples. The G' peak, also known as the 2D peak, is a two-phonon resonant second-order Raman peak and can be used to characterize the interlayer stacking type of carbon atoms in graphene samples. The Raman spectrum of graphene conductive composites contains I D The peak height is 1250-1450 cm -1 D peak in the wavelength region of and I G and has a peak height of 1500 to 1700 cm -1 G peak in the wavelength region of and I 2D and has a peak height of 2600 to 2800 cm -1 and a 2D peak in the wavelength region of . Raman spectroscopy has advantages in characterizing defects in graphene materials. The defect density is I D / I GIt is generally believed that the conductivity of graphene composites is proportional to I D / I G is lower, indicating fewer defects in the graphene conductive composite.

[0023] Based on the total amount of the graphene conductive composite, the graphene nanosheets are present in an amount of 75 to 99 mass %, preferably 85 to 99 mass %, and the conjugated copolymer is present in an amount of 1 to 25 mass %, preferably 1 to 15 mass %.

[0024] The graphene nanosheet is a low-layer graphene, preferably a low-layer graphene containing 3 to 5 layers of graphene.

[0025] Graphene nanosheets show I in their Raman spectra. D and I G and a D peak and a G peak, each having a peak height of I D / I G is less than 0.50. D / I G may be 0.01 to 0.50, preferably 0.03 to 0.30, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, etc., but is not limited to these.

[0026] The Raman spectrum of graphene nanosheets contains I D The peak height is 1250-1450 cm -1 D peak in the wavelength region of and I G and has a peak height of 1500 to 1700 cm -1 G peak in the wavelength region of and I 2D and has a peak height of 2600 to 2800 cm -1 Graphene nanosheets have a 2D peak in the wavelength region of I D / I Gis lower, indicating fewer defects in the graphene nanosheets.

[0027] Graphene nanosheets are commercially available or can be prepared according to methods known in the art.

[0028] In one variation, graphene nanosheets may be produced by the following process: Step (1) heating expandable graphite at 800 to 950°C for 10 to 60 seconds to perform an expansion treatment, thereby obtaining pre-expanded graphite; Step (2) is a step of mixing the pre-expanded graphite obtained in Step (1), an aliphatic amine polyoxyethylene ether, and water, and then sequentially subjecting the mixture to a first high-pressure homogenization treatment and a second high-pressure homogenization treatment to obtain a slurry containing a laminate of graphene nanosheets, the first high-pressure homogenization treatment is carried out at a pressure of 30 to 40 MPa for 20 to 60 minutes, and the second high-pressure homogenization treatment is carried out at a pressure of 40 to 50 MPa for 10 to 30 minutes, the pressure of the second high-pressure homogenization treatment being 10 to 20 MPa higher than the pressure of the first high-pressure homogenization treatment; Step (3) A step of drying the slurry obtained in step (2) to obtain a stack of graphene nanosheets.

[0029] In one variant, compared to the expandable graphite, the pre-expanded graphite obtained in step (1) has an expansion rate that is 200 to 300 times higher.

[0030] In the conjugated copolymer, the alkynyl group is attached to a conjugated moiety that includes a conjugated group, such as one independently selected from a phenyl ring, a polycyclic aromatic hydrocarbon, an aromatic heterocycle, and the like.

[0031] Preferably, the conjugated copolymer is one or more of an arylalkyne copolymer, a fluorene copolymer, a p-phenylenevinylene copolymer, a p-phenyleneethynylene copolymer, a thiophene copolymer, a thiophene derivative copolymer, a pyrrole copolymer, and a pyrrole derivative copolymer; more preferably, it is at least one of an arylalkyne copolymer, a fluorene copolymer, a thiophene copolymer, and a thiophene derivative copolymer. For example, the arylalkyne copolymer can be poly(1,4-dialkynylbenzene-co-triphenylamine). The fluorene copolymer can be poly(1,4-dialkynylbenzene-co-9-hexylfluorene). The thiophene copolymer can be at least one of poly(1,4-dialkynylbenzene-co-3-hexylthiophene) and poly(1,4-dialkynylbenzene-co-thiophene). The thiophene derivative copolymer can be poly(1,4-dialkynylbenzene-co-3,4-ethylenedioxythiophene).

[0032] Another aspect of the present disclosure provides a method for producing a conductive composite of graphene, comprising graphene nanosheets and a conjugated copolymer, wherein the conjugated copolymer comprises an alkynyl group, has a linear structure, and is grafted to the graphene nanosheets, the method comprising pretreating the graphene nanosheets with 4-bromobenzenediazonium tetrafluoroborate, and forming the conjugated copolymer in the presence of the pretreated graphene nanosheets.

[0033] In one embodiment, the pretreatment is carried out by adding an aqueous solution of 4-bromobenzenediazonium tetrafluoroborate dropwise to the aqueous dispersion of graphene nanosheets while vigorously stirring, treating at a temperature of -5°C to 40°C for 30 to 180 minutes, and then subjecting the mixture to solid-liquid separation. The resulting solid is then washed and dried to obtain pretreated graphene nanosheets. In one variant, the aqueous solution of 4-bromobenzenediazonium tetrafluoroborate has a concentration of 40% to 70% by mass. The aqueous dispersion of graphene nanosheets contains graphene nanosheets at a concentration of 5% to 50% by mass. The aqueous dispersion of graphene nanosheets is obtained by adding graphene nanosheets to water and dispersing them. The dispersion can be carried out by stirring, ultrasonic treatment, or the like. In the pretreatment, the mass ratio of 4-bromobenzenediazonium tetrafluoroborate and graphene nanosheets is 3 to 6:1. The solid-liquid separation can be carried out by filtration. To facilitate separation, an organic solvent such as acetone may be added before separation. Washing can be performed using an organic solvent (e.g., acetone, dimethylformamide (DMF)) and deionized water. Washing may be performed one or more times. Drying may be performed by vacuum drying, preferably at 60 to 80°C for 2 to 10 hours.

[0034] forming the conjugated copolymer in the presence of pretreated graphene nanosheets, The method may include polymerizing a monomer to form the conjugated copolymer in the presence of a catalyst, a solvent, and the pretreated graphene nanosheets to obtain the conductive composite of graphene.

[0035] The catalyst may be at least one selected from the group consisting of a palladium catalyst (palladium is Pd[0], Pd[I], or Pd[II]) and a nickel catalyst (nickel is Ni[0] or Ni[II]). The catalyst is present in an amount of 0.5% to 3.0% of the molecular weight of the monomer.

[0036] The monomers for forming the conjugated copolymer may include at least two monomers, where the first monomer includes a halogen, preferably either bromine or iodine, and the second monomer is a compound containing an alkynyl group. The first and second monomers may be in a molar ratio of 1:1 to 1:1. The specific monomer may be a monomer commonly used to form conjugated copolymers. For example, the first monomer may be one or more of 4,4'-dibromotriphenylamine, 1,4-dibromobenzene, 1,4-diiodobenzene, 2,7-dibromofluorene, 2,7-dibromo-9-hexylfluorene, 2,5-dibromothiophene, 2,5-dibromo-3-hexylthiophene, etc. For example, the second monomer may be at least one of 1,4-diethynylbenzene, 1,3-diethynylbenzene, 4,4'-diethynylbiphenyl, and the like.

[0037] The solvent may be at least one of N,N'-dimethylformamide and N-methylpyrrolidone, and may be added in an amount of 1% by mass to 10% by mass of the monomer.

[0038] In one variant, the polymerization is carried out under conditions of 12 to 36 hours at a temperature of 80 to 150° C. in an inert atmosphere, which may be a nitrogen atmosphere.

[0039] Optionally, the polymerization product may be subjected to conventional post-treatment steps such as solid-liquid separation, washing, and drying. The solid-liquid separation may be filtration. To facilitate separation, an organic solvent such as methanol may be added before separation. For washing, an organic solvent (e.g., methanol) and deionized water may be used as washing liquids. The washing may be performed one or more times. The drying may be performed under vacuum, preferably at 60 to 80°C for 2 to 10 hours.

[0040] The graphene conductive composite material according to the present disclosure has excellent solvent dispersibility and conductivity, making it particularly suitable for use in lithium-ion batteries.

[0041] In a further aspect of the present disclosure, there is provided a lithium-ion battery comprising an anode comprising a conductive composite of graphene and a silicon-containing anode material according to the present disclosure, a cathode comprising a lithium-containing cathode material, a separator, and an electrolyte.

[0042] The lithium-ion battery according to the present disclosure may have a structure well known to those skilled in the art. Generally, the separator is disposed between a positive electrode and a negative electrode. The positive electrode includes a positive electrode material, and the negative electrode includes a silicon-containing negative electrode material and a graphene conductive composite material. The chemical composition of the positive electrode material is not particularly limited. The positive electrode material may be a lithium-containing positive electrode material commonly used in the art.

[0043] The separator is known to those skilled in the art and may be selected from a variety of separators commonly used in lithium ion batteries, such as polypropylene microporous film, polyethylene mat, glass fiber mat, or ultra-fine glass fiber paper.

[0044] The electrolyte may be any of a variety of conventional electrolytes, such as a non-aqueous electrolyte. A non-aqueous electrolyte is a solution formed by an electrolyte lithium salt in a non-aqueous solvent. Any conventional non-aqueous electrolyte known to those skilled in the art may be used. For example, the electrolyte may be at least one selected from the group consisting of lithium hexafluorophosphate (LiPF), lithium perchlorate (LiClO), lithium tetrafluoroborate (LiBF), lithium hexafluoroarsenate (LiAsF), and lithium hexafluorosilicate (LiSiF). The non-aqueous solvent may be selected from the group consisting of linear esters, cyclic esters, and mixtures thereof. The linear ester may be at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), and dipropyl carbonate (DPC). The cyclic ester may be at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC).

[0045] [Example] The present invention will now be described in detail through the following examples.

[0046] In the following examples and comparative examples, the morphology of the materials was characterized using a scanning electron microscope. Specifically, the scanning electron microscope used was a TECNA L G2F20 (200 kv) manufactured by FEI Corporation, USA. Testing was performed by pressing the sample directly onto a sample stage containing conductive tape and then inserting it into the electron microscope for observation. A magnification of 8,000x was used for observation.

[0047] In the following examples and comparative examples, the electrochemical properties of the assembled lithium-ion batteries were tested using a Wuhan Blue Battery Test System (CT2001B). The test conditions included a voltage range of 0.005 V to 3 V and a current range of 0.05 A to 2 A. Each sample was assembled into 10 coin cells. Their battery performance was tested under the same voltage and current, and the average value was used as the measurement result.

[0048] Infrared spectra were measured using a Spectrum 100 (obtained from Perkin Elmer) Fourier transform infrared spectrometer according to the potassium bromide tablet method. -1 From 4000cm -1 The scan range included up to 32 scans for each sample.

[0049] The specific surface area was measured with an ASAP2010 specific surface area and pore size distribution tester manufactured by Micromeritics, USA. The test conditions included a temperature of 77 K and a nitrogen atmosphere.

[0050] The Raman spectra were measured using an Invia / Reflrx Laser Micro-Raman analyzer with a 785 nm wavelength laser as the excitation source, with the material sample placed on a slide.

[0051] In the following examples and comparative examples, room temperature refers to 25°C.

[0052] In the following examples and comparative examples, 4-bromobenzenediazonium tetrafluoroborate, tetra(triphenylphosphine)palladium [Pd(PPh3)4], triethylamine, cuprous iodide (CuI), 1,4-diethynylbenzene, 4,4'-dibromotriphenylamine, and N,N'-dimethylformamide (DMF) were commercially available from Shanghai Aladdin Biochemical Technology Co., Ltd. The graphene nanosheet feedstock was commercially available from Sixth Element Changzhou Materials Technology Co., Ltd. and was low-layer graphene with planar dimensions of 2.0 to 5.0 μm.

[0053] Example 1 (1) 25 g of 4-bromobenzenediazonium tetrafluoroborate was dissolved in 25 mL of water to obtain solution A. Solution A was added dropwise to 15 g of an aqueous dispersion of graphene nanosheets (containing 5 g of graphene nanosheets) under vigorous stirring. The mixture was stirred at room temperature for 1 hour, then poured into acetone and filtered to obtain a solid, which was washed once each with acetone, DMF, and deionized water, and dried under vacuum (at a temperature of 60 °C for 4 hours) to obtain pretreated graphene nanosheets, designated as A-1.

[0054] (2) 1 g of A-1 was ultrasonically dispersed in 100 mL of N,N'-dimethylformamide. Under a nitrogen atmosphere, 326 mg of 4,4'-dibromotriphenylamine, 138.6 mg of 1,4-diethynylbenzene, 35 mg of tetra(triphenylphosphine)palladium, 7 mg of cuprous iodide, and 4 mL of triethylamine were added to the dispersion. The reaction mixture was heated to 80°C under a nitrogen atmosphere and stirred for 72 hours.

[0055] (3) After the reaction, the reaction solution was poured into methanol. The mixture was filtered under vacuum to obtain a black solid product. The resulting product was then washed several times with methanol and deionized water to remove unreacted monomers and catalyst, and dried in a vacuum oven (at 60°C for 12 hours) to obtain graphene conductive composite A-2. Graphene conductive composite A-2 was graphene nanosheets grafted with an arylalkyne copolymer, and the mass content of the graphene nanosheets was 98.2%.

[0056] For comparison, conjugated copolymer A-3 was prepared as follows: 326 mg of 4,4'-dibromotriphenylamine and 138.6 mg of 1,4-diethynylbenzene were added to 100 mL of N,N'-dimethylformamide. After stirring to dissolve the materials, 35 mg of tetra(triphenylphosphine)palladium, 7 mg of cuprous iodide, and 4 mL of triethylamine were added. The reaction mixture was heated to 80°C under a nitrogen atmosphere and stirred for 72 hours. After the reaction, the reaction solution was poured into methanol. The mixture was filtered under vacuum to obtain a brown solid product. The resulting product was washed several times with methanol and deionized water to remove unreacted monomer and catalyst, and then dried in a vacuum oven at 60°C for 12 hours. The product was conjugated copolymer A-3.

[0057] The specific surface areas of A-1, A-2, and A-3 were determined according to the BET method as described above. The results showed that the specific surface area of ​​the pretreated graphene nanosheet A-1 was 420 m 2 / g, and the specific surface area of ​​the conductive composite of graphene A-2 is 185 m 2 / g, and the specific surface area of ​​the comparative conjugated polymer A-3 is 5.5 m 2 / g. The above results indicate that the surface morphology of graphene nanosheets changes after polymer grafting. That is, by coating the surface of graphene nanosheets with a polymer, the specific surface area of ​​the graphene nanosheets themselves is reduced.

[0058] The infrared spectra of A-1, A-2, and A-3 were obtained by the test method described above. The results are shown in Figure 2. As can be seen from the figure, A-2 and A-3 have a peak at 2170 cm -1 and 2150 cm -1 This indicated the presence of an alkynyl structure in A-2 and A-3. Furthermore, the absorption peak of A-2 was 20 cm apart from the absorption peak of A-3. -1 The red shift to . This may be due to the graphene nanosheets in A-2 being bonded to the conjugated polymer A-3 via the -C6H6-C≡C- structure, which resulted in the flow of electron clouds between the graphene nanosheets and the polymer. This indicated that the conjugated copolymer was successfully grafted onto the graphene nanosheets to form a conductive composite of graphene.

[0059] FIG. 3 shows an SEM image of the conductive composite material of graphene A-2 obtained in Example 1. Figure 4 shows an SEM image of the graphene nanosheet feedstock related to Example 1. Figure 5 shows an SEM image of A-3. By comparing Figure 3 with Figure 4, it was found that the surface of the grafted graphene nanosheets was smoother and no layer stacking was present. In contrast, stacking was more evident in the graphene nanosheet feedstock. Figure 5 shows that when the conjugated copolymer was produced in the absence of pretreated graphene nanosheets, the resulting conjugated copolymer was only in the form of small balls.

[0060] The Raman spectrum of the conductive composite material of graphene A-2 obtained in Example 1 was obtained by the test method described above. The result was a peak at 1354 cm -1 D peak at 1574 cm -1 The G peaks are shown in the graph, and the ratio of their peak heights (I D / I G ) was 0.09.

[0061] Example 2 (1) 25 g of 4-bromobenzenediazonium tetrafluoroborate was dissolved in 35 mL of water to obtain solution A. While vigorously stirring, solution A was added dropwise to 15 g of an aqueous dispersion of graphene nanosheets (containing 5 g of graphene nanosheets). The mixture was stirred at room temperature for 1 hour, then poured into acetone and filtered to obtain a solid, which was washed once each with acetone, DMF, and deionized water, and dried in vacuum (at a temperature of 60°C for 4 hours) to obtain pretreated graphene nanosheets, designated as A-4.

[0062] (2) 1 g of A-4 was ultrasonically dispersed in 100 mL of N,N'-dimethylformamide. Under a nitrogen atmosphere, 326 mg of 4,4'-dibromotriphenylamine, 138.6 mg of 1,4-diethynylbenzene, 35 mg of tetra(triphenylphosphine)palladium, 7 mg of cuprous iodide, and 4 mL of triethylamine were added to the dispersion. The reaction mixture was heated to 80°C under a nitrogen atmosphere and stirred for 72 hours.

[0063] (3) After the reaction, the reaction solution was poured into methanol. The mixture was filtered under vacuum to obtain a black solid product. The resulting product was then washed several times with methanol and deionized water to remove unreacted monomers and catalyst, and dried in a vacuum oven (at 60°C for 12 hours) to obtain graphene conductive composite A-5. Graphene conductive composite A-5 was graphene nanosheets grafted with an arylalkyne copolymer, and the mass content of the graphene nanosheets was 86.5%.

[0064] The specific surface area of ​​A-5 was determined according to the BET method as described above. The results showed that the specific surface area of ​​the graphene conductive composite A-5 was 120 m 2 / g. Compared with Example 1, a larger amount of conjugated polymer was grafted in Example 2, which further reduced the specific surface area of ​​the graphene conductive composite.

[0065] The Raman spectrum of the graphene conductive composite material A-5 obtained in Example 2 was obtained by the test method described above. The result was a peak at 1354 cm -1 D peak at 1580 cm -1 The G peaks are shown in the graph, and the ratio of their peak heights (I D / I G ) was 0.07.

[0066] Example 3 (1) 25 g of 4-bromobenzenediazonium tetrafluoroborate was dissolved in 12 mL of water to obtain solution A. With vigorous stirring, solution A was added dropwise to 15 g of an aqueous dispersion of graphene nanosheets (containing 5 g of graphene nanosheets). The mixture was stirred at room temperature for 1 hour, then poured into acetone and filtered to obtain a solid, which was washed once each with acetone, DMF, and deionized water, and dried in vacuum (at a temperature of 60°C for 4 hours) to obtain pretreated graphene nanosheets, which was recorded as A-6.

[0067] (2) 1 g of A-6 was ultrasonically dispersed in 100 mL of N,N'-dimethylformamide. Under a nitrogen atmosphere, 326 mg of 4,4'-dibromotriphenylamine, 138.6 mg of 1,4-diethynylbenzene, 35 mg of tetra(triphenylphosphine)palladium, 7 mg of cuprous iodide, and 4 mL of triethylamine were added to the dispersion. The reaction mixture was heated to 80°C under a nitrogen atmosphere and stirred for 72 hours.

[0068] (3) After the reaction, the reaction solution was poured into methanol. The mixture was filtered under vacuum to obtain a black solid product. The resulting product was then washed several times with methanol and deionized water to remove unreacted monomers and catalyst, and dried in a vacuum oven (at 60°C for 12 hours) to obtain graphene conductive composite A-7. Graphene conductive composite A-7 was graphene nanosheets grafted with an arylalkyne copolymer, and the mass content of the graphene nanosheets was 90.5%.

[0069] The specific surface area of ​​A-7 was determined according to the BET method as described above. The results showed that the specific surface area of ​​the graphene conductive composite A-7 was 144 m 2 / g.

[0070] The Raman spectrum of the graphene conductive composite material A-7 obtained in Example 3 was obtained by the test method described above. The result was a peak at 1354 cm -1 D peak at 1580 cm -1 The G peaks are shown in the graph, and the ratio of their peak heights (I D / I G ) was 0.07.

[0071] Example 4 (1) 25 g of 4-bromobenzenediazonium tetrafluoroborate was dissolved in 25 mL of water to obtain Solution A. While vigorously stirring, Solution A was added dropwise to 10 g of an aqueous dispersion of graphene nanosheets (containing 5 g of graphene nanosheets). The mixture was stirred at room temperature for 1 hour, then poured into acetone and filtered to obtain a solid, which was washed once each with acetone, DMF, and deionized water, and dried in vacuo (at 60°C for 4 hours) to obtain pretreated graphene nanosheets, designated as A-8.

[0072] (2) 1 g of A-8 was ultrasonically dispersed in 100 mL of N,N'-dimethylformamide. Under a nitrogen atmosphere, 326 mg of 4,4'-dibromotriphenylamine, 138.6 mg of 1,4-diethynylbenzene, 35 mg of tetra(triphenylphosphine)palladium, 7 mg of cuprous iodide, and 4 mL of triethylamine were added to the dispersion. The reaction mixture was heated to 80°C under a nitrogen atmosphere and stirred for 72 hours.

[0073] (3) After the reaction, the reaction solution was poured into methanol. The mixture was filtered under vacuum to obtain a black solid product. The resulting product was then washed several times with methanol and deionized water to remove unreacted monomers and catalyst, and then dried in a vacuum oven (at 60°C for 12 hours) to obtain graphene conductive composite A-9. Graphene conductive composite A-9 was graphene nanosheets grafted with an arylalkyne copolymer, and the mass content of the graphene nanosheets was 92.4%.

[0074] The specific surface area of ​​A-9 was determined according to the BET method as described above. The results showed that the specific surface area of ​​the graphene conductive composite A-9 was 152 m 2 / g.

[0075] The Raman spectrum of the graphene conductive composite material A-9 obtained in Example 4 was obtained by the test method described above. The result was a peak at 1354 cm -1 D peak at 1580 cm -1 The G peaks are shown in the graph, and the ratio of their peak heights (I D / I G ) was 0.07.

[0076] Example 5 (1) 25 g of 4-bromobenzenediazonium tetrafluoroborate was dissolved in 25 mL of water to obtain solution A. While vigorously stirring, the solution A was added dropwise to 15 g of an aqueous dispersion of graphene nanosheets (containing 7.5 g of graphene nanosheets). The mixture was stirred at room temperature for 1 hour, then poured into acetone and filtered to obtain a solid, which was washed once each with acetone, DMF, and deionized water, and dried in vacuo (at a temperature of 60°C for 4 hours) to obtain pretreated graphene nanosheets, designated as A-10.

[0077] (2) 1 g of A-10 was ultrasonically dispersed in 100 mL of N,N'-dimethylformamide. Under a nitrogen atmosphere, 326 mg of 4,4'-dibromotriphenylamine, 138.6 mg of 1,4-diethynylbenzene, 35 mg of tetra(triphenylphosphine)palladium, 7 mg of cuprous iodide, and 4 mL of triethylamine were added to the dispersion. The reaction mixture was heated to 80°C under a nitrogen atmosphere and stirred for 72 hours.

[0078] (3) After the reaction, the reaction solution was poured into methanol. The mixture was filtered under vacuum to obtain a black solid product. The resulting product was then washed several times with methanol and deionized water to remove unreacted monomers and catalyst, and dried in a vacuum oven (at 60°C for 12 hours) to obtain graphene conductive composite A-11. Graphene conductive composite A-11 was graphene nanosheets grafted with an arylalkyne copolymer, and the mass content of the graphene nanosheets was 94.6%.

[0079] The specific surface area of ​​A-11 was determined according to the BET method as described above. The results showed that the specific surface area of ​​the graphene conductive composite A-11 was 155 m 2 / g.

[0080] The Raman spectrum of the graphene conductive composite material A-11 obtained in Example 5 was obtained by the test method described above. The result was a peak at 1354 cm -1 D peak at 1580 cm -1 The G peaks are shown in the graph, and the ratio of their peak heights (I D / I G ) was 0.08.

[0081] Example 6 (1) 25 g of 4-bromobenzenediazonium tetrafluoroborate was dissolved in 25 mL of water to obtain solution A. While vigorously stirring, solution A was added dropwise to 15 g of an aqueous dispersion of graphene nanosheets (containing 5 g of graphene nanosheets). The mixture was stirred at room temperature for 1 hour, then poured into acetone and filtered to obtain a solid, which was washed once each with acetone, DMF, and deionized water, and dried in vacuo (at a temperature of 60°C for 4 hours) to obtain pretreated graphene nanosheets, designated as A-1.

[0082] (2) 1 g of A-1 was ultrasonically dispersed in 100 mL of N,N'-dimethylformamide. Under a nitrogen atmosphere, 324 mg of 2,7-dibromofluorene, 138.6 mg of 1,4-diethynylbenzene, 35 mg of tetra(triphenylphosphine)palladium, 7 mg of cuprous iodide, and 4 mL of triethylamine were added to the dispersion. The reaction mixture was heated to 100°C under a nitrogen atmosphere and stirred for 72 hours.

[0083] (3) After the reaction, the reaction solution was poured into methanol. The mixture was filtered under vacuum to obtain a dark green solid product. The resulting product was then washed several times with methanol and deionized water to remove unreacted monomers and catalyst, and dried in a vacuum oven (at 60°C for 12 hours) to obtain graphene conductive composite A-12. Graphene conductive composite A-12 was graphene nanosheets grafted with a fluorene copolymer, and the mass content of the graphene nanosheets was 92.1%.

[0084] The specific surface area of ​​A-12 was determined according to the BET method as described above. The results showed that the specific surface area of ​​the graphene conductive composite A-12 was 160 m 2 / g.

[0085] The Raman spectrum of the graphene conductive composite material A-12 obtained in Example 6 was obtained by the test method described above. The result was a peak at 1354 cm -1 D peak at 1570 cm -1The G peaks are shown in the graph, and the ratio of their peak heights (I D / I G ) was 0.15.

[0086] Example 7 (1) 25 g of 4-bromobenzenediazonium tetrafluoroborate was dissolved in 25 mL of water to obtain solution A. With vigorous stirring, solution A was added dropwise to 15 g of an aqueous dispersion of graphene nanosheets (containing 5 g of graphene nanosheets). The mixture was stirred at room temperature for 1 hour, then poured into acetone and filtered to obtain a solid, which was washed once each with acetone, DMF, and deionized water, and dried in vacuo (at 60°C for 4 hours) to obtain pretreated graphene nanosheets, designated as A-1.

[0087] (2) 1 g of A-1 was ultrasonically dispersed in 100 mL of N,N'-dimethylformamide. Under a nitrogen atmosphere, 241.9 mg of 2,5'-dibromothiophene, 138.6 mg of 1,4-diethynylbenzene, 35 mg of tetra(triphenylphosphine)palladium, 7 mg of cuprous iodide, and 4 mL of triethylamine were added to the dispersion. The reaction mixture was heated to 80°C under a nitrogen atmosphere and stirred for 72 hours.

[0088] (3) After the reaction, the reaction solution was poured into methanol. The mixture was filtered under vacuum to obtain a deep red-purple solid product. The resulting product was then washed several times with methanol and deionized water to remove unreacted monomer and catalyst, and then dried in a vacuum oven (at 60°C for 12 hours) to obtain graphene conductive composite A-13. Graphene conductive composite A-13 was graphene nanosheets grafted with a thiophene copolymer, and the mass content of the graphene nanosheets was 90.5%.

[0089] The specific surface area of ​​A-13 was determined according to the BET method as described above. The results showed that the specific surface area of ​​the graphene conductive composite A-13 was 150 m 2 / g.

[0090] The Raman spectrum of the graphene conductive composite material A-13 obtained in Example 7 was obtained by the test method described above. The result was a peak at 1354 cm -1 D peak at 1580 cm -1 The G peaks are shown in the graph, and the ratio of their peak heights (I D / I G ) was 0.07.

[0091] Example 8 (1) 100 g of expandable graphite (75 mesh) was subjected to expansion treatment at 900 °C for 20 seconds to obtain pre-expanded graphite. Compared with the expandable graphite, the pre-expanded graphite had an expansion rate 220 times higher.

[0092] (2) 10 g of the pre-expanded graphite obtained in step (1), 0.25 g of Surfonic T-10 (available from Huntsman Chemical Trading (Shanghai) Co., Ltd., an aliphatic amine polyoxyethylene ether having an HLB value of 12.4), and 239.75 g of deionized water were added together to a high-pressure homogenizer. They were homogenized at 30 MPa for 30 minutes, and then the pressure was increased to 45 MPa for 30 minutes to obtain a slurry containing stacks of graphene nanosheets.

[0093] (3) The slurry was dried in a spray dryer, with the inlet flow controlled at 350°C, the outlet flow controlled at 100°C, and the centrifugal disk of the spray dryer controlled at a rotation speed of 20,000 rpm. The powder collected at the outlet was a stack of graphene nanosheets.

[0094] 0.1 g of the above graphene nanosheet laminate was ultrasonically dispersed in an ethanol solvent for 10 minutes, and the graphene nanosheet laminate was separated into the corresponding graphene nanosheets. The dispersion was then dropped onto a slide, dried at room temperature, and detected using the test method described above to obtain the Raman spectrum of the resulting graphene nanosheet. The results were as follows: -1 D peak at 1575 cm-1 The G peaks are shown in the graph, and the ratio of their peak heights (I D / I G ) was 0.05.

[0095] Example 1 was repeated to produce a conductive composite material of graphene A-14, except that the nanosheet feedstock was replaced with the obtained graphene nanosheets.

[0096] The specific surface area of ​​A-14 was determined according to the BET method as described above. The results showed that the specific surface area of ​​the graphene conductive composite A-14 was 175 m 2 The Raman spectrum of the resulting graphene conductive composite material A-14 was obtained. The result was a peak at 1355 cm -1 D peak at 1580 cm -1 The G peaks are shown in the graph, and the ratio of their peak heights (I D / I G ) was 0.05.

[0097] Comparative Example 1 (1) 1 g of graphene nanosheet raw material was ultrasonically dispersed in 100 mL of N,N'-dimethylformamide. Under a nitrogen atmosphere, 326 mg of 4,4'-dibromotriphenylamine, 138.6 mg of 1,4-diethynylbenzene, 35 mg of tetra(triphenylphosphine)palladium, 7 mg of cuprous iodide, and 4 mL of triethylamine were added to the dispersion. The reaction mixture was heated to 80 °C under a nitrogen atmosphere and stirred for 72 hours.

[0098] (2) After the reaction, the reaction solution was poured into methanol. The mixture was filtered under vacuum to obtain a black solid. The resulting mixture was then washed several times with methanol and deionized water to remove unreacted monomers and catalyst, and dried in a vacuum oven (at 60°C for 12 hours). The resulting mixture was added to toluene at 80°C, after which the solution turned brown and a black flocculent precipitate was found to be present in the solution.

[0099] The specific surface area of ​​the product of Comparative Example 1 was determined according to the BET method as described above. 2 / g, which was substantially identical to the specific surface area of ​​the graphene nanosheet feedstock, indicating that the polymer was not grafted onto the surface of the graphene nanosheets.

[0100] The above results indicated that the flocculent precipitate was the unreacted graphene nanosheet feedstock, while the conjugated copolymer obtained from the polymerization of 4,4'-dibromotriphenylamine and 1,4-diethynylbenzene was dissolved in the solvent.

[0101] Application example 1 A negative electrode was fabricated using the graphene conductive composite material A-2 obtained in Example 1 as the conductive agent and a silicon-carbon material as the active material. Specifically, 8 g of the silicon-carbon material, 1 g of A-2 as the conductive agent, and 1 g of an adhesive (polymethylacrylic acid) were added to a 50 ml beaker and stirred at 800 rpm for 30 minutes to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on copper foil (having a thickness of 100 μm) using a coating machine and dried overnight at 80°C in a vacuum drying box to obtain a negative electrode according to the present disclosure. An SEM image of the negative electrode was obtained using a scanning electron microscope, and the resulting SEM image is shown in FIG. 6.

[0102] Next, CR2016 coin cells were assembled using the above-mentioned negative electrode, a metallic lithium sheet as the positive electrode, a 1 mol / L LiPF solution as the electrolyte (a 3:7 volume ratio mixture of vinyl carbonate and diethyl carbonate was used as the solvent), and a polypropylene microporous film as the separator. The fabricated coin cells were subjected to the test method described above to characterize their cycling performance at various current rates. The results are shown in Figure 8.

[0103] Application example 2 A control negative electrode was produced by repeating Application Example 1 by using commercially available SuperP as the conductive agent. An SEM image of the control negative electrode was obtained using a scanning electron microscope, and the obtained SEM image is shown in Figure 7.

[0104] Next, CR2016 coin cells were assembled using the above-mentioned control anode, a metallic lithium sheet as the cathode, a 1 mol / L LiPF solution as the electrolyte (a 3:7 volume ratio mixture of vinyl carbonate and diethyl carbonate was used as the solvent), and a polypropylene microporous film as the separator. The fabricated coin cells were subjected to the test method described above to characterize their cycling performance at various current rates. The results are shown in Figure 8.

[0105] Referring to Figures 6 and 7, these are SEM images of the negative electrode according to the present disclosure and the control negative electrode obtained in Application Examples 1 and 2, respectively. As can be seen from the drawing in Figure 6, the graphene conductive composite material was coated on the surface of the silicon-carbon negative electrode material particles. Without being bound by any theory, it is believed that such a structure is advantageous not only for forming surface conduction of electrons but also for mitigating the volume expansion of the silicon-carbon material during charge-discharge cycles, thereby improving the cycle performance of the cell. In Figure 7, Super P was dispersed among the particles of the silicon-carbon negative electrode material. Therefore, the electron conduction mode was linear. In addition, there was no contribution to mitigating the volume expansion of the silicon-carbon material.

[0106] Referring to FIG. 8, the cycle performance at various current rates for the cells obtained in Application Examples 1 and 2 is shown. As can be seen from the figure, the cells using the negative electrodes according to the present disclosure achieved higher capacity retention at the same number of cycles. The negative electrodes according to the present disclosure used the graphene conductive composite material A-2 as a conductive agent. This indicates that A-2 can improve the conductivity of the electrode, suppress the occurrence of polarization in the battery, and improve the stability of the battery.

[0107] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Various simple modifications, including combinations of various technical features in any other suitable manner, may be made to the embodiments of the present invention within the technical scope of the present invention. These simple modifications and combinations are also considered to be the contents disclosed in this specification and should be considered to be within the scope of protection of the present disclosure. [Brief explanation of the drawings]

[0108] [Figure 1] 1 is a schematic diagram showing the structure of the conductive composite material of graphene obtained in Example 1, in which A is graphene and B is a conjugated copolymer. [Figure 2] 1 shows the infrared spectra of A-1, A-2, and A-3 obtained in Example 1. [Figure 3] 1 shows an SEM image of the conductive composite material of graphene obtained in Example 1. [Figure 4] 1 shows an SEM image of the graphene nanosheet feedstock included in Example 1. [Figure 5] 1 shows an SEM image of A-3 obtained in Example 1. [Figure 6] 1 shows an SEM image (plan view) of a negative electrode according to the present disclosure in Application Example 1. [Figure 7] 10 shows an SEM image (plan view) of the control negative electrode in Application Example 2. [Figure 8] 1 shows the cycling performance at various current rates of the cells obtained in Application Examples 1 and 2.

Claims

1. A conductive composite of graphene, comprising graphene nanosheets and a conjugated copolymer, the conjugated copolymer contains an alkynyl group, has a linear structure, and is grafted to the graphene nanosheet; the graphene nanosheet is a low-layer graphene containing 3 to 5 layers of graphene; The graphene nanosheets are characterized by the following characteristics in their Raman spectrum: Ｄ and I Ｇ and a D peak and a G peak, each having a peak height of I Ｄ / I Ｇ is 0.03 to 0.30, and The electrically conductive composite of graphene has a Raman spectrum comprising a D peak and a G peak having peak heights of I D and I G , respectively, and I D / I G is less than 0.

50.

2. The graphene conductive composite material has a thickness of 50 to 300 m ２ The conductive composite material of claim 1, characterized in that it has a specific surface area of ​​1 / g.

3. The graphene conductive composite material has a thickness of 100 to 250 m ２ 3. The conductive composite of graphene according to claim 2, having a specific surface area of ​​1000 W / g.

4. 2. The graphene conductive composite according to claim 1, wherein the graphene nanosheets are present in an amount of 85 to 99 mass % and the conjugated copolymer is present in an amount of 1 to 15 mass %, based on the total amount of the graphene conductive composite.

5. The graphene conductive composite material according to claim 1, wherein the planar dimensions of the graphene nanosheets are 0.05 to 5.0 μm.

6. 2. The graphene conductive composite material according to claim 1, wherein the conjugated copolymer is at least one of an arylalkyne copolymer, a fluorene copolymer, a p-phenylenevinylene copolymer, a p-phenyleneethynylene copolymer, a thiophene copolymer, a thiophene derivative copolymer, a pyrrole copolymer, and a pyrrole derivative copolymer.

7. 2. The graphene conductive composite material of claim 1, wherein the conjugated copolymer is at least one of a copolymer of an arylalkyne, a copolymer of fluorene, a copolymer of thiophene, and a copolymer of a thiophene derivative.

8. 2. The graphene conductive composite of claim 1, wherein the conjugated copolymer is at least one of poly(1,4-dialkynylbenzene-co-triphenylamine), poly(1,4-dialkynylbenzene-co-9-hexylfluorene), poly(1,4-dialkynylbenzene-co-3-hexylthiophene), poly(1,4-dialkynylbenzene-co-thiophene), and poly(1,4-dialkynylbenzene-co-3,4-ethylenedioxythiophene).

9. Pretreating the graphene nanosheets with 4-bromobenzenediazonium tetrafluoroborate; and forming the conjugated copolymer in the presence of the pretreated graphene nanosheets. The method for producing the conductive composite material of graphene according to claim 1, comprising:

10. 10. The method according to claim 9, wherein the pretreatment comprises the steps of adding dropwise an aqueous solution of 4-bromobenzenediazonium tetrafluoroborate to the aqueous dispersion of graphene nanosheets while stirring, treating the mixture at a temperature of −5 to 40° C. for 30 to 180 minutes, and then drying the product to obtain the pretreated graphene nanosheets.

11. 11. The method of claim 10, wherein the aqueous solution of 4-bromobenzenediazonium tetrafluoroborate has a concentration of 40 to 70% by mass, and the graphene nanosheets are present in the aqueous dispersion of graphene nanosheets at a concentration of 5 to 50% by mass.

12. The method according to claim 10, wherein the 4-bromobenzenediazonium tetrafluoroborate and the graphene nanosheets are in a mass ratio of 3 to 6:

1.

13. The method according to claim 10, wherein the drying is performed by vacuum drying at a temperature of 60 to 80°C for 2 to 10 hours.

14. 10. The method of claim 9, wherein forming the conjugated copolymer in the presence of the pretreated graphene nanosheets comprises polymerizing a monomer to form the conjugated copolymer in the presence of a catalyst, a solvent, and the pretreated graphene nanosheets to obtain a conductive composite of the graphene.

15. 15. The method of claim 14, wherein the monomers for forming the conjugated copolymer comprise at least two monomers, wherein a first monomer comprises a halogen and a second monomer is a compound comprising an alkynyl group.

16. 15. The method of claim 14, wherein the catalyst is at least one selected from the group consisting of a palladium catalyst and a nickel catalyst.

17. 15. The method of claim 14, wherein the polymerization is carried out under an inert atmosphere at a temperature of 80 to 150°C for a period of 12 to 36 hours.

18. 10. Use of the conductive composite of graphene according to claim 1 in a lithium ion battery.

19. A lithium ion battery comprising the conductive composite of graphene according to claim 1.

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