Graphene carbon negative electrode material and preparation method and application thereof

Abstract

The invention discloses a graphene carbon negative electrode material and a preparation method and application thereof, and belongs to the technical field of lithium ion battery negative electrode materials. Metal ions of cerous nitrate and 2, 5-dihydroxy terephthalic acid grafted on the surfaces of conductive core-shell microspheres are subjected to a coordination reaction to generate a metal framework; the polystyrene nano-microsphere is a non-polar polymer, has high solubility in DMF, and can be removed as a sacrificial template by utilizing the characteristic, so that conductive double-shell hollow microsphere powder is obtained; a three-dimensional conductive network is constructed through sulfonated graphene, conductive core-shell microspheres and a metal framework to increase conductivity and promote rapid transmission of lithium ions, volume expansion in the charging and discharging process can be buffered through hollow structures of the conductive core-shell microspheres and shell gaps of the metal framework, cerium metal ions in the metal framework have excellent anti-corrosion performance, and the lithium ion battery can be used for lithium ion battery charging and discharging. The electrode material can be prevented from being corroded by components in the electrolyte, and the service life of the negative electrode material is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery negative electrode materials, and specifically relates to a graphene carbon negative electrode material and a preparation method and application thereof. Background Art

[0002] Graphene materials are inexpensive and easy to synthesize, making them extremely attractive energy storage materials. They are nanomaterials with excellent electrical conductivity and high mechanical strength, and are widely used in new energy devices such as lithium-ion batteries, metal-air batteries, and fuel cells. Graphene is used as a raw material. Graphene has a large conjugated structure, rich microstructure, and large specific surface area. Graphene is highly modifiable and has abundant pores, excellent physical and chemical stability, adjustable pore size, and low thermal conductivity. Therefore, it has attracted widespread attention from researchers. However, graphene is prone to agglomeration, which will affect the specific surface area and electrochemical properties of electrode materials. Combining graphene with porous carbon materials can effectively bring out the advantages of both.

[0003] Chinese patent publication number CN113113574B discloses a method for preparing a graphene-modified silicon-carbon negative electrode material. This method uses hydrophilic silicone oil as a modifier and cross-linker for SiOx and carbon materials. After step-by-step modification, liquid phase mixing is performed to achieve better bonding between SiOx and carbon material particles and graphene oxide. However, in this solution, graphene oxide easily agglomerates and the flakes are prone to excessive accumulation. Liquid phase mixing alone does not involve chemical bonding, and thus the bonding between graphene oxide and the various materials cannot be effectively guaranteed.

[0004] Introducing specific functional groups on the surface of graphene oxide through chemical grafting can significantly enhance its dispersibility and increase the bonding strength between it and various materials. Chinese patent publication number CN117263174B discloses a sulfonic acid graphene electrode material and its synthesis method. This method introduces sulfonic acid on the graphene sheets to avoid excessive accumulation of the sheets and overcome defects such as the small specific surface area of ​​graphene. However, the introduction of sulfonic acid groups will cause the conjugated structure of some graphene to be destroyed, the original π-π conjugated system to break, the conductivity to decrease, and the mechanical stability to be reduced, which is not conducive to lithium electron transmission and thus affects the performance of lithium batteries. Summary of the Invention

[0005] The present invention aims to provide a graphene carbon negative electrode material and a preparation method and application thereof. The metal ions of cerium nitrate react with 2,5-dihydroxyterephthalic acid grafted on the surface of conductive core-shell microspheres to generate a metal skeleton. Polystyrene nanospheres are non-polar polymers with high solubility in DMF. By utilizing this feature, they can be removed as a sacrificial template to obtain conductive double-shell hollow microsphere powder. Graphene is sulfonated, and a three-dimensional conductive network is constructed between the conductive core-shell microspheres and the metal skeleton to increase conductivity and promote rapid lithium ion transmission. In addition, the hollow structure of the conductive core-shell microspheres and the gaps between the metal skeleton shells can buffer volume expansion during charging and discharging.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a graphene carbon negative electrode material comprises the following steps:

[0008] Step 1: The sulfonic acid group of 2-acrylamide-2-methylpropanesulfonic acid is grafted onto the surface of polystyrene nanospheres with a particle size of 20-30 nm through free radical polymerization under the action of an initiator, and is ionically bonded with aniline monomer to obtain conductive core-shell microspheres; the conductive core-shell microspheres, cerium nitrate and deionized water are added to a reactor, stirred at 120-130° C. and 400-500 r / min for 12-14 hours, filtered, and the filter cake is washed with N,N-dimethylformamide to remove the polystyrene template, then washed with anhydrous ethanol 2-3 times, and vacuum dried at 60-80° C. for 1-2 hours to obtain conductive double-shell hollow microsphere powder.

[0009] Step 2: Add sulfonated graphene, conductive double-shell hollow microsphere powder, silicon powder and deionized water into a reactor, ultrasonically disperse for 40-60 minutes, stir for 1-2 hours at 20-25°C and 400-500r / min to obtain a mixed suspension, place the mixed suspension in a freeze dryer, freeze-dry for 12-14 hours, disperse the product in anhydrous ethanol, heat to 170-180°C, and continue the reaction for 12-14 hours to obtain a graphene carbon negative electrode material.

[0010] Furthermore, in step 1, the ratio of the conductive core-shell microspheres, cerium nitrate and deionized water is 50-60 g: 30-40 g: 800-900 mL.

[0011] Furthermore, in step 2, the usage ratio of sulfonated graphene, conductive double-shell hollow microsphere powder, silicon powder, deionized water and anhydrous ethanol is 50-60 g: 40-50 g: 80-90 g: 800-900 mL: 400-500 mL.

[0012] Furthermore, the specific steps of the conductive core-shell microspheres in step 1 are as follows:

[0013] The precursor solution, aniline, 2,5-dihydroxyterephthalic acid and 10-12% ethanol solution are added to a reactor, stirred at 80-90°C and 400-500 r / min for 30-40 minutes, then ammonium persulfate is added, the temperature is lowered to 0-4°C, the reaction is continued for 12-14 hours, and the reaction is filtered. The filter cake is washed with deionized water and anhydrous ethanol for 2-3 times respectively, and vacuum dried at 60-80°C for 1-2 hours to obtain conductive core-shell microspheres.

[0014] Furthermore, the usage ratio of the precursor solution, aniline, 2,5-dihydroxyterephthalic acid, ethanol solution and ammonium persulfate is 120-140 mL: 80-90 mL: 70-80 g: 800-900 mL: 5-6 g.

[0015] Furthermore, the sulfonated graphene powder in step 2 is prepared by the following steps:

[0016] The acyl chloride graphene powder, sodium sulfite and N,N-dimethylacetamide were added to a reactor, ultrasonically dispersed for 40-60 minutes, stirred at 150-160° C. and 400-500 r / min for 24-26 hours, cooled naturally to room temperature, and then deionized water was added. The mixture was stirred for 2-3 hours and filtered. The filter cake was washed with deionized water and anhydrous ethanol for 2-3 times, respectively, and vacuum dried at 60-80° C. for 1-2 hours to obtain sulfonated graphene powder.

[0017] Furthermore, the usage ratio of the chlorinated graphene powder, sodium sulfite, N,N-dimethylacetamide and deionized water is 50-60 g: 56-58 g: 300-400 mL: 700-800 mL.

[0018] Further, the chlorinated graphene powder is prepared by the following steps:

[0019] Graphene oxide powder and a 20-30% by mass thionyl chloride solution are added to a reactor in a ratio of 60-70 g: 400-600 mL, stirred for 3-4 hours at a vacuum degree of -0.1 to -0.03 MPa, a temperature of 80-85° C., and a speed of 400-500 r / min, and the unreacted thionyl chloride is removed by rotary evaporation. The mixture is vacuum dried at 60-80° C. for 1-2 hours to obtain graphene chloride powder.

[0020] Further, the graphene oxide powder is processed through the following steps:

[0021] Flake graphite, phosphorus pentoxide, potassium persulfate and a 98% concentrated sulfuric acid solution are added to a reactor, stirred at 80-85° C. and 400-500 r / min for 3-4 hours, filtered, and the filter cake is washed with deionized water and anhydrous ethanol 2-3 times, respectively, and vacuum dried at 60-80° C. for 1-2 hours to obtain pre-oxidized graphite; pre-oxidized graphite, potassium permanganate, a 98% concentrated sulfuric acid solution and a 30-40% hydrogen peroxide solution are added to a reactor, stirred at 80-85° C. and 400-500 r / min for 3-4 hours, filtered, and the filter cake is washed with deionized water and anhydrous ethanol 2-3 times, respectively, and vacuum dried at 60-80° C. for 1-2 hours to obtain graphene oxide powder with a particle size of 30-40 μm.

[0022] Furthermore, the usage ratio of flake graphite, phosphorus pentoxide, potassium persulfate and concentrated sulfuric acid solution is 80-90 g: 40-50 g: 40-50 g: 800-900 mL.

[0023] Furthermore, the usage ratio of pre-oxidized graphite, potassium permanganate, concentrated sulfuric acid solution and hydrogen peroxide solution is 70-80 g: 30-40 g: 800-900 mL: 200-300 mL.

[0024] Further, the precursor solution is subjected to the following steps:

[0025] Polystyrene nanospheres with a particle size of 20-30 nm, 2-acrylamide-2-methylpropanesulfonic acid and deionized water are added to a reactor, stirred at 20-25° C. and 400-500 r / min for 20-30 minutes, and then ammonium persulfate as an initiator is added. The mixture is heated to 60-70° C. and stirred for 4-5 hours. The mixture is naturally cooled to room temperature to obtain a precursor solution.

[0026] Furthermore, the usage ratio of polystyrene nanospheres, 2-acrylamide-2-methylpropanesulfonic acid, deionized water and ammonium persulfate is 80-90 g: 50-60 g: 700-800 mL: 1.5-2 g.

[0027] The present invention also provides an application of graphene carbon negative electrode material in lithium ion battery negative electrode material.

[0028] Beneficial effects of the present invention:

[0029] 1. The graphene carbon negative electrode material prepared by the present invention can significantly increase the electrical conductivity of lithium batteries, promote the rapid transmission of lithium ions, alleviate the volume expansion of lithium batteries during charging and discharging, and increase the cycle capacity, first discharge capacity and first coulombic efficiency of lithium batteries.

[0030] 2. The conductive double-shell hollow microsphere powder of the present invention is prepared by a coordination reaction between the metal ions of cerium nitrate and 2,5-dihydroxyterephthalic acid grafted on the surface of the conductive core-shell microspheres to form a metal skeleton. The polystyrene nanospheres are a non-polar polymer with a high solubility in DMF. By utilizing this feature, they can be removed as a sacrificial template to obtain the conductive double-shell hollow microsphere powder. By sulfonating graphene, the conductive core-shell microspheres and the metal skeleton construct a three-dimensional conductive network to increase conductivity and promote rapid lithium ion transmission. The hollow structure of the conductive core-shell microspheres and the gaps between the metal skeleton shells can buffer the volume expansion during charging and discharging. The cerium metal ions in the metal skeleton have excellent corrosion resistance, which can prevent the electrode material from being corroded by components in the electrolyte and ensure the service life of the negative electrode material.

[0031] 3. The conductive core-shell microspheres of the present invention are formed by grafting sulfonic acid groups of 2-acrylamide-2-methylpropanesulfonic acid onto the surface of polystyrene nanospheres through free radical polymerization initiated by ammonium persulfate, thereby forming sulfonated polystyrene. The sulfonic acid groups and aniline monomers are ionically bonded, promoting the directional growth of polyaniline on the surface of the sulfonated polystyrene nanospheres. The polyaniline has excellent electrical conductivity, can increase the conductivity of graphene, and can avoid the introduction of sulfonic acid groups that lead to the destruction of the conjugated structure of graphene, the breakage of the original π-π conjugated system, and the decrease in electrical conductivity. The sulfonic acid groups can participate in the formation of the SEI film, generating a stable interface layer rich in LiF, thereby reducing electrolyte decomposition and irreversible consumption of active lithium. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] Example 1: A method for preparing a graphene carbon negative electrode material, comprising the following steps:

[0034] S1: 80g of flake graphite, 40g of phosphorus pentoxide, 40g of potassium persulfate and 800mL of 98% concentrated sulfuric acid solution were added to a reactor, stirred at 80°C and 400r / min for 3h, filtered, and the filter cake was washed twice with deionized water and anhydrous ethanol respectively, and vacuum dried at 60°C for 1h to obtain pre-oxidized graphite; 70g of pre-oxidized graphite, 30g of potassium permanganate, 800mL of 98% concentrated sulfuric acid solution and 200mL of 30% hydrogen peroxide solution were added to a reactor, stirred at 80°C and 400r / min for 3h, filtered, and the filter cake was washed twice with deionized water and anhydrous ethanol respectively, and vacuum dried at 60°C for 1h to obtain graphene oxide powder with a particle size of 30-40μm.

[0035] S2: 60 g of graphene oxide powder and 400 mL of 20% by mass thionyl chloride solution were added to a reactor, stirred for 3 h at a vacuum degree of -0.1 MPa, a temperature of 80°C, and a speed of 400 r / min, and the unreacted thionyl chloride was removed by rotary evaporation. The mixture was vacuum dried at 60°C for 1 h to obtain graphene chloride powder.

[0036] The carboxyl groups on the surface of graphene oxide generate acyl chloride groups through nucleophilic substitution reaction under the action of dichlorothionyl.

[0037] S3: 50 g of acyl chloride graphene powder, 56 g of sodium sulfite and 300 mL of N,N-dimethylacetamide were added to the reactor, ultrasonically dispersed for 40 min, stirred at 150°C and 400 r / min for 24 h, cooled naturally to room temperature, then added with 700 mL of deionized water, continued stirring for 2 h, filtered, and the filter cake was washed twice with deionized water and anhydrous ethanol respectively, and vacuum dried at 60°C for 1 h to obtain sulfonated graphene powder.

[0038] The sulfite ion in sodium sulfite acts as a nucleophile to attack the acyl chloride group on the acylated graphene oxide to generate a sulfonate intermediate, which is then hydrolyzed to obtain a sulfonic acid group.

[0039] S4: 80 g of polystyrene nanospheres with a particle size of 20-30 nm, 50 g of 2-acrylamide-2-methylpropanesulfonic acid and 700 mL of deionized water were added to a reactor, stirred at 20°C and 400 r / min for 20 min, then 1.5 g of ammonium persulfate as an initiator was added, heated to 60°C, stirred for 4 h, and naturally cooled to room temperature to obtain a precursor solution; 120 mL of the precursor solution, 80 mL of aniline, 70 g of 2,5-dihydroxyterephthalic acid and 800 mL of 10% ethanol solution were added to a reactor, stirred at 80°C and 400 r / min for 30 min, then 5 g of ammonium persulfate was added, the temperature was lowered to 0°C, the reaction was continued for 12 h, filtered, the filter cake was washed twice with deionized water and anhydrous ethanol respectively, and vacuum dried at 60°C for 1 h to obtain conductive core-shell microspheres.

[0040] Under the initiation of ammonium persulfate, the sulfonic acid groups of 2-acrylamide-2-methylpropanesulfonic acid are grafted onto the surface of polystyrene nanospheres through free radical polymerization to form sulfonated polystyrene. The sulfonic acid groups and aniline monomers are combined through ionic bonds, promoting the directional growth of polyaniline on the surface of the sulfonated polystyrene nanospheres. In addition, the amino groups on the surface of the conductive core-shell microspheres are combined with the carboxyl groups of 2,5-dihydroxyterephthalic acid to graft 2,5-dihydroxyterephthalic acid onto the conductive core-shell microspheres.

[0041] S5: Add 50 g of conductive core-shell microspheres, 30 g of cerium nitrate and 800 mL of deionized water into a reactor, stir at 120°C and 400 r / min for 12 h, filter, wash the filter cake with N,N-dimethylformamide to remove the polystyrene template, then wash it twice with anhydrous ethanol, and vacuum dry it at 60°C for 1 h to obtain conductive double-shell hollow microsphere powder.

[0042] The metal ions of cerium nitrate react with 2,5-dihydroxyterephthalic acid grafted on the surface of the conductive core-shell microspheres to form a metal skeleton. The polystyrene nanospheres are used as a sacrificial template and removed due to their high solubility in DMF to obtain conductive double-shell hollow microsphere powder.

[0043] Sulfonic acid groups can participate in the formation of SEI film, generate a stable interface layer rich in LiF, reduce electrolyte decomposition and irreversible consumption of active lithium, and construct a three-dimensional conductive network of sulfonated graphene, conductive core-shell microspheres and metal skeleton to increase conductivity and promote rapid lithium ion transmission. The hollow structure of the conductive core-shell microspheres and the gap between the metal skeleton shells can buffer the volume expansion during charging and discharging.

[0044] The cerium metal ions in the metal skeleton have excellent anti-corrosion properties, which can prevent the electrode material from being corroded by components in the electrolyte and ensure the service life of the negative electrode material.

[0045] S6: Add 50g of sulfonated graphene powder, 40g of conductive double-shell hollow microsphere powder, 80g of silicon powder and 800mL of deionized water into a reactor, ultrasonically disperse for 40min, stir at 20℃ and 400r / min for 1h to obtain a mixed suspension, place the mixed suspension in a freeze dryer, freeze-dry for 12h, disperse the product in 400mL of anhydrous ethanol, heat to 170℃, and continue the reaction for 12h to obtain a graphene carbon negative electrode material.

[0046] Example 2: A method for preparing a graphene carbon negative electrode material, comprising the following steps:

[0047] S1: 85g of flake graphite, 45g of phosphorus pentoxide, 45g of potassium persulfate and 850mL of 98% concentrated sulfuric acid solution were added to a reactor, stirred at 82.5°C and 450r / min for 3.5h, filtered, and the filter cake was washed twice with deionized water and anhydrous ethanol, respectively, and vacuum dried at 70°C for 1.5h to obtain pre-oxidized graphite; 75g of pre-oxidized graphite, 35g of potassium permanganate, 850mL of 98% concentrated sulfuric acid solution and 250mL of 35% hydrogen peroxide solution were added to a reactor, stirred at 82.5°C and 450r / min for 3.5h, filtered, and the filter cake was washed twice with deionized water and anhydrous ethanol, respectively, and vacuum dried at 70°C for 1.5h to obtain graphene oxide powder with a particle size of 30-40μm.

[0048] S2: 65 g of graphene oxide powder and 500 mL of 25% by mass thionyl chloride solution were added to a reactor, stirred for 3.5 h under vacuum conditions of -0.065 MPa, 82.5 ° C and 450 r / min, and the unreacted thionyl chloride was removed by rotary evaporation. The mixture was vacuum dried at 70 ° C for 1.5 h to obtain graphene chloride powder.

[0049] S3: 55 g of acyl chloride graphene powder, 57 g of sodium sulfite and 350 mL of N,N-dimethylacetamide were added to a reactor, ultrasonically dispersed for 50 min, stirred at 155 ° C and 450 r / min for 25 h, and naturally cooled to room temperature. Then, 750 mL of deionized water was added and stirring was continued for 2.3 h. The filter cake was washed twice with deionized water and anhydrous ethanol, respectively, and vacuum dried at 70 ° C for 1.5 h to obtain sulfonated graphene powder.

[0050] S4: 85g of polystyrene nanospheres with a particle size of 20-30nm, 55g of 2-acrylamide-2-methylpropanesulfonic acid and 750mL of deionized water were added to the reactor, stirred at 22.5℃ and 450r / min for 25min, then 1.75g ​​of ammonium persulfate as an initiator was added, heated to 65℃, stirred for 4.5h, and naturally cooled to room temperature to obtain a precursor solution; 130mL of the precursor solution, 85mL of aniline, 75g of 2,5-dihydroxyterephthalic acid and 850mL of an ethanol solution with a mass fraction of 11% were added to the reactor, stirred at 85℃ and 450r / min for 35min, then 5.5g of ammonium persulfate was added, cooled to 2℃, the reaction was continued for 13h, filtered, and the filter cake was washed twice with deionized water and anhydrous ethanol respectively, and vacuum dried at 70℃ for 1.5h to obtain conductive core-shell microspheres.

[0051] S5: Add 55 g of conductive core-shell microspheres, 35 g of cerium nitrate and 850 mL of deionized water into a reactor, stir at 125°C and 450 r / min for 13 h, filter, wash the filter cake with N,N-dimethylformamide to remove the polystyrene template, then wash it twice with anhydrous ethanol, and vacuum dry it at 70°C for 1.2 h to obtain conductive double-shell hollow microsphere powder.

[0052] S6: Add 55g of sulfonated graphene powder, 45g of conductive double-shell hollow microsphere powder, 85g of silicon powder and 850mL of deionized water into a reactor, ultrasonically disperse for 50min, stir for 1.5h at 22.5℃ and 450r / min to obtain a mixed suspension, place the mixed suspension in a freeze dryer, freeze-dry for 13h, disperse the product in 450mL of anhydrous ethanol, heat to 175℃, and continue the reaction for 13h to obtain a graphene carbon negative electrode material.

[0053] Example 3: A method for preparing a graphene carbon negative electrode material, comprising the following steps:

[0054] S1: 90g of flake graphite, 50g of phosphorus pentoxide, 50g of potassium persulfate and 900mL of 98% concentrated sulfuric acid solution were added to a reactor, stirred at 85°C and 500r / min for 4h, filtered, and the filter cake was washed with deionized water and anhydrous ethanol three times, respectively, and vacuum dried at 80°C for 2h to obtain pre-oxidized graphite; 80g of pre-oxidized graphite, 40g of potassium permanganate, 900mL of 98% concentrated sulfuric acid solution and 300mL of 40% hydrogen peroxide solution were added to a reactor, stirred at 85°C and 500r / min for 4h, filtered, and the filter cake was washed with deionized water and anhydrous ethanol three times, respectively, and vacuum dried at 80°C for 2h to obtain graphene oxide powder with a particle size of 30-40μm.

[0055] S2: 70 g of graphene oxide powder and 600 mL of 30% by mass thionyl chloride solution were added to a reactor, stirred for 4 h under the conditions of a vacuum degree of -0.1 MPa, a temperature of 85°C and a speed of 500 r / min, and the unreacted thionyl chloride was removed by rotary evaporation. The mixture was vacuum dried at 80°C for 2 h to obtain graphene chloride powder.

[0056] S3: 60 g of acyl chloride graphene powder, 58 g of sodium sulfite and 400 mL of N,N-dimethylacetamide were added to the reactor, ultrasonically dispersed for 60 min, stirred at 160°C and 500 r / min for 26 h, and naturally cooled to room temperature. Then, 800 mL of deionized water was added and stirring was continued for 3 h. The filter cake was washed with deionized water and anhydrous ethanol three times respectively, and vacuum dried at 80°C for 2 h to obtain sulfonated graphene powder.

[0057] S4: 90 g of polystyrene nanospheres with a particle size of 20-30 nm, 60 g of 2-acrylamide-2-methylpropanesulfonic acid and 800 mL of deionized water were added to a reactor, stirred at 25°C and 500 r / min for 30 min, then 2 g of ammonium persulfate as an initiator was added, heated to 70°C, stirred for 5 h, and naturally cooled to room temperature to obtain a precursor solution; 140 mL of the precursor solution, 90 mL of aniline, 80 g of 2,5-dihydroxyterephthalic acid and 900 mL of an ethanol solution with a mass fraction of 12% were added to a reactor, stirred at 90°C and 500 r / min for 40 min, then 6 g of ammonium persulfate was added, the temperature was lowered to 4°C, the reaction was continued for 14 h, filtered, and the filter cake was washed 3 times with deionized water and anhydrous ethanol respectively, and vacuum dried at 80°C for 2 h to obtain conductive core-shell microspheres.

[0058] S5: Add 60 g of conductive core-shell microspheres, 40 g of cerium nitrate and 900 mL of deionized water into a reactor, stir at 130°C and 500 r / min for 14 h, filter, wash the filter cake with N,N-dimethylformamide to remove the polystyrene template, then wash it with anhydrous ethanol three times, and vacuum dry it at 80°C for 2 h to obtain conductive double-shell hollow microsphere powder.

[0059] S6: Add 60g of sulfonated graphene powder, 50g of conductive double-shell hollow microsphere powder, 90g of silicon powder and 900mL of deionized water into a reactor, ultrasonically disperse for 60min, stir for 2h at 25°C and 500r / min to obtain a mixed suspension, place the mixed suspension in a freeze dryer, freeze-dry for 14h, disperse the product in 500mL of anhydrous ethanol, heat to 180°C, and continue the reaction for 14h to obtain a graphene carbon negative electrode material.

[0060] Comparative Example 1: Based on Example 3, the sulfonated graphene powder in step S5 was replaced by the graphene oxide powder in step S1, and the other steps remained unchanged to prepare a graphene carbon negative electrode material.

[0061] Comparative Example 2: Based on Example 3, aniline in step S4 was omitted so that polyaniline could not be formed, and the remaining steps remained unchanged to prepare a graphene carbon negative electrode material.

[0062] Comparative Example 3: Based on Example 3, without step S5, the conductive double-shell hollow microsphere powder in step S6 is replaced by the conductive core-shell microspheres in step S4, and the other steps remain unchanged to prepare a graphene carbon negative electrode material.

[0063] The graphene carbon negative electrode materials obtained from Examples 1-3 and Comparative Examples 1-3 were prepared into lithium battery negative electrodes and then into lithium battery samples, and performance tests were performed: the graphene negative electrode material, acetylene black, and polyvinylidene fluoride were dispersed in N-methylpyrrolidone at a mass ratio of 8:1:1, then coated on the surface of copper foil. After drying, a negative electrode sheet was formed using a sheet press. A metal lithium sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution of ethylene carbonate + diethyl carbonate was used as the electrolyte. The battery was assembled with a Celgard 2500 diaphragm in a glove box to form a button cell. The battery's charge and discharge performance was tested using a battery tester. The voltage range was 0.01-3V, and the results are shown in Table 1:

[0064] Table 1 Performance test results of various lithium battery samples

[0065]

[0066]

[0067] As can be seen from Table 1, the graphene carbon negative electrode materials obtained in Examples 1 to 3 are prepared into lithium battery negative electrodes and then prepared into lithium batteries. Their first discharge capacity, first charge specific capacity, first coulombic efficiency and conductivity are significantly better than those of the comparative example, and the volume change percentage is significantly lower than that of the comparative example, indicating that the graphene carbon negative electrode material prepared by the present invention can significantly increase the conductivity of the lithium battery, promote the rapid transmission of lithium ions, alleviate the volume expansion during the charge and discharge process of the lithium battery, and increase the cycle capacity, first discharge capacity and first coulombic efficiency of the lithium battery.

[0068] In Comparative Example 1, the sulfonated graphene powder was replaced with graphene oxide powder. The sulfonated graphene powder's surface is rich in sulfonic acid groups, which participate in the formation of the SEI film, creating a stable LiF-rich interfacial layer, reducing electrolyte decomposition and irreversible consumption of active lithium. The cerium ions in the metal skeleton possess excellent corrosion resistance, protecting the electrode material from corrosion by electrolyte components and ensuring the lifespan of the negative electrode material.

[0069] In Comparative Example 2, aniline is discarded, so that it cannot form polyaniline. The sulfonic acid groups contained in the polyaniline structure can cooperate with the sulfonated graphene powder to stabilize the SEI film, reduce the decomposition of the electrolyte and the consumption of active lithium. In addition, polyaniline has excellent conductivity and can construct a three-dimensional conductive network with the sulfonated graphene and the metal skeleton to promote the rapid transmission of lithium ions.

[0070] In Comparative Example 3, the conductive double-shell hollow microsphere powder is replaced with conductive core-shell microspheres, sulfonated graphene, and the conductive core-shell microspheres and metal skeleton construct a three-dimensional conductive network to increase conductivity and promote rapid lithium ion transmission. The hollow structure of the conductive core-shell microspheres and the gap between the metal skeleton shells can buffer the volume expansion during charging and discharging, and the cerium metal ions in the metal skeleton have excellent anti-corrosion properties, which can prevent the electrode material from being corroded by components in the electrolyte, thereby ensuring the service life of the negative electrode material.

[0071] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0072] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a graphene carbon negative electrode material, characterized in that: The following steps are included: Step 1: The sulfonic acid group of 2-acrylamide-2-methylpropanesulfonic acid is grafted onto the surface of polystyrene nanospheres with a particle size of 20-30 nm through free radical polymerization under the action of an initiator, and the sulfonic acid group is ionically bonded with an aniline monomer to obtain conductive core-shell microspheres; the conductive core-shell microspheres, cerium nitrate and deionized water are added to a reactor, stirred at 120-130° C. and 400-500 r / min for 12-14 hours, filtered, and the filter cake is washed with N,N-dimethylformamide to remove the polystyrene template, then washed with anhydrous ethanol 2-3 times, and vacuum dried to obtain a conductive double-shell hollow microsphere powder; Step 2: Add sulfonated graphene, conductive double-shell hollow microsphere powder, silicon powder and deionized water into a reactor, ultrasonically disperse for 40-60 minutes, stir at 20-25°C and 400-500r / min for 1-2 hours to obtain a mixed suspension, place the mixed suspension in a freeze dryer, freeze-dry for 12-14 hours, disperse the product in anhydrous ethanol, heat to 170-180°C, and continue the reaction for 12-14 hours to obtain a graphene carbon negative electrode material.

2. The method for preparing a graphene carbon negative electrode material according to claim 1, wherein: The conductive core-shell microspheres, cerium nitrate and deionized water in step 1 are used in a ratio of 50-60 g: 30-40 g: 800-900 mL.

3. The method for preparing a graphene carbon negative electrode material according to claim 1, wherein: The usage ratio of the sulfonated graphene, the conductive double-shell hollow microsphere powder, the silicon powder, the deionized water and the anhydrous ethanol in step 2 is 50-60 g: 40-50 g: 80-90 g: 800-900 mL: 400-500 mL.

4. The method for preparing a graphene carbon negative electrode material according to claim 1, wherein: The specific steps of the conductive core-shell microspheres in step 1 are as follows: The precursor solution, aniline, 2,5-dihydroxyterephthalic acid and 10-12% ethanol solution were added to a reactor, stirred at 80-90°C and 400-500 r / min for 30-40 minutes, and then ammonium persulfate was added. The temperature was lowered to 0-4°C, and the reaction was continued for 12-14 hours. The product was filtered, washed, and vacuum dried to obtain conductive core-shell microspheres. The usage ratio of the precursor solution, aniline, 2,5-dihydroxyterephthalic acid, ethanol solution and ammonium persulfate is 120-140 mL: 80-90 mL: 70-80 g: 800-900 mL: 5-6 g.

5. The method for preparing a graphene carbon negative electrode material according to claim 1, wherein: The sulfonated graphene powder in step 2 is prepared by the following steps: Add chlorinated graphene powder, sodium sulfite and N,N-dimethylacetamide into a reactor, perform ultrasonic dispersion for 40-60 min, stir at 150-160° C. and 400-500 r / min for 24-26 h, cool naturally, then add 700-800 mL of deionized water, continue stirring for 2-3 h, filter, wash, and vacuum dry to obtain sulfonated graphene powder; The usage ratio of the acyl chloride graphene powder, sodium sulfite, N,N-dimethylacetamide and deionized water is 50-60 g: 56-58 g: 300-400 mL: 700-800 mL.

6. The method for preparing a graphene carbon negative electrode material according to claim 5, wherein: The chlorinated graphene powder is prepared by the following steps: Graphene oxide powder and 20-30wt% thionyl chloride solution are added to a reactor in a dosage ratio of 60-70g:400-600mL, stirred for 3-4h under vacuum conditions of -0.1 to -0.03MPa, 80-85°C and 400-500r / min, and the unreacted thionyl chloride is removed by rotary evaporation, and vacuum drying is performed to obtain acylated graphene powder.

7. The method for preparing a graphene carbon negative electrode material according to claim 6, wherein: The graphene oxide powder is prepared by the following steps: flake graphite, phosphorus pentoxide, potassium persulfate and a 98% by mass concentrated sulfuric acid solution are added to a reactor, stirred at 80-85° C. and 400-500 r / min for 3-4 hours, filtered, washed, and vacuum dried to obtain pre-oxidized graphite; pre-oxidized graphite, potassium permanganate, a 98% by weight concentrated sulfuric acid solution and a 30-40% by weight hydrogen peroxide solution are added to a reactor, stirred at 80-85° C. and 400-500 r / min for 3-4 hours, filtered, washed, and vacuum dried to obtain graphene oxide powder with a particle size of 30-40 μm; The usage ratio of the flake graphite, phosphorus pentoxide, potassium persulfate and concentrated sulfuric acid solution is 80-90g:40-50g:40-50g:800-900mL; the usage ratio of the pre-oxidized graphite, potassium permanganate, concentrated sulfuric acid solution and hydrogen peroxide solution is 70-80g:30-40g:800-900mL:200-300mL.

8. The method for preparing a graphene carbon negative electrode material according to claim 4, wherein: The precursor solution is prepared by the following steps: Add polystyrene nanospheres with a particle size of 20-30 nm, 2-acrylamide-2-methylpropanesulfonic acid and deionized water into a reactor, stir at 20-25°C and 400-500 r / min for 20-30 minutes, then add ammonium persulfate, heat to 60-70°C, continue stirring for 4-5 hours, and cool naturally to room temperature to obtain a precursor solution; The usage ratio of the polystyrene nanospheres, 2-acrylamide-2-methylpropanesulfonic acid, deionized water and ammonium persulfate is 80-90 g: 50-60 g: 700-800 mL: 1.5-2 g.

9. A graphene carbon negative electrode material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the graphene carbon negative electrode material according to claim 9 in a negative electrode material for a lithium ion battery.

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