Graphene-based silicon-carbon negative electrode material

Abstract

This invention discloses a graphene-based silicon-carbon anode material, belonging to the field of anode material technology. The raw materials, by mass fraction, are as follows: 3-5 parts triatomic-doped graphene, 51-63 parts phenolic resin monomer prepolymer solution, 0.5-0.9 parts initiator, and 1-1.6 parts foaming agent. The anode material prepared by this invention utilizes a porous carbon precursor prepared by in-situ polymerization of graphene and phenolic resin, followed by carbonization. This porous carbon exhibits exceptionally stable structure and excellent conductivity, significantly improving its performance, cycle life, stability, and conductivity. Through ternary synergistic doping, the prepared doped graphene can improve the battery's charge / discharge efficiency, specific capacity, and stability. Furthermore, by performing vapor deposition of silicon on specially manufactured porous carbon, uniform silicon loading and graphene dispersion are achieved, resulting in material consistency superior to traditional methods.

Description

Technical Field

[0001] This invention belongs to the field of anode material technology, specifically, it relates to a graphene-based silicon-carbon anode material. Background Technology

[0002] With the continued growth of global energy demand and the increasing prominence of environmental problems, the development of efficient and sustainable energy storage technologies has become an important direction for current scientific research. Lithium-ion batteries, due to their advantages such as high energy density, long cycle life, and environmental friendliness, have been widely used in electric vehicles, portable electronic devices, and smart grids.

[0003] Currently, graphite is the most widely used anode material in commercial applications. It possesses numerous advantages, such as relatively small irreversible capacity loss during charge and discharge, effectively reducing capacity loss during battery use; simultaneously, its volume expansion rate is approximately 10%, which allows the electrode structure to maintain good stability through multiple charge-discharge cycles, thus ensuring the battery's cycle life; furthermore, graphite materials exhibit relatively stable performance, maintaining relatively consistent electrochemical performance under different environmental conditions. However, graphite materials also have significant limitations, with a theoretical specific capacity of only 372 mAh / g, which largely restricts further improvements in the energy density of lithium-ion batteries. Therefore, the development of high-capacity anode materials has become a current research hotspot.

[0004] Silicon boasts a specific capacity as high as 4200 mAh / g, 11 times that of conventional graphite-based anode materials. Therefore, using silicon as an anode material can significantly improve the energy density of lithium-ion batteries, making it one of the most promising next-generation anode materials. However, during charge and discharge, silicon-based materials undergo extremely significant volume expansion, reaching up to 300%. Such a large volume change leads to the fragmentation of the silicon crystal structure, thereby damaging the conductive network inside the electrode and hindering electron transport. Simultaneously, it also causes the failure of the binder in the electrode, resulting in poor contact between the active material and the current collector, ultimately severely impacting the battery's cycle life. Therefore, it is urgent to address these industry challenges and develop a graphene-based silicon-carbon anode material to meet the higher demands of the anode material technology field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a graphene-based silicon-carbon anode material.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A graphene-based silicon-carbon anode material is prepared by the following steps:

[0008] Step A1: After ultrasonically dispersing the triatomic doped graphene and phenolic resin monomer prepolymer solution for 0.5-3 hours, a uniform dispersion system is formed, and a mixed prepolymer solution is obtained.

[0009] Step A2: Add an initiator to the mixed prepolymer liquid obtained in step A1, and raise the reaction temperature to 60-70℃. Carry out an in-situ polymerization reaction at this temperature for 2-3 hours. After the reaction is completed, add a foaming agent and raise the reaction temperature to 70-80℃. React at this temperature for 1-2 hours. After the reaction is completed, obtain graphene-modified phenolic resin material.

[0010] Step A3: Add the graphene-modified phenolic resin material obtained in step A2 into a tube furnace, introduce a protective gas, heat it to 800-1000℃ at a heating rate of 5-10℃ / min, and hold it at this temperature for 1-2 hours to carry out carbonization treatment. Carbon dioxide is introduced during the carbonization process to obtain a porous carbon / graphene composite.

[0011] Step A4: Using chemical vapor deposition, the porous carbon / graphene composite obtained in step A3 is placed in a vapor deposition furnace, a mixture of silane and argon is introduced, and the reaction is carried out at 500-600℃ for 1-3 hours. After the reaction is completed and cooled, it is taken out to obtain graphene-based silicon-carbon anode material.

[0012] As a further technical solution, the raw materials are as follows by mass: 3-5 parts of triatomic doped graphene, 51-63 parts of phenolic resin monomer prepolymer liquid, 0.5-0.9 parts of initiator, and 1-1.6 parts of foaming agent.

[0013] As a further technical solution, the initiator is one of hexamethylenetetramine, benzoyl peroxide, and p-toluenesulfonic acid.

[0014] As a further technical solution, the foaming agent is one of azodicarbonamide and ammonium bicarbonate.

[0015] As a further technical solution, the protective gas is either nitrogen or argon.

[0016] As a further technical solution, the volume ratio of the silane to argon mixture is 1:8-10.

[0017] Explanation of the preparation process: This invention first utilizes the decomposition of an initiator to generate free radicals, which initiate the polymerization reaction of phenolic monomers; the foaming agent decomposes upon heating to generate gas, forming bubbles during the polymerization process, thereby creating a porous structure in the phenolic resin. Graphene is uniformly dispersed in the phenolic resin, and then carbonization is performed. During the high-temperature carbonization process, the organic components in the phenolic resin gradually decompose, while the carbon elements are retained, forming porous carbon with a stable structure. Finally, a chemical vapor deposition method is used to deposit silicon atoms on the channels and surface of the porous carbon and graphene to obtain a graphene-based silicon-carbon anode material.

[0018] In terms of performance: Graphene has a large number of wrinkled microstructures. These wrinkles can provide sufficient expansion buffer space for the volume changes of nano-silicon during charging and discharging, effectively mitigating the damage to the material structure caused by the volume expansion of silicon and improving charging and discharging stability. Moreover, the porous carbon structure with a pore size of 2-3 nm formed by carbonization can not only ensure the stable deposition of silicon atoms, but also provide buffer space to mitigate the volume changes of silicon during charging and discharging, further improving stability.

[0019] As a further technical solution, the phenolic resin monomer prepolymer liquid is prepared through the following steps:

[0020] In a flask, phenol and formaldehyde aqueous solution (40% by mass) are added sequentially and stirred until homogeneous. Then, sodium hydroxide is added to adjust the pH of the solution to 8-9, and the reaction temperature is raised to 60-70℃. The reaction is stirred for 1-2 hours until the reaction is complete. After cooling to room temperature, a phenolic resin monomer prepolymer solution is obtained.

[0021] As a further technical solution, the raw materials are as follows by mass: 50-55 parts phenol and 60-70 parts formaldehyde aqueous solution.

[0022] Explanation of the preparation process: In this invention, phenol and formaldehyde are first prepolymerized. During the prepolymerization process, a hydroxymethylation reaction occurs to generate hydroxymethylphenol, resulting in a prepolymerized liquid.

[0023] In terms of performance: the hydroxymethyl groups in the prepolymer solution form hydrogen bonds with the oxygen-containing functional groups of graphene, which can promote the dispersion of graphene in phenolic resin and reduce the agglomeration of graphene.

[0024] As a further technical solution, the three-atom-doped graphene is prepared through the following steps:

[0025] S1. Immerse the copper foil in dilute hydrochloric acid (5% by mass) for 10-20 minutes to remove the surface oxide layer and impurities, then rinse it several times with deionized water and blow it dry to obtain pretreated copper foil.

[0026] S2. Place the pretreated copper foil obtained in step S1 into a vapor deposition furnace and introduce argon gas at a flow rate of 100 sccm for 5-10 minutes to replace the residual gas in the furnace.

[0027] S3. Heat the vapor deposition furnace to 1000℃ at a heating rate of 5-30℃ / min, and continuously introduce argon gas during the heating process. After the temperature reaches 1000℃, stabilize the temperature and start introducing methane, ammonia, hydrogen sulfide and phosphine gas. The reaction lasts for 60-90min.

[0028] S4. After the reaction is complete, turn off the methane, ammonia, hydrogen sulfide and phosphine gases, and continue to introduce argon gas to cool the vapor deposition furnace. Remove the furnace to obtain triatomic doped graphene.

[0029] As a further technical solution, the flow rate of methane is 30-60 sccm; the flow rate of ammonia is 15-35 sccm; the flow rate of hydrogen sulfide is 5-20 sccm; and the flow rate of phosphine is 3-15 sccm.

[0030] Explanation of the preparation process: This invention uses a vapor deposition method, and under the action of high temperature and a copper foil catalyst, carbon atoms generated by the decomposition of methane are deposited and grown on the surface of the copper foil. At the same time, nitrogen, sulfur and phosphorus atoms generated by the decomposition of ammonia, hydrogen sulfide and phosphine are embedded into the graphene lattice to achieve multi-atom doping.

[0031] In terms of performance: triatomic doped graphene was prepared by simultaneously doping with nitrogen, sulfur, and phosphorus. Nitrogen doping not only introduces extra electrons into the graphene lattice, improving conductivity, but also forms active sites at the edges or defects of graphene, providing more lithium-ion storage sites, reducing the damage to the structure caused by volume expansion, and improving stability. Sulfur doping can expand the interlayer spacing, allowing more lithium-ion insertion, while the polar sites increase the amount of lithium-ion adsorption, improving specific capacity. Finally, phosphorus doping causes the graphene plane to twist, forming a three-dimensional wrinkled structure. The three-dimensional structure provides more exposed active surfaces, increasing lithium-ion storage sites, and the wrinkled structure can buffer volume changes during charging and discharging, improving stability.

[0032] The beneficial effects of this invention are:

[0033] 1. The negative electrode material prepared by the present invention has an exceptionally stable porous carbon structure and extremely excellent conductivity, which is prepared by in-situ polymerization of graphene and phenolic resin to prepare a porous carbon precursor and carbonization. This significantly improves the performance of porous carbon, significantly enhances cycle life, and improves stability and conductivity.

[0034] 2. The doped graphene prepared by the present invention through ternary synergistic doping can improve the charge and discharge efficiency, specific capacity and stability of the battery;

[0035] 3. This invention achieves uniform silicon loading and graphene dispersion by vapor-phase deposition of silicon on specially manufactured porous carbon, resulting in material consistency superior to traditional methods. Detailed Implementation

[0036] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0037] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0038] Example 1

[0039] Preparation of three-atom-doped graphene:

[0040] S1. Immerse the copper foil in dilute hydrochloric acid (5% by mass) for 10 minutes to remove the surface oxide layer and impurities, then rinse it several times with deionized water and blow it dry to obtain the pretreated copper foil.

[0041] S2. Place the pretreated copper foil obtained in step S1 into a vapor deposition furnace and introduce argon gas at a flow rate of 100 sccm for 5 minutes to replace the residual gas in the furnace.

[0042] S3. The vapor deposition furnace is heated to 1000℃ at a heating rate of 5℃ / min, and argon gas is continuously introduced during the heating process. After the temperature reaches 1000℃, the temperature is stabilized, and methane, ammonia, hydrogen sulfide and phosphine gases are introduced. The flow rates of methane are 30 sccm, ammonia is 15 sccm, hydrogen sulfide is 5 sccm and phosphine is 3 sccm. The reaction lasts for 60 min.

[0043] S4. After the reaction is complete, turn off the methane, ammonia, hydrogen sulfide and phosphine gases, and continue to introduce argon gas to cool the vapor deposition furnace. Remove the furnace to obtain triatomic doped graphene.

[0044] Example 2

[0045] Preparation of three-atom-doped graphene:

[0046] S1. Immerse the copper foil in dilute hydrochloric acid (5% by mass) for 20 minutes to remove the surface oxide layer and impurities, then rinse it several times with deionized water and blow it dry to obtain pretreated copper foil.

[0047] S2. Place the pretreated copper foil obtained in step S1 into a vapor deposition furnace and introduce argon gas at a flow rate of 100 sccm for 10 min to replace the residual gas in the furnace.

[0048] S3. The vapor deposition furnace is heated to 1000℃ at a heating rate of 30℃ / min, and argon gas is continuously introduced during the heating process. After the temperature reaches 1000℃, the temperature is stabilized, and methane, ammonia, hydrogen sulfide and phosphine gases are introduced. The flow rates of methane are 60 sccm, ammonia is 35 sccm, hydrogen sulfide is 20 sccm and phosphine is 15 sccm. The reaction lasts for 90 min.

[0049] S4. After the reaction is complete, turn off the methane, ammonia, hydrogen sulfide and phosphine gases, and continue to introduce argon gas to cool the vapor deposition furnace. Remove the furnace to obtain triatomic doped graphene.

[0050] Example 3

[0051] Preparation of phenolic resin monomer prepolymer solution:

[0052] In a flask, 50g of phenol and 60g of formaldehyde aqueous solution (40% by mass) were added sequentially. After stirring and mixing evenly, sodium hydroxide was added to adjust the pH of the solution to 8. The reaction temperature was raised to 60℃ and stirred for 1 hour. After the reaction was completed, the solution was cooled to room temperature to obtain phenolic resin monomer prepolymer solution.

[0053] Example 4

[0054] Preparation of phenolic resin monomer prepolymer solution:

[0055] In a flask, 55g of phenol and 70g of formaldehyde aqueous solution (40% by mass) were added sequentially. After stirring and mixing evenly, sodium hydroxide was added to adjust the pH of the solution to 9. The reaction temperature was raised to 70℃ and stirred for 2 hours. After the reaction was completed, the solution was cooled to room temperature to obtain phenolic resin monomer prepolymer solution.

[0056] Example 5

[0057] Preparation of graphene-based silicon-carbon anode materials:

[0058] Step A1: 3g of the triatomic doped graphene prepared in Example 1 and 51g of the phenolic resin monomer prepolymer liquid prepared in Example 3 are ultrasonically dispersed for 0.5h to form a uniform dispersion system and obtain a mixed prepolymer liquid.

[0059] Step A2: Add 0.5g of hexamethylenetetramine to the mixed prepolymer solution obtained in step A1, and raise the reaction temperature to 60°C. At this temperature, carry out an in-situ polymerization reaction for 2 hours. After the reaction is completed, add 1g of azodicarbonamide, raise the reaction temperature to 70°C, and react at this temperature for 1 hour. After the reaction is completed, graphene-modified phenolic resin material is obtained.

[0060] Step A3: Add the graphene-modified phenolic resin material obtained in step A2 into a tube furnace, introduce nitrogen as a protective gas, heat to 800°C at a heating rate of 5°C / min, and hold at this temperature for 1 hour to carry out carbonization treatment. Carbon dioxide is introduced during the carbonization process to obtain a porous carbon / graphene composite.

[0061] Step A4: Using chemical vapor deposition, the porous carbon / graphene composite obtained in step A3 is placed in a vapor deposition furnace, and a mixture of silane and argon (volume ratio of 1:8) is introduced. The mixture is reacted at 500°C for 1 hour. After the reaction is completed and cooled, the composite is removed to obtain graphene-based silicon-carbon anode material.

[0062] Example 6

[0063] Preparation of graphene-based silicon-carbon anode materials:

[0064] Step A1: 4g of the triatomic doped graphene prepared in Example 2 and 57g of the phenolic resin monomer prepolymer liquid prepared in Example 4 are ultrasonically dispersed for 1.5h to form a uniform dispersion system and obtain a mixed prepolymer liquid.

[0065] Step A2: Add 0.7g of benzoyl peroxide to the mixed prepolymer solution obtained in step A1, and raise the reaction temperature to 65℃. Carry out the in-situ polymerization reaction at this temperature for 3 hours. After the reaction is completed, add 1.3g of ammonium bicarbonate, and raise the reaction temperature to 75℃. React at this temperature for 1.5 hours. After the reaction is completed, graphene-modified phenolic resin material is obtained.

[0066] Step A3: Add the graphene-modified phenolic resin material obtained in step A2 into a tube furnace, introduce nitrogen as a protective gas, heat to 900°C at a heating rate of 10°C / min, and hold at this temperature for 1.5 hours to carry out carbonization treatment. Carbon dioxide is introduced during the carbonization process to obtain a porous carbon / graphene composite.

[0067] Step A4: Using chemical vapor deposition, the porous carbon / graphene composite obtained in step A3 is placed in a vapor deposition furnace, and a mixture of silane and argon (volume ratio of 1:9) is introduced. The mixture is reacted at 600℃ for 2 hours. After the reaction is completed and cooled, the composite is removed to obtain graphene-based silicon-carbon anode material.

[0068] Example 7

[0069] Preparation of graphene-based silicon-carbon anode materials:

[0070] Step A1: 5g of the triatomic doped graphene prepared in Example 2 and 63g of the phenolic resin monomer prepolymer liquid prepared in Example 4 are ultrasonically dispersed for 3 hours to form a uniform dispersion system and obtain a mixed prepolymer liquid.

[0071] Step A2: Add 0.9g of p-toluenesulfonic acid to the mixed prepolymer solution obtained in step A1, and raise the reaction temperature to 70℃. Carry out the in-situ polymerization reaction at this temperature for 3 hours. After the reaction is completed, add 1.6g of ammonium bicarbonate, raise the reaction temperature to 80℃, and react at this temperature for 2 hours. After the reaction is completed, graphene modified phenolic resin material is obtained.

[0072] Step A3: Add the graphene-modified phenolic resin material obtained in step A2 into a tube furnace, introduce argon as a protective gas, heat to 1000℃ at a heating rate of 10℃ / min, and hold at this temperature for 2 hours to carry out carbonization treatment. Carbon dioxide is introduced during the carbonization process to obtain a porous carbon / graphene composite.

[0073] Step A4: Using chemical vapor deposition, the porous carbon / graphene composite obtained in step A3 is placed in a vapor deposition furnace, and a mixture of silane and argon (volume ratio of 1:10) is introduced. The mixture is reacted at 600℃ for 3 hours. After the reaction is completed and cooled, the composite is removed to obtain graphene-based silicon-carbon anode material.

[0074] Comparative Example 1

[0075] Using waste fruit shells, rice husks, and sugarcane bagasse as raw materials, biomass-derived porous carbon is prepared after carbonization and activation, and used as a negative electrode material.

[0076] Comparative Example 2

[0077] The anode material was prepared by replacing the three-atom-doped graphene in Example 7 with ordinary undoped graphene of the same mass, and the remaining steps were the same as in Example 7.

[0078] The negative electrode materials obtained in Examples 5, 6, and 7, and Comparative Examples 1 and 2 were assembled into coin cells, and their performance was tested.

[0079] The measurement results are shown in the table below:

[0080] Test Project Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Specific capacity (mAh / g) 2377 2412 2437 1189 1834 Capacity retention after 500 cycles at 0.5C / % 91.3 91.9 92.2 72.8 85.5 First charge / discharge efficiency / % 88.1 88.9 89.6 70.5 80.3

[0081] As can be seen from the table above, the anode material prepared in the embodiments of the present invention has higher specific capacity, cycle stability and charge-discharge efficiency than the comparative example. Therefore, the present invention has important value in the field of anode material technology.

[0082] The above description is merely an example and illustration of the present invention. Any modifications or additions made by those skilled in the art to the specific embodiments described, or any substitutions made in a similar manner, should fall within the protection scope of the present invention.

Claims

1. A graphene-based silicon-carbon anode material, characterized in that, It is prepared through the following steps: Step A1: After ultrasonically dispersing the triatomic doped graphene and phenolic resin monomer prepolymer solution for 0.5-3 hours, a mixed prepolymer solution is obtained. Step A2: Add an initiator to the mixed prepolymer liquid obtained in step A1 and react at 60-70℃ for 2-3 hours. After the reaction is complete, add a foaming agent and react at 70-80℃ for 1-2 hours. After the reaction is complete, graphene-modified phenolic resin material is obtained. Step A3: Add the graphene-modified phenolic resin material obtained in step A2 into a tube furnace, introduce a protective gas, heat it to 800-1000℃ at a heating rate of 5-10℃ / min, and hold it at this temperature for 1-2 hours to carry out carbonization treatment. Carbon dioxide is introduced during the carbonization process to obtain a porous carbon / graphene composite. Step A4: Using chemical vapor deposition, the porous carbon / graphene composite obtained in step A3 is placed in a vapor deposition furnace, and a mixture of silane and argon is introduced. The reaction is carried out at 500-600℃ for 1-3 hours. After the reaction is completed, graphene-based silicon-carbon anode material is obtained. The phenolic resin monomer prepolymer solution is prepared through the following steps: In a flask, phenol and formaldehyde aqueous solution are added in sequence and stirred until well mixed. Then sodium hydroxide is added to adjust the pH of the solution to 8-9. The reaction is carried out at 60-70℃ for 1-2 hours. Once the reaction is complete, a phenolic resin monomer prepolymer solution is obtained. The three-atom-doped graphene is prepared through the following steps: S1. Soak the copper foil in dilute hydrochloric acid for 10-20 minutes, then rinse with deionized water and dry to obtain pretreated copper foil. S2. Place the pretreated copper foil obtained in step S1 into a vapor deposition furnace and introduce argon gas. S3. Heat the vapor deposition furnace to 1000℃ at a heating rate of 5-30℃ / min, and continuously introduce argon gas during the heating process. After the temperature reaches 1000℃, stabilize the temperature and start introducing methane, ammonia, hydrogen sulfide and phosphine gas. The reaction lasts for 60-90min. S4. After the reaction is complete, turn off the methane, ammonia, hydrogen sulfide and phosphine gases, cool down, and remove the product to obtain triatomic doped graphene.

2. The graphene-based silicon-carbon anode material according to claim 1, characterized in that, The raw materials are as follows by mass: 3-5 parts triatomic doped graphene, 51-63 parts phenolic resin monomer prepolymer liquid, 0.5-0.9 parts initiator, and 1-1.6 parts foaming agent.

3. The graphene-based silicon-carbon anode material according to claim 1, characterized in that, The initiator is one of hexamethylenetetramine, benzoyl peroxide, and p-toluenesulfonic acid.

4. The graphene-based silicon-carbon anode material according to claim 1, characterized in that, The foaming agent is one of azodicarbonamide and ammonium bicarbonate.

5. The graphene-based silicon-carbon anode material according to claim 1, characterized in that, The protective gas is either nitrogen or argon.

6. The graphene-based silicon-carbon anode material according to claim 1, characterized in that, The volume ratio of the silane to argon mixture is 1:8-10.

7. The graphene-based silicon-carbon anode material according to claim 1, characterized in that, The raw materials, by weight, are as follows: 50-55 parts phenol and 60-70 parts formaldehyde aqueous solution.

8. The graphene-based silicon-carbon anode material according to claim 1, characterized in that, The flow rate of methane is 30-60 sccm; the flow rate of ammonia is 15-35 sccm; the flow rate of hydrogen sulfide is 5-20 sccm; and the flow rate of phosphine is 3-15 sccm.