Graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material as well as preparation method and application thereof

Abstract

The invention provides a graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material and a preparation method thereof. The graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material is applied to a lithium ion battery negative electrode material. The thin film material comprises graphene oxide nanosheets, silicon particles embedded between the graphene oxide nanosheets and uniformly mixed sulfonated asphalt, and the graphene oxide nanosheets are used as a basic skeleton structure of the thin film material in an irregular arrangement mode; the silicon particles serving as cores are wrapped among the graphene oxide skeleton structures; and the sulfonated asphalt is used as a reinforcing component to connect the graphene oxide sheet layer and the silicon particles wrapped in the graphene oxide sheet layer so as to reinforce the skeleton structure of the film. The method comprises the following steps: adding a sulfonated asphalt solution into a graphene oxide solution, adding silicon powder into the solution, stirring, and carrying out ultrasonic treatment; coating to form a film, and naturally airing; and sintering to obtain the compaction-resistant composite film material. The compaction-resistant composite film material disclosed by the invention has a sulfonated asphalt reinforced graphene oxide framework, so that the compaction resistance of the film material can be greatly improved, the integrity of the framework structure can be kept in a battery compaction process, and a channel is provided for transportation of lithium ions in a cycle process; the composite thin film material with rigidity and softness can resist compaction, can be bent, and has excellent electrochemical performance and wide application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a compaction-resistant graphene oxide-sulfonated asphalt-silicon composite film material and a preparation method and application thereof. Background Art

[0002] In order to meet the demand for the development of lithium-ion batteries with high energy density, high power density and long cycle life, it is necessary to develop advanced electrode materials for various applications such as portable electronic devices, electric vehicles and renewable energy integration. The composite of silicon and graphene oxide is considered to be a very promising method to overcome the above challenges. The combination of silicon and graphene oxide sheets has been shown to significantly improve the cycle stability of the battery, in which graphene oxide alleviates the volume change effect of silicon and promotes the transmission of electrons and lithium ions. The composite of silicon into randomly oriented graphene oxide assemblies can avoid the use of any adhesives and conductive additives, but as a flexible film material, its poor compaction resistance problem still exists. Sulfonated asphalt is added to the mixed solution of graphene oxide and silicon, and a composite film material with a hard skeleton structure is prepared by a doctor blade method. The graphene oxide skeleton reinforced with sulfonated asphalt can greatly improve the compaction resistance of the film material, so that it can maintain the integrity of the skeleton structure during the battery compaction process, and provide a channel for the transportation of lithium ions during the cycle. This rigid and flexible film material can not only withstand compaction but also realize the bending of the material, with excellent electrochemical properties and broad application prospects. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a graphene oxide-sulfonated asphalt-silicon compression-resistant composite film material.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] S01: uniformly coating the polymer solution on a glass plate, and drying at 70-90° C. to obtain a polymer substrate;

[0006] S02: The silicon-based material, graphene oxide solution, and sulfonated asphalt solution are uniformly mixed by a magnetic stirrer, and ultrasonically mixed using an ultrasonic machine to obtain a coating slurry;

[0007] S03: uniformly coating the slurry on the polymer substrate, and removing the graphene oxide-sulfonated asphalt-silicon layer on the polymer substrate after natural drying for 12 to 24 hours to obtain an untreated compaction-resistant composite film material;

[0008] S04: thermally reducing the graphene oxide-sulfonated asphalt-silicon film under an inert atmosphere to finally obtain a compression-resistant composite film material.

[0009] Preferably, the polymer solution in step S01 is a mixture of polyvinylidene fluoride and N,N-dimethylacetamide.

[0010] Preferably, the concentration of the graphene oxide solution in step S02 is 10 mg / ml, the particle size of the silicon-based material is 50-300 nm, accounting for 30%-90% of the film material, the concentration of the sulfonated asphalt solution is 165 mg / ml, and the mass ratio of graphene oxide to sulfonated asphalt is (84-60):(43-83.5).

[0011] Preferably, in step S04, the inert atmosphere is at least one of argon and nitrogen, the heating temperature is 700° C. to 900° C., and the heating time is 1 to 3 hours.

[0012] In addition, the present invention also provides a self-supporting negative electrode plate, which does not require a binder or a conductive agent.

[0013] Furthermore, the present invention also provides a lithium battery, comprising the above-mentioned negative electrode plate.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The graphene oxide sheet structure in the composite film material serves as a skeleton, providing a channel for the transport of lithium ions during the cycle;

[0016] (2) After the addition of the sulfonated asphalt solution, the skeleton structure of the graphene oxide is reinforced, so that the compaction resistance of the composite film material of the present invention is significantly improved, the structure is maintained under high pressure, and excellent electrochemical performance is exhibited.

[0017] (3) The surface of the internal silicon particles of the self-supporting composite film material of the present invention is coated with a thin layer of asphalt carbon, which can increase the conductivity of the silicon particles. DETAILED DESCRIPTION

[0018] The present invention provides a graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material and a preparation method thereof. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they all fall within the scope of protection of the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications of this article without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0019] Specifically, the silicon-carbon thin film negative electrode material has the disadvantages of poor conductivity of the silicon particles themselves during application, and the film support strength is insufficient during the battery compaction process, resulting in easy collapse of the structure. The above disadvantages have become an obstacle to the further application of silicon-carbon thin film negative electrode materials. The present invention adds sulfonated asphalt between the silicon particles and the graphene oxide sheets. Firstly, a thin carbon layer can be coated on the outside of the silicon particles, thereby increasing the conductivity of the silicon particles. Secondly, the purpose of strengthening the graphene oxide skeleton structure can be achieved, so that the integrity of the structure can be maintained during the battery compaction process, providing a path for the transportation of lithium ions during the cycle process.

[0020] Hereinafter, the compaction-resistant graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material according to the present invention, as well as the preparation method and application thereof will be described in detail in conjunction with embodiments.

[0021] A method for preparing a graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material, the specific method steps are as follows:

[0022] S01: uniformly coating the polymer solution on a glass plate, and drying at 70-90° C. for 1-3 hours to obtain a polymer substrate;

[0023] S02: The silicon-based material, graphene oxide solution, and sulfonated asphalt solution are uniformly mixed by a magnetic stirrer, and ultrasonically mixed using an ultrasonic machine to obtain a coating slurry;

[0024] S03: uniformly coating the slurry on the polymer substrate, removing the graphene oxide-sulfonated asphalt-silicon layer on the polymer substrate after natural drying, to obtain an untreated compaction-resistant composite film material;

[0025] S04: thermally reducing the graphene oxide-sulfonated asphalt-silicon film under an inert atmosphere to finally obtain a compression-resistant composite film material.

[0026] In the above scheme, step S01 is specifically as follows: polyvinylidene fluoride and N,N-dimethylacetamide are mixed in a mass ratio of 1:5, heated in an oil bath to 70°C, and then heated for 6 to 12 hours to obtain a polymer solution, which is evenly coated on a glass plate with a coating height of 200 μm, and dried at 70 to 90°C for 1 to 2 hours to obtain a polymer substrate.

[0027] Step S02 is specifically as follows: graphene oxide and sulfonated asphalt are mixed in a mass ratio of (84-60): (43-83.5), and 84 mg of silicon-based material is added to the above solution. The mixed solution is stirred for 1-3 hours using a magnetic stirrer and then ultrasonically dispersed for 10-30 minutes. The concentration of the graphene oxide solution used is 10 mg / ml, and the concentration of the sulfonated asphalt solution is 165 mg / ml.

[0028] Step S03 is as follows: pour the slurry onto one side of the polymer substrate, apply it at a height of 200 μm to 800 μm, and let it stand to dry naturally. After it is completely dried, carefully peel it off from the polymer substrate with tweezers, and then place it in an oven at 80°C for 6 to 12 hours to completely dry the remaining moisture in the film.

[0029] Step S04 is specifically as follows: placing the dried thin film material in an inert atmosphere of at least one of argon and nitrogen using a tube furnace for heat treatment at a heating temperature of

[0030] 700°C to 900°C, heating time is 1 to 3h, to obtain graphene oxide-sulfonated asphalt-silicon compression resistant composite film material.

[0031] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments.

[0032] Example 1

[0033] Preparation of negative electrode materials:

[0034] S1: Polyvinylidene fluoride and N,N-dimethylacetamide were mixed in a mass ratio of 1:5, heated in an oil bath to 70°C, and heated for 8 hours to obtain a polymer solution. After cooling to room temperature, a 200 μm applicator was used to evenly coat the solution on a glass plate, and dried at 80°C for 2 hours to obtain a polymer substrate.

[0035] S2: Purify the purchased sulfonated asphalt powder. Mix the sulfonated asphalt powder and deionized water at a mass ratio of 1:10 and stir for 12 hours, then centrifuge the solution at 10,000 revolutions per minute for 10 minutes, take the supernatant, dry it at 80°C to obtain purified sulfonated asphalt, and dissolve 1.65g of the purified sulfonated asphalt in 10ml of deionized water to obtain a 165mg / ml sulfonated asphalt solution.

[0036] S3: 7.6 ml of 10 mg / ml graphene oxide was mixed with 0.3 ml of 165 mg / ml sulfonated asphalt solution, 84 mg of silicon-based material with a particle size of 100-200 nm was added to the above solution, the mixed solution was stirred for 2 h using a magnetic stirrer and then ultrasonically dispersed for 20 min.

[0037] S4 Pour the above slurry onto one side of the polymer substrate, apply it with a 500μm film applicator, and then let it stand to dry naturally. After it is completely dried, carefully peel it off from the polymer substrate with tweezers, and then place it in an 80℃ oven for 8h to completely dry the remaining moisture in the film.

[0038] S5 places the dried thin film material in argon gas and uses a tubular furnace for heat treatment at a heating temperature of 800°C. After heating to 800°C at a heating rate of 10°C / min, it is kept warm for 2 hours to obtain a graphene oxide-sulfonated asphalt-silicon composite thin film material, in which the silicon-based material accounts for 67.95% of the mass percentage of the composite film, and the carbon material accounts for 32.05% of the mass percentage of the composite film.

[0039] Preparation and testing of button half-cell:

[0040] The obtained graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material was cut into a negative electrode sheet with a diameter of 10 mm using a slicer. A button-type half-cell was assembled in the order of negative electrode shell, lithium sheet, electrolyte, PP diaphragm, electrolyte, silicon negative electrode sheet, gasket, spring sheet, and positive electrode shell in a glove box. The prepared button-type half-cell was subjected to constant current charge and discharge test using a charge and discharge instrument, with a discharge cut-off voltage of 0.01 V and a charge cut-off voltage of 2 V. The first two cycles of charge and discharge tests were carried out at a current density of 0.125 A / g, and subsequent cycles were carried out at a current density of 0.625 A / g.

[0041] Example 2

[0042] This embodiment adopts the same inventive concept as that of embodiment 1, and only the amount of graphene oxide and sulfonated asphalt used is different from that of embodiment 1. In this embodiment, the amount of 10 mg / ml graphene oxide is 8.4 ml, and the amount of 165 mg / ml sulfonated asphalt is 0.26 ml. A graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material is obtained, in which the silicon-based material accounts for 66.1% of the mass percentage of the composite film, and the carbon material accounts for 33.9% of the mass percentage of the composite film.

[0043] Example 3

[0044] This embodiment adopts the same inventive concept as that of embodiment 1, and only the amount of graphene oxide and sulfonated asphalt used is different from that of embodiment 1. In this embodiment, the amount of 10 mg / ml graphene oxide is 7 ml, and the amount of 165 mg / ml sulfonated asphalt is 0.42 ml. A graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material is obtained, in which the silicon-based material accounts for 66.58% of the mass percentage of the composite film, and the carbon material accounts for 33.42% of the mass percentage of the composite film.

[0045] Example 4

[0046] This embodiment adopts the same inventive concept as that of embodiment 1, and only the amount of graphene oxide and sulfonated asphalt used is different from that of embodiment 1. In this embodiment, the amount of 10 mg / ml graphene oxide is 6 ml, and the amount of 165 mg / ml sulfonated asphalt is 0.5 ml. A graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material is obtained, in which the silicon-based material accounts for 67.32% of the mass percentage of the composite film, and the carbon material accounts for 32.68% of the mass percentage of the composite film.

[0047] Comparative Example 1

[0048] Add 84 mg of silicon-based material with a particle size of 100-200 nm to 8.4 ml of 10 mg / ml graphene oxide, stir the mixed solution for 2 hours using a magnetic stirrer, and then ultrasonically disperse it for 20 minutes. Pour the slurry on one side of the polymer substrate, coat it with a 500 μm applicator, and then let it stand to dry naturally. After it is completely dried, carefully peel it off from the polymer substrate with tweezers, and then place it in an 80°C oven for 8 hours to thoroughly dry the remaining moisture in the film. The dried film material is placed in argon and heat-treated in a tubular furnace at a heating temperature of 800°C. After heating to 800°C at a heating rate of 10°C / min, keep warm for 2 hours to obtain a graphene oxide-silicon composite film material.

[0049] Table 1

[0050]

[0051] Table 1 summarizes the thickness retention rate and capacity retention rate of Examples 1 to 4 and Comparative Example 1 after being subjected to a pressure of 40 MPa and 100 cycles, from which the following points can be seen:

[0052] According to the data of the embodiments and comparative examples in the table, it can be seen that the compaction resistance of embodiment 1 is better than that of other embodiments and comparative examples. After being compressed by 40MPa, the thickness can still be maintained at 81.78%, and the capacity retention rate can reach 91% after 100 cycles. This shows that under the same experimental conditions, by adding sulfonated asphalt to the graphene oxide film material, it plays a role in reinforcing the graphene oxide sheet structure, and the overall structure of the film material is well maintained, so that the internal pores of the material do not collapse during the battery compaction process, providing a path for the transmission of lithium ions, thereby significantly improving the capacity retention rate and cycle life.

Claims

1. A method for preparing a graphene oxide-sulfonated asphalt-silicon compaction-resistant composite film material, characterized in that: The preparation method comprises the following steps: S01: uniformly coating the polymer solution on a glass plate, and drying at 70-90° C. to obtain a polymer substrate; S02: The silicon-based material, the graphene oxide solution, and the sulfonated asphalt solution are uniformly mixed by a magnetic stirrer, and ultrasonically mixed by an ultrasonic machine for 10 to 60 minutes to obtain a coating slurry; S03: uniformly coating the slurry on the polymer substrate, and removing the graphene oxide-sulfonated asphalt-silicon layer on the polymer substrate after natural drying for 12 to 24 hours to obtain an untreated compaction-resistant composite film material; S04: thermally reducing the graphene oxide-sulfonated asphalt-silicon film under an inert atmosphere to finally obtain a compression-resistant composite film material.

2. The method for preparing the graphene oxide-sulfonated asphalt-silicon compaction resistant composite film material according to claim 1, characterized in that: The polymer solution in step S01 is a mixture of polyvinylidene fluoride and N,N-dimethylacetamide.

3. The method for preparing the graphene oxide-sulfonated asphalt-silicon compaction resistant composite film material according to claim 1, characterized in that: In step S02, the concentration of the graphene oxide solution is 10 mg / ml, the particle size of the silicon-based material is 50-300 nm, and the concentration of the sulfonated asphalt solution is 165 mg / ml.

4. The method for preparing the graphene oxide-sulfonated asphalt-silicon compaction resistant composite film material according to claim 1, characterized in that: The mass ratio of graphene oxide to sulfonated asphalt in step S02 is (84-60):(43-83.5).

5. The method for preparing the graphene oxide-sulfonated asphalt-silicon compaction resistant composite film material according to claim 1, characterized in that: The coating height of the film in step S03 is 200 μm to 800 μm.

6. The method for preparing the graphene oxide-sulfonated asphalt-silicon compaction resistant composite film material according to claim 1, characterized in that: In step S04, the inert atmosphere is at least one of argon and nitrogen, the heating temperature is 700° C. to 900° C., and the heating time is 1 to 3 hours.

7. A negative electrode for a lithium ion battery, characterized in that: The negative electrode is made of graphene oxide-sulfonated asphalt-silicon compression resistant composite film material, and the graphene oxide-sulfonated asphalt-silicon compression resistant composite film material is prepared by the preparation method of graphene oxide-sulfonated asphalt-silicon compression resistant composite film material described in claim 1.

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