Preparation method for three-dimensional graphene based in-situ grown silicon negative electrode material for lithium battery, negative electrode material, and use thereof

Abstract

A preparation method for a three-dimensional graphene based in-situ grown silicon negative electrode material for a lithium battery, comprising the following steps: uniformly mixing nano silicon particles with three-dimensional graphene particles, and then adding a dispersing agent for mixing; adding a solvent step by step for mixing, and performing kneading processing; continuing to add a solvent for mixing, and performing slurry forming processing; then performing primary grinding for mixing; adding an organic carbon source, and performing secondary grinding for mixing and coating; then performing spray drying treatment to obtain a nano silicon particle group coated with the organic carbon source and using three-dimensional graphene as a framework; sintering the nano silicon particle group in a protective inert gas atmosphere, and the organic carbon source coated on the nano silicon particle group generating a thermal cracking reaction to generate amorphous carbon; and then crushing and sieving to obtain three-dimensional graphene based in-situ grown nano silicon particles. The prepared three-dimensional graphene based in-situ grown nano silicon particles can be used as a lithium battery negative electrode material, the service life of a battery can be greatly prolonged, and the cycle performance and the low-temperature performance are remarkably improved.

Description

Preparation method of three-dimensional graphene in-situ grown silicon negative electrode material for lithium battery, negative electrode material and application thereof Technical Field

[0001] The present invention relates to the technical field of energy storage material production, and in particular to a preparation method of a three-dimensional graphene in-situ grown silicon negative electrode material for a lithium battery, the negative electrode material and applications thereof. Background Art

[0002] Lithium-ion batteries have been widely used in recent years due to their excellent performance. Currently, the primary negative electrode material for lithium-ion batteries is graphite. Graphite materials offer advantages such as low cost and excellent performance. However, as the market demands higher energy density, the disadvantage of graphite materials' lower energy density becomes more pronounced in certain applications.

[0003] Silicon can be the basis for the negative electrode material of lithium-ion batteries, with the following advantages:

[0004] 1) Silicon can form a Li4.4Si alloy with lithium, with a theoretical lithium storage capacity of up to 4200mAh / g (more than 10 times the capacity of graphite);

[0005] 2) The lithium insertion potential of silicon (0.5V) is slightly higher than that of graphite, making it difficult to form "lithium dendrites" during charging;

[0006] 3) Silicon has low reactivity with electrolyte and co-embedding of organic solvents will not occur.

[0007] However, silicon also has disadvantages as a negative electrode material for lithium-ion batteries. Silicon is a semiconductor material with low inherent electrical conductivity. During electrochemical cycling, the insertion and extraction of lithium ions causes the material's volume to expand and contract by more than 300%. The resulting mechanical forces gradually pulverize the material, causing structural collapse. This ultimately leads to the separation of the electrode active material from the current collector, loss of electrical contact, and a significant reduction in battery cycle performance. Furthermore, due to this volume effect, silicon has difficulty forming a stable solid electrolyte interface (SEI) film in the electrolyte. As the electrode structure deteriorates, new SEI films continuously form on the exposed silicon surface, exacerbating silicon corrosion and capacity degradation. Technical issues

[0008] The purpose of the present invention is to provide a preparation method of a three-dimensional graphene in-situ grown silicon negative electrode material for lithium batteries. In the pores of the three-dimensional multilayer structure of three-dimensional graphene, silicon material is grown in situ. The grown silicon material is coated with graphene, which can inhibit the expansion and pulverization of the silicon material. As a negative electrode material for lithium batteries, it can greatly increase the service life of the battery and significantly improve the cycle performance and low-temperature performance.

[0009] Another object of the present invention is to provide a three-dimensional graphene in-situ grown silicon negative electrode material for lithium batteries prepared by this method.

[0010] Another object of the present invention is to provide an application of the three-dimensional graphene in-situ grown silicon negative electrode material for lithium batteries. Technical Solutions

[0011] In order to achieve the above technical effects, the present invention adopts the following technical solutions:

[0012] A method for preparing a three-dimensional graphene in-situ grown silicon negative electrode material for a lithium battery comprises the following steps:

[0013] S1: After uniformly mixing the nano-silicon particles and the three-dimensional graphene particles, a dispersant is added and mixed;

[0014] S2: adding solvent stepwise to the mixture of S1 and kneading;

[0015] S3: continue adding solvent to S2 and mixing to form a slurry;

[0016] S4: Grind and mix the slurry of S3 once;

[0017] S5: adding an organic carbon source to the slurry of S4, and performing secondary grinding, mixing and coating;

[0018] S6: spray drying the mixed solution of S5 to obtain nano-silicon particles coated with an organic carbon source and having a three-dimensional graphene skeleton;

[0019] S7: sintering the nano-silicon particle clusters obtained in S6 under an inert gas atmosphere, so that the organic carbon source coated on the surface thereof undergoes a thermal cracking reaction to generate amorphous carbon;

[0020] S8: The S7 sintered material is crushed and sieved to obtain three-dimensional graphene in situ grown nano-silicon particles.

[0021] In a specific embodiment, the particle size of the nano-silicon particles in step S1 is 50nm-500nm; the three-dimensional graphene particles have a three-dimensional structure, a particle size of 1μm-10μm, a specific surface area of ​​500-2500㎡ / g, and a pore size of 10nm-2μm.

[0022] In a specific embodiment, the mixing equipment in step S1 is selected from any one of a double planetary mixer, a kneader, and an internal mixer; preferably, the dispersant is water or an oil-based dispersant, preferably water.

[0023] In a preferred embodiment, the mass ratio of the nano-silicon particles, the three-dimensional graphene particles and the dispersant in step S1 is 60%-90%: 8%-30%: 2%-10%, and the total mass is 100 parts.

[0024] In a specific embodiment, the solvent in step S2 is water or an organic solvent, and the solid mixture of S1 is kneaded into a muddy kneaded material; preferably, the total amount of the solvent added is 50-100 parts.

[0025] In a specific embodiment, in step S3, 50-150 parts of solvent are added and mixed to form a mixed slurry.

[0026] In a specific embodiment, the organic carbon source in step S5 is one or a combination of two or more of lactose, glucose, sucrose, and polyethylene glycol; preferably, the amount of the organic carbon source added is 1-10 parts.

[0027] In a specific embodiment, the sintering temperature in step S7 is 650-950° C., and the sintering time is 6-36 hours.

[0028] In a specific embodiment, the particle size obtained by sieving in step S8 is 1 μm-10 μm.

[0029] On the other hand, the three-dimensional graphene in-situ grown silicon negative electrode material for lithium batteries prepared by the above preparation method.

[0030] On the other hand, the three-dimensional graphene in-situ grown silicon negative electrode material for lithium batteries prepared by the above preparation method is used in lithium battery negative electrode materials. Beneficial effects

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The preparation method of the present invention in situ grows silicon material in the pores of the three-dimensional multilayer structure of three-dimensional graphene. The grown silicon material is coated with graphene, which can inhibit the expansion and pulverization of the silicon material. Even if the silicon material is pulverized, it will not undergo a separation reaction because it is coated with graphene and can continue to provide capacity, thereby greatly improving the service life of the battery.

[0033] The three-dimensional graphene in the negative electrode material of this invention possesses ultrahigh electrical conductivity. As a carrier, it can significantly enhance the electrical conductivity of the grown material, significantly increasing its power density and significantly improving cycling and low-temperature performance. The porosity of three-dimensional graphene provides excellent adsorption capacity, making it a good support for other materials and providing a foundation for in-situ growth. The high specific surface area of ​​three-dimensional graphene allows for the formation of a double-layer reaction in the ungrown pores, significantly improving the material's pulse performance and enhancing the device's response speed. Best Mode for Carrying Out the Invention

[0034] In order to better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention.

[0035] This patent provides a method for preparing a three-dimensional graphene in-situ grown silicon negative electrode, the specific steps are as follows:

[0036] S1: After the nano-silicon particles and three-dimensional graphene particles are evenly mixed using a mixing device, a dispersant is added and mixed;

[0037] S2: adding solvent step by step to the solid mixture of S1 and kneading;

[0038] S3: Continue adding solvent to S2 to mix and process into pulp

[0039] S4: Grind and mix the S3 slurry once;

[0040] S5: adding an organic carbon source to the S4 slurry for secondary grinding, mixing and coating;

[0041] S6: spray drying the S5 mixture to obtain nano-silicon particle clusters coated with an organic carbon source and having a three-dimensional graphene skeleton;

[0042] S7: The obtained S6 nano-silicon particle clusters are sintered under an inert gas atmosphere, and the organic carbon source coated on the surface undergoes a thermal cracking reaction to generate amorphous carbon;

[0043] S8: The sintered product of S7 is crushed and sieved to an appropriate particle size to obtain the three-dimensional graphene in-situ grown nano-silicon particles required by the present invention.

[0044] In step S1, the particle size of the nano-silicon particles is 50 nm-500 nm, including but not limited to 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc. The three-dimensional graphene particles have a three-dimensional structure with a particle size of 1μm-10μm, for example, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc., a specific surface area of ​​500-2500㎡ / g, for example, 500㎡ / g, 1000㎡ / g, 1500㎡ / g, 2000㎡ / g, 2500㎡ / g, etc., and a pore size of 10nm-2μm, for example, including but not limited to 10nm, 50nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1μm, 2μm, etc.

[0045] In step S1, the dispersant is for each solid material to be better compatible with the solvent, and can be water or an organic solvent according to solubility selection, the organic solvent is, for example, NMP, and the dispersant is preferably water. The mass ratio of the nano-silicon particles, the three-dimensional graphene particles and the dispersant is (60%-90%): (8%-30%): (2%-10%), and the total mass is 100 parts, and these 100 mass parts are used as a benchmark for adding mass parts of subsequent other solvents, such as 60%: 10%: 2% or 70%: 20%: 5% or 80%: 30%: 8% or 90%: 30%: 10% or 70%: 30%: 5%, but are not limited thereto.

[0046] In step S1, the mixing equipment can be any commonly used mixing equipment in the art without particular limitation, such as a double planetary mixer, a kneader, an internal mixer, etc. There is no particular limitation on the mixing time, as long as the three are substantially evenly mixed.

[0047] In step S2, the added solvent can be water or an organic solvent; preferably, it is the same dispersant as in step S1, for example, water. The solvent is added stepwise, for example, in three or more portions by volume or mass, with a final amount of 50-100 parts of solvent added. The mixture in step S1 is kneaded to form a slurry-like kneaded material, based on a total mass of 100 parts of the nano-silicon particles, three-dimensional graphene particles, and dispersant.

[0048] In step S3, solvent is further added and mixed to form a slurry. The added solvent can be water or an organic solvent; preferably, it is the same dispersant as in step S1, such as water. The solvent is added in an amount of 50-150 parts by weight, based on a total weight of 100 parts by weight of the nano-silicon particles, three-dimensional graphene particles, and dispersant, to form a mixed slurry.

[0049] In step S4, the slurry of S3 is subjected to a grinding and mixing process. The grinding and mixing process is to better adsorb the nano-silicon on the surface of the three-dimensional graphene. The grinding and mixing equipment is not particularly limited, and can be, for example, a grinding equipment commonly used in the art. The grinding time is, for example, 3-20 hours.

[0050] In step S5, an organic carbon source is added to the slurry from step S4 for secondary grinding, mixing, and coating. The organic carbon source can be, for example, one or a combination of two or more of lactose, glucose, sucrose, and polyethylene glycol. The amount of organic carbon source added is 1-10 parts (based on 100 parts by weight of the total mass of the nano-silicon particles, three-dimensional graphene particles, and dispersant). The secondary grinding and mixing time is, for example, 3-20 hours.

[0051] In step S6, the mixed solution in step S5 is spray-dried to obtain organic carbon source-coated nano-silicon particle clusters with a three-dimensional graphene framework. The spray-drying process is not particularly limited and can be performed by referring to existing techniques, which is also a common method in the art. The obtained organic carbon source-coated nano-silicon particle clusters with a three-dimensional graphene framework have a particle size of, for example, 1 μm to 10 μm.

[0052] In step S7, the nano-silicon particle clusters obtained in S6 are sintered under an inert gas protective atmosphere, wherein the inert gas is, for example, nitrogen, which is commonly used, and the sintering temperature is 650-950°C, for example, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, etc., and the sintering time is 6-36h, for example, 6h, 10h, 15h, 20h, 25h, 30h, 36h, etc.; through the sintering treatment, the organic carbon source coated on the surface of the nano-silicon particle clusters undergoes a thermal cracking reaction to generate amorphous carbon.

[0053] In step S8, the S7 sintered material is crushed and sieved to obtain three-dimensional graphene in situ grown nano-silicon particles, and the particle size can be 1μm-10μm, for example including but not limited to 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, and 10μm.

[0054] The three-dimensional graphene in-situ grown nano-silicon particles prepared by the present invention in-situ grow silicon material in the pores of the three-dimensional multilayer structure of the three-dimensional graphene. The grown silicon material is coated with graphene, which can inhibit the expansion and pulverization of the silicon material.

[0055] The present invention is further illustrated below with reference to examples, but the examples do not constitute any limitation to the present invention. Example 1

[0056] 1) Weigh 80 parts of nano-silicon particles, 15 parts of three-dimensional graphene, and 5 parts of dispersant water into a kneader and mix thoroughly. The nano-silicon particles should have a particle size of 100 nm; the three-dimensional graphene should have a particle size of 2 μm and a specific surface area of ​​approximately 1500 m2 / g.

[0057] 2) Weigh 100 parts of ultrapure water in batches and add them to a kneader for high-speed kneading. The processing time is 6 hours, and the final state is mud-like.

[0058] 3) Transfer the muddy material to a double planetary mixer, weigh 100 parts of ultrapure water, add it, and stir at high speed for 6 hours to obtain a slurry.

[0059] 4) Transfer the slurry to a grinder and grind for 6 hours.

[0060] 5) Add 8 parts of lactose and grind for a second time for 6 hours to mix and coat to obtain a mixed solution.

[0061] 6) The mixed solution is spray-dried to obtain nano-silicon particle clusters coated with an organic carbon source and having a three-dimensional graphene as a skeleton.

[0062] 7) Sintering the nano-silicon particles at 800° C. for 24 hours in a nitrogen atmosphere to form amorphous carbon on their surface.

[0063] 8) Use a jet mill to crush it and control the particle size to 2μm.

[0064] 9) The three-dimensional graphene silicon-carbon material, adhesive CMC, and adhesive SBR are mixed in a mass ratio of 96:1.6:2.4 to form a slurry, which is then coated, rolled, and cut into electrodes. The electrodes are then packaged with the positive electrode, separator, structural parts, electrolyte, etc. to form an 18650 battery cell. Example 2

[0065] 1) Weigh 90 parts of nano-silicon particles, 8 parts of 3D graphene, and 2 parts of dispersant NMP into a kneader and mix thoroughly. The nano-silicon particles should have a particle size of 100 nm; the 3D graphene should have a particle size of 2 μm and a specific surface area of ​​approximately 1500 m2 / g.

[0066] 2) Weigh 100 parts of ultrapure water in batches and add them to a kneader for high-speed kneading. The processing time is 6 hours, and the final state is mud-like.

[0067] 3) Transfer the muddy material to a double planetary mixer, weigh 100 parts of ultrapure water, add it, and stir at high speed for 6 hours to obtain a slurry.

[0068] 4) Transfer the slurry to a grinder and grind for 6 hours.

[0069] 5) Add 2 parts of lactose and grind for a second time for 6 hours to mix and coat to obtain a mixed solution.

[0070] 6) The mixed solution is spray-dried to obtain nano-silicon particle clusters coated with an organic carbon source and having a three-dimensional graphene as a skeleton.

[0071] 7) Sintering the nano-silicon particles at 800° C. for 24 hours in a nitrogen atmosphere to form amorphous carbon on their surface.

[0072] 8) Use a jet mill to crush it and control the particle size to 2μm.

[0073] 9) The three-dimensional graphene silicon-carbon material, adhesive CMC, and adhesive SBR are mixed in a mass ratio of 96:1.6:2.4 to form a slurry, which is then coated, rolled, and cut into electrodes. The electrodes are then packaged with the positive electrode, separator, structural parts, electrolyte, etc. to form an 18650 battery cell. Example 3

[0074] 1) Weigh 60 parts of nano-silicon particles, 30 parts of three-dimensional graphene, and 10 parts of dispersant water into a kneader and mix thoroughly. The nano-silicon particles should have a particle size of 100 nm; the three-dimensional graphene should have a particle size of 2 μm and a specific surface area of ​​approximately 1500 m2 / g.

[0075] 2) Weigh 100 parts of ultrapure water in batches and add them to a kneader for high-speed kneading. The processing time is 6 hours, and the final state is mud-like.

[0076] 3) Transfer the muddy material to a double planetary mixer, weigh 100 parts of ultrapure water, add it, and stir at high speed for 6 hours to obtain a slurry.

[0077] 4) Transfer the slurry to a grinder and grind for 6 hours.

[0078] 5) Add 8 parts of lactose and grind for a second time for 6 hours to mix and coat to obtain a mixed solution.

[0079] 6) The mixed solution is spray-dried to obtain nano-silicon particle clusters coated with an organic carbon source and having a three-dimensional graphene as a skeleton.

[0080] 7) Sintering the nano-silicon particles at 800° C. for 24 hours in a nitrogen atmosphere to form amorphous carbon on their surface.

[0081] 8) Use a jet mill to crush it and control the particle size to 2μm.

[0082] 9) The three-dimensional graphene silicon-carbon material, adhesive CMC, and adhesive SBR are mixed in a mass ratio of 96:1.6:2.4 to form a slurry, which is then coated, rolled, and cut into electrodes. The electrodes are then packaged with the positive electrode, separator, structural parts, electrolyte, etc. to form an 18650 battery cell. Comparative Example 1

[0083] Directly use 200nm silicon material to prepare 18650 battery cells. Comparative Example 2

[0084] Compared with Example 1, the only difference is that graphite material is used instead of three-dimensional graphene. Comparative Example 3

[0085] Compared with Example 1, the only difference is that porous carbon material is used instead of three-dimensional graphene. Comparative Example 4

[0086] Compared with Example 1, the only difference is that two-dimensional graphene material is used instead of three-dimensional graphene. Experimental group 1

[0087] The powder resistance test of the materials in the above examples and comparative examples is shown in Table 1.

[0088] Powder resistance test method: Weigh 1g of the powder materials from the examples and comparative examples, place them in a measuring jig, and then place the jig in a pre-compactor. After vibrating the pre-compactor for 15 seconds, return the jig to the powder resistivity meter and start the test software. The measured powder resistance is shown in Table 1.

[0089] Table 1 Powder resistance of powder materials of Examples and Comparative Examples

[0090] ,

[0091] From the powder resistance test results in Table 1, we can see that:

[0092] Among the three embodiments, embodiment 3 has a higher three-dimensional graphene content, so it has a lower resistivity, which means that it has a higher rate performance.

[0093] By comparing Example 1 with Comparative Examples 1-4, it can be seen that with the same addition amount, the patent of the present invention has lower resistivity and higher rate performance.

[0094] Experimental Group 2

[0095] The batteries assembled in Examples 1-3 and Comparative Examples 1-4 were subjected to rate tests and cycle life tests, and the cells after the cycle life tests were dissected and analyzed. The results are shown in Table 2.

[0096] Table 2 Performance test of batteries assembled in the embodiment and comparative example

[0097] ,

[0098] From the battery performance test data in Table 2, it can be seen that the three-dimensional graphene in situ grown silicon negative electrode material has better rate performance and cycle performance.

[0099] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. Those skilled in the art will appreciate that, based on the teachings of this specification, modifications or adjustments may be made to the present invention. Such modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing a three-dimensional graphene in-situ grown silicon negative electrode material for a lithium battery, characterized in that: The steps include: S1: After the nano silicon particles and the three-dimensional graphene particles are evenly mixed, a dispersant is added and mixed; S2: adding solvents to the mixture of S1 step by step, mixing, and kneading; S3: continue to add solvent to S2 to mix and perform slurry processing; S4: grinding and mixing the slurry of S3; S5: adding an organic carbon source to the slurry of S4, and performing secondary grinding, mixing and coating; S6: spray drying the mixed solution of S5 to obtain nano silicon particles coated with an organic carbon source and having a three-dimensional graphene as a skeleton; S7: sintering the nano-silicon particle clusters obtained in S6 under an inert gas protection atmosphere, so that the organic carbon source coated on the surface of the nano-silicon particle clusters undergoes a thermal cracking reaction to generate amorphous carbon; S8: The sintered product of S7 is crushed and sieved to obtain three-dimensional graphene in-situ grown nano-silicon particles.

2. The preparation method according to claim 1, characterized in that: The particle size of the nano silicon particles in step S1 is 50nm-500nm; the three-dimensional graphene particles are three-dimensional structures, with a particle size of 1μm-10μm, a specific surface area of ​​500-2500㎡ / g, and a pore size of 10nm-2μm.

3. The preparation method according to claim 1, characterized in that: The mixing device in step S1 is selected from any one of a double planetary mixer, a kneader, and an internal mixer; preferably, the dispersant is water or an oil-based dispersant, preferably water.

4. The preparation method according to any one of claims 1 to 3, characterized in that In the step S1, the mass ratio of the nano silicon particles, the three-dimensional graphene particles and the dispersant is 60%-90%: 8%-30%: 2%-10%, and the total mass is 100 parts.

5. The preparation method according to claim 1, characterized in that: In the step S2, the solvent is water or an organic solvent, and the solid mixture of S1 is kneaded into a muddy kneaded material; preferably, the added mass of the solvent is 50-100 parts.

6. The preparation method according to claim 1, characterized in that: In the step S3, 50-150 parts of solvent are added and mixed to form a mixed slurry.

7. The preparation method according to claim 1, characterized in that: In step S5, the organic carbon source is one or a combination of two or more of lactose, glucose, sucrose and polyethylene glycol; preferably, the amount of the organic carbon source added is 1-10 parts.

8. The preparation method according to claim 1, characterized in that: In the step S7, the sintering temperature is 650-950° C., and the sintering time is 6-36 hours; preferably, the particle size obtained by sieving in the step S8 is 1 μm-10 μm.

9. A silicon negative electrode material for lithium battery using three-dimensional graphene in-situ growth obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the three-dimensional graphene in-situ grown silicon negative electrode material for lithium battery prepared by the preparation method according to any one of claims 1 to 8 or the three-dimensional graphene in-situ grown silicon negative electrode material for lithium battery according to claim 9 in lithium battery negative electrode materials.

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