Silicon-carbon negative electrode material, preparation method and application thereof

Abstract

The application provides a silicon-carbon negative electrode material and a preparation method and application thereof, and relates to the technical field of lithium ion battery negative electrode materials.A preparation method of a silicon-carbon negative electrode material comprises the following steps: S1, activating and treating a carbon source, and performing microwave reaction to obtain a porous carbon material; S2, heating and depositing by introducing silane gas into the porous carbon material to obtain a silicon-carbon precursor; and S3, heating and reacting by introducing ammonia gas into the silicon-carbon precursor, and then heating and reacting by introducing a carbon source gas into the silicon-carbon precursor to obtain the silicon-carbon negative electrode material.The silicon-carbon negative electrode material prepared by the application has a low expansion rate, which is helpful to improve the cycle stability of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode material technology, and in particular to a silicon-carbon anode material, its preparation method, and its application. Background Technology

[0002] In 2024, the global production of lithium-ion battery anode materials reached 2.16 million tons, with China accounting for 98.5% of the market share. New materials such as silicon-based anodes accounted for over 60% of this market. The global silicon-based anode market is projected to reach 30 billion yuan in 2025. With the large-scale application of new battery technologies, the demand for silicon-based anode materials will continue to increase. The theoretical specific capacity of silicon-based anodes is as high as 4200 mAh / g, more than 10 times that of traditional graphite anodes (372 mAh / g), which can significantly improve battery energy density and become a core technological path to overcome the range bottleneck of new energy vehicles. However, existing silicon-carbon anodes suffer from high expansion rates, low coulombic efficiency, and short cycle life. Therefore, the development of a silicon-carbon anode material with a low expansion rate is urgently needed and is of great significance to the development of lithium-ion batteries. Summary of the Invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a silicon-carbon anode material, its preparation method and application.

[0004] The present invention proposes a method for preparing a silicon-carbon anode material, comprising the following steps:

[0005] S1. Activate the carbon source and perform microwave reaction to obtain porous carbon material;

[0006] S2. Silane gas is introduced into porous carbon material and heated to deposit silicon-carbon precursor.

[0007] S3. First, ammonia gas is introduced into the silicon-carbon precursor and heated to react, then carbon source gas is introduced and heated to react, to obtain silicon-carbon anode material.

[0008] The silicon-carbon anode material prepared by this invention has a low expansion rate, which helps to improve the cycle stability of the battery.

[0009] Preferably, in S1, the carbon source is selected from one or more of grapefruit peel carbon materials and coconut shell carbon materials.

[0010] Preferably, in S1, the activation treatment includes mixing a carbon source and an alkali, introducing carbon monoxide, and heating to react, thereby obtaining the product.

[0011] More preferably, the alkali is selected from one or more of sodium hydroxide and potassium hydroxide.

[0012] More preferably, the mass ratio of the carbon source to the alkali is 1:(0.5-1).

[0013] More preferably, the carbon monoxide gas flow rate is 10-20 L / min.

[0014] More preferably, the heating temperature is 1000-1100℃.

[0015] More preferably, the reaction time is 1-3 hours.

[0016] Preferably, in S1, the microwave frequency of the microwave reaction is 2-3 GHz, and the microwave reaction time is 1-5 min.

[0017] Microwave treatment acts on the interior of molecules, improving the efficiency of heat and mass transfer in the process, allowing molecules to generate heat rapidly, and increasing the specific surface area of ​​carbon materials.

[0018] Preferably, in S2, the silane gas is selected from one or more of methylsilane and disilane.

[0019] Preferably, in step S2, the flow rate of silane gas is 5-10 L / min.

[0020] Silane gas is introduced into porous carbon materials and heated for deposition, causing silane compounds to be deposited within the pores of the porous carbon materials.

[0021] Preferably, in step S2, a carrier gas is introduced simultaneously with the silane gas.

[0022] Preferably, in step S2, the heating temperature is 400-550℃.

[0023] Preferably, in S3, the temperature of the heating reaction is 600-1000℃.

[0024] Preferably, in S3, the ammonia gas flow rate is 1-5 L / h.

[0025] Preferably, in S3, the carbon source gas is selected from one or more of ethylene, acetylene, and propane.

[0026] Preferably, in step S3, the flow rate of the carbon source gas is 5-10 L / min.

[0027] Preferably, in step S3, ammonia gas can be introduced at the same time as carrier gas.

[0028] Preferably, in step S3, a carrier gas is introduced simultaneously with the carbon source gas.

[0029] More preferably, the carrier gas is selected from one or more of nitrogen and argon.

[0030] The present invention also proposes a silicon-carbon anode material prepared by the above preparation method.

[0031] Application of the above-mentioned silicon-carbon anode material or the silicon-carbon anode material prepared by the above-mentioned preparation method in lithium-ion batteries.

[0032] The beneficial effects of this invention are as follows:

[0033] This invention involves activating a carbon source and performing a microwave reaction to obtain a porous carbon material. Then, silane gas is introduced and heated to deposit within the pores of the porous carbon material, yielding a silicon-carbon precursor. Ammonia gas is first introduced into the silicon-carbon precursor for heating and reaction, followed by the introduction of a carbon source gas for heating and reaction, resulting in a silicon-carbon anode material. This invention, through multi-stage vapor deposition, helps mitigate the volume expansion of the silicon-carbon anode material during chemical cycling, thereby improving its cycle performance. Detailed Implementation

[0034] The technical solution of the present invention will be described in detail through specific embodiments.

[0035] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0036] Example 1

[0037] A method for preparing a silicon-carbon anode material includes the following steps:

[0038] S1. Mix and grind grapefruit peel carbon material with potassium hydroxide at a mass ratio of 1:1, introduce carbon monoxide at a gas flow rate of 15L / min, heat and react at 1000℃ for 2h, and then microwave it for 3min (microwave frequency of 2GHz) to obtain porous carbon material.

[0039] S2. A mixture of silane and argon (volume ratio 3:2) is introduced into the porous carbon material and heated at 500℃ for 6 hours. The flow rate of silane is 5 L / min.

[0040] S3. First, ammonia gas with a flow rate of 1 L / h is introduced into the silicon-carbon precursor and heated at 600℃ for 1 h. Then, a mixture of acetylene and argon gas (volume ratio of 7:3) is introduced and heated at 800℃ for 2 h to obtain silicon-carbon anode material. The acetylene gas flow rate is 5 L / min.

[0041] Example 2

[0042] A method for preparing a silicon-carbon anode material includes the following steps:

[0043] S1. Mix and grind grapefruit peel carbon material with potassium hydroxide at a mass ratio of 1:1, introduce carbon monoxide at a gas flow rate of 15L / min, heat and react at 1050℃ for 2h, and then microwave it for 5min (microwave frequency of 2GHz) to obtain porous carbon material.

[0044] S2. A mixture of silane and argon (volume ratio 3:2) is introduced into the porous carbon material and heated at 500℃ for 6 hours. The flow rate of silane is 5 L / min.

[0045] S3. First, a mixture of ammonia / argon (volume ratio 1:1) is introduced into the silicon-carbon precursor and heated at 600℃ for 2 hours. Then, a mixture of acetylene / argon (volume ratio 7:3) is introduced and heated at 800℃ for 2 hours to obtain the silicon-carbon anode material. The acetylene flow rate is 6 L / min.

[0046] Example 3

[0047] A method for preparing a silicon-carbon anode material includes the following steps:

[0048] S1. Mix and grind coconut shell carbon material with potassium hydroxide at a mass ratio of 1:0.8, introduce carbon monoxide at a gas flow rate of 15L / min, heat and react at 1050℃ for 2h, and then microwave it for 5min (microwave frequency of 2GHz) to obtain porous carbon material.

[0049] S2. A mixture of silane and argon (volume ratio 1:1) is introduced into the porous carbon material and heated at 500℃ for 6 hours. The flow rate of silane is 5L / min.

[0050] S3. First, a mixture of ammonia / argon (volume ratio 1:1) is introduced into the silicon-carbon precursor and heated at 600℃ for 2 hours. Then, a mixture of acetylene / argon (volume ratio 7:3) is introduced and heated at 800℃ for 2 hours to obtain the silicon-carbon anode material. The acetylene flow rate is 4 L / min.

[0051] Example 4

[0052] A method for preparing a silicon-carbon anode material includes the following steps:

[0053] S1. Mix and grind grapefruit peel carbon material with potassium hydroxide at a mass ratio of 1:0.8, introduce carbon monoxide at a gas flow rate of 16L / min, heat and react at 1050℃ for 2h, and then microwave it for 3min (microwave frequency of 2GHz) to obtain porous carbon material.

[0054] S2. A mixture of silane and argon (volume ratio 3:2) is introduced into the porous carbon material and heated at 550℃ for 6 hours. The flow rate of silane is 5 L / min.

[0055] S3. First, ammonia gas with a flow rate of 1 L / h is introduced into the silicon-carbon precursor and heated at 600℃ for 1 h. Then, a mixture of acetylene and argon gas (volume ratio of 7:3) is introduced and heated at 800℃ for 2 h to obtain silicon-carbon anode material. The acetylene gas flow rate is 5 L / min.

[0056] Example 5

[0057] A method for preparing a silicon-carbon anode material includes the following steps:

[0058] S1. Mix and grind coconut shell carbon material with potassium hydroxide at a mass ratio of 1:1, introduce carbon monoxide at a gas flow rate of 15L / min, heat and react at 1100℃ for 2h, and then microwave it for 5min (microwave frequency of 2GHz) to obtain porous carbon material.

[0059] S2. A mixture of silane and argon (volume ratio 3:2) is introduced into the porous carbon material and heated at 500℃ for 6 hours. The flow rate of silane is 5 L / min.

[0060] S3. First, a mixture of ammonia / argon (volume ratio 1:1) is introduced into the silicon-carbon precursor and heated at 650℃ for 2 hours. Then, a mixture of acetylene / argon (volume ratio 7:3) is introduced and heated at 900℃ for 2 hours to obtain the silicon-carbon anode material. The acetylene flow rate is 4 L / min.

[0061] The aforementioned grapefruit peel carbon material was obtained by calcining grapefruit peel at 900°C under nitrogen for 2 hours.

[0062] The aforementioned coconut shell carbon material was obtained by calcining coconut shells at 800°C under nitrogen for 6 hours.

[0063] Silicon-carbon anode material, conductive agent (single-walled carbon nanotubes), and binder (PAALi) were mixed uniformly at a mass ratio of 95:0.5:4. A certain amount of high-purity water was added to prepare an anode slurry with a solid content of 20%. The slurry was coated on copper foil with a coating thickness of 100 μm and dried at 110 °C for 10 h in a vacuum drying oven. The anode sheet was obtained by rolling and punching. A lithium sheet was used as the counter electrode, and 1.0 mol / L LiPF6 / EC:DEC = 1:1 Vol% + 5% FEC was used as the electrolyte. The cells were assembled into coin cells in a glove box under an argon atmosphere.

[0064] The initial coulombic efficiency and the number of cycles corresponding to 80% capacity retention of the coin cell were tested (100mA / g, 5mV-2V). The expansion rate of the negative electrode after 100 charge-discharge cycles was tested. The test results are shown in Table 1.

[0065] Negative electrode sheet expansion rate test: The expansion phenomenon of negative electrode sheet material is reflected by the change in thickness of negative electrode sheet before and after battery charge and discharge test. Specifically, the thickness L1 of negative electrode sheet before battery assembly and the thickness L2 after the battery is discharged after 100 charge and discharge cycles are measured. The expansion rate of negative electrode sheet is (L2-L1) / L1*100%.

[0066] Table 1

[0067]

[0068] As can be seen from the data in Table 1, the anode sheet prepared from the silicon-carbon anode material prepared in this invention has a low expansion rate, and its coin cell has a high initial coulombic efficiency and excellent cycle stability.

[0069] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-carbon anode material, characterized in that, Includes the following steps: S1. Activate the carbon source and perform microwave reaction to obtain porous carbon material; S2. Silane gas is introduced into porous carbon material and heated to deposit silicon-carbon precursor. S3. First, ammonia gas is introduced into the silicon-carbon precursor and heated to react, then carbon source gas is introduced and heated to react, to obtain silicon-carbon anode material. In S1, the activation treatment includes mixing a carbon source and an alkali, introducing carbon monoxide, and heating the mixture at 1000-1100℃ for 1-3 hours to obtain the final product. The carbon source is selected from one or more of grapefruit peel carbon materials and coconut shell carbon materials. The alkali is selected from one or more of sodium hydroxide and potassium hydroxide. The mass ratio of the carbon source to the alkali is 1:(0.5-1). The microwave frequency of the microwave reaction is 2-3 GHz, and the microwave reaction time is 1-5 min. In S2, the silane gas is selected from one or more of methylsilane and disilane; the flow rate of the silane gas is 5-10 L / min.

2. The preparation method according to claim 1, characterized in that, The carbon monoxide flow rate is 10-20 L / min.

3. The preparation method according to claim 1, characterized in that, In S2, the heating temperature is 400-550℃.

4. The preparation method according to claim 1, characterized in that, In S3, the ammonia gas flow rate is 1-5 L / h; the carbon source gas flow rate is 5-10 L / min.

5. The preparation method according to claim 1, characterized in that, In S3, the heating reaction temperature is 600-1000℃; the carbon source gas is selected from one or more of ethylene, acetylene, and propane.

6. A silicon-carbon anode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.

7. The application of the silicon-carbon anode material according to claim 6 or the silicon-carbon anode material prepared by any one of claims 1-5 in a lithium-ion battery.

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