A high-density, high-purity silicon-carbon anode material and its preparation method

Abstract

This invention discloses a method for preparing a high-density, high-purity silicon-carbon anode material, relating to the field of composite material preparation technology. The anode material comprises uniformly and densely distributed silicon and carbon, with a material density satisfying ρ1 / ρ2≥95%, where ρ1 is the actual measured density and ρ2 is the theoretical density. The preparation method involves physical vapor deposition of carbon and silicon raw materials, followed by cooling to obtain the high-density, high-purity silicon-carbon anode material. Physical deposition can be performed synchronously or alternately, utilizing amorphous carbon and a vapor-phase silicon source to form a uniform and dense composite material structure. This material consists of sub-nanometer-sized silicon uniformly distributed within amorphous carbon. This dense structure improves material tap and effectively mitigates volume effects during charge and discharge. Furthermore, the sub-nanometer-sized silicon particles have relatively smaller expansion compared to nano-sized silicon, further improving its cycle performance.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation technology, specifically to a high-density, high-purity silicon-carbon anode material and its preparation method. Background Technology

[0002] The performance of anode materials plays a very important role in the development prospects of lithium batteries.

[0003] Currently, lithium-ion battery anode materials mainly include the following types: First, carbon anode materials. The anode materials currently used in lithium-ion batteries are almost entirely carbon-based, such as artificial graphite, natural graphite, mesophase carbon microspheres, petroleum coke, carbon fiber, pyrolytic resin carbon, and graphite-based composite materials. Second, tin-based anode materials, which can be divided into tin oxides and tin-based composite oxides. Oxides refer to oxides of metallic tin in various valence states; currently, there are almost no commercially available products. Third, lithium-containing transition metal nitride anode materials; currently, there are also almost no commercially available products. Fourth, alloy anode materials, including tin-based alloys, silicon-based alloys, germanium-based alloys, aluminum-based alloys, antimony-based alloys, magnesium-based alloys, and other alloys; currently, there are also almost no commercially available products. Fifth, nanoscale anode materials, such as carbon nanotubes, nano-alloy materials, and nano-oxide materials.

[0004] In order to improve existing anode materials and further enhance battery performance, scientists have conducted a lot of research and obtained graphene-nano silicon composite materials and other silicon-carbon composite materials. However, the products prepared often have serious problems, which affect their application in batteries.

[0005] Among them, Chinese patent CN201810830729.X discloses a method for preparing silicon-carbon composite material. It uses a grinding method to prepare nano-silicon and then prepares silicon-carbon composite material. This results in some pores between the nano-silicon, which leads to a low tap density of the material. This is a defect that cannot be remedied by any subsequent steps. Such defects will cause the pores to collapse during the cycling process when the material is used in the battery (negative electrode), causing the material to pulverize and directly resulting in a significant reduction in the cycle performance of the battery. Summary of the Invention

[0006] To address the aforementioned issues, this method prepares a high-density, high-purity silicon-carbon anode material via vapor deposition. The specific scheme is as follows:

[0007] A high-density, high-purity silicon-carbon anode material comprises uniformly and densely distributed silicon and carbon, wherein the density of the material satisfies ρ1 / ρ2≥95%, where ρ1 is the actual tested density and ρ2 is the theoretical density (i.e., the sum of the content of each component of the material and the theoretical true density).

[0008] A method for preparing the above-mentioned high-density, high-purity silicon-carbon anode material includes: performing physical vapor deposition on carbon raw materials and silicon raw materials, and obtaining the high-density, high-purity silicon-carbon anode material after cooling.

[0009] Preferably, the above method specifically includes the following steps:

[0010] 1) At room temperature, fix the carbon raw material on the evaporation source and fix the substrate on the substrate support;

[0011] 2) Introduce silicon raw material gas towards the substrate;

[0012] 3) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform synchronous vapor deposition, stop the vapor deposition, and after cooling, obtain high-density, high-purity silicon-carbon anode material.

[0013] Preferably, the carbon raw material includes carbon rope or carbon rod. The carbon rope is made of graphite fiber with a purity of 99% and a diameter of 2 mm, and the carbon rope is 1 cm long. The carbon rod has a purity of 99%, a diameter of 2 mm, and a length of 1 cm.

[0014] Preferably, the silicon raw material gas includes one or more of silane, dichlorosilane, and dichlorosilane.

[0015] Preferably, the flow rate of the silicon raw material gas is 130-200 sccm.

[0016] Preferably, in step 3), the vapor deposition is performed by heating to a temperature of 420℃-580℃, and the current of the vapor deposition apparatus is 47-55A; the ambient pressure is maintained at 3x10. -2 pa.

[0017] Preferably, the above steps are carried out in an atmosphere of helium or argon.

[0018] Preferably, the atmosphere is achieved by a flow rate of 1000-5000 sccm.

[0019] The vapor deposition process ends when the carbon rope or carbon rod breaks.

[0020] Preferably, the above method may also consist of the following steps:

[0021] (1) Fix the substrate onto the substrate holder at room temperature;

[0022] (2) Fix the carbon raw material onto the evaporation source;

[0023] (3) Turn on the power of the vapor deposition machine, adjust the parameters, and perform carbon raw material vapor deposition;

[0024] (4) Stop the evaporation of carbon raw materials and introduce silicon raw material gas towards the substrate;

[0025] (5) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform silicon raw material gas vapor deposition, and then stop silicon raw material gas vapor deposition;

[0026] (6) Repeat steps 3-6 above, repeating n times, where n is a positive integer;

[0027] (7) After cooling, a high-density, high-purity silicon-carbon anode material is obtained.

[0028] Preferably, in step (3), the carbon raw material is vapor-deposited, and the current of the vapor deposition apparatus is 40-50A.

[0029] Preferably, the flow rate of the gas introduced into the silicon raw material in step (4) is 10-300 sccm.

[0030] Preferably, the silicon raw material gas vapor deposition in step (5) is carried out at a temperature of 420℃-580℃ and a pressure of 3x10. -2 pa.

[0031] Preferably, the above steps are carried out in an atmosphere of helium or argon.

[0032] Preferably, the atmosphere is achieved by a flow rate of 15,000-20,000 sccm.

[0033] Preferably, the carbon raw material includes carbon rope or carbon rod. The carbon rope is made of graphite fiber with a purity of 99% and a diameter of 4 mm, and the length of the carbon rope is 1-3 cm. The carbon rod has a purity of 99%, a diameter of 3 mm, and a length of 1-3 cm.

[0034] Preferably, the vapor deposition of the carbon raw material takes 1-2 minutes each time, and the vapor deposition of the silicon raw material gas takes 1-4 minutes each time.

[0035] Preferably, the substrate is a substrate for evaporation of commonly used electrode film materials, including any one of amorphous silicon substrate, Pt conductive substrate or FTO conductive substrate, etc. The substrate is routinely cleaned before use, including cleaning with acetone, ethanol, deionized water, etc.

[0036] Beneficial effects

[0037] The beneficial effects of this invention are as follows:

[0038] This invention employs physical vapor deposition (PVD) to form a uniform and dense composite material structure using amorphous carbon and a fumed silicon source. This material consists of sub-nanometer-sized silicon uniformly distributed within the amorphous carbon. This dense structure improves material tap and effectively mitigates volume effects during charge and discharge. Furthermore, the sub-nanometer-sized silicon particles exhibit relatively smaller expansion compared to nano-sized silicon, further enhancing its cycle performance. Attached Figure Description

[0039] Figure 1 The scanning electron microscope image (×3000) of the surface of the negative electrode material obtained in Example 2.

[0040] Figure 2 This is an EDS layered image of the negative electrode material obtained in Example 2;

[0041] Figure 3 The electron diffraction pattern of the negative electrode material obtained in Example 2 is shown below.

[0042] Figure 4 The electron diffraction pattern of the Si anode material obtained in Example 2;

[0043] Figure 5 The image shows a cross-sectional electron microscope (SEM) image (×5000) of the negative electrode material obtained in Example 2 after 50 cycles in the expansion test. Detailed Implementation

[0044] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0045] Unless otherwise specified, the following embodiments and comparative examples are parallel experiments, using the same processing steps and parameters. The substrates used in the embodiments and comparative examples of this invention are commonly used electrode film material vapor deposition substrates: FTO conductive substrates. The substrates are routinely cleaned before use, including cleaning with acetone, ethanol, deionized water, etc.

[0046] Example 1: Preparation (simultaneous deposition) of a high-density, high-purity silicon-carbon anode material:

[0047] 1) At room temperature, fix the carbon raw material on the evaporation source and fix the substrate on the substrate support;

[0048] 2) Introduce silicon raw material gas towards the substrate;

[0049] 3) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform synchronous vapor deposition, stop the vapor deposition, and after cooling, obtain high-density, high-purity silicon-carbon anode material.

[0050] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 2 mm, and the carbon rope is 1 cm long.

[0051] The silicon raw material gas includes silane.

[0052] The flow rate of the silicon raw material gas is 130 sccm.

[0053] Step 3) involves vapor deposition, with the temperature heated to 420°C and the current of the vapor deposition apparatus being 47A.

[0054] Step 3) involves vapor deposition while maintaining an ambient pressure of 3 x 10⁻⁶. -2 pa.

[0055] The above steps are performed in a helium atmosphere.

[0056] The helium atmosphere is achieved by a helium flow rate of 1000 sccm.

[0057] The vapor deposition process ends when the carbon rope or carbon rod breaks.

[0058] Example 2: Preparation (simultaneous deposition) of a high-density, high-purity silicon-carbon anode material:

[0059] 1) At room temperature, fix the carbon raw material on the evaporation source and fix the substrate on the substrate support;

[0060] 2) Introduce silicon raw material gas towards the substrate;

[0061] 3) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform synchronous vapor deposition, stop the vapor deposition, and after cooling, obtain high-density, high-purity silicon-carbon anode material.

[0062] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 2 mm, and the carbon rope is 1 cm long.

[0063] The silicon raw material gas includes silane.

[0064] The flow rate of the silicon raw material gas is 200 sccm.

[0065] Step 3) involves vapor deposition, heating to 580°C, with the vapor deposition apparatus using a current of 55A.

[0066] Step 3) involves vapor deposition while maintaining an ambient pressure of 3 x 10⁻⁶. -2 pa.

[0067] The above steps are performed in a helium atmosphere.

[0068] The helium atmosphere is achieved by a helium flow rate of 5000 sccm.

[0069] The vapor deposition process ends when the carbon rope or carbon rod breaks.

[0070] The negative electrode material obtained in this embodiment was characterized by scanning electron microscopy and electron diffraction, and the results are shown in the appendix. Figure 1-5 : Figure 1 The image shows a scanning electron microscope (SEM) image of the surface of the obtained negative electrode material (×3000). Figure 2 For the obtained EDS layered image of the negative electrode material, from Figure 2 It can be seen that there are no obvious pores inside the sample, and Si and C are evenly distributed (no Si or C aggregation areas are observed). Figure 3 The electron diffraction pattern of the obtained negative electrode material is shown below. Figure 3 It can be seen that C is uniformly dispersed throughout the entire particle; Figure 4 The electron diffraction pattern of the obtained negative electrode material Si is shown below. Figure 4 It can be seen that Si is uniformly dispersed throughout the entire particle; Figure 5 The image shows a cross-sectional electron microscope (SEM) image (×5000) of the obtained negative electrode material after 50 cycles in the expansion test. Figure 5 It can be seen that the silicon-carbon anode material structure remains intact after cycling, without pulverization or structural collapse, and the expansion is very small.

[0071] Comparative Example 1: Preparation (simultaneous deposition) of a high-density, high-purity silicon-carbon anode material:

[0072] 1) At room temperature, fix the carbon raw material on the evaporation source and fix the substrate on the substrate support;

[0073] 2) Introduce silicon raw material gas towards the substrate;

[0074] 3) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform synchronous vapor deposition, stop the vapor deposition, and after cooling, obtain high-density, high-purity silicon-carbon anode material.

[0075] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 2 mm, and the carbon rope is 1 cm long.

[0076] The silicon raw material gas includes silane.

[0077] The flow rate of the silicon raw material gas is 130 sccm.

[0078] Step 3) involves vapor deposition, heating to 410°C, with the vapor deposition apparatus using a current of 45A.

[0079] Step 3) involves vapor deposition while maintaining an ambient pressure of 3 x 10⁻⁶. -2 pa.

[0080] The above steps are performed in a helium atmosphere.

[0081] The helium atmosphere is achieved by a helium flow rate of 1000 sccm.

[0082] The vapor deposition process ends when the carbon rope or carbon rod breaks.

[0083] Comparative Example 2: Preparation of a high-density, high-purity silicon-carbon anode material (simultaneous deposition):

[0084] 1) At room temperature, fix the carbon raw material on the evaporation source and fix the substrate on the substrate support;

[0085] 2) Introduce silicon raw material gas towards the substrate;

[0086] 3) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform synchronous vapor deposition, stop the vapor deposition, and after cooling, obtain high-density, high-purity silicon-carbon anode material.

[0087] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 2 mm, and the carbon rope is 1 cm long.

[0088] The silicon raw material gas includes silane.

[0089] The flow rate of the silicon raw material gas is 130 sccm.

[0090] Step 3) involves vapor deposition, heating to 460°C, with the vapor deposition apparatus using a current of 45A.

[0091] Step 3) involves vapor deposition while maintaining an ambient pressure of 3 x 10⁻⁶. -2 pa.

[0092] The above steps are performed in a helium atmosphere.

[0093] The helium atmosphere is achieved by a helium flow rate of 1000 sccm.

[0094] The vapor deposition process ends when the carbon rope or carbon rod breaks.

[0095] Comparative Example 3: Preparation (simultaneous deposition) of a high-density, high-purity silicon-carbon anode material:

[0096] 1) At room temperature, fix the carbon raw material on the evaporation source and fix the substrate on the substrate support;

[0097] 2) Introduce silicon raw material gas towards the substrate;

[0098] 3) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform synchronous vapor deposition, stop the vapor deposition, and after cooling, obtain high-density, high-purity silicon-carbon anode material.

[0099] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 2 mm, and the carbon rope is 1 cm long.

[0100] The silicon raw material gas includes silane.

[0101] The flow rate of the silicon raw material gas is 200 sccm.

[0102] Step 3) involves vapor deposition, heating to 590°C, with the vapor deposition apparatus using a current of 60A.

[0103] Step 3) involves vapor deposition while maintaining an ambient pressure of 3 x 10⁻⁶. -2 pa.

[0104] The above steps are performed in a helium atmosphere.

[0105] The helium atmosphere is achieved by a helium flow rate of 5000 sccm.

[0106] The vapor deposition process ends when the carbon rope or carbon rod breaks.

[0107] Comparative Example 3: Preparation (simultaneous deposition) of a high-density, high-purity silicon-carbon anode material:

[0108] 1) At room temperature, fix the carbon raw material on the evaporation source and fix the substrate on the substrate support;

[0109] 2) Introduce silicon raw material gas towards the substrate;

[0110] 3) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform synchronous vapor deposition, stop the vapor deposition, and after cooling, obtain high-density, high-purity silicon-carbon anode material.

[0111] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 3 mm, and the carbon rope is 1 cm long.

[0112] The silicon raw material gas includes silane.

[0113] The flow rate of the silicon raw material gas is 200 sccm.

[0114] Step 3) involves vapor deposition, heating to a temperature of 590°C, with the current of the vapor deposition apparatus being 55A.

[0115] Step 3) involves vapor deposition while maintaining an ambient pressure of 3 x 10⁻⁶. -2 pa.

[0116] The above steps are performed in a helium atmosphere.

[0117] The helium atmosphere is achieved by a helium flow rate of 5000 sccm.

[0118] The vapor deposition process ends when the carbon rope or carbon rod breaks.

[0119] Example 4: Preparation of a high-density, high-purity silicon-carbon anode material (alternating deposition):

[0120] (1) Fix the substrate onto the substrate holder at room temperature;

[0121] (2) Fix the carbon raw material onto the evaporation source;

[0122] (3) Turn on the power of the vapor deposition machine, adjust the parameters, and perform carbon raw material vapor deposition;

[0123] (4) Stop the evaporation of carbon raw materials and introduce silicon raw material gas towards the substrate;

[0124] (5) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform silicon raw material gas vapor deposition, and then stop silicon raw material gas vapor deposition;

[0125] (6) Repeat steps 3-6 above, repeating n times, where n is 3;

[0126] (7) After cooling, a high-density, high-purity silicon-carbon anode material is obtained.

[0127] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 4 mm, and the carbon rope is 1 cm long.

[0128] The silicon raw material gas includes silane.

[0129] In step (3), the carbon raw material is vapor-deposited, and the current of the vapor deposition instrument is 40A.

[0130] The flow rate of the gas introduced into the silicon raw material in step (4) is 50 sccm.

[0131] Step (5) involves silicon raw material gas vapor deposition at a temperature of 420°C and a pressure of 3 x 10⁻⁶. -2 pa.

[0132] The above steps are performed in a helium atmosphere.

[0133] The helium atmosphere is achieved by a helium flow rate of 15000 sccm.

[0134] The carbon raw material is vapor-deposited for 2 minutes each time, and the silicon raw material gas is vapor-deposited for 1 minute each time.

[0135] Example 5: Preparation of a high-density, high-purity silicon-carbon anode material (alternating deposition):

[0136] (1) Fix the substrate onto the substrate holder at room temperature;

[0137] (2) Fix the carbon raw material onto the evaporation source;

[0138] (3) Turn on the power of the vapor deposition machine, adjust the parameters, and perform carbon raw material vapor deposition;

[0139] (4) Stop the evaporation of carbon raw materials and introduce silicon raw material gas towards the substrate;

[0140] (5) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform silicon raw material gas vapor deposition, and then stop silicon raw material gas vapor deposition;

[0141] (6) Repeat steps 3-6 above, repeating n times, where n is 3;

[0142] (7) After cooling, a high-density, high-purity silicon-carbon anode material is obtained.

[0143] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 4 mm, and the carbon rope is 1 cm long.

[0144] The silicon raw material gas includes silane.

[0145] In step (3), the carbon raw material is vapor-deposited, and the current of the vapor deposition instrument is 40A.

[0146] The flow rate of the gas introduced into the silicon raw material in step (4) is 50 sccm.

[0147] Step (5) involves silicon raw material gas vapor deposition at a temperature of 460°C and a pressure of 3 x 10⁻⁶. -2 pa.

[0148] The above steps are performed in a helium atmosphere.

[0149] The helium atmosphere is achieved by a helium flow rate of 15000 sccm.

[0150] The carbon raw material is vapor-deposited for 2 minutes each time, and the silicon raw material gas is vapor-deposited for 1 minute each time.

[0151] Example 6: Preparation of a high-density, high-purity silicon-carbon anode material (alternating deposition):

[0152] (1) Fix the substrate onto the substrate holder at room temperature;

[0153] (2) Fix the carbon raw material onto the evaporation source;

[0154] (3) Turn on the power of the vapor deposition machine, adjust the parameters, and perform carbon raw material vapor deposition;

[0155] (4) Stop the evaporation of carbon raw materials and introduce silicon raw material gas towards the substrate;

[0156] (5) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform silicon raw material gas vapor deposition, and then stop silicon raw material gas vapor deposition;

[0157] (6) Repeat steps 3-6 above, repeating n times, where n is 3;

[0158] (7) After cooling, a high-density, high-purity silicon-carbon anode material is obtained.

[0159] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 4 mm, and the carbon rope is 1 cm long.

[0160] The silicon raw material gas includes silane.

[0161] In step (3), the carbon raw material is vapor-deposited, and the current of the vapor deposition instrument is 50A.

[0162] The flow rate of the gas introduced into the silicon raw material in step (4) is 300 sccm.

[0163] Step (5) involves silicon raw material gas vapor deposition at a temperature of 580°C and a pressure of 3 x 10⁻⁶. -2 pa.

[0164] The above steps are performed in a helium atmosphere.

[0165] The helium atmosphere is achieved by a helium flow rate of 20,000 sccm.

[0166] The vapor deposition of the carbon raw material takes 4 minutes each time, and the vapor deposition of the silicon raw material gas takes 2 minutes each time.

[0167] Comparative Example 4: Preparation of a high-density, high-purity silicon-carbon anode material (alternating deposition):

[0168] (1) Fix the substrate onto the substrate holder at room temperature;

[0169] (2) Fix the carbon raw material onto the evaporation source;

[0170] (3) Turn on the power of the vapor deposition machine, adjust the parameters, and perform carbon raw material vapor deposition;

[0171] (4) Stop the evaporation of carbon raw materials and introduce silicon raw material gas towards the substrate;

[0172] (5) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform silicon raw material gas vapor deposition, and then stop silicon raw material gas vapor deposition;

[0173] (6) Repeat steps 3-6 above, repeating n times, where n is 3;

[0174] (7) After cooling, a high-density, high-purity silicon-carbon anode material is obtained.

[0175] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 4 mm, and the carbon rope is 1 cm long.

[0176] The silicon raw material gas includes silane.

[0177] In step (3), the carbon raw material is vapor-deposited, and the current of the vapor deposition instrument is 35A.

[0178] The flow rate of the gas introduced into the silicon raw material in step (4) is 50 sccm.

[0179] Step (5) involves silicon raw material gas vapor deposition at a temperature of 420°C and a pressure of 3 x 10⁻⁶. -2 pa.

[0180] The above steps are performed in a helium atmosphere.

[0181] The helium atmosphere is achieved by a helium flow rate of 15000 sccm.

[0182] The carbon raw material is vapor-deposited for 2 minutes each time, and the silicon raw material gas is vapor-deposited for 1 minute each time.

[0183] Comparative Example 5: Preparation of a high-density, high-purity silicon-carbon anode material (alternating deposition):

[0184] (1) Fix the substrate onto the substrate holder at room temperature;

[0185] (2) Fix the carbon raw material onto the evaporation source;

[0186] (3) Turn on the power of the vapor deposition machine, adjust the parameters, and perform carbon raw material vapor deposition;

[0187] (4) Stop the evaporation of carbon raw materials and introduce silicon raw material gas towards the substrate;

[0188] (5) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform silicon raw material gas vapor deposition, and then stop silicon raw material gas vapor deposition;

[0189] (6) Repeat steps 3-6 above, repeating n times, where n is 3;

[0190] (7) After cooling, a high-density, high-purity silicon-carbon anode material is obtained.

[0191] The carbon raw material includes carbon rope, which is made of graphite fiber with a purity of 99% and a diameter of 4 mm, and the carbon rope is 1 cm long.

[0192] The silicon raw material gas includes silane.

[0193] In step (3), the carbon raw material is vapor-deposited, and the current of the vapor deposition instrument is 55A.

[0194] The flow rate of the gas introduced into the silicon raw material in step (4) is 300 sccm.

[0195] Step (5) involves silicon raw material gas vapor deposition at a temperature of 590°C and a pressure of 3 x 10⁻⁶. -2 pa.

[0196] The above steps are performed in a helium atmosphere.

[0197] The helium atmosphere is achieved by a helium flow rate of 20,000 sccm.

[0198] The vapor deposition of the carbon raw material takes 4 minutes each time, and the vapor deposition of the silicon raw material gas takes 2 minutes each time.

[0199] Performance testing:

[0200] 1. Electrical performance testing of negative electrode materials:

[0201] Test conditions: The materials prepared in the comparative examples and embodiments were used as negative electrode materials and mixed with binder polyvinylidene fluoride (PVDF) and conductive agent (Super-P) in a mass ratio of 70:15:15. An appropriate amount of N-methylpyrrolidone (NMP) was added as a solvent to form a slurry, which was coated on copper foil and then vacuum dried and rolled to prepare a negative electrode sheet. A lithium metal sheet was used as the counter electrode. An electrolyte was prepared by mixing a 1 mol / L LiPF6 three-component mixed solvent in an EC:DMC:EMC ratio of 1:1:1 (v / v). A polypropylene microporous membrane was used as the separator. The CR2032 coin cell was assembled in an inert gas-filled glove box.

[0202] The charge and discharge tests of the button cells were conducted on the LANHE battery testing system of Wuhan Landian Electronics Co., Ltd., under normal temperature conditions, with a constant current charge and discharge of 0.1C and a charge and discharge voltage limited to 0.005-1.5V.

[0203] The volumetric expansion rate of the material was tested and calculated using the following method: A composite material with a capacity of 500 mAh / g was prepared by combining the prepared silicon-carbon composite material with graphite, and its cycling performance was tested. The expansion rate was calculated as: (electrode thickness after 50 cycles - electrode thickness before cycling) / (electrode thickness before cycling - copper foil thickness) * 100%. The test results are shown in the table below.

[0204]

[0205] As can be seen from the results in the table above, the method used in this application can achieve an initial reversible capacity of not less than 1800 mAh / g, an expansion rate of less than 35% after 50 cycles, a capacity retention rate of more than 90%, and density parameters. From the comparative performance, it can be seen that when the deposition temperature is below or above the range specified in this application, the electrochemical performance decreases significantly; when the simultaneous deposition temperature is below the range specified in this application, the silicon source gas deposition efficiency is extremely low or even non-existent; when the simultaneous deposition temperature is above the range specified in this application, the deposited nano-silicon reacts with carbon materials to produce silicon carbide.

[0206] The preferred embodiments and examples of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments and examples. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the concept of the present invention.

Claims

1. A high-density, high-purity silicon-carbon anode material, characterized in that: The material includes uniformly and densely distributed silicon and carbon, and the density of the material satisfies ρ1 / ρ2≥95%, where ρ1 is the actual tested density and ρ2 is the theoretical density. Carbon and silicon raw materials are subjected to physical vapor deposition, and after cooling, high-density, high-purity silicon-carbon anode materials are obtained. The high-density, high-purity silicon-carbon anode material is prepared by including the following steps: 1) At room temperature, fix the carbon raw material on the evaporation source and fix the substrate on the substrate support; 2) Introduce silicon raw material gas towards the substrate; 3) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform synchronous vapor deposition, stop the vapor deposition, and after cooling, obtain high-density, high-purity silicon-carbon anode material; Step 3) involves vapor deposition, heating to 420℃-580℃, with the vapor deposition apparatus current at 47-55A; maintaining an ambient pressure of 3x10. -2 pa.

2. The high-density, high-purity silicon-carbon anode material according to claim 1, characterized in that: The carbon raw material includes carbon rope or carbon rod, made of graphite fiber with a purity of 99% and a diameter of 2 mm and a length of 1 cm; the silicon raw material gas includes silane.

3. The high-density, high-purity silicon-carbon anode material according to claim 1, characterized in that: The silicon raw material gas includes one or two of silane and dichlorosilane.

4. The high-density, high-purity silicon-carbon anode material according to claim 1, characterized in that: The flow rate of the silicon raw material gas is 130-200 sccm.

5. The high-density, high-purity silicon-carbon anode material according to claim 1, characterized in that: The above steps are carried out in an atmosphere of nitrogen, hydrogen, helium or argon; the atmosphere is achieved by a flow rate of 1000-5000 sccm.

6. A high-density, high-purity silicon-carbon anode material, characterized in that: The material includes uniformly and densely distributed silicon and carbon, and the density of the material satisfies ρ1 / ρ2≥95%, where ρ1 is the actual tested density and ρ2 is the theoretical density. Carbon and silicon raw materials are subjected to physical vapor deposition, and after cooling, high-density, high-purity silicon-carbon anode materials are obtained. The high-density, high-purity silicon-carbon anode material is prepared by including the following steps: (1) Fix the substrate onto the substrate holder at room temperature; (2) Fix the carbon raw material onto the evaporation source; (3) Turn on the power of the vapor deposition machine, adjust the parameters, and perform carbon raw material vapor deposition; (4) Stop the evaporation of carbon raw materials and introduce silicon raw material gas towards the substrate; (5) Turn on the power of the vapor deposition apparatus, adjust the parameters, perform silicon raw material gas vapor deposition, and then stop silicon raw material gas vapor deposition; (6) Repeat steps 3-6 above, repeating n times, where n is a positive integer; (7) After cooling, a high-density, high-purity silicon-carbon anode material is obtained; In step (3), the carbon raw material is vapor-deposited, and the current of the vapor deposition apparatus is 40-50A. Step (5) involves silicon raw material gas vapor deposition at a temperature of 420℃-580℃ and a pressure of 3x10. -2 pa.

7. The high-density, high-purity silicon-carbon anode material according to claim 6, characterized in that: The carbon raw material includes carbon rope or carbon rod, made of graphite fiber with a purity of 99% and a diameter of 2 mm and a length of 1 cm; the silicon raw material gas includes silane.

8. The high-density, high-purity silicon-carbon anode material according to claim 6, characterized in that: The silicon raw material gas includes one or two of silane and dichlorosilane.

9. The high-density, high-purity silicon-carbon anode material according to claim 6, characterized in that: The flow rate of the gas introduced into the silicon raw material in step (4) is 10-300 sccm.

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