Silicon-carbon negative electrode material and preparation method thereof, battery and power-related equipment

Abstract

The invention provides a silicon-carbon negative electrode material and a preparation method thereof, a battery and electric equipment, and relates to the field of materials. The preparation method of the silicon-carbon negative electrode material comprises the following steps: carrying out first mixing on a silicon-based material and a first carbon source, and then carrying out first carbonization to obtain a first carbonized material; and carrying out second mixing on the first carbonized material and a second carbon source, and then carrying out second carbonization to obtain the silicon-carbon negative electrode material, the second carbonization is performed once or multiple times; when the second carbonization is carried out for multiple times, the material obtained by the previous carbonization is used as a matrix. According to the preparation method of the silicon-carbon negative electrode material provided by the invention, carbon layers are developed differently under multiple carbonization processes, interlayer gaps are formed, and a space for buffering volume expansion of the silicon material is formed, so that the specific surface area is integrally reduced, the first-circle efficiency and the cycle performance are improved, and the preparation method has a wide application prospect.

Description

Technical Field

[0001] This application relates to the field of materials, and particularly to a silicon-carbon anode material, a preparation method thereof, a battery, and an electricity-related device. Background Art

[0002] With the rapid development of the new energy industry, the requirements for the energy density of batteries in the fields of energy storage, power, and 3C are gradually increasing. Currently, the energy density of lithium-ion batteries using ternary cathode materials and graphite anode materials is about 250 - 300 Wh / kg. Improving the capacity of the anode material is an important way to increase the energy density. As a widely used commercial lithium-ion battery anode material, the specific capacity of graphite has approached the upper limit of the theoretical specific capacity of 372 mAh / g, while the theoretical specific capacity of silicon-based anodes is as high as 4200 mAh / g, which is 10 times that of graphite materials, showing obvious advantages. However, the volume expansion of silicon-based anodes is significant, resulting in material pulverization and loss of electrical contact during charge and discharge, ultimately leading to electrode failure. To alleviate the volume expansion problem, silicon-carbon anode materials have emerged. The carbon coating layer can provide space for accommodating the volume expansion of silicon-based materials and enhance the conductivity of silicon-based materials, making them silicon-based materials with great development potential.

[0003] Currently, there are two common preparation methods for silicon-carbon anode materials. One is to compound nano-silicon with carbon materials. By reducing the particle size of silicon-based materials to the nano level, a carbon layer is coated on the surface of the active material silicon to buffer the stress and deformation generated during the insertion and extraction of lithium ions by silicon and enhance the conductivity of the material. The other is to use porous carbon materials as the substrate, and deposit nano-silicon particles into the pores of the porous carbon through chemical vapor deposition to provide space for accommodating the volume expansion of silicon materials and improve the cycling performance of silicon-based materials. For example, in Patent Document 118811808A "Silicon-Carbon Composite Material and Preparation Method, Anode Sheet and Battery", graphite materials are mixed with silicon active materials above the micron level and then ground to form a silicon-carbon composite material. A carbon source gas is used to coat the surface of the silicon-carbon composite material by high-temperature pyrolysis to form a carbon coating layer. Another example is Patent Document CN118825278A "A Coated and Modified Silicon-Carbon Anode Material and Its Preparation Method and Application", where a polysiloxane shell is coated on the surface of the vapor-deposited silicon-carbon anode material. In Patent Document CN118800896A "A Preparation Method of a Doped Silicon-Carbon Composite Anode Material", using porous carbon as the substrate, heating the silicon source and the metal doping source to form vapor, and performing silicon deposition and doping on the porous carbon material to obtain the doped silicon-carbon composite anode material. However, the costs of these two processes are relatively high, which is not conducive to industrial production.

[0004] Therefore, it is of great significance to explore a coating process method with low cost and easy industrialization to prepare silicon-carbon anode materials, reduce the volume expansion of silicon-carbon materials, and improve the cycling performance. Summary of the Invention

[0005] The purpose of the present application is to provide a silicon-carbon negative electrode material, a preparation method thereof, a battery, and an electricity-related device to solve the above problems.

[0006] To achieve the above object, the present application adopts the following technical solutions:

[0007] A preparation method of a silicon-carbon negative electrode material, comprising:

[0008] First, mix a silicon-based material with a first carbon source, and then perform first carbonization to obtain a first carbonized material;

[0009] Then, mix the first carbonized material with a second carbon source, and then perform second carbonization to obtain the silicon-carbon negative electrode material;

[0010] The second carbonization is carried out once or multiple times; when the second carbonization is carried out multiple times, the material obtained from the previous carbonization is used as the matrix for the next carbonization.

[0011] Preferably, the second carbonization is carried out 1-4 times.

[0012] Preferably, the preparation method of the silicon-carbon negative electrode material satisfies one or more of the following conditions:

[0013] (1) The silicon-based material includes at least one of nano-silicon, micro-silicon, and silicon-carbon composite materials;

[0014] (2) The first carbon source and the second carbon source each independently include at least one of heavy oil, phenolic resin, epoxy resin, asphalt, polyvinylpyrrolidone, and polyacrylonitrile;

[0015] (3) When performing each carbonization, the mass ratio of the silicon-based material to the first carbon source, and the mass ratio of the first carbonized material to the second carbon source are each independently (1-20):1; preferably (2-17):1;

[0016] (4) The mixing methods of the first mixing and the second mixing each independently include one or more of grinding mixing, ball milling mixing, 3D mixing, and liquid phase mixing.

[0017] Preferably, the preparation method of the silicon-carbon negative electrode material satisfies one or more of the following conditions:

[0018] A. The temperatures of the first carbonization and the second carbonization are each independently 300-1300°C, preferably 400-1300°C; the times are each independently 1-10h, preferably 2-8h;

[0019] B. The heating rates of the first carbonization and the second carbonization are each independently 1-20°C / min.

[0020] Preferably, the temperature and / or heating rate for each carbonization are the same or different, preferably different.

[0021] Preferably, after the first carbonization, the method further includes controlling the particle size of the material to obtain a material meeting the following requirements: D 10 = 2 - 8 μm, D 50 = 8 - 16 μm, D 90 = 20 - 30 μm;

[0022] Preferably, the method for controlling the particle size includes manual grinding, mechanical crushing, and air flow crushing;

[0023] Preferably, the particle size of the silicon-carbon negative electrode material does not exceed 100 μm, preferably does not exceed 80 μm.

[0024] The present application also provides a silicon-carbon negative electrode material prepared by using the preparation method of the silicon-carbon negative electrode material described above.

[0025] The present application also provides a battery, the raw materials of which include the silicon-carbon negative electrode material described above.

[0026] The present application also provides an electricity-related device including the battery described above.

[0027] Compared with the prior art, the beneficial effects of the present application include:

[0028] For the preparation method of the silicon-carbon negative electrode material provided by the present application, by utilizing the good electrical conductivity of carbon, multiple carbon coatings can form a hierarchical conductive network, overall reducing the overall resistance of the electrode, improving the electron transfer efficiency, and enhancing the overall electrical conductivity; multiple coatings can also "check and fill the gaps", filling the surface defects to form a denser and more uniform carbon layer, effectively maintaining the integrity of the electrode structure, enabling the surface of the active material to conduct electricity uniformly, avoiding side reactions caused by direct contact between the electrode material and the electrolyte, and improving the Coulomb efficiency.

[0029] The silicon-carbon negative electrode material provided by the present application has the characteristics of low volume expansion and good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope of the present application.

[0031] Figure 1 It is a cyclic performance curve graph of Example 3 and Comparative Example 1;

[0032] Figure 2 It is a SEM photograph of the silicon-carbon negative electrode material obtained in Example 3;

[0033] Figure 3 SEM photograph of the nano-silicon provided for Comparative Example 1;

[0034] Figure 4 Graph of voltage and thickness changes of the silicon-carbon negative electrode material of Example 3 and the nano-silicon of Comparative Example 1. Detailed implementation manners

[0035] To better explain the technical solution provided by this application, before the examples, a general statement of the technical solution is given first, as follows:

[0036] A preparation method of a silicon-carbon negative electrode material, comprising:

[0037] Mixing a silicon-based material with a first carbon source for the first time, and then performing first carbonization to obtain a first carbonized material;

[0038] Mixing the first carbonized material with a second carbon source for the second time, and then performing second carbonization to obtain the silicon-carbon negative electrode material;

[0039] The second carbonization is performed once or multiple times; when the second carbonization is performed multiple times, the material obtained from the previous carbonization is used as the matrix for the next carbonization.

[0040] In an alternative embodiment, the second carbonization is performed 1 to 4 times.

[0041] It should be noted that the above "first carbonization, second carbonization" is not a limitation on the number of times. In fact, it means carbonization coating with the silicon-based material as the initial matrix, and then using the material obtained from the previous carbonization coating as the matrix for the subsequent carbonization coating; this carbonization coating needs to be performed at least 2 times; therefore, it can be understood that the preferred number of times of the second carbonization can be 1 time, 2 times, 3 times or 4 times; when the number of times of the second carbonization exceeds 2 times and the total number of carbonization times exceeds 3 times, the carbon layer is too thick, increasing the lithium ion transmission path, which will instead hinder the lithium ion transmission and reduce the performance of the material. Therefore, coating to a reasonable number of layers and achieving a balance of various performances is the key.

[0042] In an alternative embodiment, the preparation method of the silicon-carbon negative electrode material satisfies one or more of the following conditions:

[0043] (1) The silicon-based material includes at least one of nano-silicon, micro-silicon and silicon-carbon composite material;

[0044] (2) The first carbon source and the second carbon source each independently include at least one of heavy oil, phenolic resin, epoxy resin, asphalt, polyvinylpyrrolidone, and polyacrylonitrile;

[0045] It can be understood that solid block carbon sources need to be crushed into powders before use.

[0046] (3) During each carbonization, the mass ratio of the silicon-based material to the first carbon source and the mass ratio of the first carbonized material to the second carbon source are each independently (1 - 20):1; preferably (2 - 17):1;

[0047] It should be noted that the "mass ratio of the silicon-based material to the first carbon source" and the "mass ratio of the first carbonized material to the second carbon source" actually refer to the mass ratio between the substrate for each carbonization and the carbon source for that carbonization.

[0048] Optionally, the mass ratio of the silicon-based material to the first carbon source and the mass ratio of the first carbonized material to the second carbon source can each independently be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1 or any value between (1 - 20):1;

[0049] (4) The first mixing and the second mixing methods each independently include one or more of grinding mixing, ball milling mixing, 3D mixing, and liquid phase mixing.

[0050] It should be noted that if it is liquid phase mixing, a solvent such as anhydrous ethanol solution needs to be used.

[0051] In an optional embodiment, the preparation method of the silicon-carbon negative electrode material satisfies one or more of the following conditions:

[0052] A. The temperatures of the first carbonization and the second carbonization are each independently 300 - 1300 °C, preferably 400 - 1300 °C; the times are each independently 1 - 10 h, preferably 2 - 8 h;

[0053] Optionally, the temperatures of the first carbonization and the second carbonization can each independently be 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C, 1100 °C, 1200 °C, 1300 °C or any value between 300 - 1300 °C; the times can each independently be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h or any value between 1 - 10 h;

[0054] B. The heating rates of the first carbonization and the second carbonization are each independently 1 - 20 °C / min.

[0055] The heating rate of the first carbonization and the second carbonization can each independently be 1 °C / min, 5 °C / min, 10 °C / min, 15 °C / min, 20 °C / min, or any value between 1 - 20 °C / min.

[0056] In an alternative embodiment, the temperature and / or heating rate of each carbonization are the same or different, preferably different.

[0057] When the temperature and / or heating rate of each carbonization are different, different sintering temperature curves will affect the electrochemical performance of the corresponding silicon-carbon material. The main purpose is to utilize the different development of the carbon layer under different carbonization processes to form interlayer voids, creating space to buffer the volume expansion of the silicon material, overall reducing the specific surface area and improving the first-cycle efficiency and cycle performance.

[0058] Each layer adopts a different carbonization process to form carbon layers with different properties: the inner carbon layer provides more elastic strength. When the silicon material expands in volume during charge and discharge, it acts like a "protective cover" to maintain the integrity of the silicon material; the outer carbon layer has a higher degree of graphitization and provides stronger conductivity; the middle carbon layer balances elastic strength and conductivity, and the inter-shell voids formed by different carbonization processes for each layer can provide space for volume expansion, again playing a role in maintaining the integrity and conductivity of the electrode material. The multi-layer carbon produces a synergistic effect, jointly promoting the improvement of material stability.

[0059] In an alternative embodiment, after the first carbonization, it further includes controlling the particle size of the material to obtain a material that meets the following requirements: D 10 = 2 - 8 μm, D 50 = 8 - 16 μm, D 90 = 20 - 30 μm; In an alternative embodiment, the method for controlling the particle size includes manual grinding, mechanical crushing, and air jet milling.

[0060] The particle size of the material needs to be within a certain range. If the particles are too large, it is impossible to coat and prepare an electrode sheet. If they are too fine, they are prone to agglomeration, which will result in too large a specific surface area and a reduction in Coulombic efficiency. An appropriate particle size is beneficial for introducing it into the backend battery cell system, so the particle size range is defined.

[0061] In an alternative embodiment, the particle size of the silicon-carbon negative electrode material does not exceed 100 μm, preferably not exceeding 80 μm.

[0062] This application also provides a silicon-carbon negative electrode material prepared by using the preparation method of the silicon-carbon negative electrode material described above.

[0063] This application also provides a battery, the raw materials of which include the silicon-carbon negative electrode material described above.

[0064] The above-mentioned battery can be, for example, a lithium-ion button cell, and this silicon-carbon negative electrode material can also be applied to other types of lithium-ion batteries, such as lithium-ion liquid batteries, solid-state batteries, and semi-solid-state batteries.

[0065] The preparation and testing process of the button cell is as follows: Homogenize the silicon-carbon negative electrode material, conductive agent, and binder in a ratio of 8:1:1, and the coating thickness is 150 μm. Cut the electrode sheet into a circular sheet with a diameter of 12 cm, and assemble the button cell in the order of positive electrode shell - electrode sheet, separator, lithium sheet, gasket, and spring sheet.

[0066] This application also provides an electricity-related device including the above-mentioned battery.

[0067] The electricity-related device known in this application refers to a device that itself contains the above-mentioned battery or directly / indirectly uses this battery for power supply. For example, in electric vehicles, electric bicycles, and other consumer electronic products, it can also be large industrial products such as energy storage systems.

[0068] The implementation scheme of this application will be described in detail below in combination with specific embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate this application and should not be regarded as limiting the scope of this application. For those not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0069] Example 1

[0070] This example provides a silicon-carbon material, and its preparation method includes the following steps:

[0071] (1) Prepare materials

[0072] Prepare nano-silicon powder, D 50 = 369.6 nm.

[0073] Prepare powder asphalt, D 50 = 1.02 μm.

[0074] (2) Mix

[0075] Put the nano-silicon powder and asphalt powder into a 3D mixer in a mass ratio of 10:1, mix for 2 h, and then continue to mix for 2 h using a ball mill.

[0076] (3) Calcinate

[0077] Calcinate the product of step (2) at a heating rate of 5 °C / min at a temperature of 600 °C for 5 h, and use a jet mill to crush it to D 10 = 2 - 8 μm, D 50 = 8 - 16 μm, D 90 = 20 - 30 μm.

[0078] (4) Second coating

[0079] Put the above - calcined material and asphalt powder in a 3D mixer at a mass ratio of 10:1, and mix for 2 h. Calcinate at 800 °C for 5 h at a heating rate of 5 °C / min.

[0080] (5) Third coating

[0081] Put the above - calcined material and asphalt powder in a 3D mixer at a mass ratio of 10:1, and mix for 2 h. Calcinate at 1000 °C for 5 h at a heating rate of 5 °C / min.

[0082] (6) Fourth coating

[0083] Put the above - calcined material and asphalt powder in a 3D mixer at a mass ratio of 10:1, and mix for 2 h. Calcinate at 1200 °C for 5 h at a heating rate of 5 °C / min.

[0084] Example 2 - 3

[0085] The difference between Example 2 - 3 and Example 1 is only: the number of coatings, as shown in Table 1 specifically.

[0086] Table 1 Operating parameters of Example 2 - 3

[0087] Group Coating times Example 2 2 (only the first two coatings) Example 3 3 (only the first three coatings)

[0088] Examples 4 - 8

[0089] The difference in the preparation method between Examples 4 - 8 and Example 1 is only: the carbon source and the number of coatings, as shown in Table 2 specifically.

[0090] Table 2 Operating parameters of Examples 4 - 8

[0091]

[0092] Examples 9 - 13

[0093] The difference in the preparation method between Examples 9 - 13 and Example 1 is: the carbonization temperature, as shown in Table 3 specifically.

[0094] Table 3 Operating parameters of Examples 9 - 13

[0095]

[0096] Example 14

[0097] The difference in the preparation method between Example 14 and Example 1 is only: the silicon - based material, as shown in Table 4 specifically.

[0098] Table 4 Operating Parameters of Example 14

[0099] Group Silicon-based material category <![CDATA[D 50 / μm]]> Example 14 Micron silicon 49.64

[0100] Comparative Example 1

[0101] Nanosilicon material was used as a control.

[0102] Comparative Example 2

[0103] Microsilicon material was used as a control.

[0104] Comparative Examples 3 - 8

[0105] The difference between Comparative Examples 3 - 8 and Example 1 is that the coating was performed only once, and the specific carbon sources for coating are shown in Table 5.

[0106] Table 5 Operating Parameters of Comparative Examples 3 - 8

[0107] Group Carbon source type Comparative Example 3 Pitch Comparative Example 4 Heavy oil Comparative Example 5 Phenolic resin Comparative Example 6 Epoxy resin Comparative Example 7 Polyvinylpyrrolidone Comparative Example 8 Polyacrylonitrile

[0108] The charge - discharge performance of the materials of Examples 1 - 14 and Comparative Examples 1 - 8 was tested.

[0109] Testing method: The silicon - carbon negative electrode material, conductive agent, and binder were homogenized in a ratio of 8:1:1, and the coating thickness was 150 μm. The electrode sheet was cut into a circular sheet with a diameter of 12 cm, and a button battery was assembled in the order of positive electrode shell - electrode sheet, separator, lithium sheet, gasket, and spring sheet. Then, the battery was subjected to charge - discharge testing to test the charge - discharge performance of the first cycle.

[0110] The charge - discharge performance of the first cycle of the materials of Examples 1 - 14 and Comparative Examples 1 - 8 is shown in Table 6.

[0111] Table 6 Charge - Discharge Data of the First Cycle of Examples 1 - 14 and Comparative Examples 1 - 8

[0112]

[0113]

[0114] The test results show that: The results of Comparative Example 3, Example 1, Example 2, and Example 3 indicate that multiple coatings can promote the improvement of material performance, and with the increase of the coating times, the first - cycle Coulombic efficiency first increases and then decreases. This is because after the silicon material is coated with a carbon layer, it can avoid the side reaction caused by the direct contact between the electrolyte and the silicon material, and the conductivity of the silicon material is poor, while the carbon layer can enhance the conductivity of the material. However, an overly thick carbon layer will make the lithium - ion transmission path too long, hinder the transmission of lithium ions, and reduce the material performance.

[0115] The results of Example 1 and Examples 8 - 12 show that when coating multiple times, better performance can be achieved with a coating temperature that is first low and then high. When the coating temperature gradually decreases, the improvement effect is not obvious, which is related to the performance and distribution of the high - and low - temperature carbon layers. Since the carbon layer formed at low temperature has toughness, directly coating the silicon - based material makes it not easily broken when the silicon - based material expands and contracts, but it has a relatively large specific surface area and is suitable for inner - layer coating. The carbon layer formed at high temperature has a high degree of graphitization, strong conductivity, and a relatively small specific surface area, making it suitable for outer - layer coating. The medium - temperature carbon layer combines the two properties, further playing a connecting role, and can also form interlayer voids to reserve space for volume expansion, relieve the volume expansion of the silicon - based material, and enhance the material stability. The multi - layer cooperation can enhance the material stability and improve the Coulomb efficiency and cycling performance. When the temperature of each layer is the same, the morphology of each carbon layer is the same, and interlayer voids cannot be formed. Without the synergistic effect of the elastic carbon layer and the conductive carbon layer, it is only the superposition of the carbon layer thickness, which has the effect of filling surface defects and a certain effect of improving the Coulomb efficiency, but the synergistic improvement effect is not obvious.

[0116] The results of Example 1, Examples 4 - 7 and Comparative Examples 3 - 7 show that when other common coating carbon sources adopt the multi - layer coating process, the Coulomb efficiency can be significantly improved, indicating that this coating process has universality, and once again verifying that the improvement space of single - layer carbon coating is limited, and multi - layer carbon coating has an obvious synergistic improvement effect.

[0117] The test results of Example 1, Example 13, and Comparative Examples 1 - 2 show that multi - layer carbon coated with different silicon - based raw materials under different processes can all achieve the effect of significantly improving the Coulomb efficiency, once again verifying the universality of this process.

[0118] Test the cycling performance of Example 3 and Comparative Example 1.

[0119] Test method: Homogenize the silicon - carbon anode material, conductive agent, and binder in a ratio of 8:1:1, and the coating thickness is 150 μm. Cut the electrode sheet into a circular sheet with a diameter of 12 cm, and assemble a button cell in the order of positive electrode shell - electrode sheet, separator, lithium sheet, gasket, and spring sheet. Perform charge - discharge tests on the battery for 100 cycles to test the cycling performance.

[0120] The cycling performance of Example 3 and Comparative Example 1 is as Figure 1 shown. After coating the silicon - carbon material, the cycling stability is significantly improved. When cycling 100 times, the capacity retention rate of nano - silicon is 2.19%, and the capacity retention rate of the coated silicon - carbon material is 67.03%.

[0121] Test the SEM of Example 3 and Comparative Example 1 to explore the change in the microscopic morphology before and after coating.

[0122] The SEM of Example 3 and Comparative Example 1 is as Figure 2 、 Figure 3As shown, the nanosilicon material of Comparative Example 1 is in the form of irregular flakes. After coating, a large-particle amorphous structure is formed, reducing surface defects and the specific surface area.

[0123] Test the specific surface area of the materials obtained in Test Example 3 and Comparative Example 1 to explore the change in specific surface area before and after coating.

[0124] The test results are shown in Table 7.

[0125] Table 7 Specific surface area before and after coating

[0126] Material <![CDATA[BET / m 2 ·g -1 > Comparative Example 1 24.82 Example 3 5.17

[0127] The silicon-carbon negative electrode material obtained after coating in Example 3 has a lower specific surface area compared to the nanosilicon in Comparative Example 1. A lower specific surface area is beneficial for reducing the formation of the SEI film, reducing the consumption of lithium ions, and improving the first-cycle Coulombic efficiency.

[0128] Test the swelling rate of Test Example 3 and Comparative Example 1 to explore the effect on volume expansion before and after coating.

[0129] Test method: Homogenize Example 3 and Comparative Example 1 with a conductive agent and a binder in a ratio of 8:1:1, and the coating thickness is 150 μm. Cut the electrode sheet into a circular sheet with a diameter of 12 cm, and assemble a button battery in the order of positive electrode shell - electrode sheet, separator, positive electrode sheet, gasket, and spring sheet. Put the battery into a swelling rate tester RSS1400 for charge and discharge testing, measure the volume change of the button battery during charge and discharge, and convert it into the volume swelling rate of the negative electrode material.

[0130] The voltage and thickness change curves of the silicon-carbon materials in Example 3 and Comparative Example 1 are as Figure 4 shown. The black line is the swelling curve of the electrode sheet in Comparative Example 1, and the red line is the swelling thickness curve of the electrode sheet in Example 3 (the dotted line is the voltage curve, and the solid line is the swelling thickness curve). It can be seen from Figure 4 this that the swelling thickness of the electrode sheet of the coated material is significantly reduced. The specific data can be seen in the comparison table of swelling amount and swelling rate, as shown in Table 8.

[0131] Table 8 Comparison table of swelling amount

[0132]

[0133] Compared with Comparative Example 1 and Example 3, the swelling amounts during the first charge / discharge are 23.25 μm, -18.45 μm and 15.53 μm, -14.91 μm respectively, the swelling amounts during the first charge / discharge in the second cycle are 14.91 μm, -14.76 μm and 12.12 μm, -12.3 μm respectively, and the swelling amounts during the first charge / discharge in the third cycle are 12.81 μm, -13.11 μm and 10.74 μm, -11.09 μm respectively.

[0134] The expansion rate of the electrode was calculated based on the swelling thickness, and the data are shown in Table 9.

[0135] Table 9 Comparison Table of Expansion Rates

[0136]

[0137] The expansion rates during the first charge / discharge decreased from 38.11% and 30.26% to 15.38% and 14.76% respectively; during the second charge / discharge, they decreased from 24.44% and 24.2% to 12.00% and 12.18% respectively; during the third charge / discharge, they decreased from 21.00% and 21.49% to 10.63% and 10.98% respectively. The reduction of the volume expansion of the material can reduce the risks of material pulverization, repeated formation of the SEI film, and electrical contact failure caused by volume expansion, which is beneficial to the application of silicon-carbon materials in the battery cell.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A preparation method of a silicon-carbon anode material, characterized in that Comprising: Mixing a silicon-based material with a first carbon source for the first time, and then performing first carbonization to obtain a first carbonized material; Mixing the first carbonized material with a second carbon source for the second time, and then performing second carbonization to obtain the silicon-carbon negative electrode material; The second carbonization is carried out once or multiple times; when the second carbonization is carried out multiple times, the material obtained from the previous carbonization is used as the substrate for the next carbonization.

2. The preparation method of the silicon-carbon negative electrode material according to claim 1, characterized in that The second carbonization is carried out 1-4 times.

3. The preparation method of the silicon-carbon anode material according to claim 1, wherein, Satisfying one or more of the following conditions: (1) The silicon-based material includes at least one of nano-silicon, micro-silicon, and silicon-carbon composite material; (2) The first carbon source and the second carbon source each independently include at least one of heavy oil, phenolic resin, epoxy resin, asphalt, polyvinylpyrrolidone, and polyacrylonitrile; (3) When performing each carbonization, the mass ratio of the silicon-based material to the first carbon source, and the mass ratio of the first carbonized material to the second carbon source are each independently (1-20):1; preferably (2-17):1; (4) The first mixing and the second mixing methods each independently include one or more of grinding mixing, ball milling mixing, 3D mixing, and liquid phase mixing.

4. The preparation method of the silicon-carbon anode material according to claim 1, characterized in that, Satisfying one or more of the following conditions: A. The temperatures of the first carbonization and the second carbonization are each independently 300-1300 °C, preferably 400-1300 °C; the times are each independently 1-10 h, preferably 2-8 h; B. The heating rates of the first carbonization and the second carbonization are each independently 1-20 °C / min.

5. The preparation method of the silicon-carbon anode material according to claim 4, wherein The temperature and / or heating rate of each carbonization are the same or different, preferably different.

6. The preparation method of the silicon-carbon anode material according to claim 1, characterized in that, After the first carbonization, it further includes controlling the particle size of the material to obtain a material that meets the following requirements: D 10 = 2 - 8 μm, D 50 = 8 - 16 μm, D 90 = 20 - 30 μm; Preferably, the method for controlling the particle size includes manual grinding, mechanical crushing, and air flow crushing.

7. The preparation method of the silicon-carbon anode material according to any one of claims 1-6, characterized in that, The particle size of the silicon-carbon negative electrode material does not exceed 100 μm, preferably does not exceed 80 μm.

8. A silicon-carbon anode material, characterized in that, Prepared by using the preparation method of the silicon-carbon negative electrode material according to any one of claims 1-7.

9. A battery, characterized in that, Its raw materials include the silicon-carbon negative electrode material according to claim 8.

10. An electricity-related device, characterized in that, Including the battery according to claim 9.

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