Carbon-silicon material and preparation method and application thereof

Abstract

The invention provides a silicon-carbon material as well as a preparation method and application thereof. The silicon-carbon material comprises a carbon skeleton and a silicon elementary substance deposited on the carbon skeleton, the Raman spectrum of the silicon carbon material has a D peak and a G peak in a wave number range of 1350 cm <-1 > to 1650 cm <-1 >, and ID / IG is 1.0 to 1.5; and a spectrum peak of a silicon simple substance exists in a range of 460 cm <-1 > to 480 cm <-1 >. The silicon-carbon material provided by the invention is of a structure that a carbon skeleton is deposited and coated with silicon, the thickness of thin film silicon in the Z-axis direction is far smaller than the critical dimension of 150 nanometers, stress caused by volume expansion can be resisted through the Young modulus of the thin film silicon, the volume expansion rate of silicon can be effectively inhibited, and the full-electricity expansion rate of the obtained silicon-carbon material is smaller than 30%.

Description

Technical Field

[0001] The invention relates to a carbon silicon material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the new energy industry, improving the specific capacity of negative electrode materials is of great significance to improving the energy density of lithium batteries. At present, the mainstream commercial negative electrode is graphite-based materials, whose specific capacity has reached the theoretical limit of 372mAh / g, while the theoretical specific capacity of silicon materials of the same family is as high as 4200mAh / g, which is the negative electrode material with the highest known gram capacity, and has great application prospects and market value.

[0003] However, the silicon negative electrode has serious volume deformation during the charge and discharge process, with an expansion rate of up to 300%, which directly leads to structural damage and mechanical crushing of the battery pole piece, severely limiting its commercial application. To solve the above problems, silicon nano-crystallization and compounding with graphite materials are two mainstream solutions. As a "star material", graphene has been widely introduced into the silicon-carbon negative electrode system in recent years, which can significantly buffer the volume expansion of silicon and achieve the purpose of improving the material's cycle performance.

[0004] CN106941169B reported a porous graphene / silicon composite negative electrode material, which improves the conductivity and cycle stability of the material by introducing flexible graphene, while also minimizing the obstruction of the two-dimensional structure of the graphite sheet to ion transmission. However, the process still requires the use of asphalt and graphite for subsequent spray granulation, and the first coulomb efficiency of the product and the full-charge expansion rate of the electrode are not reported.

[0005] CN111498829B reported a graphene-based silicon-carbon anode material, which was prepared by electrostatic adsorption between a gel coating layer and graphene oxide. However, the specific capacity of the material is relatively low (<700 mAh / g), and it is difficult to meet the demand for high-capacity silicon-carbon anodes in the future. Summary of the invention

[0006] The purpose of the present invention is to overcome the technical defects of silicon-carbon materials in the prior art and to provide a new type of silicon-carbon material with the advantages of high specific capacity, small volume expansion and long cycle life.

[0007] According to a first aspect of the present invention, the present invention provides a silicon-carbon material, which comprises a carbon skeleton and a silicon element deposited on the carbon skeleton; the Raman spectrum of the silicon-carbon material has a wave number of 1350cm -1 -1650cm -1 There are D peak and G peak in the range, and ID / IG is 1.0~1.5; at 460cm -1 -480cm -1 There is a spectral peak of silicon element in the range.

[0008] According to a second aspect of the present invention, the present invention provides a method for preparing the silicon-carbon material of the present invention, the method comprising the following steps:

[0009] Silicon was deposited on the carbon skeleton material by vapor deposition. The Raman spectrum of the carbon skeleton material was at a wave number of 1350 cm -1 -1650cm -1 It has D peak and G peak in the range, and ID / IG is 1.0-1.5, and the specific surface area is 300-500m 2 / g.

[0010] According to a third aspect of the present invention, the present invention provides use of the silicon-carbon material of the present invention as a negative electrode material for a battery; preferably, use of the silicon-carbon material as a negative electrode material for a lithium battery.

[0011] Compared with the prior art, the excellent effects of the present invention are as follows:

[0012] 1) The silicon-carbon material provided by the present invention has a structure of silicon deposition coated with a carbon skeleton, which can resist the stress caused by volume expansion through its own Young's modulus, and can effectively suppress the volume expansion rate of silicon. The full-charge expansion rate of the obtained silicon-carbon material is less than 30%;

[0013] 2) In the silicon-carbon material provided by the present invention, carbon is a skeleton structure, and silicon is deposited on its surface by vapor deposition, which avoids the dispersion problem of carbon and silicon in traditional processes, solves the problem of lithium ion transmission obstruction caused by carbon materials, and avoids excessive local expansion caused by uneven dispersion of silicon on the surface of carbon materials.

[0014] 3) The silicon-carbon material provided by the present invention avoids the processing difficulty caused by the large specific surface area of ​​the traditional composite material based on porous carbon because it adopts the vapor deposition process. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 SEM photo of the silicon-carbon negative electrode obtained in Example 1;

[0016] Figure 2 TEM and HRTEM photos of the silicon-carbon negative electrode obtained in Example 1;

[0017] Figure 3 This is the BET curve of the silicon-carbon negative electrode obtained in Example 1;

[0018] Figure 4 This is the Raman spectrum of the silicon-carbon negative electrode obtained in Example 1. DETAILED DESCRIPTION

[0019] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0020] The present invention provides a silicon-carbon material, which comprises a carbon skeleton and a silicon element deposited on the carbon skeleton; the Raman spectrum of the silicon-carbon material has a wave number of 1350cm -1 -1650cm -1 There are D peak and G peak in the range, and ID / IG is 1.0~1.5; at 460cm -1 -480cm -1 The silicon-carbon material having the above structural characteristics of the present invention has the advantages of low full-charge volume expansion rate and small silicon loading at the same gram capacity.

[0021] According to a preferred embodiment of the present invention, the gram capacity of the silicon-carbon material is ≥1500 mAh g -1 , preferably ≥1800mAhg -1 , the first coulombic efficiency is ≥85%. This shows that the silicon-carbon material of the present invention has the advantages of high first efficiency and high specific capacity.

[0022] In the present invention, there is no special requirement for the composition of the silicon-carbon material, and its composition content can be selected in a wide range. According to a preferred embodiment of the present invention, based on the silicon-carbon material, the mass percentage of the carbon skeleton is 30wt% to 70wt%, preferably 40wt% to 60wt%; the mass percentage of silicon element is 30wt% to 70wt%, preferably 40wt% to 60wt%.

[0023] According to a preferred embodiment of the present invention, the tap density of the silicon-carbon material is 0.6 g / cm 3 ~1.0g / cm 3 , preferably 0.8 g / cm 3 ~0.9g / cm 3 ; This shows that the silicon-carbon material of the present invention has a greater advantage in bulk density.

[0024] According to a preferred embodiment of the present invention, the particle size D10 of the silicon-carbon material is 1 μm to 3 μm, D50 is 5 μm to 8 μm, and D90 is 12 μm to 16 μm, which shows that the silicon-carbon material of the present invention has the advantages of narrower particle size distribution and greater compaction density.

[0025] According to a preferred embodiment of the present invention, the silicon element in the silicon-carbon material is deposited on the carbon skeleton in the form of a thin film or a block; this indicates that the silicon-carbon material of the present invention has the advantages of smaller volume expansion rate and better cycle stability.

[0026] According to a preferred embodiment of the present invention, the specific surface area of ​​the silicon-carbon material is 1 m 2 / g~5m 2 / g, pore volume is 0.3cm 3 / g~1.2cm 3 / g; This shows that the silicon-carbon material of the present invention has a smaller liquid absorption rate and more excellent processing performance advantages.

[0027] According to a preferred embodiment of the present invention, the gram capacity of the blend of silicon-carbon material and graphite is greater than or equal to 600 mAhg -1 , the volume expansion rate in the fully charged state is ≤30%. This shows that the silicon-carbon material of the present invention has the advantage of lower volume expansion rate when the gram capacity is the same.

[0028] The silicon-carbon materials having the aforementioned characteristics of the present invention can achieve the purpose of the present invention, and there is no special requirement for their sources and preparation methods. The following exemplifies a preparation method, but the present invention is not limited to being prepared by the following method.

[0029] According to one embodiment of the present invention, the method for preparing the silicon-carbon material comprises the following steps:

[0030] Silicon was deposited on the carbon skeleton material by vapor deposition. The Raman spectrum of the carbon skeleton material was at a wave number of 1350 cm -1 -1650cm -1 It has D peak and G peak in the range, and ID / IG is 1.0-1.5, and the specific surface area is 300-500m 2 / g.

[0031] According to one embodiment of the present invention, preferably, the surface layer of the product obtained after depositing silicon element is carbon coated.

[0032] In the present invention, there is no special requirement for the conditions of vapor deposition, and the following is an exemplary description, but the scope of the present invention is not limited thereto.

[0033] According to one embodiment of the present invention, the temperature of vapor deposition is 800°C to 1200°C.

[0034] According to one embodiment of the present invention, the vapor deposition time is 2 hours to 8 hours.

[0035] In the present invention, the silicon source used for deposition can be selected from a wide range of types, which are described below by way of example only, but the scope of the present invention is not limited thereby.

[0036] According to one embodiment of the present invention, the silicon source is silane, preferably monosilane, disilane, chlorosilane, and more preferably one or more of monosilane, silicon tetrachloride, and silicon trichloride.

[0037] In the present invention, a carrier is added as needed. For example, when silicon trichloride is used, hydrogen is used as a carrier gas to provide a reducing atmosphere. An inert gas may also be added as a carrier according to actual operation.

[0038] In the present invention, the amount of silicon source used is selected according to the actual needs of silicon single substance, and the description is not repeated here.

[0039] The carbon skeleton materials having the aforementioned characteristics of the present invention can achieve the purpose of the present invention, and there are no special requirements for their sources and preparation methods. The following exemplifies a preparation method, but the present invention is not limited to being prepared using only the following method.

[0040] According to one embodiment of the present invention, the preparation method of the carbon skeleton material includes: heat treating graphene with water vapor. The present invention develops a suitable preparation process, fully utilizing the excellent conductivity and flexibility of graphene to solve the problems of volume expansion and poor conductivity in the application of silicon-carbon negative electrodes, and solves the problems that need to be solved in this field.

[0041] In the present invention, the purpose of water vapor heat treatment is etching. For example, a water vapor generating device is generally installed at the inlet of a tube furnace, and an inert gas is used as a carrier to perform etching by heating. The flow rate of the carrier gas can be selected in a wide range, generally 100-200 sccm.

[0042] There is no special requirement for the rate of heating to the heat treatment temperature, which can generally be 1-10°C / min, such as 5°C / min.

[0043] In the present invention, various graphenes can be used in the present invention, which are described below by way of example only, but the scope of the present invention is not limited thereby.

[0044] According to one embodiment of the present invention, preferably, the median particle size D50 of the graphene is 10 μm to 16 μm. Thus, the prepared carbon skeleton material has the advantages of moderate skeleton size and large silicon loading.

[0045] According to one embodiment of the present invention, preferably, the carbon content of the graphene is ≥ 90%, thereby having the advantage of high electrical conductivity.

[0046] According to one embodiment of the present invention, preferably, the specific surface area of ​​the graphene is 30m 2 / g~80m 2 / g.

[0047] In the present invention, the conditions for the heat treatment can be selected in a wide range. According to a preferred embodiment of the present invention, the conditions for the heat treatment include: a temperature of 600°C to 900°C, and the time of the heat treatment is adjusted as needed. For the present invention, the preferred heat treatment time is 0.5h to 2h.

[0048] In the present invention, after the heat treatment is completed, vacuum drying is performed to obtain the carbon skeleton material.

[0049] The present invention provides the use of the silicon-carbon material of the present invention as a negative electrode material for a battery; preferably, the use of the silicon-carbon material as a negative electrode material for a lithium battery.

[0050] The present invention has no particular limitation on the specific composition of the positive electrode material, and the positive electrode material containing lithium element conventionally used in the art may be used.

[0051] According to the lithium ion battery provided by the present invention, the separator can be selected from various separators used in lithium ion batteries known to those skilled in the art, for example, it can be a polypropylene microporous membrane, polyethylene felt, glass fiber felt or ultrafine glass fiber paper.

[0052] According to the lithium ion battery provided by the present invention, the electrolyte can be various conventional electrolytes, such as non-aqueous electrolytes. The non-aqueous electrolyte is a solution formed by electrolyte lithium salt in a non-aqueous solvent, and conventional non-aqueous electrolytes known to those skilled in the art can be used. For example, the electrolyte can be selected from at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6) and lithium hexafluorosilicate (LiSiF6). The non-aqueous solvent can be selected from a mixed solution of chain acid esters and cyclic acid esters, wherein the chain acid ester can be at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) and dipropyl carbonate (DPC). The cyclic acid ester can be at least one of ethylene carbonate (EC), propylene carbonate (PC) and vinylene carbonate (VC).

[0053] The endpoints and any values ​​of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, the endpoint values ​​of each scope, the endpoint values ​​of each scope and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

[0054] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0055] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0056] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0057] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0058] In the following examples and comparative examples, the electrochemical performance of the assembled lithium-ion batteries was tested using the Wuhan Blue Electric Battery Test System (CT2001B). The test conditions included: voltage range 0.005V-1.5V, current range 0.05A-2A. Ten button batteries were assembled for each sample, and the battery performance was tested at the same voltage and current, and the average value was taken.

[0059] In the present invention, a scanning electron microscope (SEM) is used to characterize the morphology of the electrode material. Specifically, the scanning electron microscope is a TECNALG2F20 (200 kv) model of FEI Company of the United States. The test conditions are: the sample is directly pressed on a sample stage containing a conductive tape, and then inserted into the electron microscope for observation. The observation uses a magnification of 8000 times.

[0060] In the present invention, a transmission electron microscope (TEM, HR-TEM) model JEM-2100 manufactured by JEOL Ltd. is used to characterize the morphology of the electrode material. Test conditions: The sample is placed on a copper support mesh and then inserted into the electron microscope for observation. The observation uses a magnification of 17,000 times and 380,000 times.

[0061] In the present invention, the specific surface area is tested using an ASAP2010 specific surface area and pore size distribution tester from Micromeritics, USA. Test conditions: temperature 77K, nitrogen environment.

[0062] In the present invention, the Raman spectrum is tested by an Invia / Reflrx LaserMicro-Raman spectrometer using a laser with a wavelength of 785 nm as the excitation light source, and all samples are placed on a clean glass slide for testing. -1 The highest peak height of D peak (defect peak) within the wavelength range is I D , at 1500-1700cm -1 The G peak (sp 2 The highest peak height (peak of hybrid carbon atom vibration) is G .

[0063] Example 1

[0064] (1) Take 100g of powdered graphene (parameters see Table 4), place it in a tube furnace, add a water vapor generator at the inlet of the tube furnace, and use nitrogen as the carrier gas for the whole device. Heat the tube furnace to 750℃ at 5℃ / min, then adjust the carrier gas flow rate to 100sccm, and perform etching at this temperature for 1h. After the etching is completed, the obtained graphene is vacuum dried to obtain a carbon skeleton material (properties see Table 1).

[0065] (2) The graphene obtained in step (1) is placed in a silane vapor deposition furnace, with monosilane as the silicon source, a flow rate of 220 sccm, a deposition time of 4 h, and a deposition temperature of 950°C. After the reaction is completed, the obtained material is carefully taken out, which is the silicon-carbon material of the present invention (properties are shown in Table 2).

[0066] Figure 1 This is a SEM image of the silicon-carbon material described in the embodiment. It can be seen from the image that, unlike the porous silicon-carbon or nanoparticle-loaded silicon-carbon in the past, the material obtained in the present invention is a dense block at the magnification used for detection. Figure 2 It can be seen from TEM and HRTEM that there is no obvious grain boundary between amorphous carbon and silicon, indicating that silicon is evenly distributed on the amorphous carbon surface and completely covers the carbon. Figure 3 The BET curve of the obtained material is 4.27m 2 / g, similar to traditional graphite materials, there is no problem of processing difficulties. Figure 4 The Raman spectrum of the obtained material shows that the obtained material has a Raman spectrum of 1350 cm -1 -1650cm -1 There are D peaks and G peaks in the range, and ID / IG is 1.22, indicating that the silicon-carbon material has formed numerous defects, which can provide more sites for the porous carbon skeleton to load silicon. -1 The scattering vibration peak of amorphous silicon also appeared at the position of 12cm-1 The blue shift indicates that silicon and carbon have achieved uniform dispersion at the nanoscale, and the carbon wrapped around silicon has changed its electron cloud distribution, causing the blue shift.

[0067] The electrical properties of the material obtained in Example 1 were then measured using a blue battery test system. The results showed that the gram capacity of the silicon-carbon negative electrode obtained in Example 1 was 1870 mAh / g, the first coulombic efficiency was 88.5%, and the capacity retention rate was 95% after 200 cycles of charge and discharge tests at a rate of 0.2C / 0.2C. The gram capacity of the material was 650 mAh / g after compounding with natural graphite. -1 The silicon-carbon negative electrode was used, and the expansion rate of the electrode was measured by buckling the electrode when it was fully charged. The expansion rate of the surface electrode was 22%, and the results are shown in Table 3.

[0068] Example 2

[0069] (1) Take 100g of powdered graphene and place it in a tube furnace. Add a water vapor generator at the inlet of the tube furnace, and use nitrogen as the carrier gas in the whole device. Raise the temperature of the tube furnace to 600℃ at 5℃ / min, then adjust the carrier gas flow rate to 100sccm, and perform etching at this temperature for 2h. After the etching is completed, the obtained graphene is vacuum dried to obtain a carbon skeleton material.

[0070] (2) The graphene obtained in step (1) is placed in a silane vapor deposition furnace, with monosilane as the silicon source, a gas flow rate of 350 sccm, a deposition time of 6 h, and a deposition temperature of 1100° C. After the reaction is completed, the obtained material is carefully taken out, which is the silicon-carbon material of the present invention.

[0071] The properties of carbon skeleton materials are shown in Table 1;

[0072] The properties of silicon carbon materials are shown in Table 2;

[0073] The electrical properties of the materials are shown in Table 3.

[0074] Example 3

[0075] (1) Take 100g of powdered graphene and place it in a tube furnace. Add a water vapor generator at the inlet of the tube furnace, and use nitrogen as the carrier gas in the whole device. Raise the temperature of the tube furnace to 900℃ at 5℃ / min, then adjust the carrier gas flow rate to 120sccm, and perform etching at this temperature for 2h. After the etching is completed, vacuum dry the obtained graphene to obtain a carbon skeleton material.

[0076] (2) The graphene obtained in step (1) is placed in a silane vapor deposition furnace, the raw material is 40 volume % silicon tetrachloride / 60 volume % mixed gas, the gas flow rate is 300 sccm, the deposition time is 6 hours, the deposition temperature is 1050°C, and after the reaction is completed, the obtained material is carefully taken out, which is the silicon-carbon material of the present invention.

[0077] The properties of carbon skeleton materials are shown in Table 1;

[0078] The properties of silicon carbon materials are shown in Table 2;

[0079] The electrical properties of the materials are shown in Table 3.

[0080] Example 4

[0081] The water vapor etching was performed according to the method of Example 1, except that the median particle size of the graphene was 3 μm. The results are shown in Table 1.

[0082] The properties of carbon skeleton materials are shown in Table 1;

[0083] The properties of silicon carbon materials are shown in Table 2;

[0084] The electrical properties of the materials are shown in Table 3.

[0085] Example 5

[0086] The water vapor etching was performed according to the method of Example 1, except that the median particle size of the graphene was 25 μm. The results are shown in Table 1.

[0087] The properties of carbon skeleton materials are shown in Table 1;

[0088] The properties of silicon carbon materials are shown in Table 2;

[0089] The electrical properties of the materials are shown in Table 3.

[0090] Example 6

[0091] Vapor deposition was carried out according to the method of Example 1, except that the deposition temperature was 550° C. The results are shown in Table 1.

[0092] Example 7

[0093] The graphene was treated with water vapor according to the method of Example 1, except that the temperature of the water vapor treatment was 720°C, the heating rate was 10°C / min, and after the furnace temperature reached the treatment temperature, water vapor was introduced, the carrier gas flow rate was 100 sccm, and the etching time was 45 min. The results are shown in Table 1.

[0094] The properties of carbon skeleton materials are shown in Table 1;

[0095] The properties of silicon carbon materials are shown in Table 2;

[0096] The electrical properties of the materials are shown in Table 3.

[0097] Comparative Example 1

[0098] The water vapor treatment was carried out according to the method of Example 3, and then nano-silicon with a D50 of 120 nm was used to mechanically mix with the carbon skeleton. The results are shown in Table 1.

[0099] Table 1

[0100] Carbon skeleton material ID / IG <![CDATA[Specific surface area m 2 / g]]> Example 1 1.22 390 Example 2 1.08 305 Example 3 1.5 500 Example 4 1.42 460 Example 5 1.1 323 Example 6 1.22 390 Example 7 1.35 420 Comparative Example 1 1.22 390

[0101] It can be seen from the results in Table 1 that the carbon skeleton material of the present invention has a large number of defect sites.

[0102] Table 2

[0103]

[0104] Table 3

[0105]

[0106] Table 4

[0107] Graphene Median particle size, μm <![CDATA[Specific surface area, m 2 / g]]> Carbon content, wt% Example 1 15 38 99.90％ Example 2 15 38 99.90％ Example 3 15 38 99.90％ Example 4 3 115 98.50％ Example 5 25 12 99.90％ Example 6 15 38 99.90％ Example 7 15 38 99.90％

[0108] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A silicon-carbon material, characterized in that: The silicon-carbon material comprises a carbon skeleton and a silicon element deposited on the carbon skeleton; the Raman spectrum of the silicon-carbon material has a wave number of 1350 cm -1 -1650cm -1 There are D peak and G peak in the range, and ID / IG is 1.0~1.5; at 460cm -1 -480cm -1 There is a spectral peak of silicon element in the range.

2. The silicon-carbon material according to claim 1, wherein The gram capacity of the silicon-carbon material is ≥1500 mAhg -1 , preferably ≥1800mAhg -1 ; and / or the first coulombic efficiency is ≥85%.

3. The silicon-carbon material according to claim 1 or 2, wherein: Taking the silicon-carbon material as a reference, the mass percentage of the carbon skeleton is 30wt% to 70wt%, preferably 40wt% to 60wt%; the mass percentage of silicon element is 30wt% to 70wt%, preferably 40wt% to 60wt%.

4. The silicon-carbon material according to any one of claims 1 to 3, wherein: The tap density of the silicon carbon material is 0.6 g / cm 3 ~1.0g / cm 3 , preferably 0.8 g / cm 3 ~0.98g / cm 3 ; and / or The particle size D10 of the silicon-carbon material is 1 μm to 3 μm, D50 is 5 μm to 8 μm, and D90 is 12 μm to 16 μm.

5. The silicon-carbon material according to any one of claims 1 to 4, wherein: The silicon element in the silicon-carbon material is deposited on the carbon skeleton in the form of a thin film or a block; and / or The specific surface area of ​​the silicon-carbon material is 1 m 2 / g~5m 2 / g, pore volume is 0.3cm 3 / g~1.2cm 3 / g; and / or The gram capacity of the blend of silicon-carbon material and graphite is greater than or equal to 600 mAhg -1 , the volume expansion rate under full charge state is ≤30%.

6. A method for preparing the silicon-carbon material according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: Silicon was deposited on the carbon skeleton material by vapor deposition. The Raman spectrum of the carbon skeleton material was at a wave number of 1350 cm -1 -1650cm -1 It has D peak and G peak in the range, and ID / IG is 1.0-1.5, and the specific surface area is 300-500m 2 / g.

7. The preparation method according to claim 6, wherein: The temperature of vapor deposition is 800°C to 1200°C; and / or Vapor deposition time 2h~8h; and / or The gas flow rate is 200 sccm-350 sccm.

8. The preparation method according to claim 6 or 7, wherein: The deposited silicon source is silane, preferably monosilane, disilane, chlorosilane, and more preferably one or more of monosilane, silicon tetrachloride, and trichlorosilane.

9. The preparation method according to any one of claims 6 to 8, wherein: The preparation method of the carbon skeleton material comprises: heat treating graphene with water vapor and then vacuum drying; Preferably, the median particle size D50 of the graphene is 10 μm to 16 μm, the carbon content of the graphene is ≥ 90%, and the specific surface area of ​​the graphene is 30 m 2 / g~80m 2 / g; The heat treatment conditions include: a temperature of 600° C. to 900° C., and / or a time of 0.5 h to 2 h.

10. Use of the silicon-carbon material according to any one of claims 1 to 5 as a negative electrode material for a battery; preferably, use of the silicon-carbon material as a negative electrode material for a lithium battery.

Images