Silicon-carbon material and preparation method thereof, and lithium ion battery

Abstract

The application discloses a silicon-carbon material, a preparation method thereof and a lithium ion battery. The preparation method of the silicon-carbon material comprises the following steps: S1, first gas deposition is performed on porous carbon to obtain a silicon-carbon material precursor; wherein the first gas deposition is silicon-lithium co-deposition, a first deposition gas comprises a silicon source gas and a lithium source gas, and the silicon source gas and the lithium source gas are simultaneously introduced; S2, second gas deposition is performed on the silicon-carbon material precursor to obtain the silicon-carbon material; wherein the second gas deposition is carbon deposition, and a second deposition gas comprises a carbon source gas. The obtained silicon-carbon material has a high content of lithium element and can greatly reduce the expansion of silicon. When the silicon-carbon material is applied to a lithium ion battery as a negative electrode material, the obtained lithium ion battery has excellent capacity performance and can also have excellent cycle performance, rate performance and initial efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to a silicon-carbon material and a preparation method thereof, and a lithium ion battery. BACKGROUND

[0002] The silicon-carbon negative electrode material is one of the most popular battery density improvement technologies today, and the energy density of Li4.4Si can reach about 3500 mAh / g. 15 However, in the process of use, the immature preparation process and the inherent properties of lithium intercalation and deintercalation mechanism lead to serious volume expansion of silicon in the silicon-carbon material, low rate performance and low initial efficiency of the battery, which limits its application. At present, it is mainly applied to relatively low 3C digital products with low rate requirements, mainly in the field of mobile phones and tablets, because the rate performance requirement is not high, and the rate performance of the battery is only about 3C when 10% of the silicon-carbon negative electrode material is added. In the prior art, although the rate can be improved to 4C by using double-coating technology, laser drilling technology, low binder formulation technology, and fast-charging electrolyte technology, it is still difficult to balance excellent rate performance and initial efficiency. In order to further reduce the volume expansion of silicon and improve the initial efficiency, the prior art only pre-lithiates the porous carbon by doping lithium salt before depositing silicon, which improves the lithium content and the initial efficiency of the lithium ion battery, but the lithium content of the obtained silicon-carbon material is still low, the initial efficiency of the lithium ion battery is still poor, and it is still difficult to balance excellent rate performance and excellent cycle performance and capacity performance. SUMMARY

[0003] In order to solve the defects of low lithium content and serious volume expansion of silicon in the existing silicon-carbon material, the present application provides a silicon-carbon material and a preparation method thereof, and a lithium ion battery. The obtained silicon-carbon material has a high content of lithium element and can greatly reduce the expansion of silicon. When the silicon-carbon material is used as a negative electrode material in a lithium ion battery, the obtained lithium ion battery has excellent capacity performance and can balance excellent cycle performance, rate performance and initial efficiency.

[0004] In order to achieve the above technical purposes, the present application adopts the following technical solutions.

[0005] The present application provides a preparation method of a silicon-carbon material, which comprises the following steps:

[0006] S1, first gas deposition is performed on the porous carbon to obtain a silicon-carbon material precursor;

[0007] The first gas deposition is silicon-lithium co-deposition, the first deposition gas comprises a silicon source gas and a lithium source gas, and the silicon source gas and the lithium source gas are introduced at the same time.

[0008] S2, performing second vapor deposition on the silicon-carbon material precursor to obtain the silicon-carbon material;

[0009] The second vapor deposition is carbon deposition, and the second deposition gas comprises a carbon source gas.

[0010] In the present application, in step S1, the first vapor deposition is silicon-lithium co-deposition, which takes into account that the super-micropores and oxygen-containing functional groups in the porous carbon can cause irreversible extraction and insertion of lithium ions in the battery. It is generally believed that the degree of filling of the super-micropores is the key to the expansion of the silicon-carbon negative electrode. By reducing the degree of filling of silicon in the super-micropores, the effect of reducing the expansion of the silicon-carbon negative electrode can be achieved. Based on the Langmuir principle of silane deposition, because the atomic radius of lithium is smaller, through the doping of lithium atoms, lithium will preferentially insert into these voids. These inserted lithium reduces the secondary insertion of silicon atoms, reduces the degree of filling of silicon in the super-micropores, and reduces the expansion caused by simply depositing silicon and inserting lithium. At the same time, because the oxygen in the oxygen-containing functional groups of the porous carbon has a stronger polarity, when lithium is inserted, lithium can preferentially react with the oxygen to form inorganic solid electrolytes such as Li-O and Li-N. It is generally believed that these inorganic solid electrolytes have excellent ion diffusion channels, thereby improving the shuttling ability of lithium ions. In addition, when lithium atoms are simultaneously inserted during silicon deposition, because the conductivity of lithium is better than that of pure silicon, silicon-lithium co-deposition helps to reduce the partial pressure of the silicon-carbon material, further improving the rate performance and capacity performance. At the same time, the doping of lithium causes the lattice fringes in the silicon nanoparticles to expand, making the silicon nanoparticles disordered, which is also beneficial to improving the rate performance.

[0011] In step S1, the lithium source gas preferably comprises an organic lithium gas and / or an inorganic lithium gas, and more preferably comprises an organic lithium gas. The inorganic lithium gas refers to a gas formed by lithium vapor and an inorganic compound containing lithium, and the organic lithium gas refers to a gas formed by an organic compound containing lithium.

[0012] The organic lithium gas is preferably a nitrogen-containing organic lithium gas, for example, a lithium amide gas or a lithium phenyl gas.

[0013] The inorganic lithium gas is preferably lithium vapor.

[0014] In the present application, in step S1, when the lithium source gas is a nitrogen-containing organic lithium gas, nitrogen atoms will be doped into the silicon nanoparticles, reducing the band gap of the silicon nanoparticles and improving their electrical conductivity. This can reduce the partial pressure of the internal resistance of the battery, thereby improving the rate performance and capacity performance of the battery. The combined implementation of nitrogen doping and silicon-lithium co-deposition can significantly reduce the direct current resistance of the silicon-carbon material, further improving the rate performance of the battery.

[0015] In step S1, the difference between the cracking temperatures of the lithium source gas and the silicon source gas is preferably 300°C or less.

[0016] In step S1, the silicon source gas can be a silicon source gas used in vapor deposition in the art, and preferably includes silane. The silane is preferably monosilane and / or disilane.

[0017] In some preferred embodiments, in step S1, the first deposition gas includes silane and an organic lithium gas.

[0018] In some specific embodiments, in step S1, the first deposition gas includes monosilane and aminolithium.

[0019] In some specific embodiments, in step S1, the first deposition gas includes monosilane and phenyllithium.

[0020] In some specific embodiments, in step S1, the first deposition gas includes disilane and aminolithium.

[0021] In some preferred embodiments, in step S1, the first deposition gas includes silane and an inorganic lithium gas.

[0022] In some specific embodiments, in step S1, the first deposition gas includes monosilane and lithium vapor.

[0023] In step S1, the lithium source gas is preferably formed by heating a lithium source.

[0024] In the heating process, the absolute pressure P1 is preferably 30 to 70 kPa, for example 63 kPa.

[0025] In the heating process, the temperature T1 is preferably 300 to 500°C, for example 360°C. At the above-mentioned preferred temperature of the heating process, the aminolithium can be prevented from decomposing prematurely, and the aminolithium can be ensured to form aminolithium gas.

[0026] In step S1, before the first deposition gas is introduced, the environment in which the first deposition gas is present is preferably maintained at an absolute pressure P2 of 25 to 60 kPa, for example 52 kPa.

[0027] In step S1, before the first deposition gas is introduced, the environment in which the first deposition gas is present is preferably maintained at a temperature T2 of 300 to 500°C, for example 380°C.

[0028] In step S1, the temperature T3 of the first vapor deposition is preferably 400 to 800°C, for example 550°C.

[0029] In step S1, the preferred time for the first vapor deposition is 1-100 min, for example, 5 min.

[0030] In step S1, the absolute pressure P3 of the first vapor deposition is preferably 10-50 kPa, for example, 42 kPa.

[0031] Preferably, in step S1, the first gas phase deposition satisfies: T1 < T2 < T3, and P1 > P2 > P3. Under these conditions, it can be ensured that the first deposited gas does not adhere to the wall and can maintain its gaseous state.

[0032] In step S1, the first deposition gas preferably further includes a protective gas, such as one or more of nitrogen, helium, and argon; wherein the volume ratio of the protective gas to the silicon source gas is preferably (3-5):1, for example, 4:1. Preferably, the protective gas and the silicon source gas are introduced in the form of a mixed gas.

[0033] In step S1, the flow rate of the silicon source gas is preferably 0.5-5 L·kg. -1 ·min -1 For example, 2L·kg -1 ·min -1 Among them, "L·kg -1 ·min -1 "" refers to the volume of the silicon source gas introduced per minute per unit mass of porous carbon.

[0034] In step S1, the preferred flow rate of the lithium source gas is 5-500 mg·kg⁻¹. -1 ·min -1 More preferably 5-250 mg·kg -1 ·min -1 For example, 7 mg·kg -1 ·min -1 14 mg·kg -1 ·min -1 23 mg·kg -1 ·min -1 28 mg·kg -1 ·min -1 42mg·kg -1 ·min -1 46 mg·kg -1 ·min -1 56 mg·kg -1 ·min -1 70mg·kg -1 ·min -1 84 mg·kg -1 ·min -192 mg·kg -1 ·min -1 118 mg·kg -1 ·min -1 184 mg·kg -1 ·min -1 or 230 mg·kg -1 ·min -1 . Wherein, "mg·kg -1 ·min -1 " refers to the mass of the lithium source gas per minute per unit mass of the porous carbon.

[0035] In step S2, the temperature of the second vapor deposition can be the temperature used in the art for carbon deposition, preferably 400-800 °C, for example 600 °C.

[0036] And / or, in step S2, the time of the second vapor deposition is preferably 5-15 h, for example 10 h.

[0037] And / or, in step S2, the flow rate of the second deposition gas is preferably 0.5-5 L·kg -1 ·min -1 , for example 2 L·kg -1 ·min -1 . Wherein, "L·kg -1 ·min -1 " refers to the volume of the second deposition gas per minute per unit mass of the porous carbon.

[0038] And / or, in step S2, the carbon source gas can be a carbon source gas conventionally used in the art for carbon deposition, preferably comprising one or more of alkyne, alkane, alkene, aromatic compound and carbohydrate, for example acetylene.

[0039] And / or, in step S2, the second deposition gas further comprises a protective gas, for example one or more of nitrogen, helium and argon. Preferably, in the second deposition gas, the volume ratio of the carbon source gas and the protective gas is preferably (3-5): 1, for example 4: 1. Preferably, the protective gas and the carbon source gas are introduced in the form of a mixed gas.

[0040] Preferably, the preparation method of the silicon-carbon material is carried out in a vapor deposition device, the vapor deposition device comprising a gas generator, a mixer and a reaction furnace; the gas generator is provided with a first gas outlet, the mixer comprises a first gas inlet, a second gas inlet and a deposition gas outlet arranged at different positions, and the reaction furnace is provided with a deposition gas inlet; the first gas outlet of the gas generator is in communication with the first gas inlet of the mixer, and the deposition gas outlet of the mixer is in communication with the deposition gas inlet of the reaction furnace.

[0041] In step S1, the gas generator is used to generate a lithium source gas, which is introduced into the mixer through the first gas outlet and the first gas inlet of the mixer in sequence; the silicon source gas is introduced into the mixer through the second gas inlet; the mixer is used to mix the silicon source gas and the lithium source gas to form the first deposition gas; the first deposition gas is introduced into the reaction furnace through the deposition gas outlet of the mixer and the deposition gas inlet of the reaction furnace in sequence; and the porous carbon is subjected to first vapor deposition in the reaction furnace.

[0042] In step S2, the second deposition gas is introduced into the mixer through the second gas inlet, and then introduced into the reaction furnace through the deposition gas outlet of the mixer and the deposition gas inlet of the reaction furnace in sequence, so as to perform second vapor deposition on the silicon-carbon material precursor in the reaction furnace.

[0043] In some embodiments, in step S1, the porous carbon satisfies one or more of the following conditions: ① the specific surface area is 1500-2500 m 2 / g, ② the pore volume ratio of micropores and ultramicropores is 80-98%, ③ the pore volume ratio of ultramicropores is 0-25%, ④ the pore volume ratio of mesopores and pores with a larger aperture is 2-20%, and ⑤ the pore volume is 0.7-1.4 cm 3 / g.

[0044] In some specific embodiments, the porous carbon satisfies one or more of the following conditions: ① the specific surface area is 1890 m 2 / g, ② the pore volume ratio of micropores and ultramicropores is 85.3%, ③ the pore volume ratio of ultramicropores is 17.3%, ④ the pore volume ratio of mesopores and pores with a larger aperture is 14.7%, and ⑤ the pore volume is 1.32 cm 3 / g.

[0045] In the present application, the porous carbon can be prepared by conventional methods in the art. The carbon source of the porous carbon can include one or more of resin, sucrose, glucose, fructose, starch, cellulose, triglyceride, fatty acid, hemicellulose, lignin and pitch, preferably resin, and more preferably phenolic resin.

[0046] In some embodiments, the porous carbon is prepared by taking phenolic resin as the carbon source.

[0047] In some specific embodiments, the method for preparing the porous carbon comprises the following steps:

[0048] (1) spray drying a slurry comprising phenolic resin to obtain a carbon material precursor;

[0049] (2) carbonizing the carbon material precursor to obtain a porous carbon precursor;

[0050] (3) activating the porous carbon precursor to obtain the porous carbon.

[0051] In step (1), the slurry can further comprise a curing agent and a solvent; the curing agent can be, for example, urotropine, and the solvent can be, for example, ethanol. The mass ratio of the phenolic resin to the curing agent is preferably 100:(1-20), for example 100:6.

[0052] In step (1), the temperature of the spray drying is preferably 90-180°C, for example 130°C.

[0053] In step (1), the spray drying is preferably performed until the particle diameter is 4-20 μm, for example 8 μm.

[0054] In step (2), the carbonization can be performed by conventional carbonization methods in the art, for example by using a staged heat treatment; preferably, the carbonization comprises the following stages:

[0055] Stage 1: heating at a rate of 1-10°C / min to 150-250°C, and holding for 50-180 min;

[0056] Stage 2: heating at a rate of 1-10°C / min to 600-700°C, and holding for 50-180 min.

[0057] In some specific embodiments, the carbonization comprises the following stages:

[0058] Stage 1: heating at a rate of 4°C / min to 200°C, and holding for 60 min;

[0059] Stage 2: heating at a rate of 4°C / min to 652°C, and holding for 60 min.

[0060] In step (2), the carbonization can be performed under an inert atmosphere, which preferably comprises one or more of nitrogen, helium and argon.

[0061] In step (3), the activation can be performed by a conventional activation method in the art, such as alkali activation or gas activation, preferably gas activation.

[0062] In the gas activation, the gas is preferably carbon dioxide or water vapor.

[0063] In the gas activation, the gas flow rate is preferably 10-50 L·kg -1 ·min -1 , such as 2·L·kg -1 ·min -1 .

[0064] In the gas activation, the temperature is preferably 450-800℃, such as 550℃.

[0065] In the gas activation, the time is preferably 5-15 h, such as 9 h.

[0066] The present application provides a silicon-carbon material prepared by the method for preparing a silicon-carbon material as described above.

[0067] In the present application, the silicon-carbon material can comprise a core-shell structure, which comprises an inner core and a shell, the inner core comprises porous carbon and a lithium-containing silicon layer; the lithium-containing silicon layer is arranged on the surface and in the pores of the porous carbon; the shell comprises a carbon layer, which is coated on the surface of the inner core. In the present application, the carbon layer coated on the surface of the inner core is not limited to the surface of the inner core, when the porous carbon also contains pores, the carbon layer can also be arranged in the pores of the porous carbon and coated on the surface of the lithium-containing silicon layer.

[0068] In the present application, the lithium element in the lithium-containing silicon layer exists in the form of LiC6, lithium-containing nitride and / or silicon-lithium alloy.

[0069] In the present application, the silicon element in the lithium-containing silicon layer exists in the form of silicon nanoparticles, silicon oxide and / or silicon-lithium alloy.

[0070] Preferably, the lithium content of the silicon-carbon material is 0.9%-8%, such as 0.94%, 0.95%, 0.98%, 1.85%, 1.90%, 3.45%, 3.65%, 4.40%, 5.10%, 5.45%, 6.30%, 6.55% or 7.75%, the percentage is the mass percentage of the silicon-carbon material.

[0071] Preferably, the silicon content of the silicon-carbon material is 45-55%, for example 47%, 49.72%, 50.39%, 50.79%, 51.45%, 51.34%, 51.64%, 51.69%, 51.75%, 52.66%, 53.06%, 53.12%, 53.13% or 53.14%, the percentage being a percentage by mass of the silicon-carbon material.

[0072] Preferably, the carbon content of the silicon-carbon material is 40-55%, more preferably 42-46%, for example 42.53%, 42.91%, 43.06%, 43.21%, 43.45%, 43.96%, 44.6%, 44.86%, 45.04%, 45.49%, 45.91%, 45.93% or 52.02%, the percentage being a percentage by mass of the silicon-carbon material.

[0073] Preferably, the nitrogen content of the silicon-carbon material is 30-310ppm, for example 32ppm, 33ppm, 65ppm, 132ppm, 221ppm, 290ppm or 303ppm.

[0074] Preferably, the powder conductivity of the silicon-carbon material is 13-63%, for example 13.2%, 22.2%, 24.1%, 25.3%, 25.2%, 29.4%, 26.2%, 37.3%, 40.9%, 44.2%, 49.6%, 59.3% or 62.1%.

[0075] Preferably, the Dv50 particle size of the silicon-carbon material is 7-9pm, for example 7.2pm, 7.7pm, 7.8pm, 7.9pm, 8pm, 8.1pm, 8.3pm, 8.5pm or 8.7pm.

[0076] Preferably, the specific surface area of the silicon-carbon material is 3-6m 2 / g, for example 3.4m 2 / g, 3.6m 2 / g, 3.8m 2 / g, 4m 2 / g, 4.1m 2 / g, 4.2m 2 / g, 4.3m 2 / g, 4.4m 2 / g, 5.1m 2 / g, 5.2m 2 / g, 5.3m 2 / g or 5.4m 2 / g.

[0077] The present application provides a pole piece comprising a silicon-carbon material as described above.

[0078] The application provides application of the silicon-carbon material as described above as a negative material in a lithium ion battery.

[0079] The application also provides a lithium ion battery comprising the silicon-carbon material as described above.

[0080] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining preferred examples of the application.

[0081] The reagents and raw materials used in the application are commercially available.

[0082] The positive progress effect of the application is that:

[0083] (1) In the preparation method of the silicon-carbon material in the application, the lithium-silicon co-deposition greatly reduces the lithium intercalation expansion amount of the pole piece using the silicon-carbon material, and can greatly reduce the expansion of the silicon-carbon material in the full lithium intercalation state. The prepared lithium ion battery has excellent capacity performance and can also have excellent cycle performance, rate performance and initial efficiency.

[0084] Further, when the nitrogen-containing organic lithium gas is used as the lithium source gas, the efficiency of lithium deposition in the silicon-carbon material can be improved by doping of nitrogen atoms, and the conductivity of the silicon-carbon material can be improved, and the rate performance can be further improved.

[0085] (2) The preparation method of the silicon-carbon material can be completed by only one step, which is simple in operation, high in efficiency, and has extremely high potential for industrialization. BRIEF DESCRIPTION OF DRAWINGS

[0086] Figure 1 The structure schematic view of the device used for the first gas phase deposition of Example 1.

[0087] The reference signs are as follows:

[0088] 1-gas generator; 2-mixer; 3-reaction furnace;

[0089] 101-first gas inlet; 102-second gas inlet; 103-deposition gas outlet. DETAILED DESCRIPTION

[0090] The application will be further described below by way of examples, but the application is not limited in the scope of the examples. In the following examples, the experimental methods not specified in the specific conditions are selected according to the conventional methods and conditions, or according to the product instructions.

[0091] In the following examples and comparative examples, the phenolic resin is purchased from Hubei Hengye Technology Co., Ltd., and the model number is 2135.

[0092] Example 1

[0093] 1. Preparation of porous carbon:

[0094] (1) 1 kg of phenolic resin, 2 kg of ethanol, and 60 g of urotropine (HMT) were mixed in a high-speed dispersion homogenizer at a dispersion speed of 2000 r / min for 60 min. The mixture was spray dried at 130°C to obtain a powder with a Dv50 particle size of 8 μm.

[0095] (2) The spray-dried powder was placed in a rotary furnace and subjected to crosslinking at 10 r / min, followed by carbonization. The temperature was raised at a rate of 4°C / min to 200°C and maintained for 1 h, so that the phenolic resin was crosslinked. Then, the temperature was raised at a rate of 4°C / min to 652°C and maintained for 1 h. The flow rate of nitrogen gas used for protection was 1 L·kg -1 ·min -1 . Here, “L·kg -1 ·min -1 ” refers to the volume of nitrogen gas per minute per unit mass of the spray-dried powder.

[0096] (3) Activation of the carbon material: The carbon material was activated in a CO2 atmosphere for 9 h at a flow rate of 2 L·kg -1 ·min -1 , and the temperature in the furnace was 550°C. Thus, porous carbon was obtained.

[0097] The specific parameters of the obtained porous carbon are as follows:

[0098] The specific surface area was 1890 m 2 / g, the micropore volume accounted for 85.3% (of which, the ultramicropore volume accounted for 17.3%), the mesopore volume accounted for 14.7%, and the above percentages were volume percentages of the total pore volume of the obtained porous carbon. The pore volume was 1.32 cm 3 / g.

[0099] 2. Preparation of silicon-carbon material

[0100] The method for preparing the silicon-carbon material was performed in a vapor deposition device (a structural schematic diagram is shown in Figure 1 ). The vapor deposition device comprises a gas generator 1, a mixer 2, and a reaction furnace 3. The gas generator 1 is provided with a first gas outlet. The mixer 2 comprises a first gas inlet 101, a second gas inlet 102, and a deposition gas outlet 103 arranged at different positions. The reaction furnace 3 is provided with a deposition gas inlet. The first gas outlet of the gas generator 1 is in communication with the first gas inlet 101 of the mixer 2. The deposition gas outlet 103 of the mixer 2 is in communication with the deposition gas inlet of the reaction furnace 3.

[0101] S1, a first vapor deposition is performed to prepare a silicon-carbon precursor (silicon-lithium co-deposition):

[0102] The lithium amide was placed in a gas generator with a temperature of 360℃ and an absolute pressure of 63kPa, so that the lithium amide formed lithium amide gas and flowed into the reactor at a flow rate of 23mg·kg -1 ·min -1 The flow rate passed through the first gas outlet and the first gas inlet of the mixer into the mixer with a temperature of 380℃ and an absolute pressure of 52kPa; the silane gas and argon gas (volume ratio of 20:80, flow rate of 2L·kg -1 ·min -1 ) passed through the second gas inlet into the mixer; after the silane gas, argon gas and lithium amide gas were uniformly mixed in the mixer, the first deposition gas was formed, which passed through the deposition gas outlet of the mixer and the deposition gas inlet of the reactor into the reactor (absolute pressure of 42kPa, temperature of 550℃), and the porous carbon (165g) placed in the reactor was subjected to the first vapor deposition (absolute pressure of 42kPa, temperature of 550℃, time of 8h) to obtain the silicon-carbon precursor.

[0103] S2, second vapor deposition

[0104] The acetylene gas passed through the second gas inlet into the mixer (temperature of 380℃, absolute pressure of 52kPa), and then passed through the deposition gas outlet of the mixer and the deposition gas inlet of the reactor into the reactor, and the silicon-carbon material precursor was subjected to the second vapor deposition (absolute pressure of 42kPa, time of 600min, temperature of 600℃) in the reactor. The flow rate of the acetylene was 2L·kg -1 ·min -1 .

[0105] Example 2

[0106] Example 2 and Example 1 differ in that, in the preparation of the silicon-carbon material, phenyl lithium is used instead of lithium amide in the first vapor deposition, and the flow rate of the phenyl lithium gas is 84mg·kg -1 ·min -1 , and the rest of the conditions remain the same as in Example 1.

[0107] Example 3

[0108] Example 3 and Example 1 differ in that, in the preparation of the silicon-carbon material, ethylsilane is used instead of silane in the first vapor deposition, and the rest of the conditions remain the same as in Example 1.

[0109] Example 4

[0110] Example 4 and Example 1 differ in that, in the preparation of the silicon-carbon material, the flow rate of the lithium amide gas is 46mg·kg -1• min -1 The remaining conditions and example 1 are kept unchanged.

[0111] Example 5

[0112] Example 5 differs from example 1 in that, in the preparation of the silicon-carbon material, the flow rate of the lithium amide gas during the first vapour deposition is 92 mg·kg -1 • min -1 The remaining conditions and example 1 are kept unchanged.

[0113] Example 6

[0114] Example 6 differs from example 1 in that, in the preparation of the silicon-carbon material, the flow rate of the lithium amide gas during the first vapour deposition is 118 mg·kg -1 • min -1 The remaining conditions and example 1 are kept unchanged.

[0115] Example 7

[0116] Example 7 differs from example 1 in that, in the preparation of the silicon-carbon material, the flow rate of the lithium amide gas during the first vapour deposition is 184 mg·kg -1 • min -1 The remaining conditions and example 1 are kept unchanged.

[0117] Example 8

[0118] Example 8 differs from example 1 in that, in the preparation of the silicon-carbon material, the flow rate of the lithium amide gas during the first vapour deposition is 230 mg·kg -1 • min -1 The remaining conditions and example 1 are kept unchanged.

[0119] Example 9

[0120] Example 9 differs from example 1 in that, in the preparation of the silicon-carbon material, lithium is used instead of lithium amide during the first vapour deposition, the flow rate of the lithium vapour gas being 7 mg·kg -1 • min -1 The remaining conditions and example 1 are kept unchanged.

[0121] Example 10

[0122] Example 10 differs from example 9 in that, in the preparation of the silicon-carbon material, the flow rate of the lithium vapour gas during the first vapour deposition is 14 mg·kg -1 • min -1 The remaining conditions and example 9 are kept unchanged.

[0123] Example 11

[0124] The difference between Example 11 and Example 9 is that in the preparation of the silicon-carbon material, the flow rate of lithium vapor gas is 28 mg·kg -1 ·min -1 The remaining conditions are consistent with Example 9.

[0125] Example 12

[0126] The difference between Example 12 and Example 9 is that in the preparation of the silicon-carbon material, the flow rate of lithium vapor gas is 42 mg·kg -1 ·min -1 The remaining conditions are consistent with Example 9.

[0127] Example 13

[0128] The difference between Example 13 and Example 9 is that in the preparation of the silicon-carbon material, the flow rate of lithium vapor gas is 56 mg·kg -1 ·min -1 The remaining conditions are consistent with Example 9.

[0129] Example 14

[0130] The difference between Example 14 and Example 9 is that in the preparation of the silicon-carbon material, the flow rate of lithium vapor gas is 70 mg·kg -1 ·min -1 The remaining conditions are consistent with Example 9.

[0131] Comparative Example 1

[0132] The difference between this comparative example and Example 1 is that in the preparation of the silicon-carbon material, lithium amide is not used in the first vapor deposition, and the remaining conditions are consistent with Example 1.

[0133] Comparative Example 2

[0134] The difference between this comparative example and Example 9 is that in the preparation of the silicon-carbon material, lithium vapor and monosilane are used for step-by-step deposition in the first vapor deposition, and the remaining conditions are consistent with Example 9.

[0135] Specific steps of the first vapor deposition are as follows:

[0136] ① Lithium deposition:

[0137] Lithium metal (3.36 g) is placed in a gas generator, the temperature of the gas generator is 360°C, and the absolute pressure is 63 kPa, so that the lithium metal forms lithium vapor and is deposited at a flow rate of 7 mg·kg -1 ·min -1The flow rate of the gas is 2 L·kg -1 ·min -1 The helium gas is introduced into the mixer through the second gas inlet; after the helium gas and lithium vapor are uniformly mixed in the mixer, the first deposition gas is formed, and the first deposition gas is introduced into the reaction furnace (absolute pressure of 42 kPa and temperature of 700 DEG C) through the deposition gas outlet of the mixer and the deposition gas inlet of the reaction furnace, so as to perform the first vapor deposition (absolute pressure of 42 kPa and temperature of 700 DEG C for 10 h) on the porous carbon (165 g) placed in the reaction furnace; after the first vapor deposition is completed, the mixed gas of argon and nitrogen (0.5 L·kg -1 ·min -1 of nitrogen and 1.5 L·kg -1 ·min -1 of argon) is introduced into the mixer through the second gas inlet, and the lithium-containing porous carbon is obtained after 3 h.

[0138] ②Silicon deposition:

[0139] The silane gas and argon gas (volume ratio of 20:80 and flow rate of 2 L·kg -1 ·min -1 ) are introduced into the mixer through the second gas inlet; after the silane gas, argon gas and lithium amide gas are uniformly mixed in the mixer, the first deposition gas is formed, and the first deposition gas is introduced into the reaction furnace (absolute pressure of 42 kPa and temperature of 550 DEG C) through the deposition gas outlet of the mixer and the deposition gas inlet of the reaction furnace, so as to perform the first vapor deposition (absolute pressure of 42 kPa and temperature of 550 DEG C for 8 h) on the lithium-containing porous carbon placed in the reaction furnace, and the silicon-carbon precursor is obtained.

[0140] Comparative Example 3

[0141] The difference between the present comparative example and Example 1 is that, in the preparation of the silicon-carbon material, the lithium amide gas and silane are deposited in steps during the first vapor deposition, and the other conditions are the same as those in Example 1.

[0142] The specific steps of the first vapor deposition are as follows:

[0143] ①Lithium deposition:

[0144] The lithium amide (11.04 g) is placed in the gas generator, the temperature of the gas generator is 360 DEG C and the absolute pressure is 63 kPa, so that the lithium amide forms lithium amide gas and is introduced into the mixer at a flow rate of 23 mg·kg -1 ·min -1 ·min.The flow rate of the gas mixture is 2 L·kg -1 ·min -1 The helium gas (flow rate of 2 L·kg -1 ·min -1 ·min -1 ·min -1 The mixture of argon and nitrogen gas (nitrogen 0.5 L·kg -1 ·min -1 ) is introduced into the mixer through the second gas inlet, and the lithium-containing porous carbon is obtained after 3 h.

[0145] ② Silicon deposition:

[0146] The mixture of silane gas and argon gas (volume ratio of 20:80, flow rate of 2 L·kg -1 ·min -1 ) is introduced into the mixer through the second gas inlet; the first deposition gas is formed after the silane gas, argon gas and lithium amide gas are uniformly mixed in the mixer, and the first deposition gas is introduced into the reaction furnace (absolute pressure of 42 kPa, temperature of 550°C) through the deposition gas outlet of the mixer and the deposition gas inlet of the reaction furnace. The first gas-phase deposition (absolute pressure of 42 kPa, temperature of 550°C, time of 8 h) is carried out on the lithium-containing porous carbon placed in the reaction furnace, and a silicon-carbon precursor is obtained.

[0147] Example 1

[0148] The Dv50 particle size, silicon element content, lithium element content, carbon element content, nitrogen element content, powder conductivity, specific surface area, theoretical prelithiation rate and achievement rate of the silicon-carbon materials obtained in Examples 1-14 and Comparative Examples 1-3 are tested or calculated, and the specific testing method or calculation method is as follows:

[0149] (1) Dv50 particle size: tested by a laser particle size analyzer.

[0150] (2) Content of silicon element and lithium element: the content of silicon element and lithium element in the powder of the negative electrode material layer is tested by an inductively coupled plasma spectrometer (ICP, Agilent, model Agilent 5800).

[0151] (3) Carbon content: The carbon content in the powder of the negative electrode material layer was tested using a high-frequency carbon-sulfur analyzer (model DK-606).

[0152] (4) Nitrogen content: The nitrogen content in the powder of the negative electrode material layer was tested using an oxygen-nitrogen-hydrogen analyzer (Japan Horiba, model EMGA-830).

[0153] (5) Powder conductivity: A powder conductivity meter (model FT-8100) was used based on the four-probe test principle, and the standard was GB / T 1552-1995. A known amount of porous carbon composite solid powder was compressed to a set pressure value or pressure under the action of hydraulic power, and the conductivity of the solid powder was measured online.

[0154] (6) Specific surface area: The NT-8000 of Belsorb was used for testing.

[0155] (7) Theoretical pre-lithium rate (%) and achievement rate:

[0156] Theoretical pre-lithium rate (%) = mass of lithium element in the lithium source gas used / mass of silicon-carbon material x 100

[0157] Achievement rate = actual lithium element content / theoretical pre-lithium rate

[0158] The test results are shown in Table 1.

[0159] Effect implementation example 2

[0160] Preparation of the electrode sheet and the lithium ion battery

[0161] Preparation of the negative electrode slurry and the negative electrode sheet: The negative electrode formula was designed as CMC:PAA:SBR:SP:CNTs:silicon-carbon material:graphite = 0.5:3.5:0.5:0.1:0.1:10:85.3 (by mass ratio), and the negative electrode slurry preparation process was graphite→ CMC→ silicon-carbon material→ SP→ CNTs. After dispersion for 3 h at a rotation speed of 300 r / min and a revolution speed of 1000 r / min by a planetary disperser, 80% of deionized water was injected at one time, dispersion was carried out at a rotation speed of 500 r / min and a revolution speed of 600 r / min for 1 h, PAA was added and dispersion was carried out at a rotation speed of 500 r / min and a revolution speed of 500 r / min for 1 h, 20% of deionized water was injected, and finally SBR was added and dispersion was carried out at a rotation speed of 300 r / min and a revolution speed of 300 r / min for 1 h, to obtain the negative electrode slurry (solid content of 40%). The current collector used was a copper foil with a thickness of 8 μm, and the above negative electrode slurry was used for double-sided coating on the current collector. The single-sided coating active material thickness was 40 μm, and the compacted density was 1.8 g / cm 3 , wherein the coating speed was 40 cm / s, the baking temperature was 80°C, and the drying time was 400 s.

[0162] Electrolyte preparation: the electrolyte composition is as follows in mass percentage: ethylene carbonate (EC) 10%, propylene carbonate (PC) 15%, diethyl carbonate (DEC) 20%, propylene propyl carbonate (PP) 30%, LiPF6 15%, fluoroethylene carbonate (FEC) 6%, propylene sulfite (PS) 2.5%, lithium difluoro(oxalato)borate (LiODFB) 1.5%.

[0163] Half-cell assembly: the positive electrode uses the single negative electrode sheet as above, the negative electrode uses a lithium sheet, 0.5 g of the electrolyte as above, and a CR2032 button cell is assembled, and the voltage string port is 0-1.5V. The entire battery is assembled in a glove box to avoid contact with air.

[0164] Effect example 3

[0165] The first lithium intercalation expansion amount and the compaction density of the electrode sheet prepared in effect example 2 are tested and calculated:

[0166] (1) The first lithium intercalation expansion amount: (the thickness of the lithium intercalated electrode sheet-the thickness of the copper foil) / (the thickness of the non-lithium intercalated electrode sheet-the thickness of the copper foil), and the compaction density is controlled at 1.8 g / cm 3 .

[0167] The test results are shown in Table 2.

[0168] (2) The test method of the compaction density is to punch the electrode sheet into a unit circle, test the weight, subtract the weight of the copper foil, and divide by the thickness to obtain the compaction density.

[0169] Effect example 4

[0170] The lithium ion battery prepared in effect example 2 is tested or calculated for the following first efficiency, gram capacity, cycle failure number, rate retention rate and hot box cycle retention rate, and the specific test method or calculation method is as follows:

[0171] (1) 0.8V first efficiency (%)

[0172] The CR2032 button cell prepared in effect example 2 is discharged at a constant voltage of 0.1V / h to 0.000V, and then charged at 0.1 / h to 0.8V. The charge and discharge capacity is recorded, and the first efficiency is calculated by the delithiation capacity / intercalation capacity.

[0173] (2) 0.1C 0.8V gram capacity, using new Wei CT-4008Q-5V6A

[0174] One of the CR2032 button cells prepared in Effect Example 2 was discharged at a constant voltage to 0.000 V at a rate of 0.1 V / h, and then charged to 0.8 V at a rate of 0.1 V / h. The 0.1 C charge capacity was recorded. Another of the CR2032 button cells prepared in Effect Example 2 was subjected to constant current charge-discharge testing at a rate of 0.1 C charge capacity, and was discharged to 0 V and then charged to 0.8 V. The capacity was obtained.

[0175] wherein the 0.1 C 0.8 V gram capacity = capacity / mass of active material in the electrode; wherein the mass of active material in the electrode = mass of silicon-carbon material + mass of graphite.

[0176] (3) Cycle failure number, using a new Wei CT-4008Q-5V6A

[0177] ① 0.5 C 0.8 V cycle failure number (measured at 25 °C and 45 °C, respectively)

[0178] One of the CR2032 button cells prepared in Effect Example 2 was discharged at a constant voltage to 0.000 V at a rate of 0.1 V / h, and then charged to 0.8 V at a rate of 0.1 V / h. The 0.5 C charge capacity was recorded.

[0179] Another of the CR2032 button cells prepared in Effect Example 2 was subjected to constant current charge-discharge testing at a rate of 0.5 C charge capacity, and was repeatedly charged and discharged from 0 V to 0.8 V. The discharge capacity was recorded, and the cycle number was recorded when the discharge capacity was 60% of the 0.5 C 0.8 V gram capacity, i.e., the 0.5 C 0.8 V cycle failure number.

[0180] ② 1 C 0.8 V cycle failure number (measured at 25 °C and 45 °C, respectively)

[0181] One of the CR2032 button cells prepared in Effect Example 2 was discharged at a constant voltage to 0.000 V at a rate of 0.1 V / h, and then charged to 0.8 V at a rate of 0.1 V / h. The 0.5 C charge capacity was recorded.

[0182] (4) Rate retention rate

[0183] 1 C / 0.5 C retention rate at 25 °C: 0.8 V cycle failure number at 25 °C / 0.5 C 0.8 V cycle failure number.

[0184] 1C / 0.5C retention at 45℃: 1C 0.8V cycle failure number at 45℃ / 0.5C 0.8V cycle failure number.

[0185] (5) 0.5C hot box cycle retention

[0186] 0.5C hot box cycle retention: 0.5C 0.8V cycle failure number at 45℃ / 0.5C 0.8V cycle failure number at 25℃.

[0187] The above test results are shown in Table 2.

[0188] Table 1

[0189]

[0190]

[0191] Table 2

[0192]

[0193] Note: " / " in Table 1 represents that the condition parameter is not involved in the specific experiment.

[0194] From Table 1 and Table 2, it can be seen that in Examples 1-14 of the present application, by using silicon lithium co-deposition, using the preparation method of the silicon-carbon material of the present application, the pre-lithiation rate can reach 0.6 or more, and the preparation method can effectively realize the pre-lithiation of the silicon-carbon material. The lithium content of the obtained silicon-carbon material can reach 0.9% or more, the silicon content can reach 47% or more, and the powder conductivity can reach 22% or more. The first cycle lithium intercalation expansion of the electrode sheet obtained by using the silicon-carbon material as the negative electrode material is less than 90%, the compaction density is 1.80 g / cm 3 , and the lithium ion battery obtained by using the silicon-carbon material as the negative electrode material has excellent capacity performance and can also have excellent cycle performance, rate performance and initial efficiency. Specifically, the 0.1C 0.8V specific capacity can be 1650 mAh / g or more, and even 1900 mAh / g or more; on this basis, the 0.5C 0.8V cycle failure number at 25℃ can be 190 or more, the 0.5C 0.8V cycle failure number at 45℃ can be 130 or more, the 1C 0.8V cycle failure number at 25℃ can be 150 or more, the 1C 0.8V cycle failure number at 45℃ can be 100 or more, the 1C / 0.5C retention at 25℃ can be 0.80 or more, the 1C / 0.5C retention at 45℃ can be 0.70 or more, the 0.5C hot box cycle retention can be 0.60 or more, and the 0.8V initial efficiency can be 76% or more.

[0195] Compared with Example 1, Comparative Example 1 does not use lithium source gas, but only uses silicon source gas for the first vapor deposition, and the obtained silicon-carbon material has no pre-lithium, the powder resistivity is low, the first circle lithium intercalation expansion of the obtained electrode sheet is very high, the first efficiency of the lithium ion battery is significantly deteriorated, and the cycle failure number, rate retention rate and hot box cycle retention rate are all greatly reduced.

[0196] Compared with Example 9, Comparative Example 2 does not use silicon-lithium co-deposition, but first pre-lithiates the porous carbon with lithium vapor, and then deposits silicon. The lithium content in the obtained silicon-carbon material is low, which cannot effectively deposit lithium, and the powder resistivity is poor. Although the first circle lithium intercalation expansion of the electrode sheet at 25°C is low, the cycle failure number, rate retention rate and hot box cycle retention rate are good, but the first efficiency of the lithium ion battery is deteriorated, and the 0.1C 0.8V specific capacity is greatly deteriorated.

[0197] Compared with Example 1, Comparative Example 3 does not use silicon-lithium co-deposition, but first pre-lithiates the porous carbon with lithium amide, and then deposits silicon. The lithium content in the obtained silicon-carbon material is low, which cannot effectively deposit lithium, and the powder resistivity is poor. Although the first circle lithium intercalation expansion of the electrode sheet at 25°C is low, the 0.1C 0.8V specific capacity of the lithium ion battery is significantly reduced, and the first efficiency, cycle failure number, rate retention rate and hot box cycle retention rate are all significantly deteriorated.

[0198] Compared with the lithium vapor in Examples 9-14, the use of lithium amide gas in Examples 1 and 3-8 has further advantages. As can be seen from Table 1, under the condition of high compaction density, the use of lithium amide pre-lithiation can improve the achievement rate of pre-lithiation and improve the powder conductivity. The obtained lithium ion battery has better cycle performance and rate performance. This may be because the use of lithium amide gas can achieve trace nitrogen atom doping, which enhances the lithium content in the silicon-carbon anode material under the same process as lithium metal pre-lithiation, which is mainly due to the adsorption effect of nitrogen atoms. The formation of Li-N compounds with high ion channels can reduce ion diffusion resistance and ohmic resistance, and the disorder of silicon atoms to widen the ion channel is also an important reason. In addition, it is also related to the strong electronegativity of N atoms. Even if it forms a saturated covalent bond with silicon atoms and lithium atoms, based on its strong electron adsorption effect, it still has a tendency to adsorb electrons, which is still beneficial to the intercalation of lithium ions into silicon atoms.

[0199] As can be seen from Table 2, the cycle number in Comparative Example 1 is lower than that in Examples 9-14, and the cycle number of the lithium ion battery obtained from the silicon-carbon material pre-lithiated in Examples 9-14 is higher. This may be because pre-lithiation improves the pore volume filling degree, making the material more resistant to pressure and lower expansion.

[0200] Although the specific embodiments of the present application have been described above, it is understood by those skilled in the art that the present application is only illustrated by way of example, and the scope of protection of the present application is defined by the appended claims. Those skilled in the art can make various changes or modifications to the embodiments without departing from the principles and essence of the present application, and such changes and modifications fall within the scope of protection of the present application.

Claims

1. A method for preparing a silicon-carbon material, characterized by, It comprises the following steps: S1, a first gas deposition is carried out on the porous carbon to obtain a silicon-carbon material precursor; The first gas deposition is co-deposition of silicon and lithium, the first deposition gas comprises a silicon source gas and a lithium source gas, the lithium source gas is lithium amide gas or lithium phenyl gas, and the silicon source gas is monosilane and / or disilane, and the silicon source gas and the lithium source gas are introduced simultaneously. S2, a second gas deposition is carried out on the silicon-carbon material precursor to obtain the silicon-carbon material; The second gas deposition is carbon deposition, and the second deposition gas comprises a carbon source gas.

2. The method of making a silicon-carbon material of claim 1, wherein, In step S1, the difference between the cracking temperatures of the lithium source gas and the silicon source gas is 300°C or less.

3. The method of making a silicon-carbon material of claim 1, wherein, In step S1, the first deposition gas comprises monosilane and lithium amide.

4. The method of making a silicon-carbon material of claim 1, wherein, In step S1, the first deposition gas comprises monosilane and lithium phenyl.

5. The method of making a silicon-carbon material of claim 1, wherein, In step S1, the first deposition gas comprises disilane and lithium amide.

6. The method of making a silicon-carbon material of claim 1, wherein, In step S1, the lithium source gas is formed by heating treatment of a lithium source; The absolute pressure P1 of the heating treatment is 30-70 kPa. The temperature T1 of the heating treatment is 300-500°C. In step S1, before the first deposition gas is introduced, the environment in which the first deposition gas is located is maintained at an absolute pressure P2 of 25-60 kPa. In step S1, before the first deposition gas is introduced, the environment in which the first deposition gas is located is maintained at a temperature T2 of 300-500°C. The temperature T3 of the first gas deposition is 400-800°C. In step S1, the time of the first gas deposition is 1-100 min. In step S1, the absolute pressure P3 of the first gas deposition is 10-50 kPa.

7. The method of making a silicon-carbon material according to claim 6, wherein In step S1, the absolute pressure P1 of the heating treatment is 63 kPa, and the temperature T1 of the heating treatment is 360°C. In step S1, before the first deposition gas is introduced, the environment in which the first deposition gas is located is maintained at an absolute pressure P2 of 52 kPa. In step S1, before the first deposition gas is introduced, the environment in which the first deposition gas is located is maintained at a temperature T2 of 380°C. The temperature T3 of the first gas deposition is 550°C. In step S1, the time of the first gas deposition is 5 min. In step S1, the absolute pressure P3 of the first gas deposition is 42 kPa.

8. The method for producing a silicon-carbon material according to claim 6 or 7, wherein In step S1, the first gas deposition satisfies T1 < T2 < T3 and P1 > P2 > P3.

9. The method of making a silicon-carbon material of claim 1, wherein, In step S1, the first deposition gas further comprises a protective gas. And / or, in step S1, the flow rate of the silicon source gas is 0.5-5 L·kg -1 ·min -1 ; And / or, in step S1, the flow rate of the lithium source gas is 5-500 mg·kg -1 ·min -1 .

10. The method of making a silicon-carbon material according to claim 9, wherein, In step S1, the first deposition gas is one or more of nitrogen, helium, and argon.

11. The method of producing a silicon-carbon material according to claim 9 or 10, wherein The volume ratio of the protective gas to the silicon source gas is (3-5):

1.

12. The method of making a silicon-carbon material of claim 11, wherein, The volume ratio of the protective gas to the silicon source gas is 4:

1.

13. The method of making a silicon-carbon material of claim 9, wherein, The protective gas and the silicon source gas are introduced in the form of a mixed gas.

14. The method of making a silicon-carbon material of claim 9, wherein, In step S1, the flow rate of the silicon source gas was 2 L-kg -1 ·min -1 ; And / or, in step S1, the flow rate of the lithium source gas is 5-250 mg·kg -1 ·min -1 .

15. The method of making a silicon-carbon material of claim 14, wherein, In step S1, the flow rate of the lithium source gas was 7 mg-kg -1 • min -1 , 14 mg-kg -1 • min -1 , 23 mg-kg -1 • min -1 , 28 mg-kg -1 • min -1 , 42 mg-kg -1 • min -1 , 46 mg-kg -1 • min -1 , 56 mg-kg -1 • min -1 , 70 mg-kg -1 • min -1 , 84 mg-kg -1 • min -1 , 92 mg-kg -1 • min -1 , 118 mg-kg -1 • min -1 , 184 mg-kg -1 • min -1 , or 230 mg-kg -1 • min -1 .

16. The method of making a silicon-carbon material of claim 1, wherein, In step S2, the temperature of the second gas deposition is 400-800°C. And / or, in step S2, the second vapor deposition is performed for 5-15 hours. And / or, in step S2, the flow rate of the second deposition gas is 0.5-5 L·kg -1 ·min -1 ; And / or, in step S2, the carbon source gas comprises one or more of acetylene, alkane, alkene, aromatic compound and carbohydrate. And / or, in step S2, the second deposition gas further comprises a protective gas.

17. The method of making a silicon-carbon material of claim 16, wherein, In step S2, the temperature of the second vapor deposition is 600°C. And / or, in step S2, the second vapor deposition is performed for 8 hours. And / or, in step S2, the flow rate of the second deposition gas is 2 L kg -1 ·min -1 ; And / or, in step S2, the carbon source gas comprises acetylene. And / or, in step S2, the second deposition gas further comprises one or more of nitrogen, helium and argon.

18. The method of making a silicon-carbon material of claim 16, wherein, In step S2, the protective gas and the carbon source gas are introduced in the form of a mixed gas.

19. The method of making a silicon-carbon material of claim 16, wherein, In the second deposition gas, the volume ratio of the carbon source gas to the protective gas is (3-5):

1.

20. The method of making a silicon-carbon material of claim 19, wherein, In the second deposition gas, the volume ratio of the carbon source gas to the protective gas is 4:

1.

21. The method of making a silicon-carbon material as claimed in claim 1, wherein, The method for preparing the silicon-carbon material is performed in a vapor deposition device, wherein the vapor deposition device comprises a gas generator, a mixer and a reaction furnace; the gas generator is provided with a first gas outlet, the mixer comprises a first gas inlet, a second gas inlet and a deposition gas outlet arranged at different positions, and the reaction furnace is provided with a deposition gas inlet; the first gas outlet of the gas generator is in communication with the first gas inlet of the mixer, and the deposition gas outlet of the mixer is in communication with the deposition gas inlet of the reaction furnace. In step S1, the gas generator is used to generate a lithium source gas, the lithium source gas is introduced into the mixer through the first gas outlet and the first gas inlet of the mixer in sequence, the silicon source gas is introduced into the mixer through the second gas inlet, the mixer is used to mix the silicon source gas and the lithium source gas to form the first deposition gas, and the first deposition gas is introduced into the reaction furnace through the deposition gas outlet of the mixer and the deposition gas inlet of the reaction furnace in sequence, so that the first vapor deposition is performed on the porous carbon in the reaction furnace. In step S2, the second deposition gas is introduced into the mixer through the second gas inlet, and then introduced into the reaction furnace through the deposition gas outlet of the mixer and the deposition gas inlet of the reaction furnace in sequence, so that the second vapor deposition is performed on the silicon-carbon material precursor in the reaction furnace.

22. A silicon-carbon material, characterized in that, It is prepared by the method for preparing the silicon-carbon material according to any one of claims 1-21.

23. The silicon-carbon material of claim 22, wherein, It comprises a core-shell structure, wherein the core-shell structure comprises an inner core and an outer shell, the inner core comprises porous carbon and a lithium-containing silicon layer, the lithium-containing silicon layer is arranged on the surface and in the pores of the porous carbon, and the outer shell comprises a carbon layer which is coated on the surface of the inner core.

24. The silicon-carbon material of claim 23, wherein, The lithium content of the silicon-carbon material is 0.9%-8%. And / or, the silicon content of the silicon-carbon material is 45%-55%. And / or, the carbon content of the silicon-carbon material is 40%-55%. And / or, the nitrogen content of the silicon-carbon material is 30-310 ppm. And / or, the powder conductivity of the silicon-carbon material is 13%-63%. and / or the silicon-carbon material has a Dv50 particle size of 7-9 pm; and / or the silicon-carbon material has a specific surface area of 3-6 m 2 / g.

25. The silicon-carbon material of claim 24, wherein, the silicon-carbon material has a lithium content of 0.94%, 0.95%, 0.98%, 1.85%, 1.90%, 3.45%, 3.65%, 4.40%, 5.10%, 5.45%, 6.30%, 6.55%, or 7.75%; and / or the silicon-carbon material has a silicon content of 47%, 49.72%, 50.39%, 50.79%, 51.45%, 51.34%, 51.64%, 51.69%, 51.75%, 52.66%, 53.06%, 53.12%, 53.13%, or 53.14%; and / or the silicon-carbon material has a carbon content of 42-46%; and / or the silicon-carbon material has a nitrogen content of 32 ppm, 33 ppm, 65 ppm, 132 ppm, 221 ppm, 290 ppm, or 303 ppm; and / or the silicon-carbon material has a powder electrical conductivity of 13.2%, 22.2%, 24.1%, 25.3%, 25.2%, 29.4%, 26.2%, 37.3%, 40.9%, 44.2%, 49.6%, 59.3%, or 62.1%; and / or the silicon-carbon material has a Dv50 particle size of 7.2 pm, 7.7 pm, 7.8 pm, 7.9 pm, 8 pm, 8.1 pm, 8.3 pm, 8.5 pm, or 8.7 pm; and / or a specific surface area of the silicon-carbon material of 3.4 m 2 / g, 3.6 m 2 / g, 3.8 m 2 / g, 4 m 2 / g, 4.1 m 2 / g, 4.2 m 2 / g, 4.3 m 2 / g, 4.4 m 2 / g, 5.1 m 2 / g, 5.2 m 2 / g, 5.3 m 2 / g, or 5.4 m 2 / g.

26. The silicon-carbon material of claim 25, wherein, the silicon-carbon material has a carbon content of 42.53%, 42.91%, 43.06%, 43.21%, 43.45%, 43.96%, 44.6%, 44.86%, 45.04%, 45.49%, 45.91%, 45.93%, or 52.02%.

27. A lithium-ion battery, characterized by, comprising the silicon-carbon material of any one of claims 22-26.

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