A high-efficiency vapor deposition process, products and applications thereof

Abstract

The application discloses a high-efficiency gas deposition process, which uses porous carbon material as a substrate, uses silicon-containing gas, phosphorus-containing gas, nitrogen-containing gas, sulfur-containing gas, boron-containing gas and lithium-containing gas as raw material gas, and deposits nanoparticles in the pores of the porous carbon material after stage-by-stage gas deposition; in the first stage, the temperature in the reactor is controlled to be 300-800 DEG C, the initial pressure is 10-100 KPa, and the flow rate of the raw material gas is 2-15 L / min; when the pressure in the reactor starts to drop, the next stage is entered; in the second stage, the initial pressure in the reactor is adjusted to be 5-25 KPa, the flow rate of the raw material gas is adjusted to be 8-50 L / min; and when the pressure in the reactor starts to rise, the deposition is ended. The deposition process can significantly improve the pore structure utilization rate of the porous carbon substrate and reduce the specific surface area of the porous carbon substrate; the nanoparticles in the prepared product have high deposition amount, and exist in the pores of the porous carbon and are uniformly dispersed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical vapor deposition, in particular to a high-efficiency vapor deposition process and products and applications thereof. BACKGROUND

[0002] In recent years, with the continuous development of science and technology, porous carbon materials have attracted extensive attention and research as a new type of material with unique structure and properties. Porous carbon materials have high specific surface area, excellent chemical stability and electrical conductivity, and have wide application potential in many fields.

[0003] Porous carbon materials have high specific surface area and good electrical conductivity, and can be used as electrode materials for batteries and supercapacitors. Due to their high capacitance and reversible charge-discharge characteristics, they can be used for energy storage and energy release in high-performance batteries and supercapacitors. Porous carbon materials have a large number of pore structures that can adsorb and separate gases such as CO2 and methane. Their high specific surface area and good selectivity make them useful in environmental pollution control and natural gas storage. Porous carbon materials can be used as excellent catalyst carriers, providing good active surface and pore structure, which helps to improve the efficiency and selectivity of catalytic reactions. Their chemical stability and controllable pore structure make them have potential in the field of catalysis. Ideal porous carbon materials should have uniform pore size distribution and controllable pore structure to meet the needs of different applications. At present, although many studies have focused on developing new synthesis strategies and control conditions to achieve high control of the pore structure of porous carbon materials, most of the porous carbon materials still have the problem of uneven pore size distribution, and too large or too small pore structure greatly limits their application. For example, in the case of using porous carbon materials as battery electrode materials, micropores in porous carbon materials usually have very small pore sizes, and active particles are more likely to block micropore channels. This small pore size limits the adsorption and catalytic ability of micropores for larger size active particles. Although micropores have high specific surface area, they are not suitable for adsorption and catalytic deposition of active particles due to their small pore size, limited pore volume and easy blocking. Macropores have larger pore sizes, usually between tens of nanometers and hundreds of nanometers. This larger pore size makes it easy for active particles to pass through macropores without being effectively adsorbed and catalyzed. Therefore, the macropore part cannot effectively promote the complexation of active particles, and the utilization rate is low. In contrast, the mesopore part of the porous carbon usually has a suitable pore size structure that can accommodate larger size active particles, and the mesopore part is currently the part with the highest utilization rate of porous carbon for silicon deposition.

[0004] Therefore, how to efficiently utilize the pore structure with uneven pore size distribution and improve the utilization rate of porous carbon materials is a technical problem that needs to be solved urgently. SUMMARY

[0005] In view of the above problems existing in the prior art, the application discloses a high-efficiency vapor deposition process, which uses a porous carbon material as a substrate, and through phased vapor deposition and accurate regulation of deposition process parameters of each phase, the utilization rate of the pore structure of the porous carbon substrate is significantly improved, and the specific surface area thereof is reduced; in the prepared carbon-based composite material, the nanoparticles have a high deposition amount and are substantially present in the pore channels of the porous carbon material and are uniformly dispersed.

[0006] The specific technical solutions are as follows:

[0007] The high-efficiency vapor deposition process comprises the following steps:

[0008] The porous carbon material is used as a substrate, and nanoparticles of a doping element are deposited in the pore cavities of the porous carbon material after phased vapor deposition;

[0009] The phased vapor deposition uses one or more of a silicon-containing gas, a phosphorus-containing gas, a nitrogen-containing gas, a sulfur-containing gas, a boron-containing gas and a lithium-containing gas as a raw material gas, and comprises the following steps:

[0010] In a first phase, the temperature in the reactor is controlled to be 300-800 DEG C, the initial pressure is 10-100 KPa, and the flow rate of the raw material gas is 2-15 L / min; when the pressure in the reactor starts to decrease and the pressure change value is 10-75% of the initial pressure, the next phase is entered;

[0011] In a second phase, the initial pressure in the reactor is adjusted to be 5-25 KPa, and the flow rate of the raw material gas is adjusted to be 8-50 L / min;

[0012] Furthermore, the initial pressure in the second phase is lower than that in the first phase, and the flow rate of the raw material gas in the second phase is higher than that in the first phase;

[0013] When the pressure in the reactor starts to increase and the pressure change value is 5-50% of the initial pressure, the deposition is ended;

[0014] When the pressure in the reactor starts to decrease and the pressure change value is 10-75% of the initial pressure, the pressure in the reactor is again adjusted to be 3-15 KPa, the flow rate of the raw material gas is still controlled to be 8-50 L / min, and the deposition is continued until the pressure in the reactor starts to increase and the pressure change value is 5-50% of the adjusted pressure, and then the deposition is ended;

[0015] Furthermore, the adjusted pressure is lower than the initial pressure in the second phase.

[0016] The gas phase deposition process disclosed in the application can ensure efficient deposition in different size pore structures in the porous carbon material by dividing the deposition process into stages and accurately controlling the deposition process parameters of each stage, improve the pore structure utilization rate of the porous carbon material, and ensure uniform deposition of nanoparticles in the pores of the porous carbon without falling on the surface of the porous carbon material, thereby facilitating further application downstream.

[0017] Experiments have found that, compared with traditional one-time deposition, the staged deposition disclosed in the application can make the deposited nanoparticles more uniform in distribution under a considerable deposition amount, and significantly improve the pore structure utilization rate.

[0018] Experiments have also found that if the deposition sequence of the two stages is exchanged or the process parameters in each stage of deposition are not controlled within the above-mentioned range, the pore structure utilization rate of the prepared carbon-based composite material will decrease and the specific surface area will increase. The above-mentioned influence may be because the deposition parameters are not properly controlled, resulting in incomplete deposition of pores or clogging of pores, or uneven dispersion of nanoparticles in the pores, or even enrichment of nanoparticles on the surface of the porous carbon. Therefore, only by adopting the sequence of the staged deposition disclosed in the application and accurately controlling the deposition process parameters of each stage, can the pore structure utilization rate of the porous carbon substrate be significantly improved.

[0019] Experiments have found that the gas phase deposition process disclosed in the application is suitable for different pore structure porous carbon materials.

[0020] When the volume fraction of the micropore part (<2nm) in the porous carbon material is <85%, the initial pressure in the first stage is selected from 10-50KPa;

[0021] When the volume fraction of the micropore part in the porous carbon material is ≥85%, the initial pressure in the first stage is selected from 50-100KPa.

[0022] The use of the above-mentioned corresponding process parameters can ensure that the micropore part with different contents is fully utilized.

[0023] When the volume fraction of the macropore (>50nm) in the porous carbon material is large, such as reaching 5% or more, the pressure may decrease during the second stage deposition process. Therefore, in this case, the second stage is further refined, the pressure in the reactor is adjusted again to continue deposition, and the deposition is ended when the pressure in the reactor starts to rise to a certain degree.

[0024] Preferably:

[0025] The specific surface area of the porous carbon material is 300-3000m 2 / g, the average pore size is 1-50nm, and the pore volume is 0.4-2.0cm 3 / g.

[0026] The raw gas disclosed in the present application comprises:

[0027] The silicon-containing gas is selected from one or more of monosilane, disilane, dichlorodisilane, trichlorosilane;

[0028] The phosphorus-containing gas is selected from one or more of phosphine, phosphorus chloride, phosphorus fluoride;

[0029] The nitrogen-containing gas is selected from ammonia;

[0030] The sulfur-containing gas is selected from one or more of hydrogen sulfide, sulfur dioxide, sulfur hexafluoride;

[0031] The boron-containing gas is selected from borane;

[0032] The lithium-containing gas is selected from lithium hydride.

[0033] An inert gas is further added to the raw gas to form a mixed gas, and the proportion of the inert gas in the mixed gas is 1-30 vol%.

[0034] The inert gas is selected from conventional types in the art, such as nitrogen, neon, argon, krypton, xenon, radon, etc.

[0035] Preferably:

[0036] In the first stage, the initial pressure is 20-80 KPa, and the flow rate of the raw gas is 3-10 L / min;

[0037] In the second stage, the initial pressure is 8-20 KPa, and the flow rate of the raw gas is 10-40 L / min.

[0038] Preferably:

[0039] In the first stage, when the pressure change value in the reactor is 14-60% of the initial pressure, the next stage is entered;

[0040] In the second stage, when the pressure change value in the reactor is 5-40% of the initial pressure, the deposition is ended.

[0041] Further preferably:

[0042] In the first stage, when the pressure change value in the reactor is 25-60% of the initial pressure, the next stage is entered;

[0043] In the second stage, when the pressure change value in the reactor is 8-25% of the initial pressure, the deposition is ended.

[0044] It is found through experiments that, with further optimization of the above deposition process parameters, the pore structure utilization of the prepared carbon-based composite material is higher, the specific surface area is lower, and the deposited nanoparticles are more uniform.

[0045] The nanosilicon in the carbon-based composite material prepared after the above raw gas is subjected to gas phase deposition is prone to oxidation reaction with oxygen in the air at normal temperature, the stability is affected and the safety cannot be guaranteed. Therefore, from the perspective of better implementation in actual production, preferably, the product prepared after the gas phase deposition is subjected to carbon coating.

[0046] The carbon coating adopts raw materials and process flows commonly used in the art, specifically:

[0047] A mixed gas composed of carbon source gas and inert gas is used as raw gas, and a carbon layer is coated on the surface of the carbon-based composite material prepared through the above gas phase deposition at 400-1000 DEG C.

[0048] The carbon source gas is selected from alkane gas with a cracking temperature of 400-1200 DEG C.

[0049] In the mixed gas, the volume fraction of the carbon source gas is 60-99 vol%.

[0050] The flow rate of the mixed gas is 0.1-50 L / min; preferably, 0.1-10 L / min.

[0051] Preferably, the temperature of the gas phase deposition is 400-600 DEG C.

[0052] In order not to affect the accuracy of the pore structure utilization test, the content of the deposited carbon layer is controlled to be 5 wt% or less.

[0053] The application further discloses a carbon-based composite material prepared according to the above deposition process, and the pore structure utilization is >96%, and can be up to 99%.

[0054] The application further discloses application of the carbon-based composite material in battery electrode materials and catalysts.

[0055] Compared with the prior art, the application has the following advantages:

[0056] The application discloses a high-efficiency gas phase deposition process.

[0057] The pore structure utilization rate of the carbon-based composite material prepared by the method is greater than 96%, and can be up to 99%, which is beneficial to the application in the fields of battery electrode materials, catalysts and the like. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 The pore size distribution diagram of the porous carbon material used in this embodiment;

[0059] Figure 2 The pore size distribution diagram of the porous carbon material used in this embodiment;

[0060] Figure 3 The MAPPing diagram of the silicon-carbon composite material prepared in this embodiment;

[0061] Figure 4 The SEM diagram of the silicon-carbon composite material prepared in this embodiment;

[0062] Figure 5 The TEM diagram of the silicon-carbon composite material prepared in this embodiment;

[0063] Figure 6 The SEM diagram of the silicon-carbon composite material prepared in this embodiment;

[0064] Figure 7 The TEM diagram of the silicon-carbon composite material prepared in this embodiment. DETAILED DESCRIPTION

[0065] The specific implementation method of the present application is further described below in combination with examples, and it should be noted that the specific implementation method described herein is only for the purpose of illustrating and explaining the present application, and is not used to limit the protection scope of the present application.

[0066] Embodiment 1

[0067] (1) 100 g of porous carbon material (D50 = 6 μm, span value < 1.5) was placed in a hot deposition furnace with a temperature of 500 ℃ under an argon atmosphere, and the specific surface area of the porous carbon material was 450 m 2 / g, the average pore size was 10 nm, and the pore volume was 0.57 cm 3 / g.

[0068] Figure 1 The pore size distribution diagram of the porous carbon material used in this embodiment, and the test results show that the pore volume distribution of the porous carbon material used in this embodiment is 8.34% of ultra-micropores (<1 nm part), 6.79% of micropores (1-2 nm part), 40.75% of mesopores (2-10 nm part), 32.09% of mesopores (10-50 nm part) and 12.03% of macropores (> 50 nm).

[0069] (2) First stage:

[0070] A mixture gas composed of 80 vol% of silane and 20 vol% of argon was introduced into a hot deposition furnace at a flow rate of 5 L / min, and the pressure in the furnace was maintained at 20 Kpa, so that silicon particles were continuously nucleated and deposited inside the pores of the porous carbon, and the gas was continuously introduced until the pressure in the furnace changed;

[0071] Second stage:

[0072] When the pressure in the furnace decreased to 15 Kpa, the flow rate of the mixture gas was adjusted to 30 L / min, and the pressure in the furnace was adjusted to 12 Kpa, and the gas was continuously introduced until the pressure in the furnace changed;

[0073] Third stage:

[0074] When the pressure in the furnace decreased to 7 Kpa, the flow rate of the mixture gas was adjusted to 40 L / min and the pressure in the furnace was maintained, and the gas was continuously introduced, and when the pressure increased to 10 Kpa, the deposition was ended.

[0075] (3) After the deposition of silicon was completed, a mixture gas composed of 70 vol% of acetylene and 30 vol% of argon was introduced at a flow rate of 1 L / min, and high-temperature carbon coating was performed, and the gas was continuously introduced for 3 h, and then the temperature was lowered to room temperature. After the material was dispersed, sieved, and demagnetized, a silicon-carbon composite material was obtained.

[0076] In this embodiment, a silicon-carbon composite material with a deposition silicon content of 50.57 wt%, a porous carbon content of 46.18 wt%, and a surface carbon coating layer content of 3.25 wt% was prepared.

[0077] The specific surface area and pore volume data of the silicon-carbon composite material product prepared in this embodiment are listed in Table 1 below, and the pore structure utilization rate data of the silicon-carbon composite material product prepared in this embodiment is calculated according to the following calculation formula and is also listed in Table 1.

[0078]

[0079] P1: Pore volume of raw porous carbon material;

[0080] P2: Pore volume of silicon-carbon composite material product.

[0081] Example 2

[0082] (1) 100 g of porous carbon material (D50 = 6 μm, span value <1.5) was placed in a hot deposition furnace at a temperature of 500°C under an argon atmosphere, and the specific surface area of the porous carbon material was 1980 m 2 / g, the average pore size was 1.8 nm, and the pore volume was 1.1 cm 3 / g;

[0083] Figure 2 The pore size distribution of the porous carbon material used in this example is shown in the following table. The pore volume distribution of the porous carbon material used in this example is 38.81% ultra-micropores (<1 nm fraction), 43.99% micropores (1-2 nm fraction), 15.91% mesopores (2-10 nm fraction), 0.50% mesopores (10-50 nm fraction), and 0.79% macropores (>50 nm).

[0084] (2) First stage:

[0085] A mixture of 80 vol% silane and 20 vol% argon was introduced into the hot deposition furnace at a flow rate of 6 L / min, and the pressure in the furnace was maintained at 35 Kpa. Silicon particles were continuously nucleated and deposited inside the pores of the porous carbon. The gas flow was continued until a change in pressure was observed in the furnace.

[0086] Second stage:

[0087] When the pressure in the furnace decreased to 15 Kpa, the flow rate of the mixed gas was adjusted to 10 L / min, and the pressure in the furnace was adjusted to 12 Kpa. The gas flow was continued, and when the pressure increased to 14 Kpa, the deposition was stopped.

[0088] (3) After the deposition of silicon was completed, a mixture of 70 vol% acetylene and 30 vol% argon was introduced into the furnace at a flow rate of 1 L / min for high-temperature carbon coating. The gas flow was continued for 3 hours, and then the temperature was lowered to room temperature. After the material was dispersed, sieved, and de-magnetized, a silicon-carbon composite material was obtained.

[0089] The silicon-carbon composite material prepared in this example had a silicon deposition content of 56.72 wt%, a porous carbon content of 40.21 wt%, and a surface carbon coating layer content of 3.07 wt%.

[0090] The specific surface area and pore volume data of the silicon-carbon composite material prepared in this example are shown in Table 1 below. The pore structure utilization rate data of the silicon-carbon composite material prepared in this example was calculated according to the following formula and is also shown in Table 1.

[0091] Figure 3 The MAPPing image of the silicon-carbon composite material prepared in this example is shown in the following figure. It can be observed from the image that the nano-silicon is uniformly deposited inside the porous carbon, and almost no deposition is observed on the outer surface.

[0092] Figure 4 The SEM image of the silicon-carbon composite material prepared in this example is shown in the following figure. It can be observed from the image that the nano-silicon particles are uniformly deposited on the inner wall of the porous carbon channels, and the channel structure is not blocked.

[0093] Figure 5The TEM image of the silicon-carbon composite material prepared in this example is shown in Figure 1. It can be seen from the image that the deposited silicon particles are amorphous, and no crystalline silicon is generated, which indicates that all the nano-silicon particles are deposited inside the porous carbon, and no accumulation occurs on the outer surface.

[0094] Comparative Example 1

[0095] Step (1) is the same as in Example 2;

[0096] (2) A mixture gas composed of 80 vol% silane and 20 vol% argon is introduced into the hot deposition furnace at a flow rate of 10 L / min, and the pressure in the furnace is maintained at 30 Kpa. The gas is continuously introduced for 8 h;

[0097] Step (3) is the same as in Example 1.

[0098] The silicon-carbon composite material prepared in this comparative example has a deposited silicon content of 53.2 wt%, a porous carbon content of 43.61 wt%, and a surface carbon coating layer content of 3.19 wt%.

[0099] The specific surface area, pore volume, and pore structure utilization data of the finished product of the silicon-carbon composite material prepared in this comparative example are listed in Table 1 below.

[0100] Comparative Example 2

[0101] Step (1) is the same as in Example 2;

[0102] (2) First stage:

[0103] A mixture gas composed of 80 vol% silane and 20 vol% argon is introduced into the hot deposition furnace at a flow rate of 10 L / min, and the pressure in the furnace is maintained at 12 Kpa. Silicon particles are continuously nucleated and deposited inside the pores of the porous carbon. The gas is continuously introduced for 3 h;

[0104] Second stage:

[0105] The flow rate of the mixture gas is adjusted to 6 L / min, and the pressure in the furnace is adjusted to 35 Kpa. The gas is continuously introduced for 5 h to complete the deposition;

[0106] Step (3) is the same as in Example 2.

[0107] The silicon-carbon composite material prepared in this comparative example has a deposited silicon content of 47.2 wt%, a porous carbon content of 48.02 wt%, and a surface carbon coating layer content of 4.78 wt%.

[0108] The specific surface area, pore volume, and pore structure utilization data of the finished product of the silicon-carbon composite material prepared in this comparative example are listed in Table 1 below.

[0109] Comparative Example 3

[0110] The preparation process is basically the same as in Example 2, except that the flow rate of the mixed gas in the first stage of step (2) is replaced by 25 L / min.

[0111] The silicon-carbon composite material prepared in this comparative example has a deposited silicon content of 54.2 wt%, a porous carbon content of 42.3 wt%, and a surface carbon coating layer content of 3.5 wt%.

[0112] The specific surface area, pore volume, and pore structure utilization rate data of the finished product of the silicon-carbon composite material prepared in this comparative example are all listed in Table 1 below.

[0113] Comparative Example 4

[0114] The preparation process is basically the same as in Example 2, except that the flow rate of the mixed gas in the second stage of step (2) is replaced by 2 L / min.

[0115] The silicon-carbon composite material prepared in this comparative example has a deposited silicon content of 55.9 wt%, a porous carbon content of 40.71 wt%, and a surface carbon coating layer content of 3.39 wt%.

[0116] The specific surface area, pore volume, and pore structure utilization rate data of the finished product of the silicon-carbon composite material prepared in this comparative example are all listed in Table 1 below.

[0117] Comparative Example 5

[0118] The preparation process is basically the same as in Example 2, except that the furnace pressure in the first stage of step (2) is replaced by 60 Kpa.

[0119] The silicon-carbon composite material prepared in this comparative example has a deposited silicon content of 53.1 wt%, a porous carbon content of 43.4 wt%, and a surface carbon coating layer content of 3.5 wt%.

[0120] The specific surface area, pore volume, and pore structure utilization rate data of the finished product of the silicon-carbon composite material prepared in this comparative example are all listed in Table 1 below.

[0121] Comparative Example 6

[0122] The preparation process is basically the same as in Example 2, except that the furnace pressure in the first stage of step (2) is replaced by 5 Kpa.

[0123] The silicon-carbon composite material prepared in this comparative example has a deposited silicon content of 49.1 wt%, a porous carbon content of 47.1 wt%, and a surface carbon coating layer content of 3.8 wt%.

[0124] The specific surface area, pore volume, and pore structure utilization rate data of the finished product of the silicon-carbon composite material prepared in this comparative example are all listed in Table 1 below.

[0125] Comparative Example 7

[0126] The preparation process is basically the same as in Example 2, except that the pressure in the furnace in the second stage of step (2) is changed to 30 KPa.

[0127] The silicon-carbon composite material prepared in this comparative example has a silicon deposition content of 55.7 wt%, a porous carbon content of 41.03 wt%, and a surface carbon coating content of 3.27 wt%.

[0128] The specific surface area, pore volume, and pore structure utilization rate data of the finished silicon-carbon composite material prepared in this comparative example are listed in Table 1 below.

[0129] Example 3

[0130] The preparation process is basically the same as in Example 2, except that in the second stage of step (2), when the pressure in the furnace is changed to 30 KPa, the flow rate of the mixed gas is adjusted to 10 L / min, the pressure in the furnace is adjusted to 12 KPa, and the aeration is continued until the pressure in the furnace increases to 14 KPa, and the deposition is ended.

[0131] The silicon-carbon composite material prepared in this example has a silicon deposition content of 55.17 wt%, a porous carbon content of 41.58 wt%, and a surface carbon coating content of 3.25 wt%.

[0132] The specific surface area, pore volume, and pore structure utilization rate data of the finished silicon-carbon composite material prepared in this example are listed in Table 1 below.

[0133] Example 4

[0134] The preparation process is basically the same as in Example 2, except that in the second stage of step (2), when the pressure in the furnace is changed to 10 KPa, the flow rate of the mixed gas is adjusted to 10 L / min, the pressure in the furnace is adjusted to 12 KPa, and the aeration is continued until the pressure in the furnace increases to 14 KPa, and the deposition is ended.

[0135] The silicon-carbon composite material prepared in this example has a silicon deposition content of 57.2 wt%, a porous carbon content of 39.97 wt%, and a surface carbon coating content of 2.83 wt%.

[0136] The specific surface area, pore volume, and pore structure utilization rate data of the finished silicon-carbon composite material prepared in this example are listed in Table 1 below.

[0137] Figure 6 The SEM image of the silicon-carbon composite material prepared in this example is shown in the figure. It can be seen from the figure that the deposited nanosilicon particles have a certain agglomeration inside the pores, causing some pores to be blocked.

[0138] Comparative Example 8

[0139] The preparation process is basically the same as in Example 2, except that in the second stage of step (2), when the pressure in the furnace changes to 33 Kpa, the flow rate of the mixed gas is adjusted to 10 L / min, the pressure in the furnace is adjusted to 12 Kpa, and the deposition is ended when the pressure in the furnace increases to 14 Kpa.

[0140] The silicon-carbon composite material prepared in this comparative example has a deposition silicon content of 53.71 wt%, a porous carbon content of 42.9 wt%, and a surface carbon coating layer content of 3.39 wt%.

[0141] The specific surface area, pore volume, and pore structure utilization rate data of the finished product of the silicon-carbon composite material prepared in this example are listed in Table 1 below.

[0142] Example 5

[0143] The preparation process is basically the same as in Example 2, except that in the second stage of step (2), when the pressure in the furnace changes to 33 Kpa, the flow rate of the mixed gas is adjusted to 10 L / min, the pressure in the furnace is adjusted to 12 Kpa, and the deposition is ended when the pressure in the furnace increases to 14 Kpa.

[0144] The silicon-carbon composite material prepared in this example has a deposition silicon content of 53.71 wt%, a porous carbon content of 42.9 wt%, and a surface carbon coating layer content of 3.39 wt%.

[0145] The specific surface area, pore volume, and pore structure utilization rate data of the finished product of the silicon-carbon composite material prepared in this example are listed in Table 1 below.

[0146] Example 6

[0147] The preparation process is basically the same as in Example 2, except that in the second stage of step (2), when the pressure in the furnace changes to 33 Kpa, the flow rate of the mixed gas is adjusted to 10 L / min, the pressure in the furnace is adjusted to 12 Kpa, and the deposition is ended when the pressure in the furnace increases to 14 Kpa.

[0148] The silicon-carbon composite material prepared in this example has a deposition silicon content of 53.71 wt%, a porous carbon content of 42.9 wt%, and a surface carbon coating layer content of 3.39 wt%.

[0149] The specific surface area, pore volume, and pore structure utilization rate data of the finished product of the silicon-carbon composite material prepared in this example are listed in Table 1 below.

[0150] Example 7

[0151] The preparation process is basically the same as that in Example 2, except that in step (2), in the second stage, when the pressure in the furnace changes to 15 KPa, the flow rate of the mixed gas is adjusted to 10 L / min, the pressure in the furnace is adjusted to 12 KPa, and the aeration is continued until the pressure in the furnace increases to 17 KPa, and the deposition is ended.

[0152] In this example, a silicon-carbon composite material with a silicon deposition content of 57.86 wt%, a porous carbon content of 39.5 wt%, and a surface carbon coating content of 2.64 wt% is prepared.

[0153] The specific surface area, pore volume, and pore structure utilization data of the silicon-carbon composite material prepared in this example are listed in Table 1 below.

[0154] Figure 7 The TEM image of the silicon-carbon composite material prepared in this example is shown in the figure. It can be seen from the image that the crystal lattice structure of crystalline silicon appears in the product, indicating that part of the nano-silicon particles are accumulated on the outer surface of the porous carbon and crystallized.

[0155] Example 8

[0156] (1) In an argon atmosphere, 100 g of porous carbon material is placed as a substrate (D50 = 6 μm, span value <1.5) in a hot deposition furnace at a temperature of 500°C. The specific surface area of the porous carbon material is 2400 m 2 / g, the average pore size is 1 nm, and the pore volume is 2.0 cm 3 / g; it is tested that the pore volume distribution of the porous carbon material used in this example is 42.81% of ultra-micropores (<1 nm part), 43.79% of micropores (1-2 nm part), 11.68% of mesopores (2-10 nm part), 1.33% of mesopores (10-50 nm part), and 0.39% of macropores (>50 nm).

[0157] (1) First stage:

[0158] A mixed gas composed of 80 vol% silane and 20 vol% argon is introduced into the hot deposition furnace at a flow rate of 3 L / min, and the pressure in the furnace is maintained at 70 KPa, so that silicon particles are continuously nucleated and deposited inside the pores of the porous carbon. The aeration is continued until the pressure in the furnace changes;

[0159] Second stage:

[0160] When the pressure in the furnace changes to 28 KPa, the flow rate of the mixed gas is adjusted to 40 L / min, the pressure in the furnace is adjusted to 10 KPa, and the aeration is continued until the pressure in the furnace increases to 12 KPa, and the deposition is ended;

[0161] Step (3) is the same as in Example 2.

[0162] The comparative example prepared a silicon-carbon composite material with a deposited silicon content of 60.3wt%, a porous carbon content of 37.35wt%, and a surface carbon coating content of 2.35wt%.

[0163] The specific surface area, pore volume, and pore structure utilization data of the finished silicon-carbon composite material prepared in this example are listed in Table 1 below.

[0164] Example 9

[0165] Step (1) is the same as in Example 2;

[0166] (2) First stage:

[0167] Into the hot deposition furnace with a flow rate of 6L / min, 75vol% of silane and 25vol% of argon gas mixture is introduced, the furnace pressure is maintained at 30Kpa, the internal pores of the porous carbon are continuously nucleated and deposited to form silicon particles, and the gas flow is continued until the pressure in the furnace changes;

[0168] Second stage:

[0169] When the furnace pressure changes to 12Kpa, adjust the flow rate of the mixed gas to 20L / min, adjust the furnace pressure to 10Kpa, continue to ventilate, and when the furnace pressure increases to 13Kpa, end the deposition;

[0170] Step (3) is exactly the same as in Example 2.

[0171] The comparative example prepared a lithium-carbon composite material with a deposited lithium content of 56.31wt%, a porous carbon content of 40.35wt%, and a surface carbon coating content of 3.34wt%.

[0172] The specific surface area, pore volume, and pore structure utilization data of the finished lithium-carbon composite material prepared in this example are listed in Table 1 below.

[0173] Test example

[0174] To verify the accuracy of the conclusion that the first stage is used to deposit the microporous part of the porous carbon material, the second stage is used to deposit the mesoporous part of the porous carbon material, and the third stage is used to deposit the macroporous part of the porous carbon material in the segmented deposition disclosed above, the following verification is performed:

[0175] 1. The preparation process only includes steps (1) and (2) which are basically the same as in Example 1, but does not perform the high-temperature carbon coating process, and the difference in step (2) is:

[0176] First stage:

[0177] The mixed gas composed of 80 vol% of silane and 20 vol% of argon was introduced into the hot deposition furnace at a flow rate of 5 L / min, and the pressure in the furnace was kept at 20 Kpa;

[0178] The second stage:

[0179] When the pressure in the furnace decreased to 15 Kpa, the mixed gas composed of 80 vol% of silane and 20 vol% of argon was introduced into the hot deposition furnace at a flow rate of 20 L / min, and the pressure in the furnace was adjusted to 12 Kpa, and the aeration was continued until the pressure in the furnace changed;

[0180] The third stage:

[0181] When the pressure in the furnace decreased to 7 Kpa, the flow rate of the mixed gas (acetylene and argon) was adjusted to 30 L / min and the pressure in the furnace was kept unchanged, and the aeration was continued, and when the pressure increased to 10 Kpa, the deposition was ended.

[0182] It was tested that the finally prepared silicon-carbon composite material had a deposition silicon content of 8.51 wt%, a deposition carbon content of 45.2 wt%, and a porous carbon content of 46.29 wt%.

[0183] According to the parameters of the porous carbon material in Example 1, the ratio of the total volume of mesopores (2-50 nm) and macropores (>50 nm) to the volume of micropores (≤2 nm) was about 5.609, and according to the mass fractions of the deposition carbon and the deposition silicon obtained by the above test, it was speculated that the volume ratio of the two was about 5.476, and the two values were comparable.

[0184] 2. The preparation process only contains steps (1) and (2) which are basically the same as those in Example 1, but does not perform the high-temperature carbon coating process, and the difference in step (2) is that:

[0185] The first stage:

[0186] The mixed gas composed of 80 vol% of silane and 20 vol% of argon was introduced into the hot deposition furnace at a flow rate of 5 L / min, and the pressure in the furnace was kept at 20 Kpa;

[0187] The second stage:

[0188] When the pressure in the furnace decreased to 15 Kpa, the mixed gas composed of 80 vol% of silane and 20 vol% of argon was introduced into the hot deposition furnace at a flow rate of 20 L / min, and the pressure in the furnace was adjusted to 12 Kpa, and the aeration was continued until the pressure in the furnace changed;

[0189] The third stage:

[0190] When the pressure in the furnace dropped to 7 Kpa, the mixed gas composed of 80 vol% acetylene and 20 vol% argon was introduced into the hot deposition furnace at a flow rate of 30 L / min, and the gas was continuously introduced until the pressure increased to 10 Kpa, and the deposition was ended.

[0191] Through testing, the silicon-carbon composite material with a deposition silicon content of 48.28 wt%, a deposition carbon content of 6.41 wt%, and a porous carbon content of 45.31 wt% was finally prepared.

[0192] According to the parameters of the porous carbon material in Example 1, the ratio of the volume of the micropores (0.4-50 nm) to the volume of the macropores (>50 nm) is about 7.313, and according to the mass fractions of the deposition silicon and the deposition carbon obtained through the above testing, the volume ratio of the two is about 7.291, and the two values are comparable.

[0193] According to the two sets of test data, it is inferred that the judgment basis of the segmentation interval of the segmented process meets the actual porous carbon pore structure distribution.

[0194] Performance test:

[0195] I. The specific surface area and pore volume data of the composite material products prepared in each of the above examples and each of the comparative examples were tested, and the pore structure utilization rate was calculated using the above formula (1), which are shown in Table 1 below.

[0196] Table 1

[0197]

[0198]

[0199] Data analysis:

[0200] According to the data in Table 1, the specific analysis is as follows:

[0201] According to the data of Comparative Example 2 and Comparative Examples 1-2, compared with the traditional one-time deposition (Comparative Example 1, i.e., no segmented process), the pore structure utilization rate of the porous carbon substrate can be significantly improved and the specific surface area can be reduced by setting a segmented deposition process according to the characteristics of different pore structures. According to the data of Comparative Example 2, the pore structure utilization rate of the prepared composite material is greatly reduced and the specific surface area is very high when the deposition sequence is exchanged, which may be because of the unreasonable deposition process setting, i.e., the deposition is first performed at a lower pressure and a higher flow rate, and the nano-silicon is difficult to enter the micropores, and the mesopores are blocked when the deposition of the mesopores is completed, which leads to that the micropore utilization rate cannot be improved in the second stage of deposition, and the local agglomeration phenomenon occurs due to the rapid deposition in the high-pressure environment.

[0202] Comparing Example 2 with Comparative Examples 3-4, if a faster gas flow rate is used in the first stage (Comparative Example 3), the pore structure utilization rate of the prepared composite material decreases, possibly because the deposition is too fast, causing pore blockage and reducing the utilization rate of the micropore portion. If a lower gas flow rate is used in the second stage (Comparative Example 4), the pore structure utilization rate of the prepared composite material also decreases, possibly because the lower gas flow rate combined with the lower furnace pressure results in low deposition efficiency, uneven distribution of nano-silicon particles, and a small portion of unused pore structures in the mesoporous portion.

[0203] Comparing Examples 2 and 5-7, if an excessively high reaction pressure is used in the first stage (Comparative Example 5), the pore structure utilization rate of the prepared composite material decreases, while the specific surface area increases. This may be because the deposition rate is too fast, resulting in extremely uneven distribution of nano-silicon, leading to significant pore blockage and a decrease in pore structure utilization. Similarly, if an excessively high reaction pressure is used in the second stage (Comparative Example 7), the pore structure utilization rate of the prepared composite material decreases, while the specific surface area increases. This may also be due to an excessively fast deposition rate, resulting in uneven distribution of nano-silicon, pore blockage, and a decrease in pore structure utilization. Conversely, if an excessively low reaction pressure is used in the first stage (Comparative Example 6), the capillary action of the micropores is not effectively utilized, leading to a significant decrease in micropore utilization and a significant reduction in the deposition amount.

[0204] Comparing Examples 2-4 with Comparative Example 8, it can be seen that in the first stage, a pressure change occurs. If the ratio of the pressure change to the initial pressure is too small (Comparative Example 8), the pore structure utilization rate of the prepared composite material decreases, possibly because the micropores are not fully filled. When the pressure change ranges from 14% to 75% of the initial pressure, composite materials with high pore structure utilization rates can be prepared. However, further experiments revealed that when the pressure change exceeds 70% of the initial pressure, the silicon nanoparticles deposited inside the pores become unevenly dispersed, leading to a slight decrease in pore structure utilization. When the pressure change is less than 25% of the initial pressure, the pore structure utilization rate also decreases slightly due to incomplete micropore deposition. Therefore, the preferred pressure change value in the first stage is between 25% and 60% of the initial pressure. Comparing Examples 2 and 5-7, it can be seen that the second stage, which uses pressure changes to determine whether it has ended, ensures a high pore structure utilization rate and more uniform deposition by adjusting the pressure change. When the pressure change in the second stage varies within the range of 5% to 50% of the initial pressure, composite materials with high pore structure utilization can be prepared. However, further experiments revealed that when the pressure change exceeds 40% of the initial pressure, excessive silicon nanoparticles deposit on the porous carbon surface, affecting its further application. Therefore, the optimal pressure change value for the second stage (the pressure change before the end of deposition) is between 8% and 25% of the initial pressure.

[0205] The above merely describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. The above application of specific examples to the present application is only for helping understanding the present application, and is not used to limit the present application. The skilled in the art of the present application can also make several simple deductions, deformations, substitutions or combinations according to the concept of the present application. These deductions, deformations, substitutions or combinations also fall into the protection scope of the present application.

Claims

1. A high efficiency vapor deposition process characterized by, The process comprises the following steps: Depositing nanoparticles of doping elements inside the pores of the porous carbon material by multi-stage gas phase deposition; The multi-stage gas phase deposition uses one or more of a silicon-containing gas, a phosphorus-containing gas, a nitrogen-containing gas, a sulfur-containing gas, a boron-containing gas, and a lithium-containing gas as a raw material gas, and comprises: In the first stage, the temperature in the reactor is controlled at 300-800℃, the initial pressure is 10-100KPa, and the flow rate of the raw material gas is 2-15L / min; when the pressure in the reactor starts to decrease and the pressure change value is 10-75% of the initial pressure, the next stage is entered; In the second stage, the initial pressure in the reactor is adjusted to 5-25KPa, and the flow rate of the raw material gas is adjusted to 8-50L / min; Moreover, the initial pressure in the second stage is lower than that in the first stage, and the flow rate of the raw material gas in the second stage is higher than that in the first stage; When the pressure in the reactor starts to increase and the pressure change value is 5-50% of the initial pressure, the deposition is ended; When the pressure in the reactor starts to decrease and the pressure change value is 10-75% of the initial pressure, the pressure in the reactor is again adjusted to 3-15KPa, the flow rate of the raw material gas is still controlled at 8-50L / min, and the deposition is continued until the pressure in the reactor starts to increase and the pressure change value is 5-50% of the adjusted pressure, and the deposition is ended; Moreover, the adjusted pressure is lower than the initial pressure in the second stage.

2. The high-efficiency gas phase deposition process according to claim 1, wherein: when the volume fraction of the microporous part in the porous carbon material is <85%, the initial pressure in the first stage is selected from 10-50KPa; when the volume fraction of the microporous part in the porous carbon material is ≥85%, the initial pressure in the first stage is selected from 50-100KPa.

3. The high-efficiency gas phase deposition process according to claim 1, wherein: the silicon-containing gas is selected from one or more of monosilane, disilane, dichlorodisilane, and trichlorosilane; the phosphorus-containing gas is selected from one or more of phosphine, phosphorus chloride, and phosphorus fluoride; the nitrogen-containing gas is selected from ammonia; the sulfur-containing gas is selected from one or more of hydrogen sulfide, sulfur dioxide, and sulfur hexafluoride; the boron-containing gas is selected from diborane; the lithium-containing gas is selected from lithium hydride.

4. The high-efficiency gas phase deposition process according to claim 1, wherein: an inert gas is further added to the raw material gas to form a mixed gas, and the volume fraction of the inert gas in the mixed gas is 1-30vol%.

5. The high-efficiency gas phase deposition process according to claim 1, wherein: in the first stage, when the pressure change value in the reactor is 14-60% of the initial pressure, the next stage is entered; in the second stage, when the pressure change value in the reactor is 5-40% of the initial pressure, the deposition is ended.

6. The high-efficiency gas phase deposition process according to claim 1, wherein: in the first stage, when the pressure change value in the reactor is 25-60% of the initial pressure, the next stage is entered; The second stage ends deposition when the pressure change value is 8-25% of the initial pressure.

7. The high rate physical vapor deposition process of claim 1, wherein, The specific surface area of the porous carbon material is 300-3000 m 2 / g, the average pore diameter is 1-50 nm, and the pore volume is 0.4-2.0 cm 3 / g.

8. The high-efficiency vapor deposition process of claim 1, wherein: The first stage has an initial pressure of 20-80 Kpa and a flow rate of 3-10 L / min. The second stage has an initial pressure of 8-20 Kpa and a flow rate of 10-40 L / min.

9. A carbon-based composite material prepared by the high-efficiency vapor deposition process of any one of claims 1-8.

10. Use of the carbon-based composite material of claim 9 in battery electrode materials and catalysts.

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