In-situ pre-silicified porous carbon material as well as preparation method and application thereof

Abstract

The invention provides an in-situ pre-silicified porous carbon material as well as a preparation method and application thereof. A composite particle comprises a porous carbon matrix with a plurality of pore channels and nano silicon particles distributed on the pore walls of the pore channels. According to the porous carbon prepared by utilizing the cheap silicon-containing biomass material, the pore wall of the porous carbon contains rich nano silicon or silicon dioxide sites, so that the nucleation energy barrier in the silane chemical vapor deposition process is reduced, and the connection integrity among nano silicon particles formed by vapor deposition is improved, thereby improving the transmission capability of electrons and lithium ions and improving the performance of the lithium ion battery. And the uniformity of volume change of the silicon-carbon composite material during lithium intercalation and deintercalation is improved, so that the secondary battery obtains higher first efficiency, capacity and cycle performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and relates to an in-situ pre-silicified porous carbon material, a preparation method thereof, and an application thereof. Background Art

[0002] At present, the specific capacity performance of graphite materials is gradually approaching the theoretical value (372 mAh / g). With the continuous improvement of the requirements for the endurance of new energy vehicles, the negative electrode materials of lithium batteries are also developing towards high specific capacity. Due to its extremely high energy density (the theoretical specific capacity is 4200 mAh / g, which is 10 times that of graphite negative electrode materials), low lithium deintercalation potential, and relatively excellent safety performance, silicon-based materials are expected to become the mainstream direction for the research and development of the next generation of negative electrode materials, and thus be applied to power batteries, 3C digital products, or energy storage battery systems.

[0003] Although silicon-carbon materials have greatly improved the capacity density of negative electrode materials, they still face the negative effects brought about by a high volume expansion rate, resulting in a significant deterioration of the cycling performance.

[0004] Existing technical literature:

[0005] Chinese Patent Application CN115668545A discloses a method of filling silane gas into porous carbon to form a stable silicon-carbon composite material. Summary of the Invention

[0006] The applicant of the present invention has found through research that:

[0007] Although the structure of the silicon-carbon composite material disclosed in CN115668545A improves the stability of silicon during the lithium deintercalation and insertion process, due to the narrow pore size and the large energy barrier for the gas-phase deposition of nano-silicon particles onto the porous carbon wall, the adsorption and deposition of silane cannot uniformly penetrate the entire porous carbon particle, resulting in the non-uniform deposition of nano-silicon into the pores of the porous carbon. As a result, local non-uniform stress is generated during the lithium deintercalation and insertion process of nano-silicon, and pore volume that cannot be utilized by volume expansion is produced.

[0008] The purpose of the present invention is to provide an in-situ pre-silicified porous carbon material, a preparation method thereof, and an application thereof. The porous carbon prepared by the present invention using inexpensive silicon-containing biomass materials has a pore wall containing abundant nano-silicon, which can serve as a nucleation site during the gas-phase deposition of silane, reducing the nucleation energy barrier of silicon, thereby improving the connectivity and uniformity of nano-silicon particles in the pores, enhancing the electron and lithium-ion transport capabilities, as well as the uniformity of stress generated or released during lithium-ion deintercalation and insertion, and improving the first Coulombic efficiency, specific capacity per gram, and cycling stability of secondary batteries, etc.

[0009] To achieve the object of the present invention, the following technical solutions are adopted:

[0010] In a first aspect, the present invention provides an in-situ pre-silicified porous carbon material, which comprises a plurality of composite particles. The composite particles include a porous carbon matrix having a plurality of pores and nano-silicon particles distributed on the pore walls of the pores.

[0011] The plurality of pores in the present invention means more than one pore.

[0012] The in-situ pre-silicified porous carbon material of the present invention has a high nano-silicon content. In the composite particles of the in-situ pre-silicified porous carbon material, the nano-silicon particles exposed on the pore walls of the porous carbon matrix can serve as nucleation sites during the vapor deposition of silane. These nano-silicon particles uniformly distributed on the pore walls of the porous carbon matrix can reduce the nucleation energy barrier of Si during silane deposition. Especially in dendritic narrow pores where it is difficult for silane to penetrate, the amount of Si deposited from silane is significantly increased, thereby improving the uniformity of the distribution of Si in the pores of the silicon-carbon material.

[0013] Preferably, the pores include micropores and / or mesopores.

[0014] In the present invention, according to the definition of the International Union of Pure and Applied Chemistry (IUPAC), micropores refer to pores with a pore diameter less than 2 nanometers, and mesopores refer to pores with a pore diameter in the range of 2 - 50 nm.

[0015] Preferably, at least part of the nano-silicon particles are attached to and / or embedded in the pore walls of the porous carbon matrix, and at least a part of the nano-silicon particles attached to and / or embedded in the pore walls of the porous carbon matrix are exposed on the pore walls of the porous carbon matrix.

[0016] Since the nano-silicon particles are attached to and / or embedded in the pore walls of the porous carbon, on the one hand, these existing nano-silicon particles have a rougher surface, which can reduce the nucleation energy barrier of nano-silicon during the vapor deposition of silicon; on the other hand, due to the crystal form selectivity of the vapor deposition precursor for the substrate to be deposited, the same crystal form can reduce the energy barrier for the epitaxial growth of the deposit to be formed. Therefore, in the gas-phase reaction, silicon is more likely to deposit on the surface of the existing nano-silicon.

[0017] Preferably, the particle size of the nano-silicon particles is 0.5 - 20 nm, for example: 0.5 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, 5 nm, 10 nm, 15 nm or 20 nm, etc.

[0018] The particle size of the nano-silicon particles in the present invention is not limited to the above range, and can be larger or smaller, and can be adjusted according to actual needs.

[0019] Preferably, in the in-situ pre-silicided porous carbon material, the mass fraction of the nano-silicon particles > 1%, preferably 5-20%. For example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0020] Preferably, the nano-silicon particles include amorphous silicon and / or crystalline silicon.

[0021] Preferably, the porous carbon matrix includes any one or a combination of at least two of hard carbon, soft carbon or graphite.

[0022] As is well known to those skilled in the art, hard carbon refers to carbon that is difficult to graphitize. Such carbon is difficult to graphitize even at high temperatures above 2500 °C; soft carbon refers to carbon that is easy to graphitize. Such carbon can be graphitized at high temperatures above 2500 °C.

[0023] Preferably, the microporosity of the in-situ pre-silicided porous carbon material is 30-100%, for example: 30%, 40%, 50%, 70%, 80%, 85%, 90%, 95%, 98% or 100%, etc.

[0024] Preferably, the specific surface area of the in-situ pre-silicided porous carbon material is 1000-2500 m 2 / g, for example: 1000 m 2 / g, 1500 m 2 / g, 1800 m 2 / g, 2000 m 2 / g or 2500 m 2 / g, etc.

[0025] Preferably, the pore volume of the in-situ pre-silicided porous carbon material is 0.5-1.2 cm 3 / g, for example: 0.5 cm 3 / g, 0.6 cm 3 / g, 0.8 cm 3 / g, 1 cm 3 / g or 1.2 cm 3 / g, etc.

[0026] In a second aspect, the present invention provides a method for preparing the in-situ pre-silicided porous carbon material as described in the first aspect, and the preparation method includes the following steps:

[0027] After carbonizing and activating the silicon-containing carbon source, a silicon-containing porous carbon intermediate is obtained;

[0028] Reducing silicon in the silicon-containing porous carbon intermediate to obtain the in-situ pre-silicided porous carbon material.

[0029] The present invention prepares a silicon-containing porous carbon intermediate by using a silicon-containing carbon source, in which silicon-containing particles are uniformly present in the pore walls of the porous carbon, and a composite in-situ pre-silicified porous carbon material can be obtained after reduction.

[0030] The porous carbon prepared by the present invention using a silicon-containing carbon source has pore walls containing abundant nano-silicon or silica sites, which reduces the nucleation energy barrier during the silane chemical vapor deposition process, improves the connection integrity between nano-silicon particles formed by vapor deposition, thereby improving the electron and lithium-ion transport capabilities, and improving the uniformity of volume change during lithium insertion and extraction of the silicon-carbon composite material, so that the secondary battery can obtain higher initial efficiency, capacity and cycle performance.

[0031] Preferably, the silicon-containing carbon source is rice husk, and / or herbaceous plant stems and leaves, and / or wheat husk, and / or oat husk, and / or straw, and / or bagasse, preferably rice husk.

[0032] The present invention uses low-cost biomass materials as the silicon-containing carbon source, which can reduce the cost of mass production of materials and is conducive to the industrial development of materials. In addition, since the biomass carbon source itself contains silicon and the silicon element is relatively uniformly distributed inside, the obtained porous carbon pore walls contain more silicon nucleation sites, thereby improving the uniformity of silicon distribution in the silicon-carbon product. This improvement in uniformity can greatly optimize the stress distribution generated inside the particles during lithium insertion and extraction, thereby maximizing the reduction of material expansion and at the same time improving the cycle performance of the material.

[0033] Preferably, the carbonization temperature is 700-1500 °C, for example: 700 °C, 900 °C, 1000 °C, 1200 °C or 1500 °C, etc.

[0034] Preferably, the carbonization time is 1-20 h, for example: 1 h, 5 h, 10 h, 15 h or 20 h, etc.

[0035] Preferably, the carbonization atmosphere includes argon.

[0036] Preferably, pulverization treatment is carried out after carbonization.

[0037] Preferably, the activation method includes alkali activation and / or gas activation.

[0038] Preferably, the activator for alkali activation includes potassium hydroxide.

[0039] Preferably, the mass ratio of the activator used for alkali activation to the material obtained by carbonization is 1:(1-3), for example: 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, etc.

[0040] Preferably, the atmosphere for alkali activation includes argon.

[0041] Preferably, the activation gas for the gas activation includes water vapor and carbon dioxide.

[0042] Preferably, the flow rate of the activation gas for the gas activation is 0.5 - 1 L / min, for example: 0.5 L / min, 0.6 L / min, 0.8 L / min, 0.9 L / min or 1 L / min, etc.

[0043] Preferably, the activation temperature is 600 - 900 °C, for example: 600 °C, 650 °C, 700 °C, 800 °C or 900 °C, etc.

[0044] Preferably, the activation time is 1 - 3 h, for example: 1 h, 1.5 h, 2 h, 2.5 h or 3 h, etc.

[0045] Preferably, after the activation, the obtained silicon-containing porous carbon powder is washed with water until the pH is 6.7 - 7.5, for example: 6.7, 6.8, 7, 7.2 or 7.5, etc.

[0046] Through further pore formation by using alkali or gas activation in the present invention, silicon and silicon dioxide can be uniformly distributed on the pore walls, and most of these silicon exists in the form of silicon dioxide after carbonization.

[0047] Preferably, the reduction method of the silicon includes magnesiothermic reduction. Other methods can also be used for the reduction of silicon.

[0048] Preferably, the molar ratio of metallic magnesium to silicon element in the silicon-containing porous carbon used for the magnesiothermic reduction is 1:(0.5 - 0.7), for example: 1:0.5, 1:0.55, 1:0.6, 1:0.645 or 1:0.7, etc.

[0049] Preferably, the temperature of the magnesiothermic reduction is 450 - 550 °C, for example: 450 °C, 485 °C, 500 °C, 520 °C or 550 °C, etc.

[0050] Preferably, the atmosphere of the magnesiothermic reduction includes nitrogen.

[0051] Preferably, acid etching treatment is carried out after the reduction of the silicon.

[0052] Preferably, the acid solution used for the acid etching treatment includes hydrochloric acid and hydrofluoric acid.

[0053] Preferably, the mass ratio of hydrochloric acid to hydrofluoric acid is (3 - 5):1, for example: 3:1, 3.5:1, 4:1, 4.5:1 or 5:1, etc.

[0054] Preferably, the concentration of the acid solution is 1 - 5 mol / L, for example: 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, etc.

[0055] Preferably, after the acid etching treatment, the obtained in-situ pre-silicified porous carbon material is washed with water until the pH is 6.7 to 7.5, for example: 6.7, 6.8, 7, 7.2 or 7.5, etc.

[0056] Preferably, after the water washing, pulverization and crushing treatments are carried out.

[0057] In a third aspect, the present invention provides a silicon-carbon negative electrode material, the silicon-carbon negative electrode material includes a first silicon-carbon negative electrode material, and the first silicon-carbon negative electrode material includes the in-situ pre-silicified porous carbon material as described in the first aspect and a filling silicon material located inside the pores of the porous carbon matrix of the in-situ pre-silicified porous carbon material.

[0058] Preferably, the unit specific surface silicon infiltration into pores of the silicon-carbon negative electrode material is 0.4 to 0.6 g / m 2 , for example: 0.4 g / m 2 , 0.5 g / m 2 , 0.6 g / m 2 , etc.

[0059] The present invention reflects the amount of nano-silicon captured / infiltrated by the pore walls of porous carbon per unit surface area through the unit specific surface silicon infiltration into pores. According to the decreased specific surface area of the porous carbon before and after silicon deposition, the pore wall area participating in adsorption can be deduced. Further, the unit specific surface silicon infiltration into pores can normalize and compare porous carbons with different pore volumes and pore structures, thereby reflecting the difference in the nano-silicon capture / infiltration ability of the same pore wall area. The higher this value, the more nano-silicon is infiltrated under the same pore wall area. Generally, the unit specific surface silicon infiltration into pores of CVD silicon-carbon materials < 0.4 g / m 2 , and the unit specific surface silicon infiltration into pores of the silicon-carbon material prepared by using silicon-containing porous carbon in the present invention can reach 0.4 to 0.6 g / m 2 , significantly improving the density of nano-silicon captured / infiltrated by the porous carbon, thereby optimizing the uniformity of the distribution of nano-silicon in the pores of the porous carbon, optimizing the slow-release effect of the volume expansion / contraction stress during the lithium insertion / extraction process of nano-silicon, improving the cycling performance of the material, and the calculation formula is as follows:

[0060] Unit specific surface silicon infiltration into pores (g / m 2 ) = Compaction density of the first silicon-carbon negative electrode material powder (g / cm 3 ) × Pore volume of the in-situ pre-silicified porous carbon material (cm 3 / g) ÷ [BET specific surface area of the in-situ pre-silicified porous carbon material (m 2 / g) - BET specific surface area of the first silicon-carbon negative electrode material (m 2 / g)] × 1000.

[0061] Among them, for porous carbon with similar pore volume and specific surface area, the present invention uses the product of the tap density of the obtained silicon-carbon material and the pore volume (the tap density of the first silicon-carbon negative electrode material powder (g / cm 3 ) × the pore volume of the in-situ pre-silicified porous carbon material (cm 3 / g)) to also reflect the filling amount of Si particles in the pores of the porous carbon during the gas-phase silicon infiltration process, and its trend is consistent with the silicon infiltration amount per unit specific surface area into the pores.

[0062] The silicon-carbon negative electrode material prepared by the present invention has a higher silicon infiltration amount per unit specific surface area of the filled silicon material, indicating that under the same pore volume, more silicon can be accommodated in the pores of the silicon-containing porous carbon. For porous carbon with similar pore volumes and relatively close and low BET values of the silicon-carbon material prepared after silicon deposition, it can be theoretically considered that the pores of the porous carbon have been filled with Si. The higher this value, the more Si particles are deposited in the pores under the same pore volume of the porous carbon, indicating that the distribution of Si on the pore walls of the porous carbon is more uniform, enabling the secondary battery using the above silicon-carbon negative electrode material to have good initial Coulomb efficiency, specific capacity, and cycle stability, etc.

[0063] When the specific surface area of the silicon-carbon material is close, it can be considered that the pores of the porous carbon have been filled to a similar state, and the tap density of the silicon-carbon material prepared from the Si-containing porous carbon is higher, indicating fewer internal pores. Multiplying the tap density (density) by the pore volume (volume) of the porous carbon gives a quantifiable mass value, which can be used to compare the silicon increment during the gas-phase silicon infiltration stage under similar pore volumes. An increase in this quantity indicates that Si is more fully filled in the pores, with better contact and a more uniform bulk phase.

[0064] Preferably, the silicon content of the silicon-carbon negative electrode material is 20-70%, such as: 20%, 30%, 50%, 60% or 70%, etc.

[0065] Preferably, the tap density of the silicon-carbon negative electrode material is 1.1-1.4 g / cm 3 , such as: 1.1 g / cm 3 , 1.2 g / cm 3 , 1.4 g / cm 3 , etc.

[0066] Preferably, the silicon-carbon negative electrode material further includes coated carbon, and the coated carbon coats the porous carbon matrix containing the first silicon-carbon negative electrode material and the filled silicon material. By using coated carbon in the present invention, the electronic conductivity of the silicon-carbon material can be increased, and the rate performance can be improved. In addition, the carbon coating layer inhibits the exposure of silicon and avoids the occurrence of gas generation during battery processing. Preferably, the coated carbon is amorphous carbon.

[0067] Preferably, the content of the coated carbon in the silicon-carbon negative electrode material is 1-4 wt%, such as: 1 wt%, 1.5 wt%, 2 wt%, 3 wt% or 4 wt%, etc.

[0068] In a fourth aspect, the present invention provides a method for preparing the silicon-carbon anode material as described in the third aspect, and the preparation method includes the following steps:

[0069] The in-situ pre-silicided porous carbon material is subjected to a first vapor deposition treatment using a silicon-source-containing gas to obtain the silicon-carbon anode material.

[0070] Preferably, the silicon-source-containing gas includes silane and / or disilane, and / or trichlorosilane, and / or dichlorosilane, and / or propylsilane, and / or trichlorosilane, and / or silicon chloride, etc. In some embodiments, a silicon source that is a liquid at room temperature can participate in the reaction in the form of vapor. In some embodiments, the silicon-source-containing gas may further contain an inert gas such as argon or other gases.

[0071] Preferably, the concentration of silane in the silicon-source-containing gas is 10-50%, for example: 10%, 20%, 30%, 40% or 50%, etc.

[0072] Preferably, the temperature of the first vapor deposition treatment is 380-485 °C, for example: 380 °C, 400 °C, 420 °C, 450 °C or 485 °C, etc.

[0073] Preferably, the time of the first vapor deposition treatment is 1-5 h, for example: 1 h, 2 h, 3 h, 4 h or 5 h, etc.

[0074] Preferably, the rotary furnace rotation speed of the first vapor deposition is 20-100 s / circle, for example: 20 s / circle, 40 s / circle, 60 s / circle, 80 s / circle or 100 s / circle, etc.

[0075] Preferably, after the first vapor deposition treatment, a second vapor deposition treatment is continued using a carbon-source-containing gas.

[0076] Preferably, the carbon-source-containing gas includes acetylene, and / or methane, and / or propylene, and / or ethylene, and / or toluene, and / or benzene, and / or ethanol. In some embodiments, a carbon source that is a liquid at room temperature can participate in the reaction in the form of vapor. In some embodiments, the carbon-source-containing gas may further contain an inert gas such as argon.

[0077] Preferably, the concentration of acetylene in the carbon-source-containing gas is 30-50%, for example: 30%, 35%, 40%, 45% or 50%, etc.

[0078] Preferably, the temperature of the second vapor deposition treatment is 500-800 °C, for example: 500 °C, 550 °C, 600 °C, 700 °C or 800 °C, etc.

[0079] Preferably, the time of the second vapor deposition treatment is 1 to 3 h, such as: 1 h, 1.5 h, 2 h, 2.5 h, or 3 h, etc.

[0080] Preferably, the converter rotation speed of the second vapor deposition is 20 to 100 s / circle, such as: 20 s / circle, 40 s / circle, 60 s / circle, 80 s / circle, or 100 s / circle, etc.

[0081] In a fifth aspect, the present invention provides a lithium-ion battery, which includes the in-situ pre-silicified porous carbon material as described in the first aspect, and / or the silicon-carbon negative electrode material as described in the third aspect.

[0082] Compared with the prior art, the present invention has the following beneficial effects:

[0083] (1) The present invention uses a silicon-containing biomass material to prepare silicon-containing pores. After further activating the pores with an alkali or gas, silicon and silicon dioxide are uniformly distributed on the pore walls. After carbonization, most of these silicons exist in the form of silicon dioxide. By further thermal reduction, an in-situ pre-silicified porous carbon material is obtained. The silicon uniformly distributed on the pore walls of the porous carbon can reduce the nucleation energy barrier of Si during silane deposition. Especially in dendritic narrow pores where silane is difficult to penetrate, the amount of Si deposited by silane is significantly increased, thereby improving the uniformity of the distribution of Si in the pores of the silicon-carbon material.

[0084] (2) The present invention uses inexpensive biomass materials, which can reduce the cost of mass production of materials and is conducive to the industrial development of materials. The preparation method is simple, suitable for large-scale production in batches. Moreover, during the initial stage of the gas-phase silicon infiltration process of the porous carbon prepared from the silicon-containing biomass, the tail gas silane concentration value is lower than 100 ppm, while the tail gas silane concentration of conventional porous carbon can reach more than 10,000 ppm, and even silane spontaneous combustion occurs. Therefore, this process has better environmental friendliness.

[0085] (3) The silicon content of the in-situ pre-silicified porous carbon material of the present invention can reach more than 9.2%, the silicon content of the prepared silicon-carbon negative electrode material can reach more than 48.4%, the tap density can reach more than 1.15 g / cm 3 above, the unit specific surface silicon infiltration into pores can reach more than 0.45 m2 / g, the first efficiency of the battery at 1.5 V can reach more than 91.5%, the capacity at 1.5 V can reach more than 1939 mAh / g, and the 50-cycle retention rate can reach more than 91.06%. Description of the Drawings

[0086] Figure 1 is a scanning electron microscope image of the in-situ pre-silicified porous carbon material described in Example 1.

[0087] Figure 2 is an elemental silicon analysis diagram of the in-situ pre-silicified porous carbon material described in Example 1.

[0088] Figure 3 It is the XRD pattern of the silicon-carbon negative electrode material described in Example 1.

[0089] Figure 4 It is the SEM image of the cross-section slice of the silicon-carbon composite material described in Example 1.

[0090] Figure 5 It is the SEM image of the cross-section slice of the silicon-carbon composite material described in Comparative Example 1.

[0091] Figure 6 It is the SEM image of the cross-section slice of the silicon-carbon composite material described in Comparative Example 2.

[0092] Figure 7 It is the cyclic performance graph of the button battery of the silicon-carbon negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-2. Detailed Embodiments

[0093] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0094] Example 1

[0095] This example provides a silicon-carbon negative electrode material, and the silicon-carbon negative electrode material is prepared by the following method:

[0096] (1) Under an Ar atmosphere, 500 g of rice husks are carbonized at a heating rate of 10 °C / min and held at 900 °C for 3 h, with an Ar flow rate of 1 L / min; the carbonized biomass material is pulverized in a planetary ball mill at a rotation speed of 300 rpm for 20 min to obtain a carbonized powder; 200 g of the carbonized powder is activated at 700 °C for 1 h, during which CO2 is introduced at a flow rate of 0.5 L / min. After activation, the obtained silicon-containing porous carbon powder is washed with water until the pH is 6.7-7.5 to obtain a silicon-containing porous carbon intermediate;

[0097] (2) Add 8 g of magnesium powder (the molar ratio of magnesium powder to silicon in the silicon-containing porous carbon intermediate is 1:0.6) (purity 99.0%) to 50 g of the silicon-containing porous carbon intermediate, place it in a rotary furnace, heat it to 500 °C at a rate of 5 °C / min, hold for 5 h, and during this period, the N2 flow rate is 1 L / min. Add the powder obtained in the previous step to 1000 mL of a mixed solution of hydrochloric acid and hydrofluoric acid, where the mass ratio of hydrochloric acid to hydrofluoric acid is 3:1, and the concentration of the mixed acid is 3 mol / L. During the pickling process, use a stirrer at 80 rpm to stir it for 2 h. After pickling, use a large amount of deionized water to filter the powder material by suction until the pH of the filtrate is within the range of 6.7 - 7.5. Dry it in a vacuum drying oven at 80 °C for 24 h, pulverize and crush it in a planetary ball mill at a rotation speed of 200 - 500 rpm for 5 - 30 min. After passing through a 500-mesh sieve, an in-situ pre-silicated porous carbon material is obtained. In the in-situ pre-silicated porous carbon material, the mass fraction of nano-silicon particles is 9.5%, the microporosity of the in-situ pre-silicated porous carbon material is 85%, and the scanning electron micrograph of the in-situ pre-silicated porous carbon material is as shown in Figure 1 shown, and the elemental silicon analysis diagram is as shown in Figure 2 shown. It can be seen from Figure 1-2 that obvious Si element distribution is detected in the material, and the distribution is relatively uniform.

[0098] (3) Take 40 g of the in-situ pre-silicated porous carbon material and place it in a rotary furnace. After heating it to 400 °C at a rate of 5 °C / min, introduce a mixed gas of silane with a volume fraction of 30% (the diluent gas is argon), and the rotary furnace rotates at a speed of 20 s / rotation and holds for 2 h; the silane content in the tail gas after the introduction of silane gas in this stage is 89 - 102 ppm. After the holding ends, turn off the silane gas, and after maintaining for 30 min, the rotary furnace is heated to 600 °C at a rate of 5 °C / min, introduce a mixed gas of acetylene with a volume fraction of 30% (the diluent gas is argon), and the rotary furnace rotates at a speed of 20 s / rotation and holds for 1 h to obtain the silicon-carbon negative electrode material.

[0099] The XRD diagram of the silicon-carbon negative electrode material is as shown in Figure 3 shown. It can be seen from Figure 3 that obvious amorphous silicon peaks are shown in the material after silicon filling. Due to a large amount of non-conductive Si in the bulk phase after silicon infiltration in the porous carbon material, the powder section becomes bright white. Therefore, the distribution uniformity of Si can be judged by observing the distribution of this bright white.

[0100] The SEM diagram of the cross-section slice of the silicon-carbon composite material is as shown in Figure 4 shown. It can be seen from Figure 4 that the cross-section of the silicon-carbon composite material particles of the present invention shows uniform bright white, indicating that the vapor-deposited nano-silicon particles are uniformly dispersed in the bulk phase.

[0101] Example 2

[0102] This embodiment provides a silicon-carbon anode material, which is prepared by the following method:

[0103] (1) 500 g of rice husks are carbonized in an Ar atmosphere at a heating rate of 10 °C / min and held at 700 °C for 20 h, with an Ar flow rate of 1 L / min; the carbonized biomass material is pulverized in a planetary ball mill at a speed of 400 rpm for 15 min to obtain the carbonized powder; 200 g of the carbonized powder is dry-mixed with 80 g of KOH, and the mixed material is activated at 600 °C for 3 h, during which an Ar flow rate of 1 L / min is passed. The activated Si-containing porous carbon is washed with a large amount of deionized water until the pH is in the range of 6.7 - 7.5 to obtain the Si-containing porous carbon intermediate;

[0104] (2) 50 g of the Si-containing porous carbon intermediate is added with 8 g of magnesium powder (purity 99.0%) (the molar ratio of magnesium powder to silicon in the Si-containing porous carbon intermediate is 1:0.5), and placed in a rotary furnace and heated to 450 °C at a rate of 5 °C / min and held for 5 h, with an N2 flow rate of 1 L / min during this period. The powder obtained in the previous step is added to a 1000 mL mixed solution of hydrochloric acid and hydrofluoric acid, where the mass ratio of hydrochloric acid to hydrofluoric acid is 5:1 and the concentration of the mixed acid is 5 mol / L. During the pickling process, a stirrer with a speed of 80 rpm is used to stir it for 2 h. After pickling, the powder material is filtered with a large amount of deionized water until the pH of the filtrate is in the range of 6.7 - 7.5, dried in a vacuum drying oven at 80 °C for 24 h, pulverized and crushed in a planetary ball mill at a speed of 200 - 500 rpm for 5 - 30 min, and passed through a 500-mesh sieve to obtain the in-situ pre-silicided porous carbon material. In the in-situ pre-silicided porous carbon material, the mass fraction of nano-silicon particles is 10.3%, and the microporosity of the in-situ pre-silicided porous carbon material is 86%;

[0105] (3) 40 g of the in-situ pre-silicided porous carbon material is placed in a rotary furnace, heated to 280 °C at a rate of 5 °C / min, and then a mixed gas of silane with a volume fraction of 50% (the diluent gas is argon) is introduced. The rotary furnace rotates at a speed of 100 s / turn and is held for 5 h; the silane content in the tail gas after the silane gas is introduced in this stage is 98 - 113 ppm. After the holding is completed, the silane gas is turned off, and after maintaining for 30 min, the rotary furnace is heated to 500 °C at a rate of 5 °C / min, and a mixed gas of acetylene with a volume fraction of 50% (the diluent gas is argon) is introduced. The rotary furnace rotates at a speed of 100 s / turn and is held for 3 h to obtain the silicon-carbon anode material.

[0106] Example 3

[0107] This embodiment provides a silicon-carbon anode material, which is prepared by the following method:

[0108] (1) Carbonize 500 g of rice husk in an Ar atmosphere at a heating rate of 10 °C / min and hold at 1500 °C for 1 h, with an Ar flow rate of 1 L / min; pulverize the carbonized biomass material in a planetary ball mill at a rotation speed of 300 rpm for 20 min to obtain a carbonized powder; take 200 g of the carbonized powder and activate it at 900 °C for 1 h, during which a water vapor flow rate of 1 L / min is introduced. After activation, wash the obtained silicon-containing porous carbon powder with water until the pH is 6.7 - 7.5 to obtain a silicon-containing porous carbon intermediate;

[0109] (2) Add 8 g of magnesium powder (the molar ratio of magnesium powder to silicon in the silicon-containing porous carbon intermediate is 1:0.7) (purity 99.0%) to 50 g of the silicon-containing porous carbon intermediate, place it in a rotary furnace and heat it to 480 °C at a rate of 5 °C / min, hold for 5 h, with an N2 flow rate of 1 L / min during this period. Add the powder obtained in the previous step to 1000 mL of a mixed solution of hydrochloric acid and hydrofluoric acid, where the mass ratio of hydrochloric acid to hydrofluoric acid is 5:1 and the concentration of the mixed acid is 1 mol / L. Stir the mixture with a stirrer at 80 rpm for 2 h during the pickling process. After pickling, filter the powder material with a large amount of deionized water until the pH of the filtrate is within the range of 6.7 - 7.5, dry it in a vacuum drying oven at 80 °C for 24 h, pulverize and crush it in a planetary ball mill at a rotation speed of 200 - 500 rpm for 5 - 30 min, and obtain an in-situ pre-silicified porous carbon material after passing through a 500-mesh sieve. In the in-situ pre-silicified porous carbon material, the mass fraction of nano-silicon particles is 9.2%, and the microporosity of the in-situ pre-silicified porous carbon material is 85%;

[0110] (3) Take 40 g of the in-situ pre-silicified porous carbon material and place it in a rotary furnace. After heating to 485 °C at a rate of 5 °C / min, introduce a mixed gas of silane with a volume fraction of 10% (the diluent gas is argon), and rotate the furnace at a speed of 50 s / turn and hold for 1 h; the silane content in the tail gas after the introduction of silane gas in this stage is 89 - 102 ppm. After the holding is completed, turn off the silane gas, and after maintaining for 30 min, heat the rotary furnace to 800 °C at a rate of 5 °C / min, introduce a mixed gas of acetylene with a volume fraction of 10% (the diluent gas is argon), rotate the furnace at a speed of 50 s / turn and hold for 1 h to obtain the silicon-carbon negative electrode material.

[0111] Example 4

[0112] The difference between this example and Example 1 is only that the activation temperature is 500 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0113] Example 5

[0114] The difference between this example and Example 1 is only that the activation temperature is 1000 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0115] Example 6

[0116] The difference between this example and Example 1 is only that the temperature of the first vapor deposition treatment in step (3) is 350 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0117] Example 7

[0118] The difference between this example and Example 1 is only that the temperature of the first vapor deposition treatment in step (3) is 500 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0119] Example 8

[0120] The difference between this example and Example 1 is only that the temperature of the second vapor deposition treatment in step (3) is 450 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0121] Example 9

[0122] The difference between this example and Example 1 is only that the temperature of the second vapor deposition treatment in step (3) is 1000 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0123] Example 10

[0124] The difference between this example and Example 1 is only that the second vapor deposition treatment (no carbon source deposition) is not carried out in step (3), and other conditions and parameters are exactly the same as those in Example 1.

[0125] Example 11

[0126] The difference between this example and Example 1 is only that the activation time in step (1) becomes 2 h, the time for introducing the silane mixed gas in step (3) becomes 1.5 h, and the time for introducing the acetylene mixed gas becomes 1.5 h, and other conditions and parameters are exactly the same as those in Example 1.

[0127] Comparative Example 1

[0128] This comparative example provides a silicon-carbon negative electrode material, which is prepared by the following method:

[0129] (1) Purchase porous carbon with a pore volume and pore distribution similar to those of the Si-containing porous carbon in Examples 1-3 above from the market. The silicon content of this porous carbon measured by ICP is only 356 ppm. Take 40 g of Si-free porous carbon powder and 10 g of KOH for dry mixing, and activate the mixed material at 700 °C for 1 h, with an Ar flow rate of 1 L / min during this period. Wash the activated Si-containing porous carbon with a large amount of deionized water until the pH is in the range of 6.7-7.5;

[0130] (2) Take 40 g of Si-containing porous carbon and place it in a rotary furnace. After heating it to 400 °C at a rate of 5 °C / min, introduce a mixed gas of silane with a volume fraction of 30% (the diluent gas is argon). The rotary furnace rotates at a speed of 20 s / turn and keeps the temperature for 2 h. During this stage, the tail gas catches fire after the silane gas is introduced, and the silane concentration is greater than 10,000 ppm. After the heat preservation is completed, turn off the silane gas and keep it for 30 min. Then, the rotary furnace is heated to 600 °C at a rate of 5 °C / min, and a mixed gas of acetylene with a volume fraction of 30% (the diluent gas is argon) is introduced. The rotary furnace rotates at a speed of 20 s / turn and keeps the temperature for 1 h to obtain the silicon-carbon negative electrode material. The SEM image of the cross-section slice of the silicon-carbon negative electrode material is as shown in Figure 5 shown. Compared with Example 1, there is a phenomenon that the whole or part of the silicon-carbon particles obtained in this comparative example are dark, and the nano-silicon particles deposited on the surface are not evenly dispersed in the powder matrix phase.

[0131] Comparative Example 2

[0132] This comparative example provides a silicon-carbon negative electrode material, which is prepared by the following method:

[0133] (1) Take 40 g of the Si-free porous carbon powder used in Comparative Example 1 and mix it with 10 g of KOH by dry mixing. Activate the mixed material at 700 °C for 1 h, and introduce Ar at a flow rate of 1 L / min during this period. Wash the activated Si-containing porous carbon with a large amount of deionized water until the pH is in the range of 6.7 - 7.5;

[0134] (2) Take 40 g of Si-containing porous carbon and place it in a rotary furnace. After heating it to 400 °C at a rate of 5 °C / min, introduce a mixed gas of silane with a volume fraction of 30% (the diluent gas is argon). The rotary furnace rotates at a speed of 20 s / turn and keeps the temperature for 2.5 h. During this stage, the tail gas catches fire after the silane gas is introduced, and the silane concentration is greater than 10,000 ppm. After the heat preservation is completed, turn off the silane gas and keep it for 30 min. Then, the rotary furnace is heated to 600 °C at a rate of 5 °C / min, and a mixed gas of acetylene with a volume fraction of 30% (the diluent gas is argon) is introduced. The rotary furnace rotates at a speed of 20 s / turn and keeps the temperature for 1 h to obtain the silicon-carbon negative electrode material. The SEM image of the cross-section slice of the silicon-carbon negative electrode material is as shown in Figure 6 shown. It can be seen from Figure 6 that there is a bright white edge at the boundary of the silicon-carbon negative electrode material particles obtained in this comparative example, indicating that Si particles are excessively deposited on the particle surface. This part of the Si on the surface quickly falls off from the particle surface after lithium deintercalation / insertion, reducing the initial efficiency of the silicon-carbon material and the cycle retention rate lower than that of Comparative Example 1.

[0135] Test method:

[0136] 1. Specific surface area and pore volume test

[0137] The BET and pore volume measurements (BET-SSA) for determining the specific surface area of the particles were carried out in accordance with DIN ISO 9277:2010. Measurements were performed using a NOVA 3000 (from Quantachrome), which operates according to the Sorption Method with Adaptive dosing Rate (SMART method). As for the reference materials, Quantachrome alumina SARM catalog number 2001 (13.92 m 2 / g, based on the multi-point BFT method) and SARM catalog number 2004 (214.15 m 2 / g, based on the multi-point BET method), both available from Quantachrome, were used. To reduce the dead volume, packing rods were added to the reference test tube and the sample test tube. The test tubes were installed on the BET equipment. The saturated vapor pressure of nitrogen (N2 4.0) was measured. A certain amount of the sample was weighed into a glass test tube such that the test tube containing the packing rod was completely filled and the minimum dead volume was generated. To dry the sample, the sample was held under vacuum at 200 °C for 1 hour. After cooling, the sample weight was recorded. The glass test tube containing the sample was installed on the measuring equipment. To degas the sample, it was evacuated at a selected pumping speed such that no material was sucked into the pump, reaching a final pressure of 10 mbar.

[0138] 2. Silicon content test

[0139] The silicon content was determined by roasting the silicon carbide material in a thermogravimetric analyzer at 1000 °C in air for 1 hour to completely oxidize the carbon and convert the silicon completely into silicon dioxide, and then converting the silicon content in the silicon carbide material using the increased weight of oxygen.

[0140] Specifically as follows:

[0141] (1) Weigh about 2 g of the silicon carbide material, and record the actual mass as m0; place it in a crucible with a mass of m1;

[0142] (2) Put the crucible into a tube furnace or a muffle furnace, continuously pass compressed air, heat it to 600 °C at a rate of 10 °C / min, hold for 1 hour, and then heat it to 1000 °C at the same rate and hold for 1 hour;

[0143] (3) After naturally cooling to room temperature, take out the crucible and weigh the mass as m2;

[0144] (4) Calculate the Si content Si% = (m2 - m0) * MSi / MSiO2 / m1 * 100%; where, MSiO2* is the relative molecular mass of SiO2, 60.084 g / mol; MSi is the relative molecular mass of Si, 28.0855 g / mol.

[0145] 3. Powder tap density test of silicon-carbon anode material (volumetric method):

[0146] Use a microcomputer-controlled electronic compressive testing machine (model UTM7305) for testing. Weigh the powder of the required mass and put it into the container for volume testing. Perform the compaction operation with a mechanical press, and use a pressure of 5 tons. Record the volume data after compaction, and calculate the compaction density of the powder by dividing the powder mass by the volume. Repeat the above operations, and obtain the average value as the final test result.

[0147] 4. Unit specific surface silicon infiltration pore volume

[0148] This index reflects the amount of nanosilicon deposited on the pore walls of porous carbon per unit surface area. The higher this value, the more nanosilicon infiltrates under the same pore wall area. The calculation formula is as follows:

[0149] Unit specific surface silicon infiltration pore volume (g / m 2 ) = Compaction density of silicon-carbon anode material powder (g / cm 3 ) × Pore volume of porous carbon (cm 3 / g) ÷ [BET of in-situ pre-silicified porous carbon material (m 2 / g) - BET of carbon-coated silicon-carbon material (m 2 / g)]} × 1000.

[0150] Test the BET, pore volume, silicon content of silicon-carbon materials, and compaction density of powders of the materials prepared in the test examples and comparative examples. The test results are shown in Table 1:

[0151] Table 1

[0152]

[0153]

[0154] Mix the silicon-carbon anode materials prepared in the examples and comparative examples according to the mass ratio of silicon-carbon composite material (negative electrode active material): polyacrylic acid resin (PAA): single-walled carbon nanotube (CNT): conductive carbon black (SP) of 82:7:1:10. Make it into a slurry with deionized water, evenly coat it on the copper foil, and vacuum dry it at 80°C for 24 hours to obtain the experimental battery electrode sheet. Then, use a lithium sheet as the counter electrode, use an electrolyte of 1.1 mol / L LiPF6, the solvent is a four-component mixed solvent, ethylene carbonate (EC): vinylene carbonate (VC): dimethyl carbonate (DMC): fluoroethylene carbonate (FEC) = 1:1:1:1, use a polypropylene microporous film as the separator, and assemble it into a CR2025 type button half-cell in a vacuum glove box. Use a battery testing system (half-cell test: American Arbin multi-channel battery testing system, German Braun company Labstar (1200 / 780) type glove box) to test the capacity, first charge-discharge efficiency (first efficiency), and cycle retention rate. The test results are shown in Table 2.

[0155] Charge and discharge steps of each example and comparative example

[0156] In the first cycle, it is discharged at a constant current of 0.1C to 5mV, then discharged at a constant current of 0.02C to 5mV, and charged at a constant current of 0.1C to 2V. The cycle retention rate test steps are as follows: in the first to third cycles, the first cycle steps are used; in the fourth to 50th cycles, it is discharged at a constant current of 0.3C to 5mV, then discharged at a constant current of 0.02C to 5mV, and charged at a constant current of 0.5C to 2V.

[0157] Table 2

[0158] Initial efficiency at 1.5V (%) Capacity at 1.5V (mAh / g) Retention rate after 50 cycles (%) Example 1 91.8 1955 92.17 Example 2 91.5 1939 91.06 Example 3 91.6 1951 92.36 Example 4 90.7 1910 91.08 Example 5 91.2 1932 91.21 Example 6 90.3 1821 91.01 Example 7 91.3 1935 90.87 Example 8 91.5 1898 90.89 Example 9 90.3 1910 90.10 Example 10 90.2 1933 90.21 Example 11 92.5 2126 90.25 Comparative Example 1 89.6 1587 88.99 Comparative Example 2 90.3 1721 81.52

[0159] It can be seen from Tables 1-2 that, from Examples 1-3, for the in-situ pre-silicided porous carbon material of the present invention, the silicon content can reach more than 9.2%, the silicon content of the prepared silicon-carbon negative electrode material can reach more than 48.4%, and the tap density can reach 1.15 g / cm 3 or more, and the silicon infiltration amount per unit specific surface area into pores can reach 0.45 g / m 2 or more. The first efficiency at 1.5V of the fabricated battery can reach more than 91.5%, the capacity at 1.5V can reach more than 1939 mAh / g, and the 50-cycle retention rate can reach more than 91.06%.

[0160] By comparing Example 1 with Examples 4-5, it can be obtained that during the preparation process of the silicon-carbon negative electrode material of the present invention, the activation temperature will affect the properties of the prepared in-situ pre-silicided porous carbon material, and thus affect the performance of the silicon-carbon negative electrode material. When the activation temperature is controlled at 600-900°C, the performance of the prepared silicon-carbon negative electrode material is better. If the activation temperature is too high, the interlayer spacing of the porous carbon will be reduced, and the lithium-ion conductivity will be decreased. If the activation temperature is too low, the electronic conductivity will be lower, both of which will deteriorate the material performance to a certain extent.

[0161] By comparing Example 1 with Examples 6-7, it can be obtained that during the preparation process of the silicon-carbon negative electrode material of the present invention, the temperature of the first vapor deposition treatment will affect the performance of the prepared silicon-carbon negative electrode material. When the temperature of the first vapor deposition treatment is controlled at 380-485°C, the performance of the prepared silicon-carbon negative electrode material is better. If the temperature of the first vapor deposition treatment is too high, a silicon-carbon material with a higher penetration control amount cannot be obtained, resulting in the deterioration of the material cycle. If the temperature is too low, the silane will not be completely decomposed, and the silicon content and capacity will decrease.

[0162] Comparing Example 1 with Examples 8-9, it can be obtained that during the preparation process of the silicon-carbon anode material of the present invention, the temperature of the second vapor deposition treatment will affect the performance of the obtained silicon-carbon anode material. Controlling the temperature of the second vapor deposition treatment at 500-800 °C can obtain a silicon-carbon anode material with better performance. If the temperature of the second vapor deposition treatment is too high, silicon carbide will be produced, reducing the initial efficiency of the material capacity. If it is too low, it will lead to lower electronic conductivity and deteriorate the cycle of the material.

[0163] Comparing Example 1 with Example 10, it can be obtained that by re-depositing carbon on the silicon-carbon anode material through the second vapor deposition in the present invention, the electronic conductivity of the silicon-carbon material can be increased, and the rate performance can be improved. In addition, the carbon coating layer inhibits the exposure of silicon and avoids the occurrence of gas generation during battery processing.

[0164] Comparing Example 1 with Example 11, it can be obtained that by prolonging the activation time of the porous carbon, the pore volume and specific surface area of the silicon-containing porous carbon can be increased, and a higher tap density and silicon content can be obtained in the first silicon-carbon anode material. The silicon infiltration amount per unit specific surface area of the corresponding first silicon-carbon anode material is increased to 0.56 g / m 2 , but the increase in pore volume leads to a reduction in the carbon matrix of the silicon-carbon material, causing a certain degree of attenuation in the cycle performance of the final silicon-carbon anode material.

[0165] The silicon infiltration amount per unit specific surface area can reflect the content of nano-silicon that can be captured / infiltrated by the pore walls with the same specific surface area. According to the decreased specific surface area before and after silicon deposition on the porous carbon, the area of the pore walls participating in adsorption can be calculated. Further, the silicon infiltration amount per unit specific surface area can normalize and compare porous carbons with different pore volumes and pore structures, thereby reflecting the difference in the nano-silicon capture / infiltration ability of the same pore wall area. The silicon infiltration amount per unit specific surface area of the silicon-containing porous carbon in Examples 1-3 can reach 0.45. In Examples 4-9, due to the change of process conditions, the porous carbon lost part of its nano-silicon capture / infiltration ability. However, compared with Comparative Examples 1-2, the silicon-containing porous carbon still shows a silicon infiltration amount per unit specific surface area of not less than 0.42 due to the introduction of silicon nucleation sites, which means that the distribution of nano-silicon in the silicon-carbon product is more uniform, with less silicon-rich surface, and the corresponding cycle performance is significantly improved.

[0166] The coin cell cycle performance diagrams of the silicon-carbon anode materials prepared in Examples 1-3 and Comparative Examples 1-2 are as Figure 7As shown in the figure, by comparing Example 1 with Comparative Examples 1-2, it can be obtained that the silicon-carbon material prepared using the in-situ pre-silicified porous carbon material of the present invention has a higher cycle retention rate. In Comparative Example 1, since there is no silicon in the porous carbon, the Si content in the obtained silicon-carbon material is low, and the gas-phase deposited Si particles are uneven, resulting in significantly lower capacity, initial efficiency, and cycle retention rate of the material compared to Examples 1-3. In Comparative Example 2, the amount of gas-phase deposited Si was increased, making the silicon-carbon material reach a level similar to that of Examples 1-3, but most of this increased Si exists on the particle surface and not in the pores.

[0167] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. An in-situ pre-silicified porous carbon material, comprising a plurality of composite particles, characterized in that, The composite particles include a porous carbon matrix having a plurality of pores and nano-silicon particles distributed on the pore walls of the pores.

2. The in-situ pre-silicified porous carbon material according to claim 1, wherein The pores include micropores and / or mesopores; and / or, at least part of the nano-silicon particles are attached to and / or embedded in the pore walls of the porous carbon matrix, and at least a part of the nano-silicon particles attached to and / or embedded in the pore walls of the porous carbon matrix are exposed to the pore walls of the porous carbon matrix; and / or, the particle size of the nano-silicon particles is 0.5 - 20 nm; and / or, in the in-situ pre-silicified porous carbon material, the mass fraction of nano-silicon particles > 1%, preferably 5 - 20%; and / or, the nano-silicon particles include amorphous silicon and / or crystalline silicon; and / or, the porous carbon matrix includes any one or a combination of at least two of hard carbon, soft carbon or graphite; and / or, the microporosity of the in-situ pre-silicified porous carbon material is 30 - 100%; and / or, the specific surface area of the in-situ pre-silicified porous carbon material is 1000-2500 m 2 / g; and / or, the pore volume of the in-situ pre-silicified porous carbon material is 0.5 to 1.2 cm 3 / g.

3. A method for preparing the in-situ pre-silicified porous carbon material as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: After carbonizing and activating a silicon-containing carbon source, a silicon-containing porous carbon intermediate is obtained; Reducing silicon in the silicon-containing porous carbon intermediate to obtain the in-situ pre-silicified porous carbon material.

4. The preparation method according to claim 3, characterized in that, The silicon-containing carbon source is rice husk, and / or herbaceous plant stems and leaves, and / or wheat husk, and / or oat husk, and / or straw, and / or bagasse, preferably rice husk; and / or, the temperature of the carbonization is 700 - 1500 °C; and / or, the time of the carbonization is 1 - 20 h; and / or, the atmosphere of the carbonization includes argon; and / or, pulverization treatment is performed after the carbonization; and / or, the activation method includes alkali activation and / or gas activation; and / or, the activator for the alkali activation includes potassium hydroxide; and / or, the mass ratio of the activator used for the alkali activation to the material obtained by carbonization is 1:(1 - 3); and / or, the atmosphere of the alkali activation includes argon; and / or, the activation gas for the gas activation includes water vapor and carbon dioxide; and / or, the flow rate of the activation gas for the gas activation is 0.5 - 1 L / min; and / or, the temperature of the activation is 600 - 900 °C; and / or, the time of the activation is 1 - 3 h; and / or, after the activation, the obtained silicon-containing porous carbon powder is washed with water until the pH is 6.7 - 7.

5.

5. The preparation method according to claim 3 or 4, characterized in that, The method for reducing silicon includes magnesiothermic reduction; and / or, the molar ratio of metallic magnesium used for the magnesiothermic reduction to silicon elements in the silicon-containing porous carbon intermediate is 1:(0.5 - 0.7); and / or, the temperature of the magnesiothermic reduction is 450 - 550 °C; and / or, the atmosphere of the magnesiothermic reduction includes nitrogen; and / or, acid etching treatment is performed after the reduction of silicon; and / or, the acid solution used for the acid etching treatment includes hydrochloric acid and hydrofluoric acid; and / or, the mass ratio of hydrochloric acid to hydrofluoric acid is (3 - 5):1; and / or, the concentration of the acid solution is 1 - 5 mol / L; and / or, after the acid etching treatment, the obtained in-situ pre-silicified porous carbon material is washed with water until the pH is 6.7 - 7.5; and / or, pulverization and crushing treatment are performed after the water washing.

6. A silicon-carbon negative electrode material, characterized in that, The silicon-carbon negative electrode material includes a first silicon-carbon negative electrode material, and the first silicon-carbon negative electrode material includes the in-situ pre-silicided porous carbon material as described in Claim 1 or 2 and a filled silicon material located inside the pores of the porous carbon matrix of the in-situ pre-silicided porous carbon material.

7. The silicon-carbon anode material according to claim 6, characterized in that, The silicon penetration amount per unit specific surface area of the silicon-carbon negative electrode material is 0.4 to 0.6 g / m 2 ; And / or, the silicon content of the silicon-carbon negative electrode material is 20-70%; And / or, the tap density of the silicon-carbon negative electrode material is 1.1 to 1.4 g / cm 3 ; And / or, the silicon-carbon negative electrode material further includes a coated carbon, and the coated carbon coats the porous carbon matrix of the first silicon-carbon negative electrode material and the filled silicon material; Preferably, the content of the coated carbon in the silicon-carbon negative electrode material is 1-4 wt%.

8. A method for preparing the silicon-carbon anode material according to claim 6 or 7, characterized in that, The preparation method includes the following steps: Performing a first vapor deposition treatment on the in-situ pre-silicided porous carbon material with a silicon source-containing gas to obtain the silicon-carbon negative electrode material.

9. The preparation method according to claim 8, characterized in that, The silicon source-containing gas includes silane, and / or disilane, and / or trichlorosilane, and / or dichlorosilane, and / or propylsilane, and / or trichlorosilane, and / or silicon chloride; And / or, the concentration of silane in the silicon source-containing gas is 10-50%; And / or, the temperature of the first vapor deposition treatment is 380-485 °C; And / or, the time of the first vapor deposition treatment is 1-5 h; And / or, the converter rotation speed of the first vapor deposition is 20-100 s / circle; Preferably, after the first vapor deposition treatment, a second vapor deposition treatment is continued with a carbon source-containing gas; And / or, the carbon source-containing gas includes acetylene, and / or methane, and / or propylene, and / or ethylene, and / or toluene, and / or benzene, and / or ethanol; And / or, the concentration of acetylene in the carbon source-containing gas is 30-50%; And / or, the temperature of the second vapor deposition treatment is 500-800 °C; And / or, the time of the second vapor deposition treatment is 1-3 h; And / or, the converter rotation speed of the second vapor deposition is 20-100 s / circle.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the in-situ pre-silicided porous carbon material as described in Claim 1 or 2, and / or the silicon-carbon negative electrode material as described in Claim 6 or 7.

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