Method for accurately regulating and controlling silicon content in silicon-carbon negative electrode material as well as product and application of silicon-carbon negative electrode material

Abstract

The invention discloses a method for accurately regulating and controlling the silicon content in a silicon-carbon negative electrode material, silicon deposition is carried out by taking porous carbon as a substrate, and the volume V of adopted silane gas meets the following formula (I): in the formula, a is a constant and is equal to M0 / (M1 * rho0), m0 is the relative molecular mass of the silane gas, M1 is the product of the relative atomic mass of silicon and the number of silicon in the molecular formula of the silane gas, and rho0 is the density of the silane gas at 0 DEG C under one standard atmospheric pressure; eta is the mass of the porous carbon substrate; x is the pore volume of the porous carbon substrate; d and x0 are constants; the invention discloses a method for accurately regulating and controlling the silicon content in a silicon-carbon negative electrode material, and provides a group of porous carbon substrate pore volume-silane dosage models, which is beneficial to assisting researchers in avoiding complicated process verification, linking substrate pore design and chemical vapor deposition process and efficiently controlling the preparation flow. Formula (I): V = 2.33 a eta X / [2.33 (d-1) X + dx0].

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, and in particular relates to a method for precisely controlling the silicon content in a silicon-carbon negative electrode material, and its products and applications. Background Art

[0002] Silicon has a theoretical specific capacity of 4200mAh / g, which is much higher than the traditional graphite negative electrode (372mAh / g), and is gradually becoming the absolute core of the next generation of lithium-ion battery negative electrodes. However, the practical application of silicon negative electrodes is limited by significant volume effects and low ion mobility. Due to the stable structure of carbon materials, silicon and carbon are often compounded to achieve the purpose of material improvement. However, the electrochemical performance of silicon-carbon materials prepared by conventional composite technology is poor. The new vapor deposition technology uses porous carbon as a substrate to promote the decomposition and deposition of silane in the pores of the substrate, and the prepared new generation of silicon-carbon negative electrode materials has better performance.

[0003] In the field of lithium-ion battery negative electrode material technology, the vapor deposition method for preparing silicon-carbon composite materials has attracted much attention due to its high specific capacity advantage. However, the coordinated regulation of porous carbon substrates and chemical vapor deposition (CVD) processes in existing technologies still faces significant technical bottlenecks. The pore size distribution and pore volume characteristics of the porous carbon substrate directly affect the diffusion and decomposition path of silane. However, in the current process, there is a lack of a quantitative correlation model between the substrate structure parameters (pore size / pore volume / porosity) and the CVD process conditions (temperature / pressure / gas flux). As a result, pore blockage, surface overload, and excess raw materials are prone to occur during silicon deposition, seriously affecting the electrochemical stability of the silicon-carbon composite structure. Existing technologies often determine the deposition endpoint by monitoring the silane concentration in the exhaust gas. Due to the gas storage effect in the closed chamber of the CVD reactor and the delayed gas diffusion (typical lag time of 30-60 seconds), the actual gas shut-off operation often lags behind the critical point by 5%-8%, still resulting in excessive silicon deposition. Excessive silicon deposition will accelerate the degradation of the material's electrochemical performance and increase the loss of silicon raw materials during the production process. Traditional methods rely on the "trial and error method" to match substrate design and process parameters. A single R&D cycle requires 8-10 batches of experimental verification, resulting in large differences in the initial effects between finished product batches, seriously restricting the yield of large-scale production.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] In response to the above problems, the present invention discloses a method for precisely controlling the silicon content in silicon-carbon negative electrode materials and proposes a set of porous carbon substrate pore volume-silane dosage models, which can help researchers avoid complicated process verification, link substrate pore design and chemical vapor deposition process, and efficiently control the preparation process.

[0006] The specific technical solutions of the present invention are as follows:

[0007] In a first aspect, the present invention provides a method for precisely controlling the silicon content in a silicon-carbon negative electrode material, wherein silicon deposition is performed on a porous carbon substrate, and the volume V of the silane gas used for silicon deposition satisfies the following formula:

[0008] V = 2.33aηX / [2.33(d-1)X+dx0] formula (I);

[0009] Where a is a constant, the unit is L / g;

[0010] a=M0 / (M1×ρ0) (II), M0 is the relative molecular mass of silane gas, M1 is the product of the relative atomic mass of silicon and the amount of silicon in the silane gas molecular formula, and ρ0 is the density of silane gas at 0°C and one standard atmospheric pressure;

[0011] η is the mass of the porous carbon substrate, in g;

[0012] X is the pore volume of the porous carbon substrate, in cm 3 / g;

[0013] d is a constant, d = -2.3 × 10 -4 T + 1.43 formula (III), T is the silicon deposition temperature;

[0014] In the present invention, d is a unitless constant, and T is the numerical portion of the silicon deposition temperature;

[0015] x0 is a constant, with a value of 1.0cm 3 / g.

[0016] The present invention proposes a method for precisely controlling the silicon content in silicon-carbon anode materials based on a quantitative coupling model of porous carbon pore volume and silane gas. By establishing a mathematical relationship between the pore characteristic parameters of the porous carbon carrier and the amount of silane gas used for pyrolysis, the theoretical calculation and process control of the silicon content in the silicon-carbon composite material are achieved. This method breaks through the limitations of the traditional trial-and-error method that relies on empirical parameters. It can accurately predict the amount of silicon deposition and optimize process parameters, thereby achieving the "one-time molding" preparation of the silicon-carbon composite. By replacing repetitive experiments with theoretical calculations, the R&D cycle is shortened and the loss rate of expensive porous carbon and silane gas is reduced.

[0017] In an optional embodiment, ρ0 is calculated by the formula ρ0=P×M0 / (R×T0), and the unit is g / L;

[0018] Wherein, P = 1 atm, R = 0.0821 L·atm / (mol·K), T0 = 273.15K.

[0019] In an optional embodiment, the porous carbon substrate satisfies at least one of the following conditions:

[0020] (1) Pore volume is selected from 0.1 to 1.5 cm 3 / g;

[0021] Optionally, the pore volume is selected from 0.2 to 1.2 cm 3 / g;

[0022] More preferably, the pore volume is selected from 0.3 to 1.0 cm 3 / g.

[0023] (2) the median particle size D50 is selected from 3 to 15 μm;

[0024] (3) The material is selected from one or more of biomass-based, resin-based, and asphalt-based;

[0025] Alternatively, the biomass base may be selected from common species such as coconut shell, rice, straw, bamboo, etc.;

[0026] Alternatively, the resin base may be selected from common types such as phenolic resin base, epoxy resin base, etc.

[0027] In an optional embodiment, the silicon deposition satisfies at least one of the following conditions:

[0028] (a) The gas source used for silicon deposition includes silane gas, an inert atmosphere, and an optionally added second gas source;

[0029] The inert atmosphere is used as a carrier gas, and optionally, is selected from inert gases such as argon and helium.

[0030] (b) the silane gas is selected from one or more of monosilane, disilane, monochlorotrihydrogen silicon, dichlorodihydrogen silicon, and trichlorosilane;

[0031] Optionally, the silane gas is selected from monosilane or disilane;

[0032] (c) the second gas source is selected from one or more of a carbon source gas, a nitrogen source gas, a sulfur source gas, and a phosphorus source gas;

[0033] Optionally, the carbon source gas is selected from alkane gases whose cracking temperature is within the carbon deposition temperature range, such as common types such as ethylene and acetylene;

[0034] Optionally, the nitrogen source gas is selected from ammonia;

[0035] Optionally, the sulfur source gas is selected from one or more of hydrogen sulfide, sulfur dioxide, and sulfur hexafluoride;

[0036] Optionally, the phosphorus source gas is selected from one or more of phosphine, phosphorus chloride, and phosphorus fluoride;

[0037] In an optional embodiment, the second gas source may be mixed with the silane gas and then co-deposited, or may be alternately deposited with the silane gas.

[0038] (d) the proportion of silane gas in the gas source is 20 to 99 vol%;

[0039] Optionally, the proportion of silane gas is 60-90 vol%.

[0040] In an optional embodiment, the gas source has a total flow rate of 1 to 100 L / min;

[0041] Optionally, the total flow rate of the gas source is 10 to 50 L / min.

[0042] (e) the silicon deposition, the deposition temperature is 400-800° C.;

[0043] In an optional embodiment, the heating rate is 1 to 10° C. / min.

[0044] In an optional embodiment, the silicon content in the prepared silicon-carbon negative electrode material is 20-60 wt %. When the silicon content is controlled within the above range, the actual value is closer to the theoretical value.

[0045] In a second aspect, the present invention further provides a silicon-carbon negative electrode material prepared according to the method, wherein the deviation between the actual silicon content and the theoretical silicon content in the silicon-carbon negative electrode material is no more than 0.7%.

[0046] Optionally, the deviation between the actual silicon content and the theoretical silicon content is no more than 0.2%.

[0047] Further optionally, the deviation between the actual silicon content and the theoretical silicon content is no more than 0.1%.

[0048] In a third aspect, the present invention further provides a negative electrode plate comprising the aforementioned silicon-carbon negative electrode material.

[0049] In a fourth aspect, the present invention further provides a secondary battery comprising the negative electrode plate.

[0050] Compared with the prior art, the present invention has the following beneficial results:

[0051] The present invention discloses a method for accurately controlling the silicon content in silicon-carbon negative electrode materials. This method accurately predicts the silicon atom accommodating capacity of a porous carbon substrate with a specific pore volume, and guides the amount of process silane gas used in the vapor deposition process. The theory is highly consistent with practice, reducing the current multiple experimental verification processes, saving a lot of time and raw material costs; and this method can effectively determine the reaction endpoint, avoiding excessive deposition caused by the hysteresis of the tail gas component determination, which affects the electrochemical properties of the silicon-carbon negative electrode material. At the same time, this method can accurately control the silicon content in the product according to actual production conditions, and realize customized synthesis of new vapor-deposited silicon-carbon materials according to actual needs. In addition, other vapor deposition processes can also refer to this method for species regulation, improve product stability between batches, improve yield rate, and effectively improve production efficiency.

[0052] The model constructed by the present invention can adapt to carbon carriers with different pore structures (mesoporous carbon, graphene aerogel, etc.), and provide a standardized control method for multi-component composite negative electrode materials prepared by vapor deposition method. DETAILED DESCRIPTION

[0053] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0054] In the description of the present invention, it should be noted that, for those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific circumstances. Below, based on the overall structure of the present invention, its embodiments are described. Unless otherwise specified, the raw materials in the embodiments of the present invention are purchased through commercial channels.

[0055] In a first aspect, the present invention provides a method for precisely controlling the silicon content in a silicon-carbon negative electrode material, wherein silicon deposition is performed on a porous carbon substrate, and the volume V of the silane gas used for silicon deposition satisfies the following formula:

[0056] V = 2.33aηX / [2.33(d-1)X+dx0] Formula (I);

[0057] Where a is a constant, the unit is L / g;

[0058] a=M0 / (M1×ρ0) (II), M0 is the relative molecular mass of silane gas, M1 is the product of the relative atomic mass of silicon and the amount of silicon in the silane gas molecular formula, and ρ0 is the density of silane gas at 0°C and one standard atmospheric pressure;

[0059] η is the mass of the porous carbon substrate, in g;

[0060] X is the pore volume of the porous carbon substrate, in cm 3 / g;

[0061] d is a constant, d = -2.3 × 10 -4 T + 1.43 formula (III), T is the silicon deposition temperature;

[0062] In the present invention, d is a unitless constant, and T is the numerical portion of the silicon deposition temperature;

[0063] x0 is a constant, with a value of 1.0cm 3 / g.

[0064] The present invention proposes a method for precisely controlling the silicon content in silicon-carbon anode materials based on a quantitative coupling model of porous carbon pore volume and silane gas. By establishing a mathematical relationship between the pore characteristic parameters of the porous carbon carrier and the amount of silane gas used for pyrolysis, the theoretical calculation and process control of the silicon content in the silicon-carbon composite material are achieved. This method breaks through the limitations of the traditional trial-and-error method that relies on empirical parameters. It can accurately predict the amount of silicon deposition and optimize process parameters, thereby achieving the "one-time molding" preparation of the silicon-carbon composite. By replacing repetitive experiments with theoretical calculations, the R&D cycle is shortened and the loss rate of expensive porous carbon and silane gas is reduced.

[0065] In an optional embodiment, ρ0 is calculated by the formula ρ0=P×M0 / (R×T0), and the unit is g / L;

[0066] Wherein, P = 1 atm, R = 0.0821 L·atm / (mol·K), T0 = 273.15K.

[0067] In an optional embodiment, the porous carbon substrate satisfies at least one of the following conditions:

[0068] (1) The pore volume X is selected from 0.1 to 1.5 cm 3 / g, specifically 0.1cm 3 / g, 0.2cm 3 / g, 0.3cm 3 / g, 0.4cm 3 / g, 0.5cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1.0cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g, 1.3cm 3 / g, 1.4cm3 / g, 1.5cm 3 / g or any value within the above range; optionally, X is selected from 0.2 to 1.2 cm 3 / g; More optionally, X is selected from 0.3 to 1.0 cm 3 / g.

[0069] (2) The median particle size D50 is selected from 3 to 15 μm; specifically, it can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 15 μm, or any value within the above range;

[0070] (3) The material is selected from one or more of biomass-based, resin-based, and asphalt-based;

[0071] Alternatively, the biomass base may be selected from common species such as coconut shell, rice, straw, bamboo, etc.;

[0072] Alternatively, the resin base may be selected from common types such as phenolic resin base, epoxy resin base, etc.

[0073] In an optional embodiment, the silicon deposition satisfies at least one of the following conditions:

[0074] (a) The gas source used for silicon deposition includes silane gas, an inert atmosphere, and an optionally added second gas source;

[0075] The inert atmosphere is used as a carrier gas, and optionally, is selected from inert gases such as argon and helium.

[0076] (b) the silane gas is selected from one or more of monosilane, disilane, monochlorotrihydrogen silicon, dichlorodihydrogen silicon, and trichlorosilane;

[0077] Optionally, the silane gas is selected from monosilane or disilane;

[0078] (c) the second gas source is selected from one or more of a carbon source gas, a nitrogen source gas, a sulfur source gas, and a phosphorus source gas;

[0079] Optionally, the carbon source gas is selected from alkane gases whose cracking temperature is within the carbon deposition temperature range, such as common types such as ethylene and acetylene;

[0080] Optionally, the nitrogen source gas is selected from ammonia;

[0081] Optionally, the sulfur source gas is selected from one or more of hydrogen sulfide, sulfur dioxide, and sulfur hexafluoride;

[0082] Optionally, the phosphorus source gas is selected from one or more of phosphine, phosphorus chloride, and phosphorus fluoride;

[0083] In an optional embodiment, the second gas source may be mixed with the silane gas and then co-deposited, or may be alternately deposited with the silane gas.

[0084] (d) The proportion of silane gas in the gas source is 20-99 vol%; specifically, it can be 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, 55 vol%, 60 vol%, 65 vol%, 70 vol%, 75 vol%, 80 vol%, 85 vol%, 90 vol%, 95 vol%, 99 vol%, or any value within the above range;

[0085] Optionally, the proportion of silane gas is 60-90 vol%.

[0086] In an optional embodiment, the total flow rate of the gas source is 1 to 100 L / min; specifically, it can be 1 L / min, 5 L / min, 10 L / min, 15 L / min, 20 L / min, 25 L / min, 30 L / min, 35 L / min, 50 L / min, 60 L / min, 70 L / min, 80 L / min, 90 L / min, 100 L / min or any value within the above range;

[0087] Optionally, the total flow rate of the gas source is 10 to 50 L / min.

[0088] (e) The silicon deposition temperature is 400-800°C; specifically, it can be 400°C, 420°C, 450°C, 480°C, 500°C, 520°C, 550°C, 580°C, 600°C, 620°C, 650°C, 680°C, 700°C, 720°C, 750°C, 780°C, 800°C or any value within the above range.

[0089] In an optional embodiment, the heating rate is 1 to 10°C / min; specifically, it can be 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min or any value within the above range.

[0090] In an optional embodiment, the silicon content in the prepared silicon-carbon negative electrode material is 20 to 60 wt%; specifically, it can be 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt% or any value within the above range; when the silicon content is controlled within the above range, the actual value is closer to the theoretical value.

[0091] In a second aspect, the present invention further provides a silicon-carbon negative electrode material prepared according to the method, wherein the deviation between the actual silicon content and the theoretical silicon content in the silicon-carbon negative electrode material is no more than 0.7%.

[0092] Optionally, the deviation between the actual silicon content and the theoretical silicon content is no more than 0.2%.

[0093] Further optionally, the deviation between the actual silicon content and the theoretical silicon content is no more than 0.1%.

[0094] In a third aspect, the present invention further provides a negative electrode plate comprising the aforementioned silicon-carbon negative electrode material.

[0095] In a fourth aspect, the present invention further provides a secondary battery comprising the negative electrode plate.

[0096] Example 1

[0097] 10 kg of coconut shell-based porous carbon (pore volume X = 0.802 cm 3 / g) as the substrate, monosilane was selected as the silane gas, and the silicon deposition temperature was selected as 450°C;

[0098] In this embodiment, M0=32, M1=28, ρ0=1.427 g / L, substituting into formula (II), we obtain constant a=0.801 L / g;

[0099] T = 450 (the numerical value of the silicon deposition temperature is taken), and substituting it into formula (III) yields the constant d = 1.3265;

[0100] Substituting a, η, X, d, and x0 into formula (I), the volume of monosilane is calculated to be 7728.9 L.

[0101] Experimental part: 10 kg coconut shell-based porous carbon (pore volume X = 0.802 cm 3 / g, D50 = 7.84μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 966.1min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0102] Example 2

[0103] The pore volume of 10 kg is 1.20 cm 3 / g coconut shell-based porous carbon was used as the substrate, and other conditions were the same as in Example 1.

[0104] After calculation, the volume of monosilane is 10000.9L.

[0105] Experimental part: 10 kg porous carbon (pore volume X = 1.20 cm 3 / g, D50 = 7.88μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 1250.1min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0106] Example 3

[0107] The pore volume of 10 kg is 1.021 cm 3 / g coconut shell-based porous carbon was used as the substrate, and other conditions were the same as in Example 1.

[0108] After calculation, the volume of monosilane is 9060.0L.

[0109] Experimental part: 10 kg porous carbon (pore volume X = 1.021 cm 3 / g, D50 = 7.91 μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80 vol% monosilane and 20 vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10 L / min and the deposition time was 1132.5 min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0110] Example 4

[0111] The pore volume of 10 kg is 0.603 cm 3 / g coconut shell-based porous carbon was used as the substrate, and other conditions were the same as in Example 1.

[0112] After calculation, the volume of monosilane is 6303.9L.

[0113] Experimental part: 10 kg porous carbon (pore volume X = 0.603 cm 3 / g, D50 = 7.78μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 788.0min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0114] Example 5

[0115] The pore volume of 10 kg is 0.398 cm 3 / g coconut shell-based porous carbon was used as the substrate, and other conditions were the same as in Example 1.

[0116] After calculation, the volume of monosilane is 4559.1L.

[0117] Experimental part: 10 kg porous carbon (pore volume X = 0.398 cm 3 / g, D50 = 7.85μm) was put into a rotary furnace, nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 569.9min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0118] Example 6

[0119] The pore volume of 10 kg is 0.202 cm 3 / g coconut shell-based porous carbon was used as the substrate, and other conditions were the same as in Example 1.

[0120] After calculation, the volume of monosilane is 2547.0L.

[0121] Experimental part: 10 kg porous carbon (pore volume X = 0.202 cm 3 / g, D50 = 7.82μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 318.4min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0122] Example 7

[0123] The pore volume of 10 kg is 0.101 cm 3 / g coconut shell-based porous carbon was used as the substrate, and other conditions were the same as in Example 1.

[0124] After calculation, the volume of monosilane is 1343.2L.

[0125] Experimental part: 10 kg porous carbon (pore volume X = 0.101 cm 3 / g, D50 = 7.84μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 167.9min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0126] Example 8

[0127] The pore volume of 10 kg is 1.498 cm 3 / g coconut shell-based porous carbon was used as the substrate, and other conditions were the same as in Example 1.

[0128] After calculation, the volume of monosilane is 11336.8L.

[0129] Experimental part: 10 kg porous carbon (pore volume X = 1.498 cm 3 / g, D50 = 7.85μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 1408.9min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0130] Example 9

[0131] The pore volume of 10 kg is 1.362 cm 3 / g coconut shell-based porous carbon was used as the substrate, and other conditions were the same as in Example 1.

[0132] After calculation, the volume of monosilane is 10758.9L.

[0133] Experimental part: 10 kg porous carbon (pore volume X = 1.362 cm 3 / g, D50 = 7.85μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 1344.9min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0134] Example 10

[0135] The temperature of silicon deposition was changed to 550° C., and other conditions were the same as those in Example 1.

[0136] After calculation, d = 1.3035; substituting into formula (I), the volume of monosilane is calculated to be 8001.5L.

[0137] Experimental part: 10 kg of porous carbon (pore volume X = 0.802 cm 3 / g, D50 = 7.84μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 550°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 1000.2min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0138] Example 11

[0139] The temperature of silicon deposition was changed to 650° C., and other conditions were the same as those in Example 1.

[0140] After calculation, d = 1.2805; substituting into formula (I), the volume of monosilane is calculated to be 8294.1 L.

[0141] Experimental part: 10 kg of porous carbon (pore volume X = 0.802 cm 3 / g, D50 = 7.84μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 650°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 1036.8min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0142] Example 12

[0143] The temperature of silicon deposition was changed to 800° C., and other conditions were the same as those in Example 1.

[0144] After calculation, d = 1.2460; substituting into formula (I), the volume of monosilane is calculated to be 8775.3 L.

[0145] Experimental part: 10 kg of porous carbon ((pore volume X = 0.802 cm 3 / g, D50=7.84μm)) was put into a rotary furnace, nitrogen was introduced and the temperature was raised to 800℃ at 5℃ / min. After keeping the temperature constant for 1h, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 1096.9min. After the deposition was completed and the temperature was kept constant for 1h, it was cooled and cooled to below 30℃, and the product was taken out under a nitrogen atmosphere.

[0146] Example 13

[0147] 10 kg of coconut shell-based porous carbon (pore volume X = 0.802 cm 3 / g) as the substrate, disilane as the silane gas, and 450°C as the silicon deposition temperature;

[0148] In this embodiment, M0=62, M1=56, ρ0=2.765g / L, substituting into formula (II), we obtain constant a=0.401L / g;

[0149] d = 1.3265;

[0150] Substituting a, η, X, d, and x0 into formula (I), the volume of disilane is calculated to be 3869.3 L.

[0151] Experimental part: 10 kg porous carbon (pore volume X = 0.802 cm 3 / g, D50 = 7.84μm) was put into a rotary furnace, nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% disilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 483.7min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0152] Example 14

[0153] The pore volume of 10 kg is 1.151 cm 3 / g of pitch-based porous carbon was used as the substrate, and other conditions were the same as in Example 1.

[0154] After calculation, the volume of monosilane is 9754.9L.

[0155] Experimental part: 10 kg porous carbon (pore volume X = 1.151 cm 3 / g, D50 = 7.75μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10L / min and the deposition time was 1219.4min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0156] Example 15

[0157] 10 kg of phenolic resin-based porous carbon (pore volume X = 0.799 cm 3 / g) as the substrate, monosilane was selected as the silane gas, and the silicon deposition temperature was selected as 450°C;

[0158] After calculation, the volume of monosilane is 7709.1L.

[0159] Experimental part: 10 kg porous carbon (pore volume X = 0.799 cm 3 / g, D50 = 7.81 μm) was placed in a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80 vol% monosilane and 20 vol% nitrogen was introduced for silicon deposition. The gas flow rate was 10 L / min and the deposition time was 963.6 min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0160] Example 16

[0161] 100 kg of coconut shell-based porous carbon (pore volume X = 0.802 cm 3 / g) as the substrate, monosilane was selected as the silane gas, and the silicon deposition temperature was selected as 450°C;

[0162] After calculation, the volume of monosilane is 77289.2L.

[0163] Experimental part: 100 kg of porous carbon (pore volume X = 0.802 cm 3 / g, D50 = 7.84μm) was put into a rotary furnace, and nitrogen was introduced and the temperature was raised to 450°C at 5°C / min. After maintaining the temperature for 1 hour, a gas source composed of 80vol% monosilane and 20vol% nitrogen was introduced for silicon deposition. The gas flow rate was 50L / min and the deposition time was 1932.2min. After the deposition was completed and the temperature was maintained for 1 hour, it was cooled and cooled to below 30°C, and the product was taken out under a nitrogen atmosphere.

[0164] Comparative Example 1

[0165] The experimental part is basically the same as that in Example 1, except that during silicon deposition, the gas flow rate is 10 L / min (80 vol% monosilane), the deposition time is 990.3 min, and the total amount of monosilane used is 7922.1 L, which is 2.5% more than the total amount of monosilane used in Example 1.

[0166] Comparative Example 2

[0167] The experimental part is basically the same as that in Example 1, except that during silicon deposition, the gas flow rate is 10 L / min (80 vol% monosilane), the deposition time is 942.0 min, and the total amount of monosilane used is 7535.7 L, which is 2.5% less than the total amount of monosilane used in Example 1.

[0168] Comparative Example 3

[0169] The experimental part is basically the same as that in Example 1, with the only difference being that during silicon deposition, the gas composition in the tail pipe is monitored. When monosilane appears in the tail pipe, the introduction of monosilane into the air inlet is stopped. At this time, the deposition time is 1006.5 min.

[0170] The products prepared in each embodiment and comparative example were tested for actual silicon content, powder resistivity, and specific surface area. In the present invention, particle size was measured using a Topsizer laser particle size analyzer, powder resistance was measured using a powder resistivity tester (20 MPa four-terminal method), pore volume and specific surface area were measured using a JW-BK100 precision high-pressure tester, and actual silicon content was measured using a TG method (Mettler Toledo TG-A2, 30-1000°C). Specific values are listed in Table 1 below.

[0171] Theoretical silicon content = m 硅 / (m 多孔碳 +m 硅 );

[0172] m 硅 = Gas source flow rate × time × silane gas volume ratio × silane gas density × (silicon molecular weight × quantity / silane gas molecular weight) × 10 -3 .

[0173] Table 1

[0174]

[0175] Comparing the data in Table 1, the test results of Examples 1-9 show that the theoretical and measured silicon contents in the silicon-carbon composites prepared using the preset process parameters of the present invention exhibit good correlation, but the actual silicon content is higher under low-end conditions and lower under high-end conditions. Example 16 demonstrates the batch application capability of this method. Furthermore, as the temperature increases (Examples 1, 10, 11, and 12), the d value gradually decreases, allowing for more silicon to be accommodated at the same pore volume.

[0176] Comparative Examples 1 and 2 still use the formula (I) disclosed in the present invention to determine the volume of silane gas, but use a slightly excessive amount of 2.5% (Comparative Example 1) and a slightly reduced amount of 2.5% (Comparative Example 2). Therefore, the deviation between the actual silicon content and the theoretical silicon content in Comparative Examples 1 and 2 is still very small. However, by comparing Example 1, Comparative Examples 1 and 2, it can be found that only a 2.5% excess of silane gas causes the powder resistance of the silicon-carbon composite to increase significantly and the specific surface area to be too low. This is due to excessive deposition of silicon on the porous carbon surface. When the amount of silane gas is reduced by 2.5%, the powder resistance of the silicon-carbon composite is less than 1Ω·cm and the specific surface area is higher, so there is still space to accommodate silicon particles and the critical point has not been reached. The above conclusions further confirm that the model disclosed in the present invention accurately predicts the silicon atom accommodation capacity of a porous carbon substrate with a specific pore volume.

[0177] Comparing Example 1 with Comparative Example 3 reveals that conventional processes exhibit hysteresis and prediction errors in determining the silane deposition endpoint, and that excessive deposition increases the resistance of the silicon-carbon composite powder. This demonstrates the superior accuracy of the model disclosed herein compared to conventional processes, resulting in simpler experiments and more accurate calculations.

[0178] The above-mentioned embodiments are preferred embodiments, but the protection scope of the present invention is not limited thereto. Ordinary technicians in this field can easily understand the spirit of the present invention based on the above-mentioned embodiments and make different extensions and changes. However, as long as they do not deviate from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A method for precisely controlling the silicon content in a silicon-carbon negative electrode material, wherein silicon is deposited on a porous carbon substrate, characterized in that: The volume V of silane gas used in silicon deposition satisfies the following formula: V = 2.33aηX / [2.33(d-1)X+dx0] formula (I); Wherein, a is a constant, a=M0 / (M1×ρ0)Formula (II), M0 is the relative molecular mass of silane gas, M1 is the product of the relative atomic mass of silicon and the amount of silicon in the silane gas molecular formula, ρ0 is the density of silane gas at 0℃ and one standard atmospheric pressure; η is the mass of the porous carbon substrate, in g; X is the pore volume of the porous carbon substrate, in cm 3 / g; d is a constant, d = -2.3 × 10 -4 T + 1.43 formula (III), T is the silicon deposition temperature; x0 is a constant, with a value of 1.0cm 3 / g.

2. The method for accurately controlling the silicon content in the silicon-carbon negative electrode material according to claim 1, characterized in that: ρ0 is calculated by the formula ρ0 = P × M0 / (R × T0) and the unit is g / L; Wherein, P = 1 atm, R = 0.0821 L·atm / (mol·K), T0 = 273.15K.

3. The method for accurately controlling the silicon content in the silicon-carbon negative electrode material according to claim 1, characterized in that: The porous carbon substrate satisfies at least one of the following conditions: (1) Pore volume is selected from 0.1 to 1.5 cm 3 / g; (2) the median particle size D50 is selected from 3 to 15 μm; (3) The material is selected from one or more of biomass-based, resin-based, and asphalt-based.

4. The method for accurately controlling the silicon content in the silicon-carbon negative electrode material according to claim 1, characterized in that: The silicon deposition satisfies at least one of the following conditions: (a) The gas source used for silicon deposition includes silane gas, an inert atmosphere, and an optionally added second gas source; (b) the silane gas is selected from one or more of monosilane, disilane, monochlorotrihydrogen silicon, dichlorodihydrogen silicon, and trichlorosilane; (c) the second gas source is selected from one or more of a carbon source gas, a nitrogen source gas, a sulfur source gas, and a phosphorus source gas; (d) the proportion of silane gas in the gas source is 20 to 99 vol%; (e) The silicon is deposited at a temperature of 400 to 800°C.

5. The method for accurately controlling the silicon content in the silicon-carbon negative electrode material according to claim 1, characterized in that: The pore volume of the porous carbon substrate is selected from 0.2 to 1.2 cm 3 / g.

6. The method for accurately controlling the silicon content in a silicon-carbon negative electrode material according to any one of claims 1 to 5, characterized in that: The silicon content is 20 to 60 wt%.

7. A silicon-carbon negative electrode material prepared by the method according to any one of claims 1 to 6, characterized in that: In the silicon-carbon negative electrode material, the deviation between the actual silicon content and the theoretical silicon content is no more than 0.7%.

8. The silicon-carbon negative electrode material according to claim 7, characterized in that In the silicon-carbon negative electrode material, the deviation between the actual silicon content and the theoretical silicon content is no more than 0.2%.

9. A negative electrode plate comprising the silicon-carbon negative electrode material according to claim 7 or 8. 10 . A secondary battery comprising the negative electrode sheet according to claim 9 .

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