Preparation method for preparing carbon-based silicon composite negative electrode material and double-cone rotary fluidization device

Abstract

The invention discloses a preparation method for preparing a carbon-based silicon composite negative electrode material and a double-cone rotary fluidization device, and relates to the technical field of powder material preparation and modification. According to the invention, the double-cone cavity is taken as a core and is matched with the precise temperature control module, the five groups of gas supply pipelines, the temperature control module, the tail gas detection system and the temperature sensor, five-link continuous treatment of a carbonization stage, an activation stage, a silicon deposition stage, a carbon coating stage and an ALD passivation stage is realized under the condition of a single temperature zone, and pollution and loss caused by material transfer are avoided. The single-temperature-zone powder treatment system provided by the invention is simplified in structure, controllable in cost, stable in performance and compatible with five-link continuous treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder material preparation and modification, and particularly relates to a preparation method of a carbon-based silicon composite negative electrode material and a double-torus rotating fluidization device, which is used for realizing five processes of carbonization, activation, silicon deposition, carbon coating and ALD passivation of the carbon-based silicon composite negative electrode material under single-temperature-zone conditions. BACKGROUND

[0002] The preparation of existing powder materials (such as carbon-based silicon composite negative electrodes) needs to be completed in multiple steps by multiple devices: (1) carbonization of biomass / resin raw materials in a tube furnace; (2) pore creation of the carbonization product by transferring it to an activation furnace (CO2 / H2O is passed through); (3) deposition of silicon (such as pyrolysis of silane) on the activated carbon in a fluidized bed; (4) carbon coating of the silicon-carbon composite in another CVD device; and (5) deposition of a passivation film (such as Al2O3) in an ALD device. The multi-step process has three major problems: (1) multiple transfers of the material result in pollution (such as air oxidation) and loss (transfer residual rate ≤ 90%); (2) the process parameters (temperature, atmosphere) of each device are incompatible, and repeated heating / cooling (such as 800℃ for carbonization and 300℃ for ALD) is required, resulting in high energy consumption; and (3) there is a lack of dynamic layering control, the powder easily agglomerates in the carbonization / activation stage, and the coating uniformity is poor in the silicon deposition / carbon coating / ALD stage, resulting in large fluctuations in product performance.

[0003] Existing single-temperature-zone powder processing devices (such as single-temperature-zone tube furnaces and single-temperature-zone fixed beds) can only complete a single process, and cannot realize five consecutive processes; if an "heating - cooling" alternating mode is used to adapt to different process temperature requirements, the problems of high energy consumption, cross-contamination of atmospheres, and poor coating uniformity will reappear. Therefore, a single-temperature-zone powder processing system that is simple in structure, controllable in cost, and compatible with five consecutive processes needs to be developed.

[0004] In addition, during the pyrolysis of silane, porous carbon has a wide range of applications in energy storage, electrochemistry, and electrocatalysis due to its high specific surface area and hierarchical pore structure. The micropores (<2 nm) in the porous carbon can provide a large number of active sites, but too fast clogging during the deposition process can hinder the transmission of the reaction gas to the interior, thereby affecting the uniform filling of the pores.

[0005] The common methods for introducing silane mainly include: (1) Continuous silane input under positive pressure: maintain a positive pressure condition (e.g. 1-3 bar) in the reaction chamber, input a high-speed fluidization gas flow to suspend the porous carbon particles, and continuously input silane at a set temperature until the reaction is completed. No vacuum pumping is performed during the entire process. This method is mainly aimed at uniform deposition on the surface of macroscopic particles in a fluidized state. However, the deposition rate at the micropore inlet is fast, the gas penetration is limited under positive pressure, and a blocking layer is easily formed, resulting in insufficient deposition of internal micropores and mesopores, which is not suitable for obtaining a high filling rate of a structure mainly composed of micropores and supplemented by mesopores.

[0006] (2) Uniformly input silane under negative pressure: divide the total silane gas amount into several batches, and pump the vacuum to 0.01-1.0 torr after the completion of each batch reaction to discharge the residual gas and by-products, and then input the next batch. This method can alleviate micropore blockage and improve filling uniformity, but the batch gas amount is fixed, the initial blockage is still significant, and the total number of batches is relatively large. SUMMARY

[0007] To solve the problems of multiple preparation procedures, easy loss of materials during transfer between procedures, high energy consumption, and poor uniformity of deposited silicon, coated carbon, and ALD coating of the current carbon-based silicon composite negative electrode material, in a first aspect, the present application provides a method for preparing a carbon-based silicon composite negative electrode material, comprising the following steps: loading biomass raw materials into the double-cone cavity and replacing the gas in the double-cone cavity with nitrogen / argon; increasing the temperature of the double-cone cavity to 600-800℃, continuously inputting nitrogen / argon into the double-cone cavity to start the carbonization stage, and completing the carbonization when the differential electrochemical mass spectrometer detects that the volatile organic compounds in the tail gas discharged from the double-cone cavity are ≤0.1wt%; increasing the temperature of the double-cone cavity to 850-900℃, inputting CO2 / H2O into the double-cone cavity in a pulse flow control mode to start the activation stage, and ending the activation stage when the line particle size instrument detects that the specific surface area of the particulate matter in the tail gas reaches a set value; cooling the temperature of the double-cone cavity to 350-450℃, supplying nitrogen / argon to the double-cone cavity after purging, starting the silicon deposition stage, and performing multiple batches in three stages under negative pressure, inputting a mixed gas containing silane to deposit Si, setting the amount of substance of silane input in each batch and the total amount of silane input in each stage according to the stage, the mixed gas input in each batch also containing an inert gas, the mass of the inert gas input in each batch being half of that of the silane, heating and maintaining pressure, pumping the vacuum to the initial pressure of 0.01-0.05 torr after the completion of each batch, and ending the silicon deposition stage when the set silane is completely input; The temperature of the double-cone cavity is reduced to 300-350℃, nitrogen / argon is supplied to the double-cone cavity to blow the main gas channel, the carbon coating stage is started, the double-cone cavity is supplied with a mixed gas containing acetylene and nitrogen, and the carbon coating time is 1-2h; The temperature of the double-cone cavity is reduced to 200℃, nitrogen / argon is supplied to the double-cone cavity to blow the main gas channel, the ALD passivation stage is started, trimethylaluminum and water vapor and nitrogen / argon are alternately supplied to the double-cone cavity, until the differential electrochemical mass spectrometer reaches the particle content in the exhaust gas to end the ALD passivation stage; The double-cone cavity is flipped at a set frequency during the carbonization stage, the activation stage, the silicon deposition stage, the carbon coating stage, and the ALD passivation stage, and the gas is supplied to the double-cone cavity in a direction perpendicular to the gravity drop and the exhaust gas is detected in real time.

[0008] Further, in the silicon deposition stage, the total mass of the silane supplied is 98%-102% of the mass of the porous carbon material after the activation stage, and the three stages include a preliminary stage, an intermediate stage, and a later stage. In the preliminary stage, the pressure in the reaction chamber after the mixed gas is cracked in each batch is not more than 0.5 atm, and the mass of the silane supplied in the preliminary stage is not more than 20% of the total mass of the silane. In the intermediate stage, the pressure in the reaction chamber after the mixed gas is cracked in each batch is not more than 1.5 atm, and the mass of the silane supplied in the intermediate stage is 70-90% of the total mass of the silane. In the later stage, the pressure in the reaction chamber after the mixed gas is cracked in each batch is not more than 3.0 atm, and the mass of the silane supplied in the later stage is 5-10% of the total mass of the silane.

[0009] Further, the set frequency is 1-2 times / min.

[0010] In a second aspect, the present application provides a double-cone rotating fluidization device for preparing a carbon-based silicon composite negative electrode material, comprising a double-cone cavity, five sets of gas supply pipelines, a temperature control module, an exhaust gas detection system, and a temperature sensor. The double-cone cavity comprises a fluidization chamber, a deposition tank, and a gas guide pipe. The fluidization chamber is a columnar box body with open upper and lower ends. A sedimentation channel penetrates through the upper and lower end faces of the columnar box body. Two bowl-shaped sedimentation tanks have their bowl openings facing the sedimentation channel and symmetrically closing the two ends of the sedimentation channel, respectively. Two coaxial gas guide pipes are connected to the outside of the fluidization chamber in a central and symmetrical manner. One of the two gas guide pipes is connected to a fluidization gas supply system for delivering fluidization gas containing precursor reaction gas into the fluidization chamber. The other gas guide pipe is sequentially connected to the exhaust gas detection system and a vacuum pump for discharging reaction exhaust gas. Both of the two gas guide pipes are controlled by a rotating mechanism to realize periodic flipping of the fluidization chamber. A stirrer is arranged in the double-cone cavity. One end of a sedimentation tank away from the bowl opening is provided with a driving mechanism and a vacuum sealed feeding port. The driving mechanism is pivotally connected to the stirrer. A discharge valve is installed on the conical surface of the other sedimentation tank. Resistance heating wires are arranged on the outside of the double-cone cavity. The carbonization stage, the activation stage, the silicon deposition stage, the carbon coating stage and the ALD passivation stage are supplied with gas through five groups of gas supply pipelines, i.e., a carbonization gas pipeline, an activation gas pipeline, a silicon deposition gas pipeline, a carbon coating gas pipeline and an ALD gas pipeline. The temperature control module adjusts the power of the resistance heating wire according to the temperature target values set for different process stages. The tail gas detection system comprises a laser particle size analyzer, a gas chromatograph-mass spectrometer and a differential electrochemical mass spectrometer. Temperature sensors are distributed at different positions of the double-cone cavity.

[0011] Further, the five groups of gas supply pipelines are connected to a main gas channel, and each is provided with an electromagnetic reversing valve.

[0012] Further, the discharge valve is provided with multiple grading screening components with a pore size range of 50-200 microns.

[0013] Further, the stirrer is composed of a stirring rod and spiral stirring blades.

[0014] The method for preparing the carbon-based silicon composite negative electrode material can be used in the technical field of preparation and modification of carbon-based silicon composite negative electrodes, functional ceramic powders and various high-performance powder materials.

[0015] Compared with the prior art, the present application has the following advantages: (1) Simplified structure and reduced cost: The single-temperature-zone design eliminates the need for heat insulation sealing and independent heating modules in the multi-temperature-zone system, and the device volume is reduced by 40-50% and the manufacturing cost is reduced by 30-40%.

[0016] (2) Energy consumption optimization: Precise temperature control and time-sequential gas source switching avoid repeated temperature rising and falling of multiple devices, and the total energy consumption is reduced by 25-35% compared with the traditional step-by-step process and by 10-15% compared with the multi-temperature-zone system.

[0017] (3) Dynamic sorting and stable performance: double-tapered rotary stirring sorting design solves the problem of powder agglomeration (agglomeration rate ≤5%), ALD coating layer thickness deviation is controlled within ±1nm, product cycle life deviation is reduced from ±15% to ±8%, and yield is improved to more than 90%.

[0018] (4) Safety compatibility and flexible adaptation: multi-gas path safety design (leak detection, low-temperature insulation, purging) meets industrial safety standards, and can be adapted to carbon-based silicon composite anodes, functional ceramic powders and other high-performance powder preparations by adjusting process parameters. When the equipment is scaled up, only the cavity diameter needs to be increased to increase the loading capacity, without the need to replace the core components.

[0019] (5) Compared with continuous gas feeding under positive pressure and uniform batch feeding under negative pressure, the present application can significantly improve the filling rate of micropores and mesopores by negative pressure driving and adding stage feeding to delay plugging. The process parameters in the present application can be quickly predicted by the model, reducing trial and error. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A double-tapered rotary fluidization device for preparing a carbon-based silicon composite anode material; Figure 2 A gas supply pipeline schematic diagram of the double-tapered rotary fluidization device for preparing a carbon-based silicon composite anode material; Figure 3 A gas supply pipeline schematic diagram of the double-tapered rotary fluidization device for preparing a carbon-based silicon composite anode material; Figure 4 A scanning electron microscope image of the three-stage negative pressure coated block porous carbon in Example 2 under different magnifications; Figure 5 A energy spectrum analysis image of the three-stage coated block porous carbon in Example 2. DETAILED DESCRIPTION

[0021] To make the purpose, technical scheme and advantages of the present application clearer and more apparent, the following embodiments will be further described in detail. The specific embodiments described herein are only used to explain the present application and do not limit the application.

[0022] Example 1 The present embodiment provides a double-tapered rotary fluidization device for preparing a carbon-based silicon composite anode material, comprising: Reversible double-tapered cavity: such as Figure 1As shown, the reversible double-cone cavity includes a fluidization chamber 1, a deposition tank 2, and a gas guide pipe 5. The fluidization chamber 1 is a cylindrical box with open upper and lower ends. The settling channel penetrates the upper and lower end faces of the cylindrical box. The bowl mouths of the two bowl-shaped settling tanks 2 face the settling channel and symmetrically close the two ends of the settling channel, respectively. The two coaxial gas guide pipes 5 are connected to the outside of the fluidization chamber 1 symmetrically in the middle to form a reversible double-cone cavity. One gas guide pipe 5 is connected to the fluidization gas supply system for conveying fluidization gas containing precursor reaction gas into the fluidization chamber 1. The other gas guide pipe 5 is connected to the tail gas detection system and vacuum pump in sequence for discharging reaction tail gas. The connection parts of the gas guide pipe 5 and the fluidization chamber 1 are uniformly arranged with uniform flow holes 6 (pore size 2-3 mm) to ensure that the gas enters the settling channel uniformly. The two gas guide pipes 5 are controlled by a rotating mechanism to realize periodic rotation of the fluidization chamber 1 (rotation angle 30° each time, frequency 2 r / min) to assist axial transportation and particle size separation of the material. After rotation, the large-particle-size material preferentially settles in the lower deposition tank due to the fast settling speed, reducing the contact opportunity with the precursor gas. The small-particle-size material is suspended in the fluidization gas for continuous reaction until the standard is met, realizing accurate separation of “reaction degree-particle size”. During rotation, the material is gradually transported from the feeding end to the discharging end, further enhancing the dispersibility of the material and reducing agglomeration. The stirrer is arranged in the double-cone cavity. One end of the bowl of the other settling tank 2 is provided with a driving mechanism 4 and a vacuum-sealed feeding port. The driving mechanism 4 is pivotally connected to the stirrer 8. The conical surface of the other settling tank 2 is provided with a discharge valve 7 and a detachable quartz lining 6 mm. The discharge valve 7 can be arranged at different heights on the conical surface of the settling tank 2 for discharging powder particles at different depths in the settling tank 2. When the settling tank 2 rotates to the upper position with the fluidization chamber 1, the discharge valve 7 is also used to load the powder particles. The stirrer 8 is composed of a stirring rod and a spiral stirring blade. The stirrer can lift the material with large particle size at the bottom of the deposition tank to the upper part, while making the material with small particle size at the upper part flow to the bottom, thereby shortening the settling time of the large-particle-size material and prolonging the fluidization reaction time of the small-particle-size material.

[0023] The double-cone cavity adopts a double-cone 304 stainless steel cavity structure. The outer side of the double-cone cavity is arranged with resistance heating wires, which are wrapped with a heat preservation cotton composite structure. The heating power of the resistance heating wires is 10 kW, the temperature control range is 150-950℃, and the heating layer has a temperature control accuracy of ±3℃.

[0024] Gas supply pipeline: as Figures 2-3As shown, the five groups of gas supply lines include carbonization gas line 11 (nitrogen / argon is supplied in continuous flow control mode during the carbonization stage), activation gas line 12 (CO2 / H2O is supplied in pulse flow control mode during the activation stage), silicon deposition gas line 13 (mixed gas containing silane and inert gas is supplied in stages based on flow closed-loop control during the silicon deposition stage), carbon coating gas line 14 (mixed gas containing acetylene and nitrogen is supplied in continuous flow control mode during the carbon coating stage), and ALD gas line 15 (trimethylaluminum and water vapor are supplied in pulse flow control mode during the ALD passivation stage); the five groups of gas supply lines are connected to main gas channel 16, and each is provided with an electromagnetic reversing valve group, and the end of main gas channel 16 extends to gas guide pipe 5; among them, silicon deposition gas line 13 is provided with a leak detection sensor with a response time ≤1 s; ALD gas line 15 is provided with a low-temperature insulation jacket, and the temperature is controlled at 20-30 ℃; in addition to carbonization gas line 11, each group of gas supply lines is provided with a check valve and an emergency shut-off valve; before switching the gas supply line, the main gas channel is purged for 30-60 s through the general carbonization gas line 11 to prevent cross contamination. The general carbonization gas line 11 supplies inert gases such as nitrogen or argon, and the constant pressure control is 0.1-0.2 Mpa.

[0025] The temperature control module automatically adjusts the power of the resistance heating wire according to the temperature target value set for different process stages using the "PID + fuzzy control" algorithm. When the double-cone cavity is in the carbonization stage, the resistance heating wire increases the power to raise the temperature of the double-cone cavity to 600-800℃. When the double-cone cavity is in the activation stage, the resistance heating wire increases the power to raise the temperature of the double-cone cavity to 850-900℃. When the double-cone cavity is in the silicon deposition stage, the resistance heating wire reduces the power to lower the temperature of the double-cone cavity to 350-450℃. When the double-cone cavity is in the carbon coating stage, the resistance heating wire reduces the power to lower the temperature of the double-cone cavity to 300-350℃. When the double-cone cavity is in the ALD passivation stage, the resistance heating wire reduces the power to lower the temperature of the double-cone cavity to 200-250℃. The temperature control module is linked with the electromagnetic reversing valve group of the gas supply line to ensure that the temperature of the double-cone cavity reaches the temperature target value of the selected process stage before starting the corresponding gas supply line, avoiding side reactions caused by mismatch between temperature and gas supply line.

[0026] The tail gas detection system includes a linearity particle size analyzer, a gas chromatograph-mass spectrometer, and a differential electrochemical mass spectrometer. The linearity particle size analyzer is used to monitor the particle size of the material in real time with an accuracy of ±5 μm. The gas chromatograph-mass spectrometer is used to monitor the atmosphere composition in the double-cone cavity to prevent the accumulation of impurity gases. The differential electrochemical mass spectrometer is used to monitor the reaction tail gas to judge the reaction progress.

[0027] Temperature sensors are distributed at different positions of the double-cone cavity to provide real-time feedback of temperature data. All monitoring data are transmitted to the central control system to achieve closed-loop control of process parameters.

[0028] The installation of the discharge valve 7 at different heights outside the settling tank 2 is provided with a grading screen assembly (using a screen with adjustable aperture, aperture 100 μm), which can screen qualified materials according to the particle size requirements of the ALD passivation stage, and the unqualified materials are returned to the cavity through the reflux pipe for reprocessing.

[0029] Example 2 Based on the double-cone rotary fluidized device of Example 1, the present embodiment provides a method for preparing a carbon-based silicon composite negative electrode material, comprising the following steps: The double-cone cavity is filled with biomass raw materials, and the gas in the double-cone cavity is replaced with nitrogen / argon; The temperature of the double-cone cavity is increased to 600-800℃, the carbonization gas path 11 supplies nitrogen / argon to the double-cone cavity at a flow rate of 500-1000sccm, and the double-cone cavity is flipped at a frequency of 2 times / min to start the carbonization stage. When the differential electrochemical mass spectrometer detects that the volatile organic compounds in the tail gas are ≤0.1wt%, the carbonization is completed, and the carbonization time is 1-2h; The temperature of the double-cone cavity is increased to 850-900℃, the activation gas path 12 supplies CO2 / H2O in a pulse flow control mode at a flow rate of 300sccm, and the pulse interval is 10s. The double-cone cavity is flipped at a frequency of 2 times / min to start the activation stage. When the line particle size instrument detects that the specific surface area of the particulate matter in the tail gas reaches 1500-1800m 2 / g, the activation stage is ended, and the time is 0.5-1h; The temperature of the double-cone cavity is decreased to 350-450℃, and the carbonization gas path 11 supplies nitrogen / argon to the double-cone cavity for 30-60s of purging. Then, the deposition of silicon stage is started. The vacuum pump evacuates the double-cone cavity to 0.01-0.05torr. Under negative pressure, multiple batches of mixed gas containing silane are introduced to deposit Si in three stages. The amount of silane introduced in each batch and the total amount of silane introduced in each stage are set according to the stage. Each batch of mixed gas also contains an inert gas, and the mass of the inert gas introduced in each batch is half of the mass of the silane. Each batch is heated and pressure-maintained for reaction. After each batch is reacted, the vacuum is pumped to the initial pressure of 0.01-0.05torr. The double-cone cavity is flipped at a frequency of 1r / min. When the silane is completely introduced, the deposition of silicon stage is terminated, and the silicon deposition time is 2-3h; The temperature of the double-cone cavity is decreased to 300-350℃, and the carbonization gas path 11 supplies nitrogen / argon to the double-cone cavity for 30-60s of purging of the main gas path. Then, the carbon coating stage is started. The carbon coating gas path 14 supplies a mixed gas containing acetylene and nitrogen to the double-cone cavity. The flow rate of acetylene is 300-800sccm. The double-cone cavity is flipped at a frequency of 1.5 times / min. The carbon coating time is 1-2h; The temperature of the double-cone cavity is reduced to 200°C, and the carbonization gas path 11 supplies nitrogen / argon to the double-cone cavity for 30-60 s to purge the main gas channel 30, and then the ALD passivation stage begins, the ALD gas path 15 and the carbonization gas path 11 alternately supply trimethylaluminum and water vapor and nitrogen / argon to the double-cone cavity, each cycle is 8-10 s, wherein the pulse flow control mode is adopted to supply trimethylaluminum and water vapor (trimethylaluminum pulse 100-150 ms - water pulse 100-150 ms), the inert gas supplied by the carbonization gas path 11 has a blowing time of 4-5 s, and the double-cone cavity is flipped at a frequency of 11 times / min, until the differential electrochemical mass spectrometer reaches a particle coating thickness of 2 nm in the tail gas, the ALD passivation stage is ended, and the completion time is 1-1.5 h.

[0030] In the deposition silicon stage, the total mass of silane introduced is 98%~102% of the mass of the porous carbon material (100 kg after the activation stage), and the three stages include a preliminary stage, an intermediate stage, and a late stage. In the preliminary stage, the pressure in the reaction chamber after the mixed gas is cracked is not more than 0.5 atm, and the mass of silane introduced in the preliminary stage is not more than 20% of the total mass of silane. In the intermediate stage, the pressure in the reaction chamber after the mixed gas is cracked is not more than 1.5 atm, and the mass of silane introduced in the intermediate stage is 70~90% of the total mass of silane. In the late stage, the pressure in the reaction chamber after the mixed gas is cracked is not more than 3.0 atm, and the mass of silane introduced in the late stage is 5~10% of the total mass of silane.

[0031] Preliminary stage: 3.97 mol of silane is introduced per batch, a total of 63 batches (8% of batches), the silane and nitrogen are uniformly mixed in a mass ratio of 2:1 before being introduced, the reaction chamber pressure is not higher than 0.5 atm, and the pressure is maintained for 1 minute, each batch is vacuumed to the initial pressure of 0.05 torr after reaction to inhibit the blockage of micropore inlets. In the preliminary stage, 3.97 mol of silane and 2.27 mol of nitrogen are introduced into the reaction chamber per batch, and the pressure in the reaction chamber after 98% of the silane is cracked is 0.5 atm. Effect: low-dose dilution to inhibit rapid deposition at the pore inlets.

[0032] Intermediate stage: 11.92 mol of silane is introduced per batch, a total of 215 batches (82.1% of batches), the silane and nitrogen are mixed in a mass ratio of 2:1 before being introduced, the reaction chamber pressure is increased to 1.5 atm, and the pressure is maintained for 1 minute to accelerate internal filling. In the intermediate stage, 11.92 mol of silane and 6.81 mol of nitrogen are introduced into the reaction chamber per batch, and the pressure in the reaction chamber after 98% of the silane is cracked is 1.5 atm. Each batch is allowed to stand for 1 minute after reaction, and the vacuum is applied within 1 minute after reaction to the initial pressure (6.7 Pa). Effect: increase the gas volume to accelerate internal filling.

[0033] Late stage: temperature decreased by 20℃ to 430℃, 23.84 mol of silane was introduced into the reaction chamber for each batch, a total of 13 batches (9.9% of the batches), the silane was mixed with nitrogen gas at a mass ratio of 2:1 before being introduced into the reaction chamber, the pressure in the reaction chamber was controlled at 3 atm, and the pressure was maintained for 1 minute to prevent excessive deposition on the outer surface. 23.84 mol of silane and 13.42 mol of nitrogen gas were introduced into the reaction chamber for each batch in the late stage, and the pressure in the reaction chamber after 98% of the silane was cracked was 3 atm. Each batch was allowed to stand for 1 minute, and the vacuum was drawn to the initial pressure (6.7 Pa) within 1 minute after the reaction. Function: prevent excessive deposition on the outer surface.

[0034] Throughout the process, the amount of silane and inert gas introduced into each batch was strictly controlled to ensure that the total pressure in the chamber after cracking did not exceed 3 atm, and the vacuum degree was reached within 1 minute after the reaction was completed.

[0035] Total batch number = 63 + 215 + 13 = 291 batches.

[0036] Total reaction time = 63 x 2 + 215 x 2 + 13 x 2 = 582 min ≈ 9.7 hours.

[0037] From Figure 4 and Figure 5 It can be seen that the morphology and size of the sample particles, the surface is polyhedral block, the edge is sharp, and there are obvious pores between the particles. And Si is uniformly distributed in the porous carbon, representing higher uniform filling rate of micropores and mesopores, and the pore blocking phenomenon is significantly reduced. Combined with the examples and comparative examples, it can be found that by using three-stage batch injection, the uniform filling rate of micropores and mesopores is higher, and the pore blocking phenomenon is significantly reduced, and the reaction time is increased.

[0038] Although the above examples have described the present application and its embodiments in detail, it should be noted that for ordinary skilled in the art, without departing from the technical principles of the present application, changes, modifications, substitutions, combinations, simplifications, etc. of the corresponding conditions can also be made, which should be considered as equivalent replacement methods, and these improvements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a carbon-based silicon composite negative electrode material, characterized in that, The method comprises the following steps: loading biomass raw materials into the double-cone cavity, replacing the gas in the double-cone cavity with nitrogen / argon; increasing the temperature of the double-cone cavity to 600-800 DEG C, continuously inputting nitrogen / argon into the double-cone cavity, starting the carbonization stage, and stopping the carbonization stage when the differential electrochemical mass spectrometer detects that the volatile organic compounds in the tail gas discharged from the double-cone cavity are less than or equal to 0.1 wt%; increasing the temperature of the double-cone cavity to 850-900 DEG C, inputting CO2 / H2O into the double-cone cavity in a pulse flow control mode, starting the activation stage, and stopping the activation stage when the line particle size instrument detects that the specific surface area of the particulate matter in the tail gas reaches a set value; decreasing the temperature of the double-cone cavity to 350-450 DEG C, supplying nitrogen / argon to the double-cone cavity for purging, starting the silicon deposition stage, and performing multiple batches in three stages under negative pressure by inputting a mixed gas containing silane to deposit Si, wherein the amount of silane input in each batch and the total amount of silane input in each stage are set according to the stage, each batch of mixed gas input also contains an inert gas, the mass of the inert gas input in each batch is half of the mass of the silane, heating and pressure maintaining are performed, and the initial pressure is 0.01-0.05 torr after each batch of reaction is completed, and the silicon deposition stage is terminated when the set amount of silane is input; decreasing the temperature of the double-cone cavity to 300-350 DEG C, supplying nitrogen / argon to the double-cone cavity to purge the main gas channel, starting the carbon coating stage, and supplying a mixed gas containing acetylene and nitrogen to the double-cone cavity for carbon coating for 1-2 h; decreasing the temperature of the double-cone cavity to 200 DEG C, supplying nitrogen / argon to the double-cone cavity to purge the main gas channel, starting the ALD passivation stage, and alternately supplying trimethylaluminum, water vapor, and nitrogen / argon to the double-cone cavity until the differential electrochemical mass spectrometer detects that the particulate matter in the tail gas reaches the coating thickness, and the ALD passivation stage is terminated; the double-cone cavity is flipped according to a set frequency during the carbonization stage, the activation stage, the silicon deposition stage, the carbon coating stage, and the ALD passivation stage, and the gas is input into the double-cone cavity in a direction perpendicular to the gravity drop and the discharged tail gas is detected in real time.

2. The method of claim 1, wherein, In the silicon deposition stage, the total mass of the silane input is 98% to 102% of the mass of the porous carbon material after the activation stage, the three stages include an early stage, a middle stage, and a late stage, the pressure in the reaction cavity after the mixed gas is cracked in each batch of the early stage is not more than 0.5 atm, the mass of the silane input in the early stage is not more than 20% of the total mass of the silane, the pressure in the reaction cavity after the mixed gas is cracked in each batch of the middle stage is not more than 1.5 atm, the mass of the silane input in the middle stage is 70% to 90% of the total mass of the silane, the pressure in the reaction cavity after the mixed gas is cracked in each batch of the late stage is not more than 3.0 atm, and the mass of the silane input in the late stage is 5% to 10% of the total mass of the silane.

3. The method of claim 1, wherein, The set frequency is 1 to 2 times per minute.

4. A double cone rotating fluidization device in the method of claim 1 to 3 for preparing carbon-based silicon composite negative electrode material, characterized in that, The double-cone cavity includes a fluidization chamber, a deposition groove, and a gas guide pipe, the fluidization chamber is a columnar box body with open upper and lower ends, a sedimentation channel penetrates the upper and lower end faces of the columnar box body, the bowl mouths of two bowl-shaped sedimentation grooves face the sedimentation channel and symmetrically close the two ends of the sedimentation channel respectively, two coaxial gas guide pipes are symmetrically connected to the outside of the fluidization chamber, one gas guide pipe is connected with a fluidization gas supply system and used for conveying fluidization gas containing precursor reaction gas into the fluidization chamber, and the other gas guide pipe is sequentially connected with a tail gas detection system and a vacuum pump and used for discharging reaction tail gas, both gas guide pipes are controlled by a rotating mechanism to realize periodic overturning of the fluidization chamber, an agitator is arranged in the double-cone cavity, a driving mechanism and a vacuum sealed feeding port are arranged at the end of one sedimentation groove away from the bowl mouth, the driving mechanism is pivotally connected with the agitator, a discharge valve is arranged on the conical surface of the other sedimentation groove, and resistance heating wires are arranged outside the double-cone cavity. The carbonization stage, the activation stage, the silicon deposition stage, the carbon coating stage, and the ALD passivation stage are respectively supplied with gas through five groups of gas supply pipes, i.e., carbonization gas pipes, activation gas pipes, silicon deposition gas pipes, carbon coating gas pipes, and ALD gas pipes. The temperature control module adjusts the power of the resistance heating wires according to the temperature target values of different process stages. The tail gas detection system includes a laser particle size analyzer, a gas chromatograph-mass spectrometer, and a differential electrochemical mass spectrometer, the laser particle size analyzer is used for real-time monitoring of the particle size of the material with an accuracy of ± 5 μm, the gas chromatograph-mass spectrometer is used for monitoring the atmosphere composition in the double-cone cavity to prevent accumulation of impurity gas, and the differential electrochemical mass spectrometer is used for monitoring the reaction tail gas to judge the reaction progress. Temperature sensors are distributed at different positions of the double-cone cavity.

5. The apparatus of claim 4, wherein, The five groups of gas supply pipes are connected to a main gas channel and are respectively provided with electromagnetic reversing valves, the activation gas pipes, the silicon deposition gas pipes, the carbon coating gas pipes, and the ALD gas pipes are respectively provided with check valves and emergency shut-off valves, and the end of the main gas channel extends into the double-cone cavity and is provided with a uniform flow orifice plate.

6. The apparatus of claim 1, wherein, The discharge valves are arranged at different heights on the conical surface of the sedimentation groove and used for discharging powder particles at different depths in the sedimentation groove, and a graded screening assembly is arranged at the discharge valves and has a pore size range of 50-200 μm.

7. The apparatus of claim 1, wherein, The agitator is composed of an agitator rod and helical stirring blades, and the agitator can lift the material with a large particle size at the bottom of the deposition groove to the upper part.

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