Porous silicon carbon negative electrode material, preparation system and preparation method thereof, and lithium ion battery

Abstract

The invention relates to a porous silicon carbon negative electrode material, a preparation system and a preparation method thereof, and a lithium ion battery. The preparation method comprises the steps that carrier gas and / or reaction gas are / is introduced into a preheater to be heated and measured and monitored through a temperature sensor, and the carrier gas is any one of nitrogen, hydrogen and argon; when the carrier gas and / or the reaction gas are / is heated to 200-300 DEG C in the preheater, the carrier gas and / or the reaction gas are / is introduced into the reaction chamber, and a porous carbon substrate is placed in the reaction chamber; the carrier gas and / or the reaction gas enter a reaction chamber to be subjected to gas-phase high-temperature deposition, so that silicon atoms are deposited on the porous carbon substrate; and carrying out vapor phase high-temperature deposition, cooling, and introducing unsaturated hydrocarbon to carry out material passivation, so as to obtain the required porous silicon-carbon negative electrode material after material passivation. The gas distribution uniformity and the heat transfer efficiency can be improved, and the specific capacity, the cycle life and the rate capability of the porous silicon carbon negative electrode are further remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery materials, and in particular to a porous silicon-carbon negative electrode material, a preparation system and method thereof, and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries, as high-efficiency energy storage devices, are widely used in portable electronic devices, electric vehicles, and renewable energy storage systems. With technological advancements and growing market demand, the performance of lithium-ion batteries is increasingly demanding. Anode materials, in particular, play a crucial role in the overall performance of lithium-ion batteries. Currently, graphite is the most commonly used anode material. However, its limited theoretical specific capacity (372 mAh / g) makes it difficult to meet the ever-increasing energy density requirements. Therefore, the exploration of new high-capacity anode materials has become a research hotspot.

[0003] Silicon has attracted considerable attention due to its high theoretical specific capacity (approximately 4200 mAh / g), making it a key research area for lithium-ion battery anode materials. However, silicon undergoes significant volume expansion (up to 300% or more) during charge and discharge. This volume change can damage the electrode structure and lead to a sharp decrease in the battery's cycle life. To address this issue, researchers have proposed a method for composite silicon with a porous carbon substrate. The porous carbon substrate not only provides good conductivity but also alleviates silicon's volume expansion to a certain extent, thereby improving the battery's cycling stability.

[0004] Silicon-carbon anode materials prepared by vapor deposition of porous carbon demonstrate excellent performance. This material exhibits balanced and outstanding performance in terms of capacity, initial efficiency, cycle stability, and rate performance, and has been gradually applied to various commercial batteries. The preparation process of porous silicon-carbon anode materials mainly involves: heating and decomposing silane gas, allowing it to enter the porous carbon to form a silicon-carbon composite material, and then introducing a carbon source gas for pyrolysis to form a coating layer on the surface of the silicon-carbon material to isolate it from the air.

[0005] However, with the expansion of production scale and the increasing size of equipment, the preparation process also faces certain challenges. For example, the increased diameter of the reaction equipment results in a low temperature at the center of the reaction gas during heating, while the temperature near the inner wall is high, resulting in severely uneven temperature distribution and a large temperature gradient. The reaction gas decomposition at the center is slow and inefficient, severely limiting production efficiency and the uniformity of the performance of the silicon-carbon material product.

[0006] To improve production efficiency and product quality uniformity, the following conditions must be met: improving heat transfer efficiency and increasing furnace temperature uniformity. Current technology primarily uses backmixing to increase uniformity, but this increases the difficulty of backmixing, is less effective, and has low efficiency. Furthermore, insufficient heat transfer causes unreacted gases to easily escape with the tail gas, resulting in low feed gas utilization and low production efficiency. Another technique to improve efficiency is to increase the heating power, but this can lead to excessive temperature gradients, which can cause serious side reactions.

[0007] In the prior art, the patent (application number: CN202211528061.6) discloses a chemical vapor deposition reactor and method for epitaxial growth of silicon carbide thin films. The design of the reactor includes two heat source components, wherein the first heat source component is surrounded by a surrounding type, enclosing a reaction space in which a high-temperature environment is formed by heating, and the second heat source component is arranged in the reaction space, dividing the reaction space into a first gas channel and a second gas channel that are interconnected. The reactor can increase the decomposition rate of the precursor gas-phase material in the reactor, while increasing the uniformity of the distribution of the gas-phase material in the reactor, which is conducive to the uniform growth of the film. However, this method requires the modification of the reactor, its structure is relatively complex, and the requirements for the reaction space are also relatively stringent.

[0008] Therefore, the existing technology needs to be improved. Summary of the Invention

[0009] In the prior art, the preparation method of silicon-carbon negative electrode materials still restricts the production efficiency and the uniformity of the performance of silicon-carbon material products. Therefore, the present invention provides a porous silicon-carbon negative electrode material and its preparation system and method, and a lithium-ion battery to solve the above problems.

[0010] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a porous silicon-carbon negative electrode material, which comprises the following specific steps: S1. Passing a carrier gas and / or a reaction gas into a preheater for heating, and measuring and monitoring the temperature using a temperature sensor, wherein the carrier gas is any one of nitrogen, hydrogen, and argon; S2, when the carrier gas and / or reaction gas is heated to 200-300° C. in a preheater, it is introduced into a reaction chamber, and a porous carbon substrate is placed in the reaction chamber; S3, the carrier gas and / or reaction gas enters the reaction chamber to perform vapor phase high temperature deposition, the vapor phase high temperature deposition temperature is 500-900° C., and the reaction time is 5-8 hours, so that silicon atoms are deposited on the porous carbon substrate; S4, performing vapor phase high-temperature deposition, then cooling, and introducing unsaturated hydrocarbons to passivate the material, to obtain the desired porous silicon-carbon negative electrode material after the material is passivated; Wherein, in S1, the preheater adopts a dual heating mode, heating the carrier gas and / or reaction gas by combining electric heating and hot air flow auxiliary heating.

[0011] In one implementation, in S1 , the electric heating part provides precise temperature control through electric heating elements, and the hot gas flow auxiliary heating part further heats the gas by recovering waste heat from the reaction process or an external heat source.

[0012] In one implementation, in S2, the reaction chamber is a fluidized bed or a rotary kiln, and the reaction chamber is provided with a multi-level temperature control system.

[0013] In one implementation, in S2, the method for preparing the porous carbon substrate specifically includes: Add an organic amine template, a phosphorus source, and a carbon source to deionized water and transfer the mixture to a high-pressure reactor. React for 60 to 600 minutes at a temperature of 100 to 200°C and a pressure of 5 to 10 MPa, and then filter to obtain an intermediate. The intermediate is transferred to a tube furnace, and then heated to 500-700° C. and activated by introducing water vapor for 1-6 hours, and then naturally cooled to room temperature to obtain a porous carbon substrate; The mass ratio of the added raw materials is organic amine template: phosphorus source: carbon source: deionized water = (1-5): (5-20): 100: (1000-2000).

[0014] In one implementation, in S3, the conditions for the gas phase high temperature deposition are a pressure of 10-100 Pa and a flow rate of 100-1000 ml / min, and silicon atoms are deposited on the porous carbon substrate to form a uniform silicon-carbon composite structure.

[0015] In one implementation, in S4, the material passivation condition is to introduce unsaturated hydrocarbons at a flow rate of 10-100 ml / min after cooling to 400-700°C for 30-300 minutes; wherein the unsaturated hydrocarbons include any one of acetylene, propyne, butyne, ethylene and propylene.

[0016] In one implementation, in S3, the reaction gas includes silane gas and / or a carbon source organic gas, the silane gas includes monosilane or disilane, and the carbon source organic gas includes any one of acetylene, ethylene, methane, and propylene, and the volume ratio of the reaction gas introduced into the reaction gas is reaction gas: carrier gas = (1~5):10.

[0017] In a second aspect, the present invention further provides a porous silicon-carbon negative electrode material, which is prepared by the above-mentioned method for preparing the porous silicon-carbon negative electrode material.

[0018] In a third aspect, the present invention further provides a system for preparing a porous silicon-carbon negative electrode material, which is used to prepare the above-mentioned porous silicon-carbon negative electrode material, and comprises: A gas supply system for providing carrier gas and / or reaction gas; A gas flow controller for controlling the flow of carrier gas and / or reaction gas; A preheater for heating the carrier gas and / or the reaction gas, wherein the preheater adopts a dual heating mode, including electric heating and hot air flow auxiliary heating parts; A reaction chamber for performing a vapor-phase high-temperature deposition reaction, wherein a porous carbon substrate is placed in the reaction chamber and the reaction chamber is equipped with a multi-level temperature control system; Temperature sensors for measuring and monitoring the temperature of the preheater and reaction chamber; Exhaust system, used to discharge waste gas after reaction; The gas supply system is connected to a gas flow controller, the gas flow controller is connected to a preheater, the preheater is connected to a reaction chamber, the reaction chamber is connected to an exhaust system, and temperature sensors are respectively arranged in the preheater and the reaction chamber.

[0019] In a fourth aspect, the present invention further provides a lithium-ion battery comprising the above-mentioned porous silicon-carbon negative electrode material.

[0020] Beneficial Effects: The present invention provides a method for preparing a porous silicon-carbon negative electrode material, which optimizes the preheating and reaction conditions of the carrier gas and the silicon source gas to ensure that silicon atoms are uniformly deposited on the porous carbon substrate, thereby preparing a porous silicon-carbon negative electrode material with high specific capacity and good cycle stability. The preparation method and preparation system provided by the present invention can improve the uniformity of gas distribution and heat transfer efficiency through precise gas source preheating and reaction control, thereby significantly improving the specific capacity, cycle life and rate performance of the porous silicon-carbon negative electrode; at the same time, it optimizes thermal energy utilization and reaction conditions, reduces energy consumption, shortens the production cycle, and improves production efficiency, thereby further enhancing the performance and application prospects of the silicon-carbon negative electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of the steps of the method for preparing the porous silicon-carbon negative electrode material provided by the present invention; Figure 2 This is a structural block diagram of the system for preparing the porous silicon-carbon negative electrode material provided by the present invention; Among them, the symbols in the figure respectively represent: 1. Gas supply system; 2. Preheater; 3. Reaction chamber.

[0022] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the descriptions of the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" described below mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0024] Specific reference Figure 1 , Figure 1 It is a flow chart of the steps of the method for preparing the porous silicon-carbon negative electrode material provided by the present invention.

[0025] The present invention provides a method for preparing a porous silicon-carbon negative electrode material, which comprises the following specific steps: S1. Passing a carrier gas and / or a reaction gas into a preheater for heating, and measuring and monitoring the temperature using a temperature sensor, wherein the carrier gas is any one of nitrogen, hydrogen, and argon; S2, when the carrier gas and / or reaction gas is heated to 200-300° C. in a preheater, it is introduced into a reaction chamber, and a porous carbon substrate is placed in the reaction chamber; S3, the carrier gas and / or reaction gas enters the reaction chamber to perform vapor phase high temperature deposition, the vapor phase high temperature deposition temperature is 500-900° C., and the reaction time is 5-8 hours, so that silicon atoms are deposited on the porous carbon substrate; S4. After performing vapor phase high-temperature deposition, the temperature is lowered and unsaturated hydrocarbons are introduced to passivate the material. After the material is passivated, the desired porous silicon-carbon negative electrode material is obtained.

[0026] In S1, the preheater employs a dual heating mode, heating the carrier gas and / or reaction gas through a combination of electric heating and hot air flow-assisted heating. Specifically, in S1, the electric heating portion provides precise temperature control via electric heating elements, while the hot air flow-assisted heating portion further heats the gas by recycling waste heat from the reaction process or using an external heat source, thereby improving preheating efficiency and reducing energy consumption.

[0027] Specifically, a high-efficiency electric heating element is installed inside the preheater, and the electric heating element is an electric heating wire or a heating tube, which generates heat by heating with electric current. The electric heating part is made of materials that can heat up quickly and provide a stable heat source, including nickel-chromium alloy or stainless steel wire. The electric heating part is located in the main air flow path of the preheater and is arranged around the pipes or channels through which the gas circulates. Through the thermal radiation and convection of the electric heating element, the gas can be quickly heated to a certain temperature. The electric heating part is also equipped with an intelligent temperature control system, which monitors the gas temperature in real time through a temperature sensor and automatically adjusts the power of the electric heating to ensure that the heating process is stable and uniform and reduces temperature fluctuations.

[0028] The hot air flow-assisted heating system comprises a hot air flow channel and a heat exchanger. The hot air flow channel is supplied by reactor exhaust or a dedicated air flow heating device. The heat exchanger recovers the hot air flow from the reaction process through a heat exchanger (plate or tubular heat exchanger). This heat energy is then transferred to the gas entering the preheater via a high-efficiency heat exchanger, further raising the gas temperature. The gas entering the preheater is mixed by the combination of electric heating and the hot air flow, achieving uniform heating. This dual heating mode fully utilizes the waste heat generated during the reaction, reducing the need for external electricity and improving the system's thermal energy efficiency.

[0029] This invention utilizes a dual heating mode that combines electric heating and hot air flow-assisted heating to heat the carrier gas and / or reactant gas to a specific temperature (200-300°C). This ensures that these gases reach the desired temperature before entering the reaction chamber, facilitating a smooth reaction process and improving reaction efficiency and material quality. Furthermore, by preheating the gas, the temperature of the gas entering the reaction chamber is maintained constant, resulting in a more stable temperature within the reaction chamber, reducing the adverse effects of temperature fluctuations on the reaction process and helping to improve the uniformity and consistency of the final material. The preheated gas has higher kinetic energy, allowing it to contact and react with the porous carbon substrate in the reaction chamber more quickly, thereby shortening reaction time and improving production efficiency. This dual heating mode not only improves heating efficiency but also effectively saves energy. Electric heating provides precise temperature control through electric heating elements, while hot air flow-assisted heating heats the gas by recycling waste heat or using an external heat source, reducing energy waste.

[0030] In S2, the reaction chamber is a fluidized bed or a rotary kiln. The fluidized bed utilizes gas flow to suspend solid particles, achieving a uniform reaction. The rotary kiln rotates to uniformly heat and react the materials. The reaction chamber design combines a fluidized bed with a rotary kiln to ensure more uniform and efficient contact between the gas and the porous carbon substrate, improve temperature uniformity within the reaction chamber, and prevent temperature variations from affecting deposition.

[0031] Furthermore, the reaction chamber is provided with a multi-level temperature control system. The multi-level temperature control system is used to accurately control the temperature of different stages during the reaction process and ensure that the temperature of the gas and the reaction environment is uniform. It is composed of a multi-stage heating source, a temperature control sensor, a temperature adjustment module and a multi-zone temperature control system. The multi-stage heating source includes a preheater, an electric heating element and a hot air flow heating part. Each heating source is independently controlled and can adjust the heating power according to the gas flow, reaction stage and real-time demand. The temperature sensor is installed in the preheater, reaction chamber and other locations to monitor the temperature changes in different areas in real time. The temperature sensor uses a thermocouple or RTD sensor to accurately measure the temperature. The temperature adjustment module is used to connect the temperature sensor and the heating source, and adjust the power of the heating equipment according to the information fed back by the sensor. In the multi-zone temperature control system, multiple independent temperature control areas are set in the reaction chamber and preheater, and the temperature of each area can be independently controlled to adapt to the temperature requirements in different reaction processes.

[0032] The present invention optimizes the design of a multi-level temperature control system inside the reaction chamber. The multi-level temperature control system can accurately control the reaction temperature through the configuration of multiple zones and multiple heating sources, and dynamically adjust the temperature at different stages, thereby maximizing the uniformity and controllability of the reaction.

[0033] Furthermore, in S2, the method for preparing the porous carbon substrate specifically includes: Add an organic amine template, a phosphorus source, and a carbon source to deionized water and transfer the mixture to a high-pressure reactor. React for 60 to 600 minutes at a temperature of 100 to 200°C and a pressure of 5 to 10 MPa, and then filter to obtain an intermediate. The intermediate is transferred to a tube furnace, and then heated to 500-700° C. and activated by introducing water vapor for 1-6 hours, and then naturally cooled to room temperature to obtain a porous carbon substrate; The mass ratio of the added raw materials is organic amine template: phosphorus source: carbon source: deionized water = (1-5): (5-20): 100: (1000-2000).

[0034] Specifically, in S3, the vapor phase high temperature deposition is performed at a pressure of 10-100 Pa and a flow rate of 100-1000 ml / min, wherein the vapor phase high temperature deposition temperature is 500-900° C., preferably 500-750° C., and more preferably 500-600° C.

[0035] Specifically, in S4, the material is passivated by introducing an unsaturated hydrocarbon into the reaction mixture after cooling to 400-700°C, with the temperature decreasing by 100-300°C at a flow rate of 10-100 ml / min for 30-300 minutes. The unsaturated hydrocarbon comprises any one of acetylene, propyne, butyne, ethylene, and propylene. Furthermore, in S3, the reaction gas comprises silane gas and / or a carbon source organic gas, wherein the silane gas comprises monosilane or disilane, and the carbon source organic gas comprises any one of acetylene, ethylene, methane, and propylene. The volume ratio of the reaction gas introduced into the reaction gas is (1-5):10. The passivation temperature is 400-700°C, preferably 400-600°C, and more preferably 500-600°C.

[0036] At this time, a pulsed passivation method is adopted in the passivation process, and unsaturated hydrocarbons are introduced in an intermittent pulse manner to improve the reaction efficiency and avoid the decrease in conductivity caused by excessive passivation, thereby improving the cycle life and rate performance of the porous silicon-carbon negative electrode material. Specifically, a pulsed gas supply system is used to accurately adjust the gas flow introduced during each pulse through a gas flow meter and a gas valve, and the switch is controlled according to a preset cycle to intermittently introduce unsaturated hydrocarbons into the reaction chamber. The pulse method includes timed closing and opening of the gas supply valve to control the gas flow rate and introduction time. Preferably, unsaturated hydrocarbons are introduced intermittently, and the preset cycle is set to supply gas for 10 to 30 seconds and stop for 10 to 60 seconds. After allowing the gas to fully react with the surface of the material, the next pulse is performed, and the flow rate of the gas introduced is 10 to 100 ml / min. 5 to 20 pulse cycles are performed to ensure uniform deposition of an appropriate amount of passivation layer. After the passivation is completed, the gas supply is stopped and the material is allowed to cool naturally to room temperature.

[0037] Existing passivation methods for silicon-carbon anode materials typically employ continuous gas flow, introducing unsaturated hydrocarbons to form a protective layer on the carbon surface to inhibit silicon volume expansion and interfacial side reactions. The present invention, however, employs a pulsed, intermittent flow of unsaturated hydrocarbons, allowing the carbon source gas to fully react with the silicon-carbon substrate surface, improving the uniformity of the carbon layer and avoiding localized over-deposition or defective areas. Conventional CVD (chemical vapor deposition) passivation can result in an excessively thick carbon layer, impacting conductivity. The pulsed passivation method allows for better control of the carbon layer thickness, maintaining good electron and ion transport properties. Furthermore, the continuous gas flow in conventional CVD passivation can lead to excessive carbon deposition, reducing the conductivity of the silicon-carbon anode material and affecting rate performance. The present invention employs pulsed passivation, alternating deposition and pauses, to control the carbon layer growth rate, forming a more uniform conductive network, improving the material's electronic conductivity, and thus enhancing rate performance. Furthermore, conventional CVD can lead to excessive reaction between the carbon layer and the silicon surface, resulting in high stress at the interface and affecting the material's mechanical stability. The present invention adopts a pulsed method to reduce the supersaturation of the carbon source gas and reduce the interfacial stress during the deposition process, thereby improving the structural stability of the silicon-carbon negative electrode material during the charge and discharge process and increasing the cycle life.

[0038] In the present invention, pulsed passivation can achieve finer carbon layer control, avoid the formation of an overly thick carbon layer barrier, make it easier for lithium ions to embed into the silicon substrate, and improve the specific capacity of the material. A moderate carbon layer can buffer the volume expansion of silicon during the charge and discharge process, reduce electrode pulverization, and improve cycle life. Pulsed passivation can optimize the gas supply and exhaust process, reduce the residence time of the carbon source gas in the reaction chamber, thereby reducing the occurrence of side reactions and improving the purity of the material. In the present invention, pulsed passivation is used to make the final silicon-carbon negative electrode material have a higher specific capacity, longer cycle life and better rate performance, and is suitable for high-performance lithium-ion battery applications.

[0039] Furthermore, the present invention also provides a porous silicon-carbon negative electrode material, which is prepared by the above-mentioned method for preparing the porous silicon-carbon negative electrode material. The present invention also provides a system for preparing the porous silicon-carbon negative electrode material, which is used to prepare the above-mentioned porous silicon-carbon negative electrode material, and comprises: A gas supply system 1, for providing carrier gas and / or reaction gas; A gas flow controller for controlling the flow of carrier gas and / or reaction gas; Preheater 2, used to heat the carrier gas and / or reaction gas; Reaction chamber 3, used for performing vapor phase high temperature deposition reaction, in which a porous carbon substrate is placed; Temperature sensors for measuring and monitoring the temperature of the preheater and reaction chamber; Exhaust system, used to discharge waste gas after reaction; Among them, the gas supply system 1 is connected to the gas flow controller, the gas flow controller is connected to the preheater 2, the preheater 2 is connected to the reaction chamber 3, the reaction chamber 3 is connected to the exhaust system, and the temperature sensors are respectively arranged in the preheater 2 and the reaction chamber 3. The system heats the carrier gas and / or the reaction gas through the preheater 2 to ensure that it reaches the required temperature before entering the reaction chamber 3, controls the gas flow controller to adjust the gas flow entering the reaction chamber, monitors the temperature of the preheater 2 and the reaction chamber 3 in real time through the temperature sensor to ensure that it is within the appropriate reaction temperature range, and finally discharges the waste gas after the reaction through the exhaust system to complete the efficient preparation of the porous silicon-carbon negative electrode material.

[0040] Furthermore, the connecting pipes between the preheater and the reaction chamber are insulated to reduce heat loss and improve the thermal efficiency of the entire system. Specifically, select insulation materials with high thermal resistance, such as rock wool, glass wool, polyurethane foam, calcium silicate, etc., and cut the insulation material to the appropriate size based on the diameter and length of the pipe. The insulation material is tightly wrapped around the outer surface of the pipe, ensuring there are no gaps or uneven areas to reduce thermal bridging. The insulation material is secured to the pipe using bandages or tape to ensure it does not loosen or fall off during use.

[0041] In addition, the preheater can be integrated into an automated control system to further optimize the gas preheating process and improve the intelligence level of the entire reaction system through real-time monitoring and feedback adjustment.

[0042] The present invention also illustrates the technical solution of the present invention through multiple embodiments and comparative examples.

[0043] Example 1 S1. Preheating gas: Argon (Ar), a carrier gas at room temperature, is introduced into a tubular heat exchanger through a pipeline for heating, and the preheating temperature is set to 300°C; the temperature in the preheater is measured and monitored in real time by a temperature sensor to ensure that it is stable at 300°C and to ensure the uniformity and stability of the gas heating. Among them, an electric heating wire is provided in the tubular heat exchanger, which can provide a precise and stable heating source through electric heating to ensure that the preheating gas is stably heated to 300°C. And by setting up a heat exchanger, the hot air flow from the reaction chamber or other components is introduced into the preheater, and then the argon gas entering the preheater is heated by the heat exchanger. Among them, there are multiple temperature control zones inside the tubular heat exchanger. The temperature of each zone is monitored in real time by an independent temperature sensor, and the heating power is adjusted by the intelligent control system to ensure that the gas is evenly heated to 300°C.

[0044] S2. Preheating gas is introduced into the reaction chamber: After the carrier gas argon (Ar) is heated to 300°C in the preheater, it is introduced into the reaction chamber; a porous carbon substrate is placed in the reaction chamber, and a rotary kiln is selected for the reaction chamber. At this time, multiple temperature sensors are provided in the reaction chamber to monitor the temperature changes in different areas. The reaction chamber adjusts the temperature through multiple heating zones to ensure that the gas and porous carbon substrate in the reaction chamber reach the ideal heating conditions. The heating zones are electrically heated or heated by hot air flow.

[0045] The preparation of the porous carbon substrate specifically includes: adding 1.5 g of an organic amine template, 10 g of ammonium dihydrogen phosphate, and 100 g of glucose to 2000 mL of deionized water, and transferring the mixture into a high-pressure reactor; The reaction was carried out at a temperature of 150°C and a pressure of 8 MPa for 300 minutes to ensure that the organic amine template, ammonium dihydrogen phosphate and glucose were completely reacted to form an intermediate; After the reaction is completed, the intermediate is obtained by filtration; The intermediate was transferred to a tube furnace, heated to 600°C, and activated by steam for 3 hours; After activation, the temperature was naturally lowered to room temperature to obtain a porous carbon substrate.

[0046] S3, Vapor-Phase High-Temperature Deposition: Preheated carrier gases, argon (Ar), and silane (SiH4), mixed in a volume ratio of 3:10, are introduced into the reaction chamber. Vapor-phase high-temperature deposition is performed in the reaction chamber at a temperature of 700°C, a reaction time of 6 hours, a pressure of 50 Pa, and a gas flow rate of 500 mL / min. Under these conditions, silicon atoms are deposited on the porous carbon substrate, forming a porous silicon-carbon material. During the deposition process, temperature sensors and flow controllers are used to monitor and adjust the reaction conditions in real time to ensure reaction stability and deposition uniformity.

[0047] S4. Material passivation: After completing vapor phase high-temperature deposition, the cooling process begins. When the temperature drops to 500°C, acetylene is introduced for material passivation. The preset cycle is set to supply gas for 30 seconds, pause for 60 seconds before the next pulse, and the gas flow rate is set to 50mL / min. The passivation process lasts for 120 minutes. During this process, the acetylene gas reacts with the porous silicon-carbon material, sealing the active sites on the material's surface and stabilizing the material's electrochemical properties. After the passivation is completed, the desired porous silicon-carbon anode material is obtained.

[0048] Example 2 In this embodiment, the carrier gas is not preheated in S1. Instead, in S3, room-temperature silane is introduced into a tubular heat exchanger, heated to 200°C by tubular electric heating, mixed with the carrier gas, and then introduced into the reaction chamber. The remaining steps are the same as in Example 1 and are not further described here.

[0049] Example 3 In this embodiment, in S1, a room-temperature carrier gas is introduced into a preheater, heated to 300°C by tubular electric heating, mixed with the reactant gas, and then introduced into the reaction chamber. In S3, room-temperature silane is also introduced into the preheater, heated to 200°C by tubular electric heating, mixed with the reactant gas, and then introduced into the reaction chamber. The remaining steps are the same as in Example 1 and are not repeated here.

[0050] Comparative Example 1 The difference between this comparative example and Example 1 is that the gas sources in the comparative example are not heated and there is no preheater in the reaction equipment.

[0051] The present invention conducts verification experiments on the above embodiments and comparative examples: Soft pack performance test: The silicon-carbon composite materials corresponding to Examples 1-3 and Comparative Example 1 were doped with 90% artificial graphite as the negative electrode material (i.e., the negative electrode sheet), and the positive electrode ternary material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), electrolyte and diaphragm are assembled into a 5Ah soft-pack battery; wherein, the diaphragm is celegard 2400, the electrolyte is LiPF6 solution (the solvent is a mixed solution of EC and DEC with a volume ratio of 1:1, and the concentration of LiPF6 is 1.1 mol / L) to prepare the soft-pack battery.

[0052] The following performance tests are performed on each soft pack battery: The test conditions for the cycle performance test are: charge and discharge voltage range of 2.5~4.2V, temperature of 25±3.0℃, charge and discharge rate of 1.0C / 1.0C, and cycle number of 500 times; The test conditions for the rate test are: the constant current ratio of each soft-pack battery under 2C conditions = 2C constant current capacity / (2C constant current capacity + 0.1C constant voltage capacity); the test results are shown in Table 1 below.

[0053] The relevant data of each embodiment and comparative example are shown in Table 1.

[0054] Table 1. Specific implementation data of each embodiment and comparative example.

[0055] As can be seen from Table 1, the present invention preheats the gas source, mixes the reaction gas with the carrier gas, and then continues to heat the reaction gas with subsequent equipment, so that the reaction chamber only needs less heat to heat the reaction gas to the decomposition temperature, greatly reducing the residence time of the reaction gas in the reaction chamber, increasing the required reaction gas flow rate, and significantly reducing the time required to prepare the product.

[0056] In summary, the present invention provides a method for preparing a porous silicon-carbon negative electrode material, which ensures that silicon atoms are uniformly deposited on a porous carbon substrate by optimizing the preheating and reaction conditions of the carrier gas and the silicon source gas, thereby preparing a porous silicon-carbon negative electrode material with high specific capacity and good cycle stability; in addition, the precise heating of the gas is ensured by adopting a dual heating mode, and energy consumption is reduced by recovering waste heat. A multi-level temperature control system is used to ensure the uniformity and stability of the temperature in the preheating process and the reaction chamber, thereby ensuring the uniformity of silicon atom deposition and the quality of the material. The preparation method and preparation system provided by the present invention can improve the uniformity of gas distribution and heat transfer efficiency through precise gas source preheating and reaction control, thereby significantly improving the specific capacity, cycle life and rate performance of the porous silicon-carbon negative electrode; at the same time, it optimizes thermal energy utilization and reaction conditions, reduces energy consumption, shortens the production cycle, and improves production efficiency, thereby further enhancing the performance and application prospects of silicon-carbon negative electrode materials.

[0057] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a porous silicon-carbon negative electrode material, characterized in that: The specific steps include: S1. Passing a carrier gas and / or a reaction gas into a preheater for heating, and measuring and monitoring the temperature using a temperature sensor, wherein the carrier gas is any one of nitrogen, hydrogen, and argon; S2, when the carrier gas and / or reaction gas is heated to 200-300° C. in a preheater, it is introduced into a reaction chamber, and a porous carbon substrate is placed in the reaction chamber; S3, the carrier gas and / or reaction gas enters the reaction chamber to perform vapor phase high temperature deposition, the vapor phase high temperature deposition temperature is 500-900° C., and the reaction time is 5-8 hours, so that silicon atoms are deposited on the porous carbon substrate; S4, performing vapor phase high-temperature deposition, then cooling, and introducing unsaturated hydrocarbons to passivate the material, to obtain the desired porous silicon-carbon negative electrode material after the material is passivated; Wherein, in S1, the preheater adopts a dual heating mode, heating the carrier gas and / or reaction gas by combining electric heating and hot air flow auxiliary heating.

2. The method for preparing the porous silicon-carbon negative electrode material according to claim 1, wherein: In S1, the electric heating part provides precise temperature control through electric heating elements, and the hot gas flow auxiliary heating part further heats the gas by recovering waste heat from the reaction process or an external heat source.

3. The method for preparing the porous silicon-carbon negative electrode material according to claim 1, wherein: In S2, the reaction chamber is a fluidized bed or a rotary kiln, and the reaction chamber is provided with a multi-level temperature control system.

4. The method for preparing the porous silicon-carbon negative electrode material according to claim 1, wherein: In S2, the method for preparing the porous carbon substrate specifically includes: Add an organic amine template, a phosphorus source, and a carbon source to deionized water and transfer the mixture to a high-pressure reactor. React for 60 to 600 minutes at a temperature of 100 to 200°C and a pressure of 5 to 10 MPa, and then filter to obtain an intermediate. The intermediate is transferred to a tube furnace, and then heated to 500-700° C. and activated by introducing water vapor for 1-6 hours, and then naturally cooled to room temperature to obtain a porous carbon substrate; The mass ratio of the added raw materials is organic amine template: phosphorus source: carbon source: deionized water = (1-5): (5-20): 100: (1000-2000).

5. The method for preparing the porous silicon-carbon negative electrode material according to claim 1, wherein: In S3, the conditions for the gas phase high temperature deposition are a pressure of 10-100 Pa and a flow rate of 100-1000 ml / min, and silicon atoms are deposited on the porous carbon substrate to form a uniform silicon-carbon composite structure.

6. The method for preparing the porous silicon-carbon negative electrode material according to claim 1, wherein: In S4, the material passivation condition is to introduce unsaturated hydrocarbons at a flow rate of 10-100 ml / min after cooling to 400-700° C. for 30-300 min; wherein the unsaturated hydrocarbons include any one of acetylene, propyne, butyne, ethylene and propylene.

7. The method for preparing the porous silicon-carbon negative electrode material according to claim 1, wherein: In S3, the reaction gas includes silane gas and / or carbon source organic gas, the silane gas includes monosilane or disilane, and the carbon source organic gas includes any one of acetylene, ethylene, methane, and propylene, and the volume ratio of the reaction gas introduced into the reaction gas is reaction gas: carrier gas = (1~5):

10.

8. A porous silicon-carbon negative electrode material, characterized in that: The porous silicon-carbon negative electrode material is prepared by the preparation method according to any one of claims 1 to 7.

9. A system for preparing porous silicon-carbon negative electrode materials, characterized in that: For preparing the porous silicon-carbon negative electrode material according to any one of claims 1 to 8, comprising: A gas supply system for providing carrier gas and / or reaction gas; A gas flow controller for controlling the flow of carrier gas and / or reaction gas; A preheater for heating the carrier gas and / or the reaction gas, wherein the preheater adopts a dual heating mode, including electric heating and hot air flow auxiliary heating parts; A reaction chamber for performing a vapor-phase high-temperature deposition reaction, wherein a porous carbon substrate is placed in the reaction chamber and the reaction chamber is equipped with a multi-level temperature control system; Temperature sensors for measuring and monitoring the temperature of the preheater and reaction chamber; Exhaust system, used to discharge waste gas after reaction; The gas supply system is connected to a gas flow controller, the gas flow controller is connected to a preheater, the preheater is connected to a reaction chamber, the reaction chamber is connected to an exhaust system, and temperature sensors are respectively arranged in the preheater and the reaction chamber.

10. A lithium ion battery, characterized in that: Including the porous silicon-carbon negative electrode material according to claim 8.

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