Preparation device and preparation method of lithium ion battery silicon-carbon negative electrode composite material

Abstract

The invention discloses a preparation device of a lithium ion battery silicon-carbon negative electrode composite material, which comprises a plasma generator, a supersonic injection pipe and a high-temperature reaction cavity which are sequentially arranged from top to bottom, a hydrogen and argon mixed gas is introduced into the upper part of the plasma generator, or argon is directly introduced into the upper part of the plasma generator; a feeding hole is formed in the lower part of the plasma and is used for introducing silicon powder, and an opening is formed in the top of the high-temperature reaction cavity and is used for introducing methane. The invention also provides a preparation method of the lithium ion battery silicon-carbon negative electrode composite material. According to the invention, efficient and continuous preparation of the silicon-carbon composite material can be realized, and the uniformity and consistency of the material are remarkably improved; the plasma power, the gas flow and the amount of silicon powder are accurately regulated and controlled, and the temperature of plasma high-temperature jet flow is controlled; and silicon powder and methane are put in different areas, so that generation of silicon carbide is effectively inhibited.

Description

Technical Field

[0001] This invention relates to a method and apparatus for preparing a material, specifically to an apparatus and method for preparing a silicon-carbon anode composite material for lithium-ion batteries, belonging to the field of lithium-ion battery material technology. Background Technology

[0002] Silicon-carbon composite materials, due to their excellent cycle stability and high energy density, are gradually becoming a research frontier in lithium-ion battery anode materials, and are expected to replace traditional graphite materials, leading the development of next-generation lithium-ion batteries. The choice of composite method and the type of carbon material have a profound impact on the microstructure and electrochemical behavior of silicon-carbon composite materials.

[0003] Chinese invention patent CN 118026181 A discloses a method for in-situ synthesis of silicon-carbon nanocomposites using induction thermal plasma. This method employs a segmented feeding approach, controlling the temperature range of silicon nanowire formation and the silicon-carbon composite process to suppress the silicon-carbon reaction rate and effectively prevent silicon carbide formation. First, a silicon source precursor is axially transported into the high-temperature region of the induction thermal plasma, where silicon vapor is obtained under high temperature and cooled as it leaves the high-temperature region, resulting in silicon nanowires through nucleation growth. Then, gaseous carbon sources such as acetylene and methane are added to the tail of the induction thermal plasma, and the carbon formed by pyrolysis undergoes heterogeneous nucleation on the silicon surface to obtain the silicon-carbon composite material. This method suffers from low reaction efficiency and high cost, making it unsuitable for widespread industrial application. Summary of the Invention

[0004] The purpose of this invention is to provide a process controllable and efficient preparation device and method for silicon-carbon anode composite materials for lithium-ion batteries. By utilizing the high enthalpy characteristics of thermal plasma and using supersonic jets to improve heat and mass transfer, the silicon-carbon anode composite materials for lithium-ion batteries can be prepared in a controllable manner.

[0005] The present invention is implemented as follows:

[0006] This invention provides a device for preparing silicon-carbon anode composite material for lithium-ion batteries, comprising, in order from top to bottom: a plasma generator, a supersonic jet tube, and a high-temperature reaction chamber. A mixture of hydrogen and argon gas is introduced into the upper part of the plasma generator, or argon gas is introduced directly. A feed inlet is provided at the lower part of the plasma generator for introducing silicon powder. An opening is provided at the top of the high-temperature reaction chamber for introducing methane.

[0007] A further step is:

[0008] The high-temperature reaction chamber is a cylindrical structure. Inside the high-temperature reaction chamber, from top to bottom, starting from the top of the chamber, the position one-tenth of the height of the chamber from the top is designated as the first temperature measuring point, the position two-fifths of the height of the chamber from the top is designated as the second temperature measuring point, and the position four-fifths of the height of the chamber from the top is designated as the third temperature measuring point. Temperature measuring elements are installed at each of the three temperature measuring points.

[0009] A further step is:

[0010] The ratio of the diameter of the high-temperature reaction chamber to the diameter of the Laval nozzle throat is preferably between 10 and 50, and the length-to-diameter ratio of the high-temperature reaction chamber is controlled between 2 and 4; thus, the supersonic jet can drive efficient heat and mass transfer within the high-temperature reaction chamber.

[0011] A further step is:

[0012] The high-temperature reaction chamber has a temperature-controlled wall surface made of ceramic, graphite, or high-temperature resistant alloy, which can prevent the wall surface from contaminating the product.

[0013] A further step is:

[0014] The plasma generator can be driven by a DC, high-frequency (MHz), or microwave (GHz) power supply.

[0015] The high-temperature reaction chamber is equipped with high-temperature heat-conducting oil and a temperature sensor for temperature control, thereby effectively controlling the speed of the high-temperature tail flame during large eddy cooling.

[0016] This invention provides a method for preparing a silicon-carbon anode composite material for lithium-ion batteries, employing a preparation apparatus for the silicon-carbon anode composite material for lithium-ion batteries provided by this invention, and specifically including the following steps:

[0017] Argon / hydrogen or argon gas is introduced into the plasma generator. Under the action of an external power source (which can be DC, high-frequency, or microwave), the gas is ionized to form thermal plasma with a temperature exceeding 10,000°C. At the feed inlet at the lower end of the plasma generator, silicon powder is fed downstream of the discharge zone of the plasma generator through a powder feeder using argon / hydrogen or argon gas. Utilizing the high enthalpy characteristic of plasma, the fed solid silicon particles are liquefied into silicon droplets or vaporized into silicon vapor. To reduce the problem of sputtering contamination of products by the plasma generator, the inner wall of the plasma generator is lined with graphite.

[0018] The plasma tail flame containing silicon droplets or silicon vapor enters a replaceable Laval nozzle (i.e., a supersonic jet tube), where it is accelerated to supersonic speeds. Increasing the fluid to supersonic speeds primarily enhances heat and mass transfer of the material and prevents subsequent agglomeration of silicon-carbon composite materials. The Laval nozzle is made of specially designed tungsten metal and is capable of forced water cooling.

[0019] A supersonic plasma jet containing silicon droplets or silicon vapor enters the high-temperature reaction chamber, while methane enters through an opening at the top. Due to the high velocity and viscosity of the plasma jet containing silicon droplets or silicon vapor, a vortex is generated, driving efficient heat exchange between the gas and the walls within the chamber. This vortex entrains the injected low-temperature methane into the high-temperature jet containing silicon droplets or silicon vapor. The silicon vapor is cooled and solidified or liquefied, while the methane is heated and cracked. The cracked carbon black adheres to the solidified silicon or liquefied silicon droplets. The latter continues to release heat as the silicon droplets cool and solidify, further cracking methane on the silicon particle surface, ultimately forming a silicon-carbon composite material. Finally, this material is carried by the gas flow into the product collection system.

[0020] The core principle of this invention is:

[0021] Driven by an external power source, a high-temperature, high-enthalpy plasma is formed within the plasma generator. Downstream of the torch, silicon powder is introduced and liquefied or vaporized within the plasma generator cavity. Subsequently, the high-temperature gas containing silicon droplets or silicon vapor is accelerated to supersonic speeds in a Laval nozzle. The total intake gas volume (standard state, m³ / s) above the Laval nozzle is used to generate the plasma generator. 3 / h) and the cross-sectional area of ​​the Laval nozzle throat (mm) 2 The ratio of argon to silicon vapor is preferably controlled between 1.2 and 1.8. Supersonic silicon-containing droplets or silicon vapor high-temperature fluid enters the high-temperature reaction chamber. Its input power, input gas volume, silicon powder quantity, and methane temperature and flow rate are all adjustable. The temperature and flow rate of the high-temperature fluid exiting the Laval nozzle can be controlled by adjusting the discharge power, gas flow rate, and silicon powder quantity. Preferably, the plasma generator power is between 100 and 300 kW, and the input argon gas is 4–45 m³ / h. 3 / h, input hydrogen 30-90m³ 3 / h: Silicon powder feed rate is 3.2~9.6kg / h, methane 13~40m³ / h 3 / h. The plasma generator has two air inlets, one above and one below, through which a mixture of argon and hydrogen gas is introduced. The volume ratio of the gas introduced through the two air inlets is 2 to 3.

[0022] To further achieve adjustable overall reaction kinetics, the wall temperature of the high-temperature reaction chamber is adjustable from 50℃ to 350℃ via high-temperature heat transfer oil through coils. The temperature of the methane gas fed into the chamber is adjustable from 25℃ to 400℃ via an external gas heater. The main body temperature of the reaction chamber can be controlled between 1300 and 2000℃, and it can simultaneously and continuously receive silicon-containing high-temperature jets and methane from the plasma generator. Three temperature measuring points are set at the top one-tenth of the height of the high-temperature reaction chamber, the second at two-fifths of the height, and the third at four-fifths of the height, for a total of three. A synchronous feedback temperature control system is established, and the temperature of the high-temperature reaction chamber is controllable by controlling one or more variables, including power load, discharge gas volume, methane feed temperature, and the wall temperature of the high-temperature reaction chamber. The length-to-diameter ratio of the cavity is then matched to control the eddy current and material residence time within the cavity, ensuring that silicon and carbon do not directly generate a large amount of silicon carbide, but rather that silicon is used as the core and carbon is orderly wrapped to form a silicon carbide composite material.

[0023] In this invention, the entire reaction process can be automatically controlled by a PLC. For example, the plasma generator inlet flow rate, the high-temperature reaction chamber temperature, gas delivery, and pressure feedback can all be controlled by a PLC, resulting in a high degree of intelligence in the reaction device.

[0024] In the above-mentioned method for preparing silicon-carbon composite materials by argon / hydrogen or argon plasma method, the volume flow ratio of argon to hydrogen in the argon / hydrogen mixed gas is 1:2 to 1:10.

[0025] This invention optimizes the total gas flow rate of the plasma generator by matching the Laval nozzle size, thereby accelerating the high-temperature plasma tail flame containing silicon vapor or liquid silicon to sonic or supersonic speeds. The varying fluid velocities result in different silicon sizes, thus enabling size control of the silicon core in silicon-carbon composite materials. With a fixed flow rate and temperature in the high-temperature plasma generator jet, the main temperature of the high-temperature reaction chamber can be controlled by adjusting the wall temperature of the high-temperature reaction chamber and the temperature of the incoming methane. Given a fixed gas flow rate, Laval nozzle size, and characteristic dimensions of the reaction chamber, efficient heat and mass transfer in the main reaction zone can be achieved by appropriately increasing the power load within the plasma generator, adjusting the high-temperature reaction chamber wall temperature, the temperature of the incoming methane gas, and the amount of incoming methane. This further improves reaction uniformity and the controllability of the kinetics of silicon-carbon composite material preparation. The above series of operations effectively suppresses silicon carbide formation and promotes the orderly coating of carbon on the silicon particle surface, significantly improving the material's cycle stability and rate performance, making it suitable for the large-scale production of high-energy-density lithium-ion battery anode materials.

[0026] Compared with the prior art, the present invention has at least the following outstanding technical effects:

[0027] This invention enables efficient and continuous preparation of silicon-carbon composite materials, significantly improving the uniformity and consistency of the materials; it achieves this by precisely controlling plasma power, gas flow rate, and the amount of silicon powder, as well as controlling the temperature of the high-temperature plasma jet; and it effectively suppresses the formation of silicon carbide by separating the silicon powder and methane into separate portions.

[0028] The hydrogen produced by the present invention can be recycled and used as hydrogen fuel, making the present invention more cost-effective and economical.

[0029] The process for preparing silicon-carbon composite materials using argon / hydrogen or argon plasma methods is environmentally friendly, the equipment is easy to scale up, and it is easier to produce on a large scale. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the apparatus for preparing silicon-carbon anode composite material for lithium-ion batteries according to an embodiment of the present invention.

[0031] Figure 2 This is a diagram showing the gas flow direction and temperature change inside a high-temperature reaction chamber according to an embodiment of the present invention.

[0032] Figure 3 This is a SEM image of a silicon-carbon composite material prepared according to an embodiment of the present invention;

[0033] Figure 4 This is a SEM mapping image of the silicon-carbon composite material prepared according to an embodiment of the present invention.

[0034] Figure 5 XRD pattern of silicon-carbon composite material prepared according to an embodiment of the present invention. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0036] Example 1

[0037] This embodiment provides an apparatus for preparing silicon-carbon anode composite materials for lithium-ion batteries, as shown in the attached diagram. Figure 1 As shown, the following components are installed sequentially from top to bottom: a plasma generator 1, a supersonic jet pipe 3 (also known as the Laval nozzle mentioned earlier), and a high-temperature reaction chamber 5. The upper part of the plasma generator is supplied with a mixture of hydrogen and argon gas, or argon gas is supplied directly. A feed port 2 is provided at the lower part of the plasma generator for supplying silicon powder. An opening 4 is provided at the top of the high-temperature reaction chamber for supplying methane.

[0038] The high-temperature reaction chamber 5 is a cylindrical structure. Inside the high-temperature reaction chamber, from top to bottom, starting from the top of the high-temperature reaction chamber, the position one-tenth of the height of the high-temperature reaction chamber from the top is designated as the first temperature measuring point 7, the position two-fifths of the height of the high-temperature reaction chamber from the top is designated as the second temperature measuring point 8, and the position four-fifths of the height of the high-temperature reaction chamber from the top is designated as the third temperature measuring point 9. Temperature measuring elements are respectively set at the three temperature measuring points.

[0039] The ratio of the diameter of the high-temperature reaction chamber to the diameter of the Laval nozzle throat is preferably between 10 and 50, and the length-to-diameter ratio of the high-temperature reaction chamber is controlled between 2 and 4; thus, the supersonic jet can drive efficient heat and mass transfer within the high-temperature reaction chamber.

[0040] The high-temperature reaction chamber has a temperature-controlled wall surface made of ceramic, graphite, or high-temperature resistant alloy, which can prevent the wall surface from contaminating the product.

[0041] The lower part of the high-temperature reaction chamber is equipped with a material outlet 6, which is used to discharge the silicon-carbon anode composite material generated by the reaction.

[0042] The plasma generator can be driven by a DC, high-frequency (MHz), or microwave (GHz) power supply.

[0043] The high-temperature reaction chamber is equipped with a heating resistance wire and a temperature sensor for temperature control, thereby effectively controlling the speed of the high-temperature tail flame during large eddy current cooling.

[0044] Example 2

[0045] This embodiment provides a method for preparing silicon-carbon anode composite material for lithium-ion batteries, using the preparation apparatus for silicon-carbon anode composite material for lithium-ion batteries described in Embodiment 1.

[0046] In this embodiment, a DC arc thermal plasma generator is used. The total gas intake of the plasma generator is 75m³. 3 / h, using a Laval nozzle with a throat diameter of 4mm, the cross-sectional area of ​​the finest part of the Laval nozzle is 12.56mm. 2 All air intake of the plasma generator above the Laval nozzle (standard state, m 3 / h) and the cross-sectional area of ​​the Laval nozzle throat (mm) 2 The ratio of the two components is preferably controlled between 1.2 and 1.8. The inner diameter of the high-temperature reaction chamber is 350 mm, and the ratio of the high-temperature reaction chamber diameter to the Laval nozzle throat diameter is preferably between 10 and 50. The high-temperature reaction chamber is 1200 mm long, and the length-to-diameter ratio of the chamber is preferably controlled between 2 and 4.

[0047] 1. Turn on the chiller unit to keep the entire system's protective layer in a water-cooled state;

[0048] 2. Turn on the gas source and use argon to purge the air from the entire reaction system. The temperature of the high-temperature reaction chamber wall is controlled at around 120°C using high-temperature heat transfer oil.

[0049] 3. The plasma generator first uses pure argon discharge to ignite the arc. After the arc torch stabilizes, the control system increases the power of the plasma generator to 150kW, and the total discharge gas volume of the plasma generator is 50m³. 3 / h (argon to hydrogen ratio of 1:2), continuous discharge raises the main body temperature in the high-temperature reaction chamber to over 1500℃, especially at the first temperature measuring point 7, where the temperature exceeds 1500℃. The purpose of the above operation is to utilize the heat of the plasma to raise the temperature of the entire reaction system. The gas flow direction and temperature changes within the high-temperature reaction chamber are shown in the attached figure. Figure 2 As shown.

[0050] 4. After the temperature at the first temperature measuring point 7 inside the high-temperature reaction chamber rises to 1500℃, a 25m sample is immediately drawn from the feed inlet. 3 A mixture of argon and hydrogen gas (argon to hydrogen ratio of 1:2) is fed into a silicon powder at a rate of 4.8 kg / h. The silicon powder is then liquefied and ejected at sonic speed into the high-temperature reaction chamber through a Laval nozzle.

[0051] 5. After the temperature at the second temperature measuring point 8 in the high-temperature reaction chamber reaches 1900℃, room-temperature methane gas is introduced into the opening 4 at the top of the high-temperature reaction chamber. The flow rate of room-temperature methane is automatically controlled between 24 and 26 m³ / h. Due to the endothermic effect of methane, the temperature inside the high-temperature reaction chamber drops rapidly. At this time, the temperature at the first temperature measuring point 7 fluctuates between 800℃ and 850℃, the temperature at the second temperature measuring point 8 fluctuates between 1370℃ and 1400℃, and the temperature at the third temperature measuring point 9 fluctuates between 1300℃ and 1330℃. At this time, silicon changes from a liquid droplet to a solid. The introduced methane is mainly pyrolyzed in the regions of the second temperature measuring point 8 and the third temperature measuring point 9 to generate free carbon, which is deposited on the surface of the silicon particles to form a uniform carbon coating layer. At this time, the temperature is controlled below 1400℃, thereby effectively suppressing the formation of silicon carbide. This is also the core inventive point of this invention, namely, controlling the kinetic conditions of silicon carbide formation from the flow field and controlling the thermodynamic conditions of silicon carbide formation from the temperature. By controlling the methane flow rate and reaction temperature gradient, the carbon layer thickness can be grown in a controlled manner. Meanwhile, the hydrogen produced during the reaction can be recovered and reused after cooling and separation, either for plasma generation or as a clean energy source, further reducing energy consumption and emissions.

[0052] 6. The silicon-carbon composite material generated in the reaction chamber is rapidly cooled by the airflow into a heat exchanger, and then enters a gas-solid separation system for gas-solid separation. The sample is then analyzed. It can be found that the silicon-carbon composite material is primarily composed of aggregated particles of approximately 100 nm (see attached image). Figure 3As shown in the attached figure, the carbon layer is uniformly coated on the surface of the silicon particles. Figure 4 As shown, SEM mapping reveals that carbon elements form a continuous coating structure on the surface of silicon particles, with no obvious defects or voids, confirming the good integrity of the carbon layer.

[0053] As attached Figure 5 As shown, XRD analysis revealed that the characteristic peaks were mainly diffraction peaks of elemental silicon, with no obvious silicon carbide diffraction peaks, indicating that the process effectively suppressed the formation of the SiC phase.

[0054] Although the invention has been described herein with reference to illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various variations and modifications can be made to the components and / or layout of the subject matter combination within the scope of this disclosure. Besides variations and modifications to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. An apparatus for preparing silicon-carbon anode composite material for lithium-ion batteries, characterized in that: The components, installed sequentially from top to bottom, include: a plasma generator, a supersonic jet tube, and a high-temperature reaction chamber. The upper part of the plasma generator is supplied with a mixture of hydrogen and argon gas, or argon gas is supplied directly. A feed inlet is provided at the lower part of the plasma generator for supplying silicon powder. An opening is provided at the top of the high-temperature reaction chamber for supplying methane.

2. The apparatus for preparing silicon-carbon anode composite material for lithium-ion batteries according to claim 1, characterized in that: The high-temperature reaction chamber is a cylindrical structure. Inside the high-temperature reaction chamber, from top to bottom, starting from the top of the chamber, the position one-tenth of the height of the chamber from the top is designated as the first temperature measuring point, the position two-fifths of the height of the chamber from the top is designated as the second temperature measuring point, and the position four-fifths of the height of the chamber from the top is designated as the third temperature measuring point. Temperature measuring elements are installed at each of the three temperature measuring points.

3. The apparatus for preparing silicon-carbon anode composite material for lithium-ion batteries according to claim 1, characterized in that: The ratio of the diameter of the high-temperature reaction chamber to the diameter of the Laval nozzle throat is between 10 and 50, and the length-to-diameter ratio of the high-temperature reaction chamber is controlled between 2 and 4.

4. The apparatus for preparing the silicon-carbon anode composite material for lithium-ion batteries according to claim 1, characterized in that: The high-temperature reaction chamber has a temperature-controlled wall surface, which is made of ceramic, graphite, or a high-temperature resistant alloy.

5. The apparatus for preparing silicon-carbon anode composite material for lithium-ion batteries according to claim 1, characterized in that: The plasma generator is driven by a DC, high-frequency, or microwave power supply.

6. The apparatus for preparing silicon-carbon anode composite material for lithium-ion batteries according to claim 1, characterized in that: The high-temperature reaction chamber is equipped with a heating resistance wire and a temperature sensor for temperature control, thereby effectively controlling the speed of the high-temperature tail flame during large eddy current cooling.

7. A method for preparing a silicon-carbon anode composite material for lithium-ion batteries, characterized in that... The apparatus for preparing a silicon-carbon anode composite material for lithium-ion batteries according to any one of claims 1 to 6 is adopted, and specifically includes the following steps: Argon / hydrogen mixed gas or argon is fed into the plasma generator. Under the action of an external power source, the gas is ionized to form a thermal plasma with a temperature of over 10,000°C. At the feed inlet at the lower end of the plasma generator, silicon powder is fed into the downstream of the discharge zone of the plasma generator using argon / hydrogen mixed gas or argon. Utilizing the high enthalpy characteristics of the plasma, the fed solid silicon particles are liquefied into silicon droplets or vaporized into silicon vapor. The plasma tail containing silicon droplets or silicon vapor enters a replaceable Laval nozzle and is accelerated to supersonic speeds within the nozzle. A supersonic plasma jet containing silicon droplets or silicon vapor enters a high-temperature reaction chamber, while methane enters from an opening at the top of the chamber. Due to the high velocity and viscosity of the plasma jet containing silicon droplets or silicon vapor, eddies are generated, driving efficient heat exchange between the gas and the walls within the chamber. These eddies entrain the injected low-temperature methane into the high-temperature jet containing silicon droplets or silicon vapor, where the silicon vapor is cooled, solidified, or liquefied, while the methane is heated and cracked. The cracked carbon black adheres to the solidified silicon or liquefied silicon droplets, which continue to release heat as the droplets cool and solidify. Further methane cracks on the surface of the silicon particles, ultimately forming a silicon-carbon composite material. Finally, the material is carried by the gas flow into the product collection system.

8. The method for preparing the silicon-carbon anode composite material for lithium-ion batteries according to claim 7, characterized in that: The Laval nozzle is made of tungsten metal and is capable of forced water cooling.

9. The method for preparing the silicon-carbon anode composite material for lithium-ion batteries according to claim 7, characterized in that: The plasma generator has a power of 100–300 kW and an input argon gas concentration of 4–45 m³. 3 / h, input hydrogen 30~90m 3 / h: Silicon powder feed rate is 3.2~9.6kg / h, methane 13~40m³ / h 3 / h, the plasma generator has two air inlets, one above and one below, with a volume ratio of 2 to 3 for the air entering through the two air inlets.

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