Fluidized bed equipment for gradient coating modification of silicon powder and production process

Abstract

The invention relates to the technical field of silicon powder material preparation, and discloses silicon powder gradient coating modified fluidized bed equipment, which comprises a fluidized bed reactor main body, which comprises an expansion section, a cylindrical reaction section and a conical gas distribution section which are connected from top to bottom; the multi-path precise feeding system comprises a silicon powder feeding unit used for conveying silicon powder into the reactor; the carrier gas unit is used for providing fluidizing gas and reaction carrier gas; the at least two paths of independent precursor supply units are used for conveying different coating precursors respectively; according to the multi-zone independent temperature control system, at least two independently-controlled heating zones are arranged on the outer wall of a reaction section; the gas flow distribution plate is arranged at the top end of the conical gas distribution section; the tail gas treatment and product recovery system is connected with an outlet of the expansion section. Compared with the prior art, the invention has the following advantages: multi-path precursor sequential control and partitioned temperature control are realized, continuous gradient change of coating layer components and structures is realized, the coating quality is high, the equipment can realize continuous feeding and discharging, and the production efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of silicon powder material preparation technology, and in particular to a silicon powder gradient coating modified fluidized bed equipment and production process. Background Technology

[0002] Silicon is considered the most promising anode material for next-generation high-energy-density lithium-ion batteries due to its extremely high theoretical specific capacity. However, silicon exhibits significant volume expansion during charge and discharge, leading to particle pulverization, continuous growth of the solid electrolyte interfacial film, and a sharp decline in cycle performance, which severely hinders its commercial application.

[0003] To address these issues, the most common strategy is to surface-coat silicon particles, especially with carbon. The carbon layer can both buffer volume changes and improve electronic conductivity. However, existing coating techniques (such as mechanical mixing and liquid-phase coating) suffer from problems such as uneven coating layers, weak bonding with the silicon core, and susceptibility to cracking during cycling. Simple single-layer carbon coating structures cannot simultaneously meet the conflicting requirements of "flexible buffering" and "high strength and stability."

[0004] While chemical vapor deposition (CVD) can achieve uniform coating, traditional CVD furnaces are mostly batch-based, resulting in low efficiency and difficulty in achieving complex multi-layer or gradient structures. Fluidized bed reactors have excellent gas-solid contact efficiency and can be used for continuous production, but conventional fluidized bed equipment is insufficient in achieving precise, programmable gradient coating and lacks corresponding multi-feed and zoned temperature control designs.

[0005] To address the aforementioned technical problems, this application proposes a fluidized bed equipment and production process capable of achieving gradient, homogenization, and high-strength coating modification of silicon powder. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] The technical problem to be solved by this invention is that conventional fluidized bed equipment is insufficient in achieving precise and programmable gradient coating, and lacks corresponding multi-feed and zoned temperature control designs.

[0008] (II) Technical Solution

[0009] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a silicon powder gradient coating modified fluidized bed device, comprising:

[0010] The fluidized bed reactor body includes an expansion section, a cylindrical reaction section, and a conical gas distribution section connected from top to bottom;

[0011] A multi-channel precision feeding system includes:

[0012] The silicon powder feeding unit is used to feed silicon powder into the reactor;

[0013] Carrier gas unit, used to provide fluidizing gas and reaction carrier gas;

[0014] At least two independent precursor supply units are used to deliver different coated precursors respectively;

[0015] A multi-zone independent temperature control system is provided, wherein the outer wall of the reaction section is provided with at least two independently controlled heating zones to form a temperature gradient field inside the reactor;

[0016] An airflow distribution plate is disposed at the top of the conical gas distribution section;

[0017] An exhaust gas treatment and product recovery system is connected to the outlet of the expanded section.

[0018] As an improvement, the at least two independent precursor supply units include a first precursor and a second precursor, and each unit includes a precursor source, a precision metering pump and a mass flow controller.

[0019] As an improvement, the multi-zone independent temperature control system includes an independently controlled lower heating zone and an upper heating zone, which correspond to the lower low-temperature zone and the upper high-temperature zone of the reaction section, respectively.

[0020] As an improvement, a plurality of atomizing nozzles are provided on the sidewall of the reaction section, and the atomizing nozzles are connected to the precursor supply unit.

[0021] As an improvement, the airflow distribution plate is a porous sintered metal plate.

[0022] As an improvement, the exhaust gas treatment and product recovery system includes a cyclone separator, a bag filter, and a condensation scrubber connected in sequence.

[0023] A silicon powder gradient coating modification production process for a fluidized bed equipment includes the following steps:

[0024] (1) System pretreatment: Purge the system with inert gas to remove air;

[0025] (2) Preheating and fluidization: Start the temperature control system, heat the reactor to the target temperature in sections, and introduce fluidizing carrier gas to fluidize the silicon powder bed;

[0026] (3) Inner coating: The first precursor is activated and injected into the low-temperature zone at the bottom of the reactor for chemical vapor deposition to form an inner coating layer.

[0027] (4) Gradient coating: While maintaining or adjusting the temperature, the relative flow rates of the first precursor and the second precursor are changed, so that the silicon powder particles deposit coating layers with different properties in different temperature regions during the fluidization process, thereby achieving a gradient transition.

[0028] (5) Cooling and discharge: After the coating is completed, stop feeding the precursor and collect the product after cooling.

[0029] As an improvement, in step (2), the target temperature of the lower low-temperature zone is 300-600℃, and the target temperature of the upper high-temperature zone is 600-900℃.

[0030] As an improvement, in step (3), the first precursor is one or more of ethylene, acetylene, and propylene; in step (4), the second precursor is one or more of benzene, toluene, and methane.

[0031] As an improvement, in step (4), the flow rate of the first precursor is linearly or stepwise reduced to zero from the initial value by program control, while the flow rate of the second precursor is linearly or stepwise increased to the target value from zero, with a transition time of 60 to 180 minutes.

[0032] With the above structure, the present invention has the following advantages:

[0033] Gradient structure: Through multi-path precursor timing control and zoned temperature control, continuous gradient changes in the composition and structure of the coating layer are achieved. The inner layer is flexible and buffers expansion, while the outer layer is a robust and stable SEI film, resulting in excellent overall performance.

[0034] High coating quality: Fluidized bed technology combined with vapor deposition ensures the uniformity, density and high bonding force between the coating layer and the silicon core.

[0035] Continuous production: The equipment can achieve continuous feeding and discharging, resulting in high production efficiency, easy scaling up, and good prospects for industrialization.

[0036] Flexible and adjustable: By adjusting parameters such as precursor type, flow rate, temperature and time, gradient coating structures with different requirements can be flexibly designed, making it widely applicable. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of a silicon powder gradient coating modified fluidized bed device according to the present invention.

[0038] As shown in the figure: 1. Feeding bin; 2. Screw feeder; 3. Conical gas distribution section; 4. Airflow distribution plate; 5. Reaction section; 5a. Lower low-temperature zone; 5b. Upper high-temperature zone; 6. Atomizing nozzle; 7. Expansion section; 8. Cyclone separator; 9. Bag filter; 10. Condensation scrubbing tower; 11. First precursor; 12. Second precursor; 13. Mass flow controller; 14. Carrier gas cylinder. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] As attached Figure 1 As shown, a silicon powder gradient coating modified fluidized bed device includes:

[0041] The fluidized bed reactor body includes an expansion section 7, a cylindrical reaction section 5, and a conical gas distribution section 3 connected from top to bottom;

[0042] A multi-channel precision feeding system includes:

[0043] The silicon powder feeding unit is used to feed silicon powder into the reactor;

[0044] Carrier gas unit, used to provide fluidizing gas and reaction carrier gas;

[0045] At least two independent precursor supply units, each including a first precursor 11 and a second precursor 12, each including a precursor source, a precision metering pump and a mass flow controller 13, for delivering different coated precursors respectively.

[0046] A multi-zone independent temperature control system, comprising an independently controlled lower heating zone and an upper heating zone, corresponding to the lower low-temperature zone 5a and the upper high-temperature zone 5b of the reaction section 5, respectively, for forming a temperature gradient field inside the reactor;

[0047] Multiple atomizing nozzles 6 are provided on the side wall of the reaction section 5, and the atomizing nozzles 6 are connected to the precursor supply unit.

[0048] An airflow distribution plate 4 is disposed at the top of the conical gas distribution section 3, and the airflow distribution plate 4 is a porous sintered metal plate;

[0049] The exhaust gas treatment and product recovery system includes a cyclone separator 8, a bag filter 9, and a condensation scrubbing tower 10 connected in sequence, with the cyclone separator 8 connected to the outlet of the expansion section 7.

[0050] A silicon powder gradient coating modification production process for a fluidized bed equipment includes the following steps:

[0051] (1) System pretreatment: Purge the system with inert gas to remove air;

[0052] (2) Preheating and fluidization: Start the temperature control system and heat the reactor to the target temperature in sections. The target temperature of the lower low temperature zone is 300-600℃ and the target temperature of the upper high temperature zone is 600-900℃. Fluidization carrier gas is introduced to fluidize the silicon powder bed.

[0053] (3) Inner coating: The first precursor is activated. The first precursor is one or more of ethylene, acetylene, and propylene. The first precursor is injected into the low-temperature zone at the bottom of the reactor and chemical vapor deposition is performed to form an inner coating layer.

[0054] (4) Gradient coating: While maintaining or adjusting the temperature, the relative flow rates of the first precursor and the second precursor are changed. The second precursor is one or more of benzene, toluene, and methane. The flow rate of the first precursor is linearly or stepwise reduced to zero from the initial value through program control, while the flow rate of the second precursor is linearly or stepwise increased to the target value from zero. The transition time is 60 to 180 minutes, so that the silicon powder particles deposit coating layers with different properties in different temperature regions during the fluidization process, thereby achieving a gradient transition.

[0055] (5) Cooling and discharge: After the coating is completed, stop feeding the precursor and collect the product after cooling.

[0056] The specific usage method is as follows:

[0057] The main body of the fluidized bed reactor: the expansion section 7 is used for particle settling; the reaction section 5 is the core reaction zone, and the side wall is equipped with multi-stage atomizing nozzles 6; the bottom of the conical gas distribution section 3 is connected to the carrier gas cylinder 14, and the top is equipped with an airflow distribution plate 4 made of porous sintered metal plate.

[0058] Feeding system: Silicon powder is continuously fed into the reactor from the feeding hopper 1 via the screw feeder 2. The first precursor 11 (for storing ethylene) and the second precursor 12 (for storing benzene) are precisely controlled in terms of flow rate by the mass flow controller 13 and injected into the bed through the atomizing nozzle 6. The carrier gas (Ar) enters the reactor from the carrier gas cylinder 14 via the airflow distribution plate 4.

[0059] Temperature control system: Two independently controlled heating jackets 15 are wrapped around the outer wall of the reaction section 5 to form a lower low-temperature zone 5a and an upper high-temperature zone 5b.

[0060] Exhaust gas system: After the reaction, the gas enters the cyclone separator 8 through the expansion section 7 to recover fine powder, then passes through the bag filter 9 for deep dust removal, and finally passes through the condensation and scrubbing tower 10 for treatment before being discharged.

[0061] Example 1:

[0062] Silicon powder with an average particle size of 5μm was used as raw material.

[0063] (1) Purge the system with Ar gas for 30 minutes.

[0064] (2) Start heating, set the lower zone 5a to 500℃ and the upper zone 5b to 750℃. Introduce Ar gas to fluidize the silicon powder.

[0065] (3) Turn on the first precursor 11 and introduce ethylene at a flow rate of 50 sccm. React for 30 minutes to form an inner layer of amorphous carbon.

[0066] (4) Maintain the temperature and linearly reduce the ethylene flow rate from 50 sccm to 0 within 60 minutes, while linearly increasing the benzene vapor flow rate of the second precursor 12 from 0 to 80 sccm to perform gradient coating and react for 120 minutes.

[0067] (5) Stop heating and the precursor, and cool it to below 60°C under Ar gas flow before discharging.

[0068] The resulting product, after testing, showed a total coating thickness of approximately 50 nm, with the degree of graphitization gradually increasing from the inside out. The initial coulombic efficiency reached 88%, and the capacity retention after 100 cycles at 0.5C reached 92%.

[0069] Example 2:

[0070] The procedure is basically the same as in Example 1, except that the first precursor is acetylene (500°C) and the second precursor is methane (700°C). Flow rates are superimposed through program control to form a C / C composite gradient coating layer. The product also exhibits excellent electrochemical performance.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

[0072] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0074] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A silicon powder gradient coating modified fluidized bed device, characterized in that, include: The fluidized bed reactor body includes an expansion section (7), a cylindrical reaction section (5), and a conical gas distribution section (3) connected from top to bottom; A multi-channel precision feeding system includes: The silicon powder feeding unit is used to feed silicon powder into the reactor; Carrier gas unit, used to provide fluidizing gas and reaction carrier gas; At least two independent precursor supply units are used to deliver different coated precursors respectively; A multi-zone independent temperature control system is provided, wherein the outer wall of the reaction section (5) is provided with at least two independently controlled heating zones to form a temperature gradient field inside the reactor; An airflow distribution plate (4) is disposed at the top of the conical gas distribution section (3); The exhaust gas treatment and product recovery system is connected to the outlet of the expansion section (7).

2. The silicon powder gradient coating modified fluidized bed equipment according to claim 1, characterized in that, The at least two independent precursor supply units include a first precursor (11) and a second precursor (12), and each unit includes a precursor source, a precision metering pump and a mass flow controller (13).

3. A silicon powder gradient coating modified fluidized bed device according to claim 1 or 2, characterized in that, The multi-zone independent temperature control system includes an independently controlled lower heating zone and an upper heating zone, which correspond to the lower low-temperature zone (5a) and the upper high-temperature zone (5b) of the reaction section (5), respectively.

4. The silicon powder gradient coating modified fluidized bed equipment according to claim 1, characterized in that, Multiple atomizing nozzles (6) are provided on the side wall of the reaction section (5), and the atomizing nozzles (6) are connected to the precursor supply unit.

5. The silicon powder gradient coating modified fluidized bed equipment according to claim 1, characterized in that, The airflow distribution plate (4) is a porous sintered metal plate.

6. The silicon powder gradient coating modified fluidized bed equipment according to claim 1, characterized in that, The exhaust gas treatment and product recovery system includes a cyclone separator (8), a bag filter (9), and a condensation scrubber (10) connected in sequence.

7. A silicon powder gradient coating modification production process using the fluidized bed equipment as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) System pretreatment: Purge the system with inert gas to remove air; (2) Preheating and fluidization: Start the temperature control system, heat the reactor to the target temperature in sections, and introduce fluidizing carrier gas to fluidize the silicon powder bed; (3) Inner coating: The first precursor is activated and injected into the low-temperature zone at the bottom of the reactor for chemical vapor deposition to form an inner coating layer. (4) Gradient coating: While maintaining or adjusting the temperature, the relative flow rates of the first precursor and the second precursor are changed, so that the silicon powder particles deposit coating layers with different properties in different temperature regions during the fluidization process, thereby achieving a gradient transition. (5) Cooling and discharge: After the coating is completed, stop feeding the precursor and collect the product after cooling.

8. The production process according to claim 7, characterized in that, In step (2), the target temperature of the lower low-temperature zone is 300-600℃, and the target temperature of the upper high-temperature zone is 600-900℃.

9. The production process according to claim 7, characterized in that, In step (3), the first precursor is one or more of ethylene, acetylene, and propylene; in step (4), the second precursor is one or more of benzene, toluene, and methane.

10. The production process according to claim 7, characterized in that, In step (4), the flow rate of the first precursor is linearly or stepwise reduced to zero from the initial value through program control, while the flow rate of the second precursor is linearly or stepwise increased to the target value from zero, with a transition time of 60 to 180 minutes.

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