Fluidized bed for carbon-coated chemical vapor deposition

Abstract

The utility model relates to equipment for carbon coating of a lithium battery cathode material, in particular to a fluidized bed for carbon coating chemical vapor deposition, which comprises a vertically arranged container body and a vibrating table for vibrating the container body, the lower part of the container body is provided with a baffle plate or a baffle net, a discharge port and a carbon source gas inlet, the discharge port and the carbon source gas inlet are respectively positioned above and below the baffle plate or the baffle net, a guide cylinder coaxial with the container body is also arranged above the baffle plate or the baffle net, the bottom of the guide cylinder is connected with the carbon source gas inlet, and the carbon source gas inlet is connected with the discharge port. A stirring device for driving airflow to move upwards is arranged in the guide cylinder, a heater is arranged between the outer wall of the guide cylinder and the inner wall of the container body, the inner side of the guide cylinder forms a reaction area, and the outer side forms a heating area; the device disclosed by the utility model can effectively solve the problems of agglomeration and accumulation of granular materials and poor coating consistency in the carbon-coated chemical vapor deposition process.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of equipment for carbon-coated lithium battery negative material, specifically to a kind of fluidized bed for carbon-coated chemical vapor deposition. BACKGROUND

[0002] Silicon monoxide (SiO) as lithium ion battery negative material, with higher theoretical specific capacity and suitable delithiation potential, is considered to be the next generation of lithium battery negative material. However, SiO has a serious volume effect during the process of delithiation / intercalation, which easily leads to material particle pulverization, shedding, and seriously affects the interface stability and electrochemical performance of SiO negative electrode. Therefore, carbon coating treatment needs to be carried out on the surface of silicon-based material to alleviate volume expansion and enhance the conductivity of silicon-based material. Carbon coating treatment is carried out on the surface of silicon-based material to obtain silicon-carbon negative electrode, and the technical difficulty lies in the uniformity of coating during mass production.

[0003] Currently, although attempts have been made to combine fluidized bed technology to prepare silicon-carbon negative material, such as Chinese patent CN202210186398.7, a modified silicon-oxygen negative material precursor and preparation method, the silicon monoxide raw material needs to be surface pretreated and modified to make the dispersibility of silicon monoxide better and easier to achieve fluidization state. The modifier needs to use one or more of long-chain alkyl silane coupling agent, higher fatty acid or higher fatty acid salt, which not only increases the cost of materials, but also makes the process more complex.

[0004] The ideal fluidization state is to enable the particles to fully contact with the gas phase when they are in a stable fluidization state inside the fluidized bed reactor, and the two phases are in a turbulent state, effectively reducing the reaction dead zone. However, the silicon monoxide powder used as lithium ion battery negative material belongs to Geldart C ultra-fine particles, and its intermolecular force is similar to gravity, and the inter-particle viscosity increases. When these ultra-fine powder particles are directly used for fluidization, phenomena such as channeling and agglomeration often occur, which makes the particle bed layer only partially fluidized or even completely unable to fluidize, thereby causing the surface to present island-shaped deposition problems during chemical vapor deposition, which significantly affects the electrochemical performance. The existing technology does not provide an effective solution to this problem. UTILITY MODEL CONTENTS

[0005] The utility model aims to provide a kind of fluidized bed for carbon-coated chemical vapor deposition to solve the problem of particle material agglomeration accumulation and poor uniformity of coating during carbon-coated chemical vapor deposition process.

[0006] In order to solve the above problems, the utility model provides a kind of for carbon-coated chemical vapor deposition fluidized bed, including vertically arranged container body and vibration platform of vibrating container body, the container body upper portion is provided with screw feeder and exhaust port, the container body lower portion is provided with baffle or screen, discharge port and carbon source gas inlet, the discharge port and carbon source gas inlet are located above and below baffle or screen respectively, the baffle or screen top is also equipped with the flow guide cylinder coaxial with container body, flow guide cylinder bottom is connected with carbon source gas inlet, flow guide cylinder is equipped with stirring device for driving airflow to move upwards, heater is arranged between the outer wall of flow guide cylinder and the inner wall of container body, the inside of flow guide cylinder constitutes reaction zone, and the outside constitutes heating zone.

[0007] Further, the feeding port is connected with the screw feeder, and the cyclone separator for recovering particles is arranged in the inside of the exhaust port, the particles carried out of the bed layer by fluid are collected by the cyclone separator, and the recovered particles are returned to the fluidized bed reactor.

[0008] Further, in order to better break bubbles, improve gas-solid contact and reduce backmixing, the baffle is an outer spin, inner spin or multi-spin baffle.

[0009] Further, in order to better heat the reaction zone, the side wall of the flow guide cylinder is provided with holes communicating the reaction zone and the heating zone.

[0010] Further, the gas distribution device is arranged between the baffle or screen and the fluidization gas inlet, and the gas distribution device includes a gas pre-distributor and a gas distribution plate, so that the pressure of fluidization gas is uniform, the gas uniformly enters the distribution plate, and the load of the gas distribution plate in uniformly distributing gas is reduced.

[0011] The method for vapor-deposited carbon-coated is as follows: the particles to be coated are continuously fed into the reaction zone of the fluidized bed reactor by the screw feeder and react with carbon source gas, the particle size is 20-30um, the flow of fluidization gas is adjusted to about 8L / s, so that the particles gradually reach the fluidized state, and the heating temperature of the fluidized bed is adjusted to 600-1000℃; the silicon-carbon negative electrode material coated with carbon is continuously discharged by the discharge device.

[0012] The carbon-coated chemical vapor deposition fluidized bed has the following characteristics: the silicon monoxide particle size is 20-30 um, the difference between the intermolecular force and gravity is large, the viscosity between the particles is reduced, the fluidity of the particles is improved, under the action of the stirring device and the vibration table, especially in combination with the carbon source gas connected to the bottom of the flow guide cylinder, the particles can be well turned over, the particles are in a fluidized state, agglomeration and accumulation are avoided, and the heater is arranged between the outer wall of the flow guide cylinder and the inner wall of the container body, so that the reaction zone formed on the inner side of the flow guide cylinder is continuously stirred and uniformly heated, and the consistency of the carbon coating is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application.

[0014] Figure 1 It is a structural schematic view of the fluidized bed for carbon-coated chemical vapor deposition.

[0015] The drawings include: container body 1, charging port 12, cyclone separator 13, screen 14, discharge port 15, fluidization gas inlet 16, carbon source gas inlet 17, gas distribution plate 18, vibration table 2, flow guide cylinder 3, heater 4. DETAILED DESCRIPTION

[0016] The following embodiments are used to illustrate the present application, but not to limit the scope of the present application. If the specific technology or condition is not indicated in the embodiments, the technology or condition is described in the literature in the art, or according to the product manual.

[0017] In the description of the present application, unless otherwise specified, the orientation or state relationship indicated by the terms "upper", "lower" and the like is based on the orientation or state relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0018] In the following embodiments, the instruments and equipment used without indicating the manufacturer are conventional products that can be purchased through a regular channel. The method is a conventional method unless otherwise specified, and the raw materials can be obtained from a public commercial channel unless otherwise specified.

[0019] EMBODIMENT

[0020] As Figure 1As shown, the embodiment provides a fluidized bed for carbon-coated chemical vapor deposition, which comprises a vertically arranged container body 1 and a vibrating table 2 for vibrating the container body 1, the container body 1 is installed on the vibrating table 2, the container body 1 is a cylindrical tank, the upper part of the container body is provided with a feeding port 12 and an exhaust port (not shown in the figure), the feeding port 12 is connected with a screw feeder, a cyclone separator 13 is connected in series on the exhaust port, the cyclone separator 3 is preferably arranged inside the exhaust port, the particles carried out of the bed by the fluid can be collected through the cyclone separator 13, and the recovered particles return to the bed of the fluidized bed. The lower part of the container body 1 is provided with a screen 14 and a discharge port 15, the bottom of the container body 1 is provided with a fluidization gas inlet 16 and a carbon source gas inlet 17, the screen 14 can also be replaced by a baffle, the baffle can adopt an outer spin, an inner spin or a multi-spin baffle, or holes are opened on the baffle to form an outer spin or an inner spin, which can better break the bubbles, improve the gas-solid contact, reduce the back mixing, and the discharge port 15 and the fluidization gas inlet 16 and the carbon source gas inlet 17 are located above and below the screen 14 respectively, the fluidization gas includes but is not limited to nitrogen and argon, and the carbon source gas includes but is not limited to acetylene, a flow guide cylinder 3 coaxial with the container body 1 is further arranged above the screen 14, the side wall of the flow guide cylinder 3 is provided with holes communicating the reaction zone and the heating zone, wherein a heater 4 is arranged between the outer wall of the flow guide cylinder 3 and the inner wall of the container body, the outside of the flow guide cylinder 3 is the heating zone, the inside of the flow guide cylinder 3 is the reaction zone, the bottom of the flow guide cylinder 3 communicates with the carbon source gas inlet, and the flow guide cylinder 3 is provided with a stirring device for driving the airflow to move upward, and the stirring device is preferably a stirring blade driven by a motor. The vibrating table 2 vibrates the container body 1, and the stirring device can realize sufficient stirring of the material layer. In addition, different gas pressures are supplied into the fluidization gas inlet 16 and the carbon source gas inlet 17 through the coupling pulse mode to further mix and avoid the reaction dead zone.

[0021] The screw feeder and the container body 1 are preferably made of stainless steel structure, and the whole is treated by surface treatment, grounding treatment, temperature and humidity control and / or electrostatic eliminator to further avoid the agglomeration phenomenon caused by static electricity.

[0022] A gas distribution device is further arranged between the screen 14 and the fluidization gas inlet 16, the gas distribution device comprises a gas pre-distributor and a gas distribution plate 18, so that the pressure of the fluidization gas is more uniform, the fluidization gas can uniformly enter the gas distribution plate, the load of the gas distribution plate in uniformly distributing the gas is reduced, the gas distribution plate is preferably a side-flow type distribution plate, and a conical air cap is installed on the hole of the distribution plate, so that the airflow flows out from the side seam at the bottom of the conical cap, avoiding the formation of a small dead zone at the top. Since the gas blows out close to the distribution plate surface, the plate surface dead zone can also be eliminated.

[0023] The fluidized bed reactor provided by the embodiment realizes the method of gas phase deposition carbon coating, which is that micron-sized silicon monoxide powder is added into a carbon-containing binder solution, the carbon-containing binder solution includes polyacrylonitrile, polystyrene, polyvinylpyrrolidone and / or polyvinyl alcohol, and after mixing and fully stirring, drying and shaping are performed to obtain secondary particles with a particle size of 20-30 um, the obtained secondary particles are continuously fed into a fluidized bed reaction zone through a screw feeder and react with a carbon source gas, the flow rate of fluidizing gas is controlled to be initially set as 8 L / s, the heating temperature of the fluidized bed is 600-1000 DEG C, and after the material is kept at the temperature for 1 h, the silicon-carbon negative electrode material coated with carbon is continuously discharged through a discharging device, and the discharging device can be a rotary valve or a star-shaped discharger.

[0024] The above is only an embodiment of the present application, and the common knowledge of specific structures, properties and reactant ratios in the scheme is not described in detail, and the preferred values of raw materials are given. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, such as simple changes to the feeder or discharger, simple changes to the stirring device, etc., which should also be considered as the protection scope of the present application, and these will not affect the implementation effect and the practicality of the patent. The protection scope of the present application should be subject to the content of its claims, and the specific implementation mode and the like in the specification can be used to explain the content of the claims.

Claims

1. A fluidized bed for carbon-coated chemical vapor deposition, characterized by The application relates to a vertical container body and a vibrating table for vibrating the container body, wherein the upper part of the container body is provided with a feeding port and an exhaust port, the lower part of the container body is provided with a baffle or a screen, a discharging port, the bottom of the container body is respectively provided with a fluidizing gas inlet and a carbon source gas inlet, the discharging port is located above the baffle or the screen, the fluidizing gas inlet and the carbon source gas inlet are located below the baffle or the screen, a flow guide cylinder coaxial with the container body is further arranged above the baffle or the screen, the bottom of the flow guide cylinder is connected with the carbon source gas inlet, stirring devices for driving gas flow to move upwards are arranged in the flow guide cylinder, a heater is arranged between the outer wall of the flow guide cylinder and the inner wall of the container body, the inner side of the flow guide cylinder constitutes a reaction zone, and the outer side constitutes a heating zone.

2. The fluidized bed for carbon-coated chemical vapor deposition according to claim 1, wherein: A cyclone separator for recovering particles is arranged in the exhaust port, and a screw feeder is connected with the feeding port.

3. The fluidized bed for carbon-coated chemical vapor deposition according to claim 1, wherein: The baffle is an outer spiral baffle, an inner spiral baffle or a multi-spiral baffle.

4. The fluidized bed for carbon-coated chemical vapor deposition according to claim 1, wherein: Holes for connecting the reaction zone and the heating zone are arranged in the side wall of the flow guide cylinder.

5. The fluidized bed for carbon-coated chemical vapor deposition according to claim 1, wherein: A gas distribution device is further arranged between the baffle or the screen and the fluidizing gas inlet.

6. The fluidized bed for carbon-coated chemical vapor deposition according to claim 5, wherein: The gas distribution device comprises a gas pre-distributor and a gas distribution plate.

7. The fluidized bed for carbon-coated chemical vapor deposition according to claim 6, wherein: The gas distribution plate is a side-flow type distribution plate, and a conical air cap is arranged on the distribution hole of the distribution plate.

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