A device and method for efficiently and continuously preparing silicon-based negative electrode materials
By adopting efficient continuous preparation devices and methods in the preparation process of silicon-based negative electrode materials, the problems of agglomeration and accumulation of silicon-based negative electrode materials, poor coating consistency and high energy consumption during the carbon coating process are solved, and more uniform carbon coating and lower energy consumption are achieved, and the electrochemical performance and cyclic stability of the material are improved.
Patent Information
- Application Number
- CN202411946987.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2025-04-01
AI Technical Summary
In the prior art, the silicon-based negative electrode material has problems such as agglomeration and accumulation of particulate materials, poor coating consistency and high energy consumption during the carbon coating process.
An efficient and continuous preparation of silicon-based negative electrode material is adopted, including a sublimation furnace, an air flow crusher, a secondary granulation system, a fluidized bed, a preheater, a heat exchange system and a collection control system. This method combines the heating zone and the deposition zone of the sublimation furnace to uniformly deposit the silicon oxide, and then process it through a gas flow crusher and a secondary granulation system to achieve the A-class particles of more than 30um, improve the flowability, and carry out vapor deposition carbon coating in the fluidized bed.
It effectively solves the problem of poor agglomeration and coating consistency of silicon-based anode materials during carbon coating, improves the consistency of carbon coating, reduces energy consumption, and improves the electrolyte wetting and cycle stability of the material.
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Abstract
Description
Technical Field
[0001] The present invention relates to a lithium battery negative electrode material processing technology, and in particular to a device and method for efficiently and continuously preparing silicon negative electrode materials. Background Art
[0002] Silicon dioxide (SiO) is a negative electrode material for lithium-ion batteries. It has a high theoretical specific capacity and a suitable lithium removal potential, and is considered to be the next generation of lithium battery negative electrode materials. However, SiO has a serious volume effect during the lithium removal / insertion process, which can easily lead to pulverization and shedding of material particles, seriously affecting the interface stability and electrochemical properties of the SiO negative electrode. Therefore, it is necessary to coat the surface of silicon-based materials with carbon to alleviate volume expansion and enhance the conductivity of silicon-based materials. The technical difficulty of carbon coating the surface of silicon-based materials to obtain silicon-based negative electrodes lies in the uniformity of coating during large-scale preparation.
[0003] The current mainstream method for preparing silicon-based negative electrodes uses chemical vapor deposition (CVD), which is to load silicon oxide with appropriate particle size distribution into a thermal decomposition rotary furnace, use acetylene or the like as a gas-phase coating carbon source, and use nitrogen as a carrier gas to perform vapor deposition carbon coating, and coat the surface of SiOx powder particles with a conductive carbon layer to prepare SiOx@C materials. This process uses a thermal decomposition rotary furnace, which has the problems of too many reaction dead zones, and the temperature field and fluid field are not uniform enough, which makes the particle material easy to statically accumulate and the coating consistency is poor. Some people have also tried to use a fluidized bed reactor, but because silicon oxide powder as a negative electrode material for lithium-ion batteries belongs to Geldart C ultrafine particles, its intermolecular force is similar to gravity. When these ultrafine powder particles are directly used for fluidization, channeling and agglomeration often occur, so that the particle bed can only be partially fluidized, or even completely unable to fluidize, which leads to island deposition problems on the surface during chemical vapor deposition, which significantly affects the electrochemical performance.
[0004] In addition, since the preparation of silicon monoxide and the carbon coating process of silicon-based negative electrodes both require high temperature conditions, the energy consumption is huge. It is necessary to study a preparation device and method for efficiently preparing silicon-based negative electrode materials. Summary of the invention
[0005] The purpose of the present invention is to provide a device and method for continuously preparing silicon-based negative electrode materials, so as to solve the problems of agglomeration and accumulation of granular materials, poor coating consistency and high energy consumption that are easily occurred in the process of carbon coating chemical vapor deposition.
[0006] In order to solve the above problems, the present invention provides a device for efficiently and continuously preparing silicon-based negative electrode materials, including: a sublimation furnace, an air flow pulverizer, a secondary granulation system, a fluidized bed, a preheater, a heat exchange system and a collection control system, wherein:
[0007] The sublimation furnace includes a deposition zone and a heating zone arranged in an upper and lower position. The heating zone is used to heat and react the mixed particles of photovoltaic waste crystalline silicon powder and quartz sand in a vacuum or low-pressure environment to generate silicon oxide, and to sublime the silicon oxide into the deposition zone. The deposition zone is used to uniformly deposit silicon oxide by setting a water-cooled collection plate;
[0008] Air flow mill is used to crush the silicon oxide blocks obtained in the deposition area into micron-grade silicon powder below 10um. A jaw crusher can be added at the front end for rough crushing.
[0009] The secondary granulation system is used to mix and stir the micron-sized silicon oxide powder with the carbon-containing binder solution, and dry it to obtain secondary particles with a particle size of 30 to 50 μm;
[0010] A fluidized bed reactor is used to keep the secondary particles fluidized and simultaneously perform vapor deposition carbon coating on them to obtain a carbon-coated silicon-based negative electrode material;
[0011] A preheater is used to preheat the carbon source gas and fluidized gas of the fluidized bed, the preheating temperature is not less than 400°C, and the disturbance of the temperature of the fluidized bed reaction zone is reduced;
[0012] The heat exchanger is used to cool the water-cooled collection plate and heat the preheater.
[0013] The data collection and control system includes temperature and flow control, which is used to collect and control the reaction temperature of the sublimation bed, the deposition temperature of the deposition zone, the reaction temperature of the fluidized bed, the preheater temperature, as well as the output of the sublimation bed, the feed amount of the fluidized bed, the gas source flow rate of the fluidized bed and the discharge amount.
[0014] As a preferred solution, the air flow pulverizer is a collision type air flow pulverizer to improve the problem of material contamination.
[0015] As a preferred solution, the water-cooled collection tray is provided with a condenser of a heat exchanger, and the condensation temperature is 400°C to 800°C.
[0016] The present invention also provides a method for efficiently and continuously preparing silicon-based negative electrode materials, comprising the following steps:
[0017] (1) Pre-treatment of photovoltaic waste crystalline silicon materials to remove organic matter and impurities in nano- or micro-scale silicon powder materials;
[0018] (2) Preparing SiOx material, photovoltaic waste crystalline silicon and quartz sand are mixed in a weight ratio of 1 to 1.2:2 and then placed in a sublimation furnace. Silicon dioxide is synthesized in a heating zone under a vacuum environment, sublimated into a deposition zone, and then cooled and deposited. The cooling temperature is 400 to 800° C., and then sent to a jet mill through a collection device;
[0019] (3) Air flow crushing: the silicon oxide blocks are crushed into micron-sized silicon powder with a size of less than 10 μm by a jaw crusher and an opposing air flow crusher, with a D50 of less than 10 μm.
[0020] (4) secondary granulation, adding micron-sized silicon oxide powder to a carbonaceous binder solution, stirring thoroughly, and then forming secondary granules by spray drying, which are then fed into a screw feeder of a fluidized bed reactor;
[0021] (5) Gas phase deposition carbon coating, the secondary particles continuously enter the fluidized bed reaction zone through a screw feeder to react with the carbon source gas, the fluidizing gas flow rate is controlled so that the fluid flow rate is initially set to 8L / s, and the fluidized bed heating temperature is 600-1000°C; after maintaining this temperature for 1 hour, the carbon-coated silicon-based negative electrode material is continuously discharged through the discharging device.
[0022] As a preferred solution, the temperature of the heating zone of the sublimation furnace is 1200° C. to 1800° C., and the gas pressure is 0.01 to 1000 Pa.
[0023] As a preferred solution, the water-cooled collection tray is provided with a condenser of a heat exchange system, and the condensation temperature is 400°C to 800°C.
[0024] As a preferred embodiment, the silicon-based negative electrode material discharged through the discharging device in step (5) recovers heat through a heat exchanger.
[0025] As a preferred embodiment, the carbon-containing adhesive solution includes polyacrylonitrile, polystyrene, polyvinyl pyrrolidone and / or polyvinyl alcohol; the functional groups (amino groups, hydroxyl groups) in the carbon-containing adhesive react with the -OH groups on the surface of silicon oxide to enhance the adhesion between the carbon coating and silicon oxide and increase the interface stability.
[0026] As a preferred solution, the secondary particles have a particle size of 30 to 50 μm, so that they can be better fluidized in the fluidized bed reaction, avoid agglomeration, and thus improve the consistency of carbon coating.
[0027] The device and method provided by the present invention have the following characteristics: the heating zone and the deposition zone of the sublimation furnace are arranged in coordination to make silicon oxide uniformly deposited, the obtained silicon oxide is crushed and then subjected to secondary granulation by the secondary granulation system, and the silicon oxide particles are changed from the original C-type particles below 10um to A-type particles above 30um through secondary granulation, thereby overcoming the van der Waals force, making the difference between the intermolecular force and gravity larger, reducing the viscosity between the particles, improving the fluidity of the particles, and effectively solving the problem of agglomeration and accumulation of granular materials when silicon oxide is subjected to carbon-coated chemical vapor deposition in the subsequent fluidized bed reactor, so that the consistency of carbon coating is greatly improved. In addition, during the high-temperature heat treatment process of the fluidized bed during the secondary granulation, the carbon-containing adhesive volatilizes to form a fine pore structure, which increases the surface area of the material, thereby improving the electrolyte wettability of the silicon negative electrode material, and the fine pore structure can also buffer the volume expansion of the silicon-based negative electrode material during the charging and discharging process, reducing the damage to the material structure, thereby improving the cycle stability of the battery. In addition, through the setting of the heat exchanger, the waste heat obtained by cooling the water-cooled collection plate can be reused to heat the preheater and the fluidized bed, which effectively reduces the disturbance of the carbon source gas and the fluidized gas on the temperature of the fluidized bed reaction zone and reduces the energy consumption of the preheater. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention.
[0029] Figure 1 This is a schematic diagram of a device for efficiently and continuously preparing silicon-based negative electrode materials in this embodiment. DETAILED DESCRIPTION
[0030] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product instructions are used.
[0031] In the description of the present invention, unless otherwise specified, the terms "upper", "lower", etc. indicating the orientation or state relationship are based on the orientation or state relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.
[0032] In the following examples, the instruments and equipment used without indicating the manufacturer are all conventional products that can be purchased through regular channels. The methods described are conventional methods unless otherwise specified, and the raw materials described can be obtained from public commercial channels unless otherwise specified.
[0033] Example
[0034] like Figure 1 As shown, this embodiment provides a device for efficiently and continuously preparing silicon-based negative electrode materials, comprising a sublimation furnace 1, a jet mill 2, a secondary granulation system 3 and a fluidized bed reactor 4 arranged in sequence, and a preheater 5 for preheating the carbon source gas 6 and the fluidized gas 7 of the fluidized bed reactor. The sublimation furnace 1 and the preheater 5 are heat-transferred through a heat exchange system, wherein:
[0035] Sublimation furnace 1 is divided into a heating zone and a deposition zone. Photovoltaic waste crystalline silicon and quartz sand are synthesized in the heating zone at a temperature of 1200℃ to 1800℃ and a vacuum environment of 0.01 to 1000pa. The reaction temperature is lowered by setting a low-pressure environment. A protective atmosphere can also be provided by inputting nitrogen to prevent oxidation of silicon oxide. At the same time, the sublimation gas flow is guided to the deposition zone. Silicon oxide sublimates into the deposition zone. A rotating water-cooled collection plate is set in the deposition zone for uniform cooling and deposition, and is sent to the air flow mill through a collection device. The condensation temperature of the water-cooled collection plate is 400℃ to 800℃. The feeder of the sublimation furnace can use a vacuum screw feeder to maintain a low-pressure environment. Valve A is set at the inlet of the vacuum screw feeder, and valve B is set at the outlet of the vacuum screw feeder. When loading, valve A is opened, valve B is closed, and the silo is loaded; after loading, valve A is closed, vacuum is drawn, and then valve B is opened.
[0036] The air flow mill 2 preferably adopts a jaw crusher and an impact air flow mill for mixed crushing to crush the silicon oxide blocks into micron-grade silicon powder below 10 um, so that its D50 is less than 10 um.
[0037] Secondary granulation system 3, adds micron-sized silicon oxide powder to a carbon-containing binder solution, the carbon-containing binder solution includes but is not limited to polyacrylonitrile, polystyrene, polyvinyl pyrrolidone and polyvinyl alcohol, etc., after being fully stirred, dried and formed to obtain secondary particles, the particle size of the secondary particles is 30 to 50 μm, and then sent to the screw feeder of the fluidized bed.
[0038] The fluidized bed reactor 4 includes a fluidized bed and a vibrating device. A fluidizing gas inlet and a carbon source gas inlet are respectively arranged at the bottom of the fluidized bed. The fluidizing gas includes but is not limited to nitrogen, argon, etc., and the carbon source gas includes but is not limited to acetylene, etc. The flow rate of the fluid is greater than the initial fluidization speed, but does not exceed the particle carrying speed. As Class A particles, the excess gas causes the reaction zone to form a dispersed fluidization. The fluidized bed is heated to a temperature of 600°C to 1000°C. The granular material can be added to or discharged from the fluidized bed at any time or continuously through a screw feeder and a discharging device. A valve C is arranged on the discharging device. In addition, a baffle is arranged on the inner wall of the fluidized bed. An externally rotating, internally rotating or multi-rotating baffle can be used to break bubbles, improve gas-solid contact, and reduce back mixing.
[0039] The vibration device of the fluidized bed reactor 4 is a vibration table that supports and vibrates the container body, and is also provided with a stirring device coaxial with the fluidized bed. The stirring device, such as a spiral blade, works together with the vibration table to achieve sufficient stirring of the material layer. In this embodiment, a gas pre-distributor is installed on the vibration table to generate vertical vibration.
[0040] The heat exchange system includes an evaporator, a condenser, and a driving pump for driving the coolant to circulate between the two, wherein the condenser is arranged in a water-cooled collection tray in the deposition area, and the evaporator is arranged in a preheater, so as to fully utilize the high-temperature waste heat in the system. Specifically, the preheater uses the evaporator of the heat exchanger to preheat the carbon source gas and the fluidizing gas, and the preheating temperature is not less than 400°C, and the water-cooled collection tray uses the condenser of the heat exchanger to cool down.
[0041] In addition, this embodiment is also provided with a collection and control system 8, including a temperature control system, a flow control system and a fluidization performance control, wherein the temperature control system collects and integrates the reaction temperature of the sublimation bed, the deposition temperature of the deposition zone, the reaction temperature of the fluidized bed, and the preheater temperature; the flow control system collects and integrates the output of the sublimation bed, the feed amount of the spiral feeder, the flow of the gas source system, and the discharge amount of the fluidization system; the fluidization performance control collects and integrates the particle size and distribution coefficient of the air flow breakup, the vibration and stirring speed of the fluidized bed, etc.
[0042] The present invention also provides a method for efficiently and continuously preparing silicon-based negative electrode materials, comprising the following steps:
[0043] (1) Pretreatment of photovoltaic waste crystalline silicon materials to remove organic matter and impurities in nano- or micro-scale silicon powder materials. The removal method can be conventional heat treatment technology, chemical pickling, or a combination of the two;
[0044] (2) Preparing SiOx material, mixing photovoltaic waste crystalline silicon and quartz sand in a weight ratio of 1 to 1.2:2 to prepare 5 mm mixed particles, and then putting them into a sublimation furnace, synthesizing silicon oxide in a heating zone under a vacuum environment, the temperature of the sublimation furnace heating zone is 1200° C. to 1800° C., the air pressure is 0.01 to 1000 Pa, the input gas source is nitrogen, and the silicon oxide sublimates into the deposition zone and then cools and deposits. The deposition zone is provided with a water-cooled collection tray, and the water-cooled collection tray is integrated with a condenser of a heat exchange system, and the condensation temperature is 400° C. to 800° C. The deposited silicon oxide is sent to a gas flow mill through a collection device;
[0045] (3) Air flow crushing: using a collision-type air flow crusher to crush silicon oxide blocks into micron-sized silicon powder with a D50 of less than 10 um;
[0046] (4) Secondary granulation: adding micron-sized silicon oxide powder to a carbon-containing binder solution, wherein the carbon-containing binder solution includes polyacrylonitrile, polystyrene, polyvinyl pyrrolidone and / or polyvinyl alcohol, mixing and fully stirring, and then drying and forming to obtain secondary particles, wherein the particle size of the secondary particles is 30 to 50 μm.
[0047] (5) Gas phase deposition carbon coating, the obtained secondary particles are continuously fed into the fluidized bed reaction zone through a screw feeder to react with the carbon source gas, the fluidizing gas flow rate is controlled so that the fluid flow rate is initially set to 8L / s, and the fluidized bed heating temperature is 600-1000°C; after the material is maintained at this temperature for 1 hour, the carbon-coated silicon-based negative electrode material is continuously discharged through the discharging device.
[0048] Through thermogravimetric analysis, the carbon coating rates of various batches of materials obtained by using the above system and method are between 4.5% and 5%, with good carbon coating consistency.
[0049] The above is only an embodiment of the present invention. The common sense such as the known specific structure, characteristics and reactant ratio in the scheme is not described too much here. The raw material gives a preferred numerical value or a suitable range value. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, some deformations and improvements can also be made, such as referring to the ratio of raw materials or reactants, simply changing the numerical value of the reactants, and simply adjusting the selection of parameters within or near the specified parameter range. These should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods in the specification and other records can be used to explain the content of the claims.
Claims
1. A device for efficiently and continuously preparing silicon-based negative electrode materials, characterized in that Included are: The sublimation furnace includes a deposition zone and a heating zone arranged in an upper and lower position. The heating zone is used to heat and react the mixed particles of photovoltaic waste crystalline silicon powder and quartz sand in a vacuum environment to generate silicon oxide, and to sublime the silicon oxide into the deposition zone. The deposition zone is used to uniformly deposit silicon oxide by setting a water-cooled collection plate; Air flow mill, used to crush the silicon oxide blocks obtained in the deposition area into micron-sized silicon powder below 10um; The secondary granulation system is used to mix and stir the micron-sized silicon oxide powder with the carbon-containing binder solution, and dry it to obtain secondary particles with a particle size of 30um to 50um; A fluidized bed reactor is used to keep the secondary particles fluidized and simultaneously perform vapor deposition carbon coating on them to obtain a carbon-coated silicon-based negative electrode material; A preheater, used to preheat the carbon source gas and fluidized gas of the fluidized bed, the preheating temperature being not less than 400°C; Heat exchanger, used to cool the water-cooled collection plate and heat the preheater; The data collection and control system is used to collect and control the reaction temperature of the sublimation bed, the deposition temperature of the deposition zone, the reaction temperature of the fluidized bed, the preheater temperature, as well as the output of the sublimation bed, the feed amount of the fluidized bed, the gas source flow rate of the fluidized bed and the discharge amount.
2. The device and method for efficiently and continuously preparing silicon-based negative electrode materials according to claim 1, characterized in that: The air flow pulverizer is a collision-type air flow pulverizer, and the front end thereof uses a jaw crusher to coarsely crush silicon oxide blocks to obtain millimeter-level silicon powder.
3. The device and method for efficiently and continuously preparing silicon-based negative electrode materials according to claim 1, characterized in that: The water-cooled collecting tray is provided with a condenser of a heat exchanger, and the condensation temperature is 400°C to 800°C.
4. A method for efficiently and continuously preparing silicon-based negative electrode materials using the device of claim 1, characterized in that The steps include: (1) Pre-treatment of photovoltaic waste crystalline silicon materials to remove organic matter and impurities in micron-sized silicon powder materials; (2) Preparing SiOx material, photovoltaic waste crystalline silicon and quartz sand are mixed in a weight ratio of 1 to 1.2:2 and then placed in a sublimation furnace. Silicon dioxide is synthesized in a heating zone under a vacuum environment, sublimated into a deposition zone, and then cooled and deposited. The cooling temperature is 400 to 800° C., and then sent to a jet mill through a collection device; (3) Mixed crushing: using a jaw crusher and an impact jet mill to crush the silicon oxide blocks into micron-sized silicon powder with a D50 of less than 10 μm; (4) secondary granulation, adding micron-sized silicon oxide powder to a carbon-containing binder solution, stirring thoroughly, and drying to obtain secondary particles; (5) Gas phase deposition carbon coating, the secondary particles are continuously fed into the fluidized bed reaction zone through a screw feeder to react with the carbon source gas, the fluidizing gas flow rate is controlled so that the fluid flow rate is initially set to 8L / s, the fluidized bed heating temperature is 600-1000°C, and the carbon-coated silicon-based negative electrode material is continuously discharged through a discharging device.
5. The method for efficiently and continuously preparing silicon-based negative electrode materials according to claim 4, characterized in that: In the step (2), the temperature of the heating zone of the sublimation furnace is 1200° C. to 1800° C., and the gas pressure is 0.01 to 1000 Pa.
6. The method for efficiently and continuously preparing silicon-based negative electrode materials according to claim 4, characterized in that: The carbon-containing binder solution in step (4) includes polyacrylonitrile, polystyrene, polyvinyl pyrrolidone and / or polyvinyl alcohol.
7. The method for efficiently and continuously preparing silicon-based negative electrode materials according to claim 4, characterized in that: The secondary particles in step (4) have a particle size of 30 um to 50 um.
8. The method for efficiently and continuously preparing silicon-based negative electrode materials according to claim 4, characterized in that: The fluidizing gas in step (5) includes nitrogen and / or argon, and the carbon source gas includes acetylene.