Device for efficiently and continuously preparing silicon-based negative electrode material

Abstract

The utility model relates to a lithium battery negative electrode material treatment technology, in particular to a device for efficiently and continuously preparing a silicon-based negative electrode material, which comprises a sublimation furnace, a jet mill, a secondary granulation system, a fluidized bed reactor and a preheater for preheating carbon source gas and flow state gas of the fluidized bed reactor, the sublimation furnace and the preheater carry out heat transfer through the heat exchange system; by adopting the device disclosed by the utility model, the problems of agglomeration and accumulation of granular materials and poor coating consistency in the carbon-coated chemical vapor deposition process can be effectively solved, and meanwhile, the energy consumption is effectively reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of lithium battery negative material processing technology, specifically to a kind of high-efficiency continuous preparation silicon negative material's device and method. BACKGROUND

[0002] Silicon monoxide (SiO) as lithium ion battery negative material, with high 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 and shedding, seriously affecting 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. The technical difficulty lies in the uniformity of the coating when a large amount of silicon-based negative electrode is prepared.

[0003] The current mainstream silicon-based negative electrode preparation method adopts chemical vapor deposition (CVD) method. Appropriate particle size distribution of silicon monoxide is filled in a thermal decomposition rotary furnace, acetylene is used as a gas phase carbon coating source, nitrogen is used as a carrier gas, and gas phase deposition carbon coating is carried out to coat a conductive carbon layer on the surface of SiOx powder particles to prepare SiOx@C material. The process uses a thermal decomposition rotary furnace, which has the problems of too many reaction dead zones and non-uniform temperature field and fluid field, which leads to easy static accumulation of granular material and poor uniformity of coating. Some people have also tried to use a fluidized bed reactor, but since the silicon monoxide powder used as the negative material of lithium ion battery belongs to Geldart C ultra-fine particles, the intermolecular force is similar to the gravity. 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, and further causes the surface to present island-shaped deposition problems during the chemical vapor deposition process, which significantly affects the electrochemical performance.

[0004] In addition, since the preparation of silicon monoxide and the carbon coating process of silicon-based negative electrode all need to be carried out under high temperature conditions, the energy consumption is huge, and it is necessary to study a kind of preparation device and method for efficiently preparing silicon-based negative electrode material. UTILITY MODEL CONTENTS

[0005] The utility model aims at providing a kind of device and method for continuously preparing silicon-based negative electrode material to solve the problems of easy particle material agglomeration accumulation, poor coating uniformity and high energy consumption in the process of carbon coating chemical vapor deposition.

[0006] To solve the above problems, the utility model provides a kind of device for efficiently and continuously preparing silicon-based negative electrode material, which comprises 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 comprises a deposition zone and a heating zone arranged in sequence, the heating zone is used to heat the mixed particles of photovoltaic waste silicon powder and quartz sand in a vacuum or low pressure environment to generate silicon monoxide, and the silicon monoxide is sublimated into the deposition zone, and the deposition zone is used to uniformly deposit the silicon monoxide by arranging a water-cooled collection tray;

[0008] The jet mill is used to crush the silicon monoxide blocks obtained from the deposition zone into micron-sized silicon powder below 10 um, and 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 monoxide powder with a carbon-containing binder solution, and dry to obtain secondary particles with a particle size of 30-50 um.

[0010] The fluidized bed reactor is used to keep the secondary particles in a fluidized state, and at the same time, perform gas phase deposition carbon coating to obtain a carbon-coated silicon-based negative electrode material.

[0011] The preheater is used to preheat the carbon source gas and the fluidizing gas of the fluidized bed, and the preheating temperature is not lower than 400 DEG C, so as to reduce the disturbance to the temperature of the reaction zone of the fluidized bed.

[0012] The heat exchanger is used to cool the water-cooled collection tray and heat the preheater.

[0013] The collection control system comprises temperature and flow control, and 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 temperature of the preheater, and the output of the sublimation bed, the feeding amount of the fluidized bed, the gas source flow of the fluidized bed and the discharge amount.

[0014] As a preferred scheme, the jet mill is a jet mill with a collision type, so as to improve the problem of material pollution.

[0015] As a preferred scheme, the water-cooled collection tray is provided with a condenser of the heat exchanger, and the condensing temperature is 400 DEG C-800 DEG C.

[0016] The device has the following characteristics: the heating area and the deposition area arranged in cooperation with the sublimation furnace make the silicon monoxide uniformly deposit, the obtained silicon monoxide is crushed and then subjected to secondary granulation through the secondary granulation system, the silicon monoxide particles are changed from the original C-class particles below 10um to A-class particles above 30um through the secondary granulation, thereby overcoming the Van der Waals force, making the intermolecular force and the gravity difference larger, reducing the adhesion between the particles, improving the flowability of the particles, effectively solving the problem of particle material agglomeration and accumulation when the silicon monoxide is subjected to carbon-coated chemical vapor deposition in the subsequent fluidized bed reactor, and greatly improving the consistency of carbon coating. In addition, during the fluidized bed high-temperature heat treatment process, the carbon-containing adhesive volatilizes to form a fine pore structure, thereby increasing the surface area of the material and improving the electrolyte wettability of the silicon negative electrode material. The fine pore structure can also buffer the volume expansion of the silicon-based negative electrode material during the charging and discharging process, reduce the damage to the material structure, and thereby improve the cycle stability of the battery. In addition, through the arrangement of the heat exchanger, the waste heat obtained by cooling the water-cooled collection disc is reused to preheat the preheater and the fluidized bed, thereby effectively reducing the disturbance of the carbon source gas and the flow state gas to the temperature of the fluidized bed reaction zone, and reducing the energy consumption of the preheater. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of 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.

[0018] Figure 1 It is a schematic diagram of the device for efficiently and continuously preparing silicon-based negative electrode material. DETAILED DESCRIPTION

[0019] The following examples 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 specified in the examples, it is performed according to the technology or condition described in the literature in the art, or according to the product manual.

[0020] In the description of the present application, unless otherwise specified, the orientation or state relationship indicated by the terms "upper", "lower", etc. 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, therefore it cannot be understood as a limitation on the present application.

[0021] In the following examples, the instruments and equipment used are not marked with the manufacturer, and are all conventional products that can be purchased through regular channels. The methods are conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified.

[0022] Embodiment

[0023] As Figure 1 shown, the embodiment provides a device for efficiently and continuously preparing silicon-based negative electrode material, which comprises a sublimation furnace 1, an air flow crusher 2, a secondary granulation system 3, a fluidized bed reactor 4, and a preheater 5 for preheating the carbon source gas 6 and the fluidizing gas 7 of the fluidized bed reactor, the sublimation furnace 1 and the preheater 5 are connected by a heat exchange system for heat transfer, wherein,

[0024] The sublimation furnace 1 is divided into a heating zone and a deposition zone. The photovoltaic waste crystalline silicon and quartz sand are synthesized into silicon monoxide in the heating zone at a temperature of 1200-1800°C in a vacuum environment of 0.01-1000 pa. The low-pressure environment reduces the reaction temperature, and nitrogen gas can be input to provide a protective atmosphere to prevent the oxidation of silicon monoxide. At the same time, the flow direction of the sublimation gas flow is guided to the deposition zone. The sublimation of silicon monoxide enters the deposition zone, where a rotating water-cooled collection tray is provided for uniform cooling and deposition. The collected material is then sent to the air flow crusher through a collection device. The condensation temperature of the water-cooled collection tray is 400-800°C. The feeder of the sublimation furnace can use a vacuum screw feeder to maintain a low-pressure environment. A valve A is provided at the inlet of the vacuum screw feeder, and a valve B is provided at the outlet of the vacuum screw feeder. When loading, open valve A and close valve B to load the hopper. When the loading is completed, close valve A, vacuumize, and then open valve B.

[0025] The air flow crusher 2 preferably uses a combination of a jaw crusher and a collision air flow crusher for mixed crushing to break the silicon monoxide blocks into micron-sized silicon powder with a particle size of less than 10 um, so that the D50 is less than 10 um.

[0026] The secondary granulation system 3 adds micron-sized silicon monoxide powder to a carbon-containing binder solution, which includes but is not limited to polyacrylonitrile, polystyrene, polyvinylpyrrolidone, and polyvinyl alcohol, etc. After sufficient stirring, the mixture is dried and shaped to obtain secondary particles with a particle size of 30-50 um, which are then sent to the screw feeder of the fluidized bed.

[0027] The fluidized bed reactor 4 includes a fluidized bed and a vibrating device. The bottom of the fluidized bed is provided with a fluidizing gas inlet and a carbon source gas inlet. 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 velocity but not more than the entrainment velocity of the particles, which are classified as A-type particles. Excess gas causes the reaction zone to form a dispersed fluidization. The heating temperature of the fluidized bed is 600-1000°C. The screw feeder and the discharge device can be used to add or remove particle materials from the fluidized bed at any time or continuously. A valve C is provided on the discharge device. In addition, baffles are provided on the inner wall of the fluidized bed, which can be external, internal, or multiple rotating baffles to break bubbles, improve gas-solid contact, and reduce backmixing.

[0028] The vibrating device of the fluidized bed reactor 4 is a vibrating table supporting and vibrating the container body, and a stirring device coaxial with the fluidized bed is arranged, and the stirring device such as a spiral blade cooperates with the vibrating table to realize sufficient stirring of the material layer.

[0029] The heat exchange system comprises an evaporator, a condenser and a driving pump for driving the circulation of the cooling liquid between the evaporator and the condenser, wherein the condenser is arranged on a water-cooled collection tray of the deposition area, and the evaporator is arranged in the preheater, so that the high-temperature waste heat in the system is fully utilized.

[0030] In addition, the embodiment is also provided with a collection control system 8, which comprises a temperature control system, a flow control system and a fluidization performance control, wherein the temperature control system collects and integrally controls the reaction temperature of the sublimation bed, the deposition temperature of the deposition area, the reaction temperature of the fluidized bed and the preheater temperature; the flow control system collects and integrally controls the output of the sublimation bed, the feeding amount of the screw feeder, the flow of the gas source system and the discharge amount of the fluidization system; and the fluidization performance control collects and integrally controls the particle size and distribution coefficient of the airflow broken particles, the vibration and stirring speed of the fluidized bed and the like.

[0031] The utility model discloses simultaneously provides a kind of high-efficiency continuous preparation silicon-based negative electrode material, comprising the following steps:

[0032] (1) the pretreatment of photovoltaic waste crystalline silicon material, remove nanometer or micron silicon powder material organic matter and impurities, the method for removing can be conventional heat treatment technology, chemical pickling or the method of combination of both;

[0033] (2) preparation SiOx material, photovoltaic waste crystalline silicon and quartz sand are mixed according to 1~1.2:2 weight ratio, and after preparing 5mm mixed particles, it is placed into sublimation furnace, and silicon monoxide is synthesized in heating zone under vacuum environment, the temperature of heating zone of sublimation furnace is 1200~1800 DEG C, and the gas pressure is 0.01~1000pa, and input gas source is nitrogen, and after sublimation into deposition area, silicon monoxide is deposited after cooling, and deposition area is provided with water-cooled collection tray, and water-cooled collection tray is integrated with condenser of heat exchange system, and condensing temperature is 400~800 DEG C, and the deposited silicon monoxide is sent into airflow pulverizer by collecting device.

[0034] (3) airflow breaking, by colliding airflow pulverizer, silicon monoxide block is broken into micron silicon powder below 10um, and D50 is less than 10um.

[0035] (4) secondary granulation, micron-sized silicon monoxide powder is added to a carbon-containing binder solution, the carbon-containing binder solution includes polyacrylonitrile, polystyrene, polyvinylpyrrolidone and / or polyvinyl alcohol, after mixing and fully stirring, drying and shaping to obtain secondary particles, the secondary particle size is 30-50um.

[0036] (5) vapor deposition carbon coating, the obtained secondary particles are continuously fed into a fluidized bed reaction zone through a screw feeder and reacted with a carbon source gas, the fluidized gas flow is controlled so that the fluid velocity is initially set to 8L / s, the fluidized bed heating temperature is 600-1000℃; after the material is kept at the temperature for 1h, the carbon-coated silicon-based negative electrode material is continuously discharged through a discharge device.

[0037] Through thermogravimetric analysis, the carbon coating rate of each batch of material obtained by the above system and method is between 4.5%-5%, and the carbon coating consistency is good.

[0038] The above is only an embodiment of the present application, and the specific structure, characteristics and reactant ratio of the known scheme are not described in detail, the raw material gives the preferred 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 application, a number of modifications and improvements can be made, such as referring to the raw material or the ratio of reactants, simply changing the value of the reactants, simply adjusting the selection of parameters within or near the specified parameter range, which should also be considered as the protection scope of the present application, these will not affect the effect and practicality of the present application. 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 device for efficiently and continuously producing a silicon-based negative electrode material, characterized by The application relates to a sublimation furnace, a jet mill, a secondary granulation system, a fluidized bed reactor, a preheater and a heat exchanger. The sublimation furnace comprises a deposition zone and a heating zone arranged in sequence, the heating zone is used for heating reaction of photovoltaic waste silicon powder and quartz sand mixed particles under a vacuum environment to generate silicon monoxide, and the silicon monoxide is sublimated into the deposition zone; the deposition zone is used for uniformly depositing the silicon monoxide through a water-cooled collecting disc; The jet mill is used for crushing the silicon monoxide blocks obtained from the deposition zone into micron-level silicon powder below 10 um; The secondary granulation system is used for mixing and stirring micron-level silicon monoxide powder and a carbon-containing binder solution, and drying to obtain secondary particles with a particle size of 30-50 um; The fluidized bed reactor is used for keeping the secondary particles in a fluidized state and performing gas phase deposition carbon coating on the secondary particles to obtain carbon-coated silicon-based negative electrode materials; The preheater is used for preheating carbon source gas and fluidized gas of the fluidized bed, and the preheating temperature is not lower than 400 DEG C; The heat exchanger is used for cooling the water-cooled collecting disc and simultaneously heating the preheater.

2. The apparatus for efficiently and continuously producing a silicon-based anode material according to claim 1, wherein: The jet mill is a collision type jet mill, and a jaw crusher is arranged at the front end of the jet mill to coarsely crush the silicon monoxide blocks into millimeter-level silicon powder. 3.The device for efficiently and continuously preparing a silicon-based anode material according to claim 2, characterized in that: The jet mill is a collision type jet mill, and a jaw crusher is arranged at the front end of the jet mill to coarsely crush the silicon monoxide blocks into millimeter-level silicon powder. 4.The device for efficiently and continuously preparing a silicon-based anode material according to claim 1, characterized in that: The application further comprises a collection control system which collects and controls the reaction temperature of the sublimation bed, the deposition temperature of the deposition zone, the reaction temperature of the fluidized bed, the preheater temperature, the output of the sublimation bed, the feeding amount of the fluidized bed, the gas source flow of the fluidized bed and the discharging amount of the fluidized bed. 5.The device for efficiently and continuously preparing a silicon-based anode material according to claim 1, characterized in that: The water-cooled collecting disc is provided with a condenser of the heat exchanger, and the condensing temperature is 400-800 DEG C.

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