Preparation method and device of silicon-carbon negative electrode material

Abstract

The application discloses a preparation method and device of a silicon-carbon negative electrode material. The method comprises the following steps: dispersing a porous carbon matrix in a solvent, performing spray drying in a spray drying device to obtain precursor particles; then, preheating a liquid silicon source and feeding it into the spray drying device to obtain a silicon-carbon composite material A after reaction; dispersing a high-molecular binder in a solvent to obtain a mixed liquid, preheating the mixed liquid and feeding it into the spray drying device containing the silicon-carbon composite material A to perform granulation, thereby obtaining a silicon-carbon composite material B; and sintering the silicon-carbon composite material B to obtain the silicon-carbon negative electrode material. The device comprises a spray drying device, which comprises a barrel, a material conveying device, a material collecting device and a tail gas treatment device; a gas distributor, a material collecting device, a conical feeding disc, a slurry feeding nozzle, a silicon source feeding nozzle, a binder feeding nozzle and a discharging pipe are arranged in the barrel. The material has high batch stability, low expansion and good fast-charging performance.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, and relates to a method and apparatus for preparing silicon-carbon anode materials. Background Technology

[0002] With the rapid depletion of non-renewable energy sources such as oil and natural gas, and the increasing deterioration of the ecological environment, energy efficiency is becoming increasingly important, and people are placing higher demands on energy storage and release. Compared with traditional secondary batteries such as lead-acid batteries and nickel-cadmium batteries, lithium-ion batteries have outstanding advantages such as high single-cell voltage, high specific energy, long cycle life, and environmental friendliness, making them an indispensable part of people's daily lives.

[0003] Silicon is the anode material with the highest theoretical specific capacity to date. It combines with lithium to form Li. 4.4 Si, with a theoretical specific capacity of 4200 mAh / g, is approximately 11 times that of graphite. Simultaneously, silicon has a higher voltage plateau than graphite, making it less prone to surface lithium plating during charging and offering better safety performance. However, as an anode material, crystalline silicon exhibits a volume expansion rate as high as 400% and amorphous silicon as high as 280% when fully lithium-intercalated. This results in continuous expansion and contraction of silicon volume during electrochemical cycling due to lithium-ion insertion and extraction. The resulting stress causes silicon to gradually pulverize during charge and discharge, ultimately leading to a loss of electrical contact between internal silicon particles and between silicon and the current collector, significantly degrading cycle performance.

[0004] Novel silicon-carbon anode materials can suppress and alleviate the volume expansion of nano-silicon during charging and discharging through the rigid structure of the porous carbon matrix, thereby improving the phenomenon of silicon volume expansion and contraction caused by lithium-ion insertion and extraction. However, in existing processes, porous carbon matrices are usually obtained by etching hard carbon or biomass carbon, which is a complex process. The pore size, pore volume, and porosity of porous carbon are difficult to control, resulting in low batch stability of novel silicon-carbon anode materials and further limiting their industrialization. At the same time, the high porosity and large pore volume of the porous carbon matrix lengthen the lithium-ion transport path, thus leading to poor fast-charging performance of novel silicon-carbon materials. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for preparing silicon-carbon anode materials. The spray drying reaction apparatus and method of this invention have advantages such as simplicity, convenience, rapid reaction, and low energy consumption.

[0006] The present invention provides a method for preparing a silicon-carbon anode material, comprising the following steps:

[0007] S1. Disperse the porous carbon matrix in a solvent, mill it, and then sieve it to obtain a precursor slurry. Spray dry the precursor slurry in a spray drying device to obtain precursor particles.

[0008] S2. After preheating, the liquid silicon source is introduced into the spray drying device described in step S1, and after reaction, silicon-carbon composite material A is obtained.

[0009] S3. Disperse the polymer binder in a solvent to obtain a preheated mixture, which is then passed into the spray drying device and mixed with the silicon-carbon composite material A for granulation to obtain silicon-carbon composite material B.

[0010] S4. The silicon-carbon composite material B is sintered to obtain the silicon-carbon anode material.

[0011] This invention synthesizes silicon-carbon anode materials by completing silicon deposition and granulation of small-sized silicon-carbon materials in a spray drying reactor. The synthesized silicon-carbon anode materials have advantages such as high batch stability, low expansion, and good fast-charging performance.

[0012] The method for producing the silicon-carbon anode material in this invention specifically includes the following steps:

[0013] S1. Disperse the porous carbon matrix in a solvent, mill it, and sieve it to obtain a precursor slurry. Pour the slurry into a slurry storage device. After preheating, the slurry is fed into a spray drying device through a slurry conveying device. The slurry droplets are fully dried in a drying atmosphere to obtain precursor particles.

[0014] S2. After the liquid silicon source in the silicon source storage device is preheated, it is introduced into the spray drying device through the silicon source conveying device to fully contact the precursor particles in a suspended state, while increasing the temperature of the drying atmosphere. After full reaction, silicon-carbon composite material A is obtained.

[0015] S3. Disperse the polymer binder in a solvent to obtain a mixture. After preheating, pass the mixture into the spray drying device containing the silicon-carbon composite material A for granulation to obtain silicon-carbon composite material B.

[0016] S4. Place the silicon-carbon composite material B into a tube furnace for heating and sintering to obtain the silicon-carbon composite material.

[0017] In the above method, before step S1, the spray drying device is preheated by introducing a gas, wherein the gas is selected from at least one of air, argon, nitrogen and helium;

[0018] The flow rate of the gas introduced can be 30-50 m³ / h. 3 / h, specifically 30m 3 / h;

[0019] The gas is introduced into the spray drying device for preheating; the preheating temperature can be 100-300℃, specifically 100℃.

[0020] In step S1, the porous carbon matrix is ​​selected from at least one of hard carbon, soft carbon, resin and petroleum coke;

[0021] The particle size D50 of the porous carbon matrix after sand milling and sieving can be 1-3 μm, specifically 1 μm;

[0022] The solvent is at least one of water, ethanol, and tetrahydrofuran;

[0023] The mass ratio of the porous carbon matrix to the solvent can be 1:0.6 to 2, specifically 1:0.6; the mesh size of the sieve can be 150 to 200 mesh, specifically 150 mesh; the preheating temperature of the precursor slurry can be 50 to 80°C, specifically 50°C; and the input flow rate can be 10 to 30 ml / min, specifically 10 ml / min.

[0024] In the above method, in step S2, the liquid silicon source is selected from one or a mixture of several of silicon tetrachloride, propane, n-butane and cyclopentane;

[0025] The amount of liquid silane added is such that the mass percentage of silicon in the obtained silicon-carbon composite material can be 35% to 50%, the preheating temperature of the liquid silicon source can be 50 to 80°C, the flow rate can be 10 to 30 ml / min, and the gas temperature in the spray drying device is raised to 400 to 600°C.

[0026] In the above method, in step S3, the polymeric binder is selected from at least one of polyvinylidene fluoride, polyacrylic acid, and carboxymethyl cellulose;

[0027] The solvent is at least one of water, ethanol, and tetrahydrofuran;

[0028] The preheating temperature of the mixture can be 50–80°C, and the flow rate of the mixture can be 60–100 m³ / h. 3 / h;

[0029] The average particle size of the silicon-carbon composite material B can be 10-20 μm; the average particle size of the granulation can be controlled by adjusting the flow rate of the binder nozzle.

[0030] In step S4, the sintering temperature can be 300-500℃ and the time can be 3-12h.

[0031] The present invention provides the silicon-carbon anode material prepared by the above-described preparation method.

[0032] The present invention provides a battery negative electrode sheet, wherein the active material of the battery negative electrode sheet includes the aforementioned silicon-carbon negative electrode material.

[0033] The present invention further provides an apparatus for synthesizing the above-mentioned silicon-carbon anode material, including a spray drying apparatus;

[0034] The spray drying device includes a cylinder, a material conveying device, a material collecting device, and an exhaust gas treatment device.

[0035] The cylinder is equipped with a gas distributor, a material collection device, a conical feed plate, a slurry feed nozzle, a silicon source feed nozzle, a binder feed nozzle, and a discharge pipe. The gas distributor is located at the top of the cylinder, the conical feed plate is located at the bottom of the cylinder and connected to the material collection device, the slurry feed nozzle, the silicon source feed nozzle, and the binder feed nozzle all penetrate the cavity wall of the cylinder and communicate with the inside of the cylinder, and the discharge pipe is located at the bottom of the cylinder.

[0036] In the above-described device, the distance between the drying gas inlet nozzle and the top of the cylinder is 5% to 10% of the height of the inner cavity of the cylinder.

[0037] The silicon source feed nozzle and the adhesive feed nozzle are distributed parallel to each other on the cylinder, and the distance from the bottom of the cylinder is 20% to 25% of the height of the inner cavity of the cylinder.

[0038] The distance between the slurry feed nozzle and the silicon source feed nozzle accounts for 50% to 80% of the height of the inner cavity of the cylinder;

[0039] The distance between the discharge pipe and the bottom of the cylinder is 10% to 15% of the height of the inner cavity of the cylinder;

[0040] The nozzle of the slurry feeding nozzle is arranged towards the bottom inside the cylinder, while the silicon source feeding nozzle and the binder feeding nozzle are both arranged towards the top inside the cylinder.

[0041] In the above-mentioned device, the dimensions of the slurry feeding nozzle, the silicon source feeding nozzle, and the binder feeding nozzle are all integrated and range from 0.1 to 2.5 mm.

[0042] The material collection device includes a cyclone separator and a material collection box; one end of the cyclone separator is connected to the discharge pipe, and the other end is connected to the exhaust gas treatment device; the bottom of the cyclone separator is connected to the material collection box.

[0043] In the aforementioned apparatus, the material conveying device includes a drying gas conveying device, a slurry conveying device, a silicon source conveying device, and a binder conveying device. Each of the material conveying devices includes a corresponding storage device, a heating device, a flow metering device, a temperature metering device, and the slurry feed nozzle, silicon source feed nozzle, and binder feed nozzle.

[0044] The present invention has the following beneficial effects:

[0045] 1. This invention uses small-sized porous carbon matrix particles as carbon source. Compared with traditional medium-sized porous carbon particles, the lithium-ion transport path is shortened and the particle size distribution is narrowed. The synthesized silicon-carbon anode material has the characteristics of low resistivity, low expansion, good fast charging performance and high batch stability.

[0046] 2. This invention uses a spray drying reactor instead of a fluidized bed reactor. Combined with the advantages of small-sized porous carbon matrix, it has the advantages of fast reaction and low energy consumption compared with traditional fluidized bed reactors. At the same time, silicon deposition and silicon-carbon material granulation can be completed in this reaction device. The process technology is simple and can avoid material contamination. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the apparatus for synthesizing fast-charging silicon-carbon anode materials in a specific embodiment of the present invention.

[0048] Figure 1 The markings are as follows:

[0049] 1-Cylinder; 2-Slurry storage device; 3-First flow metering device; 4-First temperature metering device; 5-Slurry feed nozzle; 6-Silicon source storage device; 7-Second flow metering device; 8-Second temperature metering device; 9-Silicon source feed nozzle; 10-Binder feed nozzle; 11-Conical feed plate; 12-Collection device; 13-Third temperature metering device; 14-Third flow metering device; 15-Gas generator; 16-Discharge pipe; 17-Cyclone separator; 18-Material collection box; 19-Tail gas treatment device; 20-Gas distributor; 21-Fourth temperature metering device; 22-Fourth flow metering device; 23-Binder storage device. Detailed Implementation

[0050] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0051] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0053] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the system or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the use of terms such as "first," "second," etc., to define components is merely for the convenience of distinguishing the aforementioned components; unless otherwise stated, these terms have no special meaning and should not be construed as indicating or implying relative importance.

[0054] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "assembly," "setup," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0055] This invention provides a method for producing silicon-carbon anode materials, comprising the following steps:

[0056] S1. The dry atmosphere generated by the gas generator is heated and then passed through the gas conveying device to the gas distributor and then into the spray drying device for preheating.

[0057] S2. Disperse the porous carbon matrix in a solvent, mill it, and then sieve it to obtain a precursor slurry. Pour the slurry into a slurry storage device. After preheating, the slurry is fed into the spray drying device through a slurry conveying device. The slurry droplets are fully dried in a drying atmosphere to obtain precursor particles.

[0058] S3. After the liquid silicon source in the silicon source storage device is preheated, it is introduced into the spray drying device through the silicon source conveying device to fully contact the precursor particles in a suspended state, while increasing the temperature of the drying atmosphere. After full reaction, silicon-carbon composite material A is obtained.

[0059] S4. Disperse the polymer binder in a solvent to obtain a mixture, pour it into a binder storage device, preheat it, and then pass it through a binder conveying device into the spray drying device to granulate the silicon-carbon composite material A to obtain silicon-carbon composite material B.

[0060] S5. Place the silicon-carbon composite material B into a tube furnace for heating and sintering to obtain the silicon-carbon composite material.

[0061] like Figure 1As shown, the present invention provides an apparatus for synthesizing silicon-carbon anode materials, comprising a cylindrical body 1, which includes, from bottom to top, a material collection device 12, a conical feed plate 11, a discharge pipe 16, a silicon source feed nozzle 9, a binder feed nozzle 10, a slurry feed nozzle 5, and a gas distributor 20. The nozzle of the slurry feed nozzle 5 is arranged downward (towards its bottom within the cylindrical body), while the silicon source feed nozzle 9 and the binder feed nozzle 10 are both arranged upward (towards its top within the cylindrical body).

[0062] According to the direction of dry gas transportation, it includes a gas generator 15, a third flow metering device 14, a third temperature metering device 13, and a gas distributor 20.

[0063] According to the direction of carbon source slurry feeding and transportation, it includes slurry storage device 2, first flow metering device 3, first temperature metering device 4, and slurry feeding nozzle 5;

[0064] According to the silicon source feeding and transportation direction, it includes silicon source storage device 6, second flow metering device 7, second temperature metering device 8, and silicon source feeding nozzle 9;

[0065] According to the direction of adhesive feeding and transportation, it includes adhesive storage device 23, fourth flow metering device 22, fourth temperature metering device 21, and adhesive feed nozzle 10;

[0066] According to the discharge direction, it includes discharge pipe 16, cyclone separator 17, material collection device 18, and exhaust gas treatment device 19.

[0067] When using,

[0068] S1. Heat the dry gas generated by gas generator 15 to 100-300℃ and then reduce it to 30-50m³. 3 The flow rate of / h is sent to the spray drying device via the third flow metering device 14 and the third temperature metering device 13 to the gas distributor 20, and the temperature inside the spray drying device is controlled to be 100~300℃ by the temperature of the drying gas.

[0069] S2. The carbon source precursor slurry is poured into the slurry storage device 2. The slurry is preheated to 50-80°C and conveyed to the slurry nozzle 5 at a rate of 10-30 ml / min via the first flow metering device 3 and the first temperature metering device 4. The slurry droplets are fully dried in a nitrogen atmosphere to obtain precursor particles.

[0070] S3. The liquid silicon source in the silicon source storage device 6 is preheated to 50-80°C and then conveyed to the silicon source feed nozzle 9 at a rate of 10-30 ml / min via the silicon source conveying device, the second flow metering device 7 and the second temperature metering device 8. It is then sprayed into the spray drying device in an atomized form, where it is in a suspended state and fully contacts the precursor particles in S2. At the same time, the temperature of the drying atmosphere is increased to 400-600°C. After a full reaction, silicon-carbon composite material A is obtained.

[0071] S4. The adhesive liquid in the adhesive storage device 23 is preheated to 50-80°C and then conveyed by the adhesive conveying device at a speed of 60-100 m. 3 / h is conveyed to the binder feed nozzle 10 via the fourth flow metering device 22 and the fourth temperature metering device 21 and sprayed into the spray drying device to fully dry and granulate the silicon-carbon composite material A formed above it, and obtain silicon-carbon composite material B with an average particle size of 10-20μm.

[0072] Some unreacted porous carbon particles enter the collection device 12 through the conical feed plate 11. The fully reacted silicon-carbon composite material B enters the discharge pipe 16 and passes through the cyclone separator 17. It is then collected in the material collection box 18, and the gas enters the tail gas treatment device 19.

[0073] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0074] Example 1

[0075] This embodiment provides an apparatus for synthesizing fast-charging silicon-carbon anode materials, such as... Figure 1 As shown, the spray drying device includes a cylinder 1, a material conveying device, a material collecting device, and an exhaust gas treatment device;

[0076] The cylinder 1 includes, from bottom to top, a material collection device 12, a conical feed plate 11, a discharge pipe 16, a silicon source feed nozzle 9, a binder feed nozzle 10, a slurry feed nozzle 5, and a gas distributor 20;

[0077] The conical feed plate 11 is located below the cylinder 1 and connected to the collecting device 12. The discharge pipe 16 is positioned at a distance from the bottom of the cylinder 1 that accounts for 10% of the height of the inner cavity of the cylinder 1. The silicon source feed nozzle 9 and the binder feed nozzle 10 are distributed parallel to each other on the left and right sides of the cylinder 1, and their positions are at a distance from the bottom of the cylinder 1 that accounts for 20% of the height of the inner cavity of the cylinder 1. The distance between the slurry feed nozzle and the silicon source feed nozzle 9 accounts for 70% of the height of the inner cavity of the cylinder. The gas distributor is located at the top of the cylinder, and its distance from the top of the cylinder accounts for 10% of the height of the inner cavity of the cylinder.

[0078] The nozzle of the slurry feeding nozzle 5 is set downwards, while the silicon source feeding nozzle 9 and the binder feeding nozzle 10 are both set upwards.

[0079] All nozzles are uniformly sized to 0.1mm.

[0080] The material conveying device includes a drying gas conveying device, a slurry conveying device, a silicon source conveying device, and a binder conveying device. Each material conveying device includes all flow metering devices (first flow metering device 3, second flow metering device 7, third flow metering device 14, fourth flow metering device 22), heating components, all temperature metering devices (first temperature metering device 4, second temperature metering device 8, third flow metering device 14, fourth flow metering device 22), valves, and all nozzles (slurry feed nozzle 5, silicon source feed nozzle 9, binder feed nozzle 10).

[0081] The material collection device includes a cyclone separator 17 and a material collection box 18; one end of the cyclone separator 17 is connected to the discharge pipe 16, and the other end is connected to the exhaust gas treatment device 19; the lower part of the cyclone separator 17 is connected to the material collection box 18.

[0082] This embodiment provides a method for preparing a fast-charging silicon-carbon anode material, which specifically includes the following steps:

[0083] S1. The nitrogen gas generated by the gas generator is heated to 100°C by the first heater and then discharged at 30m... 3 The flow rate of / h is sent into the spray drying device through the gas distributor, and the temperature inside the spray drying device is controlled to be 100℃ by the temperature of nitrogen.

[0084] S2. Take 500g of hard carbon (D50 is 1μm) and disperse it in 300g of water. After sand milling, pass it through a 150-mesh sieve to obtain a precursor slurry. Preheat the slurry to 50℃ and convey it from the slurry conveying device to the slurry nozzle at 10ml / min and spray it into the spray drying device. The slurry droplets are fully dried under a nitrogen atmosphere to obtain precursor particles.

[0085] S3 and silicon tetrachloride are preheated to 50°C and conveyed to the silicon source feed nozzle at 10ml / min via a silicon source conveying device. They are then sprayed into the spray drying device in an atomized form, where they are in a suspended state and come into full contact with the precursor particles in S2. At the same time, the drying atmosphere temperature is increased to 400°C. After full reaction, silicon-carbon composite material A is obtained, in which the mass percentage of silicon is approximately 35%.

[0086] S4. Disperse polyvinylidene fluoride in water, preheat to 50°C, and then convey it via an adhesive conveying device at a speed of 60m. 3 / h is conveyed to the binder feed nozzle and sprayed into the spray drying device to fully dry and granulate the silicon-carbon composite material A formed above it, so as to obtain silicon-carbon composite material B with an average particle size of 10μm.

[0087] S5. Place the silicon-carbon composite material B into a tube furnace for sintering and shaping. The sintering temperature is 300℃ and the holding time is 3h to obtain the silicon-carbon composite material.

[0088] Example 2

[0089] This embodiment provides a method for preparing fast-charging silicon-carbon anode material using the spray drying apparatus provided in Example 1. The method includes:

[0090] S1. The argon gas generated by the gas generator is heated to 150°C by the first heater and then discharged at 40m... 3 The flow rate of / h is sent into the spray drying device through the gas distributor, and the temperature inside the spray drying device is controlled at 150℃ by the temperature of nitrogen.

[0091] S2. Take 500g of resin (D50 is 2μm) and disperse it in 750g of ethanol. After sand milling, pass it through a 180-mesh sieve to obtain the precursor slurry. Preheat the slurry to 65℃ and convey it from the slurry conveying device to the slurry nozzle at 20ml / min and spray it into the spray drying device. The slurry droplets are fully dried under a nitrogen atmosphere to obtain precursor particles.

[0092] S3 and propane are preheated to 65°C and conveyed to the silicon source feed nozzle at 20ml / min via a silicon source conveying device. They are then sprayed into the spray drying device in an atomized form, where they are in suspension and fully contact the precursor particles in S2. At the same time, the drying atmosphere temperature is increased to 500°C. After a full reaction, silicon-carbon composite material A is obtained, in which the mass percentage of silicon is approximately 40%.

[0093] S4. Disperse polyacrylic acid in ethanol, preheat to 65°C, and then convey it via an adhesive conveying device at a speed of 80m. 3 / h is conveyed to the binder feed nozzle and sprayed into the spray drying device to fully dry and granulate the silicon-carbon composite material A formed above it, so as to obtain silicon-carbon composite material B with an average particle size of 15μm.

[0094] S5. Place the silicon-carbon composite material B into a tube furnace for sintering and shaping. The sintering temperature is 400℃ and the holding time is 7.5h to obtain the silicon-carbon composite material.

[0095] Example 3

[0096] This embodiment provides a method for preparing fast-charging silicon-carbon anode material using the spray drying apparatus provided in Example 1. The method includes:

[0097] S1. The helium gas generated by the gas generator is heated to 300°C by the first heater and then discharged at 50m... 3 The flow rate of / h is sent into the spray drying device through the gas distributor, and the temperature inside the spray drying device is controlled at 300℃ by the temperature of the helium gas.

[0098] S2. Take 500g of petroleum coke (D50 is 3μm) and disperse it in 750g of tetrahydrofuran. After sand milling, pass it through a 200-mesh sieve to obtain a precursor slurry. Preheat the slurry to 80℃ and convey it from the slurry conveying device to the slurry nozzle at 30ml / min and spray it into the spray drying device. The slurry droplets are fully dried under a nitrogen atmosphere to obtain precursor particles.

[0099] S3, n-Butylsilane is preheated to 80°C and conveyed to the silicon source feed nozzle at 30ml / min via a silicon source conveying device. It is then sprayed into the spray drying device in an atomized form, where it is in a suspended state and fully contacts the precursor particles in S2. At the same time, the drying atmosphere temperature is increased to 600°C. After full reaction, silicon-carbon composite material A is obtained, in which the mass percentage of silicon is approximately 45%.

[0100] S4. Disperse polyacrylic acid in ethanol, preheat to 80°C, and then convey it via an adhesive conveying device at a speed of 100m. 3 / h is conveyed to the binder feed nozzle and sprayed into the spray drying device to fully dry and granulate the silicon-carbon composite material A formed above it, so as to obtain silicon-carbon composite material B with an average particle size of 20μm;

[0101] S5. Place the silicon-carbon composite material B into a tube furnace for sintering and shaping. The sintering temperature is 500℃ and the holding time is 12h to obtain the silicon-carbon composite material.

[0102] Comparative Example 1

[0103] S1. Take 500g of petroleum coke particles with a D50 of 10μm and pack them into the fluidized bed reactor;

[0104] S2, silane preheated to 80℃ and fed into the fluidized bed reactor at 30ml / min, heated to 600℃ in a helium protective atmosphere and held for 10h;

[0105] S3. Preheat acetylene gas to 80°C and deliver it to the fluidized bed reactor at 30 ml / min. In a helium protective atmosphere, raise the temperature to 600°C and hold for 2 hours.

[0106] Comparative Example 2

[0107] S1. Take 500g of petroleum coke particles with a D50 of 10μm and pack them into the CVD reactor;

[0108] S2, silane is preheated to 80℃ and fed into the CVD reactor at 30ml / min. The temperature is raised to 600℃ in a helium protective atmosphere and held for 10h.

[0109] S3. Preheat acetylene gas to 80°C and deliver it to the CVD reactor at 30ml / min. Heat the gas to 600°C in a helium protective atmosphere and hold for 2 hours.

[0110] To compare and verify the effects of the above embodiments and comparative examples, this application conducted the following physicochemical properties and coin cell tests on the silicon-carbon composite materials obtained in Embodiments 1-3 and Comparative Examples 1-2:

[0111] 1) The particle size, tap density, specific surface area, silicon grain size, powder resistivity and specific capacity of the silicon-carbon composite materials obtained in Examples 1-4 and Comparative Examples 1-2 were tested according to the methods in the national standard GB / T 38823-2020 "Silicon-Carbon". The test results are shown in Table 1 below.

[0112] 2) Button cell battery testing: The novel silicon-carbon anode materials prepared in Examples 1-4 and Comparative Examples 1-2 were mixed with super-P (superconducting carbon black) conductive agent and PVDF (polyvinylidene fluoride) binder at a mass ratio of 8:1:1 and coated onto 8μm copper foil to obtain the battery anode. A CR2016 button cell was assembled using a lithium sheet as the positive electrode. The electrolyte was a 1 mol / L LiPF6 EC (ethylene carbonate) + DMC (dimethyl carbonate) solution, with EC:DMC = 1:1, and the separator was a PP (polypropylene) separator. Electrochemical performance was tested. The first-cycle charge-discharge test was conducted at 0.05C; the test results are shown in Table 1 below.

[0113] 3) Expansion test: A micrometer was used to measure the negative electrode sheets of Examples 1-4 and Comparative Examples 1-2. The measurement points were the center, middle ring, and outer ring. After the first week of charge-discharge testing, the coin cell was disassembled and in-situ measurements were performed. The average value of the measurement results was taken, and the electrode sheet expansion rebound rate was calculated; the test results are shown in Table 1 below.

[0114] Therefore, in summary, this invention provides a method and apparatus for synthesizing fast-charging silicon-carbon anode materials. This invention uses small-sized porous carbon matrix particles as the carbon source, which, compared to traditional medium-sized porous carbon particles, shortens the lithium-ion transport path and narrows the particle size distribution. The synthesized silicon-carbon anode material exhibits low resistivity, low expansion, good fast-charging performance, and high batch stability. This invention uses a spray drying reactor instead of a fluidized bed reactor, combining the advantages of a small-sized porous carbon matrix. Compared to traditional fluidized bed reactors, it offers advantages such as rapid reaction and low energy consumption. Furthermore, silicon deposition and silicon-carbon material granulation can both be completed within this reaction apparatus, simplifying the process and avoiding material contamination.

[0115] Table 1

[0116]

[0117] The present invention has been described in detail above. For those skilled in the art, the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments have been given, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein. Some of the essential features can be applied within the scope of the following appended claims.

Claims

1. A method for preparing a silicon-carbon anode material, comprising the following steps: S1. Disperse the porous carbon matrix in a solvent, mill it, and then sieve it to obtain a precursor slurry. Spray dry the precursor slurry in a spray drying device to obtain precursor particles. The particle size (D50) of the porous carbon matrix after sand milling and sieving is 1~3μm; The porous carbon matrix is ​​selected from at least one of hard carbon, soft carbon, resin and petroleum coke; S2. After preheating, the liquid silicon source is introduced into the spray drying device described in step S1, so that it is in a suspended state and fully contacts the precursor particles. After the reaction, silicon-carbon composite material A is obtained. S3. Disperse the polymer binder in a solvent to obtain a mixture. After preheating, pass the mixture into the spray drying device containing the silicon-carbon composite material A for granulation to obtain silicon-carbon composite material B. The average particle size of the silicon-carbon composite material B is 10~20μm; S4. Sinter the silicon-carbon composite material B to obtain the silicon-carbon anode material; The sintering temperature is 300~500℃ and the time is 3~12h.

2. The method according to claim 1, characterized in that, Before step S1, the spray drying device is preheated by introducing gas, which is selected from at least one of air, argon, nitrogen, and helium; the flow rate of the gas is 30-50 m³ / h. 3 / h; the preheating temperature is 100~300℃; In step S1, the solvent is at least one of water, ethanol, and tetrahydrofuran; The mass ratio of the porous carbon matrix to the solvent is 1:0.6~2, the sieve mesh size is 150~200 mesh, the preheating temperature of the precursor slurry is 50~80℃, and the input flow rate is 10~30ml / min.

3. The method according to claim 1 or 2, characterized in that, In step S2, the liquid silicon source is selected from one or a mixture of several of silicon tetrachloride, propane, n-butane and cyclopentane; The amount of liquid silicon source added is such that the mass percentage of silicon in the obtained silicon-carbon composite material is 35% to 50%. The preheating temperature of the liquid silicon source is 50 to 80°C, the flow rate is 10 to 30 ml / min, and the gas temperature in the spray drying device is raised to 400 to 600°C.

4. The method according to claim 1 or 2, characterized in that, In step S3, the polymeric binder is selected from at least one of polyvinylidene fluoride, polyacrylic acid, and carboxymethyl cellulose; The solvent is at least one of water, ethanol, and tetrahydrofuran; The preheating temperature of the mixture is 50~80℃, and the flow rate of the mixture is 60~100m³. 3 / h.

5. The silicon-carbon anode material prepared by the preparation method according to any one of claims 1-4.

6. A battery negative electrode sheet, characterized in that, The active material of the battery negative electrode sheet includes the silicon-carbon negative electrode material as described in claim 5.

7. The method according to claim 1, characterized in that, The apparatus for synthesizing the silicon-carbon anode material includes a spray drying apparatus; The spray drying device includes a cylinder, a material conveying device, a material collecting device, and an exhaust gas treatment device. The cylinder is equipped with a gas distributor, a material collection device, a conical feed plate, a slurry feed nozzle, a silicon source feed nozzle, a binder feed nozzle, and a discharge pipe. The gas distributor is located at the top of the cylinder. The conical feed plate is located at the bottom of the cylinder and connected to the material collection device. The slurry feed nozzle, the silicon source feed nozzle, and the binder feed nozzle all penetrate the cavity wall of the cylinder and communicate with the inside of the cylinder. The discharge pipe is located at the bottom of the cylinder. The distance between the gas distributor and the top of the cylinder is 5% to 10% of the height of the inner cavity of the cylinder; The silicon source feed nozzle and the binder feed nozzle are distributed parallel to each other on the cylinder, and their positions are 20% to 25% of the height of the inner cavity of the cylinder from the bottom of the cylinder. The distance between the slurry feed nozzle and the silicon source feed nozzle accounts for 50% to 80% of the height of the inner cavity of the cylinder; The distance between the discharge pipe and the bottom of the cylinder is 10% to 15% of the height of the inner cavity of the cylinder; The nozzle of the slurry feeding nozzle is arranged towards the bottom inside the cylinder, while the silicon source feeding nozzle and the binder feeding nozzle are both arranged towards the top inside the cylinder. The material conveying device includes a drying gas conveying device, a slurry conveying device, a silicon source conveying device, and a binder conveying device. Each of the material conveying devices includes a corresponding storage device, a heating device, a flow metering device, a temperature metering device, a slurry feed nozzle, a silicon source feed nozzle, and a binder feed nozzle.

8. The method according to claim 7, characterized in that, The dimensions of the slurry feeding nozzle, silicon source feeding nozzle, and binder feeding nozzle are all integrated and range from 0.1 to 2.5 mm. The material collection device includes a cyclone separator and a material collection box; one end of the cyclone separator is connected to the discharge pipe, and the other end is connected to the exhaust gas treatment device; the bottom of the cyclone separator is connected to the material collection box.

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