A method and apparatus for preparing silicon carbide anode material slurry

Abstract

This invention discloses a method and apparatus for preparing silicon-carbon anode material slurry, relating to the field of silicon-carbon anode material slurry preparation methods. The method includes: S101: mixing silicon-carbon, a conductive agent, CMC dry powder, and deionized water to form a mixture; S102: placing the mixture in a ball mill for ball milling; and S103: forming a silicon-carbon anode material slurry after ball milling. This invention uses ball milling to process the silicon-carbon anode material slurry, which helps the carbon material uniformly coat silicon particles, forming a core-shell structure or an embedded structure. This effectively buffers the volume expansion of silicon while improving the conductivity and stability of the material.

Description

Technical Field

[0001] This invention relates to the field of methods for preparing silicon-carbon anode material slurry, and particularly to a method and apparatus for preparing silicon-carbon anode material slurry. Background Technology

[0002] The patent titled "A Method for Preparing a Lithium-ion Battery Anode Sheet" (patent application number: 202010502133.4) discloses a method for preparing a lithium-ion battery anode sheet. In this method, a slurry, namely a silicon-carbon anode material slurry, needs to be prepared before preparing the lithium-ion battery anode sheet. In this method, deionized water needs to be added to the silicon-carbon anode material slurry three times to improve the stability of the slurry. It also needs to be mixed and stirred again after being made into a mud-like material, which not only improves the stability of the slurry but also optimizes the viscosity of the slurry and reduces the generation of bubbles. However, this method is relatively complex and has low production efficiency.

[0003] Therefore, it is necessary to propose a method and apparatus for preparing silicon carbide anode material slurry to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for preparing silicon-carbon anode material slurry. The method uses ball milling to process the silicon-carbon anode material slurry, which helps the carbon material to uniformly coat the silicon particles, forming a core-shell structure or an embedded structure. This effectively buffers the volume expansion of silicon, improves the conductivity and stability of the material, and optimizes the slurry viscosity, reducing the generation of bubbles.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a carbon-silicon anode material slurry, comprising:

[0006] S101: Silicon carbide, conductive agent, CMC dry powder and deionized water are mixed to form a mixture;

[0007] S102: The mixture is placed in a ball mill for ball milling. The ball milling process includes:

[0008] Step 1: Pre-ball milling stage, add the mixture into the ball mill for preliminary ball milling, set the time to 1-2 hours;

[0009] Step 2: Main grinding stage. After the pre-grinding is completed, continue with the main grinding, which takes 4-6 hours.

[0010] Step 3: Post-processing ball milling stage. After the main ball milling is completed, post-processing ball milling is carried out, and the time is set to 1-2 hours.

[0011] The ball mill's rotational speed is set to 200-300 revolutions per minute;

[0012] S103: After ball milling, a silicon carbide anode material slurry is formed.

[0013] Preferably, the ball milling process is carried out in a vacuum.

[0014] Preferably, during ball milling, the inner lining plates and balls of the ball mill are made of silicon carbide.

[0015] Preferably, during the pre-ball milling stage, the ball mill speed is 200 rpm;

[0016] During the main ball milling stage, the ball mill speed is 300 rpm;

[0017] In the post-processing ball milling stage, the ball mill speed is 250 rpm.

[0018] Preferably, ball milling is carried out at room temperature, with the temperature controlled at 20-30 degrees Celsius.

[0019] This invention also discloses a carbon-silicon anode material slurry preparation apparatus, applied to a method for preparing carbon-silicon anode material slurry, and further comprising:

[0020] The ball mill base and the ball mill tank are provided. Support bearing seats are fixedly installed at both ends of the upper surface of the ball mill base. Both ends of the ball mill tank are rotatably mounted on the support bearing seats. A transmission gear is fixedly installed at the outer ring of one end of the ball mill tank.

[0021] The ball mill tank contains multiple balls. When the ball mill tank rotates, it drives the multiple balls to perform parabolic motion, thus grinding the mixture in the ball mill tank.

[0022] The ball mill tank is equipped with a tank cover and a vacuum pump;

[0023] The inner wall of the ball mill tank is provided with an inner liner plate. The inner liner plate has an arc-shaped plate structure. There are multiple inner liner plates, which are evenly distributed. The inner liner plates are installed on the inner wall of the ball mill tank by screw and nut assemblies that extend to the outside of the ball mill tank.

[0024] Preferably, the inner liner is provided with a guide groove, which is an arc-shaped groove structure, and the diameter of the guide groove is adapted to the diameter of the ball.

[0025] Preferably, the multiple inner lining plates in the ball mill tank are divided into left and right groups. The guide grooves in the multiple inner lining plates of the left group all face the middle section of the ball mill tank, and the guide grooves in the multiple inner lining plates of the right group also all face the middle section of the ball mill tank.

[0026] Preferably, there is a sound-insulating gap between the outer wall of the inner liner and the inner wall of the ball mill tank.

[0027] Preferably, the surface of the inner liner is provided with a rough surface, and the rough surface has multiple protrusions or depressions.

[0028] The technical effects and advantages of this invention are as follows:

[0029] Using ball milling to process silicon-carbon anode material slurry helps the carbon material to uniformly coat the silicon particles, forming a core-shell structure or an embedded structure. This effectively buffers the volume expansion of silicon, while improving the conductivity and stability of the material. It also optimizes the slurry viscosity and reduces the generation of bubbles.

[0030] In this invention, silicon carbide is used to prepare ball mill balls. By utilizing its wear resistance, chemical stability and thermal stability, the problems of easy wear and impurity introduction of traditional ball mill balls when grinding silicon-based materials are solved.

[0031] Because the material used to prepare silicon carbide anode materials has a uniform particle size, it can maintain a uniform pore structure between the silicon carbide anode materials, thereby improving the permeability of the electrolyte and the ion transport efficiency, and ensuring that the active material on the electrode surface is evenly distributed.

[0032] The ball milling process is carried out in a vacuum. Ball milling under vacuum conditions can effectively reduce the contamination of materials by impurities in the air, improve the purity of silicon carbide anode materials, and avoid the phenomenon that the presence of impurities may lead to an increase in side reactions of electrode materials. In addition, vacuum ball milling can improve the crystallinity and density of materials, thereby improving the electrical conductivity and mechanical strength of materials.

[0033] The homogenization and improved stability of nanostructures achieved through ball milling are difficult to achieve using traditional preparation methods.

[0034] Based on the fact that the ball stones in this invention first generate an impact effect near the bottom of the ball mill tank, the impact force on the inner wall of the ball mill tank and the wear on the inner lining can be reduced, the service life of the inner lining is increased, and the transmission of noise is reduced, so that the mixture is first ground by the impact between multiple balls; when the ball stones contact the inner wall of the guide groove, the contact area is large, which increases the grinding contact surface and thus saves grinding time.

[0035] There is also a sound insulation gap between the outer wall of the inner liner and the inner wall of the ball mill tank. The sound insulation gap can eliminate the noise generated during the ball milling process to a certain extent and has a good noise reduction effect.

[0036] The surface of the inner liner can be roughened, with multiple protrusions or depressions forming a honeycomb-like structure. This structure enables the grinding balls to generate minute vibrations during movement, increasing the interaction between the grinding balls and the material and improving grinding efficiency. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the method for preparing the carbon-silicon anode material slurry of the present invention.

[0038] Figure 2 This is a schematic diagram of the carbon-silicon anode material slurry preparation device of the present invention.

[0039] Figure 3 This is a top view of the apparatus for preparing silicon carbide anode material slurry according to the present invention.

[0040] Figure 4 This is a cross-sectional view of the apparatus for preparing silicon carbide anode material slurry according to the present invention.

[0041] In the diagram: 1. Ball mill base; 2. Ball mill tank; 3. Screw and nut assembly; 4. Tank cover; 5. Transmission gear; 6. Support bearing seat; 7. Vacuum pump; 8. Sound insulation gap; 9. Inner liner; 10. Guide groove. Detailed Implementation

[0042] This invention provides, for example Figures 1-4 The invention discloses a method and apparatus for preparing silicon-carbon anode material slurry. The method for preparing silicon-carbon anode material slurry includes:

[0043] Step 1: Mix silicon carbide, conductive agent, CMC dry powder and deionized water to form a mixture;

[0044] The second step is to place the mixture in a ball mill for ball milling, which makes the particle size of the material in the mixture uniform. The carbon silicon anode material prepared by using carbon silicon anode material slurry with uniform particle size can adhere more stably to the copper sheet and is not easy to detach. Moreover, during the use of the carbon silicon anode (during charging and discharging), due to the uniform particle size of the material used to prepare the carbon silicon anode material, a uniform pore structure can be maintained between the carbon silicon anode materials, thereby improving the permeability of the electrolyte and the ion transport efficiency, and ensuring that the active material on the electrode surface is evenly distributed.

[0045] Using ball milling to process silicon-carbon anode material slurry helps the carbon material to uniformly coat the silicon particles, forming a core-shell structure or an embedded structure. This effectively buffers the volume expansion of silicon (the volume expansion rate of silicon can reach more than 300%, and this volume change will lead to an increase in internal stress of the electrode, thereby destroying the integrity of the electrode), while improving the conductivity and stability of the material.

[0046] By ball milling, the surface of silicon particles is nanoscaled, reducing the volume expansion effect of silicon during charging and discharging. The nanostructured silicon particles experience less stress during expansion, thereby reducing particle pulverization and shedding, and significantly improving the cycle stability of the electrode. The homogenization of the nanostructure can significantly increase the specific surface area of ​​the material, thereby enhancing the lithium ion insertion and extraction efficiency.

[0047] The homogenization and stability enhancement of nanostructures achieved through ball milling are difficult to achieve using traditional preparation methods. This not only improves the electrochemical performance of the material but also provides a new technical path for the commercial application of high-energy-density lithium-ion batteries.

[0048] The ball milling process needs to be carried out in a vacuum. Ball milling under vacuum conditions can effectively reduce the contamination of materials by impurities in the air (such as oxygen and moisture), improve the purity of silicon carbide anode materials, and avoid the phenomenon that the presence of impurities may lead to an increase in side reactions of electrode materials. In addition, vacuum ball milling can improve the crystallinity and density of materials, thereby improving the electrical conductivity and mechanical strength of materials.

[0049] The specific processes of ball milling include:

[0050] (a) Ball grinding time

[0051] 1. Pre-ball milling stage: Add silicon carbide anode material (including silicon carbide, conductive agent, CMC dry powder and deionized water) into a ball mill for preliminary ball milling. The time is set to 1-2 hours. The purpose of this stage is to initially crush and mix the material.

[0052] 2. Main ball milling stage: After the pre-ball milling is completed, the main ball milling continues for 4-6 hours. The purpose of this stage is to grind the material to the nanoscale and achieve uniform dispersion.

[0053] 3. Post-processing ball milling stage: After the main ball milling is completed, post-processing ball milling is carried out for 1-2 hours. The purpose of this stage is to further optimize the structure and surface properties of the material.

[0054] (ii) Milling media

[0055] 1. Ball mill materials: The inner wall of the ball mill tank is lined with a silicon carbide liner to prevent contamination by metal impurities.

[0056] 2. Grinding media: Silicon carbide with a diameter of 5-1 mm is used as the grinding media. The high density of the grinding balls provides sufficient grinding force while avoiding contamination of the materials.

[0057] 3. Ratio of media to material: The mass ratio of grinding media (silicon-carbon) to silicon-carbon anode material is 3:1 to 5:1. This ratio ensures that the material is fully ground and dispersed during ball milling. Both the grinding media and the inner liner are made of silicon-carbon, so even if the grinding media and the inner liner are worn, no new impurities will be introduced into the silicon-carbon anode material slurry.

[0058] It is important to note that the preparation of silicon carbide spheres involves multiple steps, including raw material proportioning, mixing, molding, and sintering. The following is a detailed preparation process and precautions:

[0059] Step 1: Raw material formulation, main components include:

[0060] Silicon source, such as silicon dioxide or nano-silicon powder;

[0061] Carbon sources, such as carbon black, graphite powder, or organic carbon sources (such as phenolic resins).

[0062] Adhesives, such as polyvinyl alcohol (PVA) or silica sol, are used to enhance the adhesion of materials;

[0063] Additives, such as alumina or boron carbide, are used to improve the wear resistance and strength of the pebbles.

[0064] The formulation includes the following components by mass percentage: silicon source (SiO2): 40-60%, carbon source (carbon black or graphite powder): 20-30%, binder (PVA or silica sol): 5-10%, additives (Al2O3 or B4C): 5-10%, and other auxiliary components (such as dispersants): 1-5%.

[0065] Step 2: Mixing and ball milling. Put the raw materials in the above proportions into a ball mill, add an appropriate amount of deionized water or ethanol as a dispersant, and use a ball mill to mix and ball mill for 2-4 hours at a speed of 200-300 rpm.

[0066] Step 3: Forming. The ball-milled slurry is spray-granulated using a spray dryer. The hot air temperature (150-200 degrees Celsius), outlet air temperature (80-100 degrees Celsius), and pressure difference of the spray drying tower are controlled. The particle size of the granulated powder is controlled at 1-3 mm and passes through a 20-mesh sieve. Pressing and molding: The granulated powder is pressed into spherical blanks using a mold. The particle size can be selected as 10 mm, 15 mm, 20 mm, etc., with a smooth surface or regular raised surfaces. The moisture content of the pressed powder is controlled below 0.5%.

[0067] Step 4: Sintering. The pressed green body is placed in a high-temperature sagger, sprinkled with 80-mesh white corundum insulating sand, and sent into a tunnel kiln or tubular furnace for sintering. The sintering temperature is 1200-1350 degrees Celsius, and the firing cycle is 24-36 hours. Sintering is carried out in an inert atmosphere (such as argon or nitrogen) to avoid oxidation.

[0068] After sintering, the sintered spheres are naturally cooled to room temperature. The sintered spheres are then cleaned to remove the surface sand and burrs, and polished to improve the surface smoothness.

[0069] In this invention, silicon-carbon materials are used to prepare ball mill balls. By utilizing their wear resistance, chemical stability, and thermal stability, the problems of easy wear and impurity introduction of traditional ball mill balls when grinding silicon-based materials are solved.

[0070] By employing processes such as vacuum or inert gas-protected ball milling, spray granulation, and high-temperature sintering, the preparation process of the spherical pellets has been optimized, thereby improving their quality and performance.

[0071] Silicon carbide spheres are particularly suitable for grinding highly active silicon-based materials, such as nano-silicon and silicon oxide, which can significantly improve the purity and performance of the materials, providing a new technical means for the preparation of high-performance lithium-ion battery anode materials.

[0072] (iii) Ball mill speed

[0073] 1. Ball mill speed: The speed of the ball mill is set to 200-300 rpm. This speed range can provide sufficient mechanical energy to allow the material to fully collide and grind in the ball mill.

[0074] 2. Rotation speed adjustment: In the pre-ball milling stage, the rotation speed can be slightly lower (200 rpm) to avoid over-grinding; in the main ball milling stage, the rotation speed is increased to 300 rpm to achieve efficient nano-sizing; in the post-processing ball milling stage, the rotation speed can be appropriately reduced (250 rpm) to optimize the material structure.

[0075] (iv) Ball milling temperature

[0076] 1. Room temperature ball milling: Ball milling is carried out under normal temperature conditions, with the temperature controlled at 20-30 degrees Celsius. Room temperature ball milling can avoid the impact of high temperature on the material structure and save energy.

[0077] 2. Temperature control measures: During the ball milling process, water cooling or air cooling devices can be used to ensure that the temperature inside the ball mill does not exceed 30 degrees Celsius.

[0078] Ball milling is performed under vacuum conditions. The vacuum level is set as follows: during the ball milling process, the vacuum level inside the mill is maintained at 10. -3 Pascal to 10 -4 Pascal, this vacuum level can effectively reduce the contamination of materials by impurities in the air (such as oxygen, moisture, etc.).

[0079] Vacuum maintenance method: A vacuum pump is installed in the sealing system of the ball mill to ensure a stable vacuum level inside the ball mill by continuously pumping vacuum.

[0080] The specific steps of vacuum ball milling include:

[0081] Step 1: Vacuuming. After adding silicon carbide anode material and grinding media (balls), close the sealing cover of the ball mill, start the vacuum pump, and extract the air from the ball mill to achieve the set vacuum level.

[0082] Step 2: Ball milling operation. After reaching the set vacuum level, start the ball mill and perform the ball milling operation according to the above-mentioned ball milling time, speed and media ratio.

[0083] Step 3: Nitrogen purging protection. After ball milling is completed, high-purity nitrogen can be purged into the ball mill to further protect the material from oxidation.

[0084] Surfactants can be added during ball milling: During ball milling, an appropriate amount of surfactant (such as polyethylene glycol, sodium dodecyl sulfate, etc.) can be added. Surfactants can form a protective film on the material surface, reduce particle agglomeration, and improve the wettability and dispersibility of the material. The amount of surfactant added is 1%-5% of the mass of the silicon carbide anode material, or it can be omitted according to actual needs.

[0085] refer to Figures 2 to 4 As shown in the figure, the ball mill in this invention includes a ball mill base 1 and a ball mill tank 2. Both ends of the upper surface of the ball mill base 1 are fixedly installed with support bearing seats 6. Both ends of the ball mill tank 2 are rotatably mounted on the support bearing seats 6. A transmission gear 5 is fixedly installed on the outer ring of one end of the ball mill tank 2. A motor, planetary gear, or other structure can be installed on the ball mill base 1 to drive the transmission gear 5 to rotate, thereby driving the ball mill tank 2 to rotate. The ball mill tank 2 stores multiple balls. When the ball mill tank 2 rotates, it drives the multiple balls to perform parabolic motion, thereby grinding the mixture in the ball mill tank 2.

[0086] It should be noted that transmission methods such as motors and planetary gears are conventional transmission mechanisms in existing technology, and will not be elaborated upon here.

[0087] A lid 4 is provided on the ball mill tank 2. When the lid 4 is opened, the mixture in the ball mill tank 2 can enter and exit. A vacuum pump 7 is connected to one end of the ball mill tank 2. The vacuum pump 7 can be used to evacuate the ball mill tank 2, thereby maintaining a vacuum state in the ball mill tank 2.

[0088] A liner 9 is provided on the inner wall of the ball mill tank 2. The liner 9 has an arc-shaped plate structure, and multiple liner 9s are provided. The multiple liner 9s are distributed at equal intervals. The liner 9s are installed on the inner wall of the ball mill tank 2 by a screw and nut assembly 3 that extends through to the outside of the ball mill tank 2. The screw and nut assembly 3 includes a screw and a nut. The connection method of the screw and nut assembly 3 extending through to the outside of the ball mill tank 2 can ensure that the surface area of ​​the liner 9 inside the ball mill tank 2 is maximized, thus ensuring the impact area between the liner 9 and the ball and material.

[0089] Furthermore, the inner liner 9 is provided with a guide groove 10. The guide groove 10 has an arc-shaped groove structure, and the diameter of the guide groove 10 is adapted to the diameter of the ball. When the ball mill tank 2 rotates and drives the ball to move, the ball can rise along the guide groove 10. When the ball reaches the top, it is guided to move in a parabolic motion in one direction. The multiple inner liner 9 in the ball mill tank 2 are divided into two groups, left and right. The guide grooves 10 in the multiple inner liner 9 in the left group are all facing the middle section of the ball mill tank 2, and the guide grooves 10 in the multiple inner liner 9 in the right group are also all facing the middle section of the ball mill tank 2. This creates the phenomenon that the balls in the ball mill tank 2 move in one direction. When the ball is about to fall to the bottom of the ball mill tank 2 in a parabolic motion, the multiple balls collide with each other first, and then fall to the bottom of the ball mill tank 2.

[0090] Based on the fact that the ball stones in this invention first generate an impact effect at a suspended position near the bottom of the ball mill tank 2, the impact force on the inner wall of the ball mill tank 2 and the wear on the inner liner 9 can be reduced, the service life of the inner liner 9 can be increased, and the propagation of noise can be reduced, so that the mixture is first ground by the impact between multiple ball stones.

[0091] The depth and diameter of the guide groove 10 can be optimized according to the size of the ball. Generally, the depth is 3-5 mm and the diameter is 5-10 mm. Since the guide groove 10 is adapted to the ball, when the ball contacts the inner wall of the guide groove 10, the contact area is large, which increases the grinding contact surface and thus saves grinding time.

[0092] Furthermore, there is a sound insulation gap 8 between the outer wall of the inner liner 9 and the inner wall of the ball mill tank 2. The sound insulation gap 8 can eliminate the noise generated during the ball milling process to a certain extent and has a good noise reduction effect.

[0093] In practical use, the surface of the inner liner 9 can be roughened, with multiple protrusions or depressions forming a honeycomb-like structure. This structure enables the grinding balls to generate minute vibrations during movement, increasing the interaction between the grinding balls and the material and improving grinding efficiency.

Claims

1. A method for preparing a silicon-carbon anode material slurry, characterized in that, include: S101: Silicon carbide, conductive agent, CMC dry powder and deionized water are mixed to form a mixture; S102: The mixture is placed in a ball mill for ball milling. The ball milling process includes: Step 1: Pre-ball milling stage, add the mixture into the ball mill for preliminary ball milling, set the time to 1-2 hours; Step 2: Main grinding stage. After the pre-grinding is completed, continue with the main grinding, which takes 4-6 hours. Step 3: Post-processing ball milling stage. After the main ball milling is completed, post-processing ball milling is carried out, and the time is set to 1-2 hours. The ball mill's rotational speed is set to 200-300 revolutions per minute; S103: After ball milling, a silicon carbide anode material slurry is formed; During ball milling, the inner lining plates and grinding balls of the ball mill are made of silicon carbide. The method for preparing the silicon-carbon anode material slurry employs a silicon-carbon anode material slurry preparation apparatus, which includes: The ball mill base (1) and the ball mill tank (2) are provided. Support bearing seats (6) are fixedly installed at both ends of the upper surface of the ball mill base (1). Both ends of the ball mill tank (2) are rotatably mounted on the support bearing seats (6). A transmission gear (5) is fixedly installed at the outer ring of one end of the ball mill tank (2). The ball mill tank (2) stores multiple balls. When the ball mill tank (2) rotates, it drives the multiple balls to make parabolic motion to ball mill the mixture in the ball mill tank (2). The ball mill tank (2) is equipped with a tank cover (4) and a vacuum pump (7). The inner wall of the ball mill tank (2) is provided with an inner liner (9). The inner liner (9) is an arc-shaped plate structure. There are multiple inner liners (9) and they are distributed at equal distances. The inner liner (9) is installed on the inner wall of the ball mill tank (2) by a screw and nut assembly (3) that extends through to the outside of the ball mill tank (2). The inner lining sheet (9) is provided with a guide groove (10), which is an arc-shaped groove structure, and the diameter of the guide groove (10) is adapted to the diameter of the ball stone. The ball mill tank (2) has multiple inner lining pieces (9) divided into two groups, left and right. The guide grooves (10) in the multiple inner lining pieces (9) of the left group are all facing the middle section of the ball mill tank (2), and the guide grooves (10) in the multiple inner lining pieces (9) of the right group are also all facing the middle section of the ball mill tank (2).

2. The method for preparing a silicon-carbon anode material slurry according to claim 1, characterized in that: The ball milling process is carried out in a vacuum.

3. The method for preparing a silicon-carbon anode material slurry according to claim 1, characterized in that: in, During the pre-ball milling stage, the ball mill speed is 200 rpm; During the main ball milling stage, the ball mill speed is 300 rpm; In the post-processing ball milling stage, the ball mill speed is 250 rpm.

4. The method for preparing a silicon-carbon anode material slurry according to claim 1, characterized in that: Ball milling is carried out at room temperature, with the temperature controlled at 20-30 degrees Celsius.

5. The method for preparing a silicon-carbon anode material slurry according to claim 1, characterized in that: There is a sound insulation gap (8) between the outer wall of the inner liner (9) and the inner wall of the ball mill tank (2).

6. The method for preparing a silicon-carbon anode material slurry according to claim 1, characterized in that: The surface of the inner liner (9) is provided with a rough surface, and the rough surface has multiple protrusions or depressions.

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