A system for preparing a nano-silicon-carbon material with reduced zirconium content

Abstract

The utility model discloses a kind of nano silicon-carbon material preparation systems of reducing zirconium content, belong to lithium battery material preparation technical field, including slurry tank (3) and sand mill (1) connected by pipeline, zirconia beads are filled in sand mill (1), the outlet of sand mill (1) is connected with a buffer tank (4) by pipeline, the outlet of buffer tank (4) is connected with a centrifuge (2) by pipeline, the outlet of centrifuge (2) is sequentially connected with drying equipment (7) and carbonization processing equipment (8) by pipeline, valve is respectively provided on pipeline;The utility model is based on traditional wet sand mill process, innovatively introduces "buffer-centrifugal" series processing unit, solves the problem that anode material electrochemical performance is reduced and safety risk is increased due to zirconium impurity excess and uncontrollable, to prepare nano silicon-carbon negative electrode material with higher specific capacity, more optimal cycle stability and higher safety.

Description

Technical Field

[0001] This utility model relates to the field of lithium battery material preparation technology, and in particular to a nano-silicon-carbon material preparation system with reduced zirconium content. Background Technology

[0002] Lithium-ion batteries are the primary energy solution for modern electronic devices and electric vehicles. In pursuit of higher energy density, silicon (Si), with a theoretical specific capacity of up to 4200 mAh / g, is considered one of the most promising next-generation anode materials to replace traditional graphite (theoretical specific capacity 372 mAh / g). However, silicon undergoes significant volume expansion (>300%) during charge and discharge, leading to the pulverization of active particles, detachment from the current collector, and the continuous growth and rupture of the unstable solid electrolyte interphase (SEI) film. Ultimately, this results in rapid capacity decay and a sharp decline in cycle life.

[0003] To overcome these problems, researchers proposed a strategy of nanostructuring silicon and combining it with carbon materials to prepare nano-silicon-carbon composites. The carbon matrix can act as a buffer layer, effectively mitigating the volume expansion of silicon, while providing an excellent conductive network to maintain the integrity of the electrode structure.

[0004] In the industrial production of nano-silicon-carbon anode materials, mechanical grinding, especially wet sand milling, is considered a potential route to nano-scale production due to its simplicity, low cost, and ease of scalability. This method typically involves mixing nano-silicon powder, a carbon source (such as graphite or pitch), and a dispersant in a solvent, followed by grinding in a sand mill for a certain period to further refine the particles and achieve uniform mixing. During the sand milling process, high-hardness zirconium oxide (ZrO2) microspheres are usually used as the grinding media to obtain sufficient grinding efficiency and energy.

[0005] In the grinding process, due to the small particle size of the grinding media (zirconium balls), approximately 0.1 mm, and the prolonged and intense collisions and friction with the equipment and materials, it is inevitable that some of the zirconium balls will break or wear down. This introduces zirconium into the material slurry in the form of zirconium oxide (ZrO2) particles, forming impurities. Existing reports (CN 111755681 A) show that zirconium content is commonly present in silicon-carbon anode materials prepared by grinding, sometimes reaching 1%-2 wt%, usually in the form of broken zirconium beads.

[0006] The introduction of appropriate amounts of zirconium can improve the cycling performance of materials. However, excessive introduction of particulate zirconium impurities can have the following negative effects:

[0007] (1) Uncontrollability of zirconium content: The amount of impurities introduced is related to various factors such as grinding time, rotation speed, zirconium ball quality, and slurry viscosity, resulting in large fluctuations in zirconium content between different batches of products, and lack of precise control. This uncertainty greatly affects the consistency and stability of the performance of the anode material.

[0008] (2) Deterioration of electrochemical performance: Zirconium itself is an electrochemically inert material and an excellent electrical insulator. When excessive zirconium oxide particles of varying sizes are mixed in the silicon-carbon anode material, the specific capacity of the entire anode material will be reduced; the interfacial impedance and ohmic internal resistance of the electrode will be increased, thereby reducing the rate performance and low-temperature performance of the material.

[0009] (3) Potential safety hazards: Zirconia is a ceramic material with extremely high hardness. Large zirconium fragments or particles generated during the grinding process, if not effectively removed, will remain in the final electrode. During battery charge and discharge cycles, as the silicon material repeatedly and violently expands and contracts, these hard, sharp-edged zirconium particles act like "daggers," posing a risk of piercing the battery separator. Once the separator is pierced, it will cause direct contact between the positive and negative electrodes inside the battery, triggering an internal short circuit, which may then lead to serious safety accidents such as thermal runaway, fire, or even explosion.

[0010] In summary, existing technologies lack effective means to control and remove zirconium impurities introduced during the grinding process, resulting in impaired electrochemical performance of the final product and significant safety hazards. This limits the further development of high-performance, high-safety nano-silicon-carbon anode materials. Summary of the Invention

[0011] The purpose of this invention is to provide a nano-silicon-carbon material preparation system that can reduce zirconium content, so as to solve the above-mentioned problems.

[0012] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a nano-silicon-carbon material preparation system with reduced zirconium content, comprising a slurry tank and a sand mill connected by pipes, wherein zirconium oxide beads are filled in the sand mill as grinding media balls, the outlet of the sand mill is connected to a buffer tank through a pipe, the outlet of the buffer tank is connected to a centrifuge through a pipe, the buffer tank is also connected to the slurry tank through a pipe, and the outlet of the centrifuge is connected in sequence to a drying device and a carbonization treatment device through pipes, with valves respectively installed on the pipes.

[0013] This invention innovatively introduces a "buffer-centrifuge" series processing unit based on the traditional wet sand milling process. That is, after the sand mill in the traditional nano-silicon carbon preparation system and before the material drying, a buffer tank and a high-speed centrifuge are set up. After homogenizing the ground material, based on the specific gravity difference between zirconium oxide and other materials, most of the zirconium impurities introduced by the wear of zirconium oxide due to the grinding media are separated and removed, thereby significantly reducing the content of impurity zirconium and thus significantly improving the performance of nano-silicon carbon anode materials.

[0014] Specifically, the separation principle is as follows: Zirconia (ZrO2) has a density of approximately 5.6-5.9 g / cm³, while silicon has a density of approximately 2.33 g / cm³, and carbon materials have a density of approximately 2.2 g / cm³. Under a strong centrifugal force field, the significantly denser zirconium oxide particles settle more quickly against the wall of the centrifuge drum, forming a "heavy phase" or "solid phase"; while the less dense target product—nano-silicon-carbon composite particles—mainly remains in the "light phase" or "liquid phase," thus achieving the separation of zirconium oxide.

[0015] As a preferred technical solution, a solenoid valve and a delivery pump are sequentially installed on the connecting pipe between the sand mill and the slurry tank. The delivery pump is further preferably a diaphragm pump with a delivery rate of 5-100 L / min, serving the purpose of slurry circulation.

[0016] As a preferred technical solution, a solenoid valve is installed on the connecting pipe between the buffer tank and the centrifuge.

[0017] As a preferred technical solution, a solenoid valve is installed on the connecting pipe between the buffer tank and the slurry tank.

[0018] As a preferred technical solution, the sand mill is a horizontal rod-pin sand mill or a turbine-type dual-power sand mill, and the diameter of the zirconia beads is 0.1-0.3mm. The working motor power of the sand mill is 20-45Hz.

[0019] As a preferred technical solution, the drying equipment is a spray dryer or a vacuum dryer.

[0020] As a preferred technical solution, the valve is a solenoid valve.

[0021] The buffer tank is connected in parallel to the sand mill. Its function is to receive the slurry from the sand mill, homogenize the material, and ensure a stable and uniform feed for the subsequent centrifuge, preventing fluctuations in the sand mill's outlet flow rate from impacting the centrifugal separation effect. The buffer tank has an outlet and an overflow port, which, by adjusting the valve opening on the corresponding pipeline, serve to divert the flow.

[0022] The centrifuge described is a high-speed centrifuge, which can be an existing tubular, horizontal, or disc centrifuge. Its core function is to achieve efficient separation based on the density differences of different substances under a strong centrifugal force field. The centrifuge operates at a speed of 7000-15000 RPM. If the speed is below 7000 RPM, the centrifugal force generated is insufficient to effectively separate micron- and submicron-sized zirconium impurity particles, resulting in poor impurity removal. If the speed is above 12000 RPM, although zirconium can be separated more thoroughly, energy consumption increases dramatically, and excessive centrifugal force may also cause some larger target products (silicon-carbon particles) to be separated along with them, reducing product yield and even potentially causing hard agglomeration of nanoparticles, which is detrimental to subsequent use.

[0023] Compared with the prior art, the advantages of this utility model are as follows: Based on the traditional wet sand milling process, this utility model innovatively introduces a "buffer-centrifugation" series processing unit, which solves the problem of decreased electrochemical performance and increased safety risks of anode materials caused by excessive and uncontrollable zirconium impurities, thereby producing nano-silicon-carbon anode materials with higher specific capacity, better cycle stability and higher safety. Attached Figure Description

[0024] Figure 1 This is a partial structural diagram of an embodiment of the present utility model;

[0025] Figure 2 This is an overall structural block diagram of an embodiment of the present utility model;

[0026] In the diagram: 1. Sand mill; 2. Centrifuge; 3. Slurry tank; 4. Buffer tank; 5. Solenoid valve; 6. Transfer pump; 7. Drying equipment; 8. Carbonization treatment equipment. Detailed Implementation

[0027] The present invention will be further described below with reference to the embodiments.

[0028] Example:

[0029] See Figure 1 and Figure 2 A nano-silicon-carbon material preparation system with reduced zirconium content includes a slurry tank 3 and a sand mill 1 connected by pipes. The slurry tank is equipped with a stirrer for stirring the material. The sand mill 1 is filled with zirconium oxide beads. The outlet of the sand mill 1 is connected to a buffer tank 4 through a pipe. The outlet of the buffer tank 4 is connected to a centrifuge 2 through a pipe. The buffer tank 4 is also connected to the slurry tank 3 through a pipe. The outlet of the centrifuge 2 is connected to a drying device 7 and a carbonization treatment device 8 in sequence through pipes. Valves are installed on the pipes.

[0030] In this embodiment, a solenoid valve 5 and a delivery pump 6 are sequentially installed on the connecting pipe between the sand mill 1 and the slurry tank 3. A solenoid valve 5 is also installed on the connecting pipe between the buffer tank 4 and the centrifuge 2, and a solenoid valve 5 is also installed on the connecting pipe between the buffer tank 4 and the slurry tank 3. The purpose of changing the slurry flow direction is achieved by switching the solenoid valves 5 on and off. The sand mill 1 is a horizontal sand mill. The drying equipment is a spray dryer or a vacuum dryer.

[0031] The slurry is prepared via a circulation path: slurry tank 3—transfer pump 6—sand mill 1—buffer tank 4—slurry tank 3. A three-way valve is located below buffer tank 3, with a solenoid valve 5 installed on each passage. When the slurry has not been ground to the target particle size, it circulates from buffer tank 4 into slurry tank 3. When the slurry has been ground to the target particle size, it enters centrifuge 2 from buffer tank 4, thus proceeding to the next process.

[0032] The method for preparing nano-silicon carbon materials using the above-mentioned preparation system includes the following steps:

[0033] (1) Slurry preparation and sand milling

[0034] Micron-sized silicon powder (D50 particle size 3-40μm, silicon content >99%), carbon source (such as artificial graphite, petroleum asphalt, etc.), dispersant (polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), and sodium dodecylbenzenesulfonate), and solvent (ethanol or isopropanol) are mixed in proportion in slurry tank 3 and an initial slurry is prepared by a high-speed mixer. Then, the slurry is pumped into a sand mill 1 and circulated for grinding using zirconia beads; the grinding time is 5-15 hours, and the spindle speed of the sand mill 1 is controlled at 20-45 Hz. The ground slurry contains the target product—nano-silicon-carbon composite particles—as well as zirconia impurity particles generated due to wear. The dispersant is added directly through the addition port during slurry preparation.

[0035] (2) Buffering and homogenization

[0036] The slurry that has been ground by sand milling is pumped from the outlet of sand mill 1 into buffer tank 4, and solenoid valve 5 adjusts the flow rate of each channel according to the processing capacity of centrifuge.

[0037] (3) High-speed centrifugal separation

[0038] The homogenized slurry in buffer tank 4 is stably delivered to the inlet of high-speed centrifuge 2 via a metering pump. The centrifuge operates at a speed of 7000-15000 RPM. Centrifuge 2 can achieve solid-liquid separation by adjusting its speed, but in this embodiment, the separation of high-density zirconium impurities from the slurry is achieved by controlling the centrifugation speed, and the separation of solids and liquids in the slurry is not realized.

[0039] (4) Follow-up processing

[0040] The low-zirconium content slurry obtained from the product outlet of the centrifuge is collected, and then the solvent is removed by spray drying, vacuum drying and other methods. Finally, it is subjected to high-temperature carbonization treatment (800-1100℃) in an inert atmosphere (such as argon or nitrogen) to obtain the final nano-silicon-carbon anode material powder.

[0041] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A system for preparing nano-silicon-carbon materials with reduced zirconium content, characterized in that, The equipment includes a slurry tank (3) and a sand mill (1) connected by a pipeline. The sand mill (1) is filled with zirconia beads as grinding media. The outlet of the sand mill (1) is connected to a buffer tank (4) through a pipeline. The outlet of the buffer tank (4) is connected to a centrifuge (2) through a pipeline. The buffer tank (4) is also connected to the slurry tank (3) through a pipeline. The outlet of the centrifuge (2) is connected to a drying device (7) and a carbonization treatment device (8) in sequence through a pipeline. Valves are installed on the pipeline.

2. The nano-silicon-carbon material preparation system with reduced zirconium content according to claim 1, characterized in that, A solenoid valve (5) and a delivery pump (6) are sequentially installed on the connecting pipe between the sand mill (1) and the slurry tank (3).

3. The nano-silicon-carbon material preparation system with reduced zirconium content according to claim 1, characterized in that, A solenoid valve (5) is installed on the connecting pipe between the buffer tank (4) and the centrifuge (2).

4. The nano-silicon-carbon material preparation system with reduced zirconium content according to claim 1, characterized in that, A solenoid valve (5) is installed on the connecting pipe between the buffer tank (4) and the slurry tank (3).

5. The nano-silicon-carbon material preparation system with reduced zirconium content according to claim 1, characterized in that, The sand mill (1) is a horizontal rod-pin sand mill or a turbine-type dual-power sand mill, and the diameter of the zirconia beads is 0.1-0.3mm.

6. The nano-silicon-carbon material preparation system with reduced zirconium content according to claim 1, characterized in that, The drying equipment is a spray dryer or a vacuum dryer.

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