Method for purifying silicon powder for electrode material

Abstract

The application discloses a kind of for electrode material's silicon powder purification method, comprising the following steps: silicon powder raw material is washed thoroughly in cleaning solution, and first semi-finished product is obtained after solid-liquid separation, wherein the cleaning solution is the mixed aqueous solution of alcohol and ketone;The first semi-finished product is washed thoroughly in mixed acid solution, and continue to wash to neutral with deionized water after solid-liquid separation, and second semi-finished product is obtained, wherein the mixed acid solution is the mixed acid solution of oxygen-free acid and oxygen-containing acid;The second semi-finished product is dried, and the required silicon powder for electrode material is obtained.The silicon powder for electrode material of the application is prepared by wet purification process to obtain high-purity silicon powder for electrode material, and the silicon powder for electrode material of the application is simple in process, high in purification efficiency and low in cost.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage, and in particular to a method for purifying silicon powder for use as an electrode material. Background Technology

[0002] With the continuous advancement of the new energy revolution, lithium-ion batteries are playing an increasingly indispensable role in portable electronic devices, new energy vehicles, and grid-scale energy storage systems. Based on the growing demand for new energy products from end-users, countries worldwide are gradually imposing stricter standards on the energy density, cycle life, and safety performance of lithium-ion batteries. Currently, graphite is the commonly used anode material for lithium-ion batteries, but its limited capacity (only 372 mAh g / g) restricts its performance. -1 Its low theoretical capacitance and low operating potential (~0.05V vs Li) + The continuous deposition of lithium ions under (Li / Li) conditions leads to the formation of lithium dendrites, which in turn poses safety hazards. Developing superior lithium-ion battery anode materials is crucial for the continued rapid development of the new energy sector. Silicon, as the most promising alternative to graphite anodes, possesses an extremely high theoretical capacity (~4200 mAh g / g). -1 ) and appropriate delithiation potential (~0.4V vs Li) + / Li).

[0003] However, the volume change of single-atom silicon in the fully lithiated state exceeds 300%, which will cause the solid electrolyte interface film to repeatedly break and accumulate, continuously consume electrolyte and cause the battery capacity to decrease rapidly.

[0004] Furthermore, considering that the side reactions caused by the dissolution of metal heteroatoms contained in elemental silicon in the electrolyte will reduce the battery's lifespan, and that metal foreign matter in the negative electrode will induce the formation of lithium dendrites to a certain extent, which can then puncture the separator and cause an internal short circuit, affecting the battery's safety performance, the People's Republic of China National Standard for Silicon-Carbon Materials (GB / T38823-2020) specifically emphasizes the range of metal content for iron (≤100ppm), aluminum (≤10ppm), cobalt, copper, nickel, chromium, and zinc (all ≤5ppm) in silicon-carbon negative electrode materials.

[0005] Existing silicon powder purification methods struggle to balance purity and purification efficiency. Therefore, developing a silicon powder purification method that combines high purity, high efficiency, and low cost for use as an electrode material is a crucial direction for the large-scale application of silicon-carbon anode materials in lithium-ion battery anodes. Summary of the Invention

[0006] Therefore, it is necessary to provide a purification method for silicon powder used in electrode materials that combines high purity, high efficiency, and low cost.

[0007] A method for purifying silicon powder for electrode materials includes the following steps:

[0008] The silicon powder raw material is thoroughly washed in a cleaning solution, and after solid-liquid separation, a first semi-finished product is obtained. The cleaning solution is a mixed aqueous solution of alcohol and ketone.

[0009] The first semi-finished product is thoroughly washed in a mixed acid solution, and after solid-liquid separation, it is further washed with deionized water until neutral to obtain the second semi-finished product. The mixed acid solution is a mixed acid solution of non-oxygen acid and oxygen acid.

[0010] The second semi-finished product is dried to obtain the silicon powder required for electrode materials.

[0011] In one embodiment, the volume concentration of the alcohol in the cleaning solution is 1% to 3%, and the volume concentration of the ketone is 3% to 7%.

[0012] In one embodiment, the alcohol is ethylene glycol or ethanol, and the ketone is acetone.

[0013] In one embodiment, the mass concentration of the non-oxygenated acid in the mixed acid solution is 2% to 10%, and the mass concentration of the aerobic acid is 1% to 5%.

[0014] In one embodiment, the non-oxygenated acid is hydrochloric acid, and the oxygenated acid is sulfuric acid, phosphoric acid, or nitric acid.

[0015] In one embodiment, the step of thoroughly cleaning the silicon powder raw material in the cleaning solution and obtaining the first semi-finished product after solid-liquid separation is as follows: the silicon powder raw material is subjected to rotary stirring and cleaning in the cleaning solution, and then spiral pressure filtration is performed to obtain the first semi-finished product.

[0016] The operation of thoroughly washing the first semi-finished product in a mixed acid solution, separating the solid and liquid, and then washing it with deionized water until neutral to obtain the second semi-finished product is as follows: the first semi-finished product is subjected to rotary stirring and washing in the mixed acid solution, and after screw filtration, it is washed with deionized water until neutral to obtain the second semi-finished product.

[0017] The operation of drying the second semi-finished product to obtain the required silicon powder for electrode materials is as follows: the second semi-finished product is dried by a rotary flash evaporation device to obtain the required silicon powder for electrode materials, wherein the inlet air temperature of the rotary flash evaporation device is 150℃~200℃, and the moisture content of the silicon powder for electrode materials is less than 0.3%.

[0018] In one embodiment, the resistivity of the deionized water is not less than 18.2 MΩ·cm.

[0019] In one embodiment, the particle size of the silicon powder raw material is 2μm to 30μm.

[0020] In one embodiment, the silicon powder raw material is prepared by the following operation: the silicon raw material is pulverized and the silicon powder raw material with a particle size of 2μm to 30μm is separated by electromagnetic vibration sieving.

[0021] In one embodiment, the silicon raw material is electronic silicon waste, photovoltaic silicon waste, or metallic silicon waste.

[0022] The present invention provides a method for purifying silicon powder for electrode materials using a wet purification process to prepare high-purity silicon powder for electrode materials. Furthermore, the method of purifying silicon powder for electrode materials of the present invention is simple, highly efficient, and low in cost.

[0023] Specifically, the purification method for silicon powder used in electrode materials of the present invention performs one-step purification processes for organic impurities and metallic impurities respectively. The mixed aqueous solution of alcohol and ketone as the cleaning solution can effectively remove organic impurities such as flocculants and antioxidants from the surface of the raw material. The mixed acid solution of non-oxygen acid and oxygen acid can selectively remove metallic impurities from the surface layer and pores of the raw material.

[0024] Based on the test examples, the purification method for silicon powder used as electrode materials prepared by the present invention produces silicon powder with a purity of not less than 4N. The production process is characterized by high efficiency and low energy consumption. Compared with the traditional silane method and electro-smelting method, the overall cost is reduced by more than 70%. It is a silicon purification method suitable for large-scale industrial use and plays a significant role in promoting the mass production of high-purity silicon powder for silicon-carbon anodes in lithium-ion batteries.

[0025] Preferably, the present invention uses a rotary flash evaporation device for drying, which not only significantly reduces production energy consumption but also significantly improves the drying rate.

[0026] Preferably, the silicon raw materials used can be electronic silicon waste, photovoltaic silicon waste, or metallic silicon waste, which are widely available and inexpensive, and also realize the recycling of waste, which is of environmental significance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] in:

[0029] Figure 1 This is a flowchart of a method for purifying silicon powder for electrode materials, according to one embodiment.

[0030] Figure 2 The image shows a scanning electron microscope (SEM) image of the silicon powder used as an electrode material prepared in Example 1.

[0031] Figure 3 The results are electrochemical test results for a coin cell containing silicon powder prepared in Example 1 as an electrode material. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention discloses a method for purifying silicon powder for electrode materials according to one embodiment, comprising the following steps:

[0034] S10. The silicon powder raw material is thoroughly cleaned in the cleaning solution, and the first semi-finished product is obtained after solid-liquid separation.

[0035] The cleaning solution is a mixed aqueous solution of alcohol and ketone.

[0036] A mixed aqueous solution of alcohol and ketone can effectively remove flocculants from the surface of silicon powder raw materials when used as a cleaning solution.

[0037] Preferably, in this embodiment, the volume concentration of alcohol in the cleaning solution is 1% to 3%, and the volume concentration of ketone is 3% to 7%.

[0038] Among them, alcohol solvents can easily remove polyethylene glycol impurities from silicon waste, while ketone solvents can easily remove ester impurities such as lubricants from silicon waste. Miscible alcohol-ketone solvents, which combine polar alcohol solvents and nonpolar ketone solvents, can remove organic impurities from silicon waste in a one-pot process, shortening the purification time and accelerating the purification efficiency.

[0039] Specifically, in this embodiment, the alcohol is ethylene glycol or ethanol, and the ketone is acetone.

[0040] Specifically, in this embodiment, the silicon powder raw material is thoroughly cleaned in the cleaning solution, and the first semi-finished product is obtained after solid-liquid separation: the silicon powder raw material is rotated and stirred in the cleaning solution, and then filtered by spiral pressure to obtain the first semi-finished product.

[0041] In S10, the rotation and stirring speed for cleaning can be 200 rpm to 400 rpm.

[0042] Preferably, in this embodiment, the particle size of the silicon powder raw material is 2μm to 30μm.

[0043] More preferably, in this embodiment, the particle size of the silicon powder raw material is 2μm to 8μm.

[0044] In this embodiment, the silicon powder raw material is prepared by the following operation: the silicon raw material is pulverized and the silicon powder raw material with a particle size of 2μm to 30μm is separated by electromagnetic vibration sieve.

[0045] Specifically, silicon raw materials include electronic silicon waste, photovoltaic silicon waste, or metallic silicon waste.

[0046] The silicon raw materials used are electronic silicon waste, photovoltaic silicon waste, or metallic silicon waste, which are widely available and inexpensive. They also enable the recycling of waste, which is of environmental significance.

[0047] S20. The first semi-finished product is thoroughly washed in a mixed acid solution. After solid-liquid separation, it is further washed with deionized water until neutral to obtain the second semi-finished product.

[0048] The mixed acid solution is a mixture of anaerobic and aerobic acids.

[0049] A mixed acid solution of non-oxygen acid and oxygen acid can selectively remove metallic impurities from the surface and pores of the raw material.

[0050] Preferably, in this embodiment, the mass concentration of the non-oxygen acid in the mixed acid solution is 2% to 10%, and the mass concentration of the aerobic acid is 1% to 5%.

[0051] Among them, non-oxygen acid is easy to remove metal impurities such as iron, aluminum, and zinc from silicon waste, while oxygen acid is easy to remove silicon suboxide impurities on the surface of silicon waste. The mixed acid solution of non-oxygen acid and oxygen acid can remove metals and surface silicon impurities in silicon waste in one pot, shortening the purification time and accelerating the purification efficiency.

[0052] Specifically, in this embodiment, the non-oxygen acid is hydrochloric acid, and the oxygen acid is sulfuric acid, phosphoric acid, or nitric acid.

[0053] Preferably, in this embodiment, the resistivity of deionized water is not less than 18.2 MΩ·cm.

[0054] Preferably, in this embodiment, the operation of thoroughly washing the first semi-finished product in a mixed acid solution, separating the solid and liquid, and then washing it with deionized water until neutral to obtain the second semi-finished product is as follows: the first semi-finished product is washed by rotating and stirring in a mixed acid solution, filtered by screw pressure, and then washed with deionized water until neutral to obtain the second semi-finished product.

[0055] In S20, the rotation and stirring speed for cleaning can be 200 rpm to 400 rpm.

[0056] S30. Dry the second semi-finished product to obtain the silicon powder required for electrode materials.

[0057] Preferably, in this embodiment, the operation of drying the second semi-finished product to obtain the required silicon powder for electrode materials is as follows: the second semi-finished product is dried by a rotary flash evaporation device to obtain the required silicon powder for electrode materials.

[0058] The inlet air temperature of the rotary flash evaporator is 150℃~200℃, and the moisture content of the silicon powder used for electrode materials is less than 0.3%.

[0059] The present invention uses a rotary flash evaporation device for drying, which not only significantly reduces production energy consumption but also significantly improves the drying rate.

[0060] The present invention provides a method for purifying silicon powder for electrode materials using a wet purification process to prepare high-purity silicon powder for electrode materials. Furthermore, the method of purifying silicon powder for electrode materials of the present invention is simple, highly efficient, and low in cost.

[0061] Specifically, the purification method for silicon powder used in electrode materials of the present invention performs one-step purification processes for organic impurities and metallic impurities respectively. The mixed aqueous solution of alcohol and ketone can effectively remove organic impurities such as flocculants and antioxidants from the surface of the raw material as a cleaning solution. The mixed acid solution of non-oxygen acid and oxygen acid can selectively remove metallic impurities from the surface layer and pores of the raw material.

[0062] Based on the test examples, the purification method for silicon powder used as electrode materials prepared by the present invention produces silicon powder with a purity of not less than 4N. The production process is characterized by high efficiency and low energy consumption. Compared with the traditional silane method and electro-smelting method, the overall cost is reduced by more than 70%. It is a silicon purification method suitable for large-scale industrial use and plays a significant role in promoting the mass production of high-purity silicon powder for silicon-carbon anodes in lithium-ion batteries.

[0063] The following are specific examples.

[0064] In this embodiment, the silicon raw material is metallic silicon waste from Hebei Ruihuang Materials Company.

[0065] Example 1

[0066] After crushing the silicon raw material using a ball mill, the silicon powder raw material with a particle size of 2μm to 8μm is separated by a vibrating screen.

[0067] A 10% (v / v) alcohol / ketone aqueous solution (3% acetone, 7% ethylene glycol) was mixed with silicon powder raw material at a mass ratio of 3:1 in a rotary stirred tank at a speed of 250 rpm for 5 hours. Solid-liquid separation was then completed using a spiral filter press to obtain the first semi-finished product.

[0068] A 15% mixed acid washing solution (10% hydrochloric acid, 5% phosphoric acid) was mixed with the first semi-finished product at a mass ratio of 2:1 in a rotary stirred tank at a speed of 250 rpm for 6 hours. After solid-liquid separation, the mixture was washed with deionized water (resistivity not less than 18.2 MΩ·cm) until neutral to obtain the second semi-finished product.

[0069] The second semi-finished product is dried using a rotary flash evaporator to obtain the silicon powder required for electrode materials. The inlet air temperature is 200℃, and the moisture content of the dried silicon powder is 0.2%.

[0070] Example 2

[0071] After crushing the silicon raw material using a ball mill, the silicon powder raw material with a particle size of 2μm to 8μm is separated by a vibrating screen.

[0072] A 10% (v / v) alcohol / ketone aqueous solution (3% acetone, 7% ethylene glycol) was mixed with silicon powder raw material at a mass ratio of 3:1 in a rotary stirred tank at a speed of 250 rpm for 5 hours. Solid-liquid separation was then completed using a spiral filter press to obtain the first semi-finished product.

[0073] A 15% mixed acid washing solution (10% hydrochloric acid, 5% nitric acid) was mixed with the first semi-finished product at a mass ratio of 2:1 in a rotary stirred tank at a speed of 250 rpm for 6 hours. After solid-liquid separation, the mixture was washed with deionized water (resistivity not less than 18.2 MΩ·cm) until neutral to obtain the second semi-finished product.

[0074] The second semi-finished product is dried using a rotary flash evaporator to obtain the silicon powder required for electrode materials. The inlet air temperature is 200℃, and the moisture content of the dried silicon powder is 0.2%.

[0075] Example 3

[0076] After crushing the silicon raw material using a ball mill, the silicon powder raw material with a particle size of 2μm to 8μm is separated by a vibrating screen.

[0077] A 10% (v / v) alcohol / ketone aqueous solution (3% acetone, 7% ethylene glycol) was mixed with silicon powder raw material at a mass ratio of 3:1 in a rotary stirred tank at a speed of 250 rpm for 5 hours. Solid-liquid separation was then completed using a spiral filter press to obtain the first semi-finished product.

[0078] A 15% mixed acid washing solution (10% hydrochloric acid, 5% sulfuric acid) was mixed with the first semi-finished product at a mass ratio of 2:1 in a rotary stirred tank at a speed of 250 rpm for 6 hours. After solid-liquid separation, the mixture was washed with deionized water (resistivity not less than 18.2 MΩ·cm) until neutral to obtain the second semi-finished product.

[0079] The second semi-finished product is dried using a rotary flash evaporator to obtain the silicon powder required for electrode materials. The inlet air temperature is 200℃, and the moisture content of the dried silicon powder is 0.2%.

[0080] Comparative Example 1

[0081] After crushing the silicon raw material using a ball mill, the silicon powder raw material with a particle size of 2μm to 8μm is separated by a vibrating screen.

[0082] A 10% (v / v) alcohol / ketone aqueous solution (3% acetone, 7% ethanol) was mixed with silica powder raw material at a mass ratio of 3:1 in a rotary stirred tank at a speed of 250 rpm for 5 hours. Solid-liquid separation was then completed using a spiral filter press to obtain the first semi-finished product.

[0083] A 15% mixed acid washing solution (10% hydrochloric acid, 5% phosphoric acid) was mixed with the first semi-finished product at a mass ratio of 2:1 in a rotary stirred tank at a speed of 250 rpm for 6 hours. After solid-liquid separation, the mixture was washed with deionized water (resistivity not less than 18.2 MΩ·cm) until neutral to obtain the second semi-finished product.

[0084] The second semi-finished product is dried using a rotary flash evaporator to obtain the silicon powder required for electrode materials. The inlet air temperature is 200℃, and the moisture content of the dried silicon powder is 0.2%.

[0085] Comparative Example 2

[0086] After crushing the silicon raw material using a ball mill, the silicon powder raw material with a particle size of 2μm to 8μm is separated by a vibrating screen.

[0087] A 10% (v / v) alcohol / ketone aqueous solution (3% acetone, 7% ethylene glycol) was mixed with silicon powder raw material at a mass ratio of 3:1 in a rotary stirred tank at a speed of 250 rpm for 3 hours. Solid-liquid separation was then completed using a spiral filter press to obtain the first semi-finished product.

[0088] A 15% mixed acid washing solution (10% hydrochloric acid, 5% phosphoric acid) was mixed with the first semi-finished product at a mass ratio of 2:1 in a rotary stirred tank at a speed of 250 rpm for 4 hours. After solid-liquid separation, the mixture was washed with deionized water (resistivity not less than 18.2 MΩ·cm) until neutral to obtain the second semi-finished product.

[0089] The second semi-finished product is dried using a rotary flash evaporator to obtain the silicon powder required for electrode materials. The inlet air temperature is 200℃, and the moisture content of the dried silicon powder is 0.2%.

[0090] Comparative Example 3

[0091] After crushing the silicon raw material using a ball mill, the silicon powder raw material with a particle size of 2μm to 8μm is separated by a vibrating screen.

[0092] A 10% (v / v) alcohol / ketone aqueous solution (3% acetone, 7% ethylene glycol) was mixed with silicon powder raw material at a mass ratio of 3:1 in a rotary stirred tank at a speed of 250 rpm for 1 hour. Solid-liquid separation was then completed using a spiral filter press to obtain the first semi-finished product.

[0093] A 15% mixed acid washing solution (10% hydrochloric acid, 5% phosphoric acid) and the first semi-finished product were treated in a rotary stirred tank at a mass ratio of 2:1 at 250 rpm for 2 hours. After solid-liquid separation, the mixture was washed with deionized water (resistivity not less than 18.2 MΩ·cm) until neutral to obtain the second semi-finished product.

[0094] Comparative Example 4

[0095] After crushing the silicon raw material using a ball mill, the silicon powder raw material with a particle size of 2μm to 8μm is separated by a vibrating screen.

[0096] An 8% (v / v) alcohol / ketone aqueous solution (2% acetone, 6% ethylene glycol) was mixed with silicon powder raw material at a mass ratio of 3:1 in a rotary stirred tank at a speed of 250 rpm for 3 hours. Solid-liquid separation was then completed using a spiral filter press to obtain the first semi-finished product.

[0097] A 12% mixed acid washing solution (8% hydrochloric acid, 4% phosphoric acid) was mixed with the first semi-finished product at a mass ratio of 2:1 in a rotary stirred tank at a speed of 250 rpm for 4 hours. After solid-liquid separation, the mixture was washed with deionized water (resistivity not less than 18.2 MΩ·cm) until neutral to obtain the second semi-finished product.

[0098] The second semi-finished product is dried using a rotary flash evaporator to obtain the silicon powder required for electrode materials. The inlet air temperature is 180℃, and the moisture content of the dried silicon powder is 0.2%.

[0099] Comparative Example 5

[0100] After crushing the silicon raw material using a ball mill, the silicon powder raw material with a particle size of 2μm to 8μm is separated by a vibrating screen.

[0101] A 6% (v / v) alcohol / ketone aqueous solution (2% acetone, 4% ethylene glycol) was mixed with silicon powder raw material at a mass ratio of 3:1 in a rotary stirred tank at a speed of 250 rpm for 3 hours. Solid-liquid separation was then completed using a spiral filter press to obtain the first semi-finished product.

[0102] A 9% (by mass) mixed acid washing solution (6% hydrochloric acid, 3% phosphoric acid) was mixed with the first semi-finished product at a mass ratio of 2:1 in a rotary stirred tank at a speed of 250 rpm for 4 hours. After solid-liquid separation, the mixture was washed with deionized water (resistivity not less than 18.2 MΩ·cm) until neutral to obtain the second semi-finished product.

[0103] The second semi-finished product is dried using a rotary flash evaporator to obtain the silicon powder required for electrode materials. The inlet air temperature is 160℃, and the moisture content of the dried silicon powder is 0.2%.

[0104] Comparative Example 6

[0105] After crushing the silicon raw material using a ball mill, the silicon powder raw material with a particle size of 2μm to 8μm is separated by a vibrating screen.

[0106] A 4% (v / v) alcohol / ketone aqueous solution (1% acetone, 3% ethylene glycol) was mixed with silicon powder raw material at a mass ratio of 3:1 in a rotary stirred tank at a speed of 250 rpm for 3 hours. Solid-liquid separation was then completed using a spiral filter press to obtain the first semi-finished product.

[0107] A 6% (4% hydrochloric acid, 2% phosphoric acid) mixed acid washing solution and the first semi-finished product were treated in a rotary stirred tank at a mass ratio of 2:1 at 250 rpm for 6 hours. After solid-liquid separation, the mixture was washed with deionized water (resistivity not less than 18.2 MΩ·cm) until neutral to obtain the second semi-finished product.

[0108] The second semi-finished product is dried using a rotary flash evaporator to obtain the silicon powder required for electrode materials. The inlet air temperature is 150℃, and the moisture content of the dried silicon powder is 0.2%.

[0109] Comparative Example 7

[0110] After crushing the silicon raw material using a ball mill, the silicon powder raw material with a particle size of 2μm to 8μm is separated by a vibrating screen.

[0111] A 4% (v / v) alcohol / ketone aqueous solution (1% acetone, 3% ethylene glycol) was mixed with silicon powder raw material at a mass ratio of 1.5:1 in a rotary stirred tank at a speed of 250 rpm for 5 hours. Solid-liquid separation was then completed using a spiral filter press to obtain the first semi-finished product.

[0112] A 6% (4% hydrochloric acid, 2% phosphoric acid) mixed acid washing solution and the first semi-finished product were treated in a rotary stirred tank at a mass ratio of 1:1 at 250 rpm for 6 hours. After solid-liquid separation, the mixture was washed with deionized water (resistivity not less than 18.2 MΩ·cm) until neutral to obtain the second semi-finished product.

[0113] The second semi-finished product is dried using a rotary flash evaporator to obtain the silicon powder required for electrode materials. The inlet air temperature is 250℃, and the moisture content of the dried silicon powder is 0.2%.

[0114] Test Example 1

[0115] The silicon powder prepared in Example 1 for use as an electrode material was observed by scanning electron microscopy, and the results were obtained. Figure 2 .

[0116] Combination Figure 2 As can be seen, the silicon powder has a three-dimensional blocky morphology with relatively uniform dimensions in both the horizontal and vertical directions.

[0117] The metal contents of iron, cobalt, copper, nickel, aluminum, chromium, and zinc in the silicon powder raw material of Example 1, and the silicon powders prepared for electrode materials in Examples 1-3 and Comparative Examples 1-7 were measured respectively. The measurement results are shown in Table 1 below.

[0118] The test method is as follows: First, add 2g of sample to 24mL of aqua regia solution and shake well. Use a microwave digestion instrument to digest the powder at 180℃ for 20min. After cooling to 25℃, filter and dilute to 200ml. Then, determine the metal content in the silicon powder using an inductively coupled plasma atomic emission spectrometer.

[0119] Table 1

[0120]

[0121] As can be seen from Table 1, the metal contents of iron, cobalt, copper, nickel, aluminum, chromium, and zinc in the silicon powder used as electrode materials prepared in Examples 1 to 3 all comply with the requirements of the national standard GB / T 38823-2020. In addition, the low content of metal impurities in the silicon powder used as electrode materials prepared by the method in Examples 1 to 3 of this invention can effectively reduce the risk of internal short circuit in the battery caused by Joule heat concentration in the electrode sheet, and help improve the battery safety performance.

[0122] Coin cells were prepared using silicon powder prepared in Examples 1-3 and Comparative Examples 1-7 as electrode materials as negative electrode materials.

[0123] The preparation method of the button cell is as follows: Silicon powder and conductive carbon black are dried in an oven at 110℃ for 3 hours. Then, 4.1g of high-purity silicon powder, 0.5g of conductive carbon black, and 0.4g of polyacrylic acid binder are weighed and dispersed in 18ml of deionized water and stirred for 60 minutes at a stirring speed of 1000r / min. After stirring, the slurry is coated onto copper foil using a 100-micron coater, dried in a forced-air drying oven at 100℃ for 60 minutes, and then transferred to a vacuum drying oven at 120℃ for 6 hours. The dried electrode is then rolled, cut, and prepared into round discs with a diameter of 14mm and a surface active material coating of 1.5mg / cm². 2 The prepared silicon-based electrode, along with a lithium metal counter electrode and a 1 mol / L ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (volume ratio 1:1:1) electrolyte, were assembled into a sealed 2430 coin cell in a glove box with an oxygen content of less than 0.1 ppm.

[0124] The specific capacity and first-cycle efficiency of the prepared coin cells were tested, and the results are shown in Table 2.

[0125] Table 2

[0126]

[0127] As can be seen from Table 2, the silicon powder prepared in Example 1 for electrode materials has higher discharge specific capacity and coulombic efficiency compared with the silicon powder prepared in other examples and comparative examples, indicating that the electrochemical utilization rate of the active silicon material is higher.

[0128] Electrochemical tests were performed on the coin cell using silicon powder prepared in Example 1 as the negative electrode material. The testing equipment was the Wuhan Landian Battery Testing System. The testing conditions were 25°C, discharge rate of 0.1C-0.05mA-0.01mA, charge rate of 0.1C, and test voltage range of 0.005V to 2V. Figure 3 .

[0129] Combination Figure 3 As can be seen, the silicon powder prepared in Example 1 for use as an electrode material exhibits a typical silicon-based negative electrode charge-discharge curve, and has an obvious charge-discharge plateau and a high charge-discharge specific capacity.

[0130] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for purifying silicon powder for electrode materials, characterized in that, Includes the following steps: The silicon powder raw material is subjected to rotary stirring and washing in a cleaning solution, followed by screw filtration to obtain the first semi-finished product. The cleaning solution is a mixed aqueous solution of alcohol and ketone; the volume concentration of the alcohol is 1%–3%, and the volume concentration of the ketone is 3%–7%. The first semi-finished product is subjected to rotary stirring and washing in the mixed acid solution, followed by spiral filtration and further washing with deionized water until neutral to obtain the second semi-finished product. The mixed acid solution is a mixture of non-oxygenated and aerobic acids; the mass concentration of the non-oxygenated acid is 2%–10%, and the mass concentration of the aerobic acid is 1%–5%. The second semi-finished product is dried using a rotary flash evaporation device to obtain the silicon powder required for electrode materials. The inlet air temperature of the rotary flash evaporation device is 150℃~200℃, and the moisture content of the silicon powder for electrode materials is less than 0.3%.

2. The method for purifying silicon powder for electrode materials according to claim 1, characterized in that, The alcohol is ethylene glycol or ethanol, and the ketone is acetone.

3. The method for purifying silicon powder for electrode materials according to claim 1, characterized in that, The non-oxygenated acid is hydrochloric acid, and the oxygenated acid is sulfuric acid, phosphoric acid, or nitric acid.

4. The method for purifying silicon powder for electrode materials according to claim 1, characterized in that, The resistivity of the deionized water is not less than 18.2 MΩ·cm.

5. The method for purifying silicon powder for electrode materials according to any one of claims 1 to 4, characterized in that, The particle size of the silicon powder raw material is 2μm~30μm.

6. The method for purifying silicon powder for electrode materials according to claim 5, characterized in that, The silicon powder raw material is prepared by the following operation: the silicon raw material is crushed and the silicon powder raw material with a particle size of 2μm~30μm is separated by electromagnetic vibration sieve.

7. The method for purifying silicon powder for electrode materials according to claim 6, characterized in that, The silicon raw material is electronic silicon waste, photovoltaic silicon waste, or metallic silicon waste.

Images