Method for preparing silicon monoxide material by regenerating photovoltaic silicon waste and application of silicon monoxide material

Abstract

The invention discloses a method for preparing a silicon monoxide material through photovoltaic silicon waste regeneration and application, and belongs to the field of secondary resource recycling. According to the method, photovoltaic cutting waste silicon sludge and silicon dioxide are taken as raw materials, silicon monoxide (SiO) gas is generated through vacuum disproportionation reaction, and a uniform high-purity SiO material is formed by controlling the temperature of a condensation thermal field. According to the preparation method, by utilizing the characteristics of fine granularity, high purity and high activity of the cut waste silicon sludge, the conversion efficiency and uniformity of the SiO product can be remarkably improved, and the SiO product obtained by the preparation method has the characteristics of high purity, good uniformity and the like, and has excellent long-cycle stability when being used as the anode of the lithium ion battery. According to the preparation method, the waste silicon powder is directly regenerated to prepare the SiO product, so that the production cost of SiO can be reduced, value-added cyclic utilization of the waste silicon powder can be realized, the raw material cost is low, the process operation is simple, the practicability is high, and meanwhile, the preparation method also has huge economic benefits and wide application prospects.

Description

Technical Field

[0001] The invention relates to a method for preparing silicon dioxide material by regenerating photovoltaic silicon waste and its application, belonging to the technical field of secondary resource recycling. Background Art

[0002] At present, the preparation of SiO mainly uses the redox method, which mainly includes:

[0003] ① Using carbon and silicon dioxide to prepare SiO2 by high-temperature solid-phase reaction method. Since carbon is used as a reducing agent, it is generally added in excess, resulting in the presence of silicon carbide impurities in the product, affecting the purity of silicon monoxide, and also generating gases such as carbon monoxide and carbon dioxide, which is not conducive to the realization of environmental protection goals.

[0004] ② Using hydrogen and silicon dioxide to prepare SiO by redox reaction. The SiO preparation reaction is affected by hydrogen, resulting in an increase in the formation rate of SiO. However, this method involves hydrogen and is dangerous to synthesize under high temperature conditions, which is not suitable for large-scale production in industry.

[0005] ③ Using industrial silicon and silicon dioxide powder as raw materials, SiO2 is prepared by high-temperature solid-phase reaction. This method has been widely used in the industrial production of SiO2 materials. However, the industrial silicon used in this method needs to undergo long-term mechanical grinding to reduce the particle size. In order to control production costs, the particle size of industrial silicon is usually larger than 10 microns, resulting in a slow reaction rate and low conversion rate in the silicon oxide synthesis process. The size of the silicon grains in the silicon oxide product prepared by condensation is also large, which affects the performance of the silicon oxide negative electrode material.

[0006] Therefore, the present invention proposes to use the crystalline silicon cutting waste generated by the photovoltaic industry as a silicon source to synthesize silicon oxide, and to use the advantages of the fine particle size (D50 less than 1 micron) and high purity of the crystalline silicon cutting waste to increase the solid-solid reaction rate of the silicon oxide synthesis process and improve the conversion rate of the raw materials. However, it was found in the study that the use of crystalline silicon cutting waste generated by the photovoltaic industry to prepare silicon oxide needs to overcome the problem of low porosity of the molded block caused by the ultra-fine particle size of the silicon raw material, which makes it difficult for the silicon oxide vapor generated by the reaction to escape. Summary of the invention

[0007] In order to solve the problems existing in preparing silicon oxide materials by regenerating photovoltaic silicon waste, the present invention provides a method for preparing silicon oxide materials by regenerating photovoltaic silicon waste, and the specific steps are as follows:

[0008] (1) Photovoltaic silicon waste is prepared into raw material I by vacuum drying.

[0009] (2) The raw material I described in step (1) is acid-washed to obtain raw material II.

[0010] (3) The raw material II described in step (2) and silicon dioxide are mixed uniformly to obtain a mixture III.

[0011] (4) Add a binder and water to the mixture III obtained in step (3), obtain a molded sample IV by controlling the molding pressure, and calcine and dry the molded sample IV to obtain a sample IV.

[0012] (5) placing the sample IV described in step (4) in a vacuum reactor to heat the sample to prepare silicon oxide vapor, cooling and condensing the silicon oxide vapor to prepare silicon oxide material.

[0013] Preferably, the photovoltaic silicon waste in step (1) is waste silicon mud generated by the crystalline silicon cutting process of the photovoltaic industry, and the particle size D50 of the waste silicon mud is 0.2 to 10 μm.

[0014] Preferably, in step (1), the drying temperature is 30 to 100° C. and the drying time is 5 to 24 hours.

[0015] Preferably, the oxygen content of raw material II in step (2) is less than 5%.

[0016] Preferably, in step (2), the pickling is performed using any one of hydrochloric acid, nitric acid, oxalic acid, citric acid, and sulfuric acid, or two or more of them mixed with hydrofluoric acid in any proportion; the pickling temperature is 20 to 100° C., and the pickling time is 0.1 to 2 h.

[0017] Preferably, in step (3), the mass ratio of raw material II to silicon dioxide is 1:2 to 1.3:2, and the particle size of the silicon dioxide is 0.1 to 1000 μm.

[0018] Preferably, in step (4), the weight percentage of the binder added is 0.1% to 5% of the mixture III, the weight percentage of water added is 0.1% to 5% of the mixture III, and the molding pressure is 5 MPa to 50 MPa; the binder is one or two of PVP (polyvinyl pyrrolidone), PVDF (polyvinylidene fluoride), CMC (carboxymethyl cellulose), PAA (high performance polymer), polyvinyl alcohol, ethylene glycol, and phenolic resin mixed in any proportion.

[0019] Preferably, in step (4), the calcination and drying temperature is 100-500° C., the calcination time is 0.5-3 h, and the porosity of sample IV is 5%-40%.

[0020] Preferably, the reaction conditions in step (5) are: heating rate of 1-20°C / min, reaction temperature of 1000°C-1500°C, reaction time of 0.2-5h, vacuum degree of 50Pa-500Pa; cooling rate of 1-20°C / min; condensation temperature of 500°C-900°C, and condensation time of 0.2-3h.

[0021] Another object of the present invention is to provide an application of the prepared silicon dioxide in preparing negative electrode materials for lithium-ion batteries.

[0022] Beneficial effects of the present invention

[0023] (1) The waste silicon mud from photovoltaic cutting has ultra-fine particles (less than 1 μm) and high reaction activity. It can replace the industrial silicon raw materials used in the traditional SiO preparation process without grinding and can be directly used as raw materials for synthesizing silicon oxide, strengthening the solid-solid reaction to generate silicon oxide vapor, increasing its reaction rate and raw material conversion rate, and reducing costs.

[0024] (2) Using waste silicon mud as a silicon source to synthesize silicon oxide, the rapid generation of steam helps to form a uniform silicon oxide material with a smaller grain size, which can be used in the negative electrode of lithium-ion batteries to help improve the cycle stability of the battery.

[0025] (3) Using the secondary silicon resources generated by the photovoltaic industry as raw materials to synthesize silicon oxide can not only achieve high-value utilization of secondary resources, but also reduce the production cost of silicon oxide negative electrode materials, and promote the green and sustainable development of the photovoltaic and lithium battery industries.

[0026] (4) Due to the fine particle size of waste silicon mud, the porosity between silicon and silicon dioxide after mixed molding is low. During the vacuum reaction process of synthesizing SiO, SiO vapor is difficult to escape, resulting in a decrease in the synthesis rate. On the other hand, during the solid-solid molding process, the strength of the molded product determines the conversion rate of the SiO product. Therefore, during the molding process, the porosity and strength of the molded sample IV are regulated by controlling the content of the binder and water, and the temperature and time of the calcination process, so that the SiO product is synthesized efficiently, uniformly and stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the TEM morphology of the silicon dioxide material prepared in specific embodiment 1 of the present invention.

[0028] Figure 2 This is the XRD diffraction pattern of the silicon dioxide material prepared in specific embodiment 1 of the present invention.

[0029] Figure 3 This is the XPS diffraction pattern of the silicon dioxide material prepared in specific embodiment 1 of the present invention.

[0030] Figure 4 This is a charge and discharge cycle performance diagram of the silicon dioxide material prepared in specific embodiment 1 of the present invention. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0032] Example 1

[0033] A method for preparing silicon dioxide material by regenerating photovoltaic silicon waste, the specific steps are as follows:

[0034] (1) The waste silicon mud with a particle size of 1 μm produced in the process of cutting crystalline silicon in the photovoltaic industry was dried at 70°C for 12 hours to obtain raw material I.

[0035] (2) Raw material I was then acid washed with hydrochloric acid and hydrofluoric acid at 25°C for 1 h to obtain raw material II.

[0036] (3) Raw material II and silicon dioxide with a particle size of 50 μm were uniformly mixed in a mass ratio of 1:2 to prepare a mixture III.

[0037] (4) Add phenolic resin and water to the mixture III obtained in step (3), wherein the weight percentage of the phenolic resin added is 2% of the mixture III, and the weight percentage of the water added is 1% of the mixture III. The molding pressure is controlled to be 30 MPa to obtain a molded sample IV, and the molded sample IV is dried at 400° C. for 1 h to obtain a sample IV.

[0038] (5) Sample IV described in step (4) is subjected to a disproportionation reaction under a vacuum degree of 270 Pa with a heating rate of 10°C / min, a reaction temperature of 1400°C, a high-temperature reaction time of 1 h, a cooling rate of 10°C / min, a condensation temperature of 900°C, a condensation reaction time of 0.5 h, and high-purity silicon dioxide material is obtained by condensation.

[0039] The TEM morphology of silicon dioxide in this example shows that ( Figure 1 ), the particle size of silicon oxide is concentrated in the range of 5 to 40 microns, and its morphology is irregular.

[0040] The XRD diffraction pattern of silicon dioxide in this embodiment shows that ( Figure 2 ), the powder XRD pattern of SiO nanoparticles showed the characteristics of amorphous materials.

[0041] The XPS diffraction pattern of silicon dioxide in this example shows that ( Figure 3 ), the Si2p peak appears at 103.2eV, and the Si2p peak of SiO recorded in the literature appears at 103.6eV, so silicon dioxide was prepared in this embodiment.

[0042] The electrochemical performance test of silicon dioxide in this implementation shows that ( Figure 4), when used as negative electrode material, its first discharge capacity can reach 2194.1 mAh / g.

[0043] Example 2

[0044] A method for preparing silicon dioxide material by regenerating photovoltaic silicon waste, the specific steps are as follows:

[0045] (1) The waste silicon mud with a particle size of 0.2 μm produced in the process of cutting crystalline silicon in the photovoltaic industry was dried at 100°C for 5 h to obtain raw material I.

[0046] (2) Raw material I is then pickled with citric acid and hydrofluoric acid at 100°C for 0.1 h to obtain raw material II.

[0047] (3) Raw material II and silicon dioxide with a particle size of 1000 μm were uniformly mixed in a mass ratio of 1.3:2 to obtain a mixture III.

[0048] (4) PVP (polyvinyl pyrrolidone) and water are added to the mixture III obtained in step (3), wherein the weight percentage of PVP added is 5% of the mixture III, and the weight percentage of water added is 5% of the mixture III. The molding pressure is controlled to be 50 MPa to obtain a molded sample IV, and the molded sample IV is dried at 500°C for 0.5 h.

[0049] (5) subjecting the sample IV described in step (4) to a disproportionation reaction under a vacuum degree of 50 Pa with a heating rate of 20°C / min, a reaction temperature of 1500°C, a high temperature reaction time of 5h, a cooling rate of 20°C / min, a condensation temperature of 900°C, a condensation reaction time of 0.2h, and condensing to obtain a high-purity silicon dioxide material;

[0050] Example 3

[0051] A method for preparing silicon dioxide material by regenerating photovoltaic silicon waste, the specific steps are as follows:

[0052] (1) The waste silicon mud with a particle size of 10 μm produced in the process of cutting crystalline silicon in the photovoltaic industry was dried at 30°C for 24 hours to obtain raw material I.

[0053] (2) Raw material I was pickled in a pickling solution consisting of nitric acid, oxalic acid and hydrofluoric acid at 20°C for 2 h to obtain raw material II.

[0054] (3) Raw material II and silicon dioxide with a particle size of 0.1 μm were uniformly mixed in a mass ratio of 1.1:2 to obtain a mixture III.

[0055] (4) Add ethylene glycol and water to the mixture III obtained in step (3), wherein the weight percentage of ethylene glycol added is 0.1% of the mixture III, and the weight percentage of water added is 0.1% of the mixture III. The molding pressure is controlled to be 5 MPa to obtain a molded sample IV. The molded sample IV is dried at 100°C for 3 h to obtain a sample IV.

[0056] (5) Sample IV described in step (4) is subjected to a disproportionation reaction under a vacuum degree of 500 Pa with a heating rate of 1°C / min, a reaction temperature of 1000°C, a high-temperature reaction time of 0.2h, a cooling rate of 1°C / min, a condensation temperature of 500°C, a condensation reaction time of 3h, and condensation to obtain a high-purity silicon dioxide material.

[0057] Comparative Example 1

[0058] A method for preparing silicon dioxide material by regenerating industrial silicon raw materials, the specific steps are as follows:

[0059] (1) Industrial silicon raw material was ground and crushed, and dried at 70° C. for 12 h to obtain raw material A with a particle size of about 10 μm.

[0060] (2) Raw material A is then pickled with hydrochloric acid and hydrofluoric acid at 25°C for 1 hour to obtain raw material B.

[0061] (3) Raw material B and silicon dioxide with a particle size of 20 μm were uniformly mixed in a mass ratio of 1:2 to prepare a mixture C.

[0062] (4) Add phenolic resin and water to the mixture C obtained in step (3), wherein the weight percentage of the phenolic resin added is 2% of the mixture C, and the weight percentage of the water added is 1% of the mixture C. The molding pressure is controlled to be 30 MPa to obtain a molded sample D, and the molded sample D is dried at 400° C. for 1 h to obtain a sample D.

[0063] (5) Sample D described in step (4) is subjected to a disproportionation reaction under vacuum at a heating rate of 10°C / min, a reaction temperature of 1400°C, a high-temperature reaction time of 1 h, a cooling rate of 10°C / min, a condensation temperature of 900°C, a condensation reaction time of 0.5 h, and high-purity silicon dioxide material is obtained by condensation.

[0064] The product conversion rate, generation rate and uniformity of Comparative Example 1 are not as good as those of Example 1. The reason is that the particle size of industrial silicon is still large and the reaction activity is low after grinding, which leads to a slow reaction rate and low conversion rate in the process of synthesizing silicon oxide products. The uniformity of the prepared silicon oxide products is poor, and the size of the silicon grains in the silicon oxide products is relatively large, resulting in poor electrochemical performance during the charge and discharge process.

[0065] Comparative Example 2

[0066] A method for preparing silicon dioxide material by regenerating photovoltaic silicon waste, the specific steps are as follows:

[0067] (1) The waste silicon mud with a particle size of 1 μm produced in the crystalline silicon cutting process of the photovoltaic industry was crushed by a crusher and dried at 70° C. for 12 h to obtain raw material A.

[0068] (2) Raw material A is then pickled with hydrochloric acid and hydrofluoric acid at 25°C for 1 hour to obtain raw material B.

[0069] (3) Raw material B and silicon dioxide with a particle size of 20 μm were uniformly mixed in a mass ratio of 1:2 to prepare a mixture C.

[0070] (4) The mixture C obtained in step (3) is directly pressed into blocks to form sample D without adding a binder and water.

[0071] (5) Sample D described in step (4) is subjected to a disproportionation reaction under a vacuum degree of 270 Pa with a heating rate of 10°C / min, a reaction temperature of 1400°C, a high-temperature reaction time of 1 h, a cooling rate of 10°C / min, a condensation temperature of 900°C, a condensation reaction time of 0.5 h, and a high-purity silicon dioxide material is obtained by condensation.

[0072] The reaction rate, product conversion rate and cycle performance of Comparative Example 2 are not as good as those of Example 1. The reason is that the raw material B and silicon dioxide are directly mixed and formed, the silicon powder in the prepared sample D is easy to agglomerate, the distribution of each component is uneven, and the strength of sample D is low. In the process of synthesizing SiO, some raw materials cannot participate in the reaction, which reduces the reaction rate and product conversion rate. The silicon grain size in the synthesized silicon dioxide product is large, which makes the electrochemical performance of the charge and discharge process poor.

[0073] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for preparing silicon dioxide material by regenerating photovoltaic silicon waste, characterized in that: The specific steps are as follows: (1) preparing photovoltaic silicon waste into raw material I by vacuum drying; (2) The raw material I in step (1) is acid-washed to obtain raw material II; (3) uniformly mixing the raw material II described in step (2) and silicon dioxide to obtain a mixture III; (4) adding a binder and water to the mixture III obtained in step (3), obtaining a molded sample IV by controlling the molding pressure, and calcining and drying the molded sample IV to obtain a sample IV; (5) placing the sample IV described in step (4) in a vacuum reactor to heat the sample to prepare silicon oxide vapor, cooling and condensing the silicon oxide vapor to prepare silicon oxide material.

2. The method for preparing silicon dioxide material by regenerating photovoltaic silicon waste according to claim 1, characterized in that: The photovoltaic silicon waste in step (1) is waste silicon mud generated in the process of cutting crystalline silicon in the photovoltaic industry, and the particle size D50 of the waste silicon mud is 0.2 to 10 μm.

3. The method for preparing silicon dioxide material by regenerating photovoltaic silicon waste according to claim 1, characterized in that: In step (1), the drying temperature is 30 to 100° C. and the drying time is 5 to 24 hours.

4. The method for preparing silicon dioxide material by regenerating photovoltaic silicon waste according to claim 1, characterized in that: In step (2), the pickling is carried out using any one of hydrochloric acid, nitric acid, oxalic acid, citric acid, and sulfuric acid, or two or more of them mixed with hydrofluoric acid in any proportion; the pickling temperature is 20 to 100° C., and the pickling time is 0.1 to 2 hours.

5. The method for preparing silicon dioxide material by regenerating photovoltaic silicon waste according to claim 1, characterized in that: In step (3), the mass ratio of raw material II to silicon dioxide is 1:2 to 1.3:2, and the particle size of the silicon dioxide is 0.1 to 1000 μm.

6. The method for preparing silicon dioxide material by regenerating photovoltaic silicon waste according to claim 1, characterized in that: In step (4), the weight percentage of the binder added is 0.1% to 5% of the mixture III, the weight percentage of water added is 0.1% to 5% of the mixture III, and the molding pressure is 5MPa to 50MPa; the binder is one or two of polyvinyl pyrrolidone, polyvinylidene fluoride, carboxymethyl cellulose, high-performance polymer, polyvinyl alcohol, ethylene glycol, and phenolic resin mixed in any proportion.

7. The method for preparing silicon dioxide material by regenerating photovoltaic silicon waste according to claim 1, characterized in that: In step (4), the calcination and drying temperature is 100 to 500° C., and the calcination time is 0.5 to 3 hours.

8. The method for preparing silicon dioxide material by regenerating photovoltaic silicon waste according to claim 1, characterized in that: The reaction conditions in step (5) are: heating rate of 1-20°C / min, reaction temperature of 1000°C-1500°C, reaction time of 0.2-5h, vacuum degree of 50Pa-500Pa; cooling rate of 1-20°C / min; condensation temperature of 500°C-900°C, and condensation time of 0.2-3h.

9. Use of silicon 2 oxide prepared by the method according to any one of claims 1 to 8 in preparing negative electrode materials for lithium ion batteries.

Images