Process for dispersing and purifying silicon nanowires and applications thereof

Abstract

The application provides a dispersion and purification process method of silicon nanowires and application thereof. The process method comprises the following steps: (1) soaking the silicon nanowires in a solvent to obtain a first slurry, adding an anionic surfactant to the first slurry to perform first mixing, standing and filtering to obtain a solid product; (2) adding the solid product in step (1) into a solvent to obtain a second slurry, adding a non-ionic surfactant and a dispersion aid to perform second mixing, centrifuging to obtain a dispersion liquid and a filter residue, and completing the dispersion and purification of the silicon nanowires. The silicon nanowires are effectively separated and purified in a simple way, and the dispersion and purification process of the silicon nanowires is combined by combining the dispersion process, so that the production process is effectively reduced, and the production efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and in particular to a dispersion and purification process for silicon nanowires and its application. Background Technology

[0002] Lithium-ion batteries are highly efficient electrochemical energy storage devices with advantages such as high voltage, long lifespan, high cycle stability, and good safety. They have been widely used in electronic products, electric vehicles, and energy storage devices. Silicon possesses an extremely high theoretical capacity of 4200 mAh / g, approximately 10 times that of currently available commercial graphite anodes. Therefore, silicon has always been the most promising anode for lithium-ion batteries. However, the extremely large volume expansion effect of silicon (>400%) causes rapid structural collapse, differentiation, and detachment from the current collector during lithium insertion / extraction. Therefore, nanostructuring silicon is a very feasible method. Silicon nanowires have gradually attracted the attention of researchers in lithium-ion battery anode materials due to their extremely high aspect ratio.

[0003] The gas-liquid-solid (VLS) method is commonly used for the generation of silicon nanowires, but it generally requires the preparation of a metal catalyst before synthesis, making it unsuitable for large-scale synthesis. Studies have shown that silicon nanowires can be produced by reducing silicon tetrachloride (SiCl4) with zinc, where the zinc liquid catalyst is believed to form during the reaction through the condensation of zinc vapor, thus eliminating the need for pre-reaction preparation of metal catalyst particles. During the production of silicon nanowires, in addition to nanowire formation, a series of other materials (such as whiskers, microparticles, chlorides, silica, and silicon nanoparticles) can be formed depending on the reaction conditions, often resulting in a mixture of these materials. Zinc chloride is hygroscopic, and silica and silicon nanoparticles can affect conductivity and electrode expansion. The presence of these impurities significantly impacts the subsequent use of silicon nanowires in lithium-ion battery materials. Therefore, after silicon nanowire production, purification and impurity removal are necessary.

[0004] CN 101830447 A discloses a method for preparing β-silicon nitride nanowires. The method involves calcining the sample in air at 600°C to remove carbon, then treating it with a mixture of hydrofluoric acid and concentrated nitric acid (volume ratio 3:1) to remove silicon dioxide, washing with deionized water until the pH is neutral, and then drying to obtain purified silicon nanowires. However, the entire process involves high-temperature sintering and strong acid solutions, resulting in high production costs and environmentally harmful waste liquid.

[0005] CN 107161962 A discloses a method for preparing silicon nitride nanowires and the silicon nitride nanowires themselves. The method utilizes LDH to prepare silicon nitride at temperatures ranging from 1110 to 1300 °C, and uses the composition of LEDs to suppress the migration and aggregation of nano-metals, thereby preparing silicon nanowires with a diameter of 30–50 nm. However, the entire process is overly complex for purifying silicon nanowires containing impurities, wasting production resources and increasing production costs.

[0006] Therefore, how to provide a low-cost, mass-producible, and environmentally friendly process for purifying silicon nanowires is an important research direction in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a dispersion and purification process for silicon nanowires and its application.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] One objective of this invention is to provide a dispersion and purification process for silicon nanowires, the process comprising the following steps:

[0010] (1) Silicon nanowires are soaked in a solvent to obtain a first slurry. An anionic surfactant is added to the silicon nanowire slurry for a first mixing, settling and filtration to obtain a solid product.

[0011] (2) The solid product described in step (1) is added to a solvent to obtain a second slurry. A nonionic surfactant and a dispersing agent are added for a second mixing. After centrifugation, a dispersion and a second filter residue are obtained. The dispersion is dried to complete the dispersion and purification of the silicon nanowires.

[0012] This invention uses flocculent silicon nanowires as raw material. Leveraging the low density, high specific surface area, and easy water absorption properties of silicon nanowires, a simple soaking and stirring process effectively separates and purifies silicon nanowires, silicon nanoparticles, and other impurities. Combined with a dispersion process, this achieves a composite process for silicon nanowire dispersion and purification, effectively reducing production steps and improving production efficiency. The removed impurities, such as chlorides, silica, and silicon nanoparticles, adhere to the surface of the silicon nanowires or are embedded between clusters, making them difficult to separate. The hygroscopic nature of zinc chloride, along with silica and silicon nanoparticles, can affect conductivity and electrode expansion, potentially impacting the electrochemical performance of the silicon nanowires in subsequent use.

[0013] The reason for adding anionic surfactants in the dispersion and purification process of this invention is as follows: After soaking silicon nanowires in deionized water, the silicon nanowires, due to their extremely large specific surface area, readily absorb water and possess highly active surfaces, easily forming Si-OH bonds with water. Impurities are then trapped inside the silicon nanowires through hydrogen bonds and physical entanglement. Adding a small amount of anionic surfactant breaks these hydrogen bonds, forming a hydrophobic layer on the Si surface. This allows the trapped nanoparticles and other impurities to separate under low-speed stirring and float on the surface of the deionized water. This achieves effective separation of silicon nanoparticles from silicon nanowires.

[0014] This invention incorporates a nonionic surfactant, which possesses excellent penetration properties, high stability, and is unaffected by acids, alkalis, and salts, exhibiting strong resistance to hard water. The hydration film formed by its excessively long polymer chains can prevent secondary aggregation of silicon nanowires after initial dispersion, thus stabilizing the dispersion. Furthermore, the nonionic surfactant has excellent compatibility with dispersing agents and can work synergistically with them to improve the dispersion effect.

[0015] As a preferred technical solution of the present invention, the solvent in step (1) includes deionized water.

[0016] Preferably, the soaking time in step (1) is 3 to 12 hours, wherein the time can be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] Preferably, the solid content of the first slurry in step (1) is 1 to 10 wt%, wherein the solid content can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] As a preferred technical solution of the present invention, the anionic surfactant in step (1) includes a carboxylic acid type anionic surfactant.

[0019] Preferably, the anionic surfactant comprises sodium N-oleoyl polyacetal and / or lauryl carboxylate AEC.

[0020] Preferably, the mass ratio of the anionic surfactant to the silicon nanowire is 1:1 to 1:10, wherein the mass ratio can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0021] As a preferred technical solution of the present invention, the stirring rate of the first mixing in step (1) is 100 to 400 rpm, wherein the stirring rate can be 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm or 400 rpm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the stirring time for the first mixture is 3 to 6 hours, wherein the stirring time can be 3 hours, 4 hours, 5 hours or 6 hours, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0023] Preferably, the stirring temperature of the first mixture is 16 to 30°C, wherein the stirring temperature can be 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0024] Preferably, the settling time is 1 to 12 hours, wherein the time can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the settling temperature is 16-30°C, and the stirring temperature can be 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] As a preferred technical solution of the present invention, the filtration process in step (1) includes filtration and vacuum filtration.

[0027] Preferably, the filtration includes filtering out floating matter from the surface of the mixed and settled slurry.

[0028] Preferably, the filtering is performed 2 to 3 times, wherein the number of times can be 2 or 3.

[0029] Preferably, the solid product is obtained after filtration.

[0030] As a preferred technical solution of the present invention, the solvent in step (2) includes deionized water.

[0031] Preferably, the solid content of the second slurry is 5 to 15 wt%, wherein the solid content can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0032] As a preferred technical solution of the present invention, the nonionic surfactant includes fatty acid polyoxyethylene ester and / or Tween 80;

[0033] Preferably, the mass ratio of the surfactant to the silicon nanowire is 1:3 to 1:5, wherein the mass ratio can be 1:3, 1:4 or 1:5, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0034] Preferably, the dispersing agent comprises any one or a combination of at least two of naphthalenesulfonic acid formaldehyde condensate, polyvinylpyrrolidone, or hexadecyltrimethylammonium bromide, wherein typical but non-limiting examples of the combination include: a combination of naphthalenesulfonic acid formaldehyde condensate and polyvinylpyrrolidone, a combination of polyvinylpyrrolidone and hexadecyltrimethylammonium bromide, or a combination of naphthalenesulfonic acid formaldehyde condensate and hexadecyltrimethylammonium bromide, etc.

[0035] Preferably, the mass ratio of the dispersing agent to the silicon nanowires is 1:10 to 1:30, wherein the mass ratio can be 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, 1:22, 1:24, 1:26, 1:28 or 1:30, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0036] In this invention, since the diameter of silicon nanowires ranges from 100 to 800 nm, corresponding to different specific surface areas, the diameter of silicon nanowires can be effectively screened by adjusting the amount of surfactant and dispersant. Small-diameter silicon nanowires can be suspended in the solution, thereby achieving effective classification of silicon nanowires.

[0037] As a preferred technical solution of the present invention, the stirring rate of the second mixing in step (2) is 800 to 1400 rpm, wherein the stirring rate can be 800 rpm, 850 rpm, 900 rpm, 950 rpm, 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm, 1250 rpm, 1300 rpm, 1350 rpm or 1400 rpm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0038] The stirring rate of the second mixing in this invention is high-speed stirring. By stirring at high speed, the coil is always subjected to shear force in the same direction in the solution, which causes the coil to be combed under the action of shear force. The coil is unwound by physical means, and a good dispersion is formed under the combined action of surfactant and dispersant.

[0039] Preferably, the second mixing time is 24 to 48 hours, wherein the time can be 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours, 40 hours, 42 hours, 44 hours, 46 hours, or 48 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] Preferably, the temperature of the second mixing is 16 to 30°C, wherein the stirring temperature can be 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0041] Preferably, the dispersion in step (2) is a small-diameter silicon nanowire dispersion.

[0042] Preferably, the diameter of the small-diameter silicon nanowire is 80-200 nm, wherein the diameter can be 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm or 200 nm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0043] Preferably, the second filter residue is large-diameter silicon nanowires.

[0044] Preferably, the diameter of the large-diameter silicon nanowire is 200-800 nm, wherein the diameter can be 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm or 800 nm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] As a preferred technical solution of the present invention, the process method includes the following steps:

[0046] (1) Soak silicon nanowires in a solvent for 3-12 hours to obtain a first slurry with a solid content of 1-10 wt%. Add anionic surfactant to the silicon nanowire slurry and mix for 3-6 hours with a stirring rate of 100-400 rpm. After standing and filtration, a solid product is obtained.

[0047] (2) The solid product described in step (1) is added to a solvent to obtain a second slurry with a solid content of 5-15 wt%. Nonionic surfactant and dispersant are added and the mixture is stirred at a speed of 800-1400 rpm for 24-48 hours. After centrifugation, a dispersion and a second filter residue are obtained to complete the dispersion and purification of the silicon nanowires.

[0048] The second objective of this invention is to provide an application of the dispersion and purification process for silicon nanowires as described in the first objective, wherein the process is applied in the field of lithium-ion batteries.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The purification and dispersion process of the present invention is simple. Purification and fractionation of silicon nanowires can be achieved through simple soaking and stirring processes.

[0051] (2) This invention effectively combines dispersion and purification processes.

[0052] (3) The present invention has a good effect on purifying silicon nanowires, and the diameter of the purified silicon nanowires can reach 80-200 nm.

[0053] (4) The purification process of this invention is simple and maintains environmental friendliness while protecting the original properties of the product. Attached Figure Description

[0054] Figure 1 These are SEM images of silicon nanowires in Examples 1-9 and Comparative Example 1 of this invention.

[0055] Figure 2 This is a SEM image of the purified silicon nanowires from Example 1 of this invention.

[0056] Figure 3 This is a SEM image of the purified silicon nanowires from Example 4 of this invention.

[0057] Figure 4 This is a SEM image of the purified silicon nanowires from Example 7 of this invention.

[0058] Figure 5 This is a SEM image of the silicon nanowires purified in Comparative Example 1 of this invention. Detailed Implementation

[0059] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0060] Example 1

[0061] This embodiment provides a dispersion and purification process for silicon nanowires, including the following steps:

[0062] (1) Weigh 10g of synthesized silicon nanowires and soak them in 1000ml of deionized water for 8 hours to obtain a first slurry with a solid content of 5wt%. Add 3g of lauryl carboxylate AEC to the first slurry and stir with a magnetic stirrer at 300rpm for 6 hours to complete the first mixing. After standing and settling, filter off the floating matter on the liquid surface. Repeat 3 times until there is no floating matter on the liquid surface. Continue to filter the solution to obtain a solid product;

[0063] (2) The solid product in step (1) was added to deionized water to prepare a second slurry with a solid content of 10 wt%. Then, 2.5 g of fatty acid polyoxyethylene ester and 0.5 g of naphthalene sulfonic acid formaldehyde condensate were added. The mixture was stirred at 1200 rpm for 24 h to complete the second mixing. After centrifugation, the upper dispersion was small-diameter silicon nanowires and the lower filter residue was large-diameter silicon nanowires. The upper dispersion was dried to obtain purified silicon nanowires.

[0064] The original SEM image of the silicon nanowires in step (1) of this embodiment is as follows: Figure 1 As shown, the SEM image of the purified silicon nanowires is as follows. Figure 2 As shown.

[0065] Example 2

[0066] This embodiment provides a dispersion and purification process for silicon nanowires, including the following steps:

[0067] (1) Weigh 10g of synthesized silicon nanowires and soak them in 1000ml of deionized water for 12h to obtain a first slurry with a solid content of 1wt%. Add 1g of N-oleoyl polyacetal sodium to the first slurry and stir at 100rpm for 6h using a magnetic stirrer to complete the first mixing. After standing and settling, filter off the floating matter on the liquid surface. Repeat 3 times until there is no floating matter on the liquid surface. Continue to filter the solution to obtain a solid product;

[0068] (2) The solid product in step (1) was added to deionized water to prepare a second slurry with a solid content of 5 wt%. Then, 3.5 g of fatty acid polyoxyethylene ester and 1 g of hexadecyltrimethylammonium bromide were added. The mixture was stirred at 800 rpm for 48 h to complete the second mixing. After centrifugation, the upper dispersion was small-diameter silicon nanowires and the lower filter residue was large-diameter silicon nanowires. The upper dispersion was dried to obtain purified silicon nanowires.

[0069] Example 3

[0070] This embodiment provides a dispersion and purification process for silicon nanowires, including the following steps:

[0071] (1) Weigh 10g of synthesized silicon nanowires and soak them in 1000ml of deionized water for 3h to obtain a first slurry with a solid content of 10wt%. Add 10g of lauryl carboxylate AEC to the first slurry and stir at 400rpm for 3h using a magnetic stirrer to complete the first mixing. After standing and settling, filter off the floating matter on the liquid surface. Repeat twice until there is no floating matter on the liquid surface. Continue to filter the solution to obtain a solid product;

[0072] (2) The solid product in step (1) was added to deionized water to prepare a second slurry with a solid content of 15wt%. Then, 2g of Tween 80 and 0.35g of polyvinylpyrrolidone were added. The mixture was stirred at 1400rpm for 32h using a mechanical stirrer to complete the second mixing. After centrifugation, the upper dispersion was small-diameter silicon nanowires and the lower filter residue was large-diameter silicon nanowires. The upper dispersion was dried to obtain purified silicon nanowires.

[0073] Example 4

[0074] In this embodiment, the only difference is that the stirring at 100 rpm for 6 hours in step (1) is replaced with stirring at 1500 rpm for 6 hours. All other conditions are the same as in Example 1. The SEM image of the purified silicon nanowires in this embodiment is shown below. Figure 3 As shown.

[0075] Example 5

[0076] In this embodiment, except that the addition of 3g of lauryl carboxylate AEC to the first slurry in step (1) is replaced by the addition of 0.5g of lauryl carboxylate AEC to the first slurry, all other conditions are the same as in Example 1.

[0077] Example 6

[0078] In this embodiment, except that the addition of 3g of lauryl carboxylate AEC to the first slurry in step (1) is replaced by the addition of 12g of lauryl carboxylate AEC to the first slurry, all other conditions are the same as in Example 1.

[0079] Example 7

[0080] In this embodiment, the only difference is that in step (2), instead of using a mechanical stirrer at 1200 rpm for 24 hours to complete the second mixing, a mechanical stirrer at 500 rpm for 24 hours is used to complete the second mixing before centrifugation. All other conditions are the same as in Example 1. The SEM image of the purified silicon nanowires in this embodiment is shown below. Figure 4 As shown.

[0081] Example 8

[0082] In this embodiment, except that the addition of 2.5g of fatty acid polyoxyethylene ester in step (2) is replaced with the addition of 1g of fatty acid oxyethylene ester, all other conditions are the same as in Example 1.

[0083] Example 9

[0084] In this embodiment, except that 2.5g of fatty acid polyoxyethylene ester is replaced with 5g of fatty acid oxyethylene ester in step (2), all other conditions are the same as in Example 1.

[0085] Comparative Example 1

[0086] Except for the absence of 3g of lauryl carboxylate AEC in step (1), all other conditions in this comparative example were the same as in Example 1. The SEM image of the silicon nanowires obtained in this comparative example is shown below. Figure 5 As shown.

[0087] The purification processes in Examples 1-9 and Comparative Example 1 were evaluated, and the average diameter of the purified silicon nanowires is shown in Table 1.

[0088] The diameter of the purified silicon nanowires was visually obtained through electron microscopy images.

[0089] Table 1

[0090] Example 1 90nm Example 2 120nm Example 3 150nm Example 4 200nm Example 5 180nm Example 6 120nm Example 7 200nm Example 8 180nm Example 9 150nm Comparative Example 1 200nm

[0091] As can be seen from the table above, compared with Example 1, when high-speed stirring is used for the first mixing in Example 4, impurities are easily mixed with silicon nanowires and are difficult to separate, resulting in poor purification results.

[0092] A comparison of Examples 5-6 with Example 1 shows that neither too much nor too little anionic surfactant can effectively achieve separation and purification.

[0093] Compared with Example 1, when using low-speed stirring for the second mixing in Example 7, the shear force is insufficient, making it difficult to break up the silicon nanowire clusters and achieve the purpose of dispersion. In this invention, low-speed stirring is used for the first mixing and high-speed stirring is used for the second mixing. After adding the corresponding surfactants and dispersants, the silicon nanowires can be effectively dispersed from the impurities, and the finer silicon nanowires can be effectively separated from the coarser silicon nanowires, thereby achieving the purpose of separation and purification.

[0094] As can be seen from the comparison between Examples 8-9 and Comparative Example 1, neither too much nor too little nonionic surfactant can effectively achieve the separation and purification effect.

[0095] In Comparative Example 1, without the addition of anionic surfactant, the hydrogen bonding between the Si-OH bonds formed between the silicon nanowire surface and water is difficult to break, making it difficult to separate impurities such as nanoparticles embedded inside.

[0096] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A dispersion and purification process for silicon nanowires, characterized in that, The process includes the following steps: (1) The silicon nanowires are soaked in a solvent to obtain a first slurry. An anionic surfactant is added to the first slurry for a first mixing, standing and filtration treatment to obtain a solid product. (2) The solid product described in step (1) is added to a solvent to obtain a second slurry. Nonionic surfactant and dispersant are added for a second mixing. After centrifugation, a dispersion and filter residue are obtained. The dispersion is dried to complete the dispersion and purification of the silicon nanowires. Step (1) The stirring rate of the first mixture is 100~400 rpm; In step (2), the stirring rate of the second mixing is 800~1400 rpm; The mass ratio of the anionic surfactant to the silicon nanowires is 1:1 to 1:10; The mass ratio of the nonionic surfactant to the silicon nanowire is 1:3 to 1:

5.

2. The process method according to claim 1, characterized in that, The solvent in step (1) includes deionized water.

3. The process method according to claim 1, characterized in that, The soaking time in step (1) is 3 to 12 hours.

4. The process method according to claim 1, characterized in that, Step (1) The solid content of the first slurry is 1~10wt%.

5. The process method according to claim 1, characterized in that, The anionic surfactant in step (1) includes carboxylic acid anionic surfactants.

6. The process method according to claim 1, characterized in that, The anionic surfactant includes sodium N-oleoyl polyacetal and / or lauryl carboxylate AEC.

7. The process method according to claim 1, characterized in that, The stirring time for the first mixture is 3 to 6 hours.

8. The process method according to claim 1, characterized in that, The stirring temperature of the first mixture is 16~30℃.

9. The process method according to claim 1, characterized in that, The settling time is 1 to 12 hours.

10. The process method according to claim 1, characterized in that, The settling temperature is 16~30℃.

11. The process method according to claim 1, characterized in that, The filtration process in step (1) includes filtration and vacuum filtration.

12. The process method according to claim 11, characterized in that, The filtration includes filtering out floating matter from the surface of the mixed and settled slurry.

13. The process method according to claim 11, characterized in that, The filtering is performed 2 to 3 times.

14. The process method according to claim 11, characterized in that, The solid product is obtained after filtration.

15. The process method according to claim 1, characterized in that, The solvent in step (2) includes deionized water.

16. The process method according to claim 1, characterized in that, The solid content of the second slurry is 5~15wt%.

17. The process method according to claim 1, characterized in that, The nonionic surfactants include fatty acid polyoxyethylene esters and / or Tween 80.

18. The process method according to claim 1, characterized in that, The dispersing agent includes any one or a combination of at least two of naphthalenesulfonic acid formaldehyde condensate, polyvinylpyrrolidone, or hexadecyltrimethylammonium bromide.

19. The process method according to claim 1, characterized in that, The mass ratio of the dispersing agent to the silicon nanowires is 1:10 to 1:

30.

20. The process method according to claim 1, characterized in that, The second mixing time is 24~48h.

21. The process method according to claim 1, characterized in that, The temperature of the second mixture is 16~30℃.

22. The process method according to claim 1, characterized in that, The dispersion in step (2) is a small-diameter silicon nanowire dispersion.

23. The process method according to claim 1, characterized in that, The dispersion was dried to obtain purified silicon nanowires.

24. The process method according to claim 22, characterized in that, The diameter of the small-diameter silicon nanowires is 80~180nm.

25. The process method according to claim 1, characterized in that, The filter residue is composed of large-diameter silicon nanowires.

26. The process method according to claim 25, characterized in that, The diameter of the large-diameter silicon nanowires is 200~800nm.

27. The process method according to claim 1, characterized in that, The process includes the following steps: (1) The silicon nanowires were soaked in a solvent for 3-12 hours to obtain a first slurry with a solid content of 1-10 wt%. An anionic surfactant was added to the first slurry and the mixture was stirred at a speed of 100-400 rpm for 3-6 hours. After standing and filtration, a solid product was obtained. (2) The solid product described in step (1) is added to a solvent to obtain a second slurry with a solid content of 5~15wt%. Nonionic surfactant and dispersant are added and the mixture is stirred at a speed of 800~1400rpm for 24~48h. After centrifugation, a dispersion and filter residue are obtained to complete the dispersion and purification of the silicon nanowires.

28. The application of a dispersion and purification process for silicon nanowires as described in any one of claims 1-27, characterized in that, The process described herein is applied in the field of lithium-ion batteries.

Images