A modified method for protecting water-based ground silicon surfaces

Abstract

The embodiment of the present application relates to a kind of modified methods for water system abrasive silicon surface protection.The modified method includes: the silicon powder to be treated is carried out drying treatment;The silicon powder after drying treatment is added to organic solvent containing silane coupling agent with hydrophobic compound, is stirred uniformly to form mixed solution;After the organic solvent in the mixed solution is removed, powder material is obtained;The powder material is placed into vacuum constant-temperature drying oven and is carried out drying treatment, and preliminary modified silicon powder is obtained;The preliminary modified silicon powder is mixed with aqueous solution dispersant containing silane coupling agent and hydrophobic compound to form abrasive slurry, and the abrasive slurry is added to grinding equipment and is carried out grinding at normal temperature, and the material after grinding is carried out drying treatment, and modified nanometer silicon powder is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials, in particular to a modification method for water-based grinding silicon surface protection. BACKGROUND

[0002] Silicon material is a lithium battery negative electrode material with excellent application prospect, and its theoretical specific capacity is as high as 4200 mAh / g. In addition, it has the advantages of abundant reserves, good temperature resistance, good corrosion resistance, stable chemical properties, and low lithium intercalation potential, which makes it widely concerned in the field of lithium batteries. However, its volume changes greatly during the intercalation and deintercalation of lithium, which limits its use in the field of lithium batteries. Nanocrystallization of silicon particles is one of the main methods to alleviate the volume change.

[0003] In order to nanocrystallize silicon particles and obtain nano-silicon powder with better performance and smaller particle size, organic grinding is generally used for grinding. However, organic grinding requires using organic solvents as wet grinding liquid medium, which pollutes the environment and is expensive. Even if improper operation occurs during operation, it may cause combustion, explosion and other risks.

[0004] In the grinding of silicon, the most ideal condition is to use water as a dispersant. However, if water is used as a dispersant, silicon will react with water to generate hydrogen gas during grinding, which is prone to explosion. Therefore, it is necessary to develop a method to prevent water from reacting with silicon when water is used as a dispersant for silicon grinding. SUMMARY

[0005] The purpose of the present application is to provide a modification method for water-based grinding silicon surface protection. The method first modifies the surface of the silicon powder to be ground to prevent reaction during grinding with water as a dispersant. Then, silane coupling agent and hydrophobic compound are added to the grinding liquid to prevent silicon from reacting with water during grinding. This method can prevent silicon from reacting with water to generate hydrogen gas when water is used as a dispersant, and at the same time solve the problems of high cost and low safety of silicon grinding.

[0006] To this end, the present application provides a modification method for water-based grinding silicon surface protection, which comprises:

[0007] The silicon powder to be treated is subjected to drying treatment;

[0008] The dried silicon powder and the hydrophobic compound are added together to an organic solvent containing silane coupling agent, and stirred uniformly to form a mixed solution;

[0009] The organic solvent in the mixed solution is removed to obtain a powder material;

[0010] The powder material is put into a vacuum constant temperature drying oven for drying treatment to obtain a preliminary modified silicon powder;

[0011] The preliminary modified silicon powder is mixed with an aqueous solution dispersant containing a silane coupling agent and a hydrophobic compound to form a grinding slurry, and the grinding slurry is added to a grinding device for grinding at room temperature, and the ground material is dried to obtain a modified nano silicon powder.

[0012] Preferably, the hydrophobic compound includes one or more of polyfluoroethylene propylene, polytetrafluoroethylene, polyvinylidene fluoride, polytrifluorochloroethylene, polyolefin, polycarbonate, polyamide, polyacrylonitrile;

[0013] The silane coupling agent includes one or more of γ-aminopropyl methyldiethoxysilane, γ-aminopropyl methyldimethoxysilane, γ-aminopropyl trimethoxysilane, γ-aminopropyl triethoxysilane.

[0014] Preferably, the organic solvent includes one or more of alcohol with a concentration of 80%-99%, methanol, acetone, carbon tetrachloride, isopropyl alcohol, pentane, hexane, cyclohexanone, dichlorobenzene, dichloromethane, methyl acetate.

[0015] Preferably, the mass ratio of the silicon powder, the silane coupling agent, and the hydrophobic compound in the mixed solution is 1:(0.01-0.05);(0.05-0.1).

[0016] Preferably, the stirring speed is 500 revolutions / minute-1200 revolutions / minute; the temperature for uniformly stirring to form a mixed solution is room temperature, and the pH of the formed mixed solution is 5-7.

[0017] Preferably, the grinding device includes any one of a nanometer sand mill, a ball mill, and a disperser, and the grinding time is 8-24 hours; the grinding medium includes at least one of alumina beads, zirconia beads, and silica beads, and the particle size of the grinding medium is 0.1-0.5mm.

[0018] Preferably, the drying treatment method includes at least one of spray drying, boiling drying, normal pressure drying, reduced pressure drying, and freeze drying, and the drying treatment temperature is 60℃-100℃, and the drying treatment time is 1-24 hours.

[0019] Preferably, the silicon powder to be treated is a spherical material with a particle size of 50um-1000um.

[0020] Preferably, after uniformly stirring to form a mixed solution, the method further includes adding a hydrolysis catalyst to the mixed solution.

[0021] Preferably, after the mixing forms the grinding slurry, the method further comprises: adding a hydrolysis catalyst in the grinding slurry.

[0022] The modification method for protecting the silicon surface during water-based grinding provided by the embodiment of the present application connects the silicon with the hydrophobic compound by using the silane coupling agent, modifies the surface of the silicon, and makes the surface of the silicon hydrophobic, so that the silicon does not react with water to generate hydrogen gas during grinding. Compared with the preparation method using other dispersants for grinding, the present application is simpler and more efficient, and can avoid the pollution to the environment caused by the use of organic solvents, and the risk of combustion and explosion that may occur during the preparation process. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The step flow chart of the modification method for protecting the silicon surface during water-based grinding provided by the present application is shown in the figure.

[0024] Figure 2 The step schematic diagram of the modification method for protecting the silicon surface during water-based grinding provided by the present application is shown in the figure.

[0025] Figure 3 The mechanism schematic diagram of the silane coupling agent modifying the silicon in the modification process of the silicon surface during water-based grinding provided by the embodiment of the present application is shown in the figure.

[0026] Figure 4 The X-ray diffraction (XRD) spectrum of the material obtained by using the modification method for protecting the silicon surface during water-based grinding provided by the embodiment 1 of the present application is shown in the figure.

[0027] Figure 5 The charge-discharge curve of the assembled battery of the material obtained by using the modification method for protecting the silicon surface during water-based grinding provided by the embodiment 1 of the present application is shown in the figure. DETAILED DESCRIPTION

[0028] The technical solutions of the present application will be further described in detail below by means of the accompanying drawings and embodiments.

[0029] The modification method for protecting the silicon surface during water-based grinding provided by the embodiment of the present application mainly includes the following steps as shown in the figure. Figure 1

[0030] Step 110, drying treatment is performed on the silicon powder to be treated.

[0031] The silicon powder to be treated is a spherical material, and the particle size is 50um-1000um.

[0032] The drying treatment method includes at least one of spray drying, boiling drying, normal pressure drying, reduced pressure drying, and freeze drying, and the drying treatment temperature is 60℃-100℃, and the drying treatment time is 1-24 hours. The drying treatment in each of the following steps can be implemented according to the method. ​

[0033] Step 120, the dried silicon powder and hydrophobic compound are added into the organic solvent containing silane coupling agent to form a mixed solution by stirring;

[0034] The hydrophobic compound used includes one or more of polyfluoroethylene propylene, polytetrafluoroethylene, polyvinylidene fluoride, polytrifluorochloroethylene, polyolefin, polycarbonate, polyamide, polyacrylonitrile.

[0035] The silane coupling agent used includes one or more of γ-aminopropyl methyldiethoxysilane, γ-aminopropyl methyldimethoxysilane, γ-aminopropyl trimethoxysilane, γ-aminopropyl triethoxysilane.

[0036] The organic solvent used includes one or more of alcohol with a concentration of 80%-99%, methanol, acetone, carbon tetrachloride, isopropyl alcohol, pentane, hexane, cyclohexanone, dichlorobenzene, dichloromethane, methyl acetate.

[0037] The stirring speed is 500-1200 rpm; the temperature for stirring to form a mixed solution is room temperature, and the pH of the formed mixed solution is 5-7. The mass ratio of silicon powder, silane coupling agent, and hydrophobic compound in the mixed solution is 1:(0.01-0.05);(0.05-0.1).

[0038] After the mixed solution is stirred to form a mixed solution, the method of this step can further include adding a hydrolysis catalyst into the mixed solution.

[0039] Step 130, the organic solvent in the mixed solution is removed to obtain a powder material;

[0040] Step 140, the powder material is placed into a vacuum constant temperature drying oven for drying treatment to obtain a preliminary modified silicon powder;

[0041] Step 150, the preliminary modified silicon powder is mixed with an aqueous solution dispersant containing silane coupling agent and hydrophobic compound to form a grinding slurry, and the grinding slurry is added into a grinding device for grinding at room temperature. The ground material is dried to obtain a modified nano silicon powder.

[0042] The grinding device includes any one of a nano sand mill, a ball mill, and a disperser. The grinding time is 8-24 hours. The grinding medium includes at least one of silicon nitride beads, zirconium oxide beads, and aluminum oxide beads. The particle size of the grinding medium is 0.1-0.5 mm.

[0043] After the grinding slurry is mixed, before the grinding is performed, the method of this step can further include adding a hydrolysis catalyst into the grinding slurry.

[0044] The modification protection method of the present application adopts secondary surface modification, the first protection is carried out in the initial stage of water-based grinding, and the second protection is carried out by adding silane coupling agent and hydrophobic compound again in the grinding process, because the surface area of the silicon powder gradually increases with the grinding process, and the hydrophobic compound and the silane coupling agent need to be continuously added to continue the protection.

[0045] The process schematic diagram of the modification method for silicon surface protection in water-based grinding of the present application is shown in Figure 2 The mechanism of the modification process of the present application is shown in the schematic diagram Figure 3 The silicon powder, silane coupling agent (γ-aminopropyl triethoxysilane KH-550) and hydrophobic compound are mixed, dried, ground and dried, the silane coupling agent is hydrolyzed, coupled with the hydrophobic compound, and by-products methanol are generated at the same time, through the coupling reaction, the silane coupling agent connects the silicon and the hydrophobic compound, and the hydrophobic compound forms the end group, so that the material surface has hydrophobicity, thereby preventing the silicon from reacting with water to generate hydrogen gas in the grinding process.

[0046] The modification method for silicon surface protection in water-based grinding of the present application is described above, and the following specific examples are further described, but the protection scope of the present application is not limited to this.

[0047] Example 1

[0048] 40 grams of spherical silicon powder with a particle size of about 100 um are dried at 100°C;

[0049] The dried silicon powder and 4 grams of polytetrafluoroethylene are added to 100 ml of an ethanol solution containing 2 grams of γ-aminopropyl triethoxysilane;

[0050] At room temperature, a uniform dispersion solution is obtained by stirring at a high speed of 1200 rpm for 24 hours using a stirrer;

[0051] The ethanol reagent in the mixed solution is removed by a vacuum filter, and the obtained powder is dried at 100°C in a vacuum constant temperature drying box to obtain modified silicon powder;

[0052] The obtained modified silicon powder is mixed with an aqueous solution dispersant containing γ-aminopropyl triethoxysilane and polytetrafluoroethylene to form a grinding slurry, the grinding slurry is added to a nano grinder, and the grinding is carried out at room temperature for 24 hours, and the obtained grinding slurry is dried in a vacuum constant temperature drying box at 100°C to obtain nano silicon powder.

[0053] The obtained negative electrode material, conductive additive carbon black, and binder (1 : 1 carboxymethyl cellulose sodium and butadiene rubber) were weighed in a mass ratio of 95:2:3. Slurry preparation was performed in a beater at room temperature. The prepared slurry was uniformly coated on a copper foil. After drying in a forced air drying oven at a temperature of 50°C for 2 hours, the electrode sheet was cut into 8x8mm, and vacuum dried in a vacuum drying oven at a temperature of 100°C for 10 hours. The dried electrode sheet was then transferred into a glove box for use in assembling batteries.

[0054] The battery assembly was performed in a glove box containing a high-purity Ar atmosphere, using metallic lithium as the counter electrode, and a solution of 1 mol LiPF6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) as the electrolyte. Constant current charge-discharge mode testing was performed using a charge-discharge tester, with a discharge cutoff voltage of 0.005 V and a charge cutoff voltage of 1.5 V, and the charge-discharge testing was performed at a current density of C / 10. The charge-discharge curve is shown in FIG. 1. Figure 5

[0055] To better compare, we prepared a comparative sample according to the following method.

[0056] Comparative Example 1

[0057] This comparative example provides a method of directly using water as a dispersant for the grinding of silicon:

[0058] Step 1: Mix the silicon powder to be ground with water to form a grinding slurry, and the viscosity of the grinding slurry is not more than 200 centi-Pascal-seconds.

[0059] Step 2: Add the grinding slurry to a grinding device and grind for 2-4 hours in an environment below 25°C to obtain a silicon powder.

[0060] The button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing, which is recorded in Table 1.

[0061] Comparative Example 2

[0062] The coarse silicon powder was air-jet milled into a micro-silicon powder with an average particle size of 100 microns. The micro-silicon powder was added to anhydrous ethanol solvent and stirred to form a silicon solution with a solid content of 10%. The silicon solution was added to a circulation grinder, the grinding medium was alumina beads with a particle size of 0.1 mm, and 1.5% of the total amount of the silicon solution was added as a cetyltrimethylammonium bromide ion dispersant during the grinding process. The nanosilicon was obtained after 10 hours of grinding at a temperature of 25°C.

[0063] The button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing, which is recorded in Table 1.

[0064] Example 2 ​

[0065] 40 grams of spherical silicon powder with a particle size of about 1000 um was dried at 100°C;

[0066] The dried silicon powder and 4 grams of polytetrafluoroethylene were added to 100 ml of an ethanol solution containing 2 grams of γ-aminopropyl triethoxysilane;

[0067] The mixture solution was stirred at a high speed of 1200 rpm for 24 hours at room temperature to obtain a uniformly dispersed mixed solution;

[0068] The ethanol reagent in the mixed solution was removed by a vacuum filter, and the obtained powder was dried in a vacuum constant temperature drying oven at 100°C to obtain modified silicon powder;

[0069] The modified silicon powder was mixed with an aqueous solution dispersant containing γ-aminopropyl triethoxysilane and polytetrafluoroethylene to form a grinding slurry, the grinding slurry was added to a nano grinder, and the grinding was carried out at room temperature for 24 hours, and the obtained grinding slurry was dried in a vacuum constant temperature drying oven at 100°C to obtain nano silicon powder.

[0070] The button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing and recorded in Table 1.

[0071] Example 3

[0072] 40 grams of spherical silicon powder with a particle size of about 50 um was dried at 100°C;

[0073] The dried silicon powder and 2 grams of polytetrafluoroethylene were added to 100 ml of an ethanol solution containing 2 grams of γ-aminopropyl triethoxysilane;

[0074] The mixture solution was stirred at a high speed of 1200 rpm for 24 hours at room temperature to obtain a uniformly dispersed mixed solution;

[0075] The ethanol reagent in the mixed solution was removed by a vacuum filter, and the obtained powder was dried in a vacuum constant temperature drying oven at 100°C to obtain modified silicon powder;

[0076] The modified silicon powder was mixed with an aqueous solution dispersant containing γ-aminopropyl triethoxysilane and polytetrafluoroethylene to form a grinding slurry, the grinding slurry was added to a nano grinder, and the grinding was carried out at room temperature for 24 hours, and the obtained grinding slurry was dried in a vacuum constant temperature drying oven at 100°C to obtain nano silicon powder.

[0077] The button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing and recorded in Table 1.

[0078] Example 4

[0079] 40 grams of spherical silicon powder with a particle size of about 100 um was dried at 100°C;

[0080] The dried silicon powder and 4 grams of polytetrafluoroethylene were added to 100 ml of an ethanol solution containing 0.04 grams of γ-aminopropyl triethoxysilane;

[0081] The mixture solution was stirred at a high speed of 1200 rpm for 24 hours at room temperature to obtain a uniformly dispersed mixed solution;

[0082] The ethanol reagent in the mixed solution was removed by a vacuum filter, and the obtained powder was placed in a vacuum constant temperature drying oven for drying treatment at 100°C to obtain modified silicon powder;

[0083] The modified silicon powder was mixed with an aqueous solution dispersant containing γ-aminopropyl triethoxysilane and polytetrafluoroethylene to form a grinding slurry, the grinding slurry was added to a nano grinder, and the grinding was carried out at room temperature for 24 hours, and the obtained grinding slurry was placed in a vacuum constant temperature drying oven for drying at 100°C to obtain nano silicon powder.

[0084] The button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing and recorded in Table 1.

[0085] Example 5

[0086] 40 grams of spherical silicon powder with a particle size of about 100 um was dried at 100°C;

[0087] The dried silicon powder and 4 grams of polytetrafluoroethylene were added to 100 ml of an ethanol solution containing 2 grams of γ-aminopropyl triethoxysilane;

[0088] The mixture solution was stirred at a high speed of 500 rpm for 24 hours at room temperature to obtain a uniformly dispersed mixed solution;

[0089] The ethanol reagent in the mixed solution was removed by a vacuum filter, and the obtained powder was placed in a vacuum constant temperature drying oven for drying treatment at 100°C to obtain modified silicon powder;

[0090] The modified silicon powder was mixed with an aqueous solution dispersant containing γ-aminopropyl triethoxysilane and polytetrafluoroethylene to form a grinding slurry, the grinding slurry was added to a nano grinder, and the grinding was carried out at room temperature for 24 hours, and the obtained grinding slurry was placed in a vacuum constant temperature drying oven for drying at 100°C to obtain nano silicon powder.

[0091] The button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing and recorded in Table 1.

[0092] Example 6

[0093] 40 grams of spherical silicon powder with a particle size of about 100 um was dried at 100°C;

[0094] The dried silicon powder and 4 grams of polytetrafluoroethylene were added to 100 ml of an ethanol solution containing 2 grams of γ-aminopropyl triethoxysilane;

[0095] The mixture solution was stirred at a high speed of 1200 rpm for 1 hour at room temperature to obtain a uniformly dispersed mixture solution;

[0096] The ethanol reagent in the mixture solution was removed by a vacuum filter, and the obtained powder was dried in a vacuum constant temperature drying oven at 100°C to obtain modified silicon powder;

[0097] The modified silicon powder was mixed with an aqueous solution dispersant containing γ-aminopropyl triethoxysilane and polytetrafluoroethylene to form a grinding slurry, the grinding slurry was added to a nano grinder, and the grinding was performed at room temperature for 24 hours, and the obtained grinding slurry was dried in a vacuum constant temperature drying oven at 100°C to obtain nano silicon powder.

[0098] The button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing and recorded in Table 1.

[0099] Example 7

[0100] 40 grams of spherical silicon powder with a particle size of about 100 um was dried at 100°C;

[0101] The dried silicon powder and 4 grams of polytetrafluoroethylene were added to 100 ml of an ethanol solution containing 2 grams of γ-aminopropyl triethoxysilane;

[0102] The mixture solution was stirred at a high speed of 1200 rpm for 1 hour at room temperature to obtain a uniformly dispersed mixture solution;

[0103] The ethanol reagent in the mixture solution was removed by a vacuum filter, and the obtained powder was dried in a vacuum constant temperature drying oven at 100°C to obtain modified silicon powder;

[0104] The modified silicon powder was mixed with an aqueous solution dispersant containing γ-aminopropyl triethoxysilane and polytetrafluoroethylene to form a grinding slurry, the grinding slurry was added to a nano grinder, and the grinding was performed at room temperature for 24 hours, and the obtained grinding slurry was dried in a vacuum constant temperature drying oven at 100°C to obtain nano silicon powder.

[0105] The button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing and recorded in Table 1.

[0106] Example 8

[0107] The 40 grams of spherical silicon powder with a particle size of about 100 um was dried at 60°C;

[0108] The dried silicon powder and 4 grams of polytetrafluoroethylene were added to 100 ml of an ethanol solution containing 2 grams of γ-aminopropyltriethoxysilane;

[0109] The mixture solution was stirred at a high speed of 1200 rpm for 24 hours at room temperature to obtain a uniformly dispersed mixed solution;

[0110] The ethanol reagent in the mixed solution was removed by a vacuum filter, and the obtained powder was placed in a vacuum constant temperature drying oven for drying treatment at 60°C to obtain modified silicon powder;

[0111] The modified silicon powder was mixed with an aqueous solution dispersant containing γ-aminopropyltriethoxysilane and polytetrafluoroethylene to form a grinding slurry, the grinding slurry was added to a nano grinder, and the grinding was performed at room temperature for 24 hours, and the obtained grinding slurry was placed in a vacuum constant temperature drying oven for drying at 60°C to obtain nano silicon powder.

[0112] The button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing and recorded in Table 1.

[0113] Example 9

[0114] The 40 grams of spherical silicon powder with a particle size of about 100 um was dried at 100°C;

[0115] The dried silicon powder and 4 grams of polytetrafluoroethylene were added to 100 ml of an ethanol solution containing 2 grams of γ-aminopropyltriethoxysilane;

[0116] The mixture solution was stirred at a high speed of 1200 rpm for 24 hours at room temperature to obtain a uniformly dispersed mixed solution;

[0117] The ethanol reagent in the mixed solution was removed by a vacuum filter, and the obtained powder was placed in a vacuum constant temperature drying oven for drying treatment at 100°C to obtain modified silicon powder;

[0118] The modified silicon powder was mixed with an aqueous solution dispersant containing γ-aminopropyltriethoxysilane and polytetrafluoroethylene to form a grinding slurry, the grinding slurry was added to a nano grinder, and the grinding was performed at room temperature for 24 hours, and the obtained grinding slurry was placed in a vacuum constant temperature drying oven for drying at 100°C to obtain nano silicon powder.

[0119] A button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing and recorded in Table 1.

[0120] Example 10

[0121] The 40 grams of spherical silicon powder with a particle size of about 100 um was dried at 100°C;

[0122] The dried silicon powder and 4 grams of polyperfluoroethylene propylene were added to 100 ml of an ethanol solution containing 2 grams of γ-aminopropyl triethoxysilane and γ-aminopropyl methyl diethoxysilane;

[0123] The mixture solution was stirred at a high speed of 1200 revolutions per minute for 24 hours at room temperature using a stirrer to obtain a uniformly dispersed mixture solution;

[0124] The ethanol reagent in the mixture solution was removed by a vacuum filter press, and the obtained powder was placed in a vacuum constant temperature drying oven for drying treatment at 100°C to obtain modified silicon powder;

[0125] The obtained modified silicon powder was mixed with an aqueous solution dispersant containing γ-aminopropyl triethoxysilane, γ-aminopropyl methyl diethoxysilane and polyperfluoroethylene propylene to form a grinding slurry, the grinding slurry was added to a nano grinder, and the grinding was performed at room temperature for 24 hours, and the obtained grinding slurry was placed in a vacuum constant temperature drying oven for drying at 100°C to obtain nano silicon powder.

[0126] A button cell was assembled according to the method of Example 1 above, and its electrochemical performance was evaluated by testing and recorded in Table 1.

[0127] Serial number Charge specific capacity (mAh / g) First cycle efficiency (%) Example 1 3307.35 92.91 Example 2 3266.14 92.76 Example 3 3257.92 92.23 Example 4 3203.03 92.94 Example 5 3203.69 92.98 Example 6 3226.94 92.27 Example 7 3244.31 92.25 Example 8 3269.42 92.15 Example 9 3256.04 92.18 Example 10 3359.71 92.18 Comparative Example 1 2666.10 76.83 Comparative Example 2 3409.51 93.09

[0128] Table 1

[0129] As can be seen from the comparative example 1 and the example, the nano silicon powder material prepared by using the present application has a higher specific capacity and a first cycle efficiency than water-based grinding. As can be seen from the comparative example 2, the material obtained by water-based grinding of the present application can almost achieve the effect of the material obtained by organic solvent grinding, but at the same time, it can solve the problems of high cost, serious environmental pollution, high operation requirement, easy combustion and explosion caused by improper operation and the like. The water-based grinding using the present method can achieve a level comparable to organic grinding, and the water-based grinding is simple, efficient, safe and pollution-free to the environment.

[0130] The modified method for protecting the water-based ground silicon surface provided by the embodiment of the present application connects silicon with a hydrophobic compound by using a silane coupling agent to modify the surface of silicon, so that the surface of silicon has hydrophobicity and will not react with water to generate hydrogen gas during grinding. Compared with the preparation method using other dispersants for grinding, the present application is more simple and efficient, and can avoid the pollution to the environment caused by the use of organic solvents, and the risk of combustion and explosion that may occur during the preparation process.

[0131] The above specific embodiments further explain the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A modified method for the protection of water-based ground silicon surfaces, characterized by, The modification method comprises: The silicon powder to be treated is subjected to drying treatment; The silicon powder after drying treatment and a hydrophobic compound are added into an organic solvent containing a silane coupling agent to form a mixed solution by stirring; wherein the hydrophobic compound is grafted onto the surface of the silicon powder in a chemical bond manner by bridging action of the silane coupling agent, so as to form a hydrophobic layer on the surface of the silicon powder; The organic solvent in the mixed solution is removed to obtain a powder material; The powder material is placed into a vacuum constant-temperature drying box for drying treatment to obtain a preliminarily modified silicon powder; The preliminarily modified silicon powder is mixed with an aqueous solution dispersant containing a silane coupling agent and a hydrophobic compound to form a grinding slurry, and the grinding slurry is added into a grinding device for grinding at room temperature, and the ground material is subjected to drying treatment to obtain a modified nano-silicon powder.

2. The modification method according to claim 1, characterized in that, The hydrophobic compound comprises one or more of polyfluoroethylene propylene, polytetrafluoroethylene, polyvinylidene fluoride, polytrifluorochloroethylene, polyolefin, polycarbonate, polyamide, polyacrylonitrile. The silane coupling agent comprises one or more of γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane.

3. The modification method of claim 1, wherein, The organic solvent comprises one or more of alcohol with a concentration of 80%-99%, methanol, acetone, carbon tetrachloride, isopropyl alcohol, pentane, hexane, cyclohexanone, dichlorobenzene, dichloromethane, methyl acetate.

4. The modification method of claim 1, wherein The mass ratio of the silicon powder, the silane coupling agent and the hydrophobic compound in the mixed solution is 1: (0.01-0.05); (0.05-0.1).

5. The modification method of claim 1, wherein The stirring speed is 500 revolutions / minute-1200 revolutions / minute; the temperature for stirring to form the mixed solution is room temperature, and the pH of the formed mixed solution is 5-7.

6. The modification method of claim 1, wherein The grinding device comprises any one of a nano sand mill, a ball mill and a disperser, and the grinding time is 8-24 hours; the grinding medium comprises at least one of silicon nitride beads, zirconium oxide beads and aluminum oxide beads, and the particle size of the grinding medium is 0.1-0.5 mm.

7. The modification method of claim 1, wherein The drying treatment method comprises at least one of spray drying, boiling drying, normal pressure drying, reduced pressure drying and freeze drying, the drying treatment temperature is 60°C-100°C, and the drying treatment time is 1-24 hours.

8. The modification method of claim 1, wherein, The silicon powder to be treated is a spherical material with a particle size of 50um-1000um.

9. The modification method of claim 1, wherein, After the mixed solution is formed by stirring, the method further comprises adding a hydrolysis catalyst into the mixed solution.

10. The modification method of claim 1, wherein After the grinding slurry is formed, the method further comprises adding a hydrolysis catalyst into the grinding slurry.

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