CN106744973B - Method for preparing amorphous silicon nano material by ultrasonic chemistry - Google Patents

Abstract

The invention discloses a method for sonochemically preparing amorphous silicon nanomaterials. The method is to prepare amorphous silicon nanomaterials by using silicon dioxide and sodium fluoride aqueous solution under the action of ultrasound: first, the fluoride reacts with solid silicon dioxide Generate water-soluble fluorosilicate ions; then use the cavitation effect of water under the action of ultrasonic waves to decompose hydrogen free radicals and hydroxyl free radicals; finally decompose hydrogen free radicals to reduce fluorosilicate ions in water to obtain Amorphous elemental silicon nanomaterials. In the process of preparing elemental silicon, fluoride acts as a catalyst and can be recycled, and silicon dioxide and water participate in the reaction. The invention adopts a relatively mild and safe sonochemical method to synthesize elemental silicon nanometer material. The preparation method has simple equipment, low energy consumption, rapid synthesis and safe process.

Description

A method for preparing amorphous silicon nanomaterials by sonochemistry

technical field

The invention belongs to the technical field of battery materials, and in particular relates to a method for sonochemically preparing amorphous silicon nanometer materials.

Background technique

At present, elemental silicon has very important applications in the fields of materials, information and energy, and its demand continues to expand with the development of the solar photovoltaic industry. Due to the increasing demand for high-capacity, long-life batteries for mobile electronic devices, people have put forward higher requirements for the performance of lithium-ion batteries. The low capacity of lithium-ion batteries has become a bottleneck restricting the development of the battery industry, and finding anode materials with higher specific capacity has become an important development direction in the field of battery materials. The current commercial negative electrode material is carbon. Since the commercialization of lithium-ion batteries, the research on carbon materials has made great progress, and it is difficult to have room for improvement. Therefore, finding alternative carbon anode materials has become an important development direction. Among the many alternative negative electrode materials, silicon has attracted much attention because of its high specific capacity (theoretical value: 4200mAh/g) and low lithium extraction and extraction voltage.

The patent application number is 201010567832.3 discloses a preparation method of elemental silicon, dissolving _SiO2 in chloride molten salt containing alkali metal or alkaline earth metal oxide, or dissolving alkali metal or alkaline earth metal silicate in chlorine In the chloride molten salt, the temperature of the chloride molten salt is 600-1000 ^o C, the electrolysis is performed with graphite or silicon or metal as the cathode and graphite or inert material as the anode, so that the electrodeposition of silicate occurs at the cathode, and the electrodeposition The deposited product is separated to obtain elemental silicon. However, this invention also needs to refine silicon by electrodeposition, which is a complicated method.

Contents of the invention

Aiming at the defects in the practical application of the traditional method for preparing elemental silicon, the present invention proposes a method for the sonochemical preparation of amorphous silicon nanomaterials, through the reaction of silicon dioxide and fluoride aqueous solution, and the generation of elemental silicon nanomaterials under the action of ultrasound . Compared with the currently commonly used method for preparing silicon simple substance, sonochemical method is a mild, safe and green method for preparing silicon nanomaterials.

The invention specifically discloses a method for ultrasonically preparing amorphous silicon nanometer materials. Under the action of ultrasonic waves and catalysts, silicon sources and water are reacted to generate amorphous silicon nanometer materials. Sonochemistry is a method of chemical reaction using high-intensity ultrasonic waves (20k-10MHz). Sonochemistry is mainly derived from ultrasonic cavitation, the physical and chemical phenomena caused by the formation, oscillation, growth, shrinkage and collapse of liquid cavitation bubbles. The liquid ultrasonic cavitation process is the process of concentrating the energy of the sound field and releasing it rapidly. When the cavitation bubble collapses, a high temperature above 5000K and a high pressure of about 5.05×10 ⁸ Pa are generated in a very short time. Localized high temperature and high pressure can lead to the recombination of chemical bonds between precursors and solvents, thereby generating reactive free radicals, which serve as intermediates for the formation of final stable nanomaterials. These free radical intermediates are either derived from the solvent or from the added stabilizer molecules. Water is used as a solvent. Under the action of ultrasound, water is decomposed into hydrogen radicals and hydroxyl radicals. Hydrogen radicals are reductive and can Shows a unique activity to reduce the precursor, so as to obtain the desired target product.

Preferably, the catalyst is a fluoride.

Any of the above schemes preferably includes the following steps:

Step (a), preparation of reaction solution: choose water as solvent, dissolve fluoride, add silicon source, and configure into a solution;

Step (b), generating amorphous silicon nanomaterials: ultrasonically sonicate the solution prepared above, then perform centrifugation, and place in a 60°C drying oven to obtain it. Centrifuge for 10 minutes at 8000 rpm.

Preferably, in any of the above schemes, the silicon source in the step (a) is silicon dioxide, and the fluoride is sodium fluoride and/or potassium fluoride.

Preferably, in any of the above schemes, the molar ratio of the silicon source to the fluoride in the step (a) is 1:6-1:24.

Preferably, in any of the above schemes, the temperature during ultrasonication in the step (b) is 50-90°C, the ultrasonic time is 1-4h, the ultrasonic frequency is 20-50 kHz, and the ultrasonic power is 100-800W.

The beneficial effects of the present invention are as follows: The present invention discloses a method for preparing amorphous silicon nanomaterials by sonochemistry, which is to prepare amorphous silicon nanomaterials by using silicon dioxide and sodium fluoride aqueous solution under ultrasonic action: first, fluorine The compound reacts with solid silicon dioxide to generate water-soluble fluorosilicate ions; then, the cavitation generated by water under the action of ultrasonic waves is used to decompose hydrogen free radicals and hydroxyl free radicals; the final decomposed hydrogen free radicals are reduced to Fluorosilicate ions in water yield amorphous elemental silicon nanomaterials:

(1) Compared with the traditional hydrothermal reduction method and high-temperature reduction method for preparing elemental silicon, the present invention provides a new method for sonochemically preparing elemental silicon nanomaterials;

(2) The preparation method provided by the present invention is a horn-type sonochemical method, the preparation method has mild conditions, is green and safe, has simple equipment, low energy consumption, rapid synthesis and safe process.

Description of drawings

Fig. 1 is the infrared spectrogram of the amorphous silicon nano material sample prepared according to the method for preparing the amorphous silicon nano material by sonochemistry of the present invention.

Fig. 2 is a high-resolution transmission electron microscope image of an amorphous silicon nanomaterial sample prepared according to the method for preparing amorphous silicon nanomaterial by sonochemistry of the present invention.

Detailed ways

The following examples are a further description of the content of the present invention as an explanation of the technical content of the present invention, but the essential content of the present invention is not limited to the following examples, those of ordinary skill in the art can and should know any Simple changes or replacements of the essential spirit of the invention shall fall within the scope of protection required by the present invention.

Example 1

(1) Configuration of the reaction solution: Weigh 0.01 mole of silicon dioxide and 0.06 mole of sodium fluoride in a flat-bottomed flask, add 90ml of water to dissolve;

(2) Ultrasonic reaction solution: put the reaction solution in a horn-type ultrasonic device, set the temperature at 60°C, and the ultrasonic power at 700W. After ultrasonication for 4 hours, the product was centrifuged and dried in an oven at 60° C. to obtain a black product. As shown in Figure 1, Fig. 1 is the infrared spectrogram of the prepared amorphous silicon nanomaterial sample; In this figure, it can be clearly seen that the characteristic peak of the Si-Si bond occurs at about 500cm ^-1 , indicating that there is the presence of elemental silicon. As shown in Figure 2, Figure 2 is a high-resolution transmission electron microscope image of the prepared amorphous silicon nanomaterial sample; in this figure, it can be seen that the prepared sample has no obvious lattice fringes and is in an amorphous state.

Example 2

(1) Configuration of the reaction solution: weigh 0.01 mole of silicon dioxide and 0.06 mole of potassium fluoride in a flat-bottomed flask, add 90ml of water to dissolve;

(2) Ultrasonic reaction solution: put the reaction solution in a horn-type ultrasonic device, set the temperature at 60°C, and the ultrasonic power at 700W. After ultrasonication for 4 hours, the product was centrifuged and dried in an oven at 60° C. to obtain a black product.

Example 3

(1) Configuration of the reaction solution: Weigh 0.005 moles of silicon dioxide and 0.06 moles of sodium fluoride in a flat-bottomed flask, add 90ml of water to dissolve;

(2) Ultrasonic reaction solution: put the reaction solution in a horn type ultrasonic device, set the temperature at 80°C, and the ultrasonic power at 700W. After ultrasonication for 2 hours, the product was centrifuged and dried in an oven at 60° C. to obtain a black product.

Example 4

(1) Configuration of the reaction solution: Weigh 0.005 moles of silicon dioxide and 0.06 moles of sodium fluoride in a flat-bottomed flask, add 90ml of water to dissolve;

(2) Ultrasonic reaction solution: put the reaction solution in a horn-type ultrasonic device, set the temperature at 50°C, and ultrasonic power at 500W. After ultrasonication for 3 hours, the product was centrifuged and dried in an oven at 60° C. to obtain a black product.

Example 5

(1) Configuration of the reaction solution: Weigh 0.005 mole of silicon dioxide and 0.12 mole of sodium fluoride into a flat-bottomed flask, add 90ml of water to dissolve;

(2) Ultrasonic reaction solution: put the reaction solution in a horn type ultrasonic device, set the temperature at 60°C, and the ultrasonic power at 600W. After ultrasonication for 2 hours, the product was centrifuged and dried in an oven at 60° C. to obtain a black product.

Example 6

(1) Configuration of the reaction solution: Weigh 0.005 moles of silicon dioxide and 0.06 moles of sodium fluoride in a flat-bottomed flask, add 90ml of water to dissolve;

(2) Ultrasonic reaction solution: put the reaction solution in a horn type ultrasonic device, set the temperature at 90°C, and the ultrasonic power at 800W. After ultrasonication for 1 hour, the product was centrifuged and dried in an oven at 60° C. to obtain a black product.

Example 7

(1) Configuration of the reaction solution: Weigh 0.005 moles of silicon dioxide and 0.06 moles of potassium fluoride in a flat-bottomed flask, add 90ml of water to dissolve;

(2) Ultrasonic reaction solution: put the reaction solution in a horn type ultrasonic device, set the temperature at 80°C, and the ultrasonic power at 700W. After ultrasonication for 2 hours, the product was centrifuged and dried in an oven at 60° C. to obtain a black product.

Example 8

(1) Configuration of the reaction solution: Weigh 0.005 moles of silicon dioxide and 0.06 moles of potassium fluoride in a flat-bottomed flask, add 90ml of water to dissolve;

(2) Ultrasonic reaction solution: put the reaction solution in a horn-type ultrasonic device, set the temperature at 50°C, and ultrasonic power at 500W. After ultrasonication for 3 hours, the product was centrifuged and dried in an oven at 60° C. to obtain a black product.

Example 9

(1) Configuration of the reaction solution: Weigh 0.005 moles of silicon dioxide and 0.12 moles of potassium fluoride in a flat-bottomed flask, add 90ml of water to dissolve;

(2) Ultrasonic reaction solution: put the reaction solution in a horn type ultrasonic device, set the temperature at 60°C, and the ultrasonic power at 600W. After ultrasonication for 2 hours, the product was centrifuged and dried in an oven at 60° C. to obtain a black product.

Example 10

(1) Configuration of the reaction solution: Weigh 0.005 moles of silicon dioxide and 0.06 moles of potassium fluoride in a flat-bottomed flask, add 90ml of water to dissolve;

(2) Ultrasonic reaction solution: put the reaction solution in a horn type ultrasonic device, set the temperature at 90°C, and the ultrasonic power at 800W. After ultrasonication for 1 hour, the product was centrifuged and dried in an oven at 60° C. to obtain a black product.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (4)

1. a kind of method that sonochemistry prepares unformed silicon nano material, which is characterized in that in the work of ultrasonic wave and catalyst Under, is reacted by silicon source with water and generate unformed silicon nano material；The catalyst is fluoride；Specifically include the following steps:

The preparation of step (a), reaction solution: it selects water as solvent, dissolves fluoride, silicon source is added, is configured to solution；

Step (b) generates unformed silicon nano material: after carrying out ultrasound with solution of the ultrasonic method to above-mentioned configuration, being centrifuged Separation, being placed in 60 DEG C of drying boxes can obtain.

2. preparing the method for unformed silicon nano material as described in claim 1, which is characterized in that the silicon in the step (a) Source is silica, and fluoride is sodium fluoride and/or potassium fluoride.

3. preparing the method for unformed silicon nano material as described in claim 1, which is characterized in that silicon source in the step (a) Molar ratio with fluoride is 1:6-1:24.

4. preparing the method for unformed silicon nano material as described in claim 1, which is characterized in that ultrasonic in the step (b) When temperature be 50-90 DEG C, ultrasonic time 1-4h, supersonic frequency be 20-50 kHz, ultrasonic power 100-800W.