KR102201589B1 - Preparation method of hollow silicon-based particles - Google Patents

Abstract

The method for producing hollow silicon-based particles according to an embodiment of the present invention includes mixing hollow SiO ₂ , NaCl, and magnesium using an acoustic mixer, and mixing the mixture at a temperature of 600° C. to 900° C. Calcining for a period of time to prepare a composite, calcining, washing, and centrifuging the composite to remove by-products, and drying the composite from which the by-product has been removed.

Description

Manufacturing method of hollow silicon-based particles {PREPARATION METHOD OF　 HOLLOW SILICON-BASED PARTICLES}

The present invention relates to a method for producing hollow silicon-based particles.

Recently, a lithium secondary battery, which has been in the spotlight as a power source for portable small electronic devices, is a battery that exhibits a high energy density by showing a discharge voltage that is twice as high as that of a battery using an aqueous alkaline solution using an organic electrolyte.

Although graphite is mainly used as a negative electrode material for a lithium secondary battery, graphite has a small capacity per unit mass of 372 mAh/g, and it is difficult to increase the capacity of a lithium secondary battery.

A negative active material exhibiting a higher capacity than graphite, for example, a material electrochemically alloyed with lithium such as silicon, tin and oxides thereof (lithium alloying material) has a high capacity of about 1000 mAh/g or more and a low of 0.3 to 0.5 V. It has been in the spotlight as a negative active material for lithium secondary batteries due to its charging/discharging potential.

However, when these materials are electrochemically alloyed with lithium, there is a problem in that the volume expands by causing a change in the crystal structure. In this case, there is a problem that the capacity of the lithium secondary battery greatly decreases due to the progress of the charge/discharge cycle due to the loss of physical contact between the active material of the electrode manufactured by coating the powder or between the active material and the current collector during charging and discharging.

Accordingly, in order to increase the capacity of a lithium secondary battery, a new development of a silicon-based material capable of effectively controlling a change in volume is required, and capacity, efficiency, and cycle life characteristics must be satisfied to replace the existing negative electrode.

An object of the present invention is to provide a method for producing hollow silicon-based particles suitable for mass production and having a low oxygen content.

In order to solve these problems, the method of manufacturing hollow silicon-based particles according to an embodiment of the present invention includes mixing hollow SiO ₂ , NaCl, and magnesium using an acoustic mixer, and mixing the mixture at 600°C to 900°C. Calcining at a temperature for 2 to 4 hours to prepare a composite, calcining, washing, and centrifuging the composite to remove by-products, and drying the composite from which the by-product has been removed.

The prepared hollow silicon-based particles are SiOx, and x may be less than 0.45.

Mixing using the acoustic mixer may be performed for 30 seconds to 10 minutes.

The hollow SiO ₂ is a step of producing the hollow SiO ₂ by stirring a TEOS (tetraethyl orthosilicate) in Polysterene dispersion mixing, drying and calcination steps, the obtained PS @ SiO ₂ particles to give a PS @ SiO ₂ particles Can be manufactured with

In the step of mixing the hollow SiO ₂ , NaCl and magnesium using an acoustic mixer, the content ratio of the hollow SiO ₂ : NaCl: magnesium may be in a weight ratio of 1:2:0.5 to 1:30:5.

In the step of removing by-products by calcination, washing, and centrifugation of the composite, the calcination process is performed at a temperature of 400°C to 500°C for 4 to 6 hours, and Mg ₂ Si can be removed through the process. have.

In the step of calcination, washing, and centrifugation of the compound to remove by-products, the washing and centrifugation are repeatedly performed until the pH of the supernatant is 6 to 8, and NaCl may be removed through the above process.

According to embodiments, a method for producing hollow silicon-based particles suitable for mass production and having a low oxygen content is provided.

1 shows the oxygen content of the final product according to the experimental and comparative examples of the present invention.

A method of manufacturing hollow silicon-based particles according to an embodiment of the present invention will be described in detail.

The method for producing hollow silicon-based particles according to an embodiment of the present invention includes mixing hollow SiO ₂ , NaCl, and magnesium using an acoustic mixer, and mixing the mixture at a temperature of 600° C. to 900° C. Calcining for a period of time to prepare a composite, calcining, washing, and centrifuging the composite to remove by-products, and drying the composite from which the by-product has been removed.

First, hollow SiO ₂ , NaCl, and magnesium are mixed using an acoustic mixer.

At this time, the hollow SiO ₂ mixing and stirring TEOS (tetraethyl orthosilicate) in a polysterene dispersion to obtain PS@SiO ₂ particles; And drying and calcining the resulting PS @ SiO ₂ particles can be prepared by a process comprising the step of producing the hollow SiO _2. PS @ SiO ₂ particles herein means the PS particles to the sphere ₂ SiO- Shell located outside. In other words, it is a particle surrounded by SiO ₂ Shell outside the spherical polysterene particle.

For example, hollow SiO ₂ may be prepared in the following manner.

3.75 Polyvinylpyrrolidone (PVA) and 1.3 g of the initiator AIBA (2,2'-azobis(2-methylpropionamidine) dihydrochloride) were dissolved in 250 g of tertiary distilled water and heated to 70 degrees Celsius. When the PVA and initiator are completely dissolved and the reaction temperature reaches 70°C, 25 g of stylene is added dropwise and stirred for 15 hours. A sufficient amount of ethanol was added to the synthesized PS (Polystylene), mixed well, centrifuged at 14000 rpm for 20 minutes, and then the clear supernatant was decanted. After washing the PS by performing these washing, centrifugation and decantation processes twice, 1 g of PS was dispersed in 70 ml of ethanol and 4 ml of tertiary distilled water, 4 ml of ammonia aqueous solution was added, and 7 ml of TEOS (tetraethyl orthosilicate) was added. ) Was added dropwise and stirred for 4 hours. Then, the solution is centrifuged to obtain PS@SiO ₂ particles. The obtained PS@SiO ₂ particles are dried at 70°C and then calcined at 700°C for 4 hours to obtain hollow SiO ₂ .

However, the manufacturing method is an example, and the hollow SiO ₂ may be prepared by a conventional method known to those skilled in the art.

In this step, the hollow SiO ₂ , NaCl, and magnesium are mixed using an acoustic mixer. When the reaction raw material is mixed with an acoustic mixer, the content of oxygen in the finally produced hollow silicon-based particles can be lowered than when the reaction raw material is mixed using a conventional rotary evaporator.

This is because the acoustic mixer does not use a solvent such as water and mixes raw materials in a dry manner. That is, in the case of the rotary evaporator, a solvent such as water is used to mix raw materials, but the acoustic mixer can reduce the oxygen content because it is possible to mix the reaction raw materials without a solvent.

When the oxygen content of the hollow silicon-based particles is increased, there is a problem that the efficiency of the secondary battery manufactured by applying the silicon-based particles having a high oxygen content is lowered. However, the hollow silicon-based particles according to an embodiment of the present invention are Since an acoustic mixer is used, it is possible to control the amount of oxygen in the hollow silicon-based particles to be produced. Therefore, in the case of manufacturing a secondary battery by applying such hollow silicon-based particles, efficiency can be improved.

In this step, mixing using the acoustic mixer may be performed for 30 seconds to 10 minutes.

If the mixing time is less than 30 seconds, there may be a problem of insufficient mixing of the reaction raw materials, and if the mixing time exceeds 10 minutes, the acoustic mixer may be overheated and there may be a problem that is not economical.

In this step, the content ratio of the hollow SiO ₂ : NaCl: magnesium may be in a weight ratio of 1:2:0.5 to 1:30:5. For example, the content ratio of hollow SiO ₂ : NaCl: magnesium may be 1:10:1 by weight.

In this way, when raw materials (hollow SiO ₂ , NaCl, magnesium) are mixed with an acoustic mixer, the content of oxygen in the finally generated hollow silicon-based particles can be reduced. That is, the hollow silicon-based particles manufactured by the present invention are SiOx, and x may be less than 0.45.

Next, the mixture is calcined at a temperature of 600°C to 900°C for 2 to 4 hours to prepare a composite. The calcination may be performed in an Ar atmosphere by placing the mixture in a SiC crucible. For example, the calcination may be performed at 700 degrees C for 3 hours.

Next, the compound is calcined, washed, and centrifuged to remove by-products. At this time, calcination in this step is a process for removing Mg ₂ Si, a by-product of the magnesium thermal reduction method. The calcination in this step can take place at a lower temperature than the calcination in the previous step.

The calcination process may be performed at a temperature of 400°C to 500°C for 4 to 6 hours. For example, the calcination process may be performed at 450°C for 5 hours.

The washing may be performed using distilled water, and the by-product salt may be removed by repeating centrifugation and decantation after washing with distilled water. For example, a sufficient amount of tertiary distilled water is added to the composite from which Mg ₂ Si has been removed through the calcination process, mixed well, centrifuged at 4000 rpm for 10 minutes, and then the clear supernatant is decanted. Salt can be removed by repeating this process twice.

Washing, centrifugation, and decantation processes are repeated for the salt-removed composite to remove MgO and Mg ₂ Si. For example, after adding a little water to the salt-removed composite to make a slurry, the slurry may be centrifuged at 10000 rpm for 8 minutes after adding a sufficient amount of tertiary distilled water to a 1M hydrochloric acid aqueous solution, mixing well. The supernatant at the next pH level of 1 is decanted, and such washing, centrifugation, and decantation processes can be repeated until the pH of the supernatant reaches the level of 7. That is, through this process, the composite can be neutralized.

By-products are removed from the composite through the above steps.

Next, the by-product is removed and the composite is dried. For example, drying may be performed by adding ethanol to the neutralized compound in the previous step, mixing well, centrifuging at 14000 rpm for 10 minutes to remove the supernatant, and drying in a vacuum oven at 70°C.

Through this step, hollow silicon-based particles are obtained. In the hollow silicon-based particles, since the reaction raw material is mixed using an acoustic mixer, the oxygen content of the finally prepared hollow silicon-based particles is lowered. That is, the hollow silicon-based particles manufactured by the method according to an embodiment of the present invention are SiOx, and x may be less than 0.45.

In addition, since the present manufacturing method uses an acoustic mixer to mix the reaction raw materials, it is advantageous for mass production compared to a rotary evaporator. This is because the acoustic mixer is an equipment that can easily mix a large amount of raw materials.

Hereinafter, a method of manufacturing a hollow silicon-based particle according to an embodiment of the present invention and its effect will be described through specific experimental examples and comparative examples.

Experimental example One: Acoustic Mixer_700

3.75 g of PVP (polyvinylpyrrolidone) and 1.3 g of the initiator AIBA (2,2'-azobis (2-methylpropionamidine) dihydrochloride) were dissolved in 250 g of tertiary distilled water and heated to 70. When PVP and initiator are completely dissolved and the reaction temperature reaches 70, 25 g of stylene is added dropwise and stirred for 15 hours. A sufficient amount of ethanol was added to the synthesized PS (polystylene), mixed well, centrifuged at 14000 rpm for 20 minutes, and then the clear supernatant was decanted. After washing the PS by performing these washing, centrifugation and decantation processes twice, 1 g of PS was dispersed in 70 ml of ethanol and 4 ml of tertiary distilled water, 4 ml of ammonia aqueous solution was added, and 7 ml of TEOS (tetraethyl orthosilicate) was added dropwise. After stirring for 4 hours, the solution was centrifuged to obtain PS@SiO ₂ particles. The PS@SiO ₂ particles thus obtained were dried at 70 and calcined at 700 for 4 hours to obtain hollow SiO ₂ .

Next, 2.5 g of hollow SiO ₂ , 25 g of salt, and 2.5 g of magnesium were well mixed using an acoustic mixer. The synthetic raw material thus prepared was put in a SiC crucible and calcined for 700, 3 hours in an Ar atmosphere. The synthesized product thus prepared is calcined for 450 to 5 hours to remove Mg ₂ Si, a by-product of the magnesium thermal reduction method. A sufficient amount of tertiary distilled water was added to the synthetic product obtained by calcining, mixed well, centrifuged at 4000 rpm for 10 minutes, and the clear supernatant was decanted. These washing, centrifugation and decantation processes are performed twice to remove salt. A little water was added to the salt-removed synthetic product to make a slurry, and the slurry was slowly titrated in 1M aqueous hydrochloric acid solution and reacted for 6 hours to remove MgO and Mg ₂ Si. A sufficient amount of tertiary distilled water was added to the obtained Si 1M hydrochloric acid aqueous solution, mixed well, centrifuged at 10000 rpm for 8 minutes, and then the supernatant at pH 1 level was decanted. This washing, centrifugation, and decantation process was repeated until the pH of the supernatant reached a level of 7. The neutralized synthetic product was finally mixed with ethanol and then centrifuged at 14000 rpm for 10 minutes to remove the supernatant, and then dried overnight in a vacuum oven at 70 to obtain a final product.

Experimental example 2: Acoustic Mixer_800

In Experimental Example 1, the synthetic raw materials were put in a SiC crucible and instead of calcined for 700 and 3 hours in an Ar atmosphere, the synthetic raw materials were placed in a SiC crucible and calcined for 800 and 3 hours in an Ar atmosphere. It carried out in the same manner to obtain a final product.

Comparative example 1: Rotary evaporator

Instead of mixing 2.5 g of hollow SiO ₂ , 25 g of salt, and 2.5 g of magnesium using an acoustic mixer in Experimental Example 1, 2.5 g of hollow SiO _2, 25 g of salt, and 80 g of water were mixed using a rotary evaporator. The final product was obtained in the same manner as in Experimental Example 1, except that the mixture and 2.5 g of magnesium were mixed using a mortar.

The O/Si ratio of the hollow silicon-based particles obtained in Experimental Example 1 (Acoustic Mixer_700), Experiment 2 (Acoustic Mixer_800) and Comparative Example 1 (rotary evaporation concentrator) is shown in FIG. 1.

In addition, the reaction conditions in each of the experimental examples and comparative examples and the x value of SiOx are shown in Table 1.

Method of mixing reaction raw materials Reduction reaction conditions Partial oxidation reaction conditions X value of SiOx Experimental Example 1 Acoustic mixer 700 degrees Celsius, 3 hours 450 degrees Celsius, 5 hours 0.44 Experimental Example 2 Acoustic mixer 800 degrees Celsius, 3 hours 450 degrees Celsius, 5 hours 0.40 Comparative Example 1 Rotary evaporator 700 degrees Celsius, 3 hours 450 degrees Celsius, 5 hours 0.50

As can be seen from Table 1 and FIG. 1, the SiOx values of Experimental Examples 1 and 2 using an acoustic mixer as a mixing method were compared to Comparative Example 1 using a rotary evaporator as a mixing method, It could be confirmed that it was lower. This is because when an acoustic mixer is used compared to a rotary evaporator, the raw materials are mixed dry without using a solvent such as water.

That is, it was confirmed that the manufacturing method according to the exemplary embodiment of the present invention can produce hollow silicon-based particles having an x value of SiOx of 0.45 or less.

As described above, the manufacturing method according to an embodiment of the present invention uses an acoustic mixer as a method of mixing reaction raw materials, so that it is suitable for mass production and lowers the oxygen content of the final product.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It belongs to the scope of rights of

Claims (7)

Hollow SiO ₂ , NaCl, magnesium is prepared by using an acoustic mixer to prepare a mixture, the mixture is mixed in a dry state that does not contain a solvent;
Calcining the mixture at a temperature of 600° C. to 900° C. for 2 to 4 hours to prepare a composite;
Calcining the compound at a temperature of 400° C. to 500° C. for 4 to 6 hours to remove a first by-product from the compound;
Washing and centrifuging the compound from which the first by-product has been removed to remove the second by-product;
Including; drying the composite from which the second by-product has been removed to obtain hollow silicon-based particles; and
The first by-product includes magnesium silicide (Mg ₂ Si),
The second by-product includes magnesium oxide (MgO) and sodium chloride (NaCl),
The hollow silicon-based particle is SiO _x , and x is 0<x<0.45. delete In claim 1,
Mixing using the acoustic mixer is performed for 30 seconds to 10 minutes, a method for producing hollow silicon-based particles. In claim 1,
The hollow SiO ₂ mixing and stirring TEOS (tetraethyl orthosilicate) in a polysterene dispersion to obtain PS@SiO ₂ particles;
The method for producing hollow silicon-based particles prepared by drying and calcining the obtained PS@SiO ₂ particles to prepare hollow SiO ₂ . In claim 1,
In the step of mixing the hollow SiO ₂ , NaCl and magnesium using an acoustic mixer,
The hollow SiO ₂ : NaCl: magnesium content ratio is 1:2:0.5 to 1:30:5 weight ratio of the hollow silicon-based particle manufacturing method. In claim 1,
The second by-product further comprises magnesium silicide (Mg ₂ Si) not removed in the step of removing the first by-product. In claim 1,
In the step of removing the second by-product,
The washing and centrifugation are repeatedly performed until the pH of the supernatant is 6 to 8,
Method for producing hollow silicon-based particles in which sodium chloride (NaCl) is removed through the above process.

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