JPWO2015015795A1 - SiOX powder manufacturing method and SiOX powder manufacturing apparatus - Google Patents

Abstract

SiOx powder used as a negative electrode active material for lithium ion secondary batteries and a vapor barrier material for gas barrier film is continuously manufactured at a low cost. A step of heating and melting the mixed granulated powder of the metal Si powder and the SiO2 powder with a plasma flame, a step of causing the molten droplets of the heated and melted mixed granulated powder to vaporize in a heating furnace, and performing a SiOX conversion reaction; And a step of rapidly cooling the generated SiOx gas with an inert gas to precipitate SiOx fine powder.

Description

The present invention relates to a method and an apparatus for producing SiO _X powder used as a negative electrode active material for a lithium ion secondary battery and a vapor deposition material for a gas barrier film.

In recent years, with the remarkable development of portable electronic devices, communication devices, etc., high energy from the viewpoint of economy or miniaturization and weight reduction of devices, and also from the viewpoint of storage of electric vehicles, wind power generation, solar cells. There is a strong demand for the development of secondary batteries with high density and high capacity. Since lithium ion secondary batteries have a long life and a high capacity, they show a high demand growth in the power supply market.
A lithium ion secondary battery has a positive electrode, a negative electrode, and a separator impregnated with an electrolytic solution between the two electrodes, and is configured such that lithium ions reciprocate between the positive electrode and the negative electrode through the electrolytic solution by charging and discharging. ing.
For the negative electrode, an active material capable of occluding and releasing lithium ions (negative electrode active material) is used, and at present, a carbon-based negative electrode material is common.

However, the improvement in the energy density of the carbon-based negative electrode active material has reached its limit, and various negative electrode active materials have been developed with the aim of further improving the energy density. Among them, Si-based negative electrode active materials are attracting attention as very promising materials.
When metal Si is used for the negative electrode active material, the lithium ion storage capacity is about 10 times that of the carbon-based negative electrode active material. However, since the storage capacity is large, the volumetric expansion and contraction of metal Si during charge / discharge is large, and the cycle characteristics of charge / discharge are rapidly deteriorated due to cracks in the metal coating film.
Lithium ion storage capacity is lower than that of metal Si, but it is known that it is effective to use SiO as a material in which volume expansion / contraction during charge / discharge is small and charge / discharge cycle characteristics are unlikely to deteriorate.

However, SiO has different lithium ion storage capacity and volume expansion / contraction due to charge / discharge depending on the change of X value of SiO _X. Accordingly, there are various means for determining the optimum point, such as the blending ratio with the carbon-based negative electrode active material and the selection of the binder. In conjunction with this, a manufacturing means capable of arbitrarily controlling the X value of SiO _X is required.
In general, many of the preparation of SiO _X, to generate a SiO _X gas in a heating furnace, it is precipitated in the precipitation substrate produce SiO _X product bulk. This is pulverized and the particle diameter is adjusted to produce a negative electrode active material powder for a lithium ion secondary battery.
In order to produce a fine powder by this method, since the material input to the heating furnace and the recovery of the deposited SiO 2 _X are batch methods, the productivity is low. In addition, there are problems that the manufacturing cost in the step of pulverizing and adjusting the particle diameter is very high, and impurities are easily mixed during pulverization.

On the other hand, various techniques relating to a method for producing SiO _X have been proposed.
For example, Patent Document 1 discloses a method for producing silicon monoxide. In the manufacturing method disclosed in Patent Document 1, first, silicon metal powder is introduced into a plasma jet ejected into an atmospheric gas at a supply rate of 70 g / min or more using a carrier gas. Next, the silicon metal powder not vaporized in the plasma jet is brought into contact with oxygen gas contained in at least one of the carrier gas and the atmospheric gas to cause a synthesis reaction. Next, silicon monoxide vapor is continuously generated while maintaining the reaction frame generated in the synthesis reaction. Next, the crude product obtained by quenching the generated silicon monoxide vapor is distilled at 1,400 ° C. to 1,800 ° C. to obtain silicon monoxide.
Patent Document 2 discloses a method for producing SiO _x (X <1) used as a negative electrode active material for a lithium ion secondary battery and a vapor deposition material for a gas barrier film. In the manufacturing method of Patent Document 2, first, a mixed raw material composed of metal Si powder and SiO ₂ powder or SiO powder is vaporized by plasma heating to form SiO gas. Next, after depositing as silicon oxide SiO _X (X <1) on the deposition substrate, it was crushed by a ball mill to obtain powdered silicon oxide.

In the field of processing food packaging, medical products, and pharmaceuticals, the packaging material is required to have high gas barrier properties so that oxygen and moisture do not permeate the packaging material in order to prevent deterioration of the food, pharmaceuticals, and the like.
In recent years, a packaging material having a SiO vapor deposition film having high gas barrier properties and excellent transparency has been attracting attention. For example, food packaging films in which a SiO film is formed on a polymer film are produced. It should be noted that excellent transparency is necessary for observing the package contents from the appearance and confirming alteration and deterioration. In particular, it can be said to be an essential property for packaging materials for packaging foods and the like.

JP-A-60-215514 JP 2011-79724 A

Patent Document 1 describes that a metal silicon supply rate of 70 g / min or more and a metal powder particle size of 400 μm or less (average particle size of 100 μm) are preferable. In addition, it is described that silicon metal powder supplied into a plasma jet becomes vapor and reacts with oxygen gas to synthesize silicon monoxide. Further, it is described that the temperature in the reaction frame is raised to 3,000 K (2,727 ° C.) or more by heat from the plasma and reaction heat.
However, in general, the speed of a plasma flame of a DC (direct current) plasma jet is as high as 300 m / sec or more. Therefore, even if a large particle having a particle diameter of metal Si powder exceeding 50 μm is melted to form droplets, there is a problem that a large amount of metal Si remains without being evaporated (vaporized) in a short time.
On the other hand, if the average particle diameter of the metal Si is a small material of 10 μm or less, the material supply becomes very unstable. Therefore, there is a problem that the mixing ratio between the material supply and the oxygen gas supply changes every moment and it is difficult to manufacture a material having a stable SiO _X composition.

Further, Patent Document 1 describes that the temperature of the plasma flame is increased to 3,000 K (2,727 ° C.) or higher by heat from the plasma flame and reaction heat between the metal Si vapor and oxygen. However, the heat of vaporization of metal Si is much larger than the heat of reaction, and when the amount of material supply increases, the temperature of the plasma flame rapidly decreases, and there is a problem that a large amount of metal Si that cannot be vaporized remains.
Moreover, even if the material supply amount and the theoretical oxygen amount were calculated and introduced at the target stoichiometric atomic weight ratio, the temperature was not uniform in the plasma flame and the temperature difference was partially large, so it was introduced and scattered. A uniform oxidation reaction with metal Si does not occur. Therefore, the oxidation reaction proceeds partially, and the ratio of vaporized metal Si to SiO ₂ becomes very large.

On the other hand, in Patent Document 2, a mixed raw material composed of metal Si powder and SiO ₂ powder or SiO powder is vaporized by plasma heating to form SiO gas, and then deposited on a deposition substrate as silicon oxide SiO _X (X <1). It is described. However, the center temperature of the plasma flame is preferably 5,000 ° C to 100,000 ° C, more preferably only 10,000 ° C to 20,000 ° C. Patent Document 2 does not describe what plasma operation conditions, raw material particle diameters, and material supply speeds are used in which plasma apparatus.
For example, when an RF (high frequency induction) thermal plasma apparatus is used, the heat capacity of the plasma flame is very small even if the temperature of the plasma flame is an ultrahigh temperature of 10,000 ° C. or higher. Accordingly, some metal Si having a small particle size melt and vaporize, but a large number of ones having a large particle size are spheroidized and solidified as they are, and it is difficult to produce SiO.

This is because the plasma flame is a very hot gas but has a very small heat capacity, while the heat of vaporization of metal Si is very large. Is because it does not vaporize. In addition, the mixed raw material consisting of the metal Si powder and the SiO ₂ powder or the SiO powder charged into the plasma flame is scattered in all directions and the vaporization temperature is greatly different, so the mixed particles of the metal Si powder and the SiO ₂ powder This is because the synthesis reaction is difficult to occur.
That is, a mixed powder of metal Si powder and SiO ₂ powder and / or SiO powder is introduced into a plasma flame at 10,000 ° C. to 20,000 ° C., and these are completely vaporized to cause SiO _X conversion reaction. For this purpose, it is necessary to use a very small amount of material or to use a large-capacity RF (high frequency induction) thermal plasma apparatus. Therefore, in Patent Document 2, it is insufficient to completely evaporate the mixed powder of the metal Si powder and the SiO ₂ powder and / or the SiO powder to cause the SiO _X conversion reaction.

Further, in Patent Document 2, in order to suppress splash, when a raw material that generates SiO gas is heated to a high temperature by a plasma flame, vaporized metallic silicon and oxygen react in an atomic state to generate SiO gas, and this SiO gas It is said that SiO _X (X <1) obtained by precipitating is effectively distributed uniformly without containing crystalline metallic silicon and silicon dioxide and becomes amorphous.
Splash is a phenomenon in which fine particles of metal silicon and silicon dioxide that are not vaporized are scattered together with vaporized SiO gas. If splash is generated when forming the SiO vapor deposition film, fine particles that are not vaporized adhere to the SiO vapor deposition film on the polymer film, causing defects such as pinholes, and gas barrier properties are deteriorated.

However, in the manufacturing method of Patent Document 2, as described above, the metal Si powder and the SiO ₂ powder are not vaporized in the plasma flame and become an atomic state, but in most cases, they are not vaporized but remain as droplets. is there. That is, it is important in what kind of particle size powder raw material is heated in which plasma flame (temperature, plasma flame speed) of the plasma apparatus, but this is described in Patent Document 2. Absent.
In the case of a temperature of 10,000 ° C. plasma flame of a DC (direct current) plasma spray gun, the average particle size D ₅₀ generally used in the DC (direct current) plasma spray gun is 30 μm because the speed of the plasma flame is high. Even if a level of metal Si powder is supplied, most of the powder is only partially melted and hardly gasified.

In addition, in a plasma flame at 10,000 ° C. of an RF (radio frequency induction) thermal plasma apparatus having a very slow plasma flame speed, a metal Si powder having a smaller average particle diameter D ₅₀ of 20 μm is obtained in an amount of 30 g / It has been confirmed that even when the operation is performed with a small supply amount of min, metal Si is not vaporized and is simply recovered as molten spheroidized particles.
As described above, it has been found that it is quite unrealistic to produce amorphous SiO _X containing no metal Si by the production method of Patent Document 2.

The present invention has been made in order to solve the above-described problems, and its purpose is to continuously and inexpensively produce SiO _X powder used as a negative electrode active material of a lithium ion secondary battery and a vapor deposition material of a gas barrier film. and to provide a SiO _X powder preparation and SiO _X powder production apparatus capable of.

The SiO _X powder production method of the present invention includes a step of heating and melting a mixed granulated powder of metal Si powder and SiO ₂ powder with a plasma flame, and vaporizing molten droplets of the heated and melted mixed granulated powder in a heating furnace. And a step of causing the SiO _X reaction to be performed, and a step of rapidly cooling the generated SiO _X gas with an inert gas to precipitate SiO _X fine powder.
Moreover, the SiO _X powder production apparatus of the present invention is a mixed granulation of a DC (direct current) plasma apparatus or an RF (high frequency induction) thermal plasma apparatus equipped with a plasma gun for ejecting a plasma flame, and a metal Si powder and SiO ₂ powder. Powder supply device for spraying powder into plasma flame, heating furnace for vaporizing molten droplets of mixed granulated powder heated and melted in plasma flame to perform SiO _X conversion reaction, and generated SiO _X gas And a cooling device for precipitating SiO _X fine powder by rapid cooling with an inert gas.

In the present invention, high purity (4N or more) Si powder is used as a metal Si powder raw material. The high-purity (4N or higher) Si powder is used by regenerating metal Si sludge generated in a silicon wafer manufacturing process such as for semiconductors and solar cells to a high purity (4N or higher).
Originally, metal Si used for semiconductors, solar cells and the like has been purified to a very high purity. However, the powder generated in the silicon wafer slicing and polishing process is very difficult to handle with fine particles, collected as sludge contaminated with impurities, and processed as waste as cost.

The present invention is a metal Si powder and SiO ₂ powder, each having an average particle diameter _{D 50} of 10μm or less, preferably have an average particle diameter _{D 50} using the following metal Si powder and SiO ₂ powder 5 [mu] m, SiO _X The mixing ratio of the metal Si powder and the SiO ₂ powder is set so that the X value of is 0.5 to 1.8.
The present invention, water in these mixed powder materials, solvent, dispersing agent, by mixing a binder, well stirred mixture by a mixer, spray drying method obtained by slurrying the average particle diameter D ₅₀ at (spray-dried) It is preferable to use a mixed granulated powder of metal Si powder and SiO ₂ powder granulated to 10 μm to 50 μm.

Further, the metal Si powder and the SiO ₂ powder are uniformly mixed and granulated at a constant ratio, and the raw material is used as a secondary raw material. This secondary raw material, which is a mixed granulation of metal Si powder and SiO ₂ powder, enhances the reactivity between fine powders, and melts the mixed granulated powder of metal Si powder and SiO ₂ powder in the plasma flame. It has a great effect on vaporization. In addition, since the metal Si powder and the SiO ₂ powder are present in a certain ratio in the particles of the mixed granulated powder of the metal Si powder and the SiO ₂ powder, the X value of the SiO _X gas has an extremely stable atomic ratio. Easy to composition.

The present invention uses a DC (direct current) plasma device or an RF (radio frequency induction) thermal plasma device as a device for generating a plasma flame, and a metal Si powder and SiO for a plasma flame of 6,000 K (5,727 ° C.) or more. The mixed granulated powder with ₂ powders is blown and melted by heating (partially vaporized). At this time, it is preferable to adjust the nozzle diameter of the plasma gun so that the material flight speed in the plasma flame is 150 m / sec to 3 m / sec.
In general, a DC (direct current) plasma apparatus is characterized by a high speed flame that is a plasma flame. A DC (direct current) plasma device is a high-adhesion coating film that is made by introducing a high melting point ceramic powder into a Mach 2 level plasma jet such as plasma spraying, instantly melting the material and welding it to the substrate at high speed. Is generally used to form

However, the DC (direct current) plasma apparatus uses the mixed granulated powder of the metal Si powder and the SiO ₂ powder as a raw material and heats and melts (partially vaporizes) the mixed granulated powder as in the present invention. The frame speed is too fast. For this reason, a material having a large heat of fusion and heat of vaporization, such as metal Si, is insufficient in terms of heat amount and reaction time for vaporization even if it is melted.
Therefore, the DC (direct current) plasma device increases the nozzle diameter at the tip of the plasma gun and makes the material flight speed in the plasma flame 150 m / sec or less, thereby increasing the reaction time and melting and vaporizing. And a special structure that promotes chemical reactions.

By the way, even if the plasma apparatus is used, it is difficult to melt and vaporize all of the mixed granulated powder of the metal Si powder and the SiO ₂ powder.
Therefore, in the present invention, a heating furnace is installed in front of the plasma gun in order to completely gasify the metal Si that is not vaporized and the SiO ₂ powder to cause a synthetic reaction.
A graphite heater heating furnace or a high-frequency induction heating furnace is used as the heating furnace, a highly heat-resistant graphite pipe is used as the reaction tube, the periphery of the graphite tube is insulated, and further water-cooled. The droplet melted by the plasma flame is further heated and vaporized while maintaining the temperature in the graphite tube at 2,000 K (1,727 ° C.) or higher, thereby completely generating SiO _X gas. That is, all of the droplets melted by the plasma flame are gasified, so that the generated SiO _X has a uniform composition.
Also SiO _X as SiO _X also gas barrier film for vapor deposition material as a negative electrode active material of a lithium ion secondary battery, when without vaporizing unreacted metal Si and SiO ₂ remains, deterioration in charge-discharge characteristics of the negative electrode And lead to deterioration of gas barrier properties.

Next, in the present invention, a compressed inert gas such as N ₂ or Ar is jetted and mixed from the ring-shaped nozzle at the outlet of the heating furnace, and the high-temperature SiO _X gas is rapidly cooled to 800 ° C. or less to 0.01 μm A cooling device for precipitating 10 μm SiO _X fine powder is provided.
High-temperature SiO _X gas of 2,000 K (1,727 ° C.) or more generated in the reaction tube of the heating furnace is N ₂ , Ar, or the like ejected from the ring-shaped nozzle of the cooling device provided at the outlet of the heating furnace. by being suddenly cooled to 800 ° C. below the compressed inert gas, can be precipitated as an amorphous SiO _X fine powder remains in the composition of the SiO _X.
If the jetted in the atmosphere directly water-cooled chamber only SiO _X gas high temperature, it is slowly cooled part of the SiO _X gas, and solidified deposited on the inner wall surface of the tubular body, a portion of the SiO _X By the disproportionation reaction, the metal Si powder and the SiO ₂ powder are separated again, and the yield of the composition of SiO _X is lowered.
As the compressed inert gas, it is preferable to use N ₂ because the cooling efficiency is good and the cost is low.

In the present invention, it is preferable to operate the inside of the heating furnace under a reduced pressure of 30 kPa to 80 kPa.
By operating the inside of the reaction tube of the heating furnace under a reduced pressure of 30 kPa to 80 kPa, the reaction temperature between the metal Si powder and the SiO ₂ powder can be lowered, and the SiO conversion reaction can be further promoted. This decompression operation is not an absolute requirement, and the decompression facility may be appropriately determined based on the investment and its effect.
The degree of decompression of 30 kPa to 80 kPa is not particularly limited to this, and is optimal depending on various operating conditions such as the particle diameter of the feed material (granulated powder), the supply amount, the output of the plasma apparatus, the temperature of the heating furnace, etc. It is only necessary to set conditions, and by adding this decompression operation, the degree of freedom of operation can be further increased.
If it is less than 30 kPa, the equipment cost becomes high, and if it exceeds 80 kPa, the effect of decompression operation cannot be expected so much.

In the present invention, the precipitated SiO _X fine powder of 0.01 μm to 10 μm is cooled with a water-cooled cyclone, and the average particle diameter D ₅₀ is preferably recovered by growing or agglomerating into a fine powder of 1 μm to 20 μm. .
The SiO _X powder produced by cooling with a compressed inert gas such as N ₂ and Ar has a particle size that is too fine and poor in recovery efficiency. However, the recovery rate of the SiO _X powder is obtained by growing the particle diameter in a water-cooled cyclone. There is an effect to raise.
The water-cooled cyclone has an outer periphery that is water-cooled, and is blown by a high-flow rate of compressed inert gas such as SiO _X fine powder and N ₂ , Ar that has been primarily cooled to 800 ° C. or less. The resulting SiO _X fine powder is cooled to 200 ° C. or lower to grow or aggregate the particle diameter. It is preferred to recover most of the SiO _X fine powder in a water-cooled cyclone. The average particle diameter D ₅₀ of the recovered SiO _X fine powder by a 1 m to 20 m, when used as the negative electrode active material of a lithium ion secondary battery, it is not necessary to pass the milling step or the like, significant cost reduction effective.

Further, in the present invention, it is preferable to collect uncollected ultra fine powder by a bag filter using a water cooling cyclone.
In the water-cooled cyclone, SiO _X fine particles of submicron (1 μm or less) or less cannot be completely recovered. Therefore, these fine particles are completely removed by a bag filter, and the exhaust gas is discharged into the atmosphere in a clean state.
In addition, the present invention is to cool N ₂ and Ar gas, which are clean exhaust gas after dust collected by a bag filter, with a water-cooled cyclone, to a room temperature with a heat exchanger, and further with a high-pressure blower. Pressurize and circulate through an inert gas cooler. Thus, new N ₂ and Ar gases for cooling are used only at the time of in-system gas purging at the initial stage of operation, and thereafter, exhaust gas is circulated and used, so that a significant cost reduction can be achieved.
In the present specification, “average particle diameter D ₅₀ ” means a particle diameter at an integrated value of 50% in a particle diameter distribution determined by a laser diffraction / scattering method.

According to the present invention, a SiO _X- based active material having a large lithium ion storage capacity, a small volume expansion / contraction shrinkage of the active material coating film due to charge / discharge, and excellent charge / discharge cycle characteristics can be controlled arbitrarily. In addition, it can be continuously produced at a low cost with an optimum particle size without going through a pulverization step.

According to the present invention, metal Si sludge (waste sludge) generated in a silicon wafer manufacturing process for semiconductors, solar cells, etc. is regenerated to high purity (4N or more) and is therefore excellent in environmental measures. .
Moreover, since this waste sludge can be regenerated for high purity at low cost, there is an advantage that raw material costs can be kept low.
In addition, this waste sludge has already had an optimal particle size distribution suitable for the purpose of granulation as a granulated powder that is a raw material used in the plasma apparatus, and the pulverization process for pulverization can be omitted. This greatly reduces costs.

According to the present invention, the molten droplets of the mixed granulated powder heated and melted (partially vaporized) by the plasma flame are vaporized in the heating furnace to cause the SiO _X conversion reaction, thereby generating the SiO _X gas. All are gasified, and the resulting SiO _X has a uniform composition.
For this reason, unreacted metal Si remains, so that it is possible to solve the conventional problem that the charge / discharge characteristics and gas barrier characteristics of the lithium ion secondary battery are deteriorated, and the recovery yield of SiO _X is increased. .

According to the present invention, the metal Si powder and the SiO ₂ powder are granulated to obtain a mixed granulated powder having an average particle diameter D ₅₀ of 10 μm to ₅₀ μm. The material can be supplied stably with the supply device. Therefore, as in the conventional powder supply device, the smaller the particle diameter, the more unstable the supply amount, and it is difficult to produce a stable and uniform mixing ratio, and there is a special material supply device. The problem of being necessary can be solved.

According to the present invention, a high temperature SiO _X gas of 2,000 K (1,727 ° C.) or higher generated in a heating furnace is provided with a cooling device at the outlet of the heating furnace, and is compressed inactive such as N ₂ and Ar. gas ejected mixture from the ring-shaped nozzle, rapidly cooled to 800 ° C. or less, since the precipitating SiO _X fine powder can remain composition SiO _X, to deposit the amorphous SiO _X microparticles.
At this time, it is preferable to use N ₂ for the compressed inert gas because the cooling efficiency is good and the cost is low.

According to the present invention, since the inside of the heating furnace is operated under a reduced pressure of 30 kPa to 80 kPa, the vaporization temperature of the mixed molten droplets of the metal Si powder and the SiO ₂ powder can be lowered, and the SiO _X conversion reaction can be further promoted. it can.

According to the present invention, since blowing SiO _X powder and N _2, compressed inert gas such as Ar that has been primary cooling to 800 ° C. or less at a high flow rate circumferentially of water cooling cyclone, SiO _X fine powder 200 Since the particle diameter grows or aggregates when cooled to below ℃, most of the SiO _X fine powder can be recovered in a water-cooled cyclone. Further, the average particle diameter _{D 50} of the SiO _X fine powder is recovered, it can be 1 m to 20 m.
According to the present invention, the average particle diameter D ₅₀ of the SiO _X fine powder is recovered by a 1 m to 20 m, when used as the negative electrode active material for lithium ion secondary batteries, the need to pass milling step, etc. There is no significant cost reduction effect.

According to the present invention, submicron (1 μm or less) SiO _X fine particles that cannot be completely recovered by a water-cooled cyclone can be completely removed by a bag filter, and the exhaust gas can be discharged into the atmosphere in a clean state.
In addition, according to the present invention, clean exhaust gas after collecting and collecting SiO _X particulates with a bag filter is cooled to room temperature with a heat exchanger, then boosted with a high-pressure blower, and recycled to the cooling device. Cost reduction is possible.
When the clean exhaust gas after the bag filter is circulated and used, the working gas (N ₂ , Ar gas, etc.) blown by the plasma gun is released into the atmosphere as surplus gas.
It should be noted that the extent to which the inert gas is circulated and used can be determined by the equipment cost and the running cost for the exhaust gas after the bag filter is clean.

The cross-sectional structure of the SiO _X powder production apparatus used in the first embodiment of the SiO _X powder production method according to the present invention is a diagram schematically showing. It is a schematic diagram which shows the cross-sectional structure of the DC plasma gun front-end | tip part in FIG. It is a diagram showing a sectional structure of a cooling device for cooling by compressed N ₂ gas in FIG. The cross-sectional structure of the SiO _X powder production apparatus used in the second embodiment of the SiO _X powder production method according to the present invention is a diagram schematically showing. It is a diagram showing a sectional structure of a cooling device for cooling by compressed N ₂ gas in FIG.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings.
1 to 3 show the steps (A) to (E) constituting the SiO _X powder production method of the present embodiment and the SiO _X powder production apparatus used therefor.

First, a description will be given of a SiO _X powder production method of the present embodiment in step (A) ~ (E).
In the step (A), the DC (direct current) plasma apparatus 1 is operated to supply the mixed granulated powder 5 of the metal Si powder and the SiO ₂ powder from the powder supply nozzle 4 to the plasma flame 3 ejected from the plasma gun 2. Then, the mixed granulated powder 5 is heated and melted (partially vaporized).
The mixed granulated powder 5 is granulated by mixing the metal Si powder and the SiO ₂ powder in the powder granulator 13, and then the powder supply disposed near the plasma gun tip 2 a via the powder feeder 14. It is supplied from the nozzle 4 to the plasma flame 3.

Next, in the step (B), the molten droplets of the mixed granulated powder 5 that has been heated and melted (partially vaporized) in the step (A) are placed in the graphite tube (reaction tube) 15 of the high-frequency induction heating furnace 19. It is vaporized at a high temperature to cause the SiO _X conversion reaction.
Next, in the step (C), the SiO _X gas generated in the step (B) is rapidly cooled using a compressed inert gas such as N ₂ or Ar in the gas cooling device 20 to precipitate the SiO _X fine powder 25a. Let
Next, in the step (D), the SiO _X fine powder 25a deposited in the step (C) is cooled by the water-cooled cyclone 24 and recovered as a fine powdery SiO _X powder 25b grown or aggregated.
Next, in the step (E), uncollected ultrafine powder is collected by the bag filter 27 by the water cooling cyclone 24 and collected.
Above, it is possible to obtain a SiO _X fine powder used as a vapor deposition material of the negative electrode active material and the gas barrier film of the lithium ion secondary battery.

Next, the SiO _X powder manufacturing apparatus of this embodiment will be described.
As shown in FIGS. 1 to 3, the SiO _X powder manufacturing apparatus of the present embodiment includes a DC (direct current) plasma apparatus 1 including a plasma gun 2 that ejects a plasma flame 3. A powder supply nozzle 4 for spraying a mixed granulated powder 5 of a metal Si powder and a SiO ₂ powder in a plasma flame 3 ejected from a DC (direct current) plasma apparatus 1 is arranged in the vicinity of the plasma gun tip 2a. .
In front of the DC (direct current) plasma apparatus 1, the molten droplets of the mixed granulated powder 5 that is heated and melted (partially vaporized) by the plasma flame 3 ejected from the DC (direct current) plasma apparatus 1 are vaporized. Then, a high frequency induction heating furnace 19 for performing the SiO _x conversion reaction is disposed.
At the outlet of the high-frequency induction heating furnace 19, a cooling device 20 is disposed that rapidly cools the SiO _x gas generated in the high-frequency induction heating furnace 19 with an inert gas to precipitate the SiO _x fine powder 25a.
At the outlet of the cooling device 20, a water-cooled cyclone 24 that cools the SiO _X fine powder 25 a deposited by the cooling device 20 and collects it as a fine powdery SiO _X powder 25 b grown or aggregated is disposed.
On the downstream side of the water-cooled cyclone 24, a bag filter 27 for collecting and collecting uncollected SiO _x fine powder by the water-cooled cyclone 24 is disposed.

Next, the step (A) will be described in detail.
In the present embodiment, the metal Si sludge generated in the semiconductor or solar cell silicon wafer manufacturing process is regenerated into the metal Si powder used in the mixed granulated powder 5 of the metal Si powder and the SiO ₂ powder in the step (A). And use it.
In this case, since the powder particle diameter, impurity content, moisture content, and the like vary depending on the location where the metal Si sludge is generated, it is pretreated according to its properties and refined into metal Si powder.
There are various purification methods, such as impurity removal, dehydration, pulverization of agglomerated powder, and drying, and the method is not particularly limited.

As the metal Si powder and the SiO ₂ powder, those having an average particle diameter D ₅₀ of 10 μm or less, more preferably, an average particle diameter D ₅₀ of 5 μm or less are used.
When each average particle diameter D ₅₀ exceeds 10 μm, the variation in the mixing ratio of the metal Si powder and the SiO ₂ powder in one particle when granulated increases. Further, the surface area of the contact interface between the metal Si powder and the SiO ₂ particles when blown into the plasma flame 3 to form a molten droplet is reduced, and the effect of increasing the reactivity between the metal Si and SiO ₂ is less likely to occur.
The lower limit of the average particle diameter _{D 50} of the SiO ₂ powder is not particularly limited. However, the metal Si powder may natural oxide film on the outermost surface, the average particle diameter D ₅₀ is fine particles of less than 1 [mu] m, high reactivity, it is difficult to handle. Therefore, the lower limit of the average particle diameter _{D 50} of the metal Si powder and 1 [mu] m.
The mixing ratio of the metal Si powder and the SiO ₂ powder is adjusted so that the X value of the target SiO _X powder is 0.5 to 1.8.

When SiO _X is used as the negative electrode active material of a lithium ion secondary battery, the lithium ion storage capacity and charge / discharge cycle characteristics due to volume expansion / contraction due to charge / discharge of the SiO _X coating film are inversely proportional to the magnitude of the X value. It is necessary to select an optimum value among X values of 0.5 to 1.8.
When the X value is less than 0.5, the lithium ion storage capacity increases, but the charge / discharge cycle characteristics due to the expansion and contraction of the active material film deteriorate, which is not practical.
When the X value exceeds 1.8, the expansion and contraction of the active material film has almost no problem, but an increase in the lithium ion storage capacity cannot be expected so much.

On the other hand, when silica and alumina are compared as a gas barrier material, silica has better gas barrier properties and flexibility, but has the disadvantage of being yellowish, and alumina is colorless and transparent and cheap, but hard and brittle. There is a disadvantage that the gas barrier property is inferior.
The silica vapor deposition film is used in an oxidized state in which the X value of SiO _X is about 1.5 to 1.8. When the X value approaches 1.0, the gas barrier property is increased, but it is yellowish. On the contrary, when the X value approaches 2.0, there is a problem that the color tone becomes thin but the gas barrier property is lowered, and the control of the degree of oxidation becomes important. Thus, the X value can be selected depending on the use of the film depending on whether the gas barrier property is taken or the transparency of the film is taken.

The important thing is that it does not contain metal Si, the X value in the case of a gas barrier material is 1.5 to 1.8, and the X value in the case of a negative electrode active material of a lithium ion secondary battery is about 0.5 to 1.8. It is to build stably to the target value.
The average particle diameter D ₅₀ of the mixed granulated powder 5 of the metal Si powder and the SiO ₂ powder is preferably 10 μm to ₅₀ μm, and the average particle diameter D ₅₀ is more preferably 15 μm to ₄₀ μm. This is because when the average particle diameter D ₅₀ is less than 10 μm, the supply amount of the powder supply device 14 to the plasma gun 2 varies greatly, and stable production of SiO _X cannot be performed. When the average particle diameter D ₅₀ exceeds ₅₀ μm, coarse particles of 60 μm or more are often mixed, and these coarse particles are sufficiently contained in the plasma flame 3 and the graphite tube (reaction furnace) 15 of the high-frequency induction heating furnace 19. This is because vaporization and reaction cannot be completed, and the proportion of unreacted coarse particles mixed in the product increases.

In this embodiment, the granulation method of the metal Si powder and the SiO ₂ powder is not particularly limited, such as a spray drying method, a tumbling granulation method, a fluidized granulation method, a stirring granulation method, etc. A spray drying method (spray drying) is preferred.
In the spray drying method (spray drying), fine particles (primary particles) of up to several μm and a liquid organic binder are mixed in a mixing tank, slurried, then fed into a chamber by a pump and sprayed with compressed air. This is dried as agglomerated particles (secondary particles) from above by a dry air stream and collected by the lower collector.
For the organic binder, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), starch, paraffin, resin or the like is used.

Next, the apparatus used at a process (A) is demonstrated.
In step (A), a DC (direct current) plasma apparatus 1 was used as the plasma heating apparatus.
For example, as shown in FIG. 2, the plasma gun tip 2 a is an electrode in which the cathode 7 is disposed in the working gas passage 8 and the working gas (N ₂ or the like) 9 is ejected from the working gas passage 8 along the cathode 7. A holder 6 and a nozzle 10 composed of an anode communicating with the electrode holder 6 are provided. A water jacket 11 that is cooled by cooling water 12 is provided on the outer periphery of the nozzle 10. A working gas (N ₂ or the like) 9 ejected from the electrode holder 6 is ejected from the plasma gun tip 2a as a plasma flame 3 by discharge between the cathode 7 and the anode.
Further, the plasma gun tip 2a increases the diameter of the nozzle 10 in order to slow down the ejection speed of the plasma flame 3, so that the speed of the plasma flame 3 is 150 m / sec or less, and the reaction time is increased to increase the metal Si powder. This is a special structure that promotes the melting and vaporization of the mixed granulated powder 5 of SiO ₂ and SiO ₂ powder.

In the vicinity of the plasma gun tip 2a, there is an interior in which a mixed granulated powder 5 of metal Si powder and SiO ₂ powder is supplied by a carrier gas (N ₂ or the like) toward a plasma flame 3 ejected from the plasma gun 2 A powder supply nozzle 4 of a supply system is arranged.
The powder supply nozzle 4 has an internal supply system and an external supply system (not shown). From the viewpoint of efficiently supplying the material to the high temperature part of the plasma flame 3 and increasing the melting efficiency of the material, the internal supply method is preferable. However, in the internal supply method, the anode constituting the nozzle 10 is easily damaged. Moreover, there exists a fault that the fuse | melted material adheres in the nozzle 10 comprised with an anode, and the hole of the nozzle 10 is easy to block | close. Each method has its advantages and disadvantages, but any method can be used. Although the supply location of the powder depends on the amount of material supply, it is desirable to supply from 1 to 4 locations in the circumferential direction of the nozzle 10 toward the center of the plasma flame 3.
A powder supply device 14 for supplying a mixed granulated powder 5 of a metal Si powder and a SiO ₂ powder granulated by the powder granulator 13 is connected to the powder supply nozzle 4 via a pipe.

In the present embodiment, the DC (direct current) plasma device 1 is used as the plasma device for realizing the step (A). However, the present invention is not limited to the DC (direct current) plasma device 1, but RF (high frequency induction). A thermal plasma apparatus or the like may be used. However, the DC (direct current) plasma apparatus 1 is preferable in order to have high thermal energy conversion efficiency, to completely vaporize the metal Si powder, and to efficiently process the SiO _X conversion reaction in a large amount.
In particular, the DC (direct current) plasma apparatus 1 can melt the mixed granulated powder 5 of metal Si powder and SiO ₂ powder at a high temperature of 6,000 K (5,727 ° C.) or more with the plasma flame 3. , SiO _X can be combined with the step (B) of completely vaporizing the high temperature induction furnace 19 at a high temperature of 2,000 K (1,727 ° C.) or higher.

In addition, a normal DC (direct current) plasma apparatus is characterized in that the velocity of the flame, which is the plasma flame 3 of the plasma jet, is obtained at a high flow rate of Mach 2 level. However, in this embodiment, since the mixed granulated powder 5 of the metal Si powder and the SiO ₂ powder is melted (partially vaporized), the speed of the frame at the outlet of the plasm gun tip 2a is made as low as possible. Therefore, the diameter of the nozzle 10 of the plasma gun tip 2a is increased so as to slow down the flying speed of the raw material powder, and the flying speed of the SiO _X droplet is set to 150 m / sec to 3 m / sec. 19 is blown into the structure.
The diameter of the nozzle 10 of the plasma gun tip 2a is configured to expand stepwise or in a curve toward the tip of the nozzle 10 in order to adjust the flying speed of the SiO _X droplet, and the anode and cathode 7 is a structure that can be exchanged as a pair of parts combined with a structure that maintains the distance to 7 appropriately.

When the flying speed of the SiO _X droplet exceeds 150 m / sec, the reaction time in the high-frequency induction heating furnace 19 is short, and it is difficult to cause the reaction to be completely vaporized in the high-frequency induction heating furnace 19. When the flying speed of the SiO _X droplet is less than 3 m / sec, a coarse droplet that cannot be vaporized does not fly to the optimum reaction temperature portion in the high-frequency induction heating furnace 19 and may accumulate on the bottom of the high-frequency induction heating furnace 19. is there.
On the other hand, an RF (high frequency induction) thermal plasma apparatus can produce a high-temperature plasma flame of 10,000 K (9,727 ° C.) or higher, but has a low thermal energy conversion efficiency to plasma, and a feed rate of 10 g / min. Therefore, the productivity is poor and the production cost is high, which is not preferable as a mass production apparatus.

Next, the step (B) will be described.
As shown in FIG. 1, a high frequency induction heating furnace 19 is connected to the tip of the DC (direct current) plasma apparatus 1 in order to realize the step (B).
In the high frequency induction heating furnace 19, a graphite tube (reaction tube) 15 having a heat-resistant temperature of 3,000 ° C., which is covered with a heat insulating material 16, is inserted into the water-cooled quartz tube 17, and the high-frequency induction furnace is disposed around the water-cooled quartz tube 17. In this structure, the coil 18 is arranged.
The internal temperature of the graphite tube (reaction tube) 15 can be arbitrarily controlled from 1,600 ° C. to 2,700 ° C.

As shown in FIG. 1, the opening 15a provided in the upper part of the graphite tube (reaction tube) 15 is cooled by cooling with a compressed inert gas such as N ₂ or Ar in order to realize the step (C). A device 20 is arranged.
The high-frequency induction heating furnace 19 for realizing the step (B) has a temperature in the graphite tube (reaction tube) 15 of 2,000 K (1,727 ° C.) or higher so that the SiO _X conversion reaction is sufficiently performed. It is preferable to use a graphite tube having a high heat resistance temperature.
A method of producing SiO _X by blowing metal Si powder into a DC (direct current) plasma jet and using oxygen gas O ₂ as a working gas is also conceivable. However, in this method, a uniform reaction between the metal Si powder and oxygen gas does not occur in a DC (direct current) plasma jet. Therefore, it is also conceivable to provide a high-frequency induction heating furnace 19 after the plasma gun 2 as in the present embodiment to cause sufficient vaporization to cause a uniform reaction.
However, in this case, since the unreacted oxygen gas _{O 2} with a metal Si is CO reacts with 2,000K (1,727 ℃) or high temperature graphite tube (reaction tube) 15, as SiO _X The composition is not stable. Therefore, it is difficult to cause the gas phase reaction between the metal Si powder and the oxygen gas O ₂ by the plasma flame 3 in the high frequency induction heating furnace 19 using the graphite tube (reaction tube) 15.
In addition, although this embodiment demonstrated the case where the high frequency induction heating furnace 19 was used for the heating furnace, this invention is not restricted to this, The graphite heater heating furnace which heats a graphite tube (reaction tube) with a graphite heater is used. May be.

Next, process (C) is demonstrated.
As shown in FIGS. 1 and 3, a cooling device 20 that performs cooling with a compressed inert gas such as N ₂ or Ar is connected to an opening 15 a provided at an upper portion of a graphite tube (reaction tube) 15, and has a normal temperature. A ring-shaped nozzle 22 for injecting a compressed inert gas such as N ₂ and Ar in a ring shape obliquely, and a high-temperature SiO _X gas 800 connected to the ring-shaped nozzle 22 with a compressed inert gas such as N ₂ and Ar. It is comprised with the heat insulation double tube 23 which cools rapidly to degreeC.
The ring-shaped nozzle 22 is connected to a pipe line 22a that communicates with a device (not shown) that supplies a compressed inert gas such as N ₂ or Ar at room temperature.
The heat insulation double pipe 23 is provided with an inlet 23a for taking in cooling water or a compressed inert gas such as N ₂ and Ar, and an outlet 23b.
The high temperature SiO _X gas of 2,000 K (1,727 ° C.) or more generated in the graphite tube (reaction tube) 15 of the high frequency induction heating furnace 19 is the upper part of the graphite tube (reaction tube) 15 of the high frequency induction heating furnace 19. It is introduced into the cooling device 20 that is connected to the opening 15a. A compressed inert gas such as N ₂ or Ar is jetted in an oblique direction from a ring-like nozzle 22 that jets in a ring shape, and high-temperature SiO _X gas is sucked by the ejector effect and instantly cooled to 800 ° C. or less, Amorphous SiO _X fine powder 25a is deposited. This SiO _X gas becomes an almost stable solid at 800 ° C. or lower.

Therefore, the SiO _X precipitate is deposited as submicron (1 μm or less) amorphous SiO _X fine powder 25a without being disproportionated into the metal Si powder and the SiO ₂ powder.
Since the particle diameter of the SiO _X fine powder 25a is very fine with a submicron (1 μm or less), it is difficult to collect with a normal cyclone. Therefore, by blowing compressed inert gas such as N ₂ or Ar for primary cooling, the gas flow rate in the heat insulating double pipe 23 is increased, and the water is cooled primarily to 800 ° C. or less in the circumferential direction in the water cooling cyclone 24. Introduced high temperature gas.
At this time, since the high temperature (about 800 ° C.) gas passes through the heat insulating double pipe 23 serving as a guide pipe to the water cooling cyclone 24, the heat insulating double pipe 23 is N ₂ , Ar for cooling water or primary cooling. In this structure, cooling is performed through a compressed inert gas such as the like, and the inert gas is blown from the ring-shaped nozzle 22.

The heat insulation double tube 23 is cooled with water or a cooling gas. However, if it is cooled too much, SiO _X gas is deposited as a SiO _X solid and deposited in the heat insulation double tube 23, and the heat insulation double tube 23 is clogged. End up. In order to collect the SiO _X solid (powder or flakes) deposited and deposited in the heat insulating double tube 23, the operation must be a batch operation in a short cycle. Therefore, when the heat insulation double pipe 23 is indirectly cooled with water, it is necessary to adjust the flow rate and the like so as to maintain a temperature at which the SiO _X gas does not precipitate in the heat insulation double pipe 23. Alternatively, if cooling the N _2, Ar insulated double pipe 23 with compressed inert gas such as for blowing, the insulated double pipe 23 temperature can be maintained at a high temperature. Moreover, since the gas flow rate in the pipe is very fast, problems such as deposit clogging do not occur.

Next, process (D) is demonstrated.
As shown in FIGS. 1 and 3, the heat insulating double tube 23 of the cooling device 20 that performs cooling with a compressed inert gas such as N ₂ or Ar communicates with the water cooling cyclone 24.
The SiO _X fine powder 25a cooled here grows or aggregates as the particle size grows and agglomerates and deposits on the side walls and the lower part of the cyclone.
Below the water-cooled cyclone 24 is disposed a hopper 26 that recovers the SiO _X powder 25b that has been cooled by the water-cooled cyclone 24 and whose particle diameter has grown or aggregated and deposited and deposited on the side wall and the lower part of the cyclone.

Since the high temperature SiO _X gas flows along the side wall of the low temperature water cooling cyclone 24, the cooling efficiency is very good, and the fine powder SiO _X powder 25b is further rapidly cooled, so that the particle size becomes a secondary particle. greatly grow or aggregate as an average particle diameter _{D 50} is the powder of 10 m to 20 m.
By increasing the particle diameter, most of the SiO _X powder 25b is recovered in the water-cooled cyclone 24.
The SiO _X powder 25b accumulated in the water-cooled cyclone 24 can be produced almost continuously as SiO _X powder by periodically collecting the SiO _X powder 25b when it accumulates in the lower hopper 26 over a certain level.

When the SiO _X gas at a high temperature is slowly cooled slowly, crystal nuclei gradually precipitate in the SiO _X gas from about 1700 ° C. or lower, adhere to the wall surface, etc., and grow into bulk precipitates. In particular, since the SiO precipitate is in the form of a sintered bulk, it is necessary to separately pulverize the removed bulk in order to make this a powder.
For this reason, the removal of the bulk lump becomes a batch type and not only the workability is deteriorated, but also it is necessary to go through a pulverization process to make it a fine powder, and the cost is high, and impurities are easily mixed. .
On the other hand, when the SiO _X gas is rapidly cooled with a compressed inert gas such as N ₂ or Ar, the size of the precipitation growth nuclei varies depending on the cooling rate, but generally becomes a fine powder of 0.01 μm to several μm, and the amorphous non-crystalline It can be a crystal structure.
SiO usually has a metastable crystal structure and has an amorphous aggregate structure of metal Si and SiO ₂ , but when heated in a high temperature region of 800 ° C. or higher, it gradually becomes dissociated by the disproportionation reaction. Separated into SiO ₂ region.

Therefore, it is very important to dilute and quench the SiO _X gas with a compressed inert gas such as N ₂ or Ar to 800 ° C. or less, and deposit and recover it as amorphous SiO _X fine powder. In this case, the particle diameter is preferably adjusted to 0.01 μm to 10 μm by adjusting the amount of compressed inert gas blown such as N ₂ or Ar.
Nanoparticles with a particle size of SiO _X fine powder of less than 0.01 μm have a large particle surface area and are difficult to knead with a binder when used as a negative electrode active material for a lithium ion secondary battery. Problems are likely to occur. In addition, particles having a particle size of SiO _X fine powder exceeding 10 μm are liable to crack or peel off from the electrode due to volume expansion / contraction due to absorption / release of lithium ions, and as a negative electrode active material for lithium ion secondary batteries. Is not preferred.

Next, process (E) is demonstrated.
The water-cooled cyclone 24 communicates with a bag filter 27 that sucks and collects the SiO _X fine powder not deposited here by a vacuum pump 28 via a pipe line 24a.
The submicron (1 μm or less) SiO _X fine powder that could not be collected in the water-cooled cyclone 24 is removed by the bag filter 27 in step (E), and clean exhaust gas is released to the atmosphere. Of course, since the dust collected here is also collected as a SiO _X powder product, the product yield is also increased.

In the present embodiment, the inside of the high-frequency induction heating furnace 19 is operated under a reduced pressure of 30 kPa to 80 kPa, thereby lowering the reaction temperature between the metal Si powder and the SiO ₂ powder and further promoting the SiO _X conversion reaction. Can do.
In this case, all the processes from the high-frequency induction heating furnace 19 to the bag filter 27 are operated under reduced pressure by suctioning with the vacuum pump 28 behind the bag filter 27.
By operating under reduced pressure, the vaporization temperature of SiO _X is lowered, so that the temperature in the high-frequency induction heating furnace 19 can be kept low, and the heating capacity of the high-frequency induction coil 18 can also be reduced.
However, in the case of a decompression operation, in order to cool the inlet temperature of the bag filter 27 below the heat resistance temperature of the filter cloth of the bag filter 27, the heat transfer area of the water cooling cyclone 24 is increased and the water cooling cyclone 24 is sufficiently cooled. There is a need. In this case, it is difficult to circulate clean exhaust gas after the bag filter 27 as a refrigerant of the cooling device 20.
This decompression operation is a sufficient condition and not necessarily an absolute requirement, and the decompression facility can be appropriately determined based on the investment and its effect.

(Second embodiment)
A second embodiment of the present invention will be described with reference to FIG.
In this embodiment, instead of the method of the first embodiment in which the clean exhaust gas that has passed through the bag filter 27 in the step (E) is discharged to the atmosphere by the vacuum pump 28, the clean exhaust gas that has passed through the bag filter 27 is used. The second embodiment is different from the first embodiment in that an inert gas circulation device for circulating gas as an inert gas is provided between the cooling device 20 and the gas.
Therefore, in this embodiment, description of the process (A) in the first embodiment, the process (B), and the process (D) is omitted.
First, the step (C) will be described.
As shown in FIG. 5, the cooling device 20 introduces an initially charged compressed inert gas into a pipeline 22 a connected to the ring-shaped nozzle 22 via a three-way valve 22 b and a circulating compressed inert gas. The pipe line 22d to be connected is connected.

Next, process (E) is demonstrated.
The inert gas circulation device includes a bag filter 27 and an inert gas cooling device 34. The bag filter 27 is provided with a conduit 29 that guides clean exhaust gas that has passed through the bag filter 27.
The bag filter 27 communicates with the water cooling cyclone 24 via a pipe line 24a.
The inert gas cooling device 34 is provided on the downstream side of the pipe line 29, the heat exchanger 30 for cooling the exhaust gas to room temperature, the pipe line 31 provided on the downstream side of the heat exchanger 30, and the pipe line The high pressure blower 32 is provided downstream of the high pressure blower 31 and boosts the exhaust gas. The high pressure blower 32 is connected to the downstream side of the high pressure blower 32 and the pipe 22 d of the cooling device 20. The pipe 33 is provided with an exhaust pipe 35 through a three-way valve 36 that discharges surplus gas equivalent to the working gas (N ₂ , Ar gas, etc.) blown by the plasma gun 2 to the atmosphere.

According to this embodiment, clean exhaust gas after collecting and collecting SiO _X fine particles by the bag filter 27 is cooled to room temperature by the heat exchanger 30 and then pressurized by the high-pressure blower 32 and circulated for use in the cooling device 20. Therefore, significant cost reduction is possible.
Moreover, according to this embodiment, there can exist an effect similar to 1st embodiment.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, the scope of the present invention is not limited only to these Examples.

Example 1
As a primary raw material of metal Si powder, metal Si powder regenerated from metal Si sludge generated in a silicon wafer production process for semiconductor production was used.
The purity of the metal Si powder was impurity heavy metal <50 μg / g, average particle diameter D ₅₀ : 3.7 μm.
The particle size distribution of the SiO ₂ powder was an average particle size D ₅₀ : 2.4 μm.
A powder obtained by mixing metal Si powder and SiO ₂ at a weight ratio (wt%) of 1: 2.14 (X value of SiO _X : 1.0), water, an organic binder (PVA), and a dispersant. It mix | blended, made into stirring slurry, and granulated by the spray-drying method, and manufactured the secondary raw material powder (mixed granulated powder 5).
The average particle diameter _{D 50} of the mixed granulated powder 5 was 17μm (<60μm).

In this embodiment, as shown in FIG. 1, a DC (direct current) plasma apparatus (manufactured by Nippon Yutech Co., Ltd .: SG-100 spray gun) 1 was used as the plasma heating apparatus. However, a special nozzle in which the diameter of the nozzle 10 at the plasma gun tip 2a is increased in order to slow down the ejection speed of the plasma flame 3.
A mixed granulated powder 5 of metal Si powder and SiO ₂ powder was supplied to a DC (direct current) plasma apparatus 1 by a carrier gas (N ₂ ) at a supply rate of 30 g / min.
N ₂ (60 L / min) was used as the working gas 9 and the operation was performed at an output of 35 V × 750 A.
A high frequency induction heating furnace 19 was connected to the tip of the DC (direct current) plasma apparatus 1.
The high frequency induction heating furnace 19 has a structure in which a heat insulating material 16 and a graphite tube (reaction tube) 15 having a heat resistant temperature of 3,000 ° C. are inserted into a water-cooled quartz tube 17 and heated by a high frequency induction coil 18.
The internal temperature of the graphite tube (reaction tube) 15 was operated at 2,500 ° C. with a structure capable of arbitrarily controlling the temperature from 1,600 ° C. to 2,700 ° C.

The SiO _{X that} has become molten droplets (partially gasified) by the plasma flame 3 is entirely turned into SiO _X gas by being blown into the high-frequency induction heating furnace 19, and is inert from the upper part of the induction induction furnace 19. It is sent to the outlet pipe 21 of the gas cooling device 20.
A compressed N ₂ gas at room temperature was blown into the SiO _X gas at 400 L / min from the ring-shaped nozzle 22 at the outlet of the outlet pipe 21 and rapidly cooled to 800 ° C.
The SiO _X primarily cooled to 800 ° C. becomes a fine powder from the gas, and is further blown into the water-cooled cyclone 24.
The SiO _X fine powder cooled by the water cooling cyclone 24 grows in particle size, adheres and accumulates on the side wall and the lower portion of the water cooling cyclone 24, and is collected in a hopper 26 provided at the lower portion of the water cooling cyclone 24.
The SiO _X recovered powder collected at the bottom of the water-cooled cyclone 24 was sampled and subjected to particle size analysis and component analysis.

(Example 2)
Operation was performed under the same conditions as in Example 1, except that powder mixed with metal Si powder: SiO ₂ = 1: 0.71 (weight ratio) (X value of SiO _X : 0.5) was used.
The SiO _X recovered powder collected at the bottom of the water-cooled cyclone 24 was sampled and subjected to particle size analysis and component analysis.

(Example 3)
Operation was performed under the same conditions as in Example 1 except that powder mixed with metal Si powder: SiO ₂ = 1: 6.43 (weight ratio) (X value of SiO _X : 1.5) was used.
The SiO _X recovered powder collected at the bottom of the water-cooled cyclone 24 was sampled and subjected to particle size analysis and component analysis.

For the SiO _X recovered powder samples of Examples 1 to 3, particle size analysis with a laser diffraction particle size distribution meter (LMS-2000e: manufactured by SEISHIN), morphology observation by FE-SEM (SU8020: manufactured by Hitachi High Technologies), Quantitative analysis of Si and O by EPMA (EPMA-1610: manufactured by Shimadzu Corporation) and surface analysis results of Si and O in particles, and XPS (X-ray Photoelectron Spectrometer / JPS-9010 / X-ray photoelectron spectroscopy, JEOL Ltd.) As a result of measurement of the bonding state of SiO _X using Co., Ltd., the results are summarized in Table 1.

As shown in Table 1, with respect to the Si / SiO ₂ mixing ratio of Example 1 to Example 3 (calculated X value), the analysis result of the SiO _X recovered powder sample is X in both EDS analysis and XPS analysis. The value was almost the same as the calculated X value at the raw material powder mixing ratio. In addition, it was confirmed that the raw material Si component and SiO ₂ component were almost lost even in the SiO _X combined state of the SiO _X recovered powder sample, and Sub-oxide (Si ¹⁺ , Si ²⁺ , Si ³⁺ ) was generated. .
The particle size distribution of the SiO _X recovered powder sample is also suitable for application of the negative electrode active material of a lithium ion secondary battery having an average particle size D ₅₀ : 18 μm to 33 μm (> 50 μm: 0% to 26%). It could be recovered as a fine powder of distribution.
As described above, the X value of SiO _X can be optimally controlled according to the use, and the recovered SiO _X is a powder having a particle size distribution suitable for application of the negative electrode active material of the lithium ion secondary battery. The pulverization step for adjusting the particle size can be omitted, and the SiO _X powder production cost can be greatly reduced.

(Comparative Example 1)
The raw material of the metal Si powder is put in a powder at a supply rate of 70 g / min into a plasma jet of a DC (direct current) plasma apparatus (manufactured by Nippon Yutech Co., Ltd .: SG-100 spray gun), and further SiO in the plasma flame 3 The operation was performed under the same conditions as in Example 1 except that oxygen gas O ₂ corresponding to the molar ratio (Si: O = 1: 1) was blown to synthesize SiO _X.
As a result, the fine powder having an average particle diameter D _{50 of about} 5 μm cannot be stably supplied by the powder supply device 14 of the plasma gun 2 because the powder is too fine. Moreover, it is difficult for the Si fine powder to be put into the high temperature part (10,000 ° C.) at the center of the plasma flame 3, and many metal Si powders are only melted and solidified to be spheroidized. Most of them had a metal Si composition with insufficient synthesis reaction.

(Comparative Example 2)
Example 1 is the same as Example 1 except that the powder mixed with metal Si powder: SiO ₂ = 1: 2.14 (weight ratio) (X value of SiO _X : 1.0) is used as it is without using granulated powder. Operated under the same conditions.
In this comparative example, the material supply was very unstable, and the recovered powder was composed of metal Si and SiO ₂ despite being heated in the high-frequency induction heating furnace 19 after the plasma jet. There were many compositions, and SiO conversion reaction did not occur so much.
Although the metal Si powder is not granulated because it is not granulated, it is difficult for the powder to enter the center of the plasma flame 3, and the metal Si cannot be completely vaporized due to its high vaporization temperature. The gas phase reaction was difficult to occur.

(Comparative Example 3)
The operation was performed under the same conditions as in Example 1 except that heating in the high-frequency induction heating furnace 19 was not performed.
Since the material is granulated, the material is melted in the plasma flame 3 because the raw material particle diameter is large. However, since the temperature of the plasma flame 3 rapidly decreases, the molten droplets of the mixed granulated powder 5 are solidified without being vaporized as they are. Moreover, since the particle diameter of the recovered powder is very large and no gas phase reaction is performed, a mixture of metal Si and SiO _{2 in} the form of particulate powder is large.

(Comparative Example 4)
A normal DC (direct current) plasma device (manufactured by Nippon Yutec Corp .: SG-100 spray gun) is used instead of a special nozzle in which the diameter of the nozzle 10 at the tip 2a of the plasma gun is increased in order to slow down the ejection speed of the plasma flame 3. Was operated under the same conditions as in Example 1 except that.
In a normal DC (direct current) plasma apparatus that does not employ a special nozzle, the flying speed of molten droplets is very fast, and the residence time in the high-frequency induction heating furnace 19 is very short. Compared with Comparative Example 3, vaporization of the molten droplets was considerably carried out, but it was not sufficient.

(Comparative Example 5)
The same conditions as in Example 1 except that the high-temperature gas (about 1,700 ° C.) discharged from the high-frequency induction heating furnace 19 is discharged as it is into the heat insulating double tube 23 without performing the primary quenching with the compressed N ₂ gas. Operated at.
The high-temperature SiO _X gas is released into the atmosphere of the water-cooled cyclone 24 through the heat insulating double tube 23, but the gas flow rate is slow and most of the gas is precipitated and solidified in the heat insulating double tube 23 or enters the cyclone. The particles also did not settle in the water cooled cyclone 24 and the yield was very bad.

DESCRIPTION OF SYMBOLS 1 DC (direct current) plasma apparatus 2 Plasma gun 2a Plasma gun front-end | tip part 3 Plasma flame 4 Powder supply nozzle 5 Mixed granulated powder 6 Electrode holder 7 Cathode 8 Working gas passage 9 Working gas 10 Nozzle (anode)
11 Water jacket 12 Cooling water 13 Powder granulator 14 Powder feeder 15 Graphite tube (reaction tube)
16 Heat insulating material 17 Water-cooled quartz tube 18 High-frequency induction coil 19 High-frequency induction heating furnace 20 Cooling device 22 Ring-shaped nozzle 23 Heat-insulating double tube 24 Water-cooling cyclone 25a SiO _X fine powder 25b deposited in the heat-insulating double tube 23 Water-cooling cyclone SiO _X powder recovered at 24 26 Hopper 27 Bag filter 28 Vacuum pump 30 Heat exchanger 32 High pressure blower 34 Inert gas cooling device

Claims (23)

A step of heating and melting a mixed granulated powder of metal Si powder and SiO ₂ powder with a plasma flame;
A step of evaporating molten droplets of the mixed granulated powder heated and melted in a heating furnace to perform a SiO _x conversion reaction;
SiO _X powder production method characterized by a step of depositing a SiO _X fine powder generated the SiO _X gas is quenched with an inert gas. The method for producing SiO _x powder according to claim 1, wherein the metal Si powder is a high-purity (4N or more) Si powder. 3. The method for producing SiO _x powder according to claim 2, wherein the high-purity (4N or more) Si powder is a recycled product of metal Si sludge generated in a silicon wafer production process for semiconductors or solar cells. The metal Si powder and the SiO ₂ powder have an average particle diameter D ₅₀ of 10 μm or less, and the mixing ratio is set so that the X value of the SiO _X fine powder is 0.5 to 1.8. The method for producing SiO _x powder according to any one of claims 1 to 3, wherein: The metal Si powder and the SiO ₂ powder have an average particle diameter D ₅₀ of 5 μm or less, and the mixing ratio is set so that the X value of the SiO _X fine powder is 0.5 to 1.8. The method for producing SiO _x powder according to any one of claims 1 to 3, wherein: 6. The SiO _x powder production according to claim 1, wherein the mixed granulated powder is granulated to an average particle diameter D ₅₀ of 10 μm to ₅₀ μm by a spray drying method (spray drying). Law. The mixed granulated powder is heated and melted by being blown into a plasma flame of 6,000 K (5,727 ° C.) or more generated in a DC (direct current) plasma apparatus or an RF (high frequency induction) thermal plasma apparatus. The method for producing SiO _x powder according to any one of claims 1 to 6. 8. The mixed granulated powder is ejected so that a material flight speed in the plasma flame is 150 m / sec to 3 m / sec. 9. SiO _x powder production method. The heating furnace is a graphite heater heating furnace or a high frequency induction heating furnace, and the mixed molten droplets of the mixed granulated powder heated and melted by the plasma flame are further heated to 2,000 K (1,727 ° C.) or more. The method for producing SiO _x powder according to any one of claims 1 to 8, wherein the SiO _x gas is generated by vaporization. The SiO _x gas vaporized in the heating furnace is rapidly cooled to 800 ° C. or less with a compressed inert gas at the outlet of the heating furnace to precipitate 0.01 μm to 10 μm SiO _x fine powder. The method for producing SiO _x powder according to any one of claims 1 to 9. The method for producing SiO _x powder according to any one of claims 1 to 10, wherein the heating furnace is operated under a reduced pressure of 30 kPa to 80 kPa. The method for producing SiO _x powder according to any one of claims 1 to 10, further comprising a step of cooling and collecting the deposited fine SiO _x powder with a water-cooled cyclone. The water cooling cyclone, the outer periphery was water cooled, blowing the SiO _X powder and inert gas primary cooling to 800 ° C. or less, the cooled SiO _X gas to 200 ° C. or less, the SiO _X fine powder 13. The method for producing SiO _x powder according to claim 12, wherein the particle diameter is grown and recovered. 14. The method for producing SiO _x powder according to claim 13, wherein the recovered SiO _x fine powder has an average particle diameter D ₅₀ of 1 μm to 20 μm. The method for producing SiO _x powder according to any one of claims 12 to 14, further comprising a step of collecting dust by collecting the SiO _x fine powder unrecovered in the water-cooled cyclone with a bag filter. Clean exhaust gas after dust collected by the bag filter is cooled to room temperature by a heat exchanger, further pressurized by a high pressure blower, and the SiO _x gas vaporized in the heating furnace at the outlet of the heating furnace The method for producing SiO _x powder according to claim 15, wherein the inert gas for rapidly cooling is used in a circulating manner. A DC (direct current) plasma device or an RF (radio frequency induction) thermal plasma device comprising a plasma gun for ejecting a plasma flame;
A powder supply device for spraying mixed granulated powder of metal Si powder and SiO ₂ powder into the plasma flame;
A heating furnace for vaporizing the molten droplets of the mixed granulated powder heated and melted by the plasma flame to perform a SiO _x conversion reaction;
SiO _X powder production apparatus characterized by comprising a cooling device for precipitating SiO _X fine powder generated the SiO _X gas is quenched with an inert gas. 18. The SiO _X powder according to claim 17, wherein the plasma gun is provided with a speed adjusting portion at a nozzle so that a material flight speed in the plasma flame is 150 m / sec to 3 m / sec. manufacturing device. The heating furnace is a graphite heater heating furnace or a high frequency induction heating furnace, and the mixed molten droplets of the mixed granulated powder heated and melted by the plasma flame are further heated to 2,000 K (1,727 ° C.) or more. vaporized, SiO _X powder production apparatus as claimed in claim 17 or claim 18 further characterized in that to produce the SiO _X gas. The SiO _{x according to} any one of claims 17 to 19, wherein the cooling device includes a ring-shaped nozzle that blows an inert gas onto the SiO _x gas vaporized in the heating furnace to quench the gas. Powder manufacturing equipment. SiO _X powder production apparatus according to any one of claims 17 to claim 19, SiO _X fine powder precipitated and further comprising a water cooling cyclone to recover by cooling. 21. The apparatus for producing SiO _x powder according to claim 20, further comprising a bag filter for collecting and collecting the uncollected SiO _x fine powder by the water-cooled cyclone. A heat exchanger that cools the clean exhaust gas after dust collection by the bag filter to room temperature, and pressurizes the clean exhaust gas cooled to room temperature by the heat exchanger to the ring-shaped nozzle of the cooling device SiO _X powder production apparatus according to claim 22, further comprising an inert gas cooling system comprising a high pressure blower circulating.

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