Method for producing lithium-containing silicon oxide

Abstract

The present invention addresses the problem of providing a method for producing lithium-containing silicon oxide, the method making it possible to improve the yield in the production of the lithium-containing silicon oxide. This method for producing lithium-containing silicon oxide includes a reaction step in which a silicon- and lithium-silicate-containing raw material, which comprises a silicon powder and lithium silicate, is vaporized and reacted. The method further includes a precipitation step in which a gas produced in the reaction step is cooled to cause precipitation. The method furthermore includes a pulverization step in which the precipitate obtained in the precipitation step is collected and pulverized to obtain a powder of lithium-containing silicon oxide. The method furthermore includes a recycle step in which an excessively finely pulverized portion of the powder of lithium-containing silicon oxide obtained in the pulverization step is recycled to the reaction step.

Description

Method for producing lithium-containing silicon oxide

[0001] The present invention relates to a method for producing lithium (Li)-containing silicon oxide used as a negative electrode material for lithium ion secondary batteries, etc.

[0002] One method for producing lithium-containing silicon oxide used as a negative electrode material for lithium-ion secondary batteries is the method disclosed in JP 2021-051904 A. This method produces lithium-containing silicon oxide by heating a silicon / lithium silicate-containing raw material under reduced pressure to generate gases from the raw material, cooling the gases at a predetermined temperature, and powdering the resulting precipitate.

[0003] Patent Publication No. 2021-051904

[0004] The method for producing lithium-containing silicon oxide used as a negative electrode material for lithium-ion secondary batteries, as described above, includes a step (pulverization step) of pulverizing (powdering) the lithium-containing silicon oxide obtained by calcination. The lithium-containing silicon oxide powder obtained by this pulverization step is classified to obtain a lithium-containing silicon oxide powder (fine powder) having a target median diameter (D50), a lithium-containing silicon oxide powder (coarse powder) having a median diameter (D50) larger than that of the fine powder, and a lithium-containing silicon oxide powder (extra-fine powder) having a median diameter (D50) smaller than that of the fine powder. In this case, the coarse powder is often returned to the pulverization step and reused. However, the extra-fine powder has problems such as a higher oxygen content than the fine powder or coarse powder due to its large surface area, a tendency for impurities from the pulverizer to be mixed in (high surface impurity content), and the generation of excessive decomposition products with the electrolyte during charge / discharge reactions within the battery. For this reason, if the extra-fine powder is used as a negative electrode material, either directly or mixed with the fine powder, to fabricate a lithium-ion secondary battery, the performance of the battery may be degraded. Therefore, in the conventional method for producing lithium-containing silicon oxide, there has been a problem in that excessively fine powder is generated, resulting in a decrease in the yield of the obtained lithium-containing silicon oxide.

[0005] An object of the present invention is to provide a method for producing lithium-containing silicon oxide that can improve the yield during the production of lithium-containing silicon oxide.

[0006] The method for producing lithium-containing silicon oxide according to the present invention includes a reaction step in which a silicon / lithium silicate-containing raw material (gas-generating raw material) containing silicon powder and lithium silicate is vaporized and reacted. It also includes a precipitation step in which the gas generated in the reaction step is cooled and precipitated. It further includes a pulverization step in which the precipitate obtained in the precipitation step is recovered and pulverized to obtain lithium-containing silicon oxide powder. It also includes a reuse step in which the ultrafine lithium-containing silicon oxide powder obtained in the pulverization step is reused in the reaction step.

[0007] In this method for producing lithium-containing silicon oxide, the ultrafine lithium-containing silicon oxide powder obtained in the pulverization step is reused in the reaction step, thereby improving the yield during the production of lithium-containing silicon oxide.

[0008] In the method for producing lithium-containing silicon oxide according to the present invention, it is preferable that the ultrafine lithium-containing silicon oxide powder obtained in the pulverization step has a median diameter (D50) of less than 5 μm.

[0009] Furthermore, in the method for producing lithium-containing silicon oxide according to the present invention, it is preferable that the recycling step further comprises a silicon (Si) powder supplying step of supplying silicon (Si) powder.

[0010] In this method for producing lithium-containing silicon oxide, when the surface-oxidized excessively fine powder is reused as a synthesis raw material (gas generating raw material) in the reaction step, silicon powder is supplied (mixed). Therefore, the reaction rate in the reaction step in which the excessively fine powder is reused can be improved.

[0011] 1 is a schematic diagram of a lithium-containing silicon oxide manufacturing apparatus according to an embodiment of the present invention.

[0012] REFERENCE SIGNS LIST 100 Vapor deposition apparatus 110 Crucible 120 Heater 130 Vapor deposition drum 141 Scraper 143 Particle guide 150 Chamber 151 Chamber body 152 Recovery section 153 Exhaust pipe 160 Raw material supply hopper 170 Raw material introduction pipe 180 Recovery container 190 Recovery pipe Gg Gas guide OP Opening RM Deposition chamber Sr Molten metal VL1 First valve VL2 Second valve

[0013] A method for producing lithium-containing silicon oxide according to an embodiment of the present invention includes a reaction step of vaporizing and reacting a silicon / lithium silicate-containing raw material (gas-generating raw material) containing silicon powder and lithium silicate. In this step, the gas-generating raw material, such as the silicon / lithium silicate-containing raw material, is heated under reduced pressure in a reaction vessel to generate a raw material gas from the silicon and lithium silicate in the raw material.

[0014] The method for producing lithium-containing silicon oxide according to the embodiment of the present invention also includes a deposition step of cooling and depositing the gas generated in the reaction step, in which the mixed gas (reaction gas) obtained by mixing and reacting the gases generated from the gas-generating raw materials in the reaction step is cooled and deposited on the surface of a deposition table arranged outside the reaction vessel.

[0015] Furthermore, the method for producing lithium-containing silicon oxide according to the embodiment of the present invention includes a pulverization step in which the precipitate obtained in the precipitation step is recovered and pulverized to obtain lithium-containing silicon oxide powder. In this step, the lithium-containing silicon oxide obtained in the precipitation step is pulverized using a pulverizer such as a bead mill. The lithium-containing silicon oxide powder obtained by pulverization using the pulverizer is then classified into fine powder, coarse powder, and ultrafine powder. The pulverization and classification may be performed simultaneously using a pulverizer or the like equipped with a classification function. In the method for producing lithium-containing silicon oxide according to the present invention, it is preferable to classify lithium-containing silicon oxide powder having a median diameter (D50) of 5 μm or more and 10 μm or less as fine powder and lithium-containing silicon oxide powder having a median diameter (D50) of less than 5 μm as ultrafine powder. Furthermore, lithium-containing silicon oxide powder (coarse powder) having a median diameter (D50) of more than 10 μm is pulverized (reused) again in the pulverization step. Therefore, the coarse particles do not affect the yield of the entire process.

[0016] The method for producing lithium-containing silicon oxide according to the embodiment of the present invention further includes a recycling step of recycling the ultrafine lithium-containing silicon oxide powder obtained in the above-mentioned pulverization step in the reaction step. In this step, the ultrafine lithium-containing silicon oxide powder obtained in the pulverization step is recycled as a gas generating raw material in the reaction step. At this time, the ultrafine lithium-containing silicon oxide powder is supplied into a reaction vessel. Then, in the reaction vessel, the ultrafine lithium-containing silicon oxide powder is heated under reduced pressure.

[0017] Furthermore, since the lithium silicate contained in the lithium-containing silicon oxide powder has a low melting point, by setting the reaction temperature in the reaction step to be equal to or higher than the melting point of lithium silicate, at least a portion of the ultrafine powder of the lithium-containing silicon oxide powder in the reaction vessel can be brought into a molten state. This prevents the ultrafine powder from being stirred up by the raw material gas (or reaction gas) generated by heating the ultrafine powder when it is supplied into the reaction vessel, and from being mixed into the deposit (deposit) deposited on the surface of the deposition table arranged outside the reaction vessel. The reaction temperature is set to be equal to or higher than the melting point of the lithium silicate contained in the lithium-containing silicon oxide powder (for example, Li ２ Si ２ O ５ If it is about 1030°C, Li ２ SiO ３ Adjust the temperature accordingly (for example, about 1200°C).

[0018] In the method for producing lithium-containing silicon oxide according to an embodiment of the present invention, the recycling step preferably further comprises a silicon (Si) powder supplying step of supplying silicon (Si) powder. Furthermore, in this silicon (Si) powder supplying step, the silicon (Si) powder supplied is preferably mixed with the silicon (Si) powder in the ultrafine powder of the lithium-containing silicon oxide powder recycled in the recycling step so that the molar ratio is 1 / 10 or less to prepare a mixed powder (gas generating raw material). The lower limit of this molar ratio is not particularly limited as long as it does not impair the gist of the present invention, but if a lower limit is required, it is preferably 1 / 20. In this case, the prepared mixed powder (gas generating raw material) is supplied into a reaction vessel.

[0019] An example of carrying out the method for producing lithium-containing silicon oxide according to the embodiment of the present invention will be described below with reference to FIG.

[0020] (Regarding the method for producing lithium-containing silicon oxide) The method for producing lithium-containing silicon oxide according to the embodiment of the present invention can be carried out using a vapor deposition apparatus 100 as shown in Fig. 1. Fig. 1 is a diagram showing an example of the configuration of an apparatus for producing lithium-containing silicon oxide. Hereinafter, the vapor deposition apparatus 100 will be described, and then the above-mentioned production method will be described.

[0021] As shown in FIG. 1, the vapor deposition apparatus 100 is mainly composed of a crucible 110, a heater 120, a vapor deposition drum 130, a scraper 141, a particle guide 143, a chamber 150, a raw material supply hopper 160, a raw material introduction pipe 170, a recovery container 180, a first valve VL1, and a second valve VL2.

[0022] As shown in FIG. 1 , the crucible 110 is a heat-resistant container with an opening in the central portion of the top wall, and is installed in the chamber 150. A through-hole (not shown) is formed in one location on the periphery of the top wall of the crucible 110, and a raw material introduction pipe 170 is inserted through this through-hole. That is, raw material in the raw material supply hopper 160 is supplied to the crucible 110 through the raw material introduction pipe 170. A gas guide Gg is disposed above the top wall of the crucible 110. The gas guide Gg is a member that guides the raw material gas generated in the crucible 110 to the evaporation drum 130, and as shown in FIG. 1 , is installed on the upper surface of the top wall so as to surround the central portion of the top wall.

[0023] The heater 120 is for heating the crucible 110 to a high temperature, and is disposed so as to surround the outer periphery of the crucible 110 .

[0024] The evaporation drum 130 is, for example, a cylindrical horizontal drum. As shown in FIG. 1 , it is disposed above the opening OP in the top wall of the crucible 110, and its lower portion is surrounded by a gas guide Gg. The evaporation drum 130 is driven to rotate in one direction by a drive mechanism (not shown). The evaporation drum 130 is provided with a temperature regulator (not shown) for maintaining a constant temperature on its outer circumferential surface. This temperature regulator uses an externally supplied cooling medium to cool the outer circumferential surface temperature of the evaporation drum 130 to a temperature suitable for the evaporation of the evaporation source gas. The outer circumferential surface temperature of the evaporation drum 130 can also affect the crystallinity of the precipitate deposited on the precipitate remaining on the evaporation drum. If this temperature is too low, the structuring of the precipitate may become too sparse; conversely, if it is too high, crystal growth due to disproportionation may proceed. This temperature is preferably 900°C or less, more preferably in the range of 150°C or more and 800°C or less, and particularly preferably in the range of 150°C or more and 700°C or less.

[0025] The scraper 141 is a member that serves to scrape the thin film formed on the deposition drum 130 from the deposition drum 130, and is disposed near the deposition drum 130 as shown in FIG. 1 . The flakes (active material particles) scraped off by the scraper 141 fall into a particle guide 143. The material of the scraper 141 affects impurity contamination of the active material particles. To suppress this effect, the material of the scraper 141 is preferably stainless steel or ceramic, and particularly preferably ceramic. The scraper 141 is preferably not brought into contact with the outer peripheral surface of the deposition drum 130. This is because this prevents impurity contamination, which may occur due to direct contact between the deposition drum 130 and the scraper 141, from being mixed into the recovered active material particles.

[0026] The particle guide 143 is, for example, a vibrating conveying member, and as shown in Figure 1, is arranged so that it slopes downward as it moves from the vicinity of the evaporation drum toward the collection section 152 of the chamber 150.It receives thin film fragments scraped off by the scraper 141 arranged above it and sends them to the collection section 152 of the chamber 150.

[0027] As shown in FIG. 1 , the chamber 150 is mainly composed of a chamber main body 151, a recovery section 152, and an exhaust pipe 153. As shown in FIG. 1 , the chamber main body 151 is a box-shaped section having a deposition chamber RM therein, and accommodates the crucible 110, the heater 120, the evaporation drum 130, the scraper 141, and the particle guide 143. As shown in FIG. 1 , the recovery section 152 is a section that protrudes outward from the side wall of the chamber main body 151, and has a space that communicates with the deposition chamber RM of the chamber main body 151. As described above, the tip of the particle guide 143 is located in the recovery section 152.

[0028] The raw material supply hopper 160 is a raw material supply source, and as shown in Fig. 1, its outlet is connected to the raw material introduction pipe 170. That is, the raw material charged into the raw material supply hopper 160 is supplied to the crucible 110 via the raw material introduction pipe 170 at an appropriate timing. The raw material supplied to the crucible 110 becomes molten Sr and then vaporizes to become raw material gas.

[0029] The raw material introduction pipe 170 is a round-hole nozzle for supplying the solid raw material placed in the raw material supply hopper 160 to the crucible 110, and is arranged in the center of the top plate of the crucible 110 with its mouth facing upward.

[0030] The collection container 180 is a container for collecting thin film pieces that have passed through the first valve VL1 and the second valve VL2.

[0031] The first valve VL1 and the second valve VL2 are used to adjust the amount of thin film pieces collected into the collection container 180 by opening and closing them, and are provided on a collection pipe 190 connecting the collection section 152 of the chamber 150 and the collection container 180.

[0032] The raw material (mixed powder or granulated material) is fed from a raw material supply hopper 160 to the crucible 110 through a raw material introduction pipe 170, or the raw material is directly fed into the crucible 110. Here, silicon (Si) and lithium disilicate (Li ２ Si ２ O ５ ) and other silicate powders, and lithium carbonate (Li２ CO ３ ), silicon dioxide (SiO ２ A mixed powder of SiO (SiO 2 ) and silicon (Si) is used. In this case, the mixed powder generates SiO gas containing a metal element such as Li as a raw material gas when heated to a predetermined temperature.

[0033] After the raw materials are loaded into the crucible 110, the pressure in the precipitation chamber RM is reduced while the crucible 110 is heated by the heater 120. If the pressure in the precipitation chamber RM is too high, the reaction that generates SiO gas from the raw materials becomes difficult to occur. Therefore, the pressure in the precipitation chamber RM is preferably 1000 Pa or less, more preferably 750 Pa or less, even more preferably 100 Pa or less, and particularly preferably 20 Pa or less. The temperature in the precipitation chamber RM also affects the SiO reaction rate. If the temperature is too low, the reaction rate slows, while if the temperature is too high, there are concerns about side reactions due to melting of the raw materials and reduced energy efficiency. Furthermore, there is also a concern that the temperature may damage the crucible 110. From this perspective, the temperature in the precipitation chamber RM is preferably in the range of 1000°C to 1600°C, more preferably 1100°C to 1500°C, and particularly preferably 1200°C to 1400°C.

[0034] By heating the raw material under reduced pressure as described above, raw material gas is generated from the raw material in the crucible 110, and the raw material gas is supplied to the evaporation drum 130 through the gas guide Gg. At this time, the evaporation drum 130 is rotated by a drive source. The temperature of the outer circumferential surface of the evaporation drum 130 is set lower than the temperature in the deposition chamber RM. More specifically, this temperature is set lower than the condensation temperature of the raw material gas. With this setting, the raw material gas generated from the crucible 110 is evaporated (deposited) and deposited on the outer circumferential surface of the rotating evaporation drum 130, and the deposit is scraped off from the evaporation drum 130 by the scraper 141. The scraped pieces of the deposit fall along the outer circumferential surface of the evaporation drum 130 into the particle guide 143.

[0035] In the vapor deposition apparatus 100 according to the embodiment of the present invention, lithium-containing silicon oxide is produced as described above.

[0036] Next, the lithium-containing silicon oxide obtained as described above is pulverized by a pulverizer such as a bead mill. In this step, the lithium-containing silicon oxide powder obtained by pulverization by the pulverizer is classified into fine powder, coarse powder, and superfine powder.

[0037] Subsequently, the ultrafine powder of the lithium-containing silicon oxide powder obtained by the above-mentioned classification is reused as a gas generating raw material in the next reaction step. In this case, the ultrafine powder is supplied into the crucible 110 from a raw material supply hopper 160 as shown in FIG. 1 through a raw material introduction pipe 170, or is supplied directly into the crucible 110.

[0038] Furthermore, when the ultrafine powder of the lithium-containing silicon oxide powder obtained by classification as described above is reused, it is preferable to prepare a mixed powder (gas generating raw material) by mixing silicon (Si) powder with the ultrafine powder at a molar ratio of 1 / 10 to the silicon (Si) in the ultrafine powder. In this case, the prepared mixed powder (gas generating raw material) is supplied from a raw material supply hopper 160 as shown in FIG. 1 through a raw material introduction pipe 170 into the crucible 110, or is supplied directly into the crucible 110.

[0039] <Modifications> In the method for producing lithium-containing silicon oxide according to the previous embodiment, silicon (Si) powder is mixed with the silicon (Si) in the ultrafine powder of the lithium-containing silicon oxide powder so that the molar ratio relative to the silicon (Si) in the ultrafine powder of the lithium-containing silicon oxide powder is 1 / 10 to prepare a mixed powder, and then the mixed powder is supplied from the raw material supply hopper 160 through the raw material introduction pipe 170 into the crucible 110 as the gas generation raw material in the above-mentioned reaction step. However, in the present invention, silicon (Si) powder may be weighed as the gas generation raw material in the above-mentioned reaction step so that the molar ratio relative to the silicon (Si) in the ultrafine powder of the lithium-containing silicon oxide powder is 1 / 10, and then separately supplied from the raw material supply hopper 160 through the raw material introduction pipe 170 into the crucible 110.

[0040] EXAMPLES In the following, examples and comparative examples are shown to explain the present invention in more detail, but the present invention is not limited to these examples.

[0041] (1) Reaction and precipitation process Silicon (Si) powder having a median diameter (D50) of 2.5 μm and lithium disilicate (Li ２ Si ２ O ５ ) powders were mixed at a molar ratio of 3:1 to prepare a mixed powder. This mixed powder was then charged as a gas-generating raw material into the crucible 110 of the vapor deposition apparatus 100 shown in FIG. 1 . The pressure in the deposition chamber RM was reduced to 5 Pa, and the temperature inside the crucible 110 was raised to 1400°C over 30 minutes. The temperature inside the crucible 110 was then maintained at 1400°C for 30 minutes, allowing Li gas and SiO gas to be generated, mixed, and reacted. Next, the vapor deposition drum 130 was rotated while controlling the temperature of the outer peripheral surface of the vapor deposition drum 130 to 25°C, and a mixed gas (reaction gas) of Li gas and SiO gas was condensed and precipitated on the outer peripheral surface of the vapor deposition drum 130. A scraper 141 was then brought close to the vapor deposition drum 130, and the lithium-containing silicon oxide thin film deposited on the outer peripheral surface of the vapor deposition drum 130 was scraped off, thereby obtaining a lithium-containing silicon oxide powder.

[0042] (2) Pulverization Step The lithium-containing silicon oxide was pulverized in air using a bead mill (SDA1 manufactured by Ashizawa Finetech Co., Ltd.) to a median diameter (D50) of 5 μm or more and 10 μm or less to obtain a lithium-containing silicon oxide powder. Zirconia beads were used as the pulverizing beads. The obtained lithium-containing silicon oxide powder was classified using a classifier (TC15 manufactured by Nisshin Engineering Co., Ltd.) to obtain the desired lithium-containing silicon oxide powder (fine powder) having a median diameter (D50) of 5 μm and the lithium-containing silicon oxide powder (extra-fine powder) having a median diameter (D50) of 1.9 μm. At this time, coarse powder having a median diameter (D50) of more than 10 μm was returned to the pulverization step, and pulverization and classification were repeated until no coarse powder was obtained. The median diameter (D50) of each lithium-containing silicon oxide powder obtained by the above-mentioned classification was measured using a laser diffraction particle size distribution measuring device (Malvern Mastersizer 3000). The measurement conditions were as follows:

[0043] Dispersion medium: isopropyl alcohol (2-propanol) Particle refractive index: 3.500 Particle absorption rate: 1.000 Dispersion medium refractive index: 1.390

[0044] The zirconium concentrations of the target lithium-containing silicon oxide powder (fine powder) having a median diameter (D50) of 5 μm and the lithium-containing silicon oxide powder (extra-fine powder) having a median diameter (D50) of 1.9 μm obtained in the above-mentioned (3) pulverization step were measured and found to be 400 ppm and 737 ppm, respectively. The zirconia concentration of the above-mentioned lithium-containing silicon oxide powder was measured under the following conditions using an ICP analyzer (PS3520VDD II, manufactured by Hitachi High-Tech Science Corporation).

[0045] (Measurement conditions) Start-up time (warm-up time): 15 minutes or more Measurement mode: iFR Measurement wavelength range: 160 nm to 850 nm Spectrometer atmosphere: vacuum

[0046] (3) Reuse Step The lithium-containing silicon oxide powder (extra-fine powder) having a median diameter (D50) of 1.9 μm obtained in the above-mentioned (3) pulverization step was supplied from the raw material supply hopper 160 to the crucible 110 via the raw material introduction pipe 170 as a gas generating raw material in the reaction step following the pulverization step. Then, the reaction step and the precipitation step were carried out in the same manner as described above. Note that when the extra-fine powder was supplied to the crucible 110, it was confirmed by the zirconium concentration of the lithium-containing silicon oxide powder after the precipitation step that the extra-fine powder was not blown up onto the deposition drum. As a result, the zirconia concentration after the precipitation step was 1 ppm. From this, it was confirmed that the lithium-containing silicon oxide obtained in the reaction and precipitation steps was not contaminated with the extra-fine powder. Next, the target lithium-containing silicon oxide powder (fine powder) having a median diameter (D50) in the range of 5 μm to 10 μm was obtained through the pulverization step in the same manner as described above.

[0047] The yield of the target lithium-containing silicon oxide powder (fine powder) having a median diameter (D50) in the range of 5 μm to 10 μm by the above-mentioned process was 86% (see Table 1). Note that this yield is a percentage obtained by dividing the "weight of the fine powder" by the "weight of the raw material" (i.e., "(weight of the fine powder / weight of the raw material) × 100(%)").

[0048] Except for obtaining a target lithium-containing silicon oxide powder (fine powder) having a median diameter (D50) of 8.1 μm and a lithium-containing silicon oxide powder (ultrafine powder) having a median diameter (D50) of 4.7 μm in the pulverization step, lithium-containing silicon oxide was obtained by the same method as in Example 1. In this case, the zirconium concentration after the precipitation step was 1 ppm, and the yield of the target lithium-containing silicon oxide powder (fine powder) having a median diameter (D50) in the range of 5 μm to 10 μm was 86% (see Table 1).

[0049] Lithium-containing silicon oxide was obtained in the same manner as in Example 1, except that silicon (Si) powder was supplied in the recycling step (a silicon (Si) powder supplying step was provided). The silicon powder supplying step will be described below.

[0050] (Silicon powder supplying step) Silicon (Si) powder having a median diameter (D50) of 3 μm was mixed with the silicon (Si) in the lithium-containing silicon oxide powder (ultrafine powder) having a median diameter (D50) of 1.9 μm obtained in the above-mentioned pulverization step so that the molar ratio was 1 / 10, to prepare a mixed powder. Then, this mixed powder was supplied into the crucible 110 from the raw material supply hopper 160 via the raw material introduction pipe 170 as a gas generating raw material in the above-mentioned reaction step.

[0051] In this case, the zirconium concentration after the precipitation step was 1 ppm, and the yield of the target lithium-containing silicon oxide powder (fine powder) having a median diameter (D50) in the range of 5 μm or more and 10 μm or less was 87% (see Table 1).

[0052] (Comparative Example 1) Except for not providing the above-mentioned (4) recycling step (i.e., not reusing the superfine powder classified in the pulverization step as a gas generating raw material in the reaction step), lithium-containing silicon oxide was obtained by the same method as in Example 1. In this case, the zirconia concentration after the precipitation step was 1 ppm, and the yield of the target lithium-containing silicon oxide powder (fine powder) having a median diameter (D50) in the range of 5 μm to 10 μm was 81% (see Table 1).

[0053]

[0054] (Summary) As is clear from Table 1 above, according to the method for producing lithium-containing silicon oxide of the present invention, the yield during the production of lithium-containing silicon oxide can be improved by reusing the ultrafine powder of lithium-containing silicon oxide powder obtained in the pulverization step as a gas-generating raw material in the reaction step. Furthermore, the zirconium concentration after the precipitation step in Examples 1-3 (i.e., lithium-containing silicon oxide powder produced by a method including a recycling step) and Comparative Example 1 (i.e., lithium-containing silicon oxide powder produced by a method (conventional method) without a recycling step) was 1 ppm. From this, it is considered that the performance of a battery using a negative electrode material produced from the lithium-containing silicon oxide powder produced by the production method of the present invention is equivalent to the performance of a battery using a negative electrode material produced from the lithium-containing silicon oxide powder produced by a conventional production method.

Claims

1. A method for producing lithium-containing silicon oxide, comprising: a reaction step of vaporizing and reacting a silicon / lithium silicate-containing raw material containing silicon powder and lithium silicate; a precipitation step of cooling and precipitating the gas generated in the reaction step; and a pulverization step of recovering the precipitate obtained in the precipitation step and pulverizing the precipitate to obtain lithium-containing silicon oxide powder, the method further comprising a recycling step of reusing the ultrafine lithium-containing silicon oxide powder obtained in the pulverization step for the reaction step.

2. The method for producing lithium-containing silicon oxide according to claim 1, wherein the ultrafine lithium-containing silicon oxide powder has a median diameter (D50) of less than 5 μm.

3. The method for producing lithium-containing silicon oxide according to claim 1 or 2, wherein the recycling step further comprises a silicon powder supply step of supplying silicon powder.

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