JP2022049185A - Generation method for lithium silicate and silicon - Google Patents

Abstract

To provide a method capable of reducing the formation of silicon carbide in the formation of lithium silicate and silicon from silicon powder, lithium carbonate powder, and silicon dioxide powder.SOLUTION: In the method, lithium silicate (SiLixOy) and silicon (Si) are generated from lithium carbonate (Li2CO3) powder, silicon dioxide (SiO2) powder, and silicon (Si) powder in the same system so that discharges of carbon dioxide (CO2) take priority over generations of silicon carbide (SiC).SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing lithium silicate and silicon from lithium carbonate powder, silicon dioxide powder and silicon powder in the same system.

In the past, "a mixture of silicon powder, lithium carbonate powder, and silicon dioxide powder as needed was used as the primary raw material, and the mixed powder was charged in a reaction vessel, heated and fired, and then the secondary raw material, Kay. It has been proposed to "generate lithium acid and silicon" and "heat a secondary raw material to simultaneously generate SiO gas and Li gas from the raw material" (see, for example, International Publication No. 2018/074175). ).

International Publication No. 2018/074175

However, as described above, when silicon powder, lithium carbonate powder and silicon dioxide powder are mixed and the mixed powder is heated at a temperature exceeding the melting point (723 ° C) of lithium carbonate, lithium carbonate and silicon react and carbonize as a by-product. Silicon (SiC) is generated. The formation of silicon carbide in this way not only reduces the yields of the desired lithium silicate and silicon, but also the products thereof (ie, lithium silicate, silicon and silicon carbide) as the bulk density increases. ) Will be difficult to handle. Further, Patent Document 1 describes that the superheated firing of the primary raw material under reduced pressure makes it easier to separate impurity elements, but for carbon impurities, impurities in the carbon dioxide state cannot be separated. Even if it can be done, if it becomes silicon carbide (SiC), it becomes difficult to separate carbon impurities even under reduced pressure.

An object of the present invention is to provide a method capable of reducing the production of silicon carbide in producing lithium silicate and silicon from silicon powder, lithium carbonate powder and silicon dioxide powder.

In the method according to the first aspect of the present invention, a powder of lithium carbonate (Li ₂ CO ₃ ) in the same system so that emission of carbon dioxide (CO ₂ ) is prioritized over production of silicon carbide (SiC). Lithium silicate and silicon are produced from the powder of silicon dioxide (SiO ₂ ) and the powder of silicon (Si). Here, lithium silicate and silicon may each be a single phase product (a compound composed of a single phase (that is, a powder or the like)), or silicon as in the compound represented by the general formula _{SiLi x} Oy. It may be a compound phase (compound composed of a plurality of phases) composed of a phase, a silicon oxide phase (SiO _x phase), a lithium silicate phase (Li ₂ Si ₂ O ₅ phase, Li ₂ SiO ₃ phase, etc.) and the like. In addition, here, "lithium silicate and silicon are produced" may include the case where some pre-reaction silicon remains as it is. Further, here, the system is preferably vacuum (decompressed). Here, as a method of prioritizing the emission of carbon dioxide over the production of silicon carbonate, for example, ₍ i) Li ₂ CO _{3 +} Si → Li ₂ SiO ₃ + SiC rather than the progress of the reaction. → Li ₂ O + CO ₂ A method of prioritizing the progress of the reaction indicated by ↑, (ii) Li ₂ CO ₃ + Si → Li ₂ SiO ₃ + SiC rather than the progress of the reaction Li ₂ CO ₃ + SiO ₂ → _{SiLi x} Oy A method of prioritizing the progress of the reaction indicated by + CO ₂ ↑ can be mentioned. Here, the composition represented by the general formula _{SiLi xOy} includes a silicon phase, a silicon oxide phase (SiOx phase), a lithium silicate phase (Li ₂ Si ₂ O ₅ phase, Li ₂ SiO ₃ phase, etc.), and oxidation. It is a compound phase product (composition composed of a plurality of phases) composed of a lithium phase (Li ₂ O) phase and the like.

In this method, carbon dioxide emissions are prioritized over silicon carbide production. Therefore, this method can reduce the production of silicon carbide.

The method according to the second aspect of the present invention is the method according to the first aspect, in which the mixed powder of lithium carbonate powder, silicon dioxide powder and silicon powder is 400 under a reduced pressure atmosphere. It is heated at a temperature within the range of ° C or higher and lower than the melting point of lithium carbonate.

In this method, first, the mixed powder is heated in a reduced pressure atmosphere at a temperature within the range of 400 ° C. or higher and lower than the melting point of lithium carbonate to produce silicon carbide (Li ₂ CO ₃ + Si → Li ₂ SiO ₃ + SiC. ) Suppresses the progress of the lithium carbonate decarbonation reaction (Li ₂ CO ₃ → Li ₂ O + CO ₂ ↑ reaction). After that, when it is heated at a temperature within the range of 1150 ° C. or higher and 1400 ° C. or lower, the reaction in which Li and SiO are simultaneously generated, which is indicated by SiLi _{xO y} + (y-1) Si → xLi ↑ + ySiO ↑, proceeds. Therefore, in this method, it is possible to reduce the production of silicon carbide when producing lithium silicate and silicon from silicon powder, lithium carbonate powder and silicon dioxide powder.

The method according to the third aspect of the present invention is the method according to the first aspect, in which a layer of silicon dioxide powder is formed between a layer of lithium carbonate powder and a layer of silicon powder. Lithium carbonate powder, silicon dioxide powder and silicon powder are spread in layers so as to be located and heated at a temperature equal to or higher than the melting point of lithium carbonate. The upper limit of the heating temperature is 1400 ° C.

In this method, as described above, a layer of silicon dioxide powder is positioned between the layer of lithium carbonate powder and the layer of silicon powder. That is, in this method, the lithium carbonate powder and the silicon powder do not come into contact with each other, but the lithium carbonate powder and the silicon dioxide powder come into contact with each other. Therefore, in this method, when these powders are heated at a temperature equal to or higher than the melting point of lithium carbonate, Li ₂ CO is more than the progress of the silicon carbide formation reaction (Li ₂ CO ₃ + Si → Li ₂ SiO ₃ + SiC). ₃ + SiO ₂ → _{SiLi x} Oy + CO ₂ Priority is given to the progress of the reaction indicated by ↑. Then, when it is heated at a temperature within the range of 1150 ° C. or higher and 1400 ° C. or lower, the reaction of SiLi _{xO y} + (y-1) Si → xLi ↑ + ySiO ↑ can proceed. Therefore, in this method, it is possible to reduce the production of silicon carbide when producing lithium silicate and silicon from silicon powder, lithium carbonate powder and silicon dioxide powder.

The method according to the fourth aspect of the present invention is the method according to the first aspect, in which a layer of a mixed powder of lithium carbonate powder and a powder of silicon dioxide and a layer of a powder of silicon are used. The mixed powder and the silicon powder are spread in layers so as to be adjacent to each other, and are heated at a temperature equal to or higher than the melting point of lithium carbonate. The upper limit of the heating temperature is 1400 ° C.

In this method, as described above, a layer is formed by mixing lithium carbonate powder and silicon dioxide powder, and the layer is adjacent to the silicon powder layer. Therefore, in this method, when these powders are heated at a temperature higher than the melting point of lithium carbonate, Li ₂ CO is more than the progress of the silicon carbide formation reaction (Li ₂ CO ₃ + Si → Li ₂ SiO ₃ + SiC). ₃ + SiO ₂ → _{SiLi x} Oy + CO ₂ The progress of the reaction indicated by ↑ is prioritized, and when it is heated at a temperature within the range of 1150 ° C or higher and 1400 ° C or lower, SiLi _x Oy + ( _y -1) Si → The reaction of xLi ↑ + ySiO ↑ can be advanced. Therefore, in this method, it is possible to reduce the production of silicon carbide when producing lithium silicate and silicon from silicon powder, lithium carbonate powder and silicon dioxide powder.

The method according to the fifth aspect of the present invention is the method according to the third aspect or the fourth aspect, and in this method, the layer of the silicon powder is the lowest layer.

The melting point of silicon is 1414 ° C., and the melting point of lithium silicate is lower than the melting point of silicon (for example, the melting point of Li ₂ SiO ₃ is 1201 ° C.). Therefore, in this method, in the reaction stage of _SiLi xOy + ( _y -1) Si → xLi ↑ + ySiO ↑, the melted lithium silicate naturally infiltrates into the gaps of the silicon powder. As a result, the contact area of lithium silicate with respect to silicon becomes large, and the progress of the reaction can be promoted.

The method according to the sixth aspect of the present invention is the method according to the first aspect. The powder is charged.

Therefore, in this method, if it is presumed that the progress of the reaction indicated by Li ₂ CO ₃ + SiO ₂ → _{SiLi x} Oy + CO ₂ ↑ is completed, if the silicon powder is charged, the silicon powder is charged from that time. The reaction of SiLi _{xO y} + (y-1) Si → xLi ↑ + ySiO ↑ can be advanced. Therefore, in this method, the production of silicon carbide can be suppressed when lithium silicate and silicon are produced from silicon powder, lithium carbonate powder and silicon dioxide powder.

It is a schematic diagram of the manufacturing apparatus of the lithium-containing silicon oxide powder which concerns on embodiment of this invention.

The method for producing a lithium-containing silicon oxide powder according to an embodiment of the present invention is to generate lithium silicate and silicon from silicon powder, lithium carbonate powder and silicon dioxide powder, and then lithium-containing oxidation from lithium silicate and silicon. It is a method for producing silicon powder, and reduces the production of silicon carbide in the process of the method. The lithium-containing silicon oxide powder obtained by this method for producing a lithium-containing silicon oxide powder is used, for example, as an active material for a negative electrode of a lithium ion secondary battery.

By the way, the method for producing a lithium-containing silicon oxide powder according to an embodiment of the present invention is carried out, for example, by forming a thin film of the lithium-containing silicon oxide powder on a substrate and then scraping the thin film from the substrate. However, it is preferable to use the vapor deposition apparatus 100 as shown in FIG. 1 from the viewpoint of suppressing the manufacturing cost. Therefore, first, the vapor deposition apparatus 100 will be described, and then a method for producing a lithium-containing silicon oxide powder using the vapor deposition apparatus 100 will be described. Here, four examples of the same manufacturing method are shown.

<Explanation of thin-film deposition equipment>
As shown in FIG. 1, the vapor deposition apparatus 100 mainly includes a rutsubo 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, and a recovery container 180. , 1st valve VL1 and 2nd valve VL2.

As shown in FIG. 1, the crucible 110 is a heat-resistant container in which the central portion of the top wall opens, and is installed in the chamber 150. Further, a through hole (not shown) is formed in one place around the top wall of the crucible 110, and the raw material introduction pipe 170 is inserted through the through hole. That is, the raw material in the raw material supply hopper 160 is supplied to the crucible 110 through the raw material introduction pipe 170. Further, a gas guide Gg is arranged on the upper side of the top wall of the crucible 110. This gas guide Gg is a member that guides the raw material gas generated in the crucible 110 to the vapor deposition drum 130, and is installed on the upper surface of the top wall so as to surround the central portion of the top wall as shown in FIG.

The heater 120 is for heating the crucible 110 at a high temperature, and is arranged so as to take in the outer periphery of the crucible 110.

The vapor deposition drum 130 is, for example, a cylindrical horizontal drum, which is arranged above the opening OP of the top wall of the crucible 110 as shown in FIG. 1, and the lower portion thereof is surrounded by the gas guide Gg. ing. The thin-film deposition drum 130 is rotationally driven in one direction by a drive mechanism (not shown). The vapor deposition drum 130 is provided with a temperature controller (not shown) for keeping the outer peripheral surface at a constant temperature. This temperature controller cools the outer peripheral surface temperature of the vapor deposition drum 130 to a temperature suitable for vapor deposition of the vapor deposition source gas by a cooling medium supplied from the outside. Further, the temperature of the outer peripheral surface of the vapor deposition drum 130 may affect the crystallinity of the precipitate deposited on the precipitate remaining on the vapor deposition drum. If this temperature is too low, the structure of the precipitate may become too sparse, and if it is too high, crystal growth due to the disproportionation reaction may proceed. The temperature is preferably 900 ° C. or lower, more preferably 150 ° C. or higher and 800 ° C. or lower, and particularly preferably 150 ° C. or higher and 700 ° C. or lower.

The scraper 141 is a member that serves to scrape the thin film formed on the vapor deposition drum from the vapor deposition drum 130, and is arranged in the vicinity of the vapor deposition drum 130 as shown in FIG. The flakes (active material particles) scraped off by the scraper 141 fall on the particle guide 143. Further, the material of the scraper 141 affects the contamination of the active material particles with impurities. From the viewpoint of suppressing the influence, the material of the scraper 141 is preferably stainless steel or ceramics, and particularly preferably ceramics. Further, it is preferable that the scraper 141 does not come into contact with the outer peripheral surface of the vapor deposition drum 130. This is because it is possible to prevent the recovered active material particles from being contaminated with impurity contamination that may occur due to direct contact between the vapor deposition drum 130 and the scraper 141.

The granular material guide 143 is, for example, a vibration type transport member, and is arranged so as to incline downward from the vicinity of the vapor deposition drum toward the recovery unit 152 of the chamber 150, as shown in FIG. , The thin film piece scraped off by the scraper 141 arranged above the scraper piece is received and sent to the recovery unit 152 of the chamber 150.

As shown in FIG. 1, the chamber 150 is mainly formed of a chamber main body portion 151, a recovery portion 152, and an exhaust pipe 153. As shown in FIG. 1, the chamber main body portion 151 is a box-shaped portion having a precipitation chamber RM inside, and houses a crucible 110, a heater 120, a vapor deposition drum 130, a scraper 141, and a particle guide 143. As shown in FIG. 1, the recovery unit 152 is a portion that protrudes outward from the side wall of the chamber body portion 151, and has a space that communicates with the precipitation chamber RM of the chamber body portion 151. As described above, the tip portion of the granular material guide 143 is located in the recovery unit 152.

The raw material supply hopper 160 is a raw material supply source, and its outlet is connected to the raw material introduction pipe 170 as shown in FIG. 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 is vaporized into the raw material gas after becoming the molten metal Sr.

The raw material introduction pipe 170 is a round hole-shaped nozzle for supplying the solid raw material charged in the raw material supply hopper 160 to the crucible 110, and the mouth is directed upward at the central portion of the top plate portion of the crucible 110. It is arranged like this.

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.

The first valve VL1 and the second valve VL2 are for adjusting the amount of thin film pieces collected in the collection container 180 by opening and closing, and are connected to the collection tube 190 connecting the collection unit 152 of the chamber 150 and the collection container 180. It is provided.

<Explanation of an example of a method for producing a lithium-containing silicon oxide powder according to this embodiment>
(1) First Example In this example, a mixed powder of lithium carbonate powder, silicon dioxide powder, and silicon powder is charged into the rutsubo 110 as a raw material. The mass ratio of lithium carbonate powder, silicon dioxide powder, and silicon powder in this mixed powder is preferably 1: 0.81 to 7.73: 0.76 to 3.99. (Note that this mass ratio is determined on the assumption that the molar ratio (Li / O) of the lithium element (Li) and the oxygen element (O) is in the range of 0.10 or more and 0.66 or less. ). Further, the raw material input may be performed from the raw material supply hopper 160 via the raw material introduction pipe 170, or may be directly performed on the crucible 110.

After charging the raw material into the crucible 110, the crucible 110 is heated to a temperature within the range of 400 ° C. or higher and lower than the melting point of lithium carbonate by the heater 120 while reducing the pressure in the precipitation chamber RM. If the pressure in the precipitation chamber RM is too high, carbon dioxide and other gases are less likely to be desorbed from the raw material, and the reaction of generating SiO gas is less likely to occur. Therefore, the precipitation chamber RM is reduced to 8000 Pa or less. The pressure of the precipitation chamber RM at this time is preferably 5000 Pa or less, more preferably 2000 Pa or less, and particularly preferably 1000 Pa or less. In addition, the temperature inside the rutsubo 110 affects the progress rate of the decarbonation reaction (Li ₂ CO ₃ → Li ₂ O + CO ₂ ↑ reaction) and the silicon carbide formation reaction (Li ₂ CO ₃ + Si → Li ₂ SiO ₃ + SiC). If the temperature is too low, the decarbonation reaction rate slows down, and if the temperature exceeds the melting point of lithium carbonate, the silicon carbide formation reaction proceeds. From this point of view, the temperature inside the crucible 110 is preferably in the range of 425 ° C or higher and 720 ° C or lower, more preferably in the range of 450 ° C or higher and 715 ° C or lower, and more preferably in the range of 475 ° C or higher and 710 ° C or lower. It is more preferably in the range of 500 ° C. or higher and 705 ° C. or lower, and particularly preferably in the range of 525 ° C. or higher and 700 ° C. or lower. Decompression and temperature rise are in no particular order. In addition, the raw material powder of this example keeps its powder shape as it is. The lithium oxide (Li ₂ O) after the decarboxylation reaction may absorb CO ₂ and return to Li ₂ CO ₃ . Therefore, when it is necessary to take out lithium oxide (Li ₂ O) into the atmosphere, the inside of the precipitation chamber RM is made into an inert gas atmosphere in advance, and then heated at a temperature within the range of 800 ° C. or higher and 1400 ° C. or lower. Is desirable. By such treatment, lithium oxide (Li ₂ O) is incorporated into silicon dioxide to become lithium silicate, which makes it difficult to absorb CO ₂ .

By heating the raw material as described in the above paragraph, the progress of the silicon carbide formation reaction (Li ₂ CO ₃ + Si → Li ₂ SiO ₃ + SiC) is suppressed while the decarbonation reaction of lithium carbonate (Li ₂ CO ₃ →). (Reaction of Li ₂ O + CO ₂ ↑) proceeds. At this time, the progress of the decarboxylation reaction of lithium carbonate can be confirmed by monitoring the weight of the raw material, detecting carbon dioxide, or detecting the decrease in the rate of decrease in pressure. Further, when the method according to this example is repeated after the above confirmation, it is also possible to control the progress of the decarboxylation reaction of lithium carbonate by time control. Further, by using an external device to superheat the raw material and decarboxylate the powder as described in the above paragraph, the powder is charged from the raw material supply hopper 160 into the rutsubo 110 via the raw material introduction pipe 170, thereby decarboxylating in this example. It is also possible to omit the control of the progress of the carbonation reaction.

As described above, the progress of the decarboxylation reaction of lithium carbonate is controlled, and from the time when the decarboxylation reaction of lithium carbonate is considered to be completed, the pressure (decompressed state) of the precipitation chamber RM is maintained or the pressure is further increased. Decrease. If the pressure in the precipitation chamber RM is too high, the reaction of generating SiO gas from the raw material is less likely to occur. Therefore, the pressure in the precipitation chamber RM is preferably 1000 Pa or less, more preferably 750 Pa or less, and particularly preferably 20 Pa or less. After the precipitation chamber RM has been depressurized, the barnardia japonica 110 is heated to a temperature of more than 1050 ° C. by the heater 120. The heating temperature is preferably more than 1100 ° C, more preferably more than 1150 ° C, further preferably more than 1200 ° C, still more preferably more than 1250 ° C, and more than 1300 ° C. It is particularly preferable to have. The upper limit of this heating temperature is 1400 ° C. At this time, the raw material may be agitated by a stirrer or the like after a certain period of time has elapsed. At this time, the precipitation chamber RM is maintained in a reduced pressure state.

By heating the raw material under reduced pressure as described in the above paragraph, the reaction in which lithium oxide (Li ₂ O) is incorporated into silicon dioxide to become lithium silicate proceeds, and SiLi _x Oy + ( _y -1) Si → The reaction indicated by xLi ↑ + ySiO ↑ proceeds. When the heating temperature is in the range of 1050 ° C or higher and lower than 1150 ° C, the former reaction proceeds faster than the latter reaction, and when the heating temperature is in the range of 1150 ° C or higher and 1400 ° C or lower, the former reaction and The latter reaction proceeds almost at the same time. Then, the silicon monoxide gas and the lithium gas generated from the crucible 110 are supplied to the vapor deposition drum 130 through the gas guide Gg. At this time, the vapor deposition drum 130 is rotationally driven by a drive source. The temperature of the outer peripheral surface of the vapor deposition drum 130 is set lower than the temperature in the precipitation chamber RM. More specifically, the temperature is set lower than the condensation temperature of silicon monoxide gas and lithium gas. With this setting, silicon monoxide gas and lithium gas generated from the rutsubo 110 are deposited and deposited on the outer peripheral surface of the rotating vapor deposition drum 130, and the deposit is scraped from the vapor deposition drum 130 by the scraper 141. The scraped sediment fragments fall to the granular material guide 143 along the outer peripheral surface of the vapor deposition drum 130.

(2) Second Example In this example, when lithium carbonate powder, silicon dioxide powder, and silicon powder are charged into the rutsubo 110 as raw materials, a layer of lithium carbonate powder and silicon powder are used. The lithium carbonate powder, the silicon dioxide powder and the silicon powder are stacked in layers so that the layer of the silicon dioxide powder is located between the layers. That is, in this example, the lithium carbonate powder and the silicon powder do not come into contact with each other, but the lithium carbonate powder and the silicon dioxide powder come into contact with each other. It should be noted that such raw material input is performed directly on the crucible 110. Further, at this time, it is preferable that the layer of silicon powder is the lowest layer. Further, at this time, the layer of the lithium carbonate powder and the layer of the silicon dioxide powder may be laminated one by one, or the layer of the lithium carbonate powder and the layer of the silicon dioxide powder may be alternately laminated. Multiple layers may be stacked. Here, the thickness of the layer of the lithium carbonate powder is preferably in the range of 100 μm or more and 50 mm or less, more preferably in the range of 200 μm or more and 45 mm or less, and more preferably in the range of 500 μm or more and 40 mm or less. Is more preferable, and it is particularly preferable that the range is 1 mm or more and 35 mm or less. Further, the thickness of the silicon dioxide powder layer is preferably in the range of 85 μm or more and 400 mm or less, more preferably in the range of 170 μm or more and 360 mm or less, and more preferably in the range of 430 μm or more and 320 mm or less. It is more preferable, and it is particularly preferable that it is in the range of 850 μm or more and 280 mm or less. Further, the thickness of the silicon powder layer is preferably in the range of 84 μm or more and 220 mm or less, more preferably in the range of 168 μm or more and 198 mm or less, and further preferably in the range of 420 μm or more and 176 mm or less. It is preferably in the range of 840 μm or more and 154 mm or less. The ratio of the thickness of the silicon dioxide powder layer to the thickness of the lithium carbonate powder layer is preferably in the range of 0.25 or more and 15.0 or less, and 0.5 or more and 10.0 or less. It is more preferably within the range of 0.75 or more and 7.5 or less, and particularly preferably 1.0 or more and 5.0 or less. The ratio of the thickness of the silicon powder layer to the thickness of the lithium carbonate powder layer is preferably in the range of 0.25 or more and 10.0 or less, and is 0.5 or more and 7.5 or less. It is more preferably within the range, further preferably within the range of 0.75 or more and 5.0 or less, and particularly preferably within the range of 1.0 or more and 2.5 or less.

After charging the raw material into the crucible 110, the crucible 110 is heated to a temperature equal to or higher than the melting point of lithium carbonate by the heater 120. The temperature inside the rutsubo 110 affects the desorption rate of carbon dioxide. If the temperature is too low, the desorption rate will be slow, and if the temperature is too high, both lithium carbonate and silicon will melt and the layer will collapse. Lithium carbonate and silicon come into contact with each other to form silicon carbide. From this point of view, the temperature inside the crucible 110 is preferably in the range of 800 ° C. or higher and 1400 ° C. or lower, more preferably in the range of 900 ° C. or higher and 1300 ° C. or lower, and in the range of 1000 ° C. or higher and 1200 ° C. or lower. It is more preferable to be inside. The upper limit of this temperature is 1400 ° C. At this stage, since the desorption of carbon dioxide is prioritized over the generation of SiO gas, the pressure in the precipitation chamber RM is set to 1000 Pa to atmospheric pressure + 1000 Pa. At this time, an inert gas such as argon (Ar) gas is supplied to the precipitation chamber RM.

By heating the raw material as described in the above paragraph, the formation reaction of silicon carbide (Li ₂ CO ₃ + Si → Li ₂ SiO ₃ + SiC) is suppressed while the decarbonation reaction of lithium carbonate (Li ₂ CO ₃ → Li ₂ ). O + CO ₂ ↑ reaction) proceeds. The progress of the decarboxylation reaction of lithium carbonate can be realized by time management. Further, the decarboxylation reaction in this example is carried out by charging the powder obtained by overheating the raw material with an external device and decarboxylating the raw material from the raw material supply hopper 160 into the crucible 110 via the raw material introduction pipe 170. It is also possible to omit the management of the progress of the crucible.

The progress of the decarboxylation reaction of lithium carbonate is controlled as described above, and the pressure in the precipitation chamber RM is reduced from the time when the decarboxylation reaction of lithium carbonate is considered to be completed. If the pressure in the precipitation chamber RM is too high, the reaction of generating SiO gas from the raw material is unlikely to occur. Therefore, the pressure in the precipitation chamber RM is preferably 1000 Pa or less, more preferably 750 Pa or less, and particularly preferably 20 Pa or less. After the depressurization is completed, the barrel 110 is heated by the heater 120. The heating temperature is preferably more than 1050 ° C, more preferably more than 1100 ° C, even more preferably more than 1150 ° C, still more preferably more than 1200 ° C, still more preferably more than 1250 ° C. It is preferable, and it is particularly preferable that the temperature is higher than 1300 ° C. The upper limit of this temperature is 1400 ° C. At this time, the raw material may be agitated by a stirrer or the like after a certain period of time has elapsed.

By heating the raw material under reduced pressure as described in the above paragraph, Li ₂ CO ₃ + SiO ₂ → _{SiLi x} Oy + CO ₂ rather than the progress of the silicon carbide formation reaction (Li ₂ CO ₃ + Si → Li ₂ SiO ₃ + SiC). The progress of the reaction indicated by ↑ is prioritized. After that, the reaction of _SiLi xOy + ( _y -1) Si → xLi ↑ + ySiO ↑ proceeds. Then, the silicon monoxide gas and the lithium gas generated from the crucible 110 are supplied to the vapor deposition drum 130 through the gas guide Gg. At this time, the vapor deposition drum 130 is rotationally driven by a drive source. The temperature of the outer peripheral surface of the vapor deposition drum 130 is set lower than the temperature in the precipitation chamber RM. More specifically, the temperature is set lower than the condensation temperature of silicon monoxide gas and lithium gas. With this setting, silicon monoxide gas and lithium gas generated from the rutsubo 110 are deposited (precipitated) on the outer peripheral surface of the rotating vapor deposition drum 130, and the deposit is scraped from the vapor deposition drum 130 by the scraper 141. The scraped sediment fragments fall to the granular material guide 143 along the outer peripheral surface of the vapor deposition drum 130.

(3) Third Example In this example, when lithium carbonate powder, silicon dioxide powder, and silicon powder are charged into the rutsubo 110 as raw materials, the lithium carbonate powder and the silicon dioxide powder are used. Is mixed, and the mixed powder and the silicon powder are stacked in a layer so that the mixed powder layer and the silicon powder layer are adjacent to each other. The mass ratio of the lithium carbonate powder and the silicon dioxide powder in this mixed powder is preferably 1: 0.3 to 0.6 (note that this mass ratio is the same as that of the lithium element (Li). It is determined on the assumption that the molar ratio (Li / O) of the oxygen element (O) is in the range of 0.10 or more and 0.66 or less). Further, such raw material input is performed directly on the crucible 110. Further, at this time, it is preferable that the layer of the silicon powder is arranged below the layer of the mixed powder, and it is preferable that the layer of the silicon powder is the lowest layer. Further, at this time, the mixed powder layer and the silicon powder layer may be laminated one by one, or the mixed powder layer and the silicon powder layer may be alternately stacked in a plurality of layers. good. Here, the thickness of the layer of the mixed powder is preferably in the range of 185 μm or more and 450 mm or less, more preferably in the range of 370 μm or more and 405 mm or less, and further preferably in the range of 930 μm or more and 360 mm or less. It is preferable that it is in the range of 1.85 mm or more and 315 mm or less. Further, the thickness of the silicon powder layer is preferably in the range of 84 μm or more and 220 mm or less, more preferably in the range of 168 μm or more and 198 mm or less, and further preferably in the range of 420 μm or more and 176 mm or less. It is preferably in the range of 840 μm or more and 154 mm or less. The ratio of the thickness of the mixed powder layer to the thickness of the silicon powder layer is preferably in the range of 0.3 or more and 0.7 or less, and is in the range of 0.33 or more and 0.65 or less. It is more preferably in the range of 0.37 or more and 0.6 or less, and particularly preferably in the range of 0.4 or more and 0.55 or less.

After charging the raw material into the crucible 110, the crucible 110 is heated to a temperature equal to or higher than the melting point of lithium carbonate by the heater 120. The temperature inside the rutsubo 110 affects the desorption rate of carbon dioxide. If the temperature is too low, the desorption rate will be slow, and if the temperature is too high, both lithium carbonate and silicon will melt and the layer will collapse. Lithium carbonate and silicon come into contact with each other to form silicon carbide. From this point of view, the temperature inside the crucible 110 is preferably in the range of 800 ° C. or higher and 1400 ° C. or lower, more preferably in the range of 900 ° C. or higher and 1300 ° C. or lower, and in the range of 1000 ° C. or higher and 1200 ° C. or lower. It is more preferable to be inside. The upper limit of this temperature is 1400 ° C. At this stage, since the desorption of carbon dioxide is prioritized over the generation of SiO gas, the pressure in the precipitation chamber RM is set to 1000 Pa to atmospheric pressure + 1000 Pa. At this time, an inert gas such as argon (Ar) gas is supplied to the precipitation chamber RM.

By heating the raw material as described in the above paragraph, the formation reaction of silicon carbide (Li ₂ CO ₃ + Si → Li ₂ SiO ₃ + SiC) is suppressed while the decarbonation reaction of lithium carbonate (Li ₂ CO ₃ → Li ₂ ). O + CO ₂ ↑ reaction) proceeds. The progress of the decarboxylation reaction of lithium carbonate can be realized by time management. Further, the decarboxylation reaction in this example is carried out by charging the powder obtained by overheating the raw material with an external device and decarboxylating the raw material from the raw material supply hopper 160 into the crucible 110 via the raw material introduction pipe 170. It is also possible to omit the management of the progress of the crucible.

The progress of the decarboxylation reaction of lithium carbonate is controlled as described above, and the pressure in the precipitation chamber RM is reduced from the time when the decarboxylation reaction of lithium carbonate is considered to be completed. If the pressure in the precipitation chamber RM is too high, the reaction of generating SiO gas from the raw material is unlikely to occur. Therefore, the pressure in the precipitation chamber RM is preferably 1000 Pa or less, more preferably 750 Pa or less, and particularly preferably 20 Pa or less. After the depressurization is completed, the barrel 110 is heated by the heater 120. The heating temperature is preferably more than 1050 ° C, more preferably more than 1100 ° C, even more preferably more than 1150 ° C, still more preferably more than 1200 ° C, still more preferably more than 1250 ° C. It is preferable, and it is particularly preferable that the temperature is higher than 1300 ° C. The upper limit of this temperature is 1400 ° C. At this time, the raw material may be agitated by a stirrer or the like after a certain period of time has elapsed.

By heating the raw material under reduced pressure as described in the above paragraph, Li ₂ CO ₃ + SiO ₂ → _{SiLi x} Oy + CO ₂ rather than the progress of the silicon carbide formation reaction (Li ₂ CO ₃ + Si → Li ₂ SiO ₃ + SiC). The progress of the reaction indicated by ↑ is prioritized. After that, the reaction of _SiLi xOy + ( _y -1) Si → xLi ↑ + ySiO ↑ proceeds. Then, the silicon monoxide gas and the lithium gas generated from the crucible 110 are supplied to the vapor deposition drum 130 through the gas guide Gg. At this time, the vapor deposition drum 130 is rotationally driven by a drive source. The temperature of the outer peripheral surface of the vapor deposition drum 130 is set lower than the temperature in the precipitation chamber RM. More specifically, the temperature is set lower than the condensation temperature of silicon monoxide gas and lithium gas. With this setting, silicon monoxide gas and lithium gas generated from the rutsubo 110 are deposited (precipitated) on the outer peripheral surface of the rotating vapor deposition drum 130, and the deposit is scraped from the vapor deposition drum 130 by the scraper 141. The scraped sediment fragments fall to the granular material guide 143 along the outer peripheral surface of the vapor deposition drum 130.

(4) Fourth Example In this example, first, a mixed powder of lithium carbonate powder and silicon dioxide powder is charged into the rutsubo 110 as a raw material. The mass ratio of the lithium carbonate powder and the silicon dioxide powder in this mixed powder is preferably 1: 0.8 to 7.7 (note that this mass ratio is the lithium element (Li). ) And the molar ratio (Li / O) of the oxygen element (O) is determined on the assumption that it is in the range of 0.10 or more and 0.66 or less). Further, the raw material input may be performed from the raw material supply hopper 160 via the raw material introduction pipe 170, or may be directly performed on the crucible 110.

After charging the raw material into the crucible 110, the crucible 110 is heated to a temperature equal to or higher than the melting point of lithium carbonate by the heater 120. In such a case, the pressure inside the precipitation chamber RM may be reduced, or the inert gas may be passed through the precipitation chamber RM. Here, the inert gas is, for example, a rare gas (argon gasun or the like), a nitrogen gas or the like.

By heating the raw material as described above, only the reaction indicated by Li ₂ CO ₃ + SiO ₂ → _{SiLi x} Oy + CO ₂ ↑ can be preferentially carried out. At this time, the progress of the reaction can be confirmed by monitoring the weight of the raw material or detecting carbon dioxide. Further, when the method according to this example is repeated after the above confirmation, it is also possible to control the progress of the above reaction by time management.

The progress of the reaction is controlled as described above, and from the time when the reaction is considered to be completed, the silicon powder is charged from the raw material supply hopper 160 into the crucible 110 via the raw material introduction pipe 170. If the precipitation chamber RM has already been depressurized before the addition of the silicon powder, the decompression degree and temperature may be maintained as they are or may be appropriately changed. If the precipitation chamber RM is depressurized before the silicon powder is charged, the precipitation chamber RM is depressurized. If the pressure in the precipitation chamber RM is too high, the reaction of generating SiO gas from the raw material is unlikely to occur. Therefore, the pressure in the precipitation chamber RM is preferably 1000 Pa or less, more preferably 750 Pa or less, and particularly preferably 20 Pa or less. In addition, the temperature inside the precipitation chamber RM affects the reaction rate of SiO. If the temperature is too low, the reaction rate slows down, and if the temperature is too high, there are concerns about the progress of side reactions due to melting of the raw materials and the decrease in energy efficiency. Will be done. From this viewpoint, the temperature in the precipitation chamber RM is preferably more than 1050 ° C, more preferably more than 1100 ° C, further preferably more than 1150 ° C, still more preferably more than 1200 ° C. It is more preferably more than 1250 ° C, and particularly preferably more than 1300 ° C. The upper limit of this temperature is 1400 ° C. Further, at this time, the raw materials may be stirred and mixed by a stirrer or the like.

Then, the reaction of SiLi _{xO y} + (y-1) Si → xLi ↑ + ySiO ↑ proceeds. Then, the silicon monoxide gas and the lithium gas generated from the crucible 110 are supplied to the vapor deposition drum 130 through the gas guide Gg. At this time, the vapor deposition drum 130 is rotationally driven by a drive source. The temperature of the outer peripheral surface of the vapor deposition drum 130 is set lower than the temperature in the precipitation chamber RM. More specifically, the temperature is set lower than the condensation temperature of silicon monoxide gas and lithium gas. With this setting, silicon monoxide gas and lithium gas generated from the rutsubo 110 are deposited (precipitated) on the outer peripheral surface of the rotating vapor deposition drum 130, and the deposit is scraped from the vapor deposition drum 130 by the scraper 141. The scraped sediment fragments fall to the granular material guide 143 along the outer peripheral surface of the vapor deposition drum 130.

Hereinafter, Examples and Comparative Examples will be shown to explain the present invention in more detail, but the present invention is not limited to this Example.

A mixed powder of lithium carbonate powder, silicon dioxide powder and silicon powder (lithium carbonate powder: silicon dioxide powder: silicon powder = 1) is placed in the rut 110 of the vapor deposition apparatus 100 shown in FIG. : 1.63: 1.14 (mass ratio)) was added, and the rutsubo 110 was heated to 410 ° C. by the heater 120 while reducing the pressure in the precipitation chamber RM to 5 Pa. This heating was continued until carbon dioxide was no longer detected in the exhaust gas.

After confirming that carbon dioxide was no longer detected in the exhaust gas from the system, the output of the heater 120 was increased to raise the temperature of the crucible 110 to 1100 ° C. to generate silicon monoxide gas and lithium gas. .. Then, the silicon monoxide gas and the lithium gas were deposited (precipitated) on the outer peripheral surface of the vapor deposition drum 130 and deposited, and the deposit was scraped from the vapor deposition drum 130 by the scraper 141.

At this time, the yield of the lithium-containing silicon oxide powder was 47.1% by mass. Further, a small amount of silicon carbide remained in the crucible 110, and the production rate thereof was 1.4% by mass.

A lithium-containing silicon oxide powder was produced in the same manner as in Example 1 except that the initial heating temperature was changed to 700 ° C. and the heating temperature after confirmation of non-detection of carbon dioxide was changed to 1400 ° C. The yield of the lithium-containing silicon oxide powder at this time was 96.2% by mass. Further, silicon carbide hardly remained in the crucible 110, and the production rate thereof was less than 0.1% by mass.

A layer of silicon powder is formed on the rutsubo 110 of the vapor deposition apparatus 100 shown in FIG. 1, a layer of silicon dioxide powder is formed on the layer of the silicon powder, and the silicon dioxide powder is further formed. A layer of silicon carbonate powder was formed on top of the layer. At this time, the thickness of the silicon powder layer was 16.8 mm, the thickness of the silicon dioxide powder layer was 17.0 mm, and the thickness of the lithium carbonate powder layer was 20.0 mm. Next, the crucible 110 was heated to 1100 ° C. by the heater 120 while passing argon (Ar) gas through the precipitation chamber RM so that the atmospheric pressure was +100 Pa. After confirming that carbon dioxide was no longer detected in the exhaust gas from the system, the pressure in the precipitation chamber RM was reduced to 5 Pa to generate silicon monoxide gas and lithium gas. Then, the silicon monoxide gas and the lithium gas were deposited (precipitated) on the outer peripheral surface of the vapor deposition drum 130 and deposited, and the deposit was scraped from the vapor deposition drum 130 by the scraper 141.

At this time, the yield of the lithium-containing silicon oxide powder was 43.7% by mass. Further, almost no silicon carbide remained in the crucible 110, and the production rate thereof was 0.5% by mass.

A lithium-containing silicon oxide powder was produced in the same manner as in Example 3 except that the heating temperature was changed to 1400 ° C. The yield of the lithium-containing silicon oxide powder at this time was 94.1% by mass. Further, almost no silicon carbide remained in the crucible 110, and the production rate thereof was 0.3% by mass.

A layer of silicon powder is formed on the rutsubo 110 of the vapor deposition apparatus 100 shown in FIG. 1, and a mixed powder of silicon dioxide powder and lithium carbonate powder is formed on the silicon powder layer (lithium carbonate). Powder: Silicon dioxide powder = 1: 0.42 (mass ratio)) was formed. At this time, the thickness of the silicon powder layer was 37.0 mm, and the thickness of the mixed powder layer was 16.8 mm. Next, the crucible 110 was heated to 1100 ° C. by the heater 120 while flowing argon (Ar) gas in the precipitation chamber RM so as to have an atmospheric pressure of + 100 Pa. After confirming that carbon dioxide was no longer detected in the exhaust gas from the system, the pressure in the precipitation chamber RM was reduced to 5 Pa to generate silicon monoxide gas and lithium gas. Then, the silicon monoxide gas and the lithium gas were deposited (precipitated) on the outer peripheral surface of the vapor deposition drum 130 and deposited, and the deposit was scraped from the vapor deposition drum 130 by the scraper 141.

At this time, the yield of the lithium-containing silicon oxide powder was 31.9% by mass. Further, almost no silicon carbide remained in the crucible 110, and the production rate thereof was 0.8% by mass.

A lithium-containing silicon oxide powder was produced in the same manner as in Example 5 except that the heating temperature was changed to 1400 ° C. The yield of the lithium-containing silicon oxide powder at this time was 91.7% by mass. Further, almost no silicon carbide remained in the crucible 110, and the production rate thereof was 0.5% by mass.

A mixed powder of lithium carbonate powder and silicon dioxide powder in the rut 110 of the vapor deposition apparatus 100 shown in FIG. 1 (lithium carbonate powder: silicon dioxide powder = 1: 1.63 (mass ratio)). Was charged, and the rutsubo 110 was heated to 1400 ° C. by the heater 120 while reducing the pressure in the precipitation chamber RM to 5 Pa. This heating was continued until carbon dioxide was no longer detected in the exhaust gas.

After confirming that carbon dioxide is no longer detected in the exhaust gas from the system, silicon powder is charged into the rutsubo 110 from the raw material supply hopper 160 via the raw material introduction pipe 170, and silicon monoxide gas and lithium gas are used. Was generated. Then, the silicon monoxide gas and the lithium gas were deposited (precipitated) on the outer peripheral surface of the vapor deposition drum 130 and deposited, and the deposit was scraped from the vapor deposition drum 130 by the scraper 141.

At this time, the yield of the lithium-containing silicon oxide powder was 75% by mass. Further, silicon carbide hardly remained in the crucible 110, and the production rate thereof was less than 0.1% by mass.

(Comparative Example 1)
A mixed powder of lithium carbonate powder, silicon dioxide powder and silicon powder (lithium carbonate powder: silicon dioxide powder: silicon powder = 1) is placed in the rut 110 of the vapor deposition apparatus 100 shown in FIG. : 1.63: 1.14 (mass ratio)) is charged, and the rutsubo 110 is heated to 1400 ° C. by the heater 120 while reducing the pressure in the precipitation chamber RM to 5 Pa to generate silicon monoxide gas and lithium gas. I let you. Then, the silicon monoxide gas and the lithium gas were deposited (precipitated) on the outer peripheral surface of the vapor deposition drum 130 and deposited, and the deposit was scraped from the vapor deposition drum 130 by the scraper 141.

At this time, the yield of the lithium-containing silicon oxide powder was 7.3% by mass. Further, silicon carbide remained in the crucible 110, and its production rate was 4.7% by mass.

(Comparative Example 2)
A layer of silicon dioxide powder is formed on the rutsubo 110 of the vapor deposition apparatus 100 shown in FIG. 1, a layer of lithium carbonate powder is formed on the layer of the silicon dioxide powder, and the carbon dioxide thereof is further formed. A layer of silicon was formed on top of the layer of powder of lithium. At this time, the thickness of the silicon dioxide powder layer was 17.0 mm, the thickness of the lithium carbonate powder layer was 20.0 mm, and the thickness of the silicon powder layer was 16.8 mm. Next, the crucible 110 was heated to 1400 ° C. by the heater 120 while reducing the pressure in the precipitation chamber RM to 5 Pa to generate silicon monoxide gas and lithium gas. Then, the silicon monoxide gas and the lithium gas were deposited (precipitated) on the outer peripheral surface of the vapor deposition drum 130 and deposited, and the deposit was scraped from the vapor deposition drum 130 by the scraper 141.

At this time, the yield of the lithium-containing silicon oxide powder was 11.7% by mass. Further, silicon carbide remained in the crucible 110, and its production rate was 3.5% by mass.

(Comparative Example 3)
A layer of a mixed powder of lithium carbonate powder and silicon powder (lithium carbonate powder: silicon powder = 1: 1.26 (mass ratio)) on the rutsubo 110 of the vapor deposition apparatus 100 shown in FIG. Was formed, and a layer of silicon dioxide powder was formed on the layer of the mixed powder. At this time, the thickness of the mixed powder layer was 36.8 mm, and the thickness of the silicon dioxide powder layer was 17.0 mm. Next, the crucible 110 was heated to 1400 ° C. by the heater 120 while reducing the pressure in the precipitation chamber RM to 5 Pa to generate silicon monoxide gas and lithium gas. Then, the silicon monoxide gas and the lithium gas were deposited (precipitated) on the outer peripheral surface of the vapor deposition drum 130 and deposited, and the deposit was scraped from the vapor deposition drum 130 by the scraper 141.

At this time, the yield of the lithium-containing silicon oxide powder was 3.9% by mass. Further, silicon carbide remained in the crucible 110, and the production rate thereof was 6.3% by mass.

(Comparative Example 4)
A mixed powder of lithium carbonate powder and silicon powder (lithium carbonate powder: silicon powder = 1: 1.26 (mass ratio)) is charged into the rubo 110 of the vapor deposition apparatus 100 shown in FIG. Then, the rutsubo 110 was heated to 1400 ° C. by the heater 120 while reducing the pressure in the precipitation chamber RM to 5 Pa.

After 1 hour, silicon dioxide powder was charged from the raw material supply hopper 160 into the rutsubo 110 via the raw material introduction pipe 170 to generate silicon monoxide gas and lithium gas. Then, the silicon monoxide gas and the lithium gas were deposited (precipitated) on the outer peripheral surface of the vapor deposition drum 130 and deposited, and the deposit was scraped from the vapor deposition drum 130 by the scraper 141.

At this time, the yield of the lithium-containing silicon oxide powder was 2.1% by mass. Further, silicon carbide remained in the crucible 110, and the production rate thereof was 6.5% by mass.

100 Evaporation device 110 Lutsubo 120 Heater 130 Evaporation drum 141 Scraper 143 Granule guide 150 Chamber 151 Chamber body 152 Recovery section 153 Exhaust pipe 160 Raw material supply hopper 170 Raw material introduction tube 180 Recovery vessel 190 Recovery tube Gg Gas guide OP Opening RM Precipitation chamber Sr molten metal VL1 1st valve VL2 2nd valve

Claims (6)

Lithium carbonate (Li ₂ CO ₃ ) powder, silicon dioxide (SiO ₂ ) powder and silicon in the same system so that elimination of carbon dioxide (CO ₂ ) takes precedence over silicon carbide (SiC) production. A method for producing lithium silicate ( _{SiLi x} Oy) and silicon (Si) from the powder of (Si). The first aspect of claim 1, wherein the lithium carbonate powder, the silicon dioxide powder, and the mixed powder of the silicon powder are heated at a temperature within the range of 400 ° C. or higher and lower than the melting point of the lithium carbonate under a reduced pressure atmosphere. the method of. Of the lithium carbonate powder, the silicon dioxide powder and the silicon so that the silicon dioxide powder layer is located between the silicon carbonate powder layer and the silicon powder layer. The method according to claim 1, wherein the powder is spread in layers and heated at a temperature equal to or higher than the melting point of the silicon carbonate. The mixed powder and the silicon powder are spread in layers so that the layer of the mixed powder of the lithium carbonate powder and the silicon dioxide powder and the layer of the silicon powder are adjacent to each other. The method according to claim 1, wherein the powder is heated at a temperature equal to or higher than the melting point of the lithium carbonate. The method according to claim 3 or 4, wherein the layer of the silicon powder is the lowest layer. The method according to claim 1, wherein the silicon powder is charged into the system while the mixed powder of the lithium carbonate powder and the silicon dioxide powder is heated.

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