SILICON MONOXIDE GAS GENERATING RAW MATERIAL AND METHOD FOR CONTINUOUSLY GENERATING SILICON MONOXIDE GAS

Abstract

An object of the present invention is to provide a silicon monoxide gas generating raw material in which a reaction that generates a silicon monoxide (SiO) gas is hardly inhibited. The silicon monoxide gas generating raw material according to the present invention has a water content of 0.6 wt % or less.

Claims

1-4. (canceled)

5. A method for continuously generating silicon monoxide gas, wherein a silicon monoxide gas generating raw material having a water content of 0.6 wt % or less is continuously charged into a reaction chamber for generating silicon monoxide (SiO) gas.

6. The method for continuously generating silicon monoxide gas according to claim 5, wherein the silicon monoxide gas generating raw material contains at least one of silicon dioxide (SiO.sub.2) and silicate, and silicon (Si).

7. The method for continuously generating silicon monoxide gas according to claim 6, wherein the silicate is lithium silicate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 It is a schematic view of a manufacturing apparatus of active material particles using a silicon monoxide gas generating raw material according to an embodiment of the present invention.

[0015] FIG. 2 It is a schematic view of adding a drying mechanism to the manufacturing apparatus shown in FIG. 1.

REFERENCE SIGNS LIST

[0016] 100 Vapor-deposition apparatus [0017] 110 Crucible [0018] 120 Heater [0019] 130 Vapor-deposition drum [0020] 141 Scraper [0021] 143 Particle guide [0022] 150 Chamber [0023] 151 Chamber body portion [0024] 152 Collection portion [0025] 153 Exhaust pipe [0026] 160 Raw material supply hopper [0027] 170 Raw material introducing pipe [0028] 180 Collection container [0029] 190 Collection pipe [0030] 200 Drying mechanism [0031] 210 Raw material introducing pipe [0032] Gg Gas guide [0033] OP Opening [0034] RM Deposition chamber [0035] Sr Silicon monoxide gas generating raw material [0036] VL1 First valve [0037] VL2 Second valve

MODE FOR CARRYING OUT THE INVENTION

[0038] The silicon monoxide gas generating raw material Sr according to the embodiment of the present invention is used for generating the silicon monoxide (SiO) gas. As the silicon monoxide gas generating raw material Sr, for example, “a mixed powder of silicon (Si) and silicon dioxide (SiO.sub.2)” or “a mixed powder of silicon and silicate such as lithium silicate (Li.sub.2Si.sub.2O.sub.5 or the like) or the like” is used. The “mixed powder of silicon and silicon dioxide” is used when manufacturing silicon oxide particles, and is heat-treated to generate the silicon monoxide gas. The “mixed powder of silicon and a silicate such as lithium silicate” is used when manufacturing metal element-containing silicon oxide particles, and is heat-treated to generate the silicon monoxide gas containing the metal element such as lithium (Li) or the like. Incidentally, the metal element may be an element capable of reducing silicon monoxide and stabilizing oxygen, such as an alkali metal such as sodium (Na) or the like in addition to lithium, an alkaline earth metal such as magnesium (Mg) and calcium (Ca) or the like.

[0039] Incidentally, the silicon monoxide gas generating raw material Sr according to the embodiment of the present invention is dry-treated (described later) before being heat-treated. This dry-treatment is performed to reduce the amount of water in the silicon monoxide gas generating raw material Sr. Examples of the dry-treatment method include heat-drying, reduced pressure drying and the like.

[0040] Then, the active material particles are manufactured from the silicon monoxide gas generated by heat-treating the silicon monoxide gas generating raw material Sr after the dry—treatment to a predetermined temperature through a process to be described later. As such active material particles, for example, silicon oxide particles or metal element-containing silicon oxide particles used as active materials of electrodes (particularly, negative electrodes) of a lithium ion secondary battery is used.

[0041] Incidentally, in order to finally manufacture the active material particles using the silicon monoxide gas generating raw material Sr according to the embodiment of the present invention, it is preferable to use a vapor-deposition apparatus 100 as shown in FIG. 1. The vapor-deposition apparatus 100 is excellent from the viewpoint of suppression of manufacturing costs and the like. Hereinafter, the vapor-deposition apparatus 100 will be described in detail.

[0042] As shown in FIG. 1, the vapor-deposition apparatus 100 mainly comprises 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 introducing pipe 170, a collection container 180, a first valve VL1, and a second valve VL2.

[0043] As shown in FIG. 1, the crucible 110 is a heat resistant container having an opening in the central portion of the top wall, and is installed in the chamber 150. Further, a through hole (not shown) is formed in one portion around the top wall of the crucible 110, and the raw material introducing pipe 170 is inserted into the through hole. That is, the silicon monoxide gas generating raw material Sr after being dry-treated in the raw material supply hopper 160 is supplied to the crucible 110 through the raw material introducing pipe 170. Further, the gas guide Gg is disposed on the upper side of the top wall of the crucible 110. The gas guide Gg is a member for guiding the silicon monoxide 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. 1.

[0044] The heater 120 is for heating the crucible 110 at a high temperature, and is disposed so as to take in the outer periphery of the crucible 110.

[0045] The vapor-deposition drum 130 is, for example, a cylindrical horizontal drum, and is disposed above the opening OP of the top wall of the crucible 110 as shown in FIG. 1, and the lower portion of the vapor-deposition drum 130 is surrounded by the gas guide Gg. Then, the vapor-deposition drum 130 is driven to rotate in one direction by a driving mechanism which is not shown. Incidentally, a temperature controller (not shown) for maintaining the outer peripheral surface at a constant temperature is provided on the vapor-deposition drum 130. The 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. In addition, the outer peripheral surface temperature of the vapor-deposition drum 130 may affect the crystallinity of the deposit accumulated on the deposit remaining on the vapor-deposition drum. If this temperature is too low, the tissue structure of the deposit may become too sparse, and on the contrary, if this temperature is too high, crystal growth due to the disproportionation reaction may proceed. When the silicon monoxide gas is vapor-deposited, this temperature is preferably 900° C. or less, more preferably within a range of 150° C. or more and 800° C. or less, particularly preferably within a range of 150° C. or more and 700° C. or less.

[0046] 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. The scraped-off thin film pieces (active material particles) fall into the particle guide 143. Further, the material of the scraper 141 affects impurity contamination of the active material particles. From the viewpoint of suppressing the affect, the material of the scraper 141 is preferably stainless steel or ceramic, particularly preferably ceramic. In addition, the scraper 141 is preferably not in contact with the outer peripheral surface of the vapor-deposition drum 130. This is because the impurity contamination that may occur due to direct contact between the vapor-deposition drum 130 and the scraper 141 can be prevented from being mixed into the collected active material particles.

[0047] The particle guide 143 is, for example, a vibrating conveying member and is disposed so as to be inclined downward from the vicinity of the vapor-deposition drum 130 toward the collection portion 152 of the chamber 150 as shown in FIG. 1, and receives thin film pieces scraped off by the scraper 141 disposed above to send the thin film pieces to the collection portion 152 of the chamber 150.

[0048] As shown in FIG. 1, the chamber 150 is mainly formed of a chamber body portion 151, a collection portion 152, and an exhaust pipe 153. As shown in FIG. 1, the chamber body portion 151 is a box-shaped portion having a deposition chamber RM inside, and houses the crucible 110, the heater 120, the vapor-deposition drum 130, the scraper 141, and the particle guide 143. As shown in FIG. 1, the collection portion 152 is a portion protruding outward from the side wall of the chamber body portion 151, and has a space communicating with the deposition chamber RM of the chamber body portion 151. As described above, the distal end portion of the particle guide 143 is located in the collection portion 152.

[0049] The raw material supply hopper 160 is a supply source of the silicon monoxide gas generating raw material. As shown in FIG. 1, an outlet of the raw material supply hopper is connected to the raw material introducing pipe 170. That is, the silicon monoxide gas generating raw material Sr after being dry-treated charged into the raw material supply hopper 160 is continuously supplied to the crucible 110 via the raw material introducing pipe 170 at appropriate timing. Incidentally, the silicon monoxide gas generating raw material Sr after being dry-treated supplied to the crucible 110 becomes silicon monoxide gas.

[0050] The raw material introducing pipe 170 is nozzle having a round hole shape for continuously charging the silicon monoxide gas generating raw material Sr after being dry-treated which is charged into the raw material supply hopper 160 into the crucible 110, and is disposed so that the outlet faces upward in the central portion of the top plate portion of the crucible 110.

[0051] 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.

[0052] The first valve VL1 and the second valve VL2 adjust the collection amount of the thin film pieces into the collection container 180 by opening and closing, and are provided in a collection pipe 190 connecting the collection portion 152 of the chamber 150 and the collection container 180.

[0053] Hereinafter, a description will be given of a case where silicon oxide particles or metal element-containing silicon oxide particles used for a negative electrode material for a lithium ion secondary battery is finally manufactured from the silicon monoxide gas generating raw material Sr by using the vapor-deposition apparatus 100 described above.

[0054] First, the silicon monoxide gas generating raw material Sr is dry-treated (e.g., heat-drying, reduced pressure drying). Here, When the silicon monoxide gas generating raw material Sr is dry-treated by, for example, heat-drying, it is preferable that the silicon monoxide gas generating raw material Sr is dry-treated within a range of 100° C. or more and 400° C. or less for the period within a range of 1 hour or more and 240 hours or less, more preferably within a range of 200° C. or more and 350° C. or less for the period within a range of 4 hours or more and 120 hours or less. Further, when the silicon monoxide gas generating raw material Sr is dry-treated by, for example, reduced pressure drying, it is preferable that the silicon monoxide gas generating raw material is dry-treated under reduced pressure in which the pressure is controlled by a vacuum pump so as to be within a range of 10 Pa or more and 100 Pa or less for the period within a range of 12 hours or more and 120 hours or less and, and more preferable that the silicon monoxide gas generating raw material is dry-treated under reduced pressure in which the pressure is controlled by a vacuum pump so as to be within a range of 0.1 Pa or more and 100 Pa or less for the period within a range of 12 hours or more and 240 hours or less. When the silicon monoxide gas generating raw material Sr is dry-treated under these conditions, water in the silicon monoxide gas generating raw material Sr can be removed without generating the silicon monoxide gas as much as possible. Then, as described above, the water content of the silicon monoxide gas generating raw material Sr after being dry-treated is 0.6 wt % or less, preferably 0.3 wt % or less, more preferably 0.1 wt % or less. Further, the silicon monoxide gas generating raw material Sr after being dry-treated is preferably stored in a sealed container or under reduced pressure.

[0055] Next, the silicon monoxide gas generating raw material Sr after being dry-treated is charged into the raw material supply hopper 160. Then, the silicon monoxide gas generating raw material Sr after being dry-treated is continuously charged into the crucible 110 from the raw material supply hopper 160 via the raw material introducing pipe 170.

[0056] Next, when the silicon monoxide gas generating raw material Sr after being dry-treated is charged into the crucible 110, the crucible 110 is heated by the heater 120 while the pressure in the deposition chamber RM is reduced. Incidentally, when the water content (wt %) of the silicon monoxide gas generating raw material Sr is high, a large amount of water vapor, a large amount of hydrogen gas, and the like are generated by the heating of the heater 120. When a large amount of water vapor, a large amount of hydrogen gas, or the like is generated, the pressure in the deposition chamber RM increases. Then, if the pressure in the deposition chamber RM is too high, the reaction that generates the silicon monoxide gas from the silicon monoxide gas generating raw material Sr after being dry-treated is less likely to occur. Here, the pressure in the deposition chamber RM is preferably 100 Pa or less, more preferably 75 Pa or less, particularly preferably 20 Pa or less. Further, the temperature in the deposition chamber RM affects the reaction rate of silicon monoxide. If the temperature is too low, the reaction rate becomes slow, and if the temperature is too high, there are concerns that side reaction due to the melting of the silicon monoxide gas generating raw material Sr after being dry-treated will proceed, energy efficiency will decrease and so on. Also, there is a concern that the crucible 110 may be damaged at the temperature. From this viewpoint, the temperature in the deposition chamber RM is preferably within a range of 1000° C. or more and 1600° C. or less, more preferably within a range of 1100° C. or more and 1500° C. or less, particularly preferably within a range of 1100° C. or more and 1400° C. or less.

[0057] As described above, by heat-treating under reduced pressure the silicon monoxide gas generating raw material Sr after being dry-treated, the silicon monoxide gas is generated from the silicon monoxide gas generating raw material Sr after being dry-treated in the crucible 110. The silicon monoxide gas is supplied to the vapor-deposition drum 130 through the gas guide Gg. At this time, the vapor-deposition drum 130 is rotatably driven by a driving source. Incidentally, the temperature of the outer peripheral surface of the vapor-deposition drum 130 is set lower than the temperature in the deposition chamber RM. More specifically, the temperature is set lower than the condensation temperature of the silicon monoxide gas. With this setting, the silicon monoxide gas generated from the crucible 110 is vapor-deposited, deposited and accumulated on the outer peripheral surface of the rotating vapor-deposition drum 130. Then, a thin film is formed on the vapor-deposition drum 130. Thereafter, the thin film on the vapor-deposition drum 130 comes into contact with the scraper 141, and the thin film is scraped off from the vapor-deposition drum 130. Incidentally, the scraped off pieces of the thin film (active material particles) fall along the outer peripheral surface of the vapor-deposition drum 130 to the particle guide 143.

[0058] In the vapor-deposition apparatus 100 of the present embodiment, as described above, high quality active material particles are finally manufactured from the silicon monoxide gas generating raw material Sr.

[0059] Incidentally, when the silicon monoxide gas generating raw material Sr after being dry-treated is charged into the raw material supply hopper 160, it is preferable to prevent the silicon monoxide gas generating raw material Sr after being dry-treated from being exposed to the atmosphere. This is because water in the atmosphere may adsorb to the silicon monoxide gas generating raw material Sr after being dry-treated. The vapor-deposition apparatus 100 may comprise, for example, a drying mechanism 200 and a raw material introducing pipe 210 (see FIG. 2) so that the silicon monoxide gas generating raw material Sr after being dry-treated is not exposed to the atmosphere. According to this configuration, first, as shown in FIG. 2, the silicon monoxide gas generating raw material Sr before being dry-treated is charged into the drying mechanism 200. Then, the silicon monoxide gas generating raw material Sr is dry-treated in the drying mechanism 200, and water vapor is discharged from a steam port (not shown) of the drying mechanism 200. Here, as described above, when the silicon monoxide gas generating raw material Sr is dry-treated by, for example, heat-drying, it is preferable that the silicon monoxide gas generating raw material Sr is dry-treated within a range of 100° C. or more and 400° C. or less for the period within a range of 1 hour or more and 240 hours or less, more preferably within a range of 200° C. or more and 350° C. or less for the period within a range of 4 hours or more and 120 hours or less. Further, when the silicon monoxide gas generating raw material Sr is dry-treated by, for example, reduced pressure drying, it is preferable that the silicon monoxide gas generating raw material is dry-treated under reduced pressure in which the pressure is controlled by a vacuum pump so as to be within a range of 10 Pa or more and 100 Pa or less for the period within a range of 12 hours or more and 120 hours or less, and more preferable that the silicon monoxide gas generating raw material is dry-treated under reduced pressure in which the pressure is controlled by a vacuum pump so as to be within a range of 0.1 Pa or more and 100 Pa or less for the period within a range of 12 hours or more and 240 hours or less. Then, the silicon monoxide gas generating raw material Sr after being dry-treated is charged into the raw material supply hopper 160 from the drying mechanism 200 via the raw material introducing pipe 210. With this configuration, it is possible to prevent the silicon monoxide gas generating raw material Sr after being dry-treated from being exposed to the atmosphere.

[0060] Hereinafter, working examples and comparative examples are described in order to explain the present invention in more detail, but the present invention is not limited to these examples.

WORKING EXAMPLE 1

[0061] The silicon monoxide (SiO) gas generating raw material Sr containing silicon dioxide (SiO.sub.2) and silicon (Si) was dry-treated at 200° C. for 4 hours. The weight of this silicon monoxide gas generating raw material Sr was 524 g. Further, when the water content of this silicon monoxide gas generating raw material Sr was measured by a heat drying type water meter, the water content was 0.05 wt %. Then, using the vapor-deposition apparatus 100 shown in FIG. 1, this silicon monoxide gas generating raw material Sr was continuously charged into the crucible 110 in the deposition chamber RM (pressure: 10 Pa, temperature: 1300° C.) for 2 hours. Then, the silicon monoxide gas was generated, and the reactor was stopped 30 minutes after the completion of charging the silicon monoxide gas generating raw material Sr. After that, through the above described steps, the silicon oxide particles (weights: 487 g) used for the negative electrode material for lithium ion secondary battery were finally manufactured. At this time, the pressure in the deposition chamber RM was increased to 15 Pa, and the reaction rate (weight of the particles/amount of the charged raw material×100) was 93%.

WORKING EXAMPLE 2

[0062] The silicon monoxide gas generating raw material Sr containing silicon dioxide and silicon was dry-treated at 100° C. for 1 hour. The weight of this silicon monoxide gas generating raw material Sr was 507 g. Further, when the water content of the silicon monoxide gas generating raw material Sr was measured by a heat drying type water meter, the water content was 0.29 wt %. Then, using the vapor-deposition apparatus 100 shown in FIG. 1, this silicon monoxide gas generating raw material Sr was continuously charged into the crucible 110 in the deposition chamber RM (pressure: 10 Pa, temperature: 1300° C.) for 2 hours. Then, the silicon monoxide gas was generated, and the reactor was stopped 30 minutes after the completion of charging the silicon monoxide gas generating raw material Sr. After that, through the above described steps, the silicon oxide particles (weights: 446 g) used for the negative electrode material for lithium ion secondary battery were finally manufactured. At this time, the pressure in the deposition chamber RM increased to 38 Pa, and the reaction rate was 88%.

WORKING EXAMPLE 3

[0063] The silicon monoxide gas generating raw material Sr containing silicon dioxide and silicon was dry-treated under reduced pressure in 100 Pa for 12 hours. The weight of this silicon monoxide gas generating raw material Sr was 520 g. Further, when the water content of this silicon monoxide gas generating raw material Sr was measured by a heat drying type water meter, the water content was 0.33 wt %. Then, using the vapor-deposition apparatus 100 shown in FIG. 1, this silicon monoxide gas generating raw material Sr was continuously charged into the crucible 110 in the deposition chamber RM (pressure: 10 Pa, temperature: 1300° C.) for 2 hours. Then, the silicon monoxide gas was generated, and the reactor was stopped 30 minutes after the completion of charging the silicon monoxide gas generating raw material Sr. After that, through the above described steps, the silicon oxide particles (weights: 447 g) used for the negative electrode material for lithium ion secondary battery were finally manufactured. At this time, the pressure in the deposition chamber RM increased to 44 Pa, and the reaction rate was 86%.

WORKING EXAMPLE 4

[0064] The silicon monoxide gas generating raw material Sr containing lithium silicate (Li.sub.2Si.sub.2O.sub.5) and silicon was dry-treated at 200° C. for 4 hours. The weight of this silicon monoxide gas generating raw material Sr was 508 g. Further, when the water content of this silicon monoxide gas generating raw material Sr was measured by a heat drying type water meter, the water content was 0.05 wt %. Then, using the vapor-deposition apparatus 100 shown in FIG. 1, this silicon monoxide gas generating raw material Sr was continuously charged into the crucible 110 in the deposition chamber RM (pressure: 10 Pa, temperature: 1300° C.) for 2 hours. Then, the silicon monoxide gas was generated, and the reactor was stopped 30 minutes after the completion of charging the silicon monoxide gas generating raw material Sr. After that, through the above described steps, the metal element-containing silicon oxide particles (weights: 477 g) used for the negative electrode material for lithium ion secondary battery were finally manufactured. At this time, the pressure in the deposition chamber RM increased to 16 Pa, and the reaction rate was 94%.

COMPARATIVE EXAMPLE 1

[0065] When the water content of the silicon monoxide gas generating raw material Sr (without drying treatment) (weight: 530 g) containing silicon dioxide and silicon was measured by a heat drying type water meter, the water content was 0.96 wt %. Then, using the vapor-deposition apparatus 100 shown in FIG. 1, this silicon monoxide gas generating raw material Sr was continuously charged into the crucible 110 in the deposition chamber RM (pressure: 10 Pa, temperature: 1300° C.) for 2 hours. Then, the silicon monoxide gas was generated, and the reactor was stopped 30 minutes after the completion of charging the silicon monoxide gas generating raw material Sr. After that, through the above described steps, the silicon oxide particles (weights: 360 g) used for the negative electrode material for lithium ion secondary battery were finally manufactured. At this time, the pressure in the deposition chamber RM increased to 123 Pa, and the reaction rate was 68%.

COMPARATIVE EXAMPLE 2

[0066] The silicon monoxide gas generating raw material Sr containing silicon dioxide and silicon was dry-treated at 100° C. for 1 hour. The weight of this silicon monoxide gas generating raw material Sr was 511 g. Further, this silicon monoxide gas generating raw material Sr was exposed to the atmosphere for 24 hours. The weight of the silicon monoxide gas generating raw material Sr after being exposed to the atmosphere was 513 g. Then, the water content of this silicon monoxide gas generating raw material Sr was measured by a heat drying type water meter, and the water content was 0.68 wt %. Then, using the vapor-deposition apparatus 100 shown in FIG. 1, this silicon monoxide gas generating raw material Sr was continuously charged into the crucible 110 in the deposition chamber RM (pressure: 10 Pa, temperature: 1300° C.) for 2 hours. Then, the silicon monoxide gas was generated, and the reactor was stopped 30 minutes after the completion of charging the silicon monoxide gas generating raw material Sr. After that, through the above described steps, the silicon oxide particles (weights: 393 g) used for the negative electrode material for lithium ion secondary battery were finally manufactured. At this time, the pressure in the deposition chamber RM increased to 80 Pa, and the reaction rate was 74%.

COMPARATIVE EXAMPLE 3

[0067] When the water content of the silicon monoxide gas generating raw material Sr (without drying treatment) (weight: 503 g) containing lithium silicate (Li.sub.2Si.sub.2O.sub.6) and silicon was measured by a heat drying type water meter, the water content was 0.81 wt %. Then, using the vapor-deposition apparatus 100 shown in FIG. 1, this silicon monoxide gas generating raw material Sr was continuously charged into the crucible 110 in the deposition chamber RM (pressure: 10 Pa, temperature: 1300° C.) for 2 hours. Then, the silicon monoxide gas was generated, and the reactor was stopped 30 minutes after the completion of charging the silicon monoxide gas generating raw material Sr. After that, through the above described steps, the metal element-containing silicon oxide particles (weights: 312 g) used for the negative electrode material for lithium ion secondary battery were finally manufactured. At this time, the pressure in the deposition chamber RM increased to 104 Pa, and the reaction rate was 62%.