JP6298623B2 - Silicon powder production method and silicon powder production apparatus - Google Patents

Description

  The present invention relates to a silicon powder generation method and a silicon powder generation device, and more particularly to a silicon powder generation method and a silicon powder generation device that can collect silicon powder by grinding crystalline silicon.

  Conventionally, in a storage battery such as a lithium ion battery, a carbon-based material is used as a material for the negative electrode. On the other hand, the use of silicon as a negative electrode material has attracted attention in order to make it possible to rapidly charge or discharge a lithium ion battery or to cope with an increase in capacity (for example, patent documents). 1). In silicon, the storage capacity is expected to be several times that of carbon-based materials, and for that purpose, it is important to make silicon fine powder. Specifically, silicon fine particles used for the negative electrode of a lithium ion battery are required to have a particle size of 10 μm or less, usually 5 μm or less, and uniform in size.

  In the production of silicon fine particles in Patent Document 1, first, the surface of silicon is ground using a grinding blade to form a fine powder. Then, after maintaining the fine powdery silicon dispersed in the dispersion, the silicon fine particles having a predetermined particle diameter are separated and taken out by performing a centrifugal separation method or a wet cyclone separation.

JP 2012-206923 A

  However, even in Patent Document 1, it has been difficult to collect silicon powder having a uniform particle diameter.

  The present invention has been made in view of the above points, and provides a silicon powder generation method and a silicon powder generation apparatus capable of equalizing the particle diameter of silicon powder and easily collecting silicon powder. The purpose is to do.

The silicon powder generating method of the present invention is a silicon mixed liquid generating step of grinding crystalline silicon using a grindstone while supplying a processing liquid, and mixing the ground silicon powder into the processing liquid to generate a silicon mixed liquid. A silicon powder collecting step of energizing a negative electrode and a positive electrode disposed in a water storage tank for storing the silicon mixed liquid generated in the silicon mixed liquid generating step, and collecting silicon powder with the positive electrode; And a drying step for removing moisture from the silicon powder collected in the powder collection step , and the processing liquid is characterized by using pure water that has undergone a deoxygenation step for removing oxygen in the processing liquid .

According to this configuration, since the electrophoresis is used for collecting the silicon powder, it is possible to easily collect only the silicon powder having a uniform particle diameter. Moreover, since the silicon powder is formed by grinding the silicon plate with a grindstone, the particle size of the silicon powder can be adjusted by changing the grindstone of the grindstone. It can be easily generated. Further, it is possible to prevent the oxide film from adhering to the silicon powder surface.

Further, a method of generating a silicon powder of the present invention, of silicon mixed solution producing step and the silicon powder collected process, it is preferable to maintain the silicon mixed liquid weakly acidic. With this configuration, it is possible to prevent the oxide film from adhering to the surface of the silicon powder.

Moreover, in the method for producing silicon powder of the present invention, it is preferable to use ultrapure water in which carbon dioxide is dissolved and conductivity is increased as the processing liquid. According to this configuration, it is possible to efficiently collect silicon powder by electrophoresis. In the silicon powder production method of the present invention, the silicon powder collecting step and the drying step may be performed in a deoxygenated state.

The silicon powder generating apparatus of the present invention generates a silicon powder by bringing a grindstone into contact with a chuck table that holds a silicon plate made of crystalline silicon and a silicon plate held by the chuck table while supplying a machining liquid. A mixed liquid generating means for generating silicon mixed liquid by mixing silicon powder into a processing liquid to be pure water from which oxygen in the liquid is removed, and a silicon mixed liquid generated by the mixed liquid generating means is provided with a negative electrode. The silicon powder collecting means for collecting the silicon powder collected by the silicon powder collecting means, storing the water in the water storage tank, immersing the adsorbing member having a positive electrode in the stored silicon mixed liquid, and adsorbing the silicon powder on the adsorbing member And a drying means for removing moisture. In this configuration, the silicon powder can be collected by electrophoresis, and the particle size of the silicon powder can be equalized.

  Moreover, the silicon powder production | generation apparatus of this invention has a collection chamber which can enclose and seal a silicon powder collection means and a drying means, and it is preferable to provide a deoxygenation means in a collection chamber. With this configuration, the formation of an oxide film on the silicon powder can be suppressed.

Moreover, the silicon powder production | generation apparatus of this invention is good to provide the pH adjustment means which maintains a silicon | silicone mixing liquid in weak acidity. With this configuration, it is possible to prevent the oxide film from adhering to the silicon powder surface.

  According to the present invention, the particle diameter of the silicon powder can be equalized, and the silicon powder can be easily collected.

1 is an overall schematic perspective view of a silicon powder generating apparatus according to an embodiment. It is a cross-sectional schematic diagram of the said silicon powder production | generation apparatus. It is a schematic perspective view of the silicon powder collection | recovery means which the said silicon powder production | generation apparatus has.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an overall schematic perspective view of a silicon powder generating apparatus according to an embodiment.

  As shown in FIG. 1, the silicon powder generating apparatus 10 processes a chuck table 12 provided on an upper portion of a substantially rectangular parallelepiped base 11 and a silicon plate S held on the chuck table 12 to mix silicon described later. A mixed liquid generating means 13 for generating the liquid L (see FIG. 2) is provided. The silicon plate S is made of crystalline silicon formed in a disc shape.

  The chuck table 12 has a disk shape and is provided so as to be rotatable about a disk center by a chuck rotating means (not shown). A holding surface 12 a for attracting and holding the silicon plate S is provided on the upper surface of the chuck table 12. The holding surface 12a is made of, for example, a porous ceramic material, and the porous ceramic material is connected to a suction source (not shown).

  The chuck table 12 is supported by a substantially square table support 16. The table support 16 is disposed in an opening 11a formed on the upper surface of the base 11, and the opening 11a has a rectangular shape extending in the X-axis direction. The table support 16 is connected to a drive mechanism (not shown), and slides in the X-axis direction within the opening 11a by a drive force supplied from the drive mechanism. Thereby, the chuck table 12 supplies the unprocessed silicon plate S, and also includes a replacement position for collecting the processed silicon plate S and a grinding position where the grindstone 28 and the silicon plate S described later face each other. Move between slides.

  The inside of the opening 11 a is covered with a bellows-like cover member 18 in addition to the table support 16. The cover member 18 is attached to the front surface and the rear surface of the table support base 16, and is provided so as to be extendable / contractable according to the movement position.

  On the upper surface of the base 11, a column 19 extending in the vertical direction is disposed behind the opening 11 a, and a grinding means 21 constituting the mixed liquid generating means 13 is provided on the front surface of the column 19. . In the grinding means 21, a wheel mount 23 is provided at the lower end of a cylindrical spindle 22, and a grinding wheel 24 is attached to the lower surface of the wheel mount 23. The spindle 22 is fixed to the output shaft of a drive motor 26 that serves as a rotating means. Therefore, the grinding wheel 24 is rotated via the spindle 22 by the drive of the drive motor 26.

  The grinding wheel 24 is configured by annularly arranging a plurality of grindstones 28 on the lower surface of the wheel base. The grindstone 28 is composed of, for example, a vitrified bond grindstone, and rotates at high speed around the Z axis as the spindle 22 is driven. The grindstone 28 comes into contact with the silicon plate S while the lower surface is a ground surface, and the silicon plate S is ground by this contact to generate fine silicon powder P (see FIG. 2). The grinding means 21 includes a nozzle (not shown), and when the silicon plate S is ground by the grindstone 28, the machining liquid is supplied from the nozzle to the silicon plate S held on the chuck table 12. The supplied processing liquid is mixed with silicon powder P during grinding, and the processing liquid in which the silicon powder P is mixed becomes silicon mixed liquid L (see FIG. 2).

  Here, since the generation of the silicon powder P is performed by grinding the silicon plate S with the grindstone 28, the particle diameter of the silicon powder P can be adjusted by exchanging with the grindstone 28 having a different particle diameter of the abrasive grains. . The silicon powder P is formed to have a smaller particle diameter as the particle diameter of the abrasive grains in the grindstone 28 becomes smaller. Regarding the grindstone count of the grindstone 28, the abrasive particle diameter, and the silicon powder particle diameter, the relationship shown in Table 1 below is established.

  The grinding means 21 is driven by a grinding feed means 30 provided on the column 19 so as to be movable in the vertical direction (Z-axis direction), and relatively moves the grinding means 21 and the chuck table 12 closer to and away from each other. Is possible. The grinding feed means 30 has a Z-axis table 31, and the grinding means 21 is supported via a support portion 32 attached to the front side of the Z-axis table 31. A nut portion (not shown) protruding rearward is provided on the back surface of the Z-axis table 31. A ball screw 33 provided on the front surface of the column 19 is screwed into the nut portion of the Z-axis table 31. Then, when the servo motor 34 connected to one end of the ball screw 33 is driven to rotate, the grinding means 21 is moved in the vertical direction (Z-axis direction).

  Inside the base 11, a collecting means 36 constituting the mixed liquid generating means 13 is disposed. The collection means 36 includes a cover member 18 and a water case 37 provided at a lower position on the outer periphery of the cover member 18.

  FIG. 2 is a schematic cross-sectional view showing the recovery means and its peripheral structure. As shown in FIG. 2, the water case 37 constituting the collecting means 36 is formed in a bowl shape extending along the forming edge of the opening 11 a and is open upward. Inside the water case 37, the silicon mixed liquid L generated by the grinding means 21 flows and is stored. The water case 37 has a drain outlet 37a for discharging the stored silicon mixed liquid L at the bottom. Although the water case 37 is illustrated at two positions on the left and right in FIG. 2, the water case 37 is also formed on both sides in the direction orthogonal to the paper surface in FIG. Has a space.

  The cover member 18 includes a hanging portion 18a formed in a region adjacent to the forming edge of the opening 11a. The drooping portion 18 a has a lower end immersed in the silicon mixed liquid L collected in the water case 37 to form a water seal. This water seal seals the space between the cover member 18 and the water case 37 to prevent the silicon mixed liquid L from entering the apparatus.

  The water case 37 is provided with pH adjusting means 39 for adjusting the pH of the silicon mixed liquid L. The pH adjusting means 39 includes a pH sensor 40 and an injection device 41 for adding acid and / or alkali. As the acid, hydrochloric acid, sulfuric acid, nitric acid and the like can be used, and as the alkali, sodium hydroxide, potassium hydroxide and the like can be used.

  The pH sensor 40 is electrically linked to the injection device 41. The injection device 41 puts acid or alkali chemicals into the water case 37 in accordance with the measured pH value in the pH sensor 40, and maintains the silicon mixed solution L at a neutral to slightly acidic pH. The water case 37 is provided with a stirring means (not shown) that stirs the silicon mixed liquid L into which the chemical is injected from the injection device 414.

  Returning to FIG. 1, a sampling chamber 43 is provided inside the base 11. The collection chamber 43 is formed in a box shape, and is provided so as to be capable of sealing and surrounding a silicon powder collection unit 50 and a drying unit 80 described later. The collection chamber 43 is connected to a deoxygenation means 44, and the deoxygenation means 44 supplies nitrogen gas blown to the collection box 77 by a drying means 80 described later.

  As shown in FIG. 2, the silicon powder collecting means 50 constituting the silicon powder generating apparatus 10 is disposed inside the collection chamber 43. Subsequently, the silicon powder collecting means will be described with reference to FIGS. FIG. 3 shows a perspective view of the silicon powder collecting means. As shown in FIG. 3, the silicon powder collecting means 50 is incorporated in the tank 51 disposed below the support rack 56, the water tank 52 placed on the upper surface of the support rack 56, and the water tank 52. A separation mechanism 53 and a recovery mechanism 54 disposed behind the water storage tank 52 and below the separation mechanism 53 are provided.

  A supply port 51 a is formed in the tank 51, and the supply port 51 a communicates with the drain port 37 a by a hose 57 as shown in FIG. Thereby, the silicon mixed liquid L in the water case 37 flows into the tank 51 and is stored therein. The tank 51 includes a pump 58 that sends the internal silicon mixed liquid L to the water storage tank 52. The water storage tank 52 is provided with an inflow port 52 a, and this inflow port 52 a is connected to the discharge port of the pump 58 via a hose 59.

  The separation mechanism 53 separates the silicon powder P from the silicon mixed liquid L stored in the water storage tank 52. The separation mechanism 53 has a plurality of cathode plates 61 provided in the water storage tank 52 and a plurality of lower rollers 62. The cathode plates 61 are provided side by side in the left-right direction in FIG. 2, and a lower roller 62 is provided between the adjacent cathode plates 61. Further, an upper roller 63 is provided above each cathode plate 61. A driving roller 66 that is rotationally driven by the electric motor 65 is provided above the upper roller 63 and at the left side in FIG. 2, while a driven roller 67 is provided at the right side in FIG. 2. An endless belt 68 as an adsorbing member is wound around the driving roller 66, the driven roller 67, the plurality of upper rollers 63, and the plurality of lower rollers 62. The endless belt 68 is made of a conductive stainless steel plate having conductivity, for example, a thickness of 50 μm. The periphery of the lower roller 62 of the endless belt 68 and the cathode plate 61 are immersed in the silicon mixed liquid L stored in the water storage tank 52.

  A DC voltage is applied between the endless belt 68 and the cathode plate 61. That is, the plus (+) of the DC power source 70 is connected to the endless belt 68 to become a plus electrode, and the minus (−) of the DC power source 70 is connected to the cathode plate 61 to become a minus electrode.

  Each lower roller 62 and upper roller 63 are rotatably supported on the inner surface side of the water storage tank 52. As shown in FIG. 3, the drive roller 66 and the electric motor 65 are rotatably supported via a bracket 71 formed above the water storage tank 52, and the driven roller 67 is located above a collection box 77 described later. It is rotatably supported via a bracket 72 formed in the above.

  Returning to FIG. 2, the recovery mechanism 54 includes an upper peeling portion 75, a lower peeling portion 76, and a collection box 77. The upper peeling portion 75 and the lower peeling portion 76 are provided so as to sandwich an endless belt 68 positioned between the upper roller 63 and the driven roller 67 on the right side in FIG. The upper peeling portion 75 and the lower peeling portion 76 are configured so that the tip portion in contact with the endless belt 68 is formed in a tapered shape, and the silicon powder P adsorbed on the endless belt 68 is scraped off. The collection box 77 is provided below the upper peeling portion 75 and the lower peeling portion 76, and is provided so as to accommodate the silicon powder P that has been scraped and dropped by the upper peeling portion 75 and the lower peeling portion 76. The collection box 77 is made of a material that can transmit nitrogen gas, which will be described later.

  Here, in addition to the silicon powder collection means 50, a drying means 80 is installed inside the collection chamber 43. The drying means 80 is provided so as to be able to blow nitrogen gas toward the collection box 77 and removes the moisture of the silicon powder P collected by the silicon powder collecting means 50.

  Returning to FIG. 1, in the base 11, a control unit 85 that performs overall control of each unit of the silicon powder generating apparatus 10 is provided. The control unit 85 includes a processor that executes various processes, and a storage medium such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The control unit 85 controls, for example, the voltage applied from the DC power supply 70, the drive of the drive motor 26 and the electric motor 65, and the like.

  Next, a method for generating silicon powder P using the silicon powder generating apparatus 10 of the present embodiment will be described. First, as shown in FIG. 1, the silicon plate S is sucked and held by the holding surface 12a of the chuck table 12, and then the table support base 16 is driven to move the chuck table 12 in the X-axis direction. It is set as the state positioned in the grinding position facing 28.

  From this state, a silicon mixed liquid generating step for generating the silicon mixed liquid L is performed. In this step, first, the grinding means 21 is lowered while rotating the grindstone 28, and grinding is performed by bringing the grindstone 28 into contact with the silicon plate S while supplying the processing liquid to the silicon plate S from a nozzle (not shown). By this grinding process, the silicon plate S is ground to form a fine powdery silicon powder P, and the silicon powder P is mixed into the processing liquid to generate a silicon mixed liquid L. As shown in FIG. 2, the generated silicon mixed liquid L flows into the water case 37 through the cover member 18, and then is stored in the water storage tank 52 through the tank 51.

  In the silicon mixed solution generation step, a process of maintaining the pH of the silicon mixed solution L flowing into the water case 37 from neutral to weakly acidic is performed. In this process, the pH of the silicon mixed solution L is measured by the pH sensor 40 of the pH adjusting means 39, and acid or alkali chemicals are introduced into the water case 37 from the injection device 41 according to the measured value. Thereby, it is possible to perform deoxygenation treatment until the silicon mixed liquid L is sent to the water storage tank 52, and adhesion of an oxide film on the surface of the silicon powder P can be prevented.

  Next, a silicon mixed liquid collecting step is performed for collecting silicon powder P from the silicon mixed liquid L stored in the water storage tank 52. In this step, plus (+) of the DC power supply 70 is energized to the endless belt 68, and minus (−) of the DC power supply 70 is energized to the cathode plate 61. Then, the electric motor 65 is driven to operate the endless belt 68 in the direction of arrow A in FIG. When energized in this way, the silicon powder P mixed with the silicon mixed liquid L and charged negative (−) is repelled from the negative (−) charged cathode plate 61 by electrophoresis, and positive (+) ) Is adsorbed to the endless belt 68 charged. At this time, the particle diameter of the silicon powder P adsorbed on the endless belt 68 also changes according to the voltage change of the DC power supply 70. Accordingly, the particle diameter of the silicon powder P can be equalized, and the particle diameter of the silicon powder P to be adsorbed can be easily changed by controlling the voltage of the DC power supply 70 via the control unit 85. can do.

  The endless belt 68 adsorbing the silicon powder P passes between the upper peeling portion 75 and the lower peeling portion 76 in the movement in the direction of arrow A in FIG. At that time, the silicon powder P adsorbed on the endless belt 68 is peeled off by the tip portions of the upper peeling portion 75 and the lower peeling portion 76. The peeled silicon powder P falls into the collection box 77, and the silicon powder P can be collected in the collection box 77.

  Subsequently, a drying process is performed in which nitrogen gas is blown from the drying means 80 toward the collection box 77 to remove the moisture of the silicon powder P collected in the collection box 77. In this step, since nitrogen gas is blown, the silicon powder P can be maintained in a dry state while preventing the oxide film from growing.

  In addition, it is preferable to use pure water that has undergone a deoxygenation process in which the working liquid is in gas-liquid contact with fine nitrogen bubbles and moves dissolved oxygen in the liquid to nitrogen to remove oxygen in the liquid. It is possible to prevent the oxide film from adhering to the surface of the silicon powder P. Moreover, it is good to use the ultrapure water which melt | dissolved the carbon dioxide and raised the electrical conductivity as a processing liquid, and, thereby, can extract | collect the silicon powder P by electrophoresis efficiently.

  As described above, according to the present embodiment, since electrophoresis is used for collecting the silicon powder P, it is possible to easily collect the silicon powder P having a uniform particle diameter. Moreover, since the silicon powder P is formed by grinding with the grindstone 28, the particle diameter of the silicon powder P can be easily reduced by reducing the abrasive grains. Thereby, by using the silicon powder P of the present embodiment for the negative electrode of the lithium ion battery, it is possible to contribute to the rapid charge and rapid discharge of the lithium ion battery and the increase in the capacity of power storage.

  Further, since the silicon powder collecting means 50 is disposed in the collection chamber 43, the space for generating the silicon powder P from the silicon mixed liquid L can be deoxygenated. Thereby, the growth of the natural oxide film in the silicon powder P can be prevented.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, the configuration of the plus electrode and the minus electrode connected to the DC power supply 70 can be variously modified as long as the plus electrode is immersed in the silicon mixed liquid L and the silicon powder P is adsorbed and collected.

  Further, the pH adjusting means 39 may change the installation position to the water storage tank 52 or may be additionally installed in the water storage tank 52. In short, the pH of the silicon mixed solution L may be maintained from neutral to weakly acidic by the pH adjusting means 39.

  Further, instead of the silicon plate S in the above embodiment, those powders may be generated from plate-like cadmium selenide (CdSe) or zinc sulfide (ZnS). The above powder can be used for a silicon photovoltaic power generation panel by forming a nano luminescent material having a luminous body of several tens of nanometers or less. In silicon solar cells that can be manufactured at low cost, only long-wavelength light can be converted into electric power, so a nanoparticle light emitter film is produced with a nanolight emitter, and sunlight passes through the nanoparticle light emitter film. Short wavelength light can be converted into long wavelength light and converted into electric power, and the amount of power generation can be increased. Further, if a nanoparticle light emitter film is manufactured using nanoparticles having a uniform and smaller particle diameter, the transmittance can be improved and efficient wavelength conversion can be performed.

  As described above, the present invention relates to an apparatus and method for generating silicon powder by mixing silicon powder formed by grinding crystalline silicon into a processing liquid and generating silicon powder from the silicon mixed liquid. Useful.

DESCRIPTION OF SYMBOLS 10 Silicon powder production | generation apparatus 12 Chuck table 13 Mixed liquid production | generation means 28 Grinding stone 39 pH adjustment means 43 Sampling chamber 44 Deoxygenation means 50 Silicon powder collection means 52 Water storage tank 61 Cathode plate (minus electrode)
68 Endless belt (adsorption member, positive electrode)
L Silicon mixed solution S Silicon plate P Silicon powder

Claims (7)

A method for producing silicon powder,
Grinding crystalline silicon using a grindstone while supplying a processing liquid, and mixing silicon powder ground into the processing liquid to generate a silicon mixed liquid,
A silicon powder collecting step of energizing a negative electrode and a positive electrode disposed in a water storage tank for storing the silicon mixed solution generated in the silicon mixed solution generating step, and collecting the silicon powder with the plus electrode; ,
And a drying step for removing the water of the silicon powder collected in the silicon powder collecting step,
The process liquid is a method for producing silicon powder using pure water that has undergone a deoxygenation process for removing oxygen in the process liquid . The method for producing silicon powder according to claim 1, wherein the silicon-containing liquid is kept weakly acidic in the silicon-containing liquid generating step and the silicon powder collecting step. The method for producing silicon powder according to claim 1 or 2 , wherein the processing liquid uses ultrapure water in which carbon dioxide is dissolved and conductivity is increased. 4. The method for producing silicon powder according to claim 1, wherein the silicon powder collecting step and the drying step are performed in a deoxygenated state . A silicon powder generating device for generating silicon powder,
A chuck table for holding a silicon plate made of crystalline silicon;
A silicon stone is generated by bringing a grinding wheel into contact with a silicon plate held by the chuck table while supplying a processing liquid that is pure water from which oxygen in the liquid is removed , and the silicon powder is mixed into the processing liquid. A mixed liquid generating means for generating a silicon mixed liquid;
The silicon mixed liquid generated by the mixed liquid generating means is stored in a water storage tank equipped with a negative electrode, the adsorbing member having a positive electrode is immersed in the stored silicon mixed liquid, and the silicon powder is put on the adsorbing member. Silicon powder collecting means for collecting by adsorption,
A silicon powder generating apparatus, comprising: a drying unit that removes moisture from the silicon powder collected by the silicon powder collecting unit.   6. The silicon powder generating apparatus according to claim 5, further comprising a sampling chamber that can be sealed so as to surround the silicon powder sampling means and the drying means, and wherein the sampling chamber is provided with a deoxygenating means. The silicon powder production | generation apparatus of Claim 5 or 6 provided with the pH adjustment means which maintains this silicon | silicone mixing liquid in weak acidity.

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