Silicon-based active material particles and silicon-based active material precursor particles and methods for producing the same

Abstract

The present application provides an active material particle having excellent ion introduction ability. The silicon-based active material particle has a layered structure. Note that the "silicon-based active material particle" described herein is, for example, an active material particle used for forming a negative electrode of a lithium-ion secondary battery. As the active material particle used for forming a negative electrode of a lithium-ion secondary battery, for example, a so-called Si-based active material such as silicon (Si), or silicon oxide (SiO x ), metal element-containing silicon oxide containing an alkali metal element such as lithium (Li) or an alkaline earth metal element such as magnesium (Mg), a silicon alloy, or the like is used. In the active material particle, the thickness of the layer is preferably 1 μm or less. In this case, the thickness of the layer is preferably 0.01 μm or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a silicon-based active material particle. In addition, the present application also relates to a silicon-based active material precursor particle and a method for producing the same. BACKGROUND

[0002] Various silicon oxide-based active material particles used for formation of a negative electrode of a lithium secondary battery have been proposed in the past (for example, refer to Japanese Patent Application Publication No. 2019-67644, etc.).

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-67644 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In recent years, however, there is a demand for improvement in the lithium ion ion introduction ability of active material particles.

[0008] An object of the present application is to provide an active material particle having excellent ion introduction ability.

[0009] TECHNICAL MEANS FOR SOLVING THE PROBLEMS

[0010] The silicon-based active material particle of the first aspect of the present application has a layered structure. Note that the "silicon-based active material particle" referred to here is, for example, an active material particle used for formation of a negative electrode of a lithium ion secondary battery. As the active material particle used for formation of a negative electrode of a lithium ion secondary battery, for example, there are silicon (Si) or silicon alloy, metal element-containing silicon oxide such as silicon oxide (SiO x ) containing an alkali metal element such as lithium (Li) or an alkaline earth metal element such as magnesium (Mg), and the like, i.e., a Si-based active material. Note that the thickness of the layer in the silicon-based active material particle is preferably 1 μm or less. Note that from the viewpoint of preventing the initial efficiency and capacity from being too small, the thickness of the layer is preferably 0.01 μm or more.

[0011] As described above, the silicon-based active material particle has a layered structure. The layered oxygen is enriched in the layer in the silicon-based active material particle. The silicon oxide (SiO x) is oxidized by charging to react with lithium (Li) to form lithium silicate, which has high lithium conductivity. Therefore, in the silicon-based active material particle, a region having high lithium conductivity in a layered structure exists, and lithium can move smoothly. As a result, when the silicon-based active material particle is used as a negative electrode active material, the silicon-based active material particle has higher ion introduction capacity than a conventional silicon-based active material particle that does not have a layered structure, and thus it is possible to improve the output characteristics of a battery such as a lithium secondary battery.

[0012] The silicon-based active material precursor particle of the second aspect of the present application has a layered structure. Note that the "silicon-based active material precursor particle" referred to here is a silicon-based active material particle that is obtained by pulverization, such as a silicon-based active material precursor particle for forming a negative electrode of a lithium ion secondary battery. As a silicon-based active material particle for forming a negative electrode of a lithium ion secondary battery, for example, a silicon (Si) or silicon alloy particle, an oxide silicon (SiO x ) particle, an alkali metal element such as lithium (Li) or an oxide silicon containing an alkaline earth metal element such as magnesium (Mg), a silicon alloy, or the like, i.e., a Si-based active material. Note that the thickness of the layer in the silicon-based active material precursor particle is preferably 1 μm or less. Note that the thickness of the layer is preferably 0.01 μm or more.

[0013] As described above, the silicon-based active material precursor particle has a layered structure. Therefore, when the silicon-based active material precursor particle is pulverized, the layer is more easily broken from the surface of the layer. Thus, the silicon-based active material precursor particle can be pulverized to form a silicon-based active material particle with less energy than a silicon-based active material precursor particle that does not have a layered structure. In addition, when a silicon-based active material particle obtained by the above-described method has a layered structure, the silicon-based active material particle can exhibit the same effects as the silicon-based active material particle of the first aspect.

[0014] The method for manufacturing a silicon-based active material precursor particle having a layered structure of the second aspect of the present application includes a layered film forming step and a scraping step. In the layered film forming step, a silicon-based active material forming material is repeatedly evaporated on a substrate to form a layered film of a silicon-based active material on the substrate. Note that the substrate is preferably a rotating body having an axis in the horizontal direction or a plate body that can move relative to a supply path of the silicon-based active material forming material. In the scraping step, the layered film of the silicon-based active material is scraped.

[0015] Therefore, in the method of manufacturing the silicon-based active material precursor particle, the binding force between the layers of the silicon-based active material laminated film can be adjusted by adjusting the temperature of the base and the like. Therefore, in the method, the crushing property of the obtained silicon-based active material precursor particle can be adjusted, and in the case where a silicon-based active material particle having a layer structure is obtained from the silicon-based active material precursor particle, the ion introduction ability of the silicon-based active material particle can be adjusted. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a schematic diagram of a manufacturing apparatus of a silicon-based active material precursor particle according to an embodiment of the present application.

[0017] Figure 2 is a 2000-fold SEM image of the negative electrode of Example 1.

[0018] Figure 3 is a 5000-fold SEM image of the negative electrode of Example 1.

[0019] Figure 4 is a 20000-fold SEM image of the negative electrode of Example 1.

[0020] Figure 5 is a 50000-fold SEM image of the negative electrode of Example 1.

[0021] Figure 6 is a 2000-fold SEM image of the negative electrode of Comparative Example 1.

[0022] Figure 7 is a 5000-fold SEM image of the negative electrode of Comparative Example 1.

[0023] Figure 8 is a 20000-fold SEM image of the negative electrode of Comparative Example 1.

[0024] Figure 9 is a 50000-fold SEM image of the negative electrode of Comparative Example 1.

[0025] REFERENCE NUMERALS

[0026] 100 vapor deposition apparatus

[0027] 110 crucible

[0028] 120 heater

[0029] 130 vapor deposition cylinder

[0030] 141 scraper

[0031] 143 particle guide

[0032] 150 chamber

[0033] 151 chamber body portion

[0034] 152 recovery section

[0035] 153 exhaust pipe

[0036] 160 raw material supply hopper

[0037] 170 raw material introduction pipe

[0038] 180 recovery container

[0039] 190 recovery pipe

[0040] Gg gas guide

[0041] OP opening

[0042] RM extraction chamber

[0043] Sr melt

[0044] VL1 first valve

[0045] VL2 second valve DETAILED DESCRIPTION

[0046] The silicon-based active material precursor particle of the embodiment of the present application is pulverized to become a silicon-based active material particle, and has a layer structure (a multi-layer structure). As such a silicon-based active material precursor particle, for example, a silicon (Si) or silicon oxide (SiO x ) containing an alkali metal element such as lithium (Li) or an alkaline earth metal element such as magnesium (Mg), a silicon alloy, or the like is used as an active material for a negative electrode of a lithium ion secondary battery. In addition, the silicon-based active material precursor particle of the present embodiment is pulverized to a prescribed particle diameter to be manufactured as a silicon-based active material particle for forming an electrode (particularly, a negative electrode). Note that in the silicon-based active material particle, the thickness of the layer is preferably 1 μm or less, further preferably 0.5 μm or less, still further preferably 0.2 μm or less, yet further preferably 0.1 μm or less, yet further preferably 0.05 μm or less, and particularly preferably 0.02 μm or less. In addition, from the viewpoint of preventing the initial efficiency and capacity of the battery from being too small, the thickness of the layer is preferably 0.01 μm or more.

[0047] However, such a silicon-based active material precursor particle can be obtained, for example, by forming a laminated film on a substrate and then scraping the laminated film from the substrate, but from the viewpoint of controlling manufacturing costs and the like, it is preferable to manufacture using the vapor deposition apparatus 100 as shown in Figure 1 . Hereinafter, the vapor deposition apparatus 100 as shown in Figure 1 will be described in detail.

[0048] The vapor deposition apparatus 100 is as shown inFigure 1 As shown, it mainly consists of a crucible 110, a heater 120, a vapor deposition cylinder 130, a scraper 141, a particle guide 143, a cavity 150, a raw material supply hopper 160, a raw material inlet pipe 170, a recovery container 180, a first valve VL1, and a second valve VL2.

[0049] Crucible 110 Figure 1 As shown, a heat-resistant container with an opening in the center of its top wall is disposed in the cavity 150. Furthermore, a through hole (not shown) is formed around the periphery of the top wall of the crucible 110, and a raw material inlet pipe 170 is inserted through this through hole. That is, the raw material in the raw material supply hopper 160 is supplied to the crucible 110 through the raw material inlet pipe 170. Additionally, a gas guide Gg is disposed on the upper side of the top wall of the crucible 110. This gas guide Gg is a component that guides the raw material gas generated in the crucible 110 into the vapor deposition cylinder 130, such as... Figure 1 As shown, it is set on the upper surface of the top wall in a manner that surrounds the central part of the top wall.

[0050] The heater 120 is a component used for heating the crucible 110 at high temperature, and is arranged such that the outer periphery of the crucible 110 is placed therein.

[0051] The vapor deposition cylinder 130 is, for example, a horizontal cylinder in the shape of a cylinder, such as... Figure 1 As shown, the crucible 110 is positioned above the opening OP on its top wall, and its lower part is surrounded by a gas guide Gg. Furthermore, the vapor deposition cylinder 130 is driven to rotate in one direction by a drive mechanism (not shown). It should be noted that the vapor deposition cylinder 130 is equipped with a temperature regulator (not shown) for maintaining a certain temperature on its outer peripheral surface. This temperature regulator cools the temperature of the outer peripheral surface of the vapor deposition cylinder 130 to a temperature suitable for vapor deposition of the source gas by means of a cooling medium supplied from the outside. In addition, the temperature of the outer peripheral surface of the vapor deposition cylinder 130 affects the crystallinity of the precipitates deposited on the residual precipitates on the vapor deposition cylinder. If the temperature is too low, the precipitate structure may be too porous; conversely, if it is too high, crystal growth due to heterogeneous reactions may progress. When the source gas is SiO gas, this temperature is preferably below 900°C, more preferably in the range of 150°C to 800°C, and particularly preferably in the range of 150°C to 700°C. Furthermore, the thickness of the layer constituting the silicon-based active material precursor particles can be controlled by adjusting the rotation speed or the outer peripheral surface temperature of the vapor deposition cylinder 130.

[0052] Scraper 141 is a component responsible for scraping the laminated film formed on the vapor deposition cylinder 130, such as... Figure 1As shown, the scraper 141 is arranged to move freely up and down near the vapor deposition cylinder 130. During the formation of the laminated film, the scraper 141 is in a standby state at the top, and at the end of the film formation, it is moved to the bottom to scrape off the laminated film. It should be noted that the scraped-off laminated film (silicon-based active material precursor particles) falls into the particle guide 143. Furthermore, the material of the scraper 141 can affect the contamination of the silicon-based active material particles by impurities. From the viewpoint of suppressing this effect, the material of the scraper 141 is preferably stainless steel or ceramic, and particularly preferably ceramic. Additionally, the scraper 141 preferably does not contact the outer peripheral surface of the vapor deposition cylinder 130. This prevents the recovered silicon-based active material precursor particles from being contaminated by impurities caused by direct contact between the vapor deposition cylinder 130 and the scraper 141.

[0053] The particle guide 143 is, for example, a vibrating conveying component, such as... Figure 1 As shown, it is arranged at an angle from near the vapor deposition cylinder toward the recovery section 152 of the cavity 150, receiving the stacked film scraped off by the scraper 141 arranged above it and sending it to the recovery section 152 of the cavity 150.

[0054] 150 cubic meters Figure 1 As shown, it is mainly formed by a cavity body 151, a recovery section 152, and an exhaust pipe 153. The cavity body 151 is as follows... Figure 1 As shown, this is a box-shaped section with a precipitation chamber RM inside, housing a crucible 110, a heater 120, a vapor deposition cylinder 130, a scraper 141, and a particle guide 143. The recovery section 152 is as follows... Figure 1 As shown, the portion protrudes outward from the side wall of the cavity body 151 and has a space communicating with the precipitation chamber RM of the cavity body 151. It should be noted that, as described above, the front end of the particle guide 143 is located in the recovery section 152.

[0055] The raw material supply hopper 160 is the source of raw material supply, such as... Figure 1 The outlet shown is connected to the raw material inlet pipe 170. That is, the raw material fed into the raw material supply hopper 160 is supplied to the crucible 110 through the raw material inlet pipe 170 at the appropriate time. It should be noted that the raw material supplied to the crucible 110 vaporizes into raw material gas after becoming molten Sr.

[0056] The raw material inlet pipe 170 is a round-hole nozzle used to supply solid raw materials fed into the raw material supply hopper 160 to the crucible 110. It is arranged in the central part of the top of the crucible 110 with the opening facing upward.

[0057] The recycling container 180 is a container for recycling the laminated membrane sheets that have passed through valves 1 VL1 and 2 VL2.

[0058] The first valve VL1 and the second valve VL2 are components that are opened and closed to adjust the amount of the laminated film sheet recovered to the recovery container 180, and are provided on the recovery pipe 190 that connects the recovery portion 152 of the accommodation chamber 150 and the recovery container 180.

[0059] Next, a case where the above-described evaporation apparatus 100 is used to manufacture silicon oxide powder or silicon oxide powder containing a metal element used for a negative electrode material for a lithium ion secondary battery will be described.

[0060] The raw material is fed to the crucible 110 from the raw material supply hopper 160 via the raw material introduction pipe 170. Note that, in the case of manufacturing silicon oxide particles, a mixed powder of Si and SiO2is used as the raw material. Note that, the mixed particles generate SiO gas as a raw material gas by being heated to a predetermined temperature. In the case of manufacturing silicon oxide powder containing a metal element, a mixed particle of Si and silicate such as Li2Si2O5, or a mixed powder of carbonate such as lithium carbonate (Li2CO3), silicon dioxide (SiO2), and silicon (Si) is used as the raw material. In this case, the mixed particle generates SiO gas containing a metal element such as Li as a raw material gas by being heated to a predetermined temperature. Note that, as the metal element, in addition to Li, an alkali metal such as Na, an alkaline earth metal such as Mg, and Ca, and the like, which can reduce SiO to stabilize oxygen, can be used.

[0061] If the raw material is fed to the crucible 110, the pressure in the deposition chamber RM is reduced, and the crucible 110 is heated by the heater 120. Note that, if the pressure in the deposition chamber RM is too high, it becomes difficult for the reaction that generates SiO gas from the raw material to occur. Therefore, the pressure in the deposition chamber RM is preferably 100 Pa or less, more preferably 750 Pa or less, and particularly preferably 20 Pa or less. In addition, the temperature in the deposition chamber RM affects the reaction rate of SiO, and if the temperature is too low, the reaction rate becomes slow, and if the temperature is too high, there are concerns that a side reaction progresses due to melting of the raw material, or the energy efficiency decreases, and the like. In addition, there is a possibility that the crucible 110 is damaged at this temperature. From this viewpoint, the temperature in the deposition chamber RM is preferably in the range of 1000°C or higher and 1600°C or lower, more preferably in the range of 1100°C or higher and 1500°C or lower, and particularly preferably in the range of 1100°C or higher and 1400°C or lower.

[0062] As described above, by heating the raw material under reduced pressure, a raw material gas is generated from the raw material in the crucible 110. This raw material gas is supplied to the vapor deposition cylinder 130 through the gas guide Gg. Meanwhile, the vapor deposition cylinder 130 is driven to rotate by a drive source. It should be noted that the temperature of the outer peripheral surface of the vapor deposition cylinder 130 is set lower than the temperature inside the precipitation chamber RM. More specifically, this temperature is set lower than the condensation temperature of the raw material gas. With this setting, the raw material gas generated from the crucible 110 is vaporized and precipitated, accumulating on the outer peripheral surface of the rotating vapor deposition cylinder 130. Furthermore, the scraper 141 is kept in a standby state at the top, and the vapor deposition cylinder 130 is rotated multiple times to form a laminated film on the vapor deposition cylinder 130. Subsequently, if the rotation speed of the vapor deposition cylinder 130 reaches a predetermined number, the scraper 141 is moved downwards, scraping the laminated film from the vapor deposition cylinder 130. It should be noted that the scraped fragments of the laminated film fall along the outer peripheral surface of the vapor deposition cylinder 130 onto the particle guide 143.

[0063] In the vapor deposition apparatus 100 of this embodiment, high-quality silicon-based active material precursor particles are manufactured in the manner described above.

[0064] Hereinafter, embodiments and comparative examples are shown to illustrate the present invention in more detail, but the present invention is not limited to these embodiments.

[0065] Example 1

[0066] 1. Preparation of silicon-based active material powder

[0067] exist Figure 1 The crucible 110 of the vapor deposition apparatus 100 shown is filled with a mixture of silicon (Si) powder and silicon dioxide (SiO2) powder (a mixture of silicon powder and silicon dioxide powder in a Si:O = 1:1 ratio) as raw materials for generating silicon monoxide (SiO) gas. The precipitation chamber RM is depressurized to 1 Pa and the crucible 110 is heated to 1300°C to generate silicon monoxide gas. On the other hand, the temperature of the vapor deposition cylinder 130 is managed to reach 150°C, and the vapor deposition cylinder 130 is rotated to condense and precipitate silicon monoxide gas on the outer peripheral surface of the vapor deposition cylinder 130. At this time, the rotation speed of the vapor deposition cylinder 130 is adjusted so that silicon monoxide accumulates on the outer peripheral surface of the vapor deposition cylinder 130 to a thickness of 0.18 μm during a single rotation. Then, after rotating the vapor deposition cylinder 130 50 times, the scraper 141 is brought close to the vapor deposition cylinder 130 to remove the silicon monoxide film deposited (layered) on the outer peripheral surface of the vapor deposition cylinder 130, obtaining silicon monoxide powder. The silicon monoxide powder is then heat-treated at 700°C in an argon atmosphere to obtain silicon-based active material precursor powder. This silicon-based active material precursor powder is then finely granulated in a pulverizer and sieved through a 20μm sieve; the portion passing through the sieve is taken as the silicon-based active material powder.

[0068] 2. Determination of pulverization characteristics of silicon-based active material precursor powder

[0069] The silicon-based active material precursor powder was sieved with a double sieve formed by superimposing a sieve with a mesh size of 45 μm on a sieve with a mesh size of 20 μm, and the fraction that passed through the sieve with a mesh size of 45 μm but did not pass through the sieve with a mesh size of 20 μm (i.e., the fraction that remained on the sieve with a mesh size of 20 μm) was used as a pulverization sample for the determination of the pulverization characteristics. Then, 1 L of the volume of the pulverization sample was filled into a Japanese Carbon dry mill MA1D (dry mill), and the device was operated for 5 minutes. Note that at this time, a zirconia sphere with a diameter of 5 mm was used as the grinding ball for pulverization, and the rotation speed of the mill was set to 300 rpm. Next, the particle size distribution of the pulverization sample after pulverization by the mill for 5 minutes was measured with a Mastersizer 2000 (laser diffraction type particle size distribution measuring device) manufactured by Malvern, and the volume-standardized median particle diameter D50 (hereinafter referred to as "average particle diameter") was calculated. The results of the measurement are shown in Table 1. Note that isopropyl alcohol was used as the solvent at the time of the measurement of the particle size distribution.

[0070] 3. Determination of electrode characteristics of silicon-based active material powder

[0071] (1) Production of negative electrode and SEM observation

[0072] The silicon-based active material powder (SiO powder), Ketjen black, and a polyimide precursor as the non-aqueous solvent-based binder were mixed at a mass ratio of 85:5:10, and the mixture was kneaded after adding N-methylpyrrolidone to the mixture, thereby preparing a slurry. Then, the slurry was applied to a copper foil with a thickness of 40 μm, and the coated film was pre-dried at 80°C for 15 minutes, and then the copper foil with the dried coated film was punched into a disk with a diameter of 11 mm, and then the copper foil with the dried coated film was heated at 350°C under reduced pressure, thereby producing a negative electrode. Note that the polyimide precursor in the dried coated film was imidized by heating the copper foil with the dried coated film at 350°C. Then, the negative electrode was photographed with a scanning electron microscope (SEM), and the images shown in FIG. 1 were obtained. From these images, it was confirmed that the silicon-based active material particles in the silicon-based active material powder had a layered structure, and the thickness of each layer was 0.2 μm or less. Figure 2 to Figure 5

[0073] ​Note that the thickness of the layer is determined as follows. First, in a 50,000-fold SEM image of the cross section of one silicon-based active material particle, the thickness of the layer is determined by dividing the length of a line segment drawn perpendicularly across any 10 layers of the multiple layers appearing as striped patterns (striped light and dark portions of the SEM image) by 10. Then, this operation is performed for 10 50,000-fold SEM images of the cross section of silicon-based active material particles, and the average of the thickness of the layer in the 10 silicon-based active material particles is taken as the final thickness of the layer of the silicon-based active material particle.

[0074] (2) Production of coin cell (lithium-ion secondary cell) and measurement of cell properties

[0075] A coin cell was produced using lithium foil as the counter electrode, a solution in which lithium hexafluorophosphate (LiPF6) was dissolved in a solution in which ethylene carbonate and diethyl carbonate were mixed in a volume ratio of 1 : 1 at a concentration of 1 mole / L of LiPF6 as the electrolyte, and a polyethylene porous film having a thickness of 20 μm as the separator.

[0076] Then, a charge-discharge test of the coin cell was performed using a secondary cell charge-discharge test device manufactured by electrofield co., ltd. Note that the test conditions for the charge-discharge test are shown in Table 2. Through the charge-discharge test, the initial charge capacity, the initial discharge capacity, the ratio of the initial discharge capacity to the initial charge capacity (initial coulombic efficiency), and the ratio of the 3rd discharge capacity to the initial discharge capacity (output characteristics) were obtained. The results of the measurement are shown in Table 1. Note that the "output characteristics" referred to here means the ratio of the discharge capacity at 0.5 C in the 3rd cycle to the discharge capacity at 0.1 C in the initial cycle.

[0077] Example 2

[0078] The silicon-based active material powder was produced in the same manner as in Example 1 except that the rotation speed of the evaporation cylinder 130 was adjusted so that the accumulated thickness of silicon monoxide would be 0.98 μm, and the crushing property measurement of the silicon-based active material precursor powder and the electrode property measurement of the silicon-based active material powder were performed. The results of the measurement are shown in Table 1. In addition, a negative electrode was produced in the same manner as in Example 1, and the silicon-based active material particles in the silicon-based active material powder were confirmed to have a layer structure and the thickness of each layer was 1 μm or less from the image taken by a scanning electron microscope (SEM).

[0079] Example 3

[0080] The silicon-based active material powder was produced in the same manner as in Example 1 except that the rotation speed of the evaporation cylinder 130 was adjusted so that the accumulated thickness of silicon monoxide reached 0.48 μm. The pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured. The results of the measurements are shown in Table 1. In addition, a negative electrode was produced in the same manner as in Example 1, and the negative electrode was photographed with a scanning electron microscope (SEM). From the image, it was confirmed that the silicon-based active material particles in the silicon-based active material powder had a layered structure, and the thickness of each layer was 0.5 μm or less.

[0081] Example 4

[0082] The silicon-based active material powder was produced in the same manner as in Example 1 except that the rotation speed of the evaporation cylinder 130 was adjusted so that the accumulated thickness of silicon monoxide reached 0.08 μm. The pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured. The results of the measurements are shown in Table 1. In addition, a negative electrode was produced in the same manner as in Example 1, and the negative electrode was photographed with a scanning electron microscope (SEM). From the image, it was confirmed that the silicon-based active material particles in the silicon-based active material powder had a layered structure, and the thickness of each layer was 0.1 μm or less.

[0083] Example 5

[0084] The silicon-based active material powder was produced in the same manner as in Example 1 except that the rotation speed of the evaporation cylinder 130 was adjusted so that the accumulated thickness of silicon monoxide reached 0.05 μm. The pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured. The results of the measurements are shown in Table 1. In addition, a negative electrode was produced in the same manner as in Example 1, and the negative electrode was photographed with a scanning electron microscope (SEM). From the image, it was confirmed that the silicon-based active material particles in the silicon-based active material powder had a layered structure, and the thickness of each layer was 0.05 μm or less.

[0085] Example 6

[0086] The silicon-based active material powder was produced in the same manner as in Example 1 except that the rotation speed of the evaporation cylinder 130 was adjusted so that the accumulated thickness of silicon monoxide reached 0.02 μm. The pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured. The results of the measurements are shown in Table 1. In addition, a negative electrode was produced in the same manner as in Example 1, and the negative electrode was photographed with a scanning electron microscope (SEM). From the image, it was confirmed that the silicon-based active material particles in the silicon-based active material powder had a layered structure, and the thickness of each layer was 0.02 μm or less.

[0087] Example 7

[0088] The silicon-based active material powder was prepared in the same manner as in Example 1, except that the rotation speed of the evaporation cylinder 130 was adjusted in such a manner that the accumulated thickness of the silicon monoxide reached a level of 0.01 μm, and the pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured. The results of the measurement are shown in Table 1. Further, the negative electrode was produced in the same manner as in Example 1, and the silicon-based active material particles in the silicon-based active material powder were confirmed to have a layered structure and the thickness of each layer was confirmed to be in the order of 0.01 μm from the image taken by a scanning electron microscope (SEM) of the negative electrode.

[0089] Example 8

[0090] The silicon-based active material powder was prepared in the same manner as in Example 1, except that a mixed powder of a powder of silicon (Si) and a powder of lithium silicate (Si02 / Li20 = 2) was used as a raw material for silicon monoxide (SiO) gas instead of a mixed powder of a powder of silicon (Si) and a powder of silicon dioxide (Si02), and the pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured. The results of the measurement are shown in Table 1. Note that the silicon monoxide thin film obtained in this example contained lithium. Further, the negative electrode was produced in the same manner as in Example 1, and the silicon-based active material particles in the silicon-based active material powder were confirmed to have a layered structure and the thickness of each layer was confirmed to be less than 0.2 μm from the image taken by a scanning electron microscope (SEM) of the negative electrode.

[0091] Example 9

[0092] The silicon-based active material powder was prepared in the same manner as in Example 8, except that the rotation speed of the evaporation cylinder 130 was adjusted in such a manner that the accumulated thickness of the silicon monoxide reached a level of 0.98 μm, and the pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured in the same manner as in Example 1. The results of the measurement are shown in Table 1. Further, the negative electrode was produced in the same manner as in Example 1, and the silicon-based active material particles in the silicon-based active material powder were confirmed to have a layered structure and the thickness of each layer was confirmed to be less than 1 μm from the image taken by a scanning electron microscope (SEM) of the negative electrode.

[0093] Example 10

[0094] The silicon-based active material powder was prepared in the same manner as in Example 8 except that the rotation speed of the evaporation cylinder 130 was adjusted so that the accumulated thickness of silicon monoxide reached 0.48 μm, and the pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured in the same manner as in Example 1. The results of the measurement are shown in Table 1. Further, in the same manner as in Example 1, a negative electrode was produced from the silicon-based active material powder, and the negative electrode was photographed with a scanning electron microscope (SEM), and from the image it was confirmed that the silicon-based active material particles in the silicon-based active material powder had a layered structure, and the thickness of each layer was 0.5 μm or less.

[0095] Example 11

[0096] The silicon-based active material powder was prepared in the same manner as in Example 8 except that the rotation speed of the evaporation cylinder 130 was adjusted so that the accumulated thickness of silicon monoxide reached 0.08 μm, and the pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured in the same manner as in Example 1. The results of the measurement are shown in Table 1. Further, in the same manner as in Example 1, a negative electrode was produced from the silicon-based active material powder, and the negative electrode was photographed with a scanning electron microscope (SEM), and from the image it was confirmed that the silicon-based active material particles in the silicon-based active material powder had a layered structure, and the thickness of each layer was 0.1 μm or less.

[0097] Example 12

[0098] The silicon-based active material powder was prepared in the same manner as in Example 8 except that the rotation speed of the evaporation cylinder 130 was adjusted so that the accumulated thickness of silicon monoxide reached 0.05 μm, and the pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured in the same manner as in Example 1. The results of the measurement are shown in Table 1. Further, in the same manner as in Example 1, a negative electrode was produced from the silicon-based active material powder, and the negative electrode was photographed with a scanning electron microscope (SEM), and from the image it was confirmed that the silicon-based active material particles in the silicon-based active material powder had a layered structure, and the thickness of each layer was 0.05 μm or less.

[0099] Example 13

[0100] The silicon-based active material powder was prepared in the same manner as in Example 8 except that the rotation speed of the evaporation cylinder 130 was adjusted so that the accumulated thickness of silicon monoxide reached 0.02 μm, and the pulverization characteristics of the silicon-based active material precursor powder and the electrode characteristics of the silicon-based active material powder were measured in the same manner as in Example 1. The results of the measurement are shown in Table 1. Further, in the same manner as in Example 1, a negative electrode was produced from the silicon-based active material powder, and the negative electrode was photographed with a scanning electron microscope (SEM), and from the image it was confirmed that the silicon-based active material particles in the silicon-based active material powder had a layered structure, and the thickness of each layer was 0.02 μm or less.

[0101] Example 14

[0102] The silicon-based active material powder was prepared in the same manner as in Example 8 except that the rotation speed of the evaporation cylinder 130 was adjusted in such a manner that the deposited thickness of silicon monoxide reached a level of 0.01 μm, and the pulverization property measurement of the silicon-based active material precursor powder and the electrode property measurement of the silicon-based active material powder were performed in the same manner as in Example 1. The measurement results are shown in Table 1. Further, in this example, too, the negative electrode was produced in the same manner as in Example 1, and the negative electrode was photographed with a scanning electron microscope (SEM), and from the image thereof, it was confirmed that the silicon-based active material particles in the silicon-based active material powder had a layer structure, and the thickness of each layer reached a level of 0.01 μm.

[0103] (Comparative Example 1)

[0104] Silicon monoxide gas was condensed and precipitated without rotating the evaporation cylinder 130, and a silicon monoxide thin film was obtained. The silicon monoxide powder was obtained by scraping the silicon monoxide thin film with the scraper 141, and the silicon-based active material particles were obtained by pulverizing the silicon monoxide powder to an average particle diameter D50 of 5 μm with a dry-type pulverizer. The silicon-based active material powder was prepared in the same manner as in Example 1 except for this, and the pulverization property measurement of the silicon-based active material precursor powder and the electrode property measurement of the silicon-based active material powder were performed. The measurement results are shown in Table 1. Further, in this comparative example, too, the negative electrode was produced in the same manner as in Example 1, and the negative electrode was photographed with a scanning electron microscope (SEM). The photographing results are shown in FIGS. 10 and 11. In particular, from the images shown in FIGS. 10 and 11, it was confirmed that the silicon-based active material particles in the silicon-based active material powder did not have a layer structure. Figure 6 to Figure 9 Figure 8 Figure 9

[0105] (Comparative Example 2)

[0106] Silicon monoxide gas was condensed and precipitated without rotating the evaporation cylinder 130, and a silicon monoxide thin film was obtained. The silicon monoxide powder was obtained by scraping the silicon monoxide thin film with the scraper 141, and the silicon-based active material particles were obtained by pulverizing the silicon monoxide powder to an average particle diameter D50 of 5 μm with a dry-type pulverizer. The silicon-based active material powder was prepared in the same manner as in Example 8 except for this, and the pulverization property measurement of the silicon-based active material precursor powder and the electrode property measurement of the silicon-based active material powder were performed. The measurement results are shown in Table 1. Note that the silicon monoxide thin film obtained in this comparative example contained lithium. Further, in this comparative example, too, the negative electrode was produced in the same manner as in Example 1, and the negative electrode was photographed with a scanning electron microscope (SEM), but it was not confirmed from the image thereof that the silicon-based active material particles in the silicon-based active material powder did not have a layer structure.

[0107] Table 1 ​​​

[0108]

[0109] Table 2

[0110]

[0111] (Summary)

[0112] As shown in Table 1, the average particle diameter of the pulverized sample after 5 minutes of pulverization of the silicon-based active material precursor powder of Examples 1 to 7 was smaller than that of the silicon-based active material precursor powder of Comparative Example 1, and it was clear that the pulverizability was more excellent. In addition, in the silicon-based active material precursor powder of Examples 1 to 7, it was clear that the thinner the layer thickness, the higher the pulverizability. Furthermore, the output characteristics of the coin batteries of Examples 1 to 7 were more excellent than those of the coil battery of Comparative Example 1. In addition, in the coin batteries of Examples 1 to 7, the thinner the layer thickness in the silicon-based active material particles constituting the negative electrode active material, the higher the output characteristics.

[0113] In addition, as shown in Table 1, the average particle diameter of the pulverized sample after 5 minutes of pulverization of the silicon-based active material precursor powder of Examples 8 to 14 was smaller than that of the silicon-based active material precursor powder of Comparative Example 2, and it was clear that the pulverizability was more excellent. In addition, in the silicon-based active material precursor powder of Examples 8 to 14, it was clear that the thinner the layer thickness, the higher the pulverizability. Furthermore, the output characteristics of the coin batteries of Examples 8 to 14 were more excellent than those of the coil battery of Comparative Example 2. In addition, in the coin batteries of Examples 8 to 14, the thinner the layer thickness in the silicon-based active material particles constituting the negative electrode active material, the higher the output characteristics.

Claims

1. A silicon-based active material particle, wherein, The silicon-based active material particles have a layered structure. All the layers constituting the layered structure are made of silicon-based materials. The silicon-based material is silicon oxide or silicon oxide containing metal elements. The thickness of each layer in the layered structure is less than 0.2 μm.

2. The silicon-based active material particles as described in claim 1, wherein, All the layers constituting the layered structure are made of the same silicon-based material.

3. A silicon-based active material precursor particle, wherein, The silicon-based active material precursor particles have a layered structure. All the layers constituting the layered structure are made of silicon-based materials. The silicon-based material is silicon oxide or silicon oxide containing metal elements. The thickness of each layer in the layered structure is less than 0.2 μm.

4. The silicon-based active material precursor particles as described in claim 3, wherein, All the layers constituting the layered structure are made of the same silicon-based material.

5. A method for manufacturing silicon-based active material precursor particles with a layered structure, comprising the following steps: The film-forming process involves repeatedly performing a deposition process to deposit a silicon-based active material onto a substrate, thereby forming a multilayer film of the silicon-based active material on the substrate; and The scraping process involves scraping off the laminated film of the silicon-based active material. The silicon-based material is silicon oxide or silicon oxide containing metal elements.

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