Silicon oxide and method for producing same

Abstract

The present invention addresses the problem of providing a method for reducing elemental impurities such as aluminum in silicon oxide. This method for producing silicon oxide is provided with a water treatment step, a reduced-pressure heating step, and a desublimation step. In the water treatment step, silicon is brought into contact with water and then dried to obtain water-treated silicon. In the pressure-reduced heating step, (a) the water-treated silicon is heated under reduced pressure together with (b1) silica, (b2) a metal silicate, or (b3) a mixture of a metal oxide and silicon oxide to generate a gas. In the desublimation step, the gas is desublimated to obtain a solid.

Description

Technical Field

[0001] The present invention relates to silicon oxide (including silicon oxide containing a metal element) and also to a method for producing silicon oxide. Background Art

[0002] In recent years, silicon monoxide (SiO) has been expected as a large-capacity negative electrode active material. However, silicon monoxide has the disadvantage of large irreversible capacity. As a method of reducing the irreversible capacity to improve efficiency, Japanese Patent Publication No. 2021-52014 proposes a gas-phase lithium pre-doping method. The gas-phase lithium pre-doping method disclosed in the publication is a method of obtaining lithium-containing silicon oxide (lithium-doped silicon oxide) by doping lithium in SiO in the gas phase.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-52014

[0006] Patent Document 2: Japanese Patent Application Publication No. 2014-86254 Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] However, in the silicon monoxide manufacturing method and the gas phase lithium pre-doping method, since the low vapor pressure elements such as aluminum contained in the raw material are vaporized together with the silicon monoxide, there is a problem that a certain amount of impurities remain in the target silicon oxide. Impurities at the element level such as aluminum diffuse in the active material particles during the charge and discharge process of the battery, precipitate at the grain boundaries, and promote micronization, which may deteriorate the cycle characteristics of the battery.

[0009] An object of the present invention is to provide a method for reducing the level of impurities such as aluminum and other elements in silicon oxide.

[0010] Technical means for solving technical problems

[0011] The method for producing silicon oxide (including metal element-containing silicon oxide) according to the first aspect of the present invention comprises a water treatment step, a reduced pressure heating step, and a desublimation step. In the water treatment step, silicon is contacted with water and then dried to obtain water-treated silicon. In the reduced pressure heating step, (a) water-treated silicon is heated under reduced pressure together with at least one compound selected from the group consisting of (b1) silicon dioxide, (b2) metal silicate, and (b3) metal oxide to generate gas. In the desublimation step, the gas is desublimated to obtain a solid.

[0012] As described above, the method for producing silicon oxide includes a water treatment step. As a result, the aluminum and iron elements contained in the silicon oxide powder can be changed into a form that is difficult to be vaporized in the reduced pressure heating step. Therefore, in the method for producing silicon oxide, the concentration of aluminum and iron elements in the silicon oxide (solid) can be reduced.

[0013] The method for producing silicon oxide according to the second aspect of the present invention comprises a granulation step, a reduced pressure heating step, and a desublimation step. In the granulation step, a mixture containing (A) silicon and (B) at least one compound selected from the group consisting of (b1) silicon dioxide, (b2) metal silicate, and (b3) metal oxide is granulated using water to obtain a granulated product. In the reduced pressure heating step, the granulated product is heated under reduced pressure to generate gas from the granulated product. In the desublimation step, the gas is desublimated to obtain a solid product.

[0014] As described above, a granulation step is provided in the method for producing silicon oxide. In the granulation step, the aluminum element and the iron element contained in the granulated silicon can be changed into a form that is difficult to be gasified in the reduced pressure heating step by the water used for granulation. Therefore, in the method for producing silicon oxide, the aluminum element concentration and the iron element concentration in the silicon oxide (solid) can be reduced. In addition, since the fluidity is improved and the jetting property is reduced by granulation, the operation in the process becomes easy.

[0015] The method for producing silicon oxide according to the third aspect of the present invention comprises a charging step, a reduced pressure heating step, and a desublimation step. In the charging step, (A) silicon and (B) a mixture are charged into a heat-resistant container in such a manner that the aluminum concentration in the mixture containing (A) silicon and (B) at least one compound selected from the group consisting of (b1) silicon dioxide, (b2) metal silicate, and (b3) metal oxide is less than 50 ppm by mass concentration, the iron concentration is less than 1000 ppm by mass concentration, and the copper concentration is less than 200 ppm by mass concentration. In the reduced pressure heating step, the mixture is heated under reduced pressure to generate gas from the mixture. In the desublimation step, the gas is desublimated to obtain a solid.

[0016] As described above, the silicon oxide production method is provided with a charging step. In the charging step, silicon and the mixture are charged into a heat-resistant container so that the aluminum concentration in the mixture is less than 50 ppm by mass concentration, the iron concentration is less than 1000 ppm by mass concentration, and the copper concentration is less than 200 ppm by mass concentration. Therefore, in the silicon oxide production method, the aluminum concentration, the iron concentration, and the copper concentration in the lithium-containing silicon oxide (solid matter) can be sufficiently reduced.

[0017] The method for producing silicon oxide according to the fourth aspect of the present invention comprises a charging step, a reduced pressure heating step, and a desublimation step. In the charging step, (A) silicon and (B) one or more compounds of (b1) silicon dioxide, (b2) metal silicate, and (b3) metal oxide are charged into a heat-resistant container in such a manner that the element ratio O / Si during the reaction is within a range of more than 1 and less than 1.5. In addition, from the viewpoint of maintaining the reaction rate well, the element ratio O / Si during the reaction is preferably less than 1.3, and more preferably less than 1.1. In the reduced pressure heating step, the compound charged into the heat-resistant container is heated under reduced pressure to generate gas from the compound. In the desublimation step, the gas is desublimated to obtain a solid. In addition, here, the element ratio O / Si during the reaction refers to the value obtained by dividing the amount of the O element contained in the raw material charged into the heat-resistant container by the amount of the Si element contained in the raw material charged into the heat-resistant container.

[0018] As described above, the method for producing silicon oxide is provided with a charging step. In the charging step, (A) silicon and (B) one or more compounds selected from (b1) silicon dioxide, (b2) metal silicate and (b3) metal oxide are charged into a heat-resistant container in such a manner that the element ratio O / Si during the reaction is in the range of more than 1 and less than 1.5. Therefore, in the heat-resistant container, the aluminum element in the raw material reacts with the excess silicon oxide or metal silicate and remains in the crucible, thereby suppressing the gasification of the aluminum element and the iron element, and being able to sufficiently reduce the concentration of the aluminum element and the iron element in the silicon oxide obtained as the target product. In addition, during the reaction in the heat-resistant container, the element ratio O / Si only needs to be in the range of more than 1 and less than 1.5, so it is also possible to pass through a process (granulation process) that does not affect the element ratio in the middle. As a specific method for setting the element ratio during the reaction to the target value, the following method can be considered: for the raw materials added per unit time that are pre-mixed in a manner so that the element ratio O / Si is within the range of greater than 1 and less than 1.5 and added to a heat-resistant container, the respective input amounts are set in a manner so that the element ratio O / Si is always within the range of greater than 1 and less than 1.5, and the raw materials are then added to the heat-resistant container from different paths.

[0019] The method for producing silicon oxide according to a fifth aspect of the present invention is the method for producing silicon oxide according to any one of the first to fourth aspects, wherein the heating temperature in the reduced pressure heating step is set to T R , let (A) the melting point of silicon be T A The lowest melting point among the melting points of (b1) silicon dioxide, (b2) metal silicate and (b3) metal oxide is defined as T BL The highest melting point among the melting points of (b1) silicon dioxide, (b2) metal silicate and (b3) metal oxide is defined as T BH At T A<T BL If established, T R Set to satisfy T A <T R <T BL , in T BL <T A <T BH If established, T R Set to satisfy T BL <T R <T A , in T BH <T A If established, T R Set to satisfy T BH <T R <T A .

[0020] As described above, in the method for producing silicon oxide, the heating temperature in the reduced pressure heating step is set as described above. Therefore, the heating temperature in the reduced pressure heating step can be set to a temperature suitable for generating gas.

[0021] The silicon oxide of the sixth aspect of the present invention has a x SiO y (wherein, in the composition formula, M is at least one metal element selected from Li, Na, K, Mg, and Ca, y is in the range of more than 0.5 and less than 1.5, x / y is in the range of more than 0 and less than 1, and x is more than 0.) In addition, in the silicon oxide, the concentration of aluminum as an impurity is less than 150 ppm by mass concentration, the concentration of iron is less than 100 ppm, and the concentration of copper is less than 100 ppm.

[0022] As described above, in the silicon oxide, the concentration of aluminum as an impurity is less than 150 ppm by mass concentration, the concentration of iron is less than 100 ppm, and the concentration of copper is less than 100 ppm. Therefore, when the silicon oxide is used as a negative electrode active material, it can be expected that micronization can be suppressed during the charge and discharge process, thereby suppressing the reduction in the cycle characteristics of the battery.

[0023] In addition, in the above silicon oxide, the median particle size measured by a laser diffraction particle size distribution measuring device is preferably in the range of 0.5 μm to 30 μm. This is because, when the silicon oxide is used as a negative electrode active material, it is not only possible to suppress the reduction of coulombic efficiency, but also possible to suppress micronization and suppress the reduction of the cycle characteristics of the negative electrode.

[0024] In addition, in the above-mentioned silicon oxide, at least a part of the surface is preferably covered by a conductive carbon coating. In this case, the mass ratio of carbon in the conductive carbon coating relative to the mass of the silicon oxide is preferably in the range of 0.5 mass % to 20 mass %. This is because, when the silicon oxide is used as a negative electrode active material, the charge and discharge capacity can be well maintained, and the side reaction of the silicon oxide can be suppressed while giving the silicon oxide good conductivity.

[0025] In addition, among the above silicon oxides, it is preferred that the BET specific surface area is within 1 m 2 / g above 6m 2 This is because, when the silicon oxide is used as a negative electrode active material, the output characteristics can be well maintained and a decrease in coulombic efficiency can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of a silicon oxide powder production apparatus according to an embodiment of the present invention.

[0027] Description of Reference Numerals

[0028] 100 Evaporation device

[0029] 110 Crucible

[0030] 120 Heater

[0031] 130 Evaporation Roller

[0032] 141 scraper

[0033] 143 Granular guide

[0034] 150 chambers

[0035] 151 Chamber main body

[0036] 152 Recycling Department

[0037] 153 Exhaust pipe

[0038] 160 Raw material supply hopper

[0039] 170 Raw material introduction pipe

[0040] 180 Recycling Container

[0041] 190 Recovery Tube

[0042] Gg Gas Guide

[0043] OP Opening

[0044] RM Sedimentation Room

[0045] Sr molten metal

[0046] VL1 first valve

[0047] VL2 second valve DETAILED DESCRIPTION

[0048] The silicon oxide of the embodiment of the present invention is composed of M x SiO y In this composition formula, M is at least one metal element selected from Li, Na, K, Mg, and Ca. In addition, y is in the range of more than 0.5 and less than 1.5, and x / y is in the range of more than 0 and less than 1. In addition, x is greater than 0. However, when x exceeds 0, the composition formula is M x SiO y On the other hand, when x is 0, its composition formula is SiO y That is, silicon oxide is sometimes represented by M x SiO y Indicated, sometimes by SiO y Indicated. In the former case, y is in the range of more than 0.5 and less than 1.5, and x / y is in the range of more than 0 and less than 1. Here, y is preferably in the range of more than 0.7 and less than 1.3, more preferably in the range of more than 0.9 and less than 1.1, further preferably in the range of more than 0.95 and less than 1.05, and particularly preferably in the range of more than 1.00 and less than 1.05. In addition, when M is Li, x / y is preferably in the range of more than 0.20 and less than 0.5, more preferably in the range of more than 0.30 and less than 0.4, and when M is Mg, x / y is preferably in the range of more than 0.8 and less than 1, more preferably in the range of more than 0.9 and less than 1. On the other hand, in the latter case, y is in the range of more than 0.5 and less than 1.5, and x / y is 0. For the sake of convenience of explanation, hereinafter, M is sometimes referred to as x SiO y The composition represented by the metal element is called silicon oxide, which is composed of SiO y The composition represented is called metal-free silicon oxide. In addition, silicon oxide mainly formed by metal-containing silicon oxide is sometimes called metal-containing silicon oxide, and silicon oxide mainly formed by metal-free silicon oxide is called metal-free silicon oxide. Moreover, in the silicon oxide, i.e., metal-containing silicon oxide or metal-free silicon oxide, the aluminum element as an impurity is contained in a mass concentration of only 150 ppm or less, the iron element is contained in a mass concentration of only less than 100 ppm, and the copper element is contained in a mass concentration of only less than 100 ppm. In addition, the shape of the silicon oxide in the embodiment of the present invention is not limited, and it can be powder, block, or other shapes.

[0049] In addition, the median particle size of the silicon oxide measured by a laser diffraction particle size distribution measuring device is preferably in the range of 0.5 μm to 30 μm, more preferably in the range of 1.0 μm to 20 μm, and further preferably in the range of 1.5 μm to 10 μm. This is because, when the silicon oxide is used as a negative electrode active material, not only can the reduction of coulombic efficiency be suppressed, but also micronization can be suppressed to suppress the reduction of the cycle characteristics of the negative electrode.

[0050] In addition, the silicon oxide is preferably coated with a conductive carbon coating on at least a portion of its surface. In this case, the mass ratio of carbon in the conductive carbon coating relative to the mass of the silicon oxide is preferably in the range of 0.5 mass % to 20 mass %, more preferably in the range of 0.5 mass % to 10 mass %, and further preferably in the range of 0.5 mass % to 5 mass %. This is because, when the silicon oxide is used as a negative electrode active material, the charge and discharge capacity can be well maintained, and the side reaction of the silicon oxide can be suppressed while giving the silicon oxide good conductivity.

[0051] In addition, the BET specific surface area of ​​the silicon oxide is preferably in the range of 1 m 2 / g above 6m 2 / g or less, more preferably 1.5 m 2 / g above 5m 2 / g or less, and more preferably 1.5 m 2 / g above 4m 2 / g or less, particularly preferably within 1.5 m 2 / g above 3m 2 This is because, when the silicon oxide is used as a negative electrode active material, the output characteristics can be well maintained and a decrease in coulombic efficiency can be suppressed.

[0052] Hereinafter, a method for producing silicon oxide according to an embodiment of the present invention, that is, silicon oxide containing a metal element or silicon oxide not containing a metal element will be described in detail.

[0053] Incidentally, the raw material used in the manufacture of silicon oxide without metal elements is a mixture of silicon and silicon dioxide. In addition, silicon and silicon dioxide may be in powder form, in block form, or in other shapes. On the other hand, the raw material used in the manufacture of silicon oxide containing metal elements is a mixture of silicon and at least one compound selected from the group consisting of silicon dioxide, metal silicates, and metal oxides. In addition, silicon, silicon dioxide, metal silicates, and metal oxides may be in powder form, in block form, or in other shapes. In addition, as metal silicates, for example, lithium silicates (for example, lithium disilicate Li 2 Si2 O 5 etc.), sodium silicates (e.g. sodium disilicate Na 2 Si 2 O 5 etc.), potassium silicates (e.g., potassium silicate K 2 Si 2 O 5 etc.), magnesium silicate (magnesium silicate MgSiO 3 etc.), calcium silicate (calcium silicate CaSiO 3 In addition, the metal silicate may also be a mixture of metal oxide and silicon oxide. For example, lithium disilicate Li 2 Si 2 O 5 Can be Li 2 O and 2SiO 2 A mixture of sodium disilicate Na 2 Si 2 O 5 Can be Na 2 O and 2SiO 2 A mixture of potassium silicate K 2 Si 2 O 5 Can be K 2 O and 2SiO 2 A mixture of magnesium silicate MgSiO 3 It can be MgO and SiO 2 A mixture of calcium silicate CaSiO 3 It can be CaO and SiO 2 In addition, as metal oxides, for example, lithium oxide (Li 2 O, etc.), sodium oxide (Na 2 O), potassium oxide (K 2 O), magnesium oxide (MgO, etc.), calcium oxide (CaO, etc.).

[0054] In addition, the metal element-containing silicon oxide or metal element-free silicon oxide of the embodiment of the present invention can be produced according to the production method shown below. In addition, when the metal element-containing silicon oxide or metal element-free silicon oxide is produced according to the following production method, any one of the pretreatments or preliminary preparations shown in the following (1) to (4) is performed.

[0055] (1) Silicon is treated with water before the raw materials are added, so that the aluminum and iron elements contained in the silicon are changed into a form that is difficult to be vaporized in the reduced pressure heating process.

[0056] (2) While adding water to the raw material and granulating the raw material, the aluminum element and the iron element in the raw material are changed into a form that is difficult to be vaporized in the reduced pressure heating step.

[0057] (3) The mixing ratio of each compound is determined so that the aluminum concentration is less than 50 ppm by mass, the iron concentration is less than 1000 ppm by mass, and the copper concentration is less than 200 ppm by mass before the raw materials are added.

[0058] (4) Determine the mixing ratio of (A) silicon and (B) at least one compound selected from the group consisting of (b1) silicon dioxide, (b2) metal silicate and (b3) metal oxide before the raw materials are added in such a way that the element ratio O / Si during the reaction is within the range of greater than 1 and less than 1.5.

[0059] In addition, in the above-mentioned production method, from the viewpoint of reducing production costs, it is preferable to use Figure 1 Therefore, after first describing the vapor deposition apparatus 100, the above-mentioned manufacturing method will be described.

[0060] like Figure 1 As shown, the evaporation device 100 is mainly composed of a crucible 110, a heater 120, an evaporation roller 130, a scraper 141, a particle guide 143, a chamber 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.

[0061] like Figure 1 As shown, the crucible 110 is a heat-resistant container with an opening in the center of the top wall, and is disposed in the chamber 150. In addition, a through hole (not shown) is formed at a portion of the peripheral portion of the top wall of the crucible 110, and a raw material introduction pipe 170 is inserted into the through hole. That is, the raw material in the raw material supply hopper 160 is supplied to the crucible 110 through the raw material introduction pipe 170. In addition, a gas guide Gg is provided on the upper side of the top wall of the crucible 110. The gas guide Gg is a component that guides the raw material gas generated in the crucible 110 to the vapor deposition drum 130, as shown in FIG. Figure 1 As shown, it is arranged on the upper surface of the top wall in a manner surrounding the central portion of the top wall.

[0062] The heater 120 is used to heat the crucible 110 at a high temperature, and is disposed to surround the outer circumference of the crucible 110 .

[0063] The evaporation roller 130 is, for example, a cylindrical horizontal roller. Figure 1As shown, it is arranged above the opening OP of the top wall of the crucible 110, and its lower part is surrounded by the gas guide Gg. And the evaporation drum 130 is driven to rotate in one direction by a driving mechanism not shown in the figure. In addition, a temperature regulator (not shown) for maintaining the outer peripheral surface at a certain temperature is provided on the evaporation drum 130. The temperature regulator uses a cooling medium supplied from the outside to cool the outer peripheral surface temperature of the evaporation drum 130 to a temperature suitable for evaporation of the evaporation source gas. In addition, the outer peripheral surface temperature of the evaporation drum 130 may affect the crystallinity of the precipitate deposited on the precipitate remaining on the evaporation drum. If the temperature is too low, the organizational structure of the precipitate may become too sparse, and conversely, if it is too high, crystal growth caused by the disproportionation reaction may proceed. In addition, the 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.

[0064] The scraper 141 is a member that scrapes off the thin film formed on the evaporation roller 130. Figure 1 As shown, it is arranged near the vapor deposition drum 130. The flakes (active material particles) scraped off by the scraper 141 fall into the particle guide 143. In addition, the material of the scraper 141 affects the impurity contamination of the active material particles. From the viewpoint of suppressing this influence, the material of the scraper 141 is preferably stainless steel or ceramic, and 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 it is possible to prevent impurity contamination that may be caused by direct contact between the vapor deposition drum 130 and the scraper 141 from being mixed into the recovered active material particles.

[0065] The particle guide 143 is, for example, a vibrating conveying member, such as Figure 1 As shown, it is arranged to be inclined downward from the vicinity of the vapor deposition drum toward the recovery part 152 of the chamber 150 , receives the film sheet scraped off by the scraper 141 arranged above it, and conveys it to the recovery part 152 of the chamber 150 .

[0066] like Figure 1 As shown, the chamber 150 is mainly formed by a chamber body 151, a recovery part 152 and an exhaust pipe 153. Figure 1 As shown, the chamber body 151 is a box-shaped portion having a precipitation chamber RM inside, and accommodates the crucible 110, the heater 120, the vapor deposition drum 130, the scraper 141, and the particle guide 143. Figure 1 As shown, the recovery part 152 is a part protruding outward from the side wall of the chamber body 151, and has a space communicating with the precipitation chamber RM of the chamber body 151. In addition, as described above, the front end of the particle guide 143 is located in the recovery part 152.

[0067] The raw material supply hopper 160 is a raw material supply source, such as Figure 1 As shown, the outlet is connected to the raw material introduction pipe 170. That is, the raw material put into the raw material supply hopper 160 is supplied to the crucible 110 through the raw material introduction pipe 170 at an appropriate time. In addition, the raw material supplied to the crucible 110 becomes a melt Sr and then vaporizes to become a raw material gas.

[0068] The raw material introduction pipe 170 is a circular hole-shaped nozzle for supplying the solid raw material introduced into the raw material supply hopper 160 to the crucible 110 , and is disposed at the center of the top plate of the crucible 110 with its opening facing upward.

[0069] The recovery container 180 is a container for recovering the membrane sheet that has passed through the first valve VL1 and the second valve VL2 .

[0070] The first valve VL1 and the second valve VL2 are used to adjust the amount of film sheets recovered to the recovery container 180 by opening and closing, and a recovery pipe 190 is provided to connect the recovery part 152 of the chamber 150 and the recovery container 180 .

[0071] The raw material (mixed powder or granulated material) is fed into the crucible 110 from the raw material supply hopper 160 via the raw material introduction pipe 170, or the raw material is directly fed into the crucible 110. In addition, as described above, the raw material of silicon oxide that does not contain metallic elements generates SiO gas as a raw material gas by being heated to a prescribed temperature. In addition, the prescribed temperature referred to herein is a temperature between the melting point of silicon (1414°C) and the melting point of silicon dioxide (1710°C). On the other hand, as described above, the raw material of silicon oxide that contains metallic elements generates SiO gas as a raw material gas by being heated to a prescribed temperature. In addition, the prescribed temperature referred to herein is a temperature between the melting point of silicon (1414°C) and the melting point of lithium-containing silicon oxide (Li 2 Si 2 O 5 Melting point: 1033℃, Na 2 Si 2 O 5 Melting point: 874℃, K 2 Si 2 O 5 Melting point: 1045℃, MgSiO 3 Melting point: 1558℃, CaSiO 3 Melting point: 1544℃).

[0072] After the raw material is put into the crucible 110, the crucible 110 is heated by the heater 120 while the pressure in the precipitation chamber RM is reduced. In addition, if the pressure in the precipitation chamber RM is too high, it is difficult for the reaction of generating SiO gas from the raw material to occur. Therefore, the pressure in the precipitation chamber RM is preferably below 1000Pa, more preferably below 750Pa, and particularly preferably below 20Pa. In addition, the temperature in the precipitation chamber RM affects the reaction rate of SiO. If the temperature is too low, the reaction rate slows down. If the temperature is too high, there is a concern that side reactions caused by the melting of the raw material will proceed, the energy efficiency will be reduced, etc. In addition, this temperature also worries about damage to the crucible 110. From this point of view, the temperature in the precipitation chamber RM is preferably in the range of 1000°C to 1600°C, more preferably in the range of 1100°C to 1500°C, and particularly preferably in the range of 1100°C to 1400°C.

[0073] As described above, by reducing the pressure and heating the raw material, a raw material gas is generated from the raw material in the crucible 110, and the raw material gas is supplied to the evaporation drum 130 through the gas guide Gg. Moreover, at this time, the evaporation drum 130 is driven to rotate by the driving source. In addition, the temperature of the outer peripheral surface of the evaporation drum 130 is set to be lower than the temperature in the precipitation chamber RM. More specifically, the temperature is set to be lower than the condensation temperature of the raw material gas. With this setting, the raw material gas generated from the crucible 110 is evaporated and deposited on the outer peripheral surface of the rotating evaporation drum 130. Then, here, the scraper 141 is kept in a standby state above, and the evaporation drum 130 is rotated multiple times to form a laminated film on the evaporation drum 130. After that, after the rotation speed of the evaporation drum 130 reaches a specified number, the scraper 141 is moved downward, and the laminated film is scraped from the evaporation drum 130 by the scraper 141. In addition, the scraped fragments of the laminated film fall along the outer peripheral surface of the evaporation drum 130 to the particle body guide 143. Then, finally, the fragments of the laminated film are pulverized to obtain the target metal element-containing silicon oxide or metal element-free silicon oxide.

[0074] <Features of the method for producing silicon oxide according to the embodiment of the present invention>

[0075] In the method for producing silicon oxide according to the embodiment of the present invention, any one of the pretreatments or preliminary preparations (1) to (4) above is performed. Therefore, in the method for producing silicon oxide, metal-containing silicon oxide or metal-free silicon oxide having low aluminum element concentration, iron element concentration, and copper element concentration can be obtained. Therefore, when the metal-containing silicon oxide or metal-free silicon oxide is used as a negative electrode active material, micronization can be suppressed during the charge and discharge process, thereby suppressing the reduction in the cycle characteristics of the battery.

[0076] In addition, by performing the pretreatment (1) or (2) above, low-grade silicon with high aluminum and iron concentrations can be utilized. Therefore, when performing the pretreatment (1) or (2) above, the raw material cost can be reduced.

[0077] Hereinafter, although an Example and a comparative example are shown in order to demonstrate this invention in detail, this invention is not limited to these Examples.

[0078] [Example 1]

[0079] 1. Manufacturing of silicon oxide powder

[0080] The target silicon oxide powder is produced by sequentially performing the following steps.

[0081] (1) Raw material powder preparation process

[0082] Prepare low-grade silicon (Si) powder (Al mass concentration 2000ppm, Fe mass concentration 2500ppm, Cu mass concentration 500ppm, median particle size 2.5μm) and lithium disilicate (Li 2 Si 2 O 5 ) powder (Al mass concentration 50 ppm, Fe mass concentration 15 ppm, Cu mass concentration 3 ppm, median particle size 5 μm) (see Table 1).

[0083] (2) Mixing process

[0084] The low-grade silicon (Si) powder and lithium disilicate powder prepared in the raw material powder preparation step were mixed at a mass ratio of 88.2:150 to prepare a mixed powder.

[0085] (3) Wet granulation process

[0086] The mixed powder obtained in the above mixing step was granulated with water. In addition, the Al mass concentration in the mixed powder after granulation was 772ppm, the Fe mass concentration was 936ppm, and the Cu mass concentration was 187ppm (see Table 1). The Al mass concentration, the Fe mass concentration, and the Cu mass concentration were measured by ICP emission spectrometry. In addition, the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97.

[0087] (4) Silicon oxide powder manufacturing process

[0088] use Figure 1The evaporation device 100 shown in the figure manufactures lithium-containing silicon oxide according to the manufacturing method of silicon oxide powder. In addition, the raw material heating temperature at this time is 1300°C. The raw material heating temperature is above the melting point of lithium disilicate (1033°C) and below the melting point of silicon (1414°C). In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y , where y is 1.03 and x / y is 0.35. In addition, the Al mass concentration in the lithium-containing silicon oxide powder is 150 ppm, the Fe mass concentration is 45 ppm, and the Cu mass concentration is 1 ppm (see Table 1). In addition, the Al mass concentration, the Fe mass concentration, and the Cu mass concentration are measured in the same manner as above.

[0089] (5) Heat treatment process

[0090] The bulk lithium-containing silicon oxide obtained in the silicon oxide powder production step was heat treated at 600° C. in an argon atmosphere.

[0091] (6) Crushing process

[0092] The heat-treated bulk lithium-containing silicon oxide was crushed in the air using a bead mill to a median particle size of about 5 μm to obtain the target lithium-containing silicon oxide powder. In addition, the median particle size was measured using a laser diffraction particle size distribution measuring device (Mastersizer 3000 manufactured by Malvern). In addition, the measurement conditions are as follows.

[0093] ﹒ Dispersion medium: Isopropyl alcohol (2-propanol)

[0094] ﹒ Refractive index of particles: 3.500

[0095] ﹒ Particle absorption rate: 1.000

[0096] ﹒ Refractive index of dispersion medium: 1.390

[0097] 2. Determination of BET specific surface area of ​​silicon oxide powder

[0098] The BET specific surface area of ​​the lithium-containing silicon oxide powder was measured using a single-point flow method (p / p0=0.3) using Mascorb HM-1201 manufactured by Mountech Co., Ltd. In addition, in this measurement, nitrogen was used as the adsorbent, helium was used as the carrier gas, and liquid nitrogen was used as the cooling medium. In the actual measurement, a mixed gas of 30 vol% nitrogen and 70 vol% helium was used, and the flow rate of the mixed gas was set to 25 mL / min. Then, the nitrogen was adsorbed on the lithium-containing silicon oxide powder by cooling the lithium-containing silicon oxide powder with liquid nitrogen, and then the nitrogen was desorbed by maintaining the lithium-containing silicon oxide powder at 300°C for 30 minutes. As a result of the measurement, the BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.1 m 2 / g.

[0099] 3. Cycling characteristics of batteries equipped with negative electrodes composed of lithium-containing silicon oxide powder

[0100] (1) Making batteries

[0101] (1-1) Preparation of negative electrode

[0102] The lithium-containing silicon oxide powder obtained as described above is mixed with natural graphite (median particle size 12 μm) in a mass ratio of 10:90 as a negative electrode active material. Next, the negative electrode active material, sodium polyacrylate (binder) and DENKABLACK (registered trademark) (acetylene black as a conductive aid) are put into a degassing Rentaro (registered trademark) ARE-310 manufactured by THINKY Co., Ltd. in a mass ratio of 92:3:5, and then they are kneaded to prepare a slurry. Next, the slurry is applied on a copper foil with a thickness of 10 μm, and after the coating is pre-dried at 80°C in the atmosphere, the slurry-coated copper foil is punched into a disc with a diameter of 11 mm. Then, the disc-shaped slurry-coated copper foil is dried at 150°C in a vacuum for 12 hours to obtain the target negative electrode.

[0103] (1-2) Making batteries

[0104] A button cell was prepared using the negative electrode, a Li foil as a counter electrode, a separator, and an electrolyte. A polyethylene porous film with a thickness of 20 μm was used as a separator, and the following solution was used as an electrolyte: a mixed solution obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1, and lithium hexafluorophosphate (LiPF 6 ) is dissolved in a concentration of 1 mol / L.

[0105] (2) Cycle characteristics

[0106] The button cell was subjected to a charge and discharge test using a secondary battery charge and discharge test apparatus manufactured by Electrofield Co., Ltd., and the capacity retention rate after 50 cycles was determined (the capacity retention rate after 50 cycles refers to the value obtained by dividing the 50th discharge capacity by the initial discharge capacity and multiplying by 100). The capacity retention rate was 75.7% (see Table 1). In addition, during the charge and discharge test, the conditions for the initial charge were set to "CC-CV 0.2C"·"10mV-0.01C", the conditions for the initial discharge were set to "CC 0.2C"·"1.5V cut-off", the conditions for the second and subsequent charges were set to "CC-CV 1C"·"10mV-0.01C", and the conditions for the second and subsequent discharges were set to "CC 1C"·"1.5V cut-off". Here, the current amount of 1 C was calculated using a theoretical capacity calculated by assuming that the discharge capacity of natural graphite was 360 mAh / g and the discharge capacity of silicon oxide powder was 1900 mAh / g.

[0107] [Example 2]

[0108] The target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, except that the low-grade silicon (Si) powder was replaced with medium-grade silicon (Si) powder (Al mass concentration of 1000ppm, Fe mass concentration of 600ppm, Cu mass concentration of 100ppm, and median particle size of 2.5μm). The BET specific surface area of ​​the lithium-containing silicon oxide powder was measured according to the method described in Example 1. At the same time, a negative electrode was manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, the Al mass concentration in the mixed powder after granulation was 402ppm, the Fe mass concentration was 232ppm, and the Cu mass concentration was 39ppm. The molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y , where y is 1.03 and x / y is 0.34. In addition, the Al mass concentration in the lithium-containing silicon oxide powder is 48 ppm, the Fe mass concentration is 25 ppm, and the Cu mass concentration is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the lithium-containing silicon oxide powder is 2.3 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 78.3% (see Table 1).

[0109] [Example 3]

[0110] The target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, except that the low-grade silicon (Si) powder was replaced with high-grade silicon (Si) powder (Al mass concentration of 480 ppm, Fe mass concentration of 300 ppm, Cu mass concentration of 50 ppm, and median particle size of 2.5 μm). The BET specific surface area of ​​the lithium-containing silicon oxide powder was measured according to the method described in Example 1. At the same time, a negative electrode was manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, the Al mass concentration in the mixed powder after granulation was 209 ppm, the Fe mass concentration was 121 ppm, and the Cu mass concentration was 2 ppm. The molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y , where y is 1.03 and x / y is 0.38. In addition, the mass concentration of Al in the lithium-containing silicon oxide powder is 24 ppm, the mass concentration of Fe is 20 ppm, and the mass concentration of Cu is 2 ppm (see Table 1). In addition, the BET specific surface area of ​​the lithium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.2% (see Table 1).

[0111] [Example 4]

[0112] The low-grade silicon (Si) powder is replaced with high-purity silicon (Si) powder (Al mass concentration of 10ppm, Fe mass concentration of 40ppm, Cu mass concentration of 5ppm, median particle size of 2.5μm), and the silicon oxide powder manufacturing process is performed from the mixing process without going through the wet granulation process (that is, the mixed powder obtained in the mixing process is directly put into the crucible). In addition, the target lithium-containing silicon oxide powder is obtained according to the manufacturing method described in Example 1, and the BET specific surface area of ​​the lithium-containing silicon oxide powder is measured according to the method described in Example 1. At the same time, a negative electrode is manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is measured. In addition, the Al mass concentration in the mixed powder is 35ppm, the Fe mass concentration is 24ppm, and the Cu mass concentration is 4ppm. The molar ratio of the oxygen element to the silicon element in the mixed powder (O / Si) is 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y , where y is 1.02 and x / y is 0.36. In addition, the mass concentration of Al in the lithium-containing silicon oxide powder is 5 ppm, the mass concentration of Fe is 15 ppm, and the mass concentration of Cu is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the lithium-containing silicon oxide powder is 2.3 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 83.4% (see Table 1).

[0113] (Comparative Example 1)

[0114] The low-grade silicon (Si) powder is replaced with a medium-grade silicon (Si) powder (Al mass concentration of 1000ppm, Fe mass concentration of 600ppm, Cu mass concentration of 100ppm, median particle size of 2.5μm), and the silicon oxide powder manufacturing process is performed from the mixing process without the wet granulation process (that is, the mixed powder obtained in the mixing process is directly put into the crucible). In addition, the target lithium-containing silicon oxide powder is obtained according to the manufacturing method described in Example 1, and the BET specific surface area of ​​the lithium-containing silicon oxide powder is measured according to the method described in Example 1. At the same time, a negative electrode is manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is measured. In addition, the Al mass concentration in the mixed powder is 402ppm, the Fe mass concentration is 232ppm, the Cu mass concentration is 39ppm, and the molar ratio of the oxygen element to the silicon element in the mixed powder (O / Si) is 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y , where y is 1.03 and x / y is 0.36. In addition, the Al mass concentration in the lithium-containing silicon oxide powder is 337 ppm, the Fe mass concentration is 30 ppm, and the Cu mass concentration is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the obtained lithium-containing silicon oxide powder is 2.1 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 70.1% (see Table 1).

[0115] (Comparative Example 2)

[0116] The low-grade silicon (Si) powder is replaced with a high-grade silicon (Si) powder (Al mass concentration of 480ppm, Fe mass concentration of 300ppm, Cu mass concentration of 50ppm, median particle size of 2.5μm), and the silicon oxide powder manufacturing process is performed from the mixing process without going through the wet granulation process (that is, the mixed powder obtained in the mixing process is directly put into the crucible). In addition, the target lithium-containing silicon oxide powder is obtained according to the manufacturing method described in Example 1, and the BET specific surface area of ​​the lithium-containing silicon oxide powder is measured according to the method described in Example 1. At the same time, a negative electrode is manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is measured. In addition, the Al mass concentration in the mixed powder is 209ppm, the Fe mass concentration is 121ppm, the Cu mass concentration is 20ppm, and the molar ratio of the oxygen element to the silicon element in the mixed powder (O / Si) is 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y, where y is 1.02 and x / y is 0.35. In addition, the Al mass concentration in the lithium-containing silicon oxide powder is 205 ppm, the Fe mass concentration is 25 ppm, and the Cu mass concentration is 2 ppm (see Table 1). In addition, the BET specific surface area of ​​the obtained lithium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 71.2% (see Table 1).

[0117] (Comparative Example 3)

[0118] The low-grade silicon (Si) powder was replaced with high-purity silicon (Si) powder (Al mass concentration of 10 ppm, Fe mass concentration of 40 ppm, Cu mass concentration of 5 ppm, median particle size of 2.5 μm), and copper (Cu) powder was added in an amount of 3% by mass relative to the total mass of the mixed powder. The silicon oxide powder manufacturing process was performed without a wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly put into the crucible). Otherwise, the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, and the BET specific surface area of ​​the lithium-containing silicon oxide powder was measured according to the method described in Example 1. At the same time, a negative electrode was manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, as the copper powder, a copper powder that passed through a sieve with a mesh of 45 μm was used. In addition, the mass concentration of Al in the mixed powder is 34ppm, the mass concentration of Fe is 24ppm, the mass concentration of Cu is 30004ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder is 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y , where y is 1.04 and x / y is 0.34. In addition, the mass concentration of Al, the mass concentration of Fe, and the mass concentration of Cu in the lithium-containing silicon oxide powder are 5 ppm, 14 ppm, and 3100 ppm (see Table 1). In addition, the BET specific surface area of ​​the obtained lithium-containing silicon oxide powder is 2.4 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 82.0% (see Table 1).

[0119] (Comparative Example 4)

[0120] The low-grade silicon (Si) powder was replaced with high-purity silicon (Si) powder (Al mass concentration of 10 ppm, Fe mass concentration of 40 ppm, Cu mass concentration of 5 ppm, median particle size of 2.5 μm), and copper (Cu) powder was added in a manner of 0.08 mass% relative to the total mass of the mixed powder. The silicon oxide powder manufacturing process was performed without a wet granulation process from the mixing process (that is, the mixed powder obtained in the mixing process was directly put into the crucible). Otherwise, the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, and the BET specific surface area of ​​the lithium-containing silicon oxide powder was measured according to the method described in Example 1. At the same time, a negative electrode was manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, as the powder, a powder that passed through a sieve with a mesh of 45 μm was used. In addition, the mass concentration of Al in the mixed powder was 35 ppm, the mass concentration of Fe was 24 ppm, the mass concentration of Cu was 804 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained was Li x SiO y , where y is 1.04 and x / y is 0.39. In addition, the mass concentration of Al, the mass concentration of Fe, and the mass concentration of Cu in the lithium-containing silicon oxide powder are 5 ppm, 15 ppm, and 110 ppm (see Table 1). In addition, the BET specific surface area of ​​the obtained lithium-containing silicon oxide powder is 2.4 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 82.5% (see Table 1).

[0121] (Comparative Example 5)

[0122] The low-grade silicon (Si) powder was replaced with high-purity silicon (Si) powder (Al mass concentration 10 ppm, Fe mass concentration 40 ppm, Cu mass concentration 5 ppm, median particle size 2.5 μm), and iron (Fe) powder was added to the high-purity silicon powder in a manner of 5 mass% relative to the total amount of the powder, and the silicon oxide powder manufacturing process was performed without a wet granulation process from the mixing process (that is, the mixed powder obtained in the mixing process was directly put into the crucible). In addition, the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, and the BET specific surface area of ​​the lithium-containing silicon oxide powder was measured according to the method described in Example 1. At the same time, a negative electrode was manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, as the iron powder, an iron powder that passed through a sieve with a mesh of 45 μm was used. In addition, the mass concentration of Al in the mixed powder is 35ppm, the mass concentration of Fe is 18555ppm, the mass concentration of Cu is 4ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder is 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li xSiO y , where y is 1.03 and x / y is 0.35. In addition, the mass concentration of Al in the lithium-containing silicon oxide powder is 5 ppm, the mass concentration of Fe is 250 ppm, and the mass concentration of Cu is 2 ppm (see Table 1). In addition, the BET specific surface area of ​​the obtained lithium-containing silicon oxide powder is 2.3 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.2% (see Table 1).

[0123] (Comparative Example 6)

[0124] The low-grade silicon (Si) powder was replaced with high-purity silicon (Si) powder (Al mass concentration 10 ppm, Fe mass concentration 40 ppm, Cu mass concentration 5 ppm, median particle size 2.5 μm), and iron (Fe) powder was added to the high-purity silicon powder in a manner of 1 mass % relative to the total amount of the powder, and the silicon oxide powder manufacturing process was performed without a wet granulation process from the mixing process (that is, the mixed powder obtained in the mixing process was directly put into the crucible). In addition, the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, and the BET specific surface area of ​​the lithium-containing silicon oxide powder was measured according to the method described in Example 1. At the same time, a negative electrode was manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, as the iron powder, an iron powder that passed through a sieve with a mesh of 45 μm was used. In addition, the mass concentration of Al in the mixed powder was 35 ppm, the mass concentration of Fe was 3730 ppm, the mass concentration of Cu was 4 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained was Li x SiO y , where y is 1.02 and x / y is 0.32. In addition, the Al mass concentration in the lithium-containing silicon oxide powder is 5 ppm, the Fe mass concentration is 120 ppm, and the Cu mass concentration is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the obtained lithium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.0% (see Table 1).

[0125] [Example 5]

[0126] The low-grade silicon (Si) powder was replaced with medium-grade silicon (Si) powder (Al mass concentration 1000ppm, Fe mass concentration 600ppm, Cu mass concentration 100ppm, median particle size 2.5μm), and lithium disilicate (Li 2 Si 2 O 5 ) powder is replaced by magnesium silicate (MgSiO 3) powder (Al mass concentration of 50ppm, Fe mass concentration of 15ppm, Cu mass concentration of 3ppm, median particle size of 5μm), medium-grade silicon (Si) powder and magnesium silicate are mixed in a mass ratio of 58.8:100, and the target magnesium-containing silicon oxide powder is obtained according to the manufacturing method described in Example 1, and the BET specific surface area of ​​the magnesium-containing silicon oxide powder is measured according to the method described in Example 1. At the same time, a negative electrode is manufactured from the magnesium-containing silicon oxide powder and the capacity retention rate of the negative electrode is measured. In addition, the Al mass concentration in the mixed powder after granulation is 495ppm, the Fe mass concentration is 231ppm, and the Cu mass concentration is 39ppm. The molar ratio of oxygen element to silicon element (O / Si) in the mixed powder is 0.97. In addition, the composition of the magnesium-containing silicon oxide powder finally obtained is Mg x SiO y , where y is 1.02 and x / y is 0.98. In addition, the mass concentration of Al in the magnesium-containing silicon oxide powder is 38 ppm, the mass concentration of Fe is 27 ppm, and the mass concentration of Cu is 2 ppm (see Table 1). In addition, the raw material heating temperature in the silicon oxide powder manufacturing process is 1500°C. The raw material heating temperature is above the melting point of silicon (1414°C) and below the melting point of magnesium silicate (1558°C). In addition, the BET specific surface area of ​​the obtained magnesium-containing silicon oxide powder is 2.3 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 75.3% (see Table 1).

[0127] (Comparative Example 7)

[0128] The target magnesium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 6, except that the silicon oxide powder manufacturing process was performed without the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly put into the crucible), and the BET specific surface area of ​​the magnesium-containing silicon oxide powder was measured according to the method described in Example 1. At the same time, a negative electrode was manufactured from the magnesium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, the mass concentration of Al in the mixed powder was 495ppm, the mass concentration of Fe was 231ppm, and the mass concentration of Cu was 39ppm (see Table 1). In addition, the composition of the magnesium-containing silicon oxide powder finally obtained was Mg: MgO ... x SiO y , where y is 1.03 and x / y is 0.95. In addition, the mass concentration of Al in the magnesium-containing silicon oxide powder is 345 ppm, the mass concentration of Fe is 29 ppm, and the mass concentration of Cu is 2 ppm (see Table 1). In addition, the raw material heating temperature in the silicon oxide powder manufacturing process is 1500°C. The raw material heating temperature is above the melting point of silicon (1414°C) and below the melting point of magnesium silicate (1558°C). In addition, the BET specific surface area of ​​the obtained magnesium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 69.3% (see Table 1).

[0129] [Example 6]

[0130] The low-grade silicon (Si) powder was replaced with high-purity silicon (Si) powder (Al mass concentration 10ppm, Fe mass concentration 40ppm, Cu mass concentration 5ppm, median particle size 2.5μm), and lithium disilicate (Li 2 Si 2 O 5 ) powder is replaced by magnesium silicate (MgSiO 3 ) powder (Al mass concentration of 50ppm, Fe mass concentration of 15ppm, Cu mass concentration of 3ppm, median particle size of 5μm), high-purity silicon (Si) powder and magnesium silicate are mixed in a mass ratio of 47.8:100, and the silicon oxide powder manufacturing process is carried out without going through the wet granulation process from the mixing process (that is, the mixed powder obtained in the mixing process is directly put into the crucible), and the target magnesium-containing silicon oxide powder is obtained according to the manufacturing method described in Example 1, and the BET specific surface area of ​​the magnesium-containing silicon oxide powder is measured according to the method described in Example 1. At the same time, a negative electrode is manufactured from the magnesium-containing silicon oxide powder and the capacity retention rate of the negative electrode is measured. In addition, the Al mass concentration in the mixed powder is 31ppm, the Fe mass concentration is 24ppm, and the Cu mass concentration is 4ppm. The molar ratio of the oxygen element to the silicon element in the mixed powder (O / Si) is 0.97. In addition, the composition of the magnesium-containing silicon oxide powder finally obtained is Mg x SiO y , where y is 1.01 and x / y is 0.94. In addition, the mass concentration of Al in the magnesium-containing silicon oxide powder is 5 ppm, the mass concentration of Fe is 15 ppm, and the mass concentration of Cu is 1 ppm (see Table 1). In addition, the raw material heating temperature in the silicon oxide powder manufacturing process is 1500°C. The raw material heating temperature is above the melting point of silicon (1414°C) and below the melting point of magnesium silicate (1558°C). In addition, the BET specific surface area of ​​the obtained magnesium-containing silicon oxide powder is 2.5 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 77.2% (see Table 1).

[0131] (Comparative Example 8)

[0132] The target magnesium-containing silica powder was obtained according to the manufacturing method described in Example 6, except that copper (Cu) powder was added in an amount of 3% by mass relative to the total mass of the mixed powder. The BET specific surface area of ​​the magnesium-containing silica powder was measured according to the method described in Example 1. A negative electrode was manufactured from the magnesium-containing silica powder and the capacity retention rate of the negative electrode was measured. In addition, as copper powder, copper powder that passed through a sieve with a mesh of 45 μm was used. In addition, the mass concentration of Al in the mixed powder was 30 ppm, the mass concentration of Fe was 24 ppm, the mass concentration of Cu was 30004 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the magnesium-containing silica powder finally obtained is Mg: x SiO y , where y is 1.03 and x / y is 0.97. In addition, the mass concentration of Al, the mass concentration of Fe, and the mass concentration of Cu in the magnesium-containing silicon oxide powder are 5 ppm, 14 ppm, and 3100 ppm (see Table 1). In addition, the BET specific surface area of ​​the obtained lithium-containing silicon oxide powder is 2.4 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 75.1% (see Table 1).

[0133] (Comparative Example 9)

[0134] The target magnesium-containing silica powder was obtained according to the manufacturing method described in Example 6, except that copper (Cu) powder was added in an amount of 0.08 mass % relative to the total mass of the mixed powder. The BET specific surface area of ​​the magnesium-containing silica powder was measured according to the method described in Example 1. A negative electrode was manufactured from the magnesium-containing silica powder and the capacity retention rate of the negative electrode was measured. In addition, as copper powder, copper powder that passed through a sieve with a mesh of 45 μm was used. In addition, the mass concentration of Al in the mixed powder was 31 ppm, the mass concentration of Fe was 24 ppm, the mass concentration of Cu was 804 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the magnesium-containing silica powder finally obtained is Mg: x SiO y , where y is 1.02 and x / y is 0.98. In addition, the mass concentration of Al, the mass concentration of Fe, and the mass concentration of Cu in the magnesium-containing silicon oxide powder are 5 ppm, 15 ppm, and 120 ppm (see Table 1). In addition, the BET specific surface area of ​​the magnesium-containing silicon oxide powder obtained is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 75.6% (see Table 1).

[0135] (Comparative Example 10)

[0136] The target magnesium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 6, except that iron (Fe) powder was added to the high-purity silicon powder in an amount of 5% by mass relative to the total amount of the powder. The BET specific surface area of ​​the magnesium-containing silicon oxide powder was measured according to the method described in Example 1. At the same time, a negative electrode was manufactured from the magnesium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, as the iron powder, iron powder that passed through a sieve with a mesh of 45 μm was used. In addition, the mass concentration of Al in the mixed powder was 31 ppm, the mass concentration of Fe was 18498 ppm, the mass concentration of Cu was 4 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the magnesium-containing silicon oxide powder finally obtained is Mg: x SiO y , where y is 1.02 and x / y is 0.95. In addition, the mass concentration of Al, the mass concentration of Fe, and the mass concentration of Cu in the magnesium-containing silicon oxide powder are 5 ppm, 290 ppm, and 2 ppm (see Table 1). In addition, the BET specific surface area of ​​the magnesium-containing silicon oxide powder obtained is 2.3 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 74.0% (see Table 1).

[0137] (Comparative Example 11)

[0138] The target magnesium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 6, except that iron (Fe) powder was added to the high-purity silicon powder in an amount of 1 mass % relative to the total amount of the powder. The BET specific surface area of ​​the magnesium-containing silicon oxide powder was measured according to the method described in Example 1. At the same time, a negative electrode was manufactured from the magnesium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, as the iron powder, iron powder that passed through a sieve with a mesh of 45 μm was used. In addition, the mass concentration of Al in the mixed powder was 31 ppm, the mass concentration of Fe was 3719 ppm, the mass concentration of Cu was 4 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the magnesium-containing silicon oxide powder finally obtained is Mg x SiO y , where y is 1.03 and x / y is 0.96. In addition, the mass concentration of Al in the magnesium-containing silicon oxide powder is 4 ppm, the mass concentration of Fe is 130 ppm, and the mass concentration of Cu is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the magnesium-containing silicon oxide powder obtained is 2.4 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 74.6% (see Table 1).

[0139] [Example 7]

[0140] The target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1 except that the low-grade silicon (Si) powder was brought into contact with water before the mixing step (2), and the silicon oxide powder manufacturing step was performed without the wet granulation step from the mixing step (that is, the mixed powder obtained in the mixing step was directly put into the crucible), and the BET specific surface area of ​​the lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, in the above water treatment, 100 g of silicon powder was added to 1 L of purified water at 25° C., and the mixture was stirred at 200 rpm for about 1 hour using a magnetic stirrer to disperse the silicon powder in the purified water, and then most of the water was removed using a filter paper equivalent to Type 5 C specified in JIS P3801 and a suction filter, and the remaining wet silicon powder was put into a rack hot air dryer set at 120° C. to dry it. In addition, the mass concentration of Al in the mixed powder was 772 ppm, the mass concentration of Fe was 936 ppm, the mass concentration of Cu was 187 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained was Li x SiO y , where y is 1.01 and x / y is 0.34. In addition, the Al mass concentration in the lithium-containing silicon oxide powder is 150 ppm, the Fe mass concentration is 52 ppm, and the Cu mass concentration is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the lithium-containing silicon oxide powder is 2.3 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 75.8% (see Table 1).

[0141] [Example 8]

[0142] The target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 2 except that the medium-grade silicon (Si) powder was brought into contact with water before the mixing step (2), and the silicon oxide powder manufacturing step was performed without the wet granulation step from the mixing step (i.e., the mixed powder obtained in the mixing step was directly put into the crucible). The BET specific surface area of ​​the lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, in the above water treatment, 100 g of silicon powder was added to 1 L of purified water at 25° C., and the mixture was stirred at 200 rpm for about 1 hour using a magnetic stirrer to disperse the silicon powder in the purified water. Most of the water was removed using a filter paper equivalent to Type 5 C specified in JIS P3801 and a suction filter, and the remaining wet silicon powder was then put into a rack hot air dryer set at 120° C. to dry it. In addition, the mass concentration of Al in the mixed powder was 402 ppm, the mass concentration of Fe was 232 ppm, the mass concentration of Cu was 39 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained was Li x SiO y , where y is 1.03 and x / y is 0.36. In addition, the mass concentration of Al in the lithium-containing silicon oxide powder is 62 ppm, the mass concentration of Fe is 39 ppm, and the mass concentration of Cu is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the lithium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 77.8% (see Table 1).

[0143] [Example 9]

[0144] The target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 3 except that the high-quality silicon (Si) powder was brought into contact with water before the mixing step (2), and the silicon oxide powder manufacturing step was performed without the wet granulation step from the mixing step (i.e., the mixed powder obtained in the mixing step was directly put into the crucible), and the BET specific surface area of ​​the lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. In addition, in the above water treatment, 100 g of silicon powder was added to 1 L of purified water at 25° C., and the mixture was stirred at 200 rpm for about 1 hour using a magnetic stirrer to disperse the silicon powder in the purified water, and then most of the water was removed using a filter paper equivalent to Type 5 C specified in JIS P3801 and a suction filter, and the remaining wet silicon powder was put into a rack hot air dryer set at 120° C. to dry it. In addition, the mass concentration of Al in the mixed powder was 209 ppm, the mass concentration of Fe was 121 ppm, the mass concentration of Cu was 20 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. In addition, the composition of the lithium-containing silicon oxide powder finally obtained was Li x SiO y , where y is 1.02 and x / y is 0.35. In addition, the Al mass concentration in the lithium-containing silicon oxide powder is 32 ppm, the Fe mass concentration is 25 ppm, and the Cu mass concentration is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the lithium-containing silicon oxide powder is 2.3 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 79.8% (see Table 1).

[0145] [Example 10]

[0146] In the mixing process, low-grade silicon (Si) powder and lithium disilicate powder are mixed in a mass ratio of 79.8:150 to prepare a mixed powder, and the silicon oxide powder manufacturing process is carried out from the mixing process without going through the wet granulation process (that is, the mixed powder obtained in the mixing process is directly put into the crucible). In addition, the target lithium-containing silicon oxide powder is obtained according to the manufacturing method described in Example 1, and the BET specific surface area of ​​the lithium-containing silicon oxide powder is measured according to the method described in Example 1. At the same time, a negative electrode is manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is measured. In addition, the mass concentration of Al in the mixed powder is 772ppm, the mass concentration of Fe is 879ppm, and the mass concentration of Cu is 176ppm. The molar ratio of oxygen element to silicon element in the mixed powder (O / Si) is 1.03. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y, where y is 1.02 and x / y is 0.36. In addition, the Al mass concentration in the lithium-containing silicon oxide powder is 148 ppm, the Fe mass concentration is 25 ppm, and the Cu mass concentration is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the lithium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 75.8% (see Table 1).

[0147] [Example 11]

[0148] In the mixing process, medium-grade silicon (Si) powder and lithium disilicate powder are mixed in a mass ratio of 79.8:150 to prepare a mixed powder, and the silicon oxide powder manufacturing process is carried out from the mixing process without going through the wet granulation process (that is, the mixed powder obtained in the mixing process is directly put into the crucible). In addition, the target lithium-containing silicon oxide powder is obtained according to the manufacturing method described in Example 2, and the BET specific surface area of ​​the lithium-containing silicon oxide powder is measured according to the method described in Example 1. At the same time, a negative electrode is manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is measured. In addition, the mass concentration of Al in the mixed powder is 402ppm, the mass concentration of Fe is 218ppm, and the mass concentration of Cu is 37ppm. The molar ratio of oxygen element to silicon element in the mixed powder (O / Si) is 1.03. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y , where y is 1.03 and x / y is 0.34. In addition, the mass concentration of Al in the lithium-containing silicon oxide powder is 50 ppm, the mass concentration of Fe is 24 ppm, and the mass concentration of Cu is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the lithium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 78.1% (see Table 1).

[0149] [Example 12]

[0150] In the mixing process, high-grade silicon (Si) powder and lithium disilicate powder are mixed in a mass ratio of 79.8:150 to prepare a mixed powder, and the silicon oxide powder manufacturing process is carried out from the mixing process without going through the wet granulation process (that is, the mixed powder obtained in the mixing process is directly put into the crucible). In addition, the target lithium-containing silicon oxide powder is obtained according to the manufacturing method described in Example 3, and the BET specific surface area of ​​the lithium-containing silicon oxide powder is measured according to the method described in Example 1. At the same time, a negative electrode is manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is measured. In addition, the mass concentration of Al in the mixed powder is 209 ppm, the mass concentration of Fe is 114 ppm, and the mass concentration of Cu is 19 ppm. The molar ratio of oxygen element to silicon element in the mixed powder (O / Si) is 1.03. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y , where y is 1.03 and x / y is 0.36. In addition, the mass concentration of Al in the lithium-containing silicon oxide powder is 27 ppm, the mass concentration of Fe is 20 ppm, and the mass concentration of Cu is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the lithium-containing silicon oxide powder is 2.3 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.0% (see Table 1).

[0151] [Example 13]

[0152] In the mixing process, medium-grade silicon (Si) powder and lithium disilicate powder are mixed in a mass ratio of 56:150 to prepare a mixed powder, and the silicon oxide powder manufacturing process is carried out from the mixing process without going through the wet granulation process (that is, the mixed powder obtained in the mixing process is directly put into the crucible). In addition, the target lithium-containing silicon oxide powder is obtained according to the manufacturing method described in Example 2, and the BET specific surface area of ​​the lithium-containing silicon oxide powder is measured according to the method described in Example 1. At the same time, a negative electrode is manufactured from the lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is measured. In addition, the mass concentration of Al in the mixed powder is 402ppm, the mass concentration of Fe is 174ppm, and the mass concentration of Cu is 29ppm. The molar ratio of oxygen element to silicon element in the mixed powder (O / Si) is 1.25. In addition, the composition of the lithium-containing silicon oxide powder finally obtained is Li x SiO y , where y is 1.04 and x / y is 0.35. In addition, the Al mass concentration in the lithium-containing silicon oxide powder is 40 pm, the Fe mass concentration is 21 ppm, and the Cu mass concentration is 1 ppm (see Table 1). In addition, the BET specific surface area of ​​the lithium-containing silicon oxide powder is 2.3 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 79.1% (see Table 1).

[0153] (Comparative Example 12)

[0154] In the mixing process, the medium-grade silicon (Si) powder and the lithium disilicate powder were mixed at a mass ratio of 37.2:150 to prepare the mixed powder, and the silicon oxide powder manufacturing process was performed without the wet granulation process from the mixing process (that is, the mixed powder obtained in the mixing process was directly put into the crucible). In addition, the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 2, but the reaction rate was significantly reduced and the target lithium-containing silicon oxide powder was not obtained. In addition, the mass concentration of Al in the mixed powder was 402ppm, the mass concentration of Fe was 132ppm, the mass concentration of Cu was 22ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 1.5.

[0155] [Table 1]

[0156]

[0157] (Inspection)

[0158] As shown in Table 1, the negative electrode formed by the silicon oxide powder produced by wet granulation has a higher capacity retention rate than the negative electrode formed by the silicon oxide powder produced without wet granulation. In addition, it is clear that the lower the aluminum element concentration, iron element concentration, and copper element concentration in the obtained silicon oxide powder, the higher the capacity retention rate (refer to Examples 1 to 3).

[0159] In addition, it can be seen from Table 1 that the negative electrode formed by the silicon oxide powder made by making the aluminum mass concentration in the mixed raw material less than 50ppm, the iron concentration less than 1000ppm, and the copper concentration less than 200ppm has a higher capacity retention rate than the negative electrode formed by the silicon oxide powder made by making the aluminum mass concentration of 50ppm or more, the iron concentration of 1000ppm or more, and the copper concentration of 200ppm or more. In addition, it is clear that the lower the aluminum concentration, iron concentration, and copper concentration in the obtained silicon oxide powder, the higher the capacity retention rate (refer to Example 4).

[0160] In addition, it can be seen from Table 1 that the negative electrode formed by the silicon oxide powder produced by water treatment of the silicon powder has a higher capacity maintenance rate than the negative electrode formed by the silicon oxide powder produced without water treatment of the silicon powder. In addition, it is clear that the lower the aluminum element concentration, iron element concentration, and copper element concentration in the obtained silicon oxide powder, the higher the capacity maintenance rate (refer to Examples 7 to 9).

[0161] In addition, it can be seen from Table 1 that the negative electrode formed by the silicon oxide powder produced by making the O / Si ratio in the mixed raw material greater than 1 and less than 1.5 has a higher capacity retention rate than the negative electrode formed by the silicon oxide powder produced by making the O / Si ratio in the mixed raw material less than 1. In addition, it is clear that the lower the aluminum element concentration, iron element concentration, and copper element concentration in the obtained silicon oxide powder, the higher the capacity retention rate (refer to Examples 7 to 12).

[0162] [Example 14]

[0163] The lithium-containing silicon oxide powder obtained in Example 1 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 1.9 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.5% (see Table 2).

[0164] [Example 15]

[0165] The lithium-containing silicon oxide powder obtained in Example 2 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.1 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 82.5% (see Table 2).

[0166] [Example 16]

[0167] The lithium-containing silicon oxide powder obtained in Example 3 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.0 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 87.3% (see Table 2).

[0168] [Example 17]

[0169] The lithium-containing silicon oxide powder obtained in Example 4 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.1 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 88.9% (see Table 2).

[0170] (Comparative Example 13)

[0171] The lithium-containing silicon oxide powder obtained in Comparative Example 1 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 1.9 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 78.9% (see Table 2).

[0172] (Comparative Example 14)

[0173] The lithium-containing silicon oxide powder obtained in Comparative Example 2 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.0 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 79.6% (see Table 2).

[0174] (Comparative Example 15)

[0175] The lithium-containing silicon oxide powder obtained in Comparative Example 3 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 87.1% (see Table 2).

[0176] (Comparative Example 16)

[0177] The lithium-containing silicon oxide powder obtained in Comparative Example 4 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 87.5% (see Table 2).

[0178] (Comparative Example 17)

[0179] The lithium-containing silicon oxide powder obtained in Comparative Example 5 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.1 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 85.4% (see Table 2).

[0180] (Comparative Example 18)

[0181] The lithium-containing silicon oxide powder obtained in Comparative Example 6 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.0 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 86.0% (see Table 2).

[0182] [Example 18]

[0183] The silicon oxide powder obtained in Example 5 is charged into a rotary kiln, and the magnesium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the magnesium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated magnesium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated magnesium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated magnesium-containing silicon oxide powder is 2.1 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.2% (see Table 2).

[0184] (Comparative Example 19)

[0185] The magnesium-containing silicon oxide powder obtained in Comparative Example 7 is charged into a rotary kiln, and the magnesium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the magnesium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated magnesium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated magnesium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated magnesium-containing silicon oxide powder is 2.0 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 78.3% (see Table 2).

[0186] [Example 19]

[0187] The lithium-containing silicon oxide powder obtained in Example 6 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.3 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 83.3% (see Table 2).

[0188] (Comparative Example 20)

[0189] The lithium-containing silicon oxide powder obtained in Comparative Example 8 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.0% (see Table 2).

[0190] (Comparative Example 21)

[0191] The lithium-containing silicon oxide powder obtained in Comparative Example 9 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.0 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.5% (see Table 2).

[0192] (Comparative Example 22)

[0193] The lithium-containing silicon oxide powder obtained in Comparative Example 10 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.1 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.0% (see Table 2).

[0194] (Comparative Example 23)

[0195] The lithium-containing silicon oxide powder obtained in Comparative Example 11 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.2 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.2% (see Table 2).

[0196] [Example 20]

[0197] The lithium-containing silicon oxide powder obtained in Example 7 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.1 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.4% (see Table 2).

[0198] [Example 21]

[0199] The lithium-containing silicon oxide powder obtained in Example 8 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.0 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 82.0% (see Table 2).

[0200] [Example 22]

[0201] The lithium-containing silicon oxide powder obtained in Example 9 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.1 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 85.1% (see Table 2).

[0202] [Example 23]

[0203] The lithium-containing silicon oxide powder obtained in Example 10 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.0 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.6% (see Table 2).

[0204] [Example 24]

[0205] The lithium-containing silicon oxide powder obtained in Example 11 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.0 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 82.3% (see Table 2).

[0206] [Example 25]

[0207] The lithium-containing silicon oxide powder obtained in Example 12 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 2.1 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 86.2% (see Table 2).

[0208] [Example 26]

[0209] The lithium-containing silicon oxide powder obtained in Example 13 is charged into a rotary kiln, and the lithium-containing silicon oxide powder is subjected to carbon coating by thermal CVD in which argon and propane gases are circulated at 700°C. In addition, the mass ratio of carbon to the mass of the lithium-containing silicon oxide powder is 2% by mass. This mass ratio is calculated based on the result of the carbon amount, and the result of the carbon amount is obtained by quantitatively evaluating the carbon dioxide gas by analyzing it using an oxygen flow combustion-infrared absorption method using a carbon concentration analyzer (CS400 manufactured by Leco). Then, the BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder is determined according to the method described in Example 1, and a negative electrode is manufactured from the carbon-coated lithium-containing silicon oxide powder and the capacity retention rate of the negative electrode is determined. In addition, the BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder is 1.9 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 83.8% (see Table 2).

[0210] [Table 2]

[0211]

[0212] (Inspection)

[0213] As can be seen from Tables 1 and 2, the negative electrode formed of the carbon-coated silicon oxide powder has a higher capacity retention rate than the silicon oxide powder not coated with carbon.

Claims

1. A method for producing silicon oxide, comprising: A water treatment step of contacting silicon with water and then drying it to obtain water-treated silicon; A reduced pressure heating step of heating (a) the water-treated silicon together with at least one compound selected from the group consisting of (b1) silicon dioxide, (b2) metal silicate, and (b3) metal oxide under reduced pressure to generate gas; and A desublimation step of condensing the gas to obtain a solid.

2. A method for producing silicon oxide, comprising: A granulation step of granulating a mixture containing (A) silicon and (B) at least one compound selected from the group consisting of (b1) silicon dioxide, (b2) metal silicate, and (b3) metal oxide using water to obtain a granulated product; A reduced pressure heating step of heating the granulated material under reduced pressure to generate gas from the granulated material; and A desublimation step of condensing the gas to obtain a solid.

3. A method for producing silicon oxide, comprising: A step of charging (A) silicon and (B) at least one compound selected from the group consisting of (b1) silicon dioxide, (b2) metal silicate, and (b3) metal oxide into a heat-resistant container so that the element ratio O / Si during the reaction is within a range of more than 1 and less than 1.5; A reduced-pressure heating step of heating the compound put into the heat-resistant container under reduced pressure to generate gas from the compound; and A desublimation step of condensing the gas to obtain a solid.

4. The method for producing silicon oxide according to any one of claims 1 to 3, The heating temperature in the reduced pressure heating step is set to T R , the melting point of silicon (A) is set to T A The lowest melting point among the melting point of the silicon dioxide (b1), the metal silicate (b2) and the metal oxide (b3) is defined as T BL The highest melting point among the melting point of the silicon dioxide (b1), the metal silicate (b2) and the metal oxide (b3) is defined as T BH At T A <T BL If established, T R Set to satisfy T A <T R <T BL , in T BL <T A <T BH If established, T R Set to satisfy T BL <T R <T A , in T BH <T A If established, T R Set to satisfy T BH <T R <T A .

5. A silicon oxide, It has M x SiO y The composition of the representation, in, In the composition formula, M is at least one metal element selected from Li, Na, K, Mg, and Ca, y is in the range of more than 0.5 and less than 1.5, x / y is in the range of more than 0 and less than 1, x is more than 0, The concentration of aluminum element as impurities is 150 ppm or less in terms of mass concentration, the concentration of iron element is less than 100 ppm, and the concentration of copper element is less than 100 ppm.

6. The silicon oxide according to claim 5, The median particle size measured by a laser diffraction particle size distribution analyzer is within a range of 0.5 μm to 30 μm.

7. The silicon oxide according to claim 5, At least a portion of the surface is covered with a conductive carbon film.

8. The silicon oxide according to claim 7, The mass ratio of carbon in the conductive carbon film to the mass of the silicon oxide is in a range of 0.5 mass % to 20 mass %.

9. The silicon oxide according to claim 5, BET specific surface area at 1m 2 / g above 6m 2 / g or less.

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