Metal element-containing silicon oxide and method for producing the same

Abstract

The present invention addresses the problem of providing a method for reducing impurities, e.g., aluminum, on element level in silicon oxide. The method for producing silicon oxide according to the present invention comprises a water treatment step, a reduced-pressure heating step and a sublimation step. In the water treatment step, silicon is brought into contact with water, and the resultant product is dried to produce water-treated silicon. In the reduced-pressure heating step, the water-treated silicon (a) is heated together with silicon dioxide (b1) and a mixture (b3) of a metal silicate (b2) or a metal oxide (b3) and silicon oxide under a reduced pressure to generate a gas. In the sublimation step, the gas is sublimated to produce a solid material.

Description

[Technical Field] 【0001】 The present invention Metal element-containing silicon oxide This invention relates to the following. Furthermore, this invention is Contains metal elements This also relates to methods for producing silicon dioxide. [Background technology] 【0002】 In recent years, silicon monoxide (SiO) has been attracting attention as a high-capacity negative electrode active material. However, silicon monoxide has the disadvantage of having a large irreversible capacity. As a method to reduce this irreversible capacity and improve efficiency, the gas-phase lithium pre-doping method is proposed in Japanese Patent Publication No. 2021-52014. The gas-phase lithium pre-doping method disclosed in this publication is a method to obtain lithium-containing silicon oxide (lithium-doped silicon oxide) by doping SiO with lithium in the gas phase. [Prior art documents] [Patent Documents] 【0003】 [Patent Document 1] Japanese Patent Publication No. 2021-52014 [Patent Document 2] Japanese Patent Publication No. 2014-86254 [Overview of the project] [Problems that the invention aims to solve] 【0004】 Incidentally, in the silicon monoxide manufacturing method and the gas-phase lithium pre-doping method, elements such as aluminum with low vapor pressure contained in the raw materials vaporize together with the silicon monoxide, resulting in a problem where certain impurities remain in the target silicon oxide. Elemental-level impurities such as aluminum can diffuse within the active material particles during the battery's charging and discharging process, precipitation at grain boundaries, promoting pulverization and potentially degrading the battery's cycle characteristics. 【0005】 The object of the present invention is to provide a method for reducing elemental impurities such as aluminum in silicon oxide. [Means for solving the problem] 【0006】 A method for producing silicon oxide (including silicon oxide containing metal elements) according to the first aspect of the present invention comprises a water treatment step, a reduced-pressure heating step, and a coagulation step. In the water treatment step, silicon is brought into contact 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 silicates, and (b3) metal oxides to generate gas. In the coagulation step, the gas is coagulated to obtain a solid. 【0007】 As mentioned above, this silicon dioxide manufacturing method includes a water treatment step. This allows the aluminum and iron elements contained in the silicon powder to be transformed into a form that is less likely to vaporize during the reduced-pressure heating step. Therefore, this silicon dioxide manufacturing method can reduce the concentration of aluminum and iron elements in the silicon dioxide (solid material). 【0008】 A 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 coagulation 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 with water to obtain granules. In the reduced-pressure heating step, the granules are heated under reduced pressure to generate gas from the granules. In the coagulation step, the gas is coagulated to obtain a solid. 【0009】 As mentioned above, this silicon dioxide manufacturing method includes a granulation step. In the granulation step, the water used for granulation can change the aluminum and iron elements contained in the granulated silicon into a form that is less likely to vaporize in the reduced-pressure heating step. Therefore, this silicon dioxide manufacturing method can reduce the concentration of aluminum and iron elements in the silicon dioxide (solid material). In addition, granulation improves fluidity and reduces jetting properties, making handling easier during the process. 【0010】 A third aspect of the present invention relates to a method for producing silicon oxide, comprising an input step, a reduced-pressure heating step, and a coagulation step. In the input step, the aluminum element concentration in a mixture containing (A) silicon and (B)(b1) silicon dioxide, (b2) metal silicate, and (b3) metal oxide is reduced to less than 50 ppm by mass, the iron element concentration is reduced to less than 1000 ppm by mass, and the copper element concentration is reduced to less than 200 ppm by mass. mixture The mixture is placed in a heat-resistant container. In the reduced-pressure heating process, the mixture is heated under reduced pressure, and gas is generated from the mixture. In the condensation process, the gas is condensed to obtain a solid. 【0011】 As described above, this silicon oxide manufacturing method includes an input step. In the input step, silicon and the mixture are added to a heat-resistant container such that the aluminum element concentration in the mixture is less than 50 ppm by mass, the iron element concentration is less than 1000 ppm by mass, and the copper element concentration is less than 200 ppm by mass. Therefore, this silicon oxide manufacturing method can sufficiently reduce the aluminum, iron, and copper element concentrations in lithium-containing silicon oxide (solid material). 【0012】 A method for producing silicon oxide according to the fourth aspect of the present invention comprises a feeding step, a reduced-pressure heating step, and a condensation step. In the feeding step, (A) silicon and one or more compounds from (B)(b1) silicon dioxide, (b2) metal silicates, and (b3) metal oxides are fed into a heat-resistant container such that the elemental ratio O / Si during the reaction is greater than 1 and less than 1.5. From the viewpoint of maintaining a good reaction rate, the elemental 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 compounds fed into the heat-resistant container are heated under reduced pressure, and gas is generated from the compounds. In the condensation step, the gas is condensed to obtain a solid. Here, the elemental ratio O / Si during the reaction refers to the value obtained by dividing the amount of O element substance contained in the raw materials fed into the heat-resistant container by the amount of Si element substance contained in the raw materials fed into the heat-resistant container. 【0013】 As described above, a charging step is provided in this method for producing silicon oxide. 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 so that the element ratio O / Si during the reaction is within a range greater than 1 and less than 1.5. Therefore, in the heat-resistant container, the aluminum element in the raw material reacts with excessive silicon oxide or metal silicate and Heat-resistant container remains therein, leading to suppression of the vaporization of aluminum and iron elements, and enabling sufficient reduction of the concentrations of aluminum and iron elements in the silicon oxide obtained as the target product. Note that, since it is only necessary for the element ratio O / Si to be within a range greater than 1 and less than 1.5 during the reaction in the heat-resistant container, steps (such as a granulation step) that do not affect the element ratio midway may be involved. As a specific method for setting the element ratio during the reaction to the target value, methods such as mixing in advance so that the element ratio O / Si is within a range greater than 1 and less than 1.5 and charging into a heat-resistant container, or setting the respective charging amounts so that the element ratio O / Si is always within a range greater than 1 and less than 1.5 for the raw materials charged per unit time and then charging the raw materials into the heat-resistant container from separate paths can be considered. 【0014】 The method for producing silicon oxide according to the 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 T R and the melting point of (A) silicon is T A and the lowest melting point among the melting points of (b1) silicon dioxide, (b2) metal silicate, and (b3) metal oxide is T BL and the highest melting point among the melting points of (b1) silicon dioxide, (b2) metal silicate, and (b3) metal oxide is T BH When T A < T BL is satisfied, T A < T R < T BL is set so as to satisfy T R and when T BL < T A < T BH is satisfied, TBL <T R <T A T R Set, T BH <T A If this is true, T BH <T R <T A T R This will be set. 【0015】 As described above, in this silicon dioxide production method, 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 gas generation. 【0016】 The silicon dioxide according to the sixth aspect of the present invention is M x SiO y (However, in the composition formula, M is at least one metallic element selected from Li, Na, K, Mg, and Ca, y is in the range of greater than 0.5 and less than 1.5, x / y is in the range of greater than or equal to 0 and less than 1, and x is greater than 0.) The silicon oxide has a composition represented by this formula. Furthermore, the concentration of aluminum element as an impurity is 150 ppm or less by mass, the concentration of iron element is less than 100 ppm, and the concentration of copper element is less than 100 ppm. 【0017】 As mentioned above, in this silicon dioxide, the concentration of aluminum as an impurity is 150 ppm or less by mass, the concentration of iron is less than 100 ppm, and the concentration of copper is less than 100 ppm. Therefore, when this silicon dioxide is used as a negative electrode active material, it is expected that pulverization will be suppressed during the charging and discharging process, and consequently, the deterioration of the battery's cycle characteristics will be suppressed. 【0018】 Furthermore, in the silicon dioxide described above, it is preferable that the median diameter measured by a laser diffraction particle size distribution analyzer is within the range of 0.5 μm to 30 μm. This is because when this silicon dioxide is used as a negative electrode active material, it is possible to suppress not only the decrease in the Coulomb fraction but also the reduction in pulverization, thereby suppressing the deterioration of the negative electrode's cycle characteristics. 【0019】 Furthermore, in the silicon oxide described above, it is preferable that at least a portion of the surface is covered with a conductive carbon film. In this case, it is preferable that the mass ratio of carbon in the conductive carbon film to the mass of silicon oxide is within the range of 0.5% by mass or more and 20% by mass or less. This is because when this silicon oxide is used as a negative electrode active material, it is possible to impart good conductivity to the silicon oxide while maintaining good charge and discharge capacity, and to suppress side reactions of silicon oxide. 【0020】 Furthermore, in the silicon dioxide mentioned above, the BET specific surface area is 1 m². 2 / g or more 6m 2 It is preferable that the amount be within the range of / g or less. This is because when silicon dioxide is used as the negative electrode active material, it is possible to suppress the decrease in Coulomb efficiency while maintaining good output characteristics. [Brief explanation of the drawing] 【0021】 [Figure 1] This is a schematic diagram of a silicon dioxide powder manufacturing apparatus according to an embodiment of the present invention. [Explanation of symbols] 【0022】 100 Vapor deposition equipment 110 Crucible 120 Heater 130 Evaporation Drums 141 Scraper 143 Granule Guide 150 Chambers 151 Chamber body 152 Recovery Section 153 Exhaust pipe 160 Raw material supply hopper 170 Raw material introduction pipe 180 collection containers 190 Recovery pipe Gg Gas Guide OP opening RM precipitation chamber Sr molten metal VL1 1st valve VL2 2nd valve [Modes for carrying out the invention] 【0023】 The silicon dioxide according to the embodiment of the present invention is M x SiO y It is represented as follows: However, in this empirical formula, M is at least one metallic element selected from Li, Na, K, Mg, and Ca. Also, y is in the range of greater than 0.5 and less than 1.5, and x / y is in the range of greater than or equal to 0 and less than 1. Also, x is greater than or equal to 0. By the way, if x is greater than 0, the empirical formula is M x SiO y This is the result. On the other hand, when x is 0, the empirical formula is SiO y Therefore, silicon dioxide is M x SiO y It may also be expressed as SiO y It can also be expressed as follows. In the former case, y will be in the range of greater than 0.5 and less than 1.5, and x / y will be in the range of greater than 0 and less than 1. Here, y is preferably in the range of greater than 0.7 and less than 1.3, more preferably in the range of greater than 0.9 and less than 1.1, even more preferably in the range of greater than 0.95 and less than 1.05, and particularly preferably in the range of greater than 1.00 and less than 1.05. Also, when M is Li, x / y is preferably in the range of greater than 0.20 and less than 0.5, more preferably in the range of greater than 0.30 and less than 0.4, and when M is Mg, it is preferably in the range of greater than 0.8 and less than 1, and even more preferably in the range of greater than 0.9 and less than 1. On the other hand, in the latter case, y will be in the range of greater than 0.5 and less than 1.5, and x / y will be 0. For the sake of explanation, hereafter, M x SiO y The composition represented by SiO is called metal element-containing silicon oxide, yThe composition represented by this formula is sometimes referred to as metal element-free silicon oxide. Furthermore, silicon oxide formed mainly from metal element-containing silicon oxide is sometimes referred to as metal element-containing silicon oxide, and silicon oxide formed mainly from metal element-free silicon oxide is sometimes referred to as metal element-free silicon oxide. In this silicon oxide, i.e., metal element-containing silicon oxide or metal element-free silicon oxide, the aluminum element as an impurity is contained at a mass concentration of 150 ppm or less, the iron element is contained at a mass concentration of less than 100 ppm, and the copper element is contained at a mass concentration of less than 100 ppm. The shape of the silicon oxide according to the embodiment of the present invention is not limited and may be in powder form, lump form, or other form. 【0024】 Furthermore, the silicon dioxide described above preferably has a median diameter of 0.5 μm to 30 μm as measured by a laser diffraction particle size distribution analyzer, more preferably in the range of 1.0 μm to 20 μm, and even more preferably in the range of 1.5 μm to 10 μm. This is because when this silicon dioxide is used as a negative electrode active material, it can not only suppress the decrease in Coulomb fraction but also suppress pulverization, thereby suppressing the deterioration of the negative electrode's cycle characteristics. 【0025】 Furthermore, it is preferable that at least a portion of the surface of the silicon oxide described above is covered with a conductive carbon film. In this case, it is preferable that the mass ratio of carbon in the conductive carbon film to the mass of silicon oxide be in the range of 0.5% by mass or more and 20% by mass or less, more preferably in the range of 0.5% by mass or more and 10% by mass or less, and even more preferably in the range of 0.5% by mass or more and 5% by mass or less. This is because when silicon oxide is used as a negative electrode active material, good conductivity can be imparted to the silicon oxide while maintaining good charge and discharge capacity, and side reactions of silicon oxide can be suppressed. 【0026】 Furthermore, the silicon dioxide mentioned above has a BET specific surface area of ​​1 m². 2 / g or more 6m 2It is preferable that the range be less than or equal to / g, and 1.5m 2 / g or more 5m 2 It is more preferable that the range be less than or equal to / g, and 1.5m 2 / g or more 4m 2 It is even more preferable that the range be within / g or less, and 1.5m 2 / g or more 3m 2 It is particularly preferable that the silicon dioxide is within the range of / g or less. This is because when this silicon dioxide is used as the negative electrode active material, it is possible to suppress the decrease in Coulomb efficiency while maintaining good output characteristics. 【0027】 The following describes in detail a method for producing silicon oxide according to embodiments of the present invention, namely, silicon oxide containing metal elements or silicon oxide without metal elements. 【0028】 Incidentally, the raw materials used in the production of silicon oxide without metal elements are a mixture of silicon and silicon dioxide. Silicon and silicon dioxide may be in powder form, lump form, or other forms. On the other hand, the raw materials used in the production of silicon oxide containing metal elements are a mixture of silicon and at least one compound selected from the group consisting of silicon dioxide, metal silicates, and metal oxides. Silicon, silicon dioxide, metal silicates, and metal oxides may be in powder form, lump form, or other forms. Examples of metal silicates include lithium silicate (e.g., lithium disilicate Li2Si2O5), sodium silicate (e.g., sodium disilicate Na2Si2O5), potassium silicate (e.g., potassium disilicate K2Si2O5), magnesium silicate (magnesium silicate MgSiO3), and calcium silicate (calcium silicate CaSiO3). Furthermore, the metal silicate may be a mixture of a metal oxide and silicon oxide. For example, lithium disilicate Li2Si2O5 may be a mixture of Li2O and 2SiO2, sodium disilicate Na2Si2O5 may be a mixture of Na2O and 2SiO2, potassium disilicate K2Si2O5 may be a mixture of K2O and 2SiO2, magnesium silicate MgSiO3 may be a mixture of MgO and SiO2, and calcium silicate CaSiO3 may be a mixture of CaO and SiO2. Examples of metal oxides include lithium oxide (Li2O, etc.), sodium oxide (Na2O, etc.), potassium oxide (K2O), magnesium oxide (MgO, etc.), and calcium oxide (CaO, etc.). 【0029】 Incidentally, the metal element-containing silicon oxide or metal element-free silicon oxide according to the embodiment of the present invention can be manufactured according to the manufacturing method shown below. When the metal element-containing silicon oxide or metal element-free silicon oxide is manufactured according to the manufacturing method shown below, one of the pretreatments or preparations shown in (1) to (4) below is performed. 【0030】 (1) Before the raw material is added, the silicon is treated with water, and the aluminum and iron elements contained in the silicon are changed into a form that is less likely to vaporize during the reduced-pressure heating process. 【0031】 (2) Water is added to the raw materials, and as the raw materials are granulated, the aluminum and iron elements in the raw materials are changed into a form that is less likely to vaporize in the reduced-pressure heating process. 【0032】 (3) The mixing ratio of the various compounds is determined such that, before the raw materials are added, the aluminum element concentration is less than 50 ppm by mass, the iron element concentration is less than 1000 ppm by mass, and the copper element concentration is less than 200 ppm by mass. 【0033】 (4) Before introducing the raw materials, the mixing ratio of (A) silicon and (B) at least one compound selected from the group consisting of (b1) silicon dioxide, (b2) metal silicates, and (b3) metal oxides is determined such that the elemental ratio of O / Si during the reaction is greater than 1 and less than 1.5. 【0034】 Furthermore, the above-described manufacturing method is preferably carried out using a vapor deposition apparatus 100 as shown in Figure 1, from the viewpoint of reducing manufacturing costs. For this reason, we will first describe the vapor deposition apparatus 100, and then explain the above-described manufacturing method. 【0035】 As shown in Figure 1, the vapor deposition apparatus 100 mainly consists of a crucible 110, a heater 120, a vapor deposition drum 130, a scraper 141, a granular guide 143, a chamber 150, a raw material supply hopper 160, a raw material introduction pipe 170, a recovery container 180, a first valve VL1, and a second valve VL2. 【0036】 The crucible 110 is a heat-resistant container with an opening in the center of its top wall, as shown in Figure 1, and is installed in the chamber 150. A through-hole (not shown) is formed at one point around the perimeter of the top wall of the crucible 110, and a raw material introduction pipe 170 is inserted through this through-hole. That is, the raw material in the raw material supply hopper 160 is supplied to the crucible 110 through the raw material introduction pipe 170. A gas guide Gg is also provided on the upper side of the top wall of the crucible 110. This gas guide Gg is a component that guides the raw material gas generated in the crucible 110 to the deposition drum 130, and as shown in Figure 1, it is installed on the upper surface of the top wall so as to surround the central part of the top wall. 【0037】 The heater 120 is for heating the crucible 110 to a high temperature and is positioned to cover the outer circumference of the crucible 110. 【0038】 The deposition drum 130 is, for example, a cylindrical horizontal drum, and as shown in Figure 1, is positioned above the opening OP in the top wall of the crucible 110, with its lower part surrounded by a gas guide Gg. The deposition drum 130 is rotated in one direction by a drive mechanism (not shown). The deposition drum 130 is also equipped with a temperature controller (not shown) to maintain a constant temperature on its outer surface. This temperature controller cools the outer surface temperature of the deposition drum 130 to a temperature suitable for deposition of the deposition source gas using a cooling medium supplied from the outside. Furthermore, the outer surface temperature of the deposition drum 130 can affect the crystallinity of precipitates deposited on top of precipitates remaining on the deposition drum. If this temperature is too low, the microstructure of the precipitates may become too sparse, and conversely, if it is too high, crystal growth due to disproportionation reactions may proceed. Furthermore, this temperature is preferably 900°C or lower, more preferably within the range of 150°C to 800°C, and particularly preferably within the range of 150°C to 700°C. 【0039】 The scraper 141 is a component that plays the role of scraping the thin film formed on the deposition drum from the deposition drum 130, and is positioned near the deposition drum 130 as shown in Figure 1. The thin pieces (active material particles) scraped off by the scraper 141 fall into the particle guide 143. The material of the scraper 141 also affects the contamination of the active material particles with impurities. From the viewpoint of suppressing this effect, the material of the scraper 141 is preferably stainless steel or ceramics, and is particularly preferably ceramics. Furthermore, it is preferable that the scraper 141 does not come into contact with the outer surface of the deposition drum 130. This is because it is possible to prevent impurity contamination that may occur due to direct contact between the deposition drum 130 and the scraper 141 from being mixed into the recovered active material particles. 【0040】 The granular guide 143 is, for example, a vibrating transport member, and as shown in Figure 1, is arranged to be inclined downward as it moves from the vicinity of the deposition drum toward the recovery section 152 of the chamber 150. It receives thin film fragments scraped off by the scraper 141, which is located above it, and sends them to the recovery section 152 of the chamber 150. 【0041】 As shown in Figure 1, the chamber 150 is mainly composed of a chamber body 151, a recovery section 152, and an exhaust pipe 153. The chamber body 151, as shown in Figure 1, is a box-shaped portion having a deposition chamber RM inside, and houses a crucible 110, a heater 120, a deposition drum 130, a scraper 141, and a granular guide 143. The recovery section 152, as shown in Figure 1, is a portion that protrudes outward from the side wall of the chamber body 151 and has a space that communicates with the deposition chamber RM of the chamber body 151. As mentioned above, the tip portion of the granular guide 143 is located in this recovery section 152. 【0042】 The raw material supply hopper 160 is a raw material supply source, and as shown in Figure 1, its outlet is connected to the raw material introduction pipe 170. That is, the raw material fed into the raw material supply hopper 160 is supplied to the crucible 110 via the raw material introduction pipe 170 at an appropriate timing. The raw material supplied to the crucible 110 becomes molten Sr and then vaporizes to become raw material gas. 【0043】 The raw material introduction pipe 170 is a round-hole nozzle for supplying solid raw materials that have been introduced into the raw material supply hopper 160 to the crucible 110, and is positioned in the central part of the top plate of the crucible 110 so that its opening faces upward. 【0044】 The recovery container 180 is a container for recovering thin film fragments that have passed through the first valve VL1 and the second valve VL2. 【0045】 The first valve VL1 and the second valve VL2 are used to adjust the amount of thin film fragments collected into the collection container 180 by opening and closing them, and are provided in the collection pipe 190 that connects the collection section 152 of the chamber 150 and the collection container 180. 【0046】 The raw materials (mixed powder or granules) are either fed from the raw material supply hopper 160 to the crucible 110 via the raw material introduction pipe 170, or the raw materials are fed directly into the crucible 110. The raw material for silicon oxide without metal elements is as described above, and when heated to a predetermined temperature, it generates SiO gas, which is the raw material gas. The predetermined temperature here is the temperature between the melting point of silicon (1414°C) and the melting point of silicon dioxide (1710°C). On the other hand, the raw material for silicon oxide containing metal elements is as described above, and when heated to a predetermined temperature, it generates SiO gas containing metal elements, which is the raw material gas. The specified temperature referred to here is the temperature between the melting point of silicon (1414°C) and the melting points of lithium-containing silicon oxide (Li2Si2O5: 1033°C, Na2Si2O5: 874°C, K2Si2O5: 1045°C, MgSiO3: 1558°C, CaSiO3: 1544°C). 【0047】 Once the raw materials are placed in the crucible 110, the crucible 110 is heated by the heater 120 while the pressure inside the deposition chamber RM is reduced. Note that if the pressure inside the deposition chamber RM is too high, the reaction that generates SiO gas from the raw materials becomes difficult to occur. Therefore, the pressure inside the deposition chamber RM is preferably 1000 Pa or less, more preferably 750 Pa or less, and particularly preferably 20 Pa or less. Furthermore, the temperature inside the deposition chamber RM affects the reaction rate of SiO; if the temperature is too low, the reaction rate slows down, and if the temperature is too high, there is a concern that side reactions due to the melting of the raw materials will occur, and energy efficiency will decrease. If it's too high Damage to the crucible 110 is also a concern. From this viewpoint, the temperature inside the deposition 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. 【0048】 As described above, by heating the raw materials under reduced pressure, raw material gas is generated from the raw materials in the crucible 110, and this raw material gas is supplied to the deposition drum 130 through the gas guide Gg. At this time, the deposition drum 130 is rotated by a drive source. The temperature of the outer surface of the deposition drum 130 is set lower than the temperature inside the deposition chamber RM. More specifically, this temperature is set lower than the condensation temperature of the raw material gas. With this setting, the raw material gas generated from the crucible 110 is deposited and deposited on the outer surface of the rotating deposition drum 130. Then, with the scraper 141 in a standby position above, the deposition drum 130 is rotated multiple times to form a laminated film on the deposition drum 130. After that, when the number of rotations of the deposition drum 130 reaches a specified number, the scraper 141 is moved downward, and the laminated film is scraped off the deposition drum 130 by the scraper 141. The scraped-off fragments of the laminated film fall along the outer surface of the deposition drum 130 onto the granular guide 143. Finally, these fragments of the laminated film are crushed to obtain the desired silicon oxide containing metal elements or silicon oxide without metal elements. 【0049】 <Characteristics of the method for producing silicon dioxide according to embodiments of the present invention> In the silicon oxide production method according to the embodiment of the present invention, any of the pretreatments or preparations described in (1) to (4) above are performed. As a result, this silicon oxide production method makes it possible to obtain silicon oxide containing metal elements with low concentrations of aluminum, iron, and copper, or silicon oxide without metal elements. Therefore, when this silicon oxide containing metal elements or silicon oxide without metal elements is used as a negative electrode active material, pulverization during the charge and discharge process can be suppressed, and consequently, a decrease in the battery's cycle characteristics can be suppressed. 【0050】 Furthermore, the presence of the pretreatment described in (1) or (2) above allows for the use of low-grade silicon with relatively high concentrations of aluminum and iron. Therefore, the raw material cost can be reduced when the pretreatment described in (1) or (2) above is performed. 【0051】 Examples and comparative examples are shown below to illustrate the present invention in more detail, but the present invention is not limited to these examples. [Examples] 【0052】 1. Manufacturing of silicon dioxide powder The target silicon dioxide powder was produced by sequentially carrying out the following steps. (1) Raw material powder preparation process Low-grade silicon (Si) powder (Al mass concentration 2000 ppm, Fe mass concentration 2500 ppm, Cu mass concentration 500 ppm, median diameter 2.5 μm) and lithium disilicate (Li2Si2O5) powder (Al mass concentration 50 ppm, Fe mass concentration 15 ppm, Cu mass concentration 3 ppm, median diameter 5 μm) were prepared (see Table 1). 【0053】 (2)Mixing process The low-grade silicon (Si) powder and lithium disilicate powder prepared in the raw material powder preparation process described above were mixed in a mass ratio of 88.2:150 to prepare a mixed powder. 【0054】 (3) Wet granulation process The mixed powder obtained in the above mixing process was granulated using water. After granulation, the Al mass concentration in the mixed powder was 772 ppm, the Fe mass concentration was 936 ppm, and the Cu mass concentration was 187 ppm (see Table 1). The Al, Fe, and Cu mass concentrations were measured according to ICP emission spectrometry. The molar ratio of oxygen to silicon (O / Si) in the mixed powder was 0.97. 【0055】 (4) Silicon dioxide powder manufacturing process Lithium-containing silicon oxide was produced using the deposition apparatus 100 shown in Figure 1, according to the silicon oxide powder production method described above. The raw material heating temperature was 1300°C. This raw material heating temperature is above the melting point of lithium disilicate (1033°C) and below the melting point of silicon (1414°C). The composition of the final lithium-containing silicon oxide powder was Li x SiO y Here, y was 1.03 and x / y was 0.35. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 150 ppm, the Fe mass concentration was 45 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The Al mass concentration, Fe mass concentration, and Cu mass concentration were measured according to the same method as described above. 【0056】 (5) Heat treatment process The solid lithium-containing silicon dioxide obtained in the silicon dioxide powder manufacturing process described above was heat-treated at 600°C under an argon atmosphere. 【0057】 (6) Grinding process The heat-treated, lump-shaped lithium-containing silicon oxide was pulverized in air using a bead mill until the median diameter was approximately 5 μm to obtain the desired lithium-containing silicon oxide powder. The median diameter was measured using a laser diffraction particle size distribution analyzer (Mastersizer3000, Malvern). The measurement conditions were as follows. • Dispersion medium: Isopropyl alcohol (2-propanol) Particle refractive index: 3.500 • Particle absorption rate: 1.000 • Refractive index of dispersion medium: 1.390 【0058】 2. Measurement of the specific surface area of ​​silicon dioxide powder using the BET method. The BET specific surface area of ​​the lithium-containing silicon oxide powder described above was measured using a single-point flow method (p / p0 = 0.3) with a Mascorb HM-1201 manufactured by Mountec Co., Ltd. In this measurement, nitrogen was used as the adsorbate, helium as the carrier gas, and liquid nitrogen as the cooling medium. In the actual measurement, a mixed gas of 30 vol% nitrogen and 70 vol% helium was used, with a flow rate of 25 mL / min. The nitrogen gas was adsorbed onto the lithium-containing silicon oxide powder by cooling it with liquid nitrogen, and then the nitrogen gas was desorbed by maintaining the lithium-containing silicon oxide powder at 300°C for 30 minutes. The result of this measurement was that the BET specific surface area of ​​the lithium-containing silicon oxide powder described above was 2.1 m². 2 It was / g. 【0059】 3. Cycle characteristics of a battery equipped with a negative electrode made of lithium-containing silicon oxide powder. (1) Battery production (1-1) Negative electrode fabrication As described above, lithium-containing silicon oxide powder and natural graphite (median diameter 12 μm) were mixed in a mass ratio of 10:90 to prepare the negative electrode active material. Next, the negative electrode active material, sodium polyacrylate (binder), and Denka Black (registered trademark) (acetylene black as a conductive additive) were added to Awatori Rentaro (registered trademark) ARE-310 manufactured by Thinky Co., Ltd. in a mass ratio of 92:3:5, and then mixed to prepare a slurry. Subsequently, the slurry was coated onto a 10 μm thick copper foil, and the coating was pre-dried in air at 80°C. Then, the slurry-coated copper foil was punched out into a disc shape with a diameter of 11 mm. Finally, the disc-shaped slurry-coated copper foil was dried in a vacuum at 150°C for 12 hours to obtain the desired negative electrode. 【0060】 (1-2) Battery construction A coin cell was fabricated using the above-mentioned negative electrode, Li foil as the counter electrode, separator, and electrolyte. A 20 μm thick porous polyethylene film was used as the separator, and a solution of lithium hexafluoride phosphate (LiPF6) at a concentration of 1 mol / L was used as the electrolyte, which was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1:1 volume ratio. 【0061】 (2) Cycle characteristics Using a secondary battery charge / discharge test device manufactured by Electrofield Co., Ltd., the above coin cell was subjected to charge / discharge tests, and the capacity retention rate after 50 cycles (the capacity retention rate after 50 cycles is calculated by dividing the discharge capacity at the 50th cycle by the discharge capacity at the first cycle and multiplying by 100) was determined to be 75.7% (see Table 1). During the charge / discharge tests, the conditions for the first charge were set to "CC-CV 0.2C" and "10mV-0.01C", the conditions for the first discharge were set to "CC 0.2C" and "1.5V cut-off", the conditions for the second and subsequent charges were set to "CC-CV 1C" and "10mV-0.01C", and the conditions for the second and subsequent discharges were set to "CC 1C" and "1.5V cut-off". Here, the current at 1C was calculated using theoretical capacities, assuming a discharge capacity of 360 mAh / g for natural graphite and 1900 mAh / g for silicon oxide powder. [Examples] 【0062】 Except for substituting low-grade silicon (Si) powder with medium-grade silicon (Si) powder (Al mass concentration 1000 ppm, Fe mass concentration 600 ppm, Cu mass concentration 100 ppm, median diameter 2.5 μm), the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1. 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 its capacity retention rate was measured. The Al mass concentration in the mixed powder after granulation was 402 ppm, the Fe mass concentration was 232 ppm, the Cu mass concentration was 39 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 0.97. The composition of the final lithium-containing silicon oxide powder was Li x SiO y Here, y was 1.03 and x / y was 0.34. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 48 ppm, the Fe mass concentration was 25 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.3 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 78.3% (see Table 1). [Examples] 【0063】 Except for substituting low-grade silicon (Si) powder with high-grade silicon (Si) powder (Al mass concentration 480 ppm, Fe mass concentration 300 ppm, Cu mass concentration 50 ppm, median diameter 2.5 μm), the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1. 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 its capacity retention rate was measured. The Al mass concentration in the mixed powder after granulation was 209 ppm, the Fe mass concentration was 121 ppm, the Cu mass concentration was 20 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 0.97. The composition of the final lithium-containing silicon oxide powder was Li x SiO yHere, y was 1.03 and x / y was 0.38. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 24 ppm, the Fe mass concentration was 20 ppm, and the Cu mass concentration was 2 ppm (see Table 1). The BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.2% (see Table 1). [Examples] 【0064】 Except for replacing the low-grade silicon (Si) powder with high-purity silicon (Si) powder (Al mass concentration 10 ppm, Fe mass concentration 40 ppm, Cu mass concentration 5 ppm, median diameter 2.5 μm) and performing the silicon oxide powder manufacturing process without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly placed into the crucible), the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1. 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 its capacity retention rate was measured. The Al mass concentration in the mixed powder was 35 ppm, the Fe mass concentration was 24 ppm, the Cu mass concentration was 4 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 0.97. The composition of the final lithium-containing silicon oxide powder was Li x SiO y Here, y was 1.02 and x / y was 0.36. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 5 ppm, the Fe mass concentration was 15 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.3 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 83.4% (see Table 1). 【0065】 (Comparative Example 1) Except for substituting low-grade silicon (Si) powder with medium-grade silicon (Si) powder (Al mass concentration 1000 ppm, Fe mass concentration 600 ppm, Cu mass concentration 100 ppm, median diameter 2.5 μm) and performing the silicon oxide powder manufacturing process without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly placed into the crucible), the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1. 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 its capacity retention rate was measured. The Al mass concentration in the mixed powder was 402 ppm, the Fe mass concentration was 232 ppm, the Cu mass concentration was 39 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 0.97. The composition of the final lithium-containing silicon oxide powder was Li x SiO y Here, y was 1.03 and x / y was 0.36. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 337 ppm, the Fe mass concentration was 30 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the obtained lithium-containing silicon oxide powder was 2.1 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 70.1% (see Table 1). 【0066】 (Comparative Example 2) Except for replacing the low-grade silicon (Si) powder with high-grade silicon (Si) powder (Al mass concentration 480 ppm, Fe mass concentration 300 ppm, Cu mass concentration 50 ppm, median diameter 2.5 μm) and performing the silicon oxide powder manufacturing process without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly placed into the crucible), the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1. 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 its capacity retention rate was measured. The Al mass concentration in the mixed powder was 209 ppm, the Fe mass concentration was 121 ppm, the Cu mass concentration was 20 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 0.97. The composition of the final lithium-containing silicon oxide powder was Li x SiO y Here, y was 1.02 and x / y was 0.35. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 205 ppm, the Fe mass concentration was 25 ppm, and the Cu mass concentration was 2 ppm (see Table 1). The BET specific surface area of ​​the obtained lithium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 71.2% (see Table 1). 【0067】 (Comparative Example 3) Except for replacing the low-grade silicon (Si) powder with high-purity silicon (Si) powder (Al mass concentration 10 ppm, Fe mass concentration 40 ppm, Cu mass concentration 5 ppm, median diameter 2.5 μm) and adding copper (Cu) powder in an amount of 3% by mass relative to the total mass of the mixed powder, the silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly put into the crucible), the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, 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. The copper powder used was that which had passed through a 45 μm mesh sieve. Furthermore, the mass concentration of Al in the mixed powder was 34 ppm, the mass concentration of Fe was 24 ppm, the mass concentration of Cu was 30004 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 0.97. The final composition of the lithium-containing silicon oxide powder obtained was Li x SiO y Here, y was 1.04 and x / y was 0.34. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 5 ppm, the Fe mass concentration was 14 ppm, and the Cu mass concentration was 3100 ppm (see Table 1). The BET specific surface area of ​​the obtained lithium-containing silicon oxide powder was 2.4 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 82.0% (see Table 1). 【0068】 (Comparative Example 4) Except for replacing the low-grade silicon (Si) powder with high-purity silicon (Si) powder (Al mass concentration 10 ppm, Fe mass concentration 40 ppm, Cu mass concentration 5 ppm, median diameter 2.5 μm) and adding copper (Cu) powder in an amount of 0.08% by mass relative to the total mass of the mixed powder, the silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly put into the crucible), the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, 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. The powder used was that which had passed through a 45 μm mesh sieve. Furthermore, 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 to silicon (O / Si) in the mixed powder was 0.97. The final composition of the lithium-containing silicon oxide powder obtained was Li x SiO y Here, y was 1.04 and x / y was 0.39. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 5 ppm, the Fe mass concentration was 15 ppm, and the Cu mass concentration was 110 ppm (see Table 1). The BET specific surface area of ​​the obtained lithium-containing silicon oxide powder was 2.4 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 82.5% (see Table 1). 【0069】 (Comparative Example 5) Except for replacing the low-grade silicon (Si) powder with high-purity silicon (Si) powder (Al mass concentration 10 ppm, Fe mass concentration 40 ppm, Cu mass concentration 5 ppm, median diameter 2.5 μm), and adding iron (Fe) powder to the high-purity silicon powder to a ratio of 5% by mass relative to the total amount of powder, the silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly put into the crucible), the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, 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. As for the iron powder, one that passed through a 45 μm mesh sieve was used. Furthermore, the mass concentration of Al in the mixed powder was 35 ppm, the mass concentration of Fe was 18555 ppm, the mass concentration of Cu was 4 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 0.97. The final composition of the lithium-containing silicon oxide powder obtained was Li x SiO y Here, y was 1.03 and x / y was 0.35. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 5 ppm, the Fe mass concentration was 250 ppm, and the Cu mass concentration was 2 ppm (see Table 1). The BET specific surface area of ​​the obtained lithium-containing silicon oxide powder was 2.3 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.2% (see Table 1). 【0070】 (Comparative Example 6) Except for replacing the low-grade silicon (Si) powder with high-purity silicon (Si) powder (Al mass concentration 10 ppm, Fe mass concentration 40 ppm, Cu mass concentration 5 ppm, median diameter 2.5 μm), and adding iron (Fe) powder to the high-purity silicon powder to a concentration of 1% by mass relative to the total amount of powder, the silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly put into the crucible), the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, 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, The iron powder used was that which had passed through a 45 μm mesh sieve. 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 to silicon (O / Si) in the mixed powder was 0.97. The final composition of the lithium-containing silicon oxide powder obtained was Li x SiO y Here, y was 1.02 and x / y was 0.32. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 5 ppm, the Fe mass concentration was 120 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the obtained lithium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.0% (see Table 1). [Examples] 【0071】 Except for replacing low-grade silicon (Si) powder with medium-grade silicon (Si) powder (Al mass concentration 1000 ppm, Fe mass concentration 600 ppm, Cu mass concentration 100 ppm, median diameter 2.5 μm) and lithium disilicate (Li2Si2O5) powder with magnesium silicate (MgSiO3) powder (Al mass concentration 50 ppm, Fe mass concentration 15 ppm, Cu mass concentration 3 ppm, median diameter 5 μm), and mixing the medium-grade silicon (Si) powder and magnesium silicate in a mass ratio of 58.8:100, the target magnesium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1. The BET specific surface area of ​​the magnesium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the magnesium-containing silicon oxide powder and its capacity retention rate was measured. The mass concentration of Al in the granulated mixed powder was 495 ppm, the mass concentration of Fe was 231 ppm, the mass concentration of Cu was 39 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 0.97. The final composition of the magnesium-containing silicon oxide powder obtained was Mg x SiO y Here, y was 1.02 and x / y was 0.98. Furthermore, the mass concentration of Al in the magnesium-containing silicon oxide powder was 38 ppm, the mass concentration of Fe was 27 ppm, and the mass concentration of Cu was 2 ppm (see Table 1). The raw material heating temperature in the silicon oxide powder manufacturing process was 1500°C. This raw material heating temperature is above the melting point of silicon (1414°C) and below the melting point of magnesium silicate (1558°C). The BET specific surface area of ​​the obtained magnesium-containing silicon oxide powder was 2.3 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 75.3% (see Table 1). 【0072】 (Comparative Example 7) The only difference from the example is that the silicon dioxide powder manufacturing process was carried out without going through the wet granulation process after the mixing process (i.e., the mixed powder obtained in the mixing process was directly put into the crucible). 5The target magnesium-containing silicon oxide powder was obtained according to the manufacturing method described in [reference], and the BET specific surface area of ​​the magnesium-containing silicon oxide powder was measured according to the method described in Example 1. A negative electrode was also manufactured from the magnesium-containing silicon oxide powder, and its capacity retention rate was measured. The mass concentration of Al in the mixed powder was 495 ppm, the mass concentration of Fe was 231 ppm, and the mass concentration of Cu was 39 ppm (see Table 1). The final composition of the magnesium-containing silicon oxide powder was Mg x SiO y Here, y was 1.03 and x / y was 0.95. Furthermore, the mass concentration of Al in the magnesium-containing silicon oxide powder was 345 ppm, the mass concentration of Fe was 29 ppm, and the mass concentration of Cu was 2 ppm (see Table 1). The raw material heating temperature in the silicon oxide powder manufacturing process was 1500°C. This raw material heating temperature is above the melting point of silicon (1414°C). Upper Ma The temperature is below the melting point of magnesium silicate (1558°C). Furthermore, the BET specific surface area of ​​the obtained magnesium-containing silicon oxide powder is 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 69.3% (see Table 1). [Examples] 【0073】 Low-grade silicon (Si) powder is replaced with high-purity silicon (Si) powder (Al mass concentration 10 ppm, Fe mass concentration 40 ppm, Cu mass concentration 5 ppm, median diameter 2.5 μm), and lithium disilicate (Li2Si2O5) powder is replaced with magnesium silicate (MgSiO3) powder (Al mass concentration 50 ppm, Fe mass concentration 15 ppm, Cu mass concentration 3 ppm, median diameter 5 μm), and the mass ratio of high-purity silicon powder and magnesium silicate is 4. The magnesium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1, except that the mixture was 7.8:100 and the silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly put into the crucible). The BET specific surface area of ​​the magnesium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the magnesium-containing silicon oxide powder and its capacity retention rate was measured. 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 4 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 0.97. The composition of the finally obtained magnesium-containing silicon oxide powder was Mg x SiO y Here, y was 1.01 and x / y was 0.94. Furthermore, the mass concentration of Al in the magnesium-containing silicon oxide powder was 5 ppm, the mass concentration of Fe was 15 ppm, and the mass concentration of Cu was 1 ppm (see Table 1). The raw material heating temperature in the silicon oxide powder manufacturing process was 1500°C. This raw material heating temperature is above the melting point of silicon (1414°C) and below the melting point of magnesium silicate (1558°C). The BET specific surface area of ​​the obtained magnesium-containing silicon oxide powder was 2.5 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 77.2% (see Table 1). 【0074】 (Comparative Example 8) The target magnesium-containing silicon oxide powder was obtained according to the production method described in Example 6, except that copper (Cu) powder was added so as to be 3% by mass with respect to the total mass of the mixed powder. The BET specific surface area of the magnesium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was produced from the magnesium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. As the copper powder, that which passed through a 45-μm sieve was used. Also, the Al mass concentration in the mixed powder was 30 ppm, the Fe mass concentration was 24 ppm, the Cu mass concentration was 30004 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. Also, the composition of the finally obtained magnesium-containing silicon oxide powder was Mg x SiO y where y was 1.03 and x / y was 0.97. Also, the Al mass concentration in the magnesium-containing silicon oxide powder was 5 ppm, the Fe mass concentration was 14 ppm, and the Cu mass concentration was 3100 ppm (see Table 1). Also, the obtained magnesium containing silicon oxide powder had a BET specific surface area of 2.4 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 75.1% (see Table 1). 【0075】 (Comparative Example 9) The target magnesium-containing silicon oxide powder was obtained according to the production method described in Example 6, except that copper (Cu) powder was added so as to be 0.08% by mass with respect to the total mass of the mixed powder. The BET specific surface area of the magnesium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was produced from the magnesium-containing silicon oxide powder and the capacity retention rate of the negative electrode was measured. As the copper powder, that which passed through a 45-μm sieve was used. Also, the Al mass concentration in the mixed powder was 31 ppm, the Fe mass concentration was 24 ppm, the Cu mass concentration was 804 ppm, and the molar ratio of oxygen element to silicon element (O / Si) in the mixed powder was 0.97. Also, the composition of the finally obtained magnesium-containing silicon oxide powder was Mg x SiO yHere, y was 1.02 and x / y was 0.98. Furthermore, the mass concentration of Al in the magnesium-containing silicon oxide powder was 5 ppm, the mass concentration of Fe was 15 ppm, and the mass concentration of Cu was 120 ppm (see Table 1). The BET specific surface area of ​​the obtained magnesium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 75.6% (see Table 1). 【0076】 (Comparative Example 10) Except for adding iron (Fe) powder to high-purity silicon powder in an amount of 5% by mass relative to the total amount of powder, the target magnesium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 6. The BET specific surface area of ​​the magnesium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the magnesium-containing silicon oxide powder and its capacity retention rate was measured. The iron powder used was that which had passed through a 45 μm sieve. 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 to silicon (O / Si) in the mixed powder was 0.97. The composition of the finally obtained magnesium-containing silicon oxide powder was Mg x SiO y Here, y was 1.02 and x / y was 0.95. Furthermore, the mass concentration of Al in the magnesium-containing silicon oxide powder was 5 ppm, the mass concentration of Fe was 290 ppm, and the mass concentration of Cu was 2 ppm (see Table 1). The BET specific surface area of ​​the obtained magnesium-containing silicon oxide powder was 2.3 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 74.0% (see Table 1). 【0077】 (Comparative Example 11) The target magnesium-containing silicon oxide powder was obtained according to the production method described in Example 6, except that iron (Fe) powder was added to the high-purity silicon powder so as to be 1% by mass based on 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, and a negative electrode was produced from the magnesium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. As the iron powder, the one passing through a 45-μm sieve was used. Also, the Al mass concentration in the mixed powder was 31 ppm, the Fe mass concentration was 3719 ppm, the Cu mass concentration was 4 ppm, and the molar ratio (O / Si) of oxygen element to silicon element in the mixed powder was 0.97. Also, the composition of the finally obtained magnesium-containing silicon oxide powder was Mg x SiO y where y was 1.03 and x / y was 0.96. Also, the Al mass concentration in the magnesium-containing silicon oxide powder was 4 ppm, the Fe mass concentration was 130 ppm, and the Cu mass concentration was 1 ppm (see Table 1). Also, the BET specific surface area of the obtained magnesium-containing silicon oxide powder was 2.4 m 2 / g, and the capacity retention rate of the negative electrode after 50 cycles was 74.6% (see Table 1). 【Example】 【0078】 (2) Except for contacting low-grade silicon (Si) powder with water before the mixing process and carrying out the silicon oxide powder manufacturing process without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly put into the crucible), the target lithium-containing silicon oxide powder was obtained in accordance with the manufacturing method described in Example 1, 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 the water treatment described above, 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. Then, most of the water was removed using filter paper and a suction filter corresponding to type 5C specified in JIS P 3801, and the remaining wet silicon powder was put into a shelf-type hot air dryer set to 120°C and dried. Furthermore, 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 to silicon (O / Si) in the mixed powder was 0.97. The final composition of the lithium-containing silicon oxide powder obtained was Li x SiO y Here, y was 1.01 and x / y was 0.34. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 150 ppm, the Fe mass concentration was 52 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.3 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 75.8% (see Table 1). [Examples] 【0079】 (2) 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 process, and the silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was put directly 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 the water treatment described above, 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. Then, most of the water was removed using filter paper and a suction filter corresponding to type 5C specified in JIS P 3801, and the remaining wet silicon powder was put into a shelf-type hot air dryer set to 120°C and dried. Furthermore, 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 to silicon (O / Si) in the mixed powder was 0.97. The final composition of the lithium-containing silicon oxide powder obtained was Li x SiO y Here, y was 1.03 and x / y was 0.36. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 62 ppm, the Fe mass concentration was 39 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 77.8% (see Table 1). [Examples] 【0080】 (2) The lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 3, except that the high-grade silicon (Si) powder was brought into contact with water before the mixing process, and the silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was put directly 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 the water treatment described above, 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. Then, most of the water was removed using filter paper and a suction filter corresponding to type 5C specified in JIS P 3801, and the remaining wet silicon powder was put into a shelf-type hot air dryer set to 120°C and dried. Furthermore, 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 to silicon (O / Si) in the mixed powder was 0.97. The final composition of the lithium-containing silicon oxide powder obtained was Li x SiO y Here, y was 1.02 and x / y was 0.35. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 32 ppm, the Fe mass concentration was 25 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.3 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 79.8% (see Table 1). [Examples] 【0081】 In the mixing process, low-grade silicon (Si) powder and lithium disilicate powder were mixed in a mass ratio of 79.8:150 to prepare a mixed powder. The silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly placed into the crucible). Except for these differences, the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 1. 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 to measure its capacity retention rate. The mass concentration of Al in the mixed powder was 772 ppm, the mass concentration of Fe was 879 ppm, the mass concentration of Cu was 176 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 1.03. The final composition of the obtained lithium-containing silicon oxide powder was Li x SiO y Here, y was 1.02 and x / y was 0.36. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 148 ppm, the Fe mass concentration was 25 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 75.8% (see Table 1). [Examples] 【0082】 In the mixing process, medium-grade silicon (Si) powder and lithium disilicate powder were mixed in a mass ratio of 79.8:150 to prepare a mixed powder. The silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly placed into the crucible). Except for these differences, the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 2. 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 to measure the capacity retention rate of the negative electrode. The mass concentration of Al in the mixed powder was 402 ppm, the mass concentration of Fe was 218 ppm, the mass concentration of Cu was 37 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 1.03. The final composition of the obtained lithium-containing silicon oxide powder was Li x SiO y Here, y was 1.03 and x / y was 0.34. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 50 ppm, the Fe mass concentration was 24 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 78.1% (see Table 1). [Examples] 【0083】 In the mixing process, high-grade silicon (Si) powder and lithium disilicate powder were mixed in a mass ratio of 79.8:150 to prepare a mixed powder. The silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly placed into the crucible). Except for these differences, the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 3. 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 to measure its capacity retention rate. The mass concentration of Al in the mixed powder was 209 ppm, the mass concentration of Fe was 114 ppm, the mass concentration of Cu was 19 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 1.03. The final composition of the obtained lithium-containing silicon oxide powder was Li x SiO y Here, y was 1.03 and x / y was 0.36. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 27 ppm, the Fe mass concentration was 20 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.3 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.0% (see Table 1). [Examples] 【0084】 In the mixing process, medium-grade silicon (Si) powder and lithium disilicate powder were mixed in a mass ratio of 56:150 to prepare a mixed powder. The silicon oxide powder manufacturing process was carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly placed into the crucible). Except for these differences, the target lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 2. 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 to measure the capacity retention rate of the negative electrode. The mass concentration of Al in the mixed powder was 402 ppm, the mass concentration of Fe was 174 ppm, the mass concentration of Cu was 29 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 1.25. The final composition of the obtained lithium-containing silicon oxide powder was Li x SiO y Here, y was 1.04 and x / y was 0.35. Furthermore, the Al mass concentration in the lithium-containing silicon oxide powder was 40 ppm, the Fe mass concentration was 21 ppm, and the Cu mass concentration was 1 ppm (see Table 1). The BET specific surface area of ​​the lithium-containing silicon oxide powder was 2.3 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 79.1% (see Table 1). 【0085】 (Comparative Example 12) In the mixing process, medium-grade silicon (Si) powder and lithium disilicate powder were mixed in a mass ratio of 37.2:150 to prepare a mixed powder. The silicon oxide powder manufacturing process was then carried out without going through the wet granulation process from the mixing process (i.e., the mixed powder obtained in the mixing process was directly placed into the crucible). However, the desired lithium-containing silicon oxide powder was obtained according to the manufacturing method described in Example 2, except that the reaction rate was significantly reduced, and the desired lithium-containing silicon oxide powder could not be obtained. The mass concentration of Al in the mixed powder was 402 ppm, the mass concentration of Fe was 132 ppm, the mass concentration of Cu was 22 ppm, and the molar ratio of oxygen to silicon (O / Si) in the mixed powder was 1.5. 【0086】 [Table 1] 【0087】 (Consideration) As is clear from Table 1, the negative electrode formed from silicon oxide powder manufactured via wet granulation had a higher capacity retention rate than the negative electrode formed from silicon oxide powder manufactured without wet granulation. Furthermore, it was found that the lower the concentration of aluminum, iron, and copper elements in the obtained silicon oxide powder, the higher the capacity retention rate (see Examples 1-3). 【0088】 Furthermore, as is clear from Table 1, a negative electrode formed from silicon oxide powder manufactured with an aluminum element mass concentration of less than 50 ppm, an iron element concentration of less than 1000 ppm, and a copper element concentration of less than 200 ppm in the mixed raw materials is superior. The mass concentration of aluminum element in the mixed raw materials The negative electrode formed from silicon oxide powder produced with an iron element concentration of 50 ppm or higher, an iron element concentration of 1000 ppm or higher, and a copper element concentration of 200 ppm or higher showed a higher capacity retention rate than that produced from silicon oxide powder. Furthermore, it was found 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 (see Example 4). 【0089】 Furthermore, as is clear from Table 1, the negative electrode formed from silicon oxide powder produced through water treatment of silicon powder had a higher capacity retention rate than the negative electrode formed from silicon oxide powder produced without water treatment of silicon powder. It was also found that the lower the concentration of aluminum, iron, and copper elements in the obtained silicon oxide powder, the higher the capacity retention rate (see Examples 7-9). 【0090】 Furthermore, as is clear from Table 1, the negative electrode formed from silicon oxide powder manufactured with an O / Si ratio greater than 1 and less than 1.5 in the mixed raw materials had a higher capacity retention rate than the negative electrode formed from silicon oxide powder manufactured with an O / Si ratio of 1 or less in the mixed raw materials. It was also found that the lower the concentration of aluminum, iron, and copper elements in the obtained silicon oxide powder, the higher the capacity retention rate (see Examples 7-12). [Examples] 【0091】 The lithium-containing silicon oxide powder obtained in Example 1 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 1.9 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.5% (see Table 2). [Examples] 【0092】 The lithium-containing silicon oxide powder obtained in Example 2 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing at 700°C. The mass ratio of carbon to the mass of lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.1 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 82.5% (see Table 2). [Examples] 【0093】 The lithium-containing silicon oxide powder obtained in Example 3 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.0 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 87.3% (see Table 2). [Examples] 【0094】 The lithium-containing silicon oxide powder obtained in Example 4 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.1 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 88.9% (see Table 2). 【0095】 (Comparative Example 13) The lithium-containing silicon oxide powder obtained in Comparative Example 1 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (Leco CS400). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 1.9 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 78.9% (see Table 2). 【0096】 (Comparative Example 14) The lithium-containing silicon oxide powder obtained in Comparative Example 2 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.0 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 79.6% (see Table 2). 【0097】 (Comparative Example 15) The lithium-containing silicon oxide powder obtained in Comparative Example 3 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 87.1% (see Table 2). 【0098】 (Comparative Example 16) The lithium-containing silicon oxide powder obtained in Comparative Example 4 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 87.5% (see Table 2). 【0099】 (Comparative Example 17) The lithium-containing silicon oxide powder obtained in Comparative Example 5 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.1 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 85.4% (see Table 2). 【0100】 (Comparative Example 18) The lithium-containing silicon oxide powder obtained in Comparative Example 6 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using an oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.0 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 86.0% (see Table 2). [Examples] 【0101】 The results obtained in Example 5 Magnesium-containing Silicon oxide powder was loaded into a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing at 700°C. The mass ratio of carbon to the mass of the magnesium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (Leco CS400). The BET specific surface area of ​​the carbon-coated magnesium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated magnesium-containing silicon oxide powder, and its capacity retention rate was measured. The obtained BET specific surface area of ​​the carbon-coated magnesium-containing silicon oxide powder was 2.1 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.2% (see Table 2). 【0102】 (Comparative Example 19) The magnesium-containing silicon oxide powder obtained in Comparative Example 7 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of the magnesium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using an oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated magnesium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated magnesium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated magnesium-containing silicon oxide powder was 2.0 m². 2 The value was / g, and the capacity retention rate after 50 cycles of the negative electrode was 78.3% (see Table 2). [Examples] 【0103】 The lithium-containing silicon oxide powder obtained in Example 6 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.3 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 83.3% (see Table 2). 【0104】 (Comparative Example 20) The lithium-containing silicon oxide powder obtained in Comparative Example 8 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using an oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.0% (see Table 2). 【0105】 (Comparative Example 21) The lithium-containing silicon oxide powder obtained in Comparative Example 9 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.0 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 81.5% (see Table 2). 【0106】 (Comparative Example 22) The lithium-containing silicon oxide powder obtained in Comparative Example 10 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.1 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.0% (see Table 2). 【0107】 (Comparative Example 23) The lithium-containing silicon oxide powder obtained in Comparative Example 11 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.2 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.2% (see Table 2). [Examples] 【0108】 The lithium-containing silicon oxide powder obtained in Example 7 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.1 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.4% (see Table 2). [Examples] 【0109】 The lithium-containing silicon oxide powder obtained in Example 8 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using an oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.0 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 82.0% (see Table 2). [Examples] 【0110】 The lithium-containing silicon oxide powder obtained in Example 9 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.1 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 85.1% (see Table 2). [Examples] 【0111】 The lithium-containing silicon oxide powder obtained in Example 10 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (Leco CS400). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.0 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 80.6% (see Table 2). [Examples] 【0112】 The lithium-containing silicon oxide powder obtained in Example 11 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of the lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using an oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (Leco CS400). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder to measure its capacity retention rate. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.0 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 82.3% (see Table 2). [Examples] 【0113】 The lithium-containing silicon oxide powder obtained in Example 12 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 2.1 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 86.2% (see Table 2). [Examples] 【0114】 The lithium-containing silicon oxide powder obtained in Example 13 was placed in a rotary kiln and carbon-coated using thermal CVD with argon and propane gases flowing through it at 700°C. The mass ratio of carbon to the mass of lithium-containing silicon oxide powder was 2% by mass. This mass ratio was calculated from the amount of carbon quantitatively evaluated by analyzing carbon dioxide gas using the oxygen-flow combustion-infrared absorption method with a carbon concentration analyzer (CS400, Leco). The BET specific surface area of ​​the carbon-coated lithium-containing silicon oxide powder was measured according to the method described in Example 1, and a negative electrode was manufactured from the carbon-coated lithium-containing silicon oxide powder, and the capacity retention rate of the negative electrode was measured. The BET specific surface area of ​​the obtained carbon-coated lithium-containing silicon oxide powder was 1.9 m². 2 The value was / g, and the capacity retention rate of the negative electrode after 50 cycles was 83.8% (see Table 2). 【0115】 [Table 2] 【0116】 (Consideration) As is clear from Tables 1 and 2, the negative electrode formed from carbon-coated silicon oxide powder had a higher capacity retention rate than the negative electrode formed from uncoated silicon oxide powder.

Claims

[Claim 1] A water treatment process to obtain water-treated silicon by bringing silicon into contact with water and then drying it, The water-treated silicon is heated under reduced pressure together with a metal silicate (where the metal is at least one metal element selected from Li, Na, K, Mg, and Ca) to generate a gas in a reduced-pressure heating step, A condensation step to obtain a solid by condensing the aforementioned gas. Equipped with, The heating temperature in the reduced-pressure heating step is T Ｒ and the melting point of the silicon is T Ａ and the melting point of the metal silicate is T ＢＬ When this is the case, if T Ａ < T ＢＬ is satisfied, then T Ａ < T Ｒ < T ＢＬ is set so as to satisfy T Ｒ and if T ＢＬ < T Ａ is satisfied, then T ＢＬ < T Ｒ < T Ａ is set so as to satisfy T Ｒ ​ The aforementioned solid is M ｘ SiO ｙ (However, in the composition formula, M is at least one metallic element selected from Li, Na, K, Mg, and Ca, y is in the range of greater than 0.5 and less than 1.5, x / y is in the range of greater than or equal to 0 and less than 1, and x is greater than 0.) The silicon oxide containing metallic elements has a composition represented by the formula, and the concentration of aluminum as an impurity is 150 ppm or less by mass, the concentration of iron is less than 100 ppm, and the concentration of copper is less than 100 ppm. A method for producing silicon oxide containing metal elements. [Claim 2] A granulation step is performed by granulating a mixture containing silicon and a metal silicate (where the metal is at least one metal element selected from Li, Na, K, Mg, and Ca) using water to obtain granules. A reduced-pressure heating step is performed to heat the granular material under reduced pressure to generate gas from the granular material. A condensation step to obtain a solid by condensing the aforementioned gas. Equipped with, The heating temperature in the aforementioned reduced-pressure heating process is T Ｒ It is said that the melting point of silicon is T Ａ It is said that the melting point of the metal silicate is T ＢＬ When this is the case, T Ａ <T ＢＬ If this is true, T Ａ <T Ｒ <T ＢＬ T Ｒ Set, T ＢＬ <T Ａ If this is true, T ＢＬ <T Ｒ <T Ａ T Ｒ Set The aforementioned solid is M ｘ SiO ｙ (However, in the composition formula, M is at least one metallic element selected from Li, Na, K, Mg, and Ca, y is in the range of greater than 0.5 and less than 1.5, x / y is in the range of greater than or equal to 0 and less than 1, and x is greater than 0.) The silicon oxide containing metallic elements has a composition represented by the formula, and the concentration of aluminum as an impurity is 150 ppm or less by mass, the concentration of iron is less than 100 ppm, and the concentration of copper is less than 100 ppm. A method for producing silicon oxide containing metal elements. [Claim 3] The process involves adding silicon and a metal silicate (where the metal is at least one metal element selected from Li, Na, K, Mg, and Ca) to a heat-resistant container such that the elemental ratio O / Si during the reaction is greater than 1 and less than 1.5, A vacuum heating step is performed in which the silicon and metal silicate placed in the heat-resistant container are heated under reduced pressure to generate gas from the silicon and metal silicate, A condensation step to obtain a solid by condensing the aforementioned gas. Equipped with, The heating temperature in the aforementioned reduced-pressure heating process is T Ｒ It is said that the melting point of silicon is T Ａ It is said that the melting point of the metal silicate is T ＢＬ When this is the case, T Ａ <T ＢＬ If this is true, T Ａ <T Ｒ <T ＢＬ T Ｒ Set, T ＢＬ <T Ａ If this is true, T ＢＬ <T Ｒ <T Ａ T Ｒ Set The aforementioned solid is M ｘ SiO ｙ (However, in the composition formula, M is at least one metallic element selected from Li, Na, K, Mg, and Ca, y is in the range of greater than 0.5 and less than 1.5, x / y is in the range of greater than or equal to 0 and less than 1, and x is greater than 0.) The silicon oxide containing metallic elements has a composition represented by the formula, and the concentration of aluminum as an impurity is 150 ppm or less by mass, the concentration of iron is less than 100 ppm, and the concentration of copper is less than 100 ppm. A method for producing silicon oxide containing metal elements. [Claim 4] M ｘ SiO ｙ (However, in the composition formula, M is at least one metallic element selected from Li, Na, K, Mg, and Ca, y is in the range of greater than 0.5 and less than 1.5, x / y is in the range of greater than or equal to 0 and less than 1, and x is greater than 0.) Silicon oxide containing metal elements, wherein the concentration of aluminum as an impurity is 150 ppm or less by mass, the concentration of iron is less than 100 ppm, and the concentration of copper is less than 100 ppm. [Claim 5] The median diameter measured by a laser diffraction particle size distribution analyzer is within the range of 0.5 μm to 30 μm. The metal element-containing silicon oxide according to claim 4. [Claim 6] At least a portion of the surface is covered with a conductive carbon coating. The metal element-containing silicon oxide according to claim 4. [Claim 7] The mass ratio of carbon in the conductive carbon film to the mass of the metal element-containing silicon oxide is within the range of 0.5% by mass or more and 20% by mass or less. The metal element-containing silicon oxide according to claim 6. [Claim 8] BET specific surface area is 1 m ２ / g or more 6m ２ It is within the range of / g or less. The metal element-containing silicon oxide according to claim 4. [Claim 9] A water treatment process to obtain water-treated silicon by bringing silicon into contact with water and then drying it, The water-treated silicon is heated under reduced pressure together with silicon dioxide and an oxide of at least one metal selected from Li, Na, K, Mg, and Ca to generate a gas in a reduced-pressure heating step. A condensation step to obtain a solid by condensing the aforementioned gas. Equipped with, The heating temperature in the aforementioned reduced-pressure heating process is T Ｒ It is said that the melting point of silicon is T Ａ It is determined that the lowest melting point among the melting points of silicon dioxide and the metal oxide is T ＢＬ It is determined that the highest melting point among the melting points of silicon dioxide and the metal oxide is T ＢＨ When this is the case, T Ａ <T ＢＬ If this is true, T Ａ <T Ｒ <T ＢＬ T Ｒ Set, T ＢＬ <T Ａ <T ＢＨ If this is true, T ＢＬ <T Ｒ <T Ａ T Ｒ Set, T ＢＨ <T Ａ If this is true, T ＢＨ <T Ｒ <T Ａ T Ｒ Set The aforementioned solid is M ｘ SiO ｙ (However, in the composition formula, M is at least one metallic element selected from Li, Na, K, Mg, and Ca, y is in the range of greater than 0.5 and less than 1.5, x / y is in the range of greater than or equal to 0 and less than 1, and x is greater than 0.) The silicon oxide containing metallic elements has a composition represented by the formula, and the concentration of aluminum as an impurity is 150 ppm or less by mass, the concentration of iron is less than 100 ppm, and the concentration of copper is less than 100 ppm. A method for producing silicon oxide containing metal elements. [Claim 10] A granulation step to obtain granules by granulating a mixture containing silicon, silicon dioxide, and an oxide of at least one metal selected from Li, Na, K, Mg, and Ca using water, A reduced-pressure heating step is performed to heat the granular material under reduced pressure to generate gas from the granular material. A condensation step to obtain a solid by condensing the aforementioned gas. Equipped with, The heating temperature in the reduced-pressure heating step is T Ｒ and the melting point of the silicon is T Ａ and the lowest melting point among the melting points of the silicon dioxide and the metal oxide is T ＢＬ and the highest melting point among the melting points of the silicon dioxide and the metal oxide is T ＢＨ When it is set as such, if T Ａ <T ＢＬ is satisfied, T Ａ <T Ｒ <T ＢＬ is satisfied by setting T Ｒ ; if T ＢＬ <T Ａ <T ＢＨ is satisfied, T ＢＬ <T Ｒ <T Ａ is satisfied by setting T Ｒ ; if T ＢＨ <T Ａ is satisfied, T ＢＨ <T Ｒ <T Ａ is satisfied by setting T Ｒ ; The aforementioned solid is M ｘ SiO ｙ (However, in the composition formula, M is at least one metallic element selected from Li, Na, K, Mg, and Ca, y is in the range of greater than 0.5 and less than 1.5, x / y is in the range of greater than or equal to 0 and less than 1, and x is greater than 0.) The silicon oxide containing metallic elements has a composition represented by the formula, and the concentration of aluminum as an impurity is 150 ppm or less by mass, the concentration of iron is less than 100 ppm, and the concentration of copper is less than 100 ppm. A method for producing silicon oxide containing metal elements. [Claim 11] A step of adding silicon, silicon dioxide, and an oxide of at least one metal selected from Li, Na, K, Mg, and Ca to a heat-resistant container such that the elemental ratio O / Si during the reaction is greater than 1 and less than 1.5, A reduced-pressure heating step is performed in which the compound placed in the heat-resistant container is heated under reduced pressure to generate gas from the compound. A condensation step to obtain a solid by condensing the aforementioned gas. Equipped with, The heating temperature in the aforementioned reduced-pressure heating process is T Ｒ It is said that the melting point of silicon is T Ａ It is determined that the lowest melting point among the melting points of silicon dioxide and the metal oxide is T ＢＬ It is determined that the highest melting point among the melting points of silicon dioxide and the metal oxide is T ＢＨ When this is the case, T Ａ <T ＢＬ If this is true, T Ａ <T Ｒ <T ＢＬ T Ｒ Set, T ＢＬ <T Ａ <T ＢＨ If this is true, T ＢＬ <T Ｒ <T Ａ T Ｒ Set, T ＢＨ <T Ａ If this is true, T ＢＨ <T Ｒ <T Ａ T Ｒ Set The aforementioned solid is M ｘ SiO ｙ (However, in the composition formula, M is at least one metallic element selected from Li, Na, K, Mg, and Ca, y is in the range of greater than 0.5 and less than 1.5, x / y is in the range of greater than or equal to 0 and less than 1, and x is greater than 0.) The silicon oxide containing metallic elements has a composition represented by the formula, and the concentration of aluminum as an impurity is 150 ppm or less by mass, the concentration of iron is less than 100 ppm, and the concentration of copper is less than 100 ppm. A method for producing silicon oxide containing metal elements.

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