JP5892364B2 - Method for producing oxide material - Google Patents

Description

  The present invention relates to a method for producing an oxide material, and more particularly to a method for producing an oxide material suitable as a negative electrode material for an electricity storage device such as a lithium ion secondary battery or a lithium ion capacitor.

  In recent years, with the widespread use of portable personal computers and mobile phones, there is an increasing demand for higher capacity and smaller size of power storage devices. If the capacity of the electricity storage device is increased, it will be easy to reduce the size of the battery material. Therefore, there is an urgent need to develop an electrode material for the electricity storage device with a higher capacity.

For example, high potential type LiCoO ₂ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ (0 <x <1), LiMn ₂ O _4, etc. are widely used as positive electrode materials for lithium ion secondary batteries. . On the other hand, a carbon material is generally used as the negative electrode material. These materials function as an electrode active material that reversibly occludes and releases lithium ions by charging and discharging, and constitute a so-called rocking chair type secondary battery that is electrochemically connected by a non-aqueous electrolyte or a solid electrolyte. .

  Examples of the carbon material used as the negative electrode material include graphitic carbon material, pitch coke, fibrous carbon, and high-capacity soft carbon fired at a low temperature. However, since the carbon material has a relatively small lithium storage capacity, there is a problem that the capacity is low. Specifically, even if a stoichiometric amount of lithium storage capacity can be realized, the capacity of the carbon material is limited to about 372 mAh / g.

  As a negative electrode material capable of inserting and extracting lithium ions and having a high capacity density exceeding that of a carbon-based material, Patent Document 1 discloses an amorphous oxide mainly composed of tin oxide. By using the amorphous oxide, volume change associated with insertion and extraction of lithium ions can be reduced, and a non-aqueous secondary battery excellent in charge / discharge cycle can be manufactured.

Japanese Patent No. 3498380

  In the manufacturing process of the negative electrode material described in Patent Document 1, diphosphorus pentoxide is used as a raw material. Since diphosphorus pentoxide is very hygroscopic, equipment for maintaining an atmosphere with a low dew point is necessary to produce a negative electrode material having a desired composition, resulting in high costs. Patent Document 1 also describes a method using a composite oxide such as stannous pyrophosphate as a raw material in addition to diphosphorus pentoxide. However, since stannous pyrophosphate is expensive, as a result In addition, the product cost has increased.

Orthophosphoric acid (H ₃ PO ₄ ) is also used as a relatively stable and inexpensive phosphoric acid raw material. However, orthophosphoric acid undergoes the following reaction with stannous oxide (SnO) rapidly in the raw material preparation process, generates excessive heat (for example, 200 ° C. or higher), and the raw material batch is cured, resulting in a heterogeneous bulky solid. There is a problem of becoming. As a result, not only is it difficult to obtain a homogeneous raw material batch, but also the resulting oxide material (negative electrode material) has striae or phase separation, or unwanted dissimilar crystals (for example, Sn ₂ P ₂ O ₇ or SnO ₂ ) may be precipitated.

SnO + H ₃ PO ₄ → SnHPO ₄ + H ₂ O + ΔH (1)

In view of the above, the present invention provides a method for producing an oxide material containing SnO and P ₂ O _5, and capable of producing a homogeneous oxide material having a desired composition at low cost. The purpose is to provide.

The present invention is a method for producing an oxide material containing SnO and P ₂ O ₅ and includes a step of mixing a phosphoric acid aqueous solution and SnO powder to produce a raw material batch, and a step of melting the raw material batch The present invention relates to a manufacturing method.

When an oxide material containing SnO and P ₂ O ₅ is manufactured by a melting method, when stannous oxide and phosphoric acid (for example, orthophosphoric acid) are directly mixed as raw materials, excessive heat is generated as described above. Or the raw material batch becomes agglomerated. Accordingly, the present inventors have found that the above problem can be solved by using phosphoric acid as a raw material instead of directly as a raw material. Specifically, by preparing a raw material batch by mixing an aqueous phosphoric acid solution and SnO powder, a uniform slurry-like raw material batch is prepared while suppressing excessive heat generation due to the reaction between phosphoric acid and SnO. By melting the raw material batch, it is possible to produce an oxide material having almost no defects such as striae, phase separation, or different crystals.

  2ndly, in the manufacturing method of the oxide material of this invention, it is preferable that the density | concentration of phosphoric acid aqueous solution is 10-70 mass%.

  According to the said structure, reaction of the said Formula (1) advances slowly, can suppress heat_generation | fever and agglomeration of a raw material batch effectively, and it becomes easy to obtain a homogeneous raw material batch. In the present invention, the concentration of the phosphoric acid aqueous solution refers to a concentration converted as orthophosphoric acid.

  Third, in the method for producing an oxide material of the present invention, it is preferable that phosphoric acid is orthophosphoric acid.

  Since orthophosphoric acid is relatively stable, it is easy to handle and an oxide material having a desired composition is easily obtained. Moreover, since it is cheap, raw material cost can be reduced.

  Fourth, in the method for producing an oxide material of the present invention, it is preferable to melt the raw material batch after drying it.

  According to this configuration, it is possible not only to easily feed the raw material batch into the melting furnace, but also to suppress composition deviation of the oxide material due to separation or sedimentation of the solid raw material in the raw material batch. Furthermore, it is possible not only to avoid dangers such as rapid water evaporation and steam explosion when the raw material batch is put into the melting furnace, but also to suppress the scattering of the raw material batch.

  Fifth, in the method for producing an oxide material of the present invention, the atmosphere for melting the raw material batch is preferably a reducing atmosphere or an inert atmosphere.

Since Sn is more stable when it is tetravalent than when it is divalent, SnO in the oxide material is easily oxidized in the melting step, and unwanted foreign crystals (for example, SnO ₂ and SnP ₂ O _7). ) Tends to precipitate. Therefore, by setting the atmosphere for melting the raw material batch to a reducing atmosphere or an inert atmosphere, it is possible to suppress the oxidation of SnO and the precipitation of the heterogeneous crystals.

Sixth, in the method for producing an oxide material of the present invention, the oxide material preferably contains SnO 45 to 95% and P ₂ O _{5 5 to} 55% in terms of a composition.

  Seventh, the present invention relates to an oxide material manufactured by any one of the methods described above.

Eighth, the present invention relates to an oxide material containing SnO and P ₂ O ₅ and having a β-OH value of 0.1 to 1.7 / mm.

  The “β-OH value” is an index indicating the amount of water in the composition, and can be represented by the following formula.

β-OH value = (1 / X) log ₁₀ (T1 / T2)
X: Sample thickness (mm)
T1: Transmittance (%) at a reference wavelength of 3846 cm ⁻¹ (= 2600 nm)
T2: Minimum transmittance (%) in the vicinity of a hydroxyl group absorption wavelength of 3000 to 3400 cm ⁻¹ (= 3333 to 2941 nm)

According to the investigation by the present inventors, when an oxide material is produced by the above production method, a homogeneous phosphate containing crystal water (for example, SnHPO ₄ ) is obtained as a raw material by the reaction between an aqueous phosphoric acid solution and SnO powder. It was found that the β-OH value in the resulting oxide material becomes a certain value or more because it is generated in the batch, and water is supplied from the crystal water in addition to the water in the raw material batch at the time of melting. .

  On the other hand, it was confirmed that the higher the β-OH value of the oxide material, the higher the tendency of SnO in the molten glass to be oxidized, and the amount of precipitation of the aforementioned different crystals increased. From this result, it was found that the generation of heterogeneous crystals can be effectively suppressed if the oxide material is produced so as to have a β-OH value of a certain value or less.

According to the present invention, an oxide material having a desired composition containing SnO and P ₂ O ₅ can be produced uniformly and inexpensively.

4 is a graph showing the results of a cycle test of test batteries produced in Example 1 and Comparative Example 1.

The present invention is a method for producing an oxide material containing SnO and P ₂ O ₅ , and includes a step of preparing a raw material batch by mixing an aqueous phosphoric acid solution and SnO powder, and a step of melting the raw material batch It is characterized by.

An oxide material containing SnO and P ₂ O ₅ plays a role as a negative electrode active material having a high capacity and excellent cycle characteristics in a power storage device such as a non-aqueous secondary battery. When a negative electrode active material containing SnO is used, it is known that the following reaction occurs in the negative electrode during charge and discharge.

SnO + 2Li ⁺ + 2e ⁻ → Sn + Li ₂ O (2)
Sn + yLi ⁺ + ye ⁻ ← → Li _y Sn (3)

First, during the first charge, a reaction in which SnO accepts electrons and metal Sn is generated occurs irreversibly (formula (2)). Subsequently, the produced metal Sn combines with lithium ions that have moved from the positive electrode through the electrolyte and electrons supplied from the circuit, and a reaction occurs to form a Li _y Sn alloy (formula (3)). As Li _y Sn alloys, Li _2.6 Sn, Li _3.5 Sn, Li _4.4 Sn, and the like are known. The reaction occurs as a reversible reaction that proceeds rightward during charging and proceeds leftward during discharging. Thereafter, the charge / discharge reaction of the formula (3) is repeatedly performed.

Here, the charge / discharge reaction of formula (3) involves a volume change, but when an oxide material containing SnO and P ₂ O ₅ is used as the negative electrode active material, Sn ^{x +} ions in the oxide material are phosphoric acid. Since it exists in the state included in the network, the volume change of Sn accompanying charging / discharging can be relieved with the said phosphate network. Therefore, it is possible to suppress a decrease in cycle characteristics.

As a specific example of the oxide material containing SnO and P ₂ O ₅ , it is preferable that the composition contains mol% and contains SnO 45 to 95% and P ₂ O _{5 5 to} 55%. The reason for limiting the composition in this way will be described below. In the description of the composition below, “%” means “mol%” unless otherwise specified.

SnO in the oxide material is an active material component that becomes a site for occluding and releasing lithium ions. The SnO content is preferably 45 to 95%, 50 to 90%, 55 to 87%, 60 to 85%, 68 to 83%, particularly 71 to 82%. When the content of SnO is too small, the charge / discharge capacity per unit mass of the oxide material becomes small, and as a result, the charge / discharge capacity of the negative electrode active material also becomes small. On the other hand, if the content of SnO is too large, the amorphous component in the oxide material decreases, so that the volume change associated with insertion and extraction of lithium ions during repeated charge and discharge cannot be alleviated, and the discharge capacity increases rapidly. May decrease. Incidentally, SnO ingredient content in the present invention, the tin oxide component other than SnO (SnO _2, etc.) also refers to that summed in terms of SnO.

P ₂ O ₅ is a network-forming oxide and includes lithium ion storage and release sites in Sn atoms, and functions as a solid electrolyte to which lithium ions can move. The content of P ₂ O ₅ is preferably ₅ to 55%, 10 to 50%, 13 to 45%, 15 to 40%, 17 to 32%, particularly 18 to 29%. If the content of P ₂ O ₅ is too small, the volume change of Sn atoms accompanying the insertion and extraction of lithium ions during charge / discharge cannot be alleviated, resulting in structural deterioration, and the discharge capacity tends to decrease during repeated charge / discharge. . On the other hand, when the content of P ₂ O ₅ is too large, the water resistance tends to lower. Further, by absorbing moisture, a large amount of heterogeneous crystals (for example, SnHPO ₄ ) are formed, and the capacity is likely to decrease when repeatedly charged and discharged. Further, it is easy to form a stable crystal (for example, SnP ₂ O ₇ ) together with the Sn atom, and the influence of the coordinate bond to the Sn atom by the lone electron pair of the oxygen atom in the chain P ₂ O ₅ becomes stronger. . For this reason, many electrons are required to reduce Sn ions in the initial charge reaction, and the initial charge / discharge efficiency tends to decrease.

Incidentally, SnO _/ P 2 _{O 5} (molar ratio), 0.8～19,1～18, particularly preferably from 1.2 to 17. When SnO / P ₂ O ₅ is too small, Sn atoms in SnO are easily affected by the coordination of P ₂ O ₅ , and the initial charge / discharge efficiency tends to decrease. On the other hand, if SnO / P ₂ O ₅ is too large, the discharge capacity tends to decrease when charging and discharging are repeated. This is because P ₂ O ₅ coordinated to the Sn atom in the oxide is reduced and the Sn atom cannot be sufficiently covered, and as a result, the volume change of the Sn atom due to insertion and extraction of lithium ions cannot be relaxed. This is considered to cause structural deterioration.

In addition to the above components, various components can be further added to the oxide material. For example, CuO, ZnO, B ₂ O ₃ , MgO, CaO, Al ₂ O ₃ , SiO ₂ , R ₂ O (R represents Li, Na, K, or Cs) in a total amount of 0 to 20%, 0 to It can contain 10%, especially 0.1-7%. When these components increase, the structure becomes disordered and an amorphous material is easily obtained, but the phosphate network is easily cut. As a result, the volume change of the negative electrode active material accompanying charge / discharge cannot be relaxed, and the cycle characteristics may be deteriorated.

  The oxide material is preferably amorphous. In this case, the crystallinity of the oxide material is preferably 95% or less, 80% or less, 70% or less, 50% or less, 40% or less, particularly 20% or less, and is substantially amorphous. Is most preferred. The smaller the degree of crystallinity (the greater the proportion of the amorphous phase), the more the volume change during repeated charging / discharging can be alleviated, which is advantageous from the viewpoint of suppressing the decrease in discharge capacity. Note that “substantially amorphous” means that the crystallinity is substantially 0% (specifically, less than 0.1%). Specifically, the following CuKα ray In a powder X-ray diffraction measurement using, a crystal diffraction line is not detected.

  The degree of crystallinity is obtained from a diffraction line profile of 10 to 60 degrees as a 2θ value obtained by powder X-ray diffraction measurement using CuKα rays. Specifically, the integrated intensity obtained by peak-separating a broad diffraction line (amorphous halo) at 10 to 60 ° from the total scattering curve obtained by subtracting the background from the diffraction line profile is Ia, 10 When the total integrated intensity obtained by peak separation of each crystalline diffraction line detected at ˜60 ° is Ic, the crystallinity Xc can be obtained from the following equation.

    Xc = [Ic / (Ic + Ia)] × 100 (%)

  Hereinafter, the method will be specifically described for each step of the production method of the present invention.

The concentration of the phosphoric acid aqueous solution is preferably 10 to 70% by mass, 12 to 60% by mass, and particularly preferably 15 to 50% by mass. If the concentration of the phosphoric acid aqueous solution is too low, phosphoric acid and SnO are less likely to come into contact with each other in the raw material batch, and unreacted phosphoric acid remains, so that segregation is likely to occur with the powder raw material and reaction product powder (for example, SnHPO ₄ ). The resulting oxide material tends to be heterogeneous. On the other hand, when the concentration of the phosphoric acid aqueous solution is too high, it is difficult to uniformly mix the raw materials. Moreover, the heat generation in the reaction of the above formula (1) cannot be alleviated, the water is evaporated and the powder raw material tends to be in a state of spattering, and the resulting oxide material tends to be inhomogeneous.

It is not particularly limited as phosphoric acid, for example, orthophosphoric acid _(H 3 _PO 4), pyrophosphoric acid _{(H 4 P 2 O 7)} , tripolyphosphate _{(H 5 P 3 O 10)} , metaphosphoric acid _{((HPO 3) n)} Etc. can be used.

  After mixing phosphoric acid aqueous solution and SnO powder, it is preferable to make it dry, for example to make a powdery raw material batch. The drying temperature is not particularly limited as long as moisture sufficiently evaporates. For example, the drying temperature may be appropriately adjusted within the range of 50 to 250 ° C, 80 to 200 ° C, and particularly 100 to 180 ° C. The atmosphere during drying is not particularly limited, but a reducing atmosphere or an inert atmosphere is preferable in order to suppress oxidation of the raw material batch (particularly SnO).

In order to obtain a reducing atmosphere, for example, a mixed gas of nitrogen and hydrogen is used. Specifically, it is preferable to use a mixed gas of N ₂ 90 to 99.5% and H ₂ 0.5 to 10%, particularly N ₂ 92 to 99% and H ₂ 1 to 8% in volume%. .

  As the inert atmosphere, it is preferable to use any of nitrogen, argon, and helium.

  Moreover, you may improve a homogeneity by grind | pulverizing the said raw material batch. For the pulverization, a general pulverizer such as a mortar, a rake machine, a ball mill, a vibration ball mill, a satellite ball mill, a planetary ball mill, a jet mill or the like can be used, and either a wet or dry method may be used.

  The average particle diameter of the raw material batch obtained by the present invention is preferably 2 to 500 μm, 5 to 300 μm, 10 to 250 μm, particularly 20 to 150 μm. If the average particle size of the raw material batch is too small, the fluidity is lowered and problems such as clogging of the raw material batch inlet of the melting apparatus are likely to occur. Moreover, when it puts in a melting furnace, it exists in the tendency for a raw material batch to scatter. As a result, variation in input amount not only makes stable production difficult, but also tends to cause a composition shift of the obtained oxide material. On the other hand, if the average particle size of the raw material batch is too large, undissolved material is likely to be generated during melting, and the resulting oxide material tends to be heterogeneous.

  In the present invention, the average particle diameter is a median diameter of primary particles and indicates D50 (50% volume cumulative diameter), which is a value measured by a laser diffraction particle size distribution analyzer (SALD-2000 series, manufactured by Shimadzu Corporation). .

  Next, the raw material batch is heated and melted to be vitrified. Here, the melting atmosphere at the time of melting is preferably performed in a reducing atmosphere or an inert atmosphere for the reasons described above. When melting in a reducing atmosphere or an inert atmosphere, it is preferable to supply any of the aforementioned gases into the melting furnace. The reducing gas or the inert gas may be supplied to the upper atmosphere of the molten glass in a melting furnace, may be directly supplied into the molten glass from a bubbling nozzle, or both methods may be performed simultaneously.

  The raw material batch may contain metal powder or carbon powder. Thereby, the oxidation of SnO in the molten glass can be suppressed. As the metal powder, any one of Sn, Al, Si, and Ti is preferably used. Among these, it is preferable to use Sn, Al, and Si powders.

  Thereafter, the molten glass is formed into a desired shape to obtain an oxide material. The shape of the oxide material is not particularly limited, and examples thereof include a bulk shape, a film shape, and a powder shape.

  For the reasons already described, the β-OH value of the oxide material obtained by the production method of the present invention is a certain value or more. Specifically, the oxide material of the present invention has a β-OH value of, for example, 0.1 / mm or more, particularly 0.2 / mm or more. On the other hand, if the β-OH value of the oxide material is too large, SnO in the molten glass is likely to be oxidized, and unwanted foreign crystals tend to increase. Therefore, the β-OH value of the oxide material is preferably 1.7 / mm or less, 1.6 / mm or less, and particularly preferably 1.5 / mm or less.

  The β-OH value of the oxide material can be controlled (particularly reduced) by supplying a reducing gas or an inert gas into the molten atmosphere. In particular, the β-OH value of the oxide material can be more effectively reduced by supplying the gas directly from the bubbling nozzle into the molten glass. Also, the β-OH value of the oxide material can be reduced by reducing the amount of water in the raw material batch (increasing the phosphoric acid aqueous solution concentration).

  As mentioned above, although the example which mainly applied the oxide material to the use of the negative electrode active material for lithium ion secondary batteries has been demonstrated, this invention is not limited to this, The negative electrode of another non-aqueous secondary battery The present invention can also be applied to an active material or a negative electrode active material used in a hybrid capacitor in which a negative electrode material for a lithium ion secondary battery and a positive electrode material for a non-aqueous electric double layer capacitor are combined.

  Hereinafter, although the manufacturing method of the oxide material of this invention is described about the Example applied to the use of the negative electrode material for non-aqueous secondary batteries, this invention is not limited to these Examples.

(1) Preparation of Oxide Material (Negative Electrode Active Material) Powdered stannous oxide (Japan) is used so that the composition of the oxide material is mol%, SnO 72%, P ₂ O ₅ 28%. Chemical industry SnO) and liquid orthophosphoric acid (Lhasa Industries strong phosphoric acid, H ₃ PO ₄ concentration 105 mass%) were weighed. Next, the amount of water was weighed so as to have the concentration shown in Table 1, and the weighed orthophosphoric acid was slowly added to prepare an aqueous phosphoric acid solution. Stannous oxide powder was added to the phosphoric acid aqueous solution and mixed to prepare a raw material batch. Examples 4 to 6 were dried in the atmosphere under the conditions shown in Table 1 to obtain powdery raw material batches.

  In Comparative Example 1, stannous oxide powder and orthophosphoric acid were weighed so as to have the composition described above, and the raw material batch was prepared by adding and mixing stannous oxide powder to orthophosphoric acid.

  The raw material batch was put into a quartz crucible and melted at 950 ° C. for 40 minutes in a nitrogen atmosphere using an electric furnace to be vitrified.

  Next, the molten glass was poured out between a pair of rotating rollers and formed into a film having a thickness of 0.1 to 2 mm while rapidly cooling. The film-shaped molded body was pulverized with a ball mill and then classified with an air classifier to obtain a glass powder (oxide material) having an average particle diameter of 2 μm.

The structure was identified by powder X-ray diffraction measurement for each sample. The oxide materials of Examples 1 to 6 were amorphous, and no crystals were detected. The oxide material of Comparative Example 1 was confirmed to have SnO ₂ and Sn ₂ P ₂ O ₇ crystal precipitation. The degree of crystallinity was 21%.

(2) Evaluation of battery characteristics Hereinafter, test batteries were prepared using the oxide materials (negative electrode active materials) prepared in Example 1 and Comparative Example 1, and the battery characteristics were evaluated.

(2-a) Production of Negative Electrode Weighing of glass powder with polyimide resin as binder and ketjen black as conductive substance so that glass powder: binder: conductive substance = 85: 10: 5 (mass ratio). These were dispersed in N-methylpyrrolidone (NMP), and then sufficiently stirred with a rotation / revolution mixer to form a slurry. Next, using a doctor blade with a gap of 150 μm, the obtained slurry was coated on a copper foil having a thickness of 20 μm as a negative electrode current collector, dried at 70 ° C. with a dryer, and then between a pair of rotating rollers. An electrode sheet was obtained by pressing through a sheet. The electrode sheet was punched to a diameter of 11 mm with an electrode punching machine and imidized at 300 ° C. for 1 hour while reducing the pressure to obtain a circular working electrode.

(2-b) Production of test battery A polypropylene porous membrane having a diameter of 16 mm, which was placed on the lower lid of a coin cell with the above working electrode facing the copper foil surface and dried under reduced pressure at 60 ° C. for 8 hours ( A test battery was manufactured by laminating a separator made of Hoechst Celanese Co., Ltd. Celgard # 2400) and metallic lithium as a counter electrode. As the electrolytic solution, 1M LiPF ₆ solution / EC (ethylene carbonate): DEC (diethyl carbonate) = 1: 1 was used. The test battery was assembled in an environment with a dew point temperature of −40 ° C. or lower.

(2-c) Charge / Discharge Test Charge (occlusion of lithium ions into the negative electrode material) was charged from 2 V to 0 V with a constant current of 0.1 C. Next, discharge (release of lithium ions from the negative electrode material) was performed from 0 V to 2 V with a constant current of 0.1 C. This charge / discharge cycle was repeated. The discharge capacity (mAh / g) was determined from the amount of electricity discharged from the oxide material per unit mass.

  Table 2 and FIG. 1 show the results of the initial discharge capacity when the charge / discharge test was performed for each sample and the cycle characteristics when the sample was repeatedly charged / discharged.

  As apparent from Table 2 and FIG. 1, the initial discharge capacity of the battery using the oxide material of Example 1 was 705 mAh / g, and the discharge capacity at the 80th cycle was as good as 511 mAh / g. On the other hand, the battery using the oxide material of Comparative Example 1 had an initial discharge capacity of 700 mAh / g, but the discharge capacity at the 80th cycle was significantly reduced to 261 mAh / g.

  The oxide material obtained by the production method of the present invention is used as a sealing material for wavelength conversion members that are components of light emitting devices such as white LEDs and various electronic components, in addition to the negative electrode active material for power storage devices. Is also possible.

Claims (6)

In mole percent composition containing SnO 45 to 95% and _P 2 _O 5 5 to 55%, a process for the preparation of an oxide material that is used in the negative electrode material for a power storage device, an aqueous solution of phosphoric acid and SnO powder The manufacturing method characterized by including the process of mixing and producing a raw material batch, and the process of fuse | melting a raw material batch.   The method for producing an oxide material according to claim 1, wherein the concentration of the phosphoric acid aqueous solution is 10 to 70 mass%.   The method for producing an oxide material according to claim 1, wherein the phosphoric acid is orthophosphoric acid.   The method for producing an oxide material according to claim 1, wherein the raw material batch is melted after being dried.   The method for producing an oxide material according to any one of claims 1 to 4, wherein the atmosphere for melting the raw material batch is a reducing atmosphere or an inert atmosphere. In mole percent composition containing SnO 45 to 95% and _{P 2 O 5 5~55%, β} -OH value is 0.1 to 1.7 / mm der is, is used in the negative electrode material for a power storage device An oxide material characterized by that.