JP7189006B2 - Method for producing NASICON-type oxide particles for solid electrolyte of lithium-ion secondary battery - Google Patents

Description

The present invention relates to a method for producing NASICON-type oxide particles for use in all-solid-state lithium-ion secondary batteries.

Lithium-ion secondary batteries currently in practical use use flammable organic solvents in the electrolyte, so it is necessary to take sufficient safety measures against leaks and fires. It is also highly difficult to convert. However, an all-solid-state lithium-ion secondary battery with an oxide-based or sulfide-based solid electrolyte has a high energy density and can be manufactured without using combustibles, so safety measures must be taken. The burden is reduced, and manufacturing costs and productivity can be easily increased. For these reasons, various developments are being actively carried out on solid electrolyte materials, which are expected to be highly useful.

Among them, a lithium phosphate-based composite oxide having a NASICON-type crystal structure represented by the general formula Li _1+x M ₂ (PO ₄ ) ₃ (hereinafter referred to as “NASICON-type oxide”) is a chemical In addition to being an oxide-based solid electrolyte with excellent thermal stability, it also has excellent characteristics of exhibiting lithium ion conductivity as high as 10 ^-4 S/cm at room temperature, and is highly expected. It is one of the solid electrolyte materials. For such a NASICON-type oxide, it is important to achieve high purity and fine particle size. A method for obtaining lithium ion conductive solid electrolyte particles represented by small Li1 _{+ xMxTi2 -x (} PO4) ₃ is disclosed.

JP 2017-216062 A

However, in the NASICON-type oxide particles obtained by the production method described in the above-mentioned patent document, defects are induced in the crystal structure of the NASICON-type oxide due to the pulverization treatment that must be performed for miniaturization. , may lead to a decrease in lithium ion conductivity.

Therefore, an object of the present invention is to achieve high purity and high crystallinity while appropriately miniaturizing NASICON-type oxide particles, thereby realizing excellent lithium ion conductivity. An object of the present invention is to provide a method for producing NASICON-type oxide particles useful as a solid electrolyte for secondary batteries.

As a result of various studies, the present inventors have found that by preparing a specific mixed solution and undergoing specific steps, NASICON-type oxide particles of high purity and high crystallinity can be obtained while achieving appropriate miniaturization. The present inventors have found that it is possible to achieve the present invention.

Accordingly, the present invention provides the following steps (Ix) to (IIIx):
(Ix) lithium compounds, phosphate compounds and metal (M) compounds (M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr A step (IIx ) After subjecting the obtained mixture to a hydrothermal reaction at 100 ° C. or higher, the hydrothermal reaction product is washed and then dried to obtain a precursor mixture. Provided is a method for producing NASICON-type oxide particles for a solid electrolyte of a lithium-ion secondary battery, comprising a step of firing at 0° C. to 1000° C.

The present invention also provides the following steps (Iy) to (IIIy):
(Iy) lithium compounds, phosphate compounds and metal (M) compounds (M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr , Ge, Nd, Sr, Sn, Hf, V or Zr) with water to prepare a mixed solution having a pH of 5 to 9 at 25 ° C. ( IIy) A step of subjecting the resulting mixture to a hydrothermal reaction at 100° C. or higher, washing the hydrothermal reaction product, then adding and mixing the rest of the raw material compounds and drying to obtain a precursor mixture. (IIIy) A method for producing NASICON-type oxide particles for a solid electrolyte of a lithium ion secondary battery, comprising a step of firing the obtained precursor mixture at 400°C to 1000°C.

According to the production method of the present invention, it is possible to obtain NASICON-type oxide particles having a high degree of crystallinity and a moderately fine particle size while effectively suppressing inclusion of impurities, which are used as a solid electrolyte. As a result, a lithium ion secondary battery with excellent charge/discharge characteristics can be realized.

1 is a SEM photograph of NASICON-type oxide particles obtained in Example 1. FIG. 1 is an X-ray diffraction pattern of NASICON-type oxide particles obtained in Example 1. FIG. 4 is a SEM photograph of NASICON-type oxide particles obtained in Example 2. FIG. 4 is a SEM photograph of NASICON-type oxide particles obtained in Example 3. FIG. 4 is a SEM photograph of NASICON-type oxide particles obtained in Example 4. FIG. 4 is a SEM photograph of NASICON-type oxide particles obtained in Example 5. FIG. 4 is a SEM photograph of NASICON-type oxide particles obtained in Example 6. FIG. 4 is a SEM photograph of NASICON-type oxide particles obtained in Comparative Example 1. FIG. 1 is an X-ray diffraction pattern of NASICON-type oxide particles obtained in Comparative Example 1. FIG.

The present invention will be described in detail below.
The method for producing NASICON-type oxide particles for a solid electrolyte of a lithium ion secondary battery of the present invention (hereinafter also simply referred to as "NASICON-type oxide particles") comprises the following steps (Ix) to (IIIx):
(Ix) lithium compounds, phosphate compounds and metal (M) compounds (M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr A step (IIx ) After subjecting the obtained mixture to a hydrothermal reaction at 100 ° C. or higher, the hydrothermal reaction product is washed and then dried to obtain a precursor mixture. C. to 1000.degree. C., which is referred to as production method (X) of the present invention.
Further, the production method of the present invention comprises the following steps (Iy) to (IIIy):
(Iy) lithium compounds, phosphate compounds and metal (M) compounds (M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr , Ge, Nd, Sr, Sn, Hf, V or Zr) with water to prepare a mixed solution having a pH of 5 to 9 at 25 ° C. ( IIy) A step of subjecting the resulting mixture to a hydrothermal reaction at 100° C. or higher, washing the hydrothermal reaction product, then adding and mixing the rest of the raw material compounds and drying to obtain a precursor mixture. (IIIy) A process comprising a step of firing the obtained precursor mixture at 400° C. to 1000° C. is referred to as production method (Y) of the present invention.

That is, the production method (X) of the present invention is a production method in which all of the raw material compounds are mixed together with water in step (Ix), while the production method (Y) of the present invention is the production method of the present invention. Unlike (X), this is a manufacturing method in which a part of the raw material compound is mixed with water in step (Iy), and the remainder is used in the subsequent step (IIy).
Each manufacturing method will be described below.

The step (Ix) provided in the production method (X) of the present invention comprises a lithium compound, a phosphoric acid compound and a metal (M) compound (M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, (In, Y, La, Zn, Si, Mn, Zr, Ge, Nd, Sr, Sn, Hf, V or Zr) are mixed with water, and the pH at 25° C. is It is a step of preparing a mixed solution (Ax) of 5 to 9. In this way, by using all of the raw material compounds for obtaining the NASICON-type oxide particles at once, and further using water to obtain a mixed solution (Ax) in which the pH is controlled within the above range, the step ( In the hydrothermal reaction product obtained by the hydrothermal reaction in IIx), the uniformity of the chemical composition can be enhanced, and at the same time, it can greatly contribute to the miniaturization and high crystallinity of the NASICON-type oxide particles.

Lithium compounds that can be used as one of the raw material compounds include one or more selected from hydroxides, chlorides, carbonates, sulfates, and organic acid salts. More specifically, for example, lithium hydroxide or its hydrate, lithium peroxide, lithium chloride, lithium carbonate, lithium sulfate, lithium acetate, lithium oxalate and the like can be preferably used.

Phosphoric acid compounds include orthophosphoric acid (H ₃ PO ₄ , phosphoric acid), metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid, ammonium phosphate, and ammonium hydrogen phosphate. Among them, it is preferable to use phosphoric acid from the viewpoint that it can also act as a pH adjuster for controlling the pH of the resulting mixed solution (Ax), and it is preferable to use it as an aqueous solution with a concentration of 70% by mass to 90% by mass. preferable.

Furthermore, a metal (M) compound is used as one of the raw material compounds. Here, M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr, Ge, Nd, Sr, Sn, Hf, V or It represents one or more selected from Zr. Such metal (M) compounds include compounds other than Ti compounds, such as halides, sulfates, organic acid salts, hydroxides, chlorides, sulfides, oxides, and hydrates thereof. Among them, one or more selected from sulfates, organic acid salts and hydroxides are preferable from the viewpoint of efficiently advancing the reaction in the mixed solution (Ax).

The raw material compound consists of three compounds, a lithium compound, a phosphoric acid compound and a metal (M) compound. In step (Ix), all of these raw material compounds are collectively used. On the other hand, in step (Iy) in production method (Y) of the present invention, which will be described later, part of these raw material compounds is used, and the remainder is used in step (IIy).
Therefore, in the step (Ix) in the production method (X) of the present invention, all of these raw material compounds are used, so in the subsequent step (IIx), all of these raw material compounds are subjected to a hydrothermal reaction as they are. It will happen.

Specifically, in the step (Ix), a mixed solution (ax-1) containing a lithium compound, a metal (M) compound and water and a mixed solution (ax-2) containing a phosphoric acid compound and water are prepared. After each preparation, these mixed liquids are mixed to prepare a mixed liquid (Ax). As a result, all of the raw material compounds and water are present in the resulting mixture (Ax), and the reaction product, which has a highly homogeneous chemical composition and is sufficiently small in diameter, that is, trilithium phosphate , the phosphate and/or hydroxide of the metal (M) is contained, and the NASICON-type oxide particles can be effectively made finer.

A mixed solution (ax-1) is prepared by mixing a lithium compound and a metal (M) compound with water. The total content of these lithium compounds and metal (M) compounds in the mixed solution (ax-1) is, from the viewpoint of enhancing the homogeneity of the chemical composition of the reaction product produced by mixing with the mixed solution (ax-2), It is preferably 1 part by mass to 50 parts by mass, more preferably 5 parts by mass to 30 parts by mass, and still more preferably 5 parts by mass to 20 parts by mass with respect to 100 parts by mass of water in the mixture (ax-1). Department.

Further, in preparing the mixed solution (ax-1), the mixing ratio of the lithium compound and the metal (M) compound, in terms of molar ratio (Li:M), is preferably 1:2 to 2:1, more preferably. is 1:1.9 to 1:1.2, more preferably 1:1.8 to 1:1.3.

The pH of the mixed solution (ax-1) at 25°C is preferably 12 to 14, more preferably 12.5, from the viewpoint of adjusting the pH of the resulting mixed solution (Ax) to 5 to 9 at 25°C. ~14, more preferably 13-14. A pH adjuster may be used to adjust the pH of the mixture (ax-1) to the above range. Such a pH adjuster is not particularly limited, but from the viewpoint of easily adjusting the pH of the mixture (ax-1), water such as lithium hydroxide, sodium hydroxide, potassium hydroxide or ammonium hydroxide Preference is given to using oxides.

The liquid mixture (ax-1) may be stirred in advance before being mixed with the liquid mixture (ax-2) from the viewpoint of dispersing each component more uniformly. The time for stirring the mixture (ax-1) is preferably 5 minutes to 3 hours, more preferably 10 minutes to 2 hours, still more preferably 15 minutes to 90 minutes. The stirring speed is preferably 10 cm/sec to 200 cm/sec, more preferably 15 cm/sec to 150 cm/sec, and still more preferably 20 cm/sec to 100 cm/sec.

A mixed solution (ax-2) is prepared by mixing a phosphoric acid compound and water. The content of the phosphoric acid compound in the mixed solution (ax-2) is preferably 3 parts by mass to 20 parts by mass, more preferably 5 parts by mass, relative to 100 parts by mass of water in the mixed solution (ax-2). parts to 15 parts by mass, more preferably 7 to 15 parts by mass.

The liquid mixture (ax-2) may be stirred in advance before being mixed with the liquid mixture (ax-1) from the viewpoint of dissolving or dispersing each component more uniformly. The time for stirring the mixture (ax-2) is preferably 1 minute to 30 minutes, more preferably 2 minutes to 20 minutes, still more preferably 2 minutes to 10 minutes. The stirring speed is preferably 10 cm/sec to 200 cm/sec, more preferably 15 cm/sec to 150 cm/sec, and still more preferably in terms of the flow speed of the mixed solution (ax-2) on the inner wall surface of the reaction vessel. is between 20 cm/sec and 100 cm/sec.

Next, in step (Ix), the mixed solution (ax-1) and the mixed solution (ax-2) are mixed to obtain a mixed solution (Ax). The method of mixing the mixed solution (ax-1) and the mixed solution (ax-2) is not particularly limited, but the mixed solution (ax-2) is added dropwise to the mixed solution (ax-1) being stirred. preferably. Thus, by adding dropwise the mixed solution (ax-2) containing the phosphoric acid compound to the mixed solution (ax-1) containing the lithium compound and the metal (M) compound little by little, all of the raw material compounds and The homogeneity of the chemical composition of the reaction product can be further enhanced while containing water.
At this time, the rate of dropping the mixed liquid (ax-2) into the mixed liquid (ax-1) is preferably 0.1 part by mass/min to 0.1 part by mass/min with respect to 10 parts by mass of the mixed liquid (ax-1). It is 4 parts/minute, more preferably 0.15 parts/minute to 0.4 parts/minute, still more preferably 0.2 parts/minute to 0.35 parts/minute. The stirring speed of the mixed solution (ax-1) when the mixed solution (ax-2) is added dropwise is preferably 10 cm/sec or more in terms of the flow speed of the mixed solution (ax-1) on the inner wall surface of the reaction vessel. 200 cm/sec, more preferably 15 cm/sec to 150 cm/sec, and even more preferably 20 cm/sec to 100 cm/sec.

In obtaining the mixed solution (Ax), the mass ratio ((ax-1):(ax-2)) of the mixed solution (ax-1) and the mixed solution (ax-2) to be mixed is preferably 20:1. ~1:4, more preferably 10:1 to 1:3, still more preferably 5:1 to 2:3.

The temperature of the mixture (ax-1) when mixing the mixture (ax-1) and the mixture (ax-2) is preferably 10°C to 80°C, more preferably 15°C to 70°C. and more preferably 20°C to 60°C. The temperature of the mixed liquid (ax-2) is preferably 10°C to 80°C, more preferably 15°C to 70°C, still more preferably 20°C to 60°C.

The time for mixing the mixture (ax-1) and the mixture (ax-2) is preferably 10 minutes to 24 hours, more preferably 15 minutes to 18 hours, still more preferably 30 minutes to 12 hours. is. Further, at this time, stirring may be performed from the viewpoint of dissolving or dispersing each component more uniformly and improving the homogeneity of the chemical composition of the reaction product. The stirring speed is preferably 10 cm/sec to 200 cm/sec, more preferably 15 cm/sec to 150 cm/sec, still more preferably 20 cm/sec, in terms of the flow speed of the mixed solution (Ax) on the inner wall surface of the reaction vessel. sec to 100 cm/sec.

By mixing the mixed liquid (ax-1) and the mixed liquid (ax-2), all the raw material compounds are mixed together, and lithium phosphate, metal (M) phosphate and / or water A mixture (Ax) containing oxides is obtained. These trilithium phosphate and metal (M) phosphate and/or hydroxide are fine particles having an average particle size of 100 nm or less, and are subjected to a hydrothermal reaction in step (II) described later. , yields well a precursor mixture (Bx) of NASICON-type oxide particles. The total content of the lithium phosphate and the metal (M) phosphate and hydroxide in the mixed solution (Ax) is preferably 0.5% by mass to 40% by mass in the mixed solution (Ax). , more preferably 1% by mass to 35% by mass, and still more preferably 1.5% by mass to 30% by mass. The pH of the mixture (Ax) at 25° C. is 5-9, preferably 5.5-8.5, more preferably 6-8. In adjusting the pH of the mixed solution (Ax) so that it falls within this range, the pH adjuster may be used as necessary.
In addition, it is confirmed by X-ray diffraction that these lithium phosphates and metal (M) phosphates and/or hydroxides are produced in the mixture (Ax) and contained as a mixture. be able to.

In the step (IIx), the mixture (Ax) obtained in the step (Ix) is subjected to a hydrothermal reaction at 100° C. or higher, then the hydrothermal reaction product is washed and then dried to obtain a precursor mixture ( Bx). The hydrothermal reaction in step (IIx) is carried out under pressure in a pressure vessel or the like in which a reaction vessel filled with a mixture (Ax) containing all of the raw material compounds and water is placed.

When the mixed solution (Ax) obtained in step (Ix) is stirred before proceeding to step (IIx), such stirring may be performed in a reaction vessel, and then the reaction vessel is placed in a pressure vessel or the like. It should be stored. From the viewpoint of efficiently producing a precursor mixture of NASICON-type oxide particles, such stirring is preferably continued until the hydrothermal reaction in step (IIx) is completed in a reaction vessel housed in a pressure vessel or the like. . At this time, the stirring speed of the mixed solution (Ax) is preferably 15 cm/sec or more, more preferably 15 cm/sec to 80 cm/sec in terms of the flow speed of the mixed solution (Ax) on the inner wall surface of the reaction vessel. and more preferably 15 cm/sec to 70 cm/sec. The stirring method is not particularly limited as long as this stirring speed is achievable. For example, a method using a stirring blade or a pump described in JP-A-2014-118328 is used to stir the slurry in the synthesis vessel. methods and the like can be suitably used.
Furthermore, when using the above stirring method, from the viewpoint of causing a hydrothermal reaction to occur uniformly in the entire mixed liquid (Ax), a baffle plate is installed in the reaction vessel, the rotation direction of the stirring blade, or the liquid feeding direction of the pump. is intermittently reversed to disturb the flow of the mixture (Ax).

The temperature (reaction temperature) of the mixed solution (Ax) during the hydrothermal reaction may be 100°C or higher, preferably 130°C to 250°C, more preferably 140°C to 230°C. At this time, the pressure and reaction time are preferably 0.3 MPa or more and 10 minutes or more when the reaction temperature is 100 ° C. or higher, and 0.3 MPa to 2 MPa and 10 minutes to 24 minutes when the reaction is performed at 130 ° C. to 250 ° C. When the reaction is carried out at 140° C. to 230° C., the pressure is preferably 0.4 MPa to 1.8 MPa for 10 minutes to 16 hours.

Moreover, the atmosphere in the reaction vessel in the hydrothermal reaction is not limited, but from the viewpoint of easiness of adjusting the atmosphere, it is preferably under air or under water vapor.

After subjecting the mixture (Ax) to the above hydrothermal reaction, the hydrothermal reaction product is washed and then dried. Such a hydrothermal reaction product can be obtained by solid-liquid separation of the mixed liquid (Ax) after the hydrothermal reaction, and the obtained hydrothermal reaction product is a phosphoric acid composite containing lithium and some metals (M) It contains a mixture of an oxide and a metal (M) hydroxide composed of a part of the metal (M) such as Al, ie, a precursor mixture (Bx) of NASICON-type oxide particles. Apparatuses used for solid-liquid separation include, for example, a filter press and a centrifugal filter. Among them, it is preferable to use a filter press from the viewpoint of obtaining a hydrothermal reaction product efficiently.

Next, the recovered hydrothermal reaction product is washed from the viewpoint of effectively removing water-soluble impurities such as anionic components derived from the raw materials. Water may be used for such washing, and the amount of water is preferably 5 parts by mass to 50 parts by mass, more preferably 7 parts by mass to 50 parts by mass, relative to 1 part by mass of the dry mass of the hydrothermal reaction product. parts by mass, more preferably 9 to 50 parts by mass. The temperature of such water is preferably 5° C. to 70° C., more preferably 20° C. to 70° C., from the viewpoint of effectively removing water-soluble impurities.

The washed hydrothermal reaction product is then dried. Drying means include spray drying, box drying, fluidized bed drying, external heat drying, freeze drying, vacuum drying and the like. Spray drying is preferable from the viewpoint of effectively controlling the increase of the type oxide particles more than necessary and sufficiently miniaturizing the particles.

The precursor mixture (Bx) obtained after drying is a mixture of a phosphoric acid composite oxide containing lithium and a part of the metal (M) and a metal (M) hydroxide containing the remainder of the metal (M). is. The average particle size of the precursor mixture (Bx) is preferably 5 nm to 250 nm, more preferably 10 nm to 200 nm, in terms of D ₅₀ value in particle size distribution based on laser diffraction/scattering method. Here, the _D50 value in particle size distribution measurement is a value obtained from a volume-based particle size distribution based on a laser diffraction/scattering method, and the _D50 value means the particle size (median diameter) at 50% cumulative. do. Therefore, when spray drying is employed as the drying means, the particle size of the precursor mixture (Bx) may be adjusted by appropriately optimizing the operating conditions of the spray dryer used.
Also, the precursor mixture (Bx) is preferably a mixture containing trilithium phosphate, in which case trilithium phosphate, metal (M) phosphate and water The mass ratio of the oxide to the mixture (trilithium phosphate: total amount of metal (M) phosphate and hydroxide) is preferably 1:3 to 2:1, more preferably 1:2. .5 to 1:1, more preferably 1:2 to 1:1.2.

Step (IIIx) is a step of firing the precursor mixture (Bx) obtained in step (IIx) at 400°C to 1000°C. Through such step (IIIx), it is possible to obtain NASICON-type oxide particles, which are fine particles with extremely high crystallinity and high purity, and which are very useful as a solid electrolyte for lithium ion secondary batteries.

The firing temperature in the step (IIIx) is 400° C. to 1000° C., preferably 500° C. to 900° C., from the viewpoint of effectively miniaturizing the NASICON-type oxide particles while increasing the crystallinity of the obtained NASICON-type oxide particles. , more preferably 600°C to 800°C. From the same viewpoint, the firing time is preferably 0.5 hours to 30 hours, more preferably 1 hour to 24 hours, and still more preferably 1 hour to 18 hours.

The atmosphere in the firing is not particularly limited, and may be an air atmosphere, an inert gas atmosphere, or a reducing condition, but the air atmosphere is preferable from the viewpoint of convenience. The apparatus used for such baking is not particularly limited as long as it is capable of adjusting the temperature, and any of batch type, continuous type, and heating type (indirect or direct) can be used. , an externally heated kiln or a roller hearth.

The production method (Y) of the present invention is a method for producing NASICON-type oxide particles for a solid electrolyte of a secondary battery comprising steps (Iy) to (IIIy). That is, in the step (Iy), a part of the raw material compound consisting of a lithium compound, a phosphoric acid compound, and a metal (M) compound is mixed with water to obtain a mixed solution having a pH of 5 to 9 at 25°C ( Ay).

Specific embodiments of the raw material compound used here include only one type of lithium compound, only one type of phosphoric acid compound, two types of a lithium compound and a part or all of a metal (M) compound, a lithium compound and phosphoric acid 2 types with a compound, and 2 types of modes with a part or all of a metal (M) compound and a phosphoric acid compound. Among them, it is preferable to use part or all of the metal (M) compound and the phosphoric acid compound as the raw material compounds from the viewpoint of efficiently obtaining the precursor mixture (By) in step (IIy) described later.
The metal (M) compound used in step (Iy) is the same as in step (Ix) of the production method (X).

The content of water in the mixed solution (Ay) is preferably 5 parts by mass to 50 parts by mass, more preferably 5 parts by mass, with respect to 1 part by mass of the total content of the raw material compounds in the mixed solution (Ay). parts to 40 parts by mass, more preferably 5 parts to 30 parts by mass.
The pH of the mixture (Ay) at 25° C. is 5-9, preferably 5.5-8.5, more preferably 6-8. In adjusting the pH of the mixture (Ay) so that it falls within this range, the same pH adjuster as can be used in the production method (X) may be used as necessary.

The liquid mixture (Ay) may be stirred from the viewpoint of dissolving or dispersing each component more uniformly. The time for stirring the mixture (Ay) is preferably 10 minutes to 3 hours, more preferably 20 minutes to 2 hours, even more preferably 30 minutes to 2 hours. The stirring speed is preferably 10 cm/sec to 200 cm/sec, more preferably 15 cm/sec to 150 cm/sec, still more preferably 20 cm/sec, in terms of the flow speed of the mixed solution (Ay) on the inner wall surface of the reaction vessel. sec to 100 cm/sec.

The temperature of the mixed solution (Ay) is preferably 10°C to 80°C, more preferably 15°C to 70°C, still more preferably 20°C to 60°C.

For the mixed solution (Ay), for example, when two compounds containing a phosphoric acid compound are used as starting compounds, the mixed solution (ax-1) and the mixed solution ( After preparing a mixed solution (ay-1) containing a raw material compound other than a phosphoric acid compound and water and a mixed solution (ay-2) containing a phosphoric acid compound and water in the same manner as in ax-2) , these mixtures may be mixed. The mixed solution (ay-1) is prepared according to the mixed solution (ax-1), and the mixed solution (ay-2) is prepared according to the mixed solution (ax-2). In addition, the method and conditions for mixing the mixed solution (ay-1) and the mixed solution (ay-2) may be appropriately selected according to the step (Ix) of the production method (X).
For example, the method of mixing the mixed solution (ay-1) and the mixed solution (ay-2) is not particularly limited. is preferably added dropwise. In this way, by adding the mixed solution (ay-2) containing the phosphoric acid compound dropwise to part or all of the lithium compound and the metal (M) compound little by little, the chemical composition of the reaction product becomes homogenous. can be further enhanced.

In the step (IIy) in the production method (Y) of the present invention, the mixed solution (Ay) obtained in the step (Iy) is subjected to a hydrothermal reaction at 100° C. or higher, then the hydrothermal reaction product is washed, Next, in the step of adding and mixing the remainder of the raw material compound consisting of the lithium compound, the metal (M) compound, and the phosphoric acid compound, the mixture is dried to obtain a precursor mixture (By). The hydrothermal reaction in step (IIy) is performed under pressure by storing the reaction vessel filled with the mixture (Ay) in a pressure vessel or the like.

When the mixed solution (Ay) obtained in step (Iy) is stirred before proceeding to step (IIy), such stirring may be performed in a reaction vessel, and then the reaction vessel is placed in a pressure vessel or the like. It should be stored. From the viewpoint of efficiently producing a precursor mixture of NASICON-type oxide particles, such stirring is preferably continued until the hydrothermal reaction in step (IIy) is completed in a reaction vessel housed in a pressure vessel or the like. . The stirring speed of the liquid mixture (Ay) at this time is the same as in step (IIx) in the production method (X).

The temperature (reaction temperature) of the mixed solution (Ay) during the hydrothermal reaction may be 100°C or higher, preferably 130°C to 250°C, more preferably 140°C to 230°C. The pressure and reaction time at this time are preferably 0.3 MPa or more and 10 minutes or more when the reaction temperature is 100° C. or higher, and 0.3 MPa to 2.0 MPa for 10 minutes when the reaction is performed at 130° C. to 250° C. Up to 24 hours is preferable, and when the reaction is carried out at 140° C. to 230° C., 0.4 MPa to 1.8 MPa and 10 minutes to 16 hours are preferable.

Moreover, the atmosphere in the reaction vessel in the hydrothermal reaction is not limited, but from the viewpoint of easiness of preparing the atmosphere, it is preferably under air or under water vapor.

After subjecting the liquid mixture (Ay) to the above hydrothermal reaction, the hydrothermal reaction product is washed. Such a hydrothermal reaction product can be obtained by solid-liquid separation of the mixed liquid (Ay) after the hydrothermal reaction. Apparatuses used for solid-liquid separation include, for example, a filter press and a centrifugal filter. Among them, it is preferable to use a filter press from the viewpoint of obtaining a hydrothermal reaction product efficiently.

Next, the recovered hydrothermal reaction product is washed with water from the viewpoint of effectively removing water-soluble impurities such as anionic components derived from the raw materials. The amount of such water is preferably 5 parts by mass to 50 parts by mass, more preferably 7 parts by mass to 50 parts by mass, and still more preferably 9 parts by mass with respect to 1 part by mass of the dry mass of the hydrothermal reaction product. parts to 50 parts by mass. The temperature of such water is preferably 5° C. to 70° C., more preferably 20° C. to 70° C., from the viewpoint of effectively removing water-soluble impurities.
The average particle diameter of the recovered hydrothermal reaction product is preferably 5 nm to 250 nm, more preferably 10 nm to 200 nm, as D ₅₀ value in particle size distribution based on laser diffraction/scattering method. Here, the _D50 value in particle size distribution measurement is a value obtained from a volume-based particle size distribution based on a laser diffraction/scattering method, and the _D50 value means the particle size (median diameter) at 50% cumulative. do.

The remainder of the starting compound is then added to and mixed with the washed hydrothermal reaction product. As a result, it is possible to obtain a precursor for producing NASICON-type oxide particles, which are extremely fine particles and have high purity, and which are very useful as solid electrolytes for secondary batteries.

Here, as the remainder of the raw material compound to be added and mixed with the hydrothermal reaction product, along with the raw material compound used in step (Iy), all of the raw material compound is used throughout the entire process of the production method of the present invention. It may be appropriately selected from raw material compounds. For example, when only one lithium compound is used in step (Iy), two kinds of the metal (M) compound and the phosphoric acid compound are used in step (IIy), and the phosphoric acid compound is used in step (Iy). When only one of is used, both of the lithium compound and all of the metal (M) compounds may be used in step (IIy). Among them, from the viewpoint of obtaining the precursor mixture (By) efficiently, it is preferable to use at least a lithium compound as the balance of the raw material compounds.
As a preferred embodiment of the raw material compound used in steps (Iy) and (IIy), specifically, lithium hydroxide is used in step (Iy), and metal (M)-containing hydroxide is used in step (IIy). and phosphoric acid, or an embodiment in which lithium sulfate is used in step (Iy) and a metal (M)-containing sulfate and ammonium phosphate are used in step (IIy).

Further, the raw material compound used in the step (IIy) preferably has a high purity from the viewpoint of achieving high purity of the NASICON-type oxide particles to be obtained. It is preferably 99.5% or more, more preferably 99.9% or more.

From the viewpoint of suppressing composition deviation of the NASICON-type oxide particles, the total amount of the raw material compounds added in step (IIy) is It is preferably 0.1 to 4 parts by mass, more preferably 0.2 to 3 parts by mass, still more preferably 0.3 to 2.5 parts by mass.

The average particle size of the raw material compound used in step (IIy) is preferably It is 400 nm or less, more preferably 300 nm or less, and still more preferably 250 nm or less.

As means for adding and mixing the raw material compounds to the washed hydrothermal reaction product, wet mixing is preferable from the viewpoint of achieving uniform mixing. When adding and mixing the raw material compounds to such a hydrothermal reaction product, water Use The order of addition of the hydrothermal reaction product, raw material compound and water is not particularly limited, but it is preferable to add and mix the raw material compound to a slurry in which the hydrothermal reaction product and water are previously added and mixed. The amount of water used here may be appropriately selected depending on the state of dispersion or mixture of the slurry.

The mixing time of the slurry is preferably 15 minutes to 5 hours, more preferably 30 minutes to 3 hours, from the viewpoint of sufficiently stirring and mixing. The temperature during mixing is preferably 5°C to 50°C, more preferably 10°C to 30°C. The mixing device is not particularly limited, and an ordinary device capable of mixing slurry, such as a device equipped with a magnetic stirrer or rotary blades, can be used.
The total content of hydrothermal reaction products and raw material compounds in the slurry is preferably 1% by mass to 40% by mass, more preferably 2% by mass to 30% by mass, and still more preferably 3% by mass. % to 25% by mass. Further, the mass ratio of the hydrothermal reaction product to the raw material compound in the slurry (hydrothermal reaction product: raw material compound) is preferably 10:1 to 1:4, more preferably 5:1 to 1:1. 3, more preferably 3:1 to 1:2.5.

Next, after adding and mixing the raw material compounds to the washed hydrothermal reaction product, for example, a slurry as described above is prepared and dried to obtain a precursor mixture (By). Drying means include, for example, spray drying, constant temperature drying, vacuum drying, freeze drying and the like. Among them, from the viewpoint of obtaining a uniformly fine precursor mixture (By) without pulverization and from the viewpoint of efficiently obtaining the precursor mixture (By) using the prepared slurry, spray drying is preferred. good. By such spray drying, it is possible to easily obtain a precursor mixture (By) in which the hydrothermal reaction product and the raw material compound are uniformly mixed as granules while effectively utilizing the prepared slurry. By calcining such granules in the step (IIIy) described later, it is possible to obtain NASICON-type oxide particles that are extremely fine particles with high purity and are very useful as a solid electrolyte for secondary batteries. .
When the granules are obtained by spray drying, the average particle size of the granules is preferably 5 nm to 250 nm, more preferably 10 nm to 200 nm, still more preferably 20 nm to 170 nm.

Further, the molar ratio (Li:M) of the amount of lithium and the amount of metal (M) in the precursor mixture (By) is preferably 1.01:0.01 to 1.7:0.7, and more It is preferably 1.05:0.05 to 1.5:0.5, more preferably 1.1:0.1 to 1.5:0.5.

Step (IIIy) in the production method (Y) of the present invention is a step of firing the precursor mixture (By) obtained in step (IIy) at 400°C to 1000°C. Specific firing conditions are the same as in step (IIIx) in the production method (X).

The average particle diameter of the NASICON-type oxide particles obtained by the production method (X) or the production method (Y) of the present invention is preferably 70 nm to 300 nm, more preferably 70 nm to 250 nm, and still more preferably 70 nm to 200 nm.
Furthermore, the average crystallite size is preferably 70 nm to 300 nm, more preferably 70 nm to 250 nm, and even more preferably 70 nm to 200 nm.
Here, the average particle size of the NASICON-type oxide particles means the average value of the measured values of the particle size (major axis length) of several tens of particles in observation using an SEM or TEM electron microscope. do. Further, the average crystallite size of the NASICON-type oxide means a value obtained by applying Scherrer's formula for an X-ray diffraction profile with a diffraction angle 2θ range of 10 ° to 80 ° by Cu-kα rays. .

In addition, the BET specific surface area of the obtained NASICON-type oxide particles is preferably 3 m ² /g or more, more preferably 5 m ² /g or more, from the viewpoint of obtaining a lithium ion secondary battery having excellent charge/discharge characteristics. more preferably 7 m ² /g or more.

The NASICON-type oxide particles obtained by the production method of the present invention are particles having an extremely low content of water-soluble impurities such as SO ₃ . For example, when a sulfate is used as a raw material compound, the content of water-soluble impurities (SO ₃ content) in the obtained NASICON-type oxide particles is preferably 500 ppm or less, more preferably 300 ppm or less.

The NASICON-type oxide obtained by the production method of the present invention is an oxide having a NASICON-type crystal structure, and specifically, an oxide containing no Ti represented by the following formula (1).
Li1 _{+xM2 (} PO4) ₃ ( ₁ )
(In formula (1), M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr, Ge, Nd, Sr, Sn, represents one or more selected from Hf, V or Zr, and x represents a number that satisfies 0≦x≦4 and x+(valence of M)×2=8.)
More specifically, for example, _{LiZr2 (} PO4) ₃ , _{Li1.5Al0.5Ge1.5 (} PO4) ₃ , _{Li1.2Zr1.9Ca0.1 ( PO4} ) _{3 , LiHf2 ( PO4} ) _{3 , LiGe2 ( PO4} ) _{3 , Li1.5Al0.4Cr0.1Ge1.5 ( PO4} ) ₃ .

As described above, according to the production method of the present invention, it is possible to obtain high-purity NASICON-type oxide particles having a high degree of crystallinity, effectively miniaturized particle diameters, and sufficiently reduced content of impurities. can. Therefore, it is possible to easily produce a solid electrolyte for an all-solid lithium-ion secondary battery that can exhibit excellent charge-discharge characteristics.

As a lithium-ion secondary battery to which the NASICON-type oxide particles obtained by the production method of the present invention can be appropriately applied as a solid electrolyte, a positive electrode, a negative electrode, and a solid electrolyte are essential components, and a positive electrode active material layer, There is no particular limitation as long as a laminate in which the solid electrolyte layer and the negative electrode active material layer are laminated in this order is formed.

Here, the positive electrode active material layer is not particularly limited in material composition as long as it can release metal ions such as lithium ions during charging and can absorb metal ions during discharging. can be used. For example, a positive electrode active material layer made of various polyanion-type positive electrode active materials obtained by hydrothermally reacting raw material compounds can be suitably used.

In addition, regarding the negative electrode active material layer, the material configuration is not particularly limited as long as lithium ions or the like can be occluded during charging and can be released during discharging, and known material configurations can be used. . For example, a negative electrode active material layer made of titanium niobium oxide or sodium lithium titanate composite oxide obtained by hydrothermally reacting raw materials can be preferably used.

Moreover, the method for producing a lithium ion secondary battery using the NASICON-type oxide particles of the present invention is not particularly limited, and known methods can be used. For example, as described in JP-A-2017-10816, the NASICON-type oxide particles of the present invention are used as solid electrolyte particles contained in the positive electrode active material layer and the negative electrode active material layer of a lithium ion secondary battery. A solid electrolyte other than such solid electrolyte particles may be used for the solid electrolyte layer.

The shape of the lithium-ion secondary battery having the above configuration is not particularly limited, and may be various shapes such as a coin shape, a cylindrical shape, a square shape, or an irregular shape enclosed in a laminated outer package. .

EXAMPLES The present invention will be specifically described below based on examples. In addition, unless otherwise indicated in the table, the content of each component indicates % by mass.

[Production Example 1] (Production of LiCoPO ₄ positive electrode active material particles)
12.72 g of LiOH.H ₂ O and 40 mL of water were mixed to obtain a slurry (c-1). 11.53 g of 85% by mass H ₃ PO ₄ was added dropwise to the obtained slurry (c-1) at 35 mL/min while stirring for 3 minutes while maintaining the temperature at 25° C., and the stirring rate was 400 rpm for 1 hour. A Li ₃ PO ₄ slurry (c-2) was obtained by stirring. Next, 21.08 g of CoSO ₄ .7H ₂ O was added to the total amount of Li ₃ PO ₄ slurry (c-2) thus obtained to obtain slurry (c-3), which was put into an autoclave. , and 170° C. for 1 hour. The pressure inside the autoclave was 0.8 MPa. The produced hydrothermal reactant was filtered and then washed with 12 parts by mass of water per 1 part by mass of the hydrothermal reactant. The washed hydrothermal reaction product was freeze-dried at −50° C. for 12 hours to obtain LiCoPO ₄ positive electrode active material particles (particle size: 100 nm).

[Example ₁ ] _{( Li1.5Al0.5Ge1.5 (PO4)3 )}
0.32 g of LiOH·H ₂ O, 1.76 g of 29 mass % NH ₄ OH, and 0.79 g of GeO ₂ were mixed with 40 mL of water to obtain a mixed solution (ax-1) ¹ . The pH of the mixture (ax-1) ¹ at 25° C. was 13.0. Further, 20 mL of water was mixed with 0.79 g of Al ₂ (SO ₄ ) ₃ ·16H ₂ O and 1.73 g of 85% by mass of H ₃ PO ₄ to obtain a mixed solution (ax-2) ¹ .
Next, the resulting mixed solution (ax-1) ¹ was stirred at a stirring speed of 200 rpm for 60 minutes while maintaining the temperature at 25° C., and then added to the mixed solution (ax-1) ¹ which was continuously stirred. After stirring the mixture (ax-2) 1 for 5 minutes at a stirring speed of 200 rpm, the total amount of the mixture (ax-2) ¹ was added dropwise at 50 mL/min, and then stirred for 30 minutes at a stirring speed of 200 rpm to obtain a mixture (Ax) ¹ . The mixed solution (Ax) ¹ had a pH of 6.0 at 25° C., and a total content of the produced lithium phosphate and aluminum phosphate was 2 mass %.

The mixed liquid (Ax) ¹ thus obtained was put into an autoclave and subjected to a hydrothermal reaction at 200° C. and 1.7 MPa for 1 hour. The resulting solid content was filtered by suction, and then washed with 12 parts by mass of water per ¹ part by mass of the solid content. got Qualitative analysis by X-ray diffraction revealed that the mass ratio of the mixture Li ₃ PO ₄ , AlPO ₄ and GeO ₂ in the resulting precursor mixture (Bx) ¹ was 1:0.2:0.4.
The resulting precursor mixture (Bx) ¹ was calcined at 750° C. for 4 hours in an air atmosphere to obtain NASICON-type oxide particles A ¹ . The obtained NASICON-type oxide particles A ¹ had a Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ single phase, an average particle diameter of 90 nm, an average crystallite diameter of 90 nm, and a BET specific surface area of 26 m ² /g. there were.
A SEM photograph of the obtained NASICON-type oxide particles A ¹ is shown in FIG. 1, and an X-ray diffraction pattern is shown in FIG.

[Example ₂ ] ( _{LiZr2(PO4)3 )}
The amount of LiOH.H ₂ O added was 0.21 g, GeO ₂ was not used, and 3.63 g of Zr(SO ₄ ) ₂ .4H ₂ O was added instead of Al ₂ (SO ₄ ) ₃ .16H ₂ O. Except for this, NASICON-type oxide particles B ¹ were obtained in the same manner as in Example 1. The obtained NASICON-type oxide particles B ¹ had a LiZr ₂ (PO ₄ ) ₃ single phase, an average particle diameter of 90 nm, and a BET specific surface area of 26 m ² /g.
A SEM photograph of the obtained NASICON-type oxide particles B ¹ is shown in FIG.

[Example ₃ ] ( _{Li1.2Zr1.9Ca0.1 ( PO4} ) ₃ )
The amount of LiOH.H ₂ O added was 0.26 g, no GeO ₂ was used, and instead of Al ₂ (SO ₄ ) ₃ .16H ₂ O, 3.45 g of Zr(SO ₄ ) ₂ .4H ₂ O and Ca( NASICON-type oxide particles C ¹ were obtained in the same manner as in Example 1, except that 0.12 g of NO ₃ ) ₂ .4H ₂ O was added. The obtained NASICON-type oxide particles C ¹ had a Li _1.2 Zr _1.9 Ca _0.1 (PO ₄ ) ₃ single phase, an average particle diameter of 90 nm, and a BET specific surface area of 26 m ² /g.
A SEM photograph of the obtained NASICON-type oxide particles C ¹ is shown in FIG.

[Example ₄ ] ( _LiHf2 (PO4) ₃ )
The procedure of Example 1 was repeated except that the amount of LiOH.H ₂ O added was 0.21 g, GeO ₂ was not used, and 3.20 g of HfCl ₄ was added instead of Al ₂ (SO ₄ ) ₃ .16H ₂ O. NASICON type oxide particles D ¹ were obtained. The obtained NASICON-type oxide particles D ¹ had a LiHf ₂ (PO ₄ ) ₃ single phase, an average particle diameter of 90 nm, and a BET specific surface area of 26 m ² /g.
A SEM photograph of the obtained NASICON-type oxide particles D ¹ is shown in FIG.

[Example ₅ ] ( _LiGe2 (PO4) ₃ )
NASICON-type oxide particles E ¹ were obtained in the same manner as in Example 1, except that the amount of LiOH.H ₂ O added was 0.21 g and the amount of GeO ₂ added was 1.05 g. The obtained NASICON-type oxide particles E ¹ had a LiGe ₂ (PO ₄ ) ₃ single phase, an average particle diameter of 90 nm, and a BET specific surface area of 26 m ² /g.
A SEM photograph of the obtained NASICON-type oxide particles E ¹ is shown in FIG.

[Example 6 _{] ( Li1.5Al0.4Cr0.1Ge1.5 ( PO4} ) ₃ )
Example 1 except that the amount of Al ₂ (SO ₄ ) ₃ .16H ₂ O added was 0.63 g, and 0.20 g of Cr ₂ (SO ₄ ) ₃ was added together with Al ₂ (SO ₄ ) ₃ .16H ₂ O. NASICON-type oxide particles F ¹ were obtained in the same manner as above. The obtained NASICON-type oxide particles F ¹ had a Li _1.5 Al _0.4 Cr _0.1 Ge _1.5 (PO ₄ ) ₃ single phase, an average particle diameter of 90 nm, and a BET specific surface area of 26 m ² /g.
A SEM photograph of the obtained NASICON-type oxide particles F ¹ is shown in FIG.

[Comparative Example ₁ ] _{( Li1.5Al0.5Ge1.5 (PO4)3 )}
0.64 g of LiOH·H ₂ O and 1.58 g of GeO ₂ were mixed with 40 mL of water to obtain a mixed solution (az-1) ² . 0.26 g of Al ₂ O ₃ and 3.46 g of 85 mass % H ₃ PO ₄ were mixed with the resulting mixture (az-1) ² and dried at a constant temperature of 180° C. for 12 hours to obtain a precursor mixture (Bz ) got ² . The resulting precursor mixture (Bz) ² was calcined at 750° C. for 12 hours in an air atmosphere to obtain a NASICON oxide. The resulting NASICON-type oxide was pulverized using a planetary ball mill at 450 rpm for 10 hours to obtain NASICON-type oxide particles A ² . The obtained NASICON-type oxide particles A ² had a Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ single phase, an average particle diameter of 400 nm, an average crystallite diameter of 300 nm, and a BET specific surface area of 8 m ² /g. there were.
A SEM photograph of the obtained NASICON-type oxide particles A ² is shown in FIG. 8, and an X-ray diffraction pattern is shown in FIG.

"Evaluation test"
Using the NASICON-type oxide particles A ¹ to F ¹ and A ² obtained in Examples 1 to 6 and Comparative Example 1, all-solid lithium ion secondary batteries were produced.
Specifically, the _LiCoPO4 positive electrode active material particles obtained in Production Example 1 were used for the positive electrode, and the positive electrode active material:solid electrolyte (mass ratio) was mixed at a mixing ratio of 75:25, and then put into a press jig. to form a positive electrode active material layer. Furthermore, solid electrolyte particles alone were added to the layer to form a solid electrolyte layer, which was then pressed at 16 MPa for 2 minutes using a hand press to obtain a disk-shaped positive electrode of φ14 mm. Next, by attaching a lithium foil as a negative electrode to the solid electrolyte layer side, an all-solid lithium ion lithium ion secondary battery was produced.

When using the all-solid-state lithium ion lithium ion secondary battery produced, the charging condition is 16 mA / g, the constant current charging at a voltage of 5.0 V, and the discharging condition is 16 mA / g, the constant current discharging at the final voltage of 3.5 V. , the discharge capacity at 16 mA/g was determined. All charge/discharge tests were conducted at 45°C. Table 1 shows the results.

From the above results, it can be seen that the NASICON-type oxide particles obtained by the production method of Example 1 exhibit superior discharge capacity compared to the NASICON-type oxide particles obtained by the production method of Comparative Example 1. . As can be seen from FIGS. 1 and 2, this is probably because the NASICON-type oxide particles obtained by the production method of Example 1 are fine particles with a high degree of crystallinity.

Claims (8)

Following steps (Ix) to (IIIx):
(Ix) lithium compounds, phosphate compounds and metal (M) compounds (M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr A step (IIx ) After subjecting the obtained mixture to a hydrothermal reaction at 100 ° C. or higher, the hydrothermal reaction product is washed and then dried to obtain a precursor mixture. A method for producing NASICON-type oxide particles for a solid electrolyte of a lithium-ion secondary battery represented by the following formula (1), comprising a step of firing at ℃ ~ 1000 ℃
Li1 _+xM2 ( _PO4 ) 3 _{( 1} )
(In Formula (1), M has the same meaning as M in a metal (M) compound, and x represents a number that satisfies 0≦x≦4 and x+(valence of M)×2=8) . Following steps (Iy) to (IIIy):
(Iy) lithium compounds, phosphate compounds and metal (M) compounds (M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr , Ge, Nd, Sr, Sn, Hf, V or Zr) with water to prepare a mixed solution having a pH of 5 to 9 at 25 ° C. ( IIy) A step of subjecting the resulting mixture to a hydrothermal reaction at 100° C. or higher, washing the hydrothermal reaction product, then adding and mixing the rest of the raw material compounds and drying to obtain a precursor mixture. (IIIy) A method for producing NASICON-type oxide particles for a solid electrolyte of a lithium ion secondary battery represented by the following formula (1), comprising a step of firing the obtained precursor mixture at 400°C to 1000°C.
Li1 _+xM2 ( _PO4 ) 3 _{( 1} )
(In Formula (1), M has the same meaning as M in a metal (M) compound, and x represents a number that satisfies 0≦x≦4 and x+(valence of M)×2=8) . 3. The metal (M) compound used as the raw material compound is a halide, sulfate, organic acid salt, hydroxide, chloride, sulfide, oxide, or hydrate thereof, according to claim 1 or 2. A method for producing NASICON-type oxide particles for a solid electrolyte of a lithium-ion secondary battery. Claims 1 to 5, wherein 5 parts by mass to 50 parts by mass of water is used with respect to 1 part by mass of the dry mass of the hydrothermal reaction product when washing the hydrothermal reaction product in step (IIx) or step (IIy). 4. The method for producing NASICON-type oxide particles for a solid electrolyte of a lithium ion secondary battery according to any one of 3. The solid electrolyte for a lithium ion secondary battery according to any one of claims 1 to 4, wherein the firing in step (IIIx) or step (IIIy) is performed under an air atmosphere, an inert gas atmosphere, or reducing conditions. Method for producing NASICON-type oxide particles for use. Step (Ix) is a mixed solution containing a lithium compound, a metal (M) compound and water, and wherein the molar ratio (Li:M) of the lithium compound and the metal (M) compound is 1:2 to 2:1 ( After preparing ax-1) and a mixed solution (ax-2) containing a phosphoric acid compound and water and having a phosphoric acid compound content of 3 parts by mass to 20 parts by mass relative to 100 parts by mass of water, The solid state of the lithium ion secondary battery according to any one of claims 1 or 3 to 5, which is a step of mixing the mixed solution (ax-1) and the mixed solution (ax-2) to prepare a mixed solution. A method for producing NASICON-type oxide particles for electrolytes. In mixing the liquid mixture (ax-1) and the liquid mixture (ax-2), the mass ratio of the liquid mixture (ax-1) and the liquid mixture (ax-2) ((ax-1):(ax- 7. The method for producing NASICON-type oxide particles for a solid electrolyte of a lithium ion secondary battery according to claim 6, wherein 2)) is 20:1 to 1:4. The molar ratio (Li:M) of the amount of lithium and the amount of metal (M) in the precursor mixture obtained in step (IIy) is 1.01:0.01 to 1.7:0.7. 6. A method for producing NASICON-type oxide particles for a solid electrolyte of a lithium ion secondary battery according to any one of 2 to 5.

Images