JP7179603B2 - 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.

Although such NASICON-type oxide particles can be produced by using a solid-phase method or a sol-gel method, they must be pulverized to make them finer, resulting in crystal particles with a broad particle size distribution. , may lead to a decrease in lithium ion conductivity. _On the other hand, in addition to the solid phase method and the sol _- gel method, production using a vitrification method has also been attempted. ) ₂ , and heat-treating and acid-treating the glass to produce a NASICON-type oxide porous body (vitrification method). Further, in Patent Document 2, the molar ratio of Li ₂ O:Al ₂ O ₃ :TiO ₂ :P ₂ O ₅ :ZnO=1+x:x:4−2x:3+y:y is more than 3y and less than 3y (0≦x Disclosed is a method for producing NASICON-type oxide particles by a vitrification process that produces a glass consisting of ≤1, 1≤y≤4).

JP-A-05-139781 JP 2016-155707 A

However, with the production method described in Patent Document 1, the resulting NASICON-type oxide particles contain a large amount of Ca as an impurity, have a low degree of crystallinity, and, like the solid-phase method and the sol-gel method, still require a pulverization treatment. need to apply. In addition, although the production method described in Patent Document 2 can suppress the contamination of impurities, multiple heat treatment steps for producing glass and crystallizing glass, acid treatment for elution of impurities, etc. , which inevitably complicates the process.

Therefore, an object of the present invention is to provide a method for producing NASICON-type oxide particles that can obtain fine and highly pure NASICON-type oxide particles without requiring a pulverization treatment or the like, and that can also simplify the process. That's what it is.

Therefore, as a result of various studies, the present inventors used a mixed liquid having a specific pH value prepared from a lithium compound, a metal (M) compound, a phosphoric acid compound, and a solvent, and spray pyrolyzed this at a specific temperature. As a result, the inventors have found that NASICON-type oxide particles having excellent properties as a solid electrolyte for lithium ion secondary batteries can be obtained, and have completed the present invention.

That is, the present invention provides the following steps (I) to (II):
(I) Lithium compounds, metals (M) (M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr, Ge, Nd, (1 or 2 or more selected from Sr, Sn, Hf, V, and Zr.) A mixed liquid having a pH of 0.5 to 3 at 25° C. by mixing a compound and a phosphoric acid compound with a solvent. and (II) spray pyrolyzing the resulting mixture at 600°C to 1000°C. .

According to the production method of the present invention, fine and high-purity NASICON-type oxide particles can be obtained only by preparing a predetermined mixed solution and subjecting it to spray pyrolysis, and the heat treatment process needs to be repeated multiple times. Since there is no need to perform a pulverization treatment for miniaturization of particles, the process can be simplified.
Therefore, according to the production method of the present invention, it is possible to easily obtain NASICON-type oxide particles for a solid electrolyte of a lithium ion secondary battery having excellent ion conductivity.

1 is an SEM image showing NASICON-type oxide particles obtained in Example 1. FIG. FIG. 1(a) is an SEM image of secondary particles of NASICON-type oxide particles, and FIG. 1(b) is an SEM image showing the aggregation state of primary particles constituting the secondary particles of NASICON-type oxide particles. is. 1 is an X-ray diffraction pattern of NASICON-type oxide particles obtained in Example 1. FIG. 4 is an SEM image showing 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 (I) to (II):
(I) Lithium compounds, metals (M) (M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr, Ge, Nd, (1 or 2 or more selected from Sr, Sn, Hf, V, and Zr.) A mixed liquid having a pH of 0.5 to 3 at 25° C. by mixing a compound and a phosphoric acid compound with a solvent. (II) comprising a step of spray pyrolyzing the obtained mixture at 600°C to 1000°C.

Step (I) is a lithium compound, metal (M) (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.) The compound and phosphoric acid compound are mixed with a solvent, and the pH at 25° C. is 0.5 to 3. This is a step of preparing a mixture (A). By using the liquid mixture (A) prepared in the step (I), the heat treatment for forming particles and the refinement of the particles can be performed collectively only by going through the step (II) described later. It is possible to achieve simplification of the process.

The lithium compound used in step (I) is a lithium source for forming NASICON-type oxide particles in a subsequent step. Examples of such lithium 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.

The content of the lithium compound may vary depending on its type, but it is preferably 0.01 mol/L to 1.0 mol/L, more preferably It is 0.05 mol/L to 0.7 mol/L, more preferably 0.05 mol/L to 0.5 mol/L.

The metal (M) compound used in step (I) is a metal (M) source (M is Ca, Al, Cu, Co, Fe, Ni, Ga, one or more selected from Cr, Sc, In, Y, La, Zn, Si, Mn, Zr, Ge, Nd, Sr, Sn, Hf, V and Zr). Examples of such metal (M) compounds include compounds other than Ti compounds, such as aluminum sulfates, nitrates, carbonates, acetates, lactates, oxalates, oxides, hydroxides, and halides. be done.

The content of the metal (M) compound is the molar ratio (Li/M) of lithium and metal (M) in the mixed solution (A) obtained in step (I), preferably 2 to 11, and more It is preferably 2.4-11, more preferably 3-6. The metal (M) compound may be added to the mixture so that the mixture (A) has such an amount.

The phosphoric acid compound used in step (I) is a phosphoric acid source for forming NASICON-type oxide particles in a later step, and also acts as a pH adjuster for controlling the pH of the mixture (A). can. Examples 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, phosphoric acid or ammonium hydrogen phosphate is preferably used, and ammonium hydrogen phosphate is more preferably used, from the viewpoint of utilizing the action as a pH adjuster. Moreover, these are preferably used as an aqueous solution having a concentration of 70% by mass to 90% by mass.

The content of the phosphoric acid compound is preferably 0.33 to 0.65 in terms of the molar ratio of lithium to phosphoric acid (Li/PO ₄ ) in the mixture (A) obtained in step (I), It is more preferably 0.37 to 0.6, still more preferably 0.4 to 0.55. In addition, the content of the lithium compound in the mixed solution (A) obtained in step (I) is preferably 0.01 mol/L to 1 mol/L, more preferably 0.05 mol/L to 0.5 mol. /L, more preferably 0.08 mol/L to 0.3 mol/L.

The pH of the mixed solution (A) in step (I) is preferably 0.5 to 3 from the viewpoint of favorably forming the target NASICON-type oxide particles through step (II) described later. Yes, more preferably 0.5 to 2.7, particularly preferably 0.5 to 2.5. Organic acids such as malic acid, citric acid, and lactic acid may be appropriately used as pH adjusters.

A solvent is further used in preparing the mixture (A) in step (I). Examples of such a solvent include water and/or an organic solvent. Specifically, a water-soluble organic solvent such as methanol, ethanol, isopropyl alcohol, or an aqueous solution thereof dissolved in water can also be used. The content of such a solvent is determined from the viewpoint of maintaining good solubility or dispersibility in the mixed solution (A) of the lithium compound, the metal (M) compound and the phosphoric acid compound, and the spray pyrolysis in step (II) described later. In 100% by mass of the mixed solution (A) obtained in step (I), preferably is 80% to 99% by mass, more preferably 85% to 97% by mass, and still more preferably 88% to 95% by mass.

In preparing the mixed liquid (A), from the viewpoint of increasing the solubility or dispersibility in the mixed liquid (A) of the lithium compound, the metal (M) compound and the phosphoric acid compound, each of these compounds is separately added in advance. may be prepared and mixed. Among them, from the viewpoint of facilitating pH control of the mixed liquid (A) while ensuring good solubility or dispersibility of each compound, a mixed liquid containing a lithium compound and a metal (M) compound, and a phosphorus It is preferable to prepare a mixed liquid (A) by mixing with a mixed liquid containing an acid compound.

From the viewpoint of dispersing each component more uniformly, the mixture (A) is preferably stirred before proceeding to step (II). The time for stirring the mixture (A) is preferably 5 minutes to 3 hours, more preferably 10 minutes to 2 hours, and 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 in terms of the flow speed of the mixture (A) on the inner wall surface of the container. ~100 cm/sec.

Step (II) is a step of subjecting the mixture (A) obtained in step (I) to spray pyrolysis at 600°C to 1000°C. Such spray pyrolysis uses an ultrasonic atomizer or a fluid nozzle atomizer, etc., to form droplets by spraying the raw material liquid into a furnace provided in the device, and then evaporating and drying. It is a process in which particles are formed by solidification. Among them, it is preferable to use a spraying device using a fluid nozzle such as a two-fluid nozzle or a four-fluid nozzle from the viewpoint of forming particles having a desired particle size by appropriately adjusting the particle size of droplets. There are two types of spray pyrolysis using a fluid nozzle atomizer: an internal mixing method in which air and raw material liquid are mixed inside the nozzle, and an external mixing method in which air and raw material liquid are mixed outside the nozzle. , can be adopted.

The temperature in the furnace during spray pyrolysis is 600° C. to 1000° C. from the viewpoint of ensuring the reactivity of the lithium compound, the metal (M) compound and the phosphoric acid compound and favorably forming the NASICON-type oxide particles. and preferably 650°C to 950°C.
The atmosphere in the furnace is not particularly limited, and may be an air atmosphere, an inert gas atmosphere, or a reducing condition, but from the viewpoint of simplicity, an air atmosphere is preferred.

The average particle size of the primary particles of the NASICON-type oxide particles obtained by the production method of the present invention is the particle size (long axis length) of several tens of primary particles in observation using an SEM or TEM electron microscope. is preferably 70 nm to 300 nm, more preferably 70 nm to 250 nm, 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 crystallite size of the NASICON-type oxide particles 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. do.

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 secondary battery having excellent charge-discharge characteristics, More preferably, it is 7 m ² /g or more.

The NASICON-type oxide particles obtained by the production method of the present invention are oxides having a NASICON-type crystal structure, specifically, Ti-free oxides 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, NASICON-type oxide particles having effectively fined particle diameters can be obtained. 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 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 and a solid electrolyte. There is no particular limitation as long as a layered body in which a layer and a negative electrode active material layer are stacked 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 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 the solid electrolyte particles contained in the positive electrode active material layer and the negative electrode active material layer as the solid electrolyte of the secondary battery. A solid electrolyte other than such solid electrolyte particles may be used for the solid electrolyte layer.

The shape of the secondary battery having the above configuration is not particularly limited, and may be coin-shaped, cylindrical, square, or any other shape, or may be 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 slurry x1. 11.53 g of 85% by mass H ₃ PO ₄ was added dropwise at 35 mL/min to the resulting slurry x1 while stirring for 3 minutes while maintaining the temperature at 25° C., and the slurry was stirred at a stirring speed of 400 rpm for 1 hour. , Li ₃ PO ₄ slurry x2 was obtained. Next, 21.08 g of CoSO ₄ .7H ₂ O was added to the total amount of the obtained Li ₃ PO ₄ slurry x 2 to obtain slurry x 3, which was put into an autoclave and was heated at 170°C for 1 hour with water. A thermal reaction was carried out. 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 )}
1.03 g of LiNO ₃ , 1.88 g of Al(NO ₃ ) _{3.9H 2} O and 1.57 g of GeO ₂ were mixed with 100 mL of water to obtain a mixture a1. 3.45 g of NH ₄ H ₂ PO ₄ was mixed with the obtained mixed solution a1, and stirred for 10 minutes at a stirring speed of 50 cm/sec to obtain a mixed solution A1. The pH of the mixture A1 at 25°C was 1.0.
Next, using compressed air as a carrier gas, the obtained mixture b1 is sprayed in a mist state through a four-fluid nozzle by a liquid feed pump, and passed through a spray pyrolysis furnace with the furnace temperature set at 900 ° C. to obtain NASICON-type oxide particles X1. The obtained NASICON-type oxide particles X1 are Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ single phase, the average primary particle diameter is 100 nm, the average crystallite diameter is 100 nm, and the BET specific surface area is 24 m ² /. was g.
A SEM photograph of the obtained NASICON-type oxide particles X1 is shown in FIG. 1, and an X-ray diffraction pattern is shown in FIG.

[Example ₂ ] ( _{LiZr2(PO4)3 )}
Example except that the amount of LiNO ₃ added was 0.69 g, GeO ₂ was not used, and 5.35 g of ZrO(NO ₃ ) ₂ .2H ₂ O was added instead of Al(NO ₃ ) ₃ .9H ₂ O. NASICON-type oxide particles X2 were obtained in the same manner as in Example 1. The obtained NASICON-type oxide particles X2 had a LiZr ₂ (PO ₄ ) ₃ single phase, and had an average primary particle size of 100 nm and a BET specific surface area of 24 m ² /g.

[Example ₃ ] ( _{Li1.2Zr1.9Ca0.1 ( PO4} ) ₃ )
The amount of _LiNO3 added was 0.83 g, no _GeO2 was used, and 5.08 g of ZrO( _NO3 ) _2.2H2O and Ca( _NO3 ) _{2 were} used instead of Al _{( NO3} ) _3.9H2O . * NASICON-type oxide particles X3 were obtained in the same manner as in Example 1, except that 0.24 g of 4H ₂ O was added. The obtained NASICON-type oxide particles X3 had a Li _1.2 Zr _1.9 Ca _0.1 (PO ₄ ) ₃ single phase, and had an average primary particle diameter of 100 nm and a BET specific surface area of 24 m ² /g.

[Example ₄ ] ( _LiHf2 (PO4) ₃ )
NASICON-type oxidation was performed in the same manner as in Example 1, except that the amount of LiNO ₃ added was 0.69 g, GeO ₂ was not used, and 6.41 g of HfCl ₄ was added instead of Al(NO ₃ ) ₃ .9H ₂ O. A substance particle X4 was obtained. The obtained NASICON-type oxide particles X4 had a LiHf ₂ (PO ₄ ) ₃ single phase, and the average primary particle size was 100 nm, and the BET specific surface area was 24 m ² /g.

[Example ₅ ] ( _LiGe2 (PO4) ₃ )
NASICON-type oxide particles X5 were obtained in the same manner as in Example 1, except that the amount of LiNO ₃ added was 0.69 g and the amount of GeO ₂ added was 2.09 g. The obtained NASICON-type oxide particles X5 had a LiGe ₂ (PO ₄ ) ₃ single phase, and had an average primary particle size of 100 nm and a BET specific surface area of 24 m ² /g.

[Example 6 _{] ( Li1.5Al0.4Cr0.1Ge1.5 ( PO4} ) ₃ )
Example except that the amount of Al(NO ₃ ) ₃ .9H ₂ O added was 1.50 g, and 0.40 g of Cr(NO ₃ ) ₃ .9H ₂ O was added together with Al(NO ₃ ) ₃ .9H ₂ O. NASICON-type oxide particles X6 were obtained in the same manner as in Example 1. The obtained NASICON-type oxide particles _X6 had a _{Li1.5Al0.4Cr0.1Ge1.5 ( PO4} ) ₃ single phase _, and had an average primary particle size of 100 nm and a BET specific surface area of 24 ^m2 /g.

[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 Y1. The obtained NASICON-type oxide particles Y1 are Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ single phase, and have an average particle size (D ₅₀ ) of 400 nm, an average crystallite size of 300 nm, and a BET specific surface area of 8 m ² . /g.
Here, the average particle size (D ₅₀ ) value is a value obtained from a volume-based particle size distribution based on a laser diffraction/scattering method, and the D ₅₀ value means the particle size (median diameter) at 50% cumulative. do.
A SEM photograph of the obtained NASICON-type oxide particles Y1 is shown in FIG. 3, and an X-ray diffraction pattern is shown in FIG.

"Evaluation test"
Using the NASICON-type oxide particles X1 to X6 and Y1 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: NASICON type oxide particles (mass ratio) were mixed at a mixing ratio of 75:25. It was put into a jig to form a positive electrode active material layer. Furthermore, only the NASICON-type oxide particles 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 with a diameter of 14 mm. Next, by attaching a lithium foil as a negative electrode to the solid electrolyte layer side, an all-solid lithium ion secondary battery was produced.

Using the produced all-solid-state lithium ion secondary battery, the charging condition is 16 mA / g, the constant current charging at a voltage of 5.0 V, the discharging condition is 16 mA / g, the constant current discharging at the final voltage of 3.5 V, A 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, the NASICON-type oxide particles X1 to X6 obtained by the production methods of Examples 1 to 6 have an average particle diameter as compared with the NASICON-type oxide particles Y1 obtained by the production method of Comparative Example 1. It is considered that the density of the solid electrolyte layer increased due to the small value of , and the discharge capacity increased.

Claims (3)

The following steps (I)-(II):
(I) Lithium compounds, metals (M) (M is Ca, Al, Cu, Co, Fe, Ni, Ga, Cr, Sc, In, Y, La, Zn, Si, Mn, Zr, Ge, Nd, (1 or 2 or more selected from Sr, Sn, Hf, V, and Zr.) A mixed liquid having a pH of 0.5 to 3 at 25° C. by mixing a compound and a phosphoric acid compound with a solvent. (II) NASICON-type oxide particles for a solid electrolyte of a lithium ion secondary battery represented by the following formula (1), comprising a step of spray pyrolyzing the obtained mixed solution at 600 ° C. to 1000 ° C. manufacturing method
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) . 2. The solid state of a lithium ion secondary battery according to claim 1, wherein the mixed solution obtained in step (I) has a molar ratio (Li/PO ₄ ) of lithium to phosphoric acid of 0.33 to 0.65. A method for producing NASICON-type oxide particles for electrolytes. The NASICON for a solid electrolyte of a lithium ion secondary battery according to claim 1 or 2, wherein the mixed solution obtained in step (I) has a lithium compound content of 0.01 mol/L to 1.0 mol/L. Method for producing type oxide particles.

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