JP2022138830A - Amorphous solid electrolyte precursor powder and manufacturing method thereof, and manufacturing method of solid electrolyte having nasicon crystal structure - Google Patents

Abstract

To provide an amorphous solid electrolyte precursor powder which can be crystallized to obtain a solid electrolyte with a NASICON crystal structure that exhibits high ionic conductivity, a manufacturing method thereof, and a manufacturing method of a solid electrolyte having NASICON crystal structure.SOLUTION: An amorphous solid electrolyte precursor powder contains 1 mass% to 4 mass% of lithium, 0.5 mass% to 6 mass% of aluminum, 15 mass% to 35 mass% of germanium, 10 mass% to 30 mass% of phosphorus, and 0.05 mass% to 3 mass% of nitrogen, and the balance is oxygen.SELECTED DRAWING: Figure 1

Description

The present invention relates to an amorphous solid electrolyte precursor powder, a method for producing the same, and a method for producing a solid electrolyte having a NASICON crystal structure.

Solid electrolytes having a NASICON-type crystal structure are known to have high ionic conductivity as solid electrolytes for all-solid-state batteries. As one of solid electrolytes having a NASICON-type crystal structure, for example, lithium, aluminum, germanium, phosphorus and oxygen are contained, and the general formula is Li _1+x Al _x Ge _2-x (PO ₄ ) ₃ (where x ranges from 0<). A solid electrolyte (sometimes referred to as “LAGP” in the present invention) composed of a composite oxide described in x≦1) is known.

For example, as in Patent Documents 1 and 2, it is known to form a film of a solid electrolyte on the particle surface of an electrode active material in order to increase the ionic conductivity of the electrode layer of an all-solid-state battery. In Patent Documents 1 and 2, in order to efficiently form a solid electrolyte film on the particle surface of the electrode active material, the electrode active material and LAGP are mixed in an amorphous state and fired to form an amorphous layer. A method of crystallizing LAGP to develop ionic conductivity and forming an electrode layer of an all-solid-state battery having high ionic conductivity is described. Precursor powders are known.

JP 2018-37341 A JP 2019-50083 A

However, in order to improve the output of all-solid-state batteries, further improvement in ionic conductivity is desired. According to studies by the present inventors, even LAGP crystallized by firing the amorphous LAGP produced by the methods described in Patent Documents 1 and 2 has low ionic conductivity. There is a demand for an amorphous precursor powder that, when crystallized, becomes a solid electrolyte with a NASICON-type crystal structure that exhibits higher ionic conductivity.

The present invention has been made under the circumstances described above, and the problem to be solved is to obtain a solid electrolyte with a NASICON-type crystal structure that exhibits high ionic conductivity by crystallization. An object of the present invention is to provide a crystalline solid electrolyte precursor powder, a method for producing the same, and a method for producing a solid electrolyte having a NASICON-type crystal structure.

As a result of research to solve the above problems, the present inventors have found that an amorphous solid electrolyte precursor powder containing predetermined amounts of lithium, aluminum, germanium, phosphorus and oxygen contains a predetermined amount of nitrogen. The present inventors have found that high ionic conductivity is exhibited when the amorphous solid electrolyte precursor powder is crystallized.

That is, the first invention for solving the above-mentioned problems is
1% by mass or more and 4% by mass or less of lithium,
0.5% by mass or more and 6% by mass or less of aluminum,
15% by mass or more and 35% by mass or less of germanium,
10% by mass or more and 30% by mass or less of phosphorus,
Containing 0.05% by mass or more and 3% by mass or less of nitrogen,
It is an amorphous solid electrolyte precursor powder in which the balance is oxygen.
The second invention is
The amorphous solid electrolyte precursor powder is the amorphous solid electrolyte precursor powder according to the first invention, containing 2.5% by mass or less of nitrogen.
The third invention is
The amorphous solid electrolyte precursor powder is the amorphous solid electrolyte precursor powder according to the first or second invention, containing 0.1% by mass or more of nitrogen.
The fourth invention is
The amorphous solid electrolyte precursor powder according to any one of the first to third inventions, wherein the amorphous solid electrolyte precursor powder contains 1.5% by mass or less of nitrogen and 23.5% by mass or more of germanium. It is a solid electrolyte precursor powder of high quality.
The fifth invention is
The amorphous solid electrolyte precursor powder according to any one of the first to fourth inventions, which contains the nitrogen in the form of nitrous acid.
The sixth invention is
of the first to fifth inventions, wherein the amorphous solid electrolyte precursor powder further contains one or more elements selected from the group consisting of titanium, zirconium and silicon in a range of 5% by mass or less in total. An amorphous solid electrolyte precursor powder according to any one of the items.
The seventh invention is
Contains lithium, aluminum, germanium, phosphorus, nitrogen, and oxygen, containing 1% by mass to 4% by mass of lithium, 0.5% by mass to 6% by mass of aluminum, 15% by mass to 35% by mass of germanium, and phosphorus A method for producing an amorphous solid electrolyte precursor powder containing 10% by mass or more and 30% by mass or less, 0.05% by mass or more and 3% by mass or less of nitrogen, and the balance being oxygen,
A step of adjusting the pH of a liquid containing lithium, aluminum, germanium, phosphorus and ammonia to 2 or more and less than 4.5 to obtain a pH-adjusted slurry;
spray drying the pH adjusted slurry to obtain a dry powder;
and sintering the dry powder at 300° C. or higher and 500° C. or lower.
The eighth invention is
The amorphous solid electrolyte precursor according to the seventh invention, wherein the molar ratio (NO ₃ /NH ₃ ) of nitric acid and ammonia in the pH-adjusted slurry is 1.0 or more and 3.0 or less. A powder manufacturing method.
The ninth invention is
Further, one or more selected from the group consisting of titanium, zirconium and silicon is added to the liquid containing lithium, aluminum, germanium, phosphorus and ammonia, and titanium and zirconium are added to the amorphous solid electrolyte precursor powder. and silicon in a total amount of 5% by mass or less.
A tenth invention is
A method for producing a solid electrolyte having a NASICON-type crystal structure, comprising the step of firing the amorphous solid electrolyte precursor powder according to any one of the first to sixth inventions at a temperature higher than 500°C. be.

According to the present invention, an amorphous solid electrolyte containing lithium, aluminum, germanium, phosphorus, nitrogen and oxygen, which is a precursor of a solid electrolyte having a NASICON-type crystal structure that exhibits high ionic conductivity by sintering and crystallizing It is possible to provide an amorphous solid electrolyte precursor powder, a method for producing the amorphous solid electrolyte precursor powder, and a method for producing a solid electrolyte having a NASICON-type crystal structure.

1 is an XRD spectrum of an amorphous solid electrolyte precursor powder according to Example 1. FIG. 1 is a Raman spectrum of an amorphous solid electrolyte precursor powder according to Example 1. FIG. 1 is SEM photographs of amorphous solid electrolyte precursor powders according to Example 1 and Comparative Examples 1 and 2. FIG.

The amorphous solid electrolyte precursor powder according to the present invention is an amorphous powder, but by calcining and crystallizing it, a solid electrolyte with a NASICON-type crystal structure exhibiting high ionic conductivity can be obtained. is a precursor of a solid electrolyte with a NASICON-type crystal structure.
The solid electrolyte obtained by crystallizing the amorphous solid electrolyte precursor powder according to the present invention refers to JCPDS card No. 01-080-1922, the general formula Li _1+x Al _x Ge _2-x (PO ₄ ) ₃ (where x ranges from 0<x≦1), LAGP can be used as the main phase. It may be of a mixed phase having LAGP as a main phase and other oxides as a subphase. Here, the fact that LAGP is the main phase in the obtained solid electrolyte can be confirmed by confirming that the maximum peak obtained when the solid electrolyte is subjected to XRD measurement is LAGP.

Hereinafter, the embodiments for carrying out the invention are described as follows: 1. 2. Effect and content ratio of each constituent element in the amorphous solid electrolyte precursor powder; 2. Properties of amorphous solid electrolyte precursor powder; A method for producing an amorphous solid electrolyte precursor powder and a method for producing a solid electrolyte having a NASICON-type crystal structure will be described in this order.

1. Effect and Content Ratio of Each Constituent Element in Amorphous Solid Electrolyte Precursor Powder The amorphous solid electrolyte precursor powder according to the present invention contains lithium, aluminum, germanium, phosphorus, and nitrogen as constituent elements, and is desired. contains other elements, and the balance is oxygen. Hereinafter, the effect and content ratio of each constituent element will be described (1) lithium, (2) aluminum, (3) germanium, (4) phosphorus, (5) nitrogen, (6) other elements, (7) oxygen, ( 8) Impurities.

(1) Lithium The amorphous solid electrolyte precursor powder of the present invention contains 1% by mass or more and 4% by mass or less of lithium. If the lithium content is 1% by mass or more and 4% by mass or less, when the amorphous solid electrolyte precursor powder is crystallized, it becomes a solid electrolyte with a NASICON-type crystal structure having high ionic conductivity, and lithium ions This is because conductivity is guaranteed. The content of lithium is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, and still more preferably 1.8% by mass or more, while it is preferably 4.0% by mass or less, preferably 3% by mass or less. 0.5% by mass or less, more preferably 3.3% by mass or less.

(2) Aluminum The amorphous solid electrolyte precursor powder of the present invention contains 0.5% by mass or more and 6% by mass or less of aluminum. By containing 0.5% by mass or more and 6% by mass or less of aluminum, a solid electrolyte having a NASICON-type crystal structure is obtained when the amorphous solid electrolyte precursor powder is crystallized. The aluminum content is preferably 1.0% by mass or more, more preferably 2.0% by mass or more. On the other hand, it is preferably 5.5% by mass or less, more preferably 5.0% by mass or less.

(3) Germanium The amorphous solid electrolyte precursor powder of the present invention contains 15% by mass or more and 35% by mass or less of germanium. If the germanium content is 15% by mass or more, it can form glass and be amorphous. On the other hand, if the germanium content is 35% by mass or less, a solid electrolyte having a NASICON-type crystal structure is obtained when the amorphous solid electrolyte precursor powder is crystallized. The germanium content is preferably 20% by mass or more, more preferably 22% by mass or more, and most preferably 23.5% by mass or more, so that when the amorphous solid electrolyte precursor powder is crystallized, , a solid electrolyte with higher ionic conductivity can be obtained. On the other hand, it is preferably 33% by mass or less, more preferably 30% by mass or less.

(4) Phosphorus The amorphous solid electrolyte precursor powder of the present invention contains 10% by mass or more and 30% by mass or less of phosphorus. In this case a glass is formed and can be amorphous. On the other hand, when crystallized, the amorphous solid electrolyte precursor powder has a NASICON-type crystal structure. The phosphorus content is preferably 15% by mass or more, more preferably 20% by mass or more. On the other hand, it is preferably 28% by mass or less, more preferably 25% by mass or less.

(5) Nitrogen The amorphous solid electrolyte precursor powder according to the present invention contains 0.05% by mass or more and 3% by mass or less of nitrogen. When the amorphous solid electrolyte precursor powder contains 0.05% by mass or more and 3% by mass or less of nitrogen and the amorphous solid electrolyte precursor powder is fired and crystallized, nitrogen is a sintering accelerator. It is presumed that the ionic conductivity of the solid electrolyte obtained by crystallization is improved by reducing the ionic conduction resistance because the grain boundaries of the crystals are reduced. The nitrogen content is more preferably 0.1% by mass or more, still more preferably 0.15% by mass or more, from the viewpoint of improving the ion conductivity of the solid electrolyte obtained by crystallization. On the other hand, the nitrogen content is preferably 2.5% by mass or less, preferably 1.5% by mass or less, from the viewpoint of improving the ion conductivity of the solid electrolyte obtained by crystallization.

In the present invention, the content of nitrogen contained in the amorphous solid electrolyte precursor powder can be determined using a nitrogen analyzer (a sample is heated and decomposed in an inert gas atmosphere to determine the nitrogen contained in the sample). It can be calculated from the results of quantitative analysis of the nitrogen content of the amorphous solid electrolyte precursor powder using a device for extracting nitrogen gas and quantitatively analyzing it. Nitrogen contained in the amorphous solid electrolyte precursor powder is preferably in the form of nitrous acid. As used herein, “nitrogen in the form of nitrous acid” means that the Raman spectrum of an amorphous solid electrolyte precursor powder is measured, and a peak due to symmetrical expansion and contraction of nitrous acid is detected near 1285 cm ⁻¹ ±5. It is identified by being When the nitrogen contained in the amorphous solid electrolyte precursor powder is in the form of nitrous acid, the contained nitrous acid is considered to exist mainly as lithium nitrite. Since lithium nitrite has a decomposition temperature of 600° C. or higher, it remains without being decomposed during drying and firing when producing an amorphous solid electrolyte precursor powder, and the effect of containing nitrogen is exhibited in the subsequent steps. , we believe that a solid electrolyte with a NASICON-type crystal structure that exhibits high ionic conductivity can be obtained.

(6) Other Elements The amorphous solid electrolyte precursor powder according to the present invention has elements other than lithium, aluminum, germanium, phosphorus, nitrogen and oxygen as long as they form a NASICON-type crystal structure when crystallized. In addition, one or more elements selected from the group consisting of titanium, zirconium and silicon may be contained in a total amount of 5% by mass or less. The total content is preferably 3% by mass or less, more preferably 2% by mass or less. One or more elements selected from the group consisting of titanium, zirconium and silicon may be contained in a total amount of 0.1% by mass or more.

(7) Oxygen The oxygen content contained in the amorphous solid electrolyte precursor powder according to the present invention can be obtained by (100% by mass - the total mass% of each constituent element other than oxygen). The oxygen content in the amorphous solid electrolyte precursor powder is preferably 40% by mass or more and 55% by mass or less.

(8) Impurities In the amorphous solid electrolyte precursor powder according to the present invention, lithium, aluminum, germanium, phosphorus, nitrogen, oxygen, and further impurities other than titanium, zirconium and silicon are included within a range that does not impair the effects of the present invention. The element may be contained as an impurity element. The total amount of impurity elements is preferably 5% by mass or less, more preferably 1% by mass or less.

2. Properties of the Amorphous Solid Electrolyte Precursor Powder Regarding the properties of the amorphous solid electrolyte precursor powder according to the present invention, (1) the particle size, and (2) the method for confirming that it is amorphous, in that order. explain.

(1) Particle size The particle size of the amorphous solid electrolyte precursor powder according to the present invention is not particularly limited. The volume-based cumulative 50% particle diameter (D50) obtained by the measurement is preferably 1 μm to 30 μm.
When a solid electrolyte having a NASICON-type crystal structure, which will be described later, is used as a solid electrolyte for an all-solid-state battery, the D50 of the precursor amorphous solid electrolyte precursor powder is preferably 1 μm to 5 μm. .

(2) a method for confirming that it is amorphous;
The fact that the amorphous solid electrolyte precursor powder according to the present invention is amorphous is confirmed by observing a halo in the region of 2θ: 15° to 40° by powder X-ray diffraction (XRD) measurement. can. The "halo" is a gentle undulation of X-ray intensity, which is observed as a broad bulge on the X-ray chart. If the half width of the halo is 2θ: 2° or more, it is amorphous.

3. Method for Producing Amorphous Solid Electrolyte Precursor Powder and Method for Producing Solid Electrolyte Having NASICON Crystal Structure First, a method for producing an amorphous solid electrolyte precursor powder according to the present invention will be described. Then, a method for producing a solid electrolyte having a NASICON-type crystal structure using the produced amorphous solid electrolyte precursor powder as a precursor will be described.

The amorphous solid electrolyte precursor powder according to the present invention is obtained by mixing an aqueous solution of raw materials containing each constituent element to obtain a liquid mixture, adjusting the pH of the obtained liquid mixture, and It is obtained by spray-drying a slurry to obtain a dry powder, and calcining the dry powder.
As will be described later, the liquid mixture may be a slurry in which the salts of the constituent elements are dispersed, or a solution in which the salts of the constituent elements are dissolved.

Hereinafter, the method for producing an amorphous solid electrolyte precursor powder and the method for producing a solid electrolyte having a NASICON-type crystal structure according to the present invention will be described in terms of (1) raw material aqueous solution preparation, (2) mixing, (3) pH Preparation, (4) Spray drying, (5) Firing, (6) Particle size adjustment, and (7) Production of a solid electrolyte having a NASICON-type crystal structure will be described in this order.

(1) Raw material aqueous solution preparation A raw material containing lithium, aluminum, germanium, and phosphorus, which are constituent elements of the amorphous solid electrolyte precursor powder according to the present invention, and optionally titanium, zirconia, and silicon, Each of them is completely dissolved in water to form an aqueous solution. It is preferable to use nitrate as the raw material containing each constituent element because nitrogen tends to remain in the amorphous solid electrolyte precursor powder.

(2) Mixing This is a step of mixing the raw material aqueous solution prepared in "(1) Raw material aqueous solution preparation" according to the composition of the target solid electrolyte precursor powder.
As a result of the mixing, a slurry containing constituent elements of the solid electrolyte may be obtained by so-called coprecipitation, or a mixed solution may be obtained.

For example, when an acidic aqueous solution of lithium nitrate, aluminum nitrate nonahydrate, and ammonium dihydrogen phosphate is added to an alkaline aqueous solution of germanium dissolved in ammonia, it immediately becomes turbid, and coprecipitation of lithium, aluminum, and germanium occurs. , phosphorus and ammonia can be obtained. It is not necessary to consider the temperature of the liquid in this mixing step, and the liquid may or may not be heated. It is considered that constituent elements precipitated as hydroxides and constituent elements existing as ions are present in the slurry.
On the other hand, when the constituent elements of the amorphous solid electrolyte precursor powder are completely dissolved in water as a solvent, a transparent mixed solution is formed instead of a slurry. In this case, a slurry is produced by coprecipitation in "(3) pH adjustment" described below.
In the present invention, the term "liquid" may be used as a concept including the transparent mixed solution and the slurry produced by the coprecipitation.

(3) pH adjustment Nitric acid is added to the liquid mixture, which is a mixed slurry or mixed solution containing lithium, aluminum, germanium, phosphorus and ammonia obtained in "(2) Mixing", or A step of adjusting the pH of the liquid mixture to 2 or more and less than 4.5 by increasing the proportion of the nitrate amount. As a result, even in the case of a mixed solution, a slurry is produced by coprecipitation, so that a pH-adjusted slurry having a pH of 2 or more and less than 4.5 can be obtained from the mixed slurry or from the mixed solution. .
In "(2) Mixing" or "(3) pH adjustment", a supersaturated state in which the ion concentration product of the constituent elements is higher than the solubility product, and a slurry is produced using a coprecipitation method is This is because it is important to improve the uniformity of the constituent elements in order to obtain a solid electrolyte having a NASICON-type crystal structure.

The present inventor added nitric acid in this step as follows to adjust the pH of the mixed slurry to 2 or more and less than 4.5, so that the amorphous solid electrolyte precursor powder contained nitrogen. I'm guessing. The mixed slurry obtained in "(2) Mixing" is considered to contain nitrate and ammonium salt. The present inventor added nitric acid to the mixed slurry obtained in "(2) Mixing" to adjust the pH of the mixed slurry to 2 or more and less than 4.5, so that the lithium nitrate and ammonium nitrate contained in the pH-adjusted slurry , among nitrates such as aluminum nitrate, the amount of lithium nitrate, which has a high decomposition temperature, is increasing.
Then, it is considered that the lithium nitrate contained in the pH-adjusted slurry generates lithium nitrite by heating in "(5) Firing" described later. As a result, it is speculated that nitrogen in the form of nitrous acid remains in the amorphous solid electrolyte precursor powder, and nitrogen is contained in the amorphous solid electrolyte precursor powder.

From this point of view, the pH of the pH-adjusted slurry is preferably 4.4 or less, more preferably 4.3 or less. On the other hand, the pH-adjusted slurry preferably has a pH of 2.3 or higher, more preferably 2.6 or higher.

Further, the molar ratio (NO ₃ /NH ₃ ) of nitric acid and ammonia in the pH-adjusted slurry is preferably 1.0 or more and 3.0 or less.
Here, the number of moles of nitric acid and ammonia in the pH-adjusted slurry means the total number of moles of nitric acid molecules and ammonium molecules added until the pH-adjusted slurry was prepared. In the range of pH 2 or more and pH 4.5 or less, each molecule is considered to exist in the state of nitrate ion and ammonium ion in the aqueous solution.

By adjusting the molar ratio of ammonia and nitric acid in the slurry in this way, it is believed that the amount of lithium nitrate in the slurry increases as described above. It is preferable because nitrogen in the form of nitrous acid can be contained. From this point of view, the molar ratio (NO ₃ /NH ₃ ) of nitric acid and ammonia in the pH-adjusted slurry is more preferably 1.0 or more and 2.0 or less.

(4) spray drying;
The pH-adjusted slurry having a pH of 2 or more and less than 4.5 obtained in "(3) pH adjustment" is spray-dried using a spray dryer or the like to evaporate water in the pH-adjusted slurry to obtain a dry powder. It is a process. By spray-drying the slurry obtained through "(3) pH adjustment", the constituent elements existing as ions in the slurry can be rapidly precipitated in a short time, so the solubility between the constituent elements can be improved. Deposition non-uniformities resulting from differences are reduced, resulting in dry powders of uniform composition. Furthermore, generation of germanium dioxide is suppressed, and a preferable amorphous solid electrolyte precursor powder can be obtained.

According to the inventor's preliminary test, the powder obtained by drying the pH-adjusted slurry with a pH of 2 or more and less than 4.5 by evaporation to dryness using a hot plate, etc., instead of spray drying, in "(5) Firing" described later Germanium dioxide is produced, and according to powder X-ray diffraction (XRD) measurement, a germanium dioxide peak is observed in the region of 2θ: 15° to 40°, and an amorphous solid electrolyte conductor oxide powder can be obtained. could not.

The drying temperature may be appropriately set to a temperature that does not leave moisture in the resulting dry powder. However, since it is thought that the dry powder contains nitrates and ammonium salts in the same manner as the pH-adjusted slurry, specifically, the inlet temperature of the spray dryer, which is a spray dryer, is 150 to 150. 250°C and a hot air outlet temperature of 60 to 120°C are preferred.
This is because if the inlet temperature is 150°C or higher, a sufficient drying rate can be obtained and the situation where dry powder tends to remain in the drying tower of the spray dryer can be avoided, and if the inlet temperature is 250°C or lower, the components in the slurry can be heated. This is because it is possible to avoid a situation in which the desired dry powder is not obtained due to decomposition. In addition, if the hot air outlet temperature is 60 ° C. or higher, preferably 80 ° C. or higher, the moisture content in the dry powder can be sufficiently reduced. This is because it is possible to avoid a situation in which a

(5) Firing This is a step of calcining the dry powder obtained in "(4) Spray drying" and vitrifying it to obtain an amorphous solid electrolyte precursor powder. Specifically, dry powder is placed in a container made of alumina or the like, and the temperature is raised from room temperature to 300° C. to 500° C. at a temperature elevation rate of 0.1 to 20° C./min in an air atmosphere. A crystalline solid electrolyte precursor powder can be obtained. By firing at 300° C. or higher and 500° C. or lower, the ammonium salt with a low decomposition temperature contained in the dry powder is removed, but the lithium nitrate contained in the dry powder becomes lithium nitrite, and is converted into nitrous acid. It is considered that nitrogen remains in the amorphous solid electrolyte precursor powder and nitrogen is contained in the amorphous solid electrolyte precursor powder according to the present invention.

(6) Particle size adjustment In "(7) Production of a solid electrolyte having a NASICON-type crystal structure" described later, when forming a solid electrolyte obtained by crystallizing an amorphous solid electrolyte precursor powder into a sheet, Depending on the desired sheet thickness, the particle size of the amorphous solid electrolyte precursor powder may be adjusted as needed. As a method for adjusting the particle size, a known method can be used, but wet pulverization using a bead mill or the like is preferable. When wet pulverization is performed, solid-liquid separation is performed after the wet pulverization treatment, and the recovered amorphous solid electrolyte precursor powder after wet pulverization is dried. The particle diameter of the amorphous solid electrolyte precursor powder obtained by drying is 1 μm to 5 μm in terms of volume-based cumulative 50% particle diameter (D ₅₀ ) obtained by laser diffraction scattering particle size distribution measurement. is preferred.

As a solvent for wet pulverization, an organic solvent is preferable from the viewpoint of preventing lithium in the amorphous solid electrolyte precursor powder from ion-exchanging with protons and reducing the ion conduction of the solid electrolyte. is preferably IPA. This is because IPA evaporates during drying after pulverization and does not remain in the amorphous solid electrolyte precursor powder. When using a bead mill for pulverization, the beads are preferably zirconia beads. The amorphous solid electrolyte precursor powder after wet pulverization is dried in a temperature range equal to or higher than the boiling point of the solvent used and equal to or lower than the calcination temperature in the above "(5) calcination", and the solvent used is is preferably removed.

(7) Production of Solid Electrolyte Having NASICON-type Crystal Structure In order to obtain the solid electrolyte having the NASICON-type crystal structure according to the present invention from the amorphous solid electrolyte precursor powder according to the present invention, a container made of alumina or the like is used. Into, put the amorphous solid electrolyte precursor powder obtained in the above "(6) Particle size adjustment", or, for example, after molding into a pellet shape or a sheet shape, at a temperature exceeding 500 ° C. It should be crystallized. A solid electrolyte having a NASICON-type crystal structure can be obtained by calcining preferably at a temperature of 550° C. or more and 900° C. or less to crystallize the amorphous solid electrolyte precursor powder. The NASICON-type crystal structure solid electrolyte is preferably single-phase. This is because the ionic conductivity of the solid electrolyte tends to increase due to the single phase.
The obtained solid electrolyte having a NASICON-type crystal structure can be used, for example, as a solid electrolyte in an all-solid-state battery.

The rate of temperature rise during firing is not particularly limited, but is preferably from 1 to 20°C/min. There are no particular restrictions on the firing atmosphere, but an air atmosphere is preferred. Although the firing time is not particularly limited, it is preferably 30 minutes or more and 300 minutes or less after the temperature exceeds 500° C. and reaches 900° C. or less. During the sintering, the nitrogen contained in the amorphous solid electrolyte precursor powder according to the present invention functions as a sintering aid, thereby causing crystal growth, reducing grain boundaries of crystals in the solid electrolyte, It is speculated that the ionic conductivity is improved.

The NASICON-type crystal structure solid electrolyte contains lithium, aluminum, germanium, and phosphorus, which are constituent elements of the amorphous solid electrolyte precursor powder before crystallization. Whether or not the solid electrolyte has the NASICON type crystal structure according to the present invention can be determined from the XRD profile measured using an XRD apparatus. Specifically, the obtained XRD profile is converted to PDF (Powder Diffraction File) No. 2 of ICDD (International Diffraction Data Center) using a computer attached to the XRD apparatus. It can be identified by matching with 01-080-1922, and it can also be confirmed whether it is a single phase.

<Example 1>
The amorphous solid electrolyte precursor powder according to Example 1 was manufactured according to the above-described flow showing the manufacturing process of the amorphous solid electrolyte precursor powder. Then, analysis and characteristic evaluation of the amorphous solid electrolyte precursor powder according to Example 1 were performed.

(1) Preparation of raw material aqueous solution In Example 1, (I) germanium-containing aqueous solution and (II) lithium-, aluminum-, and phosphorus-containing aqueous solution were prepared as raw material aqueous solutions. Each of these will be described below.

(I) Germanium-containing aqueous solution 192.5 g of germanium dioxide was added to 4000 g of pure water and heated to 40°C with stirring. was dissolved to prepare a germanium-containing aqueous solution. The pH of the prepared aqueous solution was 10.7 and was alkaline.

(II) Aqueous solution containing lithium, aluminum and phosphorus To 336.3 g of pure water, 15.5 g of lithium nitrate and 4.2 g of lithium hydroxide monohydrate,
38.7 g of aluminum nitrate nonahydrate and 71.2 g of ammonium dihydrogen phosphate were added to prepare an aqueous solution containing lithium, aluminum and phosphorus. The prepared lithium-, aluminum-, and phosphorus-containing aqueous solution had a pH of 1.8 and was acidic.

(2) Mixing 720 g of the alkaline germanium-containing aqueous solution was separated and heated to 40° C. while stirring, and the total amount (283.7 g) of the acidic lithium-, aluminum-, and phosphorus-containing aqueous solution was added thereto. Immediately after the addition, the aqueous solution became cloudy and a white mixed slurry containing lithium, aluminum, germanium, phosphorus, ammonia and water was obtained. The resulting mixed slurry had a pH of 4.7.

(3) pH adjustment While stirring the obtained mixed slurry, 5 g of nitric acid having a concentration of 60% by mass was added to adjust the pH to 4.3, thereby obtaining a pH-adjusted slurry. The temperature of the slurry at this time was 40°C.
Here, since 0.58 mol of nitric acid and 0.46 mol of ammonia are added until the pH-adjusted slurry is obtained, the molar ratio (NO ₃ /NH ₃ ) of the added nitric acid and ammonia is 1. .27.

In the present invention, the pH value of the liquid was measured according to JISZ8802. As pH standard solutions, oxalate and phthalate buffers are used in the acidic range, neutral phosphate and phosphate buffers are used in the neutral range, and borate and carbonate buffers are used in the alkaline range, respectively. A Horiba Estec glass electrode hydrogen ion concentration indicator (model D-53) calibrated using

(4) spray drying;
The pH-adjusted slurry is spray-dried using a spray dryer (SD-1000 manufactured by Tokyo Rikakikai Co., Ltd.) to evaporate water in the pH-adjusted slurry and precipitate solid phase at once to obtain a white powder. rice field. The spray drying conditions were an inlet temperature of 180° C., an outlet temperature of 90° C., and an addition rate of the pH-adjusted slurry of 10 g/min.

(5) Firing The dry powder obtained by the spray drying is placed in an alumina container, heated from room temperature to 400 ° C. at a temperature increase rate of 5 ° C./min, and after reaching 400 ° C., it is placed in an air atmosphere. An amorphous solid electrolyte precursor powder was obtained by firing for 120 minutes.

(6) Particle Size Adjustment 40 g of the amorphous solid electrolyte precursor powder, together with 160 g of φ1 mm Zr beads and 94.32 g of IPA, was placed in a bead mill and wet-ground for 120 minutes, then placed in a dryer and dried at 100° C. for 3 hours. , an amorphous solid electrolyte precursor powder according to Example 1 was obtained.
The amorphous solid electrolyte precursor powder according to Example 1 was measured using a laser diffraction scattering particle size distribution analyzer (HELOS particle size distribution analyzer (HELOS & RODOS (airflow dispersion module)) manufactured by SYMPATEC). , the volume-based particle size distribution was measured at a dispersion pressure of 5 bar, and the volume-based cumulative 50% particle diameter ( _D50 ) was found to be 1.8 µm.
A 30,000-fold SEM photograph of the amorphous solid electrolyte precursor powder according to Example 1 is shown in FIG.

(7) Analysis and Characterization of Amorphous Solid Electrolyte Precursor Powder The obtained amorphous solid electrolyte precursor powder according to Example 1 was subjected to (I) elemental analysis and (II) nitrogen content analysis. , (III) XRD measurement of the amorphous solid electrolyte precursor powder, and (IV) Raman spectrum measurement of the amorphous solid electrolyte precursor powder. Each method and result will be described below.
In addition, in the amorphous solid electrolyte precursor powder, the balance of (I) the amount of each element present by elemental analysis and (II) the amount of nitrogen present by nitrogen amount analysis is considered to be the amount of oxygen present. be done. This also applies to Examples 2 to 8 and Comparative Examples 1 to 3, which will be described later.

(I) Elemental Analysis To the amorphous solid electrolyte precursor powder according to Example 1, sodium carbonate was added as a melting agent and melted to prepare an alkali molten salt. Next, this molten salt was dissolved in nitric acid, and the solution was subjected to elemental analysis using an ICP-OES apparatus (ICP-720 manufactured by Agilent). Constituent element analysis values of lithium, aluminum, phosphorus, germanium, titanium, zirconia, and silicon are shown in Table 1.

(II) Nitrogen Content Analysis The nitrogen content in the amorphous solid electrolyte precursor powder according to Example 1 was analyzed using a nitrogen analyzer (EMGA-920 manufactured by Horiba, Ltd.). Nitrogen content analysis values are listed in Table 1.

(III) XRD Measurement of Amorphous Solid Electrolyte Precursor Powder The amorphous solid electrolyte precursor powder according to Example 1 was subjected to XRD measurement under the following measurement conditions. The XRD spectrum obtained is shown in FIG.
<XRD measurement conditions>
Measuring device: XRD-6100 (manufactured by Shimadzu Corporation)
Tube: Cu
Tube voltage: 40kv
Tube current: 30mA
Divergence slit: 1.0°
Scattering slit: 1.0°
Light receiving slit: 0.3 mm
Step width: 0.02°/step
Measurement time: 0.25 sec

From FIG. 1, the XRD spectrum of the amorphous solid electrolyte precursor powder according to Example 1 shows a halo with a half width of 2θ: 2° or more in the region of 2θ: 15° to 40°. It was confirmed to be amorphous. In addition, in all of the amorphous solid electrolyte precursor powders according to Examples 2 to 8 and Comparative Examples 1 to 3, which will be described later, in the region of 2θ: 15° to 40°, the half-value width is 2°: 2° or more. was observed, it was confirmed that these were also amorphous.

(IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder A laser Raman spectrophotometer (manufactured by JASCO Corporation: NRS-4500) was used for the amorphous solid electrolyte precursor powder according to Example 1. Raman spectral measurements were carried out at a laser wavelength of 532 nm. FIG. 2 shows the Raman spectrum obtained by the measurement. In the obtained Raman spectrum, a peak due to symmetrical expansion and contraction of nitrous acid (NO ₂ ) was detected at 1285 cm ⁻¹ , indicating that the nitrogen contained in the amorphous solid electrolyte precursor powder was in the form of nitrous acid. all right. In Table 1, ◯ indicates that a peak due to the symmetrical expansion and contraction of nitrous acid (NO ₂ ) was detected, and x indicates that no peak was detected.

In addition, in the amorphous solid electrolyte precursor powders according to Examples 2 to 8 described later, a peak due to the symmetrical expansion and contraction of nitrous acid (NO ₂ ) was detected at 1285 cm ⁻¹ ±5, and the peak contained in these It was also found that the nitrogen in the On the other hand, no peak was detected in the amorphous solid electrolyte precursor powders according to Comparative Examples 1 to 3.

(8) Production of Solid Electrolyte Having NASICON-Type Crystal Structure and Characteristic Evaluation A green compact obtained by firing and crystallizing the green compact of the amorphous solid electrolyte precursor powder according to Example 1. Regarding the solid electrolyte having the NASICON-type crystal structure, (I) production of the solid electrolyte having the NASICON-type crystal structure and evaluation by XRD measurement, and (II) ionic conductivity evaluation of the solid electrolyte having the NASICON-type crystal structure were performed. Each method and result will be described below.

(I) Production of Solid Electrolyte Having NASICON Crystal Structure and Evaluation by XRD Measurement 0.5 g of the amorphous solid electrolyte precursor powder according to Example 1 was placed in a cylindrical container with a diameter of 10 mm, and pressed by a press. A compact was obtained by pressing at 360 MPa. The obtained green compact was fired for 120 minutes after the temperature in the furnace reached 800° C. to produce a crystallized green compact.

XRD measurement is performed on the produced compacted sintered body under the same measurement conditions as in "(V) XRD measurement of amorphous solid electrolyte precursor powder" described above, and ICDD (International Diffraction Data Center) PDF ( Powder Diffraction File) No. 01-080-1922. Then, the same diffraction peak as that of LiGe ₂ (PO ₄ ) ₃ , which is a solid electrolyte with a NASICON-type crystal structure, was observed. It was also found to have a NASICON-type crystal structure and to be a single-phase solid electrolyte.

In addition, in Examples 2 to 8 and Comparative Examples 1 to 3, which will be described later, the crystal peak of LAGP, which is a solid electrolyte having a NASICON-type crystal structure, was obtained by crystallizing the amorphous solid electrolyte precursor powder. It was also found to have a NASICON-type crystal structure and to be a single-phase solid electrolyte.

(II) Evaluation of ionic conductivity of solid electrolyte having NASICON-type crystal structure Potentiometer/galvanostat (Solartron Co., Ltd.) 1470E (manufactured by Soratron Co., Ltd.) and a frequency response analyzer (1255B, manufactured by Solartron Co., Ltd.), measurement was performed in the range of 100 Hz to 4 MHz by the AC impedance method. Then, the resistance value of the solid electrolyte having the NASICON type crystal structure is obtained from the Cole-Cole plot (complex impedance plane plot) of the measured values, and the solid electrolyte having the NASICON type crystal structure according to Example 1 is obtained from the obtained resistance value. Table 1 shows the calculated ionic conductivity values.

<Example 2>
Except that in "(3) pH adjustment" of Example 1, 10 g of nitric acid having a concentration of 60% by mass was added while stirring the obtained mixed slurry to obtain a pH-adjusted slurry adjusted to pH 3.9. An amorphous solid electrolyte precursor powder according to Example 2 was obtained in the same manner as in Example 1.
Here, since 0.63 mol of nitric acid and 0.46 mol of ammonia are added until the pH-adjusted slurry according to Example 2 is obtained, the molar ratio of the added nitric acid and ammonia (NO ₃ /NH ₃ ) was 1.37.

For the obtained amorphous solid electrolyte precursor powder according to Example 2, in the same manner as in Example 1, "(7) Analysis and characteristic evaluation of amorphous solid electrolyte precursor powder (I) Elemental analysis, (II) Nitrogen content analysis, (III) XRD measurement of amorphous solid electrolyte precursor powder, (IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder,
(8) Production and property evaluation of solid electrolyte having NASICON-type crystal structure (I) Production of solid electrolyte having NASICON-type crystal structure and evaluation by XRD measurement, (II) Ionic conductivity of solid electrolyte having NASICON-type crystal structure evaluation,"
Table 1 shows the results of elemental analysis, nitrogen content, conductivity, pH value and (NO ₃ /NH ₃ ) ratio in the pH-adjusted slurry, and presence or absence of nitrous acid peak.

<Example 3>
Except that in "(3) pH adjustment" of Example 1, 20 g of nitric acid having a concentration of 60% by mass was added while stirring the obtained mixed slurry to obtain a pH-adjusted slurry with a pH adjusted to 3.6. An amorphous solid electrolyte precursor powder according to Example 3 was obtained in the same manner as in Example 1.
Here, since 0.73 mol of nitric acid and 0.46 mol of ammonia were added until the pH-adjusted slurry according to Example 3 was obtained, the molar ratio of the added nitric acid and ammonia (NO ₃ /NH ₃ ) was 1.58.

For the obtained amorphous solid electrolyte precursor powder according to Example 3, in the same manner as in Example 1,
"(7) Analysis and Characterization of Amorphous Solid Electrolyte Precursor Powder (I) Elemental Analysis, (II) Nitrogen Content Analysis, (III) XRD Measurement of Amorphous Solid Electrolyte Precursor Powder, (IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder,
(8) Production and property evaluation of solid electrolyte having NASICON-type crystal structure (I) Production of solid electrolyte having NASICON-type crystal structure and evaluation by XRD measurement, (II) Ionic conductivity of solid electrolyte having NASICON-type crystal structure evaluation,"
Table 1 shows the results of elemental analysis, nitrogen content, conductivity, pH value and (NO ₃ /NH ₃ ) ratio in the pH-adjusted slurry, and presence or absence of nitrous acid peak.

<Example 4>
Except that in "(3) pH adjustment" of Example 1, 35 g of nitric acid having a concentration of 60% by mass was added while stirring the obtained mixed slurry to obtain a pH-adjusted slurry with a pH adjusted to 3.1. An amorphous solid electrolyte precursor powder according to Example 4 was obtained in the same manner as in Example 1.
Here, since 0.87 mol of nitric acid and 0.46 mol of ammonia are added until the pH-adjusted slurry according to Example 4 is obtained, the molar ratio of the added nitric acid and ammonia (NO ₃ /NH ₃ ) was 1.89.

For the obtained amorphous solid electrolyte precursor powder according to Example 4, in the same manner as in Example 1,
"(7) Analysis and Characterization of Amorphous Solid Electrolyte Precursor Powder (I) Elemental Analysis, (II) Nitrogen Content Analysis, (III) XRD Measurement of Amorphous Solid Electrolyte Precursor Powder, (IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder,
(8) Production and property evaluation of solid electrolyte having NASICON-type crystal structure (I) Production of solid electrolyte having NASICON-type crystal structure and evaluation by XRD measurement, (II) Ionic conductivity of solid electrolyte having NASICON-type crystal structure evaluation,"
Table 1 shows the results of elemental analysis, nitrogen content, conductivity, pH value and (NO ₃ /NH ₃ ) ratio in the pH-adjusted slurry, and presence or absence of nitrous acid peak.

<Example 5>
Except that in "(3) pH adjustment" of Example 1, 55 g of nitric acid with a concentration of 60% by mass was added while stirring the obtained mixed slurry to obtain a pH-adjusted slurry with a pH adjusted to 2.5. An amorphous solid electrolyte precursor powder according to Example 5 was obtained in the same manner as in Example 1.
Here, since 1.06 mol of nitric acid and 0.46 mol of ammonia are added until the pH-adjusted slurry according to Example 5 is obtained, the molar ratio of the added nitric acid and ammonia (NO ₃ /NH ₃ ) was 2.30.

For the obtained amorphous solid electrolyte precursor powder according to Example 5, in the same manner as in Example 1,
"(7) Analysis and Characterization of Amorphous Solid Electrolyte Precursor Powder (I) Elemental Analysis, (II) Nitrogen Content Analysis, (III) XRD Measurement of Amorphous Solid Electrolyte Precursor Powder, (IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder,
(8) Production and property evaluation of solid electrolyte having NASICON-type crystal structure (I) Production of solid electrolyte having NASICON-type crystal structure and evaluation by XRD measurement, (II) Ionic conductivity of solid electrolyte having NASICON-type crystal structure evaluation,"
Table 1 shows the results of elemental analysis, nitrogen content, conductivity, pH value and (NO ₃ /NH ₃ ) ratio in the pH-adjusted slurry, and presence or absence of nitrous acid peak.

<Example 6>
In the same manner as in Example 1, “(I) Germanium aqueous solution” and “(II) Lithium-, aluminum-, and phosphorus-containing aqueous solution” were prepared in “(1) Raw material aqueous solution preparation”. In Example 6, "(III) Titanium-containing aqueous solution" was further prepared, and will be described.

(III) Titanium-Containing Aqueous Solution To 35.8 g of hydrogen peroxide solution with a concentration of 35% by mass, 3.0 g of ammonia water with a concentration of 28% by mass was added, and then 1.51 g of metatitanic acid was added and stirred until completely dissolved. "(II) Aqueous solution containing lithium, aluminum and phosphorus" prepared in the same manner as in Example 1 was added to the solution to prepare an aqueous solution containing lithium, aluminum, phosphorus and titanium. The pH of the solution at this point was 4.0.

(2) Mixing 684 g of the alkaline germanium aqueous solution was taken and heated to 40° C. while stirring, and the total amount of the aqueous solution containing lithium, aluminum, phosphorus, and titanium was added thereto, and the aqueous solution was immediately after the addition. It became cloudy and a white mixed slurry was obtained. The pH of the resulting mixed slurry was 7.0.

(3) pH adjustment While stirring the obtained mixed slurry, 13 g of nitric acid having a concentration of 60% by mass was added to obtain a pH-adjusted slurry adjusted to pH 3.9.
Here, since 0.66 mol of nitric acid and 0.50 mol of ammonia are added until the pH-adjusted slurry according to Example 6 is obtained, the molar ratio of the added nitric acid and ammonia (NO ₃ /NH ₃ ) was 1.33.

An amorphous solid electrolyte precursor powder according to Example 6 was obtained in the same manner as in Example 1 using the resulting pH-adjusted slurry.
For the obtained amorphous solid electrolyte precursor powder according to Example 6, in the same manner as in Example 1,
"(7) Analysis and Characterization of Amorphous Solid Electrolyte Precursor Powder (I) Elemental Analysis, (II) Nitrogen Content Analysis, (III) XRD Measurement of Amorphous Solid Electrolyte Precursor Powder, (IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder,
(8) Production and property evaluation of solid electrolyte having NASICON-type crystal structure (I) Production of solid electrolyte having NASICON-type crystal structure and evaluation by XRD measurement, (II) Ionic conductivity of solid electrolyte having NASICON-type crystal structure evaluation,"
Table 1 shows the results of elemental analysis, nitrogen content, conductivity, pH value and (NO ₃ /NH ₃ ) ratio in the pH-adjusted slurry, and presence or absence of nitrous acid peak.

<Example 7>
In the same manner as in Example 1, “(I) Germanium aqueous solution” and “(II) Lithium-, aluminum-, and phosphorus-containing aqueous solution” were prepared in “(1) Raw material aqueous solution preparation”. Then, in "(2) Mixing", 684 g of the alkaline "germanium aqueous solution" was taken and heated to 40°C with stirring, and 4.1 g of zirconium oxynitrate was added and completely dissolved. When the entire amount of the "lithium-, aluminum-, and phosphorus-containing aqueous solution" was added thereto, the aqueous solution became cloudy immediately after the addition, and a white mixed slurry was obtained. The resulting mixed slurry had a pH of 4.6.

(3) pH adjustment While stirring the obtained mixed slurry, 5 g of nitric acid having a concentration of 60% by mass was added to obtain a pH-adjusted slurry adjusted to pH 3.9.
Here, since 0.61 mol of nitric acid and 0.45 mol of ammonia are added until the pH-adjusted slurry according to Example 7 is obtained, the molar ratio of the added nitric acid and ammonia (NO ₃ /NH ₃ ) was 1.37.

An amorphous solid electrolyte precursor powder according to Example 7 was obtained in the same manner as in Example 1 using the resulting pH-adjusted slurry.
For the obtained amorphous solid electrolyte precursor powder according to Example 7, in the same manner as in Example 1,
"(7) Analysis and Characterization of Amorphous Solid Electrolyte Precursor Powder (I) Elemental Analysis, (II) Nitrogen Content Analysis, (III) XRD Measurement of Amorphous Solid Electrolyte Precursor Powder, (IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder,
(8) Production and property evaluation of solid electrolyte having NASICON-type crystal structure (I) Production of solid electrolyte having NASICON-type crystal structure and evaluation by XRD measurement, (II) Ionic conductivity of solid electrolyte having NASICON-type crystal structure evaluation,"
Table 1 shows the results of elemental analysis, nitrogen content, conductivity, pH value and (NO ₃ /NH ₃ ) ratio in the pH-adjusted slurry, and presence or absence of nitrous acid peak.

<Example 8>
In the same manner as in Example 1, “(I) Germanium aqueous solution” and “(II) Lithium-, aluminum-, and phosphorus-containing aqueous solution” were prepared in “(1) Raw material aqueous solution preparation”. Then, in "(2) Mixing", 720 g of the alkaline germanium aqueous solution was separated, and 10.2 g of Li ₂ O ₁₁ Si ₅ solution (manufactured by Sigma-Aldrich) was added. The liquid was heated to 40° C. with stirring, and the entire amount of the above-mentioned "aqueous solution containing lithium, aluminum and phosphorus" was added thereto. Immediately after the addition, the aqueous solution became cloudy to obtain a white mixed slurry. The resulting mixed slurry had a pH of 4.4.

(3) pH adjustment While stirring the obtained mixed slurry, 9 g of nitric acid having a concentration of 60% by mass was added to obtain a pH-adjusted slurry adjusted to pH 3.9.
Here, since 0.62 mol of nitric acid and 0.46 mol of ammonia are added until the pH-adjusted slurry according to Example 8 is obtained, the molar ratio of the added nitric acid and ammonia (NO ₃ /NH ₃ ) was 1.35.

An amorphous solid electrolyte precursor powder according to Example 8 was obtained in the same manner as in Example 1 using the resulting pH-adjusted slurry.
For the obtained amorphous solid electrolyte precursor powder according to Example 8, in the same manner as in Example 1,
"(7) Analysis and Characterization of Amorphous Solid Electrolyte Precursor Powder (I) Elemental Analysis, (II) Nitrogen Content Analysis, (III) XRD Measurement of Amorphous Solid Electrolyte Precursor Powder, (IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder,
(8) Production and property evaluation of solid electrolyte having NASICON-type crystal structure (I) Production of solid electrolyte having NASICON-type crystal structure and evaluation by XRD measurement, (II) Ionic conductivity of solid electrolyte having NASICON-type crystal structure evaluation,"
Table 1 shows the results of elemental analysis, nitrogen content, conductivity, pH value and (NO ₃ /NH ₃ ) ratio in the pH-adjusted slurry, and presence or absence of nitrous acid peak.

<Comparative Example 1>
Except that in "(3) pH adjustment" of Example 1, 20 g of ammonia water having a concentration of 28% by mass was added while stirring the obtained slurry to obtain a pH-adjusted slurry adjusted to pH 5.5. An amorphous solid electrolyte precursor powder according to Comparative Example 1 was obtained by operating in the same manner as in Example 1.
A 30,000-fold SEM photograph of the amorphous solid electrolyte precursor powder according to Comparative Example 1 is shown in FIG.
Here, since 0.53 mol of nitric acid and 0.79 mol of ammonia are added until the pH-adjusted slurry according to Comparative Example 1 is obtained, the molar ratio of the added nitric acid and ammonia (NO ₃ /NH ₃ ) was 0.68.

For the obtained amorphous solid electrolyte precursor powder according to Comparative Example 1, in the same manner as in Example 1, "(7) Analysis and characteristic evaluation of amorphous solid electrolyte precursor powder (I) Elemental analysis , (II) nitrogen content analysis, (III) XRD measurement of amorphous solid electrolyte precursor powder, (IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder,
(8) Production and property evaluation of solid electrolyte having NASICON-type crystal structure (I) Production of solid electrolyte having NASICON-type crystal structure and evaluation by XRD measurement, (II) Ionic conductivity of solid electrolyte having NASICON-type crystal structure evaluation,"
Table 1 shows the results of elemental analysis, nitrogen content, conductivity, pH value and (NO ₃ /NH ₃ ) ratio in the pH-adjusted slurry, and presence or absence of nitrous acid peak. The nitrogen content was below the measurement limit (0.01% by mass).

<Comparative Example 2>
32.3 g of germanium dioxide was added to 652.9 g of pure water and stirred, and 18.3 g of ammonia water having a concentration of 28% by mass was added to dissolve the germanium dioxide. Further, 21.1 g of lithium acetate, 38.7 g of aluminum nitrate nonahydrate, 71.2 g of ammonium dihydrogen phosphate, and 95 g of nitric acid having a concentration of 60% by mass are added in this order to obtain a raw material aqueous solution having a pH of 0.2. Aqueous ammonia was added to adjust the pH to 5.3 to obtain a pH-adjusted raw material aqueous solution. The resulting pH-adjusted raw aqueous solution was not a slurry but was transparent.
Here, since 1.21 mol of nitric acid and 4.61 mol of ammonia are added until the pH-adjusted transparent raw material aqueous solution according to Comparative Example 2 is obtained, the molar ratio of the added nitric acid and ammonia ( _NO3 / _NH3 ) was 0.26.

After water was removed from the pH-controlled transparent raw material aqueous solution according to Comparative Example 2 at 100° C. for 24 hours, it was further dried at 260° C. for 5 hours to obtain a dry powder. The obtained dry powder was calcined in a hydrogen atmosphere at 450° C. for 2 hours, and the obtained calcined powder was pulverized in the same manner as in Example 1 to obtain an amorphous solid electrolyte precursor according to Comparative Example 2. A powder was obtained.
A 10,000-fold SEM photograph of the amorphous solid electrolyte precursor powder according to Comparative Example 2 is shown in FIG.

For the obtained amorphous solid electrolyte precursor powder according to Comparative Example 2, in the same manner as in Example 1,
"(7) Analysis and Characterization of Amorphous Solid Electrolyte Precursor Powder (I) Elemental Analysis, (II) Nitrogen Content Analysis, (III) XRD Measurement of Amorphous Solid Electrolyte Precursor Powder, (IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder,
(8) Production and property evaluation of solid electrolyte having NASICON-type crystal structure (I) Production of solid electrolyte having NASICON-type crystal structure and evaluation by XRD measurement, (II) Ionic conductivity of solid electrolyte having NASICON-type crystal structure evaluation,"
Table 1 shows the results of elemental analysis, nitrogen content, conductivity, pH value and (NO ₃ /NH ₃ ) ratio in the pH-adjusted slurry, and presence or absence of nitrous acid peak. The nitrogen content was below the measurement limit (0.01% by mass).

<Comparative Example 3>
410 g of Ge(OEt) and 33.25 g of Al(OBt) were added to 97.68 g of butanol to obtain a germanium-aluminum solution in which germanium and aluminum were dissolved. Further, 32.61 g of lithium acetate and 9.098 g of ammonium dihydrogen phosphate were added to 379.64 g of pure water to obtain a lithium-phosphorus aqueous solution in which lithium and phosphorus were dissolved.

The germanium/aluminum solution and the lithium/phosphorus solution were mixed to obtain a mixed solution. The mixed solution was dried in an atmosphere of 100° C. and then vacuum-dried at 110° C. to obtain a dry powder. The dried powder was calcined at 400° C. in a nitrogen atmosphere, and the obtained calcined powder was pulverized in the same manner as in Example 1 to obtain an amorphous solid electrolyte precursor powder according to Comparative Example 3.
In Comparative Example 3, the solvent of the mixed solution was an organic solvent, which was different from the other Examples and Comparative Examples, and the pH value of the mixed solution was not measured because it was not necessary to adjust the pH with nitric acid. .

For the obtained amorphous solid electrolyte precursor powder according to Comparative Example 3, in the same manner as in Example 1, "(7) Analysis and characteristic evaluation of amorphous solid electrolyte precursor powder (I) Elemental analysis , (II) nitrogen content analysis, (III) XRD measurement of amorphous solid electrolyte precursor powder, (IV) Raman spectrum measurement of amorphous solid electrolyte precursor powder,
(8) Production and property evaluation of solid electrolyte having NASICON-type crystal structure (I) Production of solid electrolyte having NASICON-type crystal structure and evaluation by XRD measurement, (II) Ionic conductivity of solid electrolyte having NASICON-type crystal structure evaluation,"
Table 1 shows the results of elemental analysis, the nitrogen content, the electrical conductivity, and the presence or absence of nitrous acid peaks. The nitrogen content was below the measurement limit (0.01% by mass).

<summary>

From Table 1, solid electrolytes having a NASICON-type crystal structure obtained by crystallizing the amorphous solid electrolyte precursor powders according to Examples 1 to 8 containing a predetermined amount of nitrogen are shown in Comparative Examples 1 to 3. It was found that the ionic conductivity is higher than that of the solid electrolyte having the NASICON type crystal structure obtained by crystallizing the amorphous solid electrolyte precursor powder. The amorphous solid electrolyte precursor powder according to the present invention is an amorphous precursor containing lithium, aluminum, germanium, and phosphorus that can be crystallized to obtain a solid electrolyte exhibiting high ionic conductivity. It is a solid powder and can be suitably used as a precursor powder of a solid electrolyte used in an all-solid-state battery.

Claims (10)

1% by mass or more and 4% by mass or less of lithium,
0.5% by mass or more and 6% by mass or less of aluminum,
15% by mass or more and 35% by mass or less of germanium,
10% by mass or more and 30% by mass or less of phosphorus,
containing 0.05% by mass or more and 3% by mass or less of nitrogen, the balance being oxygen;
Amorphous solid electrolyte precursor powder. 2. The amorphous solid electrolyte precursor powder according to claim 1, wherein said amorphous solid electrolyte precursor powder contains 2.5% by mass or less of nitrogen. 3. The amorphous solid electrolyte precursor powder according to claim 1, wherein said amorphous solid electrolyte precursor powder contains 0.1% by mass or more of nitrogen. The amorphous solid electrolyte precursor powder according to any one of claims 1 to 3, wherein the amorphous solid electrolyte precursor powder contains 1.5% by mass or less of nitrogen and 23.5% by mass or more of germanium. Solid electrolyte precursor powder. 5. Amorphous solid electrolyte precursor powder according to any one of claims 1 to 4, containing the nitrogen in the form of nitrous acid. 6. Any one of claims 1 to 5, wherein the amorphous solid electrolyte precursor powder further contains one or more elements selected from the group consisting of titanium, zirconium and silicon in a total amount of 5% by mass or less. The amorphous solid electrolyte precursor powder according to item 1. Lithium, aluminum, germanium, phosphorus, nitrogen, and oxygen containing 1% by mass to 4% by mass of lithium, 0.5% by mass to 6% by mass of aluminum, 15% by mass to 35% by mass of germanium, and phosphorus A method for producing an amorphous solid electrolyte precursor powder containing 10% by mass or more and 30% by mass or less, 0.05% by mass or more and 3% by mass or less of nitrogen, and the balance being oxygen,
A step of adjusting the pH of a liquid containing lithium, aluminum, germanium, phosphorus and ammonia to 2 or more and less than 4.5 to obtain a pH-adjusted slurry;
spray drying the pH adjusted slurry to obtain a dry powder;
and sintering the dry powder at 300° C. or higher and 500° C. or lower. 8. The amorphous solid electrolyte precursor powder according to claim 7, wherein the molar ratio ( _NO3 / _NH3 ) of nitric acid and ammonia in the pH-adjusted slurry is 1.0 or more and 3.0 or less. manufacturing method. Further, one or more selected from the group consisting of titanium, zirconium and silicon is added to the liquid containing lithium, aluminum, germanium, phosphorus and ammonia, and titanium and zirconium are added to the amorphous solid electrolyte precursor powder. 9. The method for producing an amorphous solid electrolyte precursor powder according to claim 7, wherein the total amount of one or more elements selected from the group consisting of silicon and silicon is contained in a range of 5% by mass or less. A method for producing a solid electrolyte having a NASICON-type crystal structure, comprising the step of firing the amorphous solid electrolyte precursor powder according to any one of claims 1 to 6 at a temperature higher than 500°C.

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