Powder having a NASICON-type crystal structure as the main phase, and molded body made from powder having a NASICON-type crystal structure as the main phase.

Abstract

To provide powder having NASICON-type crystal structure as a main phase capable of improving density (reducing porosity) of a molded article as a solid electrolyte layer.SOLUTION: There is provided powder containing lithium, aluminum, germanium and phosphorus and having NASICON-type crystal structure as a main phase. When the composition of the powder is expressed by the general formula Li1+x+zAlxGe2-xP3+yO12+δ, the relations 0.0<x<2.0, 0.1≤y≤0.5, and 0.2≤y / z≤0.6 are satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a powder having a NASICON-type crystal structure as its main phase, a molded article using the powder having the NASICON-type crystal structure as its main phase, a method for producing the powder having the NASICON-type crystal structure as its main phase, and a method for producing the molded article. [Background technology]

[0002] Solid electrolyte powders with a NASICON-type crystal structure that have high ionic conductivity are used as the solid electrolyte material for all-solid-state batteries. As the aforementioned solid electrolyte powder, for example, a solid electrolyte powder containing lithium, aluminum, germanium, and phosphorus, as described in Patent Document 1, is known. Furthermore, Patent Document 1 describes a process to obtain an all-solid-state battery by stacking laminated units, each having a green sheet containing an oxide-based solid electrolyte powder, a paste coating for a first electrode layer formed on the first main surface of the green sheet, and a paste coating for a second electrode layer formed on the second main surface of the green sheet, and then firing the laminated units at a high temperature of 400°C to 1000°C to form a laminated chip. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-187897 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In all-solid-state batteries, the solid electrolyte layer plays the role of a separator, similar to conventional liquid-based lithium-ion batteries. To increase battery capacity by increasing the density of the electrolyte layer, one approach is to thin the solid electrolyte layer and create multiple layers. However, according to the study by the present inventors, it has been found that when the solid electrolyte layer is made thin, if the density of the solid electrolyte layer is low, the electrodes may short-circuit. The present invention has been made under the above-described circumstances, and the problem to be solved is to provide a powder having a NASICON-type crystal structure as a main phase, which can improve the density (reduce the porosity) of a molded body serving as a solid electrolyte layer.

Means for Solving the Problem

[0005] As a result of research to solve the above problems, the present inventors have found that in a powder containing lithium, aluminum, germanium, and phosphorus and having a NASICON-type crystal structure as a main phase, the composition ratio is expressed by the general formula Li 1+x Al x Ge 2-x P3O 12 and when the composition is deviated from the stoichiometric composition by containing an excess of lithium atoms and phosphorus atoms compared to the stoichiometric composition where 0 < x < 2.0, and the powder is molded and fired to obtain a molded body serving as a solid electrolyte layer, it is possible to improve the density (reduce the porosity) of the molded body. More specifically, in a powder having a NASICON-type crystal structure as a main phase, the molar ratio of lithium atoms and the molar ratio of phosphorus atoms are made excessive within a predetermined range compared to the molar ratio of the stoichiometric composition, and the molar ratio (P / Li) of lithium atoms and phosphorus atoms made excessive from the stoichiometric composition is within a predetermined range, thereby finding that the above problem can be solved and completing the present invention.

[0006] That is, a first invention for solving the above problems is a powder containing lithium, aluminum, germanium, and phosphorus and having a NASICON-type crystal structure as a main phase, where the composition of the powder is represented by the general formula Li 1+x+z Al x Ge 2-x P 3+y O 12+δWhen expressed as , it is a powder having a NASICON-type crystal structure as the main phase, where 0.0 < x < 2.0, 0.1 ≤ y ≤ 0.5, and 0.2 ≤ y / z ≤ 0.6. The second invention is a powder having a NASICON-type crystal structure as the main phase according to the first invention, wherein the X-ray diffraction peak of the main phase belongs to No. 01-080-1922 of the Powder Diffraction File provided by the International Centre for Diffraction Data. The third invention is when the powder having a NASICON-type crystal structure as the main phase has a secondary phase different from the main phase, a powder having a NASICON-type crystal structure as the main phase according to the first invention, wherein the value of (secondary phase peak intensity) / (main phase peak intensity) between the value of the maximum X-ray diffraction peak intensity in the main phase and the value of the maximum X-ray diffraction peak intensity in the secondary phase is 0.35 or less. The fourth invention is a powder having a NASICON-type crystal structure as the main phase according to the first invention, wherein the value of y is 0.2 or more. The fifth invention is a molded body which is a molded product of a powder having a NASICON-type crystal structure as the main phase according to any one of the first to fourth inventions. The sixth invention is a method for producing a powder having a NASICON-type crystal structure as the main phase, comprising: a step of obtaining a slurry containing lithium, aluminum, germanium, and phosphorus; a step of drying the slurry to obtain a dry powder; a firing step of firing the dry powder to obtain a powder having a NASICON-type crystal structure as the main phase, and in the slurry, the molar ratio of each atom of lithium, aluminum, germanium, and phosphorus is represented by the proportional formula Li:Al:Ge:P = (1 + x + z):x:(2 - x):(3 + y). The slurry is prepared such that x, y, and z in the proportional formula satisfy 0.0 < x < 2.0, 0.1 ≤ y ≤ 0.5, and 0.2 ≤ y / z ≤ 0.6, which is a method for producing a powder having a NASICON-type crystal structure as the main phase. The seventh invention is The step of obtaining the slurry includes a step of mixing an aqueous solution containing germanium and an aqueous solution containing lithium, aluminum, and phosphorus, which is a method for producing a powder having a NASICON-type crystal structure as the main phase described in the sixth invention. The eighth invention is The pH value of the aqueous solution containing lithium, aluminum, and phosphorus is pH 1 to 5.5, which is a method for producing a powder having a NASICON-type crystal structure as the main phase described in the seventh invention. The ninth invention is The pH value of the slurry is pH 1 to 6.5, which is a method for producing a powder having a NASICON-type crystal structure as the main phase described in the sixth invention. The tenth invention is A molded body is produced by a step of firing a powder produced by the method for producing a powder having a NASICON-type crystal structure as the main phase according to any one of the sixth to ninth inventions after compression molding, which is a method for producing a molded body that is a molded product of a powder having a NASICON-type crystal structure as the main phase.

Effect of the Invention

[0007] When the powder having a NASICON-type crystal structure as the main phase according to the present invention is molded into a molded body, the porosity of the molded body can be made 20% or less.

Brief Description of the Drawings

[0008] [Figure 1] It is a manufacturing flowchart of a powder having a NASICON-type crystal structure as the main phase according to the present invention. [Figure 2] It is an XRD spectrum of a powder having a NASICON-type crystal structure as the main phase according to an example.

Mode for Carrying Out the Invention

[0009] The embodiments for implementing the present invention will be described in the following order: 1. a powder having a NASICON-type crystal structure as a main phase according to the present invention; 2. a method for producing a powder having a NASICON-type crystal structure as a main phase according to the present invention; 3. an evaluation of a powder having a NASICON-type crystal structure as a main phase according to the present invention.

[0010] 1. A powder having a NASICON-type crystal structure as a main phase according to the present invention The stoichiometric composition (so-called LAGP) of a lithium ion conductor containing lithium, aluminum, germanium, and phosphorus and having a NASICON-type crystal structure as a main phase is represented by (Formula 1). General formula Li 1+x Al x Ge 2-x P3O 12 ····(Formula 1)

[0011] On the other hand, the powder having a NASICON-type crystal structure as a main phase according to the present invention is a powder containing lithium, aluminum, germanium, and phosphorus and having a NASICON-type crystal structure as a main phase, but its composition ratio contains an excess of lithium atoms and phosphorus atoms compared to the stoichiometric composition of the above-described lithium ion conductor, and deviates from the stoichiometric composition. When the powder having a NASICON-type crystal structure as a main phase according to the present invention is molded and fired to form a molded body serving as a solid electrolyte layer, the density of the molded body can be improved (the porosity is reduced), and the value of the porosity is 20% or less. That is, when the powder having a NASICON-type crystal structure as a main phase according to the present invention is specifically represented by (Formula 2), it is a powder having a NASICON-type crystal structure as a main phase where 0. < x < 2.0, 0.1 ≤ y ≤ 0.5, and 0.2 ≤ y / z ≤ 0.6. General formula Li 1+x+z Al x Ge 2-x P3+y O 12+δ ...(Formula 2)

[0012] However, in the above (Equation 2), y is Li in (Equation 1) above. 1+x Al x Ge 2-x P3O 12 This serves as an indicator of the excess amount of phosphorus atoms in the lithium-ion conductor powder, relative to the stoichiometric composition of the aforementioned powder. z is Li as in (Equation 1) above. 1+x Al x Ge 2-x P3O 12 This serves as an indicator of the excess amount of lithium atoms in the lithium ion conductor powder, relative to the stoichiometric composition of the aforementioned powder. Furthermore, the ratio (y / z), which is the ratio of the excess amount of lithium atoms to the excess amount of phosphorus atoms, is adjusted so that 0.2 ≤ y / z ≤ 0.6.

[0013] The composition of the powder having the NASICON-type crystal structure as the main phase, as described above, is obtained by preparing a solution by alkali melting the powder having the NASICON-type crystal structure as the main phase, performing quantitative analysis of each constituent element in the solution using an ICP-OES apparatus, and calculating the molar ratio of each element from the obtained quantitative analysis results of each constituent element. Furthermore, by calculating the converted molar ratio of each element when the sum of the obtained molar ratios of aluminum and germanium is fixed at 2, the values ​​of x, y, and z in (Equation 2) can be determined. Then, the excess amounts of phosphorus atoms and lithium atoms in the powder having the NASICON-type crystal structure as the main phase, relative to the stoichiometric composition of (Equation 1), can be determined.

[0014] δ is a value calculated according to the excess amounts of lithium and phosphorus atoms relative to (Equation 1) above. Specifically, in the powder having the NASICON-type crystal structure as the main phase according to the present invention, lithium is considered to be monovalent, aluminum trivalent, germanium tetravalent, and phosphorus pentavalent, so δ is expressed by (Equation 3). δ=(z×0.5)+(y×2.5) (Formula 3)

[0015] When manufacturing a molded body that forms a solid electrolyte layer using a powder having the NASICON-type crystal structure as the main phase according to the present invention, it is presumed that low-melting-point Li3PO4 is generated within the particles during the firing stage, and that this Li3PO4 acts as a sintering aid, reducing the porosity of the molded body after firing. However, even if Li3PO4 is present in the molded body, its amount is below the XRD detection limit described later, and therefore it cannot be detected by XRD.

[0016] The powder having a NASICON-type crystal structure as its main phase has, in the XRD spectrum obtained by XRD measurement, an X-ray diffraction peak of an oxide having a NASICON-type crystal structure as its main phase. Here, the main phase refers to the crystal phase to which the highest intensity diffraction peak in the XRD spectrum obtained by XRD measurement belongs. Whether or not a diffraction peak is attributed can be determined by comparing the XRD spectrum of a powder having a NASICON-type crystal structure as its main phase with the diffraction peaks of oxides having a NASICON-type crystal structure registered in the database. For example, LiGeP3O is an oxide having a NASICON-type crystal structure. 12The dominant phase can be determined by comparing it with the ICDD (International Centre for Diffraction Data) PDF (Powder Diffraction File) No. 01-080-1922. More specifically, when comparing the XRD spectrum of a powder having a NASICON-type crystal structure as the dominant phase with the ICDD PDF No. 01-080-1922 of an oxide having a NASICON-type crystal structure, the peaks detected by the peak search method are in the range of 25.1±0.5°, 30.4±0.5°, 33.3±0.5°, and 34.0°±0.5°, and the peak intensities increase in the order of 25.1±0.5°, 30.4±0.5°, 34.0°±0.5°, and 33.3±0.5°, it can be determined that the crystal phase belongs to PDF No. 01-080-1922.

[0017] The powder having the NASICON-type crystal structure as its main phase may contain a sub-phase different from the main phase. When the powder having the NASICON-type crystal structure as its main phase contains the sub-phase, it is preferable that the value of [(sub-phase peak intensity) / (main phase peak intensity)], which is the ratio of the maximum X-ray diffraction peak intensity in the main phase to the maximum X-ray diffraction peak intensity in the sub-phase, is 0.35 or less in the XRD measurement described later. On the other hand, if the powder having the NASICON-type crystal structure as its main phase does not contain the sub-phase, and the value of [(sub-phase peak intensity) / (main phase peak intensity)] is 0, there is of course no problem.

[0018] 2. Method for producing a powder having a NASICON-type crystal structure as the main phase according to the present invention The powder having a NASICON-type crystal structure as its main phase according to the present invention is obtained by mixing aqueous solutions of raw materials containing each constituent element to obtain a slurry, drying the slurry to obtain a dried powder, and calcining the dried powder.

[0019] The following describes the method for producing a powder having a NASICON-type crystal structure as the main phase according to the present invention, referring to Figure 1, which is a production flow chart, in the following order: (1) preparation of raw material aqueous solution, (2) mixing, (3) drying, (4) calcination, (5) particle size adjustment, and (6) production of molded body.

[0020] (1) Preparation of raw material aqueous solution Water-soluble raw materials containing lithium, aluminum, germanium, and phosphorus, which are constituent elements of a powder having the NASICON-type crystal structure as its main phase according to the present invention, are dissolved in water to obtain aqueous solutions. Specifically, we will prepare an aqueous solution containing germanium and an aqueous solution containing lithium, aluminum, and phosphorus. Therefore, we will explain the preparation of the aqueous solution containing germanium in the following order: (I) preparation of the aqueous solution containing germanium, and (II) preparation of the aqueous solution containing lithium, aluminum, and phosphorus.

[0021] (I) Preparation of an aqueous solution containing germanium A germanium compound powder is mixed with pure water to prepare an aqueous solution containing germanium. It is preferable to use GeO2 as the germanium compound and further add ammonia water to prepare the aqueous solution containing germanium. By dissolving GeO2 in ammonia water, germanium is converted to (NH4)3HGe7O after the drying process described later. 16 It is thought that they are in a complex state. Furthermore, it is believed that germanium maintains a complex state within the powder precursor, which has a NASICON-type crystal structure as its main phase, thereby suppressing the formation of GeO2 during calcination.

[0022] (II) Preparation of aqueous solutions containing lithium, aluminum, and phosphorus Aqueous solutions containing lithium, aluminum, and phosphorus are prepared by mixing lithium compound powder, aluminum compound powder, and phosphorus compound solution with pure water. Examples of lithium compound powders include Li2SO4, Li2CO3, LiCl, and LiNO3. Examples of aluminum compound powders include Al2(SO4)3, Al2(CO3)3, AlCl3, and Al(NO3)3. Examples of phosphorus compound aqueous solutions include (NH4)2HPO4 aqueous solution, H3PO4 aqueous solution, (NH4)H2PO4 aqueous solution, and (NH4)3PO4 aqueous solution.

[0023] When preparing an aqueous solution containing lithium, aluminum, and phosphorus, the molar ratio of each atom of lithium, aluminum, and phosphorus contained in the slurry described later is adjusted so that the proportion Li:Al:P=(1+x+z):x:(3+y), and in this case, y and z are adjusted so that 0.1≦y≦0.5 and 0.2≦y / z≦0.6. For example, if the molar ratio of aluminum atoms in the slurry is 0.5, the molar ratio of lithium atoms is (1.5 + z) and the molar ratio of phosphorus atoms is (3.0 + y), and y and z are adjusted so that 0.1 ≤ y ≤ 0.5 and 0.2 ≤ y / z ≤ 0.6.

[0024] Since the compounds of lithium, aluminum, and phosphorus are acidic, it is preferable that the aqueous solution containing lithium, aluminum, and phosphorus is also acidic. This is because if the aqueous solution is alkaline, crystalline Li3PO4 may be formed. To suppress the formation of crystalline Li3PO4 from the added lithium and phosphorus, and to prevent the inclusion of a subphase different from the main phase of the NASICON-type crystal structure, the preferred pH range for an aqueous solution containing lithium, aluminum, and phosphorus is pH 1 to 5.5.

[0025] (2) Mixture This step involves mixing the two aqueous solutions prepared in "(1) Preparation of raw material aqueous solutions" to obtain a slurry containing the constituent elements of a powder having a NASICON-type crystal structure as its main phase. For example, when an aqueous solution containing acidic lithium, aluminum, and phosphorus is added to an aqueous solution containing alkaline germanium dissolved in ammonia, turbidity immediately occurs, and a slurry containing lithium, aluminum, germanium, and phosphorus can be obtained by coprecipitation. In this mixing step, the liquid temperature does not particularly need to be considered, and it may or may not be heated. It is considered that in the slurry, there are constituent elements precipitated as hydroxides and constituent elements present as ions. Realizing a supersaturated state where the ion concentration product of the constituent elements is higher than the solubility product and generating a slurry using the coprecipitation method is essential for obtaining NASICON-type oxide powder having a NASICON-type crystal structure in order to improve the uniformity of the constituent elements. During mixing, the molar ratio of each atom of lithium, aluminum, germanium, and phosphorus is adjusted so that the proportional formula Li:Al:Ge:P = (1 + x + z):x:(2 - x):(3 + y) is satisfied. At this time, x is adjusted to be 0.0 < x < 2.0, and y and z are adjusted to be 0.1 ≤ y ≤ 0.5 and 0.2 ≤ y / z ≤ 0.6. From the viewpoint of avoiding the formation of the above-described crystalline Li3PO4, it is preferable to maintain acidity in the slurry. For example, the preferable range of the pH value of the slurry is pH 1 to 6.5. More preferably, it is pH 2 to 5.

[0026] (3) Drying This step involves drying the water in the slurry obtained in "(2) Mixing" to obtain a dried powder, which is a precursor to a powder having a NASICON-type crystal structure as its main phase. The drying method is not particularly limited, but spray drying using a spray dryer or the like is preferred. Spray drying rapidly precipitates the constituent elements that exist as ions in the slurry in a short time, thus reducing the non-uniformity of precipitation caused by differences in solubility between constituent elements. As a result, a dried powder with a uniform composition can be obtained, and a dried powder, which is a precursor to a powder having a NASICON-type crystal structure as its main phase with suppressed GeO2 formation, can be produced more reliably. The drying temperature should be set appropriately so that no water remains in the resulting precursor to the powder having a NASICON-type crystal structure as its main phase.

[0027] (4) Firing This step involves calcining the powder precursor having a NASICON-type crystal structure as the main phase, obtained in "(3) Drying" above, to obtain calcined powder having a NASICON-type crystal structure as the main phase. Specifically, the powder is heated from room temperature to 600°C or higher and up to 900°C or lower in an air atmosphere at a heating rate of 0.1°C / min or higher and up to 20°C / min or lower, and then calcined in an air atmosphere for 120 minutes to obtain calcined powder having a NASICON-type crystal structure as the main phase. Furthermore, when performing the main calcination at 600°C or higher and up to 900°C or lower, it is also preferable to first calcin the powder precursor at a temperature of 200°C or higher and up to less than 400°C. The method of calcination is not particularly limited, but calcination using a rotary kiln is preferred.

[0028] (5) Particle size adjustment In the production of a powder having a NASICON-type crystal structure as the main phase, calcined powder having a NASICON-type crystal structure as the main phase may be used as is, but the particle size and specific surface area may be adjusted as desired. Although known methods can be used to adjust the particle size and specific surface area, wet grinding using a bead mill or the like is preferred.

[0029] In wet grinding using a bead mill, particle size and specific surface area can be adjusted as appropriate by known methods such as the material of the media (beads), the diameter of the media (beads), the ratio of media (beads) to slurry, slurry concentration, grinding time, and rotation speed. If wet grinding is performed, solid-liquid separation is carried out after the wet grinding process, and the recovered powder having a NASICON-type crystalline structure as the main phase is dried. The particle size of the powder having the NASICON-type crystal structure as the main phase according to the present invention is preferably such that the volume-based cumulative particle size distribution (D50) value is 0.1 μm or more and 10 μm or less.

[0030] As the solvent during wet grinding, an organic solvent is preferred, specifically IPA, from the viewpoint of preventing lithium in the powder having a NASICON-type crystal structure as the main phase from undergoing ion exchange with protons, which would reduce the ion conductivity of the molded body, a solid electrolyte. This is because IPA volatilizes during drying after grinding and does not remain in the NASICON-type oxide powder. When using a bead mill for grinding, alumina and zirconia are preferred as bead materials from the viewpoint of preventing impurity contamination. After wet grinding, it is preferable to dry the NASICON-type oxide powder at a temperature above the boiling point of the solvent used and below the firing temperature during "(4) sintering" to remove the solvent. Furthermore, if the moisture content of the obtained powder having a NASICON-type crystal structure as the main phase is excessively low, a step may be included in which the powder is exposed to a moisture-containing atmosphere for a predetermined time to adjust its moisture content.

[0031] (6) Manufacturing of molded products A molded body can be manufactured using powder having a NASICON-type crystal structure as its main phase by filling a mold with the manufactured powder, applying pressure to compress and mold it, and then firing the resulting compressed molded body. The compression molding pressure should preferably be between 1 MPa and 300 MPa, and the compression molding should be performed for between 1 second and 10 hours. Standard molds and press equipment can be used. The firing temperature is preferably between 600°C and 1000°C.

[0032] 3. Evaluation of powder having a NASICON-type crystal structure as the main phase according to the present invention A powder having the NASICON-type crystal structure according to the present invention as its main phase was evaluated by compositional analysis, XRD measurement, molded body preparation, and porosity measurement. As a result, compositional analysis revealed that the powder having the NASICON-type crystal structure as its main phase contains lithium, aluminum, germanium, and phosphorus, and XRD measurement confirmed that it has the NASICON-type crystal structure as its main phase. Furthermore, it was found that the porosity of the molded body made using the powder having the NASICON-type crystal structure as its main phase was 20% or less. The specific details of the compositional analysis, XRD measurement, fabrication of a molded body using the powder having the NASICON-type crystal structure as the main phase, and porosity measurement of the powder according to the present invention will be explained in the examples described later. [Examples]

[0033] <Example 1> Based on the flowchart showing the manufacturing process of the powder having the NASICON-type crystal structure as the main phase described above, the powder having the NASICON-type crystal structure as the main phase according to Example 1 was manufactured, and its properties were analyzed and evaluated. The process is described in the following order: (1) preparation of an aqueous solution containing germanium, (2) preparation of an aqueous solution containing lithium, aluminum, and phosphorus, (3) preparation of a raw material slurry, (4) drying, (5) calcination, and (6) analysis and characterization of the powder having the NASICON-type crystal structure as the main phase.

[0034] (1) Preparation of an aqueous solution containing germanium, 34.54 g of GeO2 (99.999% manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to 327.22 g of pure water, and then 8.24 g of 28% by mass aqueous ammonia (28% manufactured by Nacalai Tesque) was added. The mixture was stirred at room temperature for 24 hours to obtain 370 g of a clear aqueous solution containing germanium. The formulation is shown in Table 1.

[0035] (2) Preparation of aqueous solutions containing lithium, aluminum, and phosphorus 70.47 g of 85% H3PO4 aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to 480 g of pure water, and 4.9 g of Al(OH)3 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added. The mixture was then heated to 70°C to obtain a clear aqueous solution. To the obtained aqueous solution, 13.63 g of LiOH·H2O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and stirred until a clear aqueous solution was obtained, resulting in an aqueous solution containing lithium, aluminum, and phosphorus. The pH value of the obtained aqueous solution containing lithium, aluminum, and phosphorus was 2.3. The formulation and pH value are shown in Table 1.

[0036] (3) Preparation of raw material slurry When the entire amount of the aqueous solution containing lithium, aluminum, and phosphorus was added to the germanium-containing aqueous solution while stirring, the aqueous solution became cloudy immediately after the addition, and a white raw material slurry according to Example 1 was obtained. The pH value of the obtained raw material slurry was 3.3. This pH value is shown in Table 1. The mole amounts of each element in the raw material slurry were calculated from the initial composition and found to be 0.32 mol of lithium, 0.06 mol of aluminum, 0.33 mol of germanium, and 0.61 mol of phosphorus. The molar ratios of each element were converted by fixing the sum of the molar ratios of the aluminum sites and the germanium sites to 2, and finding that the molar ratio of lithium was 1.64, the molar ratio of aluminum was 0.31, the molar ratio of germanium was 1.69, and the molar ratio of phosphorus was 3.13. These values ​​are shown in Table 2. The converted molar ratios of each element were substituted into the proportion Li:Al:P=(1+x+z):x:(3+y). This resulted in 1.64:0.31:3.13=(1+x+z):x:(3+y), leading to x=0.31, y=0.13, and z=0.33, and thus y / z=0.39. These values ​​are shown in Table 2.

[0037] (4) Drying The raw material slurry was spray-dried using a spray dryer (SD-1000, manufactured by Tokyo Rikakikai Co., Ltd.) to evaporate the water in the raw material slurry and cause a solid phase to precipitate all at once, obtaining a white precursor powder. The spray-drying conditions were an inlet temperature of 180°C, an outlet temperature of 90°C, and an addition rate of 10 g / min for the raw material slurry.

[0038] (5) Firing The precursor powder obtained by spray drying was placed in an alumina container, and the temperature was raised from room temperature to 600°C at a heating rate of 5°C / min under an atmospheric atmosphere, and then calcined at 600°C for 120 minutes to obtain a powder containing lithium, aluminum, germanium, and phosphorus according to Example 1, with a NASICON-type crystal structure as the main phase.

[0039] (6) Analysis and characterization of powders having a NASICON-type crystal structure as the main phase. The powder obtained in Example 1, which has the NASICON-type crystal structure as its main phase, was subjected to (I) compositional analysis, (II) XRD measurement, and (III) molded body preparation and porosity measurement. The methods and results for each are described below.

[0040] (I) Composition analysis An alkali molten salt was prepared by adding sodium carbonate as a flux to a powder having the NASICON-type crystal structure as the main phase according to Example 1. The alkali molten salt was dissolved in nitric acid, and elemental analysis was performed on the resulting solution using an ICP-OES instrument (Agilent ICP-720). The quantitative analysis values ​​(mass%) of the constituent elements lithium, aluminum, germanium, and phosphorus were 2.81 mass% for lithium, 2.09 mass% for aluminum, 27.7 mass% for germanium, and 22.3 mass% for phosphorus. These values ​​are shown in Table 3.

[0041] Next, the value obtained by dividing the quantitative analysis value (mass%) of each constituent element by the atomic weight of that element, the value of quantitative analysis value (mass%) / atomic weight of each constituent element (mass%) / atomic weight of each constituent element, is: The values ​​were 0.40 mass% / atomic weight for lithium, 0.08 mass% / atomic weight for aluminum, 0.38 mass% / atomic weight for germanium, and 0.72 mass% / atomic weight for phosphorus. These values ​​are listed in Table 3.

[0042] As described above, in the above formula (2) which shows a powder having the NASICON-type crystal structure as the main phase according to the present invention, the sum of the molar ratios of germanium and aluminum is fixed at 2. On the other hand, the sum of the [quantitative analysis values ​​of germanium and aluminum (mass%) / (atomic weight of each constituent element)] is 0.46. Therefore, by multiplying the value of [quantitative analysis value of each element (mass%) / sum of atomic weights of each constituent element] by a coefficient of 2 / 0.46 = 4.35, the molar ratio values ​​of each element in the aforementioned (Equation 2) of the powder having the NASICON-type crystal structure as the main phase according to the present invention can be obtained. The values ​​of this coefficient are shown in Table 3. The molar ratios of each element obtained were 1.74 for lithium, 0.35 for aluminum, 1.65 for germanium, and 3.13 for phosphorus. These values ​​are shown in Table 3.

[0043] Next, in order to calculate y and z in (Equation 2), the molar ratio values of each of the obtained elements were substituted into the proportional equation Li:Al:P = (1 + x + z):x:(3 + y). As a result, 1.74:0.35:3.13 = (1 + x + z):x:(3 + y), from which x = 0.35, y = 0.13, z = 0.39 were derived, and y / z = 0.33 was derived. These values are listed in Table 4. And, from the results of the compositional analysis described above, when the total value of the molar ratio of germanium and the molar ratio of aluminum was fixed at 2, the stoichiometric composition of the powder mainly having the NASICON-type crystal structure according to Example 1 was Li 1.32 Al 0.32 Ge 1.68 P3O 12 as follows. Also, y = 0.13 and z = 0.39 were substituted into (Equation 3). As a result, δ = 0.52 was derived. This value is listed in Table 4. Also, the value of the volume-based cumulative particle size distribution (D50) of the powder mainly having the NASICON-type crystal structure according to Example 1 was 6.0 μm. This value is listed in Table 4.

[0044] (II) XRD Measurement For the powder mainly having the NASICON-type crystal structure according to Example 1, XRD measurement was carried out under the following measurement conditions. The obtained XRD spectrum is shown in Figure 2. The round marks (●) shown in the figure are diffraction peaks attributed to the NASICON-type crystal structure, and the arrow (↓) shown in the figure is the position of the strongest peak related to the secondary phase described later. The main phase of the obtained powder mainly having the NASICON-type crystal structure according to Example 1 was a NASICON-type crystal structure having lithium, aluminum, germanium, and phosphorus.

[0045] <XRD Measurement Conditions Measuring device: XRD-6100 (manufactured by Shimadzu Corporation) X-ray tube: Cu Tube voltage: 40 kv Tube current: 30 mA Divergence slit: 1.0° Scattering slit: 1.0° Light-receiving slit: 0.3mm Step width: 0.02° / step Measurement time: 0.25 sec Peak search was performed using Shimadzu XRD-6100 software. The peak search was conducted under the following conditions. Smoothing process: Automatic Background processing: Automatic Ka1-a2 ratio: 50 Peak Search: Automatic

[0046] The XRD spectrum of the powder having the NASICON-type crystal structure as the main phase, as shown in Figure 2, is obtained for LiGeP3O, an oxide having the NASICON-type crystal structure. 12 This was compared with the ICDD PDF No. 01-080-1922. The peaks detected by the peak search method were in the range of 25.1±0.5°, 30.4±0.5°, 33.3±0.5°, and 34.0°±0.5°, and their peak intensities were largest in the order of 25.1±0.5°, 30.4±0.5°, 34.0°±0.5°, and 33.3±0.5°, so it was determined that they belonged to PDF No. 01-080-1922. Therefore, the powder having a NASICON-type crystal structure as the main phase according to Example 1 was found to contain lithium, aluminum, germanium, and phosphorus from the compositional analysis results described above, and to have a NASICON-type crystal structure as the main phase from the XRD measurement results. Similarly, Examples 2 and 3 and Comparative Examples 1 to 4, described later, were also found to belong to PDF No. 01-080-1922 after being compared with PDF No. 01-080-1922. Next, in the XRD measurement results, a GeO2 subphase was confirmed at approximately 25.9°. Therefore, the peak intensity ratio between the strongest peak of the main phase and the strongest peak of the subphase was examined, and the value of the subphase / main phase peak intensity ratio was 0.18. This result is shown in Table 4.

[0047] (III) Preparation of molded body and measurement of porosity 0.25 g of powder having the NASICON-type crystal structure according to Example 1 as the main phase was weighed, filled into a φ11 mm mold, and compressed into pellets by holding a load of 105 MPa for 10 seconds using a hydraulic press. The molded pellets were heated from room temperature to 800°C and fired at 800°C for 2 hours to obtain molded body samples. The obtained molded sample was dried at 110°C, and the mass of the dried molded sample was measured and defined as the dry mass W1.

[0048] The dried molded sample was placed at the bottom of a vacuum container, and under a vacuum of -96 kPa gauge pressure, the container was vacuumed using a vacuum pump for 15 minutes to thoroughly remove air from the pores of the molded sample. Next, IPA (isopropyl alcohol) was poured into the vacuum container until the molded sample was completely submerged. Then, the stopcock on the vacuum container was gradually opened to restore the pressure inside the container to a gauge pressure of 0 Pa, and it was left to stand for 30 minutes.

[0049] A molded sample immersed in IPA was suspended by wire, and the mass of the molded sample in the IPA was measured while it was suspended. The mass corrected for the amount of suspension by the wire was defined as the mass in the IPA, W2. Next, the molded sample was removed from the IPA, its surface was quickly wiped with gauze moistened with IPA to remove the IPA, and then the mass of the molded sample was measured and determined as the saturation mass W3. The gauze was thoroughly soaked in IPA, and then squeezed to remove only the IPA from the surface of the molded sample before use.

[0050] Using the masses W1 to W3 obtained above, the porosity Po of the molded sample according to Example 1 was calculated from (Equation 4) to be 19%. This value is shown in Table 4. Po(%)=(W3-W1) / (W3-W2)×100...(Formula 4) The measurement method described herein was based on JIS R1634.1998 (Method for measuring density and open porosity of sintered fine ceramics).

[0051] <Example 2> In the "(2) Preparation of an aqueous solution containing lithium, aluminum, and phosphorus" described in Example 1, 72.94 g of 85% H3PO4 aqueous solution was added to 480 g of pure water, 4.9 g of Al(OH)3 was added, and the mixture was heated to 70°C to obtain a clear aqueous solution. To the obtained aqueous solution, 16.32 g of LiOH·H2O was added and stirred until a clear aqueous solution was obtained to obtain the aqueous solution containing lithium, aluminum, and phosphorus according to Example 2. The pH of the obtained aqueous solution containing lithium, aluminum, and phosphorus was 2.5. These values ​​are shown in Table 1.

[0052] In Example 1, the aqueous solution containing lithium, aluminum, and phosphorus described in "(3) Preparation of raw material slurry" was replaced with the aqueous solution containing lithium, aluminum, and phosphorus described in Example 2. Then, in "(5) Firing", a rotary kiln with an inner diameter of 305 mm was first used, the kiln temperature was set to 250°C, the rotation speed to 1.2 rpm, and the angle to 0.5°. The precursor powder obtained by spray drying was placed inside and pre-fired for 120 minutes. The powder discharged from the rotary kiln was then placed in an alumina container and heated in a box-type furnace from room temperature to 600°C at a heating rate of 5°C / min, and then fired in an air atmosphere for 120 minutes. Except for these steps, the same procedure as in Example 1 was followed to prepare a powder having the NASICON-type crystal structure described in Example 2 as the main phase.

[0053] The analysis and characterization of the powder having the NASICON-type crystal structure as the main phase, prepared in Example 2, were carried out in the same manner as in Example 1. Table 1 shows the pH value of the raw material slurry for Example 2. Table 2 shows the composition (mol) of the raw material slurry, the calculated concentration of each element, the mixing ratio of each element, and the converted molar ratio of each element when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2. Furthermore, similar to Example 1, Table 3 lists the quantitative analysis values ​​(mass%) of lithium, aluminum, germanium, and phosphorus for each constituent element of the powder having the NASICON-type crystal structure according to Example 2, the value of the quantitative analysis value (mass%) of each constituent element / the value of the atomic weight of each constituent element (mass%) / atomic weight, the coefficient value, and the converted molar ratio of each element calculated by multiplying the value of [quantitative analysis value (mass%) of each element / sum of atomic weights of each constituent element] by the coefficient (when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2). Furthermore, the values ​​of x, y, z, y / z, δ, cumulative particle size distribution (D50), and porosity of the molded sample, which were determined in the same manner as in Example 1, are listed in Table 4. Then, under the same measurement conditions as in Example 1, XRD measurements were performed on the powder having the NASICON-type crystal structure according to Example 2 as the main phase. The obtained XRD spectrum is shown in Figure 2. Next, in the XRD measurement results, a GeO2 subphase was confirmed around 25.9°, so the peak intensity ratio between the strongest peak related to the main phase and the strongest peak related to the subphase was examined, and the value of the subphase / main phase peak intensity ratio was 0.23. This result is shown in Table 4.

[0054] <Example 3> In the "(2) Preparation of an aqueous solution containing lithium, aluminum, and phosphorus" described in Example 1, 75.43 g of 85% H3PO4 aqueous solution was added to 480 g of pure water, 4.9 g of Al(OH)3 was added, and the mixture was heated to 70°C to obtain a clear aqueous solution. To the obtained aqueous solution, 19.05 g of LiOH·H2O was added and stirred until a clear aqueous solution was obtained to obtain the aqueous solution containing lithium, aluminum, and phosphorus according to Example 3. The pH of the obtained aqueous solution containing lithium, aluminum, and phosphorus was 2.5. These values ​​are shown in Table 1. In the "(3) Preparation of raw material slurry" described in Example 1, the same procedure as in Example 1 was performed, except that the aqueous solution containing lithium, aluminum, and phosphorus according to Example 3 was used instead of the aqueous solution containing lithium, aluminum, and phosphorus according to Example 1, to prepare a powder having the NASICON-type crystal structure according to Example 3 as the main phase.

[0055] The analysis and characterization of the powder having the NASICON-type crystal structure as the main phase, prepared according to Example 3, were carried out in the same manner as in Example 1. Table 1 shows the pH value of the raw material slurry for Example 3. Table 2 shows the composition (mol) of the raw material slurry, the calculated concentration of each element, the mixing ratio of each element, and the converted molar ratio of each element when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2. Furthermore, similar to Example 1, Table 3 lists the quantitative analysis values ​​(mass%) of lithium, aluminum, germanium, and phosphorus for each constituent element of the powder having the NASICON-type crystal structure according to Example 3 as the main phase, the value of the quantitative analysis value (mass%) of each constituent element / the value of the atomic weight of each constituent element (mass%) / atomic weight, the coefficient value, and the converted molar ratio of each element calculated by multiplying the value of [quantitative analysis value (mass%) of each element / sum of atomic weights of each constituent element] by the coefficient (when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2). Furthermore, the values ​​of x, y, z, y / z, δ, cumulative particle size distribution (D50), and porosity of the molded sample, which were determined in the same manner as in Example 1, are listed in Table 4. Then, under the same measurement conditions as in Example 1, XRD measurements were performed on the powder having the NASICON-type crystal structure according to Example 3 as the main phase. The obtained XRD spectrum is shown in Figure 2. Next, in the XRD measurement results, an unassigned sub-phase was identified around 20.5°. Therefore, the peak intensity ratio between the strongest peak related to the main phase and the strongest peak related to the sub-phase was examined, and the value of the sub-phase / main phase peak intensity ratio was 0.11. This result is shown in Table 4.

[0056] <Comparative Example 1> In the "(2) Preparation of an aqueous solution containing lithium, aluminum, and phosphorus" described in Example 1, 67.96 g of 85% H3PO4 aqueous solution was added to 480 g of pure water, 4.9 g of Al(OH)3 was added, and the mixture was heated to 70°C to obtain a clear aqueous solution. To the obtained aqueous solution, 10.88 g of LiOH·H2O was added and stirred until a clear aqueous solution was obtained to obtain an aqueous solution containing lithium, aluminum, and phosphorus according to Comparative Example 1. The pH of the obtained aqueous solution containing lithium, aluminum, and phosphorus was 2.3. These values ​​are shown in Table 1. In the "(3) Preparation of raw material slurry" described in Example 1, the same procedure as in Example 1 was performed, except that the aqueous solution containing lithium, aluminum, and phosphorus according to Comparative Example 1 was used instead of the aqueous solution containing lithium, aluminum, and phosphorus according to Example 1, to prepare a powder having the NASICON-type crystal structure according to Comparative Example 1 as the main phase. Furthermore, the powder having a NASICON-type crystal structure as the main phase in Comparative Example 1 was intended to have a stoichiometric composition.

[0057] The analysis and characterization of the powder having the NASICON-type crystal structure as the main phase, according to the prepared Comparative Example 1, were carried out in the same manner as in Example 1. Table 1 shows the pH value of the raw material slurry for Comparative Example 1. Then, Table 2 shows the composition (mol) of the raw material slurry, the calculated concentration of each element, the mixing ratio of each element, and the converted molar ratio of each element when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2. Furthermore, similar to Example 1, Table 3 lists the quantitative analysis values ​​(mass%) of lithium, aluminum, germanium, and phosphorus for each constituent element of the powder having the NASICON-type crystal structure according to Comparative Example 1, the value of the quantitative analysis value (mass%) of each constituent element / the value of the atomic weight of each constituent element (mass%) / atomic weight, the coefficient value, and the converted molar ratio of each element calculated by multiplying the value of [quantitative analysis value (mass%) of each element / sum of atomic weights of each constituent element] by the coefficient (when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2). Furthermore, the values ​​of x, y, z, y / z, δ, cumulative particle size distribution (D50), and porosity of the molded sample, which were determined in the same manner as in Example 1, are listed in Table 4. Then, under the same measurement conditions as in Example 1, XRD measurements were performed on the powder having the NASICON-type crystal structure according to Comparative Example 1 as the main phase. The obtained XRD spectrum is shown in Figure 2. Next, in the XRD measurement results, an unassigned sub-phase was identified around 33.2°. When the peak intensity ratio between the strongest peak related to the main phase and the strongest peak related to the sub-phase was examined, the value of the sub-phase / main phase peak intensity ratio was found to be 0.04. This result is shown in Table 4.

[0058] <Comparative Example 2> In the "(2) Preparation of an aqueous solution containing lithium, aluminum, and phosphorus" described in Example 1, 67.96 g of 85% H3PO4 aqueous solution was added to 480 g of pure water, 4.9 g of Al(OH)3 was added, and the mixture was heated to 70°C to obtain a clear aqueous solution. To the obtained aqueous solution, 13.19 g of LiOH·H2O was added and stirred until a clear aqueous solution was obtained to obtain an aqueous solution containing lithium, aluminum, and phosphorus according to Comparative Example 2. The pH of the obtained aqueous solution containing lithium, aluminum, and phosphorus was 2.9. These values ​​are shown in Table 1. In the "(3) Preparation of raw material slurry" described in Example 1, the same procedure as in Example 1 was performed, except that the aqueous solution containing lithium, aluminum, and phosphorus according to Comparative Example 2 was used instead of the aqueous solution containing lithium, aluminum, and phosphorus according to Example 1. A powder having the NASICON-type crystal structure according to Comparative Example 2 as the main phase was then prepared.

[0059] The analysis and characterization of the powder having the NASICON-type crystal structure as the main phase, according to the prepared Comparative Example 2, were carried out in the same manner as in Example 1. Table 1 shows the pH value of the raw material slurry for Comparative Example 2. Then, Table 2 shows the composition (mol) of the raw material slurry, the calculated concentration of each element, the mixing ratio of each element, and the converted molar ratio of each element when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2. Furthermore, similar to Example 1, Table 3 lists the quantitative analysis values ​​(mass%) of lithium, aluminum, germanium, and phosphorus for each constituent element of the powder having the NASICON-type crystal structure according to Comparative Example 2, the value of the quantitative analysis value (mass%) of each constituent element / the value of the atomic weight of each constituent element (mass%) / atomic weight, the coefficient value, and the converted molar ratio of each element calculated by multiplying the value of [quantitative analysis value (mass%) of each element / sum of atomic weights of each constituent element] by the coefficient (when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2). Furthermore, the values ​​of x, y, z, y / z, δ, cumulative particle size distribution (D50), and porosity of the molded sample, which were determined in the same manner as in Example 1, are listed in Table 4. Then, under the same measurement conditions as in Example 1, XRD measurements were performed on the powder having the NASICON-type crystal structure according to Comparative Example 2 as the main phase. The obtained XRD spectrum is shown in Figure 2. In the XRD measurement results, a GeO2 subphase was confirmed around 25.9°, so the peak intensity ratio between the strongest peak related to the main phase and the strongest peak related to the subphase was examined, and the value of the subphase / main phase peak intensity ratio was 0.12. This result is shown in Table 4.

[0060] <Comparative Example 3> In the "(2) Preparation of an aqueous solution containing lithium, aluminum, and phosphorus" described in Example 1, 67.96 g of 85% H3PO4 aqueous solution was added to 480 g of pure water, 4.9 g of Al(OH)3 was added, and the mixture was heated to 70°C to obtain a clear aqueous solution. To the obtained aqueous solution, 15.42 g of LiOH·H2O was added and stirred until a clear aqueous solution was obtained to obtain an aqueous solution containing lithium, aluminum, and phosphorus according to Comparative Example 3. The pH of the obtained aqueous solution containing lithium, aluminum, and phosphorus was 3.3. These values ​​are shown in Table 1. In the "(3) Preparation of raw material slurry" described in Example 1, the same procedure as in Example 1 was performed, except that the aqueous solution containing lithium, aluminum, and phosphorus according to Comparative Example 3 was used instead of the aqueous solution containing lithium, aluminum, and phosphorus according to Example 1. A powder having the NASICON-type crystal structure according to Comparative Example 3 as the main phase was then prepared.

[0061] The analysis and characterization of the powder having the NASICON-type crystal structure as the main phase, according to the prepared Comparative Example 3, were carried out in the same manner as in Example 1. Table 1 shows the pH value of the raw material slurry for Comparative Example 3. Then, Table 2 shows the composition (mol) of the raw material slurry, the calculated concentration of each element, the mixing ratio of each element, and the converted molar ratio of each element when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2. Furthermore, similar to Example 1, Table 3 lists the quantitative analysis values ​​(mass%) of lithium, aluminum, germanium, and phosphorus for each constituent element of the powder having the NASICON-type crystal structure according to Comparative Example 3, the value of the quantitative analysis value (mass%) of each constituent element / the value of the atomic weight of each constituent element (mass%) / atomic weight, the coefficient value, and the converted molar ratio of each element calculated by multiplying the value of [quantitative analysis value (mass%) of each element / sum of atomic weights of each constituent element] by the coefficient (when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2). Furthermore, the values ​​of x, y, z, y / z, δ, cumulative particle size distribution (D50), and porosity of the molded sample, which were determined in the same manner as in Example 1, are listed in Table 4. Then, under the same measurement conditions as in Example 1, XRD measurements were performed on the powder having the NASICON-type crystal structure according to Comparative Example 3 as the main phase. The obtained XRD spectrum is shown in Figure 2. In the XRD measurement results, a GeO2 subphase was confirmed around 25.9°, so the peak intensity ratio between the strongest peak related to the main phase and the strongest peak related to the subphase was examined, and the value of the subphase / main phase peak intensity ratio was 0.03. This result is shown in Table 4.

[0062] <Comparative Example 4> In the "(2) Preparation of an aqueous solution containing lithium, aluminum, and phosphorus" described in Example 1, 75.51 g of 85% H3PO4 aqueous solution was added to 480 g of pure water, 4.9 g of Al(OH)3 was added, and the mixture was heated to 70°C to obtain a clear aqueous solution. To the obtained aqueous solution, 13.63 g of LiOH·H2O was added and stirred until a clear aqueous solution was obtained to obtain an aqueous solution containing lithium, aluminum, and phosphorus according to Comparative Example 4. The pH of the obtained aqueous solution containing lithium, aluminum, and phosphorus was 2.1. These values ​​are shown in Table 1. In the "(3) Preparation of raw material slurry" described in Example 1, the same procedure as in Example 1 was performed, except that the aqueous solution containing lithium, aluminum, and phosphorus according to Comparative Example 4 was used instead of the aqueous solution containing lithium, aluminum, and phosphorus according to Example 1. A powder having the NASICON-type crystal structure according to Comparative Example 4 as the main phase was prepared.

[0063] The analysis and characterization of the powder having the NASICON-type crystal structure as the main phase, according to the prepared Comparative Example 4, were carried out in the same manner as in Example 1. Table 1 shows the pH value of the raw material slurry for Comparative Example 4. Then, Table 2 shows the composition (mol) of the raw material slurry, the calculated concentration of each element, the mixing ratio of each element, and the converted molar ratio of each element when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2. Furthermore, similar to Example 1, Table 3 lists the quantitative analysis values ​​(mass%) of lithium, aluminum, germanium, and phosphorus for each constituent element of the powder having the NASICON-type crystal structure according to Comparative Example 4, the value of the quantitative analysis value (mass%) of each constituent element / the value of the atomic weight of each constituent element (mass%) / atomic weight, the coefficient value, and the converted molar ratio of each element calculated by multiplying the value of [quantitative analysis value (mass%) of each element / sum of atomic weights of each constituent element] by the coefficient (when the sum of the molar ratio of aluminum sites and the molar ratio of germanium sites is fixed at 2). Furthermore, the values ​​of x, y, z, y / z, δ, cumulative particle size distribution (D50), and porosity of the molded sample, which were determined in the same manner as in Example 1, are listed in Table 4. Then, under the same measurement conditions as in Example 1, XRD measurements were performed on the powder having the NASICON-type crystal structure according to Comparative Example 4 as the main phase. The obtained XRD spectrum is shown in Figure 2. No peaks related to the secondary phase were observed in the XRD measurement results. These results are shown in Table 4.

[0064] When the porosity of molded body samples using powders having the NASICON-type crystal structure as the main phase was evaluated in the examples and comparative examples, it was confirmed that the porosity of the molded body samples in Examples 1 to 3 was lower compared to Comparative Examples 1 to 4. In other words, according to the configuration of the present invention, it is possible to improve the density of the molded body (reduce the porosity), and in all-solid-state batteries, it is possible to suppress short circuits between electrodes even when the solid electrolyte layer is made thin and multilayered.

[0065] [Table 1] [Table 2] Table 3 Table 4

Claims

1. A powder containing lithium, aluminum, germanium, and phosphorus, having a NASICON-type crystal structure as its main phase, The composition of the aforementioned powder is given by the general formula Li １＋ｘ＋ｚ Al ｘ Ge ２－ｘ P ３＋ｙ O １２＋δ When expressed as such, it has a NASICON-type crystal structure as its main phase, where 0.0 < x < 2.0, 0.1 ≤ y ≤ 0.5, and 0.2 ≤ y / z ≤ 0.

6. Furthermore, if the powder having the NASICON-type crystal structure as its main phase has a subphase different from the main phase, A powder having a NASICON-type crystal structure as its main phase, wherein the value of (sub-phase peak intensity) / (main phase peak intensity), where the maximum X-ray diffraction peak intensity in the main phase is equal to the maximum X-ray diffraction peak intensity in the sub-phase, is 0.35 or less. However, δ = (z × 0.5) + (y × 2.5).

2. A powder having a NASICON-type crystal structure as the main phase, wherein the X-ray diffraction peak of the main phase belongs to No. 01-080-1922 of the Powder Diffraction File provided by the International Centre for Diffraction Data.

3. A powder having the NASICON-type crystal structure described in claim 1 as the main phase, wherein the value of y is 0.2 or more.

4. A molded body which is a molded product of powder having the NASICON-type crystal structure described in any one of Claims 1 to 3 as the main phase.

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