solid electrolytes

Abstract

Improvement of solid electrolyte for all-solid-state batteries [Solution] A solid electrolyte containing a composite metal oxide, wherein the composite metal oxide contains lithium (Li), aluminum (Al), germanium (Ge) as metals, and further contains molybdenum (Mo) and / or tungsten (W), and has an ionic conductivity of 10 × 10 at 25°C. -7 A solid electrolyte with a density of S / cm or higher. A method for manufacturing the above solid electrolyte. An all-solid-state battery using the above solid electrolyte.

Description

[Technical Field]

[0001] This invention relates to a solid electrolyte. Furthermore, this invention relates to an all-solid-state battery using the above-mentioned solid electrolyte and a method for producing the above-mentioned solid electrolyte. [Background technology]

[0002] Lithium-ion batteries are widely used in electronic devices and automobiles, and represent a large global market. Various next-generation products are being proposed to improve the performance and safety of lithium-ion batteries. All-solid-state lithium-ion batteries have attracted particular attention in recent years among these next-generation batteries due to their expected high level of safety. While various batteries are known as "solid-state batteries," both theoretically and practically, today the term "all-solid-state battery" narrowly refers to all-solid-state lithium-ion batteries.

[0003] As described in Non-Patent Document 1, all-solid-state lithium-ion batteries (hereinafter referred to as "solid-state batteries" in accordance with current conventions) differ completely from conventional lithium-ion batteries in that a layer of solid electrolyte, which serves as both the electrolyte and separator, is inserted between the positive and negative electrodes. For this reason, solid electrolytes for all-solid-state batteries have been actively studied in the development of all-solid-state batteries. 1.5 Al 0.5 Ge 1.5 Solid electrolytes (LAGPs) made of oxides represented by (PO4)3 are one of the representative solid electrolytes for all-solid-state batteries proposed to date.

[0004] As described in Patent Document 1, the applicant has already developed an all-solid-state battery using LAGP as a solid electrolyte and has succeeded in exhibiting excellent battery characteristics in an all-solid-state battery.

[0005] Meanwhile, as improvements to all-solid-state batteries progress, there is growing interest in manufacturing costs. Among the various factors related to manufacturing costs, the use of expensive raw materials in the components of all-solid-state batteries is considered problematic. Patent documents 2, 3, and 2 propose a solid electrolyte that replaces the solid electrolyte containing germanium, a so-called rare metal and therefore expensive, and a solid-state battery using this electrolyte.

[0006] Furthermore, the process of sintering the solid electrolyte in component shape at high temperatures (main firing) is also considered problematic because it can lead to deterioration of adjacent components. Non-patent document 3 proposes a solid electrolyte using an oxide that can be sintered at a relatively low temperature.

[0007] Thus, various improvements have been attempted to solid electrolytes. However, as described in Non-Patent Document 4, each solid electrolyte material has its own advantages and disadvantages, and a solid electrolyte material that satisfies all required performance has yet to be found. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Journal of the Japan Society for Crystal Growth, Vol. 46, No. 1 (2019), Special Issue: An Approach from Crystal Growth Towards the Creation of Next-Generation Secondary Batteries, Commentary: "Development of All-Solid-State Lithium Secondary Batteries Using Garnet-Type Solid Electrolyte Single Crystals" [Non-Patent Document 2] Tokyo Institute of Technology Press Release: "Discovery of an inexpensive and versatile solid electrolyte material exhibiting superionic conductivity" July 10, 2017 [Non-Patent Document 3] Kyushu University Press Release: "Development of Low-Temperature Sinterable Material for Oxide All-Solid-State Batteries, Achieving Room-Temperature Operation" June 29, 2023 [Non-Patent Document 4] AIST Magazine, "What are All-Solid-State Batteries?", July 20, 2022, https: / / www.aist.go.jp / aist_j / magazine / 20220720.html [Patent Documents]

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] Therefore, the present inventor utilized the knowledge of LAGP accumulated so far and searched for a novel solid electrolyte that can replace LAGP from the aspects of both raw material cost reduction and low - temperature sinterability.

Means for Solving the Problems

[0011] As a result, by substituting germanium contained in LAGP with other metal elements at a specific ratio, it was successful in manufacturing a solid electrolyte that exhibits low - temperature sinterability while maintaining the performance of LAGP. That is, the present invention is as follows.

[0012] (Invention 1) A solid electrolyte containing a composite metal oxide, wherein the composite metal oxide contains lithium (Li), aluminum (Al), germanium (Ge) as metals, and further contains molybdenum (Mo) and / or tungsten (W), and has an ionic conductivity at 25°C of 10×10 -7 S / cm or more, the solid electrolyte. (Invention 2) The solid electrolyte according to Invention 1, wherein the composite metal oxide is represented by the formula (1): Li 1.25 Al a Ge b Mo c W d (PO4)3. However, a, b, c, d in the above formula (1) are subject to the conditions: 0.70≦a≦0.95, 0.60≦b≦1.10, 0≦c≦0.50, 0≦d≦0.50, 1.95 ≤ a + b + c + d ≤ 2.50 The numbers satisfy the condition c and d are not both zero. (Invention 3) In equation (1) above, a, b, c, and d are given by the following conditions: 0.80 ≤ a ≤ 0.90, 0.95≦b≦1.05, 0.05≦c≦0.15, 0.05≦d≦0.15, Satisfying 1.95 ≤ a + b + c + d ≤ 2.50, Solid electrolyte of Invention 2. (Invention 4) An all-solid-state battery comprising a layer containing a solid electrolyte according to any of inventions 1, 2, or 3. (Invention 5) A method for producing a solid electrolyte, comprising the following steps 1, 2, and 3. Step 1: Calcining a mixture containing a lithium (Li) compound, an aluminum (Al) compound, a germanium (Ge) compound, a molybdenum (Mo) compound, and / or a tungsten (W) compound. Step 2: A step to vitrify the calcined material obtained in Step 1 above. Step 3: A step in which the vitrified material obtained in Step 2 is subjected to final firing. (Invention 6) In step 1 above, lithium carbonate (Li2CO3) is used as the lithium compound, aluminum oxide (Al2O3) as the aluminum compound, and germanium oxide (G) as the germanium compound. e A method for producing a solid electrolyte according to Invention 5, using a mixture containing molybdenum oxide (MoO3) as a molybdenum compound and tungsten oxide (WO3) as a tungsten compound. (Invention 7) In step 1 above, a mixture containing a lithium compound, an aluminum compound, a germanium compound, a molybdenum compound, and a tungsten compound is fired at a temperature of 300°C to 500°C. In step 2 above, the calcined material is melted at 1400°C or below and then rapidly cooled to vitrify the calcined material. In step 3 above, the vitrified material obtained in step 2 above is fired at a temperature of 550°C to 650°C to crystallize the vitrified material. A method for producing a solid electrolyte according to invention 5 or 6. (Invention 8) The above solid electrolyte is given by formula (1): Li 1.25 Al a Ge b Mo c W d A method for producing the solid electrolyte of inventions 5, 6, and 7, represented by (PO4)3. However, a, b, c, and d in equation (1) above are given by the following conditions: 0.70 ≤ a ≤ 0.95, 0.60≦b≦1.10, 0≦c≦0.50, 0≦d≦0.50, 1.95 ≤ a + b + c + d ≤ 2.50 The numbers satisfy the condition c and d are not both zero. (Invention 9) In equation (1) above, a, b, c, and d are given by the following conditions: 0.80 ≤ a ≤ 0.90, 0.95≦b≦1.05, 0.05≦c≦0.15, 0.05≦d≦0.15, Satisfying 1.95 ≤ a + b + c + d ≤ 2.50, A method for producing a solid electrolyte according to Invention 8. (Invention 10) The ionic conductivity of the above solid electrolyte at 25°C is 10 × 10⁻¹⁰ -7 A method for producing a solid electrolyte according to any of Inventions 5, 6, 7, 8, or 9, wherein the electrolyte density is S / cm or higher. [Effects of the Invention]

[0013] The solid electrolyte of the present invention has a lower germanium content than conventional products, making it advantageous in terms of raw material costs. Furthermore, the solid electrolyte of the present invention exhibits battery performance that is not significantly different from conventional LAGP-based solid electrolytes.

[0014] In manufacturing the solid electrolyte of the present invention, a crystallized solid electrolyte can be synthesized by sintering a solid electrolyte precursor at a relatively low temperature, for example, about 600°C. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1(a): Chart obtained by X-ray diffraction analysis of the vitrified material obtained in step 2 of Example 1. Figure 1(b): Chart obtained by X-ray diffraction analysis of the sintered material obtained in step 3 of Example 1. [Figure 2] Figure 2(a): Chart obtained by X-ray diffraction analysis of the vitrified material obtained in step 2 of Example 2. Figure 2(b): Chart obtained by X-ray diffraction analysis of the sintered material obtained in step 3 of Example 2. [Figure 3] Figure 3(a): Chart obtained by X-ray diffraction analysis of the vitrified material obtained in step 2 of Example 3. Figure 3(b): Chart obtained by X-ray diffraction analysis of the sintered material obtained in step 3 of Example 3. [Figure 4] Figure 4(a): Chart obtained by X-ray diffraction analysis of the vitrified material obtained in step 2 of Example 4. Figure 4(b): Chart obtained by X-ray diffraction analysis of the sintered material obtained in step 3 of Example 4. [Figure 5] Figure 5(a): Chart obtained by X-ray diffraction analysis of the vitrified material obtained in step 2 of Example 5. Figure 5(b): Chart obtained by X-ray diffraction analysis of the sintered material obtained in step 3 of Example 5. [Figure 6] Figure 6(a): Chart obtained by X-ray diffraction analysis of the vitrified material obtained in step 2 of Example 6. Figure 6(b): Chart obtained by X-ray diffraction analysis of the sintered material obtained in step 3 of Example 6. [Figure 7] Figure 7(a): Chart obtained by X-ray diffraction analysis of the vitrified material obtained in step 2 of Example 7. Figure 7(b): Chart obtained by X-ray diffraction analysis of the sintered material obtained in step 3 of Example 7. [Figure 8] Figure 8(a): Chart obtained by X-ray diffraction analysis of the vitrified material obtained in step 2 of Example 8. Figure 8(b): Chart obtained by X-ray diffraction analysis of the sintered material obtained in step 3 of Example 8. [Modes for carrying out the invention]

[0016] [Solid electrolyte] The solid electrolyte of the present invention comprises a composite metal oxide having a specific elemental composition. The solid electrolyte of the present invention has an ionic conductivity of 10 × 10 at 25°C. -7 Characterized by being S / cm or higher.

[0017] The above composite metal oxide contains lithium (Li), aluminum (Al), germanium (Ge) as metals, and further includes molybdenum (Mo) and / or tungsten (W). A typical composition of LAGP, known as a solid electrolyte, is Li 1.5 Al 0.5 Ge 1.5 (PO4)3 is known. The above composite metal oxide differs from the typical LAGP in that, in addition to germanium (Ge), it also essentially contains molybdenum (Mo) and / or tungsten (W).

[0018] The above composite metal oxide is preferably of formula (1):Li 1.25 Al a Ge b Mo c W d It is expressed as (PO4)3. However, in this case, a, b, c, and d in the above equation (1) are numbers that satisfy the conditions: 0.70≦a≦0.95, 0.60≦b≦1.10, 0≦c≦0.50, 0≦d≦0.50, 1.950≦a+b+c+d≦2.500, and c and d are not both 0 at the same time.

[0019] In this case, the ionic conductivity of the solid electrolyte made of the above composite metal oxide at 25°C is 10 × 10 -7 S / cm or higher, typically 11 × 10 -7 S / cm or larger, approximately 12 x 10 -7 A value of S / cm or higher can be achieved. In particular, it is even more preferable when a, b, c, and d in the above equation (1) satisfy the conditions: 0.80≦a≦0.90, 0.95≦b≦1.05, 0.05≦c≦0.15, 0.05≦d≦0.15, 1.950≦a+b+c+d≦2.500.

[0020] In this case, the ionic conductivity of the solid electrolyte made of the above composite metal oxide at 25°C is 10 × 10 -7 S / cm or more, typically 50 × 10 -7 S / cm or larger, approximately 100 x 10 -7 It is possible to achieve a value of S / cm or higher. Such ionic conductivity is comparable to the typical LAGP value.

[0021] [Method for producing solid electrolytes] The method for producing the solid electrolyte of the present invention comprises the following steps 1, 2, and 3.

[0022] Step 1: Calcining a mixture containing lithium (Li) compounds, aluminum (Al) compounds, germanium (Ge) compounds, molybdenum (Mo) compounds and / or tungsten (W) compounds.

[0023] Step 2: A step in which the calcined material obtained in Step 1 is vitrified.

[0024] Step 3: A step in which the vitrified material obtained in Step 2 is subjected to final firing.

[0025] Step 1 specifically involves mixing lithium (Li) compound, aluminum (Al) compound, germanium (Ge) compound, molybdenum (Mo) compound, and / or tungsten (W) compound, which are raw materials for the composite metal oxide, and calcining the resulting mixture. The raw material compounds used in Step 1 are not particularly limited.

[0026] In step 1, the raw material compounds are mixed so that the ratio of the metal elements contained in the above mixture—lithium (Li), aluminum (Al), germanium (Ge), molybdenum (Mo), and / or tungsten (W)—matches the ratio of the metal elements constituting the composite metal oxide. The mixing method may be dry or wet, but generally the raw material compounds are mixed dry.

[0027] The raw material compounds used in step 1 are not particularly limited. Generally, oxides, hydroxides, carbonates, etc. of the above metal elements can be used as the raw material compounds. Among the various raw material compounds, lithium carbonate (Li2CO3) can be used as the lithium compound, aluminum oxide (Al2O3) as the aluminum compound, and germanium oxide (G) can be used as the germanium compound. e As the molybdenum compound, molybdenum oxide (MoO3) is preferred, and as the tungsten compound, tungsten oxide (WO3) is preferred.

[0028] In step 1, the raw material mixture is generally fired at a temperature of 300°C to 500°C. This firing is carried out in the presence of oxygen, generally in air. The equipment used for this firing can be any equipment used in the ceramics, pottery, and battery fields without restriction. Generally, the raw material mixture is placed in the firing furnace and the temperature is increased at a rate of several tens to over a hundred degrees Celsius per hour. When the furnace temperature reaches a target temperature of approximately 500°C, the heating is stopped, and the furnace temperature is maintained at the target temperature for several hours. This completes step 1, and a calcined product of the raw material mixture is obtained.

[0029] In step 1, preferably, the calcined material thus obtained is further crushed and / or pulverized. In this case, a powdery calcined material is obtained.

[0030] Specifically, step 2 is a step of vitrifying the calcined product obtained in step 1 by melting it and then rapidly cooling it. In step 2, preferably, the powdered calcined product obtained in step 1 is melted and then rapidly cooled.

[0031] In step 2, the temperature at which the calcined material is melted is acceptable as long as it is above the temperature at which the calcined material is completely melted, but is generally 1400°C or lower, preferably 700°C to 1300°C. In this melting process, the same calcination furnace as in step 1 is used, and the furnace temperature is maintained at the target melting temperature for several hours, typically about one hour, after the furnace temperature reaches the target melting temperature, to melt the calcined material.

[0032] In step 2, the molten material obtained in the above operation is rapidly cooled to solidify the calcined material in an amorphous state, thereby producing a vitrified product of the calcined material. The means of rapid cooling can be any means used in the ceramics, pottery, and battery fields without limitation. Generally, the entire container containing the molten material is quickly transferred to a low temperature, for example, by immersion in water, to cool the molten material in an amorphous state.

[0033] In step 2, preferably, the vitrified material thus obtained is crushed and / or pulverized. In this case, a powdered vitrified material is obtained. Furthermore, in step 2, the powdered vitrified material can be molded into a shape corresponding to the electrolyte layer of an all-solid-state battery. In this case, in the next step 3, the molded body made of the vitrified material is fired.

[0034] In step 3, the vitrified material obtained in step 2 is placed in a high-temperature state in which the elements contained in the raw material mixture migrate to form a crystal lattice and align, thereby synthesizing a crystalline solid electrolyte. In step 3, the powdered vitrified material is generally fired at a temperature of 550°C to 650°C to obtain the desired solid electrolyte as a sintered product. In step 3, by firing the molded body made of the vitrified material in close contact with other material layers such as a positive electrode layer, a component consisting of a solid electrolyte layer and its adjacent layers can be manufactured.

[0035] The equipment used for firing in step 3 can be any equipment used in the ceramics, pottery, and battery fields, without restriction, similar to steps 1 and 2. Generally, the vitrified material is placed in the firing furnace and the temperature is increased at a rate of several tens of degrees (°C) to over 100 degrees (°C) per hour. When the furnace temperature reaches a target temperature of 550°C to 650°C, the heating is stopped, and the furnace temperature is maintained at the target temperature for several hours to several tens of hours. Step 3 is thus completed, and the solid electrolyte of the present invention is obtained.

[0036] [All-solid battery] The solid electrolyte of the present invention is used as the electrolyte for an all-solid-state battery. The dimensions, shape, and arrangement of each component of the all-solid-state battery of the present invention are not limited as long as the battery performance is achieved.

[0037] In manufacturing the all-solid-state battery of the present invention, generally, first, a powdery calcined material is obtained according to step 1 described above. Next, a vitrified product of the powdery calcined product is manufactured according to step 2 described above, and this vitrified product is further powdered to form the powdery vitrified product into a predetermined size. After that, the laminate consisting of the formed vitrified product and the positive electrode paste layer is fired according to step 3 described above. In this way, a sintered laminate consisting of the solid electrolyte and positive electrode layer of the all-solid-state battery of the present invention is obtained.

[0038] Next, the main body of the all-solid-state battery of the present invention is completed by fixing the negative electrode layer and auxiliary components such as leads to the sintered laminate according to a conventional method. Furthermore, the all-solid-state battery of the present invention is completed by enclosing and sealing this main body in an outer casing according to the information. [Examples]

[0039] [Examples 1-8: Examples of Solid Electrolyte Production] The following steps 1, 2, and 3 were performed to produce eight solid electrolytes of the present invention.

[0040] (Process 1) The raw material compounds are lithium carbonate (Li2CO3), aluminum oxide (Al2O3), and germanium oxide (G e O2, molybdenum trioxide (MoO3), tungsten trioxide (WO3), and phosphoric acid (H3PO4) were used. The raw material compounds in the amounts shown in Table 1 were placed in a platinum crucible and mixed.

[0041] [Table 1]

[0042] Each mixture from Examples 1 to 8 was calcined in air at 500°C for 5 hours. The resulting powder was crushed in an agate mortar. This yielded a powdery calcined product.

[0043] (Process 2) The furnace temperature of the firing furnace containing the above-mentioned calcined material was maintained at 1300°C for 1 hour to melt the calcined material. The material obtained by melting was rapidly cooled to obtain vitrified material. The vitrified material was removed from the platinum crucible and crushed in an agate mortar to obtain vitrified powder. Furthermore, 0.2 g of the vitrified powder was filled into a 14 mm diameter press jig and pressed with a pressure of 1.5 kN to form a disc-shaped pellet.

[0044] (Step 3) The above pellets were placed on a honeycomb-structured firing plate and subjected to main firing. The firing plate was held in air at a temperature of 600°C for 10 hours, and the sintered material was recovered as the solid electrolyte of the present invention. The elemental composition of the obtained sintered material is shown in Table 2. The composition formulas in Table 2 have blank spaces to facilitate comparison of the compositions of each example. These blank spaces do not have any special meaning regarding the composition, such as the presence of other elements.

[0045] (Analysis of vitrified materials) The powdered vitrified material obtained in step 2 above was analyzed by X-ray diffraction. Cukα (wavelength 1.5418 angstroms) was used as the characteristic X-ray source. The obtained diffraction chart is shown on the left side of Figures 1-8: (a). No diffraction peaks originating from the crystal structure were detected in any of the examples. It was confirmed that amorphous precursor vitrified material was indeed obtained in step 2 above.

[0046] (Analysis of solid electrolytes) The sintered material obtained in step 3 above was analyzed by X-ray diffraction. Cukα (wavelength 1.5418 angstroms) was used as the characteristic X-ray source. The obtained diffraction chart is shown on the right side of Figures 1-8: (b). In all examples, diffraction peaks originating from NASICON-type LiGe2(PO4)3 crystals were detected. High ionic conductivity is expected from the sintered material obtained in step 3 above.

[0047] [Comparative Examples 1-4, Preparation of Comparative Solid Electrolytes] Steps 2 and 3 were carried out in the same manner as above, except that the ratio of raw material compounds in step 1 was changed, to produce the comparative solid electrolytes (Comparative Examples 1-4) shown in Table 2.

[0048] [Ionic conductivity] The ionic conductivity of the sintered materials obtained in Examples 1-8 and Comparative Examples 1-4 was measured. The AC impedance method was used for measurement.

[0049] First, 10 mm diameter gold (Au) electrodes were fixed to both sides of the disc-shaped sintered pellet obtained in step 3 above. The entire pellet was vacuum-dried at 150°C for 12 hours. Separately, a Cu foil with nickel (Ni) lead tabs attached was prepared. Next, the prepared Cu foil was attached to both sides of the dried pellet to complete the sample body. This body was sealed in a laminate film casing and used as a test sample cell.

[0050] The impedance of the above cells was measured in a constant temperature bath set to 25°C using a Biologic SP-300 impedance meter. The frequency range was set from 0.1 Hz to 1 MHz, and the amplitude was set to 0.1 V.

[0051] The ionic conductivity (S / cm) of each sample was calculated from the measurement results. The calculation results are shown in Table 2. For reference, Table 2 also shows the ionic conductivity of a typical solid electrolyte LAGP.

[0052] [Table 2]

[0053] [evaluation] The ionic conductivity of the sintered material obtained in step 3 of Examples 1-8 is sufficiently close to the reference LAGP value. Examples 1-8 have succeeded in producing solid electrolytes with low germanium (Ge) content that are expected to be practical.

[0054] In particular, Examples 7 and 8 involved substituting a portion of the expensive germanium (Ge) with specific proportions of molybdenum (Mo) and tungsten (W) ((Formula (1):Li 1.25 Al a Ge b Mo c Wd The (PO4)3 example satisfies the conditions: 0.80≦a≦0.90, 0.95≦b≦1.05, 0.05≦c≦0.15, 0.05≦d≦0.15, 1.95≦a+b+c+d≦2.50, and exhibits ionic conductivity comparable to existing LAGPs. The solid electrolytes produced in Examples 7 and 8 are solid electrolytes that enable a reduction in raw material costs for all-solid-state batteries and are expected to have high practicality.

[0055] The comparative solid electrolytes for Comparative Example 1 and Comparative Example 2 had an excessive germanium (Ge) content (Equation (1):Li 1.25 Al a Ge b Mo c W d This is an example where the value of "b" in (PO4)3 is excessive. The solid electrolytes obtained in Comparative Example 1 and Comparative Example 2 have low ionic conductivity and are not practical as electrolytes for all-solid-state batteries. Furthermore, these comparative examples have a low reduction effect on the expensive germanium and are not as cost-effective as the examples.

[0056] The comparative solid electrolytes for Comparative Examples 3 and 4 were modified by changing the content of lithium (Li), aluminum (Al), germanium (Ge), molybdenum (Mo), and / or tungsten (W) (Equation (1): Li 1.25 Al a Ge b Mo c W d This is an example where the value of "a+b+c+d" in (PO4)3 is too small. The solid electrolytes obtained in Comparative Examples 3 and 4 have low ionic conductivity and are not practical as electrolytes for all-solid-state batteries. Furthermore, these comparative examples have a low reduction effect on the expensive germanium, and are not as cost-effective as the examples. [Industrial applicability]

[0057] This invention has succeeded in manufacturing a solid electrolyte with a low germanium content and ionic conductivity comparable to conventional LAGP products. It is expected that this invention will reduce the manufacturing cost of solid electrolytes for all-solid-state batteries and improve their quality. This invention will contribute to improving the performance of all-solid-state batteries and expanding the all-solid-state battery market.

Claims

1. A solid electrolyte containing a composite metal oxide, The above composite metal oxide includes lithium (Li), aluminum (Al), germanium (Ge) as metals, and further includes molybdenum (Mo) and / or tungsten (W). The ionic conductivity at 25°C is 10 × 10 －７ It is S / cm or higher. solid electrolyte.

2. The above composite metal oxide is, Formula (1): Li １．２５ Al ａ Ge ｂ Mo ｃ W ｄ (PO ４ ) ３ The solid electrolyte according to claim 1, represented as shown. However, a, b, c, and d in the above formula (1) are subject to the following conditions: 0.70 ≤ a ≤ 0.95, 0.60 ≤ b ≤ 1.10, 0 ≤ c ≤ 0.50, 0 ≤ d ≤ 0.50, 1.95≦a+b+c+d≦2.50 The numbers satisfy the condition c and d are not both zero at the same time.

3. In the above equation (1), a, b, c, and d are given by the following conditions: 0.80 ≤ a ≤ 0.90, 0.95 ≤ b ≤ 1.05, 0.05 ≤ c ≤ 0.15, 0.05 ≤ d ≤ 0.15, Satisfying 1.95 ≤ a + b + c + d ≤ 2.50, The solid electrolyte according to claim 2.

4. A solid-state battery comprising a layer containing a solid electrolyte according to any one of claims 1, 2, or 3.

5. A method for producing a solid electrolyte, comprising the following steps 1, 2, and 3. Step 1: Calcining a mixture containing a lithium (Li) compound, an aluminum (Al) compound, a germanium (Ge) compound, a molybdenum (Mo) compound, and / or a tungsten (W) compound. Step 2: A step to vitrify the calcined product obtained in Step 1. Step 3: A step in which the vitrified material obtained in Step 2 is subjected to final firing.

6. In the above step 1, lithium carbonate (Li ２ CO ３ ), aluminum oxide (Al ２ O ３ ), germanium oxide (G ｅ O ２ ), molybdenum oxide (MoO ３ ), and tungsten oxide (WO ３ ) are used as a mixture to produce the solid electrolyte according to claim 5.

7. In step 1 above, a mixture containing a lithium compound, an aluminum compound, a germanium compound, a molybdenum compound, and a tungsten compound is fired at a temperature of 300°C to 500°C. In step 2 above, the calcined material is melted at 1400°C or below and then rapidly cooled to vitrify the calcined material. In step 3 above, the vitrified material obtained in step 2 above is fired at a temperature of 550°C to 650°C to crystallize the vitrified material. A method for producing a solid electrolyte according to claim 5 or 6.

8. The above solid electrolyte is formula (1): Li １．２５ Al ａ Ge ｂ Mo ｃ W ｄ (PO ４ ) ３ A method for producing a solid electrolyte according to any one of claims 5, 6, or 7. However, a, b, c, and d in the above formula (1) are subject to the following conditions: 0.70 ≤ a ≤ 0.95, 0.60 ≤ b ≤ 1.10, 0 ≤ c ≤ 0.50, 0 ≤ d ≤ 0.50, 1.95≦a+b+c+d≦2.50 The numbers satisfy the condition c and d are not both zero at the same time.

9. In the above equation (1), a, b, c, and d are given by the following conditions: 0.80 ≤ a ≤ 0.90, 0.95 ≤ b ≤ 1.05, 0.05 ≤ c ≤ 0.15, 0.05 ≤ d ≤ 0.15, Satisfying 1.95 ≤ a + b + c + d ≤ 2.50, A method for producing a solid electrolyte according to claim 8.

10. The ionic conductivity of the above solid electrolyte at 25°C is 10 × 10 －７ A method for producing a solid electrolyte according to any one of claims 5, 6, 7, 8, or 9, wherein the concentration is S / cm or higher.

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