Producing method of sulfide solid electrolyte, sulfide solid electrolyte, all solid battery, and method for selecting raw compound used in production of sulfide solid electrolyte

Abstract

To provide a method for producing sulfide solid electrolytes that can suppress the emission of N into the environment during the producing process, a method for selecting raw compounds used in the production of sulfide solid electrolytes, as well as all-solid-state batteries equipped with the sulfide solid electrolytes, and a method for producing sulfide solid electrolytes with improved thermal stability and all-solid-state batteries equipped with the sulfide solid electrolytes.SOLUTION: A sulfide solid electrolyte contains as the constituent elements, P, S, N, element A, element X, and element M, and has a crystalline structure. The element A represents at least one element selected from the group consisting of Li, Na, and K. The element X represents at least one element selected from the group consisting of Cl, Br, and I. The element M represents at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a sulfide solid electrolyte, a sulfide solid electrolyte, an all-solid-state battery, and a method for selecting a raw material compound used in the production of a sulfide solid electrolyte.

[0002] Non-aqueous electrolyte secondary batteries typified by lithium-ion non-aqueous electrolyte secondary batteries are widely used in electronic devices such as personal computers and communication terminals, and automobiles, etc. because of their high energy density. The above non-aqueous electrolyte secondary battery generally includes an electrode body having a pair of electrodes electrically isolated from each other, and a non-aqueous electrolyte interposed between the electrodes, and is configured to charge and discharge by transferring ions between both electrodes.

[0003] In recent years, sulfide solid electrolytes have attracted attention as non-aqueous electrolytes for non-aqueous electrolyte secondary batteries, and various studies have been conducted.

[0004] Patent Document 1 describes the production of a sulfide solid electrolyte having a composition of 75Li 2 S-25P 2 S 5 using Li 3 N as starting materials. 2 S-25P 2 S 5 -yLi 3 N. Patent Document 2 describes the production of a sulfide solid electrolyte using a raw material composition consisting of Li 2 S, P 2 S 5 , LiBr, LiI, and Li 3 N.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] Patent Document 1 describes that by containing N in a sulfide solid electrolyte, the air stability (water resistance) of the sulfide solid electrolyte can be improved. However, when Li 3 N is used as a raw material for the sulfide solid electrolyte, there is a problem that N is discharged out of the system.

[0007] Patent Document 2 describes that by amorphizing and heat-treating a raw material composition containing Li 2 S, P 2 S 5 , LiI, and LiBr, a high Li-ion conductive phase precipitates. However, if the heat treatment temperature is too high, there is a problem that a low Li-ion conductive phase precipitates. Patent Document 3 describes that although the addition of Li 3 N can increase the difference between the temperature at which a high Li-ion conductive phase is formed and the temperature at which a low Li-ion conductive phase is formed, the difference is as small as about 30°C at most, and further improvement has been demanded.

[0008] The present invention has been made based on the above circumstances, and an object of one aspect of the present invention is to provide a method for producing a sulfide solid electrolyte capable of suppressing the discharge of N out of the system in the production process of the sulfide solid electrolyte, a method for selecting a raw material compound used in the production of the sulfide solid electrolyte, and a all-solid-state battery including the sulfide solid electrolyte. Another object of the present invention is to provide a method for obtaining a sulfide solid electrolyte with improved thermal stability, a method for producing the same, and a all-solid-state battery including the sulfide solid electrolyte.

MEANS FOR SOLVING THE PROBLEMS

[0009] One aspect of the present invention made to solve the above problems is a method for manufacturing a sulfide solid electrolyte, comprising: preparing a composition containing P, S, N, element A, and element M; reacting the composition to obtain an intermediate; and heating the intermediate to obtain a sulfide solid electrolyte, wherein the composition contains a raw material compound containing N, element A, and element M. A represents at least one element selected from the group consisting of Li, Na, and K. M represents at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti.

[0010] Another aspect of the present invention is a method for selecting a raw material compound used in the manufacture of a sulfide solid electrolyte, comprising: selecting a candidate material containing N, element A', and element M' as a candidate for the raw material compound; and calculating the defect formation energy E Ndefect of N inside the candidate material using first-principles calculations, Ndefect wherein when the E

[0011] is 4.00 eV or more, the candidate material is selected as the raw material compound.

Advantages of the Invention

[0012] According to the method for manufacturing a sulfide solid electrolyte, the method for selecting a raw material compound used in the manufacture of a sulfide solid electrolyte, and the sulfide solid electrolyte according to one aspect of the present invention, the discharge of N out of the system in the manufacturing process of the sulfide solid electrolyte can be suppressed. According to the sulfide solid electrolyte of another aspect of the present invention, a sulfide solid electrolyte with improved thermal stability can be obtained.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0014] First, an overview of the method for manufacturing a sulfide solid electrolyte disclosed by this specification will be described.

[0015] The method for manufacturing a sulfide solid electrolyte according to one aspect of the present invention is a method for manufacturing a sulfide solid electrolyte, including preparing a composition containing P, S, N, element A, and element M, reacting the composition to obtain an intermediate, and heating the intermediate to obtain a sulfide solid electrolyte. The composition contains a raw material compound containing N, element A, and element M. Here, A represents at least one element selected from the group consisting of Li, Na, and K. M represents at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti.

[0016] In the present invention, the "composition" means a mixture formed by mixing two or more compounds. The "raw material compound" means a specific compound constituting the above composition.

[0017] The inventors have found that by using a raw material compound containing at least one element A selected from the group consisting of Li, Na, and K, at least one element M selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti, and N, it is possible to suppress the discharge of N outside the system in the production process of the sulfide solid electrolyte, and thus have arrived at the present invention.

[0018] According to the method for producing the sulfide solid electrolyte, the discharge of N outside the system in the production process of the sulfide solid electrolyte can be suppressed. Therefore, it becomes easy to control the content of N contained in the sulfide solid electrolyte. Although the reason for this is not clear, the following reasons are speculated. Li disclosed in Patent Document 1 and Patent Document 3 3 In the method for producing a sulfide solid electrolyte using Li 3 N, the N defect generation energy of N is small, and N 2 gas is easily generated. On the other hand, in the method for producing the sulfide solid electrolyte using a raw material compound containing N, element A, and element M, the N defect generation energy is large, and N defects are less likely to be generated during the synthesis process of the sulfide solid electrolyte. Therefore, N 2 gas is less likely to be generated. Therefore, the discharge of N outside the system in the production process of the sulfide solid electrolyte can be suppressed. It should be noted that each of the element M is an element in which the N defect generation energy in the compound represented by Li α M β N (α and β are numerical values giving the stoichiometric ratio according to the type of element M) is 4.00 eV or more. The definition of the N defect generation energy will be described later.

[0019] The above raw material compound containing N, element A, and element M preferably contains Li, N, element A, and element M.

[0020] According to this, the mass energy density of an all-solid-state battery including a sulfide solid electrolyte manufactured by the manufacturing method can be increased. This is because Li has the smallest atomic weight and the smallest ionic size among alkali metal elements.

[0021] The raw material compound containing the above N, element A, and element M may be obtained by reacting a nitride of element M with a nitride of element A, or an industrially manufactured and sold one may be used.

[0022] Element M is preferably one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, and P. These elements are elements for which the defect formation energy of N calculated by first-principles calculations described later is 4.10 eV or more.

[0023] Thereby, it is possible to more reliably suppress the discharge of N to the outside of the system in the manufacturing process of the sulfide solid electrolyte.

[0024] Element M is more preferably at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, and Nb. These elements are elements for which the defect formation energy of N calculated by first-principles calculations described later is 4.35 eV or more.

[0025] Thereby, it is possible to more reliably suppress the discharge of N to the outside of the system in the manufacturing process of the sulfide solid electrolyte.

[0026] The above composition preferably includes lithium sulfide, phosphorus sulfide, and a raw material compound containing the above N, element A, and element M. Since these compounds are easy to handle, the manufacturability of the sulfide solid electrolyte can be improved.

[0027] The above composition preferably contains Li as the above element A, the content ratio of Li to P in the above composition is 2.30 or more and 4.20 or less in molar ratio, and the content ratio of N to P in the above composition is 0.0100 or more and 1.20 or less in molar ratio. Further, it is more preferable that the above element A contains Li, the content ratio of Li to P in the above composition is 2.77 or more and 3.38 or less in molar ratio, and the content ratio of N to P in the above composition is 0.280 or more and 0.650 or less in molar ratio. Thereby, a sulfide solid electrolyte excellent in air stability and having a high ionic conductivity at 25°C can be provided.

[0028] The above composition preferably contains element X. X is at least one element selected from the group consisting of Cl, Br, and I.

[0029] It is known that a metastable phase with high ionic conductivity (hereinafter also referred to as HICP (High Ion Conduction Phase)) is formed in a sulfide solid electrolyte containing Li, P, S, and element X (Patent Document 2). Further, it is known that when such a sulfide solid electrolyte contains N, the difference between the heat treatment temperature at which HICP precipitates and the heat treatment temperature at which HICP undergoes a phase transition to another phase with low ionic conductivity (hereinafter also referred to as LICP (Low Ion Conduction Phase)) widens (Patent Document 3). However, in Patent Document 3, since a sulfide solid electrolyte is produced using Li3N, N is discharged outside the system during the production process of the sulfide solid electrolyte, and the effect of expanding the heat treatment temperature range in which HICP is stable cannot be sufficiently obtained. On the other hand, in the production method of the sulfide solid electrolyte, the discharge of N outside the system is suppressed. Therefore, the effect of improving the thermal stability of HICP can be sufficiently exerted.

[0030] In the above composition, it is preferable that the content ratio of Li to P in the above composition is 3.10 or more and 4.20 or less in molar ratio, the content ratio of N to P in the above composition is 0.0600 or more and 0.750 or less in molar ratio, and the content ratio of X to P in the above composition is 0.180 or more and 1.30 or less in molar ratio.

[0031] Thereby, a sulfide solid electrolyte with high thermal stability of HICP can be provided.

[0032] The sulfide solid electrolyte according to another aspect of the present invention is a sulfide solid electrolyte manufactured by the manufacturing method of the sulfide solid electrolyte. For such a sulfide solid electrolyte, the emission of N to the outside of the system during the manufacturing process of the sulfide solid electrolyte is suppressed, so that various effects due to the inclusion of N can be sufficiently exerted.

[0033] The all-solid-state battery according to another aspect of the present invention includes a sulfide solid electrolyte manufactured by the manufacturing method of the sulfide solid electrolyte. For such an all-solid-state battery, the emission of N to the outside of the system during the manufacturing process of the sulfide solid electrolyte is suppressed, so that various effects due to the inclusion of N can be sufficiently exerted.

[0034] A method for selecting a raw material compound used in the production of a sulfide solid electrolyte according to another aspect of the present invention is a method for selecting a raw material compound used in the production of a sulfide solid electrolyte. As candidates for the raw material compound, a candidate material containing N, element A´, and element M´ is selected, and using first-principles calculations, the defect formation energy E Ndefect of N inside the candidate material is calculated, and the method for selecting a raw material compound includes selecting the candidate material as the raw material compound when the E Ndefect is 4.00 eV or more. When there are multiple N occupancy sites in the crystal structure of the candidate material, E Ndefect is calculated for each N occupancy site, and the one with the lowest value is used as the E Ndefect of the candidate material.

[0035] The raw material compound selected by the selection method has a large defect formation energy of N and is less likely to generate N defects during the synthesis process of the sulfide solid electrolyte. Therefore, N 2Gas is difficult to generate. Therefore, when manufacturing a sulfide solid electrolyte using the above raw material compound, it is possible to suppress the discharge of N outside the system in the manufacturing process of the sulfide solid electrolyte.

[0036] The above E Ndefect When the above is 4.10 eV or more, it is preferable to select the above candidate material as the above raw material compound.

[0037] According to this, it is possible to more reliably suppress the discharge of N outside the system in the manufacturing process of the sulfide solid electrolyte.

[0038] The above E Ndefect When the above is 4.35 eV or more, it is more preferable to select the above candidate material as the above raw material compound.

[0039] According to this, it is possible to more reliably suppress the discharge of N outside the system in the manufacturing process of the sulfide solid electrolyte.

[0040] A method for manufacturing a sulfide solid electrolyte according to another aspect of the present invention includes preparing a composition containing a raw material compound selected by a method for selecting a raw material compound used in the manufacture of the sulfide solid electrolyte, reacting the composition to obtain an intermediate, and heating the intermediate to obtain a sulfide solid electrolyte.

[0041] According to this, it is possible to suppress the discharge of N outside the system in the manufacturing process of the sulfide solid electrolyte. Therefore, it becomes easy to control the content of N contained in the sulfide solid electrolyte.

[0042] A sulfide solid electrolyte according to another aspect of the present invention is a sulfide solid electrolyte manufactured by the manufacturing method. With such a sulfide solid electrolyte, since the discharge of N outside the system in the manufacturing process of the sulfide solid electrolyte is suppressed, various effects due to the inclusion of N can be sufficiently exhibited.

[0043] The all-solid-state battery according to another aspect of the present invention includes a sulfide solid electrolyte manufactured using a raw material compound selected by the selection method. With such a sulfide solid electrolyte, the discharge of N to the outside of the system during the manufacturing process is suppressed, so that various effects due to the inclusion of N can be fully exhibited.

[0044] The sulfide solid electrolyte according to another aspect of the present invention is a sulfide solid electrolyte containing P, S, N, element A, element X, and element M as constituent elements and having a crystal structure. Here, A represents at least one element selected from the group consisting of Li, Na, and K. X represents at least one element selected from the group consisting of Cl, Br, and I. M represents at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti.

[0045] With such a sulfide solid electrolyte, the thermal stability of HICP can be enhanced compared to a sulfide solid electrolyte composed only of Li, P, S, N, and element X.

[0046] It is preferable that element M is at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, and B.

[0047] According to this, the thermal stability of HICP can be further enhanced.

[0048] It is preferable that the above crystal structure has diffraction peaks at 2θ = 20.2° ± 0.5° and 23.6° ± 0.5° in X-ray diffraction measurement using CuKα rays.

[0049] By having the above crystal structure, the sulfide solid electrolyte can obtain good Li ion conductivity.

[0050] The all-solid-state battery according to another aspect of the present invention is an all-solid-state battery containing a sulfide solid electrolyte containing P, S, N, element A, element X, and element M as constituent elements and having a crystal structure.

[0051] One of the advantages of all-solid-state batteries compared to non-aqueous electrolyte batteries is that the upper limit of the operating temperature is extremely high. This advantage is obtained because the solid electrolyte has high thermal stability. However, Patent Document 2 and Patent Document 3 describe that when the heating temperature is high, a sulfide solid electrolyte containing Li, P, S, N, Br, and I undergoes a phase transition from a high Li-ion conduction phase to a low Li-ion conduction phase. That is, the operating temperature of an all-solid-state battery equipped with such a sulfide solid electrolyte was limited by the phase transition temperature of the high Li-ion conduction phase. On the other hand, compared to conventional sulfide solid electrolytes that do not contain element M, the sulfide solid electrolyte of the present invention has high thermal stability of HICP. Therefore, an all-solid-state battery equipped with the sulfide solid electrolyte of the present invention can fully enjoy the advantage of an all-solid-state battery that can increase the upper limit of the operating temperature of the battery.

[0052] The sulfide solid electrolyte according to another aspect of the present invention is a crystalline sulfide solid electrolyte containing P, S, N, element A, and element M. Here, A represents at least one element selected from the group consisting of Li, Na, and K. M represents at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti.

[0053] For such a sulfide solid electrolyte, by suppressing the emission of N to the outside of the system in the manufacturing process of the sulfide solid electrolyte, the air stability and the like can be enhanced.

[0054] It is preferable that element M is at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, and B.

[0055] According to this, by more reliably suppressing the emission of N to the outside of the system in the manufacturing process of the sulfide solid electrolyte, the air stability and the like can be further enhanced.

[0056] Hereinafter, a method for manufacturing a sulfide solid electrolyte, a sulfide solid electrolyte, an all-solid-state battery, and a method for selecting a raw material compound used in the manufacture of the sulfide solid electrolyte according to an embodiment of the present invention will be described in detail. Note that matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention can be understood as design matters of those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the content disclosed in this specification and common general knowledge in the relevant field.

[0057] <Method for manufacturing sulfide solid electrolyte> [Embodiment] A method for manufacturing a sulfide solid electrolyte according to an embodiment of the present invention includes a preparation step of preparing a composition containing P, S, N, element A, and element M, a reaction step of reacting the composition to obtain an intermediate, and a heating step of heating the intermediate to obtain a sulfide solid electrolyte. The composition includes a raw material compound containing N, element A, and element M. Here, A is at least one element selected from the group consisting of Li, Na, and K. M is at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti. In this embodiment, the case where Li is contained as element A will be taken as an example to explain the method for manufacturing the sulfide solid electrolyte. FIG. 1 is a flowchart showing an example of the method for manufacturing the sulfide solid electrolyte according to this embodiment, and the following will be described along with this.

[0058] (Preparation step) In this step, a composition containing Li, P, S, N, and element M is prepared. The composition is preferably a mixture of one or more raw material compounds containing N, Li, and element M (hereinafter also referred to as Li-M-N-containing compounds) and one or more raw material compounds containing Li, P, and S.

[0059] In FIG. 1, first, Li 3Prepare nitride of N and element M and mix them in a mortar or the like. Next, produce pellets of the mixed raw material compounds. Next, produce a Li-M-N-containing compound by heat-treating the pellets.

[0060] Note that the means for preparing the Li-M-N-containing compound is not limited to this, and it may be produced by other methods. For example, the raw material of the Li-M-N-containing compound may be two or more compounds containing any one of N, Li, and element M. The Li-M-N-containing compound may be produced by mechanical milling. As the M-N-containing compound, an industrially manufactured and sold one may be prepared.

[0061] As the Li-M-N-containing compound, a lithium composite nitride of element M is preferably used. Examples of the lithium composite nitride of element M include Li 3 / 2 Al 1 / 2 N, Li 3 / 2 B 1 / 2 N, Li 5 / 3 Si 1 / 3 N, Li 9 / 5 Si 3 / 10 N, Li 7 / 4 P 1 / 4 N, LiMgN, LiHf 1 / 2 N, Li 3 / 2 Sc 1 / 2 N, LiZr 1 / 2 N, Li 5 / 3 Ti 1 / 3 N, Li 4 / 3 Ta 1 / 3 N, Li 7 / 4 Ta 1 / 4 N, Li 7 / 4 Nb 1 / 4 N, LiC 1 / 2 N and other lithium composite nitrides such as these. Among these, since they are easily available, Li 3 / 2 Al 1 / 2 N, Li 3 / 2 B 1 / 2 N, and Li 5 / 3 Si 1 / 3 N are preferred. Also, from the viewpoint of suppressing the precipitation of Li 2 S, Li 3 / 2 Al 1 / 2N is particularly preferred, and from the viewpoint of improving the thermal stability of HICP, Li 3 / 2 B 1 / 2 N and Li 5 / 3 Si 1 / 3 N is particularly preferred. From the viewpoint of suppressing the discharge of N outside the system in the manufacturing process of the sulfide solid electrolyte, Li 3 / 2 Al 1 / 2 N and Li 3 / 2 B 1 / 2 N is particularly preferred.

[0062] Examples of the raw material compound containing element M include oxides of element M, sulfides of element M, nitrides of element M, alloys of element M and Li, etc. Examples of the sulfide of element M include, for example, Al 2 S 3 SiS 2 etc. Examples of the nitride of element M include, for example, AlN, Si 3 N 4 BN, Mg 3 N 2 etc. The raw material compound containing element M may be used alone or in combination of two or more.

[0063] Element M in the manufacturing method may be at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti, and is not particularly limited. Among these, from the viewpoint of more reliably suppressing the discharge of N outside the system in the manufacturing process of the sulfide solid electrolyte, element M is preferably any one of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, and P, and more preferably any one of Al, Ta, Si, Sc, Mg, Nb, and B. Further, since it is easily available, element M is more preferably any one of Al, Si, and B. In particular, element M may be Al.

[0064] Examples of the raw material compound containing N include, for example, Li 3 N, PN, P 3 N 5 S 4 N 4 S 2 N 2 S 4N 2 and the like. Among these, Li 3 N is preferred. The raw material compound containing N may be used alone or in combination of two or more.

[0065] Examples of the raw material compound containing Li (also referred to as Li compound) include, for example, Li 2 S, Li 2 O, Li 3 N, Li 2 CO 3 , metallic lithium, and the like. Among these, Li 2 S is preferred. The raw material compound containing Li may be used alone or in combination of two or more.

[0066] Examples of the raw material compound containing P (also referred to as P compound) include, for example, P 2 S 3 , P 2 S 5 , P 2 O 5 , P 3 N 5 , elemental phosphorus, and the like. Among these, P 2 S 3 and P 2 S 5 are preferred, and P 2 S 5 is particularly preferred. The raw material compound containing P may be used alone or in combination of two or more.

[0067] Examples of the raw material compound containing S include, for example, Li 2 S, P 2 S 3 , P 2 S 5 , sulfide of element M, elemental sulfur, and the like. The raw material compound containing S may be used alone or in combination of two or more.

[0068] The above composition preferably contains a Li compound, a P compound, and a Li-M-N-containing compound, and it is more preferable that at least one of the above Li compound and the above P compound contains S. As the Li compound, the P compound, and the Li-M-N-containing compound, lithium sulfide, phosphorus sulfide, and the general formula Li α M β N (α and β are numerical values that give the stoichiometric ratio depending on the type of element M) is more preferably contained.

[0069] When the content of Li in the sulfide solid electrolyte is high, Li 2 S precipitates, resulting in a decrease in air stability. When the content is low, there is a risk of a decrease in ionic conductivity. Also, when the content of N is high, Li 2 S precipitates, leading to a decrease in air stability. When the content is low, there is a risk that the effects such as the improvement of air stability due to the inclusion of N cannot be fully exerted. From these viewpoints, it is preferable that the element ratios in the mixed state of the above composition simultaneously satisfy the following formulas in terms of molar ratio. 2.30 ≦ Li / P ≦ 4.20 0.0100 ≦ N / P ≦ 1.20 It is more preferable that the above Li / P and the above N / P simultaneously satisfy the following formulas. 2.36 ≦ Li / P ≦ 4.12 0.0200 ≦ N / P ≦ 1.11 It is even more preferable that the above Li / P and the above N / P simultaneously satisfy the following formulas. 2.36 ≦ Li / P ≦ 4.00 0.0600 ≦ N / P ≦ 0.900 It is even more preferably that the above Li / P and the above N / P simultaneously satisfy the following formulas. 2.60 ≦ Li / P ≦ 3.40 0.190 ≦ N / P ≦ 0.710 It is particularly preferable that the above Li / P and the above N / P simultaneously satisfy the following formulas. 2.77 ≦ Li / P ≦ 3.38 0.280 ≦ N / P ≦ 0.650

[0070] Further, in the above composition, it is preferable that the molar ratios of the respective elements of Li, P, S, N, and element M satisfy the general formula (100 - z)(yLi 2 S·(1 - y)P 2 S 5 )·zLi α M β N (where 0 < z ≦ 40, 0.50 ≦ y ≦ 0.75, and α and β are numerical values that give stoichiometric ratios depending on the type of element M). According to this, a sulfide solid electrolyte excellent in air stability and ionic conductivity at 25°C can be produced. Note that the above general formula indicates the content ratios of Li, S, P, N, and element M, and the above composition is not specified to consist of Li 2 S, P 2 S 5 , and Li α M β N.

[0071] In the above general formula, z is preferably greater than 0 and 40 or less, and more preferably 1 or more and 30 or less. When z in the above general formula is within the above range, a sulfide solid electrolyte excellent in air stability and ionic conductivity can be produced. Further, when 1 ≦ z ≦ 30, a sulfide solid electrolyte with increased ionic conductivity at 25°C can be produced. When 10 ≦ z ≦ 40, a so-called cross-linked sulfur P 2 S 7 4- (S 3 P - S - PS 3 ) decreases, and a sulfide solid electrolyte excellent in air stability that substantially does not contain Li 2 S, which is easily reactive with water, can be produced.

[0072] In the above general formula, y is preferably 0.50 or more and 0.75 or less, and more preferably 0.67 or more and 0.70 or less. In the above composition, Li 2 S and P 2 S 5By having the content ratio within the above range, a sulfide solid electrolyte with enhanced ionic conductivity at 25°C can be produced.

[0073] In the above general formula, α and β are numerical values that give the stoichiometric ratio according to the type of element M. The values of α and β are not particularly limited, but for example, 0.80 ≤ α ≤ 3.0 and 0.10 ≤ β ≤ 1.2 may be acceptable.

[0074] (Reaction step) In this step, the composition containing Li, P, S, N, and element M is reacted by performing mechanical milling on the composition to obtain an intermediate. Note that the means for obtaining the intermediate is not limited to this, and it may be obtained by other methods. For example, in FIG. 1, instead of mechanical milling, a melt quenching method or the like may be performed.

[0075] Mechanical milling may be either dry or wet, but wet milling is preferred because the raw material compounds can be more uniformly mixed. Examples of mechanical milling include container-driven mills, media agitation mills, milling by high-speed rotary grinders, roller mills, jet mills, etc. Examples of container-driven mills include rotary mills, vibration mills, planetary mills, etc. Examples of media agitation mills include attritors, bead mills, etc. Examples of milling by high-speed rotary grinders include hammer mills, pin mills, etc. Among these, container-driven mills are preferred, and particularly planetary mills are preferred.

[0076] The intermediate obtained in the reaction step may have a crystal structure, but is preferably a so-called sulfide glass. "Sulfide glass" means a sulfide solid electrolyte containing an amorphous structure. When the intermediate is a sulfide glass, there are fewer crystal phases with low atmospheric stability such as Li 2 S, and a sulfide solid electrolyte with high dispersion of N, element M, etc. can be obtained.

[0077] (Heat treatment step) In this process, a sulfide solid electrolyte is produced by heat-treating the intermediate at a temperature equal to or higher than the crystallization temperature. The heat treatment may be carried out under a reduced-pressure atmosphere or under an inert gas atmosphere. The crystallization temperature can be determined by measurement using a differential scanning calorimeter (DSC). For example, Li 7 P 3 S 11 To obtain a crystal structure, the heat treatment temperature is preferably 250°C or higher and 400°C or lower. For β-Li 3 PS 4 To obtain a crystal structure, the heat treatment temperature is preferably 200°C or higher and 400°C or lower. Also, in X-ray diffraction measurement using CuKα radiation, to obtain a first crystal structure having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, and 29.8° ± 0.5°, the heat treatment temperature is preferably 250°C or higher and 400°C or lower. This is because when heat-treated at a high temperature such as 500°C, there is a possibility of phase transition to the stable phase Li 4 P 2 S 6 .

[0078] [Modification Example] The method for producing a sulfide solid electrolyte according to the present invention is not limited to the above-described embodiment, and can be implemented in various modified and improved forms in addition to the above-described aspects.

[0079] In the above embodiment, a sulfide solid electrolyte of the Li 2 S-P 2 S 5 system was described as an example, but an LGPS-type sulfide solid electrolyte or an argyrodite-type sulfide solid electrolyte may also be produced by the production method. Examples of the LGPS-type sulfide solid electrolyte include Li 10 GeP 2 S 12 and the like. Li 10 GeP 2 S 12The crystal structure having the crystal phase has diffraction peaks at positions of 2θ = 14.4° ± 0.5°, 20.1° ± 0.5°, 20.4° ± 0.5°, 26.9° ± 0.5°, 29.5° ± 0.5°, and 47.3° ± 0.5° in X-ray diffraction measurement using CuKα rays. Examples of the argyrodite-type sulfide solid electrolyte include, for example, Li 6 PS 5 Cl and the like. The crystal structure having the crystal phase of Li 6 PS 5 Cl has diffraction peaks at positions of 2θ = 15.6° ± 0.5°, 25.5° ± 0.5°, 30.0° ± 0.5°, 31.4° ± 0.5°, 45.0° ± 0.5°, and 52.5° ± 0.5° in X-ray diffraction measurement using CuKα rays.

[0080] [Modification Example 1] As Modification Example 1, an embodiment of manufacturing an LGPS-type sulfide solid electrolyte will be described. By adding a raw material compound containing Ge to the composition in the above preparation step, an LGPS-type sulfide solid electrolyte can be manufactured. Examples of the raw material compound containing Ge include, for example, GeS 2 and the like. When manufacturing an LGPS-type sulfide solid electrolyte, it is preferable that the composition simultaneously satisfies the following formula in terms of molar ratio of element ratios. 5.01 ≦ Li / P ≦ 5.61 0.0051 ≦ N / P ≦ 0.41 By setting the content ratio of the elements in the composition within the above range, a sulfide solid electrolyte having a crystal phase of Li 10 GeP 2 S 12 and having high ionic conductivity at 25°C can be manufactured.

[0081] [Modification Example 2] As Modification Example 2, an embodiment of manufacturing a sulfide solid electrolyte containing Li, P, S, N, element X, and element M as constituent elements and having a crystal structure will be described. X is at least one element selected from the group consisting of Cl, Br, and I.

[0082] In Modification 2, a raw material compound containing element X is added to the above composition to produce a crystalline sulfide solid electrolyte containing Li, P, S, N, element X, and element M. According to this, a sulfide solid electrolyte having HICP and improved thermal stability of HICP can be produced.

[0083] Examples of the raw material compound containing element X include lithium halide, sulfur halide, phosphorus halide, M η X σ (However, η = 1 or 2, and σ is an integer from 1 to 10.) and halides of element M represented thereby. Examples of the lithium halide include LiCl, LiBr, LiI, etc. Examples of the sulfur halide include SCl 2 、S 2 Cl 2 、SBr 2 、S 2 Br 2 、SI 2 、S 2 I 2 etc. Examples of the phosphorus halide include PCl 3 、PCl 5 、POCl 3 、PBr 3 、PBr 5 、POBr 3 、PI 3 、PCI 4 、P 2 I 4 etc. Examples of the halide of the above element M include AlBr 3 、BBr 3 、AlCl 3 、AlBr 3 、AlI 3 、SiCl 3 、SiCl 4 、SiBr 4 、SiI 4 、SiBrI 3 、SiBr 2 I 2 、SiBr 3 I、BCl3 , BBr 3 , BI 3 etc. can be mentioned. Among these, lithium halide and phosphorus halide are preferable, and lithium halide is more preferable. As the lithium halide, LiBr and LiI are preferable. The raw material compound containing element X may be used alone or in combination of two or more. Further, the above composition may contain one kind of element X alone or two or more kinds. In particular, from the viewpoint of increasing the ionic conductivity at 25°C, it is preferable to contain Br or I alone as element X, and it is more preferable to contain Br alone. It is also preferable to contain Br and I simultaneously.

[0084] In Modification 2, when the above composition contains Br and I simultaneously, the content of Br with respect to the total amount of Br and I in the above composition is preferably 1 mol% or more and 99 mol% or less, and more preferably 5 mol% or more and 80 mol% or less.

[0085] In the case of a sulfide solid electrolyte with a high Li content, Li 2 S may precipitate, resulting in a decrease in air stability. In the case of a low content, there is a risk that HICP may not precipitate. Also, when the N content is high, Li 2 S may precipitate, resulting in a decrease in air stability. In the case of a low content, there is a risk that the effect of containing N cannot be fully exerted. Further, when the content of element X is high, a lithium halide crystal phase may remain in the sulfide solid electrolyte, resulting in a decrease in ionic conductivity. In the case of a low content, there is a risk that the effect of containing element X cannot be fully exerted. From these viewpoints, it is preferable that the composition in the preparation process of Modification 2 simultaneously satisfies the following formulas in terms of the element ratio in the mixed state, each in molar ratio. 3.10 ≤ Li / P ≤ 4.20 0.0600 ≤ N / P ≤ 0.750 0.180 ≤ X / P ≤ 1.30 Furthermore, it is more preferable that the above Li / P, the above N / P, and the above X / P simultaneously satisfy the following equations respectively. 3.10 ≦ Li / P ≦ 3.90 0.0900 ≦ N / P ≦ 0.750 0.180 ≦ X / P ≦ 1.00

[0086] It is preferable that the molar ratios of the respective elements Li, P, S, N, element X, and element M in the above composition satisfy the general formula (100 - z){(1 - y)[xLi 2 S·(1 - x)P 2 S 5 ·yLi α M β N}·zLiX (where 0.50 ≦ x ≦ 0.80, 0 < y ≦ 0.50, 5 ≦ z ≦ 40, α and β are numerical values giving stoichiometric ratios according to the type of element M). More preferably, x, y, and z are 0.67 ≦ x ≦ 0.73, 0.10 ≦ y ≦ 0.30, and 10 ≦ z ≦ 30 respectively. Thereby, the thermal stability of HICP can be improved. Furthermore, when the above composition contains two types of elements X 1 and X 2 as element X, the above general formula can also be expressed as (100 - z 1 - z 2 ){(1 - y)[xLi 2 S·(1 - x)P 2 S 5 ·yLi α M β N}·z 1 LiX 1 ·z 2 LiX 2 (where 0.50 ≦ x ≦ 0.80, 0 < y ≦ 0.50, 5 ≦ (z 1 + z 2 )≦ 40, α and β are numerical values giving stoichiometric ratios according to the type of element M). In this case, x, y, z 1 and z 2 are preferably 0.67 ≦ x ≦ 0.73, 0.10 ≦ y ≦ 0.30, and 10 ≦ (z 1 + z 2 )≦ 30 respectively. Note that the above general formula indicates the content ratios of Li, S, P, N, element M, and element X, and the above composition contains Li 2 S, P 2 S 5 Li α M β N, and LiX. It does not specify that it consists of these components.

[0087] In the above general formula, when element M is either Al or B, α = 2 / 3 and β = 1 / 2 may be applicable. In this case, x, y, and z are preferably 0.50 ≦ x ≦ 0.80, 0 < y ≦ 0.50, and 5 ≦ z ≦ 40, more preferably 0.60 ≦ x ≦ 0.75, 0.050 ≦ y ≦ 0.40, and 10 ≦ z ≦ 30, and even more preferably 0.67 ≦ x ≦ 0.73, 0.10 ≦ y ≦ 0.30, and 15 ≦ z ≦ 25.

[0088] The raw materials used in the reaction process of Modification Example 2 preferably include a Li compound, a P compound, a halogen compound, and a Li-M-N-containing compound. More preferably, at least one of the above Li compound and the above P compound contains an S element. Further, as the above Li compound, the above P compound, the above halogenated compound, and the above Li-M-N-containing compound, lithium sulfide, phosphorus sulfide, lithium halide, and a compound represented by the general formula Li α M β N (α and β are numerical values giving the stoichiometric ratio according to the type of element M) are more preferably contained.

[0089] In the heat treatment step of Modification Example 2, a sulfide solid electrolyte is produced by heat-treating the intermediate at a temperature equal to or higher than the crystallization temperature. The heat treatment may be carried out under a reduced pressure atmosphere or under an inert gas atmosphere. The crystallization temperature can be determined by measurement using a differential scanning calorimeter (DSC).

[0090] In Modification Example 2, a sulfide solid electrolyte having HICP is produced. After HICP undergoes a phase transition to either LICP or a specific crystal structure C, it further becomes β-Li 3 PS 4Of these crystal phases, HICP has the highest ionic conductivity. Therefore, in the heat treatment process in the second modification, the lower limit of the heat treatment temperature is the HICP generation temperature T H The upper limit of the heat treatment temperature is preferably β-Li 3 P.S. 4 The formation temperature T β It is preferable that the LICP generation temperature T L or the formation temperature T of a specific crystal structure C C It is more preferable that the value is less than or equal to T H , T L , T C and T β can be determined by XRD measurement. The sulfide solid electrolyte produced in the second modification is T β -T H But, T β -T H ≧40° C., and T β -T H More preferably, T is ≧50° C. β -T H More preferably, T is ≧60° C. β -T H It is particularly preferred that it is ≧70° C.

[0091] The sulfide solid electrolyte produced in Modification 2 has a wide heat treatment temperature range in which ionic conductivity does not decrease. In other words, even if the heat treatment temperature deviates from the intended temperature in the heat treatment step, there is little risk of the ionic conductivity of the produced sulfide solid electrolyte decreasing. Therefore, Modification 2 has the advantage that a sulfide solid electrolyte with high ionic conductivity can be produced without requiring strict temperature control in the heat treatment step.

[0092] Note that "HICP" represents a crystal phase having diffraction peaks at 2θ = 20.2° ± 0.5° and 23.6° ± 0.5° in X-ray diffraction measurement using CuKα line. This crystal structure is the crystal phase described in Patent Document 2 etc., and is a crystal phase with high Li ion conductivity. "LICP" is a crystal phase having diffraction peaks at 2θ = 21.0° ± 0.5° and 28.0° ± 0.5° in X-ray diffraction measurement using CuKα line. This crystal structure is the crystal phase described in Patent Document 2 etc., and is a crystal phase with low Li ion conductivity. "Specific crystal structure C" represents a crystal phase having diffraction peaks at 2θ = 17.5° ± 0.5° and 24.9° ± 0.5° in X-ray diffraction measurement using CuKα line. "β-Li 3 PS 4 " represents a crystal phase having diffraction peaks at 2θ = 17.5° ± 0.5°, 18.1° ± 0.5°, 29.1° ± 0.5°, 29.9° ± 0.5°, and 31.2° ± 0.5° in X-ray diffraction measurement using CuKα line.

[0093] The X-ray diffraction measurement using CuKα line in this specification is performed according to the following procedure. A hermetic sample holder for X-ray diffraction measurement is filled with solid electrolyte powder to be measured under an argon atmosphere with a dew point of -50°C or lower. Powder X-ray diffraction measurement is performed using an X-ray diffractometer ("MiniFlex II" manufactured by Rigaku). The radiation source is CuKα line, the tube voltage is 30 kV, the tube current is 15 mA, and the diffracted X-ray is detected by a high-speed one-dimensional detector (model number: D / teX Ultra 2) through a Kβ filter with a thickness of 30 μm. The sampling width is 0.01°, the scan speed is 5° / min, the divergence slit width is 0.625°, the receiving slit width is 13 mm (OPEN), and the scattering slit width is 8 mm.

[0094] <Method for Selecting Raw Material Compounds> According to the method for producing a sulfide solid electrolyte of the present invention, by using a raw material compound containing N, element A, and element M, it is possible to suppress the release of N outside the system during the production process of the sulfide solid electrolyte. In selecting element A and element M that can obtain such an effect, the present inventors used first-principles calculations. Hereinafter, a method for selecting a raw material compound used in the production of a sulfide solid electrolyte according to an embodiment of the present invention will be described.

[0095] In this embodiment, a raw material compound is selected according to the procedures shown in (1) to (3). (1) Select a candidate material containing N, element A´, and element M´, where the first nearest neighbor atoms of the above element A´ and the above element M´ are N. (2) Using first-principles calculations, calculate the N defect formation energy E Ndefect in the above candidate material. (3) When the above E Ndefect is 4.00 eV or more, select the above candidate material as the above raw material compound.

[0096] First-principles calculation is a calculation method for predicting physical properties non-empirically, and is a method capable of calculating the total energy of a model including atoms with known atomic numbers and spatial coordinates, and the electronic energy band structure. By calculating the forces acting on the atoms, structure optimization becomes possible, and lattice constants, the stable structure at 0 K, and band gaps can be calculated. Calculation methods are roughly classified into two types: "wave function theory" type and "density functional theory" type. The calculation method used in this specification is based on density functional theory.

[0097] The N defect formation energy E Ndefect is the energy value required to remove N from the crystal structure to generate a defect. The N defect formation energy is the total energy E perfect of a crystal structure without defects, the total energy E Nvacancy of a crystal structure containing N defects, and the chemical potential μ N of N atoms, and is a value calculated using the following formula (1) and is defined by the following formula (1). E Ndefect = (E Nvacancy + μ N ) - E perfect Formula (1) That is, the procedure for calculating the N defect formation energy E Ndefect is as follows. (a) Obtain the composition and crystal structure of the candidate material. (b) Calculate the chemical potential μ of the N atom to be desorbed as a defect. N Calculate it. (c) Calculate the total energy E of the defect-free crystal structure by a structure optimization calculation. perfect Calculate it by a structure optimization calculation. (d) Calculate the total energy E of the crystal structure containing N defects by a structure optimization calculation. Nvacancy Calculate it by a structure optimization calculation. (e) Calculate the defect formation energy E of N according to formula (1). Ndefect Calculate it. When there are multiple N occupancy sites in the crystal structure of the candidate material, calculate E for each N occupancy site, and use the one with the lowest value as the E of the candidate material. Ndefect Calculate it, and use the one with the lowest value as the E of the candidate material. Ndefect Use it. The composition and crystal structure of the candidate material can be arbitrarily selected from those available from known publications, databases, etc. The candidate material is not particularly limited as long as it is a compound containing N, element A´, and element M´, but it is preferably a compound that is stable under normal temperature and pressure.

[0098] In this embodiment, element A´ is a metal element. Element M´ is an element other than nitrogen belonging to any of Groups 2 to 15 of the periodic table and is different from element A´. N is a nitrogen element. Element A´ is not particularly limited, but is preferably any of an alkali metal element, an alkaline earth metal element, and an aluminum element, more preferably at least one selected from Li, Na, K, Mg, Ca, Al, and even more preferably Li. This makes it easier to operate the sulfide solid electrolyte as a battery.

[0099] In this embodiment, Li α M´ β N (α and β are numerical values giving the stoichiometric ratio according to the type of element M), and Li 3For N, the defect generation energy of N was calculated. That is, Li was selected as the element A´. As the element M´, B, Mg, Al, Si, P, Ca, Sr, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, Sr, Y, Zr, Nb, In, Sn, Ce, Hf, Ta, C were evaluated. For the first-principles calculation, the calculation software Vienna Ab-initio Simulation Package (VASP) was used. The calculation conditions are as follows. The k-points were set so that the value of k-resolution was about 1000. The k-resolution is the product of the number of atoms in the model and the k-points in the a, b, and c axis directions. Cutoff energy of plane-wave basis functions: 520 eV Approximation method for exchange-correlation interaction: GGA+U Pseudopotential: PAW(PBEsol) k-points: k-resolution ≈ 1000 Convergence condition for SCF calculation: 10 -4 eV Occupancy (Occ.) of each atomic site: 1 For the first-principles calculation of materials containing transition metal elements V, Cr, Mn, Fe, Co, Ni in which the 3d orbit is the outermost shell orbit and the 3d orbit is not closed-shell in the state of a cation with a stable valence and there are electrons in the 3d orbit, the Hubbard U shown in Table 1 eff values were used as the calculation conditions. Thereby, the localization effect of electrons in the d orbit was reflected in the calculation. The Hubbard U shown in Table 1 eff values were cited from the calculation conditions of the first-principles calculation carried out in the crystal structure database Materials Project (https: / / materialsproject.org / #search / materials) (as of August 22, 2019). By searching for materials containing V, Cr, Mn, Fe, Co, Ni in the database, the U eff values were obtained.

[0100]

Table 1

[0101] In the above procedure (d), in order to reduce the interaction between N defects, a calculation model cell was designed such that the lattice constants a, b, and c were all about 10 Å within a range where the total number of atoms did not exceed 200. Table 2 shows the lattice constants used in the calculation of some candidate materials.

[0102]

Table 2

[0103] Table 3 shows the element M´, the chemical composition of each candidate material, and the defect formation energy E of N. Ndefect is shown.

[0104]

Table 3

[0105] From Table 3, it can be seen that the defect formation energy E of N in Li 3 N is 2.94 eV. Ndefect It can be understood that In addition, for each of the elements V, Y, Ga, Ca, Ce, Sn, Zn, Ge, Cr, Mn, Sr, In, Co, Ni, and Fe, the defect formation energy E of N in Li α M´ β N is found to be as small as 3.88 eV or less. Therefore, in candidate materials containing any one of V, Y, Ga, Ca, Ce, Sn, Zn, Ge, Cr, Mn, Sr, In, Co, Ni, and Fe as the element M´, N defects are likely to be generated, and it is predicted that the effect of the present invention of suppressing the discharge of N out of the system in the manufacturing process of the sulfide solid electrolyte cannot be obtained or the effect is small. Ndefect On the other hand, for each of the elements Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti, the defect formation energy E of N in Li α M´ β N Ndefect ​It can be seen that it is as large as 4.00 eV or more. Therefore, if the candidate material contains any of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti as the element M´, it is predicted that N defects are less likely to be generated, and the effect of the present invention of suppressing the discharge of N out of the system in the manufacturing process of the sulfide solid electrolyte is extremely likely to be exhibited.

[0106] The candidate material has a larger N defect generation energy E Ndefect value, the less likely N defects are to be generated, and it is predicted that the discharge of N out of the system in the manufacturing process of the sulfide solid electrolyte can be further suppressed. Therefore, in this embodiment, the N defect generation energy E Ndefect of the candidate material is 4.00 eV or more, preferably 4.10 eV or more, more preferably 4.20 eV or more, still more preferably 4.30 eV or more, and particularly preferably 4.35 eV or more.

[0107] In this embodiment, calculations were performed for the case where Li is included as the element A´. That is, first-principles calculations were performed using Li α M´ β N as a model. However, the present invention is not limited to this. The element A´ may be any metal element. For example, as the element A´, a candidate material containing any of Na, K, Mg, Ca, and Al may be selected, and a raw material compound may be selected using first-principles calculations.

[0108] <Sulfide solid electrolyte> [Embodiment 1] The sulfide solid electrolyte according to an embodiment of the present invention is a composition containing P, S, N, element A, and element M, and includes preparing a raw material compound containing N, element A, and element M, reacting the above composition to obtain an intermediate, and heating the above intermediate to obtain a sulfide solid electrolyte. Hereinafter, the case where Li is contained as element A will be taken as an example to describe the sulfide solid electrolyte.

[0109] The sulfide solid electrolyte has a crystal structure. "Having a crystal structure" means that in X-ray diffraction measurement, peaks derived from the crystal structure of the sulfide solid electrolyte are observed in the X-ray diffraction pattern. The sulfide solid electrolyte may contain an amorphous portion.

[0110] Examples of the crystal structure of the sulfide solid electrolyte include HICP, LGPS type, argyrodite type, Li 7 P 3 S 11 and Thio-LISICON type, etc. Among these, as the crystal structure, from the viewpoint of lithium ion conductivity, HICP, LGPS type, argyrodite type, and Li 7 P 3 S 11 are preferable. Among these, Li 7 P 3 S 11 is more preferable because of its high stability against Li. From the viewpoint of stability against the atmosphere, Li 4 P 2 S 6 or a crystal structure having a crystal phase of β-Li 3 PS 4 or a first crystal structure having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5° and 29.8° ± 0.5° in X-ray diffraction measurement using CuKα ray is preferable. Among these, a first crystal structure having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5° and 29.8° ± 0.5° in X-ray diffraction measurement using CuKα ray is more preferable because of its high lithium ion conductivity.

[0111] The above first crystal structure may include a specific crystal structure A having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, 29.8° ± 0.5°, and 30.9° ± 0.5° in the above X-ray diffraction measurement, or a specific crystal structure B having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, and 29.8° and not having a diffraction peak at 30.9° ± 0.5° in the above X-ray diffraction measurement. With the above configuration, a sulfide solid electrolyte capable of increasing the initial Coulomb efficiency of an all-solid-state battery including the solid electrolyte can be obtained.

[0112] The diffraction peaks in the above first crystal structure may have the 2θ range within ±0.3° or within ±0.1°.

[0113] The above Li 7 P 3 S 11 The crystal structure having a crystal phase of has diffraction peaks at positions of 2θ = 17.8° ± 0.5°, 18.5° ± 0.5°, 23.7° ± 0.5°, 29.6° ± 0.5°, and 30.0° ± 0.5° in X-ray diffraction measurement using CuKα radiation.

[0114] Examples of the above LGPS-type sulfide solid electrolyte include, for example, Li 10 GeP 2 S 12 and the like. The crystal structure having a crystal phase of Li 10 GeP 2 S 12 has diffraction peaks at positions of 2θ = 14.4° ± 0.5°, 20.1° ± 0.5°, 20.4° ± 0.5°, 26.9° ± 0.5°, 29.5° ± 0.5°, and 47.3° ± 0.5° in X-ray diffraction measurement using CuKα radiation.

[0115] Examples of the above argyrodite-type sulfide solid electrolyte include, for example, Li 6 PS 5 Cl and the like. Li 6 PS 5The crystal structure having a crystal phase of Cl has diffraction peaks at positions of 2θ = 15.6° ± 0.5°, 25.5° ± 0.5°, 30.0° ± 0.5°, 31.4° ± 0.5°, 45.0° ± 0.5°, 52.5° ± 0.5° in X-ray diffraction measurement using CuKα rays.

[0116] The above Li 4 P 2 S 6 The crystal structure having a crystal phase of has diffraction peaks at positions of 2θ = 16.9° ± 0.5°, 27.1° ± 0.5°, 32.1° ± 0.5°, 32.5° ± 0.5° in X-ray diffraction measurement using CuKα rays.

[0117] The above β-Li 3 PS 4 The crystal structure having a crystal phase of has diffraction peaks at positions of 2θ = 17.5° ± 0.5°, 18.1° ± 0.5°, 29.1° ± 0.5°, 29.9° ± 0.5°, 31.2° ± 0.5° in X-ray diffraction measurement using CuKα rays.

[0118] The sulfide solid electrolyte preferably contains, as a main component, an anion structure of a so-called ortho composition. For example, when the sulfide solid electrolyte is a Li 2 S-P 2 S 5 -based solid electrolyte, it preferably contains a PS 4 3- structure as a main component. Here, "main component" means that the proportion of a specific component in all components is 50 mol% or more.

[0119] When the sulfide solid electrolyte contains an ortho-composition anion structure as a main component, the content of the ortho-composition anion structure with respect to all anion structures constituting the sulfide solid electrolyte is 50 mol% or more and less than 100 mol%, preferably 60 mol% or more and less than 100 mol%, more preferably 70 mol% or more and less than 100 mol%, still more preferably 80 mol% or more and less than 100 mol%, and particularly preferably 90 mol% or more and less than 100 mol%.

[0120] The sulfide solid electrolyte preferably does not substantially contain crosslinked sulfur. Since crosslinked sulfur reacts with water to produce hydrogen sulfide, the atmospheric stability can be improved by not substantially containing crosslinked sulfur. For example, when the sulfide solid electrolyte is Li 2 S-P 2 S 5 -based solid electrolyte, it preferably does not substantially contain the S 3 P-S-PS 3 structure. The fact that it does not substantially contain crosslinked sulfur can be confirmed by the absence of a peak corresponding to the crosslinked sulfur structure when measuring the Raman spectrum with a laser having an excitation wavelength of 532 nm. For example, the fact that it does not substantially contain the S 3 P-S-PS 3 structure can be confirmed by the absence of a peak at 402 cm -1 when measuring the Raman spectrum with a laser having an excitation wavelength of 532 nm. Note that the sulfide solid electrolyte may contain a small amount of crosslinked sulfur. In this case, the ratio I O of the peak intensity I P attributed to the crosslinked sulfur to the peak intensity I P attributed to the ortho-composition anion structure in the Raman spectrum measurement is preferably 0.7 or less, more preferably 0.5 or less, and even more preferably 0.35 or less. For example, when the sulfide solid electrolyte is Li O / I 2 S-P 2 S 5 -based solid electrolyte, the peak intensity at 417 cm 4 3- derived from the PS -1 structure corresponds to the above I O , and the peak intensity at 402 cm 3 derived from the S 3 PS-PS -1 structure corresponds to the above I P .

[0121] The sulfide solid electrolyte preferably does not substantially contain Li 2 S. Li2 Since S reacts with water to produce hydrogen sulfide, Li 2 The atmospheric stability can be improved by substantially not containing S. Here, "substantially not containing Li 2 S" means not containing a crystal structure having diffraction peaks at 2θ = 27.0 ± 0.5°, 31.2 ± 0.5°, 44.8 ± 0.5°, and 53.1 ± 0.5° in X-ray diffraction measurement using CuKα rays.

[0122] In the case of a sulfide solid electrolyte, when the Li content is high, Li 2 S precipitates and the atmospheric stability decreases. When the content is low, there is a risk of a decrease in ionic conductivity. Also, when the N content is high, Li 2 S precipitates and the atmospheric stability decreases. When the content is low, there is a risk that the effects such as the improvement of atmospheric stability due to containing N cannot be fully exerted. From these viewpoints, it is preferable that the sulfide solid electrolyte simultaneously satisfies the following formulas in terms of elemental ratios in molar ratio. 2.30 ≦ Li / P ≦ 4.20 0.0100 ≦ N / P ≦ 1.20 It is more preferable that the above Li / P and the above N / P simultaneously satisfy the following formulas respectively. 2.36 ≦ Li / P ≦ 4.12 0.0200 ≦ N / P ≦ 1.11 It is even more preferable that the above Li / P and the above N / P simultaneously satisfy the following formulas respectively. 2.36 ≦ Li / P ≦ 4.00 0.0600 ≦ N / P ≦ 0.900 It is still more preferable that the above Li / P and the above N / P simultaneously satisfy the following formulas respectively. 2.60 ≦ Li / P ≦ 3.40 0.190 ≦ N / P ≦ 0.710 It is particularly preferable that the above Li / P and the above N / P simultaneously satisfy the following formulas respectively. 2.77 ≦ Li / P ≦ 3.38 0.280 ≦ N / P ≦ 0.650

[0123] As the sulfide solid electrolyte, it preferably has a composition represented by the general formula (100 - z)(yLi 2 S·(1 - y)P 2 S 5 )·zLi α M β N (where 0 < z ≤ 40, 0.50 ≤ y ≤ 0.75, and α and β are numerical values that give the stoichiometric ratio according to the type of element M). By having the sulfide solid electrolyte have the composition represented by the above general formula, the air stability and the ionic conductivity at 25°C can be improved. Note that the above general formula shows the content ratios of Li, S, P, N, and element M, and the above composition does not specify that the composition consists of Li 2 S, P 2 S 5 , and Li α M β N.

[0124] As the lower limit of the ionic conductivity of the sulfide solid electrolyte at 25°C, 0.4×10 -3 S / cm is preferable, 1.0×10 -3 S / cm is more preferable, and 1.5×10 -3 S / cm is even more preferable. By having the ionic conductivity of the sulfide solid electrolyte at 25°C within the above range, the rate characteristics of the all-solid-state battery can be improved.

[0125] Note that the ionic conductivity of the sulfide solid electrolyte at 25°C is obtained by measuring the alternating current impedance by the following method. In an argon atmosphere with a dew point of -50°C or lower, 120 mg of sample powder is put into a powder molding die with an inner diameter of 10 mm, and then uniaxially pressed at a pressure of 50 MPa or less per sample area using a hydraulic press. After releasing the pressure, SUS316L powder is put on the upper and lower surfaces of the sample as a current collector, and then uniaxially pressed at a pressure of 360 MPa per pellet area for 5 minutes to obtain a pellet for measuring ionic conductivity. This pellet for measuring ionic conductivity is inserted into an HS cell manufactured by Hokuen Co., Ltd. to perform alternating current impedance measurement. The measurement conditions are an applied voltage amplitude of 20 mV, a frequency range from 1 MHz to 100 mHz, and a measurement temperature of 25°C.

[0126] Thus, the sulfide solid electrolyte can be suitably used as a solid electrolyte for all-solid-state batteries.

[0127] [Embodiment 2] The sulfide solid electrolyte according to another embodiment of the present invention contains Li, P, S, N, element X, and element M. Element X represents at least one element selected from the group consisting of Cl, Br, and I.

[0128] The sulfide solid electrolyte may contain one selected from the group consisting of Al, B, and Si as element M, or may contain Al as element M.

[0129] When the content of Li in the sulfide solid electrolyte is high, Li 2 S may precipitate, resulting in a decrease in air stability. When the content is low, there is a risk that HICP may not precipitate. Also, when the content of N is high, Li 2 S may precipitate, leading to a decrease in air stability. When the content is low, there is a risk that the effect of containing N cannot be fully exerted. Further, when the content of element X is high, a crystal phase of lithium halide may remain in the sulfide solid electrolyte, which may reduce the ionic conductivity. When the content is low, there is a risk that the effect of containing element X cannot be fully exerted. For these reasons, it is preferable that the sulfide solid electrolyte simultaneously satisfies the following formulas in terms of molar ratio for the content ratio Li / P of Li to P, the content ratio N / P of N to P, and the content ratio X / P of X to P, respectively. 3.10 < Li / P < 4.20 0.0600 < N / P < 0.750 0.180 < X / P < 1.30 Moreover, it is more preferable that Li / P, N / P, and X / P simultaneously satisfy the following formulas, respectively. 3.10 < Li / P < 3.90 0.0900 < N / P < 0.750 0.180 < X / P < 1.00

[0130] The sulfide solid electrolyte preferably has a composition represented by the general formula (100 - z){(1 - y)[xLi 2 S·(1 - x)P 2 S 5 ·yLi α M β N}·zLiX (where 0.50 ≤ x ≤ 0.80, 0 < y ≤ 0.50, 5 ≤ z ≤ 40, α and β are numerical values giving the stoichiometric ratio according to the type of element M), and more preferably x, y, and z are 0.67 ≤ x ≤ 0.73, 0.10 ≤ y ≤ 0.30, and 10 ≤ z ≤ 30, respectively. By having the composition represented by the above general formula, the thermal stability of HICP can be improved. Further, when the sulfide solid electrolyte contains two types of elements X1 and X2 as element X, the above general formula is (100 - z 1 -z 2 ){(1 - y)[xLi 2 S·(1 - x)P 2 S 5 ·yLi α M β N}·z 1 LiX 1 ·z 2 LiX 2 (where 0.50 ≤ x ≤ 0.80, 0 < y ≤ 0.50, 5 ≤ (z 1 +z 2 ) ≤ 40, α and β are numerical values giving the stoichiometric ratio according to the type of element M), and in this case, x, y, z 1 and z 2 are preferably 0.67 ≤ x ≤ 0.73, 0.10 ≤ y ≤ 0.30, and 10 ≤ (z 1 +z 2 ) ≤ 30, respectively. Note that the above general formula indicates the content ratios of Li, S, P, N, element M, and element X, and the above composition does not specify that the composition consists of Li 2 S, P 2 S 5 , Li α M β N, and LiX.

[0131] In the above general formula, when the element M is any one of Al, B, and Sc, α may be 2 / 3 and β may be 1 / 2. In this case, x, y, and z are preferably 0.50 ≦ x ≦ 0.80, 0 < y ≦ 0.50, and 5 ≦ z ≦ 40, more preferably 0.60 ≦ x ≦ 0.75, 0.050 ≦ y ≦ 0.40, and 10 ≦ z ≦ 30, and even more preferably 0.67 ≦ x ≦ 0.73, 0.10 ≦ y ≦ 0.30, and 15 ≦ z ≦ 25.

[0132] The sulfide solid electrolyte preferably contains Br or I alone as the element X, and more preferably contains Br alone. It is also preferable to contain Br and I simultaneously. When the sulfide solid electrolyte contains Br and I simultaneously, the content of Br with respect to the total amount of Br and I contained in the sulfide solid electrolyte is preferably 1 mol% or more and 99 mol% or less, and more preferably 5 mol% or more and 80 mol% or less.

[0133] The sulfide solid electrolyte preferably contains HICP. That is, it preferably contains a crystal structure having diffraction peaks at 2θ = 20.2° ± 0.5° and 23.6° ± 0.5° in X-ray diffraction measurement using CuKα radiation.

[0134] The sulfide solid electrolyte preferably does not contain LICP. That is, it preferably does not contain a crystal structure having diffraction peaks at 2θ = 21.0° ± 0.5° and 28.0° ± 0.5° in X-ray diffraction measurement using CuKα radiation. The sulfide solid electrolyte may contain a small amount of LICP. In this case, the diffraction peak intensity ratio I H at 2θ = 20.2° ± 0.5° to the diffraction peak intensity I L at 2θ = 21.0° ± 0.5° in X-ray diffraction measurement using CuKα radiation, the diffraction peak intensity ratio I L / I H is preferably 0 < I L / I H < 3.2, and more preferably 0 < I L / I HIt is more preferably 2.5 or less, and 0 < I L / I H It is even more preferably 2.0 or less, and 0 < I L / I H It is even more preferably 1.0 or less. The diffraction peak intensity ratio I L / I H represents the abundance ratio of HICP and LICP contained in the sulfide solid electrolyte. That is, the diffraction peak intensity ratio I L / I H being small indicates that the amount of LICP is relatively small with respect to HICP.

[0135] The ionic conductivity of the sulfide solid electrolyte of Embodiment 2 at 25°C is preferably 2.0×10 -3 S / cm or more, more preferably 2.5×10 -3 S / cm or more, even more preferably 3.0×10 -3 S / cm or more, and particularly preferably 4.0×10 -3 S / cm or more. With the above configuration, the high-rate discharge performance of the all-solid-state battery including the sulfide solid electrolyte can be improved.

[0136] <All-solid-state battery> The all-solid-state battery includes a negative electrode layer, a solid electrolyte layer, and a positive electrode layer. FIG. 2 is a schematic cross-sectional view showing an all-solid-state battery according to an embodiment of the present invention. The all-solid-state battery 10, which is a secondary battery, has a negative electrode layer 1 and a positive electrode layer 2 disposed with a solid electrolyte layer 3 therebetween. The negative electrode layer 1 has a negative electrode base layer 4 and a negative electrode mixture layer 5, and the negative electrode base layer 4 is the outermost layer of the negative electrode layer 1. The positive electrode layer 2 has a positive electrode base layer 7 and a positive electrode mixture layer 6, and the positive electrode base layer 7 is the outermost layer of the positive electrode layer 2. In the all-solid-state battery 10 shown in FIG. 2, a positive electrode mixture layer 6, a solid electrolyte layer 3, a negative electrode mixture layer 5, and a negative electrode base layer 4 are laminated in this order on the positive electrode base layer 7.

[0137] In the all-solid-state battery, the negative electrode layer 1, the solid electrolyte layer 3, the positive electrode layer 2, or a combination thereof contains the sulfide solid electrolyte. Since the negative electrode layer 1, the solid electrolyte layer 3, the positive electrode layer 2, or a combination thereof in the all-solid-state battery contains the sulfide solid electrolyte, the initial Coulomb efficiency is excellent. Since the sulfide solid electrolyte is excellent in reduction resistance, it is preferable that the negative electrode layer 1 and / or the solid electrolyte layer 3 contains the sulfide solid electrolyte. With the above configuration, the effects of the present invention become even more excellent.

[0138] The all-solid-state battery may also be configured to use another solid electrolyte in addition to the sulfide solid electrolyte. As the other solid electrolyte, a sulfide solid electrolyte other than the sulfide solid electrolyte may be used, or an oxide-based solid electrolyte, a dry polymer electrolyte, a gel polymer electrolyte, or a pseudo solid electrolyte may be used.

[0139] The sulfide solid electrolyte other than the sulfide solid electrolyte preferably has high Li ion conductivity. For example, Li 2 S-P 2 S 5 、Li 2 S-P 2 S 5 -LiI、Li 2 S-P 2 S 5 -LiCl、Li 2 S-P 2 S 5 -LiBr、Li 2 S-P 2 S 5 -Li 2 O、Li 2 S-P 2 S 5 -Li 2 O-LiI、Li 2 S-P 2 S 5 -Li 3 N、Li 2 S-SiS 2 、Li 2 S-SiS 2 -LiI、Li 2 S-SiS 2 -LiBr、Li 2 S-SiS2 - LiCl, Li 2 S - SiS 2 - B 2 S 3 - LiI, Li 2 S - SiS 2 - P 2 S 5 - LiI, Li 2 S - B 2 S 3 , Li 2 S - P 2 S 5 - Z m S 2n (However, m, n are positive numbers, and Z is any one of Ge, Zn, Ga.), Li 2 S - GeS 2 , Li 2 S - SiS 2 - Li 3 PO 4 , Li 2 S - SiS 2 - Li δ XO ε (However, δ, ε are positive numbers, and X is any one of P, Si, Ge, B, Al, Ga, In.), Li 10 GeP 2 S 12 etc. can be mentioned. Among these, from the viewpoint of good lithium ion conductivity, Li 2 S - P 2 S 5 and, Li 10 GeP 2 S 12 etc. are preferable. Li 2 S - P 2 S 5 As, xLi 2 S·(100 - x)P 2 S 5 (70 ≤ x ≤ 80) is preferable.

[0140] [Negative electrode layer] The negative electrode layer 1 includes a negative electrode substrate layer 4 and a negative electrode mixture layer 5 laminated on the surface of the negative electrode substrate layer 4. The negative electrode layer 1 may have an intermediate layer (not shown) between the negative electrode substrate layer 4 and the negative electrode mixture layer 5.

[0141] (Negative electrode substrate layer) The negative electrode base material layer 4 is a layer having conductivity. The material of the negative electrode base material layer 4 is not limited as long as it is a conductor. For example, one or more metals selected from the group consisting of copper, aluminum, titanium, nickel, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, gold, silver, iron, platinum, chromium, tin, indium, and alloys containing one or more of these, and stainless alloys can be mentioned.

[0142] As the lower limit of the average thickness of the negative electrode base material layer 4, 3 μm is preferable, 5 μm is more preferable, and 8 μm is even more preferable. As the upper limit of the average thickness of the negative electrode base material layer 4, 200 μm is preferable, 100 μm is more preferable, and 50 μm is even more preferable. By setting the average thickness of the negative electrode base material layer 4 to be equal to or greater than the above lower limit, the strength of the negative electrode base material layer 4 can be made sufficiently high, so that the negative electrode layer 1 can be formed well. By setting the average thickness of the negative electrode base material layer 4 to be equal to or less than the above upper limit, sufficient volume can be ensured for other components.

[0143] (Negative electrode binder layer) The negative electrode binder layer 5 can be formed from a so-called negative electrode binder containing a negative electrode active material. The negative electrode binder may contain a negative electrode mixture or a negative electrode composite containing the negative electrode active material and the sulfide solid electrolyte. The negative electrode binder may contain optional components such as solid electrolytes other than the sulfide solid electrolyte, conductive agents, binders, and fillers, as necessary.

[0144] 〈Negative electrode active material〉 As the negative electrode active material, a material that can usually occlude and release lithium ions is used. Specific examples of the negative electrode active material include metallic lithium; metals or semimetals such as Si and Sn; metal oxides or semimetal oxides such as SiO and SnO; polyphosphoric acid compounds; carbon materials such as graphite (graphite), non-graphitic carbon (easily graphitizable carbon or hardly graphitizable carbon); lithium metal composite oxides such as lithium titanate, etc.

[0145] As the lower limit of the content of the negative electrode active material in the negative electrode mixture, 10% by mass is preferable, and 15% by mass is more preferable. As the upper limit of the content of the negative electrode active material, 60% by mass is preferable, 70% by mass is more preferable, 80% by mass is further preferable, 90% by mass is particularly preferable, and 95% by mass may be used. By setting the content of the negative electrode active material within the above range, the capacitance of the all-solid-state battery can be increased.

[0146] 〈Negative electrode mixture or negative electrode composite〉 The above-mentioned negative electrode mixture is a mixture produced by mixing the negative electrode active material and the sulfide solid electrolyte by mechanical milling or the like. For example, a mixture of a negative electrode active material and the sulfide solid electrolyte can be obtained by mixing particulate negative electrode active material and particulate sulfide solid electrolyte. Examples of the above-mentioned negative electrode composite include a composite having a chemical or physical bond between the negative electrode active material and the sulfide solid electrolyte, and a composite in which the negative electrode active material and the sulfide solid electrolyte are mechanically combined. The above composite is one in which a negative electrode active material and the sulfide solid electrolyte are present in one particle. For example, those in which the negative electrode active material and the sulfide solid electrolyte form an aggregated state, those in which a sulfide solid electrolyte-containing film is formed on at least a part of the surface of the negative electrode active material, and the like can be mentioned. The above-mentioned negative electrode mixture or negative electrode composite may contain a solid electrolyte other than the sulfide solid electrolyte. The negative electrode active material and the sulfide solid electrolyte contained in the negative electrode mixture can improve the ionic conductivity by constituting the negative electrode mixture or negative electrode composite.

[0147] When the negative electrode mixture contains a solid electrolyte, the lower limit of the content of the solid electrolyte in the negative electrode mixture may be 5% by mass, and 10% by mass is preferable. The upper limit of the content of the solid electrolyte in the negative electrode mixture is preferably 90% by mass, more preferably 85% by mass, further preferably 80% by mass, and particularly preferably 75% by mass. By setting the content of the solid electrolyte within the above range, the capacitance of the all-solid-state battery can be increased. The negative electrode mixture may contain the sulfide solid electrolyte or a solid electrolyte other than the sulfide solid electrolyte.

[0148] <Any other optional components> The conductive agent is not particularly limited. Examples of such conductive agents include carbon blacks such as natural or artificial graphite, furnace black, acetylene black, ketjen black, metals, and conductive ceramics. The shape of the conductive agent includes powder form, fibrous form, etc. The content of the conductive agent in the negative electrode mixture can be, for example, 0.5% by mass or more and 30% by mass or less. The negative electrode mixture may not contain a conductive agent.

[0149] The binder is not particularly limited. Examples include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyimide, polyacrylic acid; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber; polysaccharide polymers, etc.

[0150] The filler is not particularly limited. The main components of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, carbon, etc.

[0151] The lower limit of the average thickness of the negative electrode mixture layer 5 is preferably 30 μm, more preferably 60 μm. The upper limit of the average thickness of the negative electrode mixture layer 5 is preferably 1000 μm, more preferably 500 μm, and even more preferably 200 μm. By setting the average thickness of the negative electrode mixture layer 5 to be not less than the above lower limit, a all-solid-state battery having a high energy density can be obtained. By setting the average thickness of the negative electrode mixture layer 5 to be not more than the above upper limit, a all-solid-state battery equipped with a negative electrode having excellent rate characteristics and a high active material utilization rate can be obtained.

[0152] (Intermediate layer) The above intermediate layer is a coating layer on the surface of the negative electrode substrate layer 4, and by containing conductive particles such as carbon particles, the contact resistance between the negative electrode substrate layer 4 and the negative electrode active material layer 5 is reduced. The configuration of the intermediate layer is not particularly limited, and for example, it can be formed by a composition containing a resin binder and conductive particles.

[0153] [Positive electrode layer] The positive electrode layer 2 includes a positive electrode substrate layer 7 and a positive electrode active material layer 6 laminated on the surface of the positive electrode substrate layer 7. Similar to the negative electrode layer 1, the positive electrode layer 2 may have an intermediate layer between the positive electrode substrate layer 7 and the positive electrode active material layer 6. This intermediate layer can have the same configuration as the intermediate layer of the negative electrode layer 1.

[0154] (Positive electrode substrate layer) The positive electrode substrate layer 7 can have the same configuration as the negative electrode substrate layer 4. The material of the positive electrode substrate layer 7 is not limited as long as it is a conductor. For example, one or more metals selected from the group consisting of copper, aluminum, titanium, nickel, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, gold, silver, iron, platinum, chromium, tin, indium, and alloys containing one or more of these, and stainless steel alloys can be mentioned.

[0155] The lower limit of the average thickness of the positive electrode substrate layer 7 is preferably 3 μm, more preferably 5 μm. The upper limit of the average thickness of the positive electrode substrate layer 7 is preferably 200 μm, more preferably 100 μm, and even more preferably 50 μm. By setting the average thickness of the positive electrode substrate layer 7 to be not less than the above lower limit, the strength of the positive electrode substrate layer 7 can be made sufficiently high, so that the positive electrode layer 2 can be formed well. By setting the average thickness of the positive electrode substrate layer 7 to be not more than the above upper limit, the volume of other components can be sufficiently ensured.

[0156] (Positive electrode active material layer) The positive electrode active material layer 6 can be formed from a so-called positive electrode active material containing a positive electrode active material. The positive electrode active material may contain a positive electrode mixture or a positive electrode composite containing a positive electrode active material and a solid electrolyte. As the solid electrolyte, the sulfide solid electrolyte may be used. The positive electrode active material forming the positive electrode active material layer 6, like the negative electrode active material, may contain optional components such as a solid electrolyte, a conductive agent, a binder, and a filler as necessary. Note that the positive electrode active material layer may be in a form that does not contain a solid electrolyte.

[0157] 〈Positive Electrode Active Material〉 As the positive electrode active material contained in the positive electrode active material layer 6, known ones commonly used in all-solid-state batteries can be used. Examples of the positive electrode active material include Li x M e O y (where Me represents at least one transition metal) composite oxides (layered α-NaFeO 2 type crystal structure of Li x CoO 2 , Li x NiO 2 , Li x MnO 3 , Li x Ni α Co (1-α) O 2 , Li x Ni α Mn β Co (1-α-β) O 2 etc., spinel-type crystal structure of Li x Mn 2 O 4 , Li x Ni α Mn (2-α) O 4 etc.), Li w Me x (AO y ) z (where Me represents at least one transition metal and A represents, for example, P, Si, B, V, etc.) polyanion compounds (LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 , Li 3 V 2(PO 4 ) 3 、 Li 2 MnSiO 4 、 Li 2 CoPO 4 F, etc.) may be mentioned. Elements or polyanions in these compounds may be partially substituted with other elements or anion species. In the positive electrode active material layer, one of these compounds may be used alone, or two or more of them may be used in combination.

[0158] As the positive electrode active material, lithium alloys such as Li-Al, Li-In, Li-Sn, Li-Pb, Li-Bi, Li-Ga, Li-Sr, Li-Si, Li-Zn, Li-Cd, Li-Ca, Li-Ba, etc. and MnO other than the compounds represented by the above general formula 2 , FeO 2 , TiO 2 , V 2 O 5 , V 6 O 13 , TiS 2 etc., materials with a redox potential nobler than that of the negative electrode material can be used.

[0159] As the lower limit of the content of the positive electrode active material in the positive electrode binder, 10% by mass is preferable, and 15% by mass is more preferable. As the upper limit of the content of the positive electrode active material, 60% by mass is preferable, 70% by mass is more preferable, 80% by mass is still more preferable, 90% by mass is particularly preferable, and 95% by mass may be used. By setting the content of the positive electrode active material within the above range, the capacitance of the all-solid-state battery can be increased.

[0160] 〈Positive Electrode Mixture or Positive Electrode Composite〉 The above positive electrode mixture is a mixture produced by mechanically milling the positive electrode active material, solid electrolyte, etc. in the same manner as in the case of the negative electrode. For example, a mixture of a positive electrode active material and a solid electrolyte, etc. can be obtained by mixing particulate positive electrode active material and particulate solid electrolyte, etc. Similar to the case of the negative electrode, the positive electrode composite may be a composite having a chemical or physical bond between a positive electrode active material and a solid electrolyte, a composite in which a positive electrode active material and a solid electrolyte are mechanically combined, or the like. The composite is one in which a positive electrode active material and a solid electrolyte are present within one particle. Examples thereof include those in which a positive electrode active material and a solid electrolyte form an aggregated state, and those in which a solid electrolyte-containing film is formed on at least a part of the surface of the positive electrode active material. The positive electrode mixture or positive electrode composite may contain a solid electrolyte other than the sulfide solid electrolyte. By configuring the positive electrode active material and the solid electrolyte contained in the positive electrode binder to form the positive electrode mixture or positive electrode composite, the ionic conductivity can be improved.

[0161] When the positive electrode binder contains a solid electrolyte, the lower limit of the content of the solid electrolyte may be 5% by mass, and 10% by mass is preferable. The upper limit of the content of the solid electrolyte in the positive electrode binder is preferably 90% by mass, more preferably 85% by mass, still more preferably 80% by mass, and particularly preferably 75% by mass. By setting the content of the solid electrolyte within the above range, the electric capacity of the all-solid-state battery can be increased.

[0162] The lower limit of the average thickness of the positive electrode binder layer 6 is preferably 30 μm, and more preferably 60 μm. The upper limit of the average thickness of the positive electrode binder layer 6 is preferably 1000 μm, more preferably 500 μm, still more preferably 200 μm. By setting the average thickness of the positive electrode binder layer 6 to be not less than the above lower limit, an all-solid-state battery having a high energy density can be obtained. By setting the average thickness of the positive electrode binder layer 6 to be not more than the above upper limit, an all-solid-state battery having excellent high-rate discharge performance and a negative electrode with a high active material utilization rate can be obtained.

[0163] [Solid electrolyte layer] The solid electrolyte layer 3 contains an electrolyte for the solid electrolyte layer. Examples of the electrolyte for the solid electrolyte layer include, in addition to the above-mentioned sulfide solid electrolyte, for example, oxide-based solid electrolytes, other sulfide solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, pseudo solid electrolytes, and the like. Among these, sulfide solid electrolytes are preferred from the viewpoints of good ionic conductivity and easy interface formation, and the sulfide solid electrolyte is more preferred. By the solid electrolyte layer 3 containing the sulfide solid electrolyte, the solid electrolyte layer can exhibit high ionic conductivity, so that the internal resistance of the all-solid-state battery can be reduced.

[0164] The content of the sulfide solid electrolyte with respect to the total amount of the solid electrolyte contained in the all-solid-state battery is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, still more preferably 80% by mass or more and 100% by mass or less, and even more preferably 90% by mass or more and 100% by mass or less. In particular, it is preferable that the solid electrolyte contained in the all-solid-state battery is composed only of the sulfide solid electrolyte. In particular, since the sulfide solid electrolyte containing element X has high thermal stability, by configuring the all-solid-state battery as described above, the advantage of the all-solid-state battery that the upper limit of the operating temperature of the battery can be increased can be fully enjoyed.

[0165] The electrolyte for the solid electrolyte layer may have a crystal structure or may be amorphous without a crystal structure. Oxides such as Li 3 PO 4 and the like, halogens, halogen compounds, etc. may be added.

[0166] The average thickness of the solid electrolyte layer 3 is preferably 1 μm or more and 50 μm or less, and more preferably 3 μm or more and 20 μm or less. By setting the average thickness of the solid electrolyte layer 3 within the above range, it is possible to increase the energy density of the all-solid-state battery while surely insulating the positive electrode and the negative electrode.

[0167] <Manufacturing method of all-solid-state battery> The manufacturing method of the all-solid-state battery mainly includes, for example, a sulfide solid electrolyte manufacturing step, a negative electrode mixture manufacturing step, an electrolyte for the solid electrolyte layer manufacturing step, a positive electrode mixture manufacturing step, and a lamination step of laminating a negative electrode layer, a solid electrolyte layer, and a positive electrode layer.

[0168] (Sulfide solid electrolyte manufacturing step) In this step, for example, a sulfide solid electrolyte is manufactured by the manufacturing method of the sulfide solid electrolyte.

[0169] (Negative electrode mixture manufacturing step) In this step, a negative electrode mixture for forming a negative electrode layer is manufactured. When the negative electrode mixture contains a mixture or composite of a negative electrode active material and the sulfide solid electrolyte, in this step, for example, the negative electrode active material and the sulfide solid electrolyte are mixed using a mechanical milling method or the like, and a mixture or composite of the negative electrode active material and the sulfide solid electrolyte is manufactured.

[0170] (Electrolyte for solid electrolyte layer manufacturing step) In this step, the electrolyte for the solid electrolyte layer for forming the solid electrolyte layer is manufactured. In this step, a predetermined material of the electrolyte for the solid electrolyte layer can be obtained by treating it by a mechanical milling method. The electrolyte for the solid electrolyte layer may be manufactured by heating a predetermined material of the electrolyte for the solid electrolyte layer to a temperature equal to or higher than the melting temperature and melt-mixing the two at a predetermined ratio and then quenching by the melt quenching method. Other synthesis methods of the electrolyte for the solid electrolyte layer include, for example, a solid phase method of firing under reduced pressure encapsulation, a liquid phase method such as dissolution precipitation, a vapor phase method (PLD), and firing in an argon atmosphere after mechanical milling. When the electrolyte for the solid electrolyte layer is the sulfide solid electrolyte, in the manufacturing step of the electrolyte for the solid electrolyte layer, the above-mentioned sulfide solid electrolyte manufacturing step is performed.

[0171] (Positive electrode mixture manufacturing step) In this process, a positive electrode mixture for forming a positive electrode layer is produced. The method for producing the positive electrode mixture is not particularly limited and can be appropriately selected according to the purpose. For example, compression molding of a positive electrode active material, mechanical milling treatment of a predetermined material of the positive electrode mixture, sputtering using a target material of the positive electrode active material, etc. can be mentioned. When the positive electrode mixture contains a mixture or composite containing a positive electrode active material and the sulfide solid electrolyte, in this process, for example, the positive electrode active material and the sulfide solid electrolyte are mixed using a mechanical milling method or the like to produce a mixture or composite of the positive electrode active material and the sulfide solid electrolyte.

[0172] (Lamination process) In this process, a negative electrode layer having a negative electrode base material layer and a negative electrode mixture layer, a solid electrolyte layer, and a positive electrode layer having a positive electrode base material layer and a positive electrode mixture layer are laminated. In this process, the negative electrode layer, the solid electrolyte layer, and the positive electrode layer may be formed sequentially, or vice versa, and the order of formation of each layer is not particularly limited. The negative electrode layer is formed by pressure molding a negative electrode base material and a negative electrode mixture, the solid electrolyte layer is formed by pressure molding an electrolyte for the solid electrolyte layer, and the positive electrode layer is formed by pressure molding a positive electrode base material and a positive electrode mixture.

[0173] The negative electrode layer, the solid electrolyte layer, and the positive electrode layer may be laminated by pressure molding the negative electrode base material, the negative electrode mixture, the electrolyte for the solid electrolyte layer, the positive electrode base material, and the positive electrode mixture at once. The positive electrode layer, the negative electrode layer, or these layers may be pre-formed and pressure molded with the solid electrolyte layer for lamination.

[0174] <Other embodiments> The present invention is not limited to the above embodiments, and can be implemented in various modified and improved forms in addition to the above aspects.

[0175] In the above embodiment, as the raw material compound containing N, element A, and element M, a raw material compound containing only N, Li, and element M was described as an example, but the present invention is not limited thereto. For example, the raw material compound containing N, element A, and element M may further contain other elements as long as it does not hinder the solution of the problems of the present invention.

[0176] The configuration of the all-solid-state battery according to the present invention is not particularly limited, and for example, it may include other layers other than the negative electrode layer, the positive electrode layer, and the solid electrolyte layer, such as an intermediate layer or an adhesive layer.

Example

[0177] Hereinafter, the present invention will be described more specifically by demonstration experiments, but the present invention is not limited to the following examples.

[0178] First, the effect of suppressing the discharge of N to the outside of the system in the manufacturing method of the sulfide solid electrolyte according to an embodiment of the present invention is shown from Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3. [Example 1] By the following treatment, 80(0.70Li 2 S·0.30P 2 S 5 )·20Li 3 / 2 Al 1 / 2 N was synthesized. (Preparation step) Li 3 N and AlN were weighed so that the molar ratio was 1.2:1, mixed in a mortar, and then pelletized. Next, heat treatment was performed at 750 ° C for 1 hour to produce Li 3 / 2 Al 1 / 2 N. The produced Li 3 / 2 Al 1 / 2 N was confirmed to have a main phase of Li 3 / 2 Al 1 / 2 N by XRD measurement. Next, in a glove box with an argon atmosphere having a dew point of -50 ° C or lower, Li 2 S(99.98%, Aldrich), P 2 S 5 (99%, Aldrich) and Li 3 / 2 Al1 / 2 After weighing N so that the molar ratio becomes 56:24:20, it was mixed in a mortar to prepare a composition containing Li, P, S, N, and Al. (Reaction step) The above composition was put into a sealed 80 mL zirconia pot containing 160 g of zirconia balls with a diameter of 4 mm. Milling treatment was performed for 45 hours at a revolution speed of 510 rpm using a planetary ball mill (manufactured by FRITSCH, model number Premium line P-7) to obtain an intermediate. (Heat treatment step) The above intermediate was heat-treated for 2 hours to obtain a sulfide solid electrolyte. This heat treatment was performed at a temperature equal to or higher than the crystallization temperature and not exceeding 100 °C above the crystallization temperature. The crystallization temperature was determined by measuring DSC. The DSC measurement was performed under the following conditions. That is, using a DSC apparatus (manufactured by Rigaku, Thermo Plus DSC8230), a sealed pan made of SUS was used, and the temperature was raised from room temperature to 400 °C at 10 °C / min. The composition prepared by the above synthesis procedure was designated as sample a, the intermediate as sample b, and the sulfide solid electrolyte as sample c.

[0179] [Example 2] Except that the preparation step was changed as follows, the same procedure as in Example 1 was followed to synthesize 80(0.70Li 2 S·0.30P 2 S 5 )·20Li 3 / 2 B 1 / 2 N. (Preparation step) Li 3 N and BN were weighed so that the molar ratio became 1.1:1, mixed in a mortar, and then pelletized. Next, they were heat-treated at 800 °C for 10 minutes to prepare Li 3 / 2 B 1 / 2 N. The prepared Li 3 / 2 B 1 / 2 N was confirmed by XRD measurement to have a main phase of Li 3 / 2 B 1 / 2 N. Next, in a glove box with an argon atmosphere having a dew point of -50 °C or lower, Li 2 S (99.98%, Aldrich), P2 S 5 (99%, Aldrich) and Li 3 / 2 B 1 / 2 Li, P, S, N, and B were weighed so that the molar ratio became 56:24:20, and then mixed in a mortar to prepare a composition containing Li, P, S, N, and B.

[0180] [Comparative Example 1] 56.8Li 2 S·27.0P 2 S 5 ·16.2Li 3 N was synthesized. (Preparation Step) In a glove box with an argon atmosphere having a dew point of -50°C or lower, Li 2 S (99.98%, Aldrich), P 2 S 5 (99%, Aldrich), and Li 3 N were weighed so that the molar ratio became 56.8:27.0:16.2, and then mixed in a mortar to prepare a composition containing Li, P, S, and N.

[0181] [Comparative Example 2] 80(0.70Li 2 S·0.30P 2 S 5 )·20Li 3 / 2 Al 1 / 2 N was synthesized. (Preparation Step) In a glove box with an argon atmosphere having a dew point of -50°C or lower, Li 2 S (99.98%, Aldrich), P 2 S 5 (99%, Aldrich), Li 3 N, and AlN were weighed so that the molar ratio became 56:24:10:10, and then mixed in a mortar to prepare a composition containing Li, P, S, N, and Al.

[0182] [Comparative Example 3] The preparation process was changed as follows, and the rest was the same as in Example 1. 80(0.70Li 2 S·0.30P 2 S 5 )·20Li 7 / 4 V 1 / 4 N was synthesized. (Preparation process) Li 3 N and VN were weighed so that the molar ratio was 3:1, mixed in a mortar, and then pelletized. Next, heat treatment was performed at 750 °C for 10 hours to prepare Li 7 / 4 V 1 / 4 N. The prepared Li 7 / 4 V 1 / 4 N was confirmed to have the main phase of Li 7 / 4 V 1 / 4 N by XRD measurement. Next, in a glove box with an argon atmosphere having a dew point of -50 °C or lower, Li 2 S (99.98%, Aldrich), P 2 S 5 (99%, Aldrich) and Li 7 / 4 V 1 / 4 N were weighed so that the molar ratio was 56:24:20, and then mixed in a mortar to prepare a composition containing Li, P, S, N, and V.

[0183] [Evaluation] (1) XRD X-ray diffraction measurement was performed by the following method. Using an airtight sample holder for X-ray diffraction measurement, the sulfide solid electrolyte powders of the examples and comparative examples were filled under an argon atmosphere with a dew point of -50 °C or lower. Powder X-ray diffraction measurement was performed using an X-ray diffractometer (Rigaku "miniFlex II"). The radiation source was CuKα radiation, the tube voltage was 30 kV, the tube current was 15 mA, and the diffracted X-rays were detected by a high-speed one-dimensional detector (model number: D / teX Ultra2) through a Kβ filter with a thickness of 30 μm. The sampling width was 0.01°, the scan speed was 5° / min, the divergence slit width was 0.625°, the receiving slit width was 13 mm (OPEN), and the scattering slit width was 8 mm.

[0184] (2) Ionic conductivity (σ) Ionic conductivity (σ25 ) The ionic conductivity at 25°C was determined by measuring the alternating current impedance using the method described above with the "VMP-300" manufactured by (Bio-Logic). For some of the examples and comparative examples, the ionic conductivity at each temperature of -30°C, -20°C, -10°C, 0°C, and 50°C was also measured, and the activation energy (E a ) was calculated using the Arrhenius equation.

[0185] Table 4 shows the XRD patterns and the ionic conductivity (σ 25 ) at 25°C for Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3. As shown in Table 4, for the sulfide solid electrolytes of all the examples and comparative examples, peaks were observed in the XRD spectrum, and it was confirmed that they had a specific crystal structure A. The specific crystal structure A is a crystal structure having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, 29.8° ± 0.5°, and 30.9° ± 0.5° in X-ray diffraction measurement. Also, it was confirmed that the sulfide solid electrolytes of Example 1, Example 2, and Comparative Example 3 showed similar ionic conductivities. Therefore, it can be said that Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 have similar structures.

[0186]

Table 4

[0187] Regarding each sample of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, the contents of Li, B, Al, and P in the sample were determined using an ICP emission spectroscopic analyzer. Also, regarding each sample of Example 1, Example 2, and Comparative Examples 1 to 3, the content of N in the sample was determined using an oxygen / nitrogen / hydrogen analyzer. From this analysis result, the change rate of the content ratio of N in the sample was calculated. Table 5 shows the analysis results. In the table, "no change" indicates that the change rate of the content ratio of N with respect to sample a was ±5 mass% or less.

[0188]

Table 5

[0189] From Table 5, it can be seen that in Example 1 and Example 2, the N content ratios in Sample a, Sample b, and Sample c hardly change. That is, in Example 1 and Example 2, it can be seen that the N content rate hardly changes even after passing through each of the reaction step and the heat treatment step, and the discharge of N to the outside of the system is suppressed. On the other hand, in Comparative Example 1, Comparative Example 2, and Comparative Example 3, it can be seen that the N content ratios in Sample a, Sample b, and Sample c decrease in the order of Sample a, Sample b, and Sample c. That is, in Comparative Example 1, Comparative Example 2, and Comparative Example 3, it can be seen that the N content rate decreases with each passing through the reaction step and the heat treatment step, and N is discharged to the outside of the system. From the above, it has been demonstrated that for Al and B, which were selected by predicting the N discharge suppression effect using first-principles calculations, the effects are actually obtained. Furthermore, for V, for which it was predicted that the N discharge suppression effect could not be obtained using first-principles calculations, it has also been demonstrated that the effect is not actually obtained.

[0190] Next, Examples 3 to 20 and Comparative Examples 4 to 8 show the effect of improving the thermal stability of the sulfide solid electrolyte according to one embodiment of the present invention. [Example 3] By the following treatment, a sulfide solid electrolyte represented by the composition formula 85(0.80(0.70Li 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 Al 1 / 2 N)·10LiBr·5LiI was synthesized. Li 3 N and AlN were weighed so that the molar ratio was 1.2:1, mixed in a mortar, and then pelletized. Next, they were heat-treated at 750°C for 1 hour to prepare Li 3 / 2 Al 1 / 2 N. The prepared Li 3 / 2 Al 1 / 2 N was confirmed by XRD measurement that the main phase was Li 3 / 2 Al 1 / 2 N. Next, in a glove box under an argon atmosphere with a dew point of -50°C or lower, Li 2 S (99.98%, Aldrich), P 2 S 5 (99%, Aldrich), LiBr (99.999%, Aldrich), LiI (99.999%, Aldrich), and Li 3 / 2 Al 1 / 2 N were weighed so that the molar ratio was 47.6:20.4:10:5:17, and then mixed in a mortar. This mixed sample was put into a sealed 80 mL zirconia pot containing 160 g of zirconia balls with a diameter of 4 mm. Milling was performed for 45 hours at a revolution speed of 510 rpm using a planetary ball mill (manufactured by FRITSCH, model number Premium line P-7). Heat treatment was performed at 245°C for 2 hours to obtain the sulfide solid electrolyte of Example 3. This heat treatment temperature was set to be equal to or higher than the crystallization temperature and not more than 100°C higher than the crystallization temperature. The crystallization temperature was determined by taking out a part of the sample after the milling treatment and subjecting it to DSC measurement. The DSC measurement was performed under the following conditions. That is, using a DSC device (manufactured by Rigaku, Thermo Plus DSC8230), using a SUS sealed pan, the temperature was raised from room temperature to 400°C at 10°C / min.

[0191] [Comparative Example 4, Comparative Example 5] The composition of the sulfide solid electrolyte was changed to 85(0.75Li 2 S·0.25P 2 S 5 )·10LiBr·5LiI, 85(0.72Li 2 S·0.25P 2 S 5 ·0.020Li 3 N)·10LiBr·5LiI, and except that the heat treatment temperature was set to 225°C in all cases, the sulfide solid electrolytes of Comparative Example 4 and Comparative Example 5 were synthesized in the same manner as in Example 3.

[0192] [Examples 4 to 7, Comparative Example 6] The composition of the sulfide solid electrolyte was 80(0.80(0.70Li 2 S·0.30P 2 S 5)·0.20Li 3 / 2 Al 1 / 2 (0.70(0.67Li)(AlN)·12LiBr·8LiI、80 2 S·0.33P 2 S 5 )·0.30Li 3 / 2 Al 1 / 2 (0.80(0.70Li)(AlN)·12LiBr·8LiI、80 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 B 1 / 2 (0.80(0.70Li)(BN)·12LiBr·8LiI、80 2 S·0.30P 2 S 5 )·0.20Li 5 / 3 Si 1 / 3 (0.6975Li)(SiN)·12LiBr·8LiI、80 2 S·0.25P 2 S 5 ·0.035Li 3 It was changed to (Li)(N)·12LiBr·8LiI, and the sulfide solid electrolytes of Examples 4 to 7 and Comparative Example 6 were synthesized in the same manner as in Example 3, except that the heat treatment temperatures were 255°C, 275°C, 270°C, 270°C, and 250°C, respectively. In addition, for the sulfide solid electrolyte of Example 4, samples with heat treatment temperatures of 215°C, 230°C, 275°C, 290°C, and 310°C were also synthesized in addition to the sample with a heat treatment temperature of 255°C. For the sulfide solid electrolyte of Example 5, samples with heat treatment temperatures of 235°C, 290°C, 310°C, and 330°C were also synthesized in addition to the sample with a heat treatment temperature of 275°C. For the sulfide solid electrolyte of Example 6, samples with heat treatment temperatures of 230°C, 270°C, 290°C, 310°C, and 330°C were also synthesized in addition to the sample with a heat treatment temperature of 270°C. For the sulfide solid electrolyte of Example 7, samples with heat treatment temperatures of 230°C, 290°C, 310°C, and 330°C were also synthesized in addition to the sample with a heat treatment temperature of 270°C. Also, for the sulfide solid electrolyte of Comparative Example 6, samples with heat treatment temperatures of 210°C and 230°C were also synthesized in addition to the sample with a heat treatment temperature of 250°C. The sulfide solid electrolytes synthesized at each heat treatment temperature are designated as Example 4-1 to Example 4-6, Example 5-1 to Example 5-5, Example 6-1 to Example 6-5, Example 7-1 to Example 7-5, and Comparative Example 6-1 to Comparative Example 6-3 in ascending order of the heat treatment temperature.

[0193] [Example 8, Comparative Example 7] The composition of the sulfide solid electrolyte was changed to 75(0.80(0.70Li 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 Al 1 / 2 N)·15LiBr·10LiI, 75(0.72Li 2 S·0.25P 2 S 5 ·0.020Li 3 N)·15LiBr·10LiI, and the heat treatment temperatures were set to 215°C and 195°C, respectively. Otherwise, in the same manner as in Example 1, the sulfide solid electrolytes of Example 8 and Comparative Example 7 were synthesized.

[0194] [Example 9 to Example 11, Comparative Example 8] The composition of the sulfide solid electrolyte was changed to 90(0.80(0.70Li 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 Al 1 / 2 N)·10LiBr, 80(0.80(0.70Li 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 Al 1 / 2 N)·20LiBr, 70(0.80(0.70Li 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 Al 1 / 2 N)·30LiBr, 90(0.72Li 2 S·0.25P 2 S 5 ·0.020Li 3It was changed to 10LiBr, and the sulfide solid electrolytes of Example 9, Example 10, Example 11 and Comparative Example 8 were synthesized in the same manner as in Example 3 except that the heat treatment temperatures were 265 °C, 250 °C, 240 °C and 225 °C, respectively.

[0195] [Example 12, Example 13] The composition of the sulfide solid electrolyte was changed to 90(0.80(0.70Li 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 Al 1 / 2 N)·10LiI, 80(0.80(0.7Li 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 Al 1 / 2 It was changed to 20LiI, and the sulfide solid electrolytes of Example 12 and Example 13 were synthesized in the same manner as in Example 3 except that the heat treatment temperatures were 255 °C and 240 °C, respectively.

[0196] [Example 14 to Example 17] The composition of the sulfide solid electrolyte was changed to 80(0.97(0.745Li 2 S·0.255P 2 S 5 )·0.03Li 3 / 2 B 1 / 2 N)·12LiBr·8LiI, 80(0.95(0.74Li 2 S·0.26P 2 S 5 )·0.05Li 3 / 2 B 1 / 2 N)·12LiBr·8LiI, 80(0.90(0.73Li 2 S·0.27P 2 S 5 )·0.10Li 3 / 2 B 1 / 2 N)·12LiBr·8LiI, 80(0.85(0.715Li 2 S·0.285P 2 S 5 )·0.15Li 3 / 2 B 1 / 2It was changed to 12LiBr·8LiI, and the heat treatment temperature was set to 250 °C for each. Except for this, the sulfide solid electrolytes of Examples 14 to 17 were synthesized in the same manner as in Example 3.

[0197] [Examples 18 to 20] The composition of the sulfide solid electrolyte was changed to 75(0.80(0.70Li 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 B 1 / 2 N)·15LiBr·10LiI, 70(0.80(0.70Li 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 B 1 / 2 N)·17LiBr·13LiI, 65(0.80(0.70Li 2 S·0.30P 2 S 5 )·0.20Li 3 / 2 B 1 / 2 N)·20LiBr·15LiI, and except that the heat treatment temperatures were set to 230 °C, 195 °C, and 185 °C for each, the sulfide solid electrolytes of Examples 18 to 20 were synthesized in the same manner as in Example 3.

[0198] The sulfide solid electrolytes of Examples 3 to 20 are represented by the general formula (100 - z 1 - z 2 ){(1 - y)[xLi 2 S·(1 - x)P 2 S 5 ·yLi α M β N}·z 1 LiX 1 ·z 2 LiX 2 The sulfide solid electrolytes of Comparative Examples 5 to 7 are represented by the general formula (100 - z 1 - z 2 ){(x - 1.5y)Li 2 S·(1 - x)P 2 S 5 ·yLi 3 N}·z 1 LiX 1 ·z2 LiX 2 It is represented by

[0199] Tables 6 to 12 show the crystal structures identified from the XRD patterns of Examples 3 to 20 and Comparative Examples 4 to 8. Table 13 shows the crystal structures identified from the XRD patterns of Examples 4-1 to 4-6, Examples 5-1 to 5-5, Examples 6-1 to 6-5, Examples 7-1 to 7-5, and Comparative Examples 6-1 to 6-3. In the table, "HICP" represents a crystal phase having diffraction peaks at 2θ = 20.2° ± 0.5° and 23.6° ± 0.5° in X-ray diffraction measurement using CuKα radiation. "LICP" represents a crystal phase having diffraction peaks at 2θ = 21.0° ± 0.5° and 28.0° ± 0.5° in X-ray diffraction measurement using CuKα radiation. "Specific crystal structure C" represents a crystal phase having diffraction peaks at 2θ = 17.5° ± 0.5° and 24.9° ± 0.5° in X-ray diffraction measurement using CuKα radiation. "β-Li 3 PS 4 " represents a crystal phase having diffraction peaks at 2θ = 17.5° ± 0.5°, 18.1° ± 0.5°, 29.1° ± 0.5°, 29.9° ± 0.5°, and 31.2° ± 0.5° in X-ray diffraction measurement using CuKα radiation. "Unknown" represents peaks with unidentified crystal phases. In addition, FIGS. 3 shows the XRD patterns of Examples 4-1 to 4-6. FIG. 4 shows the XRD patterns of Comparative Examples 6-1 to 6-3.

[0200] Tables 6 to 12 show the ionic conductivity (σ 25 ) and the activation energy (E a ) at 25°C of Examples 3 to 20 and Comparative Examples 4 to 8. Table 13 shows the ionic conductivity (σ 25 ) and the activation energy (E a ) at 25°C of Examples 4-1 to 4-6, Examples 5-1 to 5-5, Examples 6-1 to 6-5, Examples 7-1 to 7-5, and Comparative Examples 6-1 to 6-3.

[0201] (3)DSC DSC measurement was performed by the following method. Using a DSC apparatus (manufactured by Rigaku Corporation, Thermo Plus DSC8230) and a sealed pan made of SUS, the temperature was raised from room temperature to 400 °C at a rate of 10 °C / min.

[0202] For the sulfide solid electrolytes of Examples 4 to 7, Examples 14 to 17, and Comparative Example 6, the intermediate after milling treatment and before heat treatment was subjected to DSC measurement. Figures 5 and 6 show the DSC curves of these samples.

[0203] [Table 6]

[0204] [Table 7]

[0205] [Table 8]

[0206] [Table 9]

[0207] [Table 10]

[0208] [Table 11]

[0209] [Table 12]

[0210] [Table 13]

[0211] From Table 6, it can be seen that for the sulfide solid electrolytes of Comparative Example 4 and Comparative Example 5, when the heat treatment temperature is 225°C, LICP is generated and the ionic conductivity at 25°C decreases. On the other hand, for the sulfide solid electrolyte of Example 3 containing Li, P, S, N, Br, I, and Al, although it was heat-treated at a higher temperature than the sulfide solid electrolytes of Comparative Example 4 and Comparative Example 5, it can be seen that LICP is not generated and it exhibits high ionic conductivity. That is, it can be understood that for the sulfide solid electrolyte of Example 3, the lower limit of the heat treatment temperature at which the ionic conductivity decreases compared to the sulfide solid electrolytes of Comparative Example 4 and Comparative Example 5 has increased.

[0212] From Table 7, it can be seen that for the sulfide solid electrolytes of Example 4 to Example 7, although they were heat-treated at a higher temperature than the sulfide solid electrolyte of Comparative Example 6, LICP is not generated and they exhibit high ionic conductivity. That is, it can be understood that for the sulfide solid electrolytes of Example 4 to Example 7, the lower limit of the heat treatment temperature at which the ionic conductivity decreases compared to the sulfide solid electrolyte of Comparative Example 6 has increased.

[0213] From Table 8, it can be seen that the sulfide solid electrolyte of Example 8 exhibits higher ionic conductivity although it was heat-treated at a higher temperature than the sulfide solid electrolyte of Comparative Example 7. That is, it can be understood that for the sulfide solid electrolyte of Example 8, the lower limit of the heat treatment temperature at which the ionic conductivity decreases compared to the sulfide solid electrolyte of Comparative Example 7 has increased. This is presumably because in the sulfide solid electrolyte of Example 8, the phase transition of HICP to LICP is suppressed.

[0214] From Table 9, it can be seen that the sulfide solid electrolytes of Example 9 to Example 11 all exhibit higher ionic conductivity although they were heat-treated at a higher temperature than the sulfide solid electrolyte of Comparative Example 8. Also, it can be seen that even when the sulfide solid electrolyte contains only Br as element X, the effect of the present invention of improving the thermal stability of the high Li-ion conductive phase of the sulfide solid electrolyte can be obtained. Further, comparing Example 9 and Comparative Example 8 with the same Br content, it can be seen that in Comparative Example 8, neither HICP nor LICP was generated, while in Example 9, HICP was generated. That is, when the sulfide solid electrolyte contains Li, P, S, N, element X, and element M, an effect was recognized that HICP can be generated with a lower content of element X compared to the case where element M is not included.

[0215] From Table 10, it can be seen that even when the sulfide solid electrolyte contains only I as element X, a sulfide solid electrolyte containing HICP can be obtained.

[0216] From Table 11, it can be seen that the sulfide solid electrolytes of Example 6 and Examples 15 to 17 show the presence of HICP and high ionic conductivity even though they were heat-treated at a temperature higher than that of the sulfide solid electrolyte of Comparative Example 6. That is, it can be understood that for the sulfide solid electrolytes of these examples, the lower limit of the heat treatment temperature at which the ionic conductivity decreases compared to the sulfide solid electrolyte of Comparative Example 6 has increased. Also, from FIG. 6, the sulfide solid electrolytes of Example 6 and Examples 14 to 17 have a crystallization peak presumed to be derived from HICP and β-Li 3 PS 4 It can be seen that the temperature difference from the crystallization peak derived from is larger. For example, in Comparative Example 6, the crystallization peak presumed to be derived from HICP and the crystallization peak derived from β-Li 3 PS 4 were observed at around 190°C and around 260°C, respectively, while in Example 14, they were observed at around 190°C and around 280°C, respectively. From this, it can be understood that for the sulfide solid electrolytes of the examples, the temperature range in which HICP stably exists expands, and the thermal stability of the high Li ion conduction phase improves. Note that the crystallization peak presumed to be derived from HICP in FIG. 6 indicates a peak observed in the range of approximately 180°C to 220°C. The β-Li in FIG. 6 3 PS 4The crystallization peaks of origin refer to the peaks observed at around 345°C, around 280°C, around 300°C, around 310°C, around 335°C, and around 260°C in Example 6, Examples 14 to 16, and Comparative Example 6, respectively. From the above, it can be seen that even when the content ratio N / P of N to P of the sulfide solid electrolyte is 0.060, 0.10, 0.21, 0.31, or 0.42, the effect of improving the thermal stability of the high Li-ion conduction phase can be obtained.

[0217] From Table 12, it can be seen that even when the content ratio X / P of element X to P of the sulfide solid electrolyte is 0.52, 0.70, 0.90, or 1.12, a sulfide solid electrolyte containing HICP can be obtained.

[0218] From Comparative Examples 6-1 to 6-3 shown in Table 13, it can be seen that for the sulfide solid electrolyte of Comparative Example 6, when the heat treatment temperature is 250°C or higher, HICP phase-transforms into LICP and β-Li 3 PS 4 It can also be seen that accordingly, the ionic conductivity at 25°C also significantly decreases. On the other hand, from Examples 4-1 to 4-6, it can be seen that in the sulfide solid electrolyte of Example 4, HICP exists even when the heat treatment temperature is increased to 290°C, and high ionic conductivity can be maintained. Also, from Examples 5-1 to 5-5, it can be seen that in the sulfide solid electrolyte of Example 5, HICP exists in a wide temperature range, and high ionic conductivity can be maintained. Furthermore, from Examples 6-1 to 6-5 and Examples 7-1 to 7-5, it can be seen that even when B and Si are contained instead of Al as element M, the effect of the present invention of maintaining high ionic conductivity in a wide temperature range can be obtained. That is, from Table 13, it can be understood that for the sulfide solid electrolytes of Examples 4 to 7, the temperature range of heat treatment in which the ionic conductivity does not decrease expands. In addition, from the comparison of Examples 6 and 7 with Examples 4 and 5 in Table 13, when the sulfide solid electrolyte contains either Si or B as the element M, the heat treatment temperature range in which the ion conductivity does not decrease is at least 80 ° C., and it can be seen that the thermal stability of the high Li ion conductive phase is particularly excellent. The peaks near 210 ° C. in the DSC curves of Examples 6 and 7 in FIG. 5 are crystallization peaks that are presumed to be derived from HICP. Therefore, it can be presumed that in Examples 6 and 7, the heat treatment temperature range in which the ion conductivity does not decrease is 100 ° C. The reason why such results were obtained is unclear, but it is considered that, for example, the strength of the bond energy between either Si or B and N was a value suitable for exerting the effects of the present invention.

[0219] As is clear from Tables 6 to 13, it was confirmed that the lower limit of the heat treatment temperature at which the ionic conductivity decreases is increased and the heat treatment temperature range at which the ionic conductivity does not decrease is expanded in the sulfide solid electrolytes of the examples. In other words, the sulfide solid electrolytes containing Li, P, S, N, element X, and element M were excellent in thermal stability of HICP. This is thought to be because the emission of N to the outside of the system during the production process was suppressed, and the thermal stability improving effect due to the sulfide solid electrolyte containing N was fully exerted.

[0220] The method for producing a sulfide solid electrolyte according to one embodiment of the present invention can suppress the emission of N to the outside of the system, and can also suppress the emission of Li 2 It has been suggested that the precipitation of S can be suppressed. 2 If the precipitation of S can be suppressed, the atmospheric stability of the sulfide solid electrolyte can be improved, which is preferable.

[0221] That is, from Examples 21 to 41, Comparative Example 9, and Comparative Example 10, the method for producing a sulfide solid electrolyte according to one embodiment of the present invention can be understood as follows: 2 This suggests that the precipitation of S can be suppressed.

[0222] [Example 21] By the following treatment, the composition formula (100-z)(yLi 2S·(1-y)P 2 S 5 )·zLi α M β Li in N α M β N is Li 3 / 2 Al 1 / 2 N, z = 1, y = 0.70, i.e., 99(0.7Li 2 S 0.3P 2 S 5 )·1Li 3 / 2 Al 1 / 2 N was synthesized. Li 3 N and AlN were weighed out to a molar ratio of 1.2:1, mixed in a mortar, and pelletized. Then, the mixture was heat-treated at 750°C for 1 hour to obtain Li 3 / 2 Al 1 / 2 N was produced. Next, Li was placed in an argon atmosphere glove box with a dew point of -50°C or less. 2 S (99.98%, Aldrich), P 2 S 5 (99%, Aldrich) and Li 3 / 2 Al 1 / 2 N was weighed out so that the molar ratio was 69.3:29.7:1.0, and then mixed in a mortar. This mixed sample was placed in a sealed 80 mL zirconia pot containing 160 g of zirconia balls with a diameter of 4 mm. A milling process was performed for 45 hours at a revolution speed of 510 rpm using a planetary ball mill (FRITSCH, model number Premium line P-7). Heat treatment was performed for 2 hours to obtain the sulfide solid electrolyte of Example 1. This heat treatment was performed at a temperature equal to or higher than the crystallization temperature and equal to or lower than the crystallization temperature plus 100°C. The crystallization temperature was determined by measuring DSC. The DSC measurement was performed under the following conditions. That is, a DSC device (Rigaku, Thermo Plus DSC8230) was used, and a SUS sealed pan was used, and the temperature was raised from room temperature to 400°C at a rate of 10°C / min.

[0223] [Examples 22 to 29] The composition formula of sulfide solid electrolyte is (100-z)(yLi 2 S·(1-y)P 2 S5 )·zLi α M β The sulfide solid electrolytes of Examples 22 to 29 were synthesized in the same manner as in Example 21, except that the value of z in N was changed to 5, 7, 10, 15, 20, 25, 30, 40.

[0224] [Examples 30 to 32] Composition formula of sulfide solid electrolyte (100 - z)(yLi 2 S·(1 - y)P 2 S 5 )·zLi α M β In N, the sulfide solid electrolytes of Examples 30 to 32 were synthesized in the same manner as in Example 21, except that y = 0.67 and the value of z was changed to 20, 25, 30, respectively.

[0225] [Examples 33 to 36] Li 3 LiN and BN were weighed so that the molar ratio was 1.1:1, mixed in a mortar, pelletized, and then heat - treated at 800 °C for 10 minutes to prepare Li 3 / 2 B 1 / 2 N. For the prepared Li 3 / 2 B 1 / 2 N, it was confirmed by XRD measurement that the main phase was Li 3 / 2 B 1 / 2 N. Composition formula of sulfide solid electrolyte (100 - z)(yLi 2 S·(1 - y)P 2 S 5 )·zLi α M β In N, Li α M β N was changed to Li 3 / 2 B 1 / 2 N, and the sulfide solid electrolytes of Examples 33 to 36 were synthesized in the same manner as in Example 21, except that the value of z was changed to 1, 10, 20, 30.

[0226] [Examples 37 to 41] Li 3 LiN and Si 3 N 4were weighed so that the molar ratio was 5.1:1, mixed in a mortar, pelletized, and then heat-treated at 800 °C for 10 minutes to prepare Li 5 / 3 Si 1 / 3 N. For the prepared Li 5 / 3 Si 1 / 3 N, it was confirmed by XRD measurement that the main phase was Li5 / 3Si 1 / 3 N. The composition formula of the sulfide solid electrolyte (100-z)(yLi 2 S·(1-y)P 2 S 5 )·zLi α M β N, except that Li α M β N was changed to Li 5 / 3 Si 1 / 3 N and the value of z was changed to 1.5, 15, 20, 30, 45, the sulfide solid electrolytes of Examples 37 to 41 were synthesized in the same manner as in Example 21.

[0227] [Comparative Example 9] The composition formula of the sulfide solid electrolyte (100-z)(yLi 2 S·(1-y)P 2 S 5 )·zLi α M β N, except that Li α M β N was changed to Li 3 N and the value of z was changed to 20, the sulfide solid electrolyte of Comparative Example 9 was synthesized in the same manner as in Example 21.

[0228] [Comparative Example 10] In the composition formula of the sulfide solid electrolyte (100-z)(yLi 2 S·(1-y)P 2 S 5 )·zLi α M β N, except that y = 0.68 and the value of z was changed to 16, the sulfide solid electrolyte of Comparative Example 10 was synthesized in the same manner as in Comparative Example 9.

[0229] [Evaluation] (1) XRD and ionic conductivity (σ) X-ray diffraction measurement was performed by the above method. Also, the ionic conductivity (σ 25 ) at 25 °C was determined by measuring the alternating current impedance using "VMP-300" manufactured by (Bio-Logic) by the above method.

[0230] (2) Raman spectroscopic analysis The Raman spectrum was measured by the following method. Using a laser Raman spectrophotometer ("LabRAM HR Revolution" manufactured by Horiba, Ltd.), under the conditions of an excitation laser wavelength of 532 nm (YAG laser) and a grating of 600 gr / mm, 100 cm -1 to 1800 cm -1 Raman spectroscopic measurement was performed in the wavenumber range.

[0231] Table 14 shows the ionic conductivity at 25 °C, the crystal structure identified from the XRD pattern, and the Raman spectrum of Examples 21 to 41, Comparative Example 9, and Comparative Example 10. In the table, "Specific crystal structure A" represents a crystal phase having diffraction peaks at 2θ = 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, 29.8° ± 0.5°, and 30.9° ± 0.5° in X-ray diffraction measurement using CuKα radiation. "Specific crystal structure B" represents a crystal phase having diffraction peaks at 2θ = 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, and 29.8° ± 0.5° in X-ray diffraction measurement using CuKα radiation. "-" indicates that the measurement was not performed.

[0232]

Table 14

[0233] In the sulfide solid electrolyte of Comparative Example 9, only the peaks derived from the crystal structure of Li 2 S were observed. From this result, it can be seen that Li 3 N is likely to precipitate Li 2 S. The reason for such a result is not clear, but Li 3It is considered that N reacts violently with other raw material compounds to precipitate Li 2 S.

[0234] In Examples 21 to 35 and Examples 37 to 40, no peak of Li 2 S was observed. Among them, from the comparison of the examples where z = 20 and y = 0.70 (Examples 26, 35, 39, and Comparative Example 9), it was confirmed that the precipitation of Li 2 S was suppressed in the sulfide solid electrolytes of the examples.

[0235] Also, the sulfide solid electrolytes of Examples 27 to 29, Example 32, Example 39, and Example 40 all had a higher Li / P ratio of Li to P than the sulfide solid electrolyte of Comparative Example 10, yet no peak of Li 2 S was observed. In particular, Example 29 had a Li / P ratio of 4.00, which is higher than those of Comparative Example 9 and Comparative Example 10, yet no peak of Li 2 S was observed. The sulfide solid electrolytes of Examples 26 and 35 had a Li / P ratio that was substantially the same as that of the sulfide solid electrolyte of Comparative Example 10, yet no peak of Li 2 S was observed. The sulfide solid electrolyte of Example 32 had a y value that was substantially the same as that of Comparative Example 10 and the same Li / P ratio, yet no peak of Li 2 S was observed. In the sulfide solid electrolyte, when the Li content is high, there is a tendency for Li 2 S to precipitate. However, since the above results were obtained, it was suggested that the method for producing the sulfide solid electrolyte of the examples suppresses the precipitation of Li 2 S.

[0236] That is, from the comparison of Examples 28, 29, 36, 40, and 41, it was suggested that when Al is included as the element M, the suppression of the precipitation of Li 2 S is remarkable.

[0237] From the above, in the method for manufacturing the sulfide solid electrolyte of the example, Li 2 deposition of S was suggested to be suppressed. The reason why the deposition of Li 2 S can be suppressed by the sulfide solid electrolyte containing the element M is considered as follows. When Li 3 N is used as the starting material for the sulfide-based solid electrolyte containing N, Li 3 N and P 2 S 5 react violently to release N 2 and Li 2 S precipitates. This is considered to be because the defect generation energy of N in Li 3 N is small. On the other hand, in the present invention, since the defect generation energy of N in Li α M β N is larger than the defect generation energy of N in Li 3 N, the reaction proceeds gently during the synthesis process of the sulfide-based solid electrolyte, and the release of N 2 and the precipitation of Li 2 S are suppressed.

[0238] Although the present invention has been described in detail above, the above embodiments are merely examples, and the invention disclosed herein includes various modifications and changes of the above specific examples.

Industrial Applicability

[0239] The all-solid-state battery including the sulfide solid electrolyte according to the present invention is suitably used, for example, as a lithium-ion all-solid-state battery for HEV.

Explanation of Signs

[0240] 1 Negative electrode layer 2 Positive electrode layer 3 Solid electrolyte layer 4 Negative electrode substrate layer 5 Negative electrode binder layer 6 Positive electrode binder layer 7 Positive electrode substrate layer 10 All-solid-state battery

Claims

[Claim 1] A sulfide solid electrolyte having a crystal structure containing P, S, N, element A, element X, and element M as constituent elements, where A represents at least one element selected from the group consisting of Li, Na, and K. X represents at least one element selected from the group consisting of Cl, Br, and I. M represents at least one element selected from the group consisting of Al, Ta, Si, Sc, Mg, Nb, B, Hf, C, P, Zr, and Ti.

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