Solid electrolyte, solid electrolyte layer, and solid electrolyte battery

Abstract

The present invention addresses the problem of providing a solid electrolyte having high sodium ion conductivity. A solid electrolyte containing a compound represented by formula (1) or formula (2). Formula (1) Na3a + 2b + 1cM1aM2bM3cChaX6-2alpha formula (2) Na3a + 2b + 1cM1aM2bM3cX6 wherein M1 is selected from the group consisting of Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and combinations thereof, M2 is selected from the group consisting of Zr, Hf, Ti, Si, Ge, Sn and combinations thereof, and M3 is selected from the group consisting of Nb, Ta, V, P, Sb, Bi and combinations thereof. Ch is selected from O, S, Se, Te and combinations thereof, and X is selected from F, Cl, Br, I and combinations thereof.

Description

Technical Field

[0001] This invention relates to solid electrolytes, solid electrolyte layers, and solid electrolyte batteries. Background Technology

[0002] Previously, lithium-ion rechargeable batteries were widely used in electronic and electrical devices such as mobile phones, laptops, digital cameras / video recorders, and portable music players. For batteries serving as power sources for these devices, in addition to miniaturization and thinning, there is a strong demand for improved safety. In currently widely used lithium-ion rechargeable batteries, lithium ions are charged and discharged by moving back and forth between the positive and negative electrodes via an electrolyte using an organic solvent. The use of flammable organic solvents in the electrolyte raises concerns about safety in case of leakage.

[0003] Therefore, all-solid-state lithium-ion secondary batteries are being developed, which have a solid electrolyte layer between the positive and negative electrodes. Known solid electrolytes include oxide-based solid electrolytes, sulfide-based solid electrolytes, and complex hydride-based solid electrolytes. In addition, in recent years, the use of halide solid electrolytes as solid electrolytes has also been studied (Patent Documents 1 and 2).

[0004] For example, Patent Document 1 discloses a solid electrolyte formed from a compound represented by the following formula [1]. A 2+a E 1-b+α G b X d …[1] In formula [1], A is an element selected from Li, K, and Na; E is at least one element selected from Zr, Hf, Ti, and Sn; G is at least one element selected from Mg, Ca, Sr, Cs, Ba, Y, Al, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Cu, Ag, Au, Pb, Bi, In, Sn, Sb, Nb, Ta, and W; and X is at least one element selected from F, Cl, Br, and I. Furthermore, in Patent Document 1, the battery performance was evaluated only when A is Li.

[0005] In addition, Patent Document 2 discloses a solid electrolyte characterized by having A 4-2x-y-z B x Sn 3-y M y O 8- z N z Crystals with the structure shown in (1≤4-2x-yz<4, A: Li, Na, B: Mg, Ca, Sr, Ba, M: V, Nb, Ta, N: F, Cl).

[0006] Sodium resources are more abundant than lithium, so there is no need to worry about localized concentrations. Therefore, in recent years, the practical application of all-solid-state sodium-ion batteries, which could replace all-solid-state lithium-ion batteries, has been anticipated. For the practical application of all-solid-state sodium-ion batteries, the development of solid electrolyte materials exhibiting high sodium-ion conductivity is required.

[0007] Similar to lithium-ion conducting solid electrolytes, oxide-based and sulfide-based solid electrolytes are known as sodium-ion conducting solid electrolytes. In recent years, halide solid electrolytes have also been studied for use in solid electrolytes. While oxide-based solid electrolytes exhibit excellent chemical and electrochemical stability, high-temperature heat treatment is required to achieve high ionic conductivity. On the other hand, sulfide-based solid electrolytes can exhibit high ionic conductivity simply through compression molding, but they lack chemical and electrochemical stability. Therefore, there is high expectation for halide-based solid electrolytes that can be compressed at room temperature and have higher electrochemical stability than sulfide-based solid electrolytes. For example, in Non-Patent Literature 1, Na... 3-x Y 1- x Zr x Cl6. Existing technical documents Patent documents

[0008] Patent Document 1: International Publication No. 2021 / 024783 Patent Document 2: International Publication No. 2014 / 141456 Non-patent literature

[0009] Non-patent literature 1: Nature Communications, volume 12, Article number: 1256 (2021) Summary of the Invention The problem that the invention aims to solve

[0010] As mentioned above, halide-based solid electrolytes for all-solid sodium-ion secondary batteries have been reported, but their sodium-ion conductivity is insufficient, requiring the development of halide-based solid electrolyte materials exhibiting higher sodium-ion conductivity.

[0011] Therefore, in order to solve such problems in the prior art, the inventors conducted research with the aim of providing a solid electrolyte with high sodium ion conductivity. Solution for solving the problem

[0012] The following are examples of specific embodiments of the present invention.

[0013] [1] A solid electrolyte containing a compound of formula (1) or formula (2). Formula (1) Na 3a+2b+1c M 1 a M 2 b M 3 c Ch α X 6-2α (In formula (1), M) 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and their combinations, M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn and combinations thereof, M 3 The elements are selected from Nb, Ta, V, P, Sb, Bi, and combinations thereof; Ch is selected from O, S, Se, Te, and combinations thereof; X is selected from F, Cl, Br, I, and combinations thereof; a+b+c=1, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0.1≤α≤2.9. Formula (2) Na 3a+2b+1c M 1 a M 2 b M 3 c X6 (In equation (2), M) 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and their combinations, M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn and combinations thereof, M 3 The elements are selected from Nb, Ta, V, P, Sb, Bi, and combinations thereof; X is selected from F, Cl, Br, I, and combinations thereof; a + b + c = 1, 0 ≤ a ≤ 0.9, 0 ≤ b ≤ 0.9, and 0.1 ≤ c ≤ 1. [2] According to the solid electrolyte described in [1], wherein, in formula (2), M 3 Selected from Ta and Nb. [3] According to the solid electrolyte described in [1], X is Cl in formula (1). [4] According to the solid electrolyte described in [1], X is Cl in formula (2). [5] The solid electrolyte according to any one of [1] to [4], wherein, when compressed at room temperature and subjected to a pressure of 170 MPa, the sodium ion conductivity at 25°C is 1 × 10⁻⁶. -6 S / cm or higher. [6] The solid electrolyte according to any one of [1] to [5], wherein the relative density is 80% or more when compressed at room temperature and subjected to a pressure of 170 MPa. [7] A solid electrolyte containing a compound of formula (1'): Alternatively, this embodiment may also involve a solid electrolyte containing a compound represented by formula (1'). Formula (1') Na 3a+2b+1c-γ+δ M 1 a M 2 b M 3 c Ch ε X ζ (In formula (1'), M) 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and their combinations, M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn and combinations thereof, M 3 The elements are selected from Nb, Ta, V, P, Sb, Bi, and combinations thereof; Ch is selected from O, S, Se, Te, and combinations thereof; X is selected from F, Cl, Br, I, and combinations thereof; and a+b+c=1, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤γ<≤1, 0≤δ≤2, 0≤ε≤2, and 4≤ζ≤8. [8] According to the solid electrolyte described in [7], X is Cl in formula (1'). [9] The solid electrolyte according to any one of [7] to [8], wherein, when compressed at room temperature and subjected to a pressure of 170 MPa, the sodium ion conductivity at 25°C is 1 × 10⁻⁶. -6 S / cm or higher.

[10] The solid electrolyte according to any one of [7] to [9], wherein the relative density is 80% or more when it is compressed at room temperature and subjected to a pressure of 170 MPa.

[11] A solid electrolyte layer containing any one of [1] to

[10] .

[12] A solid electrolyte battery having the solid electrolyte layer described in

[11] . Invention Effects

[0014] According to the present invention, a solid electrolyte having high sodium ion conductivity can be provided. Furthermore, according to the present invention, a solid electrolyte layer exhibiting high sodium ion conductivity and a solid electrolyte battery (all-solid-state sodium-ion secondary battery) can be provided. Attached Figure Description

[0015] Figure 1 The results are from the energy X-ray diffraction analysis of NaNbCl6. Figure 2 The results are from the energy X-ray diffraction analysis of NaTaCl6. Figure 3 The results are from the energy X-ray diffraction analysis of Na3YCl6. Figure 4 The results are from the energy X-ray diffraction analysis of NaNbOCl4. Figure 5 The results are from the energy X-ray diffraction analysis of NaTaOCl4. Figure 6 The results show the sodium ion conductivity measurements of the solid electrolytes obtained in the examples and comparative examples. Figure 7 The results are from energy X-ray diffraction analysis of heat-treated NaNbCl6. Figure 8 The results are from energy X-ray diffraction analysis of heat-treated NaTaCl6. Figure 9 The results are from energy X-ray diffraction analysis of heat-treated Na3YCl6. Figure 10 The results show the sodium ion conductivity measurements of the solid electrolytes obtained in the examples and comparative examples before and after heat treatment. Figure 11 The results are analyzed by energy X-ray diffraction of NaTaCl6 in different temperature zones. Figure 12 The results are from the diffuse reflectance measurement of NaNbCl6. Figure 13 The results are from the diffuse reflectance measurement of NaTaCl6. Figure 14 The results are for the diffuse reflectance measurement of NaTaOCl4. Figure 15 The results are for the diffuse reflectance measurement of NaNbOCl4. Figure 16 for Na 1+x Ta 1-x Zr x X-ray diffraction and impedance measurement results of Cl6 (x < 1.0). Figure 17 for Na 1+x Ta 1-x Zr x Results of sodium ion conductivity measurement of Cl6 (x < 1.0). Figure 18 To synthesize NaTa using Ta2O5 as an oxygen source 1 / 5(3+2x) O x X-ray diffraction and impedance measurement results for Cl4. Figure 19 To synthesize NaTa using Ta2O5 as an oxygen source 1 / 5(3+2x) O x Results of sodium ion conductivity measurement at Cl4. Figure 20 To synthesize Na using Ta2O5 as an oxygen source 1+x TaOCl 4+x The results of X-ray diffraction and impedance measurements at that time. Figure 21 To synthesize Na using Ta2O5 as an oxygen source 1+x TaOCl 4+x The results of sodium ion conductivity measurements at that time. Figure 22 The results of sodium ion conductivity measurements when synthesizing NaTaOCl4 using Ta2O5 as the oxygen source and with changes in process time. Figure 23 The results of sodium ion conductivity measurements when synthesizing NaTaOCl4 using Ta2O5 as the oxygen source and with changes in process time. Figure 24 To synthesize Na using Na₂O as an oxygen source 2x TaO x X-ray diffraction and impedance measurement results at Cl5. Figure 25 To use Na₂O as an oxygen source to synthesize Na 2x TaO x Results of sodium ion conductivity measurement at Cl5. Detailed Implementation

[0016] The present invention will now be described in detail. The description of the constituent elements described below is sometimes based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. Furthermore, the numerical range indicated by "~" in this specification refers to the range including the values ​​described before and after "~" as both the lower and upper limits.

[0017] (Solid electrolyte) This embodiment relates to a solid electrolyte containing a compound represented by formula (1) or formula (2): Formula (1) Na 3a+2b+1c M 1 a M 2 b M 3 c Ch α X 6-2α (In formula (1), M) 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and their combinations, M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn and combinations thereof, M 3 The elements are selected from Nb, Ta, V, P, Sb, Bi, and combinations thereof; Ch is selected from O, S, Se, Te, and combinations thereof; X is selected from F, Cl, Br, I, and combinations thereof; a+b+c=1, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0.1≤α≤2.9. Formula (2) Na 3a+2b+1c M 1 a M 2 b M 3 c X6 (In equation (2), M) 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and their combinations, M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn and combinations thereof, M 3 The elements are selected from Nb, Ta, V, P, Sb, Bi, and combinations thereof; X is selected from F, Cl, Br, I, and combinations thereof; a + b + c = 1, 0 ≤ a ≤ 0.9, 0 ≤ b ≤ 0.9, and 0.1 ≤ c ≤ 1.

[0018] In equation (1), M 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof. Among them, M 1 Preferably, it is selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, more preferably from Y, Sc, and In. Furthermore, M 1In the context of a combination of elements, for example, a substance obtained by dissolving two or more of the aforementioned elements in solid solution can be cited.

[0019] In equation (1), 0 ≤ a ≤ 1, preferably 0 ≤ a ≤ 0.9, more preferably 0 ≤ a ≤ 0.7, and even more preferably 0 ≤ a ≤ 0.5. Furthermore, in equation (1), it is also preferred that a = 0; when a is 0, it does not contain M. 1 .

[0020] In equation (1), M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn, and combinations thereof. Among them, M... 2 Preferably, it is selected from Zr, Hf, Ti, Si, Ge and Sn, and more preferably, it is selected from Zr and Hf.

[0021] In equation (1), 0 ≤ b ≤ 1, preferably 0 ≤ b ≤ 0.9, more preferably 0 ≤ b ≤ 0.7, and even more preferably 0 ≤ b ≤ 0.5. Furthermore, in equation (1), b = 0 is also preferred; when b is 0, it does not contain M. 2 .

[0022] In equation (1), M 3 Selected from Nb, Ta, V, P, Sb, Bi, and combinations thereof. Among them, M 3 Preferably, it is selected from Nb, Ta, V, P, Sb and Bi, more preferably from Nb, Ta and V, and particularly preferably Nb or Ta.

[0023] In equation (1), 0 ≤ c ≤ 1, preferably 0.1 ≤ c ≤ 1, and more preferably 0.2 ≤ c ≤ 1. Furthermore, in equation (1), a + b + c = 1.

[0024] In formula (1), Ch is selected from O, S, Se, Te and combinations thereof. Ch is preferably selected from one of O, S, Se and Te, more preferably O or S, and particularly preferably O. As shown in the compound of formula (1), by introducing an element selected from O, S, Se, Te and combinations thereof into Ch, the conductivity of the solid electrolyte can be improved more effectively.

[0025] In formula (1), X is selected from F, Cl, Br, I and combinations thereof. Preferably, X is selected from one of F, Cl, Br and I, more preferably Cl or Br, and particularly preferably Cl. Furthermore, when Ch is O in formula (1), the compound represented by formula (1) becomes an acyl halide compound. In this embodiment, an acyl halide compound that can exhibit high sodium ion conductivity is preferably used.

[0026] In equation (1), 0.1≤α≤2.9, preferably 0.2≤α≤2.0, and more preferably 0.5≤α≤1.5. Among them, α is particularly preferably 1.

[0027] Alternatively, this embodiment may also involve a solid electrolyte containing a compound represented by formula (1'). Formula (1') Na= 3a+2b+1c-γ+δ M 1 a M 2 b M 3 c Ch ε X ζ (In formula (1'), M) 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and their combinations, M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn and combinations thereof, M 3 The elements are selected from Nb, Ta, V, P, Sb, Bi, and combinations thereof; Ch is selected from O, S, Se, Te, and combinations thereof; X is selected from F, Cl, Br, I, and combinations thereof; and a+b+c=1, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤γ<≤1, 0≤δ≤2, 0≤ε≤2, and 4≤ζ≤8.

[0028] Furthermore, M in equation (1') 1 M 2 M 3 Examples and preferred ranges of Ch and X are similar to M in equation (1). 1 M 2 M 3 Ch and X are the same. The preferred numerical ranges of a, b, and c in formula (1') are the same as the preferred numerical ranges of a, b, and c in formula (1). In addition, γ is preferably 0.2 or less, more preferably 0. Furthermore, (-γ+δ) is preferably 0 or more and 2 or less. Furthermore, (3a+2b+1c-γ+δ) is preferably 1 or more and 3 or less. Furthermore, ε is preferably 0.3 or more and 1 or less. Furthermore, ε is preferably 4 or more and 7 or less, more preferably 4 or more and 6 or less.

[0029] The compound represented by formula (1) is preferably the compound represented by formula (11) below. Formula (11) NaM 3 Ch α X 6-2α (In equation (11), M) 3Selected from Nb, Ta, V, P, Sb, Bi and combinations thereof; Ch selected from O, S, Se, Te and combinations thereof; X selected from F, Cl, Br, I and combinations thereof; 0.1 ≤ α ≤ 2.9.

[0030] Furthermore, M in equation (11) 3 Examples and preferred ranges of Ch and X are similar to M in equation (1). 3 Ch and X are the same.

[0031] For the compound represented by formula (1), when performing diffuse reflectance measurements, the band gap value obtained from the absorption coefficient obtained by converting the data using the Kubelka-Munk function is preferably 2 eV or more, more preferably 2.5 eV or more, and even more preferably 3 eV or more. By setting the band gap value within the above range, the compound represented by formula (1) can exhibit high electronic insulation.

[0032] In equation (2), M 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof. Among them, M 1 Preferably, it is selected from Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, more preferably selected from Y, Sc and In.

[0033] In equation (2), 0 ≤ a ≤ 0.9, preferably 0 ≤ a ≤ 0.8, more preferably 0 ≤ a ≤ 0.7, and even more preferably 0 ≤ a ≤ 0.5. Furthermore, in equation (2), it is also preferred that a = 0; when a is 0, it does not contain M. 1 .

[0034] In equation (2), M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn, and combinations thereof. Among them, M... 2 Preferably, it is selected from Zr, Hf, Ti, Si, Ge, and Sn, more preferably from Zr and Hf. Furthermore, M 2 Si or Ge are also preferred.

[0035] In equation (2), 0 ≤ b ≤ 0.9, preferably 0 ≤ b ≤ 0.8, more preferably 0 ≤ b ≤ 0.7, and even more preferably 0 ≤ b ≤ 0.5. Furthermore, in equation (2), b = 0 is also preferred; when b is 0, it does not contain M. 2 .

[0036] In equation (2), M 3Selected from Nb, Ta, V, P, Sb, Bi, and combinations thereof. Among them, M 3 Preferably, it is selected from Nb, Ta, V, P, Sb and Bi, more preferably from Nb, Ta and V, and particularly preferably Nb or Ta.

[0037] In equation (2), 0 ≤ c ≤ 1, preferably 0.1 ≤ c ≤ 1, and more preferably 0.2 ≤ c ≤ 1. Furthermore, in equation (2), a + b + c = 1.

[0038] In formula (2), X is selected from F, Cl, Br, I and combinations thereof. Preferably, X is selected from one of F, Cl, Br and I, preferably Cl or Br, and particularly preferably Cl.

[0039] The compound represented by formula (2) is preferably the compound represented by formula (12) below. Equation (12) NaM 3 X6 (In equation (12), M) 3 (Selected from Nb, Ta, V, P, Sb, Bi, and combinations thereof; X is selected from F, Cl, Br, I, and combinations thereof.)

[0040] Furthermore, M in equation (12) 3 Examples and preferred ranges of X are related to M in equation (2). 3 And X is the same.

[0041] For the compound represented by formula (2), when performing diffuse reflectance measurements, the band gap value obtained from the absorption coefficient measured using the Kuberca-Monk function conversion is preferably 2 eV or more, more preferably 2.5 eV or more, and even more preferably 3 eV or more. By setting the band gap value within the above range, the compound represented by formula (2) can exhibit high electronic insulation.

[0042] The compounds shown in formulas (1) and (2) preferably have a metal element and a halogen element in 6-coordinate to form an octahedron, which serves as the basic structure of the anionic sublattice. More preferably, they are compounds with a glassy or defective double perovskite structure. The compounds shown in formulas (1) and (2) are novel solid electrolytes and are halide solid electrolytes that exhibit high sodium ion conductivity.

[0043] This embodiment, due to its above-described configuration, exhibits high sodium ion conductivity. For example, when a solid electrolyte is compressed at room temperature under a pressure of 170 MPa, the sodium ion conductivity at 25°C is preferably 1 × 10⁻⁶. -6 S / cm or higher, preferably 5×10 -6 S / cm or higher, more preferably 1×10-5 S / cm or higher, especially preferably 1×10 -4 S / cm or higher. Thus, the solid electrolyte of this embodiment has a high sodium ion conductivity, and therefore the solid electrolyte battery having a solid electrolyte layer formed from the above-described solid electrolyte material can exhibit excellent battery performance.

[0044] In this specification, the sodium ion conductivity of the solid electrolyte is measured by compressing the solid electrolyte under a pressure of 170 MPa at room temperature. The solid electrolyte of this embodiment can exhibit high sodium ion conductivity through compression molding at room temperature, thus reducing the energy input during use.

[0045] Furthermore, the solid electrolyte of this embodiment, due to its above-described configuration, can exhibit high conductivity over a wide temperature range. For example, the solid electrolyte of this embodiment can maintain high conductivity even in relatively high temperature ranges (e.g., around 50 to 600°C), and in such cases, the decrease in its sodium ion conductivity can be suppressed.

[0046] Furthermore, even when the solid electrolyte of this embodiment is heat-treated, the decrease in sodium ion conductivity can be suppressed. For example, even when the solid electrolyte of this embodiment is heat-treated at 200°C for 12 hours, its conductivity hardly decreases, and high sodium ion conductivity can be maintained. Therefore, when using the solid electrolyte of this embodiment, the interface state can be adjusted by heat treatment.

[0047] Furthermore, the solid electrolyte of this embodiment exhibits high formability. Even during compression molding, the solid electrolyte of this embodiment maintains a high relative density. Specifically, when the solid electrolyte is compressed at room temperature and subjected to a pressure of 170 MPa, the relative density is preferably 80% or higher. Moreover, the relative density is relative to the theoretical density, which uses a value theoretically derived based on the crystal structure.

[0048] In the solid electrolyte of this embodiment, for example, by containing Ta and Nb, the electrostatic repulsion between cations within the structure is enhanced, enabling the structure to exhibit octahedral structures sharing vertices. As a result, the free volume required for sodium ion conduction is expected to increase (Pauling's third rule). Therefore, it is believed that high sodium ion conductivity can be achieved. Furthermore, it is speculated that by containing substances such as M... 3Elements with higher valences will generate vacancies at sodium sites formed by utilizing structural cations. The formation of sodium vacancies leads to a reduction in the activation energy for sodium ion conduction. In the compound shown in formula (1), by introducing elements such as oxygen into the framework of the halogen-constructed structure, the shared vertex structure between the octahedrons, which are the basic building blocks of the structure, can be stabilized, and a structure that can ensure a larger free volume can be constructed, which is expected to help improve sodium ion conduction. In addition, it is believed that if different types of anions are introduced into the structure to deform the structure and disperse the energy of the Na sites, a percolation network of Na sites with similar site energies can be constructed with a smaller activation energy. Especially when the solid electrolyte contains Nb, Ta, etc., a significantly defective double perovskite structure is formed. Therefore, it is believed that even in phases that have been considered thermodynamically stable with reduced sodium ion conductivity, the sodium ion conduction pathway can be ensured. It is speculated that this can achieve a halogen-based solid electrolyte with no reduction in sodium ion conductivity after heat treatment.

[0049] The solid electrolyte of this embodiment may contain a single compound or two or more compounds with different compositions. Furthermore, the shape of the solid electrolyte is not particularly limited; for example, it may be in powder, granule, or block form. Additionally, the solid electrolyte may be in pellet or plate form.

[0050] (Methods for manufacturing solid electrolytes) In this embodiment, when the solid electrolyte is in powder form, it can be manufactured, for example, by mixing materials containing specified elements in a predetermined molar ratio. Although care must be taken to avoid the generation of HCl gas, hydrides can also be used as the materials.

[0051] Solid electrolytes can be manufactured, for example, by a mechanochemical method. To induce a mechanochemical reaction, a planetary ball mill apparatus is used, for example. A planetary ball mill apparatus is a device that introduces media (balls for promoting pulverization or mechanochemical reactions) and materials into a closed container, which then rotates and revolves, applying kinetic energy to the materials to induce pulverization or a mechanochemical reaction. In a planetary ball mill apparatus, for example, a closed container made of zirconia and media (balls) made of zirconia can be used. When reacting materials using a planetary ball mill apparatus, the reacting materials are less likely to reach high temperatures, thus there is a tendency for phase separation to occur. Furthermore, the solid electrolyte manufacturing method of this embodiment can also be applied to the manufacture of thermodynamically quasi-stable phases. Additionally, the energy propagation caused by the impact of the media contributes to the generation and persistence of defects; therefore, by using the solid electrolyte manufacturing method of this embodiment, it is also possible to manufacture solid electrolytes exhibiting a glassy phase structure containing numerous defects.

[0052] The mechanochemical synthesis of solid electrolytes is necessary for the vitrification of the material, and it can be seen that the longer the reaction time, the higher the conductivity tends to be. For example, when using a planetary ball mill to react the material, the reaction time is preferably 5 to 200 hours, more preferably 10 to 150 hours, and even more preferably 25 to 100 hours.

[0053] Solid electrolytes can be manufactured by firing. The firing temperature is, for example, 150~600°C, and the firing time is preferably 10 minutes to 48 hours. In addition, firing is preferably carried out in a vacuum or an inert atmosphere.

[0054] Solid electrolytes can be manufactured through liquid-phase synthesis. For example, solid electrolytes can also be synthesized in specified organic solvents or aqueous solvents.

[0055] (Solid electrolyte layer) This embodiment relates to a solid electrolyte layer containing the aforementioned solid electrolyte. Preferably, the solid electrolyte layer contains 50% by mass or more of the aforementioned solid electrolyte, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. Alternatively, the solid electrolyte layer may contain 100% by mass of the aforementioned solid electrolyte, or it may be a layer composed solely of the aforementioned solid electrolyte.

[0056] The preferred sodium ion conductivity of the solid electrolyte layer at 25°C is 1×10⁻⁶. -6 S / cm or higher, preferably 5×10 -6 S / cm or higher, more preferably 1×10 -5 S / cm or higher, especially preferably 1×10 -4 S / cm or higher.

[0057] The relative density of the solid electrolyte layer is preferably 80% or higher. Furthermore, the relative density is relative to the theoretical density, which uses a value theoretically determined based on the crystal structure.

[0058] The thickness of the solid electrolyte layer is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. Furthermore, the thickness of the solid electrolyte layer is preferably 1 mm or less. By setting the thickness of the solid electrolyte layer within the above range, the sodium ion conductivity can be improved more effectively.

[0059] As long as it does not violate the spirit of the present invention, the solid electrolyte layer may contain any component other than the solid electrolyte described above. Examples of such components include binder resins. In this case, the content of any component relative to the total mass of the solid electrolyte is preferably 10% by mass or less, more preferably 1% by mass or less.

[0060] (Method for manufacturing solid electrolyte layer) The solid electrolyte layer is obtained by compressing and shaping the resulting powdered solid electrolyte. In this case, for example, the shaped body can be formed by compression at room temperature, or it can be formed by hot pressing.

[0061] The solid electrolyte layer of this embodiment can be obtained by compression molding at room temperature. The molding pressure is preferably 50 to 500 MPa. Compression molding of the solid electrolyte layer of this embodiment at room temperature can suppress energy consumption during manufacturing and reduce environmental impact.

[0062] Alternatively, the solid electrolyte layer can also be a sintered body formed by sintering the obtained powdered solid electrolyte. When forming a solid electrolyte layer by sintering, the sintering temperature is preferably around 200~500℃, and the sintering time is preferably around 5~60 minutes.

[0063] (Solid electrolyte battery) This embodiment relates to a solid electrolyte battery having the aforementioned solid electrolyte layer. The solid electrolyte battery in this embodiment is an all-solid sodium-ion secondary battery.

[0064] The solid electrolyte battery is preferably an all-solid-state sodium-ion secondary battery having a positive electrode, a solid electrolyte layer, and a negative electrode. In this embodiment, a solid electrolyte layer is provided between the positive and negative electrodes. Furthermore, in an all-solid-state sodium-ion secondary battery, a positive current collector can be stacked on the positive electrode, or a negative current collector can be stacked on the negative electrode. Moreover, the all-solid-state sodium-ion secondary battery can also be housed within a battery casing.

[0065] <Positive electrode> The positive electrode contains a positive electrode active material. Preferably, the positive electrode active material is a compound capable of adsorbing and releasing sodium. Examples of positive electrode active materials include, for example, complex compounds containing sodium and transition metals, such as complex oxides or phosphoric acid compounds. Examples of complex compounds include, for example, complex oxides containing sodium and transition metals, and phosphoric acid compounds containing sodium and transition metals. Examples of such compounds include Na₂Fe₂(SO₄)₃ and NaNi. 0.5 Mn 0.5 O2, NaFe 0.5 Mn 0.5 O2, NaFe 0.5 Co 0.5 O2 and other transition metal oxides, Na3V2(PO4)3 and other phosphoric acid-based cathodes.

[0066] The positive electrode is preferably a composite positive electrode. In this case, a composite positive electrode containing the above-mentioned positive electrode active material and the above-mentioned solid electrolyte is formed. Furthermore, in the composite positive electrode, a positive electrode layer formed by substantially uniformly mixing the positive electrode active material and the solid electrolyte can be formed, or a layer containing the positive electrode active material as the main component can be stacked on top of a layer formed by substantially uniformly mixing the positive electrode active material and the solid electrolyte.

[0067] In addition to the active material mentioned above, the positive electrode may contain any other components. Examples of such components include conductive additives and glass. In this case, the content of any component relative to the total volume of the positive electrode is preferably 20% by volume or less, and more preferably 5% by volume or less.

[0068] <Negative electrode> The negative electrode contains a negative electrode active material. Examples of negative electrode active materials include compounds that can adsorb and release sodium. Examples include: sodium metal, sodium alloys (alloys of sodium with metals such as tin, aluminum, and antimony), inorganic compounds such as tin compounds, carbon materials, silicon-based materials (Si or SiO), and conductive polymers.

[0069] In addition to the active material mentioned above, the negative electrode may contain any other components. Examples of such components include binder resin and negative electrode conductive agent. In this case, the content of any component relative to the total volume of the negative electrode is preferably 10% by volume or less, and more preferably 1% by volume or less.

[0070] The negative electrode is preferably a composite negative electrode. In this case, a composite negative electrode containing the aforementioned negative electrode active material and solid electrolyte is formed. Furthermore, in the composite negative electrode, a negative electrode layer consisting of a substantially uniform mixture of the negative electrode active material and the solid electrolyte can be formed, or a layer containing the negative electrode active material as the main component can be stacked on top of a substantially uniform mixture of the negative electrode active material and the solid electrolyte.

[0071] Positive current collector All-solid-state sodium-ion secondary batteries can have a positive current collector on the positive electrode. The positive current collector is electrically connected to the positive electrode. Materials used to construct the positive current collector include, for example, aluminum, stainless steel, and titanium. Furthermore, the form of the positive current collector can include metal plates, metal foils, foamed metal plates, and expanded metal.

[0072] <Negative current collector> All-solid-state sodium-ion secondary batteries can have a negative electrode current collector on the negative electrode. The negative electrode current collector is electrically connected to the negative electrode. Materials used to construct the negative electrode current collector include, for example, copper, stainless steel, titanium, and nickel. Furthermore, the form of the negative electrode current collector can include metal plates, metal foils, foamed metal plates, expanded metal, etc.

[0073] <Battery casing> The battery casing houses the aforementioned stack of positive current collector, positive electrode, solid electrolyte layer, negative electrode, and negative current collector. The shape of the battery casing is not particularly limited and can be appropriately selected according to various applications. Examples of battery casing shapes include cylindrical, flat oblong, flat elliptical, and square shapes. Examples of materials used to construct the battery casing include aluminum, stainless steel, nickel-plated steel, and various resins. Example

[0074] The features of the present invention are further illustrated below with examples and comparative examples. The materials, amounts, proportions, processing contents, processing order, etc., shown in the following examples can be appropriately modified without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as limited by the specific examples shown below.

[0075] (Example 1: Preparation of NaNbCl6) NaNbCl6 was synthesized via a mechanochemical method using NaCl and NbCl5 reagents. Specifically, stoichiometric amounts of the above-mentioned powdered reagents, along with Zr grinding media, were filled into an 80 mL planetary ball mill cup made of zirconia. The mechanochemical synthesis was performed for 33 hours using a Fritsch P-7 planetary ball mill at 500 rpm. To avoid internal overheating, the mechanical mixing of the ball mill was repeated every 10 minutes for 10 minutes, for a total of 198 cycles. The resulting powder (solid electrolyte) was recovered in a glove box, and its properties were verified by X-ray diffraction and impedance spectroscopy.

[0076] (Example 2: Preparation of NaTaCl6) NaTaCl6 was synthesized via a mechanochemical method using NaCl and TaCl5 reagents. Specifically, stoichiometric amounts of the above-mentioned powdered reagents were packed together with Zr grinding media into an 80 mL planetary ball mill cup made of zirconia. The mechanochemical synthesis was carried out for 33 hours using a Flying Star P-7 planetary ball mill at 500 rpm. During this process, to avoid internal overheating, the mechanical mixing of the ball mill was performed every 10 minutes for 10 minutes, repeated 198 times. The resulting powder was recovered in a glove box, and its properties were verified by X-ray diffraction and impedance spectroscopy.

[0077] (Example 3: Preparation of NaTaOCl4) NaTaOCl4 was synthesized via a mechanochemical method using NaCl, TaCl5, and Ta2O5 reagents. Specifically, stoichiometric amounts of the above-mentioned powdered reagents were packed together with Zr grinding media into an 80 mL planetary ball mill cup made of zirconia. The mechanochemical synthesis was performed for 80 hours using a Flying Star P-7 planetary ball mill at 500 rpm. To avoid internal overheating, the mechanical mixing of the ball mill was repeated every 10 minutes for 10 minutes, for a total of 480 cycles. The resulting powder was recovered in a glove box, and its properties were verified by X-ray diffraction and impedance spectroscopy.

[0078] (Example 4: Preparation of NaNbOCl4) NaTaOCl4 was synthesized via a mechanochemical method using NaCl, TaCl5, and Nb2O5 reagents. Specifically, stoichiometric amounts of the above-mentioned powdered reagents were packed together with Zr grinding media into an 80 mL planetary ball mill cup made of zirconia. The mechanochemical synthesis was carried out for 80 hours using a Flying Star P-7 planetary ball mill at 500 rpm. To avoid internal overheating, the mechanical mixing of the ball mill was performed every 10 minutes for 10 minutes, repeated 480 times. The resulting powder was recovered in a glove box, and its properties were verified by X-ray diffraction and impedance spectroscopy.

[0079] (Comparative Example 1: Preparation of Na3YCl6) As a comparative example, Na3YCl6 was synthesized via a mechanochemical method using NaCl and YCl5 reagents. Specifically, stoichiometric amounts of the powdered reagents, along with Zr grinding media, were filled into an 80ml planetary ball mill cup made of zirconia. The mechanochemical synthesis was performed for 33 hours using a Flying Star P-7 planetary ball mill at 500 rpm. To avoid internal overheating, the mechanical mixing of the ball mill was repeated every 10 minutes for 10 minutes, for a total of 198 cycles. The resulting powder was recovered in a glove box, and its properties were verified by X-ray diffraction and impedance spectroscopy.

[0080] (Measurement and Evaluation) <Confirmation of Crystallization> For the solid electrolytes obtained in the examples and comparative examples, X-ray diffraction was performed using a support capable of measuring the samples without exposure. Specifically, energy-based X-ray diffraction (XRD) analysis was performed using a Brucker D8 advanced device. Furthermore, XRD patterns with 2θ set to 12–75 degrees are shown. NaNbCl6 exhibits characteristic peaks at 15.9, 16.7, 18.9, and 31.1 Å. Almost identical patterns were observed in NaTaCl6, but due to lattice size effects, the peaks appeared at angles approximately 0.1–0.5 Å lower. Figure 1 and Figure 2 ). As a comparative example, the synthesized Na3YCl6 exhibited a pattern with the space group P21 / c, which is the existing crystal structure pattern. Figure 3 ). It was confirmed that the introduction of oxygen altered the crystal structure. In NaNbOCl4, in addition to the small peaks that could be attributed to NaNbCl6, peaks characterized by 13.9 and 16.3 were particularly observed. Figure 4 On the other hand, in NaTaOCl4, in addition to the small peaks that can be attributed to NaTaCl6 and Ta2O5, a glassy pattern was also obtained. Figure 5 ).

[0081] <Ionic conductivity (1)> A pressurized chamber capable of performing electrochemical measurements while applying pressure to the sample in a non-exposed state was fabricated. The solid electrolytes obtained in the examples and comparative examples were sealed within the chamber and formed under a pressure of 170 MPa. SUS rods were used as electrodes, and temperature-dependent AC impedance measurements were performed using a BioLogic VMP3 impedance analyzer. The obtained frequency response data were fitted using equivalent circuits in Relaxis3 software to determine the resistance values ​​at each temperature. The ionic conductivity was obtained from the resistance values ​​and the cell constant of the sample, and the activation energy was obtained from its temperature dependence. Compared to the solid electrolytes obtained in the comparative examples, the solid electrolytes obtained in the examples exhibited significantly improved conductivity. In Na3YCl6 of Comparative Example 1, it was confirmed that reducing the amount of Na in the structure increased conductivity. However, in the system of the examples where the amount of Na was already low and high ion conductivity was exhibited due to high mobility, an increase in conductivity was achieved by increasing the amount of Na. Furthermore, by introducing oxalates, significant increases in conductivity were observed in samples using both Nb and Ta, particularly in NaTaOCl4 using Ta, where conductivity comparable to that of sulfides was achieved without sulfur. Figure 6 ).

[0082] <Ionic conductivity (2)> The structural and transport variations of sintered solid electrolytes were investigated. For example... Figures 7-9 As shown, the peak intensity and crystallinity of the sample with a crystalline structure obtained by annealing are improved. Figure 10The hollow symbol indicates the conductivity of the sample after heat treatment at 200°C for 12 hours. All samples were granulated and vacuum-sealed in quartz tubes, and all operations were performed in a glove box filled with inert gas. After heat treatment, the samples were again ground into powder and placed in the pressurized chamber used for the electrochemical measurements described above to measure conductivity. The conductivity of Na3YCl6 in Comparative Example 1 decreased significantly after heat treatment (sintering). Figure 10 (The dashed arrow in the text) On the other hand, in the samples containing Ta and Nb in the examples, the decrease in conductivity caused by heat treatment (sintering) was significantly suppressed. Furthermore, for NaTaCl6, high conductivity was observed even when heat treatment was performed over a wide temperature range (200°C, 500°C, or 600°C). Figure 11 Therefore, the high conductivity maintained over a wide temperature range in samples containing Ta and Nb suggests the possibility of modulating the interfacial state through heat treatment.

[0083] <Estimation of relative density (relative to theoretical density)> The relative density was calculated using dimensional density relative to the theoretical density. 2–300 mg of sample was sealed in a cell used for electrochemical measurements and compressed under a pressure of 170 MPa. The dimensional density was calculated from the surface area and thickness of the compressed pellets and the weight of the sample. The theoretical density was the value theoretically derived from the crystal structure. The relative density relative to the theoretical density was 80–90% achieved in any composition, regardless of whether it was before or after heat treatment.

[0084] <Estimation of band gap value> To investigate the electronic properties of the solid electrolytes obtained in Examples 1-4, the band gap was measured using diffuse reflectance measurement with a UV-Vis spectrometer. The sample used was powdered solid electrolyte, and the apparatus used was a Shimadzu UV-3600 Plus. To perform measurements without exposure to the atmosphere, the solid electrolyte powder was placed in a sample holder with a window inside a glove box, and the window was sealed with vacuum grease. Measurements were performed at room temperature. The band gap value was determined based on the absorption coefficient obtained by transforming the measurement data using the Kuberca-Monk function. Figures 12-15 ). like Figure 12 As shown, the band gap of NaNbCl6 is 3.1 eV, as... Figure 13 As shown, the band gap of NaTaCl6 is 3.7 eV, as... Figure 14 As shown, the band gap of NaTaOCl4 is 3.8 eV, as... Figure 15 As shown, the band gap of NaNbOCl4 is 3.3 eV, all values ​​greater than 3 eV. This result indicates that the solid electrolyte obtained in the examples has low electronic conductivity (and high electronic insulation).

[0085] (Example 101) Na is synthesized through elemental substitution of Zr. 1+x Ta 1-x Zr x Cl6 was used to verify the effect of carrier concentration on ion conduction in solid electrolytes. Na 1+x Ta 1-x Zr x Cl6 was synthesized via a mechanochemical method using reagents NaCl, TaCl5, and ZrCl4. Specifically, stoichiometric amounts of the above-mentioned powdered reagents, along with Zr grinding media, were filled into an 80 mL planetary ball mill cup made of zirconia. The mechanochemical synthesis was performed for 33 hours using a Flying Star P-7 planetary ball mill at 500 rpm. To avoid internal overheating, the mechanical mixing of the ball mill was repeated every 10 minutes for 10 minutes, for a total of 198 cycles. The resulting powder was recovered in a glove box, and its properties were verified by X-ray diffraction and impedance spectroscopy. Figure 16 In addition, Na 1+x Ta 1-x Zr x Cl6 exhibits the same crystal structure as NaTaCl6 in the range x < 1.0, indicating the ability to modulate the amount of Na in the crystal structure. For example... Figure 17 As shown, higher ionic conductivity can be observed in the presence of trace amounts of Zr. This result indicates that adjusting the amount of Na affects ionic conductivity, suggesting that Na ion conduction is improved through enhanced electrostatic repulsion between conductive ions caused by the increase in the amount of Na ions.

[0086] (Experimental Example 1: NaTa) 1 / 5(3+2x) O x (Creation of Cl4) The NaTa shown in the table below was synthesized by mechanochemical method using NaCl, TaCl5, and Ta2O5 reagents. 1 / 5(3+2x) O x Cl4. Specifically, the reagent of the above-mentioned powder, weighed stoichiometrically, was packed together with Zr grinding media into an 80 mL planetary ball mill cup made of zirconia, and a mechanochemical synthesis was performed for 100 hours using a Flying Star P-7 planetary ball mill at 600 rpm. During this process, to avoid internal overheating, the mechanical mixing of the ball mill was performed every 10 minutes for 10 minutes, repeated 600 times. The resulting powder was recovered in a glove box, and its properties were verified by X-ray diffraction and impedance spectroscopy.

[0087] [Table 1]

[0088] When Ta2O5 is used as the oxygen source, Ta2O5 remains, and other phases become significantly amorphous. Figure 18Although it was shown that not all of the introduced oxygen was used, it was confirmed that increasing the amount of oxygen introduced significantly improved conductivity. Figure 19 (a) and (b)).

[0089] (Experimental Example 2: Na) 1+x TaOCl 4+x (Production) Using NaCl, TaCl5, and Ta2O5 reagents, the Na shown in the table below was synthesized via a mechanochemical method. 1+ x TaOCl 4+x Specifically, the stoichiometric amounts of the above-mentioned powder reagents, along with Zr grinding media, were filled into an 80 mL planetary ball mill cup made of zirconia. Mechanochemical synthesis was performed for 100 hours using a Flying Star P-7 planetary ball mill at 600 rpm. To avoid internal overheating, the mechanical mixing of the ball mill was performed every 10 minutes for 10 minutes, repeated 600 times. The resulting powder was recovered in a glove box, and its properties were verified by X-ray diffraction and impedance spectroscopy.

[0090] [Table 2]

[0091] The effect of varying NaCl concentration on conductivity was investigated, but it had almost no effect; substances with conductivity exceeding 1 mS / cm were synthesized in all cases. Figure 20 and Figure 21 ).

[0092] (Experimental Example 3: Preparation of NaTaOCl4) A mechanochemical synthesis was performed using NaCl, TaCl5, and Ta2O5 reagents in a mass ratio of 5:3:1. Specifically, weighed reagent powders were packed together with Zr grinding media into an 80 mL planetary ball mill cup made of zirconia. Mechanochemical synthesis was carried out at 600 rpm for 25, 50, 75, and 100 hours using a Flying Star P-7 planetary ball mill. To avoid internal overheating, the mechanical mixing of the ball mill was performed for 10 minutes every 10 minutes, repeated for 150, 300, 450, and 600 cycles. The powders obtained at each synthesis time were recovered in a glove box, and their properties were verified by X-ray diffraction and impedance spectroscopy.

[0093] As a result, although it is known that conductivity can be increased by extending the process time, it is also known that even a relatively short grinding time of around 25 hours will result in little change in conductivity. Figure 22 and Figure 23 ).

[0094] (Experimental Example 4: Na)2x TaO x (CLOSE production) Using Na₂O and TaCl₅ reagents, the Na shown in the table below was synthesized via a mechanochemical method. 2x TaO x Cl5. Specifically, the reagent of the above-mentioned powder, weighed stoichiometrically, was packed together with Zr grinding media into an 80 mL planetary ball mill cup made of zirconia, and subjected to mechanochemical synthesis at 600 rpm for 100 hours using a Flying Star P-7 planetary ball mill. During this process, to avoid internal overheating, the mechanical mixing of the ball mill was performed every 10 minutes for 10 minutes, repeated 600 times. The resulting powder was recovered in a glove box, and its properties were verified by X-ray diffraction and impedance spectroscopy.

[0095] [Table 3]

[0096] By changing the precursor reagent from Ta₂O₅ to Na₂O, a more homogeneous glass was successfully synthesized. As a precursor reagent, it is believed that a soft substance with high reactivity and mechanical properties similar to other precursors is required in the synthesis of homogeneous compounds. This resulted in a successful improvement in the reproducibility of the high conductivity of 3.7 mS / cm. Figure 24 and Figure 25 (a) and (b)).

Claims

1. A solid electrolyte comprising a compound represented by formula (1) or formula (2), Formula (1) Na 3a+2b+1c M 1 a M 2 b M 3 c Ch α X 6-2α In equation (1), M 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and their combinations, M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn and combinations thereof, M 3 The elements are selected from Nb, Ta, V, P, Sb, Bi, and combinations thereof; Ch is selected from O, S, Se, Te, and combinations thereof; X is selected from F, Cl, Br, I, and combinations thereof; a+b+c=1, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0.1≤α≤2.

9. Formula (2) Na 3a+2b+1c M 1 a M 2 b M 3 c X6 In equation (2), M 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and their combinations, M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn and combinations thereof, M 3 The elements are selected from Nb, Ta, V, P, Sb, Bi and their combinations, and X is selected from F, Cl, Br, I and their combinations. The conditions are a+b+c=1, 0≤a≤0.9, 0≤b≤0.9, and 0.1≤c≤1.

2. The solid electrolyte according to claim 1, wherein, In equation (2), M 3 Selected from Ta and Nb.

3. The solid electrolyte according to claim 1, wherein, In equation (1), X is Cl.

4. The solid electrolyte according to claim 1, wherein, In equation (2), X is Cl.

5. The solid electrolyte according to claim 1, wherein, When compressed at room temperature and under a pressure of 170 MPa, the sodium ion conductivity at 25°C is 1 × 10⁻⁶. -6 S / cm or higher.

6. The solid electrolyte according to claim 1, wherein, The relative density is over 80% when compressed at room temperature and under a pressure of 170 MPa.

7. A solid electrolyte comprising a compound represented by formula (1'), Formula (1') Na= 3a+2b+1c-γ+δ M 1 a M 2 b M 3 c Ch ε X ζ In equation (1'), M 1 Selected from Y, Sc, Al, Ga, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and their combinations, M 2 Selected from Zr, Hf, Ti, Si, Ge, Sn and combinations thereof, M 3 The elements are selected from Nb, Ta, V, P, Sb, Bi and their combinations; Ch is selected from O, S, Se, Te and their combinations; X is selected from F, Cl, Br, I and their combinations; a+b+c=1, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤γ<≤1, 0≤δ≤2, 0≤ε≤2 and 4≤ζ≤8.

8. The solid electrolyte according to claim 7, wherein, In equation (1'), X is Cl.

9. The solid electrolyte according to claim 7, wherein, When compressed at room temperature and under a pressure of 170 MPa, the sodium ion conductivity at 25°C is 1 × 10⁻⁶. -6 S / cm or higher.

10. The solid electrolyte according to claim 7, wherein, The relative density is over 80% when compressed at room temperature and under a pressure of 170 MPa.

11. A solid electrolyte layer comprising the solid electrolyte according to any one of claims 1 to 10.

12. A solid electrolyte battery comprising the solid electrolyte layer of claim 11.

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