Chalcogenide-containing compound, solid electrolyte, positive electrode material, dielectric, and battery

Abstract

The present disclosure provides a compound represented by the following compositional formula (1).　(1) AxMyM2 zCh4X (In formula (1), A is at least one element selected from the group consisting of alkali metals and Ag, M is at least one element selected from the group consisting of Zn, Mn, and Fe, M2 is a metal element other than A and M, Ch is at least one element selected from the group consisting of O, S, Se, and Te, X is at least one selected from the group consisting of F, Cl, Br, I, OH, SH, BF4, and BH4, and x, y, and z satisfy 3≤x≤5.5, 1.5≤y≤2.5, and 0≤z≤1.0.)

Description

Chalcogenide-containing compounds, solid electrolytes, cathode materials, dielectrics, and batteries

[0001] The present disclosure relates to chalcogenide-containing compounds, solid electrolytes, cathode materials, dielectrics, and batteries.

[0002] In recent years, solid electrolytes have been attracting attention as electrolytes for use in electrochemical devices such as lithium-ion batteries (Patent Documents 1 and 2). Compared with conventional electrolytic solutions, solid electrolytes have superior high-temperature durability, high-voltage resistance, and the like, and are therefore considered useful for improving battery performance such as safety, high capacity, rapid charge / discharge, and pack energy density.

[0003] International Publication No. 2020 / 220697 International Publication No. 2021 / 024785

[0004] Here, batteries may need to operate in high-temperature environments, and therefore, each component of the battery, such as the electrolyte and electrodes, is required to have higher heat resistance. Similarly, heat resistance is also required for electronic devices such as capacitors. In view of these circumstances, there is a great demand for materials with higher heat resistance.

[0005] The present disclosure has been made in view of the above circumstances, and aims to provide a compound having high heat resistance, as well as a solid electrolyte, a positive electrode material, a dielectric, and a battery containing such a compound.

[0006] The present disclosure includes the following exemplary embodiments: [1] A compound represented by the following composition formula (1): ｘ M ｙ M ２ ｚ Ch ４ X (1) (In formula (1), A is at least one element selected from the group consisting of alkali metals and Ag, M is at least one element selected from the group consisting of Zn, Mn, and Fe, and M ２ is a metal element other than A and M, Ch is at least one element selected from the group consisting of O, S, Se, and Te, and X is F, Cl, Br, I, OH, SH, BF ４ , and BH ４and x, y, and z are at least one selected from the group consisting of: 3≦x≦5.5, 1.5≦y≦2.5, and 0≦z≦1.0, respectively. [2] The compound of [1], which has, within its crystal structure, a one-dimensional chain in which octahedral structures centered on an alkali metal ion are connected, and a one-dimensional chain in which tetrahedral structures centered on a metal ion are connected, and the one-dimensional chain in which the octahedral structures are connected and the one-dimensional chain in which the tetrahedral structures are connected are arranged alternately. [3] The compound of [1] or [2], which has a tetragonal or orthorhombic crystal structure. [4] The compound of [1] or [2], which has a space group of I4mm, I4 / mmm, or P2 １ The compound according to any one of [1] to [3], having a crystal structure attributed to ab. [5] A solid electrolyte containing the compound according to any one of [1] to [4]. [6] A cathode material containing the compound according to any one of [1] to [4]. [7] A dielectric containing the compound according to any one of [1] to [4]. [8] A battery containing the compound according to any one of [1] to [4].

[0007] The present disclosure can provide a compound with high heat resistance, as well as a solid electrolyte, a cathode material, a dielectric, and a battery containing such a compound.

[0008] FIG. 1 shows powder X-ray diffraction patterns for Examples 1 to 3. FIG. 2 shows powder X-ray diffraction patterns for Examples 4 and 5. FIG. 3 shows the crystal structure of the chalcogenide-containing compound of Example 1 viewed from a direction perpendicular to the c-axis. FIG. 4 shows the crystal structure of the chalcogenide-containing compound of Example 1 viewed from a direction along the a-axis. FIG. 5 shows the crystal structure of the chalcogenide-containing compound of Example 1 viewed from a direction along the c-axis. FIG. 6 shows an Arrhenius plot obtained for the chalcogenide-containing compound of Example 5.

[0009] The compound of this embodiment is a compound represented by the following composition formula (1) (hereinafter also referred to as a chalcogenide-containing compound): ｘ M ｙ M ２ ｚ Ch ４X (1) (In formula (1), A is at least one element selected from the group consisting of alkali metals and Ag, M is at least one element selected from the group consisting of Zn, Mn, and Fe, and M ２ is a metal element other than A and M, Ch is at least one element selected from the group consisting of O, S, Se, and Te, and X is F, Cl, Br, I, OH, SH, BF ４ , and BH ４ and x, y, and z are 3≦x≦5.5, 1.5≦y≦2.5, and 0≦z≦1.0, respectively.

[0010] In composition formula (1), A is at least one element selected from the group consisting of alkali metals and Ag, and may contain, for example, at least one element selected from the group consisting of Li, Na, and Ag, or may contain at least one of Li and Na.

[0011] In the composition formula (1), x may be, for example, 3.5 to 5.5, 4 to 5.3, or 4.5 to 5.2.

[0012] In composition formula (1), M is at least one element selected from the group consisting of Zn, Mn, and Fe, and may contain, for example, at least one of Zn and Mn, or may contain Zn. M may contain a divalent element.

[0013] In the composition formula (1), y may be, for example, 1.6 to 2.4, or 1.7 to 2.3.

[0014] In composition formula (1), M ２ is a metal element other than A and M, and may be, for example, at least one element selected from the group consisting of Ga, In, and Nb, or at least one of Ga and In. ２ may contain a trivalent or higher metal element.

[0015] In composition formula (1), z may be, for example, greater than 0 and equal to or less than 0.8, 0.01 to 0.5, 0.05 to 0.4, 0.1 to 0.3, or 0.1 to 0.25.

[0016] In composition formula (1), Ch is a Group 16 element of the periodic table, and is at least one element selected from the group consisting of O, S, Se, and Te. For example, Ch may contain at least one element of O and S, and may also contain S.

[0017] In the composition formula (1), X is F, Cl, Br, I, OH, SH, or BF ４ , and BH ４ The alkyl group may be at least one selected from the group consisting of:

[0018] Specific examples of the ion-conductive material according to this embodiment include Na ５ Zn ２ S ４ Br, Na ４．８ Zn １．８ Ga ０．２ S ４ Br, Na ４．８ Zn １．８ In ０．２ S ４ Br, Na ５ Zn ２ S ４ SH, Na ４．８ Zn １．８ In ０．２ S ４ SH, Na ５ Mn ２ S ４ SH, Na ５ Mn ２ S ４ Br, Li ５ Zn ２ S ４ Br, Li ４．８ Zn １．８ Ga ０．２ S ４ Br, Li ５ Zn ２ S ４ S.H., and Li ４．８ Zn １．８ In ０．２ S ４ Examples of suitable ion-conductive materials include compounds having a composition formula such as SH. When preparing an ion-conductive material by oneself, the composition formula can be determined from the types and composition ratios of elements in the raw materials.

[0019] The solid (crystal) of the chalcogenide-containing compound of this embodiment may have, within its crystal structure, a one-dimensional chain of connected octahedral structures centered around an alkali metal ion and a one-dimensional chain of connected tetrahedral structures centered around a metal ion. The bond energies constituting the octahedral structure and the tetrahedral structure are different, and the presence of the octahedral structure and the tetrahedral structure adjusts the thermal decomposition rate and provides thermal stability. The solid (crystal) of the chalcogenide-containing compound may have a plurality of octahedral structures and a plurality of tetrahedral structures. The presence of a plurality of octahedral structures and a plurality of tetrahedral structures disperses the energy consumed in thermal decomposition, thereby dispersing the thermal energy supplied to the chalcogenide-containing compound from the outside, resulting in improved heat resistance of the chalcogenide-containing compound. The alkali metal ion may be an ion of the alkali metal A in composition formula (1), and the metal ion may be a metal ion M in composition formula (1). Here, a one-dimensional chain of linked octahedral structures refers to a structure in which octahedral structures are repeatedly arranged in a chain along a certain direction in the crystal, and a one-dimensional chain of linked tetrahedral structures refers to a structure in which tetrahedral structures are repeatedly arranged in a chain along a certain direction in the crystal.

[0020] In the solid (crystal) of the chalcogenide-containing compound of this embodiment, the above-mentioned one-dimensional chains of linked octahedral structures and one-dimensional chains of linked tetrahedral structures may be arranged alternately within the crystal structure. Here, "alternately arranged" refers to a structure in which one-dimensional chains of linked octahedral structures and one-dimensional chains of linked tetrahedral structures are alternately arranged along a certain direction within the crystal. The alternating arrangement of one-dimensional chains of octahedral structures and one-dimensional chains of tetrahedral structures strengthens the bonds between atoms within the crystal, thereby further increasing the resistance of the chalcogenide-containing compound to thermal energy supplied from the outside and further improving the thermal stability of the chalcogenide-containing compound. In other words, the chalcogenide-containing compound has a structure in which one-dimensional chains of octahedral structures and one-dimensional chains of tetrahedral structures are arranged alternately, resulting in even better heat resistance. Within the crystal, the one-dimensional chains of linked octahedral structures and one-dimensional chains of linked tetrahedral structures may be arranged alternately in two or more directions that are not parallel to each other.

[0021] The solid (crystal) of the chalcogenide-containing compound of this embodiment has, within its crystal structure, one-dimensional chains of connected octahedral structures centered around alkali metal ions and one-dimensional chains of connected tetrahedral structures centered around metal ions, and the one-dimensional chains of connected octahedral structures and the one-dimensional chains of connected tetrahedral structures may be arranged alternately within the crystal structure. By having such a crystal structure, the thermal stability of the crystal structure of the chalcogenide-containing compound is further improved, resulting in a compound with further improved heat resistance.

[0022] The octahedral structures in the one-dimensional chain may share corners. That is, each octahedral structure in the one-dimensional chain may share one atom with each of the two octahedral structures adjacent to the octahedral structure. The shared atom may be an atom included in X in the composition formula (1). Here, when the atom included in X is F, Cl, Br, or I, it refers to these atoms themselves, and when X is OH, SH, BF ４ , or BH ４ In the case of the formula (I), it refers to S, O, or B, respectively, and the element is shared.

[0023] The tetrahedral structures in the one-dimensional chain may share edges. That is, each tetrahedral structure in the one-dimensional chain may share two atoms with each of the two tetrahedral structures adjacent to the tetrahedral structure. The shared atoms may be atoms included in Ch in the composition formula (1).

[0024] The above-mentioned octahedral structure and tetrahedral structure may share a vertex. The shared atom may be an atom contained in Ch in the above composition formula (1). In this case, each octahedral structure contained in the one-dimensional chain may share a vertex with a tetrahedral structure contained in each one-dimensional chain in which four adjacent tetrahedral structures are connected. A tetrahedral structure may share a vertex with four adjacent octahedral structures.

[0025] In the crystal structure of the chalcogenide-containing compound of this embodiment, the metal ion A in the composition formula (1) may be contained in a gap surrounded by the tetrahedral structure and the octahedral structure, or may be contained both within the octahedral structure and in the gap.

[0026] The crystal of the chalcogenide-containing compound of this embodiment may have a tetragonal or orthorhombic crystal structure. The crystal of the chalcogenide-containing compound of this embodiment may have a space group, for example, I4mm, I4 / mmm, or P2 １ It may have a crystal structure attributed to ab.

[0027] The method for producing the chalcogenide-containing compound of this embodiment is not particularly limited, but includes a method of firing raw materials. ２ and X, for example, a chalcogenide compound of A, a chalcogenide compound of M, ２and a salt containing A and X. The raw materials may be weighed so that the resulting chalcogenide compound has the desired composition, and may be mixed in a mortar or the like before firing. The raw materials may be weighed and mixed in an atmosphere containing an inert gas such as nitrogen (in an inert atmosphere). The firing temperature of the raw materials may be changed appropriately depending on the raw materials used, but may be, for example, 300 to 700°C or 350 to 650°C. The firing may be performed on the raw materials contained in an evacuated container (for example, a container made of a heat-resistant material such as Pyrex (registered trademark)).

[0028] The chalcogenide-containing compound of this embodiment can be used as a material for electrochemical devices such as capacitors and batteries. Examples of such materials include electrolytes (solid electrolytes) and positive electrode active materials. Examples of batteries include lithium ion batteries, sodium ion batteries, and other batteries that perform charging and discharging by the movement of alkali metal ions between a positive electrode and a negative electrode. The chalcogenide-containing compound of this embodiment can also be used as an electrode material such as a positive electrode active material or an ion conductor, and may be contained in at least one of the positive electrode and the negative electrode, or may be contained in the positive electrode. The chalcogenide-containing compound of this embodiment can also be used as a dielectric.

[0029] The battery of this embodiment will be described below using a lithium-ion battery as an example. The lithium-ion battery includes a positive electrode, a negative electrode, and an electrolyte (solid electrolyte) disposed between the positive electrode and the negative electrode. The chalcogenide-containing compound of this embodiment may be contained in the electrolyte or the positive electrode of the lithium-ion battery.

[0030] The positive electrode of the lithium ion battery is not particularly limited, and may contain a positive electrode active material and, if necessary, a conductive additive, a binder, etc.

[0031] The positive electrode may be a positive electrode material layer containing these materials formed on a current collector. The positive electrode active material may contain the chalcogenide-containing compound of the present embodiment, but may also contain other materials, such as a lithium-containing composite metal oxide containing lithium (Li) and at least one transition metal selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, and Cu.

[0032] Examples of such lithium composite metal oxides include LiCoO ２ , LiNiO ２ , LiMn ２ O ４ , Li ２ MnO ３ , LiNi ｘ Mn ｙ Co １－ｘ－ｙ O ２ [0<x+y<1]), LiNi ｘ Co ｙ Al １－ｘ－ｙ O ２ [0<x+y<1]), LiCr ０．５ Mn ０．５ O ２ , LiFePO ４ , Li ２ FeP ２ O ７ , LiMnPO ４ , LiFeBO ３ , Li ３ V ２ (P.O. ４ ) ３ , Li ２ CuO ２ , Li ２ FeSiO ４ , Li ２ MnSiO ４ When the positive electrode active material contains an alkali metal element other than Li, specific examples thereof include those in which Li in the above specific examples is replaced with another alkali metal.

[0033] The negative electrode of the lithium ion battery is not particularly limited, and may contain a negative electrode active material and, if necessary, a conductive additive, a binder, etc. Examples of the negative electrode active material include metals such as Li, Si, P, Sn, Si—Mn, Si—Co, Si—Ni, In, and Au, alloys containing these metals, carbon materials such as graphite, and substances in which lithium ions are inserted between the layers of the carbon material.

[0034] The material of the current collector is not particularly limited, and may be, for example, a simple metal such as Mg, Ti, Fe, Co, Ni, Cu, Zn, Al, Ge, Pd, Ag, In, Pt, or Au, or an alloy thereof.

[0035] The electrolyte layer may have multiple layers. For example, a configuration may be provided that includes a sulfide solid electrolyte layer in addition to the solid electrolyte layer containing the chalcogenide-containing compound of this embodiment. A configuration may be provided that includes a sulfide solid electrolyte layer between the solid electrolyte containing the chalcogenide-containing compound of this embodiment and the negative electrode. However, since the solid electrolyte layer containing the chalcogenide-containing compound of this embodiment has high electrochemical stability, even if it does not include a sulfide solid electrolyte layer and is in direct contact with the negative electrode, a short circuit is unlikely to occur in the battery. The sulfide solid electrolyte is not particularly limited, but for example, Li ６ P.S. ５ Cl, Li ２ S-PS ５ , Li １０ GeP ２ S １２ , Li ９．６ P ３ S １２ , Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ , Li ３ P.S. ４ When the solid electrolyte layer contains an alkali metal element other than Li, specific examples thereof include those in which Li in the above specific examples is replaced with another alkali metal.

[0036] When the chalcogenide-containing compound of this embodiment is used as a dielectric, it can be used as a material for a wide variety of electronic devices, such as a resin for fingerprint authentication sensors, a resin for insulating materials for power applications, a resin for antenna materials, various capacitor materials, capacitor materials for passive element-embedded substrates, dielectric filters, vibration generators, conversion sensors, ignition devices, memories, piezoelectric elements, etc. The chalcogenide-containing compound of this embodiment may be a ferroelectric.

[0037] Example 1 General Formula A ｘ M ｙ M ２ ｚ Ch ４ Compounds having the composition represented by X (chalcogenide-containing compounds) can be synthesized by solid ceramic synthesis. For example, Na ５ Zn ２ S ４ A method for producing a chalcogenide-containing compound using Br will be described.

[0038] First, Na ２ Stoichiometric amounts of starting materials containing S, ZnS, and NaBr were weighed and uniformly mixed in a mortar in a nitrogen-filled glove box. Each raw material was weighed and mixed so that the resulting target weight was 1 g. The mixture was then pressed into a pellet and transferred to a Pyrex tube. The Pyrex tube was then degassed and sealed using a flame torch. The Pyrex tube was then heated to 550°C at a rate of 10°C / min, baked at that temperature for 24 hours, and then naturally cooled to room temperature. The tube was then transferred to a glove box, and the sample was recovered.

[0039] Examples 2 to 7 Other substances having the compositions shown in Table 1 were also synthesized using the corresponding starting materials in the same manner as in Example 1. That is, the chalcogenide-containing compounds of each example were produced by the same method as in Example 1, except that the firing temperature and starting materials were used as shown in Table 1.

[0040]

[0041] Comparative Example 1 Compounds having the compositions shown in Table 2 were synthesized according to the following method.

[0042] Ball mill: In an argon atmosphere having a dew point of −70° C. or less (hereinafter referred to as a dry argon atmosphere), 0.4381 g of LiCl and 0.4381 g of InCl ３ The raw material was prepared by weighing out 0.7619 g of the above. The raw material was placed in a zirconia pot for the planetary ball mill described below, and 65 g of zirconia balls with a diameter of 5 mm were added. The mixture was then treated for 30 minutes at 1200 rpm to induce a mechanochemical reaction, thereby obtaining a crude composition of Comparative Example 1. Planetary ball mill: Emax manufactured by Verder Scientific K.K.

[0043] Annealing The crude composition of Comparative Example 1 obtained above was heated at 230°C for 5 hours in a dry argon atmosphere to change the composition to Li ３ InCl ６ The compound of Comparative Example 1 was obtained.

[0044] [Comparative Example 2] Li ２ 0.1364 g of ZrCl ４ was weighed out to prepare a raw material.

[0045] The raw material was placed in a zirconia pot for the planetary ball mill, and 65 g of zirconia balls with a diameter of 5 mm were added. Thereafter, the mixture was treated for 120 minutes at 1200 rpm so as to undergo a mechanochemical reaction, resulting in a composition of Li. ２ ZrCl ４ The compound of Comparative Example 2, which is O, was obtained.

[0046] <Powder X-ray Diffraction Measurement> The crystal structure of the obtained chalcogenide-containing compounds was evaluated by powder X-ray diffraction measurement at 25°C. FIG. 1 shows the powder X-ray diffraction patterns of Examples 1 to 3. FIG. 2 shows the powder X-ray diffraction patterns of Examples 4 and 5. Table 2 shows the space group of each sample obtained by X-ray diffraction measurement. Powder X-ray diffraction measurement was performed under the following conditions. Furthermore, to prevent the sample from coming into direct contact with the atmosphere, the measurement was performed in a glove box, with the sample space protected with polyimide tape. Measurement equipment: SmartLab (manufactured by Rigaku Corporation) X-ray generator: CuKα ray source, voltage 40 kV, current 50 mA X-ray detector: Semiconductor detector Measurement range: Diffraction angle 2θ = 5° to 80° Scan speed: 2.5° / min

[0047] Fig. 3 is a view of the crystal structure of the chalcogenide-containing compound of Example 1 as viewed from a direction perpendicular to the c-axis. Fig. 4 is a view of the crystal structure of the chalcogenide-containing compound of Example 1 as viewed from a direction along the a-axis. Fig. 5 is a view of the crystal structure of the chalcogenide-containing compound of Example 1 as viewed from a direction along the c-axis.

[0048] <Evaluation of Heat Resistance for Compounds of Examples 1 to 5, Comparative Examples 1 and 2> A pressure molding die including a frame, a lower punch, and an upper punch was prepared. The frame was made of insulating polycarbonate. The upper and lower punches were both made of electronically conductive stainless steel and were electrically connected to the terminals of an impedance analyzer (S11260, manufactured by Solatron Analytical).

[0049] Using the above-mentioned pressure molding die, the ionic conductivity of the chalcogenide-containing compound was measured by the following method. First, in a dry argon atmosphere, a powder of the chalcogenide-containing compound was filled onto the lower part of a punch inserted vertically from below into the hollow part of a frame mold. Then, the upper part of the punch was pressed into the hollow part of the frame mold from above, thereby applying a pressure of 370 MPa to the powder of the chalcogenide-containing compound inside the pressure molding die. After the pressure was applied, the punch was clamped from above and below with a jig, and while maintaining a constant pressure, the impedance of the chalcogenide-containing compound was measured by electrochemical impedance measurement using the above-mentioned impedance analyzer.

[0050] A Cole-Cole diagram was created from the impedance measurement results. In the Cole-Cole diagram, the real value of the impedance at the measurement point where the absolute value of the phase of the complex impedance was smallest was considered to be the resistance value to the ionic conduction of the chalcogenide-containing compound. Using this resistance value, the ionic conductivity was calculated based on the following formula (III). The ionic conductivity (σ) of each sample at 25°C was ２５℃ ) are shown in Table 2. σ = (R ＳＥ × S / t) －１ ...(III) where, σ is the ionic conductivity, S is the contact area of ​​the chalcogenide-containing compound with the top of the punch (equal to the cross-sectional area of ​​the hollow part of the frame), and R ＳＥ is the resistance value of the chalcogenide-containing compound in the impedance measurement, and t is the thickness of the chalcogenide-containing compound when pressure is applied.

[0051] Each sample in the pressure molding die was heated to 80°C, and the ionic conductivity (σ ｂｅｆｏｒｅ After that, each sample was heated to 100°C and held at 100°C for 90 minutes. After cooling to 80°C, each sample was measured again at 80°C for ionic conductivity (σ ａｆｔｅｒ The rate of change in ionic conductivity was calculated from the measured ionic conductivity using the following formula. The rate of change is shown in Table 2. (Rate of change in ionic conductivity) = (σ ａｆｔｅｒ -σ ｂｅｆｏｒｅ ) / σ ｂｅｆｏｒｅ

[0052] Using the above method, ionic conductivity was measured at five temperatures (25°C, 40°C, 60°C, 80°C, and 100°C) within the temperature range of 25 to 100°C. Figure 6 shows an Arrhenius plot obtained for the chalcogenide-containing compound of Example 5. Ionic conductivity was measured at five points for both temperature increases and decreases. In Figure 6, the plots for temperature increases and decreases almost overlap.

[0053] <Evaluation of Heat Resistance of Examples 6 and 7, and Comparative Example 3> Using the above pressure molding die, the heat resistance of the chalcogenide-containing compounds was evaluated by the following method.

[0054] First, in a dry argon atmosphere, a powder of a chalcogenide-containing compound was filled onto the lower part of a punch inserted vertically from below into the hollow part of a frame mold, and then the upper part of the punch was pressed into the hollow part of the frame mold from above, thereby applying a pressure of 370 MPa to the powder of the chalcogenide-containing compound inside the pressure molding die.

[0055] Next, Li was placed on the top and bottom of the chalcogenide-containing compound. ６ P.S. ５ The chalcogenide-containing compound of Comparative Example 1 was used to prepare a laminate in Comparative Example 3.

[0056] After the pressure was applied, the punch was clamped from above and below with a jig to fix it in place, and while maintaining a constant pressure, the impedance of the laminate containing the chalcogenide-containing compound was measured by electrochemical impedance measurement using the impedance analyzer described above.

[0057] A Cole-Cole diagram was created from the impedance measurement results. In the Cole-Cole diagram, the real value of the impedance at the measurement point where the absolute value of the phase of the complex impedance was smallest was considered to be the resistance value to the ionic conduction of the chalcogenide-containing compound. Using this resistance value, the ionic conductivity was calculated based on the following formula (III). The ionic conductivity (σ) of each sample at 25°C was ２５℃) are shown in Table 2. σ = (R ＳＥ × S / t) －１ ...(III) where, σ is the ionic conductivity, S is the contact area of ​​the laminate with the upper part of the punch (equal to the cross-sectional area of ​​the hollow part of the frame mold), and R ＳＥ is the resistance of the laminate in the impedance measurement, and t is the thickness of the laminate when pressure is applied.

[0058] Each sample in the pressure molding die was heated to 80°C, and the ionic conductivity (σ ｂｅｆｏｒｅ After that, each sample was heated to 100°C and held at 100°C for 90 minutes. After cooling to 80°C, each sample was measured again at 80°C for ionic conductivity (σ ａｆｔｅｒ The rate of change in ionic conductivity was calculated from the measured ionic conductivity using the following formula. The rate of change is shown in Table 2. (Rate of change in ionic conductivity) = (σ ａｆｔｅｒ -σ ｂｅｆｏｒｅ ) / σ ｂｅｆｏｒｅ

[0059]

[0060] As shown in Table 2, the chalcogenide-containing compounds of Examples 1 to 7 had a positive rate of change in ionic conductivity, or even if negative, the absolute value was smaller than those of Comparative Examples 1 and 2. This indicates that the degree of deterioration due to heating was smaller than those of Comparative Examples 1 and 2, and that the compounds had high heat resistance.

[0061] <Calculation of surface energy of Li compounds and evaluation of calculation results> To evaluate the thermal stability of Li ions, the surface energy of each Li compound was calculated using density functional theory. The surface energy is an amount that indicates the degree to which a crystal becomes unstable from a bulk state by forming a surface, and is calculated using the following formula (nn): Surface energy = (E ｓｕｒｆ −n×E ｂｕｌｋ ) ÷ S... (nn) where E ｓｕｒｆ is the total energy of the system calculated by the surface slab model, and E ｂｕｌｋ is the total energy of the system calculated using a unit cell model of a bulk crystal, S is the surface area of ​​the surface slab model, and n is E ｓｕｒｆThe surface energy is the number of atoms contained in a unit cell divided by the number of atoms contained in the unit cell. Surface energy reflects the instability of the surface of the material. Generally, if the surface energy of a system is high, the surface is unstable and the thermal stability of the surface is low, resulting in low thermal stability of the interface when used as a solid electrolyte, cathode material, dielectric, or battery. The surface energies of the (001), (110), and (111) planes commonly observed in ordinary crystals were calculated, and the thermal stability was evaluated by taking the average value.

[0062] Although not wishing to limit the scope of the claims of this application, all density functional calculations shown in this application were performed using the computational chemistry software "Vienna ab initio simulation package (VASP)" provided by the University of Vienna, Republic of Austria, which is widely used and known to those skilled in the art. PBE was used as the density functional, and the slab model used in the calculations was created so that the axial lengths of the two axes in the surface extension direction were at least 10 Å, the thickness of the slab model was at least 10 Å, the number of atoms of each element contained in the system was an integer multiple of the unit crystal, and the thickness of the vacuum layer was 20 Å.

[0063] Na synthesized in Example 1 ５ Zn ２ S ４ The surface energy of Br was calculated using the above method to evaluate its thermal stability. The bulk crystal structure used in the calculation was obtained by optimizing the experimental structure. The results are shown in Table 3 below.

[0064] Na synthesized in Example 2 ４．８ Zn １．８ Ga ０．２ S ４ The surface energy of Br was calculated by the above method to evaluate the thermal stability. The bulk crystal structure used for the calculation was a supercell Na ４０ Zn １６ S ３２ Br ８ Create a new Zn atom, replace three Zn atoms with Ga atoms, and delete one Na atom adjacent to each replaced Zn atom, resulting in a total of three Na atoms.７７ Ga ３ Zn ２９ S ６４ Br １６ By doing so, Na ４．８ Zn １．８ Ga ０．２ S ４ A structure with a composition ratio close to that of Br was obtained. This structure was then optimized to produce a bulk crystal structure. The results are shown in Table 3 below.

[0065] Na synthesized in Example 3 ４．８ Zn １．８ In ０．２ S ４ The surface energy of Br was calculated by the above method to evaluate the thermal stability. The bulk crystal structure used in the calculation was obtained by substituting In for Ga in the structure of Example 2. ７７ In ３ Zn ２９ S ６４ Br １６ By doing so, Na ４．８ Zn １．８ In ０．２ S ４ A structure with a composition ratio close to that of Br was obtained. This structure was then optimized to produce a bulk crystal structure. The results are shown in Table 3 below.

[0066] Na synthesized in Example 4 ５ Zn ２ S ４ The surface energy of SH was calculated using the above method to evaluate its thermal stability. The bulk crystal structure used in the calculation was obtained by optimizing the experimental structure. The optimized structure was used as the bulk crystal structure. The results are shown in Table 3 below.

[0067] Na synthesized in Example 5 ４．８ Zn １．８ In ０．２ S ４ The surface energy of SH was calculated by the above method to evaluate its thermal stability. The bulk crystal structure used for the calculation was a supercell Na ４０ Zn １６ S ３２ (SH) ８Create a new Zn atom, replace three Zn atoms with In atoms, and delete one Na atom adjacent to each replaced Zn atom, resulting in a total of three Na atoms. ７７ Ga ３ Zn ２９ S ６４ Br １６ By doing so, Na ４．８ Zn １．８ Ga ０．２ S ４ A structure with a composition ratio close to that of Br was obtained. This structure was then optimized to produce a bulk crystal structure. The results are shown in Table 3 below.

[0068] The Li bodies in which Na in Examples 1 to 5 was replaced with Li were used as the chalcogenide-containing compounds in Examples 10 to 14, respectively, and the surface energy of the compounds was calculated using the above method to evaluate their thermal stability. These structures were obtained by replacing Na in Examples 1 to 5 with Li and optimizing the structure to form bulk crystal structures. The results are shown in Table 3 below.

[0069] Li, known as a solid electrolyte ３ ClO and LiBH ４ The surface energy was calculated using the above method to evaluate the thermal stability of the compounds of Comparative Examples 4 and 5. The structure files for these compounds were obtained from the Materials Project, and structural optimization was performed to obtain the bulk crystal structure. The results are shown in Table 3 below.

[0070]

[0071] As shown in Table 3 above, the compounds of Examples 1 to 5 and 10 to 14 each have an average surface energy of 1.5 J / m ２ The comparative compound, which is experimentally known to have low thermal stability, has a surface energy of 2.0 J / m ２ This indicates that the compounds of Examples 1 to 5 and 10 to 14 have high thermal stability.

Claims

1. A compound represented by the following composition formula (1): ｘ M ｙ M ２ ｚ Ch ４ X (1) (In formula (1), A is at least one element selected from the group consisting of alkali metals and Ag, M is at least one element selected from the group consisting of Zn, Mn, and Fe, and M ２ is a metal element other than A and M, Ch is at least one element selected from the group consisting of O, S, Se, and Te, and X is F, Cl, Br, I, OH, SH, BF ４ , and BH ４ and x, y, and z are 3≦x≦5.5, 1.5≦y≦2.5, and 0≦z≦1.0, respectively.

2. The compound according to claim 1, which has within its crystal structure a one-dimensional chain of linked octahedral structures centered around an alkali metal ion and a one-dimensional chain of linked tetrahedral structures centered around a metal ion, and the one-dimensional chains of linked octahedral structures and the one-dimensional chains of linked tetrahedral structures are arranged alternately.

3. The compound according to claim 1 or 2, having a tetragonal or orthorhombic crystal structure.

4. Space group is I4mm, I4 / mmm, or P2 １ The compound according to claim 1 or 2, having a crystal structure assigned to ab.

5. A solid electrolyte comprising the compound according to claim 1 or 2.

6. A positive electrode material containing the compound according to claim 1 or 2.

7. A dielectric material comprising the compound according to claim 1 or 2.

8. A battery containing the compound according to claim 1 or 2.

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