Compound and method for producing same, solid electrolyte, and power storage device

Abstract

This compound satisfies formula (1). In formula (1), α and β each independently represent a value more than 0, γ represents a value more than 0 but less than 6, D represents an alkali metal element, M includes an element that becomes a metallic cation other than an alkali metal element, X represents a halogen, and A represents an atomic group that becomes a polyatomic anion including two or more types of elements. (1): DαMβX6-γAγ

Description

Compound and method for producing the same, solid electrolyte, and electricity storage device

[0001] [Cross-reference to related applications] This application claims priority to Japanese Patent Application No. 2024-057325 filed on March 29, 2024, and Japanese Patent Application No. 2024-117673 filed on July 23, 2024, the entireties of which are incorporated herein by reference. The present disclosure relates to a compound and a method for producing the same, a solid electrolyte, and an electricity storage device.

[0002] Various types of power storage devices have been put to practical use, including various secondary batteries such as nickel-metal hydride secondary batteries and lithium-ion secondary batteries, as well as electric double-layer capacitors. Among these, lithium-ion secondary batteries (LIBs) are used in a wide range of applications due to their high energy density and battery capacity.

[0003] Lithium ion secondary batteries, which are widely used as energy storage devices, have a negative electrode, a positive electrode, and an electrolyte, and are charged and discharged by transferring lithium ions between the electrodes via the electrolyte. Conventionally, nonaqueous electrolytes have been primarily used as the electrolyte. However, nonaqueous electrolytes contain flammable organic solvents, which raise concerns about electrolyte leakage and short circuits within the battery due to overcharge and overdischarge. In light of these issues, all-solid-state lithium ion secondary batteries using solid electrolytes with lithium ion conductivity instead of nonaqueous electrolytes have been investigated (see, for example, Patent Document 1).

[0004] On the other hand, lithium, which is the raw material for all-solid-state lithium-ion secondary batteries, is facing concerns about rising raw material prices, depletion, etc. In recent years, various studies have been conducted on sodium-ion secondary batteries (SIBs), which use sodium, an abundant and inexpensive resource, as a post-lithium-ion secondary battery that uses an element to replace lithium, a rare metal, and perform charging and discharging by the movement of sodium ions (see, for example, Patent Document 2).

[0005] JP 2023-49975 A International Publication No. 2019 / 003846

[0006] Known ionically conductive solid electrolytes include sulfide-based solid electrolytes, oxide-based solid electrolytes, and halogen-based solid electrolytes. Among these, halogen-based solid electrolytes have high ionic conductivity and plastic deformability, and are therefore expected to be used as electrolyte materials for all-solid-state batteries. However, from the perspective of commercializing all-solid-state batteries, conventional halogen-based solid electrolytes still lack sufficient ionic conductivity, leaving room for further improvement. In particular, new solid electrolyte materials capable of exhibiting high ionic conductivity are needed to achieve high capacity and high power output in secondary batteries such as LIBs and SIBs.

[0007] The present disclosure has been made in view of the above circumstances, and one of its objects is to provide a novel halogen-based compound that exhibits high ionic conductivity.

[0008] As a result of intensive research to solve the above problems, the present inventors have found that a halogen-based compound exhibiting good ionic conductivity can be obtained by substituting a portion of the halogen element in a specific compound having a halogen element as a constituent component with an atomic group that forms a polyatomic anion containing two or more elements. Specifically, the present disclosure provides the following compound, a method for producing the same, a solid electrolyte, and an electricity storage device.

[0009] [1] A compound satisfying the following formula (1): D α M β X ６－γ A γ ... (1) (In formula (1), α and β are each independently a value greater than 0, γ is a value greater than 0 and less than 6, D is an alkali metal element, M contains an element that becomes a metal cation other than an alkali metal element, X is a halogen element, and A is an atomic group that becomes a polyatomic anion containing two or more elements.) [2] The compound according to [1], wherein D in the above formula (1) is Na. [3] The ionic radius of the element that becomes a metal cation other than an alkali metal is r Ｍ When [Å], 0.4≦r ＭThe compound according to [1] or [2], wherein M in the formula (1) contains at least one element selected from the group consisting of Ta, Zr, Hf, Ge, Ga, Sn, and Sc. [4] The compound according to any one of [1] to [3], wherein A in the formula (1) has an oxygen atom. [6] The compound according to any one of [1] to [5], wherein A in the formula (1) contains an atomic group that becomes an inorganic polyatomic anion. [7] The ionic radius of A in the formula (1) is r Ａ When [Å], 0.9≦r Ａ The compound according to any one of [1] to [6], which satisfies the following formula (2): Na1+y1+2×(y2)+3×(y3)+z1+2×(z2)+3×(z3)Ta1-y1-y2-y3M1 ｙ１ M2 ｙ２ M3 ｙ３ Cl6-z1-z2-z3A1 ｚ１ A2 ｚ２ A3 ｚ３... (2) (In formula (2), y1, y2, y3, z1, z2, and z3 each independently represent a value of 0 or greater, M1 is an element that forms a tetravalent metal cation, M2 is an element that forms a trivalent metal cation, M3 is an element that forms a divalent metal cation, A1 is an atomic group that contains two or more elements and forms a divalent polyatomic anion, A2 is an atomic group that contains two or more elements and forms a trivalent polyatomic anion, and A3 is an atomic group that contains two or more elements and forms a tetravalent polyatomic anion, and the relationships 0<y1+y2+y3<1 and 0<z1+z2+z3<6 are satisfied.)

[10] The compound according to any one of [1] to [9], in which the mass fraction of an amorphous phase is 10% or greater.

[11] A method for producing the compound according to any one of [1] to

[10] , comprising the steps of: weighing out a plurality of supply components each containing one or more elements selected from D, M, X, and A in formula (1) above so as to satisfy the stoichiometric ratio of the composition represented by formula (1), and pulverizing the weighed plurality of supply components under cooling with a cooling medium.

[12] A solid electrolyte comprising the compound according to any one of [1] to

[10] .

[13] An electricity storage device comprising the solid electrolyte according to

[12] .

[0010] According to the present disclosure, a novel halogen-based compound exhibiting high ionic conductivity can be obtained. Furthermore, by using the compound of the present disclosure as an electrolyte for an electricity storage device such as a secondary battery or a capacitor, it is possible to obtain an electricity storage device that combines high ionic conductivity with the safety ensured by solidifying the electrolyte.

[0011] Fig. 1 is a schematic diagram of a milling apparatus equipped with a cooling mechanism using a cooling medium. Fig. 2 is a schematic diagram of a press die used to prepare sample pellets. Fig. 3 shows the results of LSV evaluation of compounds SE-4 and SE-10.

[0012] The compound, solid electrolyte, and electricity storage device of the present disclosure will be described in detail below.

[0013] <Compound> The compound of the present disclosure is a halogen-based compound that satisfies the following formula (1): D α M β X ６－γ Aγ ...(1) (In formula (1), α and β are each independently a value greater than 0, γ is a value greater than 0 and less than 6, D is an alkali metal element, M contains an element other than an alkali metal element that becomes a metal cation, X is a halogen element, and A is an atomic group that contains two or more elements and becomes a polyatomic anion.)

[0014] In the above formula (1), D is an alkali metal element. Examples of D include at least one element selected from the group consisting of Li, Na, and K. In terms of exhibiting high ionic conductivity, D preferably contains at least one of Li and Na, and more preferably Li or Na. When D is Li, a compound satisfying the above formula (1) is suitable as a solid electrolyte material for an electricity storage device in which the ion-conducting carrier is a lithium ion. When D is Na, a compound satisfying the above formula (1) is suitable as a solid electrolyte material for an electricity storage device in which the ion-conducting carrier is a sodium ion. In particular, Na is an abundant and inexpensive resource, making it useful as a solid electrolyte material for practical use of electricity storage devices.

[0015] M contains an element that can form a metal cation other than an alkali metal. Examples of elements that can form a metal cation other than an alkali metal include elements that can form cations among Groups 2 to 17 of the elements. Specific examples include Ta, Y, Ce, Ti, Ni, Zr, Ga, Ge, Hf, Ca, Te, Sr, Mg, Al, V, Cr, Mn, Fe, Co, Cu, Zn, Nb, Mo, Tc, Ru, Rh, Pd, Cd, Sn, Sb, Ba, La, In, W, Pb, Sm, Eu, Tb, Dy, Tl, Bi, Sc, and Ag. M may contain only one element that can form a metal cation other than an alkali metal, or may contain two or more elements.

[0016] From the viewpoint of obtaining a compound with higher ionic conductivity, the element contained in M ​​that becomes a metal cation other than an alkali metal should have an ionic radius of r Ｍ When [Å], 0.3≦r Ｍ ≦1.0, and 0.4≦r ＭIt is more preferable that the relationship satisfies ≦0.9. The valence of the element contained in M ​​that becomes a metal cation other than an alkali metal is not particularly limited, but is preferably pentavalent or less. Furthermore, M preferably contains an element that is tetravalent or less, and more preferably contains an element that is trivalent or less. It is presumed that by lowering the valence of the element that becomes a metal cation other than an alkali metal, the amount of alkali metal ions that move within the compound increases due to charge compensation, thereby achieving both good oxidation resistance and high ionic conductivity.

[0017] When M contains a tetravalent or less element as an element that forms a metal cation other than an alkali metal, it may further contain a pentavalent or more element in addition to the tetravalent or less element as an element that forms a metal cation other than an alkali metal. Similarly, when M contains a trivalent or less element as an element that forms a metal cation other than an alkali metal, it may further contain a tetravalent or more element in addition to the trivalent or less element as an element that forms a metal cation other than an alkali metal.

[0018] In particular, the element contained in M ​​that becomes a metal cation other than an alkali metal is 0.3≦r Ｍ ≦1.0 and contains an element with a valence of 5 or less, it is preferable in that the ionic conductivity of the compound satisfying the above formula (1) can be further increased. Ｍ More preferably, M satisfies the following condition: ≦0.9. Specifically, M preferably contains at least one element selected from the group consisting of Ta, Y(3+), Ce(4+), Ti(2+), Ni(4+), Zr, Ga, Ge, Hf, Ca, Te, In, Bi, Sn, and Sc, more preferably contains at least one element selected from the group consisting of Ta, Y(3+), Ce(4+), Ti(2+), Ni(4+), In, Zr, Ga, Ge, Hf, Sn, and Sc, and particularly preferably contains at least one element selected from the group consisting of Ta, Zr, Hf, Ge, Ga, Sn, and Sc.

[0019] M may contain an element that forms a metal cation other than an alkali metal, as well as an element that forms a non-metal cation. The element that forms a non-metal cation may be at least one selected from the group consisting of Si, P, and B. From the viewpoint of obtaining a compound with superior ionic conductivity, M is preferably an element that forms a metal cation other than an alkali metal.

[0020] X is a halogen element. Examples of X include at least one selected from the group consisting of F (fluorine), Cl (chlorine), Br (bromine), and I (iodine). From the viewpoint of obtaining a compound having both good oxidation resistance and high ionic conductivity, X preferably contains Cl, and more preferably is Cl.

[0021] A is an atomic group that becomes a polyatomic anion containing two or more elements (hereinafter, simply referred to as a "polyatomic anion"). The type of elements that constitute the polyatomic anion is not particularly limited, and may be a typical element, a transition element, or a combination thereof. Specific examples of polyatomic anions that give the atomic group A include OH, － , NO ３ － , C.H. ３ COO － , (SO ４ ) ２－ , (CO ３ ) ２－ , (PO ４ ) ３－ , (BO ３ ) ３－ , (MnO) ４－ , (ZnCl ４ ) ２－ , (AlCl ４ ) － , (BCl ４ ) － , (CoF ６ ) ２－ , (BeF ４ ) ２－ , (NiF ６ ) ２－ and (SiO ４ ) ４－ A may contain only one type of atomic group that becomes a polyatomic anion, or may contain two or more types of atomic groups that become polyatomic anions.

[0022] Among the above, A preferably has an oxygen atom. Furthermore, from the viewpoint of ionic conductivity, A preferably contains an inorganic polyatomic anion. Halogen-based compounds in which a portion of halogen elements is replaced with polyatomic anions have the advantage of exhibiting high ionic conductivity and being easily synthesized.

[0023] It is also possible to use, for example, metal oxide crystals or metal peroxides as raw materials for halogen-based solid electrolytes. However, metal oxide crystals are generally hard and have poor plastic deformability. Therefore, there is a concern that the presence of metal oxide crystals in the halogen-based solid electrolyte may reduce the plastic deformability of the solid electrolyte and prevent the formation of a good interface with the electrode active material or current collector. Furthermore, when mixed with flammable or easily oxidized substances, metal peroxides generally react easily due to heating, impact, or friction, making them difficult to handle. In contrast, by substituting a portion of the halogen element with an atomic group that forms a polyatomic anion, it is possible to obtain a solid electrolyte that is easy to handle and exhibits high ionic conductivity while fully maintaining the plastic deformability, one of the characteristics of halogen-based solid electrolytes.

[0024] From the viewpoint of obtaining a compound with higher ionic conductivity, the ionic radius of A in the above formula (1) is r Ａ When [Å], 0.8≦r Ａ ≦2.9, and 0.9≦r Ａ ≦2.7, and more preferably 1.0≦r Ａ It is more preferable that 1.1≦r Ａ It is more preferable that the valence of the polyatomic anion of the atomic group constituting A is not particularly limited, but it is preferable that the atomic group constituting A is an atomic group that becomes a polyatomic anion with a valence of 2 or more, and it is more preferable that the atomic group constituting A is an atomic group that becomes a polyatomic anion with a valence of 3 or more. It is presumed that by increasing the valence of the polyatomic anion, the amount of alkali metal ions that move within the compound increases due to charge compensation, thereby realizing high ionic conductivity while exhibiting good oxidation resistance.

[0025] When A contains an atomic group that forms a divalent or higher polyatomic anion as an atomic group that forms a polyatomic anion, A may further contain an atomic group that forms a monovalent polyatomic anion in addition to the atomic group that forms a divalent or higher polyatomic anion. Similarly, when A contains an atomic group that forms a trivalent or higher polyatomic anion, A may further contain an atomic group that forms a monovalent or divalent polyatomic anion in addition to the atomic group that forms a trivalent or higher polyatomic anion.

[0026] In order to increase the ionic conductivity of the compound satisfying the above formula (1), A is an atomic group that becomes a polyatomic anion having a valence of two or more, and 0.8≦r Ａ Furthermore, A is an atomic group that becomes a divalent or higher polyatomic anion, and 0.9≦r Ａ ≦2.7, and more preferably 1.0≦r Ａ It is more preferable that 1.1≦r Ａ It is more preferable that A satisfies the following: (SO ４ ) ２－ , (CO ３ ) ２－ , (PO ４ ) ３－ , (BO ３ ) ３－ , (MnO) ４－ and (SiO ４ ) ４－ At least one selected from the group consisting of (CO ３ ) ２－ , (BO ３ ) ３－ , (PO ４ ) ３－ , (SO ４ ) ２－ and (SiO ４ ) ４－ More preferably, at least one selected from the group consisting of (CO ３ ) ２－ , (BO ３ ) ３－ and (PO ４ ) ３－Furthermore, it is particularly preferable that A contains an atomic group that becomes a trivalent or higher polyatomic anion, in that the effect of improving the ionic conductivity of the compound that satisfies the above formula (1) can be further enhanced and good oxidation resistance can be ensured.

[0027] In the above formula (1), α and β are each a value greater than 0. When α and β are expressed as the ratio of α to β (α / β), they preferably satisfy 1.0<α / β≦3.0, more preferably 1.1≦α / β≦2.5, even more preferably 1.2≦α / β≦2.4, and even more preferably 1.4≦α / β≦2.1. When α / β satisfies the above range, the ratio of alkali metal elements that can serve as ion-conducting carriers is optimized, and a compound with highly enhanced ion conductivity can be obtained.

[0028] γ is a value greater than 0 and smaller than 6. From the viewpoint of obtaining a compound with excellent ionic conductivity, γ is preferably 0.05 or more, more preferably 0.10 or more, even more preferably 0.15 or more, and even more preferably 0.20 or more. Furthermore, γ is preferably 5 or less, more preferably 3 or less, even more preferably 1 or less, and even more preferably 0.50 or less. When γ is expressed as the ratio of γ to β (γ / β), it is preferable that 0.10≦γ / β≦0.50 is satisfied, more preferably 0.15≦γ / β≦0.45 is satisfied, and even more preferably 0.20≦γ / β≦0.40 is satisfied.

[0029] The halogen-based compound of the present disclosure may satisfy the above formula (1). Among these, it is particularly preferable that the halogen-based compound of the present disclosure satisfies the following formula (2): Na1+y1+2×(y2)+3×(y3)+z1+2×(z2)+3×(z3)Ta1-y1-y2-y3M1 ｙ１ M2 ｙ２ M3 ｙ３ Cl6-z1-z2-z3A1 ｚ１ A2 ｚ２ A3 ｚ３... (2) (In formula (2), y1, y2, y3, z1, z2, and z3 each independently represent a value of 0 or greater; M1 is an element that forms a tetravalent metal cation; M2 is an element that forms a trivalent metal cation; M3 is an element that forms a divalent metal cation; A1 is an atomic group that contains two or more elements and forms a divalent polyatomic anion; A2 is an atomic group that contains two or more elements and forms a trivalent polyatomic anion; A3 is an atomic group that contains two or more elements and forms a tetravalent polyatomic anion; and the relationships 0 < y1 + y2 + y3 < 1 and 0 < z1 + z2 + z3 < 6 are satisfied.)

[0030] In the above formula (2), M1, M2, and M3 each represent an element that forms a tetravalent metal cation, an element that forms a trivalent metal cation, or an element that forms a divalent metal cation, among the above-mentioned specific examples of M. Furthermore, A1, A2, and A3 each represent an atomic group that forms a divalent polyatomic anion, an atomic group that forms a trivalent polyatomic anion, or an atomic group that forms a tetravalent polyatomic anion, among the above-mentioned specific examples of A.

[0031] Regarding y1, y2, and y3, in order to obtain a compound exhibiting higher Na ion conductivity, it is preferable that y1 > 0.10, more preferably y1 > 0.12, and even more preferably y1 > 0.15 are satisfied. Also, it is preferable that y1 < 0.40, more preferably y1 < 0.35, and even more preferably y1 < 0.30 are satisfied.

[0032] The relationship between y2 and y3 may be y2+y3=0, but it is preferable that y2+y3>0, more preferably y2+y3>0.05, and even more preferably y2+y3>0.10. It is also preferable that y2+y3<0.30, more preferably y2+y3<0.25, and even more preferably y2+y3<0.20.

[0033] Furthermore, it is preferable that y1 + y2 + y3 > 0.10 is satisfied, more preferably that y1 + y2 + y3 > 0.15 is satisfied, and even more preferably that y1 + y2 + y3 > 0.20 is satisfied. It is also preferable that y1 + y2 + y3 < 0.70 is satisfied, more preferably that y1 + y2 + y3 < 0.65 is satisfied, and even more preferably that y1 + y2 + y3 < 0.60 is satisfied.

[0034] Regarding z1, z2, and z3, in order to obtain a compound exhibiting higher Na ion conductivity, it is preferable that z1 > 0.10, more preferably z1 > 0.12, and even more preferably z1 > 0.15 are satisfied. It is also preferable that z1 < 0.40, more preferably z1 < 0.35, and even more preferably z1 < 0.30 are satisfied.

[0035] The relationship between z2 and z3 may be z2+z3=0, preferably z2+z3>0, more preferably z2+z3>0.05, and even more preferably z2+z3>0.10. Furthermore, the relationship z2+z3<0.30 is preferably satisfied, more preferably z2+z3<0.25, and even more preferably z2+z3<0.20 is satisfied.

[0036] Furthermore, it is preferable that z1 + z2 + z3 > 0.10 is satisfied, more preferably that z1 + z2 + z3 > 0.15 is satisfied, and even more preferably that z1 + z2 + z3 > 0.20 is satisfied. It is also preferable that z1 + z2 + z3 < 5 is satisfied, more preferably that z1 + z2 + z3 < 3 is satisfied, even more preferably that z1 + z2 + z3 < 1 is satisfied, and even more preferably that z1 + z2 + z3 ≦ 0.5 is satisfied.

[0037] In the above general formula representing the halogen-based compound of the present disclosure, the sum of the stoichiometric ratios of X (halogen element) and A (atomic group that becomes a polyatomic anion) is 6, but the sum of the stoichiometric ratios of X and A does not have to be strictly 6 as long as the charge neutrality of the halogen-based compound as a whole can be maintained. In other words, the sum of the stoichiometric ratios of X and A in the halogen-based compound may be a value less than 6 or may be a value greater than 6, as long as the charge neutrality of the halogen-based compound as a whole can be maintained. For example, D α M β X ６－（γ±δ） A γ±δ (where 0≦δ≦1 is satisfied, and D, M, X, A, α, β, and γ have the same meanings as D, M, X, A, α, β, and γ in formula (1) above) are also included in the halogen-based compounds of the present disclosure, as long as the compound as a whole maintains charge neutrality.

[0038] The halogen-based compound of the present disclosure is solid at room temperature (25°C). The halogen-based compound of the present disclosure may be crystalline or amorphous. In order to exhibit higher ionic conductivity, the halogen-based compound of the present disclosure preferably has an amorphous phase. Specifically, the mass fraction of the amorphous phase (hereinafter also referred to as "amorphous mass fraction") of the halogen-based compound of the present disclosure is preferably 3% or more, more preferably 10% or more, even more preferably 30% or more, even more preferably 50% or more, even more preferably 70% or more, and even more preferably 85% or more. The upper limit of the amorphous mass fraction is not particularly limited, but is, for example, 99% or less, preferably 95% or less. In this specification, the amorphous mass fraction is a value determined by X-ray diffraction (XRD) using a reference intensity ratio (RIR) as a standard. Details of the measurement method follow the method described in the Examples below.

[0039] The amorphous mass fraction of a halogen-based compound satisfying the above formula (1) can be adjusted arbitrarily by adjusting the grinding time and temperature of the raw materials when producing the halogen-based compound, or by adjusting the type of A and the amount of doping. For example, the amorphous mass fraction can be increased by bringing the grinding time of the raw materials closer to a predetermined time. This is thought to be because, while extending the grinding time of the raw materials can promote amorphization, if the grinding time of the raw materials is too long, thermal relaxation occurs due to heat generated during grinding, and crystallization progresses. Furthermore, for example, the amorphous mass fraction can be increased by increasing the type of A to make the compound multi-component.

[0040] The composition of the halogen-based compound satisfying the formula (1) can be determined by a known analytical method. Specifically, the compositions of D, M, and X can be determined by energy dispersive X-ray spectroscopy or X-ray photoelectron spectroscopy. The composition of A can also be determined by combining the above spectroscopy with Raman spectroscopy or infrared spectroscopy.

[0041] <Method for producing a compound satisfying formula (1)> The compound satisfying formula (1) is typically a compound represented by the formula D α M β X ６ In a halide having a basic skeleton of the formula (1), a part of the halogen element (X) is substituted with an atomic group (A) that becomes a polyatomic anion containing two or more elements. There are no particular limitations on the method for producing the compound satisfying the formula (1). The compound satisfying the formula (1) can be produced, for example, by a method including the following weighing and pulverizing steps. Weighing step: A step of weighing multiple feed components each containing one or more elements selected from D, M, X, and A in the formula (1) so as to satisfy the stoichiometric ratio of the composition shown in the formula (1). Pulverizing step: A step of pulverizing the multiple feed components weighed in the weighing step. Each step will be described in detail below.

[0042] (Weighing Step) As raw materials for the compound satisfying the above formula (1), for the D supply component (alkali metal element supply component), M supply component (supply component of an element that becomes a metal cation other than an alkali metal element), X supply component (halogen element supply component), and A supply component (supply component of an atomic group that becomes a polyatomic anion), supply components corresponding to elements for obtaining a target halogen-based compound can be used.

[0043] Examples of the D supply component, M supply component, X supply component, and A supply component for obtaining a compound satisfying the above formula (1) include carbonates, bicarbonates, sulfates, sulfites, nitrates, nitrites, phosphates, acetates, citrates, borates, silicates, oxides, hydroxides, halides (e.g., chlorides), sulfides, etc., containing these elements. The supply components may be compounds containing two or more of the elements D, M, X, and A. Alkali metal salts and / or halides are preferably used as supply components because they can efficiently produce compounds satisfying the above formula (1). When obtaining a halogen-based compound having an amorphous phase as a compound satisfying the above formula (1), it does not matter whether the supply component is amorphous. That is, the supply component may have a crystalline phase or an amorphous phase. Furthermore, the supply component may be solid, liquid, or gaseous.

[0044] The weighing of the feed components can be carried out according to a conventional method so as to satisfy the stoichiometric ratio of the composition shown in the above formula (1). When the feed components are weighed, it is preferable to carry out the weighing under an inert gas atmosphere (for example, an argon atmosphere or a nitrogen atmosphere). Note that, if a part of the halogen element volatilizes when the feed components are mixed while applying mechanical energy to them in the subsequent mixing step, it is advisable to weigh the feed components taking the volatile content into consideration.

[0045] (Pulverization Step) In the pulverization step, it is preferable to pulverize the multiple feed components weighed in the weighing step while applying mechanical energy. It is presumed that this method causes a mechanochemical reaction of the multiple feed components to cause the mixture to become amorphous, resulting in a compound exhibiting high ionic conductivity. The method for pulverizing the feed components while applying mechanical energy (i.e., mechanochemically) is not particularly limited. For example, the pulverization can be carried out using various devices such as a ball mill (such as a planetary ball mill), a bead mill, a blender, a homogenizer, a stamp mill, a homomixer, or a disperser mixer. Furthermore, when producing a compound satisfying the above formula (1) on a small scale, the pulverization can be carried out by mixing the multiple feed components placed in a mortar with a pestle.

[0046] The feed components may be pulverized by a dry method or a wet method. Among these, the dry pulverization method is industrially advantageous because it does not require a step of removing the solvent when producing a compound satisfying the above formula (1), yet it can produce a halogen-based compound exhibiting high ionic conductivity.

[0047] The temperature of the feed components when pulverizing the feed components is not particularly limited. In the pulverization step, the pulverization of the feed components may be performed at room temperature or under cooling. Furthermore, the treatment of pulverizing the feed components may be performed multiple times. When the treatment of pulverizing the feed components is performed multiple times, the treatment conditions (pulverization method, temperature, time, etc.) in each pulverization treatment may be the same or different. For example, a pretreatment may be performed in which multiple feed components are pulverized while being lightly mixed at room temperature, followed by a main treatment in which the mixture obtained by the pretreatment is pulverized at room temperature or under cooling, thereby obtaining the halogen-based compound of the present disclosure.

[0048] In the pulverization step, it is preferable to pulverize the multiple feed components weighed in the weighing step under cooling, as this allows for the production of halogen-based compounds with higher ionic conductivity. This method allows for continuous cooling at low temperatures (e.g., below 0°C) during the pulverization process of the feed components. This suppresses thermal relaxation during pulverization, thereby suppressing crystallization of the product (specifically, the product synthesized by the mechanochemical reaction), presumably enabling the production of halogen-based compounds with a higher amorphous mass fraction. Furthermore, it is presumed that the increased brittleness of the compound at low temperatures allows the production of compounds with smaller particle sizes compared to pulverization at room temperature.

[0049] The method for cooling the multiple feed components is not particularly limited, but is preferably carried out using a cooling medium, which simplifies the pulverization process. The cooling medium may be solid, liquid, or gas, or a combination of two or more of these. Examples of cooling mediums include ice, dry ice, cold water, liquid nitrogen, liquid argon, and liquid helium. The cooling temperature is preferably −20°C or lower, more preferably −40°C or lower, even more preferably −60°C or lower, even more preferably −80°C or lower, and particularly preferably −90°C or lower. By pulverizing the feed components at such low temperatures, a halogen-based compound exhibiting higher ionic conductivity can be obtained. Furthermore, liquid nitrogen is particularly preferred as the cooling medium, since it allows for easy cooling at temperatures of −80°C or lower, preferably −90°C or lower.

[0050] An example of a milling apparatus 10 equipped with a cooling mechanism using a cooling medium is shown in Fig. 1. The milling apparatus 10 shown in Fig. 1 is a planetary ball mill.

[0051] 1, a milling processing device 10 includes a bottomed main body 11 having an opening at the top, and a lid 12 that covers and seals the opening of the main body 11. The main body 11 is an insulated container large enough to accommodate a milling pot 13 therein, and when the milling pot 13 is accommodated therein, a gap 14 is formed between the periphery of the milling pot 13 and the inner wall of the main body 11.

[0052] The milling pot 13 is a sealed container comprising a pot body 13a and a lid 13b, and during milling, a sample M to be milled and milling balls 15 are housed inside the container. The pot body 13a is made of, for example, metal or ceramic. The milling balls 15 are appropriately selected from known milling balls made of materials such as metal, ceramic, or natural ore. The milling processing device 10 includes a support 16 that supports the milling pot 13 when it is housed inside the body 11, and a rotation mechanism 17 that rotates and revolves the milling pot 13 supported by the support 16. The support 16 supports the milling pot 13 by clamping the side surfaces of the milling pot 13 from above.

[0053] The milling processing device 10 is provided with a cooling mechanism 18 that cools the milling pot 13 housed in the main body 11 with a cooling medium L. Specifically, the milling processing device 10 has a supply port 18a formed at the opening of the main body 11, allowing the cooling medium L to be supplied to the gap 14 from the outside via the supply port 18a. In addition, a flow port 18b is formed at the top of the support 16, connecting the gap 14 with the space above the milling pot 13 installed in the main body 11, allowing the cooling medium L to be supplied above the milling pot 13 via the flow port 18b. Liquid nitrogen is preferably used as the cooling medium L.

[0054] When milling a sample M using the milling processing device 10, the sample M and milling balls 15 are first placed inside the pot body 13a, which is then sealed with the lid 13b. The milling pot 13 is then clamped by the supports 16 and set inside the body 11. Thereafter, a cooling medium L is introduced through the supply port 18a to fill the surroundings (sides and above) of the milling pot 13 with the cooling medium L. The milling pot 13 is then sealed with the lid 12, and the rotation mechanism 17 is then operated. As a result, the milling pot 13 rotates and revolves while constantly in contact with the cooling medium L, and the sample M is milled under cooling by the cooling medium L.

[0055] When the process of grinding the plurality of feed components is carried out under cooling with the cooling medium L, the milling time is, for example, 10 to 180 minutes, and preferably 20 to 150 minutes. The rotation and revolution speed of the milling pot 13 is, for example, 50 to 500 rpm, and preferably 100 to 450 rpm.

[0056] Furthermore, when the grinding treatment of the feed components is carried out at room temperature, it is preferable to alternately carry out the grinding treatment and the cooling treatment in order to prevent the promotion of crystallization of the product due to the heat generated during grinding. In this case, the cooling treatment may be natural cooling by leaving it at room temperature, or cooling using a cooling means (for example, cooling using a refrigerator, dry ice, a blower, etc.). From the viewpoint of preventing the promotion of crystallization of the product and obtaining a halogen-based compound with superior ionic conductivity, in the grinding treatment at room temperature, the total grinding treatment time is preferably 100 hours or less, more preferably 75 hours or less, and even more preferably 60 hours or less.

[0057] In this manner, a compound satisfying the above formula (1) can be obtained. Since the compound satisfying the above formula (1) has high alkali metal ion conductivity, when used as a solid electrolyte material for an electricity storage device, an electricity storage device with high ion conductivity can be obtained.

[0058] <Solid Electrolyte> The solid electrolyte of the present disclosure (hereinafter also referred to as "the present electrolyte") contains a compound satisfying the above formula (1). The present electrolyte may further contain a component (hereinafter also referred to as "other component") different from the compound satisfying the above formula (1). The other component is not particularly limited. Examples of the other component include an organic solid electrolyte, an inorganic solid electrolyte other than the compound satisfying the above formula (1) (e.g., a ceramic electrolyte, a glass electrolyte, etc.), a binder, a conductive additive (carbon, etc.), etc. The content of the other component in the present electrolyte can be appropriately set within a range that does not impair the effects of the present disclosure.

[0059] When a compound satisfying the above formula (1) is used as a solid electrolyte material, the average particle diameter of the compound satisfying the above formula (1) is, for example, a number average particle diameter of 0.01 μm or more and 20 μm or less, as determined by analyzing particle images observed with a scanning electron microscope. From the viewpoint of material handleability, the number average particle diameter of the compound satisfying the above formula (1) is preferably 0.05 μm or more, more preferably 0.1 μm or more. When a compound satisfying the above formula (1) is used as a solid electrolyte by mixing it with a positive electrode active material or a negative electrode active material, it is believed that a smaller particle diameter of the compound satisfying the above formula (1) makes it easier to penetrate into the gaps between the active materials, thereby reducing voids in the positive electrode layer or the negative electrode layer and improving the performance of the energy storage device. From this viewpoint, the number average particle diameter of the compound satisfying the above formula (1) is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 1 μm or less, and even more preferably 0.5 μm or less.

[0060] In general, to achieve high ionic conductivity in inorganic solid electrolytes, powders are compacted and then sintered at high temperatures to improve the bonding between particles and between electrodes and the electrolyte, thereby reducing interfacial resistance. However, sintering is a process that requires a lot of energy, and industrialization requires the introduction of large-area sintering equipment. In this regard, compounds that satisfy the above formula (1) are also useful in that they can exhibit high ionic conductivity without sintering.

[0061] For a compound satisfying the above formula (1), the ionic conductivity measured at 25°C using an AC impedance method is preferably 0.30 mS / cm or more. From the viewpoint of obtaining an electricity storage device with excellent performance, the ionic conductivity under the same conditions is more preferably 0.35 mS / cm or more, even more preferably 0.40 mS / cm or more, even more preferably 0.60 mS / cm or more, and even more preferably 1.0 mS / cm or more. Details of the method for measuring ionic conductivity follow the method described in the Examples below.

[0062] <Electricity Storage Device> The electricity storage device of the present disclosure (hereinafter also referred to as "the device") includes a solid electrolyte containing a compound satisfying the above formula (1). Examples of the device include secondary batteries and capacitors. When the device is a secondary battery, one embodiment is an all-solid-state battery. In this case, a compound in which D in the above formula (1) is Na is preferably applicable to sodium ion secondary batteries because of its excellent Na ion conductivity. Furthermore, a compound in which D in the above formula (1) is Li is preferably applicable to lithium ion secondary batteries because of its excellent Li ion conductivity.

[0063] In a secondary battery, assuming storage in a charged state, the higher the electronic conductivity of the solid electrolyte, the faster the self-discharge rate and the greater the energy loss. From this viewpoint, when a compound satisfying the above formula (1) is used as a solid electrolyte, it is preferable that the compound satisfying the above formula (1) has low electronic conductivity. Specifically, the electronic conductivity of the compound satisfying the above formula (1) is 1.0 × 10 －９ S / cm or less is preferable, and 7.0 × 10 －１０ S / cm or less is more preferable, and 4.0 × 10 －１０ S / cm or less is more preferable, and 2.0×10 －１０ S / cm or less is more preferable, and 1.0×10 －１０ S / cm or less is more preferable, and 9.0 × 10 －１１ It is even more preferable that the viscosity is 250 S / cm or less.

[0064] The present invention relates to an all-solid-state sodium-ion secondary battery, which is an embodiment of the device. The sodium-ion secondary battery is a laminate including a solid electrolyte layer and an electrode layer made of a positive electrode layer and a negative electrode layer, and the solid electrolyte layer is disposed between the positive electrode layer and the negative electrode layer so that the solid electrolyte layer is in contact with the electrode layer.

[0065] The materials constituting the positive electrode layer and the negative electrode layer are not particularly limited, and can be appropriately selected from materials known as electrode materials for sodium ion secondary batteries. For example, the positive electrode layer may be configured to include a positive electrode current collector and a positive electrode mixture layer. The positive electrode current collector can be a metal foil such as aluminum, titanium, or stainless steel. The positive electrode mixture layer is a layer containing a positive electrode active material and is disposed on the surface of the positive electrode current collector. The positive electrode active material is not particularly limited as long as it can occlude and release sodium. The positive electrode active material can be Na ２ FeP ２ O ７ , NaFePO ４ , Na ３ V ２ (P.O. ４ ) ３ , NaNi ０．５ Mn ０．５ O ２ Examples of the transition metal oxides include the above. The positive electrode mixture layer may contain, as necessary, a solid electrolyte powder, a conductive additive (e.g., carbon), a binder, etc. As the solid electrolyte powder, a compound satisfying the above formula (1) can be preferably used.

[0066] In particular, the compound satisfying the above formula (1) is light-colored (preferably white), and even when a dark-colored active material is blended with the compound to prepare a mixture layer, an operator can easily visually confirm that an active material has been blended with the compound satisfying the above formula (1) and the degree of mixing of the active material. Such a compound satisfying the above formula (1) is easy to use as a solid electrolyte material when manufacturing an electricity storage device, and is highly convenient.

[0067] The negative electrode layer may include a negative electrode current collector and a negative electrode mixture layer. The negative electrode current collector may be a metal foil such as copper, aluminum, or stainless steel. The negative electrode mixture layer is a layer containing a negative electrode active material and is disposed on the surface of the negative electrode current collector. Examples of the negative electrode active material include hard carbon and Na—Ti—O-based compounds. The negative electrode mixture layer may also contain a solid electrolyte powder, a conductive additive, a binder, and the like, as needed. A compound satisfying the above formula (1) may be used as the solid electrolyte powder.

[0068] The solid electrolyte layer is preferably formed of a solid electrolyte containing a compound satisfying the above formula (1). When the positive electrode mixture layer and / or the negative electrode mixture layer contain a compound satisfying the above formula (1), the solid electrolyte layer of the present device is not limited to an embodiment containing a compound satisfying the above formula (1). The thickness of the solid electrolyte layer is not particularly limited and can be appropriately set depending on the application of the secondary battery, etc. The thickness of the solid electrolyte layer is, for example, 5 to 5,000 μm. From the viewpoint of realizing a smaller, lighter, and higher-capacity all-solid-state secondary battery by making the thickness of the solid electrolyte layer as thin as possible, the thickness of the solid electrolyte layer is preferably 50 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less.

[0069] The method for producing the solid electrolyte layer and the sodium ion secondary battery is not particularly limited, and known methods can be appropriately adopted depending on the battery structure, etc. For example, a laminate including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer may be produced by sandwiching a molded body of the present electrolyte as the solid electrolyte layer between a positive electrode layer and a negative electrode layer, and preferably performing a pressure treatment for bonding. Alternatively, a laminate including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer may be produced by placing the present electrolyte before molding between the positive electrode layer and the negative electrode layer in a container, and preferably performing a pressure treatment for bonding on the container. A laminate including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer is usually housed in a case and used as a secondary battery.

[0070] The device is not limited to the above-described configuration in which the carrier for ion conduction is sodium ions, and may be a secondary battery in which, for example, other alkali metal ions such as lithium ions or potassium ions are used as the carrier. The device may also be a capacitor. One embodiment of the capacitor includes an anode body, a cathode body, and a solid electrolyte, with a solid electrolyte layer disposed between the anode body and the cathode body so that the solid electrolyte is in contact with the electrode.

[0071] The electricity storage device including the present electrolyte can be used for a variety of purposes, specifically as a power source for various mobile devices such as mobile phones, personal computers, smartphones, game consoles, and wearable devices; various moving objects such as electric vehicles, hybrid vehicles, robots, and drones; and various electric and electronic devices such as digital cameras, video cameras, music players, power tools, and home appliances.

[0072] The present invention will be described in detail below based on examples. However, the present invention is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0073] 1. Preparation of Compounds In each Example and Comparative Example, compounds were prepared by the following Preparation Method A or Preparation Method B. (1-1) Preparation Method A: The raw materials were weighed in a glove box under an argon atmosphere and mixed in an agate mortar. The resulting mixture was placed in a 45 mL zirconia container containing 30 g of φ5 mm zirconia balls and sealed. The zirconia container containing the mixture was sealed in an overpot, and milling was carried out at room temperature (25°C) using a planetary ball mill (FRITSCH, Pulverisette 7 Classic Line). Milling consisted of rotating the mill at a rotation and revolution speed of 300 rpm for 15 minutes, stopping the rotation, and allowing the mill to stand for 10 minutes after stopping the rotation, with the number of cycles shown in Examples 1, 3-5, 7-9, and Comparative Example 1 in Table 1 being repeated. The 10-minute period of leaving the mill to stand was used to cool the mixture. Thereafter, the overpot and the zirconia container were opened in a glove box under an argon atmosphere, and the zirconia balls and the powder were separated to obtain a powdery compound.

[0074] (1-2) Manufacturing Method B: The raw materials were weighed in a glove box under an argon atmosphere and mixed in an agate mortar. The resulting mixture was then milled using the milling apparatus 10 shown in Figure 1. First, the mixture was placed in a 45 mL zirconia container (milling pot 13) containing 30 g of φ5 mm zirconia balls and sealed. The zirconia container containing the mixture was then placed in an insulated container (main body 11) and secured therein. The insulated container was then filled with liquid nitrogen, and planetary ball milling was performed for 88 minutes at a rotation and revolution speed of 320 rpm. During this process, rotation was stopped every 24 minutes, liquid nitrogen was replenished into the insulated container, and rotation was restarted. The temperature of the zirconia container during milling was within the range of -100 to -196°C. The zirconia container was then opened in a glove box under an argon atmosphere, and the zirconia balls and powder were separated to obtain a powdered compound.

[0075] (2-1) Example 1 The molar ratio of each element in the final product was the molar ratio (Na:Ta:Zr:Cl:CO) shown in Example 1 of Table 1. ３ 0.178 g of sodium chloride (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity 99.5%), 0.652 g of tantalum(V) chloride (manufactured by Acros Organics, purity 99.99%), 0.142 g of zirconium(IV) chloride (manufactured by Strem Chemicals, purity 99.5%), and 0.032 g of sodium carbonate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity 99.8%) were used as feed components so that the total weight ratio was 1.5:0.75:0.25:5.75:0.25. Each feed component was weighed in a glove box under an argon atmosphere, and compound SE-1, a white powder, was obtained by the production method shown in Example 1 of Table 1 (production method A).

[0076] (2-2) Examples 2 to 9 and Comparative Example 1 In the same manner as in Example 1, each feed component was weighed in a glove box under an argon atmosphere so that the molar ratio of each element in the final product would be the molar ratio shown in Table 1, and white powder compounds SE-2 to SE-10 were obtained by the production method (production method A or production method B) shown in Examples 2 to 9 and Comparative Example 1 in Table 1. Note that gallium (III) chloride (manufactured by Thermo Scientific, purity 99.999%) was used as the Ga feed component, and BO３ The supply component is Na ３ BO ３ Using PO ４ The supply component is Na ３ P.O. ４ (Sigma-Aldrich, purity ≧97.0%) was used, and tin (IV) chloride (Sigma-Aldrich, purity 99.995%) was used as the Sn supply component.

[0077] 2. Evaluation The amorphous mass fraction and ionic conductivity were measured for compounds SE-1 to SE-10 of Examples 1 to 9 and Comparative Example 1. The electronic conductivity was measured for compound SE-4 of Example 4. Furthermore, the oxidation resistance of compound SE-4 of Example 4 and compound SE-10 of Comparative Example 1 was evaluated.

[0078] [Measurement and Results of Amorphous Mass Fraction and Ion Conductivity] Details of the measurement method for amorphous mass fraction and ionic conductivity are as follows. (1) Amorphous Mass Fraction The amorphous mass fraction of compounds SE-1 to SE-10 was determined by the reference intensity ratio (RIR) method. In a glove box under an argon atmosphere, each of compounds SE-1 to SE-10 and α-alumina (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed out to a mass ratio of 1:1 and mixed in an agate mortar. The resulting mixture was subjected to XRD measurement under the conditions shown below. The integrated intensity of the strongest lines of each of the compounds and α-alumina obtained by XRD measurement, and the intensity of NaTaCl ６ The amorphous mass fractions in the compounds SE-1 to SE-10 of Examples 1 to 9 and Comparative Example 1 were calculated using the RIR values, and are shown in Table 1. As a result of the XRD measurement, the amorphous mass fractions in the compounds SE-1 to SE-10 of Examples 1 to 9 and Comparative Example 1 were calculated using the RIR values. ２ O ５No diffraction peak was observed. <X-ray diffraction (XRD) measurement> XRD measurement of the compound was carried out under the following conditions. The compound was placed on an airtight sample stage in a glove box under an argon atmosphere and sealed, and measurement was carried out in an air atmosphere. X-ray diffraction measurement device: MiniFlex 600 (manufactured by Rigaku Corporation) Characteristic X-ray: CuKα Measurement voltage: 40 kV Measurement current: 15 mA Measurement method: continuous Measurement range: 10°≦2θ≦60° Step side: 0.01° Scan speed: 10° / min

[0079] (2) Ionic Conductivity Molded bodies of each of compounds SE-1 to SE-10 were prepared, and the AC impedance was measured. The measurement results were used to calculate the ionic conductivity. (2-1) Preparation of Molded Body Molded bodies were prepared in a glove box under an argon atmosphere using a press mold 20 consisting of a die set 21, an upper punch 22, and a lower punch 23 (see Figure 2). The die set 21 containing 0.060 g of the compound obtained in 1 above was placed on the lower punch 23, and the upper punch 22 was placed on the die set 21. The compound was then compressed using a hydraulic press at a pressure of 382 MPa for 1 minute to obtain a circular molded body with a diameter of 10 mm. (2-2) AC Impedance Measurement The AC impedance of the molded body obtained in (2-1) above was measured, and a complex impedance plot was created. The measurements were performed using a multipotentio / galvanostat (VSP, manufactured by Biologic) under conditions of a frequency of 10 Hz to 1 MHz, a voltage of 10 mV, and a temperature of 25°C. The measurements were performed in a glove box under an argon atmosphere, with the press die 20 containing the molded body fixed with a jig and restrained at 50 MPa. (2-3) Calculation of Ionic Conductivity The value at the right end of the arc in the complex impedance plot obtained in (2-2) above was taken as the resistance R of each molded body, and the ionic conductivity σ (Na ion conductivity) was calculated using the following formula. The values ​​of ionic conductivity σ for each Example and Comparative Example are shown in Table 1. σ = (t / A) × (1 / R) σ: ionic conductivity t: thickness of molded body A: area of ​​current collector layer R: resistance of molded body

[0080]

[0081] As is clear from the results in Table 1, compounds SE-1 to SE-9 of Examples 1 to 9 were excellent in Na ion conductivity. ６ In Zr, Ga, CO ３ and B.O. ３ It can be said that compounds SE-4 and SE-6 (Examples 4 and 6) doped with α-doped SiO 2 exhibited higher Na ion conductivity when Examples 1, 7 to 9 were compared with Example 4, and when Example 2 was compared with Example 6. Furthermore, it ... doped with α-doped SiO 2 exhibited higher Na ion conductivity when Examples 1, 7 to 9 were compared with Example 4, and when Example 2 was compared with Example 6.

[0082] Furthermore, comparing Examples 3 to 5 using Production Method A, Example 4, which had a cycle count of 192, showed the highest Na ion conductivity. Regarding this result, it is believed that in Example 3, which had a cycle count of 20, synthesis did not proceed sufficiently due to insufficient grinding, resulting in the remaining unreacted materials, which inhibited ion conduction, resulting in a decrease in ion conductivity. Furthermore, in Example 5, which had a cycle count of 382, ​​it is believed that excessive grinding promoted crystallization and impurity generation due to thermal relaxation, which inhibited ion conduction due to the generated crystals and impurities, resulting in a decrease in ion conductivity. Furthermore, there was a correlation between the cycle count and the amorphous mass fraction; a moderately high cycle count tended to increase the amorphous mass fraction, which in turn tended to increase the Na ion conductivity. On the other hand, both a high and a low cycle count tended to decrease the amorphous mass fraction, which in turn decreased the Na ion conductivity.

[0083] In contrast, the Na ion conductivity of the undoped compound SE-10 (Comparative Example 1) was lower than that of the compounds SE-1 to SE-9 of Examples 1 to 9, and the results indicated that it was less practical.

[0084] [Electronic Conductivity Measurement and Results] (1) Preparation of Measurement Cell A measurement cell was prepared in a glove box under an argon atmosphere using a press die 20 with gold vapor-deposited on the upper punch 22 and lower punch 23 (see FIG. 2). A die set 21 containing 0.060 g of the compound (SE-4) of Example 4 was placed on the lower punch 23, and the upper punch 22 was placed on the die set 21. The cell was then compressed for 1 minute at a pressure of 382 MPa using a hydraulic press to obtain a measurement cell. (2) Calculation of Electronic Conductivity Electronic conductivity was evaluated by DC polarization measurement. Measurements were performed using a multipotentio / galvanostat (VSP, manufactured by Biologic) at voltages of 0.1 V, 0.2 V, 0.3 V, 0.4 V, and 0.5 V, and at a temperature of 25°C. Note that measurements were performed in a glove box under an argon atmosphere, with the measurement cell fixed with a jig and restrained at 50 MPa. The steady-state current obtained by the measurement was read, the resistance (Re) was calculated according to Ohm's law, and the electronic conductivity (σe) was calculated using the following formula (i). The value of the electronic conductivity (σe) of the compound (SE-4) of Example 4 was 8.2 × 10 －１１ S / cm, which confirmed that the electronic conductivity was sufficiently low. σe=(t / A)×(1 / Re) (i) σe: electronic conductivity t: thickness of sample A: area of ​​current collector layer Re: resistance

[0085] [Evaluation and Results of Oxidation Resistance] Linear sweep voltammetry (LSV) measurements were performed on compound SE-4 of Example 4 and compound SE-10 of Comparative Example 1 to evaluate the oxidation resistance of each compound. (1) Preparation of LSV Measurement Cell An LSV measurement cell was prepared in a glove box under an argon atmosphere using a press die 20 with gold vapor-deposited on the upper punch 22 and lower punch 23 (see FIG. 2). Na ３ P.S. ４ A die set 21 containing 0.030 g of glass ceramic was placed on the lower punch 23, and an upper punch 22 was placed on the die set 21. The sample was then compressed for 1 minute at a pressure of 63 MPa using a hydraulic press. After compression, the upper punch 22 was removed, and Na １０ Sn ４0.100 g of the alloy was placed in the die set 21, and the upper punch 22 was placed on the die set 21. Then, the sample was compressed for 1 minute at a pressure of 63 MPa using a hydraulic press. After compression, the pressing die was turned upside down, the lower punch 23 was removed, and the compound SE-10 (Na during LSV measurement) was removed. ３ P.S. ４ 0.030 g of an intermediate layer for suppressing oxidation reaction derived from Na was placed in the die set 21, and the lower punch 23 was placed on the die set 21. Thereafter, the sample was compressed for 1 minute at a pressure of 63 MPa using a hydraulic press. After compression, the lower punch 23 was removed, and 0.010 g of powder that had been mixed in advance in an agate mortar to give a mass ratio of compound SE-4 (Example 4):Ketjen Black (manufactured by Lion Specialty Chemicals) of 85:15 was placed in the die set 21, and the lower punch 23 was placed on the die set 21. Thereafter, the sample was compressed for 1 minute at a pressure of 382 MPa using a hydraulic press, thereby determining the Na １０ Sn ４ Alloy / Na ３ P.S. ４ A laminate of glass ceramic / SE-10 / (a mixture of SE-4 and Ketjen black) was obtained. The press mold 20 containing the obtained laminate was fixed with a jig and restrained at 50 MPa to prepare an LSV measurement cell for compound SE-4 (Example 4). The LSV measurement cell for compound SE-10 (Comparative Example 1) was prepared by using compound SE-10 instead of compound SE-4 and measuring the thickness of a laminate (Na １０ Sn ４ Alloy / Na ３ P.S. ４ Glass ceramic / SE-10 / (mixture of SE-10 and Ketjen black)) was prepared, and the press die 20 containing the obtained laminate was fixed with a jig and constrained at 50 MPa. (2) LSV Measurement The LSV measurement cell prepared in (1) was used for measuring the LSV of Na １０ Sn ４The alloy layer side was connected to a multipotentio / galvanostat (VSP, manufactured by Biologic) so that it served as the reference electrode and counter electrode, and the layer side of the mixture of compound SE-4 and Ketjen Black (or the mixture of compound SE-10 and Ketjen Black) served as the working electrode. LSV measurement was performed in an argon atmosphere at a temperature of 25°C. The scan rate was 0.5 mV / s, starting from the open circuit voltage, and the potential was increased to 6 V (vs. Na / Na ＋ The results of the LSV evaluation of compounds SE-4 and SE-10 are shown in Figure 3. From the results of Figure 3, it can be seen that NaTaCl ６ In Zr, Ga, CO ３ and B.O. ３ It was found that the compound SE-4 (Example 4) doped with CI 10 had oxidation resistance equivalent to that of the undoped compound SE-10 (Comparative Example 1).

[0086] From the above results, it was revealed that the compound satisfying the above formula (1) exhibits high ionic conductivity. It was also revealed that the compound satisfying the above formula (1) has sufficiently low electronic conductivity and furthermore, satisfies both good oxidation resistance and high ionic conductivity.

[0087] The present invention is not limited to the above-described embodiments, and encompasses various modifications and equivalent modifications within the scope of the spirit of the present invention. Therefore, in light of the above teachings, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are to be understood as falling within the scope and spirit of the present invention.

[0088] 10... Milling processing device, 13... Milling pot, 20... Press die

Claims

1. A compound satisfying the following formula (1): D α M β X ６－γ A γ ...(1) (In formula (1), α and β are each independently a value greater than 0, γ is a value greater than 0 and less than 6, D is an alkali metal element, M contains an element other than an alkali metal element that becomes a metal cation, X is a halogen element, and A is an atomic group that contains two or more elements and becomes a polyatomic anion.) 2. The compound according to claim 1, wherein D in the above formula (1) is Na.

3. The ionic radius of the element that becomes the metal cation other than the alkali metal is r Ｍ When [Å], 0.4≦r Ｍ The compound according to claim 1, wherein the β-amino acid group is ≦0.

9.

4. The compound according to claim 1, wherein M in the formula (1) contains at least one element selected from the group consisting of Ta, Zr, Hf, Ge, Ga, Sn and Sc.

5. The compound according to claim 1, wherein A in the above formula (1) has an oxygen atom.

6. The compound according to claim 1, wherein A in the formula (1) contains an atomic group that forms an inorganic polyatomic anion.

7. The ionic radius of A in the above formula (1) is r Ａ When [Å], 0.9≦r Ａ The compound according to claim 1, wherein the compound satisfies the following formula:

8. The compound according to claim 1, wherein X in the above formula (1) is Cl (chlorine).

9. The compound according to claim 1, which satisfies the following formula (2): Na1 + y1 + 2 × (y2) + 3 × (y3) + z1 + 2 × (z2) + 3 × (z3) Ta1 - y1 - y2 - y3 M1 ｙ１ M2 ｙ２ M3 ｙ３ Cl6-z1-z2-z3A1 ｚ１ A2 ｚ２ A3 ｚ３ ... (2) (In formula (2), y1, y2, y3, z1, z2, and z3 each independently represent a value of 0 or greater; M1 is an element that forms a tetravalent metal cation; M2 is an element that forms a trivalent metal cation; M3 is an element that forms a divalent metal cation; A1 is an atomic group that contains two or more elements and forms a divalent polyatomic anion; A2 is an atomic group that contains two or more elements and forms a trivalent polyatomic anion; A3 is an atomic group that contains two or more elements and forms a tetravalent polyatomic anion; and the relationships 0 < y1 + y2 + y3 < 1 and 0 < z1 + z2 + z3 < 6 are satisfied.) 10. The compound according to claim 1, wherein the mass fraction of the amorphous phase is 10% or more.

11. A method for producing the compound according to any one of claims 1 to 10, comprising the steps of: weighing out a plurality of feed components each containing one or more elements selected from D, M, X, and A in formula (1) above, so as to satisfy the stoichiometric ratio of the composition represented by formula (1) above; and pulverizing the weighed out plurality of feed components while cooling with a cooling medium.

12. A solid electrolyte comprising a compound according to any one of claims 1 to 10.

13. An electricity storage device comprising the solid electrolyte according to claim 12.

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