Oxide and its manufacturing method, solid electrolyte, and all-solid-state battery

Abstract

To provide a zirconium phosphate-based novel oxide with high Li ion conductivity, a method of producing the same, a solid electrolyte, and an all-solid battery.SOLUTION: An oxide satisfies the following formula (1): Li1+2x+y+zM1xM2yZr2-x-ySizP3-zO12 and has Li ion conductivity, provided that M1 is divalent metal, M2 is trivalent metal, and x, y and z satisfy x≥0, y≥0, z>0 and x+y>0 in the formula (1). A solid electrolyte includes the oxide. An all-solid battery comprises the solid electrolyte. A production method comprises a mixing step of mixing a plurality of supply components each including one or more selected from Li, the M1, the M2, Zr, Si and P in a manner of satisfying the formula (1) to obtain a mixture of the supply components, and a calcination step of calcining the mixture to obtain the oxide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an oxide, a method for producing the same, a solid electrolyte, and an all-solid-state battery. More specifically, the present invention relates to a lithium-containing zirconium phosphate-based oxide, a method for producing the same, a solid electrolyte, and an all-solid-state battery. [Background technology]

[0002] The liquid electrolyte type Li-ion batteries currently in use cannot use Li in the electrodes, making it difficult to further increase the battery capacity. Furthermore, the need to use a flammable organic solvent as the electrolyte makes it impossible to eliminate the possibility of fire. Solid electrolytes with Li-ion conductivity are being investigated as a solution to these problems. Known solid electrolytes with Li-ion conductivity include sulfide-based solid electrolytes and oxide-based solid electrolytes. Of these, oxide-based solid electrolytes are considered to be more stable in the atmosphere and safer than sulfide-based solid electrolytes. On the other hand, oxide-based solid electrolytes have inferior Li-ion conductivity compared to sulfide-based solid electrolytes. For this reason, studies are underway to develop oxide-based solid electrolytes with better Li-ion conductivity. One type of oxide-based solid electrolyte is known to be Nasicon-type zirconium phosphate. The following Patent Documents 1 to 3 are known as technologies related to this zirconium phosphate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2015-065021 [Patent Document 2] International Publication No. 2017 / 141742 Brochure [Patent Document 3] International Publication No. 2018 / 088424 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned Patent Document 1 discloses an all-solid-state battery (Patent Document 1 [Claim 7]) that includes a solid electrolyte material whose main component is a lithium-containing zirconium phosphate compound, and further discloses that a lithium-containing zirconium phosphate compound (Patent Document 1 [Claim 8]) in which a part of the phosphorus element is substituted with silicon element can be used, and that triclinic LiZr2(PO4)3 and monoclinic Li 1.3 Zr2(P 0.9 Si 0.1 O4)3 is more preferable because it has an activation energy Ea of 50 kJ / mol or more (Patent Document 1

[0063] ).

[0005] The above-mentioned Patent Document 2 discloses Li 1+x Zr 2+y Mα z Mβ w Patent Document 2 discloses a solid electrolyte having a NaSICON-type crystal structure represented by (PO4)3 (wherein a portion of P may be substituted with at least one element selected from the group consisting of Si, B, and V, Mα is an element having an ionic radius larger than that of Zr and smaller than that of La, and Mβ includes at least one element that forms a monovalent to tetravalent cation, and the formulas are -0.500≦x≦3.000, -0.999≦y≦0.200, 0.000≦z≦0.999, and 0≦w≦0.600). Patent Document 2 also discloses that the X-ray diffraction patterns of the solid electrolytes in Examples 1 to 11 match the card patterns of LiZr2(PO4)3, a NaSICON-type Trigonal with a high ion conductivity phase (Patent Document 2

[0056] ).

[0006] The above-mentioned Patent Document 3 discloses a composition ratio of Li:M 1 :M 2 : P = 1.0 to 1.7: 0.10 to 0.35: 2.0: more than 3.00 and not more than 3.50, and (2) the M 1 is at least one selected from the group consisting of Ca, Mg, Sr, and Ba, and when two or more types are contained, the total composition ratio is 0.10 to 0.35; (3) the M 2consists of Zr alone or Zr and at least one selected from the group consisting of Al, Sc, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and said M 2 The article discloses a lithium-containing zirconium phosphate in which the composition ratio of Zr in the composition ratios of (a) and (b) is 1.47 to 2.00.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a novel zirconium phosphate-based oxide having high Li-ion conductivity and a method for producing the same, as well as a solid electrolyte and an all-solid-state battery using the oxide. [Means for solving the problem]

[0008] The present inventors have found that excellent Li-ion conductivity is achieved when a zirconium phosphate [LiZr2(PO4)3]-based oxide is doped with a divalent metal and / or a trivalent metal at the Zr site and with Si at the P site. Based on this finding, the present specification provides the following means.

[0009] [1] An oxide that satisfies the following formula (1) and has Li-ion conductivity. Li 1+2x+y+z M 1 x M 2 y Zr 2-x-y Si z P 3-z O 12 ··· (1) (However, in formula (1), M 1 is a divalent metal, and M 2 is a trivalent metal, and x, y, and z satisfy x≧0, y≧0, z>0, and x+y>0.

[0010] [2] The oxide according to [1] above, wherein x + y ≦ 0.2.

[0011] [3] The oxide according to [1] or [2] above, wherein z≦0.2.

[0012] [4] Said M 1 is at least one element selected from the group consisting of Mg, Ca, Sn, Sr and Ba.

[0013] [5] Said M 2 is at least one element selected from the group consisting of Al, Sc, Ga, Y, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sb, and Bi.

[0014] [6] A solid electrolyte comprising the oxide according to any one of [1] to [5] above.

[0015] [7] An all-solid-state battery comprising the solid electrolyte according to [6].

[0016] [8] A method for producing an oxide according to any one of [1] to [5] above, Li, M 1 , said M 2 a mixing step of mixing a plurality of feed components including one or more of Zr, Si, and P so as to satisfy the formula (1) to obtain a mixture of the feed components; and a calcination step of calcining the mixture to obtain the oxide.

[0017] [9] The method for producing an oxide according to the above [8], wherein layered zirconium phosphate is used as a feed component for supplying Li and Zr.

[0018]

[10] The method for producing an oxide according to [8] or [9], wherein the mixing is wet mixing. [Effects of the Invention]

[0019] According to the oxide of the present invention, high lithium ion conductivity can be obtained in a zirconium phosphate-based oxide. According to the solid electrolyte of the present invention, high lithium ion conductivity can be obtained in a zirconium phosphate-based oxide. According to the all-solid-state battery of the invention, zirconium phosphate-based oxides can be utilized as the solid electrolyte. According to the method for producing an oxide of the present invention, a zirconium phosphate-based oxide having high lithium ion conductivity can be obtained. [Brief explanation of the drawings]

[0020] [Figure 1] 1A and 1B are explanatory diagrams schematically showing an example of an all-solid-state battery; DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be described in detail below. Unless otherwise specified, "%" means "% by mass", "parts" means "parts by mass", "ppm" means "ppm by mass", and "numeric value X to numeric value Y" means "numerical value X or more and numerical value Y or less". Furthermore, each embodiment described below can be an embodiment in which two or more of each embodiment are combined.

[0022] [1] Oxides The oxide of the present invention is characterized by satisfying the following formula (1) and having Li ion conductivity. Li 1+2x+y+z M 1 x M 2 y Zr 2-x-y Si z P 3-z O 12 ··· (1) (However, in formula (1), M 1 is a divalent metal, and M 2 is a trivalent metal, and x, y, and z satisfy x≧0, y≧0, z>0, and x+y>0.

[0023] That is, this oxide is an oxide based on LiZr2(PO4)3 (parent structure), in which a part of Zr is a divalent metal, M 1 and / or trivalent metal M 2 It can be said that the P is partly substituted by Si, and that the oxide is a result of this substitution.

[0024] In formula (1), "x" is 0 or a positive number. Also, "y" is 0 or a positive number. Furthermore, "x+y" is a positive number. Therefore, "x" and "y" cannot be 0 at the same time. Also, "z" is a positive number. For example, when x=0 and y>0, equation (1) is expressed as "Li 1+y+z M 2 y Zr 2-y Si z P 3-z O 12 " is expressed as: Furthermore, when x>0 and y=0, equation (1) is expressed as "Li 1+2x+z M 1 x Zr 2-x Si z P 3-z O 12 " is expressed as: Furthermore, when x>0 and y>0, equation (1) is expressed as "Li 1+2x+y+z M 1 x M 2 y Zr 2-x-y Si z P 3-z O 12 "

[0025] M 1 is a divalent metal. That is, it is a metal (metal element) that becomes a divalent cation. M 1 M may be used alone or in combination of two or more. 1 Any metal that forms a divalent cation can be used without any limitations. Examples of such metals include alkaline earth metals (Group 2 metal elements), transition metals (Group 3 - 11 metal elements), zinc group metals (Group 12 metal elements), Sn, etc. Among these, alkaline earth metals (Group 2 elements) and Sn are preferred, and further, at least one selected from the group consisting of Mg, Ca, Sn, Sr, and Ba is preferred, and particularly Mg and / or Ca are preferred.

[0026] M 2 is a trivalent metal. That is, it is a metal (metal element) that becomes a trivalent cation. M 2 may be used alone or in combination of two or more. M 2 can be used without limitation as long as it is a metal that becomes a trivalent cation. Examples of such metals include Group 13 metal elements, Group 3 metal elements, Group 15 metal elements, etc. Among these, at least one selected from the group consisting of Al, Sc, Ga, Y, In, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sb, and Bi is preferred, and particularly Al, Sc, and / or Ga are preferred.

[0027] In formula (1), as described above, x and y only need to satisfy x≥0, y≥0, and x + y>0. However, further, by satisfying x≥0, y≥0, and 0 < x + y≤0.2, compared with the case where x≥0, y≥0, and x + y = 0, or x≥0, y≥0, and x + y>0.2, better Li ion conductivity can be obtained. This is considered to be because the segregation of M 1 and M 2 can be suppressed. When the contents of M 1 and M 2 increase, it approaches the solid solubility limit in the Zr site, and M 1 and M 2An impurity phase containing a large amount begins to form, and the impurity phase inhibits Li ion conduction. That is, even if the α-phase having high Li ion conductivity has a dominant structure, the presence of the impurity phase will inhibit Li ion conduction. Therefore, a composition in which the impurity phase is difficult to form is preferable, and from this point of view, the conditions of x≧0, y≧0 and 0<x + y≦0.2 are considered to contribute. Incidentally, M 1 and M 2 The presence or absence of segregation of can be detected by measuring the distribution of M 1 and M 2 using energy dispersive X-ray spectroscopy.

[0028] Also, in Equation (1), as described above, z only needs to satisfy z>0. Further, by satisfying 0<z≦0.2, better Li ion conductivity can be obtained compared to the case where z>0.2. Si is different from M 1 and M 2 Even when z>0.2 (for example, z = 0.3), the solid solubility limit of Si is not reached and no segregation occurs (the presence or absence of Si segregation can be detected by measuring the distribution of Si using energy dispersive X-ray spectroscopy). On the other hand, in the range of 0<z≦0.2, the α-phase and / or α'-phase are stable phases, whereas it is observed that as the Si content increases, the β-phase and / or β'-phase become stable phases. That is, among the four phases (α-phase, α'-phase, β-phase and β'-phase) that the zirconium phosphate-based oxide can take, it is known that the Li ion conductivity is high in the α-phase, and 0<z≦0.2 can be said to be a condition advantageous for α-phase formation. However, when comparing z≦0.2 and z>0.2 at the same firing temperature, the firing temperature required for α-phase formation is higher for the latter. Therefore, it is considered that the demerit caused by z>0.2 can be eliminated by raising the firing temperature, but from the viewpoint of energy cost during manufacturing, it is preferable to obtain high Li ion conductivity at a lower firing temperature.

[0029] In addition, the oxide represented by formula (1) has a stoichiometric ratio of O of 12, but in reality, it is sufficient to maintain charge neutrality as a whole oxide, and the value may be less than 12 or more than 12. For example, when formula (1) is expressed as formula (2) below (M 1 , M 2 , x, y and z are the same as in formula (1), Li 1+2x+y+z M 1 x M 2 y Zr 2-x-y Si z P 3-z O 12±α (2) α can be set to, for example, 0≦α≦1.

[0030] Furthermore, the oxide of the present invention is not limited to a specific phase structure, and as a result, an oxide with high Li-ion conductivity is preferred. Among these, a NASICON (Na Super Ionic Conductor) type is preferred. This is because the NASICON type is advantageous for use as a solid electrolyte. That is, unlike layered structures, the NASICON type has a three-dimensionally expanded space for Li-ion migration. Furthermore, zirconium is stable even under high voltages because it is not reduced by metallic lithium, making it useful as a solid electrolyte for high operating voltages. Whether or not the oxide of the present invention exhibits a NASICON type can be determined from the diffraction profile obtained by powder X-ray diffraction measurement.

[0031] Furthermore, although the phase structure of the oxide of the present invention is not limited, it is preferable that the proportion of the α phase is high. Zirconium phosphate oxides can be in four phases: α phase, α' phase, β phase, and β' phase. This is because the α phase has an isotropic crystal structure and therefore exhibits the highest Li-ion conductivity. The phase of the oxide of the present invention can be identified by X-ray diffraction measurement, specifically by the measurements in the examples described below.

[0032] The use of the oxide of the present invention is not particularly limited, but it can be used, for example, as a material for all-solid-state batteries, various secondary battery materials, CO2 sensors, etc. Specifically, examples include solid electrolytes (solid electrolyte materials) for all-solid-state batteries, electrodes (electrode materials) for all-solid-state batteries, separators, and the like.

[0033] [2] Method of manufacturing oxides The oxides described above may be produced by any method, including a solid-phase method and a liquid-phase method, but in the present invention, they can be produced by a solid-phase method, more specifically, by a method including a mixing step and a firing step.

[0034] In the above-mentioned mixing step, Li, the M 1 , said M 2 This is a step of mixing a plurality of feed components containing one or more of Zr, Si and P so as to satisfy the formula (1) to obtain a mixture of the feed components. Among the above steps, the firing step is a step of firing the mixture to obtain an oxide.

[0035] In this method, Li, M 1 , M 2 The feed components that supply each of Zr, Si, and P may be inorganic compounds or organic compounds. Among these, the Li supply component, M 1 Supply components (e.g., Ca supply components, Mg supply components), M 2 As the feed component (e.g., Al feed component), Zr feed component, and Si feed component, for example, carbonates, hydrogen carbonates, sulfates, sulfites, nitrates, nitrites, phosphates, acetates, citrates, ammonium salts, oxides, hydroxides, chlorides, sulfides, etc. of these metal elements can be used. Note that these feed components may be used in combination, where one type of feed component contains Li, M, 1 , M 2 It may also be a compound containing two or more of Zr and Si.

[0036] On the other hand, as P supplying components, for example, ammonium phosphate, ammonium hydrogen phosphate, etc. 1 , M 2 Although it is possible to use a compound that does not contain one or more of Li, Zr and Si, in the present invention, 1 , M 2 It is preferable to use a compound containing one or more of Zr and Si. Among these, in this method, it is preferable to use a zirconium phosphate compound as a supply component (a supply component for Zr and P).

[0037] Zirconium phosphate compounds include zirconium hydrogen phosphates such as Zr(HPO4)2 and Zr(HPO4)2·nH2O, zirconium phosphates such as Zr3(PO4)4, zirconium hydrogen phosphates such as Zr(PO4)(H2PO4) and Zr(PO4)(H2PO4)2·nH2O, and also HZr2(PO4)3, ZrP2O7, (ZrO)2P2O7, etc. Note that the above n is usually 0≦n≦2 (for example, n=1, n=1.5, or n=2). In the present invention, it is particularly preferable to use Zr(HPO4)2·nH2O, which is known as layered zirconium phosphate. The use of Zr(HPO4)2·nH2O facilitates the recovery of the fired product (as well as the calcined product) after firing (as well as after calcination). For example, the oxide of the present invention can be obtained by using ZrO2 and NH4H2PO4 instead of Zr(HPO4)2·nH2O. However, when attempting to produce the oxide of the present invention using these feed components, the shape of the fired product (as well as the calcined product) changes during the firing process, causing it to adhere to the container, making it difficult to recover, resulting in poor handleability. In contrast, when Zr(HPO4)2·nH2O is used as a feed component, the shape of the fired product (as well as the calcined product) remains almost unchanged and does not adhere to the container, resulting in excellent handleability.

[0038] In the above-mentioned mixing step, Li, M 1 , M 2A plurality of feed components including one or more of Zr, Si, and P are weighed so as to satisfy formula (1), i.e., so as to satisfy the stoichiometric ratio of the composition expressed by formula (1), and then the weighed components are mixed. The mixing may be performed by dry mixing, but it is preferable to use a liquid for wet mixing. By performing wet mixing, the density after firing can be increased compared to when dry mixing is performed, and the Li-ion conductivity can also be relatively improved. As the liquid used for wet mixing, water, various organic solvents, mixtures thereof, etc. can be used as appropriate.

[0039] In the firing step, the mixture obtained in the mixing step may be fired without being shaped, or may be shaped and then fired. The firing temperature is not limited, but the lower limit of the firing temperature can be, for example, 950°C, preferably 1000°C, and more preferably 1050°C. On the other hand, the upper limit of the firing temperature can be, for example, 1500°C, preferably 1400°C, and more preferably 1350°C.

[0040] Furthermore, when firing, the final firing can be performed via pre-firing. That is, the temperature can be increased stepwise from a temperature lower than the firing temperature to finally reach the temperature required for firing. Furthermore, each pre-firing can be followed by a pulverization step in which the resulting pre-firing product is pulverized. When pre-firing is performed, firing can be performed in three stages, for example, by performing a first pre-firing in a temperature range of 100°C or higher but lower than 800°C, a second pre-firing in a temperature range of 800°C or higher but lower than 1200°C, and a main firing in a temperature range of 1200°C or higher. The firing time is not limited, but for example, the pre-firing can be carried out for 1 hour to 36 hours, and the main firing can be carried out for 1 hour to 12 hours.

[0041] [2] Solid electrolyte The solid electrolyte of the present invention is characterized by containing the above-mentioned oxide having Li ion conductivity. The amount of the aforementioned oxide contained in this solid electrolyte is not limited. For example, when the entire solid electrolyte is 100% by mass, if the content of the oxide is X% by mass, then 0 < X (% by mass) ≤ 100 can be set. Also, for example, 50 ≤ X (% by mass) ≤ 100 can be set, and 75 ≤ X (% by mass) ≤ 100 can be set.

[0042] Although the solid electrolyte of the present invention has Li ion conductivity, it can contain other oxides not represented by formula (1). Examples of other solid electrolytes include oxides having Li ion conductivity that satisfy the following formula (3), oxides having Li ion conductivity that satisfy the following formula (4), oxides having Li ion conductivity that satisfy the following formula (5), and the like. These may be used alone or in combination of two or more.

[0043] Li 1+2x+y M 1 x M 2 y Zr 2-x-y P3O 12 ··· (3) (However, in formula (3), M 1 is a divalent metal, M 2 is a trivalent metal, and x and y satisfy x ≥ 0, y ≥ 0, and x + y > 0.) Li 1+z Zr2Si z P 3-z O 12 ··· (4) (However, in formula (4), z > 0 is satisfied.) Li 1+2x+y+z M 1 x M 2 y Zr 2-x-y M 3 z P 3-z O 12 ··· (5) (However, in formula (5), M 1 is a divalent metal, M 2 is a trivalent metal, M 3is a tetravalent element other than Si, and x, y, and z satisfy x≧0, y≧0, z>0, and x+y>0. In addition, M in the above formula (3) and formula (5) 1 and M 2 The various metals exemplified in relation to formula (1) can be used for the M 3 can be applied to tetravalent nonmetallic elements other than Si and tetravalent metallic elements.

[0044] [3] All-solid-state battery The all-solid-state battery 1 of the present invention is an all-solid-state battery characterized by including the above-mentioned solid electrolyte 23 (solid electrolyte body) (see FIG. 1). Typically, the all-solid-state battery 1 includes a positive electrode 22 (positive electrode layer) and a negative electrode 24 (negative electrode layer) in addition to a solid electrolyte 23. The all-solid-state battery may be a bulk type (see FIG. 1(a)) or a thin-film type (see FIG. 1(b)).

[0045] When the all-solid-state battery 1 is a bulk type (see FIG. 1(a)), the positive electrode 22 and the negative electrode 24 can be disposed opposite each other with the solid electrolyte 23 interposed therebetween. Furthermore, the positive electrode 22 and the negative electrode 24 are disposed in contact with the solid electrolyte 23, respectively. For example, the all-solid-state battery 1 can include the solid electrolyte 23, the positive electrode 22, and the negative electrode 24 as an integrated sintered body. More specifically, when the solid electrolyte 23 (solid electrolyte body) has two main surfaces, that is, when it is a plate-like body, a membrane-like body, a sheet, a film, or the like, the battery can be configured such that the positive electrode 22 is provided on one main surface and the negative electrode 24 is provided on the other main surface, with the solid electrolyte 23 interposed therebetween.

[0046] The positive electrode usually contains a positive electrode active material, and may also contain, for example, one or more of a conductive material, a solid electrolyte, a binder, and the like. Similarly, the negative electrode also generally contains a negative electrode active material, and may also contain, for example, one or more of a conductive material, a solid electrolyte, a binder, and the like. Each electrode may have its own current collector. That is, the positive electrode 22 may have a positive electrode current collector 21 on the surface that is not in contact with the solid electrolyte 23. Similarly, the negative electrode 24 may have a negative electrode current collector 25 on the surface that is not in contact with the solid electrolyte 23.

[0047] When the all-solid-state battery 1 is a thin-film type (see FIG. 1(b)), the positive electrode 22 and the negative electrode 24 can be disposed apart from each other so that a portion of each is in contact with the solid electrolyte 23. For example, the all-solid-state battery 1 can be provided as an integrated fired body in which the negative electrode 24, the solid electrolyte 23, and the positive electrode 22 are laminated in this order. When the all-solid-state battery 1 is a thin-film type, similarly to a bulk type, the positive electrode typically contains a positive electrode active material and may also contain one or more of, for example, a conductive material, a solid electrolyte, a binder, etc. The negative electrode typically contains a negative electrode active material and may also contain one or more of, for example, a conductive material, a solid electrolyte, a binder, etc. Each electrode may also be provided with a current collector. [Example]

[0048] The present invention will be specifically described below with reference to examples. However, the present disclosure is not limited to these examples.

[0049] [1] Preparation of oxide (1) Example 1 As feed components, 8.996 g of layered zirconium phosphate (Zr(HPO4)2·nH2O), 1.232 g of zirconium oxide, 0.887 g of lithium carbonate, 0.16 g of silicon dioxide, and 0.074 g of calcium hydroxide were weighed out so as to achieve the quantitative ratio (Li:Ca:Zr:P:Si=1.20:0.05:1.95:2.90:0.10) shown in Example 1 of Table 1. Each feed component was placed in a mortar, and 25 g of pure water was added and wet-mixed to obtain a feed component mixture. The resulting mixture was dried at 120°C for 1 hour, then transferred to an alumina crucible (volume 30 mL), and subjected to first pre-firing by increasing the temperature to 1100°C over 5.5 hours and maintaining that temperature for 5 hours. Thereafter, the mixture was allowed to cool to room temperature to obtain a first pre-firing product. The resulting first calcined product was pulverized in a mortar, and 0.3 g of the resulting pulverized first calcined product was placed in a 1.2 cm diameter mold and molded into a coin shape using a hydraulic press under a load of 1 ton. The resulting molded product was placed on a platinum plate and heated to 800°C over 30 minutes, then further heated to 1200°C over 2 hours and held at that temperature for 4 hours for final calcination. The product was then allowed to cool to room temperature, yielding the oxide of Example 1. In the examples herein, the value of n in Zr(HPO4)2·nH2O was determined to be 1.5 based on the results of thermogravimetric differential thermal analysis. The same applies hereinafter.

[0050] (2) Examples 2 to 4, Examples 9 to 14 As in Example 1, the same compounds as in Example 1 were used as feed components, and predetermined amounts of each were weighed out so as to achieve the quantitative ratios shown in Examples 2 to 4 and Examples 9 to 14 in Table 1. Each feed component was placed in a mortar, and 25 g of pure water was added and wet-mixed to obtain a feed component mixture. The resulting mixture was subjected to pre-baking and main baking under the same conditions as in Example 1 to obtain oxides of Examples 2 to 4 and Examples 9 to 14.

[0051] (3) Example 5 As feed components, 8.996 g of layered zirconium phosphate (Zr(HPO4)2·nH2O), 1.232 g of zirconium oxide, 0.887 g of lithium carbonate, 0.16 g of silicon dioxide, and 0.058 g of magnesium hydroxide were weighed out so as to achieve the quantitative ratio (Li:Mg:Zr:P:Si=1.20:0.05:1.95:2.90:0.10) shown in Example 5 of Table 1. Each feed component was placed in a mortar, and 25 g of pure water was added and wet-mixed to obtain a feed component mixture. The resulting mixture was dried at 120°C for 1 hour, then transferred to an alumina crucible (volume 30 mL), and subjected to first pre-firing by increasing the temperature to 1100°C over 5.5 hours and maintaining that temperature for 5 hours. Thereafter, the mixture was allowed to cool to room temperature to obtain a first pre-firing product. The resulting first calcined product was pulverized in a mortar, and 0.3 g of the resulting pulverized first calcined product was placed in a 1.2 cm diameter mold and molded into a coin shape using a hydraulic press under a load of 1 ton. The resulting molded product was placed on a platinum plate and heated to 800°C over 30 minutes, then further heated to 1200°C over 2 hours and maintained at this temperature for 4 hours, thereby carrying out main calcination. The product was then allowed to cool to room temperature, yielding the oxide of Example 5.

[0052] (4) Example 6 In the same manner as in Example 5, the same compounds as in Example 5 were used as feed components so as to obtain the quantitative ratios shown in Example 6 in Table 1, and predetermined amounts of each were weighed out. Each feed component was placed in a mortar, and 25 g of pure water was added thereto, followed by wet mixing to obtain a feed component mixture. The resulting mixture was subjected to pre-baking and main baking under the same conditions as in Example 5, to obtain the oxide of Example 6.

[0053] (5) Example 7 As feed components, 8.996 g of layered zirconium phosphate (Zr(HPO4)2·nH2O), 1.232 g of zirconium oxide, 0.85 g of lithium carbonate, 0.16 g of silicon dioxide, and 0.078 g of aluminum hydroxide were weighed out so as to achieve the quantitative ratio (Li:Al:Zr:P:Si=1.15:0.05:1.95:2.90:0.10) shown in Example 7 of Table 1. Each feed component was placed in a mortar, and 25 g of pure water was added and wet-mixed to obtain a feed component mixture. The resulting mixture was dried at 120°C for 1 hour, then transferred to an alumina crucible (volume 30 mL), and subjected to first pre-firing by increasing the temperature to 1100°C over 5.5 hours and maintaining that temperature for 5 hours. Thereafter, the mixture was allowed to cool to room temperature to obtain a first pre-firing product. The resulting first calcined product was pulverized in a mortar, and 0.3 g of the resulting pulverized first calcined product was placed in a 1.2 cm diameter mold and molded into a coin shape using a hydraulic press under a load of 1 ton. The resulting molded product was placed on a platinum plate and heated to 800°C over 30 minutes, then further heated to 1200°C over 2 hours and maintained at that temperature for 4 hours for main calcination. The product was then allowed to cool to room temperature, yielding the oxide of Example 7.

[0054] (6) Example 8 In the same manner as in Example 7, the same compounds as in Example 7 were used as feed components in the quantitative ratio shown in Example 8 in Table 1, and predetermined amounts of each were weighed out. Each feed component was placed in a mortar, and 25 g of pure water was added thereto, followed by wet mixing to obtain a feed component mixture. The resulting mixture was subjected to pre-baking and main baking under the same conditions as in Example 7, to obtain the oxide of Example 8.

[0055] (7) Comparative Example 1 As feed components, 9.306 g of layered zirconium phosphate (Zr(HPO) nH0), 1.232 g of zirconium oxide, and 0.739 g of lithium carbonate were weighed out so as to achieve the quantitative ratio (Li:Zr:P = 1.00:2.00:3.00) shown in Comparative Example 1 in Table 1. Each feed component was placed in a mortar, and 25 g of pure water was added and wet-mixed to obtain a feed component mixture. The resulting mixture was dried at 120°C for 1 hour, then transferred to an alumina crucible (volume 30 mL), and subjected to first pre-firing by increasing the temperature to 1100°C over 5.5 hours and maintaining that temperature for 5 hours. Thereafter, the mixture was allowed to cool to room temperature to obtain a first pre-firing product. The resulting first calcined product was pulverized in a mortar, and 0.3 g of the resulting pulverized first calcined product was placed in a mold with a diameter of 1.2 cm and molded into a coin shape using a hydraulic press under a load of 1 ton. The resulting molded product was placed on a platinum plate and heated to 800°C over 30 minutes, then further heated to 1200°C over 2 hours and maintained at that temperature for 4 hours for main calcination. The product was then allowed to cool to room temperature, yielding the oxide of Comparative Example 1.

[0056] (8) Comparative Example 2 As feed components, 9.151 g of layered zirconium phosphate (Zr(HPO) nH0), 1.170 g of zirconium oxide, 0.813 g of lithium carbonate, and 0.074 g of calcium hydroxide were weighed out so as to achieve the quantitative ratio (Li:Ca:Zr:P=1.10:0.05:1.95:3.00) shown in Comparative Example 2 in Table 1. Each feed component was placed in a mortar, and 25 g of pure water was added and wet-mixed to obtain a feed component mixture. The obtained mixture was subjected to pre-baking and main baking under the same conditions as in Comparative Example 1, to obtain an oxide of Comparative Example 2.

[0057] (9) Comparative Example 3 As feed components, 9.306 g of layered zirconium phosphate (Zr(HPO) nH0), 0.986 g of zirconium oxide, 0.887 g of lithium carbonate, and 0.117 g of magnesium hydroxide were weighed out so as to achieve the quantitative ratio (Li:Mg:Zr:P=1.20:0.10:1.90:3.00) shown in Comparative Example 3 in Table 1. Each feed component was placed in a mortar, and 25 g of pure water was added and wet-mixed to obtain a feed component mixture. The obtained mixture was subjected to pre-baking and main baking under the same conditions as in Comparative Example 1, to obtain an oxide of Comparative Example 3.

[0058] (10) Comparative Example 4 As feed components, 8.996 g of layered zirconium phosphate (Zr(HPO4)2·nH2O), 1.356 g of zirconium oxide, 0.813 g of lithium carbonate, and 0.16 g of silicon dioxide were weighed out so as to achieve the quantitative ratio (Li:Zr:P:Si=1.10:2.00:2.90:0.10) shown in Comparative Example 4 in Table 1, and each feed component was placed in a mortar, followed by the addition of 25 g of pure water, followed by wet mixing to obtain a feed component mixture. The obtained mixture was subjected to pre-baking and main baking under the same conditions as in Comparative Example 1, to obtain an oxide of Comparative Example 4.

[0059] [2] Explanation of evaluation method (1) Evaluation of ionic conductivity (1-1) Formation of the current collector layer Both sides of each oxide (coin-shaped sintered pellet) of Examples 1 to 14 and Comparative Examples 1 to 4 obtained in [1] (1) to (10) above were polished, and then masked with polyimide tape to leave an exposed surface of 5 mm square in the center. A current collector layer was then formed on the exposed surface by sputtering. The current collector layer was formed as a gold (Au) layer with a thickness of approximately 50 nm. A gold vapor deposition device (Ion Coater IB-2 / IB-3, manufactured by Eiko Co., Ltd.) was used for sputtering.

[0060] (1-2) AC impedance measurement In the above (1-1), the AC impedance of each oxide in Examples 1 to 14 and Comparative Examples 1 to 4 on which a current collector layer was formed was measured, and complex impedance plots were created. For Examples 1 to 8 and Comparative Examples 1 to 4, measurements were made using an impedance analyzer (manufactured by Keysight, model "E4990A") at frequencies of 20 Hz to 120 MHz, voltage of 10 mV, and temperature of 25°C. For Examples 9 to 14, measurements were made using a multipotentio / galvanostat (manufactured by Biologic, model "VMP3") equipped with an FRA (Frequency Response Analyzer), at frequencies of 1 Hz to 1 MHz, voltage of 10 mV, and temperature of 25°C.

[0061] (1-3) Calculation of ionic conductivity The value at the right end of the arc in the complex impedance plot obtained in (1-2) above was taken as the resistance R (sum of particle and grain boundary resistance) of each oxide, and the ionic conductivity σ (Li ion conductivity) was calculated using the following formula. The results are shown in Table 1. σ = (t / A) × (1 / R) σ: ionic conductivity t: sample thickness A: electrode area R: oxide resistance

[0062] (1-4) Calculation of intragranular ionic conductivity In the complex impedance plots of Examples 1 to 8 and Comparative Examples 1 to 4 obtained by (1-2) above, when a waveform with two arcs was observed, the diameter of the first arc was taken as the particle resistance (Rb) and the particle ionic conductivity σb (intra-particle Li ion conductivity) was calculated using the following formula. The results are shown below and also in Table 1. σb=(t / A)×(1 / Rb) σb: ionic conductivity t: sample thickness A: electrode area Rb: oxide resistivity

[0063] The Li ion conductivity of the oxide of Example 1 is 2.6 × 10-5 S / cm, and the intragranular Li conductivity is 2.5×10 -4 S / cm. The Li ion conductivity of the oxide of Example 2 is 2.4 × 10 -5 S / cm, and the intragranular Li conductivity is 2.3 × 10 -4 S / cm. The Li ion conductivity of the oxide of Example 3 is 1.9 × 10 -5 S / cm, and the intragranular Li conductivity is 1.8×10 -4 S / cm. The Li ion conductivity of the oxide of Example 4 is 1.5 × 10 -5 S / cm, and the intragranular Li conductivity is 1.4 × 10 -4 S / cm. The Li ion conductivity of the oxide of Example 5 is 1.0 × 10 -5 S / cm, and the intragranular Li conductivity is 1.1×10 -4 S / cm. The Li ion conductivity of the oxide of Example 6 is 1.0 × 10 -5 S / cm, and the intragranular Li conductivity is 1.0 × 10 -4 S / cm. The Li ion conductivity of the oxide of Example 7 is 1.6 × 10 -5 S / cm, and the intragranular Li conductivity is 1.5×10 -4 S / cm. The Li ion conductivity of the oxide of Example 8 is 1.5 × 10 -5 S / cm, and the intragranular Li conductivity is 1.4 × 10 -4 S / cm. The Li ion conductivity of the oxide of Example 9 is 1.5 × 10 -5 S / cm. The Li ion conductivity of the oxide of Example 10 is 8.6 × 10 -6 S / cm. The Li ion conductivity of the oxide of Example 11 is 1.2 × 10 -5 S / cm. The Li ion conductivity of the oxide of Example 12 is 1.2 × 10 -6 S / cm. The Li ion conductivity of the oxide of Example 13 is 1.5 × 10 -5S / cm. The Li ion conductivity of the oxide of Example 14 is 1.1 × 10 -5 S / cm. That is, it was found that all of the oxides of Examples 1 to 14 have the properties of a solid electrolyte having Li ion conductivity.

[0064] The Li ion conductivity of the oxide of Comparative Example 1 is 5.7 × 10 -8 S / cm. The Li ion conductivity of the oxide of Comparative Example 2 was 9.2 × 10 -7 S / cm. The Li ion conductivity of the oxide of Comparative Example 3 was 3.8 × 10 -7 S / cm. The Li ion conductivity of the oxide of Comparative Example 4 was 1.3 × 10 -7 S / cm. That is, it was found that all of the oxides of Examples 1 to 14 have properties as a solid electrolyte with Li ion conductivity. On the other hand, for all of the oxides of Comparative Examples 1 to 4, only one arc was observed in the complex impedance plot, and it was not possible to calculate the intragranular Li conductivity.

[0065] (2) Identification of crystalline phases The crystalline phase of each sample of Examples 1 to 14 and Comparative Examples 1 to 4 was identified by X-ray diffraction (XRD) measurement under the following conditions. X-ray diffraction measurement equipment: Rigaku Corporation, Mini Flex 600 Characteristic X-ray:CuKα Measurement voltage: 40kV Measurement current: 15mA Measurement method: Continuous Measurement range: 10°≦2θ≦60° Step side: 0.01° Scan speed: 10° / min

[0066] Then, using the crystalline phase data for LiZr2(PO4)3 recorded in the Inorganic Crystal Structure Database (ICSD), ICSD:201935 (α phase), ICSD:89456 (α' phase), ICSD:91113 (β phase), and ICSD:91112 (β' phase), and integrated powder X-ray analysis software (manufactured by Rigaku Corporation, product name "PDXL"), the crystalline phases formed in each sample of Examples 1 to 14 were identified and their proportions were evaluated, and the results are also shown in Table 1. In addition, the crystalline phases formed in each sample of Comparative Examples 1 to 4 were identified, and the results are also shown in Table 1. In Table 1, for example, "α:100" in Examples 1 to 14 indicates that "α phase is produced at a rate of 100%." ​​In addition, in Comparative Examples 1 to 4, "α'" indicates that the main crystalline phase is the α' phase, and "β'" indicates that the main crystalline phase is the β' phase.

[0067] [Table 1]

[0068] [3] Short circuit test A copper-lithium multilayer foil was fabricated by placing a lithium foil on a copper foil and pressing it. A test cell using the oxide of Example 1 was formed by sandwiching the lithium foil of the multilayer foil so that it was in contact with the two main surfaces of the oxide of Example 1 (coin-shaped oxide). The obtained test cell (using the oxide of Example 1) was connected to an impedance analyzer (Keysight Corporation, model "E4990A") and subjected to a constant current test. The constant current test was performed by repeating the following cycles (1) to (4) 50 times. As a result, no short circuit occurred in this test cell. (1) 50 μA / cm 2 for 1 hour (2) No current (open circuit) for 30 minutes (3)-50μA / cm 2 (opposite direction from 1) for 1 hour (4) No current (open circuit) for 30 minutes

[0069] On the other hand, the garnet-type oxide solid electrolyte Li7La3Zr2O 12 (manufactured by Toshima Manufacturing Co., Ltd.) was placed in a mold with a diameter of 1.2 cm and molded into a coin shape using a hydraulic press under a load of 1 ton. The molded product was placed on a platinum plate and fired at 1200°C to obtain the oxide of Comparative Example 5. A test cell using the oxide of Comparative Example 5 was formed by sandwiching the front and back main surfaces of the oxide of Comparative Example 5 (coin-shaped oxide) with lithium foils of the multilayer foil in contact with each other in the same manner as above. Using the obtained test cell (using the oxide of Comparative Example 5), a constant current test was carried out in the same manner as above, and a short circuit occurred after the cycle of (1) to (4) above was repeated 10 times. From these results, it is clear that the battery using the oxide of the present invention as the solid electrolyte has excellent short-circuit resistance.

[0070] The foregoing examples are for illustrative purposes only and are not to be construed as limiting the invention. While the invention has been described with reference to exemplary embodiments, it is understood that the language used in describing and illustrating the invention is descriptive and exemplary, rather than limiting. As detailed herein, changes may be made within the purview of the appended claims without departing from the scope or spirit of the invention in its form. While the description of the invention has referred to specific structures, materials, and examples, it is not intended that the invention be limited to the disclosure set forth herein; rather, the invention is intended to cover all functionally equivalent structures, methods, and uses within the scope of the appended claims. [Explanation of symbols]

[0071] 1: All-solid-state battery, 21: current collector (positive electrode current collector), 22: Positive electrode, 23: solid electrolyte, 24: Negative electrode, 25: current collector (negative electrode current collector), 26: Circuit board.

Claims

1. An oxide characterized by satisfying the following formula (1) and having Li ion conductivity: Li １＋２ｘ＋ｙ＋ｚ M １ ｘ M ２ ｙ Zr ２－ｘ－ｙ Si ｚ P ３－ｚ O １２ ・・・ (1) (However, in formula (1), M １ is a divalent metal containing Ca or Mg, and M ２ is a trivalent metal containing Al, and x, y, and z satisfy x>0, y≧0, 0.05≦z≦0.25, and 0.05≦x+y≦0.

25.

2. The oxide according to claim 1, wherein x + y ≤ 0.

2.

3. The oxide according to claim 1 or 2, wherein z≦0.2 is satisfied.

4. A solid electrolyte comprising the oxide according to any one of claims 1 to 3.

5. An all-solid-state battery comprising the solid electrolyte according to claim 4.

6. A method for producing an oxide according to any one of claims 1 to 3, Li, the M １ , said M ２ a mixing step of mixing a plurality of feed components including one or more of Zr, Si, and P so as to satisfy the formula (1) to obtain a mixture of the feed components; and a calcination step of calcining the mixture to obtain the oxide.

7. The method for producing an oxide according to claim 6, wherein layered zirconium phosphate is used as a feed component for supplying P and Zr.

8. The method for producing an oxide according to claim 6 or 7, wherein the mixing is wet mixing.

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