Lithium ion-conducting oxide material and all-solid-state lithium ion secondary battery

Abstract

To provide a lithium ion conductive oxide material capable of obtaining a solid electrolyte having excellent ion conductivity and composed of a denser sintered body while lowering a sintering temperature.SOLUTION: A lithium ion conductive oxide material comprising a composite oxide containing Li, La, Zr, O, an A element (A is one or two elements selected from the group consisting of Al and Ga), and a B element (B is one or two elements selected from the group consisting of Bi and Sb), represented by a composition formula: Li7-3z (A) - p (B) La3-xZr2-p (B) - yO12 ± δ, wherein molar ratios x, y, z, p, and δ satisfy the following conditions: 0 <x ≤ 0.60 <y ≤ 0.40 <z ≤ 0.30 <p ≤ 0.5 δ is an oxygen non-stoichiometric amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a lithium ion conductive oxide material and an all-solid-state lithium ion secondary battery using the same. [Background technology]

[0002] In recent years, attention has been focused on all-solid-state lithium ion secondary batteries (sometimes simply referred to as all-solid-state lithium secondary batteries) that use a solid electrolyte as the electrolyte. Known solid electrolytes used in lithium ion secondary batteries include sulfide-based solid electrolytes such as Li2S-P2S5, as well as oxide-based solid electrolytes with a garnet-type crystal structure containing Li, La, Zr, and O.

[0003] Compared to electrolyte solutions, solid electrolytes have a limited contact area with the electrodes (positive and negative electrodes), making it important to increase lithium ion conductivity. Generally, sulfide-based solid electrolytes exhibit better lithium ion conductivity than oxide-based solid electrolytes. However, sulfide-based solid electrolytes have the risk of generating hydrogen sulfide gas when they react with water.

[0004] In contrast, oxide-based solid electrolytes are superior in terms of safety and have high chemical stability, and therefore, their use in all-solid-state batteries has been actively researched.

[0005] These oxide-based solid electrolytes, LLZ-based materials containing Li, La, Zr, and O, exist as tetragonal or cubic crystals, and the cubic phase obtained by heat treatment at a high temperature of around 1200°C is known to exhibit higher ionic conductivity. Therefore, high-temperature heat treatment is necessary to stabilize the cubic phase and to densify the resulting electrolyte, but this heat treatment can cause problems such as lithium volatilization and reactions with the substrate and electrode materials.

[0006] To address these problems, for example, a cubic garnet-type solid electrolyte material is known, which is an oxide containing Li, La, Zr, and Bi, in which some of the Zr sites are substituted with Ta or Bi (see Patent Document 1). Patent Document 1 states that by substituting 5 to 30 mol % of the Zr sites with Ta or Bi in 100 mol % of Zr, it is possible to more reliably obtain a crystal structure that can exhibit the desired ionic conductivity, and also to complete sintering at a lower temperature and in a shorter time when producing a sintered body.

[0007] Similarly, a cubic garnet-type solid electrolyte material is known that is an oxide containing Li, La, Zr, and Bi, in which part of the La sites are substituted with Bi (see Patent Document 2). Patent Document 2 states that by substituting 1 to 20 mol % of the La sites with Bi relative to 100 mol % of La, a crystal structure that can exhibit the desired ionic conductivity can be more reliably obtained, and sintering can be completed at a lower temperature and in a shorter time during the production of a sintered body.

[0008] However, in the examples of Patent Documents 1 and 2, the sintering temperatures used in the actual production of cubic garnet-type solid electrolyte materials are 1030 to 1050°C (Patent Document 1) and 1000 to 1100°C (Patent Document 2).

[0009] On the other hand, it has been reported that, for example, by adding a sintering aid such as Li3BO3 or LiBO2 to a precursor powder of an oxide-based solid electrolyte obtained using a sol-gel method and sintering it, a cubic phase is generated by heat treatment at 900°C for 30 hours, and an LLZ-based solid electrolyte with excellent ionic conductivity and high relative density is obtained (see Non-Patent Document 1).

[0010] Also known is a garnet-type solid electrolyte used as a positive electrode layer, which includes a first phase composed of a positive electrode active material containing Li, a second phase composed of a garnet-type solid electrolyte containing Li, Bi, M2 (M2 is at least one selected from the group consisting of Ca, Sr, Ba, Mg, Y, and Rb), and O, and a third phase different from the first and second phases, which is composed of a Li-Bi-M2-O-based compound containing Li, Bi, M2 (same as above), and O (see Patent Document 3). Patent Document 3 states that during the production of a positive electrode layer for an all-solid-state battery, the Li-Bi-M2-O-based compound contained in the third phase is generated from a portion of the second phase, the solid electrolyte, at a relatively low sintering temperature of less than 900°C, thereby accelerating sintering.

[0011] However, as can be seen from the contents of the examples in Patent Document 3, in fact, all samples (Samples 2 to 34) except for one (Sample 1) use the sintering aid Li3BO3, as in Non-Patent Document 1. Furthermore, in Sample 1, which does not use a sintering aid, the relative density of the solid electrolyte obtained is inferior to that of the one that uses a sintering aid.

[0012] Also known is a solid electrolyte having solid electrolyte particles and a non-molten phase, in which the solid electrolyte particles are made of a lithium-lanthanum-zirconium-based composite oxide having a garnet-type crystal structure and containing an M3 element consisting of at least one of Bi and Sb, and the non-molten phase is made of a material having a lower lithium ion conductivity than the lithium-lanthanum-zirconium-based composite oxide and is present at least either inside or between the solid electrolyte particles (see Patent Document 4).

[0013] In Patent Document 4, it is stated that the lithium-lanthanum zirconium-based composite oxide constituting the solid electrolyte particles has a non-molten phase with a different chemical potential dispersed at least within and between the solid electrolyte particles, thereby partially increasing the defect concentration, facilitating lithium ion hopping, and improving lithium ion conductivity. Furthermore, it is stated that the lithium-lanthanum zirconium-based composite oxide constituting the solid electrolyte particles contains an M3 element consisting of at least one of Bi and Sb, which facilitates density increase even at low-temperature sintering below 900°C and contributes to increasing the number of interfaces between the solid electrolyte particles, thereby enabling the resulting solid electrolyte to achieve high lithium ion conductivity even when sintered at low temperatures below 900°C.

[0014] However, as can be seen from the contents of the examples in Patent Document 4, in reality, all samples (Samples 3C, 4C, and 1-28) except for some samples (Samples 1C and 2C) contain at least one of the non-molten phase Li2ZrO3 and the sintering aids Li7SbO6 and Li3BO3, and in Samples 1C and 2C, which do not contain these, the relative density of the solid electrolyte obtained is inferior. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Patent No. 6272229 [Patent Document 2] Patent No. 6260250 [Patent Document 3] Japanese Patent Publication No. 2022-78708 [Patent Document 4] Japanese Patent Application Publication No. 2023-016639 [Non-patent literature]

[0016] [Non-Patent Document 1] Tadanaga, Kiyoji et al. Low-temperature sintering of garnet-type Li-La-Zr-O solid electrolytes using sintering aids J.Jpn.Soc.Powder Metallurgy,69(2022)481-483 Summary of the Invention [Problem to be solved by the invention]

[0017] In LLZ-based materials containing Li, La, Zr, and O, it is necessary to prevent the loss of lithium and to control the garnet-type crystal structure by enabling sintering at as low a temperature as possible and shortening the heat treatment time.

[0018] Therefore, the inventors conducted extensive research to solve the above problems and discovered that, instead of using a sintering aid as in the past, by depleting La and Zr from the stoichiometric composition in the composition formula that constitutes the LLZ-based material, it is possible to lower the sintering temperature when obtaining a solid electrolyte and also to obtain a denser one, thereby completing the present invention.

[0019] Therefore, an object of the present invention is to provide a lithium ion conductive oxide material that can provide a solid electrolyte having excellent ionic conductivity and consisting of a denser sintered body while lowering the sintering temperature. [Means for solving the problem]

[0020] That is, the gist of the present invention is as follows. [1] A composite material containing Li, La, Zr, O, an element A (A is one or two selected from the group consisting of Al and Ga), and an element B (B is one or two selected from the group consisting of Bi and Sb), and having the composition formula: Li 7-3z (A) -p (B)La 3-x Zr 2-p (B) -y O 12±δThe lithium ion conductive oxide material is characterized by comprising a composite oxide having a garnet-type or garnet-like crystal structure, wherein the molar ratios x, y, z, p, and δ satisfy the following: 0 <x≦0.6 0 <y≦0.4 0 <z≦0.3 0 <p≦0.5 δ is the oxygen non-stoichiometry. [2] The lithium ion conductive oxide material according to [1], wherein the lithium ion conductive oxide material is a calcined powder before sintering. [3] The ionic conductivity of the sintered body of the lithium ion conductive oxide material at room temperature is 1 × 10 -4 The lithium ion conductive oxide material according to [1], having a conductivity of 1.5 S / cm or more. [4] The lithium ion conductive oxide material according to [1], wherein a sintered body of the lithium ion conductive oxide material has a relative density of 90% or more at room temperature. [5] A lithium ion secondary battery comprising a sintered body of the lithium ion conductive oxide material according to any one of [1] to [3]. [6] An all-solid-state lithium ion secondary battery comprising a sintered body of the lithium ion conductive oxide material according to any one of [1] to [3] as a solid electrolyte. [Effects of the Invention]

[0021] The lithium ion conductive oxide material of the present invention allows the sintering temperature for obtaining a solid electrolyte to be lowered, and also allows a dense solid electrolyte to be obtained. In addition, since the lithium ion conductive oxide material itself can be synthesized at a relatively low temperature, it is possible to suppress the formation of heterogeneous phases that do not contribute to charge and discharge when the lithium ion conductive oxide material is made into a lithium ion battery, and further, it is possible to prevent a decrease in battery capacity and output. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 shows the X-ray diffraction patterns of the calcined powders of Samples Nos. 1 to 4. [Figure 2]FIG. 2 shows the X-ray diffraction patterns of the sintered bodies of Samples Nos. 1 to 4 after pulverization. DETAILED DESCRIPTION OF THE INVENTION

[0023] The lithium ion conductive oxide material of the present invention is a composite oxide having a garnet-type or garnet-like crystal structure, containing Li, La, Zr, O, element A (A is one or two elements selected from the group consisting of Al and Ga), and element B (B is one or two elements selected from the group consisting of Bi and Sb), and is represented by the following composition formula: where x, y, z, p, and δ, which relate to the molar ratios in the composition formula, respectively satisfy the following: Composition formula: Li 7-3z (A) -p (B)La 3-x Zr 2-p (B) -y O 12±δ 0 <x≦0.6 0 <y≦0.4 0 <z≦0.3 0 <p≦0.5 δ is the oxygen non-stoichiometry.

[0024] The lithium ion conductive oxide material according to the present invention is synthesized through a structure formed from LaO6 octahedral sites and ZrO8 hexahedral sites, which is represented by the representative composition La2Zr2O7 of the pyrochlore type crystal structure, and the representative composition is Li7La3Zr2O 12This composite oxide forms a garnet-type crystal structure with a framework of LaO8 dodecahedral sites and ZrO6 octahedral sites, represented by (LLZ). During calcination, excess La2O3 easily forms LaAlO3. Therefore, reducing the amount of La is used to obtain a calcined powder in which the formation of LaAlO3 is suppressed, i.e., the lithium ion conductive oxide material of the present invention. Furthermore, during sintering using the calcined powder, LaAlO3 reacts with Zr during heating to form the impurity La2Zr2O7. Therefore, reducing the amount of Zr used to obtain the calcined powder suppresses the formation of the impurity La2Zr2O7. Incidentally, since La2Zr2O7 is used in thermal insulation layers for high-temperature applications above 1300°C, such as in gas turbines for aircraft engines, the heat resistance of La2Zr2O7 is thought to prevent diffusion during sintering and inhibit sintering.

[0025] Therefore, in the present invention, the amounts of La and Zr charged are reduced to obtain a composite oxide having a garnet-type or garnet-like crystal structure. Furthermore, the introduction of vacancies by La and Zr relatively increases the amounts of Li and B elements, which forms a liquid phase with a Li-BO phase having a eutectic point of 690°C, facilitating diffusion. This enables pre-sintering to obtain the lithium ion conductive oxide material according to the present invention at 900°C or less, and also accelerates the progress of sintering at low temperatures of 900°C or less to obtain a solid electrolyte from the lithium ion conductive oxide material.

[0026] Here, among the molar ratios x, y, z, p, and δ in the composition formula of the lithium ion conductive oxide material according to the present invention, x relates to the molar ratio of La, and p relates to the molar ratio of Zr. As described above, the lithium ion conductive oxide material according to the present invention can be synthesized at low temperatures due to the formation of La and Zr vacancies, and furthermore, the sintering temperature for obtaining a solid electrolyte can be lowered. However, if the amount of these vacancies is too large, the structure cannot be maintained, resulting in the formation of impurity phases and a decrease in ionic conductivity. Furthermore, the presence of impurities can cause grain growth due to reactions during sintering heating, resulting in uneven grain size, which can deteriorate fluidity and reduce the relative density of the resulting solid electrolyte. It is believed that the difference in charge between the La and Zr vacancies generates vacancies at oxygen (O) sites in the crystal structure.

[0027] Therefore, in the present invention, when reducing the amount of La added, x is set to be greater than 0, preferably 0.05 or greater, more preferably 0.1 or greater. On the other hand, x is set to be 0.6 or less, preferably 0.5 or less, more preferably 0.3 or less. Similarly, when reducing the amount of Zr added, y is set to be greater than 0, preferably 0.02 or greater, more preferably 0.05 or greater. On the other hand, y is set to be 0.4 or less, preferably 0.3 or less, more preferably 0.2 or less.

[0028] Furthermore, z is related to the molar ratio of the A element, and increasing the substitution amount of the A element can increase the Li vacancy concentration in a composite oxide having a garnet-type or garnet-like crystal structure (promoting Li ion hopping conduction). Therefore, since the ionic conductivity increases, z is greater than 0, preferably 0.01 or greater, and more preferably 0.05 or greater. On the other hand, if the substitution amount is too high, the Li content decreases and the number of conductive carrier ions becomes too small. Therefore, if the A element content exceeds a certain level, the ionic conductivity decreases. Therefore, z is 0.3 or less, preferably 0.2 or less, and more preferably 0.15 or less.

[0029] Furthermore, p is related to the molar ratio of the B element, and the B element is one or two elements selected from the group consisting of Bi and Sb. By including one or both of these elements, sintering can be carried out at a lower temperature when obtaining a solid electrolyte, resulting in high ionic conductivity. In addition, as mentioned above, the addition of the B element forms a Li-BO phase with a eutectic point of 690°C, which promotes sintering by liquid phase sintering and allows for the production of a high-density electrolyte.

[0030] In order to achieve this effect and maintain the lithium ion conductivity of the resulting solid electrolyte, p is set to be greater than 0, preferably 0.1 or greater, and more preferably 0.2 or greater. On the other hand, if the substitution amount is too large, the Li-BO phase, which has a lower conductivity than composite oxides having a garnet-type or garnet-like crystal structure, increases, inhibiting the hopping of lithium ions, resulting in a decrease in ion conductivity. Therefore, p is set to be 0.5 or less, preferably 0.4 or less, and more preferably 0.35 or less. Note that p is also related to the molar ratio of Li, and this is due to the fact that the ratio of Bi 5+ and Zr 4+ This indicates that the difference in charge between the two atoms creates a vacancy at the Li site in the crystal structure.

[0031] Furthermore, δ represents the oxygen non-stoichiometry, which means that as the amount of La or Zr charged decreases, vacancies (oxygen defects) at oxygen (O) sites or excess oxygen are present relative to the theoretical composition. The value of δ is not particularly limited, but is, for example, 0 to 1.

[0032] The lithium ion conductive oxide material of the present invention can be used as a solid electrolyte for various applications, taking advantage of its electrical conductivity and density. For example, it can be used in lithium batteries such as lithium secondary batteries, as well as in various gas sensor materials for SOx, NOx, carbon dioxide, oxygen, etc., and as a lithium ion sensor material. It is particularly suitable for use as a solid electrolyte in all-solid-state lithium secondary batteries. Furthermore, even in conventional lithium ion secondary batteries that use an electrolyte solution, by replacing at least a portion of the liquid electrolyte with the lithium ion conductive oxide material of the present invention, which is a ceramic material, the use of an organic electrolyte solution can be avoided or reduced, simplifying the battery structure and simultaneously suppressing side reactions caused by the organic electrolyte solution.

[0033] The lithium ion conductive oxide material in the present invention is a calcined powder obtained by calcination, which is a state before sintering to form a solid electrolyte. There are no particular limitations on the method for obtaining such a calcined powder lithium ion conductive oxide material, and examples include gas phase synthesis methods such as PVD and CVD, solid phase reaction methods, spray pyrolysis methods, and wet methods such as coprecipitation and sol-gel methods. Among these, the following solid phase reaction method is preferred.

[0034] That is, the raw materials may be sulfates, oxides, carbonates, hydroxides, nitrates, acetates, oxalates, halides, etc. of the constituent elements. These raw materials are mixed using a planetary mill, a bead mill, a ball mill, etc.

[0035] The resulting mixture is then calcined. The calcination temperature varies depending on the constituent components and composition, including, for example, the substitutional metal ions such as element A and element B, making it difficult to specify a specific temperature. It is preferably 700°C to 1000°C, more preferably 700°C to 900°C, and even more preferably 700°C to 800°C. Similarly, the calcination time also varies depending on the constituent components and composition, making it difficult to specify a specific temperature. It is preferably 5 hours to 20 hours, more preferably 10 hours to 15 hours. Furthermore, the calcination atmosphere is not particularly limited, but it is preferable to select an atmosphere with an appropriate oxygen partial pressure depending on the constituent components and composition. Examples of suitable atmospheres include air, nitrogen, argon, and nitrogen or argon with an adjusted oxygen partial pressure.

[0036] The powder (calcined powder) obtained in this manner may be used as is, or may be further pulverized. For pulverization, a planetary mill, a bead mill, a ball mill, or the like may be used. The particle size after pulverization can be adjusted to an appropriate particle size depending on the application, but generally, it is preferable for the D50 (average particle size) to be approximately 0.2 μm or more and 20 μm or less. D50 is the particle size (median diameter) at which the cumulative number of particles in the volume-based cumulative distribution of particle sizes is 50%.

[0037] Furthermore, the calcined powder thus obtained, i.e., the lithium ion conductive oxide material according to the present invention, can be sintered to form a solid electrolyte, as described above, and can be suitably used in lithium ion secondary batteries. The sintering conditions are not particularly limited, as in the case of obtaining a lithium ion conductive oxide material, but the sintering temperature is preferably 700°C to 1000°C, and more preferably 800°C to 900°C. The sintering time is preferably 5 hours to 20 hours, and more preferably 10 hours to 15 hours. Furthermore, the calcination atmosphere is preferably air.

[0038] Furthermore, when the lithium ion conductive oxide material of the present invention is sintered, it is preferable that the ionic conductivity at room temperature is 1×10 -4 S / cm or more, preferably 2×10 -4 S / cm or more. Similarly, when sintered, the relative density at room temperature is preferably 90% or more, and more preferably 91% or more. These values ​​are those when sintered by the method described in the examples below. [Example]

[0039] The present invention will be specifically explained below using examples, but the present invention is not limited to these examples.

[0040] [Preparation of lithium ion conducting oxide materials] The raw materials used for the lithium ion conductive oxide material were Li2CO3, Al(OH)3, MgO, Bi2O3, La(OH)3, and ZrO2. These raw material powders were weighed and mixed so that the ratio of each component would be the composition shown in Samples No. 1 to 5 in Table 1. In this case, taking into account the loss of some Li during firing, the amount of Li2CO3 was increased more than the target composition.

[0041] [Table 1]

[0042] When mixing the raw materials, the weighed raw material powders were placed in a plastic container together with zirconia balls, and mixed in ethanol using a ball mill for 15 hours, and then dried to obtain a raw material mixture.

[0043] Next, the resulting raw material mixture was pre-fired in a heat-resistant container in an air atmosphere at 900°C for 15 hours to obtain pre-fired powder of Sample No. 1. Similarly, pre-fired in a heat-resistant container in an air atmosphere at 800°C for 15 hours to obtain pre-fired powder of Samples No. 2 to 5. These pre-fired powders were each placed in a nylon pot together with zirconia balls and pulverized in ethanol using a planetary ball mill for 16 hours, and then further dried to obtain lithium ion conductive oxide materials (powders, i.e., pre-fired powders of Samples No. 1 to 5).

[0044] The ionic conductivity of the obtained lithium ion conductive oxide material (powder) was measured by preparing a sintered body as follows. First, the lithium ion conductive oxide material (powder) was placed in a mold with a diameter of 11 mm and pressed at a pressure of 150 MPa to a thickness of approximately 10 mm to obtain a compact of the lithium ion conductive oxide material (powder).

[0045] Next, the compact obtained above was fired in an air atmosphere at 800 to 900°C for 15 hours to obtain sintered bodies of the lithium ion conductive oxide material (sintered bodies of samples No. 1 to 5). Various measurements were carried out as follows.

[0046] [Crystal structure analysis] Using an X-ray diffractometer (Rigaku smartlab), the calcined powders and sintered bodies of Samples No. 1 to 5 were crushed in a mortar and then subjected to X-ray diffraction measurement to obtain X-ray diffraction patterns. As a result, the X-ray diffraction pattern No. 4422259 (Li7La3Zr2O) in the Cambridge Structural Database (CSD) was obtained. 12X-ray diffraction patterns similar to those of the Ia-3d(230) space group were primarily observed. Therefore, samples 1 to 5 can be determined to have a garnet-type or garnet-like crystal structure. Figure 1 shows the X-ray diffraction patterns of the calcined powders of samples 1 to 5. Figure 2 shows the X-ray diffraction patterns of the crushed sintered bodies of samples 1 to 5. Furthermore, Rietveld analysis was performed using Fujio Izumi's multipurpose pattern fitting system, RIETAN-FP, based on the X-ray diffraction patterns of the crushed sintered bodies of samples 1 to 5, and the lattice constants of each were calculated.

[0047] [Component analysis] The calcined powders of samples 1 to 5 were analyzed for composition by atomic absorption spectrometry or ICP atomic emission spectrometry. For ICP atomic emission spectrometry, each calcined powder was dissolved in a solvent such as an acid, and the resulting solution was analyzed using an ICP atomic emission spectrometer. The molar ratios were normalized using the La feed composition. The results are shown in Table 1.

[0048] Relative Density After measuring the mass of the sintered compacts of Samples No. 1 to 5, the length of each side or the diameter and thickness of each of the sintered compacts of Samples No. 1 to 5 were measured at several locations using a vernier caliper and a micrometer, and the average values ​​were calculated. Using these measurements, the volume of the sintered compacts of Samples No. 1 to 5 was calculated, and the apparent density was calculated. In addition, the theoretical density of each composition was calculated from the calculated lattice constant, and the apparent density was then divided by the theoretical density and multiplied by 100 to calculate the relative density, and the values ​​shown in Table 1 were obtained.

[0049] [Lithium ion conductivity measurement] After coating both sides of the sintered compacts of Samples No. 1 to 5 by Au sputtering, AC impedance measurements were performed at room temperature using an electrochemical measurement system manufactured by N4L (Newtons4th Ltd) to calculate the lithium ion conductivity. As a result, the lithium ion conductivity values ​​shown in Table 1 were obtained for each sample.

[0050] As shown in Table 1, the crystal phase of the sintered body of all samples Nos. 1 to 5 was mainly cubic LLZ, but the formation of impurity La2Zr2O7 was confirmed in sample No. 2. In contrast, the formation of impurity La2Zr2O7 was not confirmed in samples Nos. 1, 3, 4, and 5, which are within the scope of the present invention. Among them, samples Nos. 3, 4, and 5 showed relative densities of 90% or more, and furthermore, ionic conductivities of 1×10 -4 S / cm or more. It is thought that sample No. 1 showed low density due to the high calcination temperature, which caused grain growth. Incidentally, the finer the particles, the greater the surface energy, which speeds up material transfer during sintering, making it suitable for obtaining dense sintered bodies at low temperatures.

[0051] Therefore, the lithium ion conductive oxide material of the present invention has high ionic conductivity and more stable characteristics, and when used as a solid electrolyte, it can provide an all-solid-state lithium ion secondary battery with excellent battery characteristics.

Claims

1. Li, La, Zr, O, an element A (A is one or two selected from the group consisting of Al and Ga), and an element B (B is one or two selected from the group consisting of Bi and Sb), and having a composition formula: Li ７－３ｚ (A) －ｐ (B) La ３－ｘ Zr ２－ｐ (B) －ｙ O １２±δ The lithium ion conductive oxide material is characterized by comprising a composite oxide having a garnet-type or garnet-like crystal structure, wherein the molar ratios x, y, z, p, and δ are each expressed as follows: 0<x≦0.6 0<y≦0.4 0<z≦0.3 0<p≦0.5 δ is the oxygen non-stoichiometry.

2. 2. The lithium ion conductive oxide material according to claim 1, wherein the lithium ion conductive oxide material is a calcined powder before sintering.

3. The ionic conductivity of the sintered body of the lithium ion conductive oxide material at room temperature is 1×10 －４ 2. The lithium ion conductive oxide material according to claim 1, wherein the conductivity is 1.5 S / cm or more.

4. 2. The lithium ion conductive oxide material according to claim 1, wherein a sintered body of the lithium ion conductive oxide material has a relative density of 90% or more at room temperature.

5. A lithium ion secondary battery comprising a sintered body of the lithium ion conductive oxide material according to any one of claims 1 to 3.

6. An all-solid-state lithium ion secondary battery comprising a sintered body of the lithium ion conductive oxide material according to any one of claims 1 to 3 as a solid electrolyte.

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