Lithium ion conductive glass ceramic precursor

Abstract

Provided is a lithium ion conductive glass ceramic precursor of an LAGP-based glass material which is capable of forming a lithium ion conductive glass ceramic having a high density by sintering at 700 DEG C or less. The composition ratio of P, Al, Ge, and Li satisfies a composition ratio represented by a composition formula Li1 + xAlxGe2-x-zMzP3O12 (x = 0.2-0.6, z = 0-0.1, and M is one or more selected from the group consisting of Zr, Ti, Sn, and Si), or a composition ratio represented by a composition formula Li1 + xAlxGe2-x-zMzP3O12 + aLi2O + bP2O5 (x = 0.2-0.6, z = 0-0.1, a = 0.01-0.3, b = 0-0.3, and M is one or more selected from the group consisting of Zr, Ti, Sn, and Si), and the composition ratio of P, Al, Ge, and Li satisfies a composition formula Li1 + xAlxGe2-x-zMzP3O12 (x = 0.2-0.6, z = 0 and when particles of the lithium ion conductive glass ceramic precursor having a mesh of 106 [mu] m are sintered and crystallized at a temperature of 700 DEG C or less, the amount of water released at 550-700 DEG C is 60 ppm or less, and the aforementioned technical problem can be solved by a lithium ion conductive glass ceramic precursor of a glass material.

Description

Technical Field

[0001] The present invention relates to a lithium-ion conductive glass-ceramic precursor and to an all-solid-state secondary battery having a solid electrolyte formed by sintering the precursor and containing the same. Background Art

[0002] In applications such as power sources for electric vehicles and power sources for portable telephone terminals, lithium-ion secondary batteries with high energy density that can be charged and discharged are widely used.

[0003] Most commercially available lithium-ion secondary batteries currently use a liquid electrolyte (electrolyte solution) in order to have a high energy density. And as this electrolyte solution, an electrolyte solution in which a lithium salt is dissolved in an aprotic organic solvent such as a carbonate or a cyclic ester is generally used.

[0004] However, in a lithium-ion secondary battery using a liquid electrolyte (electrolyte solution), there is a risk of electrolyte leakage. In addition, the organic solvents and the like generally used in the electrolyte solution are volatile flammable substances, posing a safety hazard.

[0005] Therefore, as an electrolyte for a lithium-ion secondary battery, it has been proposed to use a solid electrolyte instead of a liquid electrolyte (electrolyte solution) such as an organic solvent. In addition, while developing an all-solid-state secondary battery using a solid electrolyte as the electrolyte, all other component elements such as the electrode layer are also entirely composed of solids.

[0006] And, as a representative property among the properties required for the solid electrolyte of an all-solid-state secondary battery, lithium-ion conductivity and sintering characteristics can be cited. In addition, in order to form an interface well with the electrode layer and the like (form an interface with a lower resistance), a high density is required after sintering.

[0007] As a solid electrolyte for an all-solid-state secondary battery, examples include sulfide-based solid electrolytes represented by Li 4-x Ge 1-x P x S 4 etc., NASICON-type structured Li 1+x Al x Ge 2-x P 3 O 12 、Li 1+x Al x Ti 2-x P 3 O 12 、perovskite-type structured La 2 / 3-x Li 3x TiO 3Oxide-based solid electrolytes represented by etc. As a more specific example than oxide-based solid electrolytes, the electrolytes described in Patent Documents 1 to 3 and Non-Patent Document 1 are shown. In particular, Li 1+x Al x Ge 2-x P 3 O 12 (LAGP) or Li 1+x Al x Ti 2-x P 3 O 12 (LATP), which can be crystallized from a glass state, so a product with high lithium ion conductivity can be obtained at a relatively low sintering temperature.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-258165

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-112599

[0012] Patent Document 3: Japanese Patent Application Laid-Open No. 2021-174766

[0013] Non-Patent Documents

[0014] Non-Patent Document 1: Journal of Power Sources 192(2009)689-692 Summary of the Invention

[0015] Technical Problem to be Solved by the Invention

[0016] Among them, the fabrication of an oxide-based all-solid-state secondary battery composed of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer can be roughly divided into two methods. The first is a method in which any one of the positive electrode layer, the solid electrolyte layer, or the negative electrode layer is used as a substrate and the remaining layers are sintered; the second is a method in which the positive electrode layer, the solid electrolyte layer, the negative electrode layer, and, if necessary, the interconnection layer are all sintered integrally to form a shape (co-sintering). In particular, in an all-solid-state solid secondary battery using an oxide-based solid electrolyte, a multilayer ceramic capacitor (MLCC)-type battery needs to be fabricated by co-sintering. Moreover, when the electrode layer and the solid electrolyte layer are integrally formed, in order to suppress the decomposition of the electrode active material and the decrease in the discharge capacity (battery capacity) as much as possible, it is desirable to sinter at as low a temperature as possible. However, from the viewpoint of forming an oxide-based solid electrolyte layer having a prescribed lithium ion conductivity, density, etc., sintering is usually carried out at a temperature higher than 700 °C.

[0017] In addition, it is known that the solid electrolyte shown in Non-Patent Document 1 reacts with the electrode active material (positive electrode active material or negative electrode active material), and it is difficult to perform co-sintering at a temperature higher than 700 °C.

[0018] On the other hand, Patent Document 1 discloses a battery sintered at 800 °C, but its resistance value is as high as 10 kΩ, and even when the lithium ion conductivity is calculated based on the area and thickness, it is as low as 3×10 1.5 Al 0.5 Ge 1.5 P 3 O 12 S / cm. -7

[0019] In addition, although there is a method focusing on changing the composition of LAGP as shown in Patent Document 2, the sintered density necessary for forming a good interface is not disclosed therein. In addition, an LAGP-based glass material (an oxide-based glass material containing Li, Al, Ge, and P as essential components, and their composition ratios satisfying Li 1+x x Al 2-x Ge 3 P 12 O 1+ or a composition ratio equivalent thereto) and an LATP-based glass material (an oxide-based glass material containing Li, Al, Ti, and P as essential components, and their composition ratios satisfying Li 1+ x Al x Ti 2-x P 3 O 12Compared with an oxide-based glass material having a component ratio equivalent thereto, although crystallization (glass-ceramicization) can be carried out at a lower sintering temperature, there is a technical problem that it is difficult to obtain a solid electrolyte with a higher density. Therefore, a high-density solid electrolyte that can satisfactorily form an electrode layer interface of an all-solid-state secondary battery has not been substantially obtained.

[0020] In addition, in Patent Document 3, a method for manufacturing a solid lithium ion conductor material is disclosed: starting materials are melted in a high-temperature step, a low-temperature step is carried out at the stage of cooling or quenching the obtained intermediate product, or at the stage of subdivision, the intermediate product is brought into contact with water or water vapor at the stage of forming powder, and then dried (for example, burned out in a nitrogen atmosphere after freeze-drying and then vacuum-dried, etc.), and ceramized at a high temperature (for example, 950 °C). However, if water or water vapor is added to the LAGP-based glass material, it will cause compositional deviation and make manufacturing difficult. In addition, low-temperature sintering will also become difficult. In addition, since a part of the components will dissolve in water, it is also difficult to densify a material containing such dissolved and hydrated components.

[0021] Therefore, an object of the present invention is to provide a lithium ion conductive glass ceramic precursor of an LAGP-based glass material, which can form a high-density lithium ion conductive glass ceramic by sintering at 700 °C or lower.

[0022] Means for solving the technical problem

[0023] To solve the above technical problem, the present inventors have conducted in-depth research and found that the reason why it is difficult to densify a glass ceramic obtained by low-temperature sintering of an LAGP-based glass material is that the water dissolved in the glass material vaporizes during the sintering, which is different from the case where the water adsorbed (chemisorbed or physically adsorbed) on the surface vaporizes, and it is difficult for the water to escape instantaneously. And it has also been found that by selecting a component ratio represented by the component formula of Li 1+x Al x Ge 2-x-z M z P 3 O 12 (x = 0.2 to 0.6, z = 0 to 0.1, M is one or more selected from the group consisting of Zr, Ti, Sn, and Si), or by satisfying Li 1+x Al x Ge 2-x-z M z P 3 O 12 +aLi 2 O+bP 2 O 5(x = 0.2 to 0.6, z = 0 to 0.1, a = 0.01 to 0.3, b = 0 to 0.3, M is one or more selected from the group consisting of Zr, Ti, Sn, and Si), and when the particles passing through a 106 μm sieve mesh are sintered and crystallized at a temperature of 700 °C or lower, the amount of water released at 550 to 700 °C is 60 ppm or less per unit of the lithium-ion conductive glass ceramic precursor, which is a glass material of the lithium-ion conductive glass ceramic precursor, and by performing low-temperature sintering at 700 °C or lower, a higher-density lithium-ion conductive glass ceramic can be formed.

[0024] That is, the present invention is as follows <1> to <5>.

[0025] <1> A lithium-ion conductive glass ceramic precursor, which is a glass material of a lithium-ion conductive glass ceramic precursor capable of forming a lithium-ion conductive glass ceramic by sintering, wherein the component ratios of P, Al, Ge, and Li satisfy Li 1+ x Al x Ge 2-x-z M z P 3 O 12 (x = 0.2 to 0.6, z = 0 to 0.1, M is one or more selected from the group consisting of Zr, Ti, Sn, and Si), and when the particles of the lithium-ion conductive glass ceramic precursor passing through a 106 μm sieve mesh are sintered and crystallized at a temperature of 700 °C or lower, the amount of water released at 550 to 700 °C is 60 ppm or less per unit of the lithium-ion conductive glass ceramic precursor.

[0026] <2> The lithium-ion conductive glass ceramic precursor according to <1>, wherein, in terms of mol% based on oxides, it contains 0.05 to 2.4% of ZrO 2 component.

[0027] <3> A lithium-ion conductive glass ceramic precursor, which is a glass material of a lithium-ion conductive glass ceramic precursor capable of forming a lithium-ion conductive glass ceramic by sintering, wherein the component ratios of P, Al, Ge, and Li satisfy Li 1+ x Al x Ge 2-x-z M z P 3 O 12 +aLi 2 O + bP 2 O 5(x = 0.2 to 0.6, z = 0 to 0.1, a = 0.01 to 0.3, b = 0 to 0.3, M is one or more selected from the group consisting of Zr, Ti, Sn, and Si) When the particles of the lithium ion conductive glass ceramic precursor passing through a sieve with a mesh size of 106 μm are sintered and crystallized at a temperature of 700 °C or lower, the amount of water released at 550 to 700 °C is 60 ppm or less per unit of the lithium ion conductive glass ceramic precursor.

[0028] <4> The lithium ion conductive glass ceramic precursor as described in <3>, which contains 0.05 to 2.4% of ZrO in terms of mol% based on the oxide standard. 2 Component.

[0029] <5> An all-solid-state secondary battery containing a lithium ion conductive glass ceramic obtained by sintering the lithium ion conductive glass ceramic precursor as described in any one of <1> to <4> as a solid electrolyte.

[0030] Effects of the Invention

[0031] According to the present invention, a lithium ion conductive glass ceramic precursor of a LAGP-based glass material can be provided, which can form a high-density lithium ion conductive glass ceramic by sintering at 700 °C or lower. Description of the Drawings

[0032] Figure 1 It is a chart showing the humidity measurement results when the lithium ion conductive glass ceramic precursors of Example 2, Example 3, and Comparative Example 4 are sintered and crystallized at low temperature.

[0033] Figure 2 It is a chart showing the humidity measurement results when the lithium ion conductive glass ceramic precursors of different particle sizes in Comparative Example 4 are sintered and crystallized at low temperature.

[0034] Figure 3 It is a chart showing the humidity measurement results when the lithium ion conductive glass ceramic precursor of Comparative Example 4 (product passing through a 25 μm sieve) is sintered and crystallized at low temperature.

[0035] Figure 4 It is a secondary electron image (photo used as a picture) of the cross-section of the sintered body particles of Comparative Example 1 (left) and Example 3 (right). Detailed Description

[0036] The present invention will be described.

[0037] The present invention relates to a precursor of a lithium-ion conductive glass-ceramic, which is a glass material capable of forming a lithium-ion conductive glass-ceramic through sintering. Among them, the component ratios of P, Al, Ge, and Li satisfy Li 1+x Al x Ge 2-x-z M z P 3 O 12 (where x = 0.2 to 0.6, z = 0 to 0.1, and M is one or more selected from the group consisting of Zr, Ti, Sn, and Si), or the component ratios of P, Al, Ge, and Li satisfy Li 1+x Al x Ge 2-x-z M z P 3 O 12 +aLi 2 O+bP 2 O 5 (where x = 0.2 to 0.6, z = 0 to 0.1, a = 0.01 to 0.3, b = 0 to 0.3, and M is one or more selected from the group consisting of Zr, Ti, Sn, and Si). When the particles of the precursor of the lithium-ion conductive glass-ceramic passing through a sieve with a mesh size of 106 μm are sintered and crystallized at a temperature of 700 °C or lower, the amount of water released at 550 to 700 °C is 60 ppm or less per unit of the precursor of the lithium-ion conductive glass-ceramic.

[0038] Hereinafter, they are sometimes referred to as "the precursor of the lithium-ion conductive glass-ceramic of the present invention". In addition, the embodiments satisfying the former component ratio are sometimes referred to as "the first embodiment", and the embodiments satisfying the latter component ratio are sometimes referred to as "the second embodiment".

[0039] First, the components and component ratios constituting the precursor of the lithium-ion conductive glass-ceramic of the present invention will be described in detail.

[0040] The precursor of the lithium-ion conductive glass-ceramic of the present invention contains a P component, an Al component, a Ge component, and a Li component as essential components. In the first embodiment, their component ratios satisfy Li 1+x Al x Ge 2-x-z M z P 3 O 12 (where x = 0.2 to 0.6, z = 0 to 0.1, and M is one or more selected from the group consisting of Zr, Ti, Sn, and Si). In the second embodiment, their component ratios satisfy Li 1+x Al x Ge2-x-z M z P 3 O 12 + aLi 2 O + bP 2 O 5 (x = 0.2 to 0.6, z = 0 to 0.1, a = 0.01 to 0.3, b = 0 to 0.3, M is one or more selected from the group consisting of Zr, Ti, Sn, and Si) The component ratio shown by the component formula.

[0041] It should be noted that the content of the components contained in the lithium ion conductive glass ceramic precursor of the present invention is expressed in mol% based on oxides as long as there is no special negation (hereinafter, when only mol% is recorded, it means mol% based on oxides only when there is no special negation). The content represented by this "mol% based on oxides" means that, assuming that oxides, double salts, metal fluorides, etc. used as raw materials for the lithium ion conductive glass ceramic precursor of the present invention are all decomposed into oxides during melting, the total number of moles of the generated oxides is recorded as 100 mol%, and the content of each component contained in the lithium ion conductive glass ceramic precursor of the present invention is expressed.

[0042] (1) Essential components and their components of the first embodiment

[0043] P 2 O 5 The component is an essential component necessary for the glass formation of the LAGP-based glass material of the first embodiment and for the lithium ion conductive glass ceramic obtained by sintering the first embodiment to contain a rhombohedral NASICON-type crystal phase and have excellent lithium ion conductivity. Therefore, the lower limit of the content of this P 2 O 5 component is preferably 34.0 mol%, more preferably 35.0 mol%, still more preferably 36.0 mol%, and further preferably 37.0 mol%. In addition, since it is possible to easily obtain a rhombohedral NASICON-type crystal phase by sintering, the upper limit of the content of the P 2 O 5 component is preferably 45.0 mol%, more preferably 44.0 mol%, still more preferably 43.0 mol%, still more preferably 42.0 mol%, further preferably 41.0 mol%, still further preferably 40.0 mol%, still more preferably 39.0 mol%, and still more preferably 38.0 mol%. For example, in the first embodiment, if it contains 37.0 to 42.0 mol% of the P 2 O 5 component, it is more preferable.

[0044] Al 2 O 3 The component is an essential component necessary for the lithium-ion conductive glass-ceramic obtained by sintering the first embodiment to contain a crystalline phase of a rhombohedral NASICON-type structure and to have excellent lithium-ion conductivity. Therefore, Al 2 O 3 The lower limit of the content of the component is preferably 0.5 mol%, more preferably 1.0 mol%, still more preferably 2.0 mol%, yet more preferably 3.0 mol%, further preferably 4.0 mol%, still further preferably 4.5 mol%. In addition, since a crystalline phase of a rhombohedral NASICON-type structure can be easily obtained by sintering, the Al 2 O 3 The upper limit of the content of the component is preferably 10.0 mol%, more preferably 9.0 mol%, still more preferably 8.0 mol%, further preferably 7.0 mol%, still further preferably 6.0 mol%, yet further preferably 5.5 mol%. For example, in the first embodiment, a composition containing 2.0 to 7.0 mol% of Al 2 O 3 component is more preferable.

[0045] GeO 2 The component is also an essential component necessary for the lithium-ion conductive glass-ceramic obtained by sintering the first embodiment to contain a crystalline phase of a rhombohedral NASICON-type structure and to have excellent lithium-ion conductivity. Therefore, GeO 2 The lower limit of the content of the component is preferably 29.0 mol%, more preferably 30.0 mol%, still more preferably 31.0 mol%, yet more preferably 32.0 mol%, further preferably 33.0 mol%, still further preferably 34.0 mol%, still further preferably 35.0 mol%, yet further preferably 36.0 mol%, still further preferably 37.0 mol%, yet further preferably 38.0 mol%, yet further preferably 39.0 mol%. In addition, since a crystalline phase of a rhombohedral NASICON-type structure can be easily obtained by sintering, GeO 2The upper limit of the content of the component is preferably 49.0 mol%, more preferably 48.0 mol%, still more preferably 47.0 mol%, yet more preferably 46.0 mol%, further preferably 45.0 mol%, still further preferably 44.0 mol%, still more preferably 43.0 mol%, yet more preferably 42.0 mol%, and yet further preferably 41.0 mol%. For example, in the first embodiment, if it is a component containing 32.0 to 46.0 mol% of GeO 2 component, it is more preferable.

[0046] Li 2 O component is an essential component necessary to impart lithium ion conductivity to the lithium ion conductive glass ceramic obtained by sintering the first embodiment. Therefore, the lower limit of the content of the Li 2 O component is preferably 12.0 mol%, more preferably 13.0 mol%, still more preferably 14.0 mol%, yet more preferably 15.0 mol%, further preferably 16.0 mol%, and still more preferably 17.0 mol%. On the other hand, since it is possible to easily obtain a rhombohedral NASICON-type crystal phase by sintering, the upper limit of the content of the Li 2 O component is preferably 22.0 mol%, more preferably 21.0 mol%, still more preferably 20.0 mol%, further preferably 19.0 mol%, and still more preferably 18.0 mol%. For example, in the first embodiment, if it is a component containing 15.0 to 19.0 mol% of Li 2 O component, it is more preferable.

[0047] And, in this first embodiment, their component ratios satisfy Li 1+x Al x Ge 2-x-z M z P 3 O 12(x = 0.2 to 0.6, z = 0 to 0.1, M is one or more selected from the group consisting of Zr, Ti, Sn, and Si) of the component ratio shown by the component formula. That is, in the first embodiment, the component ratios of P, Al, Ge, and Li are for a glass material (LAGP-based glass material) to be a component ratio of the LAGP system. It should be noted that for x in the above component formula, its lower limit is preferably 0.25 or more, more preferably 0.3 or more, and its upper limit is preferably 0.55 or less, more preferably 0.5 or less. In addition, for z in the above component formula, its lower limit can be greater than 0 or can be 0.005 or more. Further, its upper limit is preferably 0.05 or less, more preferably 0.03 or less. And for M in the above component formula, more preferably, it is one or more selected from the group consisting of Zr, Ti, and Sn, more preferably Zr and / or Sn, and still more preferably Zr.

[0048] (2) Essential components and their components of the second embodiment

[0049] P 2 O 5 The component, similarly, is an essential component necessary for glass formation of the LAGP-based glass material of the second embodiment and for the lithium-ion conductive glass ceramic obtained by sintering the second embodiment to contain a rhombohedral NASICON-type structure crystal phase and have excellent lithium-ion conductivity. Therefore, this P 2 O 5 The lower limit of the content of the component is preferably 33.0 mol%, more preferably 34.0 mol%, still more preferably 35.0 mol%, yet more preferably 36.0 mol%, and further preferably 37.0 mol%. In addition, since it is possible to easily obtain a rhombohedral NASICON-type structure crystal phase by sintering, the P 2 O 5 The upper limit of the content of the component is preferably 42.0 mol%, more preferably 41.0 mol%, still more preferably 40.0 mol%, further preferably 39.0 mol%, and even more preferably 38.0 mol%. For example, in the second embodiment, if it contains 36.0 to 39.0 mol% of P 2 O 5 The component, it is more preferable.

[0050] Al 2 O 3 The component, similarly, is an essential component necessary for the lithium-ion conductive glass ceramic obtained by sintering the second embodiment to contain a rhombohedral NASICON-type structure crystal phase and have excellent lithium-ion conductivity. Therefore, Al 2 O 3The lower limit of the content of the component is preferably 0.5 mol%, more preferably 1.0 mol%, still more preferably 2.0 mol%, yet more preferably 3.0 mol%, and further preferably 3.5 mol%. In addition, since it is possible to easily obtain a rhombohedral NASICON-type crystal phase by sintering, Al 2 O 3 The upper limit of the content of the component is preferably 10.0 mol%, more preferably 9.0 mol%, still more preferably 8.0 mol%, further preferably 7.0 mol%, and even more preferably 6.5 mol%. For example, in the second embodiment, if it contains 2.0 to 7.0 mol% of Al 2 O 3 component, it is more preferable.

[0051] GeO 2 component, similarly, is an essential component necessary for the lithium-ion conductive glass-ceramic obtained by sintering the second embodiment to contain a rhombohedral NASICON-type crystal phase and have excellent lithium-ion conductivity. Therefore, GeO 2 The lower limit of the content of the component is preferably 29.0 mol%, more preferably 30.0 mol%, still more preferably 31.0 mol%, even more preferably 32.0 mol%, yet more preferably 33.0 mol%, further preferably 34.0 mol%, still further preferably 35.0 mol%, and even more preferably 36.0 mol%. In addition, since it is possible to easily obtain a rhombohedral NASICON-type crystal phase by sintering, GeO 2 The upper limit of the content of the component is preferably 47.0 mol%, more preferably 46.0 mol%, still more preferably 45.0 mol%, further preferably 44.0 mol%, even more preferably 43.0 mol%, and yet more preferably 42.0 mol%. For example, in the second embodiment, if it contains 32.0 to 44.0 mol% of GeO 2 component, it is more preferable.

[0052] Li 2 O component, similarly, is an essential component necessary for imparting lithium-ion conductivity to the lithium-ion conductive glass-ceramic obtained by sintering the second embodiment. Therefore, Li 2 The lower limit of the content of the O component is preferably 15.0 mol%, more preferably 16.0 mol%, and further preferably 17.0 mol%. On the other hand, since it is possible to easily obtain a rhombohedral NASICON-type crystal phase by sintering, Li 2The upper limit of the content of the O component is preferably 25.0 mol%, more preferably 24.0 mol%, still more preferably 23.0 mol%, further preferably 22.0 mol%, still further preferably 21.0 mol%, and yet further preferably 20.0 mol%. For example, in the second embodiment, if it contains 18.0 to 23.0 mol% of Li 2 O component, it is more preferable.

[0053] Moreover, in this second embodiment, their component ratios satisfy Li 1+x Al x Ge 2-x-z M z P 3 O 12 +aLi 2 O+bP 2 O 5 (x = 0.2 to 0.6, z = 0 to 0.1, a = 0.01 to 0.3, b = 0 to 0.3, and M is one or more selected from the group consisting of Zr, Ti, Sn, and Si). That is, the second embodiment is a glass material as follows: the component ratios of P, Al, Ge, and Li are such that a glass material (LAGP-based glass material) can add a specified amount of lithium oxide or lithium oxide and diphosphorus pentoxide components that can serve as sintering aids in the LAGP system.

[0054] It should be noted that for x in the above component formula, its lower limit is preferably 0.25 or more, more preferably 0.3 or more, and its upper limit is preferably 0.55 or less, more preferably 0.5 or less. In addition, for z in the above component formula, its lower limit can be greater than 0 or can be 0.005 or more. Further, its upper limit is preferably 0.05 or less, more preferably 0.03 or less. Moreover, for M in the above component formula, it is more preferably one or more selected from the group consisting of Zr, Ti, and Sn, more preferably Zr and / or Sn, and still more preferably Zr. Further, for a in the above component formula, its lower limit is preferably 0.02 or more, more preferably 0.03 or more, still more preferably 0.04 or more, and its upper limit is preferably 0.2 or less, more preferably 0.1 or less, still more preferably 0.07 or less. Further, for b in the above component formula, its lower limit is preferably greater than 0, more preferably 0.01 or more, still more preferably 0.02 or more, and its upper limit is preferably 0.2 or less, more preferably 0.1 or less, still more preferably 0.05 or less.

[0055] (3) Optional components

[0056] It should be noted that either the first embodiment or the second embodiment may be a component composed of the above-mentioned essential components. Additionally, as optional components, it may also contain ZrO 2 component, TiO 2 component, SnO 2 component, SiO 2 component, or B 2 O 3 component, Nb 2 O 5 component, La 2 O 3 component, Y 2 O 3 component, Sc 2 O 3 component, CaO component, MgO component, Ta 2 O 5 component, and one or more selected from the group consisting of transition metal oxides such as Co, Ni, Mn, and Fe.

[0057] In particular, since it is possible to suppress the dissolution of moisture into the glass material during melting and further reduce the amount of moisture released at 550 - 700°C during low-temperature sintering and crystallization, either the first embodiment or the second embodiment is preferably a structure containing ZrO 2 component.

[0058] ZrO 2 component, as described above, is an optional component that can reduce the amount of moisture released at 550 - 700°C when the lithium-ion conductive glass-ceramic precursor of the present invention is crystallized by low-temperature sintering. Additionally, it is also a component that can promote the crystallization of sintering of the lithium-ion conductive glass-ceramic precursor of the present invention. Furthermore, it is also a component that can contribute to improving the chemical durability of the lithium-ion conductive glass-ceramic precursor of the present invention and the lithium-ion conductive glass-ceramic sintered therefrom. The content of ZrO 2 component is preferably 0.05 mol% or more, more preferably 0.1 mol% or more, still more preferably 0.15 mol% or more, and further preferably 0.2 mol% or more. On the other hand, from the perspective of being able to set the melting temperature during raw material melting lower and easily suppressing devitrification during casting (glass block formation), it is preferably 2.4 mol% or less, more preferably 2.0 mol% or less, still more preferably 1.5 mol% or less, yet more preferably 1.0 mol% or less, and further preferably 0.5 mol% or less.

[0059] SiO 2 component, B 2 O 3 component, La2 O 3 components and Nb 2 O 5 components are all optional components that make it easier to form a glass of the lithium-ion conductive glass-ceramic precursor of the present invention. Additionally, SiO 2 components can also improve the mechanical strength of the lithium-ion conductive glass-ceramics sintered from the lithium-ion conductive glass-ceramic precursor of the present invention. It should be noted that the content of SiO 2 components is preferably 5.0 mol% or less, more preferably 3.0 mol% or less, still more preferably 2.0 mol% or less, and further preferably 1.0 mol% or less. And, the content of B 2 O 3 components is preferably 10.0 mol% or less, more preferably 8.0 mol% or less, still more preferably 5.0 mol% or less, and further preferably 3.0 mol% or less. Additionally, the content of La 2 O 3 components is preferably 10.0 mol% or less, more preferably 8.0 mol% or less, still more preferably 5.0 mol% or less, yet more preferably 3.0 mol% or less, and further preferably 1.0 mol% or less. Furthermore, the content of Nb 2 O 5 components is preferably 50.0 mol% or less, more preferably 40.0 mol% or less, still more preferably 30.0 mol% or less, and further preferably 20.0 mol% or less.

[0060] SnO 2 components and TiO 2 components are all optional components that can promote crystallization during sintering of the lithium-ion conductive glass-ceramic precursor of the present invention. It should be noted that the content of TiO 2 components is preferably 5.0 mol% or less, more preferably 3.0 mol% or less, still more preferably 2.0 mol% or less, and further preferably 1.0 mol% or less. Additionally, the lithium-ion conductive glass-ceramic precursor of the present invention is characterized in that even a composition containing GeO 2 components and substantially free of TiO 2 components (e.g., less than 0.1 mol%) can form high-density lithium-ion conductive glass-ceramics. Additionally, the content of SnO 2 components is also preferably 5.0 mol% or less, more preferably 3.0 mol% or less, still more preferably 2.0 mol% or less, and yet more preferably 1.0 mol% or less.

[0061] Sc 2 O 3 components and Y2 O 3 components can all replace a part of Al 2 O 3 component is any component that can adjust the lithium ion conductivity in the lithium ion conductive glass-ceramic sintered from the lithium ion conductive glass-ceramic precursor of the present invention. It should be noted that the content of the Y 2 O 3 component is preferably 10.0 mol% or less, more preferably 8.0 mol% or less, still more preferably 5.0 mol% or less, yet more preferably 3.0 mol% or less, and further preferably 1.0 mol% or less. In addition, the content of the Sc 2 O 3 component is also preferably 10.0 mol% or less, more preferably 5.0 mol% or less, still more preferably 3.0 mol% or less.

[0062] The CaO component and the MgO component are both any components that can further improve the lithium ion conductivity of the lithium ion conductive glass-ceramic sintered from the lithium ion conductive glass-ceramic precursor of the present invention. It should be noted that the content of the CaO component and the content of the MgO component are both preferably 10.0 mol% or less, more preferably 8.0 mol% or less, still more preferably 5.0 mol% or less, and further preferably 3.0 mol% or less.

[0063] Ta 2 O 5 component and transition metals such as Co, Ni, Mn, and Fe are all optional components. When using the lithium ion conductive glass-ceramic sintered from the lithium ion conductive glass-ceramic precursor of the present invention as a solid electrolyte and integrally forming an electrode layer, it can inhibit the Ta 2 O 5 component or transition metals from dissolving into the solid electrolyte. It should be noted that the total content of the Ta 2 O 5 component and these transition metal oxides is preferably 20.0 mol% or less, more preferably 15.0 mol% or less, still more preferably 10.0 mol% or less, and further preferably 5.0 mol% or less.

[0064] In addition, the lithium ion conductive glass-ceramic precursor of the present invention, except as described above, may contain a small amount (for example, 5.0 mol% or less, further 3.0 mol% or less, still further 1.0 mol% or less) of Na 2 O component, K 2Oxides of component O or other transition metals (such as Ag, Cu, Au, etc.). However, it may also be substantially free (e.g., less than 0.1 mol%) of one or more selected from them.

[0065] It should be noted that for the lithium-ion conductive glass-ceramic precursor of the present invention, it is preferably to minimize the content of sulfur (S) as much as possible (e.g., less than 1 mol%, further less than 0.1 mol%), and more preferably it does not contain any. This is because by reducing the S component, in a all-solid-state secondary battery etc. using the lithium-ion conductive glass-ceramic sintered from the lithium-ion conductive glass-ceramic precursor of the present invention as a solid electrolyte, the possibility of generating harmful gases such as hydrogen sulfide can be reduced. In addition, it is also preferably to minimize zinc (Zn), arsenic (As), antimony (Sb), and lead (Pb) as much as possible, and more preferably it does not contain any. Because they are harmful substances. In addition, from the perspective of finding electronic conductivity, it is also preferably to minimize bismuth (Bi) and tellurium (Te) as much as possible, and more preferably it does not contain any. Furthermore, from the perspective of maintaining the solid electrolyte function of the sintered product at a high level, it is also preferably to minimize vanadium (V) as much as possible, and more preferably it does not contain any.

[0066] And the lithium-ion conductive glass-ceramic precursor of the present invention containing the above components and compositions becomes a glass material (amorphous material). Therefore, in the lithium-ion conductive glass-ceramic precursor of the present invention before sintering, there is substantially no crystalline phase.

[0067] <Moisture content of lithium-ion conductive glass-ceramic precursor>

[0068] For the lithium-ion conductive glass-ceramic precursor of the present invention, the component ratios of P, Al, Ge, and Li satisfy the component ratios shown in the above component formula, and the amount of moisture released within a specified temperature range during crystallization by low-temperature sintering is below a certain amount.

[0069] Specifically, when the particles of the lithium-ion conductive glass-ceramic precursor of the present invention passing through a sieve with a mesh size of 106 μm (products passing through the 106 μm sieve) are sintered and crystallized (glass-ceramified) at a temperature below 700 °C, the amount of moisture released (cumulative value) within the temperature range of 550 - 700 °C is 60 ppm or less per unit of the lithium-ion conductive glass-ceramic precursor. That is to say, when it is crystallized from the glass state by low-temperature sintering, the vaporization of the moisture dissolved in the glass material is extremely small. In other words, when the crystalline phase is formed, the generation and retention of internal gas are extremely small. Although it is a LAGP-based glass material, a high-density lithium-ion conductive glass-ceramic very close to the theoretical value (e.g., greater than 90% of the theoretical value) can still be formed.

[0070] Herein, "60 ppm or less per unit of the lithium-ion conductive glass-ceramic precursor" means that, based on the mass ratio compared to the mass of the lithium-ion conductive glass-ceramic precursor before sintering, the amount of water released in the temperature range of 550 to 700 °C described above is 60 ppm (0.006 wt%) or less. It should be noted that most of the water released in this temperature range is the water dissolved in the glass material, and most of the water adsorbed (chemisorbed or physically adsorbed) on the surface of the glass material is released in a temperature range lower than this.

[0071] It should be noted that the amount of water is preferably 55 ppm or less, more preferably 50 ppm or less, still more preferably 48 ppm or less, yet more preferably 45 ppm or less, further preferably 42 ppm or less, still further preferably 40 ppm or less, even more preferably 38 ppm or less, yet further preferably 36 ppm or less, still even more preferably 34 ppm or less, even still more preferably 32 ppm or less, yet even further preferably 30 ppm or less.

[0072] Herein, the amount of water is a value measured and calculated in the following manner. Specifically, when the particles of the lithium-ion conductive glass-ceramic precursor of the present invention passing through a sieve with a mesh size of 106 μm (for example, a product with an average particle diameter (D 50 ) of 30 μm or more to 100 μm or less, further 40 μm or more to 100 μm or less) are sintered and crystallized at a temperature of 700 °C or less, a hygrometer (for example, HN-CJ manufactured by Chino Corporation, dew point meter TK-100 manufactured by Tekhne Measurement Corporation, DM70 manufactured by Vaisala Corporation, etc.) is connected to the rear stage (for example, the outlet side) of TG-DTA (for example, TG-DTA200SA manufactured by Bruker Corporation, etc.), and recorded by a data recorder (for example, G400 manufactured by Graphtec Corporation). The amount of water released in the range of 550 to 700 °C is calculated based on the cumulative value of the humidity of the hygrometer and the flow rate of the carrier gas (for example, nitrogen gas, etc.). The flow rate of the carrier gas is, for example, 50 ml / min (converted at 0 °C and 1 atmospheric pressure).

[0073] <Morphology of the lithium-ion conductive glass-ceramic precursor>

[0074] The lithium-ion conductive glass-ceramic precursor of the present invention, as described above, can form a higher-density lithium-ion conductive glass-ceramic through sintering (crystallization) at a temperature below 700°C. In terms of its morphology, it is more preferably in powder form based on the fact that it is easier to form an interface during single sintering of all-solid-state secondary batteries, etc., and is suitable for co-sintering, etc., in which the positive electrode layer, solid electrolyte layer, negative electrode layer, and, if necessary, the interconnection layer are all sintered and formed integrally. The interface formation mentioned here refers to the formation of both the three-phase interface of the three-dimensional structure of the electrode active material, conductive additive, and solid electrolyte, and the interface between solid electrolyte materials. Therefore, since the powdered lithium-ion conductive glass-ceramic precursor softens through sintering to form an interface and can be crystallized to obtain a high-density lithium-ion conductive glass-ceramic, it is highly preferred from the perspective of forming the three-phase interface of the three-dimensional structure of the electrode active material, conductive additive, and solid electrolyte in all-solid-state secondary batteries during co-sintering, etc. In particular, when constructing an all-solid-state secondary battery, based on the viewpoints of forming an interface at a lower temperature, further increasing the reaction interface, and further reducing the film thickness of the electrolyte layer, etc., the average particle diameter (D 90 ) of the powder is preferably 2 μm or less (for example, 1 μm or more and 2 μm or less), and the average particle diameter (D 50 ) of the powder is preferably about 1 μm (for example, 2 μm or less, further 1.5 μm or less, and still further 1 μm or less).

[0075] It should be noted that although sheet forming, etc. is sometimes used when constructing an all-solid-state secondary battery, the above-mentioned powdered lithium-ion conductive glass-ceramic precursor of the present invention is also preferably used as the constituent material for sheet forming. At this time, in view of weather resistance and to avoid re-aggregation of particles, etc., the maximum particle diameter of the powder is 200 μm or less, more preferably 150 μm or less, and further preferably 120 μm or less, and the average particle diameter (D 50 ) is 100 μm or less, more preferably about 80 μm or less. Specifically, a product passing through a 106 μm sieve and a powder obtained by pulverizing it to finally make the maximum particle diameter 1 / 20 or less of the film thickness of the target sheet are preferred. For example, if the target sheet film thickness is 20 μm, a powder with a maximum particle diameter of 1 μm or less is preferred. Thus, until sheet forming, it is easy to suppress the reaction with the atmosphere. There is no particular limitation on forming a powder that can pass through a 106 μm sieve from a glass block, and a stamping mill, ball mill, jaw crusher, etc. can be used.

[0076] Here, the "maximum particle diameter" and "average particle diameter" of the particles in the present invention refer to the maximum particle diameter and the volume-based average particle diameter (the diameter at 90% volume cumulative distribution (D90 ), the diameter (D) at 50% volume cumulative distribution 50 ))).

[0077] It should be noted that the lithium-ion conductive glass-ceramic precursor of the present invention can also be a mixture obtained by mixing two or more glass materials (such as powder mixing) or by mixing and firing (heat treatment in a manner that maintains the glass state after mixing) in such a way that the component ratios of P, Al, Ge, and Li satisfy the component ratios shown in any of the above component formulas. That is to say, it can also be a mixture obtained by mixing or mixing and firing two or more glass materials, and the component ratios of P, Al, Ge, and Li satisfy the component ratios shown in any of the above component formulas. Additionally, this mixture is also preferably a powder that satisfies the above-mentioned maximum particle size, average particle size (D 90 ) or average particle size (D 50 ).

[0078] However, from the perspective of more easily exerting the effects of the present invention, the lithium-ion conductive glass-ceramic precursor of the present invention is more preferably one glass material vitrified with the component ratios of P, Al, Ge, and Li satisfying the component ratios shown in any of the above component formulas.

[0079] <Manufacturing Method of Lithium-Ion Conductive Glass-Ceramic Precursor>

[0080] Next, the manufacturing method of the lithium-ion conductive glass-ceramic precursor of the present invention will be described in detail.

[0081] For the lithium-ion conductive glass-ceramic precursor of the present invention, as long as the melting conditions described below are satisfied, other aspects can be manufactured using the usual methods for manufacturing amorphous inorganic materials, such as firing (pre-firing), melting, and vitrification of inorganic materials. The inorganic materials used in the manufacturing are not particularly limited, but lithium phosphate (Li 3 PO 4 ), lithium metaphosphate (LiPO 3 ), germanium dioxide (GeO 2 ), orthophosphoric acid (H 3 PO 4 ), aluminum phosphate (Al(PO 3 )) 3 ), zirconium phosphate ((ZrO) 2 (HPO 4 )) 2 ) etc. are preferably used, and lithium phosphate, lithium metaphosphate, germanium dioxide, aluminum phosphate, and orthophosphoric acid are particularly preferably used as manufacturing raw materials.

[0082] Further, regarding the melting conditions of the inorganic material, in order to obtain the lithium-ion conductive glass-ceramic precursor (LAGP-based glass material) with the moisture content described above being below a certain level, melting must be carried out in a nitrogen atmosphere (nitrogen atmosphere melting). Thereby, the incorporation of moisture into the melted glass material can be efficiently suppressed, and the moisture content described above can be sufficiently reduced. Without this nitrogen atmosphere melting, even if a nitrogen atmosphere is used in other glass material manufacturing steps or during its crystallization (during sintering), etc., the moisture content described above cannot be sufficiently reduced. In addition, in this melting, even if a dry atmosphere with the humidity reduced to around the dew point -10°C is used, the moisture content described above cannot be sufficiently reduced. Also, when firing (pre-firing) is carried out before melting, it is preferably carried out in a nitrogen atmosphere as well. In addition, when crushing the melted glass block, it is preferably carried out in a nitrogen atmosphere as well. The melting temperature, although not limited thereto, is preferably 1000°C or higher, more preferably 1200°C or higher and 1450°C or lower.

[0083] <Lithium-ion conductive glass-ceramic>

[0084] Next, the lithium-ion conductive glass-ceramic obtained by sintering the lithium-ion conductive glass-ceramic precursor of the present invention will be described in detail.

[0085] This lithium-ion conductive glass-ceramic is obtained by sintering the lithium-ion conductive glass-ceramic precursor of the present invention and is a lithium-ion conductive glass-ceramic containing a rhombohedral NASICON-type crystal phase and a glassy phase (amorphous phase). Therefore, the constituent components and composition are substantially the same as those of the lithium-ion conductive glass-ceramic precursor of the present invention before sintering as long as no sintering aids, etc., are used. And it can preferably be used as a solid electrolyte of an all-solid-state secondary battery. In addition, since it can be formed by low-temperature sintering at 700°C or lower, even when integrally formed with the electrode layer, the decomposition of the electrode active material (positive electrode active material or negative electrode active material) and the reduction of the discharge capacity (battery capacity) are not likely to occur. Moreover, due to its high density, its interface formation is good, and it is easy to form a dense film, etc.

[0086] Here, the "glass-ceramic" in the present invention includes a crystal phase and an amorphous phase (non-crystalline phase) formed by heat treatment. This crystallinity is obtained by heat-treating a glass material (amorphous material) as a raw material to precipitate a crystal phase, or is a crystal phase synthesized by heat-treating a glass material and other materials. That is to say, it is a mixture of ceramic and glass.

[0087] Further, as described above, the lithium ion conductive glass-ceramic can be obtained by low-temperature sintering of the lithium ion conductive glass-ceramic precursor according to the present invention. Specifically, it can be obtained by sintering and crystallizing the lithium ion conductive glass-ceramic precursor of the present invention at a sintering temperature of 700 °C or lower (for example, 550 °C or higher to 680 °C or lower, further 550 °C or higher to 660 °C or lower). It should be noted that the lithium ion conductive glass-ceramic precursor of the present invention can form a high-density lithium ion conductive glass-ceramic by direct low-temperature sintering even without adding a mixed sintering aid (a component that can reduce the grain boundary resistance after crystallization) separately.

[0088] In addition, the lithium ion conductive glass-ceramic also contains a crystalline phase of a rhombohedral NASICON-type structure as described above, but may also contain a part of a lithium ion conductive crystalline phase of other structures (for example, LISICON-type, perovskite-type, garnet-type, etc.). In this case, among all the crystalline phases (total crystalline phases) contained in the lithium ion conductive glass-ceramic, the crystalline phase of the rhombohedral NASICON-type structure is more preferably 80% by mass or more, still more preferably 90% by mass or more, further preferably 95% by mass or more, and even more preferably 99% by mass or more. That is to say, it is preferred that the crystalline phase of the rhombohedral NASICON-type structure is the main crystalline phase. In addition, the crystalline phase contained in the lithium ion conductive glass-ceramic may actually be composed of the crystalline phase of the rhombohedral NASICON-type structure.

[0089] Further, the lithium ion conductive glass-ceramic has a high density (for example, 2.85 g / cm 3 or more), and also has a high lithium ion conductivity. Its density is preferably 2.86 g / cm 3 or more, more preferably 2.87 g / cm 3 or more, still more preferably 2.88 g / cm 3 or more, further preferably 2.89 g / cm 3 or more, still further preferably 2.90 g / cm 3 or more, even more preferably 2.91 g / cm 3 or more. In addition, its lithium ion conductivity at 25 °C is preferably 4.0×10 -5 S / cm or more, more preferably 9.0×10 - 5 S / cm or more, still more preferably 1.0×10 -4 S / cm or more, yet more preferably 1.1×10 -4 S / cm or more, further preferably 1.2×10 -4 S / cm or more, still further preferably 1.3×10-4 above S / cm.

[0090] As described above, the lithium-ion conductive glass-ceramic precursor of the present invention can form a higher-density LAGP-based lithium-ion conductive glass-ceramic by low-temperature sintering below 700°C. Moreover, since this lithium-ion conductive glass-ceramic has a high density and a high lithium-ion conductivity, it can be suitably used as a solid electrolyte (such as a solid electrolyte layer) of an all-solid-state secondary battery. That is to say, an all-solid-state secondary battery can be formed that contains a lithium-ion conductive glass-ceramic obtained by sintering the lithium-ion conductive glass-ceramic precursor of the present invention as a solid electrolyte. It should be noted that it has been difficult for conventional LAGP-based glass materials to form a high-density LAGP-based lithium-ion conductive glass-ceramic as described above by low-temperature sintering. However, since the lithium-ion conductive glass-ceramic precursor of the present invention can form a high-density lithium-ion conductive glass-ceramic as described above, it can be suitably used as a raw material for manufacturing an all-solid-state secondary battery that forms a good interface by co-sintering or the like.

[0091] In the case of integrally forming a layer (a positive electrode layer and / or a negative electrode layer) that becomes an electrode layer of an all-solid-state secondary battery and an interconnection layer or the like, a known material can be used for this electrode layer. For example, an electrode layer for an all-solid-state secondary battery obtained by sintering a mixture of an electrode active material (a positive electrode active material or a negative electrode active material) with a conductive assistant, an inorganic binder, etc. as needed can be used. In addition, by performing low-temperature co-sintering of the lithium-ion conductive glass-ceramic precursor of the present invention with a positive electrode active material or a negative electrode active material, an electrode layer (an electrode layer including a solid electrolyte) of an all-solid-state secondary battery can also be obtained.

[0092] It should be noted that examples of the positive electrode active material include NASICON-type LiV 2 (PO 4 ) 3 , olivine-type Li x J y M t PO 4(wherein, J is at least one selected from Al, Mg, and W, Mt is one or more selected from Ni, Co, Fe, and Mn, x satisfies 0.9 ≤ x ≤ 1.5, and y satisfies 0 ≤ y ≤ 0.2), layered oxides, spinel-type oxides, etc. In addition, examples of the negative electrode active material include: oxides containing NASICON-type, olivine-type, and spinel-type crystals, rutile-type oxides, anatase-type oxides, amorphous metal oxides, metal alloys, etc. Further, examples of the conductive additive include: carbon compounds such as graphite, activated carbon, and carbon nanotubes, at least one metal selected from Ni, Fe, Mn, Co, Mo, Cr, Ag, and Cu, their alloys, metals such as titanium or stainless steel, aluminum, and noble metals such as platinum, gold, ruthenium, and rhodium.

[0093] The embodiments described above are merely examples shown for the purpose of facilitating understanding of the present invention and do not limit the present invention. That is, the components and the like described above can of course be changed and improved without departing from the gist of the present invention, and equivalents thereof are also included in the present invention.

[0094] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments and can be variously modified within the technical idea of the present invention.

[0095] Examples

[0096] Lithium-ion conductive glass-ceramic precursors of various components as glass materials were synthesized, and sintering tests (low-temperature sintering tests) simulating the formation of the interface of all-solid-state secondary batteries were performed on them.

[0097] <Synthesis of Lithium-Ion Conductive Glass-Ceramic Precursors>

[0098] The lithium-ion conductive glass-ceramic precursor is synthesized by pre-firing and melting in either an air atmosphere or a nitrogen atmosphere.

[0099] (1) Glass Melting

[0100] Lithium metaphosphate (LiPO 3 ), lithium phosphate (Li 3 PO 4 ), germanium dioxide (GeO 2 ), orthophosphoric acid (H 3 PO 4 ), aluminum phosphate (Al(PO 3 ) 3 ) and zirconium phosphate ((ZrO) 2 (HPO 4 ) 2 ) were used as raw materials as needed.

[0101] Then, the raw materials were mixed into the metering ratio shown in Table 1 below, stirred at 1000 rpm for 5 minutes in a stirrer (あわとり錬太郎), and then 200 g of the batch was taken out at one time using a medicine spoon. The mixed raw materials were placed in a platinum crucible, and the temperature was raised to 1000°C in 5 hours under the treatment conditions shown in Table 1 below, either in an air atmosphere or a nitrogen atmosphere, and then furnace-cooled for 1 hour to prepare a pre-fired powder. The pre-fired powder was melted in a melting furnace at 1200°C or above while being fully stirred to vitrify it (melting in an air atmosphere or melting in a nitrogen atmosphere), and cast on a casting plate made of metal to obtain various lithium ion conductive glass ceramic precursors (glass blocks) of Comparative Examples 1 to 5 and Examples 1 to 10 as glass materials. The obtained glass blocks varied in size, ranging from 5 cm×10 cm to 2×3 cm. The glass blocks (about 3 to 10 cm) of the lithium ion conductive glass ceramic precursors of Comparative Examples 1 to 5 and Examples 1 to 11 were pulverized by an impact mill until the glass blocks passed through a sieve of 106 μm or less. A nitrogen atmosphere was used for the pulverization.

[0102]

Table 1

[0103]

[0104]

[0105] <Sintering test of lithium-ion conductive glass-ceramic precursor simulating interface formation of all-solid-state secondary batteries>

[0106] In order to compare the above performance, the interface formation during the sintering of the all-solid-state secondary battery was simulated and evaluated. That is, the powder obtained by crushing the various lithium ion conductive glass ceramic precursors synthesized above was sintered after molding to make a solid electrolyte (lithium ion conductive glass ceramic), and its density and lithium ion conductivity were evaluated. Specifically, the following sequence was used.

[0107] The above-mentioned lithium ion conductive glass ceramic precursor (powder passing through a 106 μm mesh) and 1-propanol were added to a 500 cc zirconia crucible, and the mixture was ground at 250 rpm for 2 hours (5 minutes of grinding and 1 minute of pause) in a planetary ball mill using φ2 mm zirconia beads (NIKKATO, YTZ beads) as grinding media. The ground slurry was separated from the zirconia beads by a sieve, and the obtained slurry was dried using a rack-type solvent recovery dryer (manufactured by Sozo Chemical Industry Co., Ltd.). The average particle size (D 90 ) are all below 2 μm (1 to 2 μm), and the average particle size (D 50 ) are all less than 1μm.

[0108] The various dried powders obtained as described above were pulverized using an alumina mortar and an alumina pestle until they passed through a 500-μm sieve, and then 1.5 g was taken. Using a molding die with a diameter of 20 mm, a pressure of 20 kN was applied for molding, and multiple particles for measuring various lithium ion conductivities were obtained. Then, these particles for measuring various lithium ion conductivities were sintered in a nitrogen atmosphere. After holding at 550 °C, the heating rate up to 650 °C was set to be slow at 50 °C / h, and heat treatment was performed at 650 °C for 1 hour to obtain sintered body particles (sintered body particles of Examples 1 to 10 and Comparative Examples 1 to 5) as a glass-ceramic solid electrolyte.

[0109] After the obtained sintered body particles were polished and dried on the surface using #800 and #2000 waterproof abrasive papers and 1-propanol, the diameter, thickness, and weight were measured using a vernier caliper, a micrometer, and an electronic balance, respectively, and the density was calculated.

[0110] The measurement of the lithium ion conductivity of each sintered body particle was carried out by forming gold electrodes as blocking electrodes on both sides of the sintered body for density measurement using a magnetron sputtering device (manufactured by Sanyu Electronics Co., Ltd., SC-701HMC), and using an electrochemical evaluation device (manufactured by Bio-Logic Co., Ltd., SP300), impedance measurement was performed at 25 °C under the conditions of a frequency of 0.1 Hz to 7 MHz, an amplitude voltage of 10 mV, and an open-circuit voltage, and the lithium ion conductivity was calculated.

[0111] The observation of the secondary electron image of the sintered body particles was carried out using a scanning electron microscope (manufactured by JEOL Ltd., JSM-IT700HR / LA), and the cross-section was observed. The acceleration voltage was set to 5 kV, and the sample distance was set to (W.D.).

[0112] In addition to these measurements, the measurement of the amount of water released when the lithium ion conductive glass-ceramic precursor was sintered and crystallized was carried out by connecting a hygrometer (manufactured by Chino Corporation, HN-CJ) to the outlet side (rear stage) of a TG-DTA (manufactured by Bruker Corporation, TG-DTA200SA) and recording with a data recorder (manufactured by Graphtec Corporation, G400). And the crystallization start temperature (Tc) was also measured using this TG-DTA (manufactured by Bruker Corporation, TG-DTA200SA). The sample used was pulverized until it passed through a 106-μm sieve (particle size of 106 μm or less, average particle size (D 50) is about 50 to 80 μm). Since the generation of moisture is accompanied by diffusion within the material, in order to confirm the influence of the particle size, for Comparative Example 4, a ball mill was used to grind the material to a sample passing through a 25 μm sieve (particle size of less than 25 μm) for measurement and evaluation. The measurement temperature is set to include the range of 550 to 700°C, the carrier gas is nitrogen, and the carrier gas flow rate is 50 ml / min (0°C, 1 atmosphere conversion). The amount of moisture generated during crystallization (the amount of moisture released at 550 to 700°C) is calculated based on the cumulative value of the humidity of the hygrometer and the carrier gas flow rate.

[0113] <Evaluation Results>

[0114] The obtained results are shown according to the following evaluation items.

[0115] (1) Evaluation of water release during crystallization

[0116] Table 2 below shows the melting treatment conditions (treatment conditions), composition, moisture content (water content) released at 550-700°C during sintering, density of the obtained sintered body particles, and lithium ion conductivity (ion conductivity) of the synthesized samples. In addition, as representative values, a=0.05, b=0, x=0.4 were fixed, and the humidity measurement results of Comparative Example 4 melted in an air atmosphere, Example 2 melted in a nitrogen atmosphere, and Example 3 in which the zirconium component was replaced by 0.015 (the density of the obtained sintered body particles was also the highest) were calculated. Figure 1 It should be noted that Figure 1 The humidity measurement results at 550-700°C are shown in the figure. The amount of moisture detected (released) during crystallization (550-700°C) was calculated to be 101.2 ppm for Comparative Example 4, 54.2 ppm for Example 2, and 24.5 ppm for Example 3 (Table 2). It can be confirmed that the highest amount of moisture was found in the atmospheric atmosphere, which can be reduced to about half by melting in a nitrogen atmosphere, and further reduced to half of half by adding a zirconium component. In addition, the density of the sintered particles was the lowest at 2.75 g / cm in Comparative Example 4. 3 , Example 2 is 2.86 g / cm 3 , and Example 3 shows a theoretical value (3.1 g / cm 3 ) 96% of 2.97g / cm 3 The lithium ion conductivity is 1×10 -4 Above S / cm, there is no significant difference, and all are relatively high values.

[0117] In addition, from the comparison between Comparative Example 1 where none of the lithium component, phosphorus component, and zirconium component is added in the basic components of LAGP and Example 1, the comparison between Comparative Example 4 where the lithium component is added and Example 2, the comparison between Comparative Example 3 where only the zirconium component is added and Example 8, the comparison between Comparative Example 5 where the zirconium component is added to the component with the lithium component added and Examples 3 to 6, and the results of Example 7 where the phosphorus component is added on this basis, Example 9 where the aluminum component in the component with the lithium component added is changed, and Example 10, it can be seen that in all cases, the density of the sintered body particles formed from the glass material obtained by melting in an atmospheric atmosphere with a large amount of water released during crystallization is low (Comparative Example), and when the amount of water released during crystallization becomes small, the density of the sintered body particles shows an increasing trend (Example). In addition to melting in a nitrogen atmosphere, replacing the germanium component with the zirconium component is particularly effective in increasing the density. However, in Comparative Example 3 and Example 8 where the lithium component is not added, the lithium ion conductivity slightly decreases to about 4×10 -5 S / cm.

[0118] The particle size of the glass material (lithium ion conductive glass-ceramic precursor) for which the above water content was measured is the size passing through a 106 μm sieve. Regarding the water in the material, due to diffusion, the influence of the particle size is a concern. Therefore, for the sample of Comparative Example 4, the water content was also confirmed for the product passing through a 25 μm sieve. The humidity measurement results for comparing them are shown in Figure 2 . It should be noted that Figure 2 are also the humidity measurement results at 550 - 700 °C. As a result, even when the particle size becomes about one-fourth, the calculated amount of water released during crystallization (550 - 700 °C) is 137 ppm, and its variation is only 30% or less of that of the product passing through a 106 μm sieve. Therefore, it can be considered that the difference in particle size does not have a significant impact in this measurement method. Regarding the temperature at which water starts to be released during crystallization, the product passing through a 25 μm sieve is slightly shifted to the lower temperature side ( Figure 2 ). It is speculated that this is due to the promotion of crystallization by the smaller particle size. In the measurement results of the crystallization start temperature by TG-DTA, the Tc of the product passing through a 106 μm sieve is 645 °C, and the Tc of the product passing through a 25 μm sieve is 620 °C, which shows good consistency with the temperature at which water starts to be released in the 550 - 700 °C temperature range shown in Figure 2 .

[0119] In addition, the humidity measurement results starting from a low temperature of the product passing through a 25 μm sieve are shown in Figure 3It is shown in []. Among them, an increase in humidity with a peak at 100 °C can be observed. It is speculated that this is not the moisture dissolved in the glass material, but the adsorbed moisture (chemical adsorption or physical adsorption) on its surface. The amount of released moisture here (the amount of moisture released at 60 - 150 °C) is calculated to be 0.45 wt% (4500 ppm), and it can be confirmed that this is several tens of times larger than the amount of moisture released during crystallization. On the other hand, it is speculated that the increase in humidity with a peak near 620 °C is due to the moisture dissolved in the glass material being released during crystallization because it cannot be retained in the crystal.

[0120]

Table 2

[0121]

[0122] (2) Confirm the appearance by observing the secondary electron image

[0123] Since it can be confirmed that there is an inverse proportional relationship between the density of the LAGP-based glass material after low-temperature sintering and the amount of moisture released during crystallization, it can be considered that the reason why the density cannot be increased after low-temperature sintering is the gasification of the moisture dissolved in the glass material during crystallization. Then, as described above, in fact, high densification can be achieved by suppressing the above-mentioned amount of moisture release. Therefore, through visual observation, the confirmation of gasification (moisture release) and its suppression were carried out. For Comparative Example 1 and Example 3 with the most obvious differences, the cross-sections of the sintered body particles after low-temperature sintering were observed by secondary electron imaging respectively. The observation results are shown in Figure 4 It is shown in []. In Comparative Example 1, pores with an inner diameter of about 500 nm were observed to be scattered. It is considered that the pores were generated due to the gasification of the moisture dissolved inside during the crystallization of the lithium-ion conductive glass-ceramic precursor. Since the glass softened during crystallization, it became densified and sealed, and thus it is speculated that the escape channels for gas decreased, forming such pores. On the other hand, in Example 3, although a small number of pores can be seen, it can be confirmed that, compared with Comparative Example 1, they are significantly reduced and improved.

[0124] This application claims priority based on Japanese Patent Application No. 2022-181658 filed on November 14, 2022, and the entire contents disclosed therein are incorporated herein.

Claims

1. A lithium-ion conductive glass-ceramic precursor, which is a lithium-ion conductive glass-ceramic precursor of a glass material capable of forming a lithium-ion conductive glass-ceramic by sintering. Among them, The component ratios of P, Al, Ge, and Li satisfy Li 1+x Al x Ge 2-x-z M z P 3 O 12 the component ratios shown by the component formula, where x = 0.2 to 0.6, z = 0 to 0.1, and M is one or more selected from the group consisting of Zr, Ti, Sn, and Si. When the particles of the lithium-ion conductive glass-ceramic precursor passing through a sieve with a mesh size of 106 μm are sintered and crystallized at a temperature of 700 °C or lower, the amount of water released at 550 - 700 °C is 60 ppm or less per unit of the lithium-ion conductive glass-ceramic precursor.

2. The lithium-ion conductive glass-ceramic precursor according to claim 1, Among them, Containing 0.05 to 2.4% of ZrO in terms of mol% based on the oxide standard 2 component.

3. A lithium-ion conductive glass-ceramic precursor, which is a lithium-ion conductive glass-ceramic precursor of a glass material capable of forming a lithium-ion conductive glass-ceramic by sintering. Among them, The component ratios of P, Al, Ge, and Li satisfy Li 1+x Al x Ge 2-x-z M z P 3 O 12 + aLi 2 O + bP 2 O 5 and the component ratios shown by the component formula, where x = 0.2 to 0.6, z = 0 to 0.1, a = 0.01 to 0.3, b = 0 to 0.3, and M is one or more selected from the group consisting of Zr, Ti, Sn, and Si. When the particles of the lithium-ion conductive glass-ceramic precursor passing through a sieve with a mesh size of 106 μm are sintered and crystallized at a temperature of 700 °C or lower, the amount of water released at 550 - 700 °C is 60 ppm or less per unit of the lithium-ion conductive glass-ceramic precursor.

4. The lithium-ion conductive glass-ceramic precursor according to claim 3, Among them, Containing 0.05 to 2.4% of ZrO in terms of mol% based on the oxide standard 2 component.

5. A all-solid-state secondary battery, containing a lithium-ion conductive glass-ceramic sintered from the lithium-ion conductive glass-ceramic precursor according to any one of claims 1 - 4 as a solid electrolyte.

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