Lithium ion conductive material

Abstract

The present invention provides a lithium ion conductive material capable of forming a solid electrolyte having a high lithium ion conductivity at a sintering temperature of 800 °C or lower. By providing, in terms of mol% based on oxides, 36.6% to 37.3% of a P2O5 component, 43.0% to 48.1% of a TiO2 component, 0.6% to 3.2% of an Al2O3 component, 13.9% to 17.5% of a Li2O component, and the mol% of the Al2O3 component is 0.3 to 3.0 mol% less than the mol% of the Al2O3 component calculated based on the component formula of Li 1+x Al x Ti 2‑x P3O 12 (x = 0.05 to 0.4), and the mol% of the P2O5 component is 0.2 to 2.0 mol% less than the mol% of the P2O5 component calculated based on the above component formula, and includes a crystalline phase of a rhombohedral NASICON structure or Li 1+x Al x Ti 2‑x P3O 12 (x ≥ 0), the lithium ion conductive material of the crystalline phase can solve the above technical problems.

Description

Technical Field

[0001] The present invention relates to a lithium ion conductive material. Background Art

[0002] In applications such as power sources for electric vehicles and power sources for portable 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, and there are problems with safety hazards.

[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 a solid electrolyte as an electrolyte, a all-solid-state secondary battery in which all other constituent elements such as the electrode layer are also entirely solid is being developed.

[0006] In addition, as representative properties among the properties required for the solid electrolyte of the all-solid-state secondary battery, lithium ion conductivity and sintering properties can be cited.

[0007] And, as a solid electrolyte for an all-solid-state secondary battery, for example, a glass-ceramic electrolyte having a composition of Li 1+x Al x Ti 2-x P 3 O 12 as shown in Non-Patent Document 1, and a ceramic electrolyte having a composition of LiTi 2 P 3 O 12 as shown in Non-Patent Document 2 and Non-Patent Document 3 have been studied.

[0008] Prior Art Documents

[0009] Non-Patent Documents

[0010] Non-Patent Document 1: Journal of Solid State Chemistry 265(2018)381-386

[0011] Non-Patent Document 2: Journal of Materials Science 33(1998)1549-1553

[0012] Non-Patent Document 3: Solid State Ionics 47(1991)257 - 264 Summary of the Invention

[0013] Technical Problem to be Solved by the Invention

[0014] The glass-ceramic electrolyte shown in the reported Non-Patent Document 1 has a lithium ion conductivity of 1×10 -3 S / cm at 25°C. However, the sintering temperature during its synthesis is very high, above 1000°C. In addition, when resintering is performed after synthesis, a sintering temperature of 900°C or higher is also required in this case. In this situation, since the grain boundary resistance of the solid electrolyte (the resistance of ion conduction generated at the contact interface between particles) becomes higher, the lithium ion conductivity at 25°C decreases to about 1×10 - 4 S / cm, which is a problem. In addition, when integrally formed with the electrode layer, decomposition of the electrode active material (positive electrode active material or negative electrode active material) due to high-temperature sintering and reduction of the discharge capacity (battery capacity) are also problems.

[0015] On the other hand, for the ceramic electrolytes shown in Non-Patent Document 2 and Non-Patent Document 3, although the intragranular resistance (the resistance of ion conduction generated within particles) is low but the grain boundary resistance is high, it is difficult to obtain a high lithium ion conductivity. Therefore, an attempt was made to reduce the grain boundary resistance and increase the lithium ion conductivity by sintering a mixture of Li 3 PO 4 and Li 3 BO 3 and other lithium salts and Li 3 BO 3 glass, etc. However, its sintering temperature is relatively high at 900°C, and the lithium ion conductivity of the obtained solid electrolyte at 25°C is about 1.5 - 3×10 -4 S / cm.

[0016] Therefore, an object of the present invention is to provide a lithium ion conductive material capable of forming a solid electrolyte having a high lithium ion conductivity at a sintering temperature of 800°C or lower.

[0017] Method for Solving the Technical Problem

[0018] To solve the above technical problem, the present inventors conducted in-depth research and found a lithium ion conductive material which, in terms of mol% based on oxides, contains: 36.6% - 37.3% of P 2 O 5 component, 43.0% - 48.1% of TiO 2Component, 0.6% to 3.2% of Al 2 O 3 Component and 13.9% to 17.5% of Li 2 O component, and the mol% of the Al 2 O 3 component is reduced by 0.3 mol% to 3.0 mol% compared with the mol% of the Al 1+x Al x Ti 2-x P 3 O 12 (x = 0.05 to 0.4) calculated based on the component formula of Li 2 O 3 component; the mol% of the P 2 O 5 component is reduced by 0.2 mol% to 2.0 mol% compared with the mol% of the P 1+x Al x Ti 2-x P 3 O 12 (x = 0.05 to 0.4) calculated based on the component formula of Li 2 O 5 component, and contains a crystalline phase of a rhombohedral NASICON structure or a crystalline phase of Li 1+x Al x Ti 2-x P 3 O 12 (x≥0). By mixing and sintering this lithium ion conductive material with a lithium-containing lithium ion conductive glass material at 800°C or lower, a solid electrolyte (oxide-based solid electrolyte) with high lithium ion conductivity can be formed.

[0019] In addition, a lithium ion conductive material is found, which contains, in terms of mol% based on oxides: 34.0% to 36.5% of P 2 O 5 component, 42.0% to 46.5% of TiO 2 component, 0.6% to 3.1% of Al 2 O 3 component, 15.0% to 17.6% of Li 2 O component and 0.5% to 5.0% of SiO 2 component, and the mol% of the Al 2 O 3 component is compared with the mol% of Li derived from the components of Ti, Li and Si 1+x+y Al xTi 2-x Si y P 3-y O 12 (x = 0.05 to 0.4, y = 0.05 to 0.2) Component formula calculated Al 2 O 3 The component mol% is reduced by 0.3 mol% to 3.0 mol% compared to the composition; the P 2 O 5 The mol% of the component, compared with the Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (x = 0.05 to 0.4, y = 0.05 to 0.2) Component formula calculated P 2 O 5 The mol% of the component is reduced by 0.2 mol% to 2.0 mol%, and includes a rhombohedral NASICON structure crystalline phase, Li 1+x Al x Ti 2-x P 3 O 12 (x≥0) crystalline phase, or Li 1+x+ y Al x Ti 2-x Si y P 3-y O 12 (x≥0, y≥0) crystalline phase. By mixing and sintering this lithium ion conductive material with a lithium-containing lithium ion conductive glass material below 800 °C, a solid electrolyte (oxide-based solid electrolyte) with high lithium ion conductivity can be formed, thus completing the present invention.

[0020] That is, the present invention is as follows (1) to (5).

[0021] (1) A lithium ion conductive material, which contains, in terms of mol% based on oxides: 36.6% to 37.3% of P 2 O 5 component, 43.0% to 48.1% of TiO 2 component, 0.6% to 3.2% of Al 2 O 3 component and 13.9% to 17.5% of Li 2 O component, and the mol% of the Al 2 O 3 component, compared with the Li derived based on the components of Ti and Li1+ x Al x Ti 2-x P 3 O 12 Al calculated by the component formula of (x = 0.05 to 0.4) 2 O 3 The mol% of the component is reduced by 0.3 mol% to 3.0 mol% compared with the mol% of the AlO component calculated based on the components of Ti and Li; the P 2 O 5 The mol% of the component, compared with the LiPO component calculated based on the components of Ti and Li 1+x Al x Ti 2-x P 3 O 12 P calculated by the component formula of (x = 0.05 to 0.4) 2 O 5 The mol% of the component is reduced by 0.2 mol% to 2.0 mol% compared with the mol% of the P O component calculated based on the components of Ti and Li, and contains a crystalline phase of a rhombohedral NASICON structure or a Li 1+x Al x Ti 2-x P 3 O 12 (x≥0) crystalline phase.

[0022] (2) A lithium ion conductive material, which contains, in terms of mol% based on oxides: 34.0% to 36.5% of the P 2 O 5 component, 42.0% to 46.5% of the TiO 2 component, 0.6% to 3.1% of the Al 2 O 3 component, 15.0% to 17.6% of the Li 2 O component and 0.5% to 5.0% of the SiO 2 component, and the mol% of the Al 2 O 3 component, compared with the Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 Al calculated by the component formula of (x = 0.05 to 0.4, y = 0.05 to 0.2) 2 O 3 The mol% of the component is reduced by 0.3 mol% to 3.0 mol% compared with; the P 2 O 5 ​mol% of the components, compared with P calculated from the component formula based on the components of Ti, Li, and Si 1+x+y Al x Ti 2-x Si y P 3-y O 12 (x = 0.05 to 0.4, y = 0.05 to 0.2), is reduced by 0.2 mol% to 2.0 mol%, and contains a crystalline phase of a rhombohedral NASICON structure, Li 2 O 5 component, and a crystalline phase of Li 1+x Al x Ti 2-x P 3 O 12 (x≥0), or a crystalline phase of Li 1+x+y Al x Ti 2-x Si y P 3- y O 12 (x≥0, y≥0).

[0023] (3) The lithium ion conductive material according to (1) or (2), wherein the lithium ion conductive material is a lithium ion conductive glass ceramic.

[0024] (4) A solid electrolyte material, which is formed by mixing the lithium ion conductive material according to any one of (1) to (3) with a lithium-containing lithium ion conductive glass material.

[0025] (5) A all-solid-state secondary battery, which is formed by using a material containing the solid electrolyte material according to (4).

[0026] Effects of the Invention

[0027] According to the present invention, a lithium ion conductive material can be provided, and by mixing and sintering the lithium ion conductive material with a lithium-containing lithium ion conductive glass material at a temperature below 800 °C, a solid electrolyte with a high lithium ion conductivity can be formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a synthesis flowchart of the lithium ion conductive glass ceramics of Examples 1 to 4 and Comparative Examples 1 to 3 (Step 1), and the solid electrolytes of Examples 1 to 4 and Comparative Examples 1 to 3 (Step 2).

[0029] Figure 2It is a graph showing the relationship between the sintering temperature (heat treatment temperature) and the lithium ion conductivity (conductivity) for the solid electrolytes (sintered body particles) of Comparative Example 1, Comparative Example 2, and Example 4 obtained through Step 2.

[0030] Figure 3 It is a graph showing the relationship between the sintering temperature (heat treatment temperature) and the density for the solid electrolytes (sintered body particles) of Comparative Example 1, Comparative Example 2, and Example 4 obtained through Step 2.

[0031] Figure 4 It is a secondary electron image of the fracture surface of the solid electrolyte (sintered body particles) of Example 4 obtained through Step 2 (the photograph is used as the drawing).

[0032] Figure 5 It is a backscattered electron image of the fracture surface of the solid electrolyte (sintered body particles) of Example 4 obtained through Step 2 (the photograph is used as the drawing).

[0033] Figure 6 It is a synthesis flow chart of the lithium ion conductive glass ceramics of Examples 5 to 6 and Comparative Example 4 (Step 1-2), and the solid electrolytes of Examples 5 to 6 and Comparative Example 4 (Step 2-2).

[0034] Figure 7 It is a graph showing the relationship between the sintering temperature (heat treatment temperature) and the lithium ion conductivity (conductivity) for the solid electrolyte (sintered body particles) of Example 5 obtained through Step 2-2, and the solid electrolytes (sintered body particles) of Comparative Example 1 and Example 4 obtained through Step 2.

[0035] Figure 8 It is a graph showing the relationship between the sintering temperature (heat treatment temperature) and the density for the solid electrolyte (sintered body particles) of Example 5 obtained through Step 2-2, and the solid electrolytes (sintered body particles) of Comparative Example 1 and Example 4 obtained through Step 2.

[0036] Figure 9 It is a secondary electron image of the fracture surface of the solid electrolyte (sintered body particles) of Example 5 obtained through Step 2-2 (the photograph is used as the drawing). Detailed Description of the Invention

[0037] The present invention will be described.

[0038] The first embodiment of the present invention is a lithium ion conductive material, which contains, in mol% based on oxides: 36.6% to 37.3% of P 2 O 5 component, 43.0% to 48.1% of TiO 2Components, 0.6% to 3.2% of Al 2 O 3 Components, and 13.9% to 17.5% of Li 2 O components, wherein the mol% of the Al 2 O 3 components, compared with the mol% of Al 1+x Al x Ti 2-x P 3 O 12 (x = 0.05 to 0.4) calculated based on the component formula of Li 2 O 3 components, is reduced by 0.3 mol% to 3.0 mol%; the mol% of the P 2 O 5 components, compared with the mol% of P 1+ x Al x Ti 2-x P 3 O 12 (x = 0.05 to 0.4) calculated based on the component formula of Li 2 O 5 components, is reduced by 0.2 mol% to 2.0 mol%, and contains a crystalline phase of a rhombohedral NASICON structure or a Li 1+x AlxTi 2-x P 3 O 12 (x≥0) crystalline phase.

[0039] Furthermore, the second embodiment of the present invention is a lithium ion conductive material, which contains, in terms of mol% based on oxides: 34.0% to 36.5% of P 2 O 5 components, 42.0% to 46.5% of TiO 2 components, 0.6% to 3.1% of Al 2 O 3 components, 15.0% to 17.6% of Li 2 O components, and 0.5% to 5.0% of SiO 2 components, and the mol% of the Al 2 O 3 components, compared with the Li 1+x+y Al x Ti 2-x Si y P 3-y O 12Al calculated by the component formula of (x = 0.05 to 0.4, y = 0.05 to 0.2) 2 O 3 component mol% is reduced by 0.3 mol% to 3.0 mol% compared to; the P 2 O 5 mol% of the component, based on Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 P calculated by the component formula of (x = 0.05 to 0.4, y = 0.05 to 0.2) 2 O 5 mol% of the component is reduced by 0.2 mol% to 2.0 mol% compared to, and contains a crystalline phase of a rhombohedral NASICON structure, Li 1+x Al x Ti 2-x P 3 O 12 (x≥0) crystalline phase, or Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (x≥0, y≥0) crystalline phase.

[0040] Hereinafter, they are sometimes referred to as "the lithium ion conductive material of the present invention".

[0041] It should be noted that the content of each component contained in the lithium ion conductive material of the present invention, for any one of the first embodiment and the second embodiment, as long as there is no particular negation, is all expressed in mol% based on the oxide standard. Here, the content expressed in "mol% based on the oxide standard" means that in the case where oxides, double salts, metal fluorides, etc. used as raw materials for the lithium ion conductive material of the present invention are assumed to decompose completely and become oxides during melting, the total number of moles of the generated oxides is taken as 100 mol% to represent the content of each component contained in the lithium ion conductive material of the present invention. In addition, regarding the mol% of the Al 2 O 3 component and the P 2 O 5 component, similarly, it means the content of each component calculated by taking the total number of moles of the generated oxides as 100 mol% in the case where the components of the specified component formula are assumed to decompose completely into oxides during melting.

[0042] [First Embodiment]

[0043] First, each component and crystal phase of the first embodiment of the lithium ion conductive material constituting the present invention will be described.

[0044] <Composition Components>

[0045] Each component of the first embodiment of the lithium ion conductive material constituting the present invention will be described in detail.

[0046] P 2 O 5 The component is a necessary component for forming a rhombohedral NASICON-type crystal phase or a crystal phase of Li 1+x Al x Ti 2-x P 3 O 12 (x≥0) in the first embodiment of the lithium ion conductive material of the present invention. Therefore, the content of the P 2 O 5 component has a lower limit of 36.6%, preferably 36.8%, and more preferably 37.0%. On the other hand, from the viewpoint of suppressing the formation of other crystal phases and making it difficult to reduce the lithium ion conductivity of the solid electrolyte obtained by low-temperature mixed sintering with a lithium-containing lithium ion conductive glass material, the content of the P 2 O 5 component has an upper limit of 37.3%, preferably 37.2%.

[0047] TiO 2 The component is also a necessary component for forming a rhombohedral NASICON-type crystal phase or a crystal phase of Li 1+x Al x Ti 2-x P 3 O 12 (x≥0) in the first embodiment of the lithium ion conductive material of the present invention. Therefore, the content of the TiO 2 component has a lower limit of 43.0%, preferably 43.2%, and more preferably 43.5%. On the other hand, from the viewpoint of making it difficult to reduce the lithium ion conductivity of the solid electrolyte obtained by low-temperature mixed sintering with a lithium-containing lithium ion conductive glass material, the content of the TiO 2 component has an upper limit of 48.1%, preferably 47.0%, more preferably 46.0%, and further preferably 45.0%.

[0048] Al 2 O 3The component is also an essential component required for forming a rhombohedral NASICON-type crystal phase or a crystal phase of Li 1+x Al x Ti 2-x P 3 O 12 (x≥0) in the first embodiment of the lithium ion conductive material of the present invention. Therefore, the content of the Al 2 O 3 component has a lower limit of 0.6%, preferably 0.8%, more preferably 1.0%, still more preferably 1.2%, further preferably 1.5%, and even more preferably 2.0%. On the other hand, from the viewpoint of suppressing the formation of other crystal phases and making it difficult to reduce the lithium ion conductivity of the solid electrolyte obtained by low-temperature mixed sintering with a lithium-containing lithium ion conductive glass material, the content of the Al 2 O 3 component has an upper limit of 3.2%, preferably 3.0%, more preferably 2.8%, and further preferably 2.6%.

[0049] Li 2 The O component imparts lithium ion conductivity and forms a rhombohedral NASICON-type crystal phase or a crystal phase of Li 1+x Al x Ti 2-x P 3 O 12 (x≥0) in the first embodiment of the lithium ion conductive material of the present invention. Therefore, the content of the Li 2 O component has a lower limit of 13.9%, preferably 15.0%, and more preferably 16.0%. On the other hand, from the viewpoint of improving the chemical durability of the first embodiment of the lithium ion conductive material of the present invention and improving the morphological stability, the content of the Li 2 O component has an upper limit of 17.5%, preferably 17.2%, more preferably 17.0%, and further preferably 16.7%.

[0050] Furthermore, in the first embodiment of the lithium ion conductive material of the present invention, as an optional component, it may contain one or more selected from the group consisting of ZrO 2 component, Y 2 O 3 component, Sc 2 O 3 component, CaO component, MgO component, and SnO 2 component.

[0051] ZrO 2The component is an arbitrary component that can stabilize the crystal structure of the crystal phase in the first embodiment of the lithium-ion conductive material of the present invention and can improve the recyclability. Therefore, ZrO 2 The content of the component preferably has a lower limit of 0.5%, more preferably 1.0%, and further preferably 2.0%. On the other hand, from the viewpoint of easily forming a crystal phase of a rhombohedral NASICON-type structure, ZrO 2 The content of the component preferably has an upper limit of 5.0%, more preferably 4.0%, and further preferably 3.0%.

[0052] Y 2 O 3 The component and Sc 2 O 3 The component are both arbitrary components that can adjust the lithium-ion conductivity in the first embodiment of the lithium-ion conductive material of the present invention and can adjust the mechanical strength or size of the crystal phase. Therefore, Y 2 O 3 The content of the component and Sc 2 O 3 The content of either of the components preferably has a lower limit of 0.1%, more preferably 0.5%, and further preferably 1.0%. On the other hand, from the viewpoint of suppressing the formation of other crystal phases and making it difficult for the lithium-ion conductivity of the solid electrolyte obtained by low-temperature hybrid sintering with a lithium-containing lithium-ion conductive glass material to decrease, Y 2 O 3 The content of the component and Sc 2 O 3 The content of either of the components preferably has an upper limit of 2.0%, more preferably 1.5%.

[0053] The CaO component and the MgO component are arbitrary components that can increase the content of Li in the crystal phase through valence balance, thereby improving the lithium-ion conductivity. Therefore, the content of either the CaO component or the MgO component preferably has a lower limit of 0.5%, more preferably 1.0%, and further preferably 2.0%. On the other hand, from the viewpoint of avoiding a decrease in the lithium-ion conductivity of the solid electrolyte obtained by low-temperature hybrid sintering with a lithium-containing lithium-ion conductive glass material, the content of either the CaO component or the MgO component preferably has an upper limit of 5.0%, more preferably 4.0%, and further preferably 3.0%.

[0054] SnO 2 The component is an arbitrary component that can promote the crystallization of the crystal phase in the first embodiment of the lithium-ion conductive material of the present invention. Therefore, SnO 2The lower limit of the content of the component is preferably 0.1%, more preferably 0.5%, and further preferably 1.0%. On the other hand, based on the view that the lithium ion conductivity of the solid electrolyte obtained by low-temperature mixing and sintering with a lithium-containing lithium ion conductive glass material is difficult to decrease, SnO 2 The upper limit of the content of the component is preferably 2.0%, more preferably 1.5%.

[0055] In addition, in the first embodiment of the lithium ion conductive material of the present invention, an inorganic component containing boron (B) or fluorine (F) may be contained. However, in the first embodiment of the lithium ion conductive material of the present invention, it is preferred to reduce the content of sulfur (S) as much as possible (for example, less than 1%, further less than 0.1%, etc.), and it is more preferred not to contain it. This is because by reducing the S component, the possibility of the generation of harmful gases such as hydrogen sulfide can be reduced in all-solid secondary batteries using solid electrolytes obtained by low-temperature mixed sintering with lithium-containing lithium ion conductive glass materials. In addition, in order to avoid a decrease in lithium ion conductivity, it is preferred to reduce the alkali metal (Na, K, etc.) components other than Li as much as possible, and it is more preferred not to contain it.

[0056] Furthermore, in the first embodiment of the lithium ion conductive material of the present invention, the Al 2 O 3 The mol% of the components is based on the Li 1+x Al x Ti 2-x P 3 O 12 Al calculated by the composition formula (x = 0.05 to 0.4, preferably x = 0.1 to 0.3) 2 O 3 The mol% of the components is reduced by 0.3 mol% to 3.0 mol%. It should be noted that the lower limit of this range is preferably 0.4 mol%, more preferably 0.5 mol%, and even more preferably 1.0 mol%. In addition, the upper limit of this range is preferably 2.8 mol%, and more preferably 2.5 mol%.

[0057] P1101JP

[0058] Here, Li 1+x Al x Ti 2-x P 3 O 12 (x = 0.05 to 0.4) is a Li, Al, Ti, PO 4The basic components of LATP, a solid electrolyte material of the structure, can be derived based on the component of Al, or based on the components of Ti and Li. However, in the first embodiment of the lithium ion conductive material of the present invention, Li derived based on the components of Ti and Li 1+x Al x Ti 2- x P 3 O 12 (x = 0.05 to 0.4) is used as a reference for calculation.

[0059] Specifically, for example, when the component of Ti is 1.7 and the component of Li is 1.3, the component of Al becomes 0.3, and Li can be derived 1.3 Al 0.3 Ti 1.7 P 3 O 12 . And as long as the mol% of the actual Al 2 O 3 component is compared with the mol% of Al 2 O 3 component calculated based on the derived component formula, it is sufficient that it is reduced by 0.3 mol% to 3.0 mol%. It should be noted that in the first embodiment of the lithium ion conductive material of the present invention, the above-mentioned Li derived based on the components of Ti and Li 1+x Al x Ti 2-x P 3 O 12 (x = 0.05 to 0.4) component formula is more preferably Li 1.3 Al 0.3 Ti 1.7 P 3 O 12 .

[0060] Furthermore, in the first embodiment of the lithium ion conductive material of the present invention, the mol% of the above-mentioned P 2 O 5 component is compared with the P 1+x Al x Ti 2-x P 3 O 12 (x = 0.05 to 0.4) component formula calculated based on the above-mentioned Li derived based on the components of Ti and Li 2 O 5Compared with the mol% of the components, it is reduced by 0.2 mol% to 2.0 mol%. It should be noted that the lower limit of this range is preferably 0.3 mol%. In addition, the upper limit of this range is preferably 1.5 mol%, more preferably 1.2 mol%, still more preferably 1.0 mol%, and further preferably 0.8 mol%. In addition, for the derived component formula, it is the same as above.

[0061] Through Al 2 O 3 component and P 2 O 5 components are in the above contents. In the first embodiment of the lithium ion conductive material of the present invention, when mixed with a lithium-containing lithium ion conductive glass material (especially Li 2 O-P 2 O 5 -Al 2 O 3 -based glass material) and sintered at a low temperature, the lithium ion conductive glass material reacts with the material of the first embodiment at the particle interface of the material of the first embodiment, and the reaction product exists at the particle interface, so that a solid electrolyte with high lithium ion conductivity can be obtained.

[0062] <Crystalline phase>

[0063] The crystalline phase contained in the first embodiment of the lithium ion conductive material of the present invention will be described in detail.

[0064] The first embodiment of the lithium ion conductive material of the present invention contains the above-mentioned components in a specified amount, and contains a crystalline phase of a rhombohedral NASICON-type structure (Li-substituted NASICON-type structure) composed of at least a part of these components or Li 1+x Al x Ti 2-x P 3 O 12 (x≥0, preferably 2>x≥0, more preferably 0.6≥x≥0). That is to say, it contains at least one of these crystalline phases. It should be noted that the crystalline phase included in the first embodiment of the lithium ion conductive material of the present invention is preferably all one or more of the above-mentioned crystalline phases, but may contain a part of other lithium ion conductive crystalline phases (for example, LISICON type, perovskite type, garnet type, etc.). Even in this case, in all the crystalline phases contained in the first embodiment of the lithium ion conductive material of the present invention, the above-mentioned crystalline phases preferably total 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. That is to say, it is preferred that the above-mentioned crystalline phase is the main crystalline phase.

[0065] [Second Embodiment]

[0066] Next, each component and crystal phase of the second embodiment of the lithium ion conductive material constituting the present invention will be described.

[0067] <Composition Components>

[0068] Each component of the second embodiment of the lithium ion conductive material constituting the present invention will be described in detail.

[0069] P 2 O 5 The component forms a rhombohedral crystal system of P1101JP

[0070] NASICON structure crystal phase, Li 1+x Al x Ti 2-x P 3 O 12 (x≥0) crystal phase, or Li 1+x+y Al x Ti 2- x Si y P 3-y O 12 (x≥0, y≥0) crystal phase. Therefore, P 2 O 5 The content of the component has a lower limit of 34.0%, preferably 34.4%, more preferably 34.8%. On the other hand, from the viewpoint of suppressing the formation of other crystal phases and making it difficult to reduce the lithium ion conductivity of the solid electrolyte obtained by low-temperature mixed sintering with a lithium-containing lithium ion conductive glass material, P 2 O 5 The content of the component has an upper limit of 36.5%, preferably 36.0%, more preferably 35.5%, and further preferably 35.2%.

[0071] TiO 2 The component also forms a rhombohedral crystal system of NASICON structure crystal phase, Li 1+x Al x Ti 2-x P 3 O 12 (x≥0) crystal phase, or Li 1+x+y Al x Ti 2-x Si y P 3-y O 12The essential components required for the crystalline phase of (x≥0, y≥0). Therefore, TiO 2 Regarding the content of the component, the lower limit is 42.0%, preferably 43.0%, more preferably 44.0%, and still more preferably 44.3%. On the other hand, from the viewpoint of making it difficult to reduce the lithium ion conductivity of the solid electrolyte obtained by low-temperature mixed sintering with a lithium-containing lithium ion conductive glass material, for the content of the TiO 2 component, the upper limit is 46.5%, preferably 46.0%, more preferably 45.5%, and still more preferably 45.2%

[0072] Al 2 O 3 component, in the second embodiment of the lithium ion conductive material of the present invention, it is also a component essential for forming a crystalline phase of a rhombohedral NASICON structure, Li 1+x Al x Ti 2-x P 3 O 12 (x≥0), or a component essential for the crystalline phase of Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (x≥0, y≥0). Therefore, for the content of the Al 2 O 3 component, the lower limit is preferably 0.6%, more preferably 0.8%, still more preferably 1.0%, and still more preferably 1.2%. On the other hand, from the viewpoint of suppressing the formation of other crystalline phases and making it difficult to reduce the lithium ion conductivity of the solid electrolyte obtained by low-temperature mixed sintering with a lithium-containing lithium ion conductive glass material, for the content of the Al 2 O 3 component, the upper limit is 3.1%, preferably 2.5%, more preferably 2.2%, and still more preferably 2.0%.

[0073] Li 2 O component, in the second embodiment of the lithium ion conductive material of the present invention, imparts lithium ion conductivity and forms a crystalline phase of a rhombohedral NASICON structure, Li 1+x Al x Ti 2-x P 3 O 12 (x≥0), or Li 1+x+y Al x Ti 2-x Si y P 3-y O 12The essential components required for the crystalline phase of (x≥0, y≥0). Therefore, Li 2 The content of the O component has a lower limit of 15.0%, preferably 15.5%, and more preferably 16.0%. On the other hand, from the viewpoint of improving the chemical durability of the second embodiment of the lithium ion conductive material of the present invention and improving the morphological stability, the content of the Li 2 O component has an upper limit of 17.6%, preferably 17.0%, and more preferably 16.5%.

[0074] SiO 2 component, in the second embodiment of the lithium ion conductive material of the present invention, is a crystalline phase forming a rhombohedral NASICON structure or Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (x≥0, y≥0) The essential components required for the crystalline phase. Therefore, SiO 2 The content of the component preferably has a lower limit of 0.5%, more preferably 1.0%, still more preferably 1.5%. On the other hand, from the viewpoint of being able to easily form the required crystalline phase and being able to avoid easy adjacency of crystals and reduction of lithium ion conductivity, the content of the SiO 2 component has an upper limit of 5.0%, more preferably 4.0%, still more preferably 3.0%, and further preferably 2.6%.

[0075] Furthermore, in the second embodiment of the lithium ion conductive material of the present invention, as in the first embodiment described above, as optional components, it may contain one or more selected from the group consisting of ZrO 2 component, Y 2 O 3 component, Sc 2 O 3 component, CaO component, MgO component, and SnO 2 component. And their contents may be the same as those in the first embodiment described above.

[0076] In addition, the second embodiment of the lithium ion conductive material of the present invention can also contain an inorganic component containing boron (B) or fluorine (F). However, it is preferable to reduce the content of sulfur (S) component as much as possible (for example, less than 1%, further less than 0.1%, etc.), and more preferably not to contain it. And it is preferable to similarly reduce the content of alkaline metals (Na, K, etc.) other than Li as much as possible, and more preferably not to contain them.

[0077] And, in the second embodiment of the lithium ion conductive material of the present invention, the Al described above2 O 3 The mol% of the components is based on the Li derived from the Ti, Li, and S compositions. 1+x+y Al x Ti 2-x Si y P 3-y O 12 Al calculated by the composition formula (x = 0.05 to 0.4, y = 0.05 to 0.2, preferably x = 0.1 to 0.3, y = 0.05 to 0.15) 2 O 3 The mol% of the components is reduced by 0.3mol% to 3.0mol%. It should be noted that the lower limit of this range is preferably 0.4mol%, more preferably 0.5mol%. In addition, the upper limit of this range is preferably 2.8mol%, more preferably 2.5mol%, still more preferably 2.0mol%, and further preferably 1.5mol%.

[0078] Here, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (x = 0.05 ~ 0.4, y = 0.05 ~ 0.2), also as a Li, Al, Ti, PO 4 The basic components of the LATP of the solid electrolyte material having a structure of can be derived from the components of Al and Si, or from the components of Ti, Li and Si. However, in the second embodiment of the lithium ion conductive material of the present invention, the Li ion conductive material derived from the components of Ti, Li and Si is used. 1+x+y Al x Ti 2-x Si y P 3-y O 12 The calculation was performed based on the composition formula (x=0.05-0.4, y=0.05-0.2).

[0079] Specifically, for example, when the composition of Ti is 1.8, the composition of Si is 0.1, the composition of Li is 1.3, and the composition of Al is 0.2, it can be derived that Li 1.3 Al 0.2 Ti 1.8 Si 0.1 P 2.9 O 12 And, as long as the actual Al 2 O 3 The mol% of the component and the Al 2 O 3It should be noted that in the second embodiment of the lithium ion conductive material of the present invention, the Li ion conductive material derived from the composition of Ti, Li and Si is 1+x+y Al x Ti 2-x Si y P 3-y O 12 (x = 0.05 to 0.4, y = 0.05 to 0.2), more preferably Li 1.3 Al 0.2 Ti 1.8 Si 0.1 P 2.9 O 12 .

[0080] Furthermore, in a second embodiment of the lithium ion conductive material of the present invention, the above-mentioned P 2 O 5 The mol% of the components is the same as the Li mol% derived from the above compositions of Ti, Li and Si. 1+x+y Al x Ti 2-x Si y P 3-y O 12 P calculated by the component formula (x = 0.05 ~ 0.4, y = 0.05 ~ 0.2) 2 O 5 The mol% of the components is reduced by 0.2mol% to 2.0mol%. It should be noted that the lower limit of the range is preferably 0.3mol%, more preferably 0.5mol%, and even more preferably 0.8mol%. In addition, the upper limit of the range is preferably 1.5mol%, and more preferably 1.2mol%. In addition, the derived composition formula is the same as above.

[0081] By Al 2 O 3 Ingredients and P 2 O 5 The components are in the above-mentioned contents. In the second embodiment of the lithium ion conductive material of the present invention, when combined with a lithium-containing lithium ion conductive glass material (particularly Li 2 O-P 2 O 5 -Al 2 O 3 When the lithium ion conductive glass material is mixed with the material of the second embodiment and sintered at a low temperature, the lithium ion conductive glass material reacts with the material of the second embodiment at the particle interface of the material of the second embodiment, and the reaction product exists at the particle interface, thereby also obtaining a solid electrolyte with high lithium ion conductivity.

[0082] <Crystalline phase>

[0083] The crystalline phase contained in the second embodiment of the lithium ion conductive material of the present invention will be described in detail.

[0084] The second embodiment of the lithium ion conductive material of the present invention contains each of the above-described components in a specified amount, and contains a rhombohedral NASICON structure (Li-substituted NASICON type structure P1101JP) crystalline phase composed of at least a part of these components, Li

[0085] structure), a crystalline phase of Li 1+x Al x Ti 2-x P 3 O 12 (x ≥ 0, preferably 2 > x ≥ 0, more preferably 0.6 ≥ x ≥ 0), or a crystalline phase of Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (x ≥ 0, y ≥ 0, preferably 2 > x ≥ 0, 3 > y ≥ 0, more preferably 0.6 ≥ x ≥ 0, 1 ≥ y ≥ 0). That is, at least one of these crystalline phases is contained. It should be noted that although it is also preferred that all of the crystalline phases included in the second embodiment of the lithium ion conductive material of the present invention are any one or more of the above crystalline phases, it may contain a part of other lithium ion conductive crystalline phases (for example, LISICON type, perovskite type, garnet type, etc.). Even in this case, in all of the crystalline phases contained in the second embodiment of the lithium ion conductive material of the present invention, the above crystalline phases preferably total 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. That is, it is preferred that the above crystalline phase is the main crystalline phase.

[0086] [Morphology, properties, etc.]

[0087] Next, the morphology, properties, etc. of the lithium ion conductive material (first embodiment, second embodiment) of the present invention will be described in detail.

[0088] The form of the lithium ion conductive material of the present invention is a material (material for low-temperature sintering) that forms a solid electrolyte (oxide-based solid electrolyte) by mixing with a lithium-containing lithium ion conductive glass material and sintering at a low temperature. Therefore, from the viewpoint of the ease of operation of this low-temperature mixing and sintering, its form is preferably powder. It should be noted that the particles contained in the powder can be finely pulverized during use, so there is no particular limitation. Its particle size is preferably about 1 / 10 of the zirconia bead diameter used to avoid aggregation and to make fine particles. The maximum particle size is preferably 200 μm or less, and the average particle size is preferably 100 μm or less.

[0089] Here, the "maximum particle size" and "average particle size" of the particles in the present invention refer to the maximum particle size measured by a laser diffraction / scattering particle size distribution measuring device and the volume-based average particle size.

[0090] In addition, the lithium ion conductivity of the lithium ion conductive material of the present invention at 25 °C (the lithium ion conductivity of the material before low-temperature mixing and sintering) is not limited, and is preferably 1.0×10 -4 S / cm or more, more preferably 2.0×10 - 4 S / cm or more, still more preferably 3.0×10 -4 S / cm or more, further preferably 4.0×10 -4 S / cm or more. And its density is also not limited, and is preferably 2.3 g / cm 3 or more, more preferably 2.5 g / cm 3 or more, still more preferably 2.6 g / cm 3 or more.

[0091] Moreover, the lithium ion conductive material of the present invention, although not limited thereto, is preferably a lithium ion conductive glass-ceramic containing a glassy phase (amorphous phase). This is because by mixing and sintering at a low temperature with a lithium-containing lithium ion conductive glass material, it is easy to form a solid electrolyte with a higher lithium ion conductivity.

[0092] Here, the "glass-ceramic" in the present invention includes a crystalline phase and an amorphous phase (non-crystalline phase) formed by heat treatment. The crystalline phase is obtained by heat-treating the raw material glass to precipitate the crystalline phase, or by heat-treating the raw material glass with other materials to synthesize the crystalline phase. That is to say, it is a mixture of ceramic and glass.

[0093] The lithium-ion conductive material of the present invention having the above structure can increase the lithium-ion conductivity by performing pulverization and the like and mixing and sintering with a lithium-containing lithium-ion conductive glass material at a temperature of 800 °C or lower (for example, 600 to 800 °C, or 620 to 800 °C, or 650 to 780 °C), and a solid electrolyte having a high lithium-ion conductivity (for example, the lithium-ion conductivity at 25 °C is 2.0×10 -4 S / cm or more, or 3.0×10 -4 S / cm or more, or 3.5×10 -4 S / cm or more, or 4.5×10 -4 S / cm or more, or 5.0×10 -4 S / cm or more, or 1.0×10 -3 S / cm or more) can be obtained. In addition, the obtained solid electrolyte has a density of a certain value or more (for example, 2.3 g / cm 3 or more, or 2.5 g / cm 3 or more, or 2.6 g / cm 3 or more). Although using an existing lithium-ion conductive material, it is possible to reduce the lithium-ion conductivity by such a mixed sintering, the lithium-ion conductive material of the present invention has the above characteristics and can be suitably used as a raw material for manufacturing a low-temperature sintered solid electrolyte (oxide-based solid electrolyte) (a component raw material of a solid electrolyte material for low-temperature sintering).

[0094] [Manufacturing Method of Lithium-Ion Conductive Material of the Present Invention]

[0095] Next, the manufacturing method of the lithium-ion conductive material of the present invention will be described in detail.

[0096] The lithium-ion conductive material of the present invention can be manufactured by using common methods for manufacturing inorganic materials such as firing, melting, and mixed sintering of inorganic materials. And, although not limited thereto, in the case of manufacturing a lithium-ion conductive glass-ceramic, it is preferably manufactured by a method including the following steps: a step of vitrifying a vitrified raw material to obtain a raw material glass (a lithium-containing lithium-ion conductive glass material); a step of obtaining a mixture with other raw materials; a step of mixing (for example, mixing and pulverizing) and sintering the mixture of the raw material glass and other raw materials to obtain a sintered body as a lithium-ion conductive glass-ceramic. In addition, it is preferably manufactured by a method including the following steps: a step of vitrifying a vitrified raw material to obtain a raw material glass (a lithium-containing lithium-ion conductive glass material); a step of pre-firing after mixing other raw materials in the raw material glass to obtain a pre-fired body; a step of mixing (for example, mixing and pulverizing) and sintering the pre-fired body with other raw materials to obtain a sintered body as a lithium-ion conductive glass-ceramic.

[0097] It should be noted that although not limited thereto, the sintering temperature in the step of obtaining the above sintered body is preferably 1000 °C or higher, and more preferably 1000 °C or higher and 1200 °C or lower.

[0098] In addition, although not limited thereto, the above raw material glass is preferably Li 2 O-P 2 O 5 -Al 2 O 3 -based glass (basic component is Li 2 O-P 2 O 5 -Al 2 O 3 glass) or Li 2 O-P 2 O 5 -based glass (basic component is Li 2 O-P 2 O 5 glass). In the case of the second embodiment, it is preferably Li 2 O-P 2 O 5 ―SiO 2 ―Al 2 O 3 -based glass (basic component is Li 2 O-P 2 O 5 ―SiO 2 ―Al 2 O 3 glass) or Li 2 O-P 2 O 5 ―SiO 2 -based glass (basic component is Li 2 O-P 2 O 5 ―SiO 2 glass). It should be noted that these raw material glasses may also contain Y 2 O 3 etc. Further, in any one of the first embodiment and the second embodiment, the above mixture is preferably a titanium phosphate·titanium oxide (TiP 3 PO 4 ) mixture obtained by mixing and firing orthophosphoric acid (H 2 ) and titanium oxide (TiO 2 O 7 -TiO 2 ).

[0099] Manufacturing Method of Solid Electrolyte Using Lithium Ion Conductive Material of the Present Invention

[0100] Next, the manufacturing method of the solid electrolyte using the lithium ion conductive material of the present invention will be described in detail.

[0101] The solid electrolyte using the lithium ion conductive material of the present invention can be manufactured by a method including the following steps: a step of mixing the lithium ion conductive material of the present invention obtained by the manufacturing method described above, etc., with a lithium-containing lithium ion conductive glass material (glass electrolyte) as a sintering aid to produce a solid electrolyte material; a step of sintering the obtained solid electrolyte material at a sintering temperature of 800 °C or lower to form a solid electrolyte (oxide-based solid electrolyte).

[0102] It should be noted that in the production of the solid electrolyte material, it is preferable to mix and pulverize the lithium ion conductive material of the present invention (the first embodiment or the second embodiment described above) with a lithium-containing lithium ion conductive glass material as a sintering aid. That is, it is preferable to pulverize them separately and then mix them, or to mix them and then pulverize them. In addition, pulverization can be performed before or after mixing. And, as the lithium-containing lithium ion conductive glass material, it is preferable to use Li 2 O-P 2 O 5 -Al 2 O 3 -based glass (glass electrolyte having a basic component of Li 2 O-P 2 O 5 ―Al 2 O 3 ).

[0103] In addition, the sintering temperature in the step of forming the solid electrolyte is not limited as long as it is 800 °C or lower, but more preferably 780 °C or lower, still more preferably 760 °C or lower, and further preferably 740 °C or lower.

[0104] Furthermore, in this sintering, a layer that becomes an electrode layer of a all-solid-state secondary battery (for example, a sheet-like positive electrode layer and negative electrode layer, etc.) can be integrally formed. A known layer can be used as the electrode layer. For example, an electrode layer for an all-solid-state secondary battery obtained by sintering an electrode active material (positive electrode active material or negative electrode active material) mixed with a conductive aid, an inorganic binder, etc. as needed can be used. And, by performing low-temperature sintering and integral forming, etc. of a material containing the above solid electrolyte material, an all-solid-state secondary battery can be formed. It should be noted that as the positive electrode active material, examples include NASICON-type LiV 2 (PO 4) 3 , olivine-type Li x J y MtPO 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 assistant 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 and aluminum, and noble metals such as platinum, gold, ruthenium, and rhodium.

[0105] The embodiments described above are merely examples shown for the sake of easy understanding of the present invention and do not limit the present invention. That is, the components, crystal forms, etc. described above can of course be changed and improved without departing from the gist of the present invention, and their equivalents are also included in the present invention.

[0106] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples and can be variously modified within the technical idea of the present invention.

[0107]

Examples

[0108] According to Figure 1 the synthesis flowchart shown (an example of the manufacturing method of lithium ion conductive glass ceramics), after vitrifying the vitrification raw materials to produce raw glass, mixing other raw materials, pulverizing, drying, and then sintering or sintering after forming, lithium ion conductive glass ceramics of Comparative Examples 1 to 3 and Examples 1 to 4 are produced (Step 1). Further, in order to compare their performances, simulating the interface formation during sintering of all-solid secondary batteries, these lithium ion conductive glass ceramics and lithium ion conductive glass materials (sintering aids) are mixed and pulverized and then sintered at a low temperature, and solid electrolytes of Comparative Examples 1 to 3 and Examples 1 to 4 are also produced (Step 2). Specifically, the production is carried out in the following order.

[0109] First, Step 1 will be supplemented and described below. In Step 1, lithium metaphosphate, aluminum phosphate, and silicon dioxide (when included in the components) are melted and vitrified, and then a mixture (fired body) obtained by firing titanium oxide and orthophosphoric acid is mixed, pulverized, and then sintered to produce lithium ion conductive glass ceramics.

[0110] <Fabrication of Raw Material Glass>

[0111] Lithium metaphosphate (LiPO 3 ) and aluminum phosphate (Al(PO 3 ) 3 ) are formulated in a stoichiometric ratio shown in Table 1 below in terms of mol% based on oxides, or lithium metaphosphate (LiPO 3 ) and aluminum phosphate (Al(PO 3 ) 3 ) and silica (SiO 2 ) are formulated. They are put into a platinum crucible, melted and vitrified while being sufficiently stirred at 1100 °C or higher, and poured onto a casting plate made of metal to obtain various raw material glasses as amorphous materials. The raw material glass adhering to the platinum crucible is also included, and the recovery rate of the recovered raw material glass is 99% or more by weight.

[0112] <Fabrication of Titanium Phosphate - Titanium Oxide Mixture>

[0113] Titanium oxide (TiO 2 ) and orthophosphoric acid (H 3 PO 4 , 89 wt%) are formulated in a stoichiometric ratio shown in Table 1 below in terms of mol% based on oxides. After mixing them using a rotation - revolution mixer (manufactured by Thinky Corporation, Awatori Rentaro), they are put into a beaker made by Pyrex (registered trademark) and fired at 550 °C for 5 hours to obtain various titanium phosphate - titanium oxide (TiP 2 O 7 - TiO 2 ) mixtures.

[0114] [Table 1]

[0115]

[0116] <Synthesis of Lithium - Ion Conductive Glass - Ceramics>

[0117] After separately pulverizing the above - mentioned various raw material glasses and the above - mentioned various titanium phosphate - titanium oxide mixtures to 106 μm or less, they are formulated in a stoichiometric ratio shown in Table 1 above in terms of mol% based on oxides, 1 - propanol is added, and they are pulverized and mixed using zirconia beads with a diameter of φ2 mm (manufactured by Nikkato Corporation, YTZ beads) and a 500 cc zirconia pot using a planetary ball mill under the conditions of 250 rpm for 2 hours (pulverization for 5 minutes and pause for 1 minute). After separating the pulverized paste from the zirconia beads using a sieve, the obtained paste is dried using a shelf - type solvent recovery dryer (manufactured by Sosei Chemical Industry Co., Ltd.).

[0118] After pulverizing the dried mixed powder described above using an alumina mortar and an alumina pestle until it can pass through a 500-μm mesh, 1.5 g was taken and molded under a pressure of 20 kN using a φ20-mm molding die to obtain particles for measuring lithium ion conductivity.

[0119] Then, the dried mixed powder that had not been pulverized was placed in a platinum crucible. Separately, the particles for measuring lithium ion conductivity were placed on a platinum plate, and both were sintered in the atmosphere at 1100 °C for 1 hour to obtain sintered bodies and sintered body particles of Comparative Examples 1 to 3 and Examples 1 to 4 as lithium ion conductive glass ceramics. The steps up to this point are denoted as Step 1( Figure 1 ). It should be noted that Figure 1 An example showing the case where silica is not used is shown.

[0120] Among them, the P 2 O 5 component and the Al 2 O 3 component of each sintered body and sintered body particle obtained in this Step 1, and the difference from the component formula of Li 1+x Al x Ti 2-x P 3 O 12 (x = 0.05 to 0.4), which is the same as the composition of Comparative Example 1, or the difference from the P 1.3 Al 0.3 Ti 1.7 P 3 O 12 (calculated from the components of Ti, Li, and Si) of the component formula of Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (x = 0.05 to 0.4, y = 0.05 to 0.2), which is the same as the composition of Comparative Example 3, or the calculated P 1.3 Al 0.2 Ti 1.8 Si 0.1 P 2.9 O 12 (the same as the composition of Comparative Example 3) of the O 2 O 5 component and the Al 2 O 3The difference in the component composition (mol%) of the components is shown in Table 1 above. That is, Comparative Example 2, Example 1, and Example 2 show the difference in components from Comparative Example 1, and Example 3 and Example 4 show the difference in components from Comparative Example 3. According to Table 1 above, for the lithium-ion conductive glass ceramic obtained in Step 1, compared with the derived component formula above, P 2 O 5 component and Al 2 O 3 component (in other words, AlPO 4 component) is more. On the other hand, for the lithium-ion conductive glass ceramics of Examples 1 to 4 obtained in Step 1, compared with the derived component formula above, P 2 O 5 component and Al 2 O 3 component (in other words, AlPO 4 component) is less by a certain amount ( Figure 1 ).

[0121] Then, for each of the obtained sintered body particles, a gold electrode was formed as a blocking electrode on both sides of each sintered body particle by a magnetron sputtering device (manufactured by Sanyu Electronics Co., Ltd., SC-701HMC). 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. In addition, each sintered body particle was polished on the surface using #800 and #2000 waterproof abrasive papers and 1-propanol, and after drying, the diameter, thickness, and weight were measured using a caliper, a micrometer, and an electronic balance, respectively, and the density was calculated. The lithium-ion conductivity and density of each sintered body particle obtained in this Step 1 are shown in Table 2 below.

[0122] <Mixing and Low-Temperature Sintering of Lithium-Ion Conductive Glass Ceramic and Lithium-Ion Conductive Glass Material: Step 2>

[0123] Next, Step 2 is shown in the following order. First, each sintered body that is not the particle obtained in the above Step 1, and 56 mol% Li as a sintering aid 2 O - 38 mol% P 2 O 5 - 6 mol% Al 2 O 3After the glass (lithium ion conductive glass material (glass electrolyte)) is all pulverized to below 106 μm, it is formulated in a ratio of 88% by weight of the sintered body and 12% by weight of the lithium ion conductive glass material, 1-propanol is added, and using zirconia beads with a diameter of φ2 mm (manufactured by Nikkato Corporation, YTZ beads) and a 500 cc zirconia pot, it is pulverized and mixed by a planetary ball mill under the conditions of 250 rpm and 2 hours (pulverization for 5 minutes and pause for 1 minute). After separating the pulverized paste from the zirconia beads using a sieve, the obtained paste is dried using a shelf type solvent recovery dryer (manufactured by Sosei Chemical Industry Co., Ltd.).

[0124] After the above-mentioned dried mixed powder is pulverized to pass through a 500 μm mesh using an alumina mortar and an alumina pestle, 1.5 g is taken, and a pressure of 20 kN is applied using a φ20 mm molding die to form, and a plurality of various particles for measuring lithium ion conductivity are respectively obtained.

[0125] After the particles for measuring lithium ion conductivity are heat-treated at 580 °C, 620 °C, 660 °C, 700 °C, 740 °C or 780 °C for 1 hour in the atmosphere to obtain sintered body particles as solid electrolytes, for these particles, in the same method as the calculation of the sintered body particles in step 1 described above, the lithium ion conductivity and density are calculated. It should be noted that the lithium ion conductivity and density of each sintered body particle obtained by sintering at 780 °C in this step 2 are shown in Table 2 below. In addition, for Comparative Example 1, Comparative Example 2 and Example 4, the lithium ion conductivity (conductivity) and density of the sintered body particles obtained at each sintering temperature are shown in Figure 2 and Figure 3 are shown.

[0126]

Table 2

[0127]

[0128] <Evaluation Results>

[0129] According to this result, it can be confirmed that the sintered body particles of Comparative Examples 1 to 3 obtained in step 1 all have a relatively high lithium ion conductivity of 5×10 - 4 S / cm or more. In particular, although the sintered body particles of Comparative Example 2 require a relatively high sintering temperature of 1100 °C, they obtain a value of 1.2×10 -3The lithium ion conductivity is not different from the literature value of S / cm. However, for the sintered body particles of Comparative Examples 1 to 3 obtained in Step 2, the lithium ion conductivity is reduced to 1 / 2 to 1 / 3 of the sintered body particles obtained in Step 1. On the other hand, in Examples 1 to 4, it is shown that the sintered body particles obtained in Step 2 all have a higher lithium ion conductivity than the sintered body particles obtained in Step 1. Further, even when compared with the sintered body particles of Comparative Examples 1 to 3 obtained in Step 2, they also have a higher lithium ion conductivity than them. In particular, it can be confirmed that the sintered body particles of Example 3 obtained in Step 2, which simulates the interface formation during the sintering of all-solid secondary batteries, have a lithium ion conductivity of 1.5×10 -3 S / cm, which is quite high for LATP-based oxide solid electrolytes.

[0130] As shown in Table 1 above, for any of the components of the sintered body particles (lithium ion conductive glass ceramics) of Examples 1 to 4 obtained in Step 1, the Al 2 O 3 component and the P 2 O 5 component (actually the AlPO 4 component), compared with Li 1.3 Al 0.3 Ti 1.7 P 3 O 12 which is the basic component of LATP derived from the components of Ti and Li (the composition of Comparative Example 1), or compared with Li 1.3 Al 0.2 Ti 1.8 Si 0.1 P 2.9 O 12 which is the basic component of LATP derived from the components of Ti, Li and Si (the composition of Comparative Example 3), both decreased by a certain amount. It is considered that this is because when mixed with a Li 2 O-P 2 O 5 -Al 2 O 3 -based lithium ion conductive glass material (glass electrolyte) and sintered at a low temperature, the glass electrolyte reacts with the lithium ion conductive glass ceramic at the particle interface, and the reaction product exists at the particle interface, thereby avoiding an excessive glass electrolyte with a relatively low lithium ion conductivity alone (about 1×10 -7(S / cm) exists at the interface of the particles. In Comparative Examples 1 to 3, the sintered body particles (lithium ion conductive glass ceramics) obtained in Step 1 were the most suitable. Therefore, it can be considered that for the sintered body particles (solid electrolyte) obtained in Step 2, the more glass electrolyte there is at the interface of the particles, the lower the lithium ion conductivity. In addition, it can be considered that when the amount of glass electrolyte mixed in Step 2 is too small, the glass electrolyte cannot fully function, and the density and lithium ion conductivity of the obtained sintered body particles (solid electrolyte) will decrease.

[0131] It should be noted that the secondary electron image of the fracture surface of the sintered body particles obtained by sintering at 780 °C in Example 4 is shown in Figure 4 and the backscattered electron image is shown in Figure 5 This observation and detection were carried out using the electron microscope JSM-700HR manufactured by JEOL Ltd. Generally, when observing at a low acceleration voltage of about 5 kV, the secondary electron image can observe the information on the particle surface, and the backscattered electron image can observe the information inside the particles. Positions that cannot be seen in the backscattered electron image can be seen in the secondary electron image. From this, it can be known that there are attachments on the particle surface of the sintered body particles. Since this image is an image of the fracture surface, it can be speculated that there are attachments (reaction products of the glass electrolyte and the lithium ion conductive glass ceramics) at the particle interface, and it can be speculated that the glass electrolyte is beneficial to the formation of the particle interface.

[0132] Furthermore, according to Figure 6 the shown synthesis flow chart (a modification of the manufacturing method of lithium ion conductive glass ceramics), after vitrifying the vitrification raw materials to make the raw material glass, other raw materials are kneaded and pre-fired, and then mixed and pulverized with other raw materials and sintered, or sintered after molding, thereby manufacturing the lithium ion conductive glass ceramics of Comparative Example 4 and Examples 5 to 6 (Steps 1-2). In addition, in order to compare their performances and simulate the interface formation during sintering of all-solid secondary batteries, these lithium ion conductive glass ceramics were also mixed and pulverized with a lithium ion conductive glass material (sintering aid) and sintered at a low temperature to manufacture the solid electrolytes of Comparative Example 4 and Examples 5 to 6 (Steps 2-2). Specifically, the production was carried out in the following order.

[0133] First, Step 1-2 will be further described below. In Step 1-2, lithium metaphosphate and silica (when included in the components) are melted and vitrified, then titanium oxide, orthophosphoric acid, and aluminum phosphate are kneaded and pre-fired to produce a pre-sintered body. Then, lithium metaphosphate is mixed in this pre-sintered body, pulverized, and sintered, thereby manufacturing lithium ion conductive glass ceramics.

[0134] <Manufacture of Raw Material Glass>

[0135] In a manner such that the stoichiometric ratio is as shown in Table 3 below in terms of mol% based on oxides, lithium metaphosphate (LiPO 3 ) is formulated, or lithium metaphosphate (LiPO 3 ) and silicon dioxide (SiO 2 ) are formulated. Among them, since the lithium metaphosphate is also mixed after pre-firing, the amount of half of its stoichiometric ratio is selected here. It is put into a platinum crucible, melted and vitrified while being sufficiently stirred at 1100 °C or higher, and poured onto a casting plate made of metal to obtain various raw material glasses as amorphous materials. The raw material glass adhering to the platinum crucible is also included, and the yield of the recovered raw material glass is 99% or more in terms of weight ratio.

[0136] <Fabrication of Raw Material Glass, Titanium Oxide, Orthophosphoric Acid, and Aluminum Phosphate Precursor>

[0137] In a manner such that the stoichiometric ratio is as shown in Table 3 below in terms of mol% based on oxides, titanium oxide (TiO 2 ), orthophosphoric acid (H 3 PO 4 , 89 wt%), aluminum phosphate (Al(PO 3 ) 3 ) and the above-mentioned raw material glass are formulated. After kneading them using a rotation-revolution mixer (manufactured by Thinky Corporation, Awatori Rentaro), it is put into a beaker manufactured by Pyrex (registered trademark) and fired at 550 °C for 5 hours to obtain a precursor of a mixture of various raw material glasses, titanium oxide, orthophosphoric acid, and aluminum phosphate.

[0138] [Table 3]

[0139]

[0140] <Synthesis of Lithium Ion Conductive Glass-Ceramics>

[0141] After separately pulverizing the above-mentioned precursor and lithium metaphosphate to 106 μm or less, they are formulated in a manner such that the stoichiometric ratio is as shown in Table 3 above in terms of mol% based on oxides, 1-propanol is added, and pulverization and mixing are carried out using zirconia beads with a diameter of φ2 mm (manufactured by Nikkato Corporation, YTZ beads) and a 500 cc zirconia pot using a planetary ball mill under the conditions of 250 rpm and 2 hours (pulverization for 5 minutes and pause for 1 minute). After separating the pulverized paste from the zirconia beads using a sieve, the obtained paste is dried using a shelf-type solvent recovery dryer (manufactured by Sosei Chemical Industry Co., Ltd.).

[0142] After pulverizing the dried mixed powder described above using an alumina mortar and an alumina pestle until it can pass through a 500-μm mesh, 1.5 g was taken and molded under a pressure of 20 kN using a φ20-mm molding die to obtain particles for measuring lithium ion conductivity.

[0143] Then, the dried mixed powder that had not been pulverized was placed in a platinum crucible, and separately, the particles for measuring lithium ion conductivity were placed on a platinum plate. They were each sintered at 1000 °C for 1 hour in the atmosphere to obtain sintered bodies and sintered body particles of Comparative Example 4 and Examples 5 to 6 of lithium ion conductive glass ceramics. The steps up to this point are denoted as Step 1-2( Figure 6 ). It should be noted that Figure 6 An example of the case where silica was used is shown.

[0144] Among them, the P 2 O 5 component and the Al 2 O 3 component of each of the sintered bodies and sintered body particles of Example 5 and Example 6 obtained in this Step 1-2, in terms of mol% based on oxides, and the Li 1+x Al x Ti 2-x P 3 O 12 (x = 0.05 to 0.4) of the component formula of Li 1.3 Al 0.3 Ti 1.7 P 3 O 12 (the same as the component of Comparative Example 1 described above), or Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (x = 0.05 to 0.4, y = 0.05 to 0.2) of the component formula of Li 1.3 Al 0.2 Ti 1.8 Si 0.1 P 2.9 O 12 (the same as the component of Comparative Example 4) were calculated for the P 2 O 5 component and the Al 2 O 3The difference in the component composition (mol%) of the components is shown in Table 3 above. That is, Example 5 shows the difference in components from Comparative Example 4, and Example 6 shows the difference in components from Comparative Example 1 described above. According to Table 3 above, for the lithium-ion conductive glass ceramics of Examples 5-6 obtained in Step 1-2, compared with the derived component formula described above, P 2 O 5 component and Al 2 O 3 component (in other words, AlPO 4 component) decreased by a certain amount.

[0145] Then, for each of the obtained sintered body particles, gold electrodes were formed as blocking electrodes on both sides of each sintered body particle by a magnetron sputtering device (manufactured by Sanyu Electronics Co., Ltd., SC-701HMC). Using an electrochemical evaluation device (manufactured by Bio-Logic Co., Ltd., SP300), impedance measurement was carried out 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. In addition, each sintered body particle was polished on the surface using #800 and #2000 waterproof abrasive papers and 1-propanol. After drying, the diameter, thickness, and weight were measured using a caliper, a micrometer, and an electronic balance, respectively, and the density was calculated. The lithium-ion conductivity and density of each sintered body particle obtained in this Step 1-2 are shown in Table 4 below.

[0146] <Mixing and Low-Temperature Sintering of Lithium-Ion Conductive Glass Ceramics and Lithium-Ion Conductive Glass Materials: Step 2-2>

[0147] Next, Step 2-2 is shown in the following order. First, each sintered body that is not the particle obtained in the above Step 1-2 and 56 mol% Li as a sintering aid 2 O - 38 mol% P 2 O 5 - 6 mol% Al 2 O 3 glass (lithium-ion conductive glass material (glass electrolyte)) were both pulverized to less than 106 μm, and then formulated in a ratio such that the sintered body was 88 wt% and the lithium-ion conductive glass material was 12 wt%. 1-Propanol was added, and using φ2 mm zirconia beads (manufactured by Nikkato Corporation, YTZ beads) and a 500 cc zirconia pot, pulverization and mixing were carried out using a planetary ball mill under the conditions of 250 rpm and 2 hours (pulverization for 5 minutes and pause for 1 minute). After separating the pulverized paste from the zirconia beads using a sieve, the obtained paste was dried using a shelf-type solvent recovery dryer (manufactured by Sosei Chemical Industry Co., Ltd.).

[0148] After pulverizing the dried mixed powder described above using an alumina mortar and an alumina pestle to pass through a 500-μm mesh, 1.5 g was taken and molded under a pressure of 20 kN using a φ20-mm molding die to obtain a plurality of various particles for measuring lithium ion conductivity respectively.

[0149] After heat-treating the particles for measuring lithium ion conductivity in the atmosphere at 650 °C, 700 °C, 740 °C, 760 °C, 780 °C, or 800 °C for 1 hour to obtain sintered body particles as solid electrolytes, for these particles, in the same manner as the calculation of the sintered body particles in Steps 1-2 described above, the lithium ion conductivity and density were calculated. It should be noted that the lithium ion conductivity and density of each sintered body particle obtained by sintering at 740 °C in Step 2-2 are shown in Table 4 below. In addition, for Example 5, the relationship between the lithium ion conductivity (conductivity) and density of the sintered body particles obtained according to each sintering temperature is shown in Figure 7 and Figure 8 for comparison with Comparative Example 1 and Example 4 described above.

[0150]

Table 4

[0151]

[0152] <Evaluation Results>

[0153] According to this result, it was confirmed that the sintered body particles of Examples 5 to 6 obtained in Step 1-2 all had a relatively high lithium ion conductivity of 4×10 -4 S / cm or more. This was no different from the tendency of Examples 1 to 4 described above. On the other hand, it was confirmed that even when a low sintering temperature of 740 °C was selected in Step 2-2 for simulating the interface formation during the sintering of all-solid-state secondary batteries, a solid electrolyte with a lithium ion conductivity greater than 2×10 -4 S / cm and a density greater than 2.6 g / cm 3 could be obtained.

[0154] It should be noted that the secondary electron image of the fracture surface of the sintered body particles obtained by sintering at 700 °C in Step 2-2 of Example 5 is shown in Figure 9 . This observation and detection were carried out using the electron microscope JSM-700HR manufactured by JEOL Ltd., under the same conditions as Figure 4 . This result confirmed that even when sintering at 700 °C, the bonding between particles was sufficient.

[0155] This application claims priority based on Japanese Patent Application No. 2021-060218 filed on March 31, 2021, the entire disclosure of which is incorporated herein by reference.

Claims

1. A solid electrolyte, wherein, the solid electrolyte is formed by mixing and sintering a lithium-ion conductive glass-ceramic and a lithium-containing lithium-ion conductive glass material, and the lithium-ion conductive glass-ceramic contains, in mol% based on oxides: 36.6% to 37.3% of P 2 O 5 component, 43.0% to 48.1% of TiO 2 component, 0.6% to 2.56% of Al 2 O 3 component, and 13.9% to 17.5% of Li 2 O component, and The mol% of said Al 2 O 3 component, compared with the mol% of the Al 1+x Al x Ti 2-x P 3 O 12 component calculated based on the component formula of 2 O 3 is reduced by 0.3 mol% to 3.0 mol%, where x = 0.05 to 0.4, The mol% of the said P 2 O 5 component, compared with the mol% of P 1+x Al x Ti 2-x P 3 O 12 calculated based on the component formula of 2 O 5 is reduced by 0.2 mol% to 2.0 mol%, where x = 0.05 to 0.4 And, containing Li 1+x Al x Ti 2-x P 3 O 12 crystalline phase, where x ≥ 0.

2. A solid electrolyte, wherein, the solid electrolyte is formed by mixing and sintering a lithium-ion conductive glass-ceramic and a lithium-containing lithium-ion conductive glass material, and the lithium-ion conductive glass-ceramic contains, in mol% based on oxides: 34.0% to 36.5% of P 2 O 5 component, 44.3% to 46.5% of TiO 2 composition, 0.6% to 2.0% of Al 2 O 3 component, 15.0% to 17.6% of Li 2 O component, and 0.5% to 5.0% of SiO 2 component, and The mol% of said Al 2 O 3 component is reduced by 0.3 mol% to 3.0 mol% compared with the mol% of the Al 1+x+y Al x Ti 2-x Si y P 3-y O 12 component calculated based on the component formula of 2 O 3 where x = 0.05 to 0.4 and y = 0.05 to 0.2 The mol% of the said P 2 O 5 component, compared with the mol% of P 1+x+y Al x Ti 2-x SiyP 3-y O 12 component calculated according to the component formula of 2 O 5 is reduced by 0.2 mol% to 2.0 mol%, where x = 0.05 to 0.4 and y = 0.05 to 0.2 And, containing Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 crystalline phase, where x≥0, y≥0.

3. An all-solid-state secondary battery formed from a material containing the solid electrolyte according to claim 1 or 2.

Images