Garnet type crystal and precursor solution

Abstract

To provide a garnet type crystal excellent in a lithium ion conductivity of a bulk, and capable of obtaining a compact of a solid electrolyte having a sufficiently low grain boundary resistance, and to provide a precursor solution excellent in a lithium ion conductivity of a bulk, and capable of being favorably used for producing a compact of a solid electrolyte having a sufficiently low grain boundary resistance by a sufficiently low calcination temperature.SOLUTION: A garnet type crystal includes Li, La, Zr, and O, and further includes Ce, Nb, Sb, and Ta as constituent elements. The garnet type crystal further preferably includes Sn as a constituent element.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to garnet-type crystals and precursor solutions. [Background technology]

[0002] Lithium-ion batteries (including primary and secondary batteries) are used as power sources for many electrical devices, including portable information devices. Among them, all-solid-state lithium-ion batteries, which use a solid electrolyte for lithium conduction between the positive and negative electrodes, have been proposed as lithium-ion batteries that combine high energy density with safety.

[0003] Solid electrolytes are attracting attention as highly safe materials because they can conduct lithium ions without using an organic electrolyte solution and do not leak or volatilize due to heat generated by driving.

[0004] As the solid electrolyte used in such all-solid-state lithium-ion batteries, oxide-based solid electrolytes that have high lithium ion conductivity, excellent insulation properties, and high chemical stability are widely known. Among such oxides, lanthanum zirconate-based garnet-type crystals have a particularly high lithium ion conductivity and are expected to be applied to batteries.

[0005] When such a solid electrolyte is a particulate solid electrolyte particle, it is often molded into a desired shape by compression molding. However, since the solid electrolyte particle is very hard, the contact between the solid electrolyte particles in the obtained molded product is insufficient, resulting in high grain boundary resistance and low lithium ion conductivity.

[0006] Therefore, in order to obtain a solid electrolyte with high lithium ion conductivity and low grain boundary resistance even when sintered at a relatively low temperature, a compound with the composition formula Li 7-y La 3 (Zr 2-x-y Sn x M y )O 12(wherein M is one or more metal elements selected from Ta, Sb, and Nb, and satisfies 0.1≦x<0.5 and 0.1≦y≦0.7) has been proposed (see Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2020-136235 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, there is a demand for a solid electrolyte that combines high lithium ion conductivity and low interface resistance at an even higher level. [Means for solving the problem]

[0009] A garnet-type crystal according to an application example of the present invention is a garnet-type crystal containing Li, La, Zr and O, Furthermore, it contains Ce, Nb, Sb and Ta as constituent elements.

[0010] A precursor solution according to an application example of the present invention is a precursor solution used for producing a garnet-type crystal containing Li, La, Zr, and O, An organic solvent; It contains the metallic elements Li, La, Zr, Ce, Nb, Sb and Ta. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic perspective view showing a structure of a lithium ion battery as a secondary battery of the first embodiment. [Diagram 2] FIG. 2 is a schematic perspective view showing a structure of a lithium ion battery as a secondary battery of the second embodiment. [Diagram 3]FIG. 3 is a schematic cross-sectional view showing a structure of a lithium ion battery as a secondary battery of the second embodiment. [Figure 4] FIG. 4 is a schematic perspective view showing a structure of a lithium ion battery as a secondary battery of the third embodiment. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing a structure of a lithium ion battery as a secondary battery of the third embodiment. [Figure 6] FIG. 6 is a schematic perspective view showing a structure of a lithium ion battery as a secondary battery of the fourth embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing a structure of a lithium ion battery as a secondary battery of the fourth embodiment. [Figure 8] FIG. 8 is a flowchart showing a method for manufacturing a lithium ion battery as a secondary battery of the first embodiment. [Figure 9] FIG. 9 is a schematic diagram illustrating a method for manufacturing a lithium ion battery as a secondary battery of the first embodiment. [Figure 10] FIG. 10 is a schematic diagram illustrating a method for manufacturing a lithium ion battery as a secondary battery according to the first embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view showing another method for forming a solid electrolyte layer. [Figure 12] FIG. 12 is a flowchart showing a method for manufacturing a lithium ion battery as a secondary battery of the second embodiment. [Figure 13] FIG. 13 is a schematic diagram showing a method for manufacturing a lithium ion battery as a secondary battery of the second embodiment. [Figure 14] FIG. 14 is a schematic diagram showing a method for manufacturing a lithium ion battery as a secondary battery of the second embodiment. [Figure 15] FIG. 15 is a flowchart showing a method for manufacturing a lithium ion battery as a secondary battery of the third embodiment. [Figure 16] FIG. 16 is a schematic diagram showing a method for manufacturing a lithium ion battery as a secondary battery of the third embodiment. [Figure 17] FIG. 17 is a schematic diagram showing a method for manufacturing a lithium ion battery as a secondary battery according to the third embodiment. [Figure 18] FIG. 18 is a flowchart showing a method for manufacturing a lithium ion battery as a secondary battery according to the fourth embodiment. [Figure 19] FIG. 19 is a schematic diagram showing a method for manufacturing a lithium ion battery as a secondary battery according to the fourth embodiment. [Figure 20] FIG. 20 is a perspective view showing a configuration of a wearable device as an electronic device. [Figure 21] FIG. 21 is a table showing the compositions and crystal phases of the solid electrolytes of Examples 1 and 2 and Comparative Examples 1 to 6. [Figure 22] FIG. 22 is a table showing the evaluation results of Examples 1 and 2 and Comparative Examples 1 to 6. [Diagram 23] FIG. 23 is a table showing the compositions and crystal phases of the solid electrolytes of Examples 3-6. [Figure 24] FIG. 24 is a table showing the evaluation results of Examples 3 to 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Preferred embodiments of the present invention will now be described in detail. [1] Garnet-type crystals First, the garnet-type crystal of the present invention will be described.

[0013] The garnet-type crystal of the present invention is a garnet-type crystal containing Li, La, Zr and O, and further contains Ce, Nb, Sb and Ta as constituent elements.

[0014] This makes it possible to provide a garnet-type crystal as a solid electrolyte that is excellent in bulk lithium ion conductivity and can obtain a solid electrolyte molded body with sufficiently low grain boundary resistance at a sufficiently low sintering temperature. In addition, in the conventional solid electrolyte, for example, when the solid electrolyte is co-sintered with an active material such as lithium cobalt oxide, the elements of the solid electrolyte interdiffuse each other, resulting in a low lithium ion conductivity. However, in the garnet-type crystal of the present invention, even when the solid electrolyte is co-sintered with an active material such as lithium cobalt oxide, the elements of the solid electrolyte interdiffuse each other, resulting in a low lithium ion conductivity. This problem can be effectively suppressed.

[0015] On the other hand, if the above conditions are not met, the above excellent effects cannot be obtained.

[0016] For example, if at least one of Ce, Nb, Sb, and Ta is not contained, it becomes difficult to obtain a sufficiently excellent bulk lithium ion conductivity, and it becomes difficult to obtain a solid electrolyte compact having a sufficiently low grain boundary resistance at a sufficiently low sintering temperature.

[0017] As described above, the garnet-type crystal of the present invention is a garnet-type crystal containing Li, La, Zr, and O, and further containing Ce, Nb, Sb, and Ta as constituent elements. However, when the constituent elements other than Li, La, Zr, and O are the four types of Ce, Nb, Sb, and Ta, the garnet-type crystal is preferably represented by the following composition formula (1).

[0018] Li 7-3x La 3 (Zr 2-4x Ce x Nb x Sb x Ta x )O 12 (1) (In the composition formula (1), x satisfies 0.10≦x<0.30.)

[0019] This makes it possible to improve the bulk lithium ion conductivity and to obtain a solid electrolyte compact having lower grain boundary resistance at a lower sintering temperature.

[0020] However, the values ​​of x for Ce, Nb, Sb and Ta in the above composition formula (1) need only be the same when rounded to the nearest significant figure.

[0021] Furthermore, even if the garnet-type crystal of the present invention contains unavoidable impurities and other components in a very small content other than those described above, the present specification treats the crystal as satisfying the condition of the above composition formula (1) as long as Li, La, Zr, Ce, Nb, Sb, Ta and O satisfy the above ratio conditions.

[0022] The above-mentioned "extremely small content" refers to a content of 5% or less of the component that has the smallest content on a mass basis among Li, La, Zr, Ce, Nb, Sb, Ta and O in the garnet-type crystal of the present invention.

[0023] When the garnet-type crystal of the present invention is represented by the above composition formula (1), x may satisfy 0.10≦x<0.30, and preferably satisfies 0.2≦x<0.3. This makes the above-mentioned effects more pronounced.

[0024] As described above, the garnet-type crystal of the present invention is a garnet-type crystal containing Li, La, Zr and O, and further contains Ce, Nb, Sb and Ta as constituent elements, but preferably further contains Sn as a constituent element.

[0025] This makes it possible to improve the bulk lithium ion conductivity and to obtain a solid electrolyte compact having lower grain boundary resistance at a lower sintering temperature.

[0026] When the garnet-type crystal of the present invention contains five elements, Ce, Nb, Sb, Ta and Sn, as constituent elements other than Li, La, Zr and O, the garnet-type crystal is preferably represented by the following composition formula (2).

[0027] Li 7-3x La 3 (Zr 2-5x Ce x Nb x Sb x Ta x Sn x )O 12 (2) (In the composition formula (2), x satisfies 0.10≦x<0.30.)

[0028] This makes it possible to improve the bulk lithium ion conductivity and to obtain a solid electrolyte compact having lower grain boundary resistance at a lower sintering temperature.

[0029] However, the values ​​of x for Ce, Nb, Sb, Ta and Sn in the above composition formula (2) may be the same as long as the values ​​rounded to the nearest significant figure are the same.

[0030] Furthermore, even if the garnet-type crystal of the present invention contains extremely small amounts of unavoidable impurities and other components other than those described above, in this specification, it is treated as satisfying the condition of the above composition formula (2) as long as Li, La, Zr, Ce, Nb, Sb, Ta, Sn and O satisfy the above ratio conditions.

[0031] In garnet-type crystals, Li is mainly contained in the basic skeleton Li 7 La 3 Zr 2 O 12 They exist at the C site and interstitial sites in LiAl and contribute to lithium ion conductivity.

[0032] In garnet-type crystals, La is mainly mixed with the Li 7 La 3 Zr2 O 12 Configure La 3+ Occupies A site.

[0033] In garnet-type crystals, Zr is mainly mixed with the Li 7 La 3 Zr 2 O 12 Constituting Zr 4+ and occupies site B.

[0034] In garnet-type crystals, Ce, Nb, Sb, Ta and Sn mainly function to lower the tetragonal-cubic transition temperature and the melting point compared to when they are not contained, and because their oxides have a high dielectric constant, they improve the lithium ion conductivity.

[0035] The garnet-type crystal of the present invention may be used alone as a solid electrolyte, or may be used in combination with other components as a solid electrolyte. More specifically, the garnet-type crystal of the present invention may be used alone as a solid electrolyte layer in a battery, as described below, or may be used in a mixed state with other solid electrolytes to form a solid electrolyte layer. In addition, for example, the garnet-type crystal of the present invention may be used in a mixed state with a positive electrode active material to form a positive electrode layer, or may be used in a mixed state with a negative electrode active material to form a negative electrode layer.

[0036] The garnet-type crystal of the present invention may further contain other elements in addition to the above elements. The other elements may be one type or two or more types. Examples of the other elements include Hf, Ge, In, Te, W, and the like.

[0037] When the garnet-type crystal of the present invention contains the other elements, the content of the other elements in the garnet-type crystal of the present invention is preferably equal to or lower than the content of Ce, Nb, Sb and Ta in terms of molar ratio.

[0038] [2] Precursor solution Next, the precursor solution of the present invention will be described.

[0039] The precursor solution of the present invention is a precursor solution used for producing a garnet-type crystal containing Li, La, Zr and O, and contains an organic solvent and each of the metal elements Li, La, Zr, Ce, Nb, Sb and Ta.

[0040] This makes it possible to suitably obtain the garnet-type crystal of the present invention described above, and to provide a precursor solution that is excellent in bulk lithium ion conductivity and can be suitably used for manufacturing a solid electrolyte compact with sufficiently low grain boundary resistance at a sufficiently low sintering temperature. In addition, in the past, for example, when a solid electrolyte is co-sintered with an active material such as lithium cobalt oxide, there was a problem that each element caused mutual diffusion and the lithium ion conductivity was reduced. However, by using the precursor solution of the present invention, even when the solid electrolyte is co-sintered with an active material such as lithium cobalt oxide, the occurrence of the problem of each element causing mutual diffusion and the lithium ion conductivity being reduced can be effectively suppressed.

[0041] As described above, the precursor solution of the present invention is a precursor solution used for producing a garnet-type crystal containing Li, La, Zr, and O, and may contain an organic solvent and each of the metal elements Li, La, Zr, Ce, Nb, Sb, and Ta, but preferably satisfies the following condition: That is, when the constituent elements other than Li, La, Zr, and O in the garnet-type crystal are four kinds of Ce, Nb, Sb, and Ta, when x is a number satisfying 0.10≦x<0.30 and y is a number satisfying 1.05≦y≦1.40, the ratio of the contents of Li, La, Zr, Ce, Nb, Sb, and Ta in the precursor solution is preferably (7-3x)y:3:(2-4x):x:x:x:x in molar ratio.

[0042] This makes it possible to suitably produce a garnet-type crystal having the composition represented by the above composition formula (1), thereby improving the bulk lithium ion conductivity and enabling a solid electrolyte compact having lower grain boundary resistance to be obtained at a lower firing temperature.

[0043] However, in the above content ratios of Li, La, Zr, Ce, Nb, Sb and Ta, the values ​​of x for Ce, Nb, Sb and Ta may be the same when rounded to the nearest significant figure.

[0044] When the precursor solution of the present invention satisfies the above-mentioned conditions for the ratio of the content rates of Li, La, Zr, Ce, Nb, Sb, and Ta, x may satisfy 0.10≦x<0.30, and preferably satisfies 0.2≦x<0.3. This makes the above-mentioned effects more pronounced.

[0045] Furthermore, when the precursor solution of the present invention satisfies the above-mentioned condition regarding the ratio of the content rates of Li, La, Zr, Ce, Nb, Sb, and Ta, it is sufficient that y satisfies 1.05≦y≦1.40, and preferably satisfies 1.05≦y≦1.20. This makes the above-mentioned effects more pronounced.

[0046] As described above, the precursor solution of the present invention is a precursor solution used for producing a garnet-type crystal containing Li, La, Zr, and O, and may contain an organic solvent and each of the metal elements Li, La, Zr, Ce, Nb, Sb, and Ta, and preferably further contains Sn as a metal element.

[0047] As a result, the garnet-type crystal produced using the precursor solution of the present invention has superior bulk lithium ion conductivity and can be used to produce a solid electrolyte compact having lower grain boundary resistance at a lower firing temperature.

[0048] As described above, the precursor solution of the present invention is a precursor solution used for producing a garnet-type crystal containing Li, La, Zr, and O, and may contain an organic solvent and each of the metal elements Li, La, Zr, Ce, Nb, Sb, and Ta, but preferably satisfies the following condition: That is, when the constituent elements other than Li, La, Zr, and O in the garnet-type crystal are five kinds, namely Ce, Nb, Sb, Ta, and Sn, where x is a number satisfying 0.10≦x<0.30 and y is a number satisfying 1.05≦y≦1.40, the ratio of the contents of Li, La, Zr, Ce, Nb, Sb, Ta, and Sn in the precursor solution is preferably (7-3x)y:3:(2-5x):x:x:x:x:x in molar ratio.

[0049] This makes it possible to suitably produce a garnet-type crystal having the composition represented by the above composition formula (2), thereby making it possible to further improve the bulk lithium ion conductivity and to obtain a solid electrolyte compact having an even lower grain boundary resistance at a lower firing temperature.

[0050] However, in the above content ratios of Li, La, Zr, Ce, Nb, Sb, Ta, and Sn, the values ​​of x for Ce, Nb, Sb, Ta, and Sn may be the same as long as the values ​​are rounded to the nearest significant figure.

[0051] When the precursor solution of the present invention satisfies the above-mentioned condition of the ratio of the content rates of Li, La, Zr, Ce, Nb, Sb, Ta and Sn, x may satisfy 0.10≦x<0.30, and preferably satisfies 0.2≦x<0.3. This makes the above-mentioned effects more pronounced.

[0052] Furthermore, when the precursor solution of the present invention satisfies the above-mentioned condition of the ratio of the content rates of Li, La, Zr, Ce, Nb, Sb, Ta and Sn, it is sufficient that y satisfies 1.05≦y≦1.40, and preferably satisfies 1.05≦y≦1.20. This makes the above-mentioned effects more pronounced.

[0053] [3] Preparation of precursor solution Next, a method for preparing the precursor solution of the present invention will be described.

[0054] The precursor solution of the present invention can be produced, for example, by a method having a mixing step of mixing an organic solvent with a plurality of metal-containing raw materials containing at least the metal elements Li, La, Zr, Ce, Nb, Sb and Ta to obtain a mixture. In the precursor solution of the present invention, each of the above metal elements is contained in a state of being dissolved in the organic solvent.

[0055] The organic solvent is not particularly limited, and examples thereof include alcohols, glycols, ketones, esters, ethers, organic acids, aromatics, amides, etc., and a mixed solvent of one or more selected from these can be used. Examples of alcohols include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, allyl alcohol, 2-n-butoxyethanol, etc. Examples of glycols include ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, pentanediol, hexanediol, heptanediol, dipropylene glycol, etc. Examples of ketones include dimethyl ketone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, etc. Examples of esters include methyl formate, ethyl formate, methyl acetate, methyl acetoacetate, etc. Examples of ethers include diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and dipropylene glycol monomethyl ether. Examples of organic acids include formic acid, acetic acid, 2-ethylbutyric acid, and propionic acid. Examples of aromatics include toluene, o-xylene, and p-xylene. Examples of amides include formamide, N,N-dimethylformamide, N,N-diethylformamide, dimethylacetamide, and N-methylpyrrolidone. Among these, the organic solvent is preferably at least one of 2-n-butoxyethanol and propionic acid.

[0056] This makes it possible to improve the solubility of the metal-containing raw material in the organic solvent, and to dissolve the metal-containing raw material more uniformly. In addition, it becomes easier to select an organic group of the metal-containing raw material that has a molecular structure similar to that of the organic solvent, and thus it is possible to more suitably produce fine crystals with high uniformity.

[0057] At least one of the multiple metal-containing raw materials used in the mixing step may be an oxoacid compound that contains an oxoanion as well as a metal ion.

[0058] This allows the garnet-type crystal having the desired properties to be stably formed by a heat treatment at a relatively low temperature for a relatively short time in the production of a garnet-type crystal using a precursor solution. More specifically, by using an oxo acid compound in the mixing step, a pre-calcined body can be obtained that contains an oxide and an oxo acid compound different from the garnet-type crystal finally obtained in the production process of a garnet-type crystal in a production method of a garnet-type crystal as described later. As a result, the melting point of the oxide is lowered, and the crystal growth is promoted by the calcination treatment, which is a heat treatment at a relatively low temperature for a relatively short time, while an adhesive interface with the adherend can be formed.

[0059] The oxoanions constituting the oxoacid compound do not contain metal elements, and examples thereof include halogen oxoacids, borate ions, carbonate ions, orthocarbonate ions, carboxylate ions, silicate ions, nitrite ions, nitrate ions, phosphite ions, phosphate ions, arsenate ions, sulfite ions, sulfate ions, sulfonate ions, and sulfinate ions. Examples of halogen oxoacids include hypochlorite ions, chlorite ions, chlorate ions, perchlorate ions, hypobromite ions, bromite ions, bromate ions, perbromate ions, hypoiodite ions, iodite ions, iodate ions, and periodate ions. Among these, the oxoacid compound preferably contains at least one of nitrate ions and sulfate ions as the oxoanion, and more preferably contains nitrate ions.

[0060] This makes it possible to more effectively lower the melting point of the metal oxide contained in the calcined body obtained in the first heating step in the manufacturing method of the garnet-type crystal as described later in detail, and to more effectively promote the crystal growth of the lithium-containing composite oxide. As a result, even if the second heating step as described later in detail is performed at a lower temperature for a shorter period of time, it is possible to preferably obtain a garnet-type crystal having particularly excellent ion conductivity. In the following description, the metal oxide contained in the calcined body obtained in the first heating step is also referred to as a "precursor oxide."

[0061] The metal-containing raw material may be, for example, an elemental metal or an alloy, a compound containing only one type of metal element in its molecule, or a compound containing multiple types of metal elements in its molecule.

[0062] Examples of the lithium compound, which is a metal-containing raw material containing Li, include lithium metal salts and lithium alkoxides, and one or more of these can be used in combination. Examples of the lithium metal salts include lithium chloride, lithium nitrate, lithium sulfate, lithium acetate, lithium hydroxide, lithium carbonate, and (2,4-pentanedionato)lithium. Examples of the lithium alkoxides include lithium methoxide, lithium ethoxide, lithium propoxide, lithium isopropoxide, lithium butoxide, lithium isobutoxide, lithium sec-butoxide, lithium tert-butoxide, and dipivaloylmethanatolithium. Among these, the lithium compound is preferably one or more selected from the group consisting of lithium nitrate, lithium sulfate, and (2,4-pentanedionato)lithium. Hydrates may be used as the metal-containing raw material containing Li.

[0063] Examples of lanthanum compounds, which are metal-containing raw materials containing La, include lanthanum metal salts, lanthanum alkoxides, and lanthanum hydroxide, and one or more of these can be used in combination. Examples of lanthanum metal salts include lanthanum chloride, lanthanum nitrate, lanthanum sulfate, lanthanum acetate, and lanthanum tris(2,4-pentanedionato). Examples of lanthanum alkoxides include lanthanum trimethoxide, lanthanum triethoxide, lanthanum tripropoxide, lanthanum triisopropoxide, lanthanum tributoxide, lanthanum triisobutoxide, lanthanum trisec-butoxide, lanthanum tritertiarybutoxide, and lanthanum dipivaloylmethanato. Among these, the lanthanum compound is preferably at least one selected from the group consisting of lanthanum nitrate, lanthanum tris(2,4-pentanedionato), and lanthanum hydroxide. Hydrates may be used as the metal-containing raw materials containing La.

[0064] Examples of the zirconium compound, which is a metal-containing raw material containing Zr, include zirconium metal salts and zirconium alkoxides, and one or more of these can be used in combination. Examples of the zirconium metal salts include zirconium chloride, zirconium oxychloride, zirconium oxynitrate, zirconium oxysulfate, zirconium oxyacetate, and zirconium acetate. Examples of the zirconium alkoxides include zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetrapropoxide, zirconium tetraisopropoxide, zirconium tetranormal butoxide, zirconium tetraisobutoxide, zirconium tetrasecondary butoxide, zirconium tetratertiary butoxide, and dipivaloylmethanatozirconium. Among these, zirconium compounds are preferably zirconium tetranormal butoxide. Hydrates may be used as the metal-containing raw material containing Zr.

[0065] Examples of cerium compounds, which are metal-containing raw materials containing Ce, include cerium metal salts and cerium alkoxides, and one or more of these can be used in combination. Examples of cerium metal salts include cerium chloride, cerium nitrate, and cerium acetate. Examples of cerium alkoxides include cerium trimethoxide, cerium triethoxide, cerium triisopropoxide, cerium tri-n-propoxide, and cerium ethylcyclopentadienyl. Among these, cerium compounds are preferably cerium nitrate. Hydrates may be used as metal-containing raw materials containing Ce.

[0066] Examples of niobium compounds, which are metal-containing raw materials containing Nb, include niobium metal salts, niobium alkoxides, and niobium acetylacetone, and one or more of these can be used in combination. Examples of niobium metal salts include niobium chloride, niobium oxychloride, and niobium oxalate. Examples of niobium alkoxides include niobium ethoxide such as niobium pentaethoxide, niobium propoxide, niobium isopropoxide, and niobium secondary butoxide. Among these, niobium compounds are preferably niobium pentabutoxide. Hydrates may be used as metal-containing raw materials containing Nb.

[0067] Examples of the antimony compound, which is a metal-containing raw material containing Sb, include antimony metal salts and antimony alkoxides, and one or more of these can be used in combination. Examples of the antimony metal salts include antimony bromide, antimony chloride, antimony fluoride, and antimony sulfate. Examples of the antimony alkoxides include antimony trimethoxide, antimony triethoxide, antimony triisopropoxide, antimony trinormal propoxide, antimony triisobutoxide, and antimony trinormal butoxide. Among these, antimony compounds are preferably antimony triisobutoxide and antimony trinormal butoxide. Hydrates may be used as the metal-containing raw material containing Sb.

[0068] Examples of the tantalum compound, which is a metal-containing raw material containing Ta, include tantalum metal salts and tantalum alkoxides, and one or more of these can be used in combination. Examples of the tantalum metal salts include tantalum chloride and tantalum bromide. Examples of the tantalum alkoxides include tantalum pentamethoxide, tantalum pentaethoxide, tantalum pentaisopropoxide, tantalum pentanormal propoxide, tantalum pentaisobutoxide, tantalum pentanormal butoxide, tantalum pentasecondary butoxide, and tantalum pentatertiary butoxide. Among these, tantalum compounds are preferably tantalum pentaethoxide. Hydrates may be used as the metal-containing raw material containing Ta.

[0069] When the precursor solution is used for producing a garnet-type crystal containing Sn as a constituent element, a metal-containing raw material containing Sn is also used.

[0070] Examples of tin compounds, which are metal-containing raw materials containing Sn, include tin metal salts and tin alkoxides, and one or more of these can be used in combination. Examples of tin metal salts include tin chloride, tin sulfide, tin nitrate, and tin acetate. Examples of tin alkoxides include tin methoxide, tin ethoxide, tin tetraethoxide, tin tetrabutoxide, and tin tetraisopropoxide. Among these, tin compounds are preferably tin tetraisopropoxide. Hydrates may be used as metal-containing raw materials containing Sn.

[0071] [4] Manufacturing method of garnet-type crystals Next, the method for producing the garnet-type crystal of the present invention will be described.

[0072] The garnet-type crystal of the present invention can be suitably produced by, for example, a method including a precursor solution preparation step of preparing the above-mentioned precursor solution of the present invention, a first heating step of subjecting the precursor solution to a first heat treatment to form a pre-sintered body, and a second heating step of subjecting the pre-sintered body to a second heat treatment to form a garnet-type crystal containing Li, La, Zr and O and further containing Ce, Nb, Sb and Ta as constituent elements.

[0073] More specifically, a garnet-type crystal molded body having excellent bulk lithium ion conductivity and sufficiently low grain boundary resistance can be obtained at a sufficiently low sintering temperature. In addition, in the conventional solid electrolyte, for example, when the solid electrolyte is co-sintered with an active material such as lithium cobalt oxide, the elements of the solid electrolyte interdiffuse each other, resulting in a low lithium ion conductivity. However, in the above-mentioned manufacturing method, even when the solid electrolyte is co-sintered with an active material such as lithium cobalt oxide, the elements of the solid electrolyte interdiffuse each other, resulting in a low lithium ion conductivity, and the like. This problem can be effectively suppressed.

[0074] [4-1] Precursor solution preparation process In the precursor solution preparation step, the precursor solution of the present invention described above is prepared. In this step, a plurality of precursor solutions may be prepared and mixed for use.

[0075] The organic solvent constituting the precursor solution may be at least partially removed prior to the first heating step described in detail below.

[0076] The organic solvent can be removed prior to the first heating step by, for example, heating the precursor solution, placing it in a reduced pressure environment, or placing it under room temperature and normal pressure. By removing at least a portion of the organic solvent, the precursor solution can be suitably gelled. In this specification, room temperature and normal pressure refer to 25° C. and 1 atm.

[0077] Hereinafter, when the organic solvent is removed by a heat treatment, the heat treatment is also referred to as a pre-heat treatment.

[0078] The conditions of the preheating treatment depend on the boiling point and vapor pressure of the organic solvent, and the heating temperature of the preheating treatment is preferably 50°C or higher and 250°C or lower, more preferably 60°C or higher and 230°C or lower, and even more preferably 80°C or higher and 200°C or lower. The heating temperature may be changed during the preheating treatment. For example, the preheating treatment may have a first stage in which the heat treatment is performed while maintaining the temperature at a relatively low temperature, and a second stage in which the temperature is raised after the first stage and the heat treatment is performed at a relatively high temperature. In such a case, it is preferable that the maximum temperature during the preheating treatment is within the above-mentioned range.

[0079] The heating time in the preliminary heating treatment is preferably from 10 minutes to 180 minutes, more preferably from 20 minutes to 120 minutes, and even more preferably from 30 minutes to 60 minutes.

[0080] The preheating treatment may be performed in any atmosphere, including an oxidizing atmosphere such as air or an oxygen gas atmosphere, or a non-oxidizing atmosphere such as an inert gas atmosphere such as nitrogen gas, helium gas, argon gas, etc. The preheating treatment may be performed under reduced pressure or vacuum, or under pressure.

[0081] During the preheating treatment, the atmosphere may be maintained at substantially the same conditions or may be changed to different conditions. For example, the preheating treatment may have a first stage in which heat treatment is performed in a normal pressure environment and a second stage in which heat treatment is performed in a reduced pressure environment after the first stage.

[0082] [4-2] First heating process In the first heating step, the precursor solution of the present invention or a mixture obtained by removing at least a part of the organic solvent from the precursor solution, for example, a gelled mixture, is subjected to a first heat treatment to form a pre-fired body.

[0083] In particular, when an oxo acid compound is used as at least one kind of metal-containing raw material, a calcined body is obtained that contains a precursor oxide, which is an oxide different from the finally obtained garnet-type crystal, and the oxo acid compound.

[0084] The heating temperature in the first heating step is not particularly limited, but is preferably 500°C or higher and 650°C or lower, more preferably 510°C or higher and 650°C or lower, and even more preferably 520°C or higher and 600°C or lower.

[0085] This makes it possible to more effectively prevent unintended evaporation of metallic elements constituting the final garnet-type crystal, in particular, evaporation of Li which is easily volatile among metallic materials, and thus makes it possible to more strictly control the composition of the final garnet-type crystal and more efficiently produce the garnet-type crystal.

[0086] The heating temperature may be changed during the first heating step. For example, the first heating step may have a first stage in which the heat treatment is performed while maintaining the temperature at a relatively low temperature, and a second stage in which the temperature is raised after the first stage and the heat treatment is performed at a relatively high temperature. In such a case, it is preferable that the maximum temperature in the first heating step is within the above-mentioned range.

[0087] Furthermore, the heating time in the first heating step, particularly the heating time at a heating temperature of 500°C or more and 650°C or less, is preferably 5 minutes or more and 180 minutes or less, more preferably 10 minutes or more and 120 minutes or less, and even more preferably 15 minutes or more and 90 minutes or less.

[0088] The first heating step may be performed in any atmosphere, including an oxidizing atmosphere such as air or an oxygen gas atmosphere, or a non-oxidizing atmosphere such as an inert gas atmosphere such as nitrogen gas, helium gas, or argon gas. The first heating step may be performed under reduced pressure, vacuum, or pressure. In particular, the first heating step is preferably performed in an oxidizing atmosphere.

[0089] In addition, during the first heating step, the atmosphere may be kept substantially the same or may be changed to a different condition. For example, the first heating step may have a first stage in which heat treatment is performed in an inert gas atmosphere, and a second stage in which heat treatment is performed in an oxidizing atmosphere after the first stage.

[0090] The calcined body obtained as described above usually contains a precursor oxide having a crystal phase different from that of the finally obtained garnet-type crystal. In this specification, the term "different" in terms of crystal phase is a broad concept including not only crystal phases of different types but also crystal phases of the same type but with at least one lattice constant different.

[0091] Examples of the crystal phase of the precursor oxide include cubic crystals such as pyrochlore type crystals, perovskite structure, rock salt type structure, diamond structure, fluorite type structure, and spinel type structure, orthorhombic crystals such as ramsdellite type, and trigonal crystals such as corundum type, with pyrochlore type crystals being preferred.

[0092] As a result, even when the conditions in the second heating step described below are lower temperature and shorter time, a garnet-type crystal having particularly excellent ion conductivity can be suitably obtained.

[0093] The crystal grain size of the precursor oxide is not particularly limited, but is preferably 10 nm or more and 200 nm or less, more preferably 15 nm or more and 180 nm or less, and even more preferably 20 nm or more and 160 nm or less.

[0094] This makes it possible to further reduce the melting temperature of the precursor oxide and the firing temperature in the second heating step by the so-called Gibbs-Thomson effect, which is a melting point drop phenomenon caused by an increase in surface energy, and is also advantageous in improving the bonding between the produced garnet-type crystal and different materials and reducing the defect density.

[0095] The precursor oxide preferably consists essentially of a single crystalline phase. As a result, the number of crystal phase transitions that occur during the production of a garnet-type crystal, i.e., during the generation of a high-temperature crystal phase, is substantially limited to one time, so that segregation of elements accompanying the crystal phase transition and the generation of impurity crystals due to thermal decomposition are suppressed, and various properties of the produced garnet-type crystal are further improved.

[0096] In addition, when the calcined body obtained in the first heating step is measured by TG-DTA at a heating rate of 10°C / min, if only one exothermic peak is observed in the range of 300°C to 1,000°C, it can be determined that the calcined body is "substantially composed of a single crystal phase."

[0097] The composition of the precursor oxide is not particularly limited, but the precursor oxide is preferably a double oxide, and more preferably the precursor oxide is a double oxide containing Li and La.

[0098] This makes it possible to obtain garnet-type crystals with particularly excellent ion conductivity even when the heat treatment in the second heating step described later is performed at a lower temperature for a shorter time. Also, for example, in an all-solid-state secondary battery, the adhesion of the formed garnet-type crystals to the positive electrode active material and the negative electrode active material can be improved, and the materials can be combined to have a better adhesive interface, thereby improving the characteristics and reliability of the all-solid-state secondary battery.

[0099] The calcined body obtained as described above is generally one in which most of the solvent used in the manufacturing process has been removed, but some of the solvent may remain. However, the content of the solvent in the calcined body is preferably 1.0 mass % or less, and more preferably 0.1 mass % or less.

[0100] [4-3] Second heating process In the second heating step, the pre-sintered body obtained in the first heating step is subjected to a second heat treatment to form the above-mentioned garnet-type crystal of the present invention.

[0101] In particular, if the calcined body obtained in the first heating step contains an oxo acid compound, the melting point of the precursor oxide can be suitably lowered, the crystal growth of the lithium-containing double oxide can be promoted, and garnet-type crystals having desired properties can be stably formed by heat treatment at a relatively low temperature for a relatively short time. Also, the adhesion between the formed garnet-type crystals and the adherend can be improved. The second heating step may be carried out after mixing other components with the above-mentioned calcined body.

[0102] For example, the mixture of the calcined body and the oxo acid compound may be subjected to a second heating step. Even in such a case, the same effect as described above can be obtained.

[0103] Specific examples of oxo acid compounds that can be mixed with the calcined body include the oxo acid compounds contained in the metal compounds exemplified above as the metal-containing raw material.

[0104] In the second heating step, the above-mentioned pre-fired body may be subjected to the heating step in a state where it is mixed with an active material such as a positive electrode active material or a negative electrode active material.

[0105] This makes it possible to suitably manufacture electrodes such as positive and negative electrodes that contain the garnet-type crystal as a solid electrolyte together with the active material. The positive and negative electrode active materials will be described in detail later.

[0106] When the composition to be subjected to this step contains an oxo acid compound, the content of the oxo acid compound in the composition is not particularly limited, but is preferably from 0.1% by mass to 20% by mass, more preferably from 1.5% by mass to 15% by mass, and even more preferably from 2.0% by mass to 10% by mass.

[0107] This makes it possible to more reliably prevent the oxo acid compound from unintentionally remaining in the finally obtained garnet-type crystal, while suitably carrying out the heat treatment in the second heating step at a lower temperature in a shorter time, thereby making it possible to provide the obtained garnet-type crystal with particularly excellent ionic conductivity.

[0108] The content of the precursor oxide in the composition to be subjected to this step is not particularly limited, but is preferably from 35% by mass to 85% by mass, and more preferably from 45% by mass to 90% by mass.

[0109] When the content of precursor oxide in the composition subjected to this process is XP [mass%] and the content of oxo acid compound in the composition subjected to this process is XO [mass%], it is preferable that the relationship 0.013≦XO / XP≦0.58 is satisfied, it is more preferable that the relationship 0.023≦XO / XP≦0.34 is satisfied, and it is even more preferable that the relationship 0.03≦XO / XP≦0.19 is satisfied.

[0110] This makes it possible to more reliably prevent the oxo acid compound from unintentionally remaining in the finally obtained garnet-type crystal, while suitably carrying out the heat treatment in the second heating step at a lower temperature in a shorter time, thereby making it possible to provide the obtained garnet-type crystal with particularly excellent ionic conductivity.

[0111] The heating temperature in the second heating step is not particularly limited, but is usually higher than the heating temperature in the first heating step, and is preferably 800°C or higher and 1000°C or lower, more preferably 810°C or higher and 980°C or lower, and even more preferably 820°C or higher and 950°C or lower.

[0112] This allows stable formation of garnet-type crystals having desired properties by heat treatment at a relatively low temperature for a relatively short time. In addition, since garnet-type crystals can be produced by heat treatment at a relatively low temperature for a relatively short time, the productivity of garnet-type crystals and all-solid-state batteries including garnet-type crystals can be improved, and this is also preferable from the viewpoint of energy saving.

[0113] The heating temperature may be changed during the second heating step. For example, the second heating step may have a first stage in which the heat treatment is performed while maintaining the temperature at a relatively low temperature, and a second stage in which the temperature is raised after the first stage and the heat treatment is performed at a relatively high temperature. In such a case, it is preferable that the maximum temperature in the second heating step is within the above-mentioned range.

[0114] The heating time in the second heating step, particularly the heating time at a heating temperature of 800°C or more and 1000°C or less, is not particularly limited, but is preferably 5 minutes or more and 600 minutes or less, more preferably 10 minutes or more and 540 minutes or less, and even more preferably 15 minutes or more and 500 minutes or less.

[0115] This allows stable formation of garnet-type crystals having desired properties by heat treatment at a relatively low temperature for a relatively short time. In addition, since garnet-type crystals can be produced by heat treatment at a relatively low temperature for a relatively short time, the productivity of garnet-type crystals and all-solid-state batteries including garnet-type crystals can be improved, and this is also preferable from the viewpoint of energy saving.

[0116] The second heating step may be performed in any atmosphere, including an oxidizing atmosphere such as air or an oxygen gas atmosphere, or a non-oxidizing atmosphere such as an inert gas atmosphere such as nitrogen gas, helium gas, or argon gas. The heating step may be performed under reduced pressure, vacuum, or pressure. In particular, the second heating step is preferably performed in an oxidizing atmosphere.

[0117] During the second heating step, the atmosphere may be maintained at substantially the same conditions, or may be changed to different conditions.

[0118] Even when an oxo acid compound is used as a raw material, the garnet-type crystal obtained as described above usually does not substantially contain the oxo acid compound. More specifically, the content of the oxo acid compound in the obtained garnet-type crystal is usually 100 ppm or less, particularly preferably 50 ppm or less, and more preferably 10 ppm or less.

[0119] This makes it possible to suppress the content of undesirable impurities in the garnet-type crystal, thereby improving the characteristics and reliability of the garnet-type crystal.

[0120] [5] Complex Next, the composite according to the present invention will be described.

[0121] The composite according to the present invention comprises an active material and the garnet-type crystal according to the present invention coating a part of the surface of the active material.

[0122] This makes it possible to provide a composite having a sufficiently low grain boundary resistance between the active material and the garnet-type crystal. Such a composite can be suitably applied to a positive electrode composite or a negative electrode composite of a secondary battery as described below. As a result, the characteristics and reliability of the secondary battery as a whole can be excellent.

[0123] Examples of the active material constituting the composite include a positive electrode active material and a negative electrode active material. As the positive electrode active material, for example, a lithium composite oxide containing at least Li and at least one element selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, and Cu can be used. As such a composite oxide, for example, LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , Li 2 Mn 2 O 3 , LiCr 0.5 Mn 0.5 O 2 , LiFePO 4 , Li 2 FeP 2 O 7 , LiMnPO 4 , LiFeBO 3 , Li 3 V 2 (PO 4 ) 3 , Li 2 CuO 2 , Li 2 FeSiO 4 , Li 2 MnSiO 4 Examples of the positive electrode active material include LiFeF 3 Fluorides such as LiBH 4 Or Li 4 BN 3 H 10 boron complex compounds such as boron fluoride complexes, iodine complex compounds such as polyvinylpyridine-iodine complexes, and nonmetallic compounds such as sulfur can also be used.

[0124] The negative electrode active material is, for example, Nb 2O 5 , V 2 O 5 , TiO 2 , In 2 O 3 , ZnO, SnO 2 , NiO, ITO, AZO, GZO, ATO, FTO, Li 4 Ti 5 O 12 , Li 2 Ti 3 O 7 In addition, metals and alloys such as Li, Al, Si, Si-Mn, Si-Co, Si-Ni, Sn, Zn, Sb, Bi, In, and Au, carbon materials, LiC 24 , LiC 6 and the like, in which lithium ions are inserted between the layers of a carbon material.

[0125] The composite according to the present invention can be suitably produced, for example, by applying the method for producing a garnet-type crystal described in the above [4]. More specifically, for example, the composite can be suitably produced by firing the mixture of the pre-fired body and the active material, that is, by subjecting the mixture to a second heat treatment.

[0126] [6] Secondary battery Next, a secondary battery to which the present invention is applied will be described.

[0127] The secondary battery according to the present invention contains the garnet-type crystal of the present invention as described above, and can be suitably manufactured by using, for example, the precursor solution of the present invention described above. Such a secondary battery has excellent charge and discharge characteristics.

[0128] [6-1] Secondary battery of the first embodiment The secondary battery according to the first embodiment will be described below. FIG. 1 is a schematic perspective view showing a structure of a lithium ion battery as a secondary battery of the first embodiment.

[0129] 1, a lithium-ion battery 100 as a secondary battery has a positive electrode 10, a solid electrolyte layer 20 laminated in this order on the positive electrode 10, and a negative electrode 30. A current collector 41 is provided on the surface of the positive electrode 10 opposite to the surface facing the solid electrolyte layer 20, in contact with the positive electrode 10, and a current collector 42 is provided on the surface of the negative electrode 30 opposite to the surface facing the solid electrolyte layer 20, in contact with the negative electrode 30. Since the positive electrode 10, the solid electrolyte layer 20, and the negative electrode 30 are all composed of solid phases, the lithium-ion battery 100 is a chargeable and dischargeable all-solid-state secondary battery.

[0130] The shape of the lithium ion battery 100 is not particularly limited and may be, for example, a polygonal disk shape, but in the illustrated configuration, it is disk-shaped. The size of the lithium ion battery 100 is not particularly limited, but for example, the diameter of the lithium ion battery 100 is, for example, 10 mm or more and 20 mm or less, and the thickness of the lithium ion battery 100 is, for example, 0.1 mm or more and 1.0 mm or less.

[0131] The lithium ion battery 100 is thus small and thin, and, combined with being chargeable and dischargeable and being all-solid-state, can be suitably used as a power source for mobile information terminals such as smartphones. As will be described later, the lithium ion battery 100 may be used for purposes other than as a power source for mobile information terminals.

[0132] Each component of the lithium ion battery 100 will be described below. [6-1-1] Solid electrolyte layer The solid electrolyte layer 20 is made of a material containing the above-mentioned garnet-type crystal of the present invention as a solid electrolyte.

[0133] This provides excellent ionic conductivity for the solid electrolyte layer 20. Also, the solid electrolyte layer 20 can have excellent adhesion to the positive electrode 10 and the negative electrode 30. As a result, the lithium ion battery 100 as a whole can have particularly excellent characteristics and reliability.

[0134] The solid electrolyte layer 20 may contain components other than the garnet-type crystal of the present invention described above. For example, the solid electrolyte layer 20 may contain other solid electrolytes in addition to the garnet-type crystal of the present invention described above.

[0135] However, the content of the garnet-type crystal of the present invention in the solid electrolyte layer 20 is preferably 80 mass % or more, more preferably 90 mass % or more, and even more preferably 95 mass % or more. This allows the above-mentioned effects of the present invention to be more pronounced.

[0136] The thickness of the solid electrolyte layer 20 is not particularly limited, but from the viewpoint of charge / discharge rate, it is preferably 0.3 μm or more and 1000 μm or less, and more preferably 0.5 μm or more and 100 μm or less.

[0137] Furthermore, from the viewpoint of preventing a short circuit between the positive electrode 10 and the negative electrode 30 due to lithium dendrites deposited on the negative electrode 30 side, the value obtained by dividing the measured weight of the solid electrolyte layer 20 by the value obtained by multiplying the apparent volume of the solid electrolyte layer 20 by the theoretical density of the solid electrolyte material, i.e., the sintered density, is preferably 50% or more, and more preferably 90% or more.

[0138] Examples of methods for forming the solid electrolyte layer 20 include a green sheet method, a press firing method, and a casting firing method. Specific examples of methods for forming the solid electrolyte layer 20 will be described in detail later. For the purpose of improving the adhesion between the solid electrolyte layer 20 and the positive electrode 10 and the negative electrode 30, and improving the output and battery capacity of the lithium ion battery 100 by increasing the specific surface area, for example, a three-dimensional pattern structure such as dimples, trenches, and pillars may be formed on the surface of the solid electrolyte layer 20 that contacts the positive electrode 10 and the negative electrode 30.

[0139] [6-1-2] Positive electrode The positive electrode 10 may be any material as long as it is made of a positive electrode active material that is capable of repeatedly electrochemically absorbing and releasing lithium ions.

[0140] Specifically, the positive electrode active material constituting the positive electrode 10 may be, for example, a lithium composite oxide containing at least Li and at least one element selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, and Cu. Examples of such composite oxides include LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , Li 2 Mn 2 O 3 , LiCr 0.5 Mn 0.5 O 2 , LiFePO 4 , Li 2 FeP 2 O 7 , LiMnPO 4 , LiFeBO 3 , Li 3 V 2 (PO 4 ) 3 , Li 2 CuO 2 , Li 2 FeSiO 4 , Li 2 MnSiO 4 Examples of the positive electrode active material constituting the positive electrode 10 include LiFeF 3 Fluorides such as LiBH 4 Or Li 4 BN 3 H 10 boron complex compounds such as boron fluoride complexes, iodine complex compounds such as polyvinylpyridine-iodine complexes, and nonmetallic compounds such as sulfur can also be used.

[0141] In consideration of the electrical conductivity and the ion diffusion distance, the positive electrode 10 is preferably formed as a thin film on one surface of the solid electrolyte layer 20 .

[0142] The thickness of the thin film positive electrode 10 is not particularly limited, but is preferably 0.1 μm or more and 500 μm or less, and more preferably 0.3 μm or more and 100 μm or less.

[0143] Examples of methods for forming the positive electrode 10 include vapor deposition methods such as vacuum deposition, sputtering, CVD, PLD, ALD, and aerosol deposition, and chemical deposition methods using a solution such as the sol-gel method and MOD method. In addition, for example, fine particles of the positive electrode active material may be slurried together with an appropriate binder, and a coating film may be formed by performing squeegee or screen printing, and the coating film may be dried and baked to bake it onto the surface of the solid electrolyte layer 20.

[0144] [6-1-3] Negative electrode The negative electrode 30 may be made of any material so long as it is made of a so-called negative electrode active material that repeatedly electrochemically absorbs and releases lithium ions at a potential lower than that of the material selected for the positive electrode 10 .

[0145] Specifically, the negative electrode active material constituting the negative electrode 30 is, for example, Nb 2 O 5 , V 2 O 5 , TiO 2 , In 2 O 3 , ZnO, SnO 2 , NiO, ITO, AZO, GZO, ATO, FTO, Li 4 Ti 5 O 12 , Li 2 Ti 3 O 7 In addition, metals and alloys such as Li, Al, Si, Si-Mn, Si-Co, Si-Ni, Sn, Zn, Sb, Bi, In, and Au, carbon materials, LiC 24 , LiC 6 and the like, in which lithium ions are inserted between the layers of a carbon material.

[0146] In consideration of electrical conductivity and ion diffusion distance, the negative electrode 30 is preferably formed as a thin film on one surface of the solid electrolyte layer 20 .

[0147] The thickness of the thin film negative electrode 30 is not particularly limited, but is preferably 0.1 μm or more and 500 μm or less, and more preferably 0.3 μm or more and 100 μm or less.

[0148] Examples of methods for forming the negative electrode 30 include vapor deposition methods such as vacuum deposition, sputtering, CVD, PLD, ALD, and aerosol deposition, and chemical deposition methods using a solution such as the sol-gel method and MOD method. In addition, for example, fine particles of the negative electrode active material may be slurried together with an appropriate binder, and a coating film may be formed by performing squeegee or screen printing, and the coating film may be dried and baked to bake it onto the surface of the solid electrolyte layer 20.

[0149] [6-1-4] Current collector The current collectors 41, 42 are conductors provided to transfer electrons to and from the positive electrode 10 or the negative electrode 30. The current collectors are usually made of a material that has a sufficiently small electrical resistance and whose electrical conduction characteristics and mechanical structure do not change substantially due to charging and discharging. Specifically, the current collector 41 of the positive electrode 10 is made of, for example, Al, Ti, Pt, Au, or the like. The current collector 42 of the negative electrode 30 is preferably made of, for example, Cu, or the like.

[0150] Current collectors 41, 42 are usually provided so as to reduce the contact resistance with positive electrode 10 and negative electrode 30, respectively. Examples of the shape of current collectors 41, 42 include a plate shape, a mesh shape, and the like.

[0151] The thickness of the current collectors 41 and 42 is not particularly limited, but is preferably 7 μm or more and 85 μm or less, and more preferably 10 μm or more and 60 μm or less.

[0152] In the illustrated configuration, the lithium ion battery 100 has a pair of current collectors 41, 42. However, for example, when multiple lithium ion batteries 100 are stacked and electrically connected in series, the lithium ion battery 100 can also be configured to have only current collector 41 of current collectors 41, 42.

[0153] [6-2] Second embodiment of secondary battery Next, a secondary battery according to a second embodiment will be described.

[0154] FIG. 2 is a schematic perspective view showing a configuration of a lithium ion battery as a secondary battery of the second embodiment, and FIG. 3 is a schematic cross-sectional view showing a structure of a lithium ion battery as a secondary battery of the second embodiment.

[0155] The secondary battery according to the second embodiment will be described below with reference to these drawings, but the differences from the embodiment described above will be mainly described, and descriptions of similar points will be omitted.

[0156] 2, the lithium ion battery 100 as the secondary battery of this embodiment has a positive electrode composite 210 that functions as a positive electrode, an electrolyte layer 220, and a negative electrode 30 that are laminated in this order on the positive electrode composite 210. Also, a current collector 41 that contacts the positive electrode composite 210 is provided on the surface of the positive electrode composite 210 opposite to the surface that faces the electrolyte layer 220, and a current collector 42 that contacts the negative electrode 30 is provided on the surface of the negative electrode 30 opposite to the surface that faces the electrolyte layer 220.

[0157] Hereinafter, a description will be given of the positive electrode composite material 210 and the electrolyte layer 220 which have configurations different from those of the lithium ion battery 100 according to the above-described embodiment.

[0158] [6-2-1] Positive electrode mixture 3, the positive electrode composite 210 in the lithium ion battery 100 of this embodiment includes a particulate positive electrode active material 211 and a solid electrolyte 212. In such a positive electrode composite 210, the interface area where the particulate positive electrode active material 211 and the solid electrolyte 212 contact each other is increased, so that the battery reaction rate in the lithium ion battery 100 can be further increased.

[0159] The average particle size of the positive electrode active material 211 is not particularly limited, but is preferably 0.1 μm or more and 150 μm or less, and more preferably 0.3 μm or more and 60 μm or less.

[0160] This makes it easier to achieve both an actual capacity density close to the theoretical capacity of the positive electrode active material 211 and a high charge / discharge rate.

[0161] In this specification, the average particle size refers to the average particle size based on volume, and can be determined, for example, by adding a sample to methanol, dispersing the sample for 3 minutes using an ultrasonic disperser, and measuring the dispersion using a Coulter Counter particle size distribution measuring instrument (TA-II model manufactured by COULTER ELECTRONICS INS) with an aperture of 50 μm.

[0162] The particle size distribution of the positive electrode active material 211 is not particularly limited, and for example, in a particle size distribution having one peak, the half width of the peak may be 0.15 μm or more and 19 μm or less. In addition, the particle size distribution of the positive electrode active material 211 may have two or more peaks.

[0163] In FIG. 3, the particulate positive electrode active material 211 is shown to have a spherical shape; however, the shape of the positive electrode active material 211 is not limited to a spherical shape and may have various forms, such as a columnar, plate-like, scaly, hollow, or amorphous shape, and two or more of these may be mixed.

[0164] As the positive electrode active material 211, the same materials as those exemplified as the constituent materials of the positive electrode 10 in the first embodiment can be used.

[0165] The positive electrode active material 211 may have a coating layer formed on its surface for the purpose of, for example, reducing the interface resistance with the solid electrolyte 212 and improving the electronic conductivity. For example, LiCoO 2 The surface of the positive electrode active material 211 particles is coated with LiNbO 3 , Al 2 O 3 , ZrO 2 , Ta 2 O 5 The interface resistance of lithium ion conduction can be further reduced by forming a thin film such as a coating layer, etc. The thickness of the coating layer is not particularly limited, but is preferably 3 nm or more and 1 μm or less.

[0166] In this embodiment, the positive electrode composite 210 includes, in addition to the above-described positive electrode active material 211, a solid electrolyte 212. The solid electrolyte 212 is present so as to fill spaces between particles of the positive electrode active material 211 or to be in contact with, and particularly in close contact with, the surface of the positive electrode active material 211. The solid electrolyte 212 is made of the material containing the garnet-type crystal of the present invention described above.

[0167] This provides particularly excellent ion conductivity for the solid electrolyte 212. Also, the solid electrolyte 212 provides excellent adhesion to the positive electrode active material 211 and the electrolyte layer 220. As a result, the lithium ion battery 100 as a whole can have particularly excellent characteristics and reliability.

[0168] The proportion of the garnet-type crystal of the present invention in the solid electrolyte 212 is preferably 80 mass % or more, more preferably 90 mass % or more, and even more preferably 95 mass % or more. This makes the above-mentioned effects more pronounced.

[0169] When the content of the positive electrode active material 211 in the positive electrode composite 210 is XA [mass %] and the content of the solid electrolyte 212 in the positive electrode composite 210 is XS [mass %], it is preferable to satisfy the relationship of 0.1≦XS / XA≦8.3, it is more preferable to satisfy the relationship of 0.3≦XS / XA≦2.8, and it is even more preferable to satisfy the relationship of 0.6≦XS / XA≦1.4.

[0170] Moreover, the positive electrode mixture 210 may contain, in addition to the positive electrode active material 211 and the solid electrolyte 212, a conductive assistant, a binder, and the like.

[0171] However, the content of components other than the positive electrode active material 211 and the solid electrolyte 212 in the positive electrode mixture 210 is preferably 10 mass % or less, more preferably 7 mass % or less, and even more preferably 5 mass % or less.

[0172] As the conductive additive, any conductive material may be used as long as it is a conductor whose electrochemical interaction at the positive electrode reaction potential is negligible. More specifically, for example, carbon materials such as acetylene black, ketjen black, and carbon nanotubes, precious metals such as palladium and platinum, and SnO 2 , ZnO, RuO 2 or ReO 3 , Ir 2 O 3 For example, a conductive oxide such as the above can be used.

[0173] The thickness of the positive electrode composite material 210 is not particularly limited, but is preferably 0.1 μm or more and 500 μm or less, and more preferably 0.3 μm or more and 100 μm or less.

[0174] [6-2-2] Electrolyte layer From the viewpoint of the interface impedance with the positive electrode composite 210, the electrolyte layer 220 is preferably composed of the same or the same type of material as the solid electrolyte 212, but may be composed of a material different from the solid electrolyte 212. For example, the electrolyte layer 220 may be composed of a material having a composition different from that of the solid electrolyte 212, although it contains the garnet-type crystal of the present invention. In addition, the electrolyte layer 220 may be a crystalline or amorphous oxide solid electrolyte, sulfide solid electrolyte, nitride solid electrolyte, halide solid electrolyte, hydride solid electrolyte, dry polymer electrolyte, or quasi-solid electrolyte other than the garnet-type crystal of the present invention, or may be composed of a material that combines two or more selected from these.

[0175] When the electrolyte layer 220 is made of a material containing the garnet-type crystal of the present invention, the content of the garnet-type crystal of the present invention in the electrolyte layer 220 is preferably 80 mass % or more, more preferably 90 mass % or more, and even more preferably 95 mass % or more. This allows the above-mentioned effects of the present invention to be more pronounced.

[0176] Crystalline oxides include, for example, Li0.35 La 0.55 TiO 3 , Li 0.2 La 0.27 NbO 3 , and perovskite-type crystals or perovskite-like crystals in which some of the elements constituting these crystals have been replaced with N, F, Al, Sr, Sc, Nb, Ta, Sb, lanthanoid elements, etc., Li 7 La 3 Zr 2 O 12 , Li 5 La 3 Nb 2 O 12 , Li 5 Bala 2 TaO 12 , and garnet-type crystals or garnet-like crystals in which some of the elements constituting these crystals have been replaced with N, F, Al, Sr, Sc, Nb, Ta, Sb, lanthanoid elements, etc., Li 1.3 Ti 1.7 Al 0.3 (PO 4 ) 3 , Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 , Li 1.4 Al 0.4 Ti 1.4 Ge 0.2 (PO 4 ) 3 , and NASICON-type crystals in which some of the elements constituting these crystals have been replaced with N, F, Al, Sr, Sc, Nb, Ta, Sb, lanthanoid elements, etc., Li 14 ZnGe 4 O 16 LISICON type crystals such as Li 3.4 V 0.6 S 0.4 O 4 , Li 3.6 V 0.4 Ge 0.6 O 4 , Li 2+x C 1-x B x O 3 Other crystalline materials such as those mentioned above can also be mentioned.

[0177] Crystalline sulfides include, for example, Li 10 GeP 2 S 12 , Li 9.6 P 3 S 12 , Li 9.54 S 1.74 P 1.44 S 11.7 Cl 0.3 , Li 3 P.S. 4 etc. can be mentioned.

[0178] Other amorphous materials include, for example, Li 2 O-TiO 2 , La 2 O 3 -Li 2 O-TiO 2 , LiNbO 3 , LiSO 4 , Li 4 SiO 4 , Li 3 PO 4 -Li 4 SiO 4 , Li 4 GeO 4 -Li 3 VO 4 , Li 4 SiO 4 -Li 3 VO 4 , Li 4 GeO 4 -Zn 2 GeO 2 , Li 4 SiO 4 -LiMoO 4 , Li 4 SiO 4 -Li 4 ZrO 4 , SiO 2 -P 2 O 5 -Li 2 O, SiO 2 -P 2 O 5 -LiCl, Li 2 O-LiCl-B 2 O 3, LiAlCl 4 , LiAlF 4 , LiF-Al 2 O 3 , LiBr-Al 2 O 3 , Li 2.88 PO 3.73 N 0.14 , Li 3 N-LiCl, Li 6 NBr 3 , Li 2 S-SiS 2 , Li 2 S-SiS 2 -P 2 S 5 etc. can be mentioned.

[0179] When the electrolyte layer 220 is made of a crystalline material, the crystalline material preferably has a crystal structure such as a cubic crystal with small crystal plane anisotropy in the direction of lithium ion conduction. When the electrolyte layer 220 is made of an amorphous material, the anisotropy of lithium ion conduction is small. For this reason, both the crystalline material and the amorphous material as described above are preferable as the solid electrolyte constituting the electrolyte layer 220.

[0180] The thickness of the electrolyte layer 220 is preferably 0.1 μm or more and 100 μm or less, and more preferably 0.2 μm or more and 10 μm or less. When the thickness of the electrolyte layer 220 is a value within the above range, the internal resistance of the electrolyte layer 220 can be further reduced, and the occurrence of a short circuit between the positive electrode composite 210 and the negative electrode 30 can be more effectively prevented.

[0181] For the purpose of improving the adhesion between the electrolyte layer 220 and the negative electrode 30, and improving the output and battery capacity of the lithium ion battery 100 by increasing the specific surface area, for example, a three-dimensional pattern structure such as dimples, trenches, pillars, etc. may be formed on the surface of the electrolyte layer 220 that contacts the negative electrode 30.

[0182] [6-3] Secondary battery according to the third embodiment Next, a secondary battery according to a third embodiment will be described.

[0183] FIG. 4 is a schematic perspective view showing a configuration of a lithium ion battery as a secondary battery of the third embodiment, and FIG. 5 is a schematic cross-sectional view showing a structure of a lithium ion battery as a secondary battery of the third embodiment.

[0184] The secondary battery according to the third embodiment will be described below with reference to these drawings, but the differences from the above-described embodiments will be mainly described, and descriptions of similar points will be omitted.

[0185] 4, the lithium ion battery 100 as the secondary battery of this embodiment has a positive electrode 10, an electrolyte layer 220, and a negative electrode composite 330 functioning as a negative electrode, which are laminated in this order on the positive electrode 10. Also, a current collector 41 is provided in contact with the positive electrode 10 on the surface of the positive electrode 10 opposite to the surface facing the electrolyte layer 220, and a current collector 42 is provided in contact with the negative electrode composite 330 on the surface of the negative electrode composite 330 opposite to the surface facing the electrolyte layer 220.

[0186] Hereinafter, a negative electrode composite 330 having a configuration different from that of the lithium ion battery 100 according to the above-described embodiment will be described.

[0187] [6-3-1] Negative electrode composite material 5, the negative electrode composite 330 in the lithium ion battery 100 of this embodiment includes a particulate negative electrode active material 331 and a solid electrolyte 212. In such a negative electrode composite 330, the interface area where the particulate negative electrode active material 331 and the solid electrolyte 212 contact each other is increased, making it possible to further increase the battery reaction rate in the lithium ion battery 100.

[0188] The average particle size of the negative electrode active material 331 is not particularly limited, but is preferably 0.1 μm to 150 μm, and more preferably 0.3 μm to 60 μm.

[0189] This makes it easier to achieve both an actual capacity density close to the theoretical capacity of the negative electrode active material 331 and a high charge / discharge rate.

[0190] The particle size distribution of the negative electrode active material 331 is not particularly limited, and may be, for example, a particle size distribution having one peak, with the half width of the peak being 0.1 μm or more and 18 μm or less. The particle size distribution of the negative electrode active material 331 may have two or more peaks.

[0191] In FIG. 5, the particulate negative electrode active material 331 is shown to have a spherical shape; however, the shape of the negative electrode active material 331 is not limited to a spherical shape and may have various shapes such as a columnar shape, a plate shape, a scale shape, a hollow shape, an amorphous shape, etc., and two or more of these shapes may be mixed.

[0192] The negative electrode active material 331 may be the same as the materials exemplified as the constituent materials of the negative electrode 30 in the first embodiment.

[0193] In this embodiment, the negative electrode composite 330 includes the solid electrolyte 212 in addition to the above-described negative electrode active material 331. The solid electrolyte 212 is present so as to fill spaces between particles of the negative electrode active material 331 or to be in contact with, and particularly in close contact with, the surface of the negative electrode active material 331. The solid electrolyte 212 is made of the material containing the garnet-type crystal of the present invention described above.

[0194] This provides particularly excellent ion conductivity for the solid electrolyte 212. Also, it is possible to provide excellent adhesion of the solid electrolyte 212 to the negative electrode active material 331 and the electrolyte layer 220. As a result, it is possible to provide particularly excellent characteristics and reliability for the lithium ion battery 100 as a whole.

[0195] When the content of the negative electrode active material 331 in the negative electrode composite 330 is XB [mass %] and the content of the solid electrolyte 212 in the negative electrode composite 330 is XS [mass %], it is preferable to satisfy the relationship of 0.14≦XS / XB≦26, it is more preferable to satisfy the relationship of 0.44≦XS / XB≦4.1, and it is even more preferable to satisfy the relationship of 0.89≦XS / XB≦2.1.

[0196] Furthermore, the negative electrode mixture 330 may contain, in addition to the negative electrode active material 331 and the solid electrolyte 212, a conductive agent, a binder, and the like.

[0197] However, the content of components other than negative electrode active material 331 and solid electrolyte 212 in negative electrode mixture 330 is preferably 10 mass % or less, more preferably 7 mass % or less, and even more preferably 5 mass % or less.

[0198] As the conductive additive, any conductive material may be used as long as it is a conductor whose electrochemical interaction at the positive electrode reaction potential is negligible. More specifically, for example, carbon materials such as acetylene black, ketjen black, and carbon nanotubes, precious metals such as palladium and platinum, and SnO 2 , ZnO, RuO 2 or ReO 3 , Ir 2 O 3 For example, a conductive oxide such as the above can be used.

[0199] The thickness of the negative electrode composite material 330 is not particularly limited, but is preferably 0.1 μm or more and 500 μm or less, and more preferably 0.3 μm or more and 100 μm or less.

[0200] [6-4] Secondary battery according to the fourth embodiment Next, a secondary battery according to a fourth embodiment will be described.

[0201] FIG. 6 is a schematic perspective view showing a configuration of a lithium ion battery as a secondary battery of the fourth embodiment, and FIG. 7 is a schematic cross-sectional view showing a structure of a lithium ion battery as a secondary battery of the fourth embodiment.

[0202] The secondary battery according to the fourth embodiment will be described below with reference to these drawings, but the differences from the above-described embodiments will be mainly described, and descriptions of similar points will be omitted.

[0203] 6, a lithium ion battery 100 as a secondary battery of this embodiment includes a positive electrode composite 210, a solid electrolyte layer 20, and a negative electrode composite 330, which are laminated in this order on the positive electrode composite 210. Also, a current collector 41 is provided in contact with the positive electrode composite 210 on the surface of the positive electrode composite 210 opposite to the surface facing the solid electrolyte layer 20, and a current collector 42 is provided in contact with the negative electrode composite 330 on the surface of the negative electrode composite 330 opposite to the surface facing the solid electrolyte layer 20.

[0204] Each of these parts preferably satisfies the same conditions as those explained for the corresponding parts in the above-mentioned embodiment.

[0205] In the first to fourth embodiments, other layers may be provided between the layers or on the surfaces of the layers constituting the lithium ion battery 100. Examples of such layers include an adhesive layer, an insulating layer, and a protective layer.

[0206] [7] Manufacturing method of secondary battery Next, a method for producing the above-mentioned secondary battery will be described.

[0207] [7-1] Method for manufacturing secondary battery according to first embodiment Hereinafter, a method for manufacturing the secondary battery according to the first embodiment will be described.

[0208] FIG. 8 is a flowchart showing a method for manufacturing a lithium ion battery as a secondary battery of the first embodiment, FIGS. 9 and 10 are schematic views showing a method for manufacturing a lithium ion battery as a secondary battery of the first embodiment, and FIG. 11 is a schematic cross-sectional view showing another method for forming a solid electrolyte layer.

[0209] As shown in FIG. 8, the method for manufacturing the lithium ion battery 100 of this embodiment includes steps S1, S2, S3, and S4.

[0210] Step S1 is a step of forming the solid electrolyte layer 20. Step S2 is a step of forming the positive electrode 10. Step S3 is a step of forming the negative electrode 30. Step S4 is a step of forming the current collectors 41 and .

[0211] [7-1-1] Step S1 In the step S1 of forming the solid electrolyte layer 20, the pre-sintered body according to the present invention as described above, i.e., the pre-sintered body containing a precursor oxide and an oxo acid compound, is used to form the solid electrolyte layer 20 by, for example, a green sheet method. More specifically, the solid electrolyte layer 20 can be formed as follows.

[0212] That is, first, a solution is prepared by dissolving a binder such as polypropylene carbonate in a solvent such as 1,4-dioxane, and the solution is mixed with the calcined body according to the present invention to obtain the slurry 20m. In preparing the slurry 20m, a dispersant, a diluent, a moisturizing agent, etc. may be further used as necessary.

[0213] Next, the slurry 20m is used to form a sheet 20s for forming a solid electrolyte. More specifically, as shown in FIG. 9, for example, the slurry 20m is applied to a substrate 506 such as a polyethylene terephthalate film with a predetermined thickness using a fully automatic film applicator 500 to form a sheet 20s for forming a solid electrolyte. The fully automatic film applicator 500 has a coating roller 501 and a doctor roller 502. A squeegee 503 is provided so as to contact the doctor roller 502 from above. A conveying roller 504 is provided at a position facing the coating roller 501 below, and a stage 505 on which a substrate 506 is placed is inserted between the coating roller 501 and the conveying roller 504 to convey the stage 505 in a certain direction. The slurry 20m is introduced on the side on which the squeegee 503 is provided between the coating roller 501 and the doctor roller 502, which are arranged with a gap in the conveying direction of the stage 505. The application roller 501 and the doctor roller 502 are rotated so as to push the slurry 20m downward from the gap, and the surface of the application roller 501 is coated with the slurry 20m to a predetermined thickness. At the same time, the transport roller 504 is rotated, and the stage 505 is transported so that the substrate 506 comes into contact with the application roller 501 on which the slurry 20m has been applied. As a result, the slurry 20m applied to the application roller 501 is transferred in a sheet form to the substrate 506, and becomes the solid electrolyte forming sheet 20s.

[0214] Thereafter, the solvent is removed from the solid electrolyte forming sheet 20s formed on the base material 506, and the solid electrolyte forming sheet 20s is peeled off from the base material 506 and punched out to a predetermined size using a die to form a molded product 20f, as shown in FIG. 10.

[0215] Thereafter, the molded product 20f is subjected to a heating step at a temperature of 700° C. or more and 1000° C. or less to obtain a solid electrolyte layer 20 as a main sintered body. The heating time and atmosphere in the heating step are as described above.

[0216] In order to ensure that the sintered density of the solid electrolyte layer 20 after firing is 90% or more, the slurry 20m may be pressed and extruded by the application roller 501 and the doctor roller 502 to form a solid electrolyte forming sheet 20s having a predetermined thickness.

[0217] [7-1-2] Step S2 After step S1, proceed to step S2. In the step of forming the positive electrode 10 in step S2, the positive electrode 10 is formed on one surface of the solid electrolyte layer 20. More specifically, for example, first, a sputtering device is used to sputter LiCoO 2 The surface of the solid electrolyte layer 20 is coated with LiCoO 2 Then, in an oxidizing atmosphere, the LiCoO layer formed on the solid electrolyte layer 20 is 2 The layer is fired to form LiCoO 2 The crystals of the layer are converted to high-temperature phase crystals, and LiCoO 2 The layer can be the positive electrode 10. 2 The firing conditions for the layer are not particularly limited, but the heating temperature can be from 400° C. to 600° C., and the heating time can be from 1 hour to 3 hours.

[0218] [7-1-3] Step S3 After step S2, proceed to step S3. In the step of forming the negative electrode 30 in step S3, the negative electrode 30 is formed on the other surface of the solid electrolyte layer 20, i.e., the surface opposite to the surface on which the positive electrode 10 is formed. More specifically, for example, a vacuum deposition apparatus or the like is used to form a thin film of metallic Li on the surface of the solid electrolyte layer 20 opposite to the surface on which the positive electrode 10 is formed, to form the negative electrode 30. The thickness of the negative electrode 30 can be, for example, 0.1 μm or more and 500 μm or less.

[0219] [7-1-4] Step S4 After step S3, proceed to step S4. In the step S4 of forming the current collectors 41 and 42, the current collector 41 is formed so as to contact the positive electrode 10, and the current collector 42 is formed so as to contact the negative electrode 30. More specifically, for example, the current collector 41 can be formed by pressing and bonding an aluminum foil cut into a circle by die cutting or the like to the positive electrode 10. Also, for example, the current collector 42 can be formed by pressing and bonding a copper foil cut into a circle by die cutting or the like to the negative electrode 30. The thickness of the current collectors 41 and 42 is not particularly limited, and can be, for example, 10 μm or more and 60 μm or less. Note that in this step, only one of the current collectors 41 and 42 may be formed.

[0220] The method for forming the solid electrolyte layer 20 is not limited to the green sheet method shown in step S1. As another method for forming the solid electrolyte layer 20, for example, the following method can be adopted. That is, as shown in FIG. 11, a pellet die 80 may be filled with a powdered calcined body according to the present invention, i.e., a calcined body containing a precursor oxide and an oxo acid compound, and the pellet die 80 may be closed with a lid 81, and the lid 81 may be pressed to perform uniaxial press molding to obtain a molded product 20f. The subsequent treatment of the molded product 20f may be performed in the same manner as described above. As the pellet die 80, one equipped with an exhaust port (not shown) may be suitably used.

[0221] [7-2] Method for manufacturing secondary battery according to second embodiment Next, a method for manufacturing a secondary battery according to the second embodiment will be described.

[0222] FIG. 12 is a flowchart showing a method for manufacturing a lithium ion battery as a secondary battery of the second embodiment, and FIGS. 13 and 14 are schematic views showing a method for manufacturing a lithium ion battery as a secondary battery of the second embodiment.

[0223] Hereinafter, the method for producing a secondary battery according to the second embodiment will be described with reference to these drawings. The differences from the embodiment described above will be mainly described, and a description of the similar points will be omitted.

[0224] As shown in FIG. 12, the method for manufacturing the lithium ion battery 100 of this embodiment includes steps S11, S12, S13, and S14.

[0225] Step S11 is a step of forming the positive electrode composite material 210. Step S12 is a step of forming the electrolyte layer 220. Step S13 is a step of forming the negative electrode 30. Step S14 is a step of forming the current collectors 41, .

[0226] [7-2-1] Step S11 In step S11, a step of forming the positive electrode composite material 210, the positive electrode composite material 210 is formed. Positive electrode composite material 210 can be formed, for example, as follows.

[0227] That is, first, for example, LiCoO 2 A slurry 210m is obtained as a mixture of the positive electrode active material 211 such as the above, the pre-sintered body according to the present invention as described above, i.e., the pre-sintered body containing a precursor oxide and an oxo acid compound, a binder such as polypropylene carbonate, and a solvent such as 1,4-dioxane. In preparing the slurry 210m, a dispersant, a diluent, a moisturizer, etc. may be further used as necessary.

[0228] Next, the slurry 210m is used to form a positive electrode composite forming sheet 210s. More specifically, as shown in Fig. 13, for example, the slurry 210m is applied to a substrate 506 such as a polyethylene terephthalate film with a predetermined thickness using a fully automatic film applicator 500 to form the positive electrode composite forming sheet 210s.

[0229] Thereafter, the solvent is removed from the positive electrode composite forming sheet 210s formed on the base material 506, and the positive electrode composite forming sheet 210s is peeled off from the base material 506 and punched out to a predetermined size using a die to form a molded product 210f, as shown in FIG. 14.

[0230] Thereafter, formed product 210f is subjected to a heating step at a temperature of 700° C. or more and 1000° C. or less to obtain solid electrolyte-containing positive electrode composite material 210. The heating time and atmosphere in the heating step are as described above.

[0231] [7-2-2] Step S12 After step S11, proceed to step S12. In the step of forming the electrolyte layer 220 in step S12, the electrolyte layer 220 is formed on one surface 210b of the positive electrode composite material 210. More specifically, for example, a sputtering device is used to sputter LiCoO 2 The sputtering is performed using LiCoO as a target to deposit LiCoO on the surface of the positive electrode mixture 210. 2 Then, in an oxidizing atmosphere, the LiCoO 2 The layer is fired to form LiCoO 2 The crystals of the layer are converted to high-temperature phase crystals, and LiCoO 2 The layer may be the electrolyte layer 220. 2 The firing conditions for the layer are not particularly limited, but the heating temperature can be from 400° C. to 600° C., and the heating time can be from 1 hour to 3 hours.

[0232] [7-2-3] Step S13 After step S12, proceed to step S13. In the step of forming the negative electrode 30 in step S13, the negative electrode 30 is formed on the surface of the electrolyte layer 220 opposite to the surface facing the positive electrode composite material 210. More specifically, the negative electrode 30 can be formed by forming a thin film of metallic Li on the surface of the electrolyte layer 220 opposite to the surface facing the positive electrode composite material 210 using, for example, a vacuum deposition device or the like.

[0233] [7-2-4] Step S14 After step S13, proceed to step S14. In the process of forming the current collectors 41, 42 in step S14, the current collector 41 is formed so as to contact the other surface of the positive electrode composite 210, i.e., the surface 210a opposite to the surface 210b on which the electrolyte layer 220 is formed, and the current collector 42 is formed so as to contact the negative electrode 30.

[0234] The method of forming the positive electrode composite 210 and the electrolyte layer 220 is not limited to the above method. For example, the positive electrode composite 210 and the electrolyte layer 220 may be formed as follows. That is, first, a slurry is obtained as a mixture of the pre-calcined body according to the present invention, that is, a pre-calcined body containing a precursor oxide and an oxo acid compound, a binder, and a solvent. Then, the obtained slurry is put into a fully automatic film applicator 500 and applied onto a substrate 506 to form an electrolyte forming sheet. Then, the electrolyte forming sheet and the positive electrode composite forming sheet 210s formed in the same manner as described above are pressed in a stacked state, and these are bonded together. Then, the laminated sheet obtained by bonding is punched out to form a molded product, and the molded product is fired in an oxidizing atmosphere to obtain a laminate of the positive electrode composite 210 and the electrolyte layer 220.

[0235] [7-3] Method for manufacturing secondary battery according to third embodiment Next, a method for manufacturing a secondary battery according to the third embodiment will be described. FIG. 15 is a flowchart showing a method for manufacturing a lithium ion battery as a secondary battery of the third embodiment, and FIGS. 16 and 17 are schematic views showing a method for manufacturing a lithium ion battery as a secondary battery of the third embodiment.

[0236] Hereinafter, the method for manufacturing a secondary battery according to the third embodiment will be described with reference to these drawings. The differences from the above-described embodiment will be mainly described, and a description of the similar points will be omitted.

[0237] As shown in FIG. 15, the method for manufacturing the lithium ion battery 100 of this embodiment includes steps S21, S22, S23, and S24.

[0238] Step S21 is a step of forming negative electrode composite material 330. Step S22 is a step of forming electrolyte layer 220. Step S23 is a step of forming positive electrode 10. Step S24 is a step of forming current collectors 41, .

[0239] [7-3-1] Step S21 In the negative electrode composite material 330 forming step S21, the negative electrode composite material 330 is formed. The negative electrode composite material 330 can be formed, for example, as follows.

[0240] That is, first, for example, Li 4 Ti 5 O 12 A slurry 330m is obtained as a mixture of the negative electrode active material 331 such as the above, the calcined body according to the present invention, i.e., the calcined body containing a precursor oxide and an oxo acid compound, a binder such as polypropylene carbonate, and a solvent such as 1,4-dioxane. In preparing the slurry 330m, a dispersant, a diluent, a moisturizer, etc. may be further used as necessary.

[0241] Next, the slurry 330m is used to form a negative electrode composite forming sheet 330s. More specifically, as shown in Fig. 16, for example, the slurry 330m is applied to a substrate 506 such as a polyethylene terephthalate film with a predetermined thickness using a fully automatic film applicator 500 to form the negative electrode composite forming sheet 330s.

[0242] Thereafter, the solvent is removed from the negative electrode composite forming sheet 330s formed on the base material 506, and the negative electrode composite forming sheet 330s is peeled off from the base material 506 and punched out to a predetermined size using a die to form a molded product 330f, as shown in FIG. 17.

[0243] Thereafter, molded product 330f is subjected to a heating step at a temperature of 700° C. to 1000° C. to obtain solid electrolyte-containing negative electrode composite material 330. The heating time and atmosphere in the heating step are as described above.

[0244] [7-3-2] Step S22 After step S21, the process proceeds to step S22. In the step of forming the electrolyte layer 220 in step S22, the electrolyte layer 220 is formed on one surface 330a of the negative electrode composite material 330. More specifically, for example, a sputtering device is used to perform a sputtering process in an inert gas such as argon gas. 2 CO 3 and Li 3 BO 3 Solid solution of Li 2.2 C 0.8 B 0.2 O 3 By performing sputtering using a target, Li is deposited on the surface of the negative electrode mixture 330. 2.2 C 0.8 B 0.2 O 3 Then, in an oxidizing atmosphere, the Li 2.2 C 0.8 B 0.2 O 3 By sintering the layer, Li 2.2 C 0.8 B 0.2 O 3 The crystals of the layer are converted to high-temperature phase crystals, and Li 2.2 C 0.8 B 0.2 O 3 The layer may be the electrolyte layer 220. 2.2 C 0.8 B 0.2 O 3 The firing conditions for the layer are not particularly limited, but the heating temperature can be from 400° C. to 600° C., and the heating time can be from 1 hour to 3 hours.

[0245] [7-3-3] Step S23 After step S22, the process proceeds to step S23. In the step of forming the positive electrode 10 in step S23, the positive electrode 10 is formed on one surface 220a of the electrolyte layer 220, that is, the surface of the electrolyte layer 220 opposite to the surface facing the negative electrode composite material 330. More specifically, for example, first, LiCoO 2Then, LiCoO 2 The laminate of the electrolyte layer 220 and the negative electrode mixture 330 is fired to form LiCoO 2 The crystals of the layer are converted to high-temperature phase crystals, and LiCoO 2 The layer can be the positive electrode 10. 2 The firing conditions for the layer are not particularly limited, but the heating temperature can be from 400° C. to 600° C., and the heating time can be from 1 hour to 3 hours.

[0246] [7-3-4] Step S24 After step S23, proceed to step S24. In the process of forming the current collectors 41, 42 in step S24, the current collector 41 is formed so as to contact one surface 10a of the positive electrode 10, i.e., the surface 10a opposite to the surface on which the electrolyte layer 220 of the positive electrode 10 is formed, and the current collector 42 is formed so as to contact the other surface of the negative electrode composite 330, i.e., the surface 330b opposite to the surface 330a of the negative electrode composite 330 on which the electrolyte layer 220 is formed.

[0247] The method of forming the negative electrode composite 330 and the electrolyte layer 220 is not limited to the above method. For example, the negative electrode composite 330 and the electrolyte layer 220 may be formed as follows. That is, first, a slurry is obtained as a mixture of the pre-calcined body according to the present invention, that is, a pre-calcined body containing a precursor oxide and an oxo acid compound, a binder, and a solvent. Then, the obtained slurry is put into a fully automatic film applicator 500 and applied onto a substrate 506 to form an electrolyte forming sheet. Then, the electrolyte forming sheet and the negative electrode composite forming sheet 330s formed in the same manner as described above are pressed in a stacked state, and these are bonded together. Then, the laminated sheet obtained by bonding is punched out to form a molded product, and the molded product is fired in an oxidizing atmosphere to obtain a laminate of the negative electrode composite 330 and the electrolyte layer 220.

[0248] [7-4] Method for manufacturing secondary battery according to fourth embodiment Next, a method for manufacturing a secondary battery according to the fourth embodiment will be described. FIG. 18 is a flowchart showing a method for manufacturing a lithium ion battery as a secondary battery of the fourth embodiment, and FIG. 19 is a schematic diagram showing a model of the method for manufacturing a lithium ion battery as a secondary battery of the fourth embodiment.

[0249] Hereinafter, the method for manufacturing a secondary battery according to the fourth embodiment will be described with reference to these drawings. The differences from the above-described embodiments will be mainly described, and descriptions of similar points will be omitted.

[0250] As shown in FIG. 18, the method for manufacturing the lithium ion battery 100 of this embodiment includes steps S31, S32, S33, S34, S35, and S36.

[0251] Step S31 is a step of forming a sheet for forming the positive electrode composite material 210. Step S32 is a step of forming a sheet for forming the negative electrode composite material 330. Step S33 is a step of forming a sheet for forming the solid electrolyte layer 20. Step S34 is a step of forming a molded product 450f in which a laminate of a sheet for forming the positive electrode composite material 210, a sheet for forming the negative electrode composite material 330, and a sheet for forming the solid electrolyte layer 20 is molded into a predetermined shape. Step S35 is a step of firing the molded product 450f. Step S36 is a step of forming the current collectors 41, 42.

[0252] In the following explanation, step S32 is performed after step S31, and step S33 is performed after step S32; however, the order of steps S31, S32, and S33 is not limited to this, and these steps may be performed in a reversed order or simultaneously.

[0253] [7-4-1] Step S31 In step S31, a positive electrode composite material 210-forming sheet forming step, a positive electrode composite material 210s, which is a sheet for forming the positive electrode composite material 210, is formed.

[0254] The positive electrode composite forming sheet 210s can be formed, for example, by the same method as that described in the second embodiment.

[0255] The positive electrode composite forming sheet 210s obtained in this step is preferably one in which the solvent has been removed from the slurry 210m used to form the positive electrode composite forming sheet 210s.

[0256] [7-4-2] Step S32 After step S31, the process proceeds to step S32. In step S32, a negative electrode composite material 330 forming sheet formation step, a negative electrode composite material 330s, which is a sheet for forming the negative electrode composite material 330, is formed.

[0257] The negative electrode composite forming sheet 330s can be formed, for example, by the same method as that described in the third embodiment.

[0258] It is preferable that the negative electrode composite material forming sheet 330s obtained in this step is obtained by removing the solvent from the slurry 330m used in forming the negative electrode composite material forming sheet 330s.

[0259] [7-4-3] Step S33 After step S32, the process proceeds to step S33. In step S33, a solid electrolyte layer 20-forming sheet forming step, a solid electrolyte layer 20-forming sheet 20s, which is a sheet for forming the solid electrolyte layer 20, is formed.

[0260] The solid electrolyte formation sheet 20s can be formed, for example, by the same method as that described in the first embodiment.

[0261] The sheet 20s for forming a solid electrolyte obtained in this step is preferably one obtained by removing the solvent from the slurry 20m used for forming the sheet 20s for forming a solid electrolyte.

[0262] [7-4-4] Step S34 After step S33, the process proceeds to step S34. In the step of forming the molded product 450f in step S34, the positive electrode composite forming sheet 210s, the solid electrolyte forming sheet 20s, and the negative electrode composite forming sheet 330s are laminated in this order and pressed together. Then, as shown in FIG. 19, the laminated sheet obtained by lamination is punched out to obtain the molded product 450f.

[0263] [7-4-5] Step S35 After step S34, the process proceeds to step S35. In the firing process of the molded product 450f in step S35, a heating process is performed on the molded product 450f at a temperature of 700° C. or more and 1000° C. or less. As a result, the portion formed by the positive electrode composite forming sheet 210s becomes the positive electrode composite 210, the portion formed by the solid electrolyte forming sheet 20s becomes the solid electrolyte layer 20, and the portion formed by the negative electrode composite forming sheet 330s becomes the negative electrode composite 330. That is, the fired product of the molded product 450f is a laminate of the positive electrode composite 210, the solid electrolyte layer 20, and the negative electrode composite 330. The heating time and atmosphere in the heating process are as described above.

[0264] [7-4-6] Step S36 After step S35, the process proceeds to step S36. In step S36, a process of forming current collectors 41 and 42, current collector 41 is formed so as to contact surface 210a of positive electrode composite material 210, and current collector 42 is formed so as to contact surface 330b of negative electrode composite material 330.

[0265] [8]Electronic equipment Next, an electronic device according to the present invention will be described. An electronic device according to the present invention includes the battery according to the present invention described above.

[0266] Examples of electronic devices include personal computers, digital cameras, mobile phones, smartphones, music players, tablet terminals, watches, smart watches, various printers such as inkjet printers, televisions, projectors, head-up displays, wireless headphones, wireless earphones, smart glasses, wearable devices such as head-mounted displays, video cameras, video tape recorders, car navigation devices, drive recorders, pagers, electronic notebooks, electronic dictionaries, electronic translators, calculators, electronic game devices, toys, word processors, workstations, robots, videophones, security television monitors, electronic binoculars, POS terminals, medical devices, fish finders, various measuring devices, mobile terminal base station devices, various instruments such as vehicles, railroad cars, aircraft, helicopters, and ships, flight simulators, and network servers. The lithium ion battery 100 may also be applied to moving objects such as automobiles and ships. More specifically, the lithium ion battery 100 can be suitably applied as a storage battery for electric vehicles, plug-in hybrid vehicles, hybrid vehicles, fuel cell vehicles, and the like. The lithium ion battery 100 can also be applied to, for example, household power sources, industrial power sources, and solar power generation storage batteries.

[0267] Hereinafter, a wearable device will be described as a specific example of an electronic device according to the present invention. FIG. 20 is a perspective view showing a configuration of a wearable device as an electronic device. As shown in FIG. 20, a wearable device 300 as an electronic device is an information device that is worn on the human body, for example on the wrist WR, like a wristwatch and can obtain information related to the human body, and is equipped with a band 301, a sensor 302, a display unit 303, a processing unit 304, and a lithium ion battery 100.

[0268] The band 301 is in the form of a strip made of flexible resin such as rubber so that it fits closely around the wrist WR when worn, and has a joining portion at one end of the strip that allows the joining position to be adjusted. The sensor 302 is, for example, an optical sensor, and is arranged on the inner surface side of the band 301, that is, on the wrist WR side, so as to come into contact with the wrist WR when worn.

[0269] The display unit 303 is, for example, a light-receiving type liquid crystal display device, and is arranged on the outer surface of the band 301, i.e., on the opposite side to the inner surface on which the sensor 302 is attached, so that the wearer can read the information displayed on the display unit 303.

[0270] The processing unit 304 is, for example, an integrated circuit, which is built into the band 301 and is electrically connected to the sensor 302 and the display unit 303. The processing unit 304 performs calculations for measuring the pulse rate, blood glucose level, etc. based on the output from the sensor 302. It also controls the display unit 303 to display the measurement results, etc.

[0271] The lithium ion battery 100 is detachably mounted in the band 301 and serves as a power supply source for supplying power to the sensor 302, the display unit 303, the processing unit 304, and the like.

[0272] According to the wearable device 300 of this embodiment, the sensor 302 electrically detects information related to the wearer's pulse rate and blood glucose level from the wrist WR, and after arithmetic processing in the processing unit 304, the pulse rate, blood glucose level, etc. can be displayed on the display unit 303. The display unit 303 can display not only the measurement results, but also information indicating the state of the human body predicted from the measurement results, the time, etc.

[0273] In addition, because the lithium ion battery 100 used is small yet has excellent charge / discharge characteristics, it is possible to provide a wearable device 300 that is lightweight, thin, and able to withstand repeated use over a long period of time. In addition, because the lithium ion battery 100 is a solid-state secondary battery, it is possible to provide a wearable device 300 that can be used repeatedly by charging, and that can be used safely for a long period of time without worrying about leakage of electrolyte or the like.

[0274] In this embodiment, a wristwatch-type wearable device 300 is exemplified, but the wearable device 300 may be worn on the ankle, head, ear, waist, or the like, for example.

[0275] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these.

[0276] For example, the garnet-type crystal of the present invention may be produced by any method, and is not limited to the method described above.

[0277] More specifically, the garnet-type crystal of the present invention may be produced, for example, by mixing oxides corresponding to the respective metal elements constituting the garnet-type crystal, and firing the mixture.

[0278] Furthermore, when the present invention is applied to a secondary battery, the configuration of the secondary battery is not limited to that of the above-described embodiment.

[0279] For example, when the present invention is applied to a secondary battery, the secondary battery is not limited to a lithium ion battery, and may be, for example, a secondary battery in which a porous separator is provided between a positive electrode mixture and a negative electrode, and the separator is impregnated with an electrolyte.

[0280] Furthermore, when the present invention is applied to a secondary battery, the manufacturing method thereof is not limited to that of the above-described embodiment. For example, the order of steps in manufacturing the secondary battery may be different from that of the above-described embodiment.

[0281] In the above-described embodiment, the garnet-type crystal of the present invention has been described as constituting a part of a secondary battery, in particular as constituting a solid electrolyte of an all-solid-state lithium secondary battery which is an all-solid-state secondary battery. However, the garnet-type crystal of the present invention may be, for example, a part of something other than an all-solid-state secondary battery, a part of something other than a secondary battery, or may be used for purposes other than a solid electrolyte. EXAMPLES

[0282] Next, specific examples of the present invention will be described. In the following description, room temperature refers to 25°C and 1 atm. Furthermore, treatments and measurements for which no particular temperature conditions are specified were performed at 25°C, and treatments and measurements for which no particular pressure conditions are specified were performed in an environment of 1 atm.

[0283] [9] Production of solid electrolytes by solid-phase method Example 1 First, the raw material powder is Li 2 O (99% purity, manufactured by Kojundo Kagaku Kenkyusho Co., Ltd.), La 2 O 3 (Purity 99.99%, Fujifilm Wako Pure Chemical Industries, Ltd.), ZrO 2 (Special grade, Fujifilm Wako Pure Chemical Industries, Ltd.), CeO 2 (Purity 99.9%, Fujifilm Wako Pure Chemical Industries, Ltd.), Nb 2 O 5 (Purity 99.9%, Fujifilm Wako Pure Chemical Industries, Ltd.), Sb 2 O 5 (99.995% purity, Sigma-Aldrich), Ta 2 O 5 (purity 99.9%, Fujifilm Wako Pure Chemical Industries, Ltd.) and SnO 2 (purity 99.9%, manufactured by Sigma-Aldrich) powders were prepared.

[0284] These raw powders were each ground using a planetary ball mill (PL-7 Premium Line, Fritsch) at 1000 rpm for 1 hour, and then ground at 500 rpm for 1 hour. A zirconia pot, 60 g of zirconia balls (diameter 2 mm), and ethanol were used for the planetary ball milling. After the grounding process, each raw powder was collected by suction filtration.

[0285] Thereafter, each of the pulverized raw material powders was subjected to a drying treatment under the following temperature conditions: heating rate: 900°C / hour, holding temperature: 900°C, holding time at 900°C: 12 hours.

[0286] The powders of the raw materials that had been crushed and dried were weighed in a predetermined ratio and dry-mixed in an automatic mortar (ANM1000, manufactured by Nitto Kagaku Co., Ltd.) for 1 hour to obtain a mixed powder. At this time, Li was added so that the ratio of Li was 20 mass % in excess of the composition of the target garnet-type crystal. 2 O was used. 2 The raw material powders other than O were used in such proportions that the corresponding metal elements would form the desired composition of the garnet-type crystal.

[0287] The mixed powder was placed in an alumina crucible, covered with an alumina lid, and pre-fired in an electric furnace FO100 manufactured by Yamato Scientific Co., Ltd. to obtain a pre-fired body. The heating rate was 900°C / hour, the holding temperature was 900°C, and the holding time at 900°C was 12 hours.

[0288] After the electric furnace was cooled to room temperature, the calcined body was removed from the crucible. The cooling rate to 500°C was 400°C / hour, and then the crucible was left to cool. The mixed powder was placed in the electric furnace and the calcined body was removed from the electric furnace in a dry room with low moisture concentration.

[0289] The calcined body was ground and mixed for 1 hour in an automatic mortar (ANM1000, manufactured by Nitto Kagaku Co., Ltd.). 0.200 g of the ground calcined body thus obtained was weighed out and filled into a carbide die with an inner diameter of 10 mm as a mold, and the ground and mixed powder was compression molded into pellets with a diameter of 10 mm under a load of 90 kN using a uniaxial pressing machine (100 kN Newton press, manufactured by NPa Systems Co., Ltd.). After that, CIP molding was performed using a cold isostatic pressing machine (Press-CIP, manufactured by NPa Systems Co., Ltd.) to produce calcined body pellets, which are disk-shaped molded products. CIP molding was performed by pressing at a pressure of 300 MPa for 10 minutes.

[0290] Thereafter, the entire pre-sintered pellets were covered with a protective powder having the same composition as the pre-sintered pellets, and the protective powder was filled into an alumina crucible. The protective powder had the same mass as the pre-sintered pellets, 0.200 g.

[0291] Thereafter, the crucible was covered with an alumina lid, and the mixture was subjected to main firing in an electric furnace FO100 manufactured by Yamato Scientific Co., Ltd. The heating rate was 900°C / hour, the holding temperature was 1000°C, and the holding time at 1000°C was 10 hours.

[0292] After the electric furnace was cooled to room temperature, a disk-shaped solid electrolyte with a diameter of about 9.5 mm and a thickness of about 600 μm was taken out from the crucible. The cooling rate to 500° C. was 500° C. / hour, and the electrolyte was then allowed to cool naturally.

[0293] The mixing of raw materials, crushing of the fired powder, and molding were all carried out in a dry room with dew point control (-40°C).

[0294] The solid electrolyte thus obtained was confirmed by XRD measurement to be a single phase cubic garnet crystal without any impurity phase.

[0295] The composition of the obtained solid electrolyte was Li 6.25 La 3 (Zr 0.75 Ce 0.25 Nb 0.25 Sb 0.25 Ta 0.25 Sn 0.25 )O 12 It was.

[0296] The XRD diffraction pattern of the obtained solid electrolyte was subjected to LeBail analysis and Rietveld analysis to examine the site occupancy of the substitution element species, and the Rwp value was 4.023 and the S value was 2.2077, respectively. For example, if it is assumed that all Ce occupies the La site and the Ce occupancy rate at the Zr site is 0%, the Rwp value is 6.245 and the S value is 6.0570, and both the Rwp value and the S value are large. When all substitution element species occupy the Zr site, the Rwp value is the minimum value and the S value is closest to 1, so it is considered that all substitution element species occupy the Zr site. In addition, it was confirmed by SEM-EDS that the distribution state of each composition element is uniform.

[0297] Example 2 A garnet-type crystal as a solid electrolyte was produced in the same manner as in Example 1, except that the amounts of raw material powders used were adjusted so that the composition of the garnet-type crystal would be as shown in FIG. In addition, HfO 2 The used product was manufactured by Sigma-Aldrich and had a purity of 98%.

[0298] (Comparative Examples 1 to 6) A solid electrolyte was produced in the same manner as in Example 1, except that the types and amounts of raw material powders were adjusted so that the composition of the solid electrolyte was as shown in FIG. In addition, HfO 2 The used product was manufactured by Sigma-Aldrich and had a purity of 98%.

[0299] The compositions and crystal phases of the solid electrolytes of Examples 1 and 2 and Comparative Examples 1 to 6 are shown in FIG.

[0300]

[10] Evaluation of solid electrolytes obtained using solid-phase methods [10-1] Bulk resistance, grain boundary resistance, and total resistance of solid electrolytes For each of the disk-shaped solid electrolytes of the Examples and Comparative Examples, the bulk resistance Rb [Ω], the grain boundary resistance Rgb [Ω], and the total resistance Rb+Rgb [Ω] were determined as follows.

[0301] The electrochemical properties of the disk-shaped solid electrolyte were evaluated by Nyquist plot measurement using the AC impedance method. Both sides of the disk-shaped solid electrolyte were polished with abrasive paper (#400, #1000) until gloss appeared. The thickness of the molded body was measured with a micrometer. The oxide layer on the surface of the Li foil was removed with a glass plate, and a Li metal foil (thickness 20 μm, manufactured by Honjo Metals) punched into a circle with a diameter of 8 mm was attached to the disk-shaped solid electrolyte, and then the product was pressure molded at 300 MPa for 10 minutes using a cold isostatic pressing machine (NPa system, Press-CIP) to produce a non-blocking type symmetrical cell. The molded sample was then fixed in an all-solid-state battery evaluation cell (manufactured by Hosen Co., Ltd., KP-SolidCell). Note that the process from polishing the disk-shaped solid electrolyte to placing it in the evaluation cell was carried out in an Ar atmosphere glove box (manufactured by Miwa Seisakusho Co., Ltd., MDB-2LKP-OSSI type) to prevent exposure to the atmosphere. The impedance of the samples in the evaluation cell was measured using an electrochemical measurement system (VSP-300, manufactured by Biologic Corporation) at a frequency range of 7MHz to 10mHz, amplitude of 10mV, and temperature of 25°C. Frequency analysis was performed from the results, and the bulk resistance Rb and interface resistance Rgb were calculated by separating the resistance into three components: bulk resistance, grain boundary resistance, and interface resistance. In addition, the ratio of grain boundary resistance to the solid electrolyte resistance component Rb+Rgb[Ω] was calculated as Rratio=Rgb / (Rb+Rgb).

[0302] [10-2] Lithium ion conductivity The lithium ion conductivity of the disk-shaped solid electrolyte of each of the Examples and Comparative Examples was determined as follows. That is, the lithium ion conductivity was calculated by calculating the resistivity ρ from the relationship (Rb+Rgb)=ρ×(l / A) using the resistance component of the solid electrolyte, Rb+Rgb [Ω], the disk thickness l, and the electrode area A, and then converting the reciprocal of this value into the lithium ion conductivity.

[0303] [10-3] Lattice constant For each of the disk-shaped solid electrolytes in the Examples and Comparative Examples, the lattice constant was determined by X-ray diffraction (XRD). These results are summarized in FIG.

[0304] As is clear from FIG. 22, each of the above-mentioned Examples, which are garnet-type crystals containing Ce, Nb, Sb and Ta in addition to Li, La, Zr and O, obtained excellent results, whereas the Comparative Example, which did not contain at least one of Ce, Nb, Sb and Ta, obtained only poor results.

[0305] In addition, it was confirmed that the lattice constant was expanded by replacing a portion of Zr with a specific metal element, which is believed to expand the lithium conduction path and improve the lithium ion conductivity.

[0306]

[11] Production of solid electrolytes using the liquid phase method (method using precursor solutions) [11-1] Preparation of precursor solution (Example A1) First, raw materials as the source of each metal element Li, La, Zr, Ce, Nb, Sb, Ta and Sn were prepared, and each of these was mixed with 2-n-butoxyethanol (Kanto Chemical Co., Ltd., special grade) in a predetermined ratio to obtain a raw material solution, which is a solution of the raw material of each metal element source. The raw material solutions containing the elements of the raw materials used in the production of the solid electrolytes of Examples 3 to 6 are shown below.

[0307] [2mol / kg lithium nitrate in 2-butoxyethanol] 2.7578 g of lithium nitrate (3N5, Kanto Chemical Co., Ltd.) with a purity of 99.95% and 17.2420 g of 2-butoxyethanol (ethylene glycol monobutyl ether) (special grade, deer) were weighed into a 30 g Pyrex (registered trademark of Corning Co., Ltd.) reagent bottle containing a magnetic stirrer bar. The mixture was then placed on a magnetic stirrer with a hot plate function, and stirred at 190°C for 1 hour to completely dissolve the lithium nitrate in the 2-butoxyethanol. The mixture was then gradually cooled to room temperature to obtain a 2-butoxyethanol solution of lithium nitrate with a concentration of 2 mol / kg. The purity of lithium nitrate can be measured using an ion chromatography mass spectrometer.

[0308] [1 mol / kg solution of lanthanum nitrate hexahydrate in 2-butoxyethanol] Lanthanum nitrate hexahydrate (Kanto Chemical, 4N, 8.6608 g) and 2-butoxyethanol (11.3392 g) were weighed into a 30 g Pyrex reagent bottle containing a magnetic stir bar. The bottle was then placed on a magnetic stirrer with a hot plate function and stirred at 140°C for 30 minutes to completely dissolve lanthanum nitrate hexahydrate in 2-butoxyethanol. The bottle was then gradually cooled to room temperature to obtain a 1 mol / kg solution of lanthanum nitrate hexahydrate in 2-butoxyethanol.

[0309] [1 mol / kg concentration of zirconium tetra-n-butoxide in butanol] 3.8368 g of zirconium tetra-n-butoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 6.1632 g of butanol (n-butanol) were weighed into a 20 g Pyrex reagent bottle containing a magnetic stirrer bar. The bottle was then placed on a magnetic stirrer and stirred at room temperature for 30 minutes to completely dissolve the zirconium tetra-n-butoxide in butanol, yielding a butanol solution of zirconium tetra-n-butoxide with a concentration of 1 mol / kg.

[0310] [1 mol / kg solution of cerium nitrate hexahydrate in 2-butoxyethanol] 4.3422 g of 98% pure cerium nitrate hexahydrate (FUJIFILM Wako Pure Chemical Industries, Ltd., 98%) and 5.6578 g of 2-butoxyethanol were weighed into a 20 g Pyrex reagent bottle containing a magnetic stirrer bar. The bottle was then placed on a magnetic stirrer with a hot plate function and stirred at 140°C for 1 hour to completely dissolve the lithium nitrate in the 2-butoxyethanol. The bottle was then gradually cooled to room temperature to obtain a 1 mol / kg 2-butoxyethanol solution of cerium nitrate hexahydrate.

[0311] [1 mol / kg tin tetraisopropoxide in 2-butoxyethanol] First, impurities contained in tin tetraisopropoxide (3N, manufactured by Kojundo Chemical Laboratory Co., Ltd.) are adsorbed onto neutral silica (e.g., Wakosil C-300 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)) to remove them. 3.5510 g of the adsorbed tin tetraisopropoxide and 6.4490 g of 2-butoxyethanol were weighed into a 20 g Pyrex reagent bottle containing a magnetic stirrer bar. Next, the mixture was placed on a magnetic stirrer with a hot plate function, and stirred at 140° C. for 30 minutes to completely dissolve the tin tetraisopropoxide in the 2-butoxyethanol. The mixture was then slowly cooled to room temperature to obtain a 1 mol / kg concentration tin tetraisopropoxide in 2-butoxyethanol solution.

[0312] [1mol / kg concentration of niobium pentoxide in 2-butoxyethanol] 3.1821 g of niobium pentabutoxide (4N, manufactured by Kojundo Chemical Laboratory Co., Ltd.) and 6.8179 g of 2-butoxyethanol were weighed into a 20 g Pyrex reagent bottle containing a magnetic stir bar. The bottle was then placed on the magnetic stirrer and stirred at room temperature for 30 minutes to completely dissolve the niobium pentabutoxide in the 2-butoxyethanol, yielding a 1 mol / kg concentration solution of niobium pentabutoxide in 2-butoxyethanol.

[0313] [1 mol / kg solution of antimony tri-n-butoxide in 2-butoxyethanol] 3.4110 g of antimony tri-n-butoxide (5N, manufactured by Kojundo Chemical Laboratory Co., Ltd.) and 6.5890 g of 2-butoxyethanol were weighed into a 20 g Pyrex reagent bottle containing a magnetic stirrer bar. The bottle was then placed on the magnetic stirrer and stirred at room temperature for 30 minutes to completely dissolve the antimony tri-n-butoxide in the 2-butoxyethanol, yielding a 2-butoxyethanol solution of antimony tri-n-butoxide with a concentration of 1 mol / kg.

[0314] [1 mol / kg solution of tantalum pentaethoxide in 2-butoxyethanol] 5.4640 g of tantalum pentaethoxide (5N, manufactured by Kojundo Chemical Laboratory Co., Ltd.) and 4.5360 g of 2-butoxyethanol were weighed into a 20 g Pyrex reagent bottle containing a magnetic stir bar. The bottle was then placed on the magnetic stirrer and stirred at room temperature for 30 minutes to completely dissolve the tantalum pentaethoxide in the 2-butoxyethanol, yielding a 1 mol / kg concentration solution of tantalum pentaethoxide in 2-butoxyethanol.

[0315] Next, the precursor solution was obtained by mixing the raw material solutions at a predetermined ratio. At this time, the mixing ratio of the raw material solutions was adjusted so that the content ratio of Li, La, Zr, Ce, Nb, Sb, Ta, and Sn in the solid electrolyte produced using the precursor solution was 6.25:3.00:0.75:0.25:0.25:0.25:0.25:0.25 in molar ratio. The mass (g) of the 2-butoxyethanol solution of lithium nitrate with a concentration of 2 mol / kg is set in consideration of the mass of Li that volatilizes during the main firing at 1000°C. Specifically, the mass of the 2-butoxyethanol solution of lithium nitrate is set to 1.2 times the mass corresponding to Li6.25 at the stage before the main firing. The ratio of increase in the amount of lithium source considering the mass of Li that volatilizes during the main firing is not limited to 1.2 times, but depends on the firing temperature. For example, if the temperature in the heat treatment during the main firing is 800°C, the ratio of increase in the amount of lithium source may be 1.1 times. The amount of Li volatilized during the main firing is saturated when the firing time exceeds 1 hour. The amount of the raw material solution of elements other than the lithium source is set to be equal to the stoichiometric composition of the above composition formula.

[0316] (Example A2) Seven types of solutions other than the Sn-containing solution were used as raw material solutions, and the precursor solutions were obtained in the same manner as in Example A1, except that the mixing ratio of each raw material solution was adjusted so that the content ratio of Li, La, Zr, Ce, Nb, Sb, and Ta in the solid electrolyte produced using the precursor solutions was 6.25:3.00:1.00:0.25:0.25:0.25:0.25 in molar ratio.

[0317] (Examples A3 and A4) A precursor solution was obtained in the same manner as in Example A1, except that the mixing ratio of each raw material solution was adjusted so that the content ratios of Li, La, Zr, Ce, Nb, Sb, Ta, and Sn in the solid electrolyte produced using the precursor solution were 6.40:3.00:1.00:0.20:0.20:0.20:0.20:0.20 and 6.70:3.00:1.50:0.10:0.10:0.10:0.10:0.10, respectively, in molar ratio.

[0318] [11-2] Manufacturing of solid electrolytes Example 3 A part of the precursor solution obtained in Example A1 was placed in a titanium petri dish and placed on a hot plate, heated for 1 hour at a set temperature of 160°C, and then heated for 30 minutes at 180°C to remove the solvent. The hot plate was then heated for 30 minutes at a set temperature of 360°C to decompose most of the organic components contained by combustion. The hot plate was then heated for 1 hour at a set temperature of 540°C to decompose the remaining organic components by combustion. The mixture was then cooled slowly to room temperature on the hot plate to obtain a provisionally fired body.

[0319] The ash-like pyrolysis product (calcined body) obtained in this manner was a powder with an average particle size of 1 μm or less that contained a precursor oxide composed of a pyrochlore-type crystal phase and an oxo acid compound.

[0320] Next, the calcined powder was transferred to an agate mortar and thoroughly pulverized. The pulverized calcined powder was placed in a magnesium oxide crucible, covered with a magnesium oxide lid, and subjected to primary firing at 900°C for 12 hours in a Yamato Scientific electric muffle furnace FO100.

[0321] 0.200 g of the sintered powder thus obtained was weighed out and packed into a carbide die with an inner diameter of 10 mm as a molding die. The pulverized mixed powder was compression molded into pellets with a diameter of 10 mm under a load of 90 kN using a uniaxial pressure molding machine (NPa Systems, 100 kN Newton press).

[0322] Thereafter, the crucible was covered with an alumina lid, and the mixture was subjected to main firing in an electric furnace FO100 manufactured by Yamato Scientific Co., Ltd. The heating rate was 900°C / hour, the holding temperature was 1000°C, and the holding time at 1000°C was 10 hours.

[0323] After the electric furnace was cooled to room temperature, a disk-shaped solid electrolyte with a diameter of about 9.5 mm and a thickness of about 600 μm was taken out from the crucible. The cooling rate to 500° C. was 500° C. / hour, and the electrolyte was then allowed to cool naturally.

[0324] The mixing of raw materials, crushing of the fired powder, and molding were all carried out in a dry room with dew point control (-40°C).

[0325] The solid electrolyte thus obtained was confirmed by XRD measurement to be a single phase cubic garnet crystal without any impurity phase.

[0326] The composition of the obtained solid electrolyte was Li 6.25 La 3 (Zr 0.75 Ce 0.25 Nb 0.25 Sb 0.25 Ta 0.25 Sn 0.25 )O 12 It was.

[0327] The XRD diffraction pattern of the obtained solid electrolyte was subjected to LeBail analysis and Rietveld analysis to examine the site occupancy of the substitution element species, which showed an Rwp value of 4.025 and an S value of 1.6803, respectively. In addition, SEM-EDS confirmed that the distribution state of each composition element was uniform.

[0328] (Examples 4 to 6) Garnet-type crystals were produced as solid electrolytes in the same manner as in Example 3, except that the precursor solutions produced in Examples A2 to A4 were used, respectively.

[0329] The compositions and crystal phases of the solid electrolytes of Examples 3 to 6 are shown in FIG.

[0330]

[12] Evaluation of solid electrolytes obtained using liquid phase method The garnet-type crystals as the solid electrolytes of Examples 3 to 6 obtained in [11-2] above were evaluated in the same manner as in

[10] above ([10-1] to [10-3] above). These results are summarized in FIG.

[0331] As is clear from FIG. 24, the solid electrolytes of Examples 3 to 6 obtained by the liquid phase method also gave excellent results, similar to Examples 1 and 2 above.

[0332] In addition, it was confirmed that the lattice constant was expanded by replacing a portion of Zr with a specific metal element, which is believed to expand the lithium conduction path and improve the lithium ion conductivity. [Explanation of symbols]

[0333] 100...Lithium ion battery, 10...Positive electrode, 10a...Surface, 20...Solid electrolyte layer, 30...Negative electrode, 41, 42...Current collector, 210...Positive electrode composite, 210a...Surface, 210b...Surface, 211...Positive electrode active material, 212...Solid electrolyte, 220...Electrolyte layer, 220a...Surface, 300...Wearable device, 301...Band, 302...Sensor, 303...Display unit, 304...Processing unit, 330...Negative electrode composite, 330a...Surface, 330b...Surface, 331...Negative electrode active material, 500...Fully automatic film applicator, 501...Application roller, 502...Doc roller, 503... squeegee, 504... transport roller, 505... stage, 506... substrate, 80... pellet die, 81... lid, 20m... slurry, 20s... sheet for forming solid electrolyte, 20f... molded product, 210m... slurry, 210s... sheet for forming positive electrode composite material, 210f... molded product, 330m... slurry, 330s... sheet for forming negative electrode composite material, 330f... molded product, 450f... molded product, S1 to S4... steps, S11 to S14... steps, S21 to S24... steps, S31 to S36... steps, WR... wrist

Claims

1. A garnet-type crystal containing Li, La, Zr and O, The garnet-type crystal further contains Ce, Nb, Sb and Ta as constituent elements.

2. 2. The garnet-type crystal according to claim 1, which is represented by the following composition formula (1): Li ７－３ｘ La ３ (Zr ２－４ｘ Ce ｘ Nb ｘ SB ｘ Ta ｘ ) １２ ・・・(1) (In the composition formula (1), x satisfies 0.10≦x<0.30.)

3. The garnet-type crystal according to claim 1 , further comprising Sn as a constituent element.

4. 4. The garnet-type crystal according to claim 3, which is represented by the following composition formula (2): Li ７－３ｘ La ３ (Zr) ２－５ｘ Yes ｘ Nb ｘ Sb ｘ Yes ｘ Sn ｘ )O １２ ・・・(2) (In the composition formula (2), x satisfies 0.10≦x<0.30.)

5. A precursor solution used in the production of a garnet-type crystal containing Li, La, Zr and O, comprising: An organic solvent; A precursor solution containing the metal elements Li, La, Zr, Ce, Nb, Sb and Ta.

6. 6. The precursor solution according to claim 5, wherein, when x is a number that satisfies 0.10≦x<0.30 and y is a number that satisfies 1.05≦y≦1.40, a ratio of the contents of Li, La, Zr, Ce, Nb, Sb and Ta in the precursor solution is, in molar ratio, (7−3x)y:3:(2−4x):x:x:x:x.

7. The precursor solution according to claim 5 , further comprising Sn as the metal element.

8. 8. The precursor solution according to claim 7, wherein, when x is a number that satisfies 0.10≦x<0.30 and y is a number that satisfies 1.05≦y≦1.40, a ratio of contents of Li, La, Zr, Ce, Nb, Sb, Ta and Sn in the precursor solution is, in molar ratio, (7−3x)y:3:(2−5x):x:x:x:x:x.

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