Glass solid electrolyte and lithium ion battery

Abstract

The present invention provides a glass solid electrolyte that contains, as constituent elements, lithium, phosphorus, sulfur, and a halogen which includes at least bromine, wherein the molar ratio (Li / P) of lithium (Li) to phosphorus (P) is 2.0-5.3, the molar ratio (S / P) of sulfur (S) to phosphorus (P) is 2.0-4.5, the molar ratio (X / P) of halogen (X) to phosphorus (P) is 0.7-2.3, and a peak derived from lithium bromide is exhibited in a powder X-ray diffraction using CuKα rays.

Description

Glass solid electrolyte and lithium ion battery

[0001] The present invention relates to a glass solid electrolyte and a lithium ion battery.

[0002] To improve the performance of lithium-ion batteries, it is important to increase the packing ratio (compactibility) of the solid electrolyte powder. To improve the packing ratio, it is effective to make the solid electrolyte mechanically soft (to make it more easily compressible).

[0003] In lithium ion conductive sulfide solid electrolytes, glassy solid electrolytes are generally soft and have a high filling rate. ３ P.S. ４ Glass is known to have a high filling factor. ３ P.S. ４ Solid electrolytes containing glass are disclosed in, for example, Patent Documents 1 to 3. However, Li ３ P.S. ４ The glass had a low ionic conductivity of less than 1 mS / cm.

[0004] Patent No. 5349427 Patent No. 5521899 Patent No. 5757284

[0005] An object of the present invention is to provide a glass solid electrolyte having a packing density equal to or higher than that of conventional glass solid electrolytes and high ionic conductivity.

[0006] The present invention provides the following glass solid electrolytes and the like. 1. A glass solid electrolyte containing lithium, phosphorus, sulfur, and a halogen containing at least bromine as constituent elements, wherein the molar ratio (Li / P) of the lithium (Li) to the phosphorus (P) is 2.0 to 5.3, the molar ratio (S / P) of the sulfur (S) to the phosphorus (P) is 2.0 to 4.5, and the molar ratio (X / P) of the halogen (X) to the phosphorus (P) is 0.7 to 2.3, and wherein the glass solid electrolyte exhibits a peak derived from lithium bromide in powder X-ray diffraction using CuKα radiation. 2. The glass solid electrolyte according to 1, wherein the crystallite size calculated from the half-width of the peak with the maximum intensity among the peaks derived from lithium bromide is 3 to 60 nm. 3. The glass solid electrolyte according to 1 or 2, wherein the halogen contains iodine, and wherein the glass solid electrolyte exhibits a peak derived from lithium iodide in powder X-ray diffraction using CuKα radiation. 4. 5. The glass solid electrolyte according to any one of 1 to 4, wherein the crystallite size calculated from the half width of the peak having the greatest intensity among the peaks derived from lithium iodide is 3 to 60 nm. 6. The glass solid electrolyte according to any one of 1 to 4, wherein the relative density of a 400 MPa compact is 90% or more. 7. The glass solid electrolyte according to 3, wherein the true density is 2.0 to 3.0 g / cm. ３7. A glass solid electrolyte according to any one of 1 to 5, wherein the molar ratio (X / P) is greater than 0.75. 8. A glass solid electrolyte according to any one of 1 to 6, wherein the molar ratio (X / P) is greater than 0.86. 9. A glass solid electrolyte according to any one of 1 to 8, wherein the halogen comprises iodine, the molar ratio (I / P) of the iodine (I) to the phosphorus (P) is 2.0 or less, and the molar ratio (Br / P) of the bromine (Br) to the phosphorus (P) is 0.01 to 1.5. 10. A glass solid electrolyte according to any one of 1 to 9, wherein the ionic conductivity is 1 mS / cm or more. 11. A lithium ion battery comprising the glass solid electrolyte according to any one of 1 to 10. 12. A method for producing a glassy solid electrolyte, comprising combining two or more compounds or simple substances containing lithium, phosphorus, sulfur, and a halogen including at least bromine as constituent elements, and vitrifying the mixture so that a molar ratio (Li / P) of the lithium (Li) to the phosphorus (P) is 2.0 to 5.3, a molar ratio (S / P) of the sulfur (S) to the phosphorus (P) is 2.0 to 4.5, and a molar ratio (X / P) of the halogen (X) to the phosphorus (P) is 0.7 to 2.3.

[0007] According to the present invention, it is possible to provide a glass solid electrolyte having a packing rate equal to or higher than that of conventional glass solid electrolytes and having high ionic conductivity.

[0008] FIG. 1 is a schematic diagram illustrating a pellet density measuring device. FIG. 2 is an X-ray diffraction pattern of the glass solid electrolytes produced in Examples 1 to 4. FIG. 3 is an X-ray diffraction pattern of the glass solid electrolytes produced in Examples 5 to 8. FIG. 4 is an X-ray diffraction pattern of the glass solid electrolytes produced in Examples 9 to 13. FIG. 5 is an X-ray diffraction pattern of the glass solid electrolytes produced in Examples 14 and 15. FIG. 6 is an X-ray diffraction pattern of the glass solid electrolytes produced in Examples 16 to 18. FIG. 7 is an X-ray diffraction pattern of the glass solid electrolyte produced in Example 19. FIG. 8 is an X-ray diffraction pattern of the glass solid electrolytes produced in Comparative Examples 1 to 8. FIG. 9 is an X-ray diffraction pattern of the glass solid electrolytes produced in Comparative Examples 9 and 10.

[0009] Hereinafter, embodiments of the present invention will be described. In this specification, the upper and lower limit values ​​of a range expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the values ​​in the examples can also be used as the upper and lower limit values.

[0010] A glass solid electrolyte according to one embodiment of the present invention contains lithium (Li), phosphorus (P), sulfur (S), and halogen (X) including at least bromine as constituent elements, and the molar ratios of the constituent elements to phosphorus ((Li, S, X) / P) satisfy the following ranges: Li / P = 2.0 to 5.3, S / P = 2.0 to 4.5, and X / P = 0.7 to 2.3.

[0011] Furthermore, powder X-ray diffraction using CuKα radiation shows a peak derived from lithium bromide. The glass solid electrolyte of this embodiment has a higher halogen content than conventional glass solid electrolytes. This allows for a glass solid electrolyte having a packing factor equal to or higher than that of conventional glass solid electrolytes and high ionic conductivity to be obtained. For example, a glass solid electrolyte can be obtained in which the relative density of a 400 MPa compact, which is an index of packing factor, is 90% or more.

[0012] In this application, a glass solid electrolyte refers to a solid electrolyte containing a glass (amorphous) component. The presence of a glass component can be confirmed by the presence of a broad peak (halo pattern) due to the amorphous component in X-ray diffraction (XRD) measurement. In the XRD measurement of a glass solid electrolyte, peaks due to crystalline components and peaks due to raw materials may be observed in part.

[0013] In one embodiment, the molar ratio of lithium (Li) to phosphorus (P) (Li / P) is preferably 3.0 to 5.25, more preferably 3.5 to 5.20, 3.8 to 5.0, or even 4.0 to 4.8. The molar ratio of sulfur (S) to phosphorus (P) (S / P) is preferably 3.0 to 4.4, more preferably 3.5 to 4.3, 3.8 to 4.2, or even 3.9 to 4.1. Adjusting the molar ratio of sulfur to phosphorus within the above range has the effect of reducing the amount of hydrogen sulfide generated in a low dew point environment. The molar ratio of halogen (X) to phosphorus (P) (X / P) is preferably 0.75 to 2.5, more preferably 0.80 to 2.3, 0.85 to 2.0, 0.90 to 1.8, or even 0.95 to 1.5.

[0014] The glass solid electrolyte of this embodiment contains bromine and halogens other than bromine, such as fluorine, chlorine, and iodine, as constituent elements. The molar ratio of bromine (Br) to halogen (X) (Br / X) is preferably 0.05 to 1.0, and more preferably 0.1 to 0.8. The molar ratio of bromine (Br) to phosphorus (P) (Br / P) is preferably 0.05 to 2.0, and more preferably 0.1 to 1.5, and may be 0.2 to 1.4, 0.3 to 1.3, or even 0.5 to 1.0.

[0015] In one embodiment, the halogen (X) includes bromine and iodine. The molar ratio of iodine (I) to phosphorus (P) (I / P) is preferably 2.0 or less, more preferably 0.1 to 1.5, and may be 0.2 to 1.4, 0.3 to 1.3, or even 0.5 to 1.0.

[0016] The types and molar ratios of the constituent elements of the glass solid electrolyte can be confirmed, for example, by an ICP optical emission spectrometer. The molar ratio of the constituent elements of the glass solid electrolyte can be adjusted by controlling the blending of raw materials. The molar ratio of the constituent elements in the raw materials is approximately equal to the molar ratio of the constituent elements of the resulting glass solid electrolyte.

[0017] In the glass solid electrolyte of this embodiment, the molar ratio (Li / P) and the molar ratio (X / P) preferably satisfy the following formula (1): Li / P=(3±α)+X / P (1) (wherein α is 0 to 0.5).

[0018] By satisfying formula (1), the main skeleton of the glass solid electrolyte, PS ４ ３－ The amount of tetrahedral structure produced increases, which has the effect of reducing the amount of hydrogen sulfide generated in a low dew point environment. ４ ３－ Larger and more rigid than the structure, P ２ S ６ ４－ Structure and P ２ S ７ ４－ The amount of the structure produced is reduced, which has the effect of improving the softness of the glass solid electrolyte. α in formula (1) may be 0 to 0.3, 0 to 0.1, or 0.

[0019] In one embodiment, the true density of the glass solid electrolyte is 2.0 to 3.0 g / cm ３ By having the true density in the above range, Li ３ P.S. ４ This means that the glass contains a certain amount of halogen, and the halogen gives the solid electrolyte flexibility and improves ionic conductivity. ３ P.S. ４ The true density of the glass solid electrolyte is 2.05 to 2.9 g / cm ３ More preferably, it is 2.1 to 2.8 g / cm ３ The true density of the glass solid electrolyte can be measured, for example, by a gas-phase substitution method using He gas. Details of the method for measuring the true density of the glass solid electrolyte are shown in the Examples.

[0020] In one embodiment, the glass solid electrolyte has a diffraction peak of a lithium halide such as lithium iodide in addition to lithium bromide in powder X-ray diffraction measurement using CuKα radiation. The lithium halide observed in the powder X-ray diffraction measurement of the glass solid electrolyte has lower crystallinity than the lithium halide of the raw material. The presence of a diffraction peak of a lithium halide can add further softness to the mechanical softness of the glass solid electrolyte itself. Among the peaks derived from the lithium halide, the peak position with the maximum intensity is observed, for example, in the range of 2θ from 25 to 30° (deg). In one embodiment, the lithium halide is lithium iodide.

[0021] In one embodiment, the crystallite size calculated from the peak half-width of the peak with the greatest intensity among the peaks derived from lithium bromide is 3 to 60 nm. It is preferably 5 to 50 nm, and more preferably 7 to 40 nm. Generally, diffraction peaks in powder X-ray diffraction measurements have width, and the width of the peak at half the height of the peak minus the background is called the half-width. It is known that there is a correlation between the half-width and the crystallite size. Larger crystallite sizes result in higher crystallinity and a higher repeating regularity of the crystal structure, resulting in a narrower half-width of the diffraction peak in powder X-ray diffraction measurements.

[0022] The crystallite size can be adjusted by the composition. For example, the crystallite size can be adjusted by adjusting the molar ratio of lithium (Li) to phosphorus (P) (Li / P), the molar ratio of bromine (Br) to halogen (X) (Br / X), and the molar ratio of iodine (I) to phosphorus (P) (I / P). When the solid electrolyte is in a glassy state, the half-width becomes extremely large and the diffraction peak becomes broad.

[0023] In one embodiment, when there are peaks derived from lithium iodide, the crystallite size calculated from the half width of the peak having the maximum intensity among the peaks is 3 to 60 nm, preferably 5 to 50 nm, and more preferably 7 to 40 nm.

[0024] The peak half width and crystallite size are calculated from XRD. Details of the measurement and calculation methods are shown in the Examples. Whether or not a crystallite is present, that is, whether or not peaks of LiBr and LiI are exhibited, is also determined by the above calculation method. For example, the target of calculation of the peak half width is the diffraction peak at 2θ = 28 ± 1 ° in the case of LiBr, and the diffraction peak at 2θ = 25.5 ± 1 ° in the case of LiI.

[0025] The glass solid electrolyte of this embodiment has a packing ratio equal to or higher than that of conventional glass solid electrolytes and has high ionic conductivity. Specifically, the relative density of a 400 MPa compact, which is an index of packing ratio, can be 90% or higher. The relative density can be 90.5% or higher, and can also be 91% or higher. The upper limit of the relative density is not particularly limited, but is usually 99% or lower.

[0026] In the present invention, the relative density of a 400 MPa compact is the ratio of the density (referred to as pellet density) when the glass solid electrolyte powder is compressed at 400 MPa to the true density of the glass solid electrolyte (relative density (%) = pellet density × 100 / true density). A higher relative density means a higher packing ratio. Details of the method for measuring the relative density of a 400 MPa compact will be described in the Examples.

[0027] The ionic conductivity of the glass solid electrolyte of this embodiment can be 1 mS / cm or more, and can also be 1.1 mS / cm or more.

[0028] The glass solid electrolyte of this embodiment can be produced, for example, by mixing starting materials for known lithium ion sulfide solid electrolytes so that the molar ratios of the constituent elements satisfy a predetermined range, and vitrifying the mixture.

[0029] As the starting material, a combination of two or more compounds or simple substances containing lithium, phosphorus, sulfur, and halogen as constituent elements can be used, and any starting material can be used without particular limitation as long as it exhibits ionic conductivity due to the metal atoms contained therein.

[0030] Examples of raw materials containing lithium (Li) include lithium sulfide (Li ２S), lithium oxide (Li ２ O), lithium carbonate (Li ２ CO ３ Among these, lithium compounds are preferred, and lithium sulfide is more preferred.

[0031] The lithium sulfide can be used without any particular limitation, but high purity lithium sulfide is preferred. Lithium sulfide can be produced by the methods described in, for example, JP-A-7-330312, JP-A-9-283156, JP-A-2010-163356, and JP-A-2011-84438.

[0032] Specifically, lithium hydroxide and hydrogen sulfide are reacted in a hydrocarbon organic solvent at 70°C to 300°C to produce lithium hydrosulfide, and then this reaction solution is dehydrosulfided, thereby synthesizing lithium sulfide (JP 2010-163356 A).

[0033] Alternatively, lithium sulfide can be synthesized by reacting lithium hydroxide with hydrogen sulfide in an aqueous solvent at 10°C to 100°C to produce lithium hydrosulfide, and then dehydrosulfiding the reaction solution (JP 2011-84438 A).

[0034] Examples of raw materials containing phosphorus (P) include diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ) and other phosphorus sulfides, sodium phosphate (Na ３ P.O. ４ Among these, phosphorus sulfide is preferred, and diphosphorus pentasulfide (P ２ S ５ ) is more preferred. ２ S ５ The phosphorus compounds such as ammonium nitrate, ...

[0035] The raw material containing halogen (X) as a constituent element preferably contains, for example, a halogen compound represented by the following formula:

[0036] M ｌ -X ｍ In the formula, M represents sodium (Na), lithium (Li), boron (B), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), germanium (Ge), arsenic (As), selenium (Se), tin (Sn), antimony (Sb), tellurium (Te), lead (Pb), bismuth (Bi), or any of these elements bonded to an oxygen element or a sulfur element, and is preferably lithium (Li) or phosphorus (P), and more preferably lithium (Li).

[0037] X is a halogen element selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0038] Furthermore, l is an integer of 1 or 2, and m is an integer of 1 to 10. When m is an integer of 2 to 10, that is, when there are multiple Xs, the Xs may be the same or different. For example, in the case of SiBrCl ３ In the formula, m is 4 and X is composed of two different elements, Br and Cl.

[0039] Specific examples of halogen compounds include sodium halides such as NaI, NaF, NaCl, and NaBr; lithium halides such as LiF, LiCl, LiBr, and LiI; and BCl. ３ , BBr ３ , B.I. ３ Boron halides such as AlF ３ , AlBr ３ , AlI ３ , AlCl ３ aluminum halides such as SiF ４ , SiCl ４ , SiCl ３ , Si ２ Cl ６ , SiBr ４ , SiBrCl ３ , SiBr ２ Cl ２ , SiI ４ Silicon halides such as PF ３ , P.F. ５ , PCl ３ , PCl ５ , POCl ３ , PBr３ , POBr ３ , P.I. ３ , P ２ Cl ４ , P ２ I ４ Phosphorus halides such as SF ２ , SF ４ , SF ６ , S ２ F １０ , SC1 ２ , S ２ Cl ２ , S ２ Br ２ sulfur halides such as GeF ４ , GeCl ４ , GeBr ４ , GeI ４ , GeF ２ , GeCl ２ , GeBr ２ , GeI ２ Germanium halides such as AsF ３ , AsCl ３ , AsBr ３ , AsI ３ , AsF ５ arsenic halides such as SeF ４ , SeF ６ , SeCl ２ , SeCl ４ , Se ２ Br ２ , SeBr ４ selenium halides such as SnF ４ , SnCl ４ , SnBr ４ , SnI ４ , SnF ２ , SnCl ２ , SnBr ２ , SnI ２ tin halides such as SbF ３ , SbCl ３ , SbBr ３ , SbI ３ , SbF ５ , SbCl ５ antimony halides such as TeF ４ , Te ２ F １０ , TeF ６ , TeCl ２, TeCl ４ , TeBr ２ , TeBr ４ , TeI ４ Tellurium halides such as PbF ４ , PbCl ４ , PbF ２ , PbCl ２ , PbBr ２ , PbI ２ Lead halides such as BiF ３ , BiCl ３ , BiBr ３ , BiI ３ and the like.

[0040] Among these, lithium halides such as lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), phosphorus pentachloride (PCl), ５ ), phosphorus trichloride (PCl ３ ), phosphorus pentabromide (PBr ５ ), phosphorus tribromide (PBr ３ Among them, lithium halides such as LiCl, LiBr, and LiI, PBr ３ is preferred, and lithium halides such as LiCl, LiBr, and LiI are more preferred, with LiI and LiBr being more preferred.

[0041] The halogen compound may be one of the above compounds alone or a combination of two or more of them, i.e., at least one of the above compounds can be used.

[0042] In this embodiment, the raw material contains a lithium compound, a phosphorus compound, and a halogen compound containing at least bromine, and at least one of the lithium compound and the phosphorus compound preferably contains elemental sulfur. A combination of lithium sulfide, phosphorus sulfide, and two or more lithium halides is more preferable, and a combination of lithium sulfide, diphosphorus pentasulfide, and two or more lithium halides is even more preferable.

[0043] For example, when lithium sulfide, diphosphorus pentasulfide, and two or more lithium halides are used as raw materials for the glass solid electrolyte, the molar ratio of lithium sulfide to diphosphorus pentasulfide in the input raw materials is preferably 65 to 85:15 to 35, more preferably 70 to 80:20 to 30, still more preferably 72 to 78:22 to 28, and particularly preferably 75:25.

[0044] In addition, Li calculated from the constituent elements Li, P, and S of lithium sulfide and diphosphorus pentasulfide ３ P.S. ４ When the amount of the substance is taken as 100 parts by mol, the amount of lithium halide is preferably 75 to 250 parts by mol, more preferably 80 to 225 parts by mol, and may also be 85 to 200 parts by mol, 90 to 175 parts by mol, or 95 to 150 parts by mol.

[0045] In this embodiment, the raw materials are subjected to a mechanical stress to cause a reaction and produce a glass solid electrolyte. Here, "applying a mechanical stress" refers to mechanically applying a shear force, an impact force, or the like. Examples of means for applying the mechanical stress include a pulverizer such as a planetary ball mill, a vibration mill, or a tumbling mill, and a kneader. The raw material powder is pulverized and mixed by applying a strong mechanical stress until at least a portion of the raw material powder can no longer maintain its crystallinity.

[0046] As for the conditions for grinding and mixing, for example, when a planetary ball mill is used as the grinder, the rotation speed may be set to several tens to several hundreds of revolutions per minute, and the processing time may be 0.5 to 100 hours. More specifically, in the case of the planetary ball mill (manufactured by Fritsch: Model No. P-5) used in the examples of the present application, the rotation speed of the planetary ball mill is preferably 100 rpm to 400 rpm, more preferably 150 rpm to 300 rpm. The temperature during grinding may be room temperature, in which case external cooling may not be performed, and for example, a 5-minute operation pause may be provided every hour. Note that, as long as the conditions are such that crystallization does not occur during grinding, grinding may be performed while cooling without an operation pause. For example, when zirconia balls are used as grinding media, the diameter of the balls is preferably 0.2 to 20 mm.

[0047] The glass solid electrolyte of this embodiment has a packing density equal to or higher than that of conventional glass solid electrolytes and high ionic conductivity, and is therefore suitable for use in batteries. It is particularly suitable when lithium element is used as the conductive species. The glass solid electrolyte of this embodiment may be used in a positive electrode layer, a negative electrode layer, or an electrolyte layer.

[0048] A lithium ion battery according to one embodiment of the present invention includes the glass solid electrolyte of the present invention described above. For example, by using the glass solid electrolyte of the present invention in place of a liquid electrolyte, an all-solid-state lithium ion battery can be produced.

[0049] All-solid-state lithium-ion batteries are primarily composed of a positive electrode layer, a negative electrode layer, and an electrolyte layer, and the glass solid electrolyte of the present invention can be used in any of them. Each layer can be manufactured by a known method. For example, when used in the positive electrode layer and the negative electrode layer, a positive electrode active material or a negative electrode active material is mixed and dispersed in the glass solid electrolyte of the present invention to obtain a positive electrode composite or a negative electrode composite. The positive electrode active material can be any material that can promote the battery chemical reaction involving the migration of lithium ions due to the lithium element, which is preferably used in this embodiment as an element that exhibits ionic conductivity, in relation to the negative electrode active material, without particular limitation. Examples of such positive electrode active materials capable of inserting and extracting lithium ions include oxide-based positive electrode active materials and sulfide-based positive electrode active materials.

[0050] Examples of oxide-based positive electrode active materials include LMO (lithium manganese oxide), LCO (lithium cobalt oxide), NMC (lithium nickel manganese cobalt oxide), NCA (lithium nickel cobalt aluminate), LNCO (lithium nickel cobalt oxide), and olivine-type compounds (LiMeNPO ４ , Me=Fe, Co, Ni, Mn) and the like.

[0051] As a sulfide-based positive electrode active material, titanium sulfide (TiS ２ ), molybdenum sulfide (MoS ２ ), iron sulfide (FeS, FeS ２ ), copper sulfide (CuS), nickel sulfide (Ni ３S ２ In addition to the above positive electrode active materials, niobium selenide (NbSe) ３ In this embodiment, the positive electrode active material can be used alone or in combination of two or more types.

[0052] The negative electrode active material can be any material that can promote a battery chemical reaction involving the movement of lithium ions, such as an element that is preferably used in this embodiment as an element that exhibits ionic conductivity, preferably a metal that can form an alloy with lithium, an oxide thereof, an alloy of the metal with lithium, etc. As such a negative electrode active material that can insert and extract lithium ions, any material known in the battery field as a negative electrode active material can be used without any limitation.

[0053] Examples of such negative electrode active materials include metallic lithium, metallic indium, metallic aluminum, metallic silicon, metallic tin, and other metallic lithium or metals capable of forming alloys with metallic lithium, oxides of these metals, and alloys of these metals with metallic lithium.

[0054] The electrode active material used in this embodiment may have a coating layer on its surface. Examples of materials for forming the coating layer include elements that exhibit ionic conductivity in the crystalline sulfide solid electrolyte used in this embodiment, preferably ion conductors such as nitrides, oxides, or composites of lithium element. Specifically, lithium nitride (Li ３ N), Li ４ GeO ４ The main structure is, for example, Li ４－２ｘ Zn ｘ GeO ４ Conductors having a lysicone-type crystal structure such as Li ３ P.O. ４ For example, Li ４－ｘ Ge １－ｘ P ｘ S ４ Conductors having a thiolicon-type crystal structure such as La ２／３－ｘ Li ３ｘ TiO３ Conductors having a perovskite crystal structure such as LiTi ２ (P.O. ４ ) ３ Examples of such conductors include those having a NASICON type crystal structure.

[0055] Also, Li ｙ Ti ３－ｙ O ４ (0<y<3), Li ４ Ti ５ O １２ Lithium titanate (LTO), LiNbO ３ , LiTaO ３ Lithium metal oxides of metals belonging to Group 5 of the periodic table, such as Li ２ Alumni ２ O ３ -P ２ O ５ system, Li ２ Alumni ２ O ３ -ZnO-based, Li ２ O-Al ２ O ３ -SiO ２ -P ２ O ５ -TiO ２ Examples of suitable conductors include oxide-based conductors such as those based on ZnO.

[0056] An electrode active material having a coating layer can be obtained, for example, by applying a solution containing various elements constituting the material forming the coating layer to the surface of the electrode active material, and then firing the electrode active material after application at a temperature preferably of 200°C or higher and 400°C or lower.

[0057] Here, the solution containing various elements may be a solution containing alkoxides of various metals such as lithium ethoxide, titanium isopropoxide, niobium isopropoxide, or tantalum isopropoxide. In this case, the solvent may be an alcoholic solvent such as ethanol or butanol, an aliphatic hydrocarbon solvent such as hexane, heptane, or octane, or an aromatic hydrocarbon solvent such as benzene, toluene, or xylene. The deposition may be performed by immersion, spray coating, or the like.

[0058] From the viewpoint of improving production efficiency and battery performance, the firing temperature is preferably 200°C or higher and 400°C or lower, more preferably 250°C or higher and 390°C or lower, and the firing time is usually about 1 minute to 10 hours, preferably 10 minutes to 4 hours.

[0059] The coverage of the coating layer is preferably 90% or more, more preferably 95% or more, and even more preferably 100% of the surface area of ​​the electrode active material, i.e., the entire surface is covered. The thickness of the coating layer is preferably 1 nm or more, more preferably 2 nm or more, and the upper limit is preferably 30 nm or less, more preferably 25 nm or less.

[0060] The thickness of the coating layer can be measured by cross-sectional observation using a transmission electron microscope (TEM), and the coverage can be calculated from the thickness of the coating layer, the elemental analysis value, and the BET surface area.

[0061] The battery preferably includes a current collector in addition to the positive electrode layer, electrolyte layer, and negative electrode layer, and a known current collector can be used, such as a layer of Au, Pt, Al, Ti, or Cu, which reacts with the glass solid electrolyte, coated with Au or the like.

[0062] The present invention will be specifically described below based on examples. The embodiments of the present invention are not limited to the examples. The glass solid electrolytes produced in each example were evaluated as follows. (1) Powder X-ray diffraction (XRD) measurement The powder of the glass solid electrolyte produced in each example was filled into a groove 20 mm in diameter and 0.2 mm deep by leveling it with glass. The filled sample was measured using a Kapton film for XRD without exposing it to air. The 2θ position of the diffraction peak was determined by Le Bail analysis using the XRD analysis program RIETAN-FP. Powder X-ray diffraction measurement was carried out under the following conditions. Equipment used: BRUKER "D2 PHASER" Tube voltage: 30 kV Tube current: 10 mA X-ray wavelength: Cu-Kα radiation (1.5418 Å) Optical system: focusing method Slit configuration: Soller slit 4°, divergence slit 1 mm, Kβ filter (Ni plate) used Detector: semiconductor detector Measurement range: 2θ=10-60° (deg) Step width, scan speed: 0.05°, 0.05° / sec In analyzing the peak positions to confirm the presence of a crystalline structure from the measurement results, the XRD analysis program RIETAN-FP was used, and the baseline was corrected using an 11th-order Legendre orthogonal polynomial to determine the peak positions.

[0063] (2) Peak Half Width The peak half width was calculated for the peak at 2θ = 25.5 ± 1 ° in the case of LiI, and for LiBr, it was calculated for the peak at 2θ = 28 ± 1 °. In the range where the above-mentioned peaks exist (2θ = 24.5 to 26.5 ° or 2θ = 27 to 29 °), the difference between the measured intensity (vertical axis value of the XRD pattern) and the calculated value below was minimized. The half width parameter E was determined so that the difference between the measured intensity and the calculated value below was minimized. The ratio of the Lorentz function is A (0 ≦ A ≦ 1), the intensity correction value is B, the 2θ angle at which the intensity is maximum is C, the angle (2θ) of the calculated intensity is D, the half width parameter is E, the background is F, the measured intensity at the angle (2θ) of the calculated intensity is G, and the variables are A, B, C, E, and F. For each angle (2θ) at which the intensity was measured, the deviation H between the measured intensity and the calculated intensity was calculated using the following formula (3). H=G-{B×{A / (1+(D-C) ２ / E ２)+(1-A)×exp(-1×(D-C) ２ / E ２ ) + F (3)

[0064] The above variables were determined by summing H in the range of 2θ = 24.5 to 26.5° or 2θ = 27 to 29° and minimizing the sum of H with GRG nonlinearity using the solver function of spreadsheet software (Excel, Microsoft). The half-width parameter E thus obtained was used to calculate the half-width using the following equation (4): Half-width = E × 2 × (ln4) （１／２） (4) When the peak intensity is calculated to be zero, it is also impossible to calculate the half-width parameter. Therefore, in this case, no peak is present, i.e., no peak derived from LiI or LiBr is shown, and it can be considered that no crystallites are present.

[0065] (3) Crystallite size The half-width calculated by the above method was designated as b. In order to correct the broadening of the half-width due to the instrument, the half-width was corrected using NIST standard Si (640d, crystallite size 525 nm). The corrected half-width due to the instrument was designated as B. ｃｏｒｒｅｃｔ Then, the corrected half-width β for calculating the crystallite size can be expressed by the following formula (5): β = b - B ｃｏｒｒｅｃｔ (5) The actual crystallite size L can be calculated using the following formula (6): L = K × λ / (β cos(C / 2)) (6) where the constant K is 0.9, and λ is the wavelength of the X-rays used in the measurement. Note that C is 2θ at the center of the maximum peak position when the peak half width is calculated above.

[0066] (4) Relative Density of 400 MPa Compacted Powder (Measurement of True Density) The true density was measured by a gas-phase substitution method using He gas (BELMAX manufactured by Microtrackbell Co., Ltd.). The internal volume of the cell was calculated when the He gas pressure was set to 55 KPa, 60 KPa, 65 KPa, 70 KPa, 75 KPa, 80 KPa, 85 KPa, 90 KPa, 95 KPa, 100 KPa, 105 KPa, and 110 KPa, and the average value was used as the internal volume of the cell. The cell weight was calculated using an electronic balance. The volume and weight of a blank cell were measured three times using the above method, and the average value was used as the empty cell volume V １ The weight is the empty cell weight W１ The volume of the gas phase of the cell when the glass solid electrolyte was introduced into the cell and the total weight of the cell were measured three times by the above method, and the average value was taken as the volume V excluding the sample. ２ The total weight of the cell is W ２ The true density d (g / cm ３ ) was calculated using the following formula (7): d = (W ２ -W １ ) / (V １ -V ２ ) (7) The true density of the sample was the average value of the true densities d calculated three times using the above procedure and formula. The standard deviation of the true density calculated by this method was 0.05 g / cm ３ The following is the result.

[0067] (Measurement of pellet density) A schematic diagram of a pellet density measurement device is shown in Figure 1. A sample 10 was filled into a cylindrical jig 11 (manufactured by Macol (registered trademark)) and pressurized at 400 MPa by a single-axis press via a stainless steel piston 12. The length L of the device when no sample was filled (blank) was ｉｎｔ and the length L of the device containing the sample after pressure application. ａｆｔｅｒ From the difference between the height of the sample (pellet), the pellet density d ｐｅｌｌｅｔ Specifically, the diameter of the sample before insertion was 10 mm (cross-sectional area S ｐｅｌｌｅｔ : 0.785 cm ２ The piston 12 was inserted into the cylindrical jig 11. The cylindrical jig 11 was rotated 90° in a direction perpendicular to the pressure direction, and measurements were taken four times. The average value was taken as L ｉｎｔ (cm). At that time, a torque wrench was used to tighten the screw 13 and nut 14 to 8 N·m, and the measurement was performed while applying pressure to the piston 12. Next, 0.3 g of glass solid electrolyte powder, which was the sample, was weighed on an electronic balance and placed in the cylindrical jig 11. After placement, the sample was pressure-molded by applying pressure to the piston 12 using a single-axis press. The pressure was set to 185 MPa and maintained for 2 minutes, after which the pressure was released. The cell was rotated 120° vertically from the pressure application direction and pressed in the same manner. Thereafter, it was rotated 120° again and pressed in the same manner. Next, the pressure was set to 400 MPa, and the sample was pressurized in the same manner as in the case of 185 MPa. After molding, Lｉｎｔ The same measurement was carried out four times, and the average value was calculated as L ａｆｔｅｒ (cm). Pellet density d ｐｅｌｌｅｔ was calculated using the following formula (8): ｐｅｌｌｅｔ = 0.3 / {(L ａｆｔｅｒ -L ｉｎｔ ) x S ｐｅｌｌｅｔ (8)

[0068] (Calculation of relative density) Calculation was performed using the following formula (9): relative density (%) = pellet density × 100 / true density (9)

[0069] (5) Ion Conductivity From the glass solid electrolyte produced in each example, a 10 mm diameter (cross-sectional area S: 0.785 cm ２ ), and a height (L) of 0.1 to 0.3 cm were molded into a circular pellet to prepare a sample. Electrode terminals were attached to the top and bottom of the sample, and measurements were made at 25°C using an AC impedance method (frequency range: 5 MHz to 0.5 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. The real part Z' (Ω) at the point where -Z'' (Ω) is minimum near the right end of the arc observed in the high-frequency region was taken as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S / cm) was calculated according to the following formula: R = ρ (L / S) σ = 1 / ρ

[0070] (6) ICP Measurement The solid electrolyte powder produced in each example was weighed and collected in a vial in an argon atmosphere. An alkaline KOH solution was placed in the vial, and the sample was dissolved, taking care not to capture sulfur, and then diluted appropriately to obtain a measurement solution. This was measured using a Paschen-Runge type ICP-OES device (SPECTRO ARCOS, manufactured by SPECTRO) to determine the composition. Calibration curve solutions were prepared using 1000 mg / L standard solutions for ICP measurement for Li, P, and S, and 1000 mg / L standard solutions for ion chromatography for Cl and Br. Two measurement solutions were prepared for each sample, and five measurements were performed with each measurement solution, and the average value was calculated. The composition was determined by averaging the measured values ​​of the two measurement solutions.

[0071] Example 1 [Preparation of Glass Solid Electrolyte] (1) Preparation of Glass Solid Electrolyte 2.366 g of lithium sulfide, 3.815 g of diphosphorus pentasulfide, 3.446 g of lithium iodide, and 0.373 g of lithium bromide were weighed out, and 600 g of zirconia balls with a diameter of 10 mm were placed in a 500 mL zirconia pot and sealed. Table 1 shows the molar ratios of the starting materials. Using a planetary ball mill (manufactured by Fritsch, model number P-5), the mixture was milled (mechanical milled) at room temperature for 40 hours at a rotation speed of 220 rpm to obtain a glass solid electrolyte. Table 1 shows the raw material composition ratio, the molar ratio of each element relative to phosphorus (P), and the evaluation results.

[0072] Examples 2 to 19 and Comparative Examples 1 to 10 Glass solid electrolytes were prepared in the same manner as in Example 1, except that the raw material composition ratios were changed as shown in Table 1. The evaluation results are shown in Table 1. ３ P.S. ４ The amount of the substance was set to 100 molar parts, which is the starting material Li ２ S ４ 150 mol parts and P ２ S ５ corresponds to 50 molar parts. For Examples 7, 14, and 16 and Comparative Examples 1 and 7, the molar ratio (X / P) of each element relative to phosphorus (P) in the glass solid electrolyte was measured by ICP. The results are shown below. Example 7: Li / P = 4.4, S / P = 3.9, Br / P = 0.25, I / P = 1.26 Example 14: Li / P = 3.9, S / P = 3.9, Br / P = 0.53, I / P = 0.52 Example 16: Li / P = 4.0, S / P = 4.0, Br / P = 1.05 Comparative Example 1: Li / P = 3.0, S / P = 4.0 Comparative Example 7: Li / P = 4.4, S / P = 4.0, I / P = 1.52

[0073]

[0074] FIG. 2 shows the X-ray diffraction patterns of the glass solid electrolytes produced in Examples 1 to 4. FIG. 3 shows the X-ray diffraction patterns of the glass solid electrolytes produced in Examples 5 to 8. FIG. 4 shows the X-ray diffraction patterns of the glass solid electrolytes produced in Examples 9 to 13. FIG. 5 shows the X-ray diffraction patterns of the glass solid electrolytes produced in Examples 14 and 15. FIG. 6 shows the X-ray diffraction patterns of the glass solid electrolytes produced in Examples 16 to 18. FIG. 7 shows the X-ray diffraction pattern of the glass solid electrolyte produced in Example 19. FIG. 8 shows the X-ray diffraction patterns of the glass solid electrolytes produced in Comparative Examples 1 to 8. FIG. 9 shows the X-ray diffraction patterns of the glass solid electrolytes produced in Comparative Examples 9 and 10. The XRD measurement results confirmed that the glass solid electrolytes produced in Examples 1 to 19 were amorphous and that the lithium halide raw material was present in a partially crystallized state.

[0075] The glass solid electrolyte of the present invention is suitable as a structural material for lithium ion batteries, and the lithium ion batteries of the present invention are suitable for use in, for example, information-related devices and communication devices such as personal computers, video cameras, and mobile phones, and vehicles such as electric vehicles.

[0076] Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art will readily be able to make numerous modifications to these exemplary embodiments and / or examples without substantially departing from the novel teachings and advantages of the present invention. Accordingly, these numerous modifications are within the scope of the present invention. The contents of all documents cited in this specification and of the applications from which this application claims priority under the Paris Convention are incorporated by reference in their entirety.

Claims

1. containing lithium, phosphorus, sulfur, and halogens including at least bromine as constituent elements; a molar ratio (Li / P) of the lithium (Li) to the phosphorus (P) is 2.0 to 5.3; a molar ratio (S / P) of the sulfur (S) to the phosphorus (P) is 2.0 to 4.5; a molar ratio (X / P) of the halogen (X) to the phosphorus (P) is 0.7 to 2.3; A glass solid electrolyte that exhibits a peak derived from lithium bromide in powder X-ray diffraction using CuKα radiation.

2. 2. The glass solid electrolyte according to claim 1, wherein the crystallite size calculated from the half-width of the peak having the maximum intensity among the peaks derived from lithium bromide is 3 to 60 nm.

3. the halogen comprises iodine; 2. The glass solid electrolyte according to claim 1, which exhibits a peak attributable to lithium iodide in powder X-ray diffraction using CuKα radiation.

4. 4. The glass solid electrolyte according to claim 3, wherein the crystallite size calculated from the half-width of the peak having the maximum intensity among the peaks derived from lithium iodide is 3 to 60 nm.

5. 2. The glass solid electrolyte according to claim 1, wherein a relative density of a 400 MPa compact is 90% or more.

6. True density is 2.0 to 3.0 g / cm ３ 2. The glass solid electrolyte according to claim 1, wherein

7. 2. The glass solid electrolyte according to claim 1, wherein the molar ratio (X / P) is greater than 0.

75.

8. 2. The glass solid electrolyte according to claim 1, wherein the molar ratio (X / P) is greater than 0.

86.

9. the halogen comprises iodine; a molar ratio (I / P) of the iodine (I) to the phosphorus (P) is 2.0 or less; 2. The glass solid electrolyte according to claim 1, wherein a molar ratio (Br / P) of said bromine (Br) to said phosphorus (P) is 0.01 to 1.

5.

10. 2. The glass solid electrolyte according to claim 1, having an ionic conductivity of 1 mS / cm or more.

11. A lithium ion battery comprising the glass solid electrolyte according to any one of claims 1 to 10.

12. A combination of two or more compounds or simple substances containing lithium, phosphorus, sulfur, and halogens including at least bromine as constituent elements, A method for producing a glass solid electrolyte, comprising vitrifying a mixture prepared so that a molar ratio (Li / P) of the lithium (Li) to the phosphorus (P) is 2.0 to 5.3, a molar ratio (S / P) of the sulfur (S) to the phosphorus (P) is 2.0 to 4.5, and a molar ratio (X / P) of the halogen (X) to the phosphorus (P) is 0.7 to 2.3.