Glass-ceramics solid electrolyte and lithium-ion battery

Abstract

This glass-ceramics solid electrolyte includes lithium, phosphorus, sulfur, and halogen as constituent elements. The molar ratio (Li / P) of lithium (Li) to phosphorus (P) is 2.0 to 5.3, the molar ratio (S / P) of sulfur (S) to phosphorus (P) is 2.0 to 4.5, and the molar ratio (X / P) of halogen (X) to phosphorus (P) is 0.1 to 2.3. A powder X-ray diffraction analysis using CuKα ray performed on the electrolyte reveals that there is peak A at 2θ = 20±1° position and the powder X-ray diffraction analysis reveals that there is no peak B at 2θ = 23.6±1° position. If there is peak B, the peak intensity ratio (IB / IA) of peak intensity (IB) of peak B to peak intensity (IA) of peak A is less than 0.050. The crystallite size of the electrolyte is 5 nm to 20 nm.

Description

Glass-ceramic solid electrolytes and lithium-ion batteries

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

[0002] With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as power sources for these devices has become important. Among these batteries, lithium-ion batteries have attracted attention due to their high energy density.

[0003] Currently commercially available lithium-ion batteries use an electrolyte containing a flammable organic solvent, which requires the installation of a safety device to suppress temperature rise during a short circuit and improvements in structure and materials to prevent short circuits. In contrast, lithium-ion batteries that use a solid electrolyte to create an all-solid-state battery do not use a flammable organic solvent within the battery, which simplifies the safety device and is thought to be superior in terms of manufacturing cost and productivity. A sulfide solid electrolyte is known as a solid electrolyte used in lithium-ion batteries (see, for example, Patent Document 1).

[0004] To improve the performance of lithium-ion batteries, it is important to increase the packing density (compactibility) of the solid electrolyte powder. To improve the packing density, it is effective to make the solid electrolyte mechanically soft (to make it more easily compressible).

[0005] In the lithium ion conductive sulfide solid electrolyte, Li ３ P.S. ４ Glass is known to have a high filling factor. ３ P.S. ４ The glass had a low ionic conductivity of less than 1 mS / cm.

[0006] Special table 2019-506699 publication

[0007] An object of the present invention is to provide a glass-ceramic solid electrolyte having a high packing ratio and high ionic conductivity.

[0008] According to the present invention, the following glass-ceramic solid electrolytes and the like are provided: 1. A glass-ceramic solid electrolyte containing lithium, phosphorus, sulfur, and a halogen 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 0.1 to 2.3, and in powder X-ray diffraction using CuKα radiation, there is a peak A at 2θ=20±1°, and in the powder X-ray diffraction, there is no peak B at 2θ=23.6±1°, or if there is a peak B, the peak intensity (I Ｂ ) and the peak intensity of peak A (I Ａ ) peak intensity ratio (I Ｂ / I Ａ 1. A glass-ceramic solid electrolyte having a peak intensity ratio (I ) of less than 0.050 and a crystallite size of 5 to 20 nm. Ｂ / I Ａ 2. The glass-ceramic solid electrolyte according to claim 1, wherein the value of (a) is 0. 3. The glass-ceramic solid electrolyte according to claim 1 or 2, which exhibits a peak derived from lithium halide in powder X-ray diffraction using CuKα radiation. 4. The glass-ceramic solid electrolyte according to claim 3, wherein the crystallite size of lithium halide calculated from the peak with the maximum intensity among the peaks derived from lithium halide is 5 to 100 nm. 5. The glass-ceramic solid electrolyte according to any one of claims 1 to 4, wherein a 400 MPa compact has a relative density of 90% or more. 6. A true density of 2.0 to 3.0 g / cm ３7. The glass-ceramic solid electrolyte according to any one of 1 to 5, wherein the molar ratio (X / P) is greater than 0.86. 8. The glass-ceramic solid electrolyte according to any one of 1 to 7, wherein the glass-ceramic solid electrolyte comprises two or more of the halogens. 9. The glass-ceramic solid electrolyte according to 8, wherein the halogens comprise iodine and bromine. 10. The glass-ceramic solid electrolyte according to 9, wherein the molar ratio (I / P) of the iodine (I) to the phosphorus (P) is 0.0<(I / P)<1.8, and the molar ratio (Br / P) of the bromine (Br) to the phosphorus (P) is 0.0<(Br / P)<1.5. 11. The glass-ceramic solid electrolyte according to any one of 1 to 10, wherein the ionic conductivity is 1 mS / cm or more. 12. A lithium-ion battery comprising the glass-ceramic solid electrolyte according to any one of 1 to 11.

[0009] According to the present invention, it is possible to provide a glass-ceramic solid electrolyte having a high packing ratio and high ionic conductivity.

[0010] FIG. 1 is a schematic diagram illustrating a pellet density measuring device. FIG. 2 is an X-ray diffraction pattern of the glass ceramic solid electrolytes produced in Examples 1 to 4. FIG. 3 is an X-ray diffraction pattern of the glass ceramic solid electrolytes produced in Examples 5 to 8. FIG. 4 is an X-ray diffraction pattern of the glass ceramic solid electrolytes produced in Examples 9 to 12. FIG. 5 is an X-ray diffraction pattern of the glass ceramic solid electrolytes produced in Examples 13 to 16. FIG. 6 is an X-ray diffraction pattern of the glass ceramic solid electrolytes produced in Examples 17 to 21. FIG. 7 is an X-ray diffraction pattern of the glass ceramic solid electrolytes produced in Comparative Examples 1 to 5. FIG. 8 is an X-ray diffraction pattern of the glass ceramic solid electrolytes produced in Comparative Examples 6 to 11.

[0011] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") 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 numerical values ​​in the examples can also be used as the upper and lower limit values.

[0012] A glass-ceramic solid electrolyte according to one embodiment of the present invention contains lithium, phosphorus, sulfur, and a halogen 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 = 0.1 to 2.3.

[0013] Furthermore, the glass ceramic solid electrolyte of this embodiment satisfies the following requirements A to C. A. In powder X-ray diffraction using CuKα rays, peak A is present at 2θ=20±1°. B. In powder X-ray diffraction, peak B is absent at 2θ=23.6±1°, or if peak B is present, the peak intensity (I Ｂ ) and the peak intensity of peak A (I Ａ ) peak intensity ratio (I Ｂ / I Ａ C. The crystallite size of the glass-ceramic solid electrolyte calculated from Peak A by Scherrer's formula is 5 to 20 nm.

[0014] The glass ceramic solid electrolyte of the embodiment of the present invention satisfies the above-mentioned composition and diffraction peak conditions, and therefore has a packing factor equal to or higher than that of conventional glass solid electrolytes, and high ionic conductivity.

[0015] In the present application, a glass-ceramic solid electrolyte refers to a solid electrolyte in which a peak derived from the solid electrolyte is observed in the X-ray diffraction pattern in powder X-ray diffraction (XRD) measurement, regardless of whether or not a peak derived from the raw material of the solid electrolyte is present. That is, a glass-ceramic solid electrolyte includes a crystalline structure derived from the solid electrolyte, and a portion of the crystalline structure may be derived from the solid electrolyte, or the entire crystalline structure may be derived from the solid electrolyte. Furthermore, as long as the glass-ceramic solid electrolyte has the X-ray diffraction pattern described above, it may also contain an amorphous component (also referred to as a "glass component") in part. Note that crystalline solid electrolytes include so-called glass ceramics obtained by heating an amorphous solid electrolyte (glass component) above its crystallization temperature.

[0016] In the glass-ceramic solid electrolyte of this 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. 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. The molar ratio of halogen (X) to phosphorus (P) (X / P) is preferably greater than 0.75, more preferably greater than 0.86.

[0017] In the glass-ceramic solid electrolyte of this embodiment, the halogen (X) preferably contains one or more selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), and more preferably contains Br or I. The halogen (X) also preferably contains bromine (Br) and iodine (I). It is preferable that the molar ratio (I / P) of iodine (I) to phosphorus (P) is 0.0 to 1.8, and the molar ratio (Br / P) of bromine (Br) to phosphorus (P) is 0.0 to 1.5.

[0018] The types and molar ratios of the constituent elements of the glass-ceramic solid electrolyte can be confirmed, for example, by an ICP atomic emission spectrometer. The molar ratios of the constituent elements of the glass-ceramic solid electrolyte can be adjusted by controlling the blending of raw materials. The molar ratios of the constituent elements in the raw materials are approximately equal to the molar ratios of the constituent elements of the resulting glass-ceramic solid electrolyte.

[0019] In the glass-ceramic solid electrolyte of this embodiment, the molar ratio (Li / P) of lithium (Li) to phosphorus (P) and the molar ratio (X / P) of halogen (X) to phosphorus (P) preferably satisfy the following relational formula (1): Li / P=3±α+X / P (1) (where α is 0 to 0.5).

[0020] By satisfying formula (1), the main skeleton of the glass ceramic 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, P２ 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-ceramic solid electrolyte. α in formula (1) may be 0 to 0.3, 0 to 0.1, or 0.

[0021] In powder X-ray diffraction measurement using CuKα radiation, the glass-ceramic solid electrolyte of this embodiment has a peak A at 2θ = 20 ± 1°, and the crystallite size of the glass-ceramic solid electrolyte calculated from peak A is 1 to 20 nm. The crystallite size of the glass-ceramic solid electrolyte calculated from peak A is preferably 2 to 18 nm. A small crystallite size allows the glass-ceramic solid electrolyte to be compressed without breaking the crystallites. Furthermore, a crystallite size that is not too small allows the ionic conductivity of the glass-ceramic solid electrolyte to be maintained at a high level. As a result, the glass-ceramic solid electrolyte of this embodiment can achieve both a high packing factor and high ionic conductivity.

[0022] 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. As the crystallite size increases, the crystallinity increases and the repeating regularity of the crystal structure increases, so the intensity of the diffraction peak in powder X-ray diffraction measurement increases and the half-width narrows. Details of the measurement method are shown in the examples.

[0023] In addition, in the powder X-ray diffraction measurement, there is no peak B at 2θ=23.6±1°, or if there is a peak B, the peak intensity (I Ｂ ) and the peak intensity of peak A (I Ａ ) peak intensity ratio (I Ｂ / I Ａ ) is less than 0.05. ４－ｘ Ge １－ｘ P ｘ S ４These are diffraction peaks of the thio-lisicon region II type crystal structure or a crystal structure similar to the thio-lisicon region II type.

[0024] In the glass ceramic solid electrolyte of this embodiment, the peak A is observed at a high intensity, but the peak B is not observed or is extremely weak in intensity. This embodiment has discovered that a glass ceramic solid electrolyte having such a peak has a packing factor equal to or higher than that of conventional glass ceramic solid electrolytes and high ionic conductivity. Ｂ / I Ａ is preferably 0.

[0025] In one embodiment, the glass-ceramic solid electrolyte exhibits a diffraction peak derived from lithium halide in powder X-ray diffraction measurement using CuKα radiation. The lithium halide observed in powder X-ray diffraction measurement of the glass-ceramic solid electrolyte has lower crystallinity than the lithium halide raw material. Because lithium halide itself is a soft material, even if the lithium halide has enough crystallinity to detect a lithium halide peak in powder X-ray diffraction measurement, it can be considered that there is almost no hardening effect on the glass-ceramic solid electrolyte of this embodiment. Furthermore, in the glass-ceramic solid electrolyte of this embodiment, the crystallite size calculated from the half-width of the peak with the maximum intensity among the diffraction peaks derived from lithium halide is preferably 5 to 100 nm, more preferably 10 to 90 nm.

[0026] The crystallite size can be adjusted by the composition and crystallization temperature. For example, the crystallite size can be adjusted by adjusting the molar ratio (Li / P) of lithium (Li) to phosphorus (P), the molar ratio (Br / X) of bromine (Br) to halogen (X), and the molar ratio (I / P) of iodine (I) to phosphorus (P). In addition, since the crystallite size increases by increasing the crystallization temperature, the crystallite size can also be adjusted by the crystallization temperature.

[0027] The peak half width is calculated from the XRD pattern. Details of the measurement and calculation methods are shown in the Examples. The peak half width is calculated, for example, as the diffraction peak intensity at 2θ = 45.0 ± 1° when the lithium halide is LiF, as the diffraction peak intensity at 2θ = 30.1 ± 1° when the lithium halide is LiCl, as the diffraction peak intensity at 2θ = 28 ± 1° when the lithium halide is LiBr, and as the diffraction peak intensity at 2θ = 25.5 ± 1° when the lithium halide is LiI. Note that the peak half width is calculated using the peak of the lithium halide type that contains the largest amount of halogen added as a raw material in the production of the glass-ceramic solid electrolyte. When the amounts of the two types of lithium halides are equal in molar ratio, the calculation is performed using the peak of the lithium halide with the largest peak intensity.

[0028] In one embodiment, the true density (g / cm 3 ) of the glass-ceramic solid electrolyte is ３ ) is 2.0 to 3.0 g / cm ３ The true density in the above range is preferably in accordance with the PS structure of the main skeleton of the glass ceramic solid electrolyte. ４ ３－ This means that the structure and total halogen content fall within a certain range, and the glass-ceramic solid electrolyte of this embodiment can achieve both high conductivity and high softness. The true density of the glass-ceramic solid electrolyte of this embodiment is 2.01 to 2.9 g / cm ３ More preferably, it is 2.02 to 2.8 g / cm ３ The true density of the glass-ceramic solid electrolyte can be measured, for example, by a gas-phase substitution method using He gas. A method for measuring the true density of the glass-ceramic solid electrolyte is shown in the Examples.

[0029] In the glass-ceramic solid electrolyte of this embodiment, the relative density of the glass-ceramic solid electrolyte when compacted under 400 MPa is preferably 90% or more. The relative density can be 90.5% or more, or even 91% or more. Typically, the relative density of a 400 MPa compact is 99% or less.

[0030] In this application, the relative density of a 400 MPa green compact is the ratio of the density of a glass-ceramic solid electrolyte compressed at 400 MPa (referred to as pellet density) to the true density of the glass-ceramic solid electrolyte (relative density = pellet density / true density). A higher relative density indicates a higher packing fraction. Details of the method for measuring the relative density of a 400 MPa green compact will be described in the Examples.

[0031] The ionic conductivity of the glass ceramic solid electrolyte of this embodiment can be 1 mS / cm or more, and can also be 1.5 mS / cm or more. A method for measuring ionic conductivity will be described in the Examples.

[0032] The glass ceramic solid electrolyte of the present embodiment can be produced, for example, by mixing and grinding starting materials of a known lithium ion sulfide solid electrolyte so that the molar ratios of the constituent elements satisfy a predetermined range, vitrifying the mixture, and further converting the mixture into a ceramic by heat treatment.

[0033] As the raw materials for the glass-ceramic solid electrolyte of this embodiment, two or more compounds or simple substances containing lithium, phosphorus, sulfur, and a halogen as constituent elements can be used in combination, and any of them can be used without any particular limitation as long as they exhibit ionic conductivity due to the contained metal atoms.

[0034] Examples of raw materials containing lithium (Li) include lithium sulfide (Li ２ S), lithium oxide (Li ２ O), lithium carbonate (Li ２ CO ３ Among these, lithium compounds are preferred, and lithium sulfide is more preferred.

[0035] 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.

[0036] 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).

[0037] 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).

[0038] 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, ...

[0039] The raw material containing halogen (X) preferably contains, for example, a halogen compound represented by the following formula: ｌ -X ｍ

[0040] 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).

[0041] X is a halogen element selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0042] 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.

[0043] Specific examples of the halogen compounds represented by the above formula 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 , PBr ３ , 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 , GeCl４ , 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.

[0044] 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.

[0045] 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.

[0046] In this embodiment, the raw material contains a lithium compound, a phosphorus compound, and one or more halogen compounds, 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.

[0047] For example, when lithium sulfide, diphosphorus pentasulfide, and two or more lithium halides are used as raw materials for the glass-ceramic solid electrolyte of the present invention, 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, even more preferably 72 to 78:22 to 28, and particularly preferably 75:25.

[0048] 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 10 to 250 parts by mol, more preferably 50 to 225 parts by mol, and may be 70 to 200 parts by mol.

[0049] In this embodiment, mechanical stress is applied to the raw materials to cause a reaction and produce an intermediate (glass-like powder). Here, "applying mechanical stress" means mechanically applying shear force, impact force, or the like. Examples of means for applying 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.

[0050] As for the conditions for pulverization and mixing, for example, when a planetary ball mill is used as the pulverizer, 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 number P-5) used in the examples of the present application, the rotation speed of the planetary ball mill is preferably 100 rpm or more and 400 rpm or less, and more preferably 150 rpm or more and 300 rpm or less. When zirconia balls are used as the pulverization media, for example, their diameter is preferably 0.2 to 20 mm. The temperature during pulverization is not particularly specified, but 200°C or less is preferred to prevent the solid electrolyte itself from crystallizing and hardening.

[0051] The intermediate produced by pulverization and mixing is subjected to a heat treatment. Specifically, the heating temperature of the intermediate is determined by subjecting the intermediate to simultaneous differential thermal and thermogravimetric analysis (TGDTA) at a temperature increase rate of 10°C / min using a TGDTA apparatus, and determining the peak top temperature (T ｃ１ ) as a starting point, the temperature is preferably 5°C or lower, more preferably 10°C or lower, and even more preferably 15°C or lower, and there is no particular restriction on the lower limit, but it may be about 10°C or higher than the peak top temperature of the exothermic peak observed at the lowest temperature side. By setting the temperature in this range, the glass-ceramic solid electrolyte of this embodiment can be obtained more efficiently.

[0052] The heating temperature for obtaining the glass-ceramic solid electrolyte of this embodiment cannot be generally defined, but is usually preferably 250°C or lower, more preferably 225°C or lower, and even more preferably 200°C or lower. There is no particular lower limit, but the temperature is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher.

[0053] The heating time is not particularly limited as long as it is a time that allows a desired glass-ceramic solid electrolyte to be obtained, but is, for example, preferably 10 minutes or more, more preferably 30 minutes or more, even more preferably 60 minutes or more, and even more preferably 2 hours or more. The upper limit of the heating time is not particularly limited, but is preferably 10 hours or less, more preferably 8 hours or less, even more preferably 6 hours or less, and even more preferably 4 hours or less.

[0054] The atmosphere for the heat treatment is not particularly limited, and may be a hydrogen sulfide atmosphere, an inert gas atmosphere such as nitrogen or argon, or a vacuum atmosphere.

[0055] The glass-ceramic solid electrolyte of this embodiment has a packing density equal to or higher than that of conventional glass-ceramic solid electrolytes and high ionic conductivity, and is therefore suitable for use in batteries. This is particularly suitable when lithium is used as the conductive species. The glass-ceramic solid electrolyte of this embodiment may be used in a positive electrode layer, a negative electrode layer, or an electrolyte layer.

[0056] A lithium ion battery according to one embodiment of the present invention includes the glass-ceramic solid electrolyte of the present invention described above. For example, by using the glass-ceramic solid electrolyte of the present invention in place of a liquid electrolyte, an all-solid-state lithium ion battery can be produced.

[0057] An all-solid-state lithium-ion battery mainly consists of a positive electrode layer, a negative electrode layer, and an electrolyte layer, and the glass-ceramic 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-ceramic 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 movement 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 that can insert and extract lithium ions include oxide-based positive electrode active materials and sulfide-based positive electrode active materials.

[0058] 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.

[0059] 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 ３ S 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.

[0060] 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.

[0061] 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.

[0062] 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 TiO ３ 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.

[0063] Also, Li ｙTi 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] The thickness of the coating layer can be measured by observing the cross section with 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.

[0069] 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 or the like coated with a material that reacts with the glass-ceramic solid electrolyte, such as Au, Pt, Al, Ti, or Cu.

[0070] The present invention will be specifically described below based on examples. The present invention is not limited to these examples. The evaluation methods for the samples prepared in each example are as follows. (1) Powder X-ray diffraction (XRD) measurement The glass solid electrolyte powder prepared 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 Furthermore, 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.

[0071] (2) Peak Half Width As an example, the calculation method for a peak in the range of 2θ = 20 ± 1° is shown below. For lithium halide peak half widths, the calculation is performed using a peak at 2θ = 25.5 ± 1° in the case of LiI, and a peak at 2θ = 28 ± 1° in the case of LiBr. In the range (2θ = 19 to 21°) in which the above-mentioned peaks exist, the half width E was determined so as to minimize the difference between the measured intensity (vertical axis value of the XRD pattern) and the calculated value below. The ratio of the Lorentz function was defined as A (0 ≦ A ≦ 1), the intensity correction value was defined as B, the 2θ angle at which the intensity is maximized as C, the calculated intensity angle (2θ) as D, the half width as E, and the background as F. Note that the background may be affected by amorphous materials, so it may also be calculated as F = O + P × D, using a uniform background O and a linear function P that changes according to the peak position. The measured intensity at the angle (2θ) of the intensity to be calculated was designated as G, and the variables were A, B, C, E, O, and P. For each angle (2θ) at which the intensity was measured, the deviation H between the measured and calculated intensity was calculated using the following formula (2): H = G - {B × {A / (1 + 4 × (D - C)}} ２ / E ２ )+(1-A)×exp(-1×(D-C) ２ / E ２ )×(4ln(2))}+O+P×D} (2)

[0072] H was summed over the range of 2θ = 19 to 21°, and the sum was minimized using the Solver function of the spreadsheet software Excel (Microsoft) with a GRG nonlinearity to determine the above variables including the half-width E.

[0073] (3) Crystallite size In order to correct the broadening of the half-width due to the device, the half-width E calculated by the above method was corrected using NIST standard Si (640d, crystallite diameter 525 nm). The corrected half-width was B ｃｏｒｒｅｃｔｉｏｎ Then, the corrected half-width β used to calculate the crystallite size can be expressed by the following formula: β = E - B ｃｏｒｒｅｃｔｉｏｎThe actual crystallite size L was calculated using the following formula: L = K × λ / (β cos(C / 2)), where K was set to 0.9, λ was the wavelength of the X-rays used in the measurement, and C was the angle (2θ) of the peak center position when calculating the half-width.

[0074] (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 (Microtrackbell: BELMAX). 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 W １ The volume of the gas phase of the cell when the glass solid electrolyte is introduced into the cell and the total weight of the cell are measured three times by the above method, and the average value is taken as the volume V excluding the sample. ２ The total weight of the cell is W ２ The true density d of the glass solid electrolyte can be calculated using the following formula: d = (W ２ -W １ ) / (V １ -V ２ The true density of the sample was calculated three times using the above procedure and formula, and the average value was used as the true density of the sample. The standard deviation of the true density calculated by this method was 0.05 g / cm ３ The following is the result.

[0075] (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, L ｉｎｔ 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: ｐｅｌｌｅｔ = 0.3 / {(L ａｆｔｅｒ -L ｉｎｔ ) x S ｐｅｌｌｅｔ}

[0076] (Calculation of relative density) Calculation was performed using the following formula: relative density (%) = pellet density × 100 / true density

[0077] (5) Ion Conductivity From the glass ceramic 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

[0078] (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.

[0079] Example 1 [Preparation of Glass-Ceramic Solid Electrolyte] 2.319 g of lithium sulfide, 3.740 g of diphosphorus pentasulfide, and 3.941 g of lithium iodide 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 (mechanically milled) at room temperature at a rotation speed of 220 rpm for 40 hours to obtain an intermediate (glass-like powder).

[0080] Approximately 2 g of the intermediate powder was held at 155°C for 2 hours under vacuum. Then, it was slowly cooled to obtain a glass ceramic solid electrolyte. Using a thermogravimetric and differential thermal analyzer (TGDTA), TGDTA was performed at a temperature increase rate of 10°C / min. The peak top temperature (T ｃ１ ) was 170°C.

[0081] The ionic conductivity (σ) of the obtained glass-ceramic solid electrolyte was 3.8 mS / cm. The XRD pattern of the glass-ceramic solid electrolyte is shown in FIG.

[0082] Examples 2 to 21 and Comparative Examples 1 to 11 Glass ceramic solid electrolytes were prepared and evaluated in the same manner as in Example 1, except that the raw material composition ratio and the heating temperature of the intermediate were changed as shown in Table 1. The results are shown in Tables 1 and 2.３ P.S. ４ The amount of the substance was set to 100 molar parts, which is the starting material Li ２ S is 150 parts by mole and P ２ S ５ In addition, with regard to the heating temperature, in Examples 2 to 21 and Comparative Examples 1, 4 to 7, and 9 to 11, the peak top temperature (T ｃ１ ) at a temperature of 15°C or less, and in Comparative Example 2, T ｃ１ In Comparative Examples 3 and 8, the temperature was set to the same as ｃ１ The temperature was set higher than that.

[0083] The molar ratio (X / P) of each element relative to phosphorus (P) in the glass-ceramic solid electrolyte was measured by ICP for Examples 2, 17, and 19, and Comparative Examples 5 and 8. The results are shown below. Example 2: Li / P = 3.95, S / P = 3.96, Br / P = 0, I / P = 1.03 Example 17: Li / P = 3.95, S / P = 3.95, Br / P = 0.53, I / P = 0.52 Example 19: Li / P = 3.95, S / P = 3.95, Br / P = 1.04, I / P = 0 Comparative Example 5: Li / P = 3.55, S / P = 4.01, Br / P = 0.27, I / P = 0.27 Comparative Example 8: Li / P = 3.94, S / P = 3.95, Br / P = 0, I / P = 1.03

[0084]

[0085] FIG. 2 shows the X-ray diffraction patterns of the glass-ceramic solid electrolytes produced in Examples 1 to 4. FIG. 3 shows the X-ray diffraction patterns of the glass-ceramic solid electrolytes produced in Examples 5 to 8. FIG. 4 shows the X-ray diffraction patterns of the glass-ceramic solid electrolytes produced in Examples 9 to 12. FIG. 5 shows the X-ray diffraction patterns of the glass-ceramic solid electrolytes produced in Examples 13 to 16. FIG. 6 shows the X-ray diffraction patterns of the glass-ceramic solid electrolytes produced in Examples 17 to 21. FIG. 7 shows the X-ray diffraction patterns of the glass-ceramic solid electrolytes produced in Comparative Examples 1 to 5. FIG. 8 shows the X-ray diffraction patterns of the glass-ceramic solid electrolytes produced in Comparative Examples 6 to 11.

[0086] The X-ray diffraction patterns obtained in the examples show that XRD spectra with low crystallinity can be obtained, which means that high ionic conductivity can be maintained from the viewpoint of preventing the destruction of crystallites when the glass-ceramic solid electrolyte is compressed, and that large intercrystalline voids can be prevented from being formed, which means that a high packing factor can also be maintained. Furthermore, since lithium halide can be used to obtain XRD spectra with low crystallinity, it is believed that it does not have an effect of hardening the glass-ceramic solid electrolyte.

[0087] The glass-ceramic 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.

[0088] 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. Contains lithium, phosphorus, sulfur and halogen 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 0.1 to 2.3; In powder X-ray diffraction using CuKα rays, peak A is present at 2θ=20±1°, and in the powder X-ray diffraction, peak B is not present at 2θ=23.6±1°, or if peak B is present, the peak intensity (I Ｂ ) and the peak intensity of peak A (I Ａ ) peak intensity ratio (I Ｂ / I Ａ ) is less than 0.050; A glass-ceramic solid electrolyte having a crystallite size of 5 to 20 nm.

2. Peak intensity ratio (I Ｂ / I Ａ 2. The glass-ceramic solid electrolyte according to claim 1, wherein Π is 0.

3. 2. The glass-ceramic solid electrolyte according to claim 1, which exhibits a peak derived from lithium halide in powder X-ray diffraction using CuKα radiation.

4. 4. The glass-ceramic solid electrolyte according to claim 3, wherein the crystallite size of the lithium halide calculated from the peak having the maximum intensity among the peaks derived from the lithium halide is 5 to 100 nm.

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

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

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

86.

8. The glass-ceramic solid electrolyte according to claim 1 , comprising two or more types of halogen.

9. 9. The glass-ceramic solid electrolyte of claim 8, wherein the halogens include iodine and bromine.

10. a molar ratio (I / P) of the iodine (I) to the phosphorus (P) is 0.0<(I / P)<1.8; 10. The glass-ceramic solid electrolyte according to claim 9, wherein a molar ratio (Br / P) of the bromine (Br) to the phosphorus (P) is 0.0<(Br / P)<1.

5.

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

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