Solid electrolyte and method for manufacturing solid electrolyte

Abstract

A solid electrolyte comprising Li, Mα, Mβ, and F, wherein Mα is at least one element selected from the group consisting of Cs and Rb, and Mβ is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba. Accordingly, it is possible to provide a solid electrolyte that is highly safe and has high ionic conductivity.

Description

Solid electrolyte and method for producing the same

[0001] The present invention relates to a solid electrolyte and a method for producing the solid electrolyte.

[0002] In recent years, development of solid electrolytes for use in all-solid-state batteries and the like has been progressing. For example, Japanese Patent Application Laid-Open No. 2011-129312 (Reference 1) discloses a solid electrolyte made of sulfide and an all-solid-state battery including the solid electrolyte. On the other hand, solid electrolytes made of sulfide may react with moisture in the air and generate toxic hydrogen sulfide gas. Therefore, International Publication Nos. 2021 / 161604 (Reference 2) and 2021 / 186833 (Reference 3) propose solid electrolytes made of fluorine compounds. Specifically, the solid electrolyte in Reference 2 contains Li, Zr, Al, and F. The solid electrolyte in Reference 3 contains Li, Ti, Al, M, and F, where M is Zr or Mg.

[0003] Incidentally, the solid electrolytes made of fluorine compounds described in References 2 and 3 improve safety, but do not have sufficient ionic conductivity.

[0004] The present invention is directed to a solid electrolyte, and has an object to provide a solid electrolyte that is highly safe and has high ionic conductivity.

[0005] A first aspect of the invention is a solid electrolyte comprising Li, Mα, Mβ, and F, wherein Mα is at least one element selected from the group consisting of Cs and Rb, and Mβ is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba.

[0006] According to the present invention, it is possible to provide a solid electrolyte that is highly safe and has high ionic conductivity.

[0007] A second aspect of the present invention is the solid electrolyte of the first aspect, which contains a hydroxyl group.

[0008] A third aspect of the present invention is the solid electrolyte of the second aspect, wherein the water content determined by TG-DTA is 1 wt % or more.

[0009] A fourth aspect of the present invention is the solid electrolyte according to any one of the first to third aspects, in which Mα includes Cs.

[0010] A fifth aspect of the present invention is the solid electrolyte according to any one of the first to fourth aspects, in which Mβ contains Mg.

[0011] A sixth aspect of the present invention is the solid electrolyte according to any one of the first to fifth aspects, wherein an X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα radiation has an intense peak in the range of a diffraction angle 2θ of 27 to 33°.

[0012] A seventh aspect of the present invention is the solid electrolyte of any one of the first to sixth aspects, wherein when the molar ratio of Li, Mα, Mβ, and F is expressed as a:b:c:d, a+b+2c=d is satisfied.

[0013] An eighth aspect of the present invention is the solid electrolyte of the seventh aspect, wherein 0.5<a<1, 0.01<c<1, and 1.5<d<3 are satisfied.

[0014] A ninth aspect of the present invention is the solid electrolyte of the eighth aspect, in which 0.01<c<0.5 is satisfied.

[0015] A tenth aspect of the present invention is a method for producing a solid electrolyte, comprising: a) obtaining a solid electrolyte by mechanical milling a mixture containing Li, Mα, Mβ, and F; and b) heating the solid electrolyte at a temperature of 60 to 200°C, wherein Mα is at least one element selected from the group consisting of Cs and Rb, and Mβ is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba.

[0016] An eleventh aspect of the invention is a method for producing a solid electrolyte, comprising: a) heating a mixture containing Li, Mα, Mβ, and F in a non-aqueous atmosphere at 200°C or higher to obtain a solid electrolyte; and b) further heating the solid electrolyte at a temperature of 60 to 200°C, wherein Mα is at least one element selected from the group consisting of Cs and Rb, and Mβ is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba.

[0017] The above and other objects, features, aspects and advantages will become more apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings.

[0018] Fig. 1 is a diagram showing a flow of manufacturing a solid electrolyte; Fig. 2 is a diagram showing an infrared spectroscopy spectrum of a solid electrolyte of a comparative example; Fig. 3 is a diagram showing an infrared spectroscopy spectrum of a solid electrolyte; Fig. 4 is a diagram showing a TG curve and a DTA curve of a solid electrolyte; Fig. 5 is a diagram showing an X-ray diffraction pattern of a solid electrolyte of a comparative example; Fig. 6 is a diagram showing an X-ray diffraction pattern of a solid electrolyte.

[0019] The solid electrolyte according to the present invention (hereinafter also referred to as "the present solid electrolyte") is an ion-conducting material. The ions to be conducted are lithium ions (Li ions) based on the manufacturing method of the solid electrolyte and infrared spectroscopy described below. ＋ ), fluoride ion (F － ), proton (H ＋ ), hydroxide ions (OH － The present solid electrolyte can be used in a variety of products that use solid electrolytes, such as electricity storage devices such as batteries, sensors (for example, gas sensors), separation membranes, and reactors.

[0020] The present solid electrolyte contains lithium (Li), two types of metals (Mα, Mβ), and fluorine (F). As described below, a preferred solid electrolyte contains a hydroxyl group (OH group). In this case, in addition to Li, Mα, Mβ, and F, it further contains oxygen (O) and hydrogen (H). The solid electrolyte may consist only of these elements. Mα is an element that forms a monovalent cation and is at least one element selected from the group consisting of cesium (Cs) and rubidium (Rb). Mα preferably contains Cs, or may consist only of Cs. Mβ is an element that forms a divalent cation and is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Mβ preferably contains Mg, or may consist only of Mg. As described below, the present solid electrolyte achieves high ionic conductivity. Furthermore, the solid electrolyte does not generate hydrogen sulfide gas, thereby realizing high safety.

[0021] In a preferred solid electrolyte, when the molar ratio of Li, Mα, Mβ, and F is expressed as a:b:c:d, a ​​+ b + 2c = d is satisfied. To confirm whether an unknown solid electrolyte satisfies a + b + 2c = d, for example, Li, Cs, and Mg can be quantified by ICP-emission spectroscopy or the like. F can be quantified by ion chromatography, for example. If the solid electrolyte contains elements other than those listed above, a measurement method capable of quantifying those elements is appropriately selected. Taking into account measurement error and the like, for example, if the molar ratio determined by analysis of the unknown solid electrolyte is 0.9d≦a + b + 2c ≦1.1d, it can be said that a + b + 2c = d is satisfied. It is more preferable that the above molar ratios satisfy 0.5<a<1, 0.01<c<1, and 1.5<d<3, and it is even more preferable that c satisfies 0.01<c<0.5.

[0022] FIG. 1 is a diagram showing the flow of manufacturing the present solid electrolyte. In manufacturing the present solid electrolyte, for example, a powder of a fluoride containing Li, a powder of a fluoride containing Mα, and a powder of a fluoride containing Mβ are prepared. The fluoride containing Li is, for example, LiF (lithium fluoride). When Mα is Cs, the fluoride containing Cs is, for example, CsF (cesium fluoride), and when Mα is Rb, the fluoride containing Rb is, for example, RbF (rubidium fluoride). When Mβ is Mg, the fluoride containing Mg is, for example, MgF ２ As mentioned above, Mβ may be Ca, Sr, or Ba, and fluorides containing Mβ include, for example, CaF ２ (calcium fluoride), SrF ２ (strontium fluoride), BaF ２ In a non-oxidizing atmosphere (e.g., an inert gas atmosphere) with a dew point of −60° C. or less, these powders are weighed out to a predetermined molar ratio and mixed in a mortar. This yields a mixture containing Li, Mα, Mβ, and F (Step S11).

[0023] Next, the mixture is subjected to mechanical milling (mechanochemical milling) in the non-oxidizing atmosphere (step S12). Here, a planetary ball mill is used as an example of the mechanical milling. In a planetary ball mill, the pot rotates on its axis while the stage carrying the pot revolves, making it possible to generate very high impact energy. The processing time is, for example, 10 to 100 hours. The mechanical milling may also be performed using other types of grinders. The mechanical milling produces a solid electrolyte powder. In this processing example, the mechanical milling is performed at room temperature, but the temperature and other conditions may be changed as appropriate.

[0024] Thereafter, the solid electrolyte powder is heated (step S13). For example, the solid electrolyte powder is contained in a sealed container (sealed cell) having minute holes connecting the inside and outside, and is heated together with the sealed container in the atmosphere. In other words, the solid electrolyte powder is heated while in contact with an atmosphere containing water. The heating temperature is 60 to 200°C, preferably 70 to 150°C. The heating time is, for example, 1 to 50 hours, preferably 2 to 25 hours. The heat treatment increases the ionic conductivity of the solid electrolyte. Even when the solid electrolyte is returned to room temperature after the heat treatment (hereinafter simply referred to as the "solid electrolyte after the heat treatment"), the ionic conductivity remains higher than before the heat treatment. By the above-mentioned processes, the present solid electrolyte is obtained.

[0025] As will be described later, in the production of this solid electrolyte, the solid electrolyte contains hydroxyl groups due to the heat treatment. It is believed that during the heat treatment, the heated solid electrolyte reacts with water in the air introduced into the sealed container through the communication holes, generating hydroxyl groups. The ionic conductivity of the solid electrolyte after the heat treatment increases with the ambient relative humidity. The ambient relative humidity during the heat treatment (i.e., the relative humidity of the water-containing atmosphere) is preferably 40% or higher, more preferably 60% or higher. The heat treatment in step S13 may be performed during the production of a product using the solid electrolyte, and a sealed container does not necessarily need to be used for the heat treatment.

[0026] In step S12, a process other than mechanical milling may be performed. In another example of producing a solid electrolyte, a mixture containing Li, Mα, Mβ, and F is heated in a non-aqueous atmosphere at 200°C or higher to obtain a solid electrolyte powder (step S12). The non-aqueous atmosphere may be, for example, an inert gas atmosphere, and, as in the mechanical milling process, may be an atmosphere with a dew point of -60°C or lower. The heating temperature is, for example, 200°C or higher and 800°C or lower, preferably 200°C or higher and 600°C or lower, and more preferably 300°C or higher and 500°C or lower. The heating time is, for example, the same as in step S13. Thereafter, the solid electrolyte powder is further heated at a temperature of 60 to 200°C in contact with an atmosphere containing water (step S13). The solid electrolyte is obtained by the above process.

[0027] Next, experimental examples of solid electrolytes will be described. The preparation of solid electrolyte powders in the following experimental examples was carried out in a glove box in an argon (Ar) atmosphere with a dew point of -60°C or less. The conditions and measurement results for Experimental Examples 1 to 8 are shown in Table 1. Experimental Examples 2 to 8 are examples of the present invention containing Li, Mα, Mβ, and F, while Experimental Example 1 is a comparative example containing Li, Mα, and F but not Mβ. In the raw material mixing ratio column in Table 1, the raw materials LiF, CsF, RbF, MgF ２ The column for the ratio of contained elements shows the ratio of the contained elements Li, Mα, Mβ, and F.

[0028]

[0029] <Preparation of Solid Electrolyte Powder> (Experimental Example 1) Commercially available LiF powder and commercially available CsF powder were prepared as raw materials. These powders were weighed so that the molar ratio of LiF:CsF was 1:1, and mechanical milling was performed using a planetary ball mill to obtain a solid electrolyte powder having the composition formula LiCsF ２ In Table 1, the "synthesis method" column indicates that the solid electrolyte powder was obtained by mechanical milling. This is the same for Experimental Examples 2 to 7.

[0030] (Experimental Example 2) In addition to LiF powder and CsF powder, commercially available MgF２ Powders were prepared: LiF:CsF:MgF ２ were weighed out so that the molar ratio was 0.98:1:0.02, and mechanically milled using a planetary ball mill to obtain a composition having the formula Li ０．９８ CsMg ０．０２ F ２．０２ A solid electrolyte powder represented by the formula:

[0031] (Experimental Example 3) LiF:CsF:MgF ２ The same treatment as in Experimental Example 2 was carried out, except that the powder was weighed so that the molar ratio of Li was 0.9:1:0.1. ０．９ CsMg ０．１ F ２．１ A solid electrolyte powder represented by the formula:

[0032] (Experimental Example 4) LiF:CsF:MgF ２ The same treatment as in Experimental Example 2 was carried out, except that the powder was weighed so that the molar ratio of Li:Li was 0.8:1:0.2. ０．８ CsMg ０．２ F ２．２ A solid electrolyte powder represented by the formula:

[0033] (Experimental Example 5) LiF:CsF:MgF ２ The same treatment as in Experimental Example 2 was carried out, except that the powder was weighed so that the molar ratio of Li was 0.6:1:0.4. ０．６ CsMg ０．４ F ２．４ A solid electrolyte powder represented by the formula:

[0034] (Experimental Example 6) LiF:CsF:MgF ２ The same treatment as in Experimental Example 2 was carried out, except that the powder was weighed so that the molar ratio of Li:Li was 0.8:1:0.1. ０．８ CsMg ０．１ F ２．０ A solid electrolyte powder represented by the formula:

[0035] Experimental Example 7: Instead of CsF powder, commercially available RbF powder was prepared. LiF:RbF:MgF ２ The same treatment as in Experimental Example 2 was carried out, except that the powder was weighed so that the molar ratio of Li was 0.9:1:0.1.０．９ RbMg ０．１ F ２．１ A solid electrolyte powder represented by the formula:

[0036] (Experimental Example 8) LiF:CsF:MgF ２ The powders were weighed out so that the molar ratio of the powders was 0.9:1:0.1, and mixed in a mortar. The mixed powder was heat-treated at 400°C for 4 hours in an Ar atmosphere to obtain a powder having a composition formula of Li ０．９ CsMg ０．１ F ２．１ In Table 1, the "heating at 400°C" entry in the synthesis method column indicates that the solid electrolyte powder was obtained by heating at 400°C.

[0037] <Heat Treatment and Ion Conductivity Measurement> In a glove box under an argon atmosphere, the solid electrolyte powder was placed in a mold consisting of a resin sleeve and upper and lower metal punches, and uniaxial press molding was performed under a pressure of 300 MPa. The obtained sample was inserted into a sealed cell having minute holes connecting the inside and outside, and the sealed cell was then removed from the glove box (to the atmosphere) and placed in a thermostatic chamber at 100°C for 16 hours. After cooling, the impedance was measured at room temperature, and the ion conductivity was calculated. In Table 1, the ion conductivity is shown in the conductivity column.

[0038] <Infrared Spectroscopic Measurement> An infrared spectrum of the solid electrolyte after the heat treatment was obtained by the attenuated total reflectance (ATR) method. A Varian-670 (FT-IR, manufactured by Varian) was used as the measuring device, and the measurement conditions were an accumulation of 256 times and a Seagull accessory (single-reflection ATR, incident angle 45°, using a Ge prism). FIG. 2 shows the infrared spectrum of the solid electrolyte after the heat treatment of Experimental Example 1, and FIG. 3 shows the infrared spectrum of the solid electrolyte after the heat treatment of Experimental Example 3. The horizontal axis of FIGS. 2 and 3 indicates wavenumber, and the vertical axis indicates intensity.

[0039] In the infrared spectrum of FIG. 3, the wave number is 3000 cm －１ The peak around 2330 cm is due to the hydroxyl group (OH group).－１ Peaks around 1640 cm －１ The peak around 1570 cm is also due to OH groups. －１ Peaks near the wave number 1330 cm －１ The peak around this point is due to the carbonate group (CO ３ group) or CO ２ In the infrared spectrum of FIG. 3, the hydroxyl group-derived wave number of 3000 cm －１ The peak intensity value (0.0144) around 1330 cm is due to the carbonate group. －１ This is a state in which the peak intensity value (0.0073) near the solid electrolyte is greater than this. In this specification, this state is expressed as "the solid electrolyte contains hydroxyl groups." In Table 1, the hydroxyl group column is marked with "present."

[0040] In the solid electrolytes of Experimental Examples 2 to 8, the infrared spectrum showed a wave number of 3000 cm －１ The peak intensity value around the wave number 1330 cm －１ The peak intensity value around 3000 cm was larger than that around 3000 cm, indicating that the solid electrolyte contained hydroxyl groups. －１ The peak intensity value around the wave number 1330 cm －１ Therefore, it can be said that the solid electrolytes of Experimental Examples 2 to 8 contained hydroxyl groups due to the heat treatment.

[0041] On the other hand, in the solid electrolyte of Experimental Example 1, the infrared spectrum of FIG. －１ The peak intensity value (0.0017) near the wavenumber of 1330 cm －１ The peak intensity (0.0034) near the solid electrolyte peak was less than that, indicating that the solid electrolyte did not contain hydroxyl groups. That is, the solid electrolyte of Experimental Example 1 did not contain hydroxyl groups even after the heat treatment. The peaks due to hydroxyl groups in the infrared spectrum of Figure 2 are thought to be due to unavoidable impurities in the atmosphere being adsorbed on the powder surface of the solid electrolyte.

[0042] <Measurement of Moisture Content by TG-DTA> The thermal behavior of the solid electrolyte after the heat treatment was measured by TG-DTA (Thermogravimetry and Differential Thermal Analysis). The measurement device used was a Thermo Plus EVO2 (manufactured by Rigaku Corporation), and the measurement conditions were a rate of 10°C / min and a dry air atmosphere with a dew point of -40°C. FIG. 4 shows the TG curve and DTA curve of the solid electrolyte after the heat treatment of Experimental Example 3. In FIG. 4, the TG curve is labeled L1, and the DTA curve is labeled L2.

[0043] In this specification, the weight loss accompanied by an irreversible endothermic peak in the temperature range from room temperature to approximately 200°C, as shown in Figure 4, is defined as the amount of desorbed water, and this amount of desorbed water is defined as the amount of water [wt%] contained in the solid electrolyte after heat treatment (i.e., the amount of water originating from OH). In Table 1, the column for water content shows the amount of water quantified by TG-DTA. In Experimental Example 1, where the solid electrolyte after heat treatment did not contain hydroxyl groups, the amount of water quantified by TG-DTA was less than 1 wt%. In contrast, in Experimental Examples 2 and 3, where the solid electrolyte after heat treatment contained hydroxyl groups, the amount of water quantified by TG-DTA was 1 wt% or more (actually, 2 wt% or more). Note that water content measurements were not performed on the solid electrolytes of Experimental Examples 4 to 8. However, since all of them contained hydroxyl groups, it is considered that the water content was 1 wt% or more, as in Experimental Examples 2 and 3.

[0044] <X-ray Diffraction Measurement> An X-ray diffraction pattern was obtained for the solid electrolyte after the heat treatment using an X-ray diffraction (XRD) device. The measurement conditions were CuKα, 40 kV, and 40 mA, and a sealed tube X-ray diffractometer (D8-ADVANCE manufactured by Bruker AXS K.K.) was used. The measurement step width was 0.01°. FIG. 5 shows the X-ray diffraction pattern of the solid electrolyte after the heat treatment of Experimental Example 1, and FIG. 6 shows the X-ray diffraction pattern of the solid electrolyte after the heat treatment of Experimental Example 3. In FIGS. 5 and 6, the horizontal axis represents the diffraction angle 2θ, and the vertical axis represents the intensity.

[0045] The X-ray diffraction pattern of Experimental Example 1 in FIG. 5 has the strongest peak with the maximum intensity in the range of diffraction angle 2θ of 27 to 33°, and LiCsF ２ (ICDD PDF#22-1076). The X-ray diffraction pattern of Experimental Example 3 in FIG. 6 also has the strongest peak in the diffraction angle 2θ range of 27 to 33°, and the main phase is LiCsF ２ In addition, in the X-ray diffraction pattern of Experimental Example 3, the peaks at 2θ=22.4°, 23.0°, and 33.5° were respectively determined to be LiCs(OH) ２ , Li ４ (CO ４ ), LiOH·H ２ This suggests the possibility that they contain a small amount of O as a heterophase. It was also confirmed that the X-ray diffraction patterns of the solid electrolytes of Experimental Examples 2 and 4 to 8 had the strongest peak in the diffraction angle 2θ range of 27 to 33°.

[0046] <Evaluation of Experimental Examples> The solid electrolytes of Experimental Examples 2 to 8 containing Li, Cs, Mg, and F, and the solid electrolyte of Experimental Example 7 containing Li, Rb, Mg, and F, had significantly higher ionic conductivity than the solid electrolyte powder of Experimental Example 1 containing Li, Cs, and F but not Mg. Here, in these solid electrolytes, electromotive force measurement using a water vapor concentration cell revealed that at least protons (H ＋ ) conduction, and it is believed that the inclusion of hydroxyl groups in the solid electrolytes of Experimental Examples 2 to 8 resulted in high ionic conductivity. It is believed that the ionic conductivity of solid electrolytes is improved when both Cs and Rb are used as Mα. It is also believed that the ionic conductivity is improved when Ca, Sr, and Ba, which are divalent cations like Mg, are used instead of or together with Mg.

[0047] As described above, the present solid electrolyte contains Li, Mα, Mβ, and F, where Mα is at least one element selected from the group consisting of Cs and Rb, and Mβ is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba. This makes it possible to provide a solid electrolyte with high ionic conductivity. Furthermore, the solid electrolyte does not contain sulfides and does not generate hydrogen sulfide gas, making it highly safe.

[0048] The present solid electrolyte preferably contains hydroxyl groups. This ensures high ionic conductivity. A more preferred solid electrolyte has a water content of 1 wt % or more as determined by TG-DTA. In this case, the solid electrolyte is considered to contain a sufficient number of hydroxyl groups, making it possible to more reliably achieve high ionic conductivity. The upper limit of the water content is not particularly limited, but is, for example, 20 wt %. Note that, in the solid electrolyte, for example, 5×10 －６ When a high ionic conductivity exceeding 25 S / cm is obtained, the water content determined by TG-DTA may be less than 1 wt %.

[0049] In the present solid electrolyte, Mα preferably contains Cs, as in Experimental Examples 2 to 6 and 8. This makes it possible to more reliably improve ionic conductivity. Similarly, Mβ preferably contains Mg, as in Experimental Examples 2 to 8.

[0050] Preferably, when the molar ratio of Li, Mα, Mβ, and F is expressed as a:b:c:d, a ​​+ b + 2c = d is satisfied. This makes it possible to suitably realize a solid electrolyte with high ionic conductivity. More preferably, as in Experimental Examples 2 to 8, 0.5 < a < 1, 0.01 < c < 1, and 1.5 < d < 3 are satisfied. This makes it possible to more reliably improve ionic conductivity. It is even more preferable that the solid electrolyte satisfy 0.01 < c < 0.5.

[0051] The method for producing a solid electrolyte includes the steps of obtaining a solid electrolyte by mechanical milling a mixture containing Li, Mα, Mβ, and F, and heating the solid electrolyte at a temperature of 60 to 200°C. Mα is at least one element selected from the group consisting of Cs and Rb, and Mβ is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba. This makes it possible to provide a solid electrolyte that is highly safe and has high ionic conductivity. In the step of obtaining the solid electrolyte, the mixture containing Li, Mα, Mβ, and F may be heated to 200°C or higher in a non-aqueous atmosphere.

[0052] The present solid electrolyte and the method for producing the solid electrolyte can be modified in various ways.

[0053] The compounds contained in the present solid electrolyte may not satisfy the above molar ratio relationship (a + b + 2c = d). Furthermore, for the above solid electrolyte, the X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα radiation has the strongest peak in the range of diffraction angles 2θ of 27 to 33°, but the present solid electrolyte may be amorphous, and the X-ray diffraction pattern may not have the strongest peak in the range of diffraction angles 2θ of 27 to 33°.

[0054] The present solid electrolyte may be produced by a method other than the method in the above embodiment (mechanical milling treatment, etc.), for example, by firing or the like.

[0055] The present solid electrolyte may be mixed with other substances and used as an electrolyte material. In this case, the present solid electrolyte is preferably the component with the largest mass ratio among the components contained in the electrolyte material, i.e., the main component. The mass ratio of the main component in the electrolyte material is preferably 50 mass% or more, more preferably 60 mass% or more, and even more preferably 70 mass% or more.

[0056] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0057] While the invention has been particularly illustrated and described, it should be understood that the foregoing description is illustrative and not restrictive, and that numerous modifications and variations are possible without departing from the scope of the invention.

[0058] Steps S11 to S13

Claims

1. A solid electrolyte, Li, Mα, Mβ and F, Mα is at least one element selected from the group consisting of Cs and Rb; Mβ is at least one element selected from the group consisting of Mg, Ca, Sr and Ba; A solid electrolyte containing hydroxyl groups.

2. The solid electrolyte according to claim 1, A solid electrolyte having a water content of 1 wt % or more as determined by TG-DTA.

3. A solid electrolyte, Li, Mα, Mβ and F, Mα is at least one element selected from the group consisting of Cs and Rb; Mβ is at least one element selected from the group consisting of Mg, Ca, Sr and Ba; A solid electrolyte in which a+b+2c=d is satisfied when the molar ratios of Li, Mα, Mβ, and F are expressed as a:b:c:d.

4. The solid electrolyte according to claim 3, A solid electrolyte in which 0.5<a<1, 0.01<c<1, and 1.5<d<3 are satisfied.

5. The solid electrolyte according to claim 4, A solid electrolyte satisfying 0.01<c<0.

5.

6. 6. A solid electrolyte according to claim 1, Mα is a solid electrolyte containing Cs.

7. 6. A solid electrolyte according to claim 1, Mβ is a solid electrolyte containing Mg.

8. 6. A solid electrolyte according to claim 1, A solid electrolyte, the X-ray diffraction pattern obtained by X-ray diffraction measurement using CuKα rays has the strongest peak in the range of diffraction angle 2θ of 27 to 33°.

9. A method for producing a solid electrolyte, comprising the steps of: a) obtaining a solid electrolyte by mechanical milling a mixture containing Li, Mα, Mβ and F; b) heating the solid electrolyte at a temperature of 60 to 200° C.; Equipped with A method for producing a solid electrolyte, wherein Mα is at least one element selected from the group consisting of Cs and Rb, and Mβ is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba.

10. A method for producing a solid electrolyte, comprising the steps of: a) heating a mixture containing Li, Mα, Mβ and F in a non-aqueous atmosphere at 200° C. or higher to obtain a solid electrolyte; b) further heating the solid electrolyte at a temperature of 60 to 200° C.; Equipped with A method for producing a solid electrolyte, wherein Mα is at least one element selected from the group consisting of Cs and Rb, and Mβ is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba.