Solid electrolyte and battery

Abstract

Disclosed is a solid electrolyte that exhibits high ion conductivity and that can be provided at an inexpensive process cost. The solid electrolyte comprises: at least one inorganic compound selected from the group consisting of metal oxides, metal hydrogen compounds, and metal hydroxides; residual solvent; and a salt containing an alkali metal or an alkaline earth metal. The x-ray diffraction pattern of the inorganic compound has at least one peak having a full width at half maximum of no greater than 0.80°.

Description

Solid electrolytes and batteries

[0001] The present disclosure relates to solid electrolytes and batteries.

[0002] In recent years, there has been a strong demand for smaller size and improved reliability (safety) of batteries that serve as power sources for electronic devices. As a result, all-solid-state batteries, which use solid electrolytes instead of liquid electrolytes, have attracted attention.

[0003] Solid electrolytes using amorphous lithium tetraborate are known. For example, Patent Document 1 (WO2022 / 118870) and Patent Document 2 (WO2023 / 234209) disclose lithium-based solid electrolytes containing amorphous lithium tetraborate, water, and a lithium salt, which are said to exhibit high ionic conductivity at room temperature.

[0004] WO2022 / 118870WO2023 / 234209

[0005] In order to produce amorphous lithium tetraborate as disclosed in Patent Documents 1 and 2, mechanical milling using a planetary ball mill or the like must be carried out for approximately 100 hours, which requires considerable energy costs.

[0006] The present inventors have now discovered that a solid electrolyte exhibiting high ionic conductivity can be provided at low process costs by combining a predetermined inorganic compound that is not in an amorphous state, a solvent, and a predetermined salt.

[0007] Therefore, an object of the present invention is to provide a solid electrolyte exhibiting high ionic conductivity at low process costs.

[0008] The present disclosure provides the following aspects. [Aspect 1] A solid electrolyte comprising: at least one inorganic compound selected from the group consisting of a metal oxide, a metal halide, and a metal hydroxide; a residual solvent; and a salt containing an alkali metal or an alkaline earth metal, wherein the inorganic compound has at least one peak with a full width at half maximum of 0.80° or less in an X-ray diffraction pattern. [Aspect 2] The solid electrolyte according to Aspect 1, wherein the inorganic compound is crystalline. [Aspect 3] The solid electrolyte according to Aspect 1 or 2, wherein the content of the residual solvent is 30 wt % or less with respect to the total weight of the solid electrolyte. [Aspect 4] The solid electrolyte according to any one of Aspects 1 to 3, wherein the number of molecular layers that can theoretically be formed by the residual solvent on the surface of the inorganic compound is within a range of 0.7 to 350. [Aspect 5] The solid electrolyte according to any one of Aspects 1 to 4, wherein the inorganic compound comprises the metal oxide. [Aspect 6] The solid electrolyte according to Aspect 5, wherein the metal oxide comprises at least one selected from the group consisting of alumina, magnesia, and zirconia. [Aspect 7] The solid electrolyte according to any one of Aspects 1 to 6, wherein the inorganic compound comprises the metal hydroxide. [Aspect 8] The solid electrolyte according to Aspect 7, wherein the metal hydroxide comprises aluminum hydroxide. [Aspect 9] The solid electrolyte according to any one of Aspects 1 to 8, wherein the inorganic compound comprises the metal halide. [Aspect 10] The solid electrolyte according to Aspect 9, wherein the metal halide comprises lithium aluminum fluoride. [Aspect 11] The solid electrolyte according to any one of Aspects 1 to 10, wherein the salt comprises a salt having at least one selected from the group consisting of lithium, sodium, and magnesium. [Aspect 12] A battery comprising the solid electrolyte according to any one of Aspects 1 to 11.

[0009] 1 is a schematic cross-sectional view showing an example of an all-solid-state battery according to the present invention. ２ O ３ 1 is an XRD pattern of the solid electrolyte powder obtained in Example 1. 2 is a TG-DTA curve measured for the solid electrolyte powder obtained in Example 1. For comparison, 2 is a TG-DTA curve measured for the LiFSI powder alone.

[0010] Solid Electrolyte The solid electrolyte according to the present invention includes an inorganic compound, a residual solvent, and a salt. The inorganic compound is at least one selected from the group consisting of a metal oxide, a metal halide, and a metal hydroxide. The salt is a salt containing an alkali metal or an alkaline earth metal. The inorganic compound has at least one peak with a full width at half maximum of 0.80° or less in an X-ray diffraction (XRD) pattern. The presence of a peak with a full width at half maximum of 0.80° or less in an XRD pattern indicates that the inorganic compound is not in an amorphous state. In this way, by combining a predetermined inorganic compound that is not in an amorphous state, a solvent, and a predetermined salt, a solid electrolyte exhibiting high ionic conductivity can be provided at low process cost.

[0011] As mentioned above, to produce amorphous lithium tetraborate as disclosed in Patent Documents 1 and 2, mechanical milling using a planetary ball mill or the like is required for approximately 100 hours, resulting in considerable energy costs. This problem is successfully solved by the present invention. Specifically, in order to reduce process costs, such as energy costs, during electrolyte production, the inventors prepared electrolytes using various inorganic compounds and evaluated and investigated their properties. As a result, they found that even when non-amorphous inorganic compounds are used, high ionic conductivity at room temperature and good moldability can be achieved. Based on this finding, they have been able to provide a solid electrolyte exhibiting high ionic conductivity by combining a specific non-amorphous inorganic compound, identified by a specific XRD pattern, with a solvent and a specific salt. Because this inorganic compound does not need to be amorphous, it also has the advantage of being provided at low process costs.

[0012] The solid electrolyte of the present invention has a molecular weight of 1×10 at room temperature (e.g., 25° C.). －４ Preferably, the ionic conductivity is 5×10 S / cm or more, more preferably 5×10 －４ S / cm or more, more preferably 1×10 －３ Since the higher the ionic conductivity, the more desirable it is, the upper limit is not limited, but it is typically 1 S / cm or less, more preferably 1 x 10 －１S / cm or less.

[0013] The inorganic compound (so-called base material) used in the solid electrolyte of the present invention is at least one selected from the group consisting of metal oxides, metal halides, and metal hydroxides. In a preferred embodiment of the present invention, the inorganic compound contains a metal oxide. Preferred examples of metal oxides include alumina, magnesia, zirconia, and combinations thereof. In another preferred embodiment of the present invention, the inorganic compound contains a metal hydroxide. Preferred examples of metal hydroxides include aluminum hydroxide. In yet another preferred embodiment of the present invention, the inorganic compound contains a metal halide. Preferred examples of metal halide compounds include lithium fluoride (LiF), aluminum fluoride (AlF ３ ), lithium aluminum fluoride (Li ３ AlF ６ (LAF)), and combinations thereof, more preferably lithium aluminum fluoride (LAF). LAF is a mixture of LAF and lithium sulfate (Li ２ SO ４ It is particularly preferable to use the mixture of (LAF-LSO) and (LSO) in the form of (LAF-LSO) from the viewpoint of conductivity.

[0014] The inorganic compound used in the solid electrolyte of the present invention has at least one peak with a full width at half maximum of 0.80° or less in an X-ray diffraction (XRD) pattern. The XRD conditions are as described in the Examples below. The presence of a peak with a full width at half maximum of 0.80° or less in an XRD pattern means that the inorganic compound is not in an amorphous state; in other words, the inorganic compound can be considered to have crystallinity. Therefore, the inorganic compound does not need to be in an amorphous state, which requires considerable process costs (especially energy costs), and the solid electrolyte can be provided at low process costs.

[0015] Residual solvent refers to the solvent contained in the solid electrolyte obtained by drying during electrolyte preparation. That is, most of the solvent used during preparation of the raw solution or raw suspension evaporates and is lost during the drying process, but the solvent remaining in the solid electrolyte after the drying process constitutes the residual solvent. The content of the residual solvent is preferably 30 wt % or less, more preferably 1 to 25 wt %, even more preferably 1 to 20 wt %, and particularly preferably 1 to 17 wt %, relative to the total weight of the solid electrolyte. Adjusting the amount of residual solvent within the above range can more effectively increase the ionic conductivity of the solid electrolyte. The amount of residual solvent can be measured by simultaneous differential thermal analysis (TG-DTA). That is, as described in the Examples below, TG-DTA is performed on the solid electrolyte, and from the results obtained, the amount of residual solvent contained in the solid electrolyte can be calculated as the ratio (wt %) of the weight lost up to the temperature at which the exothermic peak is observed (i.e., the weight of water lost) to the weight of the solid electrolyte immediately before TG-DTA.

[0016] The residual solvent is not particularly limited as long as it is a solvent commonly used for various batteries, and examples of the residual solvent include water, alcohols such as ethanol, and organic solvents such as acetonitrile.

[0017] The amount of residual solvent can also be evaluated as the number of molecular layers that can theoretically be formed on the surface of the inorganic compound. In this case, the number of molecular layers that can theoretically be formed on the surface of the inorganic compound by the residual solvent is preferably in the range of 0.7 to 350, more preferably 1.5 to 350, even more preferably 2 to 340, and particularly preferably 2.5 to 330. The number of molecular layers that can theoretically be formed on the surface of the inorganic compound by the residual solvent can be determined as follows. First, the molecular weight (M ｗ ) and density, calculate the volume per molecule of the solvent, and assume that the molecule is a sphere to calculate the cross-sectional area of ​​the sphere. The calculated cross-sectional area is taken as the molecular occupied area Sa. Next, calculate the residual solvent amount Q from the TG-DTA measurement. ｒｓ From the weight % of the solid electrolyte, the weight of the solvent per 1 g of the mixture of inorganic compounds and salts is calculated. This weight of the solvent is divided by the molecular weight to obtain Avogadro's number (N Ａ) can be used to calculate the number of solvent molecules contained in the solid electrolyte. The surface area of ​​the inorganic compound contained in the solid electrolyte can be calculated by multiplying the specific surface area Sb of the inorganic compound measured by the BET method by the proportion of the inorganic compound in 1 g of a mixture of the inorganic compound and salt that constitutes the solid electrolyte. The number of molecules required to cover the inorganic compound with one molecular layer can be calculated by dividing this surface area by the molecular occupation area Sa of the solvent. The number of solvent molecules contained in the solid electrolyte can be calculated by dividing the number of molecules required to cover the inorganic compound with one molecular layer, N, assuming that the solvent is uniformly present on the surface of the inorganic compound. ｍｌ The number of molecular layers N can be calculated. ｍｌ is represented by the following formula: N ｍｌ = [Number of solvent molecules contained in the solid electrolyte] / [Number of molecules required to cover the inorganic compound with one layer of solvent molecules] = [{((Q ｒｓ / 100) / (1-(Q ｒｓ / 100))) / M ｗ} x N Ａ ] / [{Sb × (W ｍ / (W ｍ +W ｓ ))} / Sa] =((Q ｒｓ / 100) x N Ａ × (W ｍ +W ｓ )×Sa) / (Sb×(1-(Q ｒｓ / 100)) x W ｍ ×M ｗ ) (in the formula, W ｍ is the weight of inorganic compounds, W ｓ The salt content can be calculated according to the following formula:

[0018] The salt used in the solid electrolyte of the present invention is a salt containing an alkali metal or alkaline earth metal. Examples of alkali metals include lithium, sodium, potassium, etc. Examples of alkaline earth metals include magnesium, calcium, etc. In particular, the salt containing an alkali metal or alkaline earth metal preferably includes a salt containing at least one selected from the group consisting of lithium, sodium, and magnesium. Such salts are not particularly limited as long as they are electrolyte salts commonly used for various batteries, but preferred examples include LiCl, NaCl, MgCl, etc. ２ Chloride salts such as LiBr, LiI, NaBr, NaI, MgBr ２ Halide salts such as Li(FSO ２ ) ２ N (so-called LiFSI), Na (FSO ２ ) ２ bis(fluorosulfonyl)imide salts such as N (so-called NaFSI), Li(SO ２ CF ３ ) ２ N (so-called LiTFSI), Na(SO ２ CF ３ ) ２ N (so-called NaTFSI), Mg[(SO ２ CF ３ ) ２ N] ２ (so-called Mg(TFSI) ２ ), Ca[(SO ２ CF ３ ) ２ N] ２ (so-called Ca(TFSI) ２ and hydroxide salts such as LiOH and NaOH.

[0019] The solid electrolyte of the present invention can be produced at low process costs by combining a predetermined inorganic compound that is not in an amorphous state, a solvent, and a predetermined salt. That is, as described above, to produce an amorphous electrolyte as shown in Patent Documents 1 and 2, mechanical milling using a planetary ball mill or the like must be carried out for about 100 hours, which requires considerable energy costs. However, the present invention can significantly reduce such process costs, including energy costs.

[0020] The solid electrolyte of the present invention can be produced using the inorganic compound, solvent, and salt as described above, for example, as follows. First, a solvent is added to an inorganic compound powder as a base powder, and a suspension is obtained by subjecting the powder to ultrasonic treatment or the like. The inorganic compound used may be a metal oxide, metal halide, or metal hydroxide having at least one peak with a full width at half maximum of 0.80° or less in an XRD pattern. The inorganic compound used should have a BET specific surface area of ​​0.2 to 150 m. ２ / g, and more preferably 0.5 to 150m ２ / g, more preferably 1 to 120 m ２ / g. If necessary, the inorganic compound powder may be subjected to mechanical milling using a planetary ball mill or the like. Mechanical milling can also be used to adjust the specific surface area of ​​the inorganic compound to fall within the above range. It is preferable to limit the mechanical milling process to a relatively short period of time so as not to convert the inorganic compound to an amorphous state. This reduces process costs (especially energy costs) (compared to converting the inorganic compound to an amorphous state). For example, mechanical milling using a planetary ball mill is typically performed at 100 to 500 rpm for 1 to 30 hours, and more typically at 100 to 300 rpm for 1 to 20 hours. Meanwhile, a solution is obtained by adding a solvent to a salt containing an alkali metal or alkaline earth metal and subjecting the salt to ultrasonic treatment or the like. The resulting suspension and solution are mixed and subjected to ultrasonic treatment or the like to obtain an electrolyte precursor solution. A solid electrolyte can be obtained by vacuum drying the electrolyte precursor solution. It is preferable to carry out the vacuum drying by adjusting the conditions appropriately so that the amount of residual solvent and the number of molecular layers fall within the above-mentioned numerical ranges.

[0021] According to a preferred embodiment of the present invention, a battery containing the solid electrolyte of the present invention is provided. The battery of this embodiment is typically an all-solid-state battery. However, the battery of the present invention is not limited to all-solid-state batteries, and may be a battery that uses a combination of a solid material (such as a solid electrolyte) and a liquid material (such as an electrolytic solution or an ionic liquid), which is called a semi-solid battery, or may be another type of battery.

[0022] 1 schematically shows an example of a battery 10 according to this embodiment. The battery 10 includes a positive electrode 12, a negative electrode 14, and an electrolyte layer 16. The positive electrode 12 includes a positive electrode active material. The negative electrode 14 includes a negative electrode active material. The electrolyte layer 16 is disposed between the positive electrode 12 and the negative electrode 14. At least one of the positive electrode 12, the negative electrode 14, and the electrolyte layer 16 includes a solid electrolyte.

[0023] Battery 10 is typically an all-solid-state battery or an all-solid-state secondary battery. For example, battery 10 may be a lithium-ion secondary battery (typically an all-solid-state lithium-ion secondary battery), a sodium-ion secondary battery (typically an all-solid-state sodium-ion secondary battery), a potassium-ion secondary battery (typically an all-solid-state potassium-ion secondary battery), or a magnesium-ion secondary battery (typically an all-solid-state magnesium-ion secondary battery). An all-solid-state lithium-ion secondary battery is particularly preferred. Therefore, although the following description of the positive electrode 12 and the negative electrode 14 mainly assumes an all-solid-state lithium-ion secondary battery, this does not in any way exclude the application of the present invention to other batteries.

[0024] The positive electrode 12 includes a positive electrode active material. The positive electrode active material preferably includes a lithium composite oxide. Examples of lithium composite oxides include lithium nickel manganese oxide (LNMO) (typically LiNi ０．５ Mn １．５ O ４ ), lithium nickel cobalt manganese oxide (NCM) (typically Li(Ni,Co,Mn)O ２ ), lithium cobalt oxide (LCO) (typically LiCoO ２ ), lithium nickel cobalt aluminate (NCA) (typically Li(Ni,Co,Al)O ２ ) and lithium iron phosphate (LFP) (typically LiFePO ４ ), and combinations thereof. NCM, LCO, and NCA have a layered rock salt structure. LNMO has a spinel structure. LFP has an olivine structure. A lithium composite oxide having a layered rock salt structure, such as NCM, is preferred. The positive electrode 12 preferably further contains a solid electrolyte and / or an electron-conducting additive (carbon black, etc.) in addition to the positive electrode active material. The positive electrode 12 in this embodiment is formed by integrating these materials by pressure or heat. Therefore, as shown in FIG. 1, the positive electrode 12 is typically in the form of a positive electrode layer. When the positive electrode 12 contains a solid electrolyte, it is preferable to use the solid electrolyte according to the present invention described above as such a solid electrolyte.

[0025] The negative electrode 14 includes a negative electrode active material. Examples of the negative electrode active material include graphite, SiO, hard carbon, Li or a Li alloy, Si or a Si alloy, Sn or a Sn alloy, and lithium titanate (e.g., Li ４ Ti ５ O １２ (LTO) and Li ２ Ti ３ O ７ Examples of the negative electrode active material include graphite, SiO, titanium oxide, niobium oxide, niobium titanium oxide, and combinations thereof. In terms of energy density, graphite, SiO, or Li metal is preferred, and graphite or SiO is particularly preferred in terms of non-flammability. Meanwhile, LTO is particularly preferred in terms of cycle life. The negative electrode 14 preferably further contains a solid electrolyte in addition to the negative electrode active material from the viewpoint of improving ionic conductivity. The negative electrode 14 may further contain an electron conduction aid (carbon black, etc.). The negative electrode 14 in this embodiment is formed by integrating these materials by pressure or heat. Therefore, as shown in FIG. 1, the negative electrode 14 is typically in the form of a negative electrode layer. When the negative electrode 14 contains a solid electrolyte, it is preferable to use the solid electrolyte according to the present invention described above.

[0026] The electrolyte layer 16 is a layer containing an electrolyte and disposed between the positive electrode 12 and the negative electrode 14. Typically, the electrolyte layer 16 contains a solid electrolyte, and is preferably made of a solid electrolyte. In this case, the electrolyte layer 16 can be said to also function as a separator. The solid electrolyte contained in the electrolyte layer 16 is preferably the solid electrolyte according to the present invention described above.

[0027] At least one of the positive electrode 12, the negative electrode 14, and the electrolyte layer 16 contains a solid electrolyte according to the present invention. This solid electrolyte exhibits high ionic conductivity (e.g., lithium ion conductivity). Furthermore, this solid electrolyte is non-flammable and chemically stable, and does not generate hydrogen sulfide gas, thereby realizing an intrinsically safe battery 10. However, it is not necessary for all of the positive electrode 12, the negative electrode 14, and the electrolyte layer 16 to contain the solid electrolyte; at least one of them may contain the solid electrolyte.

[0028] The solid electrolyte according to the present invention may be mixed with other substances and used as an electrolyte material. In this case, the 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 wt % or more, more preferably 60 wt % or more, and even more preferably 70 wt % or more.

[0029] As described above, in the battery 10 of the present invention, sulfide-free materials can be used for the positive electrode 12, the negative electrode 14, and the electrolyte layer 16. In other words, it is preferable that no part of the positive electrode 12, the negative electrode 14, or the electrolyte layer 16 contains sulfide. This prevents the generation of toxic gases such as hydrogen sulfide, making the battery 10 inherently safe.

[0030] The battery 10 preferably further includes a positive electrode current collector 18 and a negative electrode current collector 20. The positive electrode current collector 18 is preferably provided on the surface of the positive electrode 12 opposite the electrolyte layer 16, and the negative electrode current collector 20 is preferably provided on the surface of the negative electrode 14 opposite the electrolyte layer 16. Examples of materials that can be used to form the positive electrode current collector 18 and the negative electrode current collector 20 include aluminum (Al), copper (Cu), titanium (Ti), nickel (Ni), stainless steel (SUS), carbon, platinum (Pt), platinum (Pt) / palladium (Pd), gold (Au), silver (Ag), and ITO (indium-tin oxide).

[0031] The container 22 is not particularly limited as long as it can accommodate a single battery 10 or a stack of multiple batteries 10 stacked in series or parallel. In particular, when the battery 10 is an all-solid-state battery, a relatively simple container shape can be adopted for the container 22 because there is no concern about electrolyte leakage. For example, a chip shape for mounting on an electronic circuit or a laminate cell shape (e.g., a multi-layer product of aluminum (Al) / polypropylene (PP)) for thin and wide space applications can be adopted.

[0032] The present invention will be explained in more detail by the following examples, but the present invention is not limited to the following examples.

[0033] Example 1 (1) Preparation of Electrolyte Alumina (γ-Al) manufactured by CIK Nanotech Co., Ltd. was used as a base material powder. ２ O ３ Ion-exchanged water was added to 3.4 g of Li(FSO) powder so that the concentration of the alumina powder was 42% by weight, and the mixture was subjected to ultrasonic treatment for 1 hour to obtain an alumina suspension. ２ ) ２ Ion-exchanged water was added to 3.82 g of N(LiFSI) powder to a LiFSI powder concentration of 87 wt %, and the mixture was sonicated for 1 hour to obtain a LIFSI solution. The resulting alumina suspension and the LiFSI solution were mixed and sonicated for 1 hour to obtain an electrolyte precursor solution. The electrolyte precursor solution was transferred to a 5.8 cm diameter dish and vacuum-dried at 40°C under a vacuum of 0.67 Pa for 105 minutes to obtain a solid electrolyte.

[0034] (2) Measurement of Specific Surface Area The specific surface area of ​​the base powder (alumina powder) was measured and calculated by the BET method. The obtained specific surface areas are shown in Table 1.

[0035] (3) XRD Measurement An XRD pattern was obtained by X-ray diffraction (XRD) for the base powder (alumina powder). This XRD was performed using a sealed tube XRD diffractometer (D8-ADVANCE, manufactured by Bruker AXS Co., Ltd.) under the following conditions: X-rays used: CuKα rays, voltage: 40 kV, current: 40 mA, step width: 0.02°. In the obtained XRD pattern, if there is a peak with a full width at half maximum of 0.80° or less within the diffraction angle 2θ range of 10 to 80°, the base powder was determined to have crystallinity. Figure 2 shows the XRD pattern of alumina powder (γ-Al ２ O ３ 1 shows an XRD pattern of a crystalline silicon dioxide film (manufactured by CIK Nanotech Co., Ltd.). In this XRD pattern, multiple peaks with a full width at half maximum of 0.80° or less were observed.

[0036] (4) Conductivity Measurement The solid electrolyte powder was placed in a mold consisting of a resin sleeve and upper and lower stainless steel punches, and uniaxial press molding was performed under a pressure of 25 MPa. Conductors were connected to the upper and lower punches, and impedance measurements were performed at room temperature. The lithium ion conductivity was calculated from the measurement results. The results are shown in Table 1.

[0037] (5) TG-DTA Thermogravimetric differential thermal analysis (TG-DTA) was performed on 5 mg of the obtained solid electrolyte using a thermogravimetric simultaneous differential thermal analyzer (Thermo plus EVO2 (TG-DTA8122 / H), manufactured by Rigaku Corporation) under the following conditions. <TG-DTA conditions> Temperature program: 25°C (room temperature) to 200°C (10°C / min) Measurement atmosphere: under air Sample weight: 5 mg Measurement container: alumina pan

[0038] Figure 2 shows the TG-DTA curve obtained by the above measurement. In this TG-DTA curve, an exothermic peak and weight loss were observed near 130°C, and this peak is believed to be due to the combustion of LiFSI. For comparison, TG-DTA measurement was also performed on LiFSI powder alone, and as shown in Figure 4, a peak believed to be due to combustion was observed near 330°C. These results suggest that the combustion peak may have shifted to a lower temperature due to the interaction between LiFSI, alumina, and water. Furthermore, from the TG-DTA results of the solid electrolyte, the amount of residual solvent contained in the solid electrolyte was calculated as the ratio (wt%) of the weight of the solid electrolyte immediately before TG-DTA to the weight of the solid electrolyte lost up to the temperature at which the exothermic peak believed to be the combustion peak of LiFSI was observed. The results are shown in Table 1.

[0039] From the area occupied by water molecules Sa and the amount of residual solvent calculated as above from the TG-DTA measurement, the number of molecular layers (N ｍｌ In this example, the specific surface area Sb of the alumina powder was 50 m as shown in Table 1. ２ / g, and the molecular area Sa of water is 0.116 nm ２ (1.16 x 10 ―１９ m ２The water molecule occupied area Sa was calculated by determining the volume per water molecule from the molecular weight and density of water, and then determining the cross-sectional area of ​​the sphere assuming that the molecule is a sphere. ｒｓ is 10.1% by weight as shown in Table 1, so the number of water molecular layers N ｍｌ is the weight of the inorganic compound (W ｍ ) 3.4 g, weight of salt (W ｓ ) 3.82g, Avogadro's number (N Ａ ), and the molecular weight of water is 18, ｍｌ = ((Q ｒｓ / 100) x N Ａ × (W ｍ +W ｓ )×Sa) / (Sb×(1-(Q ｒｓ / 100)) x W ｍ ×M ｗ ) = ((10.1 / 100) x N Ａ ×(3.4+3.82)×1.16×10 －１９ ) / (50 × (1 - (10.1 / 100)) × 3.4 × 18) = 19 layers.

[0040] Example 2 An electrolyte was prepared and evaluated in the same manner as in Example 1, except that in the preparation of the electrolyte in Example 1, a Petri dish having a diameter of 4.7 cm was used and vacuum drying was carried out for 180 minutes.

[0041] Example 3 An electrolyte was prepared and evaluated in the same manner as in Example 1, except that ethanol was used as the solvent instead of water, the vacuum drying time was set to 120 minutes, and the molding pressure in the conductivity measurement was set to 6 MPa.

[0042] Example 4 In the preparation of the electrolyte in Example 1, alumina (γ-Al) manufactured by Baikowski Corporation was used as the base material. ２ O ３ The electrolyte was prepared and evaluated in the same manner as in Example 1, except that the powder was used, the vacuum drying was carried out for 180 minutes, and the molding pressure in the conductivity measurement was set to 6 MPa.

[0043] Example 5 An electrolyte was prepared and evaluated in the same manner as in Example 4, except that the vacuum drying was carried out for 150 minutes.

[0044] Example 6 In the preparation of the electrolyte in Example 1, alumina (α-Al) manufactured by Sumitomo Chemical Co., Ltd. was used. ２ O ３ The electrolyte was prepared and evaluated in the same manner as in Example 1, except that a 4.7 cm diameter Petri dish was used, the vacuum drying time was 240 minutes, and the molding pressure in the conductivity measurement was 6 MPa.

[0045] Example 7 An electrolyte was prepared and evaluated in the same manner as in Example 1, except that the electrolyte was prepared as follows and that the molding pressure in the conductivity measurement was 6 MPa.

[0046] (Preparation of Electrolyte) 10 g of lithium fluoride (LiF) manufactured by Kojundo Chemical Laboratory Co., Ltd. was placed in a zirconia pot together with zirconia balls, and milled for 20 hours at 300 rpm using a planetary ball mill (P-5 manufactured by Fritsch) to obtain LiF powder as a base powder. 3.4 g of the obtained LiF powder was weighed out, and ion-exchanged water was added so that the concentration of the LiF powder was 42 wt %, and ultrasonic treatment was performed for 1 hour to obtain a LiF suspension. Next, Li(FSO ２ ) ２ Ion-exchanged water was added to 2.32 g of N(LiFSI) to a LiFSI concentration of 87 wt %, and the mixture was sonicated for 1 hour to obtain a LiFSI solution. The resulting LiF suspension and LiFSI solution were mixed and sonicated for 1 hour to obtain an electrolyte precursor solution. The electrolyte precursor solution was transferred to a 4.7 cm diameter dish and vacuum-dried at 40°C under a vacuum of 0.67 Pa for 150 minutes to obtain a solid electrolyte.

[0047] Example 8 An electrolyte was prepared and evaluated in the same manner as in Example 1, except that the electrolyte was prepared as follows.

[0048] (Preparation of Electrolyte) Lithium fluoride (LiF) powder and aluminum fluoride (AlF) manufactured by Kojundo Chemical Laboratory Co., Ltd. ３ ) powder was mixed with LiF:AlF ３The resulting mixture was heated at 900°C and then crushed in a mortar to obtain Li. ３ AlF ６ (i.e., LAF) powder was obtained. The LAF powder and Li ２ SO ４ (i.e., LSO) powder was weighed out so that the molar ratio of LAF:LSO was 40:60, and milled for 20 hours at 300 rpm using a planetary ball mill (P-5, manufactured by Fritsch) to obtain LAF-LSO powder. 3.4 g of the obtained LAF-LSO powder was weighed out, and ethanol was added to the mixture so that the LAF-LSO concentration became 42% by weight. The mixture was mixed with a stirrer for 1 hour to obtain an LAF-LSO suspension. Next, Li(FSO ２ ) ２ Ethanol was added to 3.02 g of N(LiFSI) to give a LiFSI concentration of 87 wt %, and the mixture was stirred for 1 hour to obtain a LiFSI solution. The resulting LAF-LSO suspension and the LiFSI solution were stirred for 1 hour to obtain an electrolyte precursor solution. The electrolyte precursor solution was transferred to a 4.7 cm diameter dish and vacuum-dried at 40°C under a vacuum of 0.67 Pa for 120 minutes to obtain a solid electrolyte.

[0049] Example 9 An electrolyte was prepared and evaluated in the same manner as in Example 8, except that acetonitrile was used instead of ethanol as the solvent and that vacuum drying was carried out for 90 minutes.

[0050] Example 10 In the preparation of the electrolyte of Example 8, Li(SO) was used as the salt instead of LiFSI. ２ CF ３ ) ２ An electrolyte was prepared and evaluated in the same manner as in Example 8, except that 4.63 g of N(LiTFSI) was used and the vacuum drying was carried out for 270 minutes.

[0051] Example 11 An electrolyte was prepared and evaluated in the same manner as in Example 1, except that the electrolyte was prepared as follows and that the molding pressure in conductivity measurement was set to 150 MPa.

[0052] (Preparation of Electrolyte) Zirconia (ZrO) manufactured by Sigma-Aldrich ２ 10 g of the powder was placed in a zirconia pot together with zirconia balls and milled for 20 hours at 300 rpm using a planetary ball mill (Fritsch, P-5) to obtain ZrO as a base powder. ２ The resulting ZrO powder ２ 3.4 g of the powder was weighed out and ZrO ２ Ion-exchanged water was added to the mixture to a concentration of 42% by weight, and ultrasonic treatment was carried out for 1 hour to obtain ZrO ２ A suspension was obtained. Next, Li(FSO ２ ) ２ Ion-exchanged water was added to 3.2 g of N(LiFSI) so that the LiFSI concentration was 87 wt %, and the mixture was subjected to ultrasonic treatment for 1 hour to obtain a LiFSI solution. ２ The suspension and the LiFSI solution were mixed and ultrasonicated for 1 hour to obtain an electrolyte precursor solution, which was then transferred to a 4.7 cm diameter dish and vacuum dried at 70°C under a vacuum of 0.67 Pa for 120 minutes to obtain a solid electrolyte.

[0053] Example 12 In the preparation of the electrolyte of Example 1, aluminum hydroxide (Al(OH) manufactured by Kojundo Chemical Laboratory Co., Ltd.) was used. ３ An electrolyte was prepared and evaluated in the same manner as in Example 1, except that the powder was used and the vacuum drying was carried out for 240 minutes.

[0054] Example 13 An electrolyte was prepared and evaluated in the same manner as in Example 1, except that in the preparation of the electrolyte in Example 1, 1.4 g of lithium chloride (LiCl) powder manufactured by Kojundo Chemical Laboratory Co., Ltd. was used as the salt instead of LiFSI, and the vacuum drying was carried out for 165 minutes using a Petri dish with a diameter of 4.7 cm.

[0055] Example 14 An electrolyte was prepared and evaluated in the same manner as in Example 13, except that in the preparation of the electrolyte in Example 13, magnesia (MgO) powder manufactured by Kyowa Chemical Industry Co., Ltd. was used as the base powder, 2.2 g of LiCl powder was used, vacuum drying was carried out for 300 minutes using a petri dish having a diameter of 5.8 cm, and the molding pressure in the conductivity measurement was 87.5 MPa.

[0056] Example 15 In the preparation of the electrolyte of Example 1, Na(FSO ) was used as the salt instead of LiFSI. ２ ) ２ An electrolyte was prepared and evaluated in the same manner as in Example 1, except that 4.2 g of N(NaFSI) powder was used, vacuum drying was performed for 150 minutes using a petri dish with a diameter of 4.7 cm, and the molding pressure in the conductivity measurement was set to 150 MPa.

[0057] Example 16 An electrolyte was prepared and evaluated in the same manner as in Example 1, except that 1.2 g of sodium chloride (NaCl) was used instead of LiFSI as the salt, that vacuum drying was carried out for 165 minutes, and that the molding pressure in conductivity measurement was set to 150 MPa.

[0058] Example 17 In the preparation of the electrolyte of Example 1, magnesium chloride (MgCl) was used as the salt instead of LiFSI. ２ An electrolyte was prepared and evaluated in the same manner as in Example 1, except that 1.97 g of the sintered body was used, that vacuum drying was carried out for 210 minutes using a petri dish with a diameter of 4.7 cm, and that the molding pressure in the conductivity measurement was 62.5 MPa.

[0059] Example 18 (Comparative) An electrolyte was prepared and evaluated in the same manner as in Example 1, except that the electrolyte was prepared as follows and the molding pressure in conductivity measurement was set to 150 MPa.

[0060] (Preparation of electrolyte) Li ２ B ４ O ７ 3.39 g of the base powder was milled at 300 rpm for 100 hours using a planetary ball mill (P-5, manufactured by Fritsch). ２ B ４ O ７ The resulting Li powder ２ B ４ O ７ Powder, Li ２ B ４ O ７ Ion-exchanged water was added to the mixture so that the concentration became 42% by weight, and the mixture was subjected to ultrasonic treatment for 1 hour to obtain Li ２ B ４O ７ A suspension was obtained. Next, Li(FSO ２ ) ２ Ion-exchanged water was added to 2.33 g of N(LiFSI) so that the LiFSI concentration was 87 wt %, and the mixture was subjected to ultrasonic treatment for 1 hour to obtain a LiFSI solution. ２ B ４ O ７ The suspension and the LiFSI solution were mixed and ultrasonicated for 1 hour to obtain an electrolyte precursor solution, which was then transferred to a 4.7 cm diameter dish and vacuum dried at 40°C under a vacuum of 0.67 Pa for 150 minutes to obtain a solid electrolyte.

[0061] Results Table 1 shows the compositions and measurement results of the components used in Examples 1 to 18, as well as the ionic conductivity of the solid electrolytes prepared.

[0062]

[0063] As shown in Table 1, the solid electrolytes prepared in Examples 1 to 17 all had a solubility of 5×10 －４ The base powders used in these solid electrolytes were all inorganic compounds having crystallinity, which differs from the amorphous powder prepared in Example 18, which is a comparative example.

[0064] Generally, obtaining an amorphous powder requires a long mechanical milling process or a high-temperature heat treatment. The solid electrolytes of Examples 1 to 17 use crystalline inorganic compound powders, and in this sense, they can be said to be materials that reduce the time and energy costs required for producing the electrolyte material.

Claims

1. A solid electrolyte comprising: at least one inorganic compound selected from the group consisting of metal oxides, metal halides, and metal hydroxides; a residual solvent; and a salt containing an alkali metal or an alkaline earth metal, wherein the inorganic compound has at least one peak with a full width at half maximum of 0.80° or less in an X-ray diffraction pattern.

2. The solid electrolyte according to claim 1, wherein the inorganic compound is crystalline.

3. The solid electrolyte according to claim 1 or 2, wherein the content of the residual solvent is 30% by weight or less based on the total weight of the solid electrolyte.

4. The solid electrolyte according to claim 1 or 2, wherein the number of molecular layers that can theoretically be formed by the residual solvent on the surface of the inorganic compound is within the range of 0.7 to 350.

5. The solid electrolyte according to claim 1 or 2, wherein the inorganic compound comprises the metal oxide.

6. The solid electrolyte of claim 5, wherein the metal oxide comprises at least one selected from the group consisting of alumina, magnesia, and zirconia.

7. The solid electrolyte according to claim 1 or 2, wherein the inorganic compound comprises the metal hydroxide.

8. The solid electrolyte of claim 7, wherein the metal hydroxide comprises aluminum hydroxide.

9. The solid electrolyte according to claim 1 or 2, wherein the inorganic compound comprises the metal halide compound.

10. The solid electrolyte of claim 9, wherein said metal halide comprises lithium aluminum fluoride.

11. The solid electrolyte according to claim 1 or 2, wherein the salt comprises a salt having at least one selected from the group consisting of lithium, sodium, and magnesium.

12. A battery comprising the solid electrolyte according to claim 1 or 2.

Images