Ionic conductor containing a high-temperature phase of LiCB9H10 and method for producing the same

Abstract

The present invention is capable of providing a method for producing an ion conductor containing LiCB9H10 and LiCB11H12, said method being characterized by comprising: a solution formation step wherein a homogeneous solution is prepared by mixing LiCB9H10 and LiCB11H12 in a solvent at a LiCB9H10 / LiCB11H12 molar ratio of from 1.1 to 20; a drying step wherein a precursor is obtained by removing the solvent from the homogeneous solution; and a heat treatment step wherein an ion conductor is obtained by subjecting the precursor to a heat treatment.

Description

Technical Field

[0001] The present invention relates to an ion conductor containing a high-temperature phase of LiCB9H 10 and a method for producing the same.

Background Art

[0002] In recent years, the demand for lithium-ion secondary batteries has been increasing in applications such as portable information terminals, portable electronic devices, electric vehicles, hybrid electric vehicles, and stationary power storage systems. However, current lithium-ion secondary batteries use a flammable organic solvent as an electrolyte, and thus require a strong outer package to prevent leakage of the organic solvent. In addition, in the case of portable personal computers and the like, it is necessary to adopt a structure to prepare for the risk in the event of electrolyte leakage, and thus there are also restrictions on the structure of the device.

[0003] Furthermore, its applications have spread to moving bodies such as automobiles and airplanes, and a large capacity is required for stationary lithium-ion secondary batteries. Under such circumstances, safety is becoming more important than ever, and efforts are being made to develop all-solid-state lithium-ion secondary batteries that do not use harmful substances such as organic solvents. For example, as a solid electrolyte in an all-solid-state lithium-ion secondary battery, the use of oxides, phosphate compounds, organic polymers, sulfides, complex hydrides, etc. has been studied.

[0004] All-solid-state batteries are roughly classified into thin-film types and bulk types. For thin-film types, although ideal interfacial bonding can be formed by using vapor deposition, the electrode layer is as thin as several μm and the electrode area is also small, so the energy stored per cell is small and the cost is high. Therefore, it is not suitable as a battery for large-scale power storage devices and electric vehicles that need to store a large amount of energy. On the other hand, the thickness of the bulk-type electrode layer can be set to several tens of μm to 100 μm, and an all-solid-state battery having a high energy density can be manufactured.

[0005] Among solid electrolytes, sulfides and complex hydrides have high ionic conductivity and are relatively soft, so they tend to form solid-solid interfaces, and their application to bulk-type all-solid-state batteries is being studied (Patent Documents 1 and 2).

[0006] However, conventional sulfide solid electrolytes have the property of reacting with water. Sulfides generate hydrogen sulfide, and after reacting with moisture, they have the problem of a decrease in ionic conductivity. On the other hand, compared with sulfide solid electrolytes, complex hydride solid electrolytes tend to have slightly lower ionic conductivity, and an improvement in ionic conductivity is desired.

[0007] Non-Patent Document 1 describes a solid electrolyte called a carbyne-based material with high ionic conductivity (6.7 mS / cm, 25°C), but it uses the mechanical milling method. The mechanical milling method has problems in mass production, and a large-scale synthesis method using a solution is desired. On the other hand, Non-Patent Document 2 discloses a method for manufacturing a highly productive all-solid-state battery by applying a solid electrolyte solution in which a boron hydride compound, which is a solid electrolyte, is dissolved to the surface where the positive electrode layer and the negative electrode layer of the electrode are joined, then removing the solvent and laminating them under a low pressing pressure.

[0008] Non-Patent Document 3 synthesizes a solid electrolyte with high ionic conductivity (5 mS / cm at 35°C) called a carbyne-based material using an aqueous solvent, but it is not only the high-temperature phase of LiCB9H 10 but also a multiphase of LiCB9H 10 and LiCB 11 H 12 and LiCB. Further improvement in ionic conductivity is desired.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0010]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0011] An object of the present invention is to provide an ion conductor having various excellent properties such as ion conductivity and a method for producing the same.

Means for Solving the Problems

[0012] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by an ion conductor obtained using a homogeneous solution prepared by mixing LiCB9H 10 and LiCB 11 H 12 in a specific molar ratio in a solvent. That is, the present invention is as follows. <1> A method for producing an ion conductor containing LiCB9H 10 and LiCB 11 H 12 comprising: LiCB9H 10 and LiCB 11 H 12 are mixed in a solvent at a molar ratio of LiCB9H 10 / LiCB 11 H 12 = 1.1 to 20 to prepare a homogeneous solution in a solution-forming step; a drying step of removing the solvent from the homogeneous solution to obtain a precursor; A heat treatment step of heat treating the precursor to obtain an ion conductor, characterized by comprising the above, which is a method for producing the ion conductor. <2> The solvent in the solubilization step is at least one selected from the group consisting of water, tetrahydrofuran, acetonitrile, acetone, ethyl acetate, methyl acetate, toluene, methylene chloride, and chloroform. The method for producing an ion conductor according to <1> above. <3> The solvent in the solubilization step is water. The method for producing an ion conductor according to <1> above. <4> The stirring and mixing time in the solubilization step is 5 minutes to 48 hours. The method for producing an ion conductor according to any one of <1> to <3> above. <5> In the solubilization step, LiCB9H 10 and LiCB 11 H 12 The molar ratio with is LiCB9H 10 / LiCB 11 H 12 = 1.5 to 9. The method for producing an ion conductor according to any one of <1> to <4> above. <6> The temperature in the drying step is 50 to 260 °C. The method for producing an ion conductor according to any one of <1> to <5> above. <7> The drying time in the drying step is 1 to 24 hours. The method for producing an ion conductor according to any one of <1> to <6> above. <8> The temperature in the heat treatment step is 150 to 260 °C. The method for producing an ion conductor according to any one of <1> to <7> above. <9> The heating time in the heat treatment step is 1 to 24 hours. The method for producing an ion conductor according to any one of <1> to <8> above. <10> The obtained ion conductor has a single-phase crystal structure of the high-temperature phase of LiCB9H 10 The method for producing an ion conductor according to any one of <1> to <9> above. <11> The obtained ion conductor has X-ray diffraction peaks at least at 2θ = 14.9 ± 0.3 deg, 16.4 ± 0.3 deg, and 17.1 ± 0.5 deg in X-ray diffraction measurement at 25°C, and the intensity ratio (B / A) calculated by A = (X-ray diffraction intensity at 16.4 ± 0.3 deg) - (X-ray diffraction intensity at 20 deg), B = (X-ray diffraction intensity at 17.1 ± 0.5 deg) - (X-ray diffraction intensity at 20 deg) is 1.0 to 20, which is the method for producing an ion conductor according to any one of <1> to <10> above. <12> The ionic conductivity of the obtained ion conductor at 25°C is 1.0 to 10 mScm -1 which is the method for producing an ion conductor according to any one of <1> to <11> above. <13> An ion conductor obtained by the method for producing an ion conductor according to any one of <1> to <12> above. <14> An electrode using the ion conductor according to <13> above. <15> An all-solid-state battery using the ion conductor according to <13> above.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide an ion conductor having various excellent properties such as ionic conductivity and a method for producing the same.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described. Note that the materials, configurations, etc. described below do not limit the present invention, and various modifications can be made within the scope of the present invention.

[0016] 1. Ionic conductors According to one embodiment of the present invention, there is provided an ionic conductor comprising lithium (Li), carbon (C), boron (B), and hydrogen (H). The embodiment is preferably a crystalline LiCB9H 10 and more preferably, LiCB9H as a crystal. 10 and LiCB9H 10 and LiCB 11 H 12 It consists of:

[0017] The ionic conductor of the present invention is LiCB9H 10 Based on 749cm -1 (±5cm -1 ) and LiCB 11 H 12 Based on 763cm -1 (±5cm -1 ) It is preferable that the peaks are in the respective regions. Peaks may also be present in other regions, but the peaks that show the characteristics of each region are as described above.

[0018] The ionic conductor of the present invention is LiCB9H as a crystal. 10 It is preferred that the high temperature phase of LiCB9H 10 has a high-temperature phase and a low-temperature phase due to its crystalline state, and has high ionic conductivity in the high-temperature phase at high temperatures (for example, about 75 to 150°C), but enters the low-temperature phase near room temperature (for example, about 20 to 65°C), where the ionic conductivity decreases. The ionic conductor of the present invention exhibits a 2θ=14.9±0.3 deg, a 2θ=16.4±0.3 deg, and a 2θ=17.1±0.5 deg at least in X-ray diffraction measurement at 25°C. 10Preferably, it has an X-ray diffraction peak based on the high-temperature phase. More preferably, A = (X-ray diffraction intensity at 16.4 ± 0.3 deg) - (X-ray diffraction intensity at 20 deg), B = (X-ray diffraction intensity at 17.1 ± 0.5 deg) - (X-ray diffraction intensity at 20 deg), and the intensity ratio (B / A) calculated thereby is in the range of 1.0 to 20, more preferably in the range of 1.0 to 15, and particularly preferably in the range of 1.0 to 10. When the intensity ratio (B / A) is in the range of 1.0 to 20, the phase transition temperature decreases due to the solid solution of LiCB9H 10 in the high-temperature phase of LiCB 11 H 12 , and the ionic conductivity can be maintained at a high level even near room temperature. This solid solution occurs when the molar ratio of LiCB9H 10 / LiCB 11 H 12 is 1.1 or more. Preferably, LiCB9H 10 / LiCB 11 H 12 = 1.1 to 20, more preferably LiCB9H 10 / LiCB 11 H 12 = 1.25 to 10, and particularly preferably LiCB9H 10 / LiCB 11 H 12 = 1.5 to 9, and in this range, the ionic conductivity shows a high value. Note that even if the ion conductor of the present invention contains X-ray diffraction peaks other than those described above, the desired effects can be obtained. In addition, the ion conductor of the present invention may contain components other than lithium (Li), carbon (C), boron (B), and hydrogen (H). Examples of other components include oxygen (O), nitrogen (N), sulfur (S), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), silicon (Si), germanium (Ge), phosphorus (P), alkali metals, alkaline earth metals, and the like.

[0019] The above ion conductor is soft and can be formed into an electrode layer and a solid electrolyte layer by cold pressing. And the thus formed electrode layer and solid electrolyte layer are excellent in strength as compared with the case where they contain a large amount of sulfide solid electrolyte or oxide solid electrolyte. Therefore, by using the ion conductor of the present invention, an electrode layer and a solid electrolyte layer with good formability and less cracking (less likely to generate cracks) can be produced. Further, since the ion conductor of the present invention has a low density, a relatively light electrode layer and solid electrolyte layer can be produced. Thereby, the weight of the whole battery can be reduced, which is preferable. Furthermore, when the ion conductor of the present invention is used in the solid electrolyte layer, the interfacial resistance with the electrode layer can be lowered. Furthermore, the above ion conductor does not decompose even when it comes into contact with moisture or oxygen, and does not generate dangerous toxic gases.

[0020] The ion conductor of the present invention preferably has an ionic conductivity of 1.0 to 10 mScm at 25 °C -1 and more preferably 2.0 to 10 mScm -1 at 25 °C.

[0021] 2. Method for manufacturing an ion conductor According to another embodiment of the present invention, there is provided a method for manufacturing an ion conductor containing LiCB9H 10 and LiCB 11 H 12 the method including a solubilization step of mixing LiCB9H 10 and LiCB 11 H 12 in a solvent at a molar ratio of LiCB9H 10 / LiCB 11 H 12 = 1.1 to 20 to prepare a homogeneous solution, a drying step of removing the solvent from the homogeneous solution to obtain a precursor, and a heat treatment step of heat treating the precursor to obtain an ion conductor. In the present invention, the "uniform solution" is defined as a solution in which at least lithium (Li), carbon (C), boron (B), and hydrogen (H) are contained in a solvent, there is no undissolved precipitate, and the raw materials are dissolved in the solvent.

[0022] As the raw materials LiCB9H 10 and LiCB 11 H 12 those that are usually commercially available can be used. Further, the purity is preferably 95% or more, and more preferably 98% or more. By using a compound having a purity within the above range, desired crystals can be easily obtained.

[0023] LiCB9H 10 and LiCB 11 H 12 The mixing ratio of LiCB9H 10 / LiCB 11 H 12 needs to be a molar ratio of 1.1 or more. Preferably, LiCB9H 10 / LiCB 11 H 12 = 1.1 to 20, more preferably LiCB9H 10 / LiCB 11 H 12 = 1.25 to 10, and particularly preferably LiCB9H 10 / LiCB 11 H 12 = 1.5 to 9. As described above, in this range, the ionic conductivity shows a particularly high value.

[0024] LiCB9H 10 and LiCB 11 H 12 can be mixed in a homogeneous solvent in the atmosphere.

[0025] As a mixing method, it can also be carried out under a solvent. The solvent is not particularly limited, and examples thereof include water, nitrile solvents such as acetonitrile, ether solvents such as tetrahydrofuran and diethyl ether, alcohol solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, methanol and ethanol, acetone, ethyl acetate, methyl acetate, toluene, methylene chloride, and chloroform. Among these solvents, water is particularly preferred for safety reasons.

[0026] The mixing time in the solvent varies depending on the mixing method. In the case of stirring and mixing in the solvent, for example, 5 minutes to 48 hours is preferred, and 5 minutes to 1 hour is more preferred.

[0027] The pressure in the solubilization step is usually in the range of 0.1 Pa to 2 MPa as the absolute pressure. Preferably, it is 101 kPa to 1 MPa. The solubilization step is preferably carried out under an inert gas atmosphere or in a sufficiently dry atmosphere. The inert gas is not particularly limited, but argon is particularly preferred.

[0028] The drying temperature of the solvent in the drying step is usually in the range of 50 to 300 °C. Preferably, it is 50 °C to 260 °C, and more preferably, it is 150 to 220 °C. Also, the drying time of the solvent in the drying step varies slightly depending on the type of solvent and the drying temperature, but the solvent can be sufficiently removed by carrying out for 1 to 24 hours. The drying time of the solvent is more preferably 10 to 14 hours. In addition, by removing the solvent under reduced pressure such as vacuum drying or flowing an inert gas such as nitrogen or argon with sufficiently little moisture, the temperature for removing the solvent can be lowered and the required time can be shortened. It is also possible to carry out the subsequent heat treatment step and the drying step simultaneously.

[0029] The reduced pressure condition of the solvent in the drying step is usually 10 -1 Pa or less. Preferably, it is 5×10 -4 Pa or less.

[0030] In the heat treatment step, the precursor obtained in the drying step is heat-treated to obtain an ion conductor. The heating temperature is preferably in the range of 150 to 260°C, more preferably in the range of 180 to 220°C. If the temperature is lower than the above range, it is difficult to form the desired crystals. On the other hand, even if the temperature is higher than the above range, crystals other than the target may be generated.

[0031] The heating time varies slightly depending on the heating temperature, but usually crystallization can be sufficiently achieved in the range of 1 to 24 hours. Heating at a high temperature for a long time beyond the above range is not preferable because there is a concern about the deterioration of the ion conductor. A more preferable heating time is in the range of 10 to 14 hours. Heating can be performed under vacuum to 1 MPa or in an inert gas atmosphere, but preferably under vacuum. As the inert gas, nitrogen, helium, argon, etc. can be used, and argon is particularly preferable. In the present invention, instead of vacuum, for example, heat treatment can also be performed under an argon atmosphere at 1 MPa. It is preferable that the oxygen and moisture are low.

[0032] The ion conductor obtained by the above production method of the present invention preferably has peaks at 749 cm 10 (±5 cm -1 ) and 763 cm -1 (±5 cm 11 H 12 based on LiCB -1 (±5 cm -1 ) in Raman spectroscopic measurement. Further, in X-ray diffraction measurement at 25°C, at least 2θ = 14.9 ± 0.3 deg, 16.4 ± 0.3 deg, 17.1 ± 0.5 deg for LiCB9H 10having an X-ray diffraction peak based on the high-temperature phase, and the intensity ratio (B / A) calculated by A = (X-ray diffraction intensity at 16.4 ± 0.3 deg) - (X-ray diffraction intensity at 20 deg), B = (X-ray diffraction intensity at 17.1 ± 0.5 deg) - (X-ray diffraction intensity at 20 deg) is preferably in the range of 1 to 20, more preferably in the range of 1.0 to 15, and particularly preferably in the range of 1.0 to 10.

[0033] 3. All-solid-state battery The ion conductor of the present invention can be used as a solid electrolyte for an all-solid-state battery. Therefore, according to one embodiment of the present invention, a solid electrolyte for an all-solid-state battery containing the above-described ion conductor is provided. Further, according to a further embodiment of the present invention, an all-solid-state battery using the above-described solid electrolyte for an all-solid-state battery is provided.

[0034] In the present specification, an all-solid-state battery is an all-solid-state battery in which lithium ions are responsible for electric conduction, particularly an all-solid-state lithium-ion secondary battery. The all-solid-state battery has a structure in which a solid electrolyte layer is disposed between a positive electrode layer and a negative electrode layer. The ion conductor of the present invention may be included as a solid electrolyte in any one or more of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer. When used in an electrode layer, it is preferably used in the negative electrode layer rather than the positive electrode layer. This is because side reactions are less likely to occur in the negative electrode layer. When the ion conductor of the present invention is included in the positive electrode layer or the negative electrode layer, it is used in combination with a known positive electrode active material or negative electrode active material for a lithium-ion secondary battery. As the negative electrode layer, a bulk type in which an active material and a solid electrolyte are mixed is preferably used because the capacity per single cell increases.

[0035] The all-solid-state battery is manufactured by forming and laminating each of the above-described layers. However, the forming method and the laminating method of each layer are not particularly limited. For example, a method of preparing a film by dispersing a solid electrolyte and / or an electrode active material in a solvent to form a slurry, coating the slurry by a doctor blade, spin coating, etc., and then rolling it; a vapor phase method of forming and laminating using a vacuum evaporation method, an ion plating method, a sputtering method, a laser ablation method, etc.; a pressing method of forming a powder by hot pressing or cold pressing without applying temperature and laminating the powder. Since the ion conductor of the present invention is relatively soft, it is particularly preferable to form and laminate by pressing to manufacture the battery. Further, an electrode layer containing a active material, a conductive assistant, and binders in advance may be formed, and a solution in which a solid electrolyte is dissolved in a solvent or a slurry in which a solid electrolyte is dispersed in a solvent is poured into the electrode layer, and then the solvent is removed to incorporate the solid electrolyte into the electrode layer.

[0036] As the atmosphere for manufacturing the all-solid-state battery, it is preferable to carry out the manufacturing in an inert gas with controlled moisture or in a dry room. The moisture control is in the range of dew point -10°C to -100°C, more preferably in the range of dew point -20°C to -80°C, and particularly preferably in the range of dew point -30°C to -75°C. This is to prevent the ion conductivity from decreasing by forming a hydrate although the hydrolysis rate of the ion conductor of the present invention is extremely slow.

Examples

[0037] Hereinafter, the present invention will be described in detail by way of examples, but the content of the present invention is not limited thereto.

[0038] <Preparation of Ion Conductor> (Example 1) In a glove box under an argon atmosphere, LiCB9H 10 :LiCB 11 H 12 =7:3 in molar ratio so that LiCB9H 10240 mg of (manufactured by Katchem), LiCB 11 H 12 122.2 mg of (manufactured by Katchem) was weighed. Next, the previously weighed LiCB9H 10 and LiCB 11 H 12 10 mL of pure water (Water, Reagent, Alfa Aesar) was added to the mixed powder of and dissolved, and the mixture was stirred for 30 minutes using a stirrer. The obtained homogeneous solution was dried under reduced pressure conditions of 0.1 Pa or less in a glass tube oven at 150 °C for 12 hours to remove the pure water, and a dried white powder (precursor) was obtained. 50 mg of the obtained white powder, which was kneaded in a mortar for 15 minutes, was pelletized at 240 MPa and subjected to vacuum heat treatment at 200 °C for 12 hours using a turbo pump. The obtained ion conductor was measured by the AC impedance method, and the ionic conductivity was measured. As a result of X-ray diffraction, the obtained ion conductor had a stabilized high-temperature phase of LiCB9H 10 . No phase transition was observed in the DTA measurement, and the Raman spectrum also showed the same spectrum as that made by milling synthesis.

[0039] (Comparative Example 1) In Example 1, an ion conductor was produced in the same manner as in Example 1, except that the raw materials were used so that the molar ratio of LiCB9H 10 :LiCB 11 H 12 was 5:5.

[0040] <X-ray Diffraction Measurement> Regarding the powder of the ion conductor obtained in Example 1, X-ray diffraction measurement (PANalytical X‘pert Pro, CuKα: λ = 1.5405 Å) was carried out using a Lindemann glass capillary (outer diameter 0.5 mm, thickness 0.01 mm) at room temperature (25 °C) under an argon atmosphere. The obtained X-ray diffraction peaks are shown in Fig. 1. For comparison, Fig. 1 also shows the X-ray diffraction peaks of the raw materials LiCB9H 10 and LiCB 11 H 12 and LiCB9H 10 (high-temperature phase at 150 °C). In Example 1, X-ray diffraction peaks were observed at least at 2θ = 14.9 ± 0.3 deg, 16.4 ± 0.3 deg, and 17.1 ± 0.5 deg. Also, for LiCB9H 10 the intensities of the peak positions at 16.44 deg and 17.07 deg, which are the peak positions of the high-temperature phase, were defined as A and B, respectively. Each intensity was calculated with the value at 2θ = 20 deg regarded as the baseline, where A = (X-ray diffraction intensity at 16.44 deg) - (X-ray diffraction intensity at 20 deg) and B = (X-ray diffraction intensity at 17.07 deg) - (X-ray diffraction intensity at 20 deg). Example 1 is found to form a solid solution because it coincides with the peak position of the high-temperature phase of LiCB9H 10 .

[0041] <Raman Spectroscopy Measurement> (1) Sample Preparation A measurement sample was prepared using a sealed container having a quartz glass (Φ60 mm, thickness 1 mm) as an optical window on the top. In a glove box under an argon atmosphere, the sample was kept in a state of contacting the quartz glass, and then the container was sealed and taken out of the glove box for Raman spectroscopy measurement. (2) Measurement Conditions A laser Raman spectrophotometer NRS-5100 (manufactured by JASCO Corporation) was used for measurement at an excitation wavelength of 532.15 nm and an exposure time of 5 seconds. The obtained Raman spectrum is shown in Figure 2. LiCB9H 10 has a peak at 749 cm -1 , and LiCB 11 H 12 has a peak at 763 cm -1 . Note that the Raman shift value is derived from the bond and is hardly affected by the crystal state. In Example 1, it can be seen that the peak at 763 cm -1 becomes a shoulder peak of the peak at 749 cm -1 .

[0042] <Ionic Conductivity Measurement> In a glove box under an argon atmosphere, the ionic conductor obtained in Example 1, LiCB9H as the raw material10 and LiCB 11 H 12 were subjected to uniaxial pressing (240 MPa) to produce disks with a thickness of approximately 1 mm and a diameter of φ8 mm. The temperature was raised and lowered at 10°C intervals in the temperature range from room temperature to 150°C or 80°C, and alternating current impedance measurements (HIOKI 3532-80, chemical impedance meter) were performed using a two-terminal method with a lithium electrode to calculate the ionic conductivity. The measurement frequency range was 4 Hz to 1 MHz, and the amplitude was 100 mV.

[0043] The measurement results of the ionic conductivity for each are shown in Figure 3. Also, the ionic conductivity and activation energy at room temperature (25°C) are shown in Table 1. Note that Example 1 uses the raw material LiCB9H 10 and LiCB 11 H 12 The phenomenon in which the ionic conductivity rapidly decreases at low temperatures as seen in was not observed. Also, the ionic conductivity of the ion conductor obtained in Comparative Example 1 is shown in Table 1.

[0044]

Table 1

[0045] <Differential Thermal Analysis DTA Measurement> Regarding the powder of the ion conductor obtained in Example 1, differential thermal analysis DTA measurements were performed from room temperature to 200°C at a heating / cooling rate of 5°C / min using a differential thermal analysis DTA apparatus (Rigaku Thermo Plus TG-8120 system) in an argon atmosphere. Note that Example 1 uses the raw material LiCB9H 10 and LiCB 11 H 12 The phase transition as seen in was not observed.

Claims

1. LiCB ９ H １０ and LiCB １１ H １２ A method for producing an ion conductor containing LiCB ９ H １０ and LiCB １１ H １２ and, LiCB ９ H １０ / LiCB １１ H １２ A solubilization step of mixing in a solvent at a molar ratio of 1.1 to 10 to prepare a homogeneous solution A drying step of removing the solvent from the homogeneous solution to obtain a precursor, A heat treatment step of heat treating the precursor to obtain an ion conductor, A method for producing the ion conductor, comprising:

2. The method for producing an ion conductor according to claim 1, wherein the solvent in the solubilization step is at least one selected from the group consisting of water, tetrahydrofuran, acetonitrile, acetone, ethyl acetate, methyl acetate, toluene, methylene chloride, and chloroform.

3. The method for producing an ion conductor according to claim 1, wherein the solvent in the solubilization step is water.

4. The method for producing an ion conductor according to any one of claims 1 to 3, wherein the stirring and mixing time in the solubilization step is 5 minutes to 48 hours.

5. LiCB in the solution preparation step ９ H １０ and LiCB １１ H １２ The molar ratio of LiCB ９ H １０ to LiCB １１ H １２ is 1.5 to 9, and the method for producing an ion conductor according to any one of claims 1 to 4.

6. The method for producing an ion conductor according to any one of claims 1 to 5, wherein the temperature in the drying step is 50 to 260°C.

7. The method for producing an ion conductor according to any one of claims 1 to 6, wherein the drying time in the drying step is 1 to 24 hours.

8. The method for producing an ion conductor according to any one of claims 1 to 7, wherein the temperature in the heat treatment step is 150 to 260°C.

9. The method for producing an ion conductor according to any one of claims 1 to 8, wherein the heating time in the heat treatment step is 1 to 24 hours.

10. The obtained ion conductor is LiCB ９ H １０ The method for producing an ion conductor according to any one of claims 1 to 9, which has a single crystal structure of a high-temperature phase of

11. The obtained ion conductor has X-ray diffraction peaks at at least 2θ = 14.9 ± 0.3 deg, 16.4 ± 0.3 deg, and 17.1 ± 0.5 deg in X-ray diffraction measurement at 25°C. The intensity ratio (B / A) calculated by A = (X-ray diffraction intensity at 16.4 ± 0.3 deg) - (X-ray diffraction intensity at 20 deg), B = (X-ray diffraction intensity at 17.1 ± 0.5 deg) - (X-ray diffraction intensity at 20 deg) is 1.0 to 20. The method for producing an ion conductor according to any one of claims 1 to 10.

12. The ionic conductivity of the obtained ionic conductor at 25 °C is 1.0 to 10 mScm -1 The method for producing an ionic conductor according to any one of claims 1 to 11, wherein the ionic conductivity is as defined above.

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