Solid Electrolyte, Secondary Battery, and Capacitor

Abstract

A solid electrolyte which contains a molecular crystal and an inorganic filler.

Description

Technical Field

[0001] The present invention relates to a solid electrolyte, a secondary battery, and a capacitor.

Background Art

[0002] In recent years, attempts have been made to apply a solid electrolyte instead of a liquid electrolyte solution in terms of weight reduction of the battery, simplification of the battery structure, etc. For example, inorganic solid electrolytes such as sulfide-based inorganic solid electrolytes and oxide-based inorganic solid electrolytes are expected to be put into practical use as solid electrolytes for secondary batteries and the like.

[0003] When an inorganic solid electrolyte such as an oxide-based inorganic solid electrolyte is used, there is a problem that it is difficult to achieve close adhesion with the electrode, and the interfacial resistance between the electrode and the inorganic solid electrolyte tends to increase. Therefore, polymer electrolytes, which are generally easier to adhere to the electrode than inorganic solid electrolytes, are also being studied as solid electrolytes for secondary batteries and the like.

[0004] However, polymer electrolytes have a problem that it is difficult to ensure high ionic conductivity.

[0005] As described above, in view of the problems when inorganic solid electrolytes and polymer electrolytes are used alone, combining an inorganic solid electrolyte and a polymer electrolyte to form a solid electrolyte, or compounding an inorganic solid electrolyte or a polymer electrolyte with other materials to form a solid electrolyte, etc. have been studied.

[0006] For example, a method of providing a solid electrolyte layer containing a binder such as a graft polymer or a resin and inorganic solid electrolyte particles to improve the adhesion between the solid electrolyte layer and the electrode and obtain high ionic conductivity has been studied (see, for example, Patent Document 1). Furthermore, a pseudo-solid electrolyte including metal oxide particles and an ion conductive material that is a mixture of an ionic liquid and a lithium salt, and the ion conductive material is supported on the metal oxide particles has been studied (see, for example, Patent Document 2). In addition, a method for producing a solid electrolyte using a coating solution containing an ionic liquid, inorganic oxide particles, and a polymer having a functional group block capable of binding to the surface of the inorganic oxide particles has been studied (see, for example, Patent Document 3).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] For example, when a polymer electrolyte and an oxide-based inorganic solid electrolyte are combined to form a solid electrolyte, the ionic conductivity of the entire solid electrolyte tends to reflect the properties of the polymer electrolyte with inferior ionic conductivity, and there is room for improvement.

[0009] The present disclosure has been made in view of the above, and an object thereof is to provide a solid electrolyte excellent in flexibility and ionic conductivity, and a secondary battery and a capacitor including the same.

Means for Solving the Problems

[0010] Means for solving the above problems include the following aspects. <1> A solid electrolyte including a molecular crystal and an inorganic filler. <2> The molecular crystal is [M a {N(SO2F)2} b X c n , [M a {N(SO2CF3)2} b X c n , [M a ​​{N(SO2CF2)2CF2} b X c n and [M a {N(SO2C4F9)2} b X c and at least one molecular crystal selected from the group consisting of (where M is each independently a monovalent to trivalent metal atom, a is each independently an integer of 1 or more, b is each independently an integer of 1 or more, c is each independently an integer of 1 or more, and n is each independently an integer of 1 or more. However, in each general formula, (valence of M) × a - b = 0 is satisfied. X each independently represents a ligand.) The solid electrolyte according to <1>. <3> The solid electrolyte according to <1> or <2>, wherein the inorganic filler is an inorganic oxide. <4> The solid electrolyte according to any one of <1> to <3>, wherein the content of the inorganic filler is 1% by mass to 85% by mass based on the total amount of the molecular crystal and the inorganic filler. <5> The molecular crystal is [LiN(SO2F)2(NCCH2CH2CN)2] n , [Li2{N(SO2CF3)2}2(NCCH2CH2CN)3] n , [Li{N(SO2CF3)2}{(CH3)2NCH2CH2N(CH3)2}] n , [Li{N(SO2CF2)2CF2}{(CH3)2NCH2CH2N(CH3)2}] n and [Li{N(SO2C4F9)2}{C6H4(OCH3)2 n and at least one selected from the group consisting of. The solid electrolyte according to any one of <1> to <4>. <6> The solid electrolyte according to any one of <1> to <5>, which is used as a solid electrolyte of a secondary battery or a capacitor.

[0011] <7> A secondary battery including the solid electrolyte according to any one of <1> to <5>. <8> A capacitor including the solid electrolyte according to any one of <1> to <5>.

Advantages of the Invention

[0012] ​ According to one embodiment of the present invention, a solid electrolyte excellent in flexibility and ion conductivity, and a secondary battery and a capacitor including the same can be provided.

Brief Description of the Drawings

[0013]

Figure 1

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Figure 4

Figure 5

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Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the present disclosure will be described in detail. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In the present disclosure, each component may contain a plurality of corresponding substances. When there are a plurality of substances corresponding to each component in the composition, the content rate or content of each component means the total content rate or content of the plurality of substances present in the composition, unless otherwise specified.

[0015] [Solid electrolyte] The solid electrolyte of the present disclosure includes a molecular crystal and an inorganic filler. Thereby, the solid electrolyte of the present disclosure is excellent in flexibility and ion conductivity. The reason for this is that by including a molecular crystal, the flexibility of the solid electrolyte becomes good, and by including an inorganic filler, the ion conductivity is improved, and by the composite of the molecular crystal and the inorganic filler, ions diffuse rapidly through the space charge layer generated at the interface between the molecular crystal and the inorganic filler (nanoionics phenomenon) occurs, and it is presumed that the ion conductivity becomes further good. Further, in the solid electrolyte of the present disclosure, even in a temperature range above the melting point of the molecular crystal, it is possible to handle the solid electrolyte as a quasi-solid by the composite of the molecular crystal and the inorganic filler, and it is considered that problems such as dissolution and elution of the molecular crystal can be suppressed.

[0016] The solid electrolyte of the present disclosure may be used, for example, as a solid electrolyte of a secondary battery, a capacitor, or an air battery, and preferably may be used as a solid electrolyte of a secondary battery or a capacitor.

[0017] (Molecular crystal) The solid electrolyte of the present disclosure contains a molecular crystal. The molecular crystal is not particularly limited as long as it is a crystal formed by a plurality of molecules bound by intermolecular interactions. The molecular crystal preferably contains an ionic compound including a cation of a monovalent to trivalent metal atom and an anion, and a ligand of the ionic compound. Note that the ligand of the ionic compound may be a ligand that coordinates the ionic compound itself, or a ligand that coordinates a free cation or anion.

[0018] As the cation of the monovalent to trivalent metal atom in the ionic compound, a cation of at least one metal atom selected from the group consisting of lithium, sodium, potassium, magnesium, and aluminum is preferable, and lithium or sodium is more preferable.

[0019] As the anion in the ionic compound, N(SO2F)2 - (FSA), N(SO2CF3)2 - (TFSA), N(SO2C4F9)2 - anions such as (NFBSA), N(SO2CF2)2CF2 - (CPFSA), N(SO2CF2)2 - and cyclic anions such as etc. are preferable.

[0020] The ionic compound may be a lithium salt, a sodium salt, a potassium salt, a magnesium salt, an aluminum salt, or the like.

[0021] The ligand of the ionic compound is not particularly limited as long as it is a compound that can form a molecular crystal as a ligand of the ionic compound. For example, an organic compound containing an atom selected from the group consisting of a nitrogen atom, an oxygen atom, a phosphorus atom, and a sulfur atom (hereinafter also referred to as a "specific atom") (hereinafter also referred to as a "specific organic compound") is preferable.

[0022] The specific atom in the specific organic compound is preferably a nitrogen atom or an oxygen atom. The number of specific atoms in the specific organic compound is preferably 1 to 3, and more preferably 2.

[0023] The specific organic compound is preferably an amine compound, a nitrile compound, an ether compound or a thioether compound, and more preferably a nitrile compound or an ether compound.

[0024] The specific organic compound is preferably a compound in which two amino groups, two nitrile groups, two alkoxy groups or two thioalkyl groups are bonded via a divalent linking group. Examples of the amino group include a primary amino group, a secondary amino group or a tertiary amino group. Examples of the divalent linking group include a substituted or unsubstituted alkylene group, a phenylene group, etc.

[0025] Specific examples of the specific organic compound are not particularly limited, and include N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, N,N,N',N'-tetramethyl-1,2-diaminopropane, N,N,N',N'-tetramethyl-1,3-diaminopropane, N,N,N',N'-tetramethyl-1,3-diaminobutane, malononitrile, succinonitrile, glutaronitrile, adiponitrile, dimethylmalononitrile, tetramethylsuccinonitrile, 1,1,3,3-propanetetracarbonitrile, 1,2,2,3-propanetetracarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,5-cyclohexanetricarbonitrile, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene and the like. Among them, from the viewpoint of excellent ionic conductivity of the solid electrolyte, N,N,N',N'-tetramethylethylenediamine ((CH3)2NCH2CH2N(CH3)2), succinonitrile (NCCH2CH2CN) and 1,2-dimethoxybenzene (C6H4(OCH3)2) are preferable, and from the viewpoints of ionic conductivity of the solid electrolyte and suppression of volatilization at high temperature, succinonitrile and glutaronitrile are more preferable. For example, since the boiling point of succinonitrile is 265 °C and the boiling point of glutaronitrile is 287 °C, which are relatively high, the evaporation of the ligand under heating conditions can be suppressed. Therefore, the solid electrolyte of the present disclosure can be expected to be used in a wide range.

[0026] The number of ligands of the ionic compound may be one or more with respect to one molecule of the ionic compound, preferably one to three, and more preferably one or two from the viewpoint of the ionic conductivity of the solid electrolyte.

[0027] The molecular crystal is [M a {N(SO2F)2} b X c n 、[M a {N(SO2CF3)2} b X c n 、[M a {N(SO2CF2)2CF2} b X c n And [M a {N(SO2C4F9)2} b X c and preferably contains at least one molecular crystal selected from the group consisting of (hereinafter also referred to as "specific molecular crystal"). M is each independently a monovalent to trivalent metal atom, a is each independently an integer of 1 or more, b is each independently an integer of 1 or more, c is each independently an integer of 1 or more, and n is each independently an integer of 1 or more. However, in each general formula, (valence of M) × a - b = 0 is satisfied. X each independently represents a ligand.

[0028] In the specific molecular crystal, M is preferably lithium, sodium, potassium, magnesium or aluminum, and more preferably lithium or sodium. The preferred configuration of the ligand represented by X is the same as the preferred configuration of the ligand of the aforementioned ionic compound.

[0029] ​​​The molecular crystal is [LiN(SO2F)2(NCCH2CH2CN)2] n , [Li2{N(SO2CF3)2}2(NCCH2CH2CN)3] n , [Li{N(SO2CF3)2}{(CH3)2NCH2CH2N(CH3)2}] n , [Li{N(SO2CF2)2CF2}{(CH3)2NCH2CH2N(CH3)2}] n and [Li{N(SO2C4F9)2}{C6H4(OCH3)2] n It is preferably at least one selected from the group consisting of. The molecular crystal is more preferably [LiN(SO2F)2(NCCH2CH2CN)2] n because of its excellent ionic conductivity of the solid electrolyte.

[0030] In the solid electrolyte of the present disclosure, the content of the molecular crystal is preferably 15% by mass to 99% by mass, more preferably 70% by mass to 95% by mass, and even more preferably 80% by mass to 95% by mass with respect to the total amount of the molecular crystal and the inorganic filler. When the content of the molecular crystal is 15% by mass or more, the flexibility of the solid electrolyte tends to be more excellent, and when the content of the molecular crystal is 99% by mass or less, the ionic conductivity of the solid electrolyte tends to be more excellent.

[0031] (Inorganic filler) The solid electrolyte of the present disclosure contains an inorganic filler.

[0032] Examples of the inorganic filler include inorganic sulfides, inorganic oxides, inorganic nitrides, etc. The inorganic filler is preferably an inorganic oxide in terms of being stable and easy to handle during exposure to the atmosphere. The inorganic oxide may be one obtained by pulverizing the oxide-based inorganic solid electrolyte described later, for example, one obtained by pulverizing a garnet-type lithium ion conductor.

[0033] Examples of the inorganic oxide include particles such as silica (SiO2), alumina (Al2O3), ceria (CeO2), zirconia (ZrO2), titanium oxide (TiO2), barium titanate (BaTiO3), strontium titanate (SrTiO3), calcium titanate (CaTiO3), iron oxide, lead oxide, tin oxide, cerium oxide, calcium oxide, zinc oxide, manganese tritoxide, magnesium oxide, niobium oxide, tantalum oxide, tungsten oxide, antimony oxide, indium tin oxide (ITO). Among them, silica particles are preferable from the viewpoint that they can be mixed with the molecular crystal with high uniformity and elution and separation of the molecular crystal can be suppressed even when the solid electrolyte is heated above the melting point of the molecular crystal. The silica particles may be hydrophilic silica particles or hydrophobic silica particles.

[0034] The average particle diameter of the inorganic filler (average diameter in the case where the inorganic filler is fibrous) is not particularly limited, and may be, for example, 1 nm to 500 nm, may be 3 nm to 300 nm, or may be 5 nm to 150 nm. The average particle diameter of the inorganic filler can be measured, for example, using a known particle size distribution measuring device that utilizes the laser scattering method. When the average particle diameter of the inorganic filler is 500 nm or less, the molecular crystal and the inorganic filler can be mixed with high uniformity, and elution and separation of the molecular crystal can be suppressed even when the solid electrolyte is heated above the melting point of the molecular crystal.

[0035] The specific surface area of the inorganic filler is not particularly limited, and may be, for example, 3 m 2 / g to 450 m 2 / g, may be 5 m 2 / g to 400 m 2 / g, or may be 10 m 2 / g to 350 m 2 / g. The specific surface area of the inorganic filler can be determined, for example, using the BET method that performs nitrogen adsorption measurement at 77K.

[0036] In the solid electrolyte of the present disclosure, the content of the inorganic filler is preferably 1% by mass to 85% by mass, more preferably 5% by mass to 30% by mass, and even more preferably 5% by mass to 20% by mass with respect to the total amount of the molecular crystal and the inorganic filler. When the content of the inorganic filler is 1% by mass or more, the ionic conductivity of the solid electrolyte tends to be more excellent, and when the content of the inorganic filler is 85% by mass or less, the flexibility of the solid electrolyte tends to be more excellent.

[0037] The solid electrolyte of the present disclosure may contain other components other than the molecular crystal or the inorganic filler. The other components are not particularly limited, and examples include gel electrolytes, polymer electrolytes such as polyethylene oxide, organic electrolyte salts such as lithium bis(trifluoromethanesulfonyl)imide, inorganic electrolyte salts such as lithium hexafluorophosphate, sulfide-based inorganic solid electrolytes, oxide-based inorganic solid electrolytes, binders, conductive aids, positive electrode active materials, negative electrode active materials, and the like. Preferable examples of the sulfide-based inorganic solid electrolyte and the oxide-based inorganic solid electrolyte include, for example, the lithium ion conductive sulfide-based inorganic solid electrolyte and the oxide-based inorganic solid electrolyte described in International Publication No. 2017 / 111131.

[0038] In the solid electrolyte of the present disclosure, the total content of the molecular crystal and the inorganic filler may be 20% by mass to 100% by mass, or may be 70% by mass to 95% by mass with respect to the total amount of the solid electrolyte.

[0039] The secondary battery of the present disclosure includes the solid electrolyte of the present disclosure described above. Since the secondary battery of the present disclosure is excellent in the flexibility and ionic conductivity of the solid electrolyte, it tends to be excellent in output characteristics, operating characteristics at low temperatures, and the like.

[0040] The type of the secondary battery is not particularly limited, and examples include lithium ion secondary batteries, sodium ion secondary batteries, potassium ion secondary batteries, magnesium ion secondary batteries, aluminum ion secondary batteries, and the like.

[0041] The secondary battery of the present disclosure preferably includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and the aforementioned solid electrolyte provided between the positive electrode and the negative electrode.

[0042] The positive electrode includes a positive electrode current collector and a positive electrode mixture layer containing a positive electrode active material. The positive electrode can be produced, for example, by forming a positive electrode mixture layer on the positive electrode current collector using a composition containing a positive electrode active material. The composition containing a positive electrode active material may be a mixture of a positive electrode active material, an organic binder, a solvent, a conductive auxiliary agent, etc. As the positive electrode current collector, positive electrode active material, organic binder, solvent, conductive auxiliary agent, etc., materials used in manufacturing a conventionally known positive electrode can be applied.

[0043] The negative electrode includes a negative electrode current collector and a negative electrode mixture layer containing a negative electrode active material. The negative electrode can be produced, for example, by forming a negative electrode mixture layer on the negative electrode current collector using a composition containing a negative electrode active material. The composition containing a negative electrode active material may be a mixture of a negative electrode active material, an organic binder, a solvent, a conductive auxiliary agent, etc. As the negative electrode current collector, negative electrode active material, organic binder, solvent, conductive auxiliary agent, etc., materials used in manufacturing a conventionally known negative electrode can be applied.

[0044] The capacitor of the present disclosure includes the aforementioned solid electrolyte of the present disclosure. Since the solid electrolyte of the present disclosure is excellent in flexibility and ion conductivity, it tends to be excellent in output characteristics, operating characteristics at low temperatures, etc.

[0045] The capacitor of the present disclosure preferably includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and the aforementioned solid electrolyte provided between the positive electrode and the negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer, and the negative electrode includes a negative electrode current collector and a negative electrode active material layer. Examples of the positive electrode active material and negative electrode active material in the capacitor include activated carbon, etc.

[0046] The secondary battery or capacitor of the present disclosure may have a series stack structure in which a plurality of configurations including a positive electrode, a solid electrolyte, and a negative electrode are stacked. When the secondary battery or capacitor of the present disclosure has a series stack structure, the container and the like can be simplified as compared with the case where a secondary battery or capacitor using an electrolytic solution is formed into a series structure, and the mass and volume of the system can be reduced.

[0047] The use of the solid electrolyte of the present disclosure is not particularly limited. For example, notebook computers, pen input computers, mobile computers, e-book players, mobile phones, mobile faxes, mobile copiers, mobile printers, headphone stereos, video movies, liquid crystal TVs, handy cleaners, portable CDs, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, airplanes, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game devices, watches, power tools, strobes, cameras, power supplies for load leveling, natural energy storage power supplies, medical devices, etc. can be mentioned.

Example

[0048] Hereinafter, the present disclosure will be described in detail by way of examples, but the present disclosure is not limited thereto.

[0049] [Example 1] Fumed silica (AEROSIL (registered trademark) 300, Nippon Aerosil Co., Ltd.), which is an inorganic filler, was vacuum dried at 100 ° C for 24 hours. Under an argon atmosphere, the vacuum-dried fumed silica and [Li(FSA)(NCCH2CH2CN)2], which is a molecular crystal n were mixed using a mortar until they appeared uniform. At this time, the amount of fumed silica was 5% by mass based on the total amount of fumed silica and molecular crystal. Next, the mixture was heated while stirring at a temperature equal to or higher than the melting point of the molecular crystal using an oil bath. Thereafter, the solid electrolyte in which the inorganic filler and the molecular crystal were combined was produced by allowing the mixture to cool to room temperature.

[0050] (Measurement of ionic conductivity) Using the measurement sample obtained by pressure-molding the solid electrolyte obtained in Example 1 into a disk shape, the ionic conductivity was measured by an AC impedance method using a gold electrode in a sealed cell. Also, the measurement of the ionic conductivity was performed while raising the temperature of the measurement sample in a temperature range below the melting point of the molecular crystal, and this operation was repeated 3 times. The results are shown in Fig. 1. In Fig. 1, the horizontal axis is 1000 / T (T represents temperature (K)), and the vertical axis is the ionic conductivity (S / cm).

[0051] [Example 2] A solid electrolyte was prepared in the same manner as in Example 1, except that the amount of fumed silica in Example 1 was 10% by mass based on the total amount of fumed silica and the molecular crystal. The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 1. The results are shown in Fig. 2.

[0052] [Example 3] A solid electrolyte was prepared in the same manner as in Example 1, except that the amount of fumed silica in Example 1 was 20% by mass based on the total amount of fumed silica and the molecular crystal. The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 1. The results are shown in Fig. 3.

[0053] (Differential Scanning Calorimetry) Solid electrolytes with the amount of fumed silica being 0% by mass, 5% by mass, 10% by mass, 15% by mass, 20% by mass, and 30% by mass based on the total amount of fumed silica and the molecular crystal were prepared respectively, and differential scanning calorimetry (DSC) was performed on the prepared solid electrolytes. Specifically, using a differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-60), the measurement was carried out at a heating rate of 10 °C per minute. The results are shown in Fig. 4. As shown in Fig. 4, similar endothermic peaks were confirmed in the solid electrolyte with the amount of fumed silica being 0% by mass and the solid electrolytes using the aforementioned amounts of fumed silica, and it was found that this endothermic peak is a peak derived from the molecular crystal.

[0054] (X-ray Diffractometer Measurement) Solid electrolytes were prepared with the amount of fumed silica being 0 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt% and 100 wt% based on the total amount of fumed silica and molecular crystals, respectively, and X-ray diffraction apparatus (XRD) measurements were performed on the prepared solid electrolytes. Specifically, using an X-ray diffraction apparatus (Rigaku Corporation's fully automatic horizontal multi-purpose X-ray diffractometer Smart-Lab), the measurements were carried out under the following conditions. The results are shown in Figure 5. X-ray: CuKα ray (wavelength: 1.54 Å) Output: 40 kV, 30 mA Scanning speed: 10 deg / min Step angle: 0.01 deg Measurement range (2θ): 5 deg to 60 deg As shown in Figure 5, since similar peaks were confirmed in the solid electrolyte containing molecular crystals, it is presumed that a similar crystal structure is formed in the solid electrolyte.

[0055] [Example 4] Fumed silica (AEROSIL® 300, Nippon Aerosil Co., Ltd.), an inorganic filler, was vacuum dried at 100 °C for 24 hours. Under an argon atmosphere, the vacuum-dried fumed silica and the molecular crystal [Li(TFSA)((CH3)2NCH2CH2N(CH3)2)] n were mixed using a mortar until visually uniform. At this time, the amount of fumed silica was 20 wt% based on the total amount of fumed silica and molecular crystals. Next, using an oil bath, the mixture was heated while stirring at a temperature above the melting point of the molecular crystal. Then, the mixture was allowed to cool to room temperature to prepare a solid electrolyte in which the inorganic filler and the molecular crystal were compounded.

[0056] [Comparative Example 1] Only the molecular crystal [Li(TFSA)((CH3)2NCH2CH2N(CH3)2)] n was used as the solid electrolyte.

[0057] (Measurement of ionic conductivity) Using the measurement samples obtained by pressure-molding the solid electrolytes obtained in Example 4 and Comparative Example 1 into a disk shape, the ionic conductivity was measured by the AC impedance method in a sealed cell. The results are shown in Fig. 6 and Table 1. In Fig. 6, the horizontal axis is 1000 / T (where T represents the temperature (K)), and the vertical axis is the ionic conductivity (S / cm).

[0058] [Example 5] In Example 4, instead of the molecular crystal [Li(TFSA)((CH3)2NCH2CH2N(CH3)2)] n a solid electrolyte was prepared in the same manner as in Example 4, except that the molecular crystal [Li(CPFSA)((CH3)2NCH2CH2N(CH3)2)] n was used. The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 4. The results are shown in Fig. 7 and Table 2.

[0059] [Comparative Example 2] Only the molecular crystal [Li(CPFSA)((CH3)2NCH2CH2N(CH3)2)] n was used as the solid electrolyte. The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 4. The results are shown in Fig. 7 and Table 2.

[0060] [Example 6] In Example 4, instead of the molecular crystal [Li(TFSA)((CH3)2NCH2CH2N(CH3)2)] n a solid electrolyte was prepared in the same manner as in Example 4, except that the molecular crystal [Li(NFBSA)(C6H4(OCH3)2)] n was used. The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 4. The results are shown in Fig. 8 and Table 3.

[0061] [Comparative Example 3] Only the molecular crystal [Li(NFBSA)(C6H4(OCH3)2)] n was used as the solid electrolyte. The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 4. The results are shown in Fig. 8 and Table 3.

[0062]

Table 1

[0063]

Table 2

[0064]

Table 3

[0065] As shown in FIGS. 6 to 8 and Tables 1 to 3, the solid electrolytes of Examples 4 to 6 were superior in ionic conductivity as compared with the solid electrolytes of Comparative Examples 1 to 3.

[0066] [Example 7] Fumed silica (AEROSIL (registered trademark) 300, Nippon Aerosil Co., Ltd., average particle size 7 nm, specific surface area 300 ± 30 m 2 / g) was vacuum dried at 100 ° C for 24 hours. Under an argon atmosphere, the vacuum-dried fumed silica and [Li(FSA)(NCCH2CH2CN)2], which is a molecular crystal, n were mixed using a mortar until they became visually uniform. At this time, the amount of fumed silica was 20% by mass based on the total amount of fumed silica and molecular crystal. Next, the mixture was heated while stirring at a temperature equal to or higher than the melting point of the molecular crystal using an oil bath. Then, the solid electrolyte in which the inorganic filler and the molecular crystal were complexed was produced by allowing the mixture to cool to room temperature. In the same manner as in Example 1, the ionic conductivities of the solid electrolyte at 30 ° C and 55 ° C were measured. The results are shown in FIGS. 9 and 10.

[0067] [Example 8] In Example 7, fumed silica was replaced with hydrophobic silica (AEROSIL (registered trademark) 812, Nippon Aerosil Co., Ltd., average particle size 7 nm, specific surface area 260 ± 30 m 2A solid electrolyte was prepared in the same manner as in Example 7 except that it was changed to / g), and the ionic conductivity of the solid electrolyte was measured. The results are shown in FIGS. 9 and 10.

[0068] [Example 9] In Example 7, fumed silica was changed to aluminum oxide (Sigma-Aldrich, average particle size 13 nm, specific surface area 85 m 2 / g to 115 m 2 A solid electrolyte was prepared in the same manner as in Example 7 except that it was changed to / g), and the ionic conductivity of the solid electrolyte was measured. The results are shown in FIGS. 9 and 10.

[0069] [Example 10] In Example 7, fumed silica was changed to aluminum oxide (Sigma-Aldrich, average particle size less than 50 nm, specific surface area more than 40 m 2 / g), and a solid electrolyte was prepared in the same manner as in Example 7 except for this change, and the ionic conductivity of the solid electrolyte was measured. The results are shown in FIGS. 9 and 10.

[0070] [Example 11] In Example 7, fumed silica was changed to zinc oxide (Sigma-Aldrich, average particle size less than 50 nm, specific surface area more than 10.8 m 2 / g), and a solid electrolyte was prepared in the same manner as in Example 7 except for this change, and the ionic conductivity of the solid electrolyte was measured. The results are shown in FIG. 10.

[0071] [Example 12] In Example 7, fumed silica was changed to zinc oxide (Sigma-Aldrich, average particle size less than 100 nm, specific surface area 10 m 2 / g to 25 m 2 / g), and a solid electrolyte was prepared in the same manner as in Example 7 except for this change, and the ionic conductivity of the solid electrolyte was measured. The results are shown in FIGS. 9 and 10.

[0072] [Example 13] A solid electrolyte was prepared in the same manner as in Example 7, except that fumed silica was changed to cerium oxide (Sigma-Aldrich, average particle size less than 25 nm), and the ionic conductivity of the solid electrolyte was measured. The results are shown in FIGS. 9 and 10.

[0073] [Example 14] A solid electrolyte was prepared in the same manner as in Example 7, except that fumed silica was changed to titanium oxide (Kanto Chemical Co., Inc., average particle size 19.7 nm to 101.0 nm, specific surface area 15 m 2 / g to 77 m 2 / g), and the ionic conductivity of the solid electrolyte was measured. The results are shown in FIGS. 9 and 10.

[0074] [Example 15] A solid electrolyte was prepared in the same manner as in Example 7, except that fumed silica was changed to titanium oxide (titanium oxide nanowire, Sigma-Aldrich, diameter 10 nm, length 10 μm), and the ionic conductivity of the solid electrolyte was measured. The results are shown in FIG. 10.

[0075] [Comparative Example 4] Only [Li(FSA)(NCCH2CH2CN)2], which is a molecular crystal in Example 7, n was used as the solid electrolyte. The ionic conductivity of the solid electrolyte at 30 °C was measured in the same manner as in Example 7. The results are shown in FIG. 9.

[0076] The ionic conductivities of the solid electrolytes of Examples 7 to 15 and Comparative Example 4 at 30 °C and 55 °C are shown in Table 4. Note that "-" in Table 4 means no data.

[0077]

Table 4

[0078] As shown in FIG. 9, the solid electrolytes of Examples 7 to 10 and 12 to 14 had better ionic conductivity at 30 °C than Comparative Example 4. As shown in FIG. 10, the solid electrolytes of Examples 11 and 15 had better ionic conductivity at 55°C than the solid electrolyte of Example 7 and had excellent ionic conductivity in a relatively high temperature range. Furthermore, in Examples 7 to 15, even at 55°C, which is a temperature range above the melting point of the molecular crystal, due to the complexation of the molecular crystal and the inorganic filler, the solid electrolyte could be treated as a quasi-solid, and problems such as dissolution and elution of the molecular crystal could also be suppressed.

[0079] [Reference Example 1] Under an argon atmosphere, Mg(TFSA)2 and NCCH2CH2CN were mixed under the condition that the molar ratio was 1:3 (Mg(TFSA)2:NCCH2CH2CN). Next, the mixture was heated using an oil bath at a temperature above the melting point of n [Mg(TFSA)2(NCCH2CH2CN)3]. n After that, by allowing the mixture to cool to room temperature, a solid electrolyte containing the molecular crystal [Mg(TFSA)2(SN)3]

[0080] [Reference Example 2] Under an argon atmosphere, Mg(TFSA)2 and NCCH2CH2CH2CN were mixed under the condition that the molar ratio was 1:3 (Mg(TFSA)2:NCCH2CH2CH2CN). Next, the mixture was heated using an oil bath at a temperature above the melting point. After that, by allowing the mixture to cool to room temperature, a solid electrolyte containing the molecular crystal [Mg a (TFSA) b (NCCH2CH2CH2CN) c n (presumed structural formula) was prepared.

[0081] (Measurement of Ionic Conductivity) Using the measurement samples obtained in Reference Example 1 and Reference Example 2, which were pressure-molded into a disc shape, the ionic conductivity was measured by the AC impedance method using gold electrodes in a sealed cell. Also, the measurement of the ionic conductivity was performed while heating the measurement sample in a temperature range below the melting point of the molecular crystal. The results are shown in FIG. 11.

[0082] ​The disclosure of Japanese Patent Application No. 2020-027439 filed on February 20, 2020 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

Claim 1 a molecular crystal, an inorganic filler, wherein the molecular crystal contains a cation of a monovalent to trivalent metal atom and an anion, and a ligand of the ionic compound, the content of the inorganic filler is 1% by mass to 85% by mass based on the total amount of the molecular crystal and the inorganic filler, the inorganic filler is an inorganic oxide, the molecular crystal is at least one solid electrolyte selected from the group consisting of [LiN(SO₂F)₂(NCC₂H₄CN)₂]n, [Li₂{N(SO₂CF₃)₂}₂(NCC₂H₄CN)₃]n, [Li{N(SO₂CF₃)₂}{(CH₃)₂NCH₂CH₂N(CH₃)₂}]n, [Li{N(SO₂CF₂)₂CF₂}{(CH₃)₂NCH₂CH₂N(CH₃)₂}]n and [Li{N(SO₂C₄F₉)₂}{C₆H₄(OCH₃)₂}]n. Claim 2 The solid electrolyte according to Claim 1, which is used as a solid electrolyte of a secondary battery or a capacitor. Claim 3 A secondary battery comprising the solid electrolyte according to Claim 1. Claim 4 A capacitor comprising the solid electrolyte according to Claim 1.

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