Solid electrolyte, secondary battery, and capacitor

Abstract

A solid electrolyte comprising a molecular crystal and an inorganic filler.

Description

Technical Field

[0001] This disclosure relates to solid electrolytes, secondary batteries, and capacitors. Background Technology

[0002] In recent years, based on the principles of reducing battery weight and simplifying battery structure, research has been conducted to explore the use of solid electrolytes in secondary batteries, replacing liquid electrolytes. For example, there is a desire to practically apply sulfide-based inorganic solid electrolytes and oxide-based inorganic solid electrolytes as solid electrolytes in secondary batteries.

[0003] When using inorganic solid electrolytes such as oxide-based inorganic solid electrolytes, there is a problem that they are difficult to bond tightly to the electrodes, and the interfacial resistance between the electrodes and the inorganic solid electrolyte tends to increase. Therefore, polymer electrolytes, which are easier to bond tightly to the electrodes compared to inorganic solid electrolytes, are often studied as solid electrolytes for secondary batteries and the like.

[0004] However, polymer electrolytes have the problem of difficulty in ensuring high ionic conductivity.

[0005] As mentioned above, considering the problems of using inorganic solid electrolytes and polymer electrolytes alone, research has been conducted on combining inorganic solid electrolytes with polymer electrolytes to form solid electrolytes, and combining inorganic solid electrolytes or polymer electrolytes with other materials to form solid electrolytes.

[0006] For example, the following method is being studied: by setting a solid electrolyte layer containing a binder such as a grafted polymer and a resin, as well as inorganic solid electrolyte particles, the tightness of the solid electrolyte layer and the electrode is improved and high ion conductivity is obtained (see, for example, Patent Document 1).

[0007] Furthermore, the following quasi-solid electrolytes are being studied: ion-conducting materials comprising metal oxide particles and an ion-conducting material that is a mixture of an ionic liquid and a lithium salt, wherein the ion-conducting material is supported on the metal oxide particles (see, for example, Patent Document 2).

[0008] In addition, methods for manufacturing solid electrolytes using coating solutions containing ionic liquids, inorganic oxide particles, and polymers having functional group blocks capable of binding to the surface of inorganic oxide particles are being studied (see, for example, Patent Document 3).

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: International Publication No. 2017 / 111131

[0012] Patent Document 2: Japanese Patent Application Publication No. 2017-59432

[0013] Patent Document 3: International Publication No. 2011 / 024848 Summary of the Invention

[0014] For example, when a polymer electrolyte is combined with an oxide-based inorganic solid electrolyte to form a solid electrolyte, the overall ionic conductivity of the solid electrolyte can easily become the property of the polymer electrolyte, which has poor ionic conductivity, thus allowing for improvement.

[0015] This disclosure was made in view of the above circumstances, with the aim of providing a solid electrolyte with excellent flexibility and ion conductivity, as well as a secondary battery and capacitor including the solid electrolyte.

[0016] To address the aforementioned issues, the following methods are employed.

[0017] <1> A solid electrolyte comprising molecular crystals and inorganic fillers.

[0018] <2> according to <1> The solid electrolyte described herein, wherein the molecular crystal comprises [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 The group consisting of at least one molecular crystal selected from the group (M is a metal atom with a valence of monovalent to trivalent, a is an integer greater than or equal to 1, b is an integer greater than or equal to 1, c is an integer greater than or equal to 1, and n is an integer greater than or equal to 1. In each general formula, (valence of M) × ab = 0. X is a ligand.

[0019] <3> according to <1> or <2> The solid electrolyte described herein, wherein the inorganic filler is an inorganic oxide.

[0020] <4> according to <1> to <3> The solid electrolyte of any one of the following, wherein the content of the inorganic filler is from 1% to 85% by mass relative to the total amount of molecular crystals and inorganic filler.

[0021] <5> according to <1> to <4> The solid electrolyte according to any one of the following, wherein the molecular crystal is derived from [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 At least one selected from the group.

[0022] <6> according to <1> to <5> The solid electrolyte described in any of the above, used as a solid electrolyte in a secondary battery or capacitor.

[0023] <7> A type of secondary battery, having <1> to <5> The solid electrolyte described in any of the above.

[0024] <8> A capacitor having <1> to <5> The solid electrolyte described in any of the above.

[0025] Technical effect

[0026] According to one aspect of the present invention, it is possible to provide a solid electrolyte with excellent flexibility and ionic conductivity, as well as a secondary battery and a capacitor comprising the solid electrolyte. Attached Figure Description

[0027] Figure 1 These are the measurement results of the ionic conductivity in the solid electrolyte of Example 1.

[0028] Figure 2 These are the measurement results of the ionic conductivity in the solid electrolyte of Example 2.

[0029] Figure 3 These are the measurement results of the ionic conductivity in the solid electrolyte of Example 3.

[0030] Figure 4 The results are obtained by DSC measurements in solid electrolytes with the amount of fumed silica relative to the total amount of fumed silica and molecular crystals set at 0%, 5%, 10%, 15%, 20%, and 30% by mass.

[0031] Figure 5The results are obtained by XRD measurements in solid electrolytes with the amount of fumed silica relative to the total amount of fumed silica and molecular crystals set at 0, 5, 10, 15, 20, 30, and 100% by mass.

[0032] Figure 6 These are the measurement results of the ionic conductivity in the solid electrolytes of Example 4 and Comparative Example 1.

[0033] Figure 7 These are the measurement results of the ionic conductivity in the solid electrolytes of Example 5 and Comparative Example 2.

[0034] Figure 8 These are the measurement results of the ionic conductivity in the solid electrolytes of Example 6 and Comparative Example 3.

[0035] Figure 9 These are the measurement results of the ionic conductivity of the solid electrolytes in Examples 7 to 10, 12 to 14 and Comparative Example 4 at 30°C.

[0036] Figure 10 These are the measurement results of the ionic conductivity of the solid electrolytes in Examples 7 to 15 at 55°C.

[0037] Figure 11 These are the measurement results of the ionic conductivity in the solid electrolytes of Reference Example 1 and Reference Example 2. Detailed Implementation

[0038] The following details this disclosure.

[0039] Within the numerical ranges segmented in this disclosure, the upper or lower limit value recorded in one numerical range may be replaced with the upper or lower limit value of other numerical ranges segmented in the disclosure. Additionally, within the numerical ranges recorded in this disclosure, the upper or lower limit value of the numerical range may be replaced with the value shown in the embodiments.

[0040] In this disclosure, each component may also contain multiple equivalent substances. When multiple equivalent substances are present in the composition, unless otherwise specified, the content or percentage of each component refers to the total content or percentage of those multiple substances present in the composition.

[0041] [Solid electrolyte]

[0042] The solid electrolyte disclosed herein comprises molecular crystals and inorganic fillers. Therefore, the solid electrolyte of this disclosure exhibits excellent flexibility and ionic conductivity. This is presumably because the inclusion of molecular crystals improves the flexibility of the solid electrolyte, while the inclusion of inorganic fillers enhances ionic conductivity. Furthermore, the combination of molecular crystals and inorganic fillers creates a phenomenon where ions diffuse rapidly through a space charge layer at the interface between the molecular crystals and inorganic fillers (the nano-ion phenomenon), further improving ionic conductivity. Moreover, it is believed that in the solid electrolyte of this disclosure, even at temperatures above the melting point of the molecular crystals, the combination of molecular crystals and inorganic fillers allows the solid electrolyte to be considered a quasi-solid, thereby suppressing problems such as dissolution and precipitation of the molecular crystals.

[0043] The solid electrolyte disclosed herein can be used, for example, as a solid electrolyte for secondary batteries, capacitors, and air batteries, and is preferably used as a solid electrolyte for secondary batteries or capacitors.

[0044] (Molecular crystal)

[0045] The solid electrolyte disclosed herein comprises a molecular crystal. There is no particular limitation if the molecular crystal is a crystal formed by the bonding of multiple molecules through intermolecular interactions. The molecular crystal preferably comprises an ionic compound and ligands of the ionic compound, wherein the ionic compound comprises cations and anions of monovalent to trivalent metal atoms.

[0046] Furthermore, the ligands of ionic compounds can be ligands that coordinate the ionic compound itself, or ligands that coordinate free cations or anions.

[0047] The cation of the monovalent to trivalent metal atom in the ionic compound is preferably a cation of at least one metal atom selected from the group consisting of lithium, sodium, potassium, magnesium and aluminum, more preferably lithium or sodium.

[0048] The preferred anions in the ionic compounds are anions such as N(SO2F)2-(FSA), N(SO2CF3)2-(TFSA), N(SO2C4F9)2-(NFBSA), cyclic anions such as N(SO2CF2)2CF2-(CPFSA) and N(SO2CF2)2-.

[0049] Ionic compounds can be lithium salts, sodium salts, potassium salts, magnesium salts, aluminum salts, etc.

[0050] If the ligand of the ionic compound is a compound that can form a molecular crystal as a ligand of the ionic compound, there is no particular limitation. For example, it is preferable to include an organic compound (hereinafter also referred to as "specific organic compound") containing atoms selected from the group consisting of nitrogen atoms, oxygen atoms, phosphorus atoms and sulfur atoms.

[0051] The specific atom in a particular organic compound is preferably a nitrogen atom or an oxygen atom. The number of the specific atom in a particular organic compound is preferably one to three, more preferably two.

[0052] The specific organic compound is preferably an amine compound, a nitrile compound, an ether compound, or a thioether compound, more preferably a nitrile compound or an ether compound.

[0053] The preferred organic compound is one in which two amino groups, two nitrile groups, two alkoxy groups, or two thioalkyl groups are linked via a divalent linker. Examples of amino groups include primary, secondary, or tertiary amino groups. Examples of divalent linkers include substituted or unsubstituted alkylene groups, phenylene groups, etc.

[0054] Specific examples of particular organic compounds are not particularly limited, but may include N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, N,N,N',N'-tetramethyl-1,2-propanediamine, N,N,N',N'-tetramethyl-1,3-propanediamine, N,N,N',N'-tetramethyl-1,3-butanediamine, malononitrile, succinic anionyl glutaronitrile, adiponitrile, dimethylmalononitrile, tetramethylsuccinic anionyl glutaronitrile, 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, etc. Among them, N,N,N',N'-tetramethylethylenediamine ((CH3)2NCH2CH2N(CH3)2), succinic acid (NCCH2CH2CN), and 1,2-dimethoxybenzene (C6H4(OCH3)2) are preferred for their superior ionic conductivity to solid electrolytes. Succinic acid and glutaronitrile are even more preferred for their ionic conductivity to suppress volatilization at high temperatures.

[0055] For example, succinate has a high boiling point of 265°C and glutaronitrile has a high boiling point of 287°C, which can suppress the volatilization of ligands under heating conditions, thus allowing the solid electrolyte of this disclosure to be used over a wide range of applications.

[0056] The number of ligands in an ionic compound is one or more relative to one molecule of the ionic compound, preferably one to three, and more preferably one or two, depending on the ionic conductivity of the solid electrolyte.

[0057] Molecular crystals preferably contain components derived from [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 At least one molecular crystal selected from the group consisting of (hereinafter also referred to as "specific molecular crystal").

[0058] M represents a single to trivalent metal atom, a represents an integer greater than or equal to 1, b represents an integer greater than or equal to 1, c represents an integer greater than or equal to 1, and n represents an integer greater than or equal to 1. In each general formula, (valence of M) × ab = 0. X represents a ligand.

[0059] In a specific molecular crystal, M is preferably lithium, sodium, potassium, magnesium or aluminum, and more preferably lithium or sodium.

[0060] The preferred structure of the ligand represented by X is the same as the preferred structure of the ligand of the aforementioned ionic compound.

[0061] The molecular crystal is preferably made from [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 At least one selected from the group consisting of [LiN(SO2F)2(NCCH2CH2CN)2]. The molecular crystal is more preferably [LiN(SO2F)2(NCCH2CH2CN)2] due to its superior ionic conductivity for solid electrolytes. n .

[0062] In the solid electrolyte of this disclosure, the content of molecular crystals relative to the total amount of molecular crystals and inorganic fillers is preferably 15% to 99% by mass, more preferably 70% to 95% by mass, and even more preferably 80% to 95% by mass. A content of 15% by mass or more tends to result in better flexibility of the solid electrolyte, while a content of 99% by mass or less tends to result in better ionic conductivity of the solid electrolyte.

[0063] (Inorganic packing)

[0064] The solid electrolytes disclosed herein include inorganic fillers.

[0065] Inorganic fillers include inorganic sulfides, inorganic oxides, and inorganic nitrates. Due to their stability when exposed to the atmosphere and ease of handling, inorganic oxides are preferred as inorganic fillers. Inorganic oxides can be substances obtained by pulverizing oxide-based inorganic solid electrolytes (described later), or, for example, substances obtained by pulverizing garnet-type lithium-ion conductors.

[0066] Examples of inorganic oxides include particles of silicon dioxide (SiO2), aluminum oxide (Al2O3), cerium dioxide (CeO2), zirconium dioxide (ZrO2), titanium dioxide (TiO2), barium titanate (BaTiO3), strontium titanate (SrTiO3), calcium titanate (CaTiO3), iron oxide, lead oxide, tin oxide, cerium oxide, calcium oxide, zinc oxide, manganese tetroxide, magnesium oxide, niobium oxide, tantalum oxide, tungsten oxide, antimony oxide, and indium tin oxide (ITO). Among these, silicon dioxide particles are preferred because they can mix with molecular crystals with high uniformity and can suppress the dissolution and separation of molecular crystals even when the solid electrolyte is heated above the melting point of the molecular crystals. The silicon dioxide particles can be either hydrophilic or hydrophobic.

[0067] The average particle size of the inorganic filler (average diameter when the inorganic filler is fibrous) is not particularly limited; for example, it can be 1 nm to 500 nm, 3 nm to 300 nm, or 5 nm to 150 nm. The average particle size of the inorganic filler can be measured, for example, using a known particle size distribution measuring device based on laser scattering. When the average particle size of the inorganic filler is below 500 nm, the molecular crystals and inorganic filler can be mixed with high uniformity, and even when the solid electrolyte is heated above the melting point of the molecular crystals, the dissolution of the molecular crystals can be suppressed and separation can be achieved.

[0068] The specific surface area of ​​inorganic fillers is not particularly limited; for example, it can be 3 m². 2 / g~450m 2 / g, or 5m 2 / g~400m 2 / g, or 10m 2 / g~350m 2 / g. The specific surface area of ​​inorganic fillers can be determined, for example, using the BET method, which measures nitrogen adsorption at 77 K.

[0069] In the solid electrolyte of this disclosure, the content of inorganic filler relative to the total amount of molecular crystals and inorganic filler is preferably 1% to 85% by mass, more preferably 5% to 30% by mass, and even more preferably 5% to 20% by mass. When the content of inorganic filler is 1% by mass or more, the solid electrolyte tends to have better ionic conductivity, and when the content of inorganic filler is 85% by mass or less, the solid electrolyte tends to have better flexibility.

[0070] The solid electrolyte disclosed herein may also contain components other than molecular crystals or inorganic fillers. Other components are not particularly limited and may 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 additives, positive electrode active materials, negative electrode active materials, etc.

[0071] Preferred examples of sulfide-based inorganic solid electrolytes and oxide-based inorganic solid electrolytes include lithium-ion conductive sulfide-based inorganic solid electrolytes and oxide-based inorganic solid electrolytes as described in International Publication No. 2017 / 111131.

[0072] In the solid electrolyte of this disclosure, the total content of molecular crystals and inorganic fillers relative to the total amount of solid electrolyte can be from 20% to 100% by mass, or from 70% to 95% by mass.

[0073] The secondary battery disclosed herein possesses the aforementioned solid electrolyte. The solid electrolyte of the secondary battery disclosed herein exhibits excellent flexibility and ion conductivity, thus showing superior output characteristics and operating characteristics under low-temperature conditions.

[0074] The types of secondary batteries are not particularly limited, but can include lithium-ion secondary batteries, sodium-ion secondary batteries, potassium-ion secondary batteries, magnesium-ion secondary batteries, aluminum-ion secondary batteries, etc.

[0075] The secondary battery disclosed herein preferably comprises a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a solid electrolyte disposed between the positive electrode and the negative electrode.

[0076] The positive electrode comprises a positive current collector and a positive electrode binder layer containing a positive active material. For example, a positive electrode can be manufactured by forming a positive electrode binder layer on the positive current collector using a composition containing a positive active material. In addition to the positive active material, the composition containing the positive active material can also be a mixture of organic binders, solvents, conductive additives, etc. The positive current collector, positive active material, organic binder, solvent, conductive additives, etc., can be materials used in the manufacture of conventionally known positive electrodes.

[0077] The negative electrode comprises a negative current collector and a negative electrode binder layer containing a negative electrode active material. For example, a negative electrode can be manufactured by forming a negative electrode binder layer on the negative current collector using a composition containing a negative electrode active material. In addition to the negative electrode active material, the composition containing the negative electrode active material can also be a mixture of organic binders, solvents, conductive additives, etc. The negative current collector, negative electrode active material, organic binder, solvent, conductive additives, etc., can be materials used in the manufacture of conventionally known negative electrodes.

[0078] The capacitor disclosed herein possesses the aforementioned solid electrolyte. The solid electrolyte in the capacitor of this disclosure exhibits excellent flexibility and ionic conductivity, thus tending to have superior output characteristics and operating characteristics under low-temperature conditions.

[0079] The capacitor disclosed herein preferably comprises a positive electrode containing a positive active material, a negative electrode containing a negative active material, and a solid electrolyte disposed between the positive electrode and the negative electrode. The positive electrode includes a positive current collector and a layer of positive active material, and the negative electrode includes a negative current collector and a layer of negative active material. Examples of positive and negative active materials in the capacitor include activated carbon.

[0080] The secondary battery or capacitor disclosed herein may also have a series-layered structure formed by stacking a positive electrode, a solid electrolyte, and a negative electrode. When the secondary battery or capacitor of this disclosure has a series-layered structure, compared to a secondary battery or capacitor using an electrolyte in a series structure, the container and other components can be simplified, thereby potentially reducing the system's mass and size.

[0081] The applications of the solid electrolyte disclosed herein are not particularly limited, and examples include laptops, pen input computers, mobile computers, e-book players, mobile phones, mobile fax machines, mobile copiers, mobile printers, headphone stereo players, video movies, LCD TVs, handheld cleaners, portable CD players, mini disk drives, walkie-talkies, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, electric motors, aircraft, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, gaming devices, clocks, power tools, strobe lights, cameras, load balancing power supplies, renewable energy storage power supplies, medical devices, etc.

[0082] Example

[0083] The present disclosure will be described in detail below through examples, but the present disclosure is not limited thereto.

[0084] [Example 1]

[0085] Fumed silica (AEROSIL 300, registered trademark, AEROSIL Corporation, Japan), used as an inorganic filler, was vacuum dried at 100°C for 24 hours. Under an argon atmosphere, the vacuum-dried fumed silica was mixed with [Li(FSA)(NCCH2CH2CN)2], a molecular crystal, using a mortar. n The mixture is stirred until it becomes homogeneous. At this point, the amount of fumed silica is 5% by mass relative to the total amount of fumed silica and molecular crystals. Next, the mixture is heated while stirring in an oil bath at a temperature above the melting point of the molecular crystals. Afterward, the mixture is cooled to room temperature, thus producing a solid electrolyte composed of inorganic filler and molecular crystals.

[0086] (Measurement of ionic conductivity)

[0087] Using a measurement sample formed by pressurizing and molding the solid electrolyte obtained in Example 1 into a disk shape, the ionic conductivity was measured by AC impedance method using a gold electrode in a closed cell. Furthermore, in the measurement of ionic conductivity, the measurement sample was heated while being measured within a temperature range below the melting point of the molecular crystal, and this operation was repeated three times. Figure 1 The results are shown. Figure 1 The middle and horizontal axes represent 1000 / T (T represents temperature (K)), and the vertical axis represents ionic conductivity (S / cm).

[0088] [Example 2]

[0089] The solid electrolyte was prepared in the same manner as in Example 1, except that the amount of fumed silica was 10% by mass relative to the total amount of fumed silica and molecular crystals.

[0090] The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 1. Figure 2 The results are shown.

[0091] [Example 3]

[0092] The solid electrolyte was prepared in the same manner as in Example 1, except that the amount of fumed silica was 20% by mass relative to the total amount of fumed silica and molecular crystals.

[0093] The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 1. Figure 3 The results are shown.

[0094] Differential scanning calorimetry

[0095] Solid electrolytes were prepared with 0%, 5%, 10%, 15%, 20%, and 30% by mass of fumed silica relative to the total amount of fumed silica and molecular crystals, respectively. Differential scanning calorimetry (DSC) was performed on the prepared solid electrolytes. Specifically, a differential scanning calorimeter (Shimadzu Corporation, DSC-60) was used, and measurements were taken at a heating rate of 10°C per minute. Figure 4 The results are shown.

[0096] like Figure 4 As shown, the same endothermic peak was confirmed in both the solid electrolyte with 0% by mass of fumed silica and the solid electrolyte using the aforementioned amount of fumed silica, indicating that the endothermic peak originates from the molecular crystal.

[0097] (Measured by X-ray diffractometer)

[0098] Solid electrolytes were prepared with 0%, 5%, 10%, 15%, 20%, 30%, and 100% by mass of fumed silica relative to the total amount of fumed silica and molecular crystals, respectively. The prepared solid electrolytes were then measured using X-ray diffraction (XRD). Specifically, an X-ray diffractometer (RIGAKU Smart-Lab fully automated horizontal multi-functional X-ray diffractometer) was used, and measurements were performed under the following conditions. Figure 5 The results are shown.

[0099] X-rays: CuKα rays (wavelength: )

[0100] Output: 40kV, 30mA

[0101] Scanning speed: 10 degrees / minute

[0102] Step angle: 0.01 degrees

[0103] Measurement range (2θ): 5 degrees to 60 degrees

[0104] like Figure 5 As shown, the same peaks were confirmed in solid electrolytes including molecular crystals, thus suggesting that the same crystal structure was generated within the solid electrolyte.

[0105] [Example 4]

[0106] Fumed silica (AEROSIL 300, registered trademark, AEROSIL Corporation, Japan), used as an inorganic filler, was vacuum dried at 100°C for 24 hours. Under an argon atmosphere, the vacuum-dried fumed silica was mixed with [Li(TFSA)((CH3)2NCH2CH2N(CH3)2)], a molecular crystal, using a mortar.n The mixture is stirred until it becomes homogeneous. At this point, the amount of fumed silica is 20% by mass relative to the total amount of fumed silica and molecular crystals. Next, the mixture is heated while stirring in an oil bath at a temperature above the melting point of the molecular crystals. Afterward, the mixture is cooled to room temperature, thus producing a solid electrolyte composed of inorganic filler and molecular crystals.

[0107] [Comparative Example 1]

[0108] Only [Li(TFSA)((CH3)2NCH2CH2N(CH3)2)], which is a molecular crystal, will be considered. n As a solid electrolyte.

[0109] (Measurement of ionic conductivity)

[0110] Using a measurement sample formed by pressurizing and molding the solid electrolyte obtained in Example 4 and Comparative Example 1 into a disk shape, the ionic conductivity was measured in a closed cell by AC impedance method. Figure 6 The results are shown in Table 1. Figure 6 In the figure, the horizontal axis represents 1000 / T (T represents temperature (K)) and the vertical axis represents ionic conductivity (S / cm).

[0111] [Example 5]

[0112] Except for [Li(TFSA)((CH3)2NCH2CH2N(CH3)2)] which was used as a molecular crystal in Example 4 n The molecular crystal [Li(CPFSA)((CH3)2NCH2CH2N(CH3)2)] is used. n In addition, a solid electrolyte was prepared in the same manner as in Example 4.

[0113] The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 4. Figure 7 The results are shown in Table 2.

[0114] [Comparative Example 2]

[0115] Only [Li(CPFSA)((CH3)2NCH2CH2N(CH3)2)], which is a molecular crystal, will be considered. n As a solid electrolyte.

[0116] The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 4. Figure 7 The results are shown in Table 2.

[0117] [Example 6]

[0118] Except for [Li(TFSA)((CH3)2NCH2CH2N(CH3)2)] which was used as a molecular crystal in Example 4 n [Li(NFBSA)(C6H4(OCH3)2)] is used as a molecular crystal. n In addition, a solid electrolyte was prepared in the same manner as in Example 4.

[0119] The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 4. Figure 8 The results are shown in Table 3.

[0120] [Comparative Example 3]

[0121] Only [Li(NFBSA)(C6H4(OCH3)2)], which is a molecular crystal, is considered. n As a solid electrolyte.

[0122] The ionic conductivity of the solid electrolyte was measured in the same manner as in Example 4. Figure 8 The results are shown in Table 3.

[0123] [Table 1]

[0124] Temperature (°C) 1000 / T(K) Example 4 Comparative Example 1 -10 3.800114 - 3.40E-07 0 3.660992 - 7.16E-07 10 3.531697 - 1.21E-06 20 3.411223 - 2.31E-06 25 3.354016 6.68E-06 - 30 3.298697 - 3.77E-06 40 3.193358 - 5.99E-06 50 3.094538 - 9.48E-06 60 3.001651 6.86E-05 1.54E-05 65 2.957267 8.56E-05 -

[0125] [Table 2]

[0126] Temperature (°C) 1000 / T(K) Example 5 Comparative Example 2 10 3.531697 - 1.01E-07 20 3.411223 - 3.54E-07 25 3.354016 1.89E-06 - 30 3.298697 - 1.25E-06 40 3.193358 - 3.11E-06 50 3.094538 - 6.37E-06 55 3.047387 8.82E-05 - 60 3.001651 - 1.46E-05 65 2.957267 - 2.52E-05

[0127] [Table 3]

[0128] Temperature (°C) 1000 / T(K) Example 6 Comparative Example 3 70 2.915452 - 2.47E-08 80 2.832861 - 4.87E-08 90 2.754821 - 8.47E-08 100 2.680965 - 1.59E-07 110 2.610966 - 2.38E-07 120 2.544529 3.21E-06 -

[0129] like Figures 6 to 8 As shown in Tables 1 to 3, the solid electrolytes of Examples 4 to 6 exhibit superior ion conductivity compared to the solid electrolytes of Comparative Examples 1 to 3.

[0130] [Example 7]

[0131] Fumed silica (AEROSIL 300, registered trademark, AEROSIL Corporation, Japan) was used as an inorganic filler, with an average particle size of 7 nm and a specific surface area of ​​300 ± 30 m². 2 / g) was vacuum dried at 100℃ for 24 hours. Under an argon atmosphere, the vacuum-dried fumed silica was mixed with [Li(FSA)(NCCH2CH2CN)2], which is a molecular crystal, using a mortar. nThe mixture is stirred until it becomes homogeneous. At this point, the amount of fumed silica is 20% by mass relative to the total amount of fumed silica and molecular crystals. Next, the mixture is heated while stirring in an oil bath at a temperature above the melting point of the molecular crystals. Afterward, the mixture is cooled to room temperature, thus producing a solid electrolyte that combines inorganic filler with molecular crystals.

[0132] The ionic conductivity of the solid electrolyte was measured at 30°C and 55°C, similar to that in Example 1. Figure 9 and Figure 10 The results are shown.

[0133] [Example 8]

[0134] Except in Example 7, where the fumed silica was replaced with hydrophobic silica (AEROSIL (registered trademark) 812, AEROSIL Corporation of Japan, with an average particle size of 7 nm and a specific surface area of ​​260 ± 30 m²), 2 Except for g), a solid electrolyte was prepared in the same manner as in Example 7, and the ionic conductivity of the solid electrolyte was measured. Figure 9 and Figure 10 The results are shown.

[0135] [Example 9]

[0136] Except in Example 7, where fumed silica was replaced with aluminum oxide (SIGMA ALDRICH, average particle size 13 nm, specific surface area 85 m²), 2 / g~115m 2 Except for g), a solid electrolyte was prepared in the same manner as in Example 7, and the ionic conductivity of the solid electrolyte was measured. Figure 9 and Figure 10 The results are shown.

[0137] [Example 10]

[0138] Except in Example 7, where fumed silica was replaced with aluminum oxide (SIGMA ALDRICH, with an average particle size of less than 50 nm and a specific surface area exceeding 40 m²), 2 Except for g), a solid electrolyte was prepared in the same manner as in Example 7, and the ionic conductivity of the solid electrolyte was measured. Figure 9 and Figure 10 The results are shown.

[0139] [Example 11]

[0140] Except in Example 7, where fumed silica was replaced with zinc oxide (SIGMA ALDRICH, with an average particle size of less than 50 nm and a specific surface area exceeding 10.8 m²),... 2Except for g), a solid electrolyte was prepared in the same manner as in Example 7, and the ionic conductivity of the solid electrolyte was measured. Figure 10 The results are shown.

[0141] [Example 12]

[0142] Except in Example 7, where fumed silica was replaced with zinc oxide (SIGMA ALDRICH, with an average particle size of less than 100 nm and a specific surface area of ​​10 m²), 2 / g~25m 2 Except for g), a solid electrolyte was prepared in the same manner as in Example 7, and the ionic conductivity of the solid electrolyte was measured. Figure 9 and Figure 10 The results are shown.

[0143] [Example 13]

[0144] Except that in Example 7, the fumed silica was replaced with cerium dioxide (SIGMA ALDRICH, with an average particle size of less than 25 nm), the solid electrolyte was prepared in the same manner as in Example 7, and the ionic conductivity of the solid electrolyte was measured. Figure 9 and Figure 10 The results are shown.

[0145] [Example 14]

[0146] Except that in Example 7, fumed silica was replaced with titanium dioxide (Kanto Chemical Co., Ltd., with an average particle size of 19.7 nm to 101.0 nm and a specific surface area of ​​15 m²). 2 / g~77m 2 Except for g), a solid electrolyte was prepared in the same manner as in Example 7, and the ionic conductivity of the solid electrolyte was measured. Figure 9 and Figure 10 The results are shown.

[0147] [Example 15]

[0148] Except for replacing fumed silica with titanium dioxide (titanium oxide nanowires, SIGMAALDRICH, 10 nm in diameter and 10 μm in length) in Example 7, a solid electrolyte was prepared in the same manner as in Example 7, and the ionic conductivity of the solid electrolyte was measured. Figure 10 The results are shown.

[0149] [Comparative Example 4]

[0150] [Li(FSA)(NCCH2CH2CN)2] will only be used as a molecular crystal in Example 7. n As a solid electrolyte.

[0151] The ionic conductivity of the solid electrolyte was measured at 30°C, similar to that in Example 7. Figure 9 The results are shown.

[0152] Table 4 shows the ionic conductivity results of the solid electrolytes for Examples 7 to 15 and Comparative Example 4 at 30°C and 55°C. Furthermore, "-" in Table 4 indicates no data.

[0153] [Table 4]

[0154]

[0155] like Figure 9 As shown, the solid electrolytes of Examples 7 to 10 and 12 to 14 exhibited superior ionic conductivity at 30°C compared to Comparative Example 4.

[0156] like Figure 10 As shown, the solid electrolytes of Examples 11 and 15 exhibit superior ionic conductivity at 55°C compared to the solid electrolyte of Example 7, and also demonstrate excellent ionic conductivity over a higher temperature range.

[0157] Furthermore, in Examples 7 to 15, even at 55°C, which is above the melting point of the molecular crystal, the solid electrolyte can be regarded as a quasi-solid by combining the molecular crystal with the inorganic filler, thereby suppressing problems such as dissolution and precipitation of the molecular crystal.

[0158] [Reference Example 1]

[0159] Under an argon atmosphere, Mg(TFSA)₂ and NCCH₂CH₂CN were mixed at a molar ratio of 1:3. Then, an oil bath was used to prepare [Mg(TFSA)₂(NCCH₂CH₂CN)₃]. n The mixture was heated to a temperature above its melting point. Afterward, the mixture was cooled to room temperature to produce [Mg(TFSA)2(SN)3], which is a molecular crystal. n Solid electrolytes.

[0160] [Reference Example 2]

[0161] Under an argon atmosphere, Mg(TFSA)₂ and NCCH₂CH₂CH₂CN were mixed in a molar ratio of 1:3. The mixture was then heated in an oil bath at a temperature above its melting point. Afterward, the mixture was cooled to room temperature to prepare a [Mg]₂ as a molecular crystal. a (TFSA) b (NCCH2CH2CH2CN)c ] n (Specified structural formula) solid electrolyte.

[0162] (Measurement of ionic conductivity)

[0163] Using a measurement sample obtained by pressurizing and molding the solid electrolytes obtained in Reference Examples 1 and 2 into a disk shape, the ionic conductivity was measured in a closed cell using AC impedance spectroscopy with a gold electrode. Furthermore, the ionic conductivity was measured while heating the measurement sample within a temperature range below the melting point of the molecular crystal. Figure 11 The results are shown.

[0164] The entire disclosure of Japanese Patent Application 2020-027439, filed on February 20, 2020, is incorporated herein by reference.

[0165] All documents, patent applications, and technical standards described in this specification, and where specifically and separately stated, are incorporated herein by reference to other documents, patent applications, and technical standards, are incorporated herein by reference to the same extent.

Claims

1. A solid electrolyte, comprising: Molecular crystals; and Inorganic packing, The inorganic filler is an inorganic oxide. The molecular crystal is composed of [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 At least one selected from the group.

2. The solid electrolyte according to claim 1, wherein, The content of the inorganic filler is from 1% to 85% by mass relative to the total amount of molecular crystals and inorganic filler.

3. The solid electrolyte according to claim 1 or 2, wherein, The solid electrolyte is used as a solid electrolyte in secondary batteries or capacitors.

4. A secondary battery comprising the solid electrolyte according to any one of claims 1 to 3.

5. A capacitor comprising the solid electrolyte according to any one of claims 1 to 3.

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