Solid electrolyte, power storage device, and method for manufacturing solid electrolyte

Abstract

Provided is a flexible-crystalline solid electrolyte having high ion conductivity, a power storage device, and a method for producing a solid electrolyte. The solid electrolyte contains a flexible-crystalline electrolyte-doped electrolyte. The flexible-crystalline electrolyte contains two or more kinds of cations selected from the group consisting of various imidazoliums and various quaternary ammoniums.

Description

TECHNICAL FIELD

[0001] The present application relates to a solid electrolyte including a flexible-crystalline, a power storage device using the same, and a manufacturing method of the solid electrolyte. BACKGROUND

[0002] A secondary battery, an electric double layer capacitor, a fuel cell, a solar cell, and other power storage devices are roughly configured such that positive and negative electrodes face each other with an electrolyte layer interposed therebetween. A lithium ion secondary battery has a Faraday reaction electrode, and charges and discharges electric energy by reversibly inserting and extracting lithium ions in the electrolyte layer into and out of the electrode. As for an electric double layer capacitor, one or both of the electrodes is a polarizable electrode, and charging and discharging is performed by the power storage action of an electric double layer formed at the interface between the polarizable electrode and the electrolyte layer.

[0003] A solid electrolyte layer can be selected as the electrolyte layer of the power storage device. In the solid electrolyte layer, a region in which chemical reactions occur in the electrode due to hydration deterioration or the like is limited only to the vicinity of the electrode. Therefore, compared with an electrolytic solution, the leakage current is small, and self-discharge can be suppressed. In addition, compared with an electrolytic solution, the amount of gas generated due to chemical reactions with the electrode is also small, and the possibility of valve opening or liquid leakage is also reduced.

[0004] As the solid electrolyte, there are known sulfide-based solid electrolytes such as Li2S / P2S5, oxide-based solid electrolytes such as Li7La3Zr2O 12 polymer-based solid electrolytes such as polyethylene glycol, and the like. Further, a secondary battery dopes lithium ions as an electrolyte in a selected parent phase as needed, and an electric double layer capacitor dopes, for example, TEMABF4 as an electrolyte in a selected parent phase as needed.

[0005] A flexible-crystalline is soluble in an organic solvent. On the other hand, sulfide-based and oxide-based are insoluble. Therefore, when a flexible-crystalline is used in a solid electrolyte or a parent phase of a solid electrolyte, a manufacturing method can be employed in which an anion component and a cation component of the flexible-crystalline, or a salt thereof is dissolved in a solvent and then cast into an electrode. Therefore, compared with sulfide-based and oxide-based, a solid electrolyte of a flexible-crystalline has the following advantages: adhesion to the electrode is improved, and further, if the active material phase of the electrode is a porous structure, it easily enters the structure.

[0006] [Patent Literature]

[0007] [Patent Literature]

[0008] Patent Literature 1: Japanese Patent Laid-Open No. 2014-504788

[0009] Patent Literature 2: Japanese Patent Laid-Open No. 2017-91813 SUMMARY

[0010] [Problems to be Solved by the Invention]

[0011] However, it is pointed out that the ion conductivity of a solid electrolyte of a flexible-viscous crystalline system is lower than that of a sulfide system and an oxide system by 2 to 3 orders of magnitude or more. For example, it is reported that a solid electrolyte containing a flexible-viscous crystal including N,N-diethylpyrrolidinium cation and bis(fluorosulfonyl)amide anion has an ion conductivity of 1 x 10 -5 S / cm at 25°C. In addition, it is reported that a solid electrolyte containing a flexible-viscous crystal including N,N-dimethylpyrrolidinium cation and bis(trifluoromethanesulfonyl)amide anion has an ion conductivity of 1 x 10 -8 S / cm.

[0012] On the contrary, it is reported that if a solid electrolyte such as Li2S / P2S5 is used, the ion conductivity is 1 x 10 -2 S / cm. In addition, it is reported that if a solid electrolyte such as Li7La3Zr2O 12 is used, the ion conductivity is 1 x 10 -3 S / cm.

[0013] The present application has been made in order to solve the problems described above, and an object thereof is to provide a solid electrolyte of a flexible-viscous crystalline system having high ion conductivity and a power storage device using the same.

[0014] [Technical Means for Solving the Problems]

[0015] As a result of diligent studies by the present inventors, the following insights were obtained: if two kinds of cations, each of which is a necessary component to enable the formation of a flexible-viscous crystal, are used in combination, the ion conductivity of the solid electrolyte is improved as compared with the case where the cations are used in monomer form. It was also found that if one of the two kinds of cations is an imidazolium-based cation, the degree of improvement in the ion conductivity of the solid electrolyte is large, and it was also found that if two kinds of anions, each of which is capable of forming a flexible-viscous crystal, are used in combination, the ion conductivity of the solid electrolyte is improved as compared with the case where the anions are used in monomer form.

[0016] The present invention was accomplished based on the above insight, and in order to solve the above problem, a solid electrolyte of the present invention is characterized by containing a flexible and viscous crystal doped with an electrolyte, the flexible and viscous crystal containing two or more cations selected from each of a group of various imidazoliums and a group of various quaternary ammoniums.

[0017] In addition, the present invention was accomplished based on the above insight, and the flexible and viscous crystal can also contain two or more anions. For example, the flexible and viscous crystal can contain two or more anions selected from a group of various amide anions in which two hydrogen atoms of an NH2 anion are substituted with a perfluoroalkylsulfonyl group, a fluorosulfonyl group, or both, and a tris(trifluoromethanesulfonyl)methanide anion.

[0018] In addition, the present invention was accomplished based on the above insight, and the flexible and viscous crystal can contain two cations selected from the group of various quaternary ammoniums, or two cations selected from the group of various imidazoliums, or cations selected from each of the group of various imidazoliums and the group of various quaternary ammoniums, or one cation selected from each of the group of various imidazoliums and the group of various quaternary ammoniums, and another cation other than the group of various imidazoliums and the group of various quaternary ammoniums.

[0019] Preferably, one cation selected from the group of various imidazoliums is a 1,3-dimethylimidazolium cation, a 1-ethyl-3-methylimidazolium cation, a 1-methyl-3-propylimidazolium cation, or an imidazolium substituted with a methyl group at the 2-position of these cations, and the flexible and viscous crystal contains an N,N-hexafluoro-1,3-disulfonylamide anion as an anion with respect to one cation selected from the group of various imidazoliums.

[0020] In addition, preferably, one cation selected from the group of various imidazoliums is a 1,3-dimethylimidazolium or a 1-ethyl-3-methylimidazolium, and the flexible and viscous crystal contains a perfluoroalkylsulfonate anion in which a hydrocarbon group extending from a sulfonic acid skeleton is substituted with a perfluoroalkyl group as an anion with respect to one cation selected from the group of various imidazoliums.

[0021] If these anions are combined with imidazoliums, a flexible and viscous crystal can be simply synthesized, and in addition, the degree of improvement in ion conductivity of the flexible and viscous crystal becomes high.

[0022] A power storage device using the solid electrolyte is also an embodiment of the present invention.

[0023] In addition, the manufacturing method of the solid electrolyte of the present application is completed based on the above-mentioned insight, and in order to solve the above-mentioned problem, the manufacturing method of the solid electrolyte of the present application is characterized by comprising a step of producing a soft sticky crystal containing two kinds of cations selected from the group of various pyrrolidiniums, various imidazoliums, various quaternary amines, and various phosphoniums.

[0024] [Effects of the Invention]

[0025] According to the present application, the ion conductivity of the solid electrolyte using the soft sticky crystal is improved. DETAILED DESCRIPTION

[0026] Hereinafter, a mode of carrying out the present application will be described. Further, the present application is not limited to the following described embodiments.

[0027] (Solid electrolyte)

[0028] The solid electrolyte is interposed between positive and negative electrodes of an electricity storage device, and mainly conducts ions. The electricity storage device is a passive element that charges and discharges electric energy, such as a lithium ion secondary battery and an electric double layer capacitor. The lithium ion secondary battery has a Faraday reaction electrode, and charges and discharges electric energy by reversibly inserting and extracting lithium ions in the solid electrolyte into and from the electrode. In the electric double layer capacitor, one or both of the electrodes is a polarizable electrode, and charges and discharges electric energy by the electric double layer formation at the interface between the electrode and the solid electrolyte.

[0029] The solid electrolyte is formed of a soft sticky crystal that becomes an ion conduction medium, and contains an ionic salt doped in the soft sticky crystal as an electrolyte. The soft sticky crystal is also called plastic crystal, and has an ordered arrangement and a disordered orientation. That is, the so-called soft sticky crystal has a three-dimensional lattice structure in which anions and cations are regularly arranged, and on the other hand, these anions and cations have rotational irregularity. In the soft sticky crystal, the anions and cations generated by dissociation of the electrolyte jump by rotation of the anions and cations, and move in the gaps in the lattice.

[0030] (Cation of soft sticky crystal)

[0031] The soft sticky crystal contains at least two kinds of cations. The cation of the soft sticky crystal is selected from at least one of the group of various imidazoliums and various quaternary amines. That is, the soft sticky crystal contains two different kinds of imidazoliums, two different kinds of quaternary amines, one kind of imidazolium and one kind of quaternary amine, one kind of imidazolium and another cation, or one kind of quaternary amine and another cation. As the other cation, for example, various phosphoniums can be listed.

[0032] The imidazolium contains a five-membered ring having a nitrogen atom at positions 1 and 3. The five-membered ring is a cyclic conjugated system, and since π electrons are delocalized, surface charge density decreases, and apparent charge amount q decreases. Therefore, the Coulomb force with the cation constituting a flexible and viscous crystal decreases. In addition, the positions 1 and 3 of the imidazolium are substituted with alkyl groups. The alkyl groups keep a distance from the anion, and the Coulomb force generated between the imidazolium and the anion decreases.

[0033] By these, the interaction between the imidazolium and the anion decreases, and the rotational freedom of the imidazolium and the anion increases, and thus improvement of ion conductivity can be expected particularly, and thus selection is preferably made.

[0034] The various imidazoliums are 1,3-dialkyl imidazoliums or 1,2,3-trialkyl imidazoliums represented by the following Chemical Formula (A).

[0035] [Chemical 1]

[0036]

[0037] In the formula of Chemical Formula (A), n and m are integers of 1 or more and 3 or less, and p is 0 or 1.

[0038] In the formula of Chemical Formula (A), when p is 0, n and m are 1, it is a 1,3-dimethyl imidazolium (DMI) represented by the following Chemical Formula (Al). The position 2 of the DMI can be substituted with a methyl group.

[0039] [Chemical 2]

[0040]

[0041] In the formula of Chemical Formula (A), when p is 0, n is 1 and m is 2, it is a 1-ethyl-3-methyl imidazolium (EMI) represented by the following Chemical Formula (A2). The position 2 of the EMI can be substituted with a methyl group.

[0042] [Chemical 3]

[0043]

[0044] In the formula of Chemical Formula (A), when p is 0, n is 1 and m is 3, it is a 1-methyl-3-propyl imidazolium (MPI) represented by the following Chemical Formula (A3). The position 2 of the MPI can be substituted with a methyl group.

[0045] [Chemical 4]

[0046]

[0047] As a quaternary ammonium, a tetraalkylammonium substituted with a straight-chain alkyl group regardless of the number of carbons can be exemplified, which is represented by the following Chemical Formula (B). In the following Chemical Formula (B), when a, b, and c are 2 and d is 1, it is triethylmethylammonium (TEMA).

[0048] [Chemical 5]

[0049]

[0050] In the formula, a, b, c, and d are integers of 1 or more, and the number of carbons can be arbitrary.

[0051] In addition, as a quaternary ammonium, a pyrrolidinium having a five-membered ring to which a methyl group, an ethyl group, or an isopropyl group is bonded can be exemplified, which is represented by the following Chemical Formula (C).

[0052] [Chemical 6]

[0053]

[0054] In the formula, R1and R2are a methyl group, an ethyl group, or an isopropyl group.

[0055] As a specific example of the pyrrolidinium having a five-membered ring generalized in the Chemical Formula (C), for example, N-ethyl-N-methylpyrrolidinium (P12) represented by the following Chemical Formula (C1), N-isopropyl-N-methylpyrrolidinium (P13iso) represented by the following Chemical Formula (C2), and N,N-diethylpyrrolidinium (P22) represented by the following Chemical Formula (C3) can be exemplified.

[0056] [Chemical 7]

[0057]

[0058] [Chemical 8]

[0059]

[0060] [Chemical 9]

[0061]

[0062] In addition, as a quaternary ammonium, a spiro-type pyrrolidinium (SBP) represented by the following Chemical Formula (D) can be exemplified.

[0063] [Chemical 10]

[0064]

[0065] As various phosphonium cations of other cations, tetraalkylphosphonium substituted with straight-chain alkyl groups regardless of the number of carbons can be exemplified. As the tetraalkylphosphonium, for example, tetraethylphosphonium (TEP) cation can be exemplified.

[0066] [Chemical Formula 11]

[0067]

[0068] In the formula, e, f, g, and h are integers of 1 or more, and the number of carbons can be arbitrary.

[0069] Although not limited to the mechanism, it is presumed that if the cation is one of the soft sticky crystals, the crystal structure is changed by mixing of two kinds, and due to the change, the jumping of the cations and anions in the electrolyte becomes easy, resulting in an increase in the ionic conductivity of the solid electrolyte.

[0070] However, it is not simply the mixing of two kinds, but when the crystal structure of the soft sticky crystal containing the various imidazolium monomers represented by the chemical formula (A) is changed due to the inclusion of other cations, an increase in the ionic conductivity of the solid electrolyte occurs. In addition, when the crystal structure of the soft sticky crystal containing the quaternary ammonium monomers represented by the chemical formula (B) is changed due to the inclusion of other cations, an increase in the ionic conductivity of the solid electrolyte occurs.

[0071] If the mixing ratio of two kinds is set to be in the range of 10:90 to 90:10 in terms of molar ratio, in other words, the mixing ratio of two kinds is set to be in the range of 10 mol% or more and 90 mol% or less of one of the total moles of the cations constituting the soft sticky crystal, the ionic conductivity of the solid electrolyte is greatly increased. Especially, if the mixing ratio of two kinds is set to be in the range of 20:80 to 80:20 in terms of molar ratio, in other words, the mixing ratio of two kinds is set to be in the range of 20 mol% or more and 80 mol% or less of one of the total moles of the cations constituting the soft sticky crystal, the ionic conductivity of the solid electrolyte is further greatly increased.

[0072] The anion constituting the soft sticky crystal can be any known one as long as it can not become an ionic liquid but maintain a solid state in the temperature range of use of the power storage device to constitute the soft sticky crystal, and two or more kinds can also be selected with respect to the anion. The imidazolium is a cation that constitutes an ionic liquid in the temperature range including room temperature, and when the imidazolium is selected, the anion used to constitute the soft sticky crystal can be selected to be a specific kind.

[0073] (Soft Sticky Crystal Anion)

[0074] As the anion, various amide anions, tris(trifluoromethanesulfonyl)methane anions, hexafluorophosphate anions (PF6 anions), various perfluoroalkylphosphate anions in which part of the fluorine atoms of PF6 are substituted with fluoroalkyl groups, various perfluoroalkylborate anions in which part of the fluorine atoms of BF4 anions are substituted with fluoroalkyl groups, various perfluoroalkylsulfonate anions (NFS anions) in which the hydrocarbon groups extending from the sulfonic acid skeleton are substituted with perfluoroalkyl groups can be exemplified.

[0075] Among the various amide anions, two hydrogen atoms of the NH2 anion are substituted with perfluoroalkylsulfonyl groups, fluorosulfonyl groups, or both. Various bis(perfluoroalkylsulfonyl)amide anions, bis(fluorosulfonyl)amide anions, and various N-(fluorosulfonyl)-N-(perfluoroalkylsulfonyl)amide anions represented by the following formula (F) are included in the various amide anions, for example.

[0076] [Chemical Formula 12]

[0077]

[0078] In the formula of formula (F), n and m are integers of 0 or more, and the number of carbons can be arbitrary.

[0079] In the formula of formula (F), if n and m are 1 or more, it is a bis(perfluoroalkylsulfonyl)amide anion. As the bis(perfluoroalkylsulfonyl)amide anion, specifically, bis(trifluoromethane sulfonyl)amide anion (TFSA anion) represented by the following formula (F1), bis(pentafluoro ethyl sulfonyl)amide anion (BETA anion) represented by the following formula (F2) can be exemplified.

[0080] [Chemical Formula 13]

[0081]

[0082] [Chemical Formula 14]

[0083]

[0084] In the formula of formula (F), that is, the group having a carbon number of 0 is a fluorosulfonyl group, and if n and m are 0, it is a bis(fluorosulfonyl)amide anion (FSA anion) represented by the following formula (F3).

[0085] [Chemical Formula 15]

[0086]

[0087] In the formula (F), if n is 0 and m is 1 or more, it is an N- (fluorosulfonyl) -N- (perfluoroalkylsulfonyl) amide anion represented by the following formula (F4).

[0088] [Chemical Formula 16]

[0089]

[0090] In addition, various amide anions include, for example, heterocyclic rings of five-membered rings and six-membered rings, and include an N, N-hexafluoro-1, 3-disulfonyl amide anion (CFSA anion) represented by the following formula (G) and an N, N-pentafluoro-1, 3-disulfonyl amide represented by the following formula (H).

[0091] [Chemical Formula 17]

[0092]

[0093] [Chemical Formula 18]

[0094]

[0095] A tris (trifluoromethane sulfonyl) methanide anion (TFSM anion) is represented by the following formula (I).

[0096] [Chemical Formula 19]

[0097]

[0098] Various perfluoroalkyl phosphate anions in which part of the fluorine atoms of PF6 is substituted with a fluoroalkyl group can include a tris (fluoroalkyl) trifluorophosphate anion represented by the following formula (J).

[0099] [Chemical Formula 20]

[0100]

[0101] In the formula (J), q is an integer of 1 or more, and the number of carbons can be arbitrary.

[0102] Specifically, a tris (pentafluoroethyl) trifluorophosphate anion (FAP anion) represented by the following formula (J1) can be included.

[0103] [Chem. 21]

[0104]

[0105] Various perfluoroalkylborate anions include monofluoroalkyl trifluoroborate anions represented by the following formula (K) and difluoroalkyl fluoroborate anions.

[0106] [Chem. 22]

[0107]

[0108] In the formula (K), s is an integer of 0 or more, and t is an integer of 1 or more. The number of carbons can be arbitrary.

[0109] In the formula (K), when s is 0 and t is an integer of 1 or more, it is a monofluoroalkyl trifluoroborate anion represented by the following formula (K1). Specifically, a monofluoromethyl trifluoroborate anion represented by the following formula (K2) can be exemplified.

[0110] [Chem. 23]

[0111]

[0112] In the formula (K), t is an integer of 1 or more. The number of carbons can be arbitrary.

[0113] [Chem. 24]

[0114]

[0115] Various perfluoroalkylsulfonate anions (NFS anions) are represented by the following formula (L).

[0116] [Chem. 25]

[0117]

[0118] In the formula (L), r is an integer of 1 or more and 4 or less.

[0119] Specifically, various perfluoroalkylsulfonate anions are preferably trifluoromethanesulfonate anions in which r is 1 in the following formula (L), pentafluoroethylsulfonate anions in which r is 2 in the following formula (L), heptafluoropropane sulfonate anions in which r is 3 in the following formula (L), and nonafluorobutanesulfonate anions in which r is 4 in the following formula (L).

[0120] In the case of selecting an imidazolium as the cation of the flexible viscous crystal, the anion constituting the flexible viscous crystal together with the imidazolium is preferably an N,N-hexafluoro-l,3-disulfonyl amide anion (CFSA anion) represented by the chemical formula (G) or a perfluoroalkyl sulfonic acid anion (NFS anion) represented by the chemical formula (L) in which a hydrocarbon group extending from a sulfonic acid skeleton is substituted with a perfluoroalkyl group.

[0121] An imidazolium is known as a cation constituting an ionic liquid having a melting point of -3°C in combination with a bis(trifluoromethanesulfonyl)amide anion also referred to as a TFSA anion. The increase or decrease in the Coulomb force caused by the apparent charge amount q or the presence of an alkyl group is sensitive.

[0122] On the other hand, a CFSA anion or an NFS anion, for example, in the case of P12CFSA in combination with N-ethyl-N-methylpyrrolidinium also referred to as P12 cation, constitutes a flexible viscous crystal having a melting point of 302°C. That is, it is considered that the melting point of the flexible viscous crystal containing these anions is high. Therefore, it is considered that these anions play a role in increasing the melting point of a salt with a cation having a low melting point and easily constituting an ionic liquid. Furthermore, it is considered that by adjusting the chain length of the alkyl group of the cation to be 3 or less or 2 or less in terms of the number of carbons depending on the anion, a balance between the constitutability of a flexible viscous crystal and the degree of improvement in ionic conductivity can be achieved.

[0123] As a result, an imidazolium constitutes a flexible viscous crystal exhibiting higher ionic conductivity by being combined with these anions.

[0124] As for the anion, it is not limited to one, but two can also be combined. If two anions are used, the ionic conductivity is improved. Although not limited to the mechanism, it is presumed that if the flexible viscous crystal of one anion is taken as a reference, the crystal structure changes in the mixture of two, and due to the change, the jumping of the anion and the cation in the electrolyte becomes easy, resulting in an improvement in the ionic conductivity of the solid electrolyte. Therefore, if the crystal structure changes compared to the monomer, the mixing ratio of the total of two can be arbitrary.

[0125] However, if the mixing ratio of the two is set to a range of 10:90 to 90:10 in terms of molar ratio, in other words, if the mixing ratio of the two is set to a range in which one of the total moles of the anions constituting the flexible anisotropic crystal is 10 mol% or more and 90 mol% or less, the ion conductivity of the solid electrolyte is greatly improved. Particularly, if the mixing ratio of the two is set to a range of 20:80 to 80:20 in terms of molar ratio, in other words, if the mixing ratio of the two is set to a range in which one of the total moles of the anions constituting the flexible anisotropic crystal is 20 mol% or more and 80 mol% or less, the ion conductivity of the solid electrolyte is further greatly improved.

[0126] (Electrolyte)

[0127] The ionic salt doped in the flexible anisotropic crystal to become the electrolyte can correspond to the type of the power storage device. As the ionic salt for a lithium ion secondary battery, Li(CF3SO2)2N (commonly known as LiTFSA), Li(FSO2)2N (commonly known as LiFSA), Li(C2F5SO2)2N, LiPF6, LiBF4, LiAsF6, LiTaF6, LiClO4, LiCF3SO3, and the like can be used alone or in combination with two or more kinds. The ionic salt for an electric double layer capacitor is a salt of an organic acid, a salt of an inorganic acid, or a salt of a complex compound of an organic acid and an inorganic acid, and can be used alone or in combination with two or more kinds.

[0128] As the organic acid, oxalic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, benzoic acid, toluic acid, heptanoic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, and the like carboxylic acids, phenols, sulfonic acids can be exemplified. In addition, as the inorganic acid, boric acid including tetrafluoroborate, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, silicic acid, and the like can be exemplified. As the complex compound of an organic acid and an inorganic acid, boro-bis-salicylic acid, boro-bis-oxalic acid, boro-bis-glycolic acid, and the like can be exemplified.

[0129] As the at least one salt of a salt of these organic acids, a salt of an inorganic acid, and a complex compound of an organic acid and an inorganic acid, there can be mentioned: an ammonium salt, a quaternary ammonium salt, a quaternary amidinium salt, an amine salt, a sodium salt, a potassium salt, and the like. As the quaternary ammonium ion of the quaternary ammonium salt, there can be mentioned: tetramethylammonium, triethylmethylammonium, tetraethylammonium, and the like. As the quaternary amidinium, there can be mentioned: ethyldimethylimidazolium, tetramethylimidazolium, and the like. As the amine of the amine salt, there can be mentioned: a primary amine, a secondary amine, a tertiary amine. As the primary amine, there can be mentioned: methylamine, ethylamine, propylamine, and the like, as the secondary amine, there can be mentioned: dimethylamine, diethylamine, ethylmethylamine, dibutylamine, and the like, and as the tertiary amine, there can be mentioned: trimethylamine, triethylamine, tripropylamine, tributylamine, ethyldimethylamine, ethyldiisopropylamine, and the like. In addition, as the ionic salt for a double-layer capacitor, there can be mentioned a salt containing the cationic component of the chemical formula (N), the chemical formula (P), the chemical formula (Q), and the chemical formula (R) that constitute the flexible viscous crystal.

[0130] (Method for manufacturing)

[0131] An example of the method for manufacturing the solid electrolyte containing such a flexible viscous crystal is as follows. An alkali metal salt of a first anion constituting a flexible viscous crystal and a halogenated cation are separately dissolved in a solvent. As the alkali metal, there can be mentioned Na, L, Li, Cs. As the halogen, there can be mentioned F, Cl, Br, I. As the solvent, water is preferable. The solution of the halogenated cation is dropwise added with the solution of the metal salt of the anion and an ion exchange reaction is performed. The solution of the halogenated cation is added with an equimolar amount of the solution of the metal salt of the anion and stirred.

[0132] At this time, by the ion exchange, the flexible viscous crystal containing the first anion is generated, and a halogenated alkali metal is generated. Since the flexible viscous crystal is hydrophobic and the halogenated alkali metal is hydrophilic, the flexible viscous crystal exists in a solid state in the aqueous solution and the halogenated alkali metal is dissolved in the aqueous solution. An organic solvent such as dichloromethane is mixed in the aqueous solution in which the flexible viscous crystal exists in a solid state. If the organic solvent such as dichloromethane is mixed and left to stand, the mixed solution is separated into a water layer and a layer of the organic solvent.

[0133] By removing the water layer from the separation, the halogenated alkali metal is removed. The operation can be repeated as many times as 5 or more. Thereby, after the halogenated alkali metal is removed, the organic solvent such as dichloromethane is evaporated, and the flexible viscous crystal containing the first anion is obtained. Further, it can be provided that if left to stand without mixing the organic solvent such as dichloromethane, a precipitate of the flexible viscous crystal containing the first anion is obtained, and therefore the precipitate can be recovered by filtration, and after washing with water, vacuum drying is performed.

[0134] The flexible and cohesive crystal containing the second anion can also be obtained by the same production method as the flexible and cohesive crystal containing the first anion. That is, an alkali metal salt of the second anion and the halogenated cation are separately dissolved in a solvent, an ion exchange reaction is performed by dropwise addition, an organic solvent such as dichloromethane is mixed, and the water layer is removed.

[0135] If the flexible and cohesive crystals containing the first anion and the second anion are separately refined, they are added to a glass vial in a mol ratio of 1 : 1, and an ionic salt as an electrolyte is further added to the glass vial. The ionic salt is preferably 0.1 mol% or more and 50 mol% or less with respect to the total of the flexible and cohesive crystals. Then, an organic solvent in which the flexible and cohesive crystals and the electrolyte can be dissolved, such as acetone or acetonitrile, is further added to the glass vial, and an organic solvent solution in which both the flexible and cohesive crystals and the electrolyte are dissolved is prepared.

[0136] The organic solvent solution is cast on an object such as an active material layer of an electrode to which a solid electrolyte is attached, a separator, or both. After casting, it is left in a temperature environment in which the organic solvent volatilizes, such as 80°C, and the solvent is volatilized by drying, and then the remaining moisture and the like are volatilized in a temperature environment of 150°C or the like. Thus, a solid electrolyte is formed on the object.

[0137] Further, as the production method of the solid electrolyte containing the flexible and cohesive crystal, various methods can be used. For example, it can be configured to prepare each solution in which the flexible and cohesive crystal to be a powder and the electrolyte are separately dissolved in an organic solvent, and mix these solutions. The two kinds of flexible and cohesive crystals can be separately dissolved in an organic solvent, or the two kinds of flexible and cohesive crystals can be simultaneously dissolved in an organic solvent. In addition, it can be configured to add the electrolyte to the organic solvent after the flexible and cohesive crystal to be a powder is dissolved in the organic solvent. In addition, it can be configured to add the flexible and cohesive crystal to be a powder to the organic solvent after the electrolyte is dissolved in the organic solvent. Then, it is only necessary to cast the organic solvent on an object.

[0138] (Power storage device)

[0139] The power storage device is formed by facing the positive and negative electrodes with the solid electrolyte therebetween. In order to prevent contact between the positive and negative electrodes and maintain the shape of the solid electrolyte, a separator is disposed between the positive and negative electrodes. However, if the solid electrolyte has a thickness that can prevent contact between the positive and negative electrodes and has a hardness that can maintain the shape alone, it can also be a so-called separatorless.

[0140] The positive and negative electrodes of the electric double layer capacitor are formed by forming an active material layer on a current collector. The current collector can use aluminum foil, platinum, gold, nickel, titanium, steel, carbon, and other metals having valve action. The shape of the current collector can be any of a film, a foil, a plate, a mesh, an expanded metal, a cylinder, and the like. In addition, the surface of the current collector can be formed into a concave-convex surface by etching treatment or the like, or can be a flat surface. Furthermore, surface treatment can be performed to cause phosphorus to adhere to the surface of the current collector.

[0141] At least one of the positive electrode or the negative electrode is a polarizable electrode. The active material layer of the polarizable electrode contains a carbon material having a porous structure with a double layer capacity. For an electric double layer capacitor having an active material layer with a porous structure, it is particularly suitable to use the solid electrolyte of the soft crystalline. Since the soft crystalline is soluble, it easily enters the porous structure, improving the filling rate of the active material layer. On the other hand, the filling property of the solid electrolyte of the sulfide system and the oxide system to the porous structure is low. Therefore, the electric double layer capacitor using the soft crystalline has both good filling property to the porous structure and high ion conductivity, and becomes high capacity and high output. Further, it can be provided that the other of the positive electrode or the negative electrode can form an active material layer containing metal compound particles or a carbon material that undergoes a Faraday reaction.

[0142] The carbon material in the polarizable electrode is mixed with a conductive aid and a binder, and is applied to the current collector by a doctor blade method or the like. It can also be provided that the mixture of the carbon material, the conductive aid, and the binder is molded into a sheet shape, and is pressure-bonded to the current collector. Here, the porous structure is composed of gaps between primary particles and between secondary particles when the carbon material has a particle shape, or is composed of gaps between fibers when the carbon material is fibrous.

[0143] The carbon material of the active material layer in the polarizable electrode can be listed as: natural plant tissues such as coconut, synthetic resins such as phenol, activated carbon using a substance derived from fossil fuels such as coal, coke, pitch, and the like as a raw material, carbon black such as Ketjen black, acetylene black, channel black, carbon nanohorn, amorphous carbon, natural black lead, artificial black lead, black leadized Ketjen black, mesoporous carbon, carbon nanotube, carbon nanofiber, and the like. The carbon material can be subjected to activation treatment such as steam activation, alkali activation, zinc chloride activation, or electric field activation, and opening treatment to increase the specific surface area.

[0144] As the binder, for example, rubber-based materials such as fluorine-based rubber, diene-based rubber, styrene-based rubber, fluorine-containing polymers such as polytetrafluoroethylene, polyvinylidene fluoride, celluloses such as carboxymethyl cellulose, nitrocellulose, polyolefin resins other than the above, polyimide resins, acrylic resins, nitrile resins, polyester resins, phenol resins, polyvinyl acetate resins, polyvinyl alcohol resins, epoxy resins, and the like can be listed. These binders can be used alone, or two or more can be mixed and used.

[0145] As the conductive aid, Ketjen black, acetylene black, natural / artificial black lead, fibrous carbon, etc. can be used, and as the fibrous carbon, carbon nanotube, carbon nanofiber (hereinafter CNF), etc. can be listed. The carbon nanotube can be single-walled carbon nanotube (SWCNT) in which a graphene sheet is one layer, or multi-walled carbon nanotube (MWCNT) in which two or more graphene sheets are coaxially rolled and a tube wall is formed in multiple layers, or a mixture thereof.

[0146] A carbon coating layer containing a conductive agent such as black lead can be provided between the current collector and the active material layer. The carbon coating layer can be formed by coating a slurry containing a conductive agent such as black lead, a binder, etc. on the surface of the current collector and drying.

[0147] The positive and negative electrodes of the lithium ion secondary battery are formed by forming an active material layer on a current collector. As the current collector, a metal such as aluminum foil, platinum, gold, nickel, titanium, and steel, carbon, a conductive polymer material such as polyaniline, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, polystyrene acetylene, polyphenylene vinylene, polyacrylonitrile, and polyoxadiazole, and a resin in which a conductive filler is filled in a non-conductive polymer material can be used. The shape of the current collector can be any shape such as a film, a foil, a plate, a mesh, an expanded metal, a cylinder, etc.

[0148] The active material is mixed with a binder and applied to the current collector by a doctor blade method, etc. Alternatively, a mixture of a carbon material and a binder can be molded into a sheet shape and pressure-bonded to the current collector. In the active material layer, a conductive carbon such as carbon black, acetylene black, Ketjen black, and graphite as a conductive aid can be added, and the conductive carbon can be added to the active material and the binder, mixed, and then applied or pressure-bonded to the current collector.

[0149] As the active material of the positive electrode, metal compound particles capable of occluding and releasing lithium ions can be listed, and layered rock salt type LiMO2, layered Li2MnO3-LiMO2 solid solution, and spinel type LiM2O4 (M in the formula represents Mn, Fe, Co, Ni, or a combination thereof) can be listed. As specific examples thereof, LiCoO2, LiNiO2, LiNi 4 / 5 Co1 / 5 O2, LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2, LiNi 1 / 2 Mn 1 / 2 O2, LiFeO2, LiMnO2, Li2MnO3-LiCoO2, Li2MnO3-LiNiO2, Li2MnO3-LiNi 1 / 3Co1 / 3 Mn 1 / 3 O2, Li2MnO3 - LiNi 1 / 2 Mn 1 / 2 O2, Li2MnO3 - LiNi 1 / 2 Mn 1 / 2 O2 - LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMn2O4, LiMn 3 / 2 Ni 1 / 2 O4. In addition, the metal compound particles can be sulfides such as S, Li2S, TiS2, MoS2, FeS2, VS2, Cr 1 / 2 V 1 / 2 S2, etc., selenides such as NbSe3, VSe2, NbSe3, etc., oxides such as Cr2O5, Cr3O8, VO2, V3O8, V2O5, V6O 13 , etc., LiNi 0.8 Co 0.15 A l0.05 O2, LiVOPO4, LiV3O5, LiV3O8, MoV2O8, Li2FeSiO4, Li2MnSiO4, LiFePO4, LiFe 1 / 2Mn 1 / 2 PO4, LiMnPO4, Li3V2(PO4)3, etc.

[0150] As the active material of the negative electrode, metal compound particles capable of occluding and releasing lithium ions can be exemplified, such as oxides such as FeO, Fe2O3, Fe3O4, MnO, MnO2, Mn2O3, Mn3O4, CoO, Co3O4, NiO, Ni2O3, TiO, TiO2, TiO2(B), CuO, NiO, SnO, SnO2, SiO2, RuO2, WO, WO2, WO3, MoO3, ZnO, etc., metals such as Sn, Si, Al, Zn, etc., LiVO2, Li3VO4, Li4Ti5O 12 , Sc2TiO5, Fe2TiO5, etc., complex oxides, Li 2.6 Co 0.4 N, Ge3N4, Zn3N2, Cu3N, etc., nitrides, Y2Ti2O5S2, MoS2.

[0151] When a separator is used in the power storage device, as the separator, the following can be listed: kraft paper, manila hemp, esparto grass, jute, cellulose such as rayon, and mixed paper thereof, polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and derivatives thereof, polytetrafluoroethylene-based resins, polyvinylidene fluoride-based resins, vinylon-based resins, aliphatic polyamides, semi-aromatic polyamides, wholly aromatic polyamides, polyamide-based resins, polyimide-based resins, polyethylene resins, polypropylene resins, trimethylpentene resins, polyphenylene sulfide resins, acrylic resins, and the like, which can be used alone or in combination.

[0152] In such a power storage device, a soft-crystalline is dissolved in a solvent such as acetonitrile, and cast on the active material layer and the separator. After casting, the solvent is volatilized by drying in a temperature environment of 80°C or the like, and the active material layers of the positive and negative electrodes are made to face each other through the separator, and further, the remaining moisture or the like is volatilized in a temperature environment of 150°C or the like. Then, the current collector of the positive and negative electrodes is connected to the lead terminal, and sealed with an outer case, whereby the power storage device is produced.

[0153] [Examples]

[0154] (Examples 1 to 5)

[0155] A solid electrolyte for an electric double layer capacitor was produced using a soft-crystalline containing two kinds of quaternary ammonium as cations in Examples 1 to 5. Further, the ion conductivity of the solid electrolyte of Examples 1 to 5 was measured.

[0156] The solid electrolyte of Example 1 contains N-ethyl-N-methylpyrrolidinium (P12) of a five-membered ring pyrrolidinium as the first quaternary ammonium. In addition, the solid electrolyte of Example 1 contains a spiro ring type pyrrolidinium (SBP) as the second quaternary ammonium. The P12 cation and the SBP cation are contained in the soft-crystalline at a molar ratio of 1:1.

[0157] The solid electrolyte of Example 2 contains N-isopropyl-N-methylpyrrolidinium (P13iso) of a five-membered ring pyrrolidinium as the first quaternary ammonium. In addition, the solid electrolyte of Example 1 contains a spiro ring type pyrrolidinium (SBP) as the second quaternary ammonium. The P13iso cation and the SBP cation are contained in the soft-crystalline at a molar ratio of 1:1.

[0158] The solid electrolyte of Example 3 contains N,N-diethylpyrrolidinium (P22) of a five-membered ring pyrrolidinium as the first quaternary ammonium. In addition, the solid electrolyte of Example 1 contains a spiro ring type pyrrolidinium (SBP) as the second quaternary ammonium. The P22 cation and the SBP cation are contained in the soft-crystalline at a molar ratio of 1:1.

[0159] The solid electrolyte of Example 4 contains N-ethyl-N-methylpyrrolidinium (P12) of five-membered ring pyrrolidinium as the first quaternary ammonium. In addition, the solid electrolyte of Example 1 also contains N,N-diethylpyrrolidinium (P22) of five-membered ring pyrrolidinium as the second quaternary ammonium. The P12 cation and the P22 cation are contained in the flexible viscous crystal at a molar ratio of 1:1.

[0160] The solid electrolyte of Example 5 contains triethylmethylammonium (TEMA) of tetraalkylammonium as the first quaternary ammonium. In addition, the solid electrolyte of Example 1 contains N,N-diethylpyrrolidinium (P22) of five-membered ring pyrrolidinium as the second quaternary ammonium. The TEMA cation and the P22 cation are contained in the flexible viscous crystal at a molar ratio of 1:1.

[0161] The production method of the solid electrolyte of each example is as follows. First, the anion constituting the flexible viscous crystal of each example is set to N,N-hexafluoro-1,3-disulfonyl amide anion (CFSA anion). That is, the flexible viscous crystal containing the first anion and the CFSA cation, and the flexible viscous crystal containing the second anion and the CFSA cation are added to a glass vial at a molar ratio of 1:1.

[0162] Further, the P12CFSA flexible viscous crystal containing the P12 cation and the CFSA anion is produced as follows. First, an aqueous solution of a halide in which the P12 cation is halogenated with bromine Br is prepared. In addition, an aqueous solution of an alkali metal salt of the CFSA anion and lithium Li is prepared. The aqueous solution of the halide is added dropwise with the aqueous solution of the alkali metal salt little by little to perform an ion exchange reaction. After the ion exchange reaction is performed, dichloromethane is mixed, the organic solvent layer is extracted from the separation into an aqueous layer and an organic solvent layer, activated carbon is added and stirred for one night. Then, further, the precipitate is recovered by filtration, and the precipitate is dried, whereby the flexible viscous crystal is obtained.

[0163] The SBPCFSA flexible viscous crystal containing the SBP cation and the CFSA anion is produced as follows. First, an aqueous solution of a halide in which the SBP cation is halogenated with chlorine Cl is prepared. In addition, an aqueous solution of an alkali metal salt of the CFSA anion and lithium Li is prepared. The aqueous solution of the halide is added dropwise with the aqueous solution of the alkali metal salt little by little to perform an ion exchange reaction. After the ion exchange reaction is performed, dichloromethane is mixed, the organic solvent layer is extracted from the separation into an aqueous layer and an organic solvent layer, activated carbon is added and stirred for one night. Then, further, the precipitate is recovered by filtration, and the precipitate is dried, whereby the flexible viscous crystal is obtained.

[0164] P13isoCFSA soft sticky crystal containing P13iso cation and CFSA anion was prepared in the following manner. First, an aqueous solution of halide of P13iso cation halogenated with iodine I was prepared. In addition, an aqueous solution of alkali metal salt of CFSA anion and lithium Li was prepared. Ion exchange reaction was performed by dropwise adding the aqueous solution of alkali metal salt to the aqueous solution of halide little by little. After the ion exchange reaction, dichloromethane was mixed, and the organic solvent layer was extracted from the separation into an aqueous layer and an organic solvent layer, activated carbon was added and stirred overnight. Then, further, the precipitate was recovered by filtration, and the precipitate was dried, whereby the soft sticky crystal was obtained.

[0165] P22CFSA soft sticky crystal containing P22 cation and CFSA anion was prepared in the following manner. First, an aqueous solution of halide of P22 cation halogenated with iodine I was prepared. In addition, an aqueous solution of alkali metal salt of CFSA anion and lithium Li was prepared. Ion exchange reaction was performed by dropwise adding the aqueous solution of alkali metal salt to the aqueous solution of halide little by little. After the ion exchange reaction, dichloromethane was mixed, and the organic solvent layer was extracted from the separation into an aqueous layer and an organic solvent layer, activated carbon was added and stirred overnight. Then, further, the precipitate was recovered by filtration, and the precipitate was dried, whereby the soft sticky crystal was obtained.

[0166] TEMACFSA soft sticky crystal containing TEMA cation and CFSA anion was prepared in the following manner. First, an aqueous solution of halide of TEMA cation halogenated with chlorine Cl was prepared. In addition, an aqueous solution of alkali metal salt of CFSA anion and lithium Li was prepared. Ion exchange reaction was performed by dropwise adding the aqueous solution of alkali metal salt to the aqueous solution of halide little by little. After the ion exchange reaction, dichloromethane was mixed, and the organic solvent layer was extracted from the separation into an aqueous layer and an organic solvent layer, activated carbon was added and stirred overnight. Then, further, the precipitate was recovered by filtration, and the precipitate was dried, whereby the soft sticky crystal was obtained.

[0167] In a glass vial, SBPBF4 (spirobipyrralidinium tetrafluoroborate, Tokyo Chemical Industry Co., Ltd.) as an electrolyte was further added in a manner that the total became 30 mol% with respect to the soft sticky crystal, and acetonitrile (Wako Pure Chemical Industries, Ltd.) was added in a manner that the solid content concentration of the total of the soft sticky crystal and the electrolyte was 10 wt%. The acetonitrile solution was added dropwise to a glass separator, and acetonitrile was evaporated by drying at 80°C. The evaporation operation was repeated three times. By the evaporation operation, the glass separator impregnated with the solid electrolyte was dried in a vacuum environment at 80°C for 12 hours, further dried at 120°C for 3 hours, and further dried at 150°C for 2 hours, whereby moisture was removed, and the solid electrolyte of each example and Comparative Example was obtained.

[0168] Then, the ion conductivity of each of the examples was measured. That is, a glass separator impregnated with a solid electrolyte was sandwiched with two platinum electrodes, and the electrodes were brought into contact with each other using an electrode holder, whereby a two-electrode type closed cell (manufactured by Toyo System) was assembled, and impedance measurement was performed. Based on the results of the impedance measurement and the thickness of the glass separator impregnated with the solid electrolyte, the ion conductivity was calculated. The results of the measurement of the ion conductivity are shown in Table 1 below.

[0169] [Table 1]

[0170]

[0171] Further, the ion conductivities of solid electrolytes each of which uses only one kind of flexible-crystal were also described in Table 1. The solid electrolytes used as the comparison objects were produced under the same conditions as the solid electrolytes of each of the examples except that one kind of flexible-crystal was contained.

[0172] As shown in Table 1, it was confirmed that the ion conductivities of the solid electrolytes for electric double layer capacitors of each of the examples were increased by at most about 10 times, and at most more than 300 times, as compared with the solid electrolytes each of which uses one kind of flexible-crystal. Thus, it was confirmed that the ion conductivities of the solid electrolytes each of which uses a flexible-crystal containing two kinds of cations selected from the group of various quaternary ammonium groups were increased.

[0173] (Example 6)

[0174] A solid electrolyte for electric double layer capacitors of Example 6 was produced using a flexible-crystal containing two kinds of imidazolium as cations. Then, the ion conductivity of the solid electrolyte of Example 6 was measured. The solid electrolyte of Example 6 contains 1-ethyl-3-methylimidazolium (EMI) as the first kind of imidazolium. In addition, the solid electrolyte of Example 6 contains 1,3-dimethylimidazolium (DMI) as the second kind of imidazolium. The EMI cation and the DMI cation are contained in the flexible-crystal at a molar ratio of 1:1.

[0175] The anion constituting the flexible-crystal of Example 6 was set to N,N-hexafluoro-1,3-disulfonyl amide anion (CFSA anion). The solid electrolyte of Example 6 was produced under the same conditions and by the same method as Examples 1 to 5, and the first kind of flexible-crystal and the second kind of flexible-crystal were added to a glass vial at a molar ratio of 1:1.

[0176] Then, the ion conductivity of the solid electrolyte of Example 6 was measured. The result thereof is shown in Table 2. Further, the method of measuring the ion conductivity and the method of calculating were the same as those of Examples 1 to 5. The ion conductivities of the solid electrolytes using each of the flexible-crystalline alone are also described in Table 2. The solid electrolytes as the comparative examples were produced under the same conditions as those of each of the examples except that one flexible-crystalline was contained.

[0177] [Table 2]

[0178]

[0179] As shown in Table 2, it was confirmed that the ion conductivity of the solid electrolyte for a double-layer capacitor of Example 6 was improved by 10 times or more at the minimum compared with the solid electrolyte using one flexible-crystalline. Thus, it was confirmed that the ion conductivity of the solid electrolyte using the flexible-crystalline containing two kinds of cations selected from the group of various imidazoliums was improved.

[0180] (Examples 7 to 11)

[0181] A solid electrolyte for a double-layer capacitor of Example 7 to Example 11 was produced using a flexible-crystalline containing two kinds of cations in total, one selected from imidazoliums and one selected from quaternary ammoniums. Then, the ion conductivity of the solid electrolytes of Example 7 to Example 11 was measured.

[0182] The solid electrolyte of Example 7 contains 1-ethyl-3-methylimidazolium (EMI) as the first imidazolium. In addition, the solid electrolyte of Example 7 contains triethylmethylammonium (TEMA) as the second quaternary ammonium. The EMI cation and the TEMA cation are contained in the flexible-crystalline at a molar ratio of 1:1.

[0183] The solid electrolyte of Example 8 contains 1-ethyl-3-methylimidazolium (EMI) as the first imidazolium. In addition, the solid electrolyte of Example 8 contains N-ethyl-N-methylpyrrolidinium (P12) as the second quaternary ammonium. The EMI cation and the P12 cation are contained in the flexible-crystalline at a molar ratio of 1:1.

[0184] The solid electrolyte of Example 9 contains 1-ethyl-3-methylimidazolium (EMI) as the first imidazolium. In addition, the solid electrolyte of Example 9 contains spiro-type pyrrolidinium (SBP) as the second quaternary ammonium. The EMI cation and the SBP cation are contained in the flexible-crystalline at a molar ratio of 1:1.

[0185] The solid electrolyte of Example 10 contains 1,3-dimethylimidazolium (DMI) as the first imidazolium. In addition, the solid electrolyte of Example 10 contains spirocyclic pyrrolidinium (SBP) as the second quaternary ammonium. The DMI cation and the SBP cation are contained in the flexible viscous crystal at a molar ratio of 1:1.

[0186] The solid electrolyte of Example 11 contains 1-methyl-3-propylimidazolium (MPI) as the first imidazolium. In addition, the solid electrolyte of Example 11 contains spirocyclic pyrrolidinium (SBP) as the second quaternary ammonium. The MPI cation and the SBP cation are contained in the flexible viscous crystal at a molar ratio of 1:1.

[0187] Then, the ion conductivity of the solid electrolytes of Examples 7 to 11 was measured. The results thereof are shown in Table 3 below. Further, the method of measuring and the method of calculating the ion conductivity were the same as those of Examples 1 to 5. The ion conductivity of the solid electrolyte using each of the flexible viscous crystals alone is also described in Table 3. The solid electrolyte used as the comparative example was produced under the same conditions as the solid electrolytes of the respective examples except that one kind of flexible viscous crystal was contained.

[0188] [Table 3]

[0189]

[0190] As shown in Table 3, it was confirmed that the ion conductivity of the solid electrolyte for a double-layer capacitor of each example was at least the same as that of the solid electrolyte using one kind of flexible viscous crystal, and was maximally improved by about four digits. Thus, it was confirmed that the ion conductivity of the solid electrolyte using the flexible viscous crystal containing the cation of each kind selected from the group of various imidazoliums and the group of various quaternary ammoniums was improved.

[0191] (Example 12)

[0192] A solid electrolyte for a double-layer capacitor of Example 12 was produced using a flexible viscous crystal containing two kinds of imidazolium and other kinds of cations in total as the cation. Then, the ion conductivity of the solid electrolyte of Example 12 was measured. The solid electrolyte of Example 12 contains 1-ethyl-3-methylimidazolium (EMI) as the first imidazolium. In addition, the solid electrolyte of Example 12 contains a tetraethylphosphonium cation (TEP) as phosphonium as the second cation. The EMI cation and the TEP cation are contained in the flexible viscous crystal at a molar ratio of 1:1.

[0193] The anion constituting the flexible-crystalline of Example 12 was set to N,N-hexafluoro-1,3-disulfonyl amide anion (CFSA anion). The solid electrolyte of Example 12 was produced under the same conditions and by the same production method as those of Examples 1 to 5, and the first flexible-crystalline and the second flexible-crystalline were added to a glass vial in a molar ratio of 1:1.

[0194] Then, the ion conductivity of the solid electrolyte of Example 12 was measured. The result thereof is shown in Table 2 below. Further, the method of measuring and the method of calculating the ion conductivity were the same as those of Examples 1 to 5. The ion conductivity of the solid electrolyte using each of the flexible-crystallines alone is also described in Table 4. The solid electrolyte used as the comparative object was produced under the same conditions as those of the solid electrolyte of each example except that one kind of flexible-crystalline was contained.

[0195] [Table 4]

[0196]

[0197] As shown in Table 4, it was confirmed that the ion conductivity of the solid electrolyte for a double-layer capacitor of Example 6 was improved by about 30 times at the lowest compared to the solid electrolyte using one kind of flexible-crystalline. Thus, it was confirmed that the ion conductivity of the solid electrolyte was improved even if other cations were contained.

[0198] As described above, with respect to the solid electrolyte using the flexible-crystalline containing a total of two or more kinds of cations selected from the group of various imidazoliums and various quaternary amines, it was confirmed that the ion conductivity was improved.

[0199] (Example 13)

[0200] Two kinds of cations were combined with two kinds of anions to constitute two kinds of flexible-crystallines in a molar ratio of 1:1, and the solid electrolyte for a double-layer capacitor of Example 13 was produced using these flexible-crystallines. Then, the ion conductivity of the solid electrolyte of Example 13 was measured. The solid electrolyte of Example 13 used a first flexible-crystalline containing spirocyclic pyrrolidinium (SBP) as a quaternary amine as a first cation and combining the cation with N,N-hexafluoro-1,3-disulfonyl amide (CFSA). In addition, the solid electrolyte of Example 13 used a second flexible-crystalline containing N-ethyl-N-methyl pyrrolidinium (P12) as a quaternary amine as a second cation and combining the cation with bis(trifluoromethanesulfonyl)amide (TFSA).

[0201] Then, the ion conductivity of the solid electrolyte of Example 13 was measured. The result thereof is shown in Table 5 below. Further, the method of measurement and the method of calculation of the ion conductivity were the same as those of Examples 1 to 5. The ion conductivities of the solid electrolytes each using only one kind of flexible-crystalline were also described in Table 5. The solid electrolytes as the comparative examples were produced under the same conditions as the solid electrolytes of the respective examples except that one kind of flexible-crystalline was contained. Furthermore, the ion conductivity of the solid electrolyte of Example 1 was also described as a comparative example.

[0202] [Table 5]

[0203]

[0204] As shown in Table 5, it was confirmed that the ion conductivity of the solid electrolyte for electric double layer capacitors of Example 13 was improved by about 100 times or more at the minimum and more than 20,000 times at the maximum, as compared with the solid electrolyte using one kind of flexible-crystalline. Moreover, although two kinds of quaternary ammonium were used as cations in common, as compared with the ion conductivity of the solid electrolyte of Example 1 in which one kind of anion was used, the ion conductivity of Example 13 in which two kinds of cations and two kinds of anions were used was closer to 100 times.

[0205] (Examples 14 to 16)

[0206] Unlike Example 13, two kinds of cations and two kinds of anions were combined to form two kinds of flexible-crystalline in a 1:1 molar ratio, and the solid electrolyte for electric double layer capacitors of Example 14 was produced using these flexible-crystalline. The solid electrolyte of Example 14 used a first flexible-crystalline containing spirocyclic pyrrolidinium (SBP) as a quaternary ammonium as a first cation and combining the cation with N,N-hexafluoro-1,3-disulfonyl amide (CFSA). In addition, the solid electrolyte of Example 14 used a second flexible-crystalline containing triethylmethylammonium (TEMA) as a quaternary ammonium as a second cation and combining the cation with bis(trifluoromethanesulfonyl)amide (TFSA).

[0207] A mixture containing TEMA cations and TFSA anions was prepared in such a manner that it became a soft sticky crystal by adjusting the amount of addition. That is, first, an aqueous solution of a halide in which a TEMA cation was halogenated with chlorine Cl was prepared. In addition, an aqueous solution of an alkali metal salt of a CFSA anion and lithium Li was prepared. The aqueous solution of the halide was added dropwise with the aqueous solution of the alkali metal salt in an equal amount little by little to perform an ion exchange reaction. After the ion exchange reaction was performed, dichloromethane was mixed at 60 wt% with respect to the total amount of the solution, and the organic solvent layer was extracted from the separation into an aqueous layer and an organic solvent layer, activated carbon was added, and stirring was performed for one night. Then, further, a precipitate was recovered by filtration, and the precipitate was dried. Thus, a TEMA TFSA soft sticky crystal could be obtained. Furthermore, the TEMA TFSA soft sticky crystal had the properties as a soft sticky crystal by containing 30% or more of the TEMA TFSA soft sticky crystal with respect to the total mol% of the soft sticky crystal and the electrolyte.

[0208] In addition, as a comparative object of Example 14, a solid electrolyte for a double layer capacitor of Example 15 was produced. The solid electrolyte of Example 15 was configured in such a manner that two kinds of soft sticky crystals were combined with one kind of anion and contained two kinds of soft sticky crystals at a molar ratio of 1:1. The solid electrolyte of Example 15 used a first soft sticky crystal in which a spiro ring type pyrrolidinium (SBP) was used as a quaternary ammonium as a first cation and the cation was combined with N,N-hexafluoro-1,3-disulfonyl amide (CFSA). In addition, the solid electrolyte of Example 15 used a second soft sticky crystal in which triethylmethylammonium (TEMA) was used as a quaternary ammonium as a second cation and the cation was combined with N,N-hexafluoro-1,3-disulfonyl amide (CFSA).

[0209] Further, two kinds of cations were combined with two kinds of anions, two kinds of soft sticky crystals at a molar ratio of 1:1 were configured, and a solid electrolyte for a double layer capacitor of Example 16 was produced using these soft sticky crystals. The solid electrolyte of Example 16 used a first soft sticky crystal in which a spiro ring type pyrrolidinium (SBP) was used as a quaternary ammonium as a first cation and the cation was combined with N,N-hexafluoro-1,3-disulfonyl amide (CFSA). In addition, the solid electrolyte of Example 14 used a second soft sticky crystal in which N-ethyl-N-methyl pyrrolidinium (P12) was used as a quaternary ammonium as a second cation and the cation was combined with a tris(trifluoromethane sulfonyl)methanide anion (TFSM anion).

[0210] In addition, as a comparative example to Example 16, a solid electrolyte for a double layer capacitor of Example 1 was produced. The solid electrolyte of Example 1 was configured in a manner that two kinds of cations were combined with one kind of anion and contained two kinds of flexible-crystalline in a molar ratio of 1 : 1.

[0211] Then, the ion conductivity of the solid electrolytes of Examples 14 to 16 and Example 1 was measured. The results thereof are shown in Table 6 below. Further, the measurement method and calculation method of the ion conductivity were the same as those of Examples 1 to 5. The ion conductivity of the solid electrolyte using each of the flexible-crystalline alone is also described in Table 6. The solid electrolyte as the comparative example was produced under the same conditions as the solid electrolyte of each example except that it contained one kind of flexible-crystalline.

[0212] [Table 6]

[0213]

[0214] As shown in Table 6, it was confirmed that the ion conductivity of the solid electrolyte for a double layer capacitor of Example 14 was improved by about 10,000 times or more at the minimum compared to the solid electrolyte using one kind of flexible-crystalline. Further, although it was common that two kinds of quaternary ammonium were used as the cations, if the ion conductivity of the solid electrolyte of Example 15 in which the anion was one kind was compared, the ion conductivity of Example 14 in which two kinds of cations and two kinds of anions were used was more than 1,000 times.

[0215] In addition, it was confirmed that the ion conductivity of the solid electrolyte for a double layer capacitor of Example 16 was improved by about 76 times or more at the minimum compared to the solid electrolyte using one kind of flexible-crystalline. Further, although it was common that two kinds of quaternary ammonium were used as the cations, if the ion conductivity of the solid electrolyte of Example 1 in which the anion was one kind was compared, the ion conductivity of Example 16 in which two kinds of cations and two kinds of anions were used was more than 16 times.

[0216] As shown in the comparison between Example 14 and Example 15 and the comparison between Example 16 and Example 17, it was confirmed that the ion conductivity of the solid electrolyte using two kinds of flexible-crystalline in which two kinds of anions selected from the group of various amide anions in which two hydrogen atoms of NH2 anion were substituted with perfluoroalkylsulfonyl group, fluorosulfonyl group, or both thereof, and tris(trifluoromethanesulfonyl)methanide anion, and the like was further improved.

[0217] (Example 17)

[0218] Three kinds of flexible-crystalline were used to make solid electrolytes for lithium-ion secondary batteries of Example 17. Then, the ion conductivity of the solid electrolytes of Example 17 was measured. The solid electrolytes of Example 17 used P12FSA flexible-crystalline that contains N-ethyl-N-methylpyrrolidinium (P12) that is a quaternary ammonium of a five-membered ring as a first kind of cation and is combined with bis(fluorosulfonyl)amide anion (FSA anion) that is an amide anion as a second kind of anion.

[0219] In addition, the solid electrolytes of Example 17 used TEMA FSA flexible-crystalline that contains triethylmethylammonium (TEMA) that is a quaternary ammonium of a tetraalkylammonium as a second kind of cation and is combined with bis(fluorosulfonyl)amide anion (FSA anion) that is an amide anion as a second kind of anion.

[0220] Furthermore, the solid electrolytes of Example 17 used P12TFSA flexible-crystalline that contains N-ethyl-N-methylpyrrolidinium (P12) that is a quaternary ammonium of a five-membered ring and is combined with bis(trifluoromethanesulfonyl)amide (TFSA) that is an amide anion as a second kind of anion as a third kind of flexible-crystalline.

[0221] In addition to these three kinds of flexible-crystalline, LiTFSA (lithium bis(trifluoromethanesulfonyl)amide, manufactured by Kishida Chemical Co., Ltd.) was further added as an electrolyte in a manner that the total amount of the flexible-crystalline became 10 mol% with respect to the flexible-crystalline, and acetonitrile (Wako Pure Chemical) was added in a manner that the total solid content concentration of the flexible-crystalline and the electrolyte became 10 wt% in the glass vial. P12FSA flexible-crystalline (A), TEMA FSA flexible-crystalline (B), and P12TFSA flexible-crystalline (C) were added to the glass vial in a manner that A:B:C = 4:4:2.

[0222] The acetonitrile solution was dropped onto the glass separator and dried at 80°C to evaporate the acetonitrile. The evaporation operation was repeated three times. Through the evaporation operation, the glass separator impregnated with the solid electrolyte was dried in a vacuum environment at 80°C for 12 hours, further dried at 120°C for 3 hours, and further dried at 150°C for 2 hours to remove moisture, thereby obtaining the solid electrolytes of Example 16.

[0223] Then, the ion conductivity of the solid electrolyte of Example 17 was measured. The results thereof are shown in Table 7 below. Further, the measurement method and the calculation method of the ion conductivity were the same as those of Examples 1 to 5. The ion conductivities of the solid electrolytes using each of the flexible-adhesive crystals alone are also described in Table 7. The solid electrolytes used as the comparative examples were produced under the same conditions as the solid electrolyte of Example 17 except that one flexible-adhesive crystal was contained.

[0224] [Table 7]

[0225]

[0226] As shown in Table 7, it was confirmed that the ion conductivity of the solid electrolyte for lithium-ion secondary batteries of Example 17 was improved by at least 2 times and at most more than 600 times compared with the solid electrolyte using one flexible-adhesive crystal. Thus, it was confirmed that the ion conductivity was improved even in the solid electrolyte for lithium-ion secondary batteries.

Claims

1. A solid electrolyte, characterized by A soft-crystalline electrolyte-doped flexible crystal, The soft-crystalline electrolyte-doped flexible crystal contains at least a first cation and a second cation of different species, The first cation is a quaternary ammonium, The second cation is triethylmethylammonium, spiro-type pyrrolidinium, N,N-diethylpyrrolidinium, N-isopropyl-N-methylpyrrolidinium, 1-methyl-3-propylimidazolium, or tetraethylphosphonium.

2. The solid electrolyte according to claim 1, wherein The quaternary ammonium is represented by Chemical Formula B and contains a tetraalkylammonium substituted with a linear alkyl group having an arbitrary carbon number, In Chemical Formula B, a, b, c, and d are integers of 1 or more, and the carbon number can be arbitrary.

3. The solid electrolyte according to claim 1, wherein The quaternary ammonium contains a five-membered ring ammonium pyrrolidinium represented by Chemical Formula C and a spiro-type pyrrolidinium represented by Chemical Formula D, In Chemical Formulas C and D, R1 and R2 are methyl, ethyl, or isopropyl, 4. The solid electrolyte according to claim 1 or 2, wherein The soft-crystalline electrolyte-doped flexible crystal contains two or more anions.

5. A power storage device characterized by including: The solid electrolyte according to any one of claims 1 to 4; and Two electrodes facing each other with the solid electrolyte therebetween.

6. The power storage device according to claim 5, wherein One or both of the two electrodes is a polarizable electrode having an active material layer containing a porous material and a current collector, A double electric layer is formed at a boundary surface between the polarizable electrode and the solid electrolyte.

7. A method for manufacturing a solid electrolyte, comprising: a step of producing a soft-crystalline electrolyte-doped flexible crystal containing at least a first cation and a second cation of different species, The first cation is a quaternary ammonium, The second cation is triethylmethylammonium, spiro-type pyrrolidinium, N,N-diethylpyrrolidinium, N-isopropyl-N-methylpyrrolidinium, 1-methyl-3-propylimidazolium, or tetraethylphosphonium. ​

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