JP7253098B2 - Ionic liquids and composite electrolytes - Google Patents

Description

The present invention relates to ionic liquids and composite electrolytes.

In recent years, as the performance of electrochemical devices such as lithium ion batteries has improved, electrolytes used in electrochemical devices are required to have higher lithium ion conductivity, withstand voltage characteristics, and the like.

Ionic liquids are attracting attention as components of electrolytes (Patent Literature). Ionic liquids have the following useful properties compared to other electrolytes. First, ionic liquids have a wider potential window than organic solvents used in conventional electrolytic solutions, and have less of a problem of gas generation due to electrolysis of the solvent. In solid electrolytes, the contact area between solids is small, so the energy barrier tends to increase and the lithium ion conductivity tends to decrease. Conductivity is seen.

In addition, the use of gel polymers in electrolytes (gel polymer electrolytes) is being studied as a means of solving the energy barrier problem of solid electrolytes. Gel polymer electrolytes tend to have improved lithium ion conductivity compared to solid electrolytes. However, the polymer used is flammable, and there are concerns about safety. On the other hand, ionic liquids are flame-retardant and thus have a high degree of safety.

Chinese Patent Application Publication No. 109776423 Chinese Patent Application Publication No. 110429338

J.F. Velez et al., "Geminal pyrrolidinium and piperidinium dicationic ionic liquid electrolytes. Synthesis, characterization and cellperformance in LiMn2O4 rechargeable lithium cells",Journal of Power Sources, 2019, vol. 439, page 227098.

However, as a result of intensive studies by the present inventors, it was found that conventional electrolytes (composite electrolytes) containing an ionic liquid and a lithium salt have room for improvement in terms of lithium ion transference numbers.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ionic liquid and a dicationic ionic liquid that can improve the transference number of lithium ions when used as a composite electrolyte. . Another object of the present invention is to provide a composite electrolyte having an improved transference number of lithium ions.

The ionic liquids of the present invention contain a cation comprising two moieties each containing a heteroatom having a formal positive charge and a linking group that binds to the heteroatoms of each of the two moieties to link the two moieties. A dicationic ionic liquid having a linking group represented by the formula: —CR ¹ R ² OCR ³ R ⁴ CR ⁵ R ⁶ OCR ⁷ R ⁸ —.
(wherein R ¹ to R ⁸ are each a hydrogen atom, a fluorine atom, or a monovalent organic group having 1 to 20 carbon atoms, and the organic group is represented by the formula —R ^A —(X—R ^B ) _n —R ^C , R ^A is a covalent bond or a substituted or unsubstituted divalent hydrocarbon group, and X is —O—, —S—, —C(=O)—, —C( =O)O- or -OC(=O)-, R ^B is a covalent bond or a substituted or unsubstituted divalent hydrocarbon group, and R ^C is a substituted or unsubstituted monovalent hydrocarbon and n is 0 or more, provided that 4 or more of R ¹ to R ⁸ are hydrogen atoms.)

All of R ¹ to R ⁸ in the linking group are preferably hydrogen atoms.

The ionic liquid preferably has a 10% weight loss temperature of 280° C. or higher when measured at a heating rate of 5° C./min.

Preferably, in the ionic liquid, the two portions have different chemical structures.

The ionic liquid of the present invention contains the ionic liquid and a lithium salt, and when a composite electrolyte having a lithium salt concentration of 0.5 mol / kg in terms of lithium ions is prepared, the following about the composite electrolyte at 25 ° C. The ratio represented by the formula may be 10% or more. The ionic liquid is preferably a dicationic ionic liquid.
Formula: I _lim /I _ini
(In the formula, I _lim is the limiting current density of the composite electrolyte, and I _ini is the start of application of the constant voltage when a constant voltage is applied to the composite electrolyte at the voltage value that first reaches the limiting current density. is the current density one second after ).

It is preferable that the upper limit of the potential window of the ionic liquid is 2.0 V or more based on Fc/Fc 2 ⁺ electrode, and that the ion conductivity at 25° C. is 0.1 S/cm or more.

The composite electrolyte of the present invention contains a lithium salt and the dicationic ionic liquid.

Preferably, the composite electrolyte further contains a viscosity reducing agent.

The composite electrolyte of the present invention contains an ionic liquid and a lithium salt, and the ratio represented by the following formula is 20% or more. The ionic liquid is preferably a dicationic ionic liquid.
Formula: I _lim /I _ini
(In the formula, I _lim is the limiting current density, and when the value of the current density is measured while applying a constant voltage of 0.1 V to the composite electrolyte at 25 ° C., the current density is substantially constant for 1 hour or more. I _ini is the current density 1 second after starting to apply a constant voltage of 0.1 V to the composite electrolyte.)

It is preferable that the value of the limiting current density of the composite electrolyte is 90 μA/cm ² or more.

According to the present invention, it is possible to provide an ionic liquid and a dicationic ionic liquid that can improve the transference number of lithium ions when used as a composite electrolyte. In addition, according to the present invention, a composite electrolyte having an improved lithium ion transference number can be provided.

FIG. 1 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Example B6. FIG. 2 is a diagram showing the results of a lithium dissolution-precipitation cycle test of Comparative Example B1. FIG. 3 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Example B7. FIG. 4 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Example B8. FIG. 5 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Example B9. FIG. 6 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Example B10. FIG. 7 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Comparative Example B2. FIG. 8 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Example B11. FIG. 9 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Example B12. FIG. 10 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Example B13. FIG. 11 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Example B14.

(First embodiment)
The invention according to a first embodiment relates to a dicationic ionic liquid, wherein the dicationic ionic liquid comprises two moieties each comprising a heteroatom having a formal positive charge and bound to the heteroatom of each of the two moieties. and a linking group linking the two moieties, wherein ^the linking group is represented by the formula: -CR ¹ R ² OCR ³ R 4 CR ⁵ R ⁶ OCR ⁷ R ⁸ - . An ionic liquid is, for example, a compound that is liquid at 25°C.

In other words, the dicationic ionic liquid of the present embodiment has two moieties within the cation, and the two moieties are linked by the linking group. Since both moieties contain heteroatoms with a formal positive charge, each is a positively charged moieties (hereinafter also referred to as cationic moieties). The linking group directly bonds to the positively charged heteroatom in the cationic moiety. The two moieties can be represented as A and B, respectively, the linking group as Y, and the cation as AYB, and A and B may have the same chemical structure or different It may have a chemical structure. That is, the dicationic ionic liquid of the present embodiment may be a symmetrical dicationic ionic liquid (two cation moieties have the same chemical structure), or an asymmetric dicationic ionic liquid (two cation moieties have different chemical structures). ) may be a dicationic ionic liquid. Asymmetric dicationic liquids tend to be more thermally stable and have better 10% weight loss temperatures.

In the linking group, R ¹ to R ⁸ are each a hydrogen atom, a fluorine atom, or a monovalent organic group having 1 to 20 carbon atoms, and the organic group is represented by the formula —R ^A —(X—R ^B ) _n —R ^C , R ^A is a covalent bond or a substituted or unsubstituted divalent hydrocarbon group, and X is —O—, —S—, —C(=O)—, —C( =O)O- or -OC(=O)-, R ^B is a covalent bond or a substituted or unsubstituted divalent hydrocarbon group, and R ^C is a substituted or unsubstituted monovalent hydrocarbon is the base. n is 0 or more, may be 1 to 8, may be 1 to 5, or may be 1 to 3.

The organic group may be a hydrocarbon group or a substituted hydrocarbon group (ie, ^RA is a covalent bond and n is 0). The hydrocarbon group is not particularly limited, and may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group. In the present specification, the term "aromatic hydrocarbon group" means a hydrocarbon group containing an aromatic moiety, including those having an aliphatic moiety. An aromatic hydrocarbon group is a hydrocarbon group containing an aromatic moiety, and includes a phenyl group, a benzyl group, and the like. The aliphatic hydrocarbon group includes a hydrocarbon group containing an alicyclic moiety such as a cyclohexyl group and a cyclohexylethyl group, a straight chain aliphatic hydrocarbon group such as a methyl group, an ethyl group and an allyl group, and a branched chain such as an isopropyl group. may be an aliphatic hydrocarbon group of The substituted hydrocarbon group may be the above hydrocarbon group substituted with a monovalent group such as a halogen atom, an alkoxy group, or a polyalkylene oxide group. Substituted hydrocarbon groups include partially fluorinated or fully fluorinated hydrocarbon groups, groups having an alkoxy group such as a methoxyethyl group and an ethoxyethyl group.

The organic group may have 1 to 15 carbon atoms, may have 1 to 10 carbon atoms, may have 1 to 5 carbon atoms, may have 1 to 3 may have one carbon atom. The organic group is preferably an alkyl group or a group containing one or more of the above Xs in the chain of the alkyl group, where X forms a carbon atom-X-carbon atom bond.

In the linking group, 4 or more of R ¹ to R ⁸ are hydrogen atoms, preferably 6 or more are hydrogen atoms, and all are hydrogen atoms (that is, the linking group is —CH ₂ —O—CH ₂ --CH ₂ --O--CH ₂ -- group)).

A composite electrolyte containing a dicationic ionic liquid and a lithium salt according to the present embodiment exhibits a high lithium ion transference number when a current is applied by applying a voltage to the composite electrolyte. The reason why the dicationic ionic liquid of the present embodiment can provide a composite electrolyte exhibiting such a high transference number of lithium ions has not been completely elucidated. I think so. Composite electrolytes in which a lithium salt is dissolved in an ionic liquid having only one cation moiety in the cation chemical structure such as conventional imidazolium salts and pyrrolidinium salts (hereinafter also referred to as monocation type ionic liquids) are widely used. there is However, when used as a battery electrolyte, the monocationic ionic liquid has a high cation mobility such as imidazolium ions, so the contribution of the monocationic ionic liquid to the overall current is large. In other words, the contribution of lithium ions to the current (that is, the transference number) in the composite electrolyte containing the monocationic ionic liquid and the lithium salt becomes relatively small. In addition, since the oxygen atom in the linking group and the heteroatom in the cation moiety are linked by a very short carbon chain (one carbon), the electrochemical stability of the cation (high voltage resistance) is excellent.

A cationic moiety in a dicationic ionic liquid is an organic cationic moiety having one or more heteroatoms with a formal positive charge. Here, heteroatoms mean atoms other than carbon atoms and hydrogen atoms. The heteroatom having a positive formal charge may be at least one selected from nitrogen group atoms and chalcogen, preferably a nitrogen atom, a phosphorus atom, or a sulfur atom.

The cationic moiety may have a heterocyclic ring and may have a heteroatom with the formal positive charge as a ring member in the heterocyclic ring. Cationic moieties may also be those that do not include heteroatoms having the above formal positive charge as ring members within the ring structure.

The charge possessed by the cationic moiety may be +1 or more, +1 to +3, or +1. The charges possessed by the two cationic moieties in the cation may be the same or different, preferably both cationic moieties have a +1 valence. In addition, when the cation moiety has a plurality of heteroatoms and the charge is dispersed among the plurality of heteroatoms due to the resonance effect, the charge of the cation moiety is the sum of the charges of the plurality of heteroatoms. good.

Specific examples of cationic moieties include cationic groups such as quaternary ammonium groups, quaternary phosphonium groups, sulfonium groups, oxazolium groups, and thiazolium groups.

The quaternary ammonium group and quaternary phosphonium group include cationic groups represented by the following chemical formulas.

R ¹¹ to R ¹³ , R ¹⁵ , R ¹⁹ , R ²¹ , R ²⁵ and R ³¹ to R ³³ may be monovalent hydrocarbon groups having 1 to 20 carbon atoms, It may be a substituted hydrocarbon group. The hydrocarbon group may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The number of carbon atoms in the hydrocarbon group is preferably 1-10, more preferably 1-5. An aromatic hydrocarbon group is a hydrocarbon group containing an aromatic moiety, and includes a phenyl group, a benzyl group, and the like. Aliphatic hydrocarbon groups include hydrocarbon groups containing alicyclic moieties such as cyclohexyl groups and cyclohexylmethyl groups, methyl groups, ethyl groups, n-propyl groups, n-butyl groups, n-octyl groups and n-decyl groups. , an allyl group, an oleyl group, and other straight-chain aliphatic hydrocarbon groups, and an isopropyl group, and other branched-chain aliphatic hydrocarbon groups. A substituted hydrocarbon group may be a hydrocarbon group having 1 to 20 carbon atoms further substituted with a monovalent group such as a halogen atom, an alkoxy group, or a polyalkylene oxide group. Substituted alkyl groups include partially fluorinated or fully fluorinated alkyl groups, methoxyethyl groups, ethoxyethyl groups, and the like.

R ¹¹ to R ¹³ are preferably hydrocarbon groups having 1 to 10 carbon atoms, more preferably hydrocarbon groups having 1 to 5 carbon atoms, and 1 to 3 carbon atoms. It is more preferable that it is a hydrocarbon group having Preferably, the hydrocarbon group is an alkyl group. R ¹¹ to R ¹³ may be the same or different. For example, R ¹¹ and R ¹² are the same alkyl group having 1 to 5 carbon atoms, and R ¹³ is an alkyl group having 1 to 5 carbon atoms different from R ¹¹ and R ¹² . Preferably, R ¹¹ and R ¹² are the same alkyl group having 1 to 3 carbon atoms, and R ¹³ is an alkyl group having 1 to 3 carbon atoms different from R ¹¹ and R ¹² . More preferably, R ¹¹ and R ¹² are ethyl groups and R ¹³ is a methyl group.

R ¹⁵ is preferably a hydrocarbon group with 1 to 10 carbon atoms, more preferably a hydrocarbon group with 1 to 5 carbon atoms, and a hydrocarbon group with 1 to 3 carbon atoms. A hydrogen group is more preferable. The hydrocarbon group is preferably an alkyl group, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

R ¹⁹ is preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 5 carbon atoms, and a hydrocarbon group having 1 to 3 carbon atoms. A hydrogen group is more preferable. The hydrocarbon group is preferably an alkyl group, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

R ²¹ is preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 5 carbon atoms, and a hydrocarbon group having 1 to 3 carbon atoms. A hydrogen group is more preferable. The hydrocarbon group is preferably an alkyl group, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

R ²⁵ is preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 5 carbon atoms, and a hydrocarbon group having 1 to 3 carbon atoms. A hydrogen group is more preferable. The hydrocarbon group is preferably an alkyl group, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

R ³¹ to R ³³ are preferably hydrocarbon groups having 1 to 10 carbon atoms, more preferably hydrocarbon groups having 1 to 8 carbon atoms, and 1 to 5 carbon atoms and more preferably a hydrocarbon group having 1 to 3 carbon atoms. Preferably, the hydrocarbon group is an alkyl group. R ³¹ to R ³³ may be the same or different. For example, R ³¹ to R ³³ are preferably alkyl groups having 1 to 5 carbon atoms, preferably alkyl groups having 1 to 4 carbon atoms, methyl group, ethyl group or butyl group. is more preferable, and a butyl group is particularly preferable.

The polyalkylene oxide group is a group represented by the formula: -(OR) _r OR', in which r is preferably 1 to 10, more preferably 1 to 5, even more preferably 1 to 2. When there is more than one R, they may be different from each other. R is an alkylene group having 1 to 3 carbon atoms, preferably an ethylene group or a 1,2-propylene group, more preferably an ethylene group. R' is an alkyl group having 1 to 3 carbon atoms, preferably a methyl group or an ethyl group.

In chemical formulas (a) to (g), * indicates the position of bonding to the above linking group. Hydrogen atoms bonded to carbon atoms contained in the ring structures represented by chemical formulas (b) to (f) may be substituted with substituents. Examples of substituents include monovalent groups such as halogen atoms, hydrocarbon groups having 1 to 10 carbon atoms, heterocyclic groups, alkoxy groups, and polyalkylene oxide groups. The hydrocarbon group as a substituent may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group. An aromatic hydrocarbon group is a hydrocarbon group containing an aromatic moiety, and includes a phenyl group, a benzyl group, and the like. The aliphatic hydrocarbon group includes a hydrocarbon group containing an alicyclic moiety such as a cyclohexyl group and a cyclohexylethyl group, a straight-chain aliphatic hydrocarbon group such as a methyl group, an ethyl group and an allyl group, and a branched chain such as an isopropyl group. may be an aliphatic hydrocarbon group of The hydrocarbon group as a substituent may be further substituted with a monovalent group such as a halogen atom, a hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group, or a polyalkylene oxide group.

The cationic groups of the chemical formulas (b) to (f) are substituted with two or more hydrogen atoms bonded to the carbon atoms contained in the ring structures represented by the chemical formulas (b) to (f). It may have another ring structure (condensed ring) condensed with the ring structure. The condensed ring may be either aliphatic or aromatic, and may be either a hydrocarbon ring having only carbon atoms as a ring member or a heterocyclic ring having a heteroatom as a ring member. Examples of cationic groups having condensed rings include benzimidazolium groups and acridinium groups. The hydrogen atoms of the condensed ring may also be substituted with monovalent groups such as halogen atoms, hydrocarbon groups having 1 to 10 carbon atoms, heterocyclic groups, alkoxy groups, and polyalkylene oxide groups. .

As cations contained in the dicationic ionic liquid, those represented by the following chemical formulas (I) to (V) are preferable.

The anion of the dicationic ionic liquid is not particularly limited, and may be appropriately selected according to the charge of the cation of the dicationic ionic liquid. Examples of anions include Cl ⁻ , Br ⁻ , I ⁻ , ClO ₄ ⁻ , PF ₆ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (FSO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C _m F _2m+1 SO _{2 ) 2} N ⁻ (m is an integer of 2 ^or more), and HSO ₃ ⁻ ; PF ₆ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (FSO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ or (C _m F _2m+1 SO ₂ ) ₂ N ⁻ is preferred from the viewpoint of , (CF ₃ SO ₂ ) ₂ N ^— are more preferred. The dicationic ionic liquid may contain only one type of anion, or may contain two or more types of anions.

The upper limit of the potential window of the dicationic ionic liquid of the present embodiment is preferably 2.0 V or higher, more preferably 2.05 or higher, based on the Fc/Fc ⁺ (ferrocene/ferrocenium) electrode. Potential windows can be measured, for example, by cyclic voltammetry. The potential window is a potential range in which substantially no oxidation-reduction reaction occurs. For example, it can be a range in which a current of 50 μA/cm ² or more does not flow in a cyclic voltammetry test. That is, in the cyclic voltammetry test, the potential at which a current of 50 μA/cm ² or more flows for the first time when the potential is swept to the oxidation side is the upper limit of the potential window, and the potential at which 50 μA/cm ² or more flows for the first time when the potential is swept to the reduction side. The potential at which the current flows can be the lower limit of the potential window. The lower limit of the potential window may be, for example, -2.40 V or less on the basis of Fc/Fc ⁺ electrodes. In addition, the lower limit of the potential window of the dicationic ionic liquid is -2.40 or less on the basis of Fc/Fc ⁺ electrode, and the upper limit of the potential window is 2.0 V or more on the basis of Fc/Fc ⁺ electrode.

Moreover, it is preferable that the ion conductivity at 25° C. of the dicationic ionic liquid of the present embodiment is 0.1 S/cm or more.

The 10% weight loss temperature of the dicationic ionic liquid of the present embodiment is preferably 280° C. or higher, more preferably 290° C. or higher, when measured at a heating rate of 5° C./min (measurement condition 1). More preferably, it is still more preferably 300° C. or higher. The 10% weight loss temperature can be measured with a thermogravimetric analyzer. In the case of measurement condition 1, the measurement start temperature may be 40°C, and the final temperature is not particularly limited, but may be 500°C. In the case of measurement condition 1, the 10% weight loss temperature of the dicationic ionic liquid of the present embodiment may be 370° C. or less, may be 280 to 370° C., may be 290 to 360° C., may be 300 to It may be 350°C.
Further, the 10% weight loss temperature of the dicationic ionic liquid of the present embodiment is obtained by heating to 150°C at a temperature increase rate of 10°C/min, and then from 150°C to 350°C at a temperature increase rate of 1°C/min. may be measured by heating at (Measurement condition 2). In the case of measurement condition 2, the 10% weight loss temperature is preferably 190° C. or higher, more preferably 200° C. or higher, and even more preferably 300° C. or higher. The measurement start temperature may be room temperature (25°C), and the final temperature is not particularly limited, but may be 500°C. In the case of measurement condition 2, the 10% weight loss temperature of the dicationic ionic liquid of the present embodiment may be 310° C. or less, may be 190 to 310° C., may be 200 to 300° C., may be 210 to It may be 290°C. In the measurement condition 2, in order to stabilize the temperature control, the temperature may be maintained at 150° C. for 10 minutes or longer, or for 10 minutes. The holding time for such temperature control can be appropriately set according to the device to be used. Also, the temperature may be raised at a rate of 10°C/min from 350°C to 500°C.

The method for obtaining the dicationic ionic liquid of the present embodiment is not particularly limited, and there is no problem as long as a structure in which two cationic moieties are linked by the linking group can be obtained. For example, there is a method including the following steps.

[Step 1] Under a protective gas atmosphere, for example, 1,2-bischloromethoxyethane or a derivative thereof and an amine are mixed at a molar ratio of 1:2 to 1:2.5, and then heated to 25°C to 60°C. and reacted with stirring to obtain an ammonium halide salt. 1,2-bischloromethoxyethane or a derivative thereof is selected so as to correspond to the chemical structure of the linking portion of the dicationic ionic liquid to be obtained, and has the same groups as R ¹ to R ⁸ possessed by the linking portion. (For example, when R ¹ to R ⁸ are all hydrogen atoms, 1,2-bischloromethoxyethane corresponds to the above linking group). Also, the amine is selected so as to correspond to the chemical structure of the cation portion of the dicationic ionic liquid to be obtained.

[Step 2] The ammonium halide salt prepared in Step 1 and the salt having the general formula M _a Y _b are mixed at a molar ratio of 1:2 to 1:2.5, and then stirred to initiate an ion exchange reaction. By doing so, a dicationic ionic liquid is obtained. Here, M is the counter cation of the anion Y, and a and b are the number ratios of both ions when the charges of the cation M and the anion Y are balanced. Examples of cations M include alkali metal ions.

The composite electrolyte of this embodiment contains the dicationic ionic liquid and a lithium salt. Such a composite electrolyte can be used as an electrolyte (nonaqueous electrolyte) for electrochemical devices such as lithium ion batteries and capacitors.

The lithium salt is not particularly limited, but LiCl, LiBr, LiI, _LiClO4 , _LiPF6 , _{LiBF4 , LiCF3SO3} , Li _[ ( _FSO2 ) _2N ], Li[( _CF3SO2 ) _2N ], Li[( _{CmF2m +1SO2 ) 2N} ] (m is an integer of 2 or more), _LiHSO3 , _{Li2SO3 ,} and the like. The anion contained in the lithium salt may be the same as or different from the anion contained in the dicationic ionic liquid.

The composite electrolyte may further contain a viscosity reducing agent. By reducing the viscosity of the composite electrolyte, the ionic conductivity in the electrolyte can be further improved. Viscosity reducing agents include, for example, organic solvents. The organic solvent is not particularly limited, but may be an aprotic solvent such as chain carbonates such as dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate. ; aliphatic carboxylic acid esters such as methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, and methyl trimethyl acetate; tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, etc. chain ethers such as 1,2-diethoxyethane and ethoxymethoxyethane; lactones such as γ-butyrolactone; lactams such as ε-caprolactam and N-methylpyrrolidone; sulfones such as sulfolane, or these Examples thereof include halogen-substituted solvents. A single solvent may be used, or a mixed solvent of two or more solvents may be used. Among these, a cyclic carbonate is preferable, and a mixed solvent of ethylene carbonate and propylene carbonate is preferable.

The content of the viscosity reducing agent in the composite electrolyte is not particularly limited, and is preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more relative to the dicationic ionic liquid. Moreover, it is preferably 100% by mass or less, more preferably 85% by mass or less, and particularly preferably 70% by mass or less.

Although the concentration of the lithium salt in the composite electrolyte is not particularly limited, it is preferably 0.1 mol/kg or more in terms of lithium ions (that is, the lithium ion concentration) (in this case, the upper limit may be the saturated concentration of the lithium salt), It is more preferably 0.1 to 2.0 mol/lkg. The unit mol/kg is mass mol concentration, which is the molar amount of the lithium salt (in terms of lithium ion) per unit mass (kg) of the solvent.

(Second embodiment)
The invention according to the second embodiment relates to an ionic liquid. The ionic liquid according to the second embodiment contains the ionic liquid and a lithium salt, and when a composite electrolyte having a lithium salt concentration of 0.5 mol / kg in terms of lithium ions is prepared, the composite at 25 ° C. The ratio represented by the following formula (I) for the electrolyte is 10% or more.
Formula: I _lim /I _ini
(Wherein, I _lim is the limiting current density of the composite electrolyte, and I _ini is the method of measuring the limiting current density while stepwise increasing the voltage applied to the composite electrolyte. The current density is the current density one second after the start of voltage application at the stage of reaching.) The composite electrolyte for I _lim /I _ini measurement for the ionic liquid was 90 masses of the ionic liquid and the lithium salt with respect to the total amount of the composite electrolyte. % or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, particularly preferably 99% by mass or more, preferably containing substantially no components other than the ionic liquid and the lithium salt. .

When a voltage is applied to the composite electrolyte, all the ions contained in the electrolyte move and contribute to the current at the initial stage of voltage application. At steady state 30 minutes after voltage application, only lithium ions contribute to the current. Therefore, I _lim /I _ini is an index of the contribution of lithium ions to the total current density. It can also be said that the higher the contribution of lithium ions to the total current density, the higher the transport number of lithium ions.

I _lim /I _ini for the ionic liquid is preferably 12% or more, more preferably 15% or more, even more preferably 20% or more, even more preferably 25% or more, and 30% or more. is particularly preferred.

The ionic liquid according to the second embodiment is preferably a dicationic ionic liquid. A dicationic ionic liquid is an ionic liquid containing a cation that has two cationic moieties in its structure. A dicationic ionic liquid has a larger cation size than a monocationic ionic liquid, and also has a larger interaction with an anion, and therefore tends to have a lower mobility when a voltage is applied. Therefore, there is a tendency that I _lim /I _ini can be further improved. The anions possessed by the ionic liquid according to the second embodiment are not particularly limited, and the same anions as those of the dicationic ionic liquid of the first embodiment can be exemplified.

The dicationic ionic liquid preferably has a structure in which two cationic moieties are linked by a linking group. The linking group is preferably a group having 6 atoms counted along the chain linking the atom directly bonded to one of the cationic moieties and the atom directly bonded to the other cationic moiety in the linking group. Of the six atoms, two are preferably oxygen atoms or sulfur atoms and the rest are carbon atoms.

As the ionic liquid according to the second embodiment, the dicationic ionic liquid according to the first embodiment is preferable.

The composite electrolyte of this embodiment contains the ionic liquid and a lithium salt. When I _lim /I _ini of the composite electrolyte is measured at 25° C., I _lim /I _ini may be 10% or more, preferably 12% or more, more preferably 15% or more, and 20%. It is more preferably 25% or more, even more preferably 25% or more, and particularly preferably 30% or more. In addition, I _ini is the current density 1 second after the start of voltage application at the stage where the limiting current density is first reached in the method of measuring the limiting current density while gradually increasing the voltage applied to the composite electrolyte. . The concentration of the lithium salt in the composite electrolyte is not particularly limited, but is preferably 0.1 mol/kg or more in terms of lithium ions (that is, the lithium ion concentration) (in this case, the upper limit may be the saturated concentration of the lithium salt), It is more preferably 0.1 to 2.0 mol/lkg.

The composite electrolyte of this embodiment may further contain a viscosity reducing agent.

Specific examples of the lithium salt and the viscosity-lowering agent in the composite electrolyte are the same as the specific examples of the lithium salt and the viscosity-lowering agent that can be contained in the composite electrolyte containing the ionic liquid of the first embodiment. The same applies to specific examples of content.

The limiting current density and initial current density of the composite electrolyte can be measured, for example, by measurement method I below. In measurement method I, first, a step of applying a constant voltage to the composite electrolyte for a predetermined time t is repeatedly performed while increasing the applied voltage stepwise. In each step, the current density _{It at time t} is measured with the voltage application start time as the origin, and when the measured current density becomes substantially constant regardless of the applied voltage, the current density is defined as the limiting current. do.
Specifically, for example, as the first step, a constant voltage of 0.4 V is applied for 30 minutes (t=30 minutes), and after 30 minutes, the current density I ₃₀ Current density at time 30 minutes) is measured. Next, after the composite electrolyte is allowed to stand without applying a voltage for a predetermined time interval (for example, 10 to 15 minutes), the voltage applied to the composite electrolyte is 0.2 V higher than the voltage value in the first step for 30 minutes. Apply a high constant voltage (ie 0.6 V) and measure the current density after 30 minutes as in the first step. Thereafter, the step of applying a constant voltage for 30 minutes is repeated while increasing the applied voltage by 0.2 V from the previous step, and I ₃₀ is similarly measured at each step. Then, it is confirmed that the current density does not change even if the voltage is increased, and the constant current density is defined as the limit current density.
The current density I ini measured 1 second after the start of voltage application when the voltage value of the step at which I ₃₀ first reaches the limiting current density among the I ₃₀ measured in each step is applied to the composite electrolyte _. and Let the I _ini be the initial current density.
It should be noted that the voltage value of the first step, the width of increase of the voltage value at each step, and the time interval between steps can be appropriately changed according to the properties of the sample.

The limiting current density of the composite electrolyte can also be measured by measurement method II below. In measurement method II, first, a constant voltage (for example, 0.1 V) is continuously applied to the composite electrolyte, and the current density value when the current density does not change over time for 1 hour or more is defined as the limiting current. In this case, the initial current value is the value of the current density one second after starting to apply the constant voltage to the composite electrolyte.

When the limiting current density and the initial current value are measured by measurement method II, I _lim /I _ini is preferably 20% or more, more preferably 22% or more, and even more preferably 25% or more.

Measurement method II is a particularly effective method for measuring the limiting current density and initial current value of a composite electrolyte containing a viscosity-lowering agent (eg, solvent). The limiting current density of the composite electrolyte measured by measurement method II is preferably 90 μA/cm ² or more, more preferably 150 μA/cm ² or more, even more preferably 200 μA/cm ² or more, and even more preferably 300 μA/cm ² . It is especially preferable in it being above.

The ionic liquids of the first and second embodiments are useful as electrolytes for electrochemical devices such as lithium ion batteries and capacitors, since the ionic liquids of the first and second embodiments have a high transference number of lithium ions when used as a composite electrolyte. In addition, the composite electrolytes containing the ionic liquids of the first and second embodiments tend to be able to effectively suppress the generation of dendrites.

<Sample>
Compounds AE, and compounds CA and CB were prepared as described below.

で表される化合物Ａ（［（Ｐｙｒ_１）_２ＭＥＭ］［２ＴＦＳＩ］）を以下のとおり合成した。
１，２－ビスクロロメトキシエタン（３．３０ｇ、２０．８ｍｍｏｌ）をＣＨ_２Ｃｌ_２（３０ｍＬ）に溶かした後、Ｎ－メチルピロリジン（３．６３ｇ、４２．６ｍｍｏｌ）を加え、Ａｒ雰囲気下にて一晩室温で撹拌した。溶媒を留去した後、ジエチルエーテルによる洗浄を行い、真空乾燥を行い、白色の固体として［（Ｐｙｒ_１）_２ＭＥＭ］［２Ｃｌ］（６．６９ｇ、２０．３ｍｍｏｌ、収率：９８％）を得た。以下に生成物のＮＭＲのデータを示す。
^１Ｈ－ＮＭＲ（ＣＤＣｌ_３，６００ＭＨｚ）δ（ｐｐｍ）：２．２２－２．３５（ｍ，８Ｈ），３．３６（ｓ，６Ｈ），３．６７（ｍ，４Ｈ），３．９５（ｍ，４Ｈ），４．２３（ｓ，４Ｈ），５．４７（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：２３．５，４８．４，６２．５，７３．６，９１．４
得られた［（Ｐｙｒ_１）_２ＭＥＭ］［２Ｃｌ］（２．５１ｇ、７．６２ｍｍｏｌ）とＬｉＴＦＳＩ（４．１７ｇ、１４．５ｍｍｏｌ）とをＣＨ_３ＯＨ（１５ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、ジクロロメタンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。当該有機相に真空乾燥を行い、無色透明の液体（４．３５ｇ、５．３１ｍｍｏｌ、７０％）を得た。以下に生成物のＮＭＲのデータを示す。なお、特に断らない限り、^１Ｈ－ＮＭＲ及び^１３Ｃ－ＮＭＲの化学シフトは、測定に使用した重溶媒が重クロロホルム（ＣＤＣｌ_３）である場合は、クロロホルムのＨ又はＣを基準とし、重溶媒が重メタノール（ＣＤ_３ＯＤ）である場合は、メタノールのメチル基のＨ又はＣを基準とする。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：２．３８（ｄ，Ｊ＝９．０Ｈｚ，８Ｈ），３．６１（ｍ，４Ｈ），３．７６（ｔ，Ｊ＝５．６Ｈｚ，４Ｈ），４．２３（ｓ，４Ｈ），４．８８（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：２３．３，６２．４，７３．４，９１．５，１２１（ｑ，Ｊ＝３１９Ｈｚ） <Compound A>
The formula below:

Compound A ([(Pyr ₁ ) ₂ MEM][2TFSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (3.30 g, 20.8 mmol) in CH ₂ Cl ₂ (30 mL), N-methylpyrrolidine (3.63 g, 42.6 mmol) was added and stirred under Ar atmosphere. and stirred overnight at room temperature. After distilling off the solvent, the residue was washed with diethyl ether and vacuum dried to give [(Pyr ₁ ) ₂ MEM][2Cl] (6.69 g, 20.3 mmol, yield: 98%) as a white solid. Obtained. The NMR data of the product are shown below.
¹ H-NMR (CDCl ₃ , 600 MHz) δ (ppm): 2.22-2.35 (m, 8H), 3.36 (s, 6H), 3.67 (m, 4H), 3.95 ( m, 4H), 4.23 (s, 4H), 5.47 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 23.5, 48.4, 62.5, 73.6, 91.4
The resulting [(Pyr ₁ ) ₂ MEM][2Cl] (2.51 g, 7.62 mmol) and LiTFSI (4.17 g, 14.5 mmol) were dissolved in CH ₃ OH (15 mL) and stirred overnight at room temperature. bottom. CH ₃ OH was distilled off. Thereafter, the product was dissolved in dichloromethane, washed with water, and the organic phase was separated by liquid separation. The organic phase was vacuum dried to obtain a colorless transparent liquid (4.35 g, 5.31 mmol, 70%). The NMR data of the product are shown below. Unless otherwise specified, ¹ H-NMR and ¹³ C-NMR chemical shifts are based on H or C of chloroform when the deuterated solvent used for measurement is deuterated chloroform (CDCl ₃ ). is heavy methanol (CD ₃ OD), it is based on the H or C of the methyl group of methanol.
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 2.38 (d, J=9.0 Hz, 8H), 3.61 (m, 4H), 3.76 (t, J=5. 6Hz, 4H), 4.23 (s, 4H), 4.88 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 23.3, 62.4, 73.4, 91.5, 121 (q, J = 319 Hz)

で表される化合物Ｂ（［（Ｎ_２２１）_２ＭＥＭ］［２ＴＦＳＩ］）を以下のとおり合成した。
１，２－ビスクロロメトキシエタン（３．２９ｇ、２０．７ｍｍｏｌ）をＣＨ_２Ｃｌ_２（３０ｍＬ）に溶かした後、Ｎ，Ｎ－ジエチルメチルアミン（３．７３ｇ、４２．８ｍｍｏｌ）を加え、Ａｒ雰囲気下にて一晩室温で撹拌した。溶媒を留去した後、ジエチルエーテルによる洗浄を行い、真空乾燥を行い、白色の固体として［（Ｎ_２２１）_２ＭＥＭ］［２Ｃｌ］（ｑｕａｎｔ）を得た。以下に生成物のＮＭＲのデータを示す。なお、生成物の収率がほぼ１００％であった場合、ｑｕａｎｔと記載する。
^１Ｈ－ＮＭＲ（ＣＤＣｌ_３，６００ＭＨｚ）δ（ｐｐｍ）：１．４２（ｔ，Ｊ＝１７．５Ｈｚ，１２Ｈ），３．２６（ｓ，６Ｈ），３．５９（ｍ，８Ｈ），４．２４（ｓ，４Ｈ），５．４０（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：８．１９，４５．１，５５．２，７３．３，８９．０
得られた［（Ｎ_２２１）_２ＭＥＭ］［２Ｃｌ］（５．４４ｇ、１６．３ｍｍｏｌ）とＬｉＴＦＳＩ（９．８２ｇ、３４．２ｍｍｏｌ）とをＣＨ_３ＯＨ（３５ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、ジクロロメタンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。当該有機相に真空乾燥を行い、無色透明の液体（７．３１ｇ、８．８９ｍｍｏｌ、５５％）を得た。以下に生成物のＮＭＲのデータを示す。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．３７（ｔ，Ｊ＝７．３Ｈｚ，１２Ｈ），３．０１（ｓ，６Ｈ），３．４２（ｍ，８Ｈ），４．０８（ｓ，４Ｈ），４．７４（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：８．０６，４５．１，５５．４，７３．２，８７．０，１２１（ｑ，Ｊ＝３１９Ｈｚ） <Compound B>
The formula below:

Compound B ([(N ₂₂₁ ) ₂ MEM][2TFSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (3.29 g, 20.7 mmol) in CH ₂ Cl ₂ (30 mL), N,N-diethylmethylamine (3.73 g, 42.8 mmol) was added and Ar Stir at room temperature overnight under atmosphere. After distilling off the solvent, the residue was washed with diethyl ether and vacuum-dried to obtain [(N ₂₂₁ ) ₂ MEM][2Cl](quant) as a white solid. The NMR data of the product are shown below. In addition, when the yield of the product is almost 100%, it is described as quant.
¹ H-NMR (CDCl ₃ , 600 MHz) δ (ppm): 1.42 (t, J=17.5 Hz, 12 H), 3.26 (s, 6 H), 3.59 (m, 8 H), 4. 24 (s, 4H), 5.40 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 8.19, 45.1, 55.2, 73.3, 89.0
The resulting [( _N221 ) _2MEM ][2Cl] (5.44 g, 16.3 mmol) and LiTFSI (9.82 g, 34.2 mmol) were dissolved in _CH3OH (35 mL) and stirred overnight at room temperature. bottom. The _CH3OH was distilled off. Thereafter, the product was dissolved in dichloromethane, washed with water, and the organic phase was separated by liquid separation. The organic phase was vacuum dried to obtain a colorless transparent liquid (7.31 g, 8.89 mmol, 55%). The NMR data of the product are shown below.
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.37 (t, J = 7.3 Hz, 12H), 3.01 (s, 6H), 3.42 (m, 8H), 4 .08 (s, 4H), 4.74 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 8.06, 45.1, 55.4, 73.2, 87.0, 121 (q, J = 319 Hz)

で表される化合物Ｃ（［（Ｍｉｍ）_２ＭＥＭ］［２ＴＦＳＩ］）を以下のとおり合成した。
１，２－ビスクロロメトキシエタン（３．４４ｇ、２１．６ｍｍｏｌ）をＣＨ_２Ｃｌ_２（３０ｍＬ）に溶かした後、Ｎ－メチルイミダゾール（３．９６ｇ、４８．２ｍｍｏｌ）を加え、Ａｒ雰囲気下にて一晩室温で撹拌した。溶媒を留去した後、ジエチルエーテルによる洗浄を行い、真空乾燥を行い、白色の固体として［（Ｍｉｍ）_２ＭＥＭ］［２Ｃｌ］（６．８５ｇ、２１．２ｍｍｏｌ、９８％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：３．８１（ｓ，４Ｈ），４．０３（ｓ，６Ｈ），５．６９（ｓ，４Ｈ），７．７０（ｓ，２Ｈ），７．８１（ｓ，２Ｈ），９．２３（ｓ，２Ｈ）
得られた［（Ｍｉｍ）_２ＭＥＭ］［２Ｃｌ］（３．１８ｇ、９．８４ｍｍｏｌ）とＬｉＴＦＳＩ（５．８６ｇ、２０．４ｍｍｏｌ）とをＣＨ_３ＯＨ（２０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、ジクロロメタンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。当該有機相に真空乾燥を行い、無色透明の液体（４．１０ｇ、５．０５ｍｍｏｌ、５１％）を得た。
^１Ｈ－ＮＭＲ（ＣＤＣｌ_３，６００ＭＨｚ）δ（ｐｐｍ）：３．６６（ｓ，４Ｈ），４．１２（ｑ，Ｊ＝７．２Ｈｚ，６Ｈ），５．４７（ｓ，４Ｈ），７．３４（ｓ，２Ｈ），７．４４（ｓ，２Ｈ），８．６１（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：３７．５，７１．３，８１．２，１２４，１２３（ｑ，Ｊ＝３１９Ｈｚ），１３９ <Compound C>
The formula below:

Compound C ([(Mim) ₂ MEM][2TFSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (3.44 g, 21.6 mmol) in CH ₂ Cl ₂ (30 mL), N-methylimidazole (3.96 g, 48.2 mmol) was added and stirred under Ar atmosphere. and stirred overnight at room temperature. After distilling off the solvent, the residue was washed with diethyl ether and vacuum dried to obtain [(Mim) ₂ MEM][2Cl] (6.85 g, 21.2 mmol, 98%) as a white solid.
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 3.81 (s, 4H), 4.03 (s, 6H), 5.69 (s, 4H), 7.70 (s, 2H ), 7.81 (s, 2H), 9.23 (s, 2H)
The resulting [(Mim) ₂ MEM][2Cl] (3.18 g, 9.84 mmol) and LiTFSI (5.86 g, 20.4 mmol) were dissolved in CH ₃ OH (20 mL) and stirred overnight at room temperature. . The _CH3OH was distilled off. Thereafter, the product was dissolved in dichloromethane, washed with water, and the organic phase was separated by liquid separation. The organic phase was vacuum dried to obtain a colorless transparent liquid (4.10 g, 5.05 mmol, 51%).
¹ H-NMR (CDCl ₃ , 600 MHz) δ (ppm): 3.66 (s, 4H), 4.12 (q, J=7.2 Hz, 6H), 5.47 (s, 4H), 7. 34 (s, 2H), 7.44 (s, 2H), 8.61 (s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 37.5, 71.3, 81.2, 124, 123 (q, J = 319 Hz), 139

で表される化合物Ｄ（［（Ｐｉｐ_１）_２ＭＥＭ］［２ＴＦＳＩ］）を以下のとおり合成した。
１，２－ビスクロロメトキシエタン（３．３６ｇ、２１．２ｍｍｏｌ）をＣＨ_２Ｃｌ_２（３０ｍＬ）に溶かした後、Ｎ－メチルピペリジン（４．３６ｇ、４４．０ｍｍｏｌ）を加え、Ａｒ雰囲気下にて一晩室温で撹拌した。溶媒を留去した後、ジエチルエーテルによる洗浄を行い、真空乾燥を行い、白色の固体として［（Ｐｉｐ_１）_２ＭＥＭ］［２Ｃｌ］（４．１９ｇ、１１．９ｍｍｏｌ、５９％）を得た。
^１Ｈ－ＮＭＲ（ＣＤＣｌ_３，６００ＭＨｚ）δ（ｐｐｍ）：１．７０－１．７４（ｍ，４Ｈ），１．８６－１．９７（ｍ，１６Ｈ），３．３３（ｓ，６Ｈ），４．２４（ｓ，４Ｈ），５．５３（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：２０．９，２２．６，４５．７，５８．９，７４．２，９２．７
得られた［（Ｐｉｐ_１）_２ＭＥＭ］［２Ｃｌ］（２．５１ｇ、７．０２ｍｍｏｌ）とＬｉＴＦＳＩ（４．１７ｇ、１４．５ｍｍｏｌ）をＣＨ_３ＯＨ（１５ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、ジクロロメタンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。真空乾燥を行い、黄色の液体（４．３５ｇ、５．１４ｍｍｏｌ、７３％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．６４（ｍ，２Ｈ），１．７９（ｍ，２Ｈ），１．９５（ｍ，８Ｈ），３．０７（ｓ，６Ｈ），３．３０－３．４１（ｍ，８Ｈ），４．０９（ｓ，４Ｈ），４．７８（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：２０．８，２２．４，４５．８，５９．０，７４．１，９２．８，１２１（ｑ，Ｊ＝３１９Ｈｚ） <Compound D>
The formula below:

Compound D ([(Pip ₁ ) ₂ MEM][2TFSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (3.36 g, 21.2 mmol) in CH ₂ Cl ₂ (30 mL), N-methylpiperidine (4.36 g, 44.0 mmol) was added and stirred under Ar atmosphere. and stirred overnight at room temperature. After distilling off the solvent, the residue was washed with diethyl ether and vacuum dried to obtain [(Pip ₁ ) ₂ MEM][2Cl] (4.19 g, 11.9 mmol, 59%) as a white solid.
¹ H-NMR (CDCl ₃ , 600 MHz) δ (ppm): 1.70-1.74 (m, 4H), 1.86-1.97 (m, 16H), 3.33 (s, 6H), 4.24 (s, 4H), 5.53 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 20.9, 22.6, 45.7, 58.9, 74.2, 92.7
The resulting [(Pip ₁ ) ₂ MEM][2Cl] (2.51 g, 7.02 mmol) and LiTFSI (4.17 g, 14.5 mmol) were dissolved in CH ₃ OH (15 mL) and stirred overnight at room temperature. . The _CH3OH was distilled off. Thereafter, the product was dissolved in dichloromethane, washed with water, and the organic phase was separated by liquid separation. Vacuum drying was performed to obtain a yellow liquid (4.35 g, 5.14 mmol, 73%).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.64 (m, 2H), 1.79 (m, 2H), 1.95 (m, 8H), 3.07 (s, 6H ), 3.30-3.41 (m, 8H), 4.09 (s, 4H), 4.78 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 20.8, 22.4, 45.8, 59.0, 74.1, 92.8, 121 (q, J = 319 Hz)

で表される化合物Ｅ（［（Ｐｙｒ_１）ＭＥＭ（ＰＢｕ_３）］［２ＴＦＳＩ］）を以下のとおり合成した。
Ａｒ雰囲気下にて、１，２－ビスクロロメトキシエタン（７１２ｍｇ、４．４８ｍｍｏｌ）をテトラヒドロフラン（１．５ｍＬ）に溶かした後、－１０℃下でＮ－メチルピロリジン（３８４ｍｇ、４．５１ｍｍｏｌ）を２．８７４ｍＬ／ｈの速度で１０分滴下後、３５℃で５分間撹拌をした。ＣＨ_３ＣＮ（３．０ｍＬ）添加後、３５℃で５分撹拌した後、トリブチルホスフィン（１．０７ｇ、５．３０ｍｍｏｌ）を加え、３５℃で５時間撹拌した。溶媒を留去した後、ジエチルエーテル及びアセトンによる洗浄を行い、真空乾燥後、無色透明の液体として［（Ｐｙｒ_１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（純度９０％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０２－１．０５（ｍ，９Ｈ），１．５３－１．６５（ｍ，１２Ｈ），２．３０－２．３５（ｍ，６Ｈ），３．４９（ｍ，２Ｈ），３．６３（ｍ，２Ｈ），３．９１（ｍ，２Ｈ），４．０８（ｍ，２Ｈ），４．５３（ｄ，Ｊ＝５．４Ｈｚ，２Ｈ），４．７８（ｓ，２Ｈ）
得られた［（Ｐｙｒ_１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（１．８２ｇ、４．０８ｍｍｏｌ）とＬｉＴＦＳＩ（３．２７ｇ、１１．４ｍｍｏｌ）とをＣＨ_３ＯＨ（２５ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、ジクロロメタンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。真空乾燥を行い、無色透明の液体（３．３３ｇ、純度９０％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０１－１．０４（ｍ，９Ｈ），１．５３－１．６６（ｍ，１２Ｈ），２．２７－２．３３（ｍ，６Ｈ），３．４６－３．５０（ｍ，２Ｈ），３．６１－３．６３（ｍ，２Ｈ），３．９１－３．９２（ｍ，２Ｈ），４．０６－４．０８（ｍ，２Ｈ），４．４７－４．５１（ｄ，Ｊ＝５．３Ｈｚ，２Ｈ），４．７４（ｓ，２Ｈ） <Compound E>
The formula below:

Compound E ([(Pyr ₁ )MEM(PBu ₃ )][2TFSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (712 mg, 4.48 mmol) in tetrahydrofuran (1.5 mL) under Ar atmosphere, N-methylpyrrolidine (384 mg, 4.51 mmol) was added at -10°C. After dropping at a rate of 2.874 mL/h for 10 minutes, the mixture was stirred at 35°C for 5 minutes. After adding CH ₃ CN (3.0 mL) and stirring at 35° C. for 5 minutes, tributylphosphine (1.07 g, 5.30 mmol) was added and stirred at 35° C. for 5 hours. After distilling off the solvent, the residue was washed with diethyl ether and acetone, and after vacuum drying, [(Pyr ₁ )MEM(PBu ₃ )][2Cl] (purity 90%) was obtained as a colorless transparent liquid.
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.02-1.05 (m, 9H), 1.53-1.65 (m, 12H), 2.30-2.35 ( m, 6H), 3.49 (m, 2H), 3.63 (m, 2H), 3.91 (m, 2H), 4.08 (m, 2H), 4.53 (d, J=5 .4Hz, 2H), 4.78(s, 2H)
The resulting [(Pyr ₁ )MEM(PBu ₃ )][2Cl] (1.82 g, 4.08 mmol) and LiTFSI (3.27 g, 11.4 mmol) were dissolved in CH ₃ OH (25 mL) and stirred at room temperature. Stir overnight. The _CH3OH was distilled off. Thereafter, the product was dissolved in dichloromethane, washed with water, and the organic phase was separated by liquid separation. Vacuum drying was performed to obtain a colorless transparent liquid (3.33 g, purity 90%).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.01-1.04 (m, 9H), 1.53-1.66 (m, 12H), 2.27-2.33 ( m, 6H), 3.46-3.50 (m, 2H), 3.61-3.63 (m, 2H), 3.91-3.92 (m, 2H), 4.06-4. 08 (m, 2H), 4.47-4.51 (d, J=5.3Hz, 2H), 4.74 (s, 2H)

で表される化合物Ｆ（［（ＰＢｕ_３）_２ＭＥＭ］［２ＴＦＳＩ］）を以下のとおり合成した。
１，２－ビスクロロメトキシエタン（２．４９ｇ、１５．６ｍｍｏｌ）をＣＨ_２Ｃｌ_２（２５ｍＬ）に溶かした後、トリブチルホスフィン（６．４３ｇ、３１．８ｍｍｏｌ）を加え、Ａｒ雰囲気下にて一晩室温で撹拌した。溶媒を留去した後、ジエチルエーテルによる洗浄を行い、真空乾燥を行い、白色の固体として［（ＰＢｕ_３）_２ＭＥＭ］［２Ｃｌ］（ｑｕａｎｔ）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０４(ｔ，Ｊ＝７．２６Ｈｚ，１８Ｈ)，１．５２－１．５８(ｍ，１２Ｈ)，１．６１－１．６７(ｍ，１２Ｈ)，２．２９－２．３４(ｍ，１２Ｈ)，３．８９（ｓ，４Ｈ），４．５２（ｓ，４Ｈ）；
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：１３．９，１８．２（ｄ，Ｊ＝４６．５Ｈｚ），２４．９（ｄ，Ｊ＝８４．０Ｈｚ），６２．２（ｄ，Ｊ＝６４．５Ｈｚ），７４．４
得られた［（ＰＢｕ_３）_２ＭＥＭ］［２Ｃｌ］（３．７６ｇ、６．６９ｍｍｏｌ）とＬｉＴＦＳＩ（４．０８ｇ、１４．２ｍｍｏｌ）をＣＨ_３ＯＨ（３０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、ジクロロメタンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。真空乾燥を行い、黄色の液体（５．４４ｇ、５．１７ｍｍｏｌ、７７％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．００（ｔ，Ｊ＝７．２６Ｈｚ，１８Ｈ），１．４９－１．５５（ｍ，１２Ｈ），１．５８－１．６４（ｍ，１２Ｈ），２．２５－２．３０（ｍ，１２Ｈ），３．８６（ｓ，４Ｈ），４．４６（ｓ，４Ｈ）；^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：１４．０，１８．２（ｄ，Ｊ＝４６．５Ｈｚ），２４．９（ｄ，Ｊ＝８５．５Ｈｚ），６２．１（ｄ，Ｊ＝６４．５Ｈｚ），７４．５，１２２（ｑ，Ｊ＝３１９Ｈｚ） <Compound F>
The formula below:

Compound F ([(PBu ₃ ) ₂ MEM][2TFSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (2.49 g, 15.6 mmol) in CH ₂ Cl ₂ (25 mL), tributylphosphine (6.43 g, 31.8 mmol) was added and the mixture was stirred under Ar atmosphere. Stir overnight at room temperature. After distilling off the solvent, the residue was washed with diethyl ether and vacuum dried to obtain [(PBu ₃ ) ₂ MEM][2Cl](quant) as a white solid.
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.04 (t, J=7.26 Hz, 18H), 1.52-1.58 (m, 12H), 1.61-1. 67 (m, 12H), 2.29-2.34 (m, 12H), 3.89 (s, 4H), 4.52 (s, 4H);
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 13.9, 18.2 (d, J = 46.5 Hz), 24.9 (d, J = 84.0 Hz), 62.2 ( d, J = 64.5 Hz), 74.4
The resulting [(PBu ₃ ) ₂ MEM][2Cl] (3.76 g, 6.69 mmol) and LiTFSI (4.08 g, 14.2 mmol) were dissolved in CH ₃ OH (30 mL) and stirred overnight at room temperature. . CH ₃ OH was distilled off. Thereafter, the product was dissolved in dichloromethane, washed with water, and the organic phase was separated by liquid separation. Vacuum drying was performed to obtain a yellow liquid (5.44 g, 5.17 mmol, 77%).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.00 (t, J=7.26 Hz, 18H), 1.49-1.55 (m, 12H), 1.58-1. 64 (m, 12H), 2.25-2.30 (m, 12H), 3.86 (s, 4H), 4.46 (s, 4H); ¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 14.0, 18.2 (d, J = 46.5 Hz), 24.9 (d, J = 85.5 Hz), 62.1 (d, J = 64.5 Hz), 74.5 , 122 (q, J=319 Hz)

で表される化合物ＣＡ（１－エチル－３－メチルイミダゾリウム ビス（トリフルオロメチルスルホニル）イミド、ＩｏＬｉＴｅｃ ＧｍｂＨ社製）を使用した。 <Compound CA>
The formula below:

The compound CA represented by (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, manufactured by IoLiTec GmbH) was used.

で表される化合物ＣＢ（［Ｐｙｒ_１ＭＥＭ］［ＴＦＳＩ］）を以下のとおり合成した。
Ａｒ雰囲気下にて、Ｎ－メチルピロリジン（４．１５ｇ、４８．７ｍｍｏｌ）をアセトニトリル（２５ｍＬ）に溶かした後、０℃下で２－メトキシエトキシメチルクロライド（６．０９ｇ、４８．９ｍｍｏｌ）を滴下後、０℃で約１時間撹拌した。溶媒を留去した後、活性炭とエタノールを加えて室温にて１５時間撹拌した。ろ過によって活性炭を除去したのち溶媒を留去し、減圧条件下で乾燥し、［Ｐｙｒ_１ＭＥＭ］［Ｃｌ］（１０．４ｇ、４９．６ｍｍｏｌ）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：２．２０－２．３１（ｍ，４Ｈ），３．１５（ｓ，３Ｈ），３．４３（ｓ，３Ｈ），３．４６－３．５０（ｍ，２Ｈ），３．６５（ｔ，Ｊ＝４．２Ｈｚ，２Ｈ），３．６６－３．７０（ｍ，２Ｈ），４．０３（ｔ，Ｊ＝４．２Ｈｚ，２Ｈ），４．７７（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：δ２３．２，４８．０，５９．３，６２．１，７２．９，７３．５，９１．３
得られた［Ｐｙｒ_１ＭＥＭ］［Ｃｌ］（１０．４ｇ、４９．６ｍｍｏｌ）とＬｉＴＦＳＩ（１４．３ｇ、４９．８ｍｍｏｌ）を水（６０ｍＬ）で溶かし、室温で一晩撹拌した。塩化メチレンにて抽出したのち、得られた有機層を水で洗浄した。溶媒留去ののち、活性炭とエタノールを加えて室温で約１日攪拌した。ろ過によって活性炭を除去したのち溶媒を留去し、さらに減圧条件下で乾燥し、［Ｐｙｒ_１ＭＥＭ］［ＴＦＳＩ］（１７．４ｇ、３８．２ｍｍｏｌ）を得た。目的物の生成は^１Ｈ－ＮＭＲにより確認した。
^１Ｈ－ＮＭＲ（６００ＭＨｚ，ＣＤＣｌ_３）δ（ｐｐｍ）：２．２０－２．３０（ｍ，４Ｈ），３．１２（ｓ，３Ｈ），３．３８（ｓ，３Ｈ），３．４０－３．４４（ｍ，２Ｈ），３．５８（ｔ，Ｊ＝４．２Ｈｚ，２Ｈ），３．６６－３．７０（ｍ，２Ｈ），３．９７（ｔ，Ｊ＝４．２Ｈｚ，２Ｈ），４．６９（ｓ，２Ｈ）；
^１３Ｃ－ＮＭＲ（１２５ＭＨｚ，ＣＤＣｌ_３）δ（ｐｐｍ）：２２．０，４７．４，５８．８，６１．０，７１．４，７２．３，８９．８，１１９．８（ｑ，Ｊ＝３２１．１Ｈｚ）． <Compound CB>
The formula below:

Compound CB ([Pyr ₁ MEM][TFSI]) represented by was synthesized as follows.
After dissolving N-methylpyrrolidine (4.15 g, 48.7 mmol) in acetonitrile (25 mL) under Ar atmosphere, 2-methoxyethoxymethyl chloride (6.09 g, 48.9 mmol) was added dropwise at 0°C. After that, the mixture was stirred at 0°C for about 1 hour. After distilling off the solvent, activated carbon and ethanol were added and the mixture was stirred at room temperature for 15 hours. After removing the activated carbon by filtration, the solvent was distilled off and dried under reduced pressure to obtain [Pyr ₁ MEM][Cl] (10.4 g, 49.6 mmol).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 2.20-2.31 (m, 4H), 3.15 (s, 3H), 3.43 (s, 3H), 3.46 -3.50 (m, 2H), 3.65 (t, J = 4.2Hz, 2H), 3.66-3.70 (m, 2H), 4.03 (t, J = 4.2Hz, 2H), 4.77(s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): δ 23.2, 48.0, 59.3, 62.1, 72.9, 73.5, 91.3
The resulting [Pyr ₁ MEM][Cl] (10.4 g, 49.6 mmol) and LiTFSI (14.3 g, 49.8 mmol) were dissolved in water (60 mL) and stirred overnight at room temperature. After extraction with methylene chloride, the resulting organic layer was washed with water. After distilling off the solvent, activated carbon and ethanol were added and the mixture was stirred at room temperature for about one day. After removing activated charcoal by filtration, the solvent was distilled off and dried under reduced pressure to obtain [Pyr ₁ MEM][TFSI] (17.4 g, 38.2 mmol). Production of the target product was confirmed by ¹ H-NMR.
¹ H-NMR (600 MHz, CDCl ₃ ) δ (ppm): 2.20-2.30 (m, 4H), 3.12 (s, 3H), 3.38 (s, 3H), 3.40- 3.44 (m, 2H), 3.58 (t, J = 4.2Hz, 2H), 3.66-3.70 (m, 2H), 3.97 (t, J = 4.2Hz, 2H) ), 4.69 (s, 2H);
¹³ C-NMR (125 MHz, CDCl ₃ ) δ (ppm): 22.0, 47.4, 58.8, 61.0, 71.4, 72.3, 89.8, 119.8 (q, J = 321.1 Hz).

“TFSI ⁻ ” represents bis(trifluoromethylsulfonyl)imide anion ([N(CF ₃ SO ₂ ) ₂ ] ⁻ ).

<Measurement of ionic conductivity>
The ionic conductivity of compounds A to E at 25° C. was measured by the impedance method under the following conditions.
1. An evaluation cell of a coin-type lithium battery CR2032 was assembled in a glove box under a dry argon atmosphere. Specifically, each layer was laminated in the following order in an evaluation cell to prepare a test laminate.
(Stainless steel plate/doughnut-shaped silicone sheet (outer circle 15 mmφ, inner circle diameter 5 mmφ, thickness 0.5 mm)/ionic liquid (injected into the inner circle part of the donut-shaped silicone sheet)/stainless steel plate)
2. Measurement is performed at 25° C. with a frequency range of 0.1 Hz to 1 MHz and an applied voltage of 10 mV using an impedance measuring device. The ionic conductivity σ can be calculated by the following formula.
σ (S cm ⁻¹ )=t (cm)×R (Ω)/A (cm ² )
In the formula, R represents the impedance value. A represents the area of the sample. t represents the thickness of the sample.

<Measurement of potential window>
In addition, about 1.0 mL of each of compounds A to E and compound CB was placed in a three-electrode cell (manufactured by Toyo Technica) in a nitrogen-purged glove box, and an argon atmosphere was measured using a measuring device (ALS 700E electrochemical analyzer). Linear sweep voltammetry (scanning speed: 1 mV / s, sweep range: -4.0 V on the reduction side from the open circuit potential, +4.0 V on the oxidation side, working electrode: glassy carbon (diameter: 3.0 mm), counter electrode: A platinum wire (outer diameter: 0.5 mm)) was used to measure the potential window (reference electrode: Ag/AgNO ₃ ). After the measurement, ferrocene was added and cyclic voltammetry was performed, and the potential obtained at the reference electrode was corrected with the oxidation-reduction potential of ferrocene. Potential windows were determined by taking potentials at which a current of 50 μA/cm ² flowed during sweeping to the reduction side and oxidation side as the reduction potential and the oxidation potential, respectively. Table 1 shows the results.

From Table 1, it can be seen that the dicationic ionic liquid of the present embodiment has a wider potential window than the compound CB, which is a conventional ionic liquid. In addition, the dicationic ionic liquid of the present embodiment has higher ionic conductivity than compound CB, which is a conventional ionic liquid.

(Examples A1 to A6 and Comparative Examples A1 to A3)
LiTFSI was added to each ionic liquid so as to have concentrations as shown in Tables 2 and 3, and composite electrolytes of Examples A1 to A6 and Comparative Examples A1 to A3 were prepared.

(Measurement of critical current density and initial current density)
The limiting current density of the composite electrolyte prepared as described above was measured by a DC test. In this test, a coin-type lithium battery CR2032 was used as an evaluation cell. Specifically, each layer was laminated in the following order in an evaluation cell to prepare a test laminate.
(Stainless steel plate/metallic lithium foil/doughnut-shaped silicone sheet (outer circle 15mmφ, inner diameter 5mmφ, thickness 0.5mm) and composite electrolyte/metallic lithium foil injected into the inner circular portion of the donut-shaped silicone sheet)

The voltage applied to the evaluation cell was applied for 30 minutes to measure changes in current density over time. Current density was calculated by dividing the observed current by the inner circle area of the silicone sheet. The current density 30 minutes after voltage application was defined as _I30 . The applied voltage was stepped up, typically by 0.2 V, and _I30 was measured at each applied voltage. When the applied voltage was small, _I30 also increased with increasing applied voltage. When the applied voltage was increased to a certain extent, _I30 did not increase any more and showed a constant value even if the applied voltage was increased. The maximum value of _I30 at this time was defined as the limiting current density _Ilim . The measured limiting current density indicates the maximum current density that can flow when a steady applied voltage is applied to the composite electrolyte to be measured. The test temperature was 25° C. unless otherwise specified.

The initial current density was defined as the current density 1 second after the application of the voltage giving the above limiting current density.

^＊「Ｌｉ^＋／全イオン」は、複合電解質に含まれる全イオンに対するリチウムイオンのモル数の割合である。

^* "Li ⁺ /total ions" is the ratio of the number of moles of lithium ions to the total ions contained in the composite electrolyte.

^＊「Ｌｉ^＋／全イオン」は、複合電解質に含まれる全イオンに対するリチウムイオンのモル数の割合である。

^* "Li ⁺ /total ions" is the ratio of the number of moles of lithium ions to the total ions contained in the composite electrolyte.

The contribution ratio of the current contributed by the lithium ions to the total current was calculated by dividing the above limit current value by the initial current value. At the initial stage of voltage application, all the ions contained in the electrolyte contribute to the moving current. At steady state 30 minutes after voltage application, only lithium ions contribute to the current.

(Examples B1 to B5)
Composite electrolytes of Examples B1 to B5 were prepared by mixing an ionic liquid, a lithium salt (LiTFSI) and a viscosity reducing agent with the composition as shown in Table 4. As a viscosity reducing agent, a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio EC:PC=1:1) was added. The limiting current values of ionic liquid electrolytes containing viscosity reducing agents were verified by DC tests. This test used the same configuration as the test laminates described above, except that a viscosity reducing agent was added to the composite electrolyte.

(Measurement of critical current density and initial current density)
A voltage of 0.1 V was continuously applied to the test laminate, and changes in current density over time were observed. The limit current density was defined as the value at which the current density did not change for one hour or longer. The test temperature was 25°C.
The initial current density was the current density after 1 second from the application of a voltage of 0.1V.

The contribution ratio of the current contributed by the lithium ions to the total current corresponds to I _lim /I _ini calculated by dividing the above limiting current density by the initial current density. At the initial stage of voltage application, all the ions contained in the electrolyte contribute to the moving current. At steady state 30 minutes after voltage application, only lithium ions contribute to the current.

^＊「Ｌｉ^＋／全イオン」は、複合電解質に含まれる全イオンに対するリチウムイオンのモル数の割合である。
^＊＊混合溶媒の含有量は、イオン液体１００質量％に対する質量％である。

^* "Li ⁺ /total ions" is the ratio of the number of moles of lithium ions to the total ions contained in the composite electrolyte.
^** The content of the mixed solvent is % by mass with respect to 100% by mass of the ionic liquid.

(Lithium dissolution deposition cycle test)
As a sample, 0.125 mmol of lithium salt, 250 mg of ionic liquid, and 62.5 mg of viscosity reducing agent (mixed solvent containing EC and PC at a volume ratio of 1: 1) were mixed to obtain Examples B6 to B9 and Comparative Example B1. A composite electrolyte was prepared. The ionic liquid contained in each composite electrolyte is as follows. Using these composite electrolytes, the test laminates were produced.
Example B6: Compound C
Example B7: Compound A
Example B8: Compound B
Example B9: Compound D
Example B10: Compound E
Comparative Example B1: Compound CA
Comparative Example B2: Compound CB
Example B11: Compound E'
Example B12: Compound A'
Example B13: Compound H'
Example B14: Compound B'

A current of +200 μA/cm ² was applied for 1 hour to deposit lithium on the metallic lithium foil of the test laminate. After that, at an interval of 10 minutes, a current of −200 μA/cm ² was applied for 1 hour so that lithium was eluted from the metal lithium foil, and lithium was eluted. Again, at intervals of 10 minutes, the deposition and elution of lithium were repeated. The behavior of the voltage value was observed, and the stability of the voltage value over time was evaluated. From the viewpoint of controlling the dissolution and deposition of lithium, it is desirable that the voltage fluctuation when current is applied is small and that the voltage is stable even after multiple cycles are repeated.

FIG. 1 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Example B6. FIG. 2 is a diagram showing the results of the lithium dissolution-precipitation cycle test of Comparative Example B1. 1 and 2, the vertical axis is voltage (V) and the horizontal axis is time (h). As is clear from the comparison between FIGS. 1 and 2, in the composite electrolyte of Example B6, even when the cycle test was repeated for 250 hours, the voltage fluctuation was small and the amplitude was substantially constant. On the other hand, as shown in FIG. 2, in the sample of Comparative Example B1, the voltage fluctuation increased after about 100 hours, and the voltage fluctuation increased further after about 140 hours, and the cycle stabilized. I didn't.

Similarly, FIGS. 3 to 7 are diagrams showing the results of the lithium dissolution-precipitation cycle test of Examples B7 to B10 and Comparative Example B2, respectively. As shown in FIGS. 3 and 4, in the composite electrolytes of Examples B7 and B8, even when the cycle test was repeated for 250 hours, the voltage fluctuation was small and the fluctuation width was substantially constant. In addition, as shown in FIG. 5, in the composite electrolyte of Example B9, even when the cycle test was repeated for about 250 hours, the voltage fluctuation was small and the fluctuation width was substantially constant. Further, as shown in FIG. 6, in the composite electrolyte of Example B10, even when the cycle test was repeated for about 250 hours, the voltage fluctuation was relatively small and the fluctuation width was substantially constant.
On the other hand, as shown in FIG. 7, in the composite electrolyte of Comparative Example B2, the voltage value continued to rise between 50 and 150 hours, and was particularly unstable after 200 hours. In particular, in the range after 200 hours, the behavior of the voltage suddenly changing immediately after +200 μA/cm ² or −200 μA/cm ² was applied, and then the absolute value of the voltage dropping and becoming almost constant was repeated. ing. From this, it can be seen that precipitation of lithium dendrites was remarkable after 200 hours.
8 to 11 are diagrams showing the results of lithium dissolution-precipitation cycle tests of Examples B11 to B14, respectively. As can be seen from FIGS. 8 to 11, even when the composite electrolytes of Examples B11 to B14 were used, the voltage fluctuation was relatively small and the amplitude was substantially constant even after repeating the cycle test for about 250 hours. rice field.

(10% weight loss temperature 1)
For thermal analysis (TG-DTA), the 10% weight loss temperature (° C.) of compounds A to F was measured using Thermo plus EVOII manufactured by Rigaku Corporation. Specifically, a sample of 3 to 5 mg is heated in an aluminum container under the conditions of a starting temperature of 40 ° C., a final temperature of 500 ° C., and a heating rate of 5 ° C./min, and the temperature at which it reaches 90% of the initial weight is The temperature was taken as 10% weight loss temperature. Tables 5 and 6 show the results. Compound F is solid at room temperature (25° C.).

(10% weight loss temperature 2)
For thermal analysis (TG-DTA), the 10% weight loss temperature (° C.) of compounds A to F was measured using a simultaneous differential thermal/calorimeter DTG-60A manufactured by Shimadzu Corporation. Specifically, a sample of 3 to 5 mg was heated from room temperature to 150° C. in an aluminum container at a temperature increase rate of 10° C./min and held at 150° C. for 10 minutes. After that, it was heated from 150° C. to 350° C. at a temperature increase rate of 1° C./min, and from 350° C. to 500° C. at a temperature increase rate of 10° C./min. The temperature at which the initial weight reached 90% was defined as the 10% weight loss temperature. Table 6 shows the results.

As shown in Table 5, it can be said that the ionic liquid of this embodiment is excellent in heat resistance. In particular, compound E, which is an asymmetric type, has an improved 10% weight loss temperature compared to compounds A to D and compound F, which are symmetric types.

で表される化合物Ａ’（［（Ｐｙｒ_１）_２ＭＥＭ］［２ＦＳＩ］）を以下のとおり合成した。
１，２－ビスクロロメトキシエタン（７９０ｍｇ、４．９７ｍｍｏｌ）をＣＨ_２Ｃｌ_２（３０ｍＬ）に溶かした後、Ｎ－メチルピロリジン（９６１ｍｇ、１１．３ｍｍｏｌ）を加え、Ａｒ雰囲気下にて一晩室温で撹拌した。溶媒を留去した後、ジエチルエーテルによる洗浄を行い、真空乾燥を行い、白色の固体として［（Ｐｙｒ_１）_２ＭＥＭ］［２Ｃｌ］（ｑｕａｎｔ）を得た。以下に生成物のＮＭＲのデータを示す。なお、生成物の収率がほぼ１００％であった場合、ｑｕａｎｔと記載する。
^１Ｈ－ＮＭＲ（ＣＤＣｌ_３，６００ＭＨｚ）δ（ｐｐｍ）：２．２２－２．３５（ｍ，８Ｈ），３．３６（ｓ，６Ｈ），３．６５－３．６９（ｍ，４Ｈ），３．９３－３．９７（ｍ，４Ｈ），４．２３（ｓ，４Ｈ），５．４７（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：２３．０，４８．４，６２．５，７３．６，９１．４
得られた［（Ｐｙｒ_１）_２ＭＥＭ］［２Ｃｌ］（１．９８ｇ、６．００ｍｍｏｌ）とＬｉＦＳＩ（２．３０ｇ、１２．３ｍｍｏｌ）とをＣＨ_３ＯＨ（５０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、酢酸エチルに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。当該有機相に真空乾燥を行い、無色透明の液体（２．８８ｇ、４．６６ｍｍｏｌ、７８％）を得た。以下に生成物のＮＭＲのデータを示す。なお、特に断らない限り、^１Ｈ－ＮＭＲ及び^１３Ｃ－ＮＭＲの化学シフトは、測定に使用した重溶媒が重クロロホルム（ＣＤＣｌ_３）である場合は、クロロホルムのＨ又はＣを基準とし、重溶媒が重メタノール（ＣＤ_３ＯＤ）である場合は、メタノールのメチル基のＨ又はＣを基準とする。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：２．２２－２．２６（ｍ，８Ｈ），３．１３（ｓ，６Ｈ），３．４６－３．４８（ｍ，４Ｈ），３．６１－３．６３（ｍ，４Ｈ），４．０９（ｓ，４Ｈ），４．７５（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：２３．０，４８．０，６２．２，７３．１，９１．１ <Compound A'>
The formula below:

Compound A′ ([(Pyr ₁ ) ₂ MEM][2FSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (790 mg, 4.97 mmol) in CH ₂ Cl ₂ (30 mL), N-methylpyrrolidine (961 mg, 11.3 mmol) was added and the mixture was stirred at room temperature overnight under Ar atmosphere. was stirred. After distilling off the solvent, the residue was washed with diethyl ether and vacuum-dried to obtain [(Pyr ₁ ) ₂ MEM][2Cl](quant) as a white solid. The NMR data of the product are shown below. In addition, when the yield of the product is almost 100%, it is described as quant.
¹ H-NMR (CDCl ₃ , 600 MHz) δ (ppm): 2.22-2.35 (m, 8H), 3.36 (s, 6H), 3.65-3.69 (m, 4H), 3.93-3.97 (m, 4H), 4.23 (s, 4H), 5.47 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 23.0, 48.4, 62.5, 73.6, 91.4
The resulting [(Pyr ₁ ) ₂ MEM][2Cl] (1.98 g, 6.00 mmol) and LiFSI (2.30 g, 12.3 mmol) were dissolved in CH ₃ OH (50 mL) and stirred overnight at room temperature. bottom. CH ₃ OH was distilled off. Thereafter, the product was dissolved in ethyl acetate, washed with water, and the organic phase was separated by liquid separation. The organic phase was vacuum dried to obtain a colorless transparent liquid (2.88 g, 4.66 mmol, 78%). The NMR data of the product are shown below. Unless otherwise specified, ¹ H-NMR and ¹³ C-NMR chemical shifts are based on H or C of chloroform when the deuterated solvent used for measurement is deuterated chloroform (CDCl ₃ ). is heavy methanol (CD ₃ OD), it is based on the H or C of the methyl group of methanol.
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 2.22-2.26 (m, 8H), 3.13 (s, 6H), 3.46-3.48 (m, 4H) , 3.61-3.63 (m, 4H), 4.09 (s, 4H), 4.75 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 23.0, 48.0, 62.2, 73.1, 91.1

で表される化合物Ｂ’（［（Ｎ_２２１）_２ＭＥＭ］［２ＦＳＩ］）を以下のとおり合成した。
１，２－ビスクロロメトキシエタン（７９５ｍｇ、４．９４ｍｍｏｌ）をＣＨ_２Ｃｌ_２（３０ｍＬ）に溶かした後、Ｎ，Ｎ－ジエチルメチルアミン（１．００ｇ、１１．５ｍｍｏｌ）を加え、Ａｒ雰囲気下にて一晩室温で撹拌した。溶媒を留去した後、ジエチルエーテルによる洗浄を行い、真空乾燥を行い、白色の固体として［（Ｎ_２２１）_２ＭＥＭ］［２Ｃｌ］（ｑｕａｎｔ）を得た。以下に生成物のＮＭＲのデータを示す。
^１Ｈ－ＮＭＲ（ＣＤＣｌ_３，６００ＭＨｚ）δ（ｐｐｍ）：１．４２（ｔ，Ｊ＝１７．５Ｈｚ，１２Ｈ），３．２６（ｓ，６Ｈ），３．５６－３．６２（ｍ，８Ｈ），４．２４（ｓ，４Ｈ），５．４０（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：８．１９，４５．１，５５．２，７３．３，８９．０
得られた［（Ｎ_２２１）_２ＭＥＭ］［２Ｃｌ］（２．１８ｇ、６．５４ｍｍｏｌ）とＬｉＦＳＩ（２．８０ｇ、１４．９ｍｍｏｌ）とをＣＨ_３ＯＨ（５０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、酢酸エチルに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。当該有機相に真空乾燥を行い、無色透明の液体（３．１８ｇ、５．１０ｍｍｏｌ、７８％）を得た。以下に生成物のＮＭＲのデータを示す。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．３２－１．３７（ｍ，１２Ｈ），２．９９（ｓ，６Ｈ），３．３６－３．４２（ｍ，１２Ｈ），４．０６（ｓ，４Ｈ），４．７２（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：７．５０，４４．４，５１．５，７２．７，８８．４ <Compound B'>
The formula below:

Compound B′ ([(N ₂₂₁ ) ₂ MEM][2FSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (795 mg, 4.94 mmol) in CH ₂ Cl ₂ (30 mL), N,N-diethylmethylamine (1.00 g, 11.5 mmol) was added and stirred under Ar atmosphere. was stirred overnight at room temperature. After distilling off the solvent, the residue was washed with diethyl ether and vacuum-dried to obtain [(N ₂₂₁ ) ₂ MEM][2Cl](quant) as a white solid. The NMR data of the product are shown below.
¹ H-NMR (CDCl ₃ , 600 MHz) δ (ppm): 1.42 (t, J = 17.5 Hz, 12H), 3.26 (s, 6H), 3.56-3.62 (m, 8H ), 4.24 (s, 4H), 5.40 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 8.19, 45.1, 55.2, 73.3, 89.0
The resulting [(N ₂₂₁ ) ₂ MEM][2Cl] (2.18 g, 6.54 mmol) and LiFSI (2.80 g, 14.9 mmol) were dissolved in CH ₃ OH (50 mL) and stirred overnight at room temperature. bottom. CH ₃ OH was distilled off. Thereafter, the product was dissolved in ethyl acetate, washed with water, and the organic phase was separated by liquid separation. The organic phase was vacuum dried to obtain a colorless transparent liquid (3.18 g, 5.10 mmol, 78%). The NMR data of the product are shown below.
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.32-1.37 (m, 12H), 2.99 (s, 6H), 3.36-3.42 (m, 12H) , 4.06(s, 4H), 4.72(s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 7.50, 44.4, 51.5, 72.7, 88.4

で表される化合物Ｉ（［（Ｍｉｍ）_２ＭＥＭ］［２ＦＳＩ］）を以下のとおり合成した。
１，２－ビスクロロメトキシエタン（２．２３ｇ、１４．０ｍｍｏｌ）をＣＨ_２Ｃｌ_２（２０ｍＬ）に溶かした後、Ｎ－メチルイミダゾール（２．４９ｇ、３０．３ｍｍｏｌ）を加え、Ａｒ雰囲気下にて一晩室温で撹拌した。溶媒を留去した後、ジエチルエーテルによる洗浄を行い、真空乾燥を行い、白色の固体として［（Ｍｉｍ）_２ＭＥＭ］［２Ｃｌ］（ｑｕａｎｔ）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：３．８１（ｓ，４Ｈ），４．０３（ｓ，６Ｈ），５．６９（ｓ，４Ｈ），７．７０（ｓ，２Ｈ），７．８１（ｓ，２Ｈ），９．２３（ｓ，２Ｈ）
得られた［（Ｍｉｍ）_２ＭＥＭ］［２Ｃｌ］（２．８３ｇ、８．７５ｍｍｏｌ）とＬｉＦＳＩ（３．４９ｇ、１８．６ｍｍｏｌ）とをＣＨ_３ＯＨ（５０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、酢酸エチルに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。当該有機相に真空乾燥を行い、無色透明の液体（３．７０ｇ、６．０４ｍｍｏｌ、６９％）を得た。
^１Ｈ－ＮＭＲ（ＣＤＣｌ_３，６００ＭＨｚ）δ（ｐｐｍ）：３．７６（ｓ，４Ｈ），３．９７（ｓ，６Ｈ），５．６０（ｓ，４Ｈ），７．６４（ｓ，２Ｈ），７．７２（ｓ，２Ｈ），９．０４（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：３６．６，６９．９，８０．１，１２２．９，１２５．３，１３８．０ <Compound C'>
The formula below:

Compound I ([(Mim) ₂ MEM][2FSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (2.23 g, 14.0 mmol) in CH ₂ Cl ₂ (20 mL), N-methylimidazole (2.49 g, 30.3 mmol) was added and the mixture was stirred under Ar atmosphere. and stirred overnight at room temperature. After distilling off the solvent, the residue was washed with diethyl ether and vacuum dried to obtain [(Mim) ₂ MEM][2Cl](quant) as a white solid.
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 3.81 (s, 4H), 4.03 (s, 6H), 5.69 (s, 4H), 7.70 (s, 2H ), 7.81 (s, 2H), 9.23 (s, 2H)
The resulting [(Mim) ₂ MEM][2Cl] (2.83 g, 8.75 mmol) and LiFSI (3.49 g, 18.6 mmol) were dissolved in CH ₃ OH (50 mL) and stirred overnight at room temperature. . The _CH3OH was distilled off. Thereafter, the product was dissolved in ethyl acetate, washed with water, and the organic phase was separated by liquid separation. The organic phase was vacuum dried to obtain a colorless transparent liquid (3.70 g, 6.04 mmol, 69%).
¹ H-NMR (CDCl ₃ , 600 MHz) δ (ppm): 3.76 (s, 4H), 3.97 (s, 6H), 5.60 (s, 4H), 7.64 (s, 2H) , 7.72(s, 2H), 9.04(s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 36.6, 69.9, 80.1, 122.9, 125.3, 138.0

で表される化合物Ｄ’（［（Ｐｉｐ_１）_２ＭＥＭ］［２ＦＳＩ］）を以下のとおり合成した。
１，２－ビスクロロメトキシエタン（１．６３ｇ、１０．２ｍｍｏｌ）をＣＨ_２Ｃｌ_２（３０ｍＬ）に溶かした後、Ｎ－メチルピペリジン（２．１０ｇ、２１．２ｍｍｏｌ）を加え、Ａｒ雰囲気下にて一晩室温で撹拌した。溶媒を留去した後、ジエチルエーテルによる洗浄を行い、真空乾燥を行い、白色の固体として［（Ｐｉｐ_１）_２ＭＥＭ］［２Ｃｌ］（ｑｕａｎｔ）を得た。
^１Ｈ－ＮＭＲ（ＣＤＣｌ_３，６００ＭＨｚ）δ（ｐｐｍ）：１．７０－１．７４（ｍ，４Ｈ），１．８６－１．９７（ｍ，１６Ｈ），３．３３（ｓ，６Ｈ），４．２４（ｓ，４Ｈ），５．５３（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：２０．９，２２．６，４５．７，５８．９，７４．２，９２．７
得られた［（Ｐｉｐ_１）_２ＭＥＭ］［２Ｃｌ］（３．６６ｇ、１０．２ｍｍｏｌ）とＬｉＦＳＩ（３．９９ｇ、２１．３ｍｍｏｌ）をＣＨ_３ＯＨ（３０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、ジクロロメタンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。真空乾燥を行い、無色透明の液体（４．２８ｇ、６．６２ｍｍｏｌ、６５％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．６２－１．６８（ｍ，２Ｈ），１．７８－１．８２（ｍ，２Ｈ），１．９２－２．００（ｍ，８Ｈ），３．０８（ｓ，６Ｈ），３．３３－３．４２（ｓ，８Ｈ），４．１０（ｓ，４Ｈ），４．７８（ｓ，４Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：２０．４，２２．１，４５．４，５８．６，７３．７，９２．４ <Compound D'>
The formula below:

A compound D' ([(Pip ₁ ) ₂ MEM][2FSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (1.63 g, 10.2 mmol) in CH ₂ Cl ₂ (30 mL), N-methylpiperidine (2.10 g, 21.2 mmol) was added and stirred under Ar atmosphere. and stirred overnight at room temperature. After distilling off the solvent, the residue was washed with diethyl ether and vacuum dried to obtain [(Pip ₁ ) ₂ MEM][2Cl](quant) as a white solid.
¹ H-NMR (CDCl ₃ , 600 MHz) δ (ppm): 1.70-1.74 (m, 4H), 1.86-1.97 (m, 16H), 3.33 (s, 6H), 4.24 (s, 4H), 5.53 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 20.9, 22.6, 45.7, 58.9, 74.2, 92.7
The resulting [(Pip ₁ ) ₂ MEM][2Cl] (3.66 g, 10.2 mmol) and LiFSI (3.99 g, 21.3 mmol) were dissolved in CH ₃ OH (30 mL) and stirred overnight at room temperature. . CH ₃ OH was distilled off. Thereafter, the product was dissolved in dichloromethane, washed with water, and the organic phase was separated by liquid separation. Vacuum drying was performed to obtain a colorless and transparent liquid (4.28 g, 6.62 mmol, 65%).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.62-1.68 (m, 2H), 1.78-1.82 (m, 2H), 1.92-2.00 ( m, 8H), 3.08 (s, 6H), 3.33-3.42 (s, 8H), 4.10 (s, 4H), 4.78 (s, 4H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 20.4, 22.1, 45.4, 58.6, 73.7, 92.4

で表される化合物Ｅ’（［（Ｐｙｒ_１）ＭＥＭ（ＰＢｕ_３）］［２ＦＳＩ］）を以下のとおり合成した。
Ａｒ雰囲気下にて、１，２－ビスクロロメトキシエタン（７１５ｍｇ、４．５０ｍｍｏｌ）を酢酸エチル（１．５ｍＬ）に溶かした後、－１０℃下でＮ－メチルピロリジン（３８２ｍｇ、４．４８ｍｍｏｌ）を２．８７４ｍＬ／ｈの速度で滴下後、－１０℃で２分間撹拌、続けて３５℃で５分間撹拌をした。ＣＨ_３ＣＮ（３．０ｍＬ）添加後、３５℃で５分撹拌した後、トリブチルホスフィン（１．０９ｇ、５．３８ｍｍｏｌ）を加え、３５℃で５時間撹拌した。溶媒を留去した後、ジエチルエーテルおよびアセトンによる洗浄を行い、真空乾燥後、無色透明の液体として［（Ｐｙｒ_１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（純度９３％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０２－１．０５（ｍ，９Ｈ），１．５３－１．６５（ｍ，１２Ｈ），２．３０－２．３５（ｍ，６Ｈ），３．４５－３．５０（ｍ，２Ｈ），３．６１－３．６５（ｍ，２Ｈ），３．８９－３．９１（ｍ，２Ｈ），４．０６－４．０８（ｍ，２Ｈ），４．５３（ｄ，Ｊ＝５．４Ｈｚ，２Ｈ），４．７８（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：１３．６，１７．７，１８．０，２３．１，２４．１８，２４．２５，２４．２８，２４．８，２４．９，４８．０，６１．７，６２．１，７２．９，７４．１６，７４．２４，９１．０
得られた［（Ｐｙｒ_１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（７４８ｍｇ、１．６７ｍｍｏｌ）とＬｉＦＳＩ（８７６ｍｇ、４．６８ｍｍｏｌ）とをＣＨ_３ＯＨ（３０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、酢酸エチルに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。真空乾燥を行い、無色透明の液体（１．０９ｇ、純度９２％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０１（ｔ，Ｊ＝７．２Ｈｚ，９Ｈ），１．５０－１．５６（ｍ，６Ｈ），１．５９－１．６５（ｍ，６Ｈ），２．２１－２．３１（ｍ，１０Ｈ），３．１２（ｓ，３Ｈ），３．４４－３．４９（ｍ，２Ｈ），３．５９－３．６３（ｍ，２Ｈ），３．８９－３．９０（ｍ，２Ｈ），４．０５－４．０６（ｍ，２Ｈ），４．４８（ｄ，Ｊ＝５．４Ｈｚ，２Ｈ），４．７２（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：１３．５，１７．６，１７．９，２３．１，２４．１７，２４．２０，２４．８，２４．９，４８．０，６１．５，６２．２，７２．９，７４．２，７４．３，９１．０ <Compound E′>
The formula below:

A compound E′ ([(Pyr ₁ )MEM(PBu ₃ )][2FSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (715 mg, 4.50 mmol) in ethyl acetate (1.5 mL) under Ar atmosphere, N-methylpyrrolidine (382 mg, 4.48 mmol) was added at -10°C. was added dropwise at a rate of 2.874 mL/h, followed by stirring at -10°C for 2 minutes and then stirring at 35°C for 5 minutes. After adding CH ₃ CN (3.0 mL) and stirring at 35° C. for 5 minutes, tributylphosphine (1.09 g, 5.38 mmol) was added and stirring was performed at 35° C. for 5 hours. After distilling off the solvent, the residue was washed with diethyl ether and acetone, and after vacuum drying, [(Pyr ₁ )MEM(PBu ₃ )][2Cl] (purity 93%) was obtained as a colorless transparent liquid.
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.02-1.05 (m, 9H), 1.53-1.65 (m, 12H), 2.30-2.35 ( m, 6H), 3.45-3.50 (m, 2H), 3.61-3.65 (m, 2H), 3.89-3.91 (m, 2H), 4.06-4. 08 (m, 2H), 4.53 (d, J=5.4Hz, 2H), 4.78 (s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 13.6, 17.7, 18.0, 23.1, 24.18, 24.25, 24.28, 24.8, 24. 9, 48.0, 61.7, 62.1, 72.9, 74.16, 74.24, 91.0
The resulting [(Pyr ₁ )MEM(PBu ₃ )][2Cl] (748 mg, 1.67 mmol) and LiFSI (876 mg, 4.68 mmol) were dissolved in CH ₃ OH (30 mL) and stirred overnight at room temperature. . CH ₃ OH was distilled off. Thereafter, the product was dissolved in ethyl acetate, washed with water, and the organic phase was separated by liquid separation. Vacuum drying was performed to obtain a colorless transparent liquid (1.09 g, purity 92%).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.01 (t, J=7.2 Hz, 9H), 1.50-1.56 (m, 6H), 1.59-1. 65 (m, 6H), 2.21-2.31 (m, 10H), 3.12 (s, 3H), 3.44-3.49 (m, 2H), 3.59-3.63 ( m, 2H), 3.89-3.90 (m, 2H), 4.05-4.06 (m, 2H), 4.48 (d, J = 5.4Hz, 2H), 4.72 ( s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 13.5, 17.6, 17.9, 23.1, 24.17, 24.20, 24.8, 24.9, 48. 0, 61.5, 62.2, 72.9, 74.2, 74.3, 91.0

で表される化合物Ｇ（［（Ｎ_２２１）ＭＥＭ（ＰＢｕ_３）］［２ＴＦＳＩ］）を以下のとおり合成した。
Ａｒ雰囲気下にて、１，２－ビスクロロメトキシエタン（１．９１ｇ、１２．０ｍｍｏｌ）をＴＨＦ（４．０ｍＬ）に溶かした後、－１０℃下でＮ，Ｎ－ジエチルメチルアミン（１．０５ｇ、１２．１ｍｍｏｌ）を２.９０ｍＬ／ｈの速度で滴下後、－１０℃で２分間撹拌、続けて撹拌３５℃で５分間撹拌した。ＣＨ_３ＣＮ（８．０ｍＬ）添加後、３５℃で５分撹拌した後、トリブチルホスフィン（２．９３ｇ、１４．５ｍｍｏｌ）を加え、３５℃で５時間撹拌した。溶媒を留去した後、ジエチルエーテルおよびアセトンによる洗浄を行い、ゲルろ過、真空乾燥後、無色透明の液体として［（Ｎ_２２１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（純度９３％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０３－１．０６（ｍ，９Ｈ），１．４０（ｔ，Ｊ＝７．２Ｈｚ，６Ｈ），１．５４－１．６０（ｍ，６Ｈ），１．６３－１．７０（ｍ，６Ｈ），２．３４－２．３９（ｍ，６Ｈ），３．０５（ｍ，３Ｈ），３．４２－３．４９（ｍ，４Ｈ），３．９３－３．９５（ｍ，２Ｈ），４．０８－４．１２（ｍ，２Ｈ），４．５９（ｄ，Ｊ＝５．４Ｈｚ，２Ｈ），４．８０（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：７．８，１３．６，１７．７，１８．０，２４．２６，２４．２９，２４．８，２５．０，４４．８，５４．９，６１．７，６２．１，７２．８，７４．１，７４．２，８６．６
得られた［（Ｎ_２２１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（９１６ｍｇ、２．０４ｍｍｏｌ）とＬｉＴＦＳＩ（１．２１ｇ、４．２１ｍｍｏｌ）とをＣＨ_３ＯＨ（３０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、塩化メチレンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。真空乾燥を行い、無色透明の液体（１．０３ｇ、純度９６％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０５（ｔ，Ｊ＝７．３Ｈｚ，９Ｈ），１．４０（ｔ，Ｊ＝７．３Ｈｚ，６Ｈ），１．５５－１．５９（ｍ，６Ｈ），１．６４－１．６７（ｍ，６Ｈ），２．３０－２．３５（ｍ，６Ｈ），３．０３（ｓ，３Ｈ），３．３５－３．４５（ｍ，４Ｈ），３．９３－３．９４（ｍ，２Ｈ），４．０６－４．０８（ｍ，２Ｈ），４．５２（ｄ，Ｊ＝５．３Ｈｚ，２Ｈ），４．７３（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：７．７，１３．５，１７．６，１７．９，２４．１９，２４．２２，２４．８，２４．９，４４．７，５５．０，６１．６，６２．０，７２．７，７４．１，７４．２，８６．６，１２１.１（ｑ，Ｊ＝３１９Ｈｚ） <Compound G>
The formula below:

Compound G ([(N ₂₂₁ )MEM(PBu ₃ )][2TFSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (1.91 g, 12.0 mmol) in THF (4.0 mL) under Ar atmosphere, N,N-diethylmethylamine (1. 05 g, 12.1 mmol) was added dropwise at a rate of 2.90 mL/h, followed by stirring at -10°C for 2 minutes, followed by stirring at 35°C for 5 minutes. After adding CH ₃ CN (8.0 mL) and stirring at 35° C. for 5 minutes, tributylphosphine (2.93 g, 14.5 mmol) was added and stirring was performed at 35° C. for 5 hours. After distilling off the solvent, the product was washed with diethyl ether and acetone, gel-filtered, and vacuum-dried to obtain [(N ₂₂₁ )MEM(PBu ₃ )][2Cl] (purity 93%) as a colorless transparent liquid. .
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.03-1.06 (m, 9H), 1.40 (t, J=7.2 Hz, 6H), 1.54-1. 60 (m, 6H), 1.63-1.70 (m, 6H), 2.34-2.39 (m, 6H), 3.05 (m, 3H), 3.42-3.49 ( m, 4H), 3.93-3.95 (m, 2H), 4.08-4.12 (m, 2H), 4.59 (d, J = 5.4Hz, 2H), 4.80 ( s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 7.8, 13.6, 17.7, 18.0, 24.26, 24.29, 24.8, 25.0, 44. 8, 54.9, 61.7, 62.1, 72.8, 74.1, 74.2, 86.6
The resulting [(N ₂₂₁ )MEM(PBu ₃ )][2Cl] (916 mg, 2.04 mmol) and LiTFSI (1.21 g, 4.21 mmol) were dissolved in CH ₃ OH (30 mL) and stirred overnight at room temperature. Stirred. CH ₃ OH was distilled off. Thereafter, the product was dissolved in methylene chloride, washed with water, and the organic phase was separated by liquid separation. Vacuum drying was performed to obtain a colorless transparent liquid (1.03 g, purity 96%).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.05 (t, J = 7.3 Hz, 9H), 1.40 (t, J = 7.3 Hz, 6H), 1.55- 1.59 (m, 6H), 1.64-1.67 (m, 6H), 2.30-2.35 (m, 6H), 3.03 (s, 3H), 3.35-3. 45 (m, 4H), 3.93-3.94 (m, 2H), 4.06-4.08 (m, 2H), 4.52 (d, J=5.3Hz, 2H), 4. 73 (s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 7.7, 13.5, 17.6, 17.9, 24.19, 24.22, 24.8, 24.9, 44. 7, 55.0, 61.6, 62.0, 72.7, 74.1, 74.2, 86.6, 121.1 (q, J = 319Hz)

で表される化合物Ｇ’（［（Ｎ_２２１）ＭＥＭ（ＰＢｕ_３）］［２ＦＳＩ］）を以下のとおり合成した。
Ａｒ雰囲気下にて、１，２－ビスクロロメトキシエタン（６２１ｍｇ、３．９１ｍｍｏｌ）をテトラヒドロフラン（１．３ｍＬ）に溶かした後、－１０℃下でＮ，Ｎ－ジエチルメチルアミン（３５６ｍｇ、４．０９ｍｍｏｌ）を２．８７４ｍＬ／ｈの速度で滴下後、－１０℃で２分間撹拌、続けて３５℃で５分間撹拌をした。ＣＨ_３ＣＮ（２．６ｍＬ）添加後、３５℃で５分撹拌した後、トリブチルホスフィン（８１７ｍｇ、４．０４ｍｍｏｌ）を加え、３５℃で５時間撹拌した。溶媒を留去した後、ジエチルエーテルおよびアセトンによる洗浄を行い、ゲルろ過、真空乾燥後、無色透明の液体として［（Ｎ_２２１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（純度９２％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０３－１．０６（ｍ，９Ｈ），１．４０（ｔ，Ｊ＝７．２Ｈｚ，６Ｈ），１．５４－１．６０（ｍ，６Ｈ），１．６３－１．７０（ｍ，６Ｈ），２．３４－２．３９（ｍ，６Ｈ），３．０５（ｍ，３Ｈ），３．４２－３．４９（ｍ，４Ｈ），３．９３－３．９５（ｍ，２Ｈ），４．０８－４．１２（ｍ，２Ｈ），４．５９（ｄ，Ｊ＝５．４Ｈｚ，２Ｈ），４．８０（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：７．８，１３．６，１７．７，１８．０，２４．２６，２４．２９，２４．８，２５．０，４４．８，５４．９，６１．７，６２．１，７２．８，７４．１，７４．２，８６．６
得られた［（Ｎ_２２１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（７７８ｍｇ、１．７４ｍｍｏｌ）とＬｉＦＳＩ（７５１ｍｇ、４．０２ｍｍｏｌ）とをＣＨ_３ＯＨ（３０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、塩化メチレンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。真空乾燥を行い、無色透明の液体（７８１ｍｇ、純度９９％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．００（ｔ，Ｊ＝７．２Ｈｚ，９Ｈ），１．３５（ｔ，Ｊ＝７．２Ｈｚ，６Ｈ），１．４９－１．５５（ｍ，６Ｈ），１．５８－１．６５（ｍ，６Ｈ），２．２５－２．３０（ｍ，６Ｈ），２．９８（ｓ，３Ｈ），３．３５－３．４２（ｍ，４Ｈ），３．８８－３．８９（ｍ，２Ｈ），４．０２－４．０３（ｍ，２Ｈ），４．４７（ｄ，Ｊ＝５．４Ｈｚ，２Ｈ），４．６８（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：７．７，１３．５，１７．６，１７．９，２４．１８，２４．２１，２４．８，２４．９，４４．７，５５．０，６１．５，６２．０，７２．８，７４．１，７４．２，８６．６ <Compound G'>
The formula below:

A compound G′ ([(N ₂₂₁ )MEM(PBu ₃ )][2FSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (621 mg, 3.91 mmol) in tetrahydrofuran (1.3 mL) under an Ar atmosphere, N,N-diethylmethylamine (356 mg, 4.4 mL) was added at -10°C. 09 mmol) was added dropwise at a rate of 2.874 mL/h, followed by stirring at −10° C. for 2 minutes, followed by stirring at 35° C. for 5 minutes. After adding CH ₃ CN (2.6 mL) and stirring at 35° C. for 5 minutes, tributylphosphine (817 mg, 4.04 mmol) was added and stirring was performed at 35° C. for 5 hours. After distilling off the solvent, the product was washed with diethyl ether and acetone, gel-filtered, and vacuum-dried to obtain [(N ₂₂₁ )MEM(PBu ₃ )][2Cl] (purity 92%) as a colorless transparent liquid. .
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.03-1.06 (m, 9H), 1.40 (t, J=7.2 Hz, 6H), 1.54-1. 60 (m, 6H), 1.63-1.70 (m, 6H), 2.34-2.39 (m, 6H), 3.05 (m, 3H), 3.42-3.49 ( m, 4H), 3.93-3.95 (m, 2H), 4.08-4.12 (m, 2H), 4.59 (d, J = 5.4Hz, 2H), 4.80 ( s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 7.8, 13.6, 17.7, 18.0, 24.26, 24.29, 24.8, 25.0, 44. 8, 54.9, 61.7, 62.1, 72.8, 74.1, 74.2, 86.6
The resulting [( _N221 )MEM( _PBu3 )][2Cl] (778 mg, 1.74 mmol) and LiFSI (751 mg, 4.02 mmol) were dissolved in _CH3OH (30 mL) and stirred overnight at room temperature. . CH ₃ OH was distilled off. Thereafter, the product was dissolved in methylene chloride, washed with water, and the organic phase was separated by liquid separation. Vacuum drying was performed to obtain a colorless transparent liquid (781 mg, purity 99%).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.00 (t, J = 7.2 Hz, 9H), 1.35 (t, J = 7.2 Hz, 6H), 1.49- 1.55 (m, 6H), 1.58-1.65 (m, 6H), 2.25-2.30 (m, 6H), 2.98 (s, 3H), 3.35-3. 42 (m, 4H), 3.88-3.89 (m, 2H), 4.02-4.03 (m, 2H), 4.47 (d, J=5.4Hz, 2H), 4. 68 (s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 7.7, 13.5, 17.6, 17.9, 24.18, 24.21, 24.8, 24.9, 44. 7, 55.0, 61.5, 62.0, 72.8, 74.1, 74.2, 86.6

で表される化合物Ｈ（［（Ｐｉｐ_１）ＭＥＭ（ＰＢｕ_３）］［２ＴＦＳＩ］）を以下のとおり合成した。
Ａｒ雰囲気下にて、１，２－ビスクロロメトキシエタン（１．４３ｇ、９．０２ｍｍｏｌ）をテトラヒドロフラン（３．０ｍＬ）に溶かした後、０℃下でＮ－メチルピペリジン（８６７ｍｇ、８．７４ｍｍｏｌ）を２．９０ｍＬ／ｈの速度で滴下後、０℃で２分間撹拌、続けて３５℃で３０分間撹拌をした。ＣＨ_３ＣＮ（６．０ｍＬ）添加後、３５℃で５分撹拌した後、トリブチルホスフィン（２．１８ｇ、１０．８ｍｍｏｌ）を加え、３５℃で４.５時間撹拌した。溶媒を留去した後、ジエチルエーテルおよびアセトンによる洗浄を行い、ゲルろ過、真空乾燥後、無色透明の液体として［（Ｐｉｐ_１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（純度９１％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０５（ｔ，Ｊ＝７．２Ｈｚ，９Ｈ），１．５２－１．６０（ｍ，６Ｈ），１．６０－１．７２（ｍ，７Ｈ），１．８１－１．８４（ｍ，１Ｈ），１．９５－２．０２（ｍ，４Ｈ），２．３２－２．３７（ｍ，６Ｈ），３．１３（ｓ，３Ｈ），３．３８－３．４９（ｍ，４Ｈ），３．９３－３．９４（ｍ，２Ｈ），４．１１－４．１３（ｍ，２Ｈ），４．４９（ｄ，Ｊ＝５．４Ｈｚ，２Ｈ），４．８７（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：１３．６, １７．７，１８．０，２０．５，２２．２，２４．３，２４．８，２５．０，４５．３，５８．５，６１．７，６２．１，７３．５，７４．２，７４．３
得られた［（Ｐｉｐ_１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（２．１２ｇ、４．６０ｍｍｏｌ）とＬｉＴＦＳＩ（２．８４ｇ、９．８９ｍｍｏｌ）とをＣＨ_３ＯＨ（２０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、塩化メチレンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。真空乾燥を行い、無色透明の液体（２．８０ｇ、純度９３％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０３（ｔ，Ｊ＝７．２Ｈｚ，９Ｈ），１．５２－１．５８（ｍ，６Ｈ），１．６１－１．７０（ｍ，７Ｈ），１．８１－１．８４（ｍ，１Ｈ），１．９１－２．０２（ｍ，４Ｈ），２．２８－２．３４（ｍ，６Ｈ），３．１０（ｓ，３Ｈ），３．３４－３．４４（ｍ，４Ｈ），３．９１－３．９３（ｍ，２Ｈ），４．０８－４．０９（ｍ，２Ｈ），４．５１（ｄ，Ｊ＝５．４Ｈｚ，２Ｈ），４．７８（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：１３．５，１７．６，１７．９，２０．４，２２．１，２４．２，２４．８，２４．９，４５．４，５８．６，６１．６，６２．０，７３．５，７４．２，９２．３，１２１．１（ｑ，Ｊ＝３１８Ｈｚ） <Compound H>
The formula below:

Compound H ([(Pip ₁ )MEM(PBu ₃ )][2TFSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (1.43 g, 9.02 mmol) in tetrahydrofuran (3.0 mL) under Ar atmosphere, N-methylpiperidine (867 mg, 8.74 mmol) was added at 0°C. was added dropwise at a rate of 2.90 mL/h, followed by stirring at 0°C for 2 minutes and then stirring at 35°C for 30 minutes. After adding CH ₃ CN (6.0 mL) and stirring at 35° C. for 5 minutes, tributylphosphine (2.18 g, 10.8 mmol) was added and stirred at 35° C. for 4.5 hours. After distilling off the solvent, the product was washed with diethyl ether and acetone, gel filtered, and vacuum dried to obtain [(Pip ₁ )MEM(PBu ₃ )][2Cl] (purity 91%) as a colorless transparent liquid. .
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.05 (t, J=7.2 Hz, 9H), 1.52-1.60 (m, 6H), 1.60-1. 72 (m, 7H), 1.81-1.84 (m, 1H), 1.95-2.02 (m, 4H), 2.32-2.37 (m, 6H), 3.13 ( s, 3H), 3.38-3.49 (m, 4H), 3.93-3.94 (m, 2H), 4.11-4.13 (m, 2H), 4.49 (d, J = 5.4 Hz, 2H), 4.87 (s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 13.6, 17.7, 18.0, 20.5, 22.2, 24.3, 24.8, 25.0, 45. 3, 58.5, 61.7, 62.1, 73.5, 74.2, 74.3
The resulting [(Pip ₁ )MEM(PBu ₃ )][2Cl] (2.12 g, 4.60 mmol) and LiTFSI (2.84 g, 9.89 mmol) were dissolved in CH ₃ OH (20 mL) and stirred at room temperature. Stir overnight. CH ₃ OH was distilled off. Thereafter, the product was dissolved in methylene chloride, washed with water, and the organic phase was separated by liquid separation. Vacuum drying was performed to obtain a colorless transparent liquid (2.80 g, purity 93%).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.03 (t, J=7.2 Hz, 9H), 1.52-1.58 (m, 6H), 1.61-1. 70 (m, 7H), 1.81-1.84 (m, 1H), 1.91-2.02 (m, 4H), 2.28-2.34 (m, 6H), 3.10 ( s, 3H), 3.34-3.44 (m, 4H), 3.91-3.93 (m, 2H), 4.08-4.09 (m, 2H), 4.51 (d, J=5.4Hz, 2H), 4.78(s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 13.5, 17.6, 17.9, 20.4, 22.1, 24.2, 24.8, 24.9, 45. 4, 58.6, 61.6, 62.0, 73.5, 74.2, 92.3, 121.1 (q, J = 318Hz)

で表される化合物Ｉ（［（Ｐｉｐ_１）ＭＥＭ（ＰＢｕ_３）］［２ＦＳＩ］）を以下のとおり合成した。
Ａｒ雰囲気下にて、１，２－ビスクロロメトキシエタン（１．４４ｇ、９．０４ｍｍｏｌ）をテトラヒドロフラン（３．０ｍＬ）に溶かした後、－１０℃下でＮ－メチルピペリジン（８４１ｍｇ、８．４８ｍｍｏｌ）を２．９０ｍＬ／ｈの速度で滴下後、０℃で２分間撹拌、続けて３５℃で３０分間撹拌をした。ＣＨ_３ＣＮ（６．０ｍＬ）添加後、３５℃で５分撹拌した後、トリブチルホスフィン（２．１６ｇ、１０．７ｍｍｏｌ）を加え、３５℃で５時間撹拌した。溶媒を留去した後、ジエチルエーテルおよびアセトンによる洗浄を行い、ゲルろ過、真空乾燥後、無色透明の液体として［（Ｐｉｐ_１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（純度８８％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０５（ｔ，Ｊ＝７．２Ｈｚ，９Ｈ），１．５２－１．６０（ｍ，６Ｈ），１．６０－１．７２（ｍ，７Ｈ），１．８１－１．８４（ｍ，１Ｈ），１．９５－２．０２（ｍ，４Ｈ），２．３２－２．３７（ｍ，６Ｈ），３．１３（ｓ，３Ｈ），３．３８－３．４９（ｍ，４Ｈ），３．９３－３．９４（ｍ，２Ｈ），４．１１－４．１３（ｍ，２Ｈ），４．４９（ｄ，Ｊ＝５．４Ｈｚ，２Ｈ），４．８７（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：１３．６, １７．７，１８．０，２０．５，２２．２，２４．３，２４．８，２５．０，４５．３，５８．５，６１．７，６２．１，７３．５，７４．２，７４．３
得られた［（Ｐｉｐ_１）ＭＥＭ（ＰＢｕ_３）］［２Ｃｌ］（１．２４ｇ、２．７０ｍｍｏｌ）とＬｉＦＳＩ（１．０８ｇ、５．７６ｍｍｏｌ）とをＣＨ_３ＯＨ（３０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、塩化メチレンに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。真空乾燥を行い、無色透明の液体（２．１０ｇ、純度９３％）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０３（ｔ，Ｊ＝７．２Ｈｚ，９Ｈ），１．５２－１．６０（ｍ，６Ｈ），１．６０－１．７０（ｍ，６Ｈ），１．８０－１．８４（ｍ，１Ｈ），１．９４－２．０１（ｍ，４Ｈ），２．２７－２．３１（ｍ，６Ｈ），３．１０（ｓ，３Ｈ），３．３５－３．４４（ｍ，４Ｈ），３．９１－３．９３（ｍ，２Ｈ），４．０８－４．１０（ｍ，２Ｈ），４．４９（ｄ，Ｊ＝５．４Ｈｚ，２Ｈ），４．７６（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：１３．５，１７．６，１７．９，２０．４，２２．０，２４．１，２４．８，４５．４，５８．６，６１．５，６１．９，７３．５，７４．１，７４．２，９２．２ <Compound H'>
The formula below:

Compound I ([(Pip ₁ )MEM(PBu ₃ )][2FSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (1.44 g, 9.04 mmol) in tetrahydrofuran (3.0 mL) under Ar atmosphere, N-methylpiperidine (841 mg, 8.48 mmol) was dissolved at −10° C. ) was added dropwise at a rate of 2.90 mL/h, followed by stirring at 0° C. for 2 minutes and then stirring at 35° C. for 30 minutes. After adding CH ₃ CN (6.0 mL) and stirring at 35° C. for 5 minutes, tributylphosphine (2.16 g, 10.7 mmol) was added and stirring was performed at 35° C. for 5 hours. After distilling off the solvent, the residue was washed with diethyl ether and acetone, gel filtered, and vacuum dried to obtain [(Pip ₁ )MEM(PBu ₃ )][2Cl] (purity 88%) as a colorless transparent liquid. .
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.05 (t, J=7.2 Hz, 9H), 1.52-1.60 (m, 6H), 1.60-1. 72 (m, 7H), 1.81-1.84 (m, 1H), 1.95-2.02 (m, 4H), 2.32-2.37 (m, 6H), 3.13 ( s, 3H), 3.38-3.49 (m, 4H), 3.93-3.94 (m, 2H), 4.11-4.13 (m, 2H), 4.49 (d, J = 5.4 Hz, 2H), 4.87 (s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): ¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 13.6, 17.7, 18.0, 20.5, 22. 2, 24.3, 24.8, 25.0, 45.3, 58.5, 61.7, 62.1, 73.5, 74.2, 74.3
The resulting [(Pip ₁ )MEM(PBu ₃ )][2Cl] (1.24 g, 2.70 mmol) and LiFSI (1.08 g, 5.76 mmol) were dissolved in CH ₃ OH (30 mL) and stirred at room temperature. Stir overnight. CH ₃ OH was distilled off. Thereafter, the product was dissolved in methylene chloride, washed with water, and the organic phase was separated by liquid separation. Vacuum drying was performed to obtain a colorless transparent liquid (2.10 g, purity 93%).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.03 (t, J=7.2 Hz, 9H), 1.52-1.60 (m, 6H), 1.60-1. 70 (m, 6H), 1.80-1.84 (m, 1H), 1.94-2.01 (m, 4H), 2.27-2.31 (m, 6H), 3.10 ( s, 3H), 3.35-3.44 (m, 4H), 3.91-3.93 (m, 2H), 4.08-4.10 (m, 2H), 4.49 (d, J = 5.4 Hz, 2H), 4.76 (s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 13.5, 17.6, 17.9, 20.4, 22.0, 24.1, 24.8, 45.4, 58. 6, 61.5, 61.9, 73.5, 74.1, 74.2, 92.2

で表される化合物Ｆ’（ＰＢｕ_３）_２ＭＥＭ］［２ＴＦＳＩ］）を以下のとおり合成した。
１，２－ビスクロロメトキシエタン（２．３０ｇ、１４．５ｍｍｏｌ）をＣＨ_２Ｃｌ_２（２５ｍＬ）に溶かした後、トリブチルホスフィン（６．３９ｇ、３１．６ｍｍｏｌ）を加え、Ａｒ雰囲気下にて一晩室温で撹拌した。溶媒を留去した後、ジエチルエーテルによる洗浄を行い、真空乾燥を行い、白色の固体として［（ＰＢｕ_３）_２ＭＥＭ］［２Ｃｌ］（ｑｕａｎｔ）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０４(ｔ，Ｊ＝７．２６Ｈｚ，１８Ｈ)，１．５２－１．５８(ｍ，１２Ｈ)，１．６１－１．６７(ｍ，１２Ｈ)，２．２９－２．３４(ｍ，１２Ｈ)，３．８９（ｓ，４Ｈ），４．５２（ｓ，４Ｈ）；
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：１３．９，１８．２（ｄ，Ｊ＝４６．５Ｈｚ），２４．９（ｄ，Ｊ＝８４．０Ｈｚ），６２．２（ｄ，Ｊ＝６４．５Ｈｚ），７４．４
得られた［（ＰＢｕ_３）_２ＭＥＭ］［２Ｃｌ］（２．８６ｇ、５．０９ｍｍｏｌ）とＬｉＦＳＩ（２．４９ｇ、１３．３ｍｍｏｌ）をＣＨ_３ＯＨ（５０ｍＬ）に溶かし、室温で一晩撹拌した。ＣＨ_３ＯＨを留去した。その後、酢酸エチルに生成物を溶解させてから水で洗浄し、分液により有機相を分離した。真空乾燥を行い、白色固体（ｑｕａｎｔ）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：１．０１（ｔ，Ｊ＝７．２Ｈｚ，１８Ｈ），１．５１－１．５６（ｍ，１２Ｈ），１．５８－１．６４（ｍ，１２Ｈ），２．２５－２．３０（ｍ，１２Ｈ），３．８７（ｓ，４Ｈ），４．４６（ｄ，Ｊ＝４．８Ｈｚ，４Ｈ）；
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：１３．６，１７．６，１７．９，２４．１９，２４．２２，２４．８，２４．９，６１．５，６２．０，７４．２，７４．３ <Compound F'>
The formula below:

A compound F′(PBu ₃ ) ₂ MEM][2TFSI]) represented by was synthesized as follows.
After dissolving 1,2-bischloromethoxyethane (2.30 g, 14.5 mmol) in CH ₂ Cl ₂ (25 mL), tributylphosphine (6.39 g, 31.6 mmol) was added and the mixture was stirred under Ar atmosphere. Stir overnight at room temperature. After distilling off the solvent, the residue was washed with diethyl ether and vacuum dried to obtain [(PBu ₃ ) ₂ MEM][2Cl](quant) as a white solid.
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.04 (t, J=7.26 Hz, 18H), 1.52-1.58 (m, 12H), 1.61-1. 67 (m, 12H), 2.29-2.34 (m, 12H), 3.89 (s, 4H), 4.52 (s, 4H);
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 13.9, 18.2 (d, J = 46.5 Hz), 24.9 (d, J = 84.0 Hz), 62.2 ( d, J = 64.5 Hz), 74.4
The resulting [(PBu ₃ ) ₂ MEM][2Cl] (2.86 g, 5.09 mmol) and LiFSI (2.49 g, 13.3 mmol) were dissolved in CH ₃ OH (50 mL) and stirred overnight at room temperature. . The _CH3OH was distilled off. Thereafter, the product was dissolved in ethyl acetate, washed with water, and the organic phase was separated by liquid separation. Vacuum drying was performed to obtain a white solid (quant).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 1.01 (t, J=7.2 Hz, 18 H), 1.51-1.56 (m, 12 H), 1.58-1. 64 (m, 12H), 2.25-2.30 (m, 12H), 3.87 (s, 4H), 4.46 (d, J = 4.8Hz, 4H);
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): 13.6, 17.6, 17.9, 24.19, 24.22, 24.8, 24.9, 61.5, 62. 0, 74.2, 74.3

で表される化合物ＣＢ’（［Ｐｙｒ_１ＭＥＭ］［ＦＳＩ］）を以下のとおり合成した。
Ａｒ雰囲気下にて、Ｎ－メチルピロリジン（４．３６ｇ、５１．１ｍｍｏｌ）をアセトニトリル（２５ｍＬ）に溶かした後、０℃下で２－メトキシエトキシメチルクロライド（６．５４ｇ、５２．５ｍｍｏｌ）を滴下後、０℃で終夜撹拌した。溶媒を留去した後、活性炭とメタノールを加えて室温にて撹拌した。ろ過によって活性炭を除去したのち溶媒を留去し、減圧条件下で乾燥し、［Ｐｙｒ_１ＭＥＭ］［Ｃｌ］（１２．３ｇ、ｑｕａｎｔ）を得た。
^１Ｈ－ＮＭＲ（ＣＤ_３ＯＤ，６００ＭＨｚ）δ（ｐｐｍ）：２．２０－２．３１（ｍ，４Ｈ），３．１５（ｓ，３Ｈ），３．４３（ｓ，３Ｈ），３．４６－３．５０（ｍ，２Ｈ），３．６５（ｔ，Ｊ＝４．２Ｈｚ，２Ｈ），３．６６－３．７０（ｍ，２Ｈ），４．０３（ｔ，Ｊ＝４．２Ｈｚ，２Ｈ），４．７７（ｓ，２Ｈ）
^１３Ｃ－ＮＭＲ（ＣＤ_３ＯＤ，１５０Ｈｚ）δ（ｐｐｍ）：δ２３．２，４８．０，５９．３，６２．１，７２．９，７３．５，９１．３
得られた［Ｐｙｒ_１ＭＥＭ］［Ｃｌ］（４．２ｇ、２０．０ｍｍｏｌ）とＬｉＦＳＩ（１３．９ｇ、２１．１ｍｍｏｌ）をメタノール（３０ｍＬ）で溶かし、室温で２１時間撹拌した。塩化メチレンにて抽出したのち、得られた有機層を水で洗浄した。その後、減圧条件下で乾燥し、［Ｐｙｒ_１ＭＥＭ］［ＦＳＩ］（２．７６ｇ、７．７９ｍｍｏｌ）を得た。目的物の生成は^１Ｈ－ＮＭＲにより確認した。
^１Ｈ－ＮＭＲ（６００ＭＨｚ，ＣＤＣｌ_３）δ（ｐｐｍ）：２．２５－２．３２（ｍ，４Ｈ），３．１４（ｓ，３Ｈ），３．３９（ｓ，３Ｈ），３．４０－３．４５（ｍ，２Ｈ），３．５９（ｔ，Ｊ＝４．２Ｈｚ，２Ｈ），３．６８－３．７１（ｍ，２Ｈ），３．９９（ｔ，Ｊ＝４．２Ｈｚ，２Ｈ），４．７０（ｓ，２Ｈ） <Compound CB'>
The formula below:

A compound CB′ ([Pyr ₁ MEM][FSI]) represented by was synthesized as follows.
After dissolving N-methylpyrrolidine (4.36 g, 51.1 mmol) in acetonitrile (25 mL) under Ar atmosphere, 2-methoxyethoxymethyl chloride (6.54 g, 52.5 mmol) was added dropwise at 0°C. After that, the mixture was stirred overnight at 0°C. After distilling off the solvent, activated carbon and methanol were added and the mixture was stirred at room temperature. After removing activated carbon by filtration, the solvent was distilled off and dried under reduced pressure to obtain [Pyr ₁ MEM][Cl] (12.3 g, quant).
¹ H-NMR (CD ₃ OD, 600 MHz) δ (ppm): 2.20-2.31 (m, 4H), 3.15 (s, 3H), 3.43 (s, 3H), 3.46 -3.50 (m, 2H), 3.65 (t, J = 4.2Hz, 2H), 3.66-3.70 (m, 2H), 4.03 (t, J = 4.2Hz, 2H), 4.77(s, 2H)
¹³ C-NMR (CD ₃ OD, 150 Hz) δ (ppm): δ 23.2, 48.0, 59.3, 62.1, 72.9, 73.5, 91.3
The resulting [Pyr ₁ MEM][Cl] (4.2 g, 20.0 mmol) and LiFSI (13.9 g, 21.1 mmol) were dissolved in methanol (30 mL) and stirred at room temperature for 21 hours. After extraction with methylene chloride, the resulting organic layer was washed with water. Then, it was dried under reduced pressure conditions to obtain [Pyr ₁ MEM][FSI] (2.76 g, 7.79 mmol). Production of the target product was confirmed by ¹ H-NMR.
¹ H-NMR (600 MHz, CDCl ₃ ) δ (ppm): 2.25-2.32 (m, 4H), 3.14 (s, 3H), 3.39 (s, 3H), 3.40- 3.45 (m, 2H), 3.59 (t, J = 4.2Hz, 2H), 3.68-3.71 (m, 2H), 3.99 (t, J = 4.2Hz, 2H) ), 4.70 (s, 2H)

“FSI ⁻ ” represents a bis(fluorosulfonyl)imide anion ([N(FSO ₂ ) ₂ ] ⁻ ).

Compounds A' to H', and compounds G and H were also measured for ionic conductivity, potential window, and 10% weight loss temperature by the methods described above. Table 6 shows the results.

A composite electrolyte having the composition shown in Table 7 was prepared in the same manner as in Example A1, and I _ini and I _lim were measured in the same manner as in Example A1. Table 7 shows the results. A composite electrolyte having the composition shown in Table 8 was prepared in the same manner as in Example B1, and I _ini and I _lim were measured in the same manner as in Example B1. Table 8 shows the results.

The present invention includes the following exemplary embodiments [1]-[12].
[1]
two moieties each containing a heteroatom with a formal positive charge;
A dicationic ionic liquid containing a cation comprising:
The ionic liquid, wherein the linking group is represented by the formula: -CR ¹ R ² OCR ³ R ⁴ CR ⁵ R ⁶ OCR ⁷ R ⁸ -.
(wherein R ¹ to R ⁸ are each a hydrogen atom, a fluorine atom, or a monovalent organic group having 1 to 20 carbon atoms, and the organic group is represented by the formula —R ^A —(X—R ^B ) _n —R ^C , where R ^A is a covalent bond or a substituted or unsubstituted divalent hydrocarbon group, and X is —O—, —S—, —C(═O)—, —C (=O) O- or -OC(=O)-, R ^B is a covalent bond or a substituted or unsubstituted divalent hydrocarbon group, and R ^C is a substituted or unsubstituted monovalent carbon is a hydrogen group, and n is 0 or more, provided that 4 or more of R ¹ to R ⁸ are hydrogen atoms.)
[2]
The ionic liquid of [2], wherein all of R ¹ to R ⁸ are hydrogen atoms.
[3]
The ionic liquid of [1] or [2], which has a 10% weight loss temperature of 280° C. or higher when measured at a heating rate of 5° C./min.
[4]
The ionic liquid according to any one of [1] to [3], wherein the two portions have different chemical structures.
[5]
an ionic liquid,
When a composite electrolyte containing the ionic liquid and a lithium salt and having a concentration of the lithium salt of 0.5 mol/kg in terms of lithium ions is prepared, the composite electrolyte at 25° C. is represented by the following formula: An ionic liquid having a ratio of 10% or more.
Formula: I _lim /I _ini
(In the formula, I _lim is the limiting current density of the composite electrolyte, and I _ini is the start of application of the constant voltage when a constant voltage is applied to the composite electrolyte at the voltage value that first reaches the limiting current density. is the current density one second after ).
[6]
The ionic liquid of [6], which is a dicationic ionic liquid.
[7]
Any of [1] to [6], wherein the upper limit of the potential window of the ionic liquid is 2.0 V or more based on Fc/Fc ⁺ electrode, and the ion conductivity at 25 ° C. is 0.1 S / cm or more. or an ionic liquid.
[8]
A composite electrolyte comprising a lithium salt and the ionic liquid of any one of [1] to [7].
[9]
The composite electrolyte of [8], further comprising a viscosity reducing agent.
[10]
A composite electrolyte comprising an ionic liquid and a lithium salt,
A composite electrolyte having a ratio represented by the following formula of 20% or more.
Formula: I _lim /I _ini
(In the formula, I _lim is the limiting current density, and when the current density value is measured while applying a constant voltage of 0.1 V to the composite electrolyte at 25 ° C., the current density is substantially constant for 1 hour or more. and I _ini is the current density 1 second after starting to apply a constant voltage of 0.1 V to the composite electrolyte.)
[11]
The composite electrolyte of [10], wherein the limiting current density value is 90 μA/cm ² or more.
[12]
The composite electrolyte of [10] or [11], wherein the ionic liquid is a dicationic ionic liquid.

Claims (9)

two moieties each containing a heteroatom with a formal positive charge;
A dication-type ionic liquid containing a cation comprising:
The ionic liquid, wherein the linking group is represented by the formula: -CR ¹ R ² OCR ³ R ⁴ CR ⁵ R ⁶ OCR ⁷ R ⁸ -.
(wherein R ¹ to R ⁸ are each a hydrogen atom, a fluorine atom, or a monovalent organic group having 1 to 20 carbon atoms, and the organic group is represented by the formula —R ^A —(X—R ^B ) _n —R ^C , where R ^A is a covalent bond or a substituted or unsubstituted divalent hydrocarbon group, and X is —O—, —S—, —C(═O)—, —C (=O) O- or -OC(=O)-, R ^B is a covalent bond or a substituted or unsubstituted divalent hydrocarbon group, and R ^C is a substituted or unsubstituted monovalent carbon is a hydrogen group, and n is 0 or more, provided that 4 or more of R ¹ to R ⁸ are hydrogen atoms.) The ionic liquid according to claim 1, wherein all of R ¹ to R ⁸ are hydrogen atoms. 3. The ionic liquid according to claim 1, which has a 10% weight loss temperature of 280[deg.] C. or higher when measured at a heating rate of 5[deg.] C./min. 3. The ionic liquid according to claim 1 or 2, wherein the two moieties have chemical structures different from each other. an ionic liquid,
When a composite electrolyte containing the ionic liquid and a lithium salt and having a concentration of the lithium salt of 0.5 mol/kg in terms of lithium ions is prepared, the composite electrolyte at 25° C. is represented by the following formula: An ionic liquid having a ratio of 10% or more.
Formula: I _lim /I _ini
(In the formula, I _lim is the limiting current density of the composite electrolyte, and I _ini is the start of application of the constant voltage when a constant voltage is applied to the composite electrolyte at the voltage value that first reaches the limiting current density. is the current density one second after ). 6. The ionic liquid according to claim 5, which is a dicationic ionic liquid. The ion according to claim 1 or 5, wherein the upper limit of the potential window of the ionic liquid is 2.0 V or more based on the Fc / Fc ⁺ electrode, and the ion conductivity at 25 ° C. is 0.1 S / cm or more. liquid. A composite electrolyte comprising a lithium salt and the ionic liquid according to claim 1 or 5. 9. The composite electrolyte of Claim 8, further comprising a viscosity reducing agent.

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