SOLID ELECTROLYTE, ELECTRICITY STORAGE DEVICE AND METHOD FOR PRODUCING SOLID ELECTROLYTE

Abstract

Provided are plastic crystal-type solid electrolyte having high ion conductivity and a power storage device using the solid electrolyte. The solid electrolyte contains a plastic crystal doped with an electrolyte. The plastic crystal contains two or more types of cations in total, at least one of which is selected from the group of imidazoliums and quaternary ammoniums.

Claims

1. A solid electrolyte, comprising a plastic crystal doped with an electrolyte, wherein the plastic crystal contains two or more types of cations in total, at least one of which is selected from the group of imidazoliums and quaternary ammoniums.

2. The solid electrolyte according to claim 1, wherein the plastic crystal contains two types of cations selected from the group of the quaternary ammoniums.

3. The solid electrolyte according to claim 1, wherein the plastic crystal contains two types of cations selected from the group of the imidazoliums.

4. The solid electrolyte according to claim 1, wherein the plastic crystal contains: one type of cation selected from the group of the imidazoliums; and one type of cation selected from the group of the quaternary ammoniums.

5. The solid electrolyte according to claim 1, wherein the plastic crystal contains: one type of cation selected from the group of imidazoliums and quaternary ammoniums; and another type of cation excluding the imidazoliums and the quaternary ammoniums.

6. The solid electrolyte according to claim 1, wherein the imidazoliums are a 1,3-dialkylimidazolium or a 1,2,3-trialkylimidazolium represented by the following chemical formula (A): ##STR00022## wherein n and m represent integers of 1 or more and 3 or less, and p represents 0 or 1.

7. The solid electrolyte according to claim 1, wherein the quaternary ammoniums include a tetraalkylammonium represented by the following chemical formula (B) and substituted with a linear alkyl group having any number of carbon atoms: ##STR00023## wherein a, b, c, and d represent integers of 1 or more, and the number of carbon atoms may be any number.

8. The solid electrolyte according to claim 1, wherein the quaternary ammoniums include a five-membered ring ammonium pyrrolidinium represented by the following chemical formula (C) and spiro-pyrrolidinium represented by the following chemical formula (D): ##STR00024## wherein R1 and R2 represent a methyl group, an ethyl group, or an isopropyl group; ##STR00025##

9. The solid electrolyte according to claim 5, wherein the another type of cation is one of phosphoniums represented by the following chemical formula (E): ##STR00026## wherein e, f, g, and h represent integers of 1 or more, and the number of carbon atoms may be any number.

10. The solid electrolyte according to claim 1, wherein the plastic crystal contains two or more types of anions.

11. A power storage device, comprising: the solid electrolyte according to claim 1; and both electrodes disposed opposite to each other with the solid electrolyte sandwiched therebetween.

12. The power storage device according to claim 11, wherein one or both of both the electrodes are polarizable electrode having: an active material layer composed of a porous material; and a current collector, and an electric double layer is formed on an interface between the polarizable electrode and the solid electrolyte.

13. (canceled)

14. The solid electrolyte according to claim 2, wherein the quaternary ammoniums include a tetraalkylammonium represented by the following chemical formula (B) and substituted with a linear alkyl group having any number of carbon atoms: ##STR00027## wherein a, b, c, and d represent integers of 1 or more, and the number of carbon atoms may be any number.

15. The solid electrolyte according to claim 2, wherein the quaternary ammoniums include a five-membered ring ammonium pyrrolidinium represented by the following chemical formula (C) and spiro-pyrrolidinium represented by the following chemical formula (D): ##STR00028## wherein R1 and R2 represent a methyl group, an ethyl group, or an isopropyl group; ##STR00029##

16. The solid electrolyte according to claim 3, wherein the imidazoliums are a 1,3-dialkylimidazolium or a 1,2,3-trialkylimidazolium represented by the following chemical formula (A): ##STR00030## wherein n and m represent integers of 1 or more and 3 or less, and p represents 0 or 1.

17. The solid electrolyte according to claim 4, wherein the quaternary ammoniums include a tetraalkylammonium represented by the following chemical formula (B) and substituted with a linear alkyl group having any number of carbon atoms: ##STR00031## wherein a, b, c, and d represent integers of 1 or more, and the number of carbon atoms may be any number.

18. The solid electrolyte according to claim 4, wherein the quaternary ammoniums include a five-membered ring ammonium pyrrolidinium represented by the following chemical formula (C) and spiro-pyrrolidinium represented by the following chemical formula (D): ##STR00032## wherein R1 and R2 represent a methyl group, an ethyl group, or an isopropyl group; ##STR00033##

19. The solid electrolyte according to claim 2, wherein the plastic crystal contains two or more types of anions.

20. A method of manufacturing a solid electrolyte, comprising: a step of producing a plastic crystal containing two or more types of cations at least one of which is selected from the group of imidazoliums and quaternary ammoniums.

Description

EXAMPLES

Examples 1 to 5

[0098] A plastic crystal containing two types of quaternary ammonium as cations was used to produce solid electrolytes for an electric double-layer capacitor of Examples 1 to 5. Ion conductivity of the solid electrolytes of Examples 1 to 5 was measured.

[0099] The solid electrolyte of Example 1 contains N-ethyl-N-methylpyrrolidinium (P12), which is a five-membered ring pyrrolidinium, as the first type of quaternary ammonium. The solid electrolyte of Example 1 also contains spiro-pyrrolidinium (SBP) as the second type of quaternary ammonium. The P12 cation and the SBP cation are contained in the plastic crystal at a molar ratio of 1:1.

[0100] The solid electrolyte of Example 2 contains N-isopropyl-N-methylpyrrolidinium (P13iso), which is a five-membered ring pyrrolidinium, as the first type of quaternary ammonium. The solid electrolyte of Example 1 also contains spiro-pyrrolidinium (SBP) as the second type of quaternary ammonium. The P13iso cation and the SBP cation are contained in the plastic crystal at a molar ratio of 1:1.

[0101] The solid electrolyte of Example 3 contains N,N-diethylpyrrolidinium (P22), which is a five-membered ring pyrrolidinium, as the first type of quaternary ammonium. The solid electrolyte of Example 1 also contains spiro-pyrrolidinium (SBP) as the second type of quaternary ammonium. The P22 cation and the SBP cation are contained in the plastic crystal at a molar ratio of 1:1.

[0102] The solid electrolyte of Example 4 contains N-ethyl-N-methylpyrrolidinium (P12), which is a five-membered ring pyrrolidinium, as the first type of quaternary ammonium. The solid electrolyte of Example 1 also contains N,N-diethylpyrrolidinium (P22), which is also a five-membered ring pyrrolidinium, as the second type of quaternary ammonium. The P12 cation and the P22 cation are contained in the plastic crystal at a molar ratio of 1:1.

[0103] The solid electrolyte of Example 5 contains triethylmethylammonium (TEMA), which is a tetraalkylammonium, as the first type of quaternary ammonium. The solid electrolyte of Example 1 also contains N,N-diethylpyrrolidinium (P22), which is a five-membered ring pyrrolidinium, as the second type of quaternary ammonium. The TEMA cation and the P22 cation are contained in the plastic crystal at a molar ratio of 1:1.

[0104] A method of manufacturing the solid electrolyte of each Example is same and is as follows. First, an anion constituting the plastic crystal of each Example was N,N-hexafluoro-1,3-disulfonylamide anion (CFSA anion). That is, a plastic crystal constituted with the first type of anion and the CFSA cation and a plastic crystal constituted with the second type of anion and the CFSA cation were added into a vial bottle at a molar ratio of 1:1.

[0105] The P12CFSA plastic crystal containing the P12 cation and the CFSA anion was prepared as follows. First, an aqueous solution of a halide in which the P12 cation was halogenated with bromine Br was prepared. An aqueous solution of an alkali metal salt between the CFSA anion and lithium Li was prepared. Into the aqueous solution of the halide, the aqueous solution of the alkali metal salt was gradually dropped to perform an ion-exchange reaction. After the ion-exchange reaction, dichloromethane was mixed, an organic solvent layer was extracted from separated layers separated into an aqueous layer and the organic solvent layer, and active carbon was added to be stirred overnight. Then, a precipitate was recovered with filtration, and this precipitate was dried to obtain the plastic crystal.

[0106] The SBPCFSA plastic crystal containing the SBP cation and the CFSA anion was prepared as follows. First, an aqueous solution of a halide in which the SBP cation was halogenated with chlorine Cl was prepared. An aqueous solution of an alkali metal salt between the CFSA anion and lithium Li was prepared. Into the aqueous solution of the halide, the aqueous solution of the alkali metal salt was gradually dropped to perform an ion-exchange reaction. After the ion-exchange reaction, dichloromethane was mixed, an organic solvent layer was extracted from separated layers separated into an aqueous layer and the organic solvent layer, and active carbon was added to be stirred overnight. Then, a precipitate was recovered with filtration, and this precipitate was dried to obtain the plastic crystal.

[0107] The P13isoCFSA plastic crystal containing the P13iso cation and the CFSA anion was prepared as follows. First, an aqueous solution of a halide in which the P13iso cation was halogenated with iodine I was prepared. An aqueous solution of an alkali metal salt between the CFSA anion and lithium Li was prepared. Into the aqueous solution of the halide, the aqueous solution of the alkali metal salt was gradually dropped to perform an ion-exchange reaction. After the ion-exchange reaction, dichloromethane was mixed, an organic solvent layer was extracted from separated layers separated into an aqueous layer and the organic solvent layer, and active carbon was added to be stirred overnight. Then, a precipitate was recovered with filtration, and this precipitate was dried to obtain the plastic crystal.

[0108] The P22CFSA plastic crystal containing the P22 cation and the CFSA anion was prepared as follows. First, an aqueous solution of a halide in which the P22 cation was halogenated with iodine I was prepared. An aqueous solution of an alkali metal salt between the CFSA anion and lithium Li was prepared. Into the aqueous solution of the halide, the aqueous solution of the alkali metal salt was gradually dropped to perform an ion-exchange reaction. After the ion-exchange reaction, dichloromethane was mixed, an organic solvent layer was extracted from separated layers separated into an aqueous layer and the organic solvent layer, and active carbon was added to be stirred overnight. Then, a precipitate was recovered with filtration, and this precipitate was dried to obtain the plastic crystal.

[0109] The TEMACFSA plastic crystal containing the TEMA cation and the CFSA anion was prepared as follows. First, an aqueous solution of a halide in which the TEMA cation was halogenated with chlorine Cl was prepared. An aqueous solution of an alkali metal salt between the CFSA anion and lithium Li was prepared. Into the aqueous solution of the halide, the aqueous solution of the alkali metal salt was gradually dropped to perform an ion-exchange reaction. After the ion-exchange reaction, dichloromethane was mixed, an organic solvent layer was extracted from separated layers separated into an aqueous layer and the organic solvent layer, and active carbon was added to be stirred overnight. Then, a precipitate was recovered with filtration, and this precipitate was dried to obtain the plastic crystal.

[0110] Into the vial bottle, an electrolyte SBPBF.sub.4 (spiro-bipyrrolidinium tetrafluoroborate, manufactured by Tokyo Chemical Industry Co., Ltd.) was further added so that the concentration was 30 mol % relative to the total of the plastic crystals, and acetonitrile (Wako Pure Chemical Industries, Ltd.) was added so that the solid content concentration of the total of the plastic crystals and the electrolyte was 10 wt %. This acetonitrile solution was dropped on a glass separator, and dried at 80° C. to evaporate acetonitrile. This evaporation procedure was repeated three times. The glass separator immersed with the solid electrolyte by this evaporation procedure was dried under a vacuum environment at 80° C. for 12 hours, further dried under a vacuum environment at 120° C. for 3 hours, and further dried under a vacuum environment at 150° C. for 2 hours for removing moisture to obtain the solid electrolyte of each Example.

[0111] Then, the ion conductivity in each Example was measured. That is, the glass separator immersed with the solid electrolyte was sandwiched with two platinum electrodes for disposing the electrodes opposite to each other with electrode pressing to assemble a bipolar sealed cell (manufactured by TOYO SYSTEM Co., LTD.). An impedance was measured, and the ion conductivity was calculated from the measurement result of the impedance and a thickness of the glass separator permeated with the solid electrolyte. The following Table 1 shows the measurement results of this ion conductivity.

TABLE-US-00001 TABLE 1 Plastic crystal 1 Plastic crystal 2 Ion Ion Ion conductivity conductivity conductivity in Example Electrolyte Type (S/cm) Type (S/cm) (S/cm) Example 1 SBPBF.sub.4 P12CFSA 2.52 × 10.sup.−7 SBPCFSA 2.28 × 10.sup.−7 5.23 × 10.sup.−5 Example 2 P13iso CFSA 3.46 × 10.sup.−8 SBPCFSA 2.28 × 10.sup.−7 6.13 × 10.sup.−5 Example 3 P22CFSA 5.83 × 10.sup.−7 SBPCFSA 2.26 × 10.sup.−7 1.39 × 10.sup.−5 Example 4 P12CFSA 2.52 × 10.sup.−7 P22CFSA 5.63 × 10.sup.−7 2.74 × 10.sup.−6 Example 5 TEMACFSA 2.67 × 10.sup.−5 P12CFSA 2.52 × 10.sup.−7 9.15 × 10.sup.−6

[0112] Table 1 also shows ion conductivity of a solid electrolyte using each plastic crystal alone. This comparative solid electrolyte was produced under the same condition as of the solid electrolyte of each Example except for being constituted with one type of plastic crystal.

[0113] As shown in Table 1, it can be confirmed that the ion conductivity of the solid electrolyte for an electric double-layer capacitor of each Example increases at least 10 times, and at maximum more than 300 times compared with the solid electrolyte using one type of plastic crystal. From the results, the solid electrolyte using the plastic crystal containing the two types of cations selected from the group of the quaternary ammoniums has been confirmed to have increased ion conductivity.

Example 6

[0114] A solid electrolyte for an electric double-layer capacitor of Example 6 was produced by using a plastic crystal containing two types of imidazolium as a cation. Then, ion conductivity of the solid electrolyte of Example 6 was measured. The solid electrolyte of Example 6 contains 1-ethyl-3-methylimidazolium (EMI) as the first type of imidazolium. The solid electrolyte of Example 6 also contains 1,3-dimethylimidazolium (DMI) as the second type of imidazolium. The EMI cation and the DMI cation are contained in the plastic crystal at a molar ratio of 1:1.

[0115] An anion constituting the plastic crystal of Example 6 was N,N-hexafluoro-1,3-disulfonylamide anion (CFSA anion). A method of manufacturing the solid electrolyte of Example 6 was the same condition and the same manufacturing method as in Examples 1 to 5. The first type of plastic crystal and the second type of plastic crystal were added into a vial bottle at a molar ratio of 1:1.

[0116] Then, the ion conductivity of the solid electrolyte of Example 6 was measured. The following Table 2 shows the results. The measuring method and calculating method of the ion conductivity are same as in Examples 1 to 5. Table 2 also shows ion conductivity of a solid electrolyte using each plastic crystal alone. This comparative solid electrolyte was produced under the same condition as of the solid electrolyte of each Example except for being constituted with one type of plastic crystal.

TABLE-US-00002 TABLE 2 Plastic crystal 1 Plastic crystal 2 Ion Ion Ion conductivity conductivity conductivity in Example Electrolyte Type (S/cm) Type (S/cm) (S/cm) Example 6 SBPBF.sub.4 EMICFSA 5.19 × 10.sup.−4 DMICFSA 3.46 × 10.sup.−4 3.09 × 10.sup.−3

[0117] As shown in Table 2, it can be confirmed that the ion conductivity of the solid electrolyte for an electric double-layer capacitor of Example 6 increases at least 10 times or more compared with the solid electrolyte using one type of plastic crystal. From the results, the solid electrolyte using the plastic crystal containing the two types of cations selected from the group of the imidazolium has been confirmed to have increased ion conductivity.

Examples 7 to 11

[0118] One type of cation was selected from the imidazoliums, one type of cation was selected from the quaternary ammoniums, and solid electrolytes for an electric double-layer capacitor of Examples 7 to 11 were produced by using a plastic crystal containing the two types of cations. Then, ion conductivity of the solid electrolytes of Example 7 to 11 was measured.

[0119] The solid electrolyte of Example 7 contains 1-ethyl-3-methylimidazolium (EMI) as the first type of imidazolium. The solid electrolyte of Example 7 also contains triethylmethylammonium (TEMA) as the second type of quaternary ammonium. The EMI cation and the TEMA cation are contained in the plastic crystal at a molar ratio of 1:1.

[0120] The solid electrolyte of Example 8 contains 1-ethyl-3-methylimidazolium (EMI) as the first type of imidazolium. The solid electrolyte of Example 8 also contains N-ethyl-N-methylpyrrolidinium (P12) as the second type of quaternary ammonium. The EMI cation and the P12 cation are contained in the plastic crystal at a molar ratio of 1:1.

[0121] The solid electrolyte of Example 9 contains 1-ethyl-3-methylimidazolium (EMI) as the first type of imidazolium. The solid electrolyte of Example 9 also contains spiro-pyrrolidinium (SBP) as the second type of quaternary ammonium. The EMI cation and the SBP cation are contained in the plastic crystal at a molar ratio of 1:1.

[0122] The solid electrolyte of Example 10 contains the first 1,3-dimethylimidazolium (DMI). The solid electrolyte of Example 10 also contains spiro-pyrrolidinium (SBP) as the second type of quaternary ammonium. The DMI cation and the SBP cation are contained in the plastic crystal at a molar ratio of 1:1.

[0123] The solid electrolyte of Example 11 contains 1-methyl-3-propylimidazolium (MPI) as the first type of imidazolium. The solid electrolyte of Example 11 also contains spiro-pyrrolidinium (SBP) as the second type of quaternary ammonium. The MPI cation and the SBP cation are contained in the plastic crystal at a molar ratio of 1:1.

[0124] Then, the ion conductivity of the solid electrolytes of Examples 7 to 11 was measured. The following Table 3 shows the results. The measuring method and calculating method of the ion conductivity are same as in Examples 1 to 5. Table 3 also shows ion conductivity of a solid electrolyte using each plastic crystal alone. This comparative solid electrolyte was produced under the same condition as of the solid electrolyte of each Example except for being constituted with one type of plastic crystal.

TABLE-US-00003 TABLE 3 Plastic crystal 1 Plastic crystal 2 Ion Ion Ion conductivity conductivity conductivity in Example Electrolyte Type (S/cm) Type (S/cm) (S/cm) Example 7 SBPBF.sub.4 EMICFSA 5.19 × 10.sup.−4 TEMACFSA 2.67 × 10.sup.−8 7.62 × 10.sup.−4 Example 8 EMICFSA 5.19 × 10.sup.−4 P12CFSA 2.52 × 10.sup.−7 1.41 × 10.sup.−3 Example 9 EMICFSA 5.19 × 10.sup.−4 SBPCFSA 2.28 × 10.sup.−7 2.55 × 10.sup.−3 Example 10 DMICFSA 3.46 × 10.sup.−4 SBPCFSA 2.28 × 10.sup.−7 2.15 × 10.sup.−3 Example 11 MPICFSA 6.76 × 10.sup.−4 SBPCFSA 2.28 × 10.sup.−7 1.11 × 10.sup.−3

[0125] As shown in Table 3, it can be confirmed that the ion conductivity of the solid electrolyte for an electric double-layer capacitor of each Example is at least same as in Example 7, and increases at maximum approximately four orders of magnitude compared with the solid electrolyte using one type of plastic crystal. From the results, the solid electrolyte using the plastic crystal containing the cations each selected from the group of the imidazoliums and the group of the quaternary ammoniums has been confirmed to have increased ion conductivity.

Example 12

[0126] A solid electrolyte for an electric double-layer capacitor of Example 12 was produced by using a plastic crystal containing two types of cations in total, that is an imidazolium and another cation. Then, ion conductivity of the solid electrolyte of Example 12 was measured. The solid electrolyte of Example 12 contains 1-ethyl-3-methylimidazolium (EMI) as the first type of imidazolium. The solid electrolyte of Example 12 also contains a tetraethylphosphonium cation (TEP), which is a phosphonium, as the second type of cation. The EMI cation and the TEP cation are contained in the plastic crystal at a molar ratio of 1:1.

[0127] An anion constituting the plastic crystal of Example 12 was N,N-hexafluoro-1,3-disulfonylamide anion (CFSA anion). A method of manufacturing the solid electrolyte of Example 12 was the same condition and the same manufacturing method as in Examples 1 to 5. The first type of plastic crystal and the second type of plastic crystal were added into a vial bottle at a molar ratio of 1:1.

[0128] Then, the ion conductivity of the solid electrolyte of Example 12 was measured. The following Table 2 shows the results. The measuring method and calculating method of the ion conductivity are same as in Examples 1 to 5. Table 4 also shows ion conductivity of a solid electrolyte using each plastic crystal alone. This comparative solid electrolyte was produced under the same condition as of the solid electrolyte of each Example except for being constituted with one type of plastic crystal.

TABLE-US-00004 TABLE 4 Plastic crystal 1 Plastic crystal 2 Ion Ion Ion conductivity conductivity conductivity in Example Electrolyte Type (S/cm) Type (S/cm) (S/cm) Example 12 SBPBF.sub.4 EMICFSA 5.19 × 10.sup.−4 TEPCFSA 4.5 × 10.sup.−4 1.57 × 10.sup.−3

[0129] As shown in Table 4, it can be confirmed that the ion conductivity of the solid electrolyte for an electric double-layer capacitor of Example 6 increases at least 30 times compared with the solid electrolyte using one type of plastic crystal. From the results, the solid electrolyte even containing another cation has also been confirmed to have increased ion conductivity.

[0130] As above, the solid electrolyte using the plastic crystal containing the two or more types of cations in total, at least one of which is selected from the group of the imidazoliums and the quaternary ammoniums has been confirmed to increase the ion conductivity.

Example 13

[0131] Two types of cations and two types of anions were combined to constitute two types of plastic crystal at a molar ratio of 1:1, and these plastic crystals were used to produce a solid electrolyte for an electric double-layer capacitor of Example 13. Then, ion conductivity of the solid electrolyte of Example 13 was measured. The solid electrolyte of Example 13 contains spiro-pyrrolidinium (SBP), which is a quaternary ammonium, as the first type of cation, and the first type of plastic crystal in which this cation and N,N-hexafluoro-1,3-disulfonylamide (CFSA) were combined was used. The solid electrolyte of Example 13 also contains N-ethyl-N-methylpyrrolidinium (P12) as the second type of cation and as the quaternary ammonium, and the second type of plastic crystal in which this cation and bis(trifluoromethanesulfonyl)amide (TFSA) were combined was used.

[0132] Then, the ion conductivity of the solid electrolyte of Example 13 was measured. The following Table 5 shows the results. The measuring method and calculating method of the ion conductivity are same as in Examples 1 to 5. Table 5 also shows ion conductivity of a solid electrolyte using each plastic crystal alone. This comparative solid electrolyte was produced under the same condition as of the solid electrolyte of each Example except for being constituted with one type of plastic crystal. For comparison, the ion conductivity of the solid electrolyte of Example 1 is further shown.

TABLE-US-00005 TABLE 5 Plastic crystal 1 Plastic crystal 2 Ion Ion Ion conductivity conductivity conductivity in Example Electrolyte Type (S/cm) Type (S/cm) (S/cm) Example 13 SBPBF.sub.4 SBPCFSA 2.28 × 10.sup.−7 P12TFSA 3.43 × 10.sup.−4 5.00 × 10.sup.−3 Example 1 SBPCFSA 2.28 × 10.sup.−7 P12CFSA 2.52 × 10.sup.−7 5.23 × 10.sup.−8

[0133] As shown in Table 5, it can be confirmed that the ion conductivity of the solid electrolyte for an electric double-layer capacitor of Example 13 increases at least approximately 100 times, and increases at maximum 20 thousand times compared with the solid electrolyte using one type of plastic crystal. In addition, compared with the ion conductivity of the solid electrolyte of Example 1, which was same in terms of using the two types of quaternary ammonium as the cations but used one type of anion, Example 13, which used the two types of cations and the two types of anions in combination, had approximately further 100 time higher ion conductivity.

Examples 14 to 16

[0134] Separately to Example 13, two types of cations and two types of anions were combined to constitute two types of plastic crystal at a molar ratio of 1:1, and these plastic crystals were used to produce a solid electrolyte for an electric double-layer capacitor of Example 14. The solid electrolyte of Example 14 contains spiro-pyrrolidinium (SBP), which is a quaternary ammonium, as the first type of cation, and the first type of plastic crystal in which this cation and N,N-hexafluoro-1,3-disulfonylamide (CFSA) were combined was used. The solid electrolyte of Example 14 also contains triethylmethylammonium (TEMA) as the second type of cation and as the tetraalkylammonium, and the second type of plastic crystal in which this cation and bis(trifluoromethanesulfonyl)amide (TFSA) were combined was used.

[0135] The mixture containing the TEMA cation and the TFSA anion was prepared as follows, and an addition amount is regulated to form the plastic crystal. That is, first, an aqueous solution of a halide in which the TEMA cation was halogenated with chlorine Cl was prepared. An aqueous solution of an alkali metal salt between the CFSA anion and lithium Li was prepared. Into the aqueous solution of the halide, an equivalent amount of the aqueous solution of the alkali metal salt was gradually dropped to perform an ion-exchange reaction. After the ion-exchange reaction, dichloromethane at 60 wt % relative to the total amount of the solution was mixed, an organic solvent layer was extracted from separated layers separated into an aqueous layer and the organic solvent layer, and active carbon was added to be stirred overnight. Then, a precipitate was recovered with filtration, and this precipitate was dried. This procedure yields the TEMATFSA plastic crystal. The TEMATFSA plastic crystal contains 30% or more of the TEMATFSA plastic crystal relative to a total mol % of the plastic crystal and the electrolyte to have a property as the plastic crystal.

[0136] As a comparison to Example 14, a solid electrolyte for an electric double-layer capacitor of Example 15 was produced. The solid electrolyte of Example 15 is constituted with combining two types of cations and one type of anion to contain two types of plastic crystal at a molar ratio of 1:1. The solid electrolyte of Example 15 contains spiro-pyrrolidinium (SBP), which is a quaternary ammonium, as the first type of cation, and the first type of plastic crystal in which this cation and N,N-hexafluoro-1,3-disulfonylamide (CFSA) were combined was used. The solid electrolyte of Example 15 also contains triethylmethylammonium (TEMA), which is a tetraalkylammonium, as the second type of cation and as the quaternary ammonium, and the second type of plastic crystal in which this cation and N,N-hexafluoro-1,3-disulfonylamide (CFSA) were combined was used.

[0137] Furthermore, two types of cations and two types of anions were combined to constitute two types of plastic crystal at a molar ratio of 1:1, and these plastic crystals were used to produce a solid electrolyte for an electric double-layer capacitor of Example 16. The solid electrolyte of Example 16 contains spiro-pyrrolidinium (SBP), which is a quaternary ammonium, as the first type of cation, and the first type of plastic crystal in which this cation and N,N-hexafluoro-1,3-disulfonylamide (CFSA) were combined was used. The solid electrolyte of Example 14 also contains N-ethyl-N-methylpyrrolidinium (P12), which is a five-membered ring pyrrolidinium, as the second type of cation and as the quaternary ammonium, and the second type of plastic crystal in which this cation and a bis(trifluoromethanesulfonyl)methanide anion (TFSM anion) were combined was used.

[0138] As a comparison to Example 16, a solid electrolyte for an electric double-layer capacitor of Example 1 was produced. The solid electrolyte of Example 1 is constituted with combining two types of cations and one type of anion to contain two types of plastic crystal at a molar ratio of 1:1.

[0139] Then, the ion conductivity of the solid electrolytes of Examples 14 to 16 and Example 1 was measured. The following Table 6 shows the results. The measuring method and calculating method of the ion conductivity are same as in Examples 1 to 5. Table 6 also shows ion conductivity of a solid electrolyte using each plastic crystal alone. This comparative solid electrolyte was produced under the same condition as of the solid electrolyte of each Example except for being constituted with one type of plastic crystal.

TABLE-US-00006 TABLE 6 Plastic crystal 1 Plastic crystal 2 Ion Ion Ion conductivity conductivity conductivity in Example Electrolyte Type (S/cm) Type (S/cm) (S/cm) Example 14 SBPBF.sub.4 SBPCFSA 2.28 × 10.sup.−7 TEMATFSA 3.96 × 10.sup.−8 1.93 × 10.sup.−3 Example 15 SBPCFSA 2.28 × 10.sup.−7 TEMACFSA 2.67 × 10.sup.−8 1.60 × 10.sup.−6 Example 16 SBPCFSA 2.28 × 10.sup.−7 P12TFSM 1.13 × 10.sup.−9 8.60 × 10.sup.−4 Example 1 SBPCFSA 2.28 × 10.sup.−7 P12CFSA 2.52 × 10.sup.−7 5.23 × 10.sup.−5

[0140] As shown in Table 6, it can be confirmed that the ion conductivity of the solid electrolyte for an electric double-layer capacitor of Example 14 increases at least approximately 10 thousand times compared with the solid electrolyte using one type of plastic crystal. In addition, compared with the ion conductivity of the solid electrolyte of Example 15, which was same in terms of using the two types of quaternary ammonium as the cation but used one type of anion, Example 14, which used the two types of cations and the two types of anions in combination, had more than 1000 times higher ion conductivity.

[0141] It can be confirmed that the ion conductivity of the solid electrolyte for an electric double-layer capacitor of Example 16 increases at least approximately 76 times compared with the solid electrolyte using one type of plastic crystal. In addition, compared with the ion conductivity of the solid electrolyte of Example 1, which was same in terms of using the two types of quaternary ammoniums as the cation but used one type of anion, Example 16, which used the two types of cations and the two types of anions in combination, had more than 16 times higher ion conductivity.

[0142] As shown in the comparison between Example 14 and Example 15 and the comparison between Example 16 and Example 17, it has been confirmed that the solid electrolyte using the plastic crystal using combination of two types of anions such as, for example, two or more types of anions in total selected from the group of the amide anions in which two hydrogen atoms of an NH.sub.2 anion are substituted with a perfluoroalkylsulfonyl group, a fluorosulfonyl group, or both of them, and a tris(trifluoromethanesulfonyl)methanide anion further increases the ion conductivity.

Example 17

[0143] Three types of plastic crystal were used to produce a solid electrolyte for a lithium-ion secondary battery of Example 17. Then, ion conductivity of the solid electrolyte of Example 17 was measured. The solid electrolyte of Example 17 contains N-ethyl-N-methylpyrrolidinium (P12) of the pyrrolidinium, which is a five-membered ring quaternary ammonium, as the first type of cation. This cation and a bis(fluorosulfonyl)amide anion (FSA anion), which was an amide anion, were combined to use a P12FSA plastic crystal, the first type.

[0144] The solid electrolyte of Example 17 also contains triethylmethylammonium (TEMA) of the tetraalkylammonium as the second type of cation and as the quaternary ammonium. This cation and a bis(fluorosulfonyl)amide anion (FSA anion), which was an amide anion, were combined to use a TEMAFSA plastic crystal, the second type.

[0145] The solid electrolyte of Example 17 further contains N-ethyl-N-methylpyrrolidinium (P12) of the pyrrolidinium, which is a five-membered ring quaternary ammonium. Bis(trifluoromethanesulfonyl)amide (TFSA), which is an amide anion, was combined as the second type of anion to use a P12TFSA plastic crystal, the third type.

[0146] Into a vial bottle, an electrolyte LiTFSA (lithium bis(trifluoromethanesulfonyl)amine, manufactured by KISHIDA CHEMICAL CO., LTD.) was further added so that the concentration was 10 mol % relative to the total of the plastic crystals, in addition to these three types of plastic crystal. Acetonitrile (Wako Pure Chemical Industries, Ltd.) was added so that the solid content concentration of the total of the plastic crystals and the electrolyte was 10 wt %. The P12FSA plastic crystal (A), the TEMAFSA plastic crystal (B), and the P12TFSA plastic crystal (C) were added into the vial bottle at A:B:C=4:4:2.

[0147] This acetonitrile solution was dropped on a glass separator, and dried at 80° C. to evaporate acetonitrile. This evaporation procedure was repeated three times. The glass separator immersed with the solid electrolyte by this evaporation procedure was dried under a vacuum environment at 80° C. for 12 hours, further dried under a vacuum environment at 120° C. for 3 hours, and further dried under a vacuum environment at 150° C. for 2 hours for removing moisture to obtain the solid electrolyte of Example 16.

[0148] Then, ion conductivity of the solid electrolyte of Example 17 was measured. The following Table 7 shows the results. The measuring method and calculating method of the ion conductivity are same as in Examples 1 to 5. Table 7 also shows ion conductivity of a solid electrolyte using each plastic crystal alone. This comparative solid electrolyte was produced under the same condition as of the solid electrolyte of Example 17 except for being constituted with one type of plastic crystal.

TABLE-US-00007 TABLE 7 Plastic crystal 1 Plastic crystal 2 Plastic crystal 3 Ion Ion Ion Ion conductivity conductivity conductivity conductivity in Example Electrolyte Type (S/cm) Type (S/cm) Type (S/cm) (S/cm) Example 17 LiTFSA P12FSA 1.03 × 10.sup.−4 TEMAFSA 2.48 × 10.sup.−3 P12TFSA 7.00 × 10.sup.−6 4.24 × 10.sup.−2

[0149] As shown in Table 7, it can be confirmed that the ion conductivity of the solid electrolyte for a lithium-ion secondary battery of Example 17 increases at least approximately twice, and at maximum more than 600 times compared with the solid electrolyte using one type of plastic crystal. From the results, the solid electrolyte for a lithium-ion secondary battery also has been confirmed to have increased ion conductivity.