An energy storage device can include a cathode, an anode, and a separator between the cathode and the anode, and an electrolyte where the electrolyte includes one or more additives and/or solvent components selected from vinylene carbonate (VC), vinyl ethylene carbonate (VEC), dimethylacetamide (DMAc), hydro fluorinated ether branched cyclic carbonate, a hydro fluorinated ether ethylene carbonate (HFEEC), hydro fluorinated ether (HFE), and fluorinated ethylene carbonate (FEC). The electrolyte may include a carbonate based solvent and one or more solvent components and/or one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), dimethylacetamide (DMAc), hydro fluorinated ether branched cyclic carbonate, a hydro fluorinated ether ethylene carbonate (HFEEC), hydro fluorinated ether (HFE), and fluorinated ethylene carbonate (FEC).

All-temperature flexible supercapacitors are prepared using a hydrogel electrolyte including a poly(vinyl alcohol) (PVA) substrate a montmorillonite (MMT) dopant, along with a 2M sulfuric acid and dimethyl sulfoxide/water aqueous electrolyte dispersed therein. Incorporation of MMT material enhances the thermal stability of PVA polymers, whereas the DMSO/H.sub.2O binary system endows the hydrogel with an ultralow freezing point below −50° C. The hydrogel electrolyte displays good mechanical properties and shows superior electrochemical properties in a wide temperature range. The ionic conductivities are 0.17×10.sup.−4 and 0.76×10.sup.−4 S cm.sup.−1 under operation temperatures of −50 and 90° C., respectively. The supercapacitor exhibits a high specific capacity of 161 F g.sup.−1 with a high rate capability and life over 10,000 cycles. The flexible supercapacitors deliver a stable energy supply under various flexible conditions, including bending, twisting, and stretching states, and its capacity does not degrade obviously even after 1,000 bending cycles.

All-temperature flexible supercapacitors are prepared using a hydrogel electrolyte including a poly(vinyl alcohol) (PVA) substrate a montmorillonite (MMT) dopant, along with a 2M sulfuric acid and dimethyl sulfoxide/water aqueous electrolyte dispersed therein. Incorporation of MMT material enhances the thermal stability of PVA polymers, whereas the DMSO/H.sub.2O binary system endows the hydrogel with an ultralow freezing point below −50° C. The hydrogel electrolyte displays good mechanical properties and shows superior electrochemical properties in a wide temperature range. The ionic conductivities are 0.17×10.sup.−4 and 0.76×10.sup.−4 S cm.sup.−1 under operation temperatures of −50 and 90° C., respectively. The supercapacitor exhibits a high specific capacity of 161 F g.sup.−1 with a high rate capability and life over 10,000 cycles. The flexible supercapacitors deliver a stable energy supply under various flexible conditions, including bending, twisting, and stretching states, and its capacity does not degrade obviously even after 1,000 bending cycles.

An electrolyte solution containing a compound (1) represented by the formula (1):

##STR00001##

wherein R.sup.1 and R.sup.2 are each independently a C1-C4 alkyl group optionally containing an ether bond; and a compound (11) represented by the formula (11):

##STR00002##

wherein R.sup.101 and R.sup.102 are each independently a substituent that is a C1-C7 alkyl group or the like. The substituent optionally contains one or more divalent to hexavalent hetero atoms in its structure, with one or more hydrogen atoms each optionally replaced by a fluorine atom or a C0-C7 functional group. Also disclosed is an electrochemical device containing the electrolyte solution, a lithium ion secondary battery containing the electrolyte solution, and a module including the electrochemical device or the lithium ion secondary battery.

An electrolyte solution applicable to high-voltage electrochemical devices and capable of improving the cycle characteristics of electrochemical devices even at high voltage, and an electrochemical device. The electrolyte solution contains a fluorinated diether and a metal salt having a specific structure. The fluorinated diether is represented by CFR.sup.11R.sup.12—O—CH.sub.2CH.sub.2—O—R.sup.13, wherein R.sup.11 and R.sup.12 are each individually H, CH.sub.3, F, CH.sub.2F, CHF.sub.2, or CF.sub.3; and R.sup.13 is a C1 or C2 non-fluorinated alkyl group or a C1 or C2 fluorinated alkyl group.

An electrolyte solution applicable to high-voltage electrochemical devices and capable of improving the cycle characteristics of electrochemical devices even at high voltage, and an electrochemical device. The electrolyte solution contains a fluorinated diether and a metal salt having a specific structure. The fluorinated diether is represented by CFR.sup.11R.sup.12—O—CH.sub.2CH.sub.2—O—R.sup.13, wherein R.sup.11 and R.sup.12 are each individually H, CH.sub.3, F, CH.sub.2F, CHF.sub.2, or CF.sub.3; and R.sup.13 is a C1 or C2 non-fluorinated alkyl group or a C1 or C2 fluorinated alkyl group.

Provided are a nonaqueous electrolyte capable of providing a nonaqueous electrolyte energy storage device with reduced direct current resistance and an increased capacity retention ratio after charge-discharge cycles, a nonaqueous electrolyte energy storage device including such a nonaqueous electrolyte, and a method for producing such a nonaqueous electrolyte energy storage device. One mode of the present invention is a nonaqueous electrolyte for an energy storage device, containing an additive represented by the following Formula (1) or Formula (2). In Formula (1), R.sup.1 to R.sup.4 are each independently a hydrogen atom or a group represented by —NR.sup.a.sub.2, —OR.sup.a, —SR.sup.a, etc., with the proviso that at least one of R.sup.1 to R.sup.4 is a group represented by —OR.sup.a, —SR.sup.a, —COOR.sup.a, —COR.sup.a, —SO.sub.2R.sup.a, or —SO.sub.3R.sup.a. In Formula (2), R.sup.5 to R.sup.7 are each independently a hydrogen atom or a group represented by —NR.sup.b.sub.2, —OR.sup.b, or —SR.sup.b, with the proviso that at least one of R.sup.5 to R.sup.7 is a group represented by —SR.sup.b.

##STR00001##

Provided are a nonaqueous electrolyte capable of providing a nonaqueous electrolyte energy storage device with reduced direct current resistance and an increased capacity retention ratio after charge-discharge cycles, a nonaqueous electrolyte energy storage device including such a nonaqueous electrolyte, and a method for producing such a nonaqueous electrolyte energy storage device. One mode of the present invention is a nonaqueous electrolyte for an energy storage device, containing an additive represented by the following Formula (1) or Formula (2). In Formula (1), R.sup.1 to R.sup.4 are each independently a hydrogen atom or a group represented by —NR.sup.a.sub.2, —OR.sup.a, —SR.sup.a, etc., with the proviso that at least one of R.sup.1 to R.sup.4 is a group represented by —OR.sup.a, —SR.sup.a, —COOR.sup.a, —COR.sup.a, —SO.sub.2R.sup.a, or —SO.sub.3R.sup.a. In Formula (2), R.sup.5 to R.sup.7 are each independently a hydrogen atom or a group represented by —NR.sup.b.sub.2, —OR.sup.b, or —SR.sup.b, with the proviso that at least one of R.sup.5 to R.sup.7 is a group represented by —SR.sup.b.

##STR00001##

An electrolytic solution contains: an electrolyte including a lithium salt represented by general formula (1) below; an organic solvent including a linear carbonate represented by general formula (2) below; and an unsaturated cyclic carbonate, wherein the linear carbonate is contained at a mole ratio of 3 to 6 relative to the lithium salt, and/or the lithium salt is contained at a concentration of 1.1 to 3.8 mol/L.
(R.sup.1X.sup.1)(R.sup.2SO.sub.2)NLi  general formula (1)
R.sup.20OCOOR.sup.21  general formula (2)

An electrolytic solution contains: an electrolyte including a lithium salt represented by general formula (1) below; an organic solvent including a linear carbonate represented by general formula (2) below; and an unsaturated cyclic carbonate, wherein the linear carbonate is contained at a mole ratio of 3 to 6 relative to the lithium salt, and/or the lithium salt is contained at a concentration of 1.1 to 3.8 mol/L.
(R.sup.1X.sup.1)(R.sup.2SO.sub.2)NLi  general formula (1)
R.sup.20OCOOR.sup.21  general formula (2)