An electrolyte solution containing a solvent. The solvent contains a compound (1) represented by the following formula (1), wherein R.sup.a, R.sup.b, R.sup.c, and R.sup.d are the same as or different from each other, and are each —H, —F, —CH.sub.3, or —CF.sub.3; at least one of R.sup.a, R.sup.b, R.sup.c, or R.sup.d is —F or —CF.sub.3; and at least one of R.sup.a, R.sup.b, R.sup.c, or R.sup.d is —CH.sub.3, and a compound (2) represented by the following formula (2), wherein R.sup.e is a C1-C5 linear or branched alkyl or alkoxy group optionally containing an ether bond; R.sup.f is a C1-C5 linear or branched alkyl group optionally containing an ether bond; and at least one of R.sup.e or R.sup.f contains a fluorine atom. Also disclosed is an electrochemical device including the electrolyte solution, a lithium-ion secondary battery including the electrolyte solution and a module including the electrochemical device. ##STR00001##

An electrolyte solution containing a solvent. The solvent contains a compound (1) represented by the following formula (1), wherein R.sup.a, R.sup.b, R.sup.c, and R.sup.d are the same as or different from each other, and are each —H, —F, —CH.sub.3, or —CF.sub.3; at least one of R.sup.a, R.sup.b, R.sup.c, or R.sup.d is —F or —CF.sub.3; and at least one of R.sup.a, R.sup.b, R.sup.c, or R.sup.d is —CH.sub.3, and a compound (2) represented by the following formula (2), wherein R.sup.e is a C1-C5 linear or branched alkyl or alkoxy group optionally containing an ether bond; R.sup.f is a C1-C5 linear or branched alkyl group optionally containing an ether bond; and at least one of R.sup.e or R.sup.f contains a fluorine atom. Also disclosed is an electrochemical device including the electrolyte solution, a lithium-ion secondary battery including the electrolyte solution and a module including the electrochemical device. ##STR00001##

The invention provides an electrolyte solution capable of providing an electrochemical device having low resistance and excellent high-temperature storage characteristics and cycle characteristics. The electrolyte solution contains lithium fluorosulfonate and a solvent containing a compound (1) represented by the following formula (1): CF.sub.2HCOOCH.sub.3.

An ultracapacitor that includes an energy storage cell immersed in an electrolyte and disposed within an hermetically sealed housing, the cell electrically coupled to a positive contact and a negative contact, wherein the ultracapacitor is configured to output electrical energy within a temperature range between about 80 degrees Celsius to about 210 degrees Celsius. Methods of fabrication and use are provided.

An ultracapacitor that includes an energy storage cell immersed in an electrolyte and disposed within an hermetically sealed housing, the cell electrically coupled to a positive contact and a negative contact, wherein the ultracapacitor is configured to output electrical energy within a temperature range between about 80 degrees Celsius to about 210 degrees Celsius. Methods of fabrication and use are provided.

Formation process for a potassium-ion hybrid supercapacitor, the process comprising: a) supplying the potassium-ion hybrid supercapacitor comprising: a negative electrode comprising graphite, a positive electrode comprising activated carbon, an electrolyte comprising a potassium salt, b) charging the supercapacitor at constant current in a protocol of between C.sub.x/50 and C.sub.x/2, to a charge cutoff voltage of between 3.0 V and 3.3 V, c) holding the supercapacitor at the charge cutoff voltage until the leakage current is between C.sub.x/2000 and C.sub.x/500, d) discharging the supercapacitor at constant current in a protocol of between C.sub.x/50 and C.sub.x, to a discharge cutoff voltage of between 0 V and 2 V,
where the process further comprises degassing the supercapacitor after one of steps b) to d).

Formation process for a potassium-ion hybrid supercapacitor, the process comprising: a) supplying the potassium-ion hybrid supercapacitor comprising: a negative electrode comprising graphite, a positive electrode comprising activated carbon, an electrolyte comprising a potassium salt, b) charging the supercapacitor at constant current in a protocol of between C.sub.x/50 and C.sub.x/2, to a charge cutoff voltage of between 3.0 V and 3.3 V, c) holding the supercapacitor at the charge cutoff voltage until the leakage current is between C.sub.x/2000 and C.sub.x/500, d) discharging the supercapacitor at constant current in a protocol of between C.sub.x/50 and C.sub.x, to a discharge cutoff voltage of between 0 V and 2 V,
where the process further comprises degassing the supercapacitor after one of steps b) to d).

An electrolytic solution comprising N-(fluorosulfonyl)-N-(fluoroalkylsulfonyl)imide or di(fluorosulfonyl)imide, from which a residual solvent that affects the properties of the electrolyte solution material is reduced, is provided. A method for producing an electrolyte solution material containing fluorosulfonyl imide salt represented by the following general formula (1) and an electrolyte solution preparation solvent comprises decompressing and/or heating a solution containing the fluorosulfonyl imide salt and the electrolyte solution preparation solvent to volatilize a production solvent for the fluorosulfonyl imide salt. ##STR00001##
In general formula (1), R.sub.1 represents a fluorine atom or a fluorinated alkyl group having 1 to 6 carbon atoms, R.sub.2 represents an alkali metal ion.

An electrolytic solution comprising N-(fluorosulfonyl)-N-(fluoroalkylsulfonyl)imide or di(fluorosulfonyl)imide, from which a residual solvent that affects the properties of the electrolyte solution material is reduced, is provided. A method for producing an electrolyte solution material containing fluorosulfonyl imide salt represented by the following general formula (1) and an electrolyte solution preparation solvent comprises decompressing and/or heating a solution containing the fluorosulfonyl imide salt and the electrolyte solution preparation solvent to volatilize a production solvent for the fluorosulfonyl imide salt. ##STR00001##
In general formula (1), R.sub.1 represents a fluorine atom or a fluorinated alkyl group having 1 to 6 carbon atoms, R.sub.2 represents an alkali metal ion.

The present disclosure relates to the synthesis and evaluation of difluorophosphate additives for use in energy storage devices. The difluorophosphate additive may be selected from the group consisting of lithium difluorophosphate (LFO), sodium difluorophosphate (NaFO), ammonium difluorophosphate (AFO), tetramethylammonium difluorophosphate (MAFO), potassium difluorophosphate (KFO), and combinations thereof. In some instances, the difluorophosphate additive is not lithium difluorophosphate (LFO).