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.

A non-aqueous lithium power storage element that includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, the positive electrode having a positive electrode collector and a positive electrode active material layer that includes active carbon, and the non-aqueous lithium power storage element having configuration (1) and/or (2). (1) The negative electrode includes a negative electrode collector and a negative electrode active material layer (2) The non-aqueous electrolyte contains (A) LiPF.sub.6 and/or LiBF.sub.4, (B) an imide lithium salt, and (C) an oxalate-complex lithium salt, the ratio of the mass of component (C) to the total mass of components (A) and (B) being 1.0-10.0 mass %.

Ultra-thin lithium ion capacitors with ultra-high power performance are provided. Ultra-thin electrodes and ultra-thin lithium films can be used for the ultra-thin lithium ion capacitor. A lithium ion capacitor can include a first positive electrode and a second positive electrode, a negative electrode disposed between the first positive electrode and the second positive electrode, a first lithium film disposed between the first positive electrode and the negative electrode, and a second lithium film disposed between the second positive electrode and the negative electrode. Each of the first and second lithium films can include an electrolyte. In addition, at least one separator can be provided between the first positive electrode and the first lithium film, and at least one separator can be provided between the second positive electrode and the second lithium film.

An electrochemical device, which is a non-aqueous electrochemical device, comprising a polymer (P) enclosed in an inside of the electrochemical device, wherein the polymer (P) is a polymer having a molecular structure containing a unit (P) represented by the following formula (P), the polymer (P) having a weight-average molecular weight of greater than 50,000, as well as an electrode for an electrochemical device, a coating liquid for an electrochemical device, an insulating layer for an electrochemical device, an undercoat layer for an electrochemical device, and an electrolytic solution for an electrochemical device including the polymer (P) and other ingredients:

##STR00001## in the formula (P), R.sup.P is a group of 1 to 20 carbon atoms.

An alkali metal ion capacitor that is capable of operating in a high-temperature environment at 85° C. The alkali metal ion capacitor is provided with: a positive electrode active material capable of adsorbing and desorbing alkali metal ions; a positive electrode binder for binding the positive electrode active material; a negative electrode active material capable of storing and releasing alkali metal ions; a negative electrode binder for binding the negative electrode active material; and an electrolytic solution that contains an organic solvent and an imide-based alkali metal salt. The negative electrode active material is predoped with alkali metal ions. The positive electrode binder has a Hansen solubility parameter-based RED value of more than 1 with respect to the electrolytic solution.

An alkali metal ion capacitor that is capable of operating in a high-temperature environment at 85° C. The alkali metal ion capacitor is provided with: a positive electrode active material capable of adsorbing and desorbing alkali metal ions; a positive electrode binder for binding the positive electrode active material; a negative electrode active material capable of storing and releasing alkali metal ions; a negative electrode binder for binding the negative electrode active material; and an electrolytic solution that contains an organic solvent and an imide-based alkali metal salt. The negative electrode active material is predoped with alkali metal ions. The positive electrode binder has a Hansen solubility parameter-based RED value of more than 1 with respect to the electrolytic solution.

An aspect of the present invention is a nonaqueous electrolyte energy storage device including: a negative electrode including a negative active material layer with a thickness expansion rate of 10% or more due to charge; and a separator, in which the absolute value (|dR/dP|) of an increase in resistance (dR) to a change in pressure (dP) in pressurization is 0.15 Ω.Math.cm.sup.2/MPa or less in the separator impregnated with a measurement electrolyte solution, the measurement electrolyte solution contains an ethylene carbonate and an ethyl methyl carbonate as a solvent, and a lithium hexafluorophosphate as an electrolyte salt, the volume ratio between the ethylene carbonate and the ethyl methyl carbonate is 30:70, and the concentration of the lithium hexafluorophosphate is 1.0 mol/L.

A process for preparing surface-modified carbon, comprising adding carbon material to a solution of a reaction product of primary aromatic amine and excess molar amount of nitrite source, and recovering surface-modified carbon bearing redox-active sites. Surface-modified carbon material, electrodes and capacitors based thereon are also provided.

A process for preparing surface-modified carbon, comprising adding carbon material to a solution of a reaction product of primary aromatic amine and excess molar amount of nitrite source, and recovering surface-modified carbon bearing redox-active sites. Surface-modified carbon material, electrodes and capacitors based thereon are also provided.

The present disclosure is directed to a phosphorus-modified ionic liquid compound, the synthesis thereof and an electrochemical cell electrolyte containing the phosphorus-modified ionic liquid compound.