An electrolyte suitable for use in lithium ion batteries contains 100 parts by weight of aprotic solvent, 1 to 50 parts by weight of lithium-containing conducting salt, 4 to 50 parts by weight of vinylene carbonate, and cyclic phosphonamide of the general formula 1

##STR00001## in which R.sup.1, R.sup.2, R.sup.3 are each hydrocarbyl which is unsubstituted or substituted by fluoro, chloro or silyl groups and which has 1-20 carbon atoms, where two or three of the radicals R.sup.1, R.sup.2, R.sup.3 may be joined to one another, and n has a value of 0, 1, 2, 3, 4 or 5. The electrolyte is used in a lithium-ion battery which comprises a cathode, an anode, a separator, and the electrolyte.

The exemplary embodiment has an object to provide a nonaqueous electrolyte solution having a flame retardancy over a long period and having a good capacity maintenance rate. The exemplary embodiment is a nonaqueous electrolyte solution containing a lithium salt, at least one oxo-acid ester derivative of phosphorus selected from compounds represented by a predetermined formula, and at least one disulfonate ester selected from a cyclic disulfonate ester and a linear disulfonate ester represented by the predetermined formulae.

A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The electrolytic solution includes a solvent, an electrolyte salt, a diester compound represented by Formula (1), and at least one of respective sulfur-containing compounds represented by Formulae (2) to (14).

A nanocomposite electrode and a method of making the nanocomposite. The nanocomposite electrode includes an electrode substrate, nitrogen-doped molybdenum carbide nanosheets, at least one electrolyte, at least one binding compound, and at least one conductive additive. The electrode substrate is coated with a mixture of the nitrogen-doped molybdenum carbide nanosheets, at least one binding compound, at least one conductive additive, and at least one electrolyte, where the electrolyte penetrates the pores of the nitrogen-doped molybdenum carbide nanosheets, and where the nitrogen-doped molybdenum carbide nanosheets are an outer layer of the electrode.

A nanocomposite electrode and a method of making the nanocomposite. The nanocomposite electrode includes an electrode substrate, nitrogen-doped molybdenum carbide nanosheets, at least one electrolyte, at least one binding compound, and at least one conductive additive. The electrode substrate is coated with a mixture of the nitrogen-doped molybdenum carbide nanosheets, at least one binding compound, at least one conductive additive, and at least one electrolyte, where the electrolyte penetrates the pores of the nitrogen-doped molybdenum carbide nanosheets, and where the nitrogen-doped molybdenum carbide nanosheets are an outer layer of the electrode.

A hybrid supercapacitor, including at least one negative electrode that includes a statically capacitive active material, an electrochemical redox active material, or a mixture thereof, at least one positive electrode that includes a statically capacitive active material, an electrochemical redox active material, or a mixture thereof, at least one separator that is situated between the at least one negative electrode and the at least one positive electrode, and an electrolyte composition, with the condition that at least one electrode includes a statically capacitive active material, and at least one electrode includes an electrochemical redox active material, the electrolyte composition being a liquid electrolyte composition and including at least one liquid, aprotic, organic solvent, at least one conducting salt, and at least one additive.

A hybrid supercapacitor, including at least one negative electrode that includes a statically capacitive active material, an electrochemical redox active material, or a mixture thereof, at least one positive electrode that includes a statically capacitive active material, an electrochemical redox active material, or a mixture thereof, at least one separator that is situated between the at least one negative electrode and the at least one positive electrode, and an electrolyte composition, with the condition that at least one electrode includes a statically capacitive active material, and at least one electrode includes an electrochemical redox active material, the electrolyte composition being a liquid electrolyte composition and including at least one liquid, aprotic, organic solvent, at least one conducting salt, and at least one additive.

A hybrid supercapacitor, including at least one negative electrode having a statically capacitive active material, an electrochemical redox-active material, or a mixture of them; at least one positive electrode having a statically capacitive active material, an electrochemical redox-active material, or a mixture of them; at least one separator situated between the at least one negative electrode and the at least one positive electrode; and an electrolyte mixture; with the provision that at least one electrode includes a statically capacitive active material, and at least one electrode includes an electrochemical, redox-active material; the electrolyte mixture being a liquid electrolyte mixture and including at least one liquid, aprotic, organic solvent, at least one conducting salt, and at least one at least partially halogenated, aromatic compound.

A hybrid supercapacitor, including at least one negative electrode having a statically capacitive active material, an electrochemical redox-active material, or a mixture of them; at least one positive electrode having a statically capacitive active material, an electrochemical redox-active material, or a mixture of them; at least one separator situated between the at least one negative electrode and the at least one positive electrode; and an electrolyte mixture; with the provision that at least one electrode includes a statically capacitive active material, and at least one electrode includes an electrochemical, redox-active material; the electrolyte mixture being a liquid electrolyte mixture and including at least one liquid, aprotic, organic solvent, at least one conducting salt, and at least one at least partially halogenated, aromatic compound.

An electrolyte includes a lithium salt dissolved in a solvent mixture. The solvent mixture may include a first solvent component including an organic solvent having no carbonate groups; a second solvent component configured to improve the electrochemical properties of the first solvent at low temperatures; a third solvent compound configured to promote formation of a passivating SEI layer between the electrolyte and an electrode layer; and a fourth solvent compound configured to stabilize a lithium salt at high temperatures.