NOVELTY - A non-aqueous electrolyte contains unsaturated phosphoric acid ester compound (I or II) as a component (A), sulfite ester compound, sulfonic-acid ester compound, imide salt compound of an alkali metal, fluorosilane compound and organic disilane or organic disiloxane compound as component (B), organic solvent as a component (C), and electrolytic salt as a component (D).    USE - Non-aqueous electrolyte for a secondary battery (claimed). Uses include but are not limited to video camera, digital camera, portable music player, sound recorder, portable DVD player, handheld game machine, notebook personal computer, electronic dictionary, electronic organizer, electronic book, mobile telephone, portable TV, electric power-assisted bicycle, and battery motor vehicle and hybrid vehicle.    ADVANTAGE - The non-aqueous electrolyte has high charging and discharging capacity, cycling characteristics, electrical property and durability. The non-aqueous electrolyte maintains high electrical capacitance and internal resistance during long-term use.    DETAILED DESCRIPTION - A non-aqueous electrolyte contains unsaturated phosphoric acid ester compound of formula ((HC?=C-C(R1)(R2)-O)2-P(=O)-O-R3) (I) or ((R1-O)2-P(=O)-O-C(R4)(R5)-(C=C)m-C(R4)(R5)-O-P(=O)-(O-R6)2) (II) as a component (A), sulfite ester compound, sulfonic-acid ester compound, imide salt compound of an alkali metal, fluorosilane compound and organic disilane or organic disiloxane compound as component (B), organic solvent as a component (C), and electrolytic salt as a component (D).    R1,R2,R4,R5=H or 1-8C alkyl;    R3=1-8C alkyl, 2-8C alkenyl, 2-8C alkynyl or 1-8C halogenoalkyl;    R6=1-8C alkyl, 2-8C alkenyl, 2-8C alkynyl or 1-8C halogenoalkyl;and    m=1 or 2.    An INDEPENDENT CLAIM is also included for a non-aqueous electrolyte secondary battery comprising a negative electrode, a positive electrode and the non-aqueous electrolyte.    DESCRIPTION OF DRAWING(S) - The drawing shows a longitudinal cross-sectional view of a coin-shaped non-aqueous-electrolyte secondary battery.    Positive electrode (1)    Positive electrode collector (1a)    Negative electrode (2)    Negative electrode collector (2a)    Electrolyte solution (3)    Positive electrode case (4)    Negative electrode case (5)    Gasket (6)    Separator (7)    Coin-shaped non-aqueous-electrolyte secondary battery (10)