NOVELTY - A nonaqueous electrolyte solution comprises lithium salt, oxo-acid ester derivative of phosphorus (I)-(III), and disulfonic-acid ester chosen from chain-shaped disulfonic-acid ester (IV) or (V).    USE - Nonaqueous electrolyte solution for lithium ion secondary battery and capacitor (both claimed), used for mobile telephones, notebook personal computers, large sized electric power storage and motor vehicles.    ADVANTAGE - The nonaqueous electrolyte solution provides batteries with improved flame retardance, lifetime and capacity maintenance factor.    DETAILED DESCRIPTION - A nonaqueous electrolyte solution comprises lithium salt, oxo-acid ester derivative of phosphorus chosen from formulae: R13O-P(-OR12)(=O)-OR11 (I), X21-P(-OR22)(=O)-OR21 (II) and X31-P(-OR31)(=O)-X32 (III), and disulfonic-acid ester chosen from chain-shaped disulfonic-acid ester of formula (IV) or of formula: R3-S(=O)2-C(-R4)(-R1)-S(=O)2-R2 (V).    R11-R13,R21,R22,R31=alkyl, aryl, alkenyl, cyano, phenyl, amino, nitro, alkoxy, cycloalkyl or halogen-substituted groups;    two or more of R11-R13,R21,R22=cyclic structure;    X21,X31,X32=halo;    Q=oxygen, methylene or single bond;    A1=optionally branched (1-5C alkylene, 1-5C perfluoro alkylene, 2-6C fluoro alkylene, 1-6C alkylene containing ether bond, 1-6C perfluoro alkylene containing ether bond or 2-6C fluoro alkylene containing ether bond) (all optionally substituted), carbonyl or sulfinyl;    A2=alkylene or fluoro alkylene (both optionally substituted) or O;    R1,R4=1-5C alkyl, 1-5C alkoxy, 1-5C fluoroalkyl (all optionally substituted), 1-5C polyfluoroalkyl, H, -SO2X11, -SY'11, -COZ, or halo;    X11,Y'11=optionally substituted 1-5C alkyl;    Z=H or X11;    R2,R3=1-5 alkyl, 1-5C alkoxy, phenoxy, 1-5C fluoroalkyl, 1-5C fluoro alkoxy (all optionally substituted), 1-5C polyfluoroalkyl,1-5C polyfluoro alkoxy, hydroxy, halo, -NX12X13 or -NY'12CONY'13Y'14;and    X12,X13,Y'12-Y'14=H or optionally substituted 1-5C alkyl.    INDEPENDENT CLAIMS are included for the following:    (1) lithium ion secondary battery provided with the nonaqueous electrolyte solution; and    (2) capacitor provided with the non-aqueous electrolyte solution.    DESCRIPTION OF DRAWING(S) - The drawings show the top view and side view of the positive electrode.    Positive electrode (1)    Aluminum foil (2)    Positive electrode active material double-spread portion (3)    Positive electrode active material non-coated portion (6)    Positive electrode active material layer (14)