NOVELTY - An nonaqueous electrolyte solution comprises lithium salt, phosphazene structure-containing compound (I), 0.05-12 %mass of cyclic disulfonate (II) and/or chain-shaped disulfonate (III). The nonaqueous electrolyte solution is used in device provided with positive electrode, negative electrode and nonaqueous electrolyte solution.    USE - Nonaqueous electrolyte solution is used for device e.g. capacitor and lithium ion secondary battery (all claimed) used as power supply for motor vehicles, mobile telephone and notebook personal computer.    ADVANTAGE - The lithium ion secondary battery using nonaqueous electrolyte solution has excellent capacity and flame retardant property.    DETAILED DESCRIPTION - An nonaqueous electrolyte solution comprises lithium salt, phosphazene structure-containing compound of formula: -(P(-X1)(-X2)=N)n- (I), 0.05-12 %mass of cyclic disulfonate of formula (II) and chain-shaped disulfonate of formula: R3-S(=O)2 -C(-R4)(-R1)-S(=O)2-R2 (III).    X1,X2=halo, alkyl, alkoxy, aryl, acyl, aryloxy, amino, alkylthio, arylthio, halogenoalkyl, halogenoalkoxy, halogenated aryl, halogenated acyl, halogenated aryloxy, halogenated amino, halogenated alkylthio, or halogenated arylthio;    n=3-5;    Q=O, methylene or single bond;    A1=branched 1-5C alkylene, branched 1-5C perfluoroalkylene, 2-6C branched fluoroalkylene, 1-6C branched alkylene having ether bond, 2-6C branched fluoroalkylene containing ether bond, 1-6C branched perfluoroalkylene (all optionally substituted), carbonyl or sulfinyl;    A2=optionally substituted branched alkylene;    R1,R4=1-5C alkyl, 1-5C alkoxy, 1-5C fluoroalkyl (all optionally substituted), H, 1-5C polyfluoroalkyl, -SO2X11, SY'11, -COZ or halo;    X11, Y'11=(un)substituted 1-5C alkyl;    R2,R3=1-5C alkyl, 1-5C alkoxy, phenoxy, 1-5C fluoroalkyl, 1-5C polyfluoroalkyl, 1-5C fluoro alkoxy, 1-5C polyfluoroalkoxy (all optionally substituted), hydroxy, halo, -NX12X13 or -NY12CONY'13Y'14;and    X12,X13,Y12-Y14,Z=H or (un)substituted 1-5C alkyl.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of battery element after winding of lithium ion secondary battery.    Aluminum foil (2)    Positive electrode electrically conductive tab (6)    Copper foil (8)    Negative electrode electrically conductive tab (12)    Separator (13)