NOVELTY - A lithium ion secondary battery (10) has positive electrode (15) including collector (12) and active material layer, negative electrode (13), and electrolyte solution containing supporting electrolyte. The negative electrode has collector (11) including aluminum and lithium and active material layer containing alloyed element (a) excluding graphite. The concentration of supporting electrolyte is 0.4 M or more. The supporting electrolyte contains lithium borate (I), lithium phosphate (II) and/or lithium salt of imide (III).    USE - Lithium ion secondary battery is used for assembled battery used as power supply for vehicles (both claimed) e.g. electric vehicle and hybrid electric vehicle. Uses include but are not limited to passenger car, truck, bus, motorbike, mobile telephone and personal computer.    ADVANTAGE - The lithium ion secondary battery is lightweight, economical, and has high energy density, durability, charging characteristics and reduced fuel consumption.    DETAILED DESCRIPTION - A lithium ion secondary battery has positive electrode including collector and active material layer, negative electrode, and electrolyte solution containing supporting electrolyte. The negative electrode has collector including aluminum and lithium and active material layer containing alloyed element (a) excluding graphite. The concentration of supporting electrolyte is 0.4 M or more. The supporting electrolyte contains lithium borate of formula (I), lithium phosphate of formula (II) and/or lithium salt of imide of formula: (A6-S(=O)2-N--S(=O)2-A7)Li+ (III).    A1-E5=dicarbonyl, linear or branched 1-10C alkylene, 2-11C linear or branched alkylene carbonyl, 3-12C linear or branched alkylene dicarbonyl, 6-20C arylene, 7-21C arylene carbonyl or 8-22C arylene dicarbonyl;and    A6,A7=fluoro or 1-12C fluoroalkyl.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the lithium ion secondary battery.    Lithium ion secondary battery (10)    Negative electrode collector (11)    Positive electrode collector (12)    Negative electrode (13)    Positive electrode (15)