NOVELTY - A lithium ion secondary battery (10) has a positive electrode in which a positive electrode active material layer (15) is formed on a surface of a positive electrode collector (12), a negative electrode in which a negative electrode active material layer (13) is formed on a surface of a negative electrode collector (11), an electrolyte layer (17), and an electric power generation element (21) provided with a cell layer (19). The electrolyte contains boron-containing organic compound (I). The positive and negative electrode active material layers contain high molecular compound (II).    USE - Lithium ion secondary battery for use in electric vehicle, hybrid electric vehicle and fuel-cell vehicle.    ADVANTAGE - The lithium ion secondary battery is light in weight, and has high durability, ion conductivity, charging and discharging capacity, heat insulation resistance, corrosion resistance and interfacial resistance. The lithium ion secondary battery suppresses the concentration polarization of an electrolyte anion, and prevents the increase of the movement resistance of a lithium ion.    DETAILED DESCRIPTION - A lithium ion secondary battery has a positive electrode in which a positive electrode active material layer is formed on a surface of a positive electrode collector, a negative electrode in which a negative electrode active material layer is formed on a surface of a negative electrode collector, an electrolyte layer, and an electric power generation element provided with a cell layer, where the electrolyte layer is interposed between the positive electrode active material layer and the negative electrode active material layer. The negative electrode active material layer contains negative electrode active material(s) consisting of lithium titanate, tungsten oxide, molybdenum oxide, iron sulfide, lithium iron sulfide and titanium sulfide. The electrolyte contains boron-containing organic compound of formula (Z1-(OA1)h-O-B(O-(A2O)i-Z2)(O-(A3O)j-Z3)) (I). The positive and negative electrode active material layers contain high molecular compound of formula (R1O-(A4O)k-R2) (II) arranged between the electrolyte layer, the positive electrode active material layer, or the negative electrode active material layer.    B=boron atom;    Z1-Z3=acryloyl or methacryloyl;    A1O,A2O,A3O=2-6C oxyalkylene;    h,i,j=less than 100 or larger than 0, where h, i and j are average added mole numbers of oxyalkylene group;    h+i+j=1 or more;    R1,R2=1-10C hydrocarbon;    A4O=2-3C oxyalkylene;and    k=4-20, where k is average added mole number of oxyalkylene group.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic cross-sectional view of a lithium ion secondary battery.    Lithium ion secondary battery (10)    Negative electrode collector (11)    Positive electrode collector (12)    Negative electrode active material layer (13)    Positive electrode active material layer (15)    Electrolyte layer (17)    Cell layer (19)    Electric power generation element (21)