NOVELTY - A lithium ion battery has a positive electrode (10) comprising a positive electrode mixture layer on a current collector, a negative electrode (12) comprising a negative electrode mixture layer on a current collector, an electrolyte and separator (11). The positive electrode comprises positive electrode active material containing lithium composite oxide. The negative electrode comprises graphite having interlayer distance of 0.335-0.338 nm. The product of thickness (A) and density (B) of positive and negative electrode mixture layers is 160-220 and 65-105, respectively.    USE - Lithium ion battery is used for electric automobiles and plug-in hybrid automobiles (claimed), mobile telephone and personal computer.    ADVANTAGE - The lithium ion battery has high output and energy density.    DETAILED DESCRIPTION - A lithium ion battery has a positive electrode comprising a positive electrode mixture layer on a current collector, a negative electrode comprising a negative electrode mixture layer on a current collector, an electrolyte and separator provided between electrodes. The positive electrode comprises positive electrode active material containing lithium composite oxide having compositional formula: LiNiaMnbCocMdO2, where M is iron, vanadium, titanium, copper, aluminum, tin, zinc, magnesium, boron and tungsten, a+b+c+d is 1, a is 0.2-0.8, b is 0.1-0.4, c is 0.l-0.4 and d is 0-0.1. The negative electrode comprises graphite as a negative electrode active material. The interlayer distance of graphite is 0.335-0.338 nm. The one-side thickness of positive and negative electrode mixture layers is 60-85 mu m and 40-75 mu m, respectively. The product of thickness (A) and density (B) of positive and negative electrode mixture layers is 160-220 and 65-105, respectively.    DESCRIPTION OF DRAWING(S) - The drawing shows the cross-sectional view of lithium ion battery.    Positive electrode (10)    Separator (11)    Negative electrode (12)    Battery can (13)    Inner lid (16)