NOVELTY - A lithium ion secondary battery has a positive electrode and a negative electrode containing electrolyte solution. The positive electrode contains lithium complex oxide. The negative electrode contains silicon and/or tin as a constituent element, a first element and a second element. The first element comprises two or more lithium, manganese, nickel and cobalt. The second element comprises aluminum, titanium, magnesium and boron.    USE - Lithium ion secondary battery for an electric tool i.e. electrically-driven drill or electric saw, electric vehicle i.e. hybrid vehicle, and an electric power storage system i.e. domestic-use battery system (all claimed). Can also be used for portable electronic devices such as video camera, digital still camera, mobile telephone, notebook personal computer, cordless telephone apparatus, headphone stereo cassette tape recorder, portable radio, portable TV or portable information terminal, personal digital assistant, electric appliances for such as electric shaver, storage apparatus such as backup power supply or memory card, and medical electronic devices such as pacemaker and hearing aid.    ADVANTAGE - The battery has improved cycling characteristics and charging and discharging capacity, and high internal resistance, energy density and durability.    DETAILED DESCRIPTION - A lithium ion secondary battery has a positive electrode and a negative electrode containing electrolyte solution. The positive electrode contains lithium complex oxide. The negative electrode contains silicon and/or tin as a constituent element, a first element and a second element. The first element comprises two or more lithium, manganese, nickel and cobalt. The second element comprises aluminum, titanium, magnesium and boron, where the composition ration of the elements satisfies the following relation: 'a' is greater than 1.1 but less than 1.3, 'b+c' is greater than 0.7 but less than 1.1, 'c' is greater than 0 but less than 0.1, and 'a' is greater than b+c.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of a part of a winding electrode body.    Winding electrode body (20)    Positive electrode (21)    Positive electrode collector (21A)    Positive electrode active material layer (21B)    Negative electrode (22)    Separator (23)