NOVELTY - Lithium ion secondary battery comprises: positive electrode; negative electrode; and electrolytic solution. At least one of the positive and negative electrodes is capable of storing and releasing lithium ions, and comprises active material that satisfies conditions including e.g.: (a) the active material comprising a lithium complex oxide or a lithium complex oxoacid salt that contains lithium, oxygen and at least one of Groups 2-15 elements; and (b) active material containing many primary particles having a particle size distribution with D10 which is greater than 1 nm and less than 65 nm.    USE - The lithium secondary battery is useful: in electronic device, electric power tool, electric vehicle and in power storage system (all claimed); and in e.g. video cameras, digital still cameras, mobile phones, laptop personal computers, cordless telephones, stereophones, portable radios, portable televisions, portable information terminals, personal digital assistant, electric shaver, backup power supply, a memory card, a pacemaker or a hearing aid.    ADVANTAGE - The lithium secondary battery: suppresses the over voltage at the late stage of charging or discharge, and improves the input-output characteristics of lithium ions; suppress the accidental deposition of the lithium metal as might occur, during high-speed charging or low-temperature charging; and exhibits improved electrical conductivity and ion conductivity.    DETAILED DESCRIPTION - Lithium ion secondary battery comprises: a positive electrode; a negative electrode; and an electrolytic solution. At least one of the positive electrode and the negative electrode is capable of storing and releasing lithium ions, and comprises an active material that satisfies the conditions including: (a) the active material comprising a lithium complex oxide or a lithium complex oxoacid salt that contains lithium, oxygen, and at least one of Groups 2-15 elements; (b) the active material containing many primary particles having a particle size distribution (median diameter: nm) with D10 which is greater than 1 nm and less than 65 nm, D50 which is greater than 5 nm and less than 75 nm, and D90 which is greater than 50 nm and less than 100 nm; (c) the active material having many pores between the primary particles, where the maximum peak pore size A (nm) in a pore size distribution as measured by a mercury intrusion technique is 10-75 nm; and (d) the ratio B/A of the maximum peak pore size A (nm) and the crystallite size B (nm) determined from the half width of the X-ray diffraction pattern of the active material as measured by X-ray diffractometry of greater than 0.5 to 1. INDEPENDENT CLAIMS are also included for:    (1) an electrode for lithium ion secondary batteries, comprising an active material capable of storing and releasing lithium ions, where the electrode satisfies the conditions (a)-(d); and    (2) an active material for lithium ion secondary batteries, where the active material is capable of storing and releasing lithium ions and satisfies the conditions (a)-(d).    DESCRIPTION OF DRAWING(S) - The figure illustrates a cross sectional view of illustrating the configuration of a lithium ion secondary battery using the active material.    Cylindrical battery canister (11)    Battery lid (14)    Safety valve mechanism (15)    Heat-sensitive resistive element (16)    Gasket (17)