Abstract: Using a crystal (lithium cobaltate) having a crystallite size in the direction of (003) plane of not less than 800 angstrom and a coordination number of a cobalt atom to a different cobalt atom of not less than 5.7 as a positive electrode active material, a lithium ion secondary battery is formed. As a result, the rate characteristic, low temperature characteristic, cycle characteristic and the like of the lithium ion secondary battery can be improved. In addition, by combining a preferable embodiment of the positive plate such as (an embodiment wherein not more than 50% of the surface of a positive electrode active material is covered with a conductive material), (an embodiment wherein two kinds of conductive materials having a particle size of not less than 3 &mgr;m and a particle size of not more than 2 &mgr;m are used, or one kind of a conductive material having a particle size of not more than 10 &mgr;m is used and the porosity of the positive electrode coating layer is 0.08 cc/g-0.

Abstract: The present invention relates to a positive electrode active material, a negative electrode active material and an electrolyte that are used alone or in combination to improve charge and discharge cycle characteristic, low temperature characteristic and safety of a non-aqueous electrolyic secondary battery, particularly a lithium ion secondary battery. Specifically, a particulate Li-transition metal composite oxide having an average particle size of not less than 10 &mgr;m, wherein [20/(specific surface area×average particle size)]=7-9, is used as a positive electrode active material.