| 摘要 |
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 mum and a particle size of not more than 2 mum are used, or one kind of a conductive material having a particle size of not more than 10 mum is used and the porosity of the positive electrode coating layer is 0.08 cc/g-0.14 cc/g), (an embodiment wherein a conductive material containing at least carbon black is used and a specific surface area of the positive electrode coating layer is 0.5 m2/g-1.0 m2/g) and the like, and further incorporating a combination of an embodiment of a preferable negative electrode active material and an electrolyte, a more preferable lithium ion secondary battery having sufficient battery capacity, which is superior in cycle characteristic, preservation property, safety, low temperature characteristic and the like is obtained.
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