PURPOSE: To reduce capacity degradation caused by a charge and discharge cycle by specifying a lattice constant of the (c) axis of an LiCoO2 crystal, and specifying also the surface directional crystallite size in a nonaqueous solvent secondary battery formed by using a hexagonal crystal LiCoO2 as a positive electrode active material.
CONSTITUTION: For example, a coin type nonaqueous solvent secondary battery is composed of a stainless steel made positive electrode container 1, a positive electrode 3 through a current collecting body 2, a separator 4 to hold electrolytic solution, a negative electrode 5 and a negative electrode container 7 through a packing 6. Here, propylene carbonate, ethylene carbonate and the like are used in solvent as the electrolytic solution, and LiClO2, LiAsF6 and the like are used in electrolyte, and a hexagonal crystal LiCoO2 is used in a positive electrode active material. A porous thin film or nonwoven fabric composed of polypropylene or polyethylene is used as a separator. At this time, a lattice constant of the (c) axis of the hexagonal crystal LiCoO2 is set not less than 14.05, and the crystal size is set not more than 400 in a (100) surface direction, and is set not more than 300 in a (003) surface direction.