Patent ID: 8382860

Claim:
A process for producing a lithium secondary battery, comprising: preparing the lithium secondary battery including a positive electrode having an active material comprising a solid solution of a lithium transition metal composite oxide having an α-NaFeO 2 crystal structure; wherein a composition ratio of Li, Co, Ni, and Mn contained in the solid solution satisfies Li 1+(1/3)x Co 1−x−y Ni (1//2)y Mn (2//3)x+(1/2)y wherein x+y≦1, 0≦y and 1−x−y=z; in an Li[Li 1/3 Mn 2/3 ]O 2 (x)-LiNi 1/2 Mn 1/2 O 2 (y)-LiCoO 2 (z) ternary phase diagram, the active material is used where (x, y, z) is represented by values in a range present on or within a line of a heptagon (ABCDEFG) defined by the vertexes; point A(0.45, 0.55, 0), point B(0.63, 0.37, 0), point C(0.7, 0.25, 0.05), point D(0.67, 0.18, 0.15), point E(0.75, 0, 0.25), point F(0.55,0, 0.45), and point G(0.45, 0.2, 0.35); and an intensity ratio between diffraction peaks on (003) plane and (104) plane measured by X-ray diffractometry before charge-discharge is 2.25≧l (003) /l (104) ≧1.56, and charging the positive electrode of the lithium secondary battery in an initial charge-discharge process after preparing the lithium secondary battery and before an actual usage, the positive electrode of the lithium secondary battery being charged in said initial charge-discharge process to reach at least a region with relatively flat fluctuation of potential appearing relative to a charging electric amount in a positive electrode potential region, and exceeding 4.3V (vs. Li/Li + ) but lower than 4.8V (vs. Li/Li + ) or lower, wherein in charging the battery in the actual usage after said initial charge-discharge process, the positive electrode of the lithium secondary battery is always charged at a maximum achieved potential of 4.3V (vs. Li/Li + ) or lower.