Patent ID: 6913856

Claim:
A nonaqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material, a negative electrode containing a negative electrode active material capable of being doped/undoped with lithium nonaqueous electrolyte, a separator, and an exterior casing, wherein, the positive electrode comprises a positive electrode sheet comprising a positive electrode collector and positive electrode active material layers containing the positive electrode active material formed on both surfaces of the positive electrode collector, the negative electrode comprises a negative electrode sheet comprising a negative electrode collector and negative electrode active material layers containing the negative electrode active material formed on both surface of the negative electrode collector, the negative electrode active material comprises a graphite material with a true density of 2.1 g/cm 3 or more, a (002) interplanar distance of less than 0.340 nm, and an average value of the shape parameter X of 125 or less, the shape parameter X being equal to (W/T)×(L/T), W being the length of a parameter in a direction perpendicular to the longitudinal axis, T being the thickness of the thinnest portion of the particle, L being the length of the particle in the longitudinal direction, the positive electrode and the negative electrode are stacked with the separator there between and the resulting stack is rolled in a longitudinal direction to form spirally-wound electrodes, the spirally-wound electrodes are accommodated within the exterior casing; and the nonaqueous electrolyte contains a thioacetate in a range from 0.03 to 10 percent by weight of the electrolyte.