Patent ID: 7976984

Claim:
A nonaqueous electrolyte secondary battery comprising: a positive electrode including a positive electrode collector composed of a belt-shaped metal foil and a positive electrode active material layer provided thereon; a negative electrode including a negative electrode collector composed of a belt-shaped metal foil and a negative electrode active material layer provided thereon; and a separator, wherein the positive electrode and the negative electrode are provided with the separator therebetween being spirally wound, and wherein the negative electrode active material layer comprises a graphite powder obtained by spheroidizing natural graphite grains including dividing the graphite grains into at least two groups based on size, pulverizing each group separately, and subsequently mixing the groups wherein the graphite grains are bent during processing so as to spheroidize the graphite grains, a binder, and a viscosity improver, wherein the negative electrode collector provided with the negative electrode active material layer thereon is applied with a magnetic field so that edges of the graphite grains are oriented in a same direction, followed by drying to remove a solvent and compression molding, wherein when a perimeter of a circle having an area equivalent to that of an image of one of the spheroidized natural graphite grains is represented by L, an actual perimeter of an image of said one of the spheroidized natural graphite grains is represented by I, and the ratio L/I is defined as a circularity, a number of grains having a circularity of 0.85 or less is 20% or less of a total number of the grains, and wherein the spheroidized natural graphite grains have a strength ratio represented by {(110) face/(002) face} that ranges from 0.07 to 0.1 and wherein the strength ratio is measured by an X-ray diffraction method, and wherein the average circularity is 0.936 or more.