Patent ID: 7498101

Claim:
A nonaqueous electrolyte secondary battery comprising: a positive electrode comprising a positive-electrode active material; a negative electrode comprising a particulate negative-electrode active material, carbon fibers, and carbon flakes; and a nonaqueous electrolyte solution, wherein, said positive-electrode active material and said negative-electrode active material are capable of intercalating and deintercalating lithium, said carbon fibers and said carbon flakes are disposed in interstices between said particulate negative electrode active material, a ratio by weight of said carbon flakes to said carbon fibers in said negative electrode is in a range of about 0.2 to about 100, said carbon flakes have a (002) interplanar spacing of less than about 0.3360 nm by X-ray diffractometry and a thickness of (002) c-axis crystallites of at least about 100 nm, said carbon flakes have a bulk density, as measured in accordance with Japanese Industrial Standard K-1469, is about 0.4 g/cm 3 or less, a maximum particle size of said carbon flakes, as measured by laser diffraction, is about 50 μm or less, and the particulate negative-electrode active material is substantially spherical.