Sanyo Electric Co., Ltd.

Sumitomo Metal Mining Company, Ltd.

Fukui Atsushi

Taizou Sunano

Kouhei Tuduki

Oda Shuhei

Inoue Katsuya

Toya Hiroyuki

The invention provides a nonaqueous electrolyte secondary battery having a large battery capacity and excellent charge/discharge cycle characteristics. The nonaqueous electrolyte secondary battery includes a negative electrode including a particulate negative electrode active material (), a positive electrode and a nonaqueous electrolyte. The particulate negative electrode active material () includes a plurality of two-phase regions () in the particle wherein the two-phase regions include a first phase (A) containing silicon and a second phase (B) containing silicon oxide disposed on the periphery of the first phase, the negative electrode active material being such that the ratio of the intensity at 480 cmwavelength to the intensity at 510 cmwavelength in a Raman spectrum obtained by Raman spectroscopy is not more than 0.1 and the ratio of the intensity at 2&#x3b8;=21.6 to the intensity at 2&#x3b8;=28.4 in an X-ray diffraction pattern obtained by X-ray diffractometry is not more than 0.1.

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Hyogo, Japan

Fukui Atsushi