| 摘要 |
PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery of large capacity and long life which is excellent in a cycle characteristic and an output characteristic, by relaxing a stress caused by volume expansion/contraction at the time of charging/discharging and assuring conductivity.SOLUTION: A negative electrode composition contains negative electrode active material, conductive assistant, and binding agent. The negative electrode active material contains compound particles in which a percentage of cobalt against a total amount of tin and cobalt is 5-40 atom%. The compound particles have a structure in which tin is arranged at the center and cobalt is localized on an outer surface of tin, or a structure in which the compound particles have a plurality of pores communicating with the surface of the compound particles at a cut plane, and cobalt is localized on an outer surface of the compound particles and an inner surface of the pores. A powder X-ray diffraction method shows a crystal phase having a peak at 2&thetas;=28.9°, 32.8°, 41.4°, 42.6°, and 44.3°. The conductive assistant is carbon material such as carbon nanofiber and sticks to the outer surface of the compound particles or the like in mesh. |
