POWDER FOR NEGATIVE ELECTRODE OF LITHIUM ION SECONDARY CELL, AND METHOD FOR PRODUCING SUCH POWDER

摘要

Provided is a powder for the negative electrode of a lithium ion secondary cell, the powder including a silicon oxide powder containing Li. The average composition of the powder overall satisfies the relationships 0.5 < x < 1.5 and 0.1 < y/x < 0.8 when the molar ratio of Li, Si, and O is y:1:x. The volume median diameter of the powder for the negative electrode is within a range of 0.5 to 30 µm. When X-ray diffraction measurement of the powder is performed using CuKα rays, the relationships P2/P1 ≤ 1.0 and P3/P1 ≤ 1.0 are satisfied if P1 is the height of the peak attributed to Li2SiO3, P2 is the height of the peak attributed to crystalline Si, and P3 is the height of the peak attributed to Li4SiO4. When the powder is used in the negative electrode of a lithium ion secondary cell, the initial efficiency and capacity retention rate of a long-term cycle can be increased.