NEGATIVE-ELECTRODE ACTIVE MATERIAL, NEGATIVE ELECTRODE USING SAME, AND LITHIUM-ION SECONDARY BATTERY

摘要

[Problem] To provide a negative-electrode active material for use in lithium-ion secondary batteries that results in a sufficiently high initial charging/discharging efficiency. [Solution] This negative-electrode active material, which contains silicon and a silicon oxide, is characterized by containing two phases that have different compositions and is also characterized in that one of said phases, a filamentous phase that forms a reticulated structure in cross-sections of primary particles of the negative-electrode active material, has a lower concentration of silicon than the other phase. The use of this negative-electrode active material substantially improves initial charging/discharging efficiency.