Negative electrode material for use in non-aqueous electrolyte secondary battery, method of producing the same, and lithium-ion secondary battery

A method of producing a negative electrode material for use in a non-aqueous electrolyte secondary battery, comprising:

• making base powder out of silicon oxide powder expressed by a general formula of SiOx, where 0.5≦x≦1.6, as a silicon-contained material capable of occluding and emitting lithium ions;
• measuring a volume average particle diameter of the made base powder by using particle size distribution with laser diffractometry;
• randomly sampling 5000 particles or more from the base powder and measuring roundness of the sampled particles by image analysis of the particles, the roundness being defined by (a perimeter of a circle having the same projected area)/(a perimeter of the particle);
• selecting the base powder such that when the volume average particle diameter ranges from 0.5 to 20 μm, the roundness of the sampled particles is 0.93 or more on average, and a ratio of the number of particles having a roundness of 0.85 or less among the sampled particles is 5% or less;
• and
• coating a surface of the selected base powder with a carbon coating.