Method for manufacturing negative electrode material particles

A method for manufacturing negative electrode material particles, comprising the steps of:

• (a) mixing silicon oxide granules with a powder of a pitch without using any liquid organic solvents, so as to obtain a mixture;
• and
• (b) heating the mixture at a heating rate of 0.71° C./min to a carbonization temperature of 900° C., followed by maintaining the carbonization temperature for 5 hours, so that the thus melted pitch is carbonized and forms a carbon film on a surface of each of the silicon oxide granules, thereby obtaining the negative electrode material particles,
• wherein in step (a),
• the silicon oxide granules have a D10 particle size of 2.240 μm, a D50 particle size of 4.839 μm, and a D90 particle size of 7.876 μm,
• the pitch has a D10 particle size ranging from 0.5 μm to 2.0 μm, a D50 particle size ranging from 2 μm to 4 μm, and a D90 particle size ranging from 5 μm to 9 μm, the pitch having a softening point of not lower than 250° C., and a carbon to hydrogen ratio ranging from 1.43 to 1.66, and
• the pitch is present in an amount of 4 parts by weight based on 100 parts by weight of the silicon oxide granules, and
• wherein in step (b), each of the negative electrode material particles has a mean particle size ranging from 2 μm to 11 μm.