To obtain a new carbonaceous insertion compd. for batteries of a high capacity which is insertable with an alkali metal.

This carbonaceous insertion compd. consists of silicon and oxygen and are characterized by X-ray diffraction patterns that resemble that of amorphous silicon oxide. The carbonaceous insertion compd. is expressed by the following formula: AxSiyC1-yOz, where (a) A is an inserted alkali metal, (b) (x), (y) and (z) are x>0, 0<y<1 and 0<z/y<4. The process for production of such compd. and the lithium ion batteries using the compd. described above as the negative electrode are provided.