Silica and its preparation method

The present invention relates to a method for preparing silicon oxide, silicon oxide prepared by this and a secondary battery including the silicon oxide, in the preparation process, by reducing the amount of oxygen from the silicon oxide containing a larger amount of oxygen to the amount of silicon and oxygen is appropriately controlled. The method of preparing the silicon oxide containing heat-treated in a reducing atmosphere relatively large amount of oxygen of the silica (first silica) to reduce the silica (first silica) the amount of oxygen, and a suitable amount of the preparation comprising the oxygen of silicon oxide and silicon (the second silicon) (Si: SiO2 = 1: 0.7 ~ 0.98), thereby improving the characteristics of the secondary battery capacity and the initial efficiency and to ensure its stability and the cycle characteristics and (life characteristics ).