Method of producing silicon oxide, negative electrode active material for lithium ion secondary battery and lithium ion secondary battery using the same

Abstract

A method for producing a silicon oxide including the steps of supplying silicon atoms onto a substrate through an oxygen atmosphere to form a silicon oxide layer on the substrate, and separating the silicon oxide layer from the substrate and pulverizing the separated silicon oxide layer to obtain silicon oxide containing silicon and oxygen in predetermined proportions, and a negative electrode active material obtained by the production method.

1 - 4 . (canceled) 
   
   
       5 . A negative electrode active material for a lithium ion secondary battery, comprising silicon oxide particles including a chemical compound expressed by SiO x  (0.2≦x≦0.9), wherein the content of an impurity in the silicon oxide particles is 1 wt % or less. 
   
   
       6 . A negative electrode active material for a lithium ion secondary battery according to  claim 5 , wherein the average particle size of the silicon oxide particles is 0.5 to 20 μm. 
   
   
       7 . A negative electrode active material for a lithium ion secondary battery according to  claim 5 , further comprising carbon nanofibers and a catalyst element for promoting the growth of the nanofibers, wherein the carbon nanofibers bond to surfaces of the silicon oxide particles. 
   
   
       8 . A lithium ion secondary battery comprising a positive electrode, a negative electrode containing the negative electrode active material according to  claim 5 , a separator placed between the positive electrode and the negative electrode, and an electrolyte.