Nanocomposite silicon electrode and method

Abstract

A silicon based micro-structured material and methods are shown. In one example, the silicon based micro-structured material includes a carbon coating. In one example, the silicon based micro-structured material is used as an electrode in a battery, such as a lithium ion battery.

What is claimed is: 
     
         1 . A method of forming a battery electrode, comprising:
 mixing silicon oxide spheres and sodium chloride;   adding a reducing agent;   reducing the silicon oxide spheres and sodium chloride mixture to form silicon spheres;   etching the reduced silicon spheres to form porous silicon spheres; and   forming a carbon coating over a surface of the porous silicon spheres, wherein the porous silicon spheres includes a surface area of between 20 m 2 g −1  and 40 m 2 g −1  with the carbon coating covering a surface portion of the porous silicon spheres.   
     
     
         2 . The method of  claim 1 , wherein reducing the silicon oxide spheres and sodium chloride mixture includes magnesiothermically reducing the silicon oxide spheres and sodium chloride mixture. 
     
     
         3 . The method of  claim 2 , wherein mixing silicon oxide spheres and sodium chloride includes mixing silicon oxide spheres and sodium chloride in a ratio of approximately 1:10 silicon oxide to sodium chloride by weight. 
     
     
         4 . The method of  claim 3 , further including mixing magnesium powder with the silicon oxide spheres and sodium chloride in a ratio of approximately 1:0.9 silicon oxide to magnesium by weight. 
     
     
         5 . The method of  claim 1 , wherein forming the carbon coating over the surface of the porous silicon sphere includes CVD coating of carbon over the surface of the porous silicon sphere. 
     
     
         6 . The method of  claim 5 , wherein forming the carbon coating over the surface of the porous silicon sphere includes converting C 2 H 2  at elevated temperature into a carbon coating. 
     
     
         7 . The method of  claim 6 , wherein forming the carbon coating over the surface of the porous silicon sphere includes heating to about 900 degrees Celsius in an inert gas atmosphere along with the C 2 H 2 . 
     
     
         8 . A method of forming a battery electrode, comprising:
 mixing silicon oxide nanoparticles and sodium chloride;   adding a reducing agent;   reducing the silicon oxide nanoparticles and sodium chloride mixture to form silicon nanoparticles in substantially the same geometry as the silicon oxide nanoparticles;   etching the silicon nanoparticles to form porous silicon nanoparticles; and   forming a carbon coating over a surface of the porous silicon nanoparticles, wherein the number of porous silicon nanoparticles include a surface area of between 20 m 2 g −1  and 40 m 2 g −1  with the carbon coating covering a surface portion of the porous silicon nanoparticles.   
     
     
         9 . The method of  claim 8 , wherein mixing silicon oxide nanoparticles includes mixing silicon oxide nanospheres.