Patent ID: 7560085

Claim:
Porous silicon particles prepared from a metallurgical grade silicon powder having a starting composition consisting of from about 98.6 to about 99.0 weight percent Si; from about 0.03 to about 0.50 weight percent Fe; from about 0.05 to about 0.2 weight percent Al; from about 0.00 to about 0.08 weight percent Ca; from about 0.00 to about 0.15 weight percent C; and from about 0.2 to about 1.0 weight percent O 2 and wherein the metallurgical grade silicon powder has an initial particle size greater than about 1 micron wherein each porous silicon particle comprises a solid core consisting of the metallurgical grade silicon surrounded by a porous silicon layer having a thickness ranging from about 0.6 microns to about 2.0 microns; wherein each porous silicon particle comprises pores having an average pore diameter ranging from about 2.0 nm to about 8.0 nm as calculated from nitrogen adsorption isotherm data using the Barret-Joyner-Halenda scheme; and a BET surface area of at least 56.65 m 2 /g.