A new approach to synthesis of porous SiO_x anode for Li-ion batteries via chemical etching of si crystallites

Unlike previous HF etching of Si oxides to produce porous Si a new concept for the preparation of porous SiO_x was suggested adopting Si as a pore generating agent and Si oxides as template using NaOH solution. The heat treatment of pristine SiO at 900 C provided nano-crystalline Si within the SiO_x matrix. The nano-crystalline Si was dissolved to provide pore size of 200∼500 nm, while most of the SiO_x matrix remained as a template during NaOH etching. The surface area of the etched SiO was increased more than 5 times compared with not-etched SiO. The porous SiO_x anode exhibited a stable reversible capacity of about 1240 mAh g^-1 over 100 cycles at 0.2 C.