Porous silicon nano-aggregate from silica fume as an anode for high-energy lithium-ion batteries

A porous silicon nano-aggregate (PSNA) has been prepared using a conproportionation'' reaction of magnesium silicide and silica fume, which is a waste by-product from the manufacture of metallurgical grade silicon. The as-prepared PSNA, with a pore diameter of 10-100 nm, is composed of Si nanoparticles with diameters of 10-50 nm. As an anode for a rechargeable lithium ion battery, it delivers a high reversible specific capacity (3224 mA h g(-1) at 0.36 A g(-1)) and significant cycling stability (similar to 90% capacity retention after 500 cycles and similar to 69% capacity retention even after 1000 cycles at a current density of 1.8 A g(-1)).