Nano-featured porous silicon materials

A nano-featured porous silicon material comprising:

• a skeletal density less than 2.2 g/cm3 as measured by helium pcynometry;
• ii) a friability greater than 10%;
• iii) a specific surface area between 30 and 230 m2/g;
• and
• iv) a pore volume between 0.1 and 0.5 cm3/g,
• wherein the friability is the percent reduction in volume average particle size when the nano-featured porous silicon material is particle size reduced by jet milling.