Ab initio calculations of hybrid carbon-silicon nanostructures for new high performance lithium ion batteries

Graphite has been used as an anode in lithium ion batteries for a few decades now due to its coulombic efficiency and high charge/discharge cycling performance. However, with an increase in energy demand in newer electronic devices or future electric cars, and added to the low theoretical specific capacity of 372 mAh/g in graphite (one lithium atom for six carbon atom via intercalation), new kind of anodes has to be found. To satisfy this request, a lot of effort has already been made, from transition metal oxides to mesoporous carbon as candidates for anode materials. In recent years, research has been focused on silicon due to a theoretical specific capacity more than ten times higher than of graphite (4212 mAh/g, Li4.4Si). [5] Unfortunately the large volume change (> 300%) during lithiation and a poor cycle performance make bulk silicon unusable as a conventional anode material. Here, we present ab initio simulations for new nanostructures , as possible anode materials. We first investigated the structural and electronic properties of such structures. The electrical conductances of these hybrid nanostructures are also predicted for both pristine case and under lithiation.