Germanium–single-wall carbon nanotube anodes for lithium ion batteries

High-capacity thin-film germanium was coupled with free-standing single-wall carbon nanotube (SWCNT) current collectors as a novel lithium ion battery anode. A series of Ge–SWCNT compositions were fabricated and characterized by scanning electron microscopy and Raman spectroscopy. The lithium ion storage capacities of the anodes were measured to be proportional to the Ge weight loading, with a 40 wt% Ge–SWCNT electrode measuring 800 mAh/g. Full batteries comprising a Ge–SWCNT anode in concert with a LiCoO₂ cathode have demonstrated a nominal voltage of 3.35 V and anode energy densities 3× the conventional graphite-based value. The higher observed energy density for Ge–SWCNT anodes has been used to calculate the relative improvement in full battery performance when capacity matched with conventional cathodes (e.g., LiCoO₂, LiNiCoAlO₂, and LiFePO₄). The results show a >50% increase in both specific and volumetric energy densities, with values approaching 275 Wh/kg and 700 Wh/L.