The C-Zn system was investigated for use as anode materials for Li-ion cells. Thin films of the entire composition range were made by combinatorial sputtering. The grain size of Zn was reduced and became nanocrystalline as the carbon content in the film increased. Sputtered films rich in amorphous carbon were found to have a high capacity, corresponding to the formation of Li0.5C during lithiation, confirming previous studies. The presence of Zn was found to significantly reduce the irreversible capacity and improve cycle life over that of pure carbon films. However, Zn was also found to catalytically decompose electrolyte at the electrode surface during cycling, resulting in poor coulombic efficiency. This brings into doubt the usefulness of Zn as a component of anode materials for Li-ion cells. (C) 2014 The Electrochemical Society. All rights reserved.