Sn-induced low-temperature growth of Ge nanowire electrodes with a large lithium storage capacity

We herein present the synthesis of germanium (Ge) nanowires on Au-catalyzed low-temperature substrates using a simple thermal Ge/Sn co-evaporation method. Incorporation of a low-melting point metal (Sn) enables the efficient delivery of Ge vapor to the substrate, even at a source temperature below 600 °C. The as-synthesized nanowires were found to be a core/shell heterostructure, exhibiting a uniform single crystalline Ge sheathed within a thin amorphous germanium suboxide (GeO_x) layer. Furthermore, these high-density Ge nanowires grown directly on metal current collectors can offer good electrical connection and easy strain relaxation due to huge volume expansion during Li ion insertion/extraction. Therefore, the self-supported Ge nanowire electrodes provided excellent large capacity with little fading upon cycling (a capacity of ∼900 mA h g^-1 at 1C rate).