Alkanethiol-Passivated Ge Nanowires as High-Performance Anode Materials for Lithium-Ion Batteries: The Role of Chemical Surface Functionalization

We demonstrate that dodecanethiol monolayer passivation can significantly enhance the anode performance of germanium (Ge) nanowires in lithium-ion batteries. The dodecanethiol-passivated Ge nanowires exhibit an excellent electrochemical performance with a reversible specific capacity of 1130 mAh/g at 0.1 C rate after 100 cycles. The functionalized Ge nanowires show high-rate capability having charge and discharge capacities of similar to 555 mAh/g at high rates of 11 C. The functionalized Ge nanowires also performed well at 55 degrees C, showing their thermal stability at high working temperatures. Moreover, full cells using a LiFePO4 cathode were assembled and the electrodes still have stable capacity retention. An aluminum pouch type lithium cell was also assembled to provide larger current (similar to 30 mA) for uses on light-emitting-diodes (LEDs) and audio devices. Investigation of the role of organic monolayer coating showed that the wires formed a robust nanowire/PVDF network through strong C F bonding so as to maintain structure Integrity during the lithiation/delithiation process Organic monolayer-coated Ge nanowires re-present promising Ge C anodes with controllable low carbon content (ca. 2-3 wt %) for high capacity, high rate lithium Ion batteries and are readily compatible with the commercial slurry coating process for cell fabrication.