Cu-Ge core-shell nanowire arrays as three-dimensional electrodes for high-rate capability lithium-ion batteries

We demonstrate the synthesis of three-dimensional Cu-Ge core-shell nanowire array electrodes by directly depositing Ge on the surface of pre-synthesized Cu nanowire arrays via an rf-sputtering method. When used as anodes of lithium-ion batteries, the Cu-Ge nanowire arrays display a high capacity of 1419 mAh g(-1) at 0.5 C after 40 cycles and 734 mAh g(-1) at 60 C after 80 cycles, which is better than planar electrodes. The improved performance can be attributed to the good electrical contact, fast electron transport and good strain accommodation of the nanowire array electrodes. The effect of the thickness of Ge layer on the electrochemical performance of the three-dimensional electrodes has also been investigated.