Ge/C Nanowires as High-Capacity and Long-Life Anode Materials for Li-Ion Batteries

摘要

Germanium-based materials (Ge and GeO_x) have recently demonstrated excellent lithium-ion storage ability and are being considered as the most promising candidates to substitute commercial carbon-based anodes of lithium-ion batteries. Nevertheless, practical implementation of Ge-based materials to lithiumion batteries is greatly hampered by the poor cyclability that resulted from the huge volume variation during lithiation/delithiation processes. Herein, uniform carbonencapsulated Ge and GeO_x nanowires were synthesized by a one-step controlled pyrolysis of organic-inorganic hybrid GeO_x/ethylenediamine (GeO_x/EDA) nanowires in H_2/Ar and Ar atmospheres, respectively. The as-obtained Ge/C and GeO_x/C nanowires possess well-defined 0D-in-1D morphology and homogeneous carbon encapsulation, which exhibit excellent Li storage properties including high specific capacities (approximate 1200 and 1000 mA h g~(-1) at 0.2C for Ge/C and GeO_x/C, respectively). The Ge/C nanowires, in particular, demonstrate superior rate capability with excellent capacity retention and stability (producing high stable discharge capacities of about 770 mA h g~(-1) after 500 cycles at 10C), making them promising candidates for future electrodes for high-power Li-ion batteries. The improved electrochemical performance arises from synergistic effects of 0D-in-1D morphology and uniform carbon coating, which could effectively accommodate the huge volume change of Ge/GeO_x during cycling and maintain perfect electrical conductivity throughout the electrode.