Germanium oxide (GeO2) is a high theoretical capacity electrode material due to its alloying and conversion reaction. However, the actual cycling capacity is rather poor on account of suffering low electron/ion conductivity, enormous volume change and agglomeration in the repeated lithiation/delithiation process, which renders quite a low reversible electrochemical lithium storage reaction. In this work, highly amorphous GeO2 particles are uniformly distributed in the carbon nanofiber framework, and the amorphous carbon nanofiber not only improves the conduction and buffers the volume changes but also prevents active material agglomeration. As a result, the present GeO2 and carbon composite electrode exhibits highly reversible alloying and conversion processes during the whole cycling process. The two reversible electrochemical reactions are verified by differential capacity curves and cyclic voltammetry measurements during the whole cycling process. The corresponding reversible capacity is 747 mAh g-1 after 300 cycles at a current density of 0.3 A g-1. The related reversible capacities are 933, 672, 487 and 302 mAh g-1 at current densities of 0.2, 0.4, 0.8 and 1.6 A g-1, respectively. The simple strategy for the design of amorphous GeO2/carbon composites enables potential application for high-performance LIBs.
Keywords: GeO2; alloy reaction; amorphous; conversion reaction; lithium-ion batteries; reversible electrode.