Facile one-pot synthesis of Ge/TiO2 nanocomposite structures with improved electrochemical performance.

Abstract

Germanium (Ge) as an alternative to graphite exhibits a fairly high theoretical energy density and improved Li+ ion diffusivity. However, the seriously deteriorated electrochemical performance of Ge during cycling and the difficulty in the preparation of Ge-based nanostructures can hinder the utilization of Ge as an anode. Thus, in this study, a nanocomposite structure with Ge and TiO2 (Ge/TiO2) was synthesized using a facile one-pot method with different ratios of a Ge source with a dominant GeO2 phase and titanium isopropoxide. From X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy, the Ge/TiO2 nanocomposites were found to be spherical structures homogeneously consisting of the reduced Ge as an active material and amorphous TiO2 as a matrix. In particular, the Ge/TiO2 nanocomposite with an appropriate amount of TiO2 exhibited improved electrochemical properties, i.e., a coulombic efficiency of 97% and a retention of 61% for 100 cycles, compared to commercial Ge (a coulombic efficiency of 82% and a retention of 16%). This demonstrates that the amorphous TiO2 matrix could relieve a volumetric expansion of the Ge active material in the nanocomposite electrode generated during the cycling process.