Hierarchical Structural Evolution of Zn2GeO4 in Binary Solvent and Its Effect on Li-ion Storage Performance
Zinc germinate (Zn2GeO4) with a hierarchical structure was successfully synthesized in a binary ethylenediamine/water (En/H2O) solvent system by wet chemistry methods. The morphological evolution process of the Zn2GeO4 was investigated in detail by tuning the ratio of En to H2O in different solvent systems, and a series of compounds with awl-shaped, fascicular, and cross-linked hierarchical structures was obtained and employed as anode materials in lithium-ion batteries. The materials with fascicular structure exhibited excellent electrochemical performance, and a specific reversible capacity of 1034 mA h g-1 was retained at a current density of 0.5 A g-1 after 160 cycles. In addition, the as-prepared nanostructured electrode also delivered impressive rate capability of 315 mA h g-1 at the current density of 10 A g-1. The remarkable electrochemical performances could be ascribed to the following aspects. First, each unit in the three-dimensional fascicular structure can effectively buffer the volume expansions during the Li+ extraction/insertion process, accommodate the strain induced by the volume variation, and stabilize its whole configuration. Meanwhile, the small fascicular units can enlarge the electrode/electrolyte contact area and form an integrated interlaced conductive network which provides continuous electron/ion pathways.