Preparation And Electrochemical Performance Research Of Germanate Composites As Anode Materials For Lithium-ion Batteries

The metal-based anode materials, owning very high specific capacity in the first cycle, undergo serious capacity fading by virtue of experiencing large volume changes during lithium insertion and extraction process. In this work, ternary oxides, i.e. CuGeO3nanowires, Zn2GeO4nanorods, are prepared via hydrothermal methods and solid-state synthesis. To further stabilize the performance, graphene and graphite are added to the above materials to form composite materials. The composition and microstructure of these materials are characterized using XRD、SEM、TEM、XPS、Raman. And the electrochemical performance of above materials is measured by galvanostatic cycling、CV、EIS. The paper has carried out the following works:CuGeO3nanowires/graphene composites are also prepared by hydrothermal methods. During the process, Cu(CHCOO)2reacts with the GeO2transparent solution, yielding crystalline CuGeO3nanowires. Under the current density of200mA/g, the material, which contains37wt.%graphene, presents high capacity retention (1265mAh/g at the first cycle),71.6%coulombic efficiency in the first cycle, wonderful cyclic performance (853mAh/g after50cycles under a current density of200mA/g), high coulombic efficiency (～100%).A two-step hydrothermal synthesis method has been applied to prepare Zn2GeO4nanorods and graphene composites successfully. Partially crystalline Zn2GeO4nanorods have been prepared and applied as anode material. In addition, contents of graphene in the composites are about10wt.%and the material still presents great stability under large current density (0.8A/g), i.e. retaining a reversible specific capacity of514mAh/g after50cycles. In test of cyclic and rate capability, the coulombic efficiency is nearly100%.Considering the development of industrialization, Zn2GeO4is prepared by traditional solid-state method and mixed with graphite in different proportions by ball-milling. The composites present excellent cyclic performance under large current density, improving the attenuation of pure graphite. Finally, the20wt.%additive amount of Zn2GeO4is considered as the best proportion and the reversible specific capacity retains nearly500mAh/g after50cycles.