Enhancing the electrochemical performance of a micron-sized Ge anode through in situ surface composite flower-like Zn2GeO4 for Li-ion batteries

Abstract

The large volume changes of Ge-based electrode result in poor electrochemical cycling and rate performance and are the important factors hampering the practical implementation of Ge-based materials in Li-ion batteries (LIBs). Here we fabricated a fascicular structure Ge/Zn₂GeO₄ (Ge/Zn₂GeO₄NFs) by an in situ growth of flower-like Zn₂GeO₄ on micron-sized Ge. In an EDTA/water solvent system, Zn₂GeO₄ were generated on the Ge substrate, and self-assembled into a flower-like structure through coordination and H-bonding. Benefiting from the improved structural stability and abundant transmission channels of lithium ions and electrons, the as-fabricated Ge/Zn₂GeO₄NFs anodes exhibited excellent cyclability and rate performance. At a current density of 0.2 A g⁻¹, Ge/Zn₂GeO₄NFs delivered a high capacity of 1621 mA h g⁻¹ with an initial coulombic efficiency of 62%, and even after the 200th cycle a capacity of 816 mA h g⁻¹ could be maintained. Further, the Ge/Zn₂GeO₄NFs anode delivered excellent rate capabilities of 567 and 388 mA h g⁻¹ at high current densities of 2 and 5 A g⁻¹, which were superior to the micron-sized Ge electrode (133 mA h g⁻¹ at 5 A g⁻¹). The results show that the Zn₂GeO₄ nanoflower, which adheres on the micron Ge substrate inseparably, could buffer the volume change of Ge, enlarge the electrolyte contact area, provide continuous lithium-ion and electron pathways, and thus improve the lithium-storage performance of the micron-sized Ge electrodes. This synthesis strategy provides new ideas for the development of micron-sized anode materials for LIBs.