Size-controllable synthesis of Zn2GeO4 hollow rods supported on reduced graphene oxide as high-capacity anode for lithium-ion batteries.

Abstract

Germanium-based ternary oxides have aroused wide attention as an anode for high-performance lithium-ion batteries (LIBs). Nevertheless, they usually suffer a large volume expansion and rapid capacity fading during lithiation/delithiation cycles. To address this issue, herein, Zn2GeO4/RGO composites are synthesized with Zn2GeO4 hollow rods in-situ grown on reduced graphene oxide (RGO) sheets. The Zn2GeO4 hollow rods can be facilely adjusted from nano- to micro-size. The lithium storage performances of the composites strongly depend on the size of Zn2GeO4 hollow rods and the content of RGO. The optimized Zn2GeO4/RGO composite exhibits a pseudocapacitance-dominated Li+ storage performance, with a large reversible capacity of 1005 mAh g-1 after 100 cycles at 0.5 A g-1, an excellent rate capability (515 mAh g-1 at a high rate of 5 A g-1) and a good long cycling stability of 500 cycles with a low capacity loss of 0.05% per cycle at 1 A g-1. The outstanding electrochemical performance can be attributed to the unique composition and microstructure of the material as well as the synergistic effect of the conductive RGO sheets and the hollow Zn2GeO4 nanostructure. This work provides a promising anode for high-performance LIBs and a useful inspiration for further improving the Ge-based ternary oxide anodes.