Cobalt-doped Zn2GeO4 nanorods assembled into hollow spheres as high-performance anode materials for lithium-ion batteries

Abstract

In the search for high-performance anodes for next-generation lithium-ion batteries (LIBs), germanium-based compounds are recognized as one of the most promising candidates due to their extremely high theoretical capacity. In this study, a facile TEOA-assisted technology is presented to successfully fabricate Co-doped Zn₂GeO₄ hollow microspheres. The shell of the hollow microspheres is constructed by the self-assembly of uniform 1D single-crystalline nanorods with a length and diameter of about 2 μm and 100 nm, respectively. The reaction mechanism of the Co-doped Zn₂GeO₄ and the formation mechanism of the uniquely hollow structure were discussed. When used as an anode material for LIBs, the optimized Co-doped Zn₂GeO₄ hollow microspheres deliver a high discharge capacity of 1419 mA h g⁻¹ and a high charge capacity of 1063 mA h g⁻¹ for the first cycle, corresponding to a very high initial coulombic efficiency of 75%. A high capacity of 882 mA h g⁻¹ at 1.0 A g⁻¹ after 100 discharge–charge cycles was maintained and a capacity of 464 mA h g⁻¹ can be retained even at a high current density of 5.0 A g⁻¹. The remarkable electrochemical lithium storage performance can be a result of the synergistic effect of the hierarchical hollow structure and unique chemical composition. The hierarchical hollow structure allows for easy diffusion of electrolytes and shortens the pathway of Li⁺ transport during repeated Li⁺ extraction/insertion. Meanwhile, the Co doping can effectively improve charge transport for enhanced reaction kinetics.