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

Lu, Jiaxue, Li, Deli, Li, Li, Chai, Yao, Li, Meng, Yang, Shun, Liang, Jun
Journal of materials chemistry 2018 v.6 no.14 pp. 5926-5934
anodes, chemical composition, cobalt, electrochemistry, electrolytes, lithium, lithium batteries, microparticles, nanorods, reaction kinetics, reaction mechanisms, synergism
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.