Enhancing lithium ion diffusion kinetic in hierarchical lithium titanate@erbium oxide from coating to doping via facile one-step co-precipitation.

Hierarchical lithium titanate@erbium oxide (Li4Ti5O12@Er2O3) microspheres from coating to doping were successfully synthesised by a simple and scalable one-step co-precipitation method. Microscopic observations revealed that the Li4Ti5O12@Er2O3 microspheres present a well-defined hierarchical structure and that Li4Ti5O12 is coated by the Er2O3 layer. The X-ray photoelectron spectroscopy (XPS) results demonstrate that partial Ti4+ is reduced to Ti3+ and induces oxygen vacancy because partial Er3+ dope into octahedral 16d Li+/Ti4+ sites of Li4Ti5O12. Owing to the hierarchical microsphere structure, Er2O3 coating, and Er3+ doping, the material exhibits excess rate capacity (183.7 mAh g-1 at 30C). The hierarchical microsphere structure shortens the diffusion pathways for Li+ ions. The Er2O3 coating on the surface reduces the adverse interface reaction. Importantly, oxygen vacancy induced by Er3+ doping enhances Li+ ion diffusion kinetics and offers extra space to store Li+ ions, which endows this sample with excess rate capacity.