The electrochemical and local structural analysis of the mesoporous Li4Ti5O12 anode

Mesoporous lithium titanate microsphere anodes have been made by hydrothermal synthesis. Layered hydrous lithium titanate was obtained after hydrothermal reaction and Li4Ti5O12 microspheres assembled from nanosheets were subsequently formed by thermal treatment. This results in improved voltage profiles and charge/discharge dynamics. Mesoporous lithium titanate microspheres showed stable cycling performances, with high capacity retention (140 mAh g−1) even after 4000 cycles. In order to understand the functioning of this promising anode material at the molecular level, we used in-situ X-ray absorption spectroscopy (XAS). The XAS results verify the Ti conversion between Ti4+ and Ti3+ during charge/discharge cycling and demonstrate that this reduction is accompanied by small changes Ti-O distance but no detectable change in Ti-Ti distance. This anion re-arrangement suggests a structural explanation for the fact that this material is electrochemically very stable even under higher current density cycling.