Preferentially Orientated Li-Deficient Li4Ti5O12 Nanosheet Anode and Its Excess Charge Storage Properties

Mesoporous Li deficient Li₄Ti₅O₁₂ nanosheets with major [110] preferred orientation were prepared by a novel low T (<100 °C) aqueous synthesis process. Surface relaxation due to nanosize effect in the near surface region and 10 % deficiency of lithium were found to lead to local chemical bond length extension that influences the electronic structure and Li storage capacity. Thus the lithiated material over the potential range from 1 to 2.5 V vs. Li/Li⁺ reaches the following over-stoichiometrical composition: Li_7.92Ti₅O₁₂. As determined by XANES the excess Li-ion storage is the result of preferential crystal orientation along the (110) and (111), facets. During lithiation, it was further determined the charge compensation to occur primarily by oxygen, rather than by titanium. Finally, both the oxygen and titanium in the near surface region exhibit different electronic structure from bulk. Those results point to the importance of surface reconstruction and relaxation in accommodating excess Li storage. As a consequence, the newly prepared Li₄Ti₅O₁₂ nanosheets exhibit superior Li-ion storage performance exceeding by far most of the alternatively prepared LTO anode materials.