Amorphous titanium oxide nanoparticles were prepared from titanium isopropoxide. In situ measurements reveal an extraordinary high capacity of 810 mAh/g on the first discharge. Upon cycling at a charge/discharge rate of 33.5 mA/g, this capacity gradually decreases to 200 mAh/g after 50 cycles. The origin of this fading was investigated using X-ray absorption spectroscopy and solid-state nuclear magnetic resonance. These measurements reveal that a large fraction of the total amount of the consumed Li atoms is due to the reaction of H2 O/OH species adsorbed at the surface to Li2 O, explaining the irreversible capacity loss. The reversible capacity of the bulk, leading to the Li0.5 TiO2 composition, does not explain the relatively large reversible capacity, implying that part of Li2 O at the TiO2 surface may be reversible. The high reversible capacity, also at large (dis)charge rates up to 3.35 A/g (10C), makes this amorphous titanium oxide material suitable as a low cost electrode material in a high power battery.@en

Lithium intercalation and deintercalation in crystalline TiO 2-electrodes (rutile and anatase modifications) was investigated ex situ using grazing incidence reflection mode x-ray absorption spectroscopy in a specialized cell which permits the removal of the electrolyte and the subsequent measurement of grazing incidence x-ray absorption spectra under a protecting noble gas atmosphere. Small changes observed in near edge x-ray absorption spectra indicated that the Ti4+ ions are reduced by the electrochemical lithiation, depending on the TiO2 modification, Ti3.5+ states as well as Ti3+ states are observed for rutile and anatase, respectively. Angle dependent experiments reveal that the intercalation is not complete for rutile, while anatase seems to be fully intercalated. In addition, a certain amount of Li remains in the anatase electrode after a complete intercalation - deintercalation cycle. The results suggest that Li-ions are generally accumulated at the electrode/electrolyte interface during both intercalation and deintercalation.@en