A combined structural and electrochemical study of the compounds Na2Ti6O13 and Li2Ti6O13 titanates as anode electrodes for Li-ion batteries is presented. The structural differences between both titanates, where Na and Li atoms are located in an eightfold and [3+1] coordination, respectively, play a crucial role in the electrochemical behavior. Two-dimensional difference Fourier synthesis maps of LixNa2Ti6O13 and LixLi2Ti6O13 using NPD data provide valuable information about the possible reaction mechanism. In the first stages of Li insertion into Na2Ti6O13, Li enters the central tunnel site position (0.5, 0.5, 0.5), whereas the site of truly inserted Li in Li2Ti6O13 could not yet be unequivocally assessed. The different electrochemical behavior of Na2Ti6O13 and Li2Ti6O13 as electrodes in lithium rechargeable batteries is thought to be determined by the structural difference arising from the tunnel alkali metals Na+ and Li+.

A new protonated oxide has been synthesized by ion exchange of lithium by proton in lithium metazirconate, Li 2 ZrO 3 . Easy and complete ion exchange has been achieved in acidic medium. Characterization of the protonated solid by means of XϪray powder diffraction and thermogravimetric analysis allow to propose the nominal formulation "H 2 ZrO 3 ". However vibrational 1991 spectroscopy suggests that a more appropriate formulation would be as an oxyhydroxide ZrO(OH) 2 .

Zirconium I 4400 Synthesis and Characterization of a H + Exchanged Zirconate. -Complete ion exchange of Li + by H + in lithium metazirconate, Li2ZrO3, is achieved in acidic medium (5M aq. HNO3, 80°C, 24 h). Characterization of the protonated solid by means of powder XRD and TGA allows to propose the nominal formulation H2ZrO3. However vibrational spectroscopy suggests that a more appropriate formulation would be ZrO(OH)2. -(ORERA*, A.; KUHN, A.; GARCIA ALVARADO, F.; Z. Anorg. Allg. Chem. 631 (

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