H2Ti6O13, a new protonated titanate prepared by Li+/H+ ion exchange: synthesis, crystal structure and electrochemical Li insertion properties

The hexatitanate H2Ti6O13 is obtained by a simple successive Na+/Li+/H+ ion exchange of Na2Ti6O13. The crystal structure of H2Ti6O13 was solved from both synchrotron and neutron powder diffraction. H2Ti6O13 crystallizes in the monoclinic space group C2/m, with a = 14.6702(3) angstrom; b = 3.7447(1) angstrom; c = 9.2594(2) angstrom; beta = 96.941(2)degrees. The monoclinic symmetry of the Ti6O13 was developed. H2Ti6O13 then yielded a higher reversible specific capacity than Na2Ti6O13 and comparable to Li2Ti6O13. Besides structural details, IR spectroscopy has been used to further assess possible reaction mechanisms pointing to the transformation of H2Ti6O13 to Li2Ti6O13 when reacting with the very first two lithium ions.