Lithium intercalation into the titanosilicate sitinakite

A preliminary investigation of lithium intercalation into the microporous titanosilicate sitinakite (with nominal formula Na2Ti 2O3SiO4·2.76H2O), along with its ion-exchanged (H+ and Li+) and niobium-doped variant, Na2Ti1.9Nb0.1O3SiO 4·2.76.H2O, is reported. The sitinakite framework intercalates lithium with some degree of reversibility; however, capacity fade and a steep voltage profile are observed. Furthermore the low potential of the intercalation reactions appears to coincide with the breakdown of the electrolyte and solvent components used in this study. Ion exchange of Na + in the parent sitinakite framework for H+ shows improved electrochemical performance of the titanosilicate-based electrode composition, while Li+ exchange affords the opposite. It is postulated that the ion-exchanged Li+ occupies sites within the sitinakite framework which are desirable for electrochemically inserted lithium, reducing electrochemical occupancy and hence capacity. Improved electrochemical performance has been realized through the heat treatment of electrodes with capacities after 20 cycles in the range 180-200 mA h g-1. This capacity compares favorably with that reported for rutile at high temperature and the recently commercialized Li4Ti5O12. © 2006 American Chemical Society.