| Abstract
| - A preliminary investigation of lithium intercalation into the microporous titanosilicate sitinakite (withnominal formula Na2Ti2O3SiO4·2.76H2O), along with its ion-exchanged (H+ and Li+) and niobium-doped variant, Na2Ti1.9Nb0.1O3SiO4·2.76H2O, is reported. The sitinakite framework intercalates lithiumwith 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 ofthe electrolyte and solvent components used in this study. Ion exchange of Na+ in the parent sitinakiteframework for H+ shows improved electrochemical performance of the titanosilicate-based electrodecomposition, while Li+ exchange affords the opposite. It is postulated that the ion-exchanged Li+ occupiessites within the sitinakite framework which are desirable for electrochemically inserted lithium, reducingelectrochemical occupancy and hence capacity. Improved electrochemical performance has been realizedthrough 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 recentlycommercialized Li4Ti5O12.
- The crystalline microporous titanosilicate known as sitinakite has a one-dimensional channel architecture consisting of titanate wires running down the c-axis. The framework is therefore redox active and displays reversible lithium intercalation. The electrochemical and structural properties of this novel redox-active microporous oxide during Li insertion are described for the first time.
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