Characterisation of the system Li–Na0.90Fe0.90Ti1.10O4 by electrochemical techniques

Abstract

The electrochemical insertion of lithium has been studied in order to determine, from the potential–composition curves, the domains of single-phase (or solid solution) and two-phase regions in the Li–Na0.90Fe0.90Ti1.10O4 (Li–NFTO) phase diagram. For this, the step potential electrochemical spectroscopy technique was applied to analyse the Li–NFTO system over a potential range from 3.1 to 1 V vs. lithium. In this voltage range 0.9 lithium ions/formula can be intercalated. Between 0≤x≤0.38, where the variable x is referred as x in LixNFTO, a solid solution is obtained. This process takes place in the potential range from 3 to 1.7 V. On the other hand, for x values greater than 0.38 a two-phase domain is developed, which finishes with the complete transformation of Li0.38NFTO to a compound of formal composition Li0.90NFTO. This second reduction falls into a lower potential range (1.7–1.3 V).