Revisiting Rb2TiNb6O18 as electrode materials for energy storage devices
Résumé
In the search of new materials for the future generation of Li-ion batteries, a look into the past has brought the multicationic oxide Rb2TiNb6O18 to the foreground. Structural characterization of this material has been carried out thanks to the combination of XRD, SEM and HRTEM highlighting the complex structure of this material. Ion exchange was performed in order to replace the rubidium ions by hydrated protons. Then, a comparative study of Rb2TiNb6O18 and the obtained proton exchanged analogues H2TiNb6O18 when used as negative electrode materials is depicted in terms of both structure and electrochemical behavior. Interestingly, while only a negligible Li+ insertion is evidenced in the rubidium phase, the H2TiNb6O18 exhibits a much higher lithium intercalation between 1 V and 3 V vs Li/Li+. A specific capacity of 118 mAh.g(-1) is reported when cycled at 0.02 A.g(-1). A solid solution type mechanism has been revealed by in situ XRD experiments. Moreover, during the lithiation, the volume of the material increases by only 1% showing the interest of this type of phase to develop "zero-strain" materials.
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