with the O3 (RNaFeO 2 ) structure has been prepared from the analogous P3 sodium phase by ion exchange using LiBr in either ethanol at 80 °C or hexanol at 160 °C. The former preserves, to some extent, vacancies present on the transitional metal sites of the sodium phase, whereas the latter eliminates the vacancies. Materials with vacancies exhibit better performance as cathodes in rechargeable lithium batteries. The 2.5% Co doped material prepared in ethanol exhibits capacities of 200 mAhg -1 when cycled at C/8 between 2.4 and 4.6 V at 30 °C and with a fade of only 0.08% per cycle. A capacity of 180 mA h g -1 can be obtained at C/2 and 200 mAhg -1 at C rate and 55 °C. Importantly, this performance is obtained despite the fact that the materials convert to spinel-like phases on cycling. The spinel-like phases that form are nanostructured, with each crystallite being composed of a mosaic of nanodomains. The relief of strain at the domain wall boundaries accompanying the cubic-tetragonal phase transition may explain, at least in part, the facile cycling of these materials over a wide composition range (including the 3 V plateau) compared with high-temperature spinel which does not possess such nanodomains. Furthermore, vacancies present in the ethanol materials appear to migrate to the domain walls on cycling, rendering even more facile the Jahn-Teller-driven phase transformation on cycling these materials compared with those prepared in hexanol.
Oxygen intercalation into a pyrochlore at room temperature is reported. A simple chemical route was employed. Previously only perovskite or a few closely related phase have demonstrated an ability to act as hosts for such intercalation. The specific system studied was the interstitial solid solution Ce 2 Zr 2 O 7+x (0 e x e 0.36). Neutron diffraction reveals that interstitial oxygen enters the tetrahedral 8b sites (space group Fd3 hm), which are empty in stoichiometric pyrochlore, but displacement of existing oxygen from the tetrahedral 8a sites also occurs. The lattice contracts on intercalation due to oxidation of Ce 3+ . The changes in structure and the diffusion pathways for oxygen are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.