Fine Li(4 - x)/3Ti(2 - 2x)/3FexO2 (0.18 ≤ x < 0.67) powder with cubic rock-salt structure as a positive electrode material for rechargeable lithium batteries

Mitsuharu Tabuchi, Akiko Nakashima, Hikari Shigemura, Kazuaki Ado, Hironori Kobayashi, Hikari Sakaebe, Kuniaki Tatsumi, Hiroyuki Kageyama, Tatsuya Nakamura, Ryoji Kanno

Research output: Contribution to journalArticlepeer-review

Abstract

Li4/3Ti2/3O2-LiFeO2 solid solution, Li(4 - x)/3Ti(2 - 2x)/3FexO2 (0.18 ≤ × ≤ 0.67), which has the cubic rock-salt structure (Fm3m, average particle size less than 100 nm), was synthesized from Fe-Ti co-precipitates by hydrothermal reaction with excess LiOH and KClO3 at 220 °C. Calcination of the products with lithium hydroxide in an oxidative atmosphere leads to the oxidation of trivalent iron to a 3+/4+ mixed valence state. Hydrothermally-obtained Li1.2Ti0.4Fe0.4O2 gave maximum initial charge (266 mA h g-1) and discharge capacities (153 mA h g-1 around 3 V) between 2.5 and 4.8 V. Calcination enabled us not only to improve the crystallinity, but also suppress the discharge capacity fading with cycle number. Two plateaus around 3 and 4 V were observed on discharging by decreasing the amount of Li extraction (0.4 Li per chemical formula). Although the cubic rock-salt structure was retained during both charge and discharge processes, a partial 3d-cation displacement from octahedral 4a to tetrahedral 8c sites and some oxygen loss were observed after electrochemical delithiation. In-situ 57Fe Mössbauer spectroscopy showed evidence of the Fe3+/Fe4+ redox only around the 4 V region.

Original languageEnglish
Pages (from-to)1747-1757
Number of pages11
JournalJournal of Materials Chemistry
Volume13
Issue number7
DOIs
Publication statusPublished - Jul 1 2003
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Chemistry

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