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

• Published in: Journal of materials chemistry Vol. 13; no. 7; pp. 1747 - 1757
• Main Authors: TABUCHI, Mitsuharu, NAKASHIMA, Akiko, SHIGEMURA, Hikari, ADO, Kazuaki, KOBAYASHI, Hironori, SAKAEBE, Hikari, TATSUMI, Kuniaki, KAGEYAMA, Hiroyuki, NAKAMURA, Tatsuya, KANNO, Ryoji
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2003
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Ternary compound; Dynamic characteristic; Iron oxide; Cathode; Alkaline storage battery; Lithium batteries; Secondary cell; Electrode material; Solid solution; Discharge charge cycle; Calcining; Lithium oxide; Chemical synthesis; Titanium oxide
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/b209569f

Li4/3Ti2/3O2-LiFeO2 solid solution, Li(4-x)/3Ti(2-2x)/3FexO2 (x = 0.18-0.67), which has the cubic rock-salt structure (Fmbar3m, average particle size < 100 nm), was synthesised 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) and discharge capacities (153 mA.h/g around 3 V) between 2.5 and 4.8 V. Calcination not only improves the crystallinity, but also suppresses discharge capacity fading with cycle number. Two plateaus around 3 and 4 V were seen on discharging by decreasing the amount of Li extraction (0.4 Li per chemical formula). Although the cubic 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 seen after electrochemical delithiation. In-situ 57Fe Mossbauer spectroscopy showed evidence of the Fe3+/Fe4+ redox only around the 4 V region. 28 refs.