High-capacity Li-excess lithium nickel manganese oxide as a Co-free positive electrode material. (May 2021)

• Record Type: Journal Article
• Authors: Tabuchi, Mitsuharu; Kataoka, Riki; Yazawa, Koji
• Is Part Of: Materials research bulletin. Volume 137(2021)
• Publication Date: 2021-05
• Subjects: Layered compounds -- Oxides -- Chemical synthesis -- Nuclear magnetic resonance (NMR) -- XANES; Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2020.111178
• Languages: English
• ISSNs: 0025-5408

Abstract

Graphical abstract: Highlights: LiNi1/2 Mn1/2 O2 and Li1+x (Niy Mn1-y )1-x O2 (y = 0.4 and 0.5) samples are prepared. The Li-excess samples calcined in air exhibits better electrochemical performance. The Li1+x (Niy Mn1-y )1-x O2 samples are attractive Co-free positive electrode material. Abstract: For the design of high-capacity and Co-free positive electrode material, stoichiometric LiNi1/2 Mn1/2 O2 and Li-excess Li1+x (Niy Mn1-y )1-x O2 (0< x <1/3, y = 0.4 and 0.5) samples were prepared using coprecipitation–calcination. The basic LiNi1/2 Mn1/2 O2 structure is hexagonal layered rock-salt structure ( R 3 ¯ m ), but the sample has a biphasic composite of main Li-poor Li1-x TM1+x O2 (TM, transition metal) and minor Li-rich Li1+x TM1-x O2 phases after calcination below 950 °C. The fraction of the minor Li-rich phase decreased concomitantly with increasing calcination temperature. Only at 1000 °C was single-phase LiNi1/2 Mn1/2 O2 obtainable. The biphasic samples exhibited better electrochemical performance than that for the single-phase sample. Based on this result, two Li-excess Li1+x (Niy Mn1-y )1-x O2 (0< x <1/3, y = 0.4 and 0.5) samples were synthesized by setting an excess amount of Li2 CO3 (nominal Li/(Ni + Mn) ratio = 2) and calcination in air. Both samples were usefulness as a high-capacity positive electrode material exceeding 180 mA h g −1, with good cycling properties at 2.0–4.6 V.