Issue 11, 2015

A new class of high capacity cation-disordered oxides for rechargeable lithium batteries: Li–Ni–Ti–Mo oxides

Abstract

Recent successes with disordered Li-excess materials and applications of percolation theory have highlighted cation-disordered oxides as high capacity and energy density cathode materials. In this work, we present a new class of high capacity cation-disordered oxides, lithium-excess nickel titanium molybdenum oxides, which deliver capacities up to 250 mA h g−1. These materials were designed from percolation theory which predicts lithium diffusion to become facile in cation-disordered oxides as the lithium-excess level increases (x > 1.09 in LixTM2−xO2). The reversible capacity and rate capability in these compounds are shown to considerably improve with lithium excess. In particular, Li1.2Ni1/3Ti1/3Mo2/15O2 delivers up to 250 mA h g−1 and 750 W h kg−1 (∼3080 W h l−1) at 10 mA g−1. Combining in situ X-ray diffraction, X-ray absorption near edge spectroscopy, electron energy loss spectroscopy, and electrochemistry, we propose that first charging Li1.2Ni1/3Ti1/3Mo2/15O2 to 4.8 V occurs with Ni2+/Ni∼3+ oxidation, oxygen loss, and oxygen oxidation in this sequence, after which Mo6+ and Ti4+ can be reduced upon discharge. Furthermore, we discuss how oxygen loss with lattice densification can affect lithium diffusion in the material by decreasing the Li-excess level. From this understanding, strategies for further improvements are proposed, setting new guidelines for the design of high performance cation-disordered oxides for rechargeable lithium batteries.

Graphical abstract: A new class of high capacity cation-disordered oxides for rechargeable lithium batteries: Li–Ni–Ti–Mo oxides

Supplementary files

Article information

Article type
Paper
Submitted
28 Jul 2015
Accepted
07 Sep 2015
First published
07 Sep 2015

Energy Environ. Sci., 2015,8, 3255-3265

A new class of high capacity cation-disordered oxides for rechargeable lithium batteries: Li–Ni–Ti–Mo oxides

J. Lee, D. Seo, M. Balasubramanian, N. Twu, X. Li and G. Ceder, Energy Environ. Sci., 2015, 8, 3255 DOI: 10.1039/C5EE02329G

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