Modeling the effect of occupational disorder in Lithium-Titanium-Oxide materials
Hendrik Heenen, Saskia Stegmaier, Christoph Scheurer, and Karsten Reuter
Li4Ti5O12 lithium-titanium-oxide (LTO) materials represent an interesting alternative to conventional graphite based anodes for Li ion batteries, due to their high cycling stability, safe operation at high working potentials and a fast charge-discharge behavior [1,2]. In order to rationalize and improve the material's properties and performance, a detailed understanding of the underlying atomic scale features and processes is required. In this context, different studies have been conducted to evaluate transition state energies and diffusion pathways in LTO [3-6]. The structural models of LTO used in these studies are all lacking a proper treatment of the statistics of the system's configuration space. The spinel structure phase of Li4Ti5O12 exhibits mixed occupancy of octahedral sites by Li and Ti ions in the LTO bulk phase which allows for a high degree of occupational disorder. In order tos ample a thermodynamically valid representation of said disorder, it is necessary to consider larger structural supercells.
In the present study force field calculations have been used and validated by DFT data to get a glimpse of the system's vast configuration space and elucidate the impact of its proper sampling. This approach will be extended to a full multiscale representation of LTO in the future.
[1] M.V. Reddy, G.V. Subba Rao, B.V.R. Chowdari, Chem. Rev., 2013, 113(7), 5364-457.
[2] M.K. Song, S. Park, F.M. Alamgir, J. Cho, M. Liu, Mat. Sci. Eng. R, 2011, 72(11), 203-252.
[3] Z. Zhong, C. Ouyang, S. Shi, M. Lei, Chem. Phys. Chem., 2008, 9(14), 2104-8.
[4] H. Shiiba, M. Nakayama, M. Nogami, Solid State Ionics, 2010, 181(21-22), 994-1001.
[5] M. Vijayakumar, S. Kerisit, K.M. Rosso, S.D. Burton, J.A. Sears, Z. Yang, G.L. Graff, J. Liu, J. Hu, J. Power Sources, 2011, 196(4), 2211-2220.
[6] B. Ziebarth, M. Klinsmann, T. Eckl, C. Elsässer, Phys. Rev. B, 2014, 89, 174301.