cm7b04038_si_001.pdf (3.67 MB)
First-Principles Study of the Voltage Profile and Mobility of Mg Intercalation in a Chromium Oxide Spinel
journal contribution
posted on 2017-12-06, 00:00 authored by Tina Chen, Gopalakrishnan Sai Gautam, Wenxuan Huang, Gerbrand CederThe
development of Mg batteries, which can potentially achieve
higher energy densities than Li-ion systems, is in need of cathodes
that can reversibly intercalate Mg2+ and exhibit a higher
energy density than the state-of-the-art Chevrel and thio-spinel cathodes.
Recent theoretical and experimental studies indicate that the oxide
spinel family presents a set of promising Mg cathodes. Specifically,
in this work, we investigate Mg intercalation into the spinel-MgxCr2O4 system. Using
first-principles calculations in combination with a cluster expansion
model and the nudged elastic band theory, we calculate the voltage
curve for Mg insertion at room temperature and the activation barriers
for Mg diffusion, respectively, at different Mg concentrations in
the Cr2O4 structure. Our results identify a
potential limitation to Mg intercalation in the form of stable Mg-vacancy
orderings in the Cr2O4 lattice, which exhibit
high migration barriers for Mg diffusion in addition to a steep voltage
change. Additionally, we propose cation substitution as a potential
mechanism that can be used to suppress the formation of the stable
Mg-vacancy ordering, which can eventually enable the practical usage
of Cr2O4 as a Mg-cathode.