TY - JOUR
T1 - Building a fast lane for Mg diffusion in α-MoO3 by fluorine doping
AU - Wan, Liwen F.
AU - Incorvati, Jared T.
AU - Poeppelmeier, Kenneth R.
AU - Prendergast, David
N1 - Funding Information:
We acknowledge Dr. J. T. Vaughey for very helpful discussions. This work was supported by the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. The computations were supported by a User Project at The Molecular Foundry using the computing cluster (vulcan), managed by the High Performance Computing Services Group, at Lawrence Berkeley National Laboratory (LBNL) and the resources of the National Energy Research Scientific Computing Center, LBNL, both of which are supported by the Office of Science of the U.S. Department of Energy under contract No. DE-AC02-05CH11231.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/10/11
Y1 - 2016/10/11
N2 - Following previous experimental work examining a layered oxyfluoride as cathode material for Mg-ion batteries [ Incorvati et al., Chem. Mater. 2016, 28, 17 ], we study the role of fluorination on the structural and electronic properties of molybdenum trioxide and its impact on Mg intercalation and diffusion using first-principles methods. Although bulk α-MoO3 is a 2D layered compound, we find that it provides 3D channels for Mg diffusion. When F atoms are incorporated into the α-MoO3 lattice, they replace the O atoms sitting at a specific crystallographic site that is linked by two nearest Mo atoms within a single Mo-O layer. As a consequence of F substitution, the local Mo-anion bonds are distorted, which leads to closure of the electronic band gap. From the analysis of zone center phonon vibrational frequencies, it is found that the local Mo-anion bonding strength is weakened by replacing O2- with F-, which ultimately facilitates Mg diffusion through the F-substituted lattice. For example, it is shown that upon fluorination the activation barriers for Mg diffusion along selected pathways can be lowered by as much as 0.6 eV, estimated from our nudged elastic band simulations at 0K. Our results imply that direct anion doping can be a viable approach toward improving ion diffusivity in Mg-ion battery cathodes.
AB - Following previous experimental work examining a layered oxyfluoride as cathode material for Mg-ion batteries [ Incorvati et al., Chem. Mater. 2016, 28, 17 ], we study the role of fluorination on the structural and electronic properties of molybdenum trioxide and its impact on Mg intercalation and diffusion using first-principles methods. Although bulk α-MoO3 is a 2D layered compound, we find that it provides 3D channels for Mg diffusion. When F atoms are incorporated into the α-MoO3 lattice, they replace the O atoms sitting at a specific crystallographic site that is linked by two nearest Mo atoms within a single Mo-O layer. As a consequence of F substitution, the local Mo-anion bonds are distorted, which leads to closure of the electronic band gap. From the analysis of zone center phonon vibrational frequencies, it is found that the local Mo-anion bonding strength is weakened by replacing O2- with F-, which ultimately facilitates Mg diffusion through the F-substituted lattice. For example, it is shown that upon fluorination the activation barriers for Mg diffusion along selected pathways can be lowered by as much as 0.6 eV, estimated from our nudged elastic band simulations at 0K. Our results imply that direct anion doping can be a viable approach toward improving ion diffusivity in Mg-ion battery cathodes.
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U2 - 10.1021/acs.chemmater.6b02223
DO - 10.1021/acs.chemmater.6b02223
M3 - Article
AN - SCOPUS:84991379352
SN - 0897-4756
VL - 28
SP - 6900
EP - 6908
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 19
ER -