title: Quantitatively Predict the Potential of MnO2 Polymorphs as Magnesium Battery Cathodes.
abstract: Despite tremendous efforts denoted to magnesium battery research, the realization of magnesium battery is still challenged by the lack of cathode candidate with high energy density, rate capability and good recyclability. This situation can be largely attributed to the failure to achieve sustainable magnesium intercalation chemistry. In current work we explored the magnesiation of distinct MnO2 polymorphs using first-principles calculations, focusing on providing quantitative analysis about the feasibility of magnesium intercalation. Consistent with experimental observations, we predicted that ramsdellite-MnO2 and α-MnO2 are conversion-type cathodes while nanosized spinel-MnO2 and MnO2 isostructual to CaFe2O4 are better candidates for Mg intercalation. Key properties that restrict Mg intercalation include not only sluggish Mg migration but also stronger distortion that damages structure integrity and undesirable conversion reaction. We demonstrate that by evaluating the reaction free energy, structural deformation associated with the insertion of magnesium, and the diffusion barriers, a quantitative evaluation about the feasibility of magnesium intercalation can be well established. Although our current work focuses on the study of MnO2 polymorphs, the same evaluation can be applied to other cathode candidates, thus paving the road to identify better cathode candidates in future.
authors.affiliation: Toyota Research Institute of North America , 1555 Woodridge Avenue, Ann Arbor, Michigan 48105, United States.
authors.forename: Chen
authors.initials: C
authors.lastname: Ling
authors.affiliation: Toyota Research Institute of North America , 1555 Woodridge Avenue, Ann Arbor, Michigan 48105, United States.
authors.forename: Ruigang
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Toyota Research Institute of North America , 1555 Woodridge Avenue, Ann Arbor, Michigan 48105, United States.
authors.forename: Fuminori
authors.initials: F
authors.lastname: Mizuno
keywords: Mg battery; MnO2; cathode; conversion; intercalation