Comparative computational investigation of N and F substituted polyoxoanionic compounds: The case of Li2FeSiO4 electrode material |
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Authors: | M Armand J-M Tarascon ME Arroyo-de Dompablo |
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Institution: | aLRCS, Université de Picardie Jules-Verne, UMR 6007 CNRS, 33 rue Saint-Leu, 80039 Amiens, France;bFacultad de Cc. Químicas, Universidad Complutense de Madrid, Avda. Complutense sn, 28040 Madrid, Spain |
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Abstract: | First principles calculations are used to anticipate the electrochemistry of polyoxoanionic materials consisting of XO4 − yAy (A = F, N) groups. As an illustrative case, this work focuses on the effect of either N or F for O substitution upon the electrochemical properties of Li2FeSiO4. Within the Pmn21–Li2FeSiO4 structure, virtual models of Li2Fe22.5+SiO3.5N0.5 and Li1.5Fe2+SiO3.5F0.5 have been analyzed. We predict that the lithium deinsertion voltage associated to the Fe3+/Fe4+ redox couple is decreased by both substituents. The high theoretical specific capacity of Li2FeSiO4 (330 mAh/g) could be retained in N-substituted silicates thanks to the oxidation of N3− anions, whilst Li1.5Fe2+SiO3.5F0.5 has a lower specific capacity inherent to the F substitution. Substitution of N/F for O will respectively improve/worsen the electrode characteristics of Li2FeSiO4. |
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Keywords: | Li2FeSiO4 Electrode materials DFT Silicates |
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