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A DFT study of VO43- polyanion substitution into the Li-ion battery cathode material Li2FeSiO4
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
2010 (English)In: Computational materials science, ISSN 0927-0256, Vol. 50, no 1, 191-197 p.Article in journal (Refereed) Published
Abstract [en]

Density Functional Theory (DFT) has here been used to study the substitution of SiO44- for VO43- polyanions in the orthosilicate Li-ion battery cathode material Li2FeSiO4, in order to enhance electron transfer between the TM-ions and thereby achieve a capacity increase from the potential redox activity of the orthovanadate polyanion. Comparison of results for five different model structures for LiFeXO4, X = Si, P and V, reveals that VO43- substitution destabilizes the tetrahedral structures towards olivine- or spinel-type structures. Our modelling of lithiation of the hypothetical 100% substituted system LiFeVO4 to Li2FeVO4 predicts the reduction of V5+ in the VO43- anion to V4+ at a potential of 2.1 V. While complete delithiation of LiFeVO4 to FeVO4 is accompanied by Fe2+/Fe3+ oxidation at similar to 3.1 V. These lithiation and delithiation processes trigger changes in the unit-cell volume: -6% and +10%, respectively. Notably, only minor structural distortions were observed in both VO43- and the more exotic VO44- tetrahedra. Thermodynamically feasible VO43- substitution levels are also shown to be <30%. This is exemplified for a 12.5% VO4-substituted system which exhibits similar to 50% smaller band-gap and increased capacity at an average deintercalation potential of similar to 3.2 V compared to the un-substituted system.

Place, publisher, year, edition, pages
2010. Vol. 50, no 1, 191-197 p.
Keyword [en]
Li-ion battery, Positive electrode material, Silicates, DFT calculations, Polyanion, Crystal structure, Redox activity
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
URN: urn:nbn:se:uu:diva-135362DOI: 10.1016/j.commatsci.2010.07.025ISI: 000284250700026OAI: oai:DiVA.org:uu-135362DiVA: diva2:375253
Available from: 2010-12-07 Created: 2010-12-06 Last updated: 2010-12-21Bibliographically approved

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Liivat, AntiThomas, John O.
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