Structural changes on cycling Li 2FeSiO 4 polymorphs from DFT calculations
2012 (English)In: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 228, 19-24 p.Article in journal (Refereed) Published
Cation mixing has been demonstrated experimentally in the Li-ion battery cathode material Li 2FeSiO 4. This feature is investigated here using DFT calculations. It is shown that full reversal of Li/Fe site occupations is energetically favoured on delithiation for all three electrochemically active Li 2FeSiO 4 polymorphs. The common layered topology in the arrangement of SiO 4 and FeO 4 tetrahedra in all three polymorphs transforms into a 3D-framwork. Calculations show here that such a change in structure leads to a lowering of electrochemical insertion potential from ~ 3.1 to ~ 2.8 V, in good agreement with experimental data. Calculations also predict the correct anisotropy in the cell expansion on delithiation on Li/Fe site reversals. Partial mixing of Li and Fe site occupations is energetically less favourable, which supports a two-phase transformation mechanism.
Place, publisher, year, edition, pages
2012. Vol. 228, 19-24 p.
Crystal structure, Density functional theory, Lithium iron silicate, Solid state electrochemistry
IdentifiersURN: urn:nbn:se:uu:diva-188115DOI: 10.1016/j.ssi.2012.08.016ISI: 000312522800004OAI: oai:DiVA.org:uu-188115DiVA: diva2:576669