Origin of the 3.6 V to 3.9 V voltage increase in the LiFeSO4F cathodes for Li-ion batteries

• DOI: 10.1039/c2ee22699e
• Publication Date: 2012-09-04T11:30:18Z
• Authors: Mouna Ben Yahia; Frédéric Lemoigno; Gwenaëlle Rousse; Florent Boucher; Jean-Marie Tarascon; Marie-Liesse Doublet
• Keywords: Polyhedron; Fluorine

Recently, the LiFeSO4F material has been reported as highest potential Fe-based cathode for Li-ion batteries. Its working voltage vs. Li+/Li0 jumps from 3.6 V to 3.9 when is synthesized with fully ordered tavorite structure and disordered triplite structure, respectively. The present study aims at rationalizing this increase by means of DFT + U calculations combined crystallographic electrostatic analyses. We show that polymorph, although characterized two distinct edge-shared sites, locally exhibits corner-sharing connections between consecutive FeO4F2 octahedra, exactly in polymorph. As a consequence, edge-sharing exist lithiated LiO4F2 polyhedra. then demonstrate origin lies difference anionic networks polymorphs, more specifically repulsions induced configuration fluorine atoms around transition metal polymorphs (trans- cis-configurations polymorphs). Such finding should help design novel high fluorosulphate materials, which beyond enhanced performances sustainability attributes they can be made abundant elements via low temperature eco-efficient processes.