posted on 2012-11-27, 00:00authored byNadir Recham, Gwenaëlle Rousse, Moulay T. Sougrati, Jean-Noël Chotard, Christine Frayret, Sathiya Mariyappan, Brent C. Melot, Jean-Claude Jumas, Jean-Marie Tarascon
Polyanionic electrode materials offer an attractive combination
of safety benefits and tunable redox potentials. Thus far, phosphate-based
phases have drawn the most interest with a subsequent surge of activity
focused on the newly discovered family of fluorosulfate phases. Here,
we report the preparation of a new potassium-based fluorosulfate,
KFeSO4F, which, with removal of K, leads to a new polymorph
of FeSO4F crystallizing in the high-temperature structure
of KTiOPO4. This new phase which contains large, empty
channels, is capable of reversibly inserting 0.9 Li+ per
unit formula and can accommodate a wide variety of alkali ions including
Li+, Na+, or K+. This finding not
only expands the rich crystal chemistry of the fluorosulfate family
but further suggests that a similar strategy can apply to other K-based
polyanionic compounds in view of stabilizing new attractive host structures
for insertion reactions.