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Preparation and Characterization of a Stable FeSO4F‑Based Framework for Alkali Ion Insertion Electrodes

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journal contribution
posted on 27.11.2012, 00:00 authored by Nadir 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.