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Journal Articles Chemistry of Materials Year : 2022

Controlling the Cathodic Potential of KVPO4F through Oxygen Substitution

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Abstract

Exploring and tailoring new high energy density positive electrode materials is still a challenge for alkali-ion batteries. In this work, we synthesized the mixed anion phases KVPO4F1-yOy (y = 0, 0.25, 0.5, 0.75, 1) and determined their crystallographic and electronic structures by combining synchrotron X-ray diffraction, X-ray absorption spectroscopy at the vanadium K edge, and 31P MAS NMR coupled with density functional theory calculations. These experiments confirmed that the substitution of F- for O2- anions occurs as a solid solution across the whole composition domain. The local environments of vanadium ions are complex and diverse since the cis and trans octahedra undergo different distortions in the presence of a vanadyl bond. The simultaneous existence of ionic VIII-F bonds and covalent (VIV=O)2+ vanadyl type entities is strongly affecting the electrochemical properties and potassium deinsertion/insertion mechanisms upon cycling. Ultimately, KVPO4F0.5O0.5 appears as a promising positive electrode material due to its high capacity (105 mAh·g-1), working potential (4.2 V vs K+/K), and sloping electrochemical curve.
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hal-03690171 , version 1 (09-06-2022)

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Romain Wernert, Long Nguyen, Emmanuel Petit, Paula Sanz Camacho, Antonella Iadecola, et al.. Controlling the Cathodic Potential of KVPO4F through Oxygen Substitution. Chemistry of Materials, 2022, 34 (10), pp.4523-4535. ⟨10.1021/acs.chemmater.2c00295⟩. ⟨hal-03690171⟩
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