Details

Autor(en) / Beteiligte

• Wernert, Romain
• Nguyen, Long H. B.
• Petit, Emmanuel
• Camacho, Paula Sanz
• Iadecola, Antonella
• Longo, Alessandro
• Fauth, François
• Stievano, Lorenzo
• Monconduit, Laure
• Carlier, Dany
• Croguennec, Laurence

Titel

Controlling the Cathodic Potential of KVPO4F through Oxygen Substitution

Ist Teil von

• Chemistry of materials, 2022-05, Vol.34 (10), p.4523-4535

Ort / Verlag

American Chemical Society

Erscheinungsjahr

2022

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• 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–y O y (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.