Structural features of the oxidonitridophosphates K₃ M ^III(PO₃)₃N (M ^III = Al, Ga)

Abstract

Cubic crystals of tripotassium aluminium (or gallium) nitridotriphosphate, K3 M III(PO3)3N (M III = Al, Ga), were grown by application of the self-flux method. In their isostructural crystal structures, all metal cations and the N atom occupy special positions with site symmetry 3, while the P and O atoms are situated in general positions. The three-dimensional framework of these oxidonitridophosphates is built up from [M IIIO6] octahedra linked together via (PO3)3N groups. The latter are formed from three PO3N tetrahedra sharing a common N atom. The coordination environments of the three potassium cations are represented by two types of polyhedra, viz. KO9 for one and KO9N for the other two cations. An unusual tetradentate type of coordination for the latter potassium cations by the (PO3)3N6– anion is observed. These K3 M III(PO3)3N (M III = Al, Ga) compounds are isostructural with the Na3 M III(PO3)3N (M III = Al, V, Ti) compounds.

Novel NASICON‐Type Na‐V‐Mn‐Ni‐Containing Cathodes for High‐Rate and Long‐Life SIBs

“…The Na ions occupy two independent crystal sites: Na(1) and Na(2). [ 17 ] During the charge‐discharge process at around 3.4 V, the V 3+ ⇔V 4+ redox reaction can occur in NVP, which causes the Na ions reversible insertion/extraction at the Na(2) site, resulting in the two‐phase transformation of Na 3 V 2 (PO 4 ) 3 ⇔ NaV 2 (PO 4 ) 3 . This results in a high theoretical capacity of about 117 mAh g −1 for NVP.…”