Li P N -A Lithium Nitridophosphate with Unprecedented Tricyclic [P N ] Ions.

Li P N was synthesized by reaction of LiPN and Li PN at 5.5 GPa and 1273 K employing the multi-anvil technique. It is the first lithium nitridophosphate obtained by high-pressure synthesis. Moreover, it is the first example received by reaction of two ternary lithium nitrides. The combination of high-pressure conditions with a Li N flux enabled a complete structure determination using single-crystal X-ray diffraction. The hitherto unknown tricyclic [P N ] anion is composed of six vertex-sharing PN tetrahedra forming one vierer- and two additional dreier-rings. To confirm the structure, Rietveld refinement, Li and P solid-state NMR spectroscopy, FTIR spectroscopy and EDX measurements were carried out. To validate the ionic properties, the migration pathways of the Li ions were evaluated, and the conductivity and its temperature dependence were determined by impedance spectroscopy measurements. In order to obtain a clearer picture of the formation mechanism of this compound class, different synthetic approaches were compared, enabling targeted syntheses of unprecedented P/N-anion topologies with intriguing properties.