Li₁₈P₆N₁₆—A Lithium Nitridophosphate with Unprecedented Tricyclic [P₆N₁₆]¹⁸⁻ Ions

Abstract

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.

Li+ Ion Conductors with Adamantane‐Type Nitridophosphate Anions β‐Li10P4N10 and Li13P4N10X3 with X=Cl, Br

“…[6,[15][16][17][18][19] Reactiono ft he binary nitrides P 3 N 5 and Li 3 Nb etween 620 and 800 8Cl ed to four lithium nitridophosphates with different complex P/N anions in am atrix of Li + ions. [20][21][22][23] Recently,w e succeeded in expanding this substance class with two new complex P/N anions by using the multianvil technique in combination with the Li 3 Ns elf-flux method. [22,24] Li 7 PN 4 (620 8C, ambient pressure) is the lithium nitridophosphate with the lowest P/N atomicr atio and consists of non-condensed [PN 4 ] 7À tetrahedra.…”

“…[20][21][22][23] Recently,w e succeeded in expanding this substance class with two new complex P/N anions by using the multianvil technique in combination with the Li 3 Ns elf-flux method. [22,24] Li 7 PN 4 (620 8C, ambient pressure) is the lithium nitridophosphate with the lowest P/N atomicr atio and consists of non-condensed [PN 4 ] 7À tetrahedra. [23] Non-condensed [P 3 N 9 ] 12À dreier-rings, [25,26] which are isoelectronic with [Si 3 O 9 ] 6À ,a re observed in Li 12 P 3 N 9 (790 8C, ambient pressure).…”

“…[23] Non-condensed [P 3 N 9 ] 12À dreier-rings, [25,26] which are isoelectronic with [Si 3 O 9 ] 6À ,a re observed in Li 12 P 3 N 9 (790 8C, ambient pressure). [22] At 820 8Ca nd 6GPa,t hese non-condensed [P 3 N 9 ] 12À dreier-rings polymerize to infinite zweierchains of corner-sharing PN 4 tetrahedra (Li 4 PN 3 ). [22] At ricyclic ring structure of one vierer-ring with two annelated dreier-rings is the characteristic structural motif [P 6 N 16 ] 18À in Li 18 P 6 N 16 , which has hitherto only been accessible under conditions of high temperature and high pressure (1000 8C, 5.5 GPa).…”

“…[22] At 820 8Ca nd 6GPa,t hese non-condensed [P 3 N 9 ] 12À dreier-rings polymerize to infinite zweierchains of corner-sharing PN 4 tetrahedra (Li 4 PN 3 ). [22] At ricyclic ring structure of one vierer-ring with two annelated dreier-rings is the characteristic structural motif [P 6 N 16 ] 18À in Li 18 P 6 N 16 , which has hitherto only been accessible under conditions of high temperature and high pressure (1000 8C, 5.5 GPa). [24] aLi 10 P 4 N 10 (720 8C, ambient pressure) consists of adamantane-like [P 4 N 10 ] 10À ions, isoelectronic with [P 4 O 10 ].…”

“…[22] At ricyclic ring structure of one vierer-ring with two annelated dreier-rings is the characteristic structural motif [P 6 N 16 ] 18À in Li 18 P 6 N 16 , which has hitherto only been accessible under conditions of high temperature and high pressure (1000 8C, 5.5 GPa). [24] aLi 10 P 4 N 10 (720 8C, ambient pressure) consists of adamantane-like [P 4 N 10 ] 10À ions, isoelectronic with [P 4 O 10 ]. [21] Ah igherr eaction temperature (800 8C) at ambient pressure is necessary for the synthesis of LiPN 2 .I tc onsistso fc orner-sharing PN 4 tetrahedra forming at hree-dimensional network structure isoelectronic to that of SiO 2 .…”