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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Na4TiP2O9 by Materials Project

Na4TiO(PO4)2 crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. there are eleven inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.36–2.79 Å. In the second Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with two equivalent PO4 tetrahedra, and edges with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. There are a spread of Na–O bond distances ranging from 2.44–2.55 Å. In the third Na1+ site, Na1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Na–O bond distances ranging from 2.33–3.01 Å. In the fourth Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.22–2.50 Å. In the fifth Na1+ site, Na1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Na–O bond distances ranging from 2.31–2.49 Å. In the sixth Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.35–2.64 Å. In the seventh Na1+ site, Na1+ is bonded in a distorted pentagonal planar geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.26–2.53 Å. In the eighth Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.59 Å. In the ninth Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.26–2.71 Å. In the tenth Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.23–2.62 Å. In the eleventh Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with two equivalent PO4 tetrahedra, and edges with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 65°. There are a spread of Na–O bond distances ranging from 2.42–2.52 Å. There are three inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two TiO6 octahedra and corners with four PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–47°. There are a spread of Ti–O bond distances ranging from 1.91–2.07 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one NaO6 octahedra, corners with two TiO6 octahedra, and corners with four PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 45–58°. There are a spread of Ti–O bond distances ranging from 1.91–2.04 Å. In the third Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent NaO6 octahedra, corners with two equivalent TiO6 octahedra, and corners with four PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 45–65°. There is two shorter (1.91 Å) and four longer (2.01 Å) Ti–O bond length. There are five inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TiO6 octahedra. The corner-sharing octahedra tilt angles range from 40–48°. There are a spread of P–O bond distances ranging from 1.53–1.58 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent TiO6 octahedra. The corner-sharing octahedra tilt angles range from 38–48°. There are a spread of P–O bond distances ranging from 1.53–1.58 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TiO6 octahedra and edges with two NaO6 octahedra. The corner-sharing octahedra tilt angles range from 42–46°. There is two shorter (1.53 Å) and two longer (1.58 Å) P–O bond length. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NaO6 octahedra and corners with two TiO6 octahedra. The corner-sharing octahedra tilt angles range from 42–70°. There are a spread of P–O bond distances ranging from 1.53–1.58 Å. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NaO6 octahedra and corners with two TiO6 octahedra. The corner-sharing octahedra tilt angles range from 40–64°. There are a spread of P–O bond distances ranging from 1.53–1.58 Å. There are twenty-three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one P5+ atom. In the second O2- site, O2- is bonded to two Na1+ and two Ti4+ atoms to form distorted corner-sharing ONa2Ti2 tetrahedra. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Na1+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Na1+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Ti4+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Ti4+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a 5-coordinate geometry to four Na1+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Ti4+, and one P5+ atom. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+, one Ti4+, and one P5+ atom. In the twelfth O2- site, O2- is bonded in a 2-coordinate geometry to two Na1+, one Ti4+, and one P5+ atom. In the thirteenth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Ti4+, and one P5+ atom. In the fourteenth O2- site, O2- is bonded in a distorted tetrahedral geometry to two equivalent Na1+ and two equivalent Ti4+ atoms. In the fifteenth O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one P5+ atom. In the sixteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Na1+ and one P5+ atom. In the seventeenth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Ti4+, and one P5+ atom. In the eighteenth O2- site, O2- is bonded in a distorted tetrahedral geometry to three Na1+ and one P5+ atom. In the nineteenth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Ti4+, and one P5+ atom. In the twentieth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+ and two Ti4+ atoms. In the twenty-first O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one P5+ atom. In the twenty-second O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Ti4+, and one P5+ atom. In the twenty-third O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Ti4+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na4TiP2O9 by Materials Project

Na4TiO(PO4)2 crystallizes in the orthorhombic Cmme space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 4-coordinate geometry to eight O2- atoms. There are four shorter (2.46 Å) and four longer (2.91 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded in a 4-coordinate geometry to eight O2- atoms. There are four shorter (2.42 Å) and four longer (2.89 Å) Na–O bond lengths. In the third Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.21–2.52 Å. Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent TiO6 octahedra and corners with four equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There is two shorter (1.91 Å) and four longer (2.00 Å) Ti–O bond length. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent TiO6 octahedra. The corner-sharing octahedral tilt angles are 42°. There is two shorter (1.53 Å) and two longer (1.58 Å) P–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to three Na1+, one Ti4+, and one P5+ atom. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Na1+ and one P5+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two equivalent Ti4+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Na1+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Synthetic Accessibility and Sodium Ion Conductivity of the Na8–x A x P2O9 (NAP) High-Temperature Sodium Superionic Conductor Framework

Advancement of solid-state electrolytes (SSEs) for all solid-state batteries typically focuses on modification of a known structural framework to improve conductivity, e.g., cation substitution for an immobile ion or varying the concentration of the mobile ions. Novel frameworks can be disruptive by enabling fast ion conduction aided by different structure and diffusion mechanisms, thereby unlocking optimal conductors with different properties. Herein, we perform a high-throughput survey of a structural framework for sodium ion conduction, Na8–x A x P2O9 (NAP), to understand the family’s thermodynamic stability, synthesizability, and ionic conduction. We show that the parent phase Na4TiP2O9 (NTP) undergoes a structural distortion (with accompanying conductivity transition) due to unstable phonons arising from pseudo-Jahn–Teller mode in the 1D titanium chains. Screening compounds in which Ti is substituted by other metals computationally reveal a number of candidates that are predicted to be low in formation energy and have high predicted ionic conductivities. High-throughput experimental and subsequent methodology optimization trials deliver one new compound, Na4SnP2O9 (NSP). X-ray diffraction (XRD), microscopy, and spectroscopy characterization indicate that the room-temperature structure of NSP is similar to the high-temperature, orthorhombic NTP phase but with some small unresolved structural differences. These uncharacterized structural details are speculated to limit the ion conductivity. Temperature-dependent XRD and electrochemical impedance spectroscopy indicate multiple coupled conductivity–structure transitions at a high temperature. We demonstrate the challenges with synthesis development and a priori identification of promising SSE phases as a major bottleneck in new (energy) materials development.

Chemical reactions↗