Sodium superionic conduction in tetragonal Na{sub 3}PS{sub 4}

Journal Article · Sat Sep 15 04:00:00 EDT 2018 · Journal of Solid State Chemistry (Print)

DOI:https://doi.org/10.1016/J.JSSC.2018.06.023· OSTI ID:22890218

Takeuchi, Shigeo ^[1]; Suzuki, Kota; Hirayama, Masaaki; Kanno, Ryoji ^[1]

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1. Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)

Highlights: • Na{sub 3}PS{sub 4} base solid electrolytes were fabricated by various synthetic routes. • The formation of phases in Na{sub 3+5x}P{sub 1–x}S{sub 4} depends on reaction conditions. • Tetragonal phase III showed the highest conductivity of 3.39 × 10{sup -3} S cm{sup -1}at 25 °C. • Structural analysis revealed the 3D conduction pathway in the tetragonal phase III. • Na{sub 3}PS{sub 4} functions as a solid electrolyte in all-solid-state sodium batteries. - Abstract: Sodium superionic conductors are highly promising as solid electrolytes for all-solid-state sodium batteries, with the capacity to improve energy and power density of liquid-electrolyte-based batteries and to address their safety issues. However, the ionic conductivity of sodium electrolytes remains roughly one order of magnitude lower than that of lithium systems. Herein, we report a synthesis method for a sodium superionic conductor, tetragonal Na{sub 3}PS{sub 4}, with an ionic conductivity of 3.39 × 10{sup −3} Scm{sup −1} at 25 °C—the highest value yet reported among sulfide-type sodium conductors. The high conductivity is achieved through quenching from 700 °C, which introduces sodium vacancies, and annealing at 450 °C, which increases vacancies and expands lattice volume. The phase is comprised of a framework of isolated PS{sub 4} tetrahedra, with partial distribution of Na over 3D pathways. The high intrinsic conductivity together with low grain boundary contribution and soft mechanical properties make Na{sub 3}PS{sub 4} a promising candidate for sodium solid electrolytes.

• OSTI ID: 22890218
• Journal Information: Journal of Solid State Chemistry (Print), Journal Name: Journal of Solid State Chemistry (Print) Vol. 265; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: Netherlands
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
GRAIN BOUNDARIES
IONIC CONDUCTIVITY
MECHANICAL PROPERTIES
POWER DENSITY
SODIUM IONS
SODIUM PHOSPHIDES
SODIUM SULFIDES
SOLID ELECTROLYTES