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Hee-Dae Lim1 Xing Xing1 Ping Liu1

1, University of California San Diego, San Diego, California, United States

Sulfide-based solid electrolytes have attracted much attention due to their high conductivities, which are far beyond those of oxide-based solid electrolytes.[1,2] However, They (Li2S-P2S5 system, i.e., LPS) have been normally synthesized by solid state synthesis such as mechanical ball milling. These methods require rigorous control of reaction environment as well as high temperature heat treatment and repeated pelletizing steps. In contrast, solution-based synthesis methods can induce chemical reaction among precursor particles (Li2S and P2S5) at low temperatures resulting in the formation of conductive phases of β-Li3PS4 and Li3P7S11 with only moderate thermal treatment.[3,4] The method deserves great attention since it simplifies synthesis process, yields products of great purity, and may facilitate the fabrication of composite electrodes with improved interfaces.
In this work, we report a new liquid-based synthesis method supported by a strong nucleophile. Addition of the compound enables dissolution of P2S5 in common ether based solvents. Such a precursor solution was found to be highly effective in reacting with Li2S to produce highly crystalline and conductive β-Li3PS4 under with moderate heat treatment (140 degrees celsius). Details of the solution reactions and postulated reaction pathways based on IR, NMR, and GC-MS will be discussed. The tuning of the liquid-based synthesis chemistry can open new research directions for solution-based synthesis of solid electrolytes.

[1] Kamaya, N. et al. A lithium superionic conductor. Nature Mater. 10, 682-686 (2011).
[2] Yamane, H. et al. Crystal structure of a superionic conductor, Li7P3S11. Solid State Ion. 178, 1163-1167 (2007).
[3] Ito, S. et al. A synthesis of crystalline Li7P3S11 solid electrolyte from 1,2-dimethoxyethane solvent. J. Power Sources 271, 342-345 (2014).
[4] Liu, Z. et al. Anomalous High Ionic Conductivity of Nanoporous β-Li3PS4. J. Am. Chem. Soc. 135, 975-978 (2013).

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