Pyridine Complexes as Tailored Precursors for Rapid Synthesis of Thiophosphate Superionic Conductors

Abstract

Room temperature solution synthesis of electrolytes for all‐solid‐state batteries has garnered much interest in the past years as a more scalable and efficient alternative to traditional solid‐state syntheses. Li3PS4, a model solid electrolyte often studied, is typically produced from Li2S and P4S10; the latter exists as a molecular solid in an adamantane‐like cage structure, and it has been posited that from its robustness arises a rate‐limiting reaction step. In this work, we have applied chemistry inspired from the organic thionation literature to easily transform the cage‐like P4S10 into more reactive stabilized linear P2S5 molecules. This new reagent was used to drastically reduce the synthesis time of Li3PS4 in acetonitrile from days to hours. Because the long reaction time of many solvent routes to produce solid electrolytes is considered a bottleneck for commercialization, this work shows great promise for looking toward more fundamental chemistry in order to optimize solution syntheses.

Chemical Stability and Ionic Conductivity of LGPS-Type Solid Electrolyte Tetra-Li7SiPS8 after Solvent Treatment

“…It was recently reported that strong interactions of pyridine (py) and thiophosphate groups lead to the breakage of P 4 S 10 adamantane cages into the stabilized py 2 P 2 S 5 complex. 65 Interestingly, the conductivity after treatment with pyridine is still relatively high (6•10 −4 S cm −1 ), indicating that strong solvent−thiophosphate interactions are not necessarily detrimental for the performance. Taken together, the results indicate that the residual solvent acts as a low conductivity phase that significantly hinders, and possibly dominates, the measured ionic conductivity of the processed samples.…”

“…The latter is most evident for the pyridine-treated LiSiPS in which, despite a vapor pressure similar to toluene (20 hPa at 20 °C), a large fraction of it remains in the sample. It was recently reported that strong interactions of pyridine (py) and thiophosphate groups lead to the breakage of P 4 S 10 adamantane cages into the stabilized py 2 P 2 S 5 complex . Interestingly, the conductivity after treatment with pyridine is still relatively high (6·10 –4 S cm –1 ), indicating that strong solvent–thiophosphate interactions are not necessarily detrimental for the performance.…”

Rapid Synthesis of Highly Conductive Li6PS5Cl Argyrodite-Type Solid Electrolytes Using Pyridine Solvent

“…Solution synthesis is an efficient and cost-effective approach to prepare sulfide based solid electrolytes, with a large number of organic solvents, such as ethanol, acetonitrile (ACN), N -methylformamide (NMF), and tetrahydrofuran (THF). ,, Recently, researchers have prepared Li 3 PS 4 solid electrolyte using pyridine solvent and have obtained well-crystallized material with reasonable ionic conductivity . Pyridine is a well-known thionation agent and easily dissolves P 2 S 5 to form the P 2 S 5 ·pyridine complex.…”

“…1,8,9 Recently, researchers have prepared Li 3 PS 4 solid electrolyte using pyridine solvent and have obtained well-crystallized material with reasonable ionic conductivity. 10 Pyridine is a well-known thionation agent and easily dissolves P 2 S 5 to form the P 2 S 5 •pyridine complex. Li 2 S can easily react with the P 2 S 5 • pyridine complex to form Li 2 S−P 2 S 5 -type solid electrolytes.…”

Preparation of Li3PS4–Li3PO4 Solid Electrolytes by Liquid-Phase Shaking for All-Solid-State Batteries

“…The synthesis of Li 3 PS 4 using liquid-phase synthesis with organic solvents as reaction media has been intensively investigated recently as an alternate chemical route for the preparation of sulfide-based solid electrolytes rather than the conventional solid state reaction [11][12][13][14][15][16]. In most of the reports, the effect of the solvents on the formation of Li 3 PS 4 was of primary interest [17][18][19][20][21].…”