Résumé
Mixed anion materials are promising for application as solid electrolytes in all-solid-state batteries, offering enhanced chemical and electrochemical stability alongside balanced ionic conductivity. This work reports a novel lithium oxythiophosphate Li3PO3S·5H2O, synthesized at a low temperature in an aqueous medium. The crystal structure and properties of Li3PO3S·5H2O were investigated through 3-dimensional electron diffraction, combined with powder X-ray and neutron diffraction, thermogravimetric analysis, nuclear magnetic resonance spectroscopy, and electrochemical impedance spectroscopy. Li3PO3S·5H2O crystallizes in the hexagonal space group P63cm with a = 16.48462(4), c = 5.36224(2) Å, V = 1261.928(6) Å3, and Z = 6. 31P solid-state MAS NMR spectroscopy revealed the presence of pure and ordered PO3S tetrahedra. The dehydration of Li3PO3S·5H2O was studied via TGA and temperature-dependent XRD, demonstrating the formation of the anhydrous phase Li3PO3S at 200 °C. The conductivity of anhydrous Li3PO3S (2.6 × 10−6 S cm−1 at room temperature and Ea = 0.51 eV) is three orders of magnitude higher than that of the parent material Li3PO4 prepared by further heating the sample at 400°C, with a significantly lower activation energy. Our findings highlight the potential of mixed anion materials in improving solid electrolyte performance. This work brings new insight into the crystal chemistry of oxythiophosphate anions, which is key in developing fast ionic conductors for solid-state batteries.