Synergic effect of CaI2 and LiI on ionic conductivity of solution-based synthesized Li7P3S11 solid electrolyte.

Li7P3S11 doped with CaX2 (X = Cl, Br, I) and LiI solid electrolytes were successfully prepared by liquid-phase synthesis using acetonitrile as the reaction medium. Their structure was investigated using XRD, Raman spectroscopy and SEM-EDS. The data obtained from complex impedance spectroscopy was analyzed to study the ionic conductivity and relaxation dynamics in the prepared samples. The XRD results suggested that a part of CaX2 and LiI incorporated into the structure of Li7P3S11, while the remaining part existed at the grain boundary of the Li7P3S11 particle. The Raman peak positions of PS43- and P2S74- ions in samples 90Li7P3S11-5CaI2 and 90Li7P3S11-5CaI2-5LiI had shifted as compared to the Li7P3S11 sample, showing that CaI2 addition affected the vibration of PS43- and P2S74- ions. EDS results indicated that CaI2 and LiI were well dispersed in the prepared powder sample. The ionic conductivity at 25 °C of sample 90Li7P3S11-5CaI2-5LiI reached a very high value of 3.1 mS cm-1 due to the improvement of Li-ion movement at the grain boundary and structural improvement upon CaI2 and LiI doping. This study encouraged the application of Li7P3S11 in all-solid-state Li-ion batteries.

Solid-State Reaction Synthesis of MgAl2O4 Spinel from MgO-Al2O3 Composite Particles Prepared via Electrostatic Adsorption.

This paper presents the formation of magnesium aluminate spinel using composite particles prepared via electrostatic adsorption (ESA). Scanning electron microscopy (SEM) images confirmed the presence of Al2O3-MgO composite particles. A mixture of Al2O3 and MgO raw materials was also prepared by using the conventional bead-milling method for comparison. The samples sintered at elevated temperatures were characterized through X-ray diffraction, SEM, and relative density measurements. Additionally, the lattice parameter and strain of the samples were determined using the Nelson-Riley function and the Williamson-Hall equation. A pure spinel phase formed in the ESA-derived sample sintered at 1400 °C, while the MgO structure remained in the conventionally prepared sample sintered at 1600 °C. The densities of samples sintered at 1450 °C or higher exceeded 90%. The lattice strain of the prepared samples was inversely proportional to the sintering temperature, attributed to the formation of large grains at higher temperatures. However, the sample sintered at 1600 °C for 8 h exhibited the highest strain of 0.0074 because the crystals grew in a certain direction.

High Ionic Conductivity with Improved Lithium Stability of CaS- and CaI2-Doped Li7P3S11 Solid Electrolytes Synthesized by Liquid-Phase Synthesis.

Li7P3S11 solid electrolytes (SEs) subjected to liquid-phase synthesis with CaS or CaI2 doping were investigated in terms of their ionic conductivity and stability toward lithium anodes. No peak shifts were observed in the XRD patterns of CaS- or CaI2-doped Li7P3S11, indicating that the doping element remained at the grain boundary. CaS- or CaI2-doped Li7P3S11 showed no internal short circuit, and the cycling continued, indicating that not only CaI2 including I- but also CaS could help increase the lithium stability. These results provide insights for the development of sulfide SEs for use in all-solid-state batteries in terms of their ionic conductivity and stability toward lithium anodes.

Synthesis of Sulfide Solid Electrolytes through the Liquid Phase: Optimization of the Preparation Conditions.

All-solid-state lithium batteries using inorganic sulfide solid electrolytes have good safety properties and high rate capabilities as expected for a next-generation battery. Presently, conventional preparation methods such as mechanical milling and/or solid-phase synthesis need a long time to provide a small amount of the product, and they have difficult in supplying a sufficient amount to meet the demand. Hence, liquid-phase synthesis methods have been developed for large-scale synthesis. However, the ionic conductivity of sulfide solid electrolytes prepared via liquid-phase synthesis is typically lower than that prepared via solid-phase synthesis. In this study, we have controlled three factors: (1) shaking time, (2) annealing temperature, and (3) annealing time. The factors influencing lithium ionic conductivity of Li3PS4 prepared via liquid-phase synthesis were quantitatively evaluated using high-energy X-ray diffraction (XRD) measurement coupled with pair distribution function (PDF) analysis. It was revealed from PDF analysis that the amount of Li2S that cannot be detected by Raman spectroscopy or XRD decreased the ionic conductivity. Furthermore, it was revealed that the ionic conductivity of Li3PS4 is dominated by other parameters, such as remaining solvent in the sample and high crystallinity of the sample.

Preparation of cubic Na3PS4 by liquid-phase shaking in methyl acetate medium.

Cubic Na3PS4 (c-Na3PS4), a high temperature phase of Na3PS4, is successfully prepared by liquid-phase shaking from Na2S and P2S5 in methyl acetate medium. The effects of the amount of solvents, Na2S and heat treatment on the formation of c-Na3PS4 are carefully investigated. In addition to c-Na3PS4, an unknown phase is also detected in the sample containing an excess amount of Na2S in the starting materials mixture.

Raman study of the formation of beta silicomolybdic acid supported on silica, prepared by impregnation method.

Beta silicomolibdic acid/silica (ß-SMA, a metastable form of silicomolybdic acid - H(4)SiMo(12)O(40)) forms by the impregnation of fumed silica into molybdenum solution obtained by hydrolyzation of MoO(2)Cl(2.) ß-SMA/silica is found to be stable up to 300 °C after calcination for 1h due to the existence of an interlayer MoO(3) between silica surface and ß-SMA. Structures of molybdenum species in the preparation process (including precursor solution) were analyzed by Raman spectroscopy and XRD.