We report on the facile solid-state synthesis and characterization of Li7SiPS8, a new member of the tetragonal Li10GeP2S12 (LGPS)-type family of ultrafast Li+ solid electrolytes. We analyze the structure, phase stability, and Li+ conductivity of tetragonal and orthorhombic LSiPS by pulsed field gradient NMR and impedance spectroscopy, which show conductivities at room temperature of up to 2 mS cm–1. Although ranking tetragonal LiSiPS as an ultrafast solid electrolyte, the observed conductivity is unexpectedly low compared to other members of this solid-solution system. Utilizing solid-state NMR, quantitative phase analysis, and impedance spectroscopy, we identify an amorphous thiophosphate side phase with low Si content, which limits the intergrain conductivity and, hence, a potentially higher total conductivity. This case study thus highlights the need for comprehensive structural analysis of LGPS-type materials beyond the crystalline fractions to fully characterize the structure–property relationships in these glass-ceramic compounds.

Fast sodium-ion conductors are key components of Na-based all-solid-state batteries which hold promise for large-scale storage of electrical power. We report the synthesis, crystal-structure determination, and Na -ion conductivities of six new Na-ion conductors, the phosphidosilicates Na Si P , Na Si P , Na Si P , Na Si P , LT-NaSi P and HT-NaSi P , based entirely on earth-abundant elements. They have SiP tetrahedra assembled interpenetrating networks of T3 to T5 supertetrahedral clusters and can be hierarchically assigned to sphalerite- or diamond-type structures. Na solid-state NMR spectra and geometrical pathway analysis show Na -ion mobility between the supertetrahedral cluster networks. Electrochemical impedance spectroscopy shows Na -ion conductivities up to σ (Na )=4×10 S cm . The conductivities increase with the size of the supertetrahedral clusters through dilution of Na -ions as the charge density of the anionic networks decreases.

Hybrid perovskites have evolved into an exciting materials platform supporting a wide variety of optoelectronic applications including solar cells and light-emitting devices. In spite of their rapid deployment in devices, a detailed understanding of their structure−property relationships is scarce. In this study, we comprehensively analyze the crystal and electronic structures as well as thermal, optical, and electronic properties of a series of 2-(aminomethylpyridinium) lead halides including the isotypic hybrid perovskites (C 6 H 10 N 2 )PbX 4 (X = Cl, Br, and I) and the hybrid compound (C 6 H 10 N 2 ) 6 IPb 5 I 21 •3H 2 O. The thermal transformation of (C 6 H 10 N 2 ) 6 IPb 5 I 21 •3H 2 O into (C 6 H 10 N 2 )PbI 4 was studied by thermal analysis and powder X-ray diffraction and used to reverse engineer a synthesis route for phase-pure (C 6 H 10 N 2 )-PbI 4 . The very broad PL emission of (C 6 H 10 N 2 ) 6 IPb 5 I 21 •3H 2 O is traced back to the largest octahedral distortion found in this compound among all studied 2-(aminomethylpyridinium) lead halides. We further find that (C 6 H 10 N 2 )PbI 4 and (C 6 H 10 N 2 ) 6 IPb 5 I 21 •3H 2 O are mixed ionic−electronic conductors and identify the diffusing ionic species as iodine and protons, respectively, by combining solid-state NMR measurements with a.c. impedance spectroscopy and d.c. galvanostatic polarization measurements.