Syntheses, structural variants and characterization of AInM′S4 (A=alkali metals, Tl; M′ = Ge, Sn) compounds; facile ion-exchange reactions of layered NaInSnS4 and KInSnS4 compounds

AInSn2S6 (A = K, Rb, Cs)─Layered Semiconductors Based on the SnS2 Structure

RbInSn₂S₆ and CsInSn₂S₆ are yellow two-dimensional (2D) semiconductors featuring anionic SnS₂-type layers of edge-sharing (In/Sn)S₆ octahedra. These structures are directly derived from the parent structure of SnS₂ by replacement of Sn⁴⁺ atoms with A⁺ and In³⁺ atoms. The compounds crystallize, isotypic to the ion-exchange material KInSn₂S₆. They adopt the triclinic space group R3̅m (no. 166). The compounds have similar indirect optical band gaps of 2.31(5) eV for Rb and 2.47(5) eV Cs. The measured work functions for each material are ∼5.38 eV. The density functional theory-calculated effective mass values exhibit strong anisotropy due to the 2D nature of the crystal structures and in the case of CsInSn₂S₆ for hole carriers along the a, b, and c crystallographic directions are 0.30 m₀, 0.34 m₀, and 2.54 m₀, respectively, while for electrons are 0.06 m₀, 0.07 m₀, and 0.47 m₀, respectively.

Highly selective cesium(I) capture under acidic conditions by a layered sulfide

Radiocesium remediation is desirable for ecological protection, human health and sustainable development of nuclear energy. Effective capture of Cs+ from acidic solutions is still challenging, mainly due to the low stability of the adsorbing materials and the competitive adsorption of protons. Herein, the rapid and highly selective capture of Cs+ from strongly acidic solutions is achieved by a robust K+-directed layered metal sulfide KInSnS4 (InSnS-1) that exhibits excellent acid and radiation resistance. InSnS-1 possesses high adsorption capacity for Cs+ and can serve as the stationary phase in ion exchange columns to effectively remove Cs+ from neutral and acidic solutions. The adsorption of Cs+ and H3O+ is monitored by single-crystal structure analysis, and thus the underlying mechanism of selective Cs+ capture from acidic solutions is elucidated at the molecular level.

Superior All-Solid-State Batteries Enabled by a Gas-Phase-Synthesized Sulfide Electrolyte with Ultrahigh Moisture Stability and Ionic Conductivity

Sulfide solid electrolytes (SEs) are recognized as one of the most promising candidates for all-solid-state batteries (ASSBs), due to their superior ionic conductivity and remarkable ductility. However, poor air stability, complex synthesis process, low yield, and high production cost obstruct the large-scale application of sulfide SEs. Herein, a one-step gas-phase synthesis method for sulfide SEs with oxide raw materials in ambient air, completely getting rid of the glovebox and thus making large-scale production possible, is reported. By adjusting substituted elements and concentrations, the ionic conductivity of Li_{4- x} Sn_{1- x} M_x S₄ can reach 2.45 mS cm^-1 , which represents the highest value among all reported moist-air-stable and recoverable lithium-ion sulfide SEs reported. Furthermore, ASSBs with air/water-exposed and moderate-temperature-treated Li_3.875 Sn_0.875 As_0.125 S₄ even maintains superior performances with the highest reversible capacity (188.4 mAh g^-1 ) and the longest cycle life (210 cycles), which also breaks the record. Therefore, it may become one of the most critical breakthroughs during the development of sulfide ASSBs toward its practical application and commercialization.

Applying band gap engineering to tune the linear optical and nonlinear optical properties of noncentrosymmetric chalcogenides La4Ge3SexS12−x (x = 0, 2, 4, 6, 8, 10)

Band gap engineering was applied to tune the properties of a phase-matchable La4Ge3S12 by replacing S with Se, which uncovered five new compounds: La4Ge3SexS12−x (x = 2, 4, 6, 8, 10).