Four two-dimensional ternary selenides based on group 13 and 14 metals: Syntheses, crystal structures, and electrochemical properties

A series of two-dimensional ternary selenides, [NH₄]₂[Ga₂Sn₂Se₈] (1), [NH₄]₂[In₂Ge₂Se₈] (2), [NH₄]₂[In₂Sn₂Se₈] (3), [NH₄]₂[Ga₂Ge₂Se₈] (4), have been solvothermally synthesized and characterized by single crystal X-ray diffraction, energy dispersive X-ray (EDX) spectroscopy, solid-state UV–Vis diffuse reflectance spectroscopy, and thermogravimetric analyses. The solid-state optical absorption spectra indicated that these compounds were semiconductors with band gaps of 1.71 eV for 1, 1.95 eV for 2, 1.85 eV for 3, and 1.83 eV for 4. In addition, compound 2 was employed as an anode material for lithium ion battery application, which exhibited a high specific capacity of 479 mA h g⁻¹ over 200 cycles at a current density of 200 mA g⁻¹, and an excellent rate capability of 425.2 mA h g⁻¹ at a current density of 1000 mA g⁻¹. Our results suggest that crystalline chalcogenides could be an alternative anode material for high performance LIBs application.