Ionothermal synthesis and electrochemical properties of a selenidostannate containing the mixed cations of Na⁺ and enH⁺

In this report, by taking advantages of the competitive and synergistic effects of mixed-cations under the ionothermal conditions, a novel selenidostannate compound containing the mixed cations, namely (enH)₃Na[Sn₃Se₇]₂·1.5Me₂NH·1.5H₂O (1, en=ethylenediamine, Me₂NH=dimethylamine) was obtained in the presence of the ionic liquid (IL) [DAMS]I (4-N,N-Dimethylamino-4′-N′-methylstilbazolium iodide) with a bulky and more structurally rigid organic cation as the main solvent and en as the auxiliary solvent. The compound features anionic [Sn₃Se₇]_n²ⁿ layers that are interconnected by sodium ions to form a three-dimensional (3D) structure. The syntheses, structure, thermal, optical and electrochemical properties of 1 were investigated. 1 showed good thermal stability and a Na⁺ ion storage property without capacity fading over 150 cycles.