Green ionothermal synthesis of hierarchical nanostructures of SnS₂ and their Li-ion storage properties

Abstract

Flower-like hierarchical architectures of layered SnS₂ have been synthesized ionothermally for the first time, using a water soluble [EMIM]BF₄ ionic liquid (IL) as the solvent medium. At lower reaction temperatures, the hierarchical structures are formed of few-layered polycrystalline 2D nanosheet-petals composed of randomly oriented nanoparticles of SnS₂. The supramolecular networks of the IL serve as templates on which the nanoparticles of SnS₂ are glued together by combined effects of hydrogen bonding, electrostatic, hydrophobic and imidazolium stacking interactions of the IL, giving rise to polycrystalline 2D nanosheet-petals. At higher reaction temperatures, single crystalline plate-like nanosheets with well-defined crystallographic facets are obtained due to rapid inter-particle diffusion across the IL. Efficient surface charge screening by the IL favors the aggregation of individual nanosheets to form hierarchical flower-like architectures of SnS₂. The mechanistic aspects of the ionothermal bottom-up hierarchical assembly of SnS₂ nanosheets are discussed in detail. Li-ion storage properties of the pristine SnS₂samples are examined and the electrochemical performance of the sample synthesized at higher temperatures is found to be comparable to that reported for pristine SnS₂ samples in the literature.