Growth characteristics and influencing factors of 3D hierarchical flower-like SnS2 nanostructures and their superior lithium-ion intercalation performance

• The morphology, phase and composition of SnS2 nanostructures evolves simultaneously.
• Increased hydrothermal temperature turns thin SnS2 nanosheets to hexagonal nanoplates.
• Reduction of thiourea/SnCl4 ratios can turn curly SnS2 nanosheets to flat nanosheets.
• Hierarchical SnS2 nanoflowers show better electrode property than SnS2 nanoparticles.

3D hierarchical SnS2 nanoflowers are prepared by a template-free, inexpensive and controllable approach for their application to Li-ion batteries. They are composed of intertwining twisted nanosheets as the building unit. Their formation mechanism is explored through a group of time-dependent experiments. It is for the first time found that the morphological evolution, phase transition and composition changes occur simultaneously during their growth process. Three influencing factors, namely precursor concentration, reaction temperature and time, are examined by the observation of SnS2 nanostructures, to achieve the controlled synthesis of high-quality 3D SnS2 hierarchitectures. Irregular SnS2 nanoparticles are produced for a comparison with the SnS2 nanoflowers in terms of Li-ion insertion properties. The former shows smaller capacities and poorer rate capability than the latter. In tests the former exhibits capacities of 249.5–404.5 mA h g−1 at 100 mA g−1 over 50 battery cycles, while the latter could deliver capacities of 432–519 mA h g−1. In addition, the former displays capacities of 372 to 105 mA h g−1 while the latter shows capacities of 498 to 297 mA h g−1 as the current arises from 100 to 800 mA g−1. Redox reaction characteristics and Li-ion transfer kinetics at the two SnS2 anodes are studied with differential capacity curves and electrochemical impedance spectroscopy. It is concluded that the excellent electrochemical behaviors of SnS2 nanoflowers derive from their structural merits such as large surface area, hierarchical porous structure and sheet-like building units that endow them with improved electrode reactions and charge transfer kinetics.