Hierarchical flower-like SnO2 nanomicrostructure has been synthesized via a solvent-induced and surfactant assisted self-assembly technique at ambient temperature followed by a suitable thermal treatment. A possible growth mechanism governing the formation of such a nanomicrostructure is discussed. The applications in gas sensors for detecting CO and H2 reveal that the obtained SnO2 material exhibits a remarkable sensitivity and extremely low detecting limit (5 ppm), as well as good reproducibility and short response/recovery times, which benefit a lot from its unique flower-like nanomicrostructure consisting of three-dimensional interconnected SnO2 nanoparticles and nanopores. In order to use the present SnO2 nanomicrostructure in lithium-ion batteries, carbon coatings are introduced to the surface of them by pyrolysis of glucose under hydrothermal conditions. Both SnO2−C and Sn−C nanocomposites are obtained by taking thermal treatment of the precursors at different temperatures. The conversion processes are investigated by thermogravimetrics (TG) analyses under N2 and air atmosphere. All three Sn-based nanostructures are investigated with XRD, SEM, TEM, and electrochemical tests toward lithium storage. It is found that the SnO2−C composite shows a very high reversible capacity (700 mA h g−1 after 20 cycles) and high Coulombic efficiency in the initial few cycles, as well as significantly enhanced cycling performance compared with bare SnO2 nanostructure and Sn−C nanocomposite, exhibiting great potential as an anode material in lithium-ion batteries. The improvements can be attributed to the outside carbon coating layer as well as the in situ formed buffer, Li2O matrix, upon initial Li uptake.