Uniform single-crystalline SnS nanobelts have been prepared via a simple wet-chemical route, in which SnCl2 was used as tin source and Na2S as sulfur source. Direct conversion of these SnS nanobelts with two pyramidal tips to porous-walled SnO2 nanocapsules was achieved by oxidizing in atmospheric ambient at 500–700 °C. The formation mechanism of these porous nanocapsules is a combination of non-equilibrium interdiffusion, volume loss, and gas release. With these uniform SnS nanobelts as precursors, carbon-coated metal Sn nanorods (Sn@C core-shell structure) were also synthesized by decomposition of sulfide SnS nanobelts with carbon coatings in N2 atmosphere. A strong UV emission peak at 365 nm is demonstrated for the SnO2 porous nanocapsules, which makes these promising materials for applications such as optical sensors. Furthermore, energy storage performances of these Sn-based nanomaterials (porous SnO2 nanocapsules and Sn@C core-shell nanocomposites) as anodes for Li-ion batteries were investigated in detail.