A facile one-step template-free method based on a novel inside-out Ostwald ripening mechanism is developed for inexpensive mass preparation of hollow and hollow core/shell-type SnO2 nanostructures using potassium stannate as the precursor. As-prepared SnO2 hollow nanospheres (see figure) exhibit ultrahigh lithium storage capacity and improved cycle performance as high-energy anode materials in lithium-ion secondary batteries.