Rational design and synthesis of hierarchically structured SnO₂ microspheres assembled from hollow porous nanoplates as superior anode materials for lithium-ion batteries

Herein, hierarchically structured SnO₂ microspheres are designed and synthesized as an efficient anode material for lithium-ion batteries using hollow SnO₂ nanoplates. Three-dimensionally ordered macroporous (3-DOM) SnO_x-C microspheres synthesized by spray pyrolysis are transformed into hierarchically structured SnO₂ microspheres by a two-step post-treatment process. Sulfidation produces hierarchically structured SnS-SnS₂-C microspheres comprising tin sulfide nanoplate and carbon building blocks. A subsequent oxidation process produces SnO₂ microspheres from hollow SnO₂ nanoplate building blocks, which are formed by Kirkendall diffusion. The discharge capacity of the hierarchically structured SnO₂ microspheres at a current density of 5 A·g^-1 for the 600^th cycle is 404 mA·h·g^-1. The hierarchically structured SnO₂ microspheres have reversible discharge capacities of 609 and 158 mA·h·g^-1 at current densities of 0.5 and 30 A·g^-1, respectively. The ultrafine nanosheets contain empty voids that allow excellent lithium-ion storage performance, even at high current densities.