Hollow SnO2 nanospheres with oxygen vacancies entrapped by a N-doped graphene network as robust anode materials for lithium-ion batteries

Abstract

The practical application of tin dioxide (SnO₂) in lithium-ion batteries has been greatly hindered by its large volumetric expansion and low conductivity. Thus, a rational design of the size, geometry and the pore structure of SnO₂-based nanomaterials is still a dire demand. To this end, herein we report an effective approach for engineering hollow-structured SnO₂ nanospheres with adequate surface oxygen vacancies simultaneously wrapped by a nitrogen-doped graphene network (SnO_2−x/N-rGO) through an electrostatic adsorption-induced self-assembly together with a thermal reduction process. The close electrostatic attraction achieved a tight and uniform combination of positively charged SnO₂ nanospheres with negatively charged graphene oxide (GO), which can alleviate the aggregation and volume expansion of the entrapped SnO₂ nanospheres. Subsequent thermal treatment not only ensures a significant reduction of the GO sheets accompanying nitrogen-doping, but also induces the generation of oxygen vacancies on the surface of the SnO₂ hollow nanospheres, together building up a long-range and bicontinuous transfer channel for rapid electron and ion transport. Because of these structural merits, the as-built SnO_2−x/N-rGO composite used as the anode material exhibits excellent robust cycling stability (∼912 mA h g⁻¹ after 500 cycles at 0.5 A g⁻¹ and 652 mA h g⁻¹ after 200 cycles at 1 A g⁻¹) and superior rate capability (309 mA h g⁻¹ at 10 A g⁻¹). This facile fabrication strategy may pave the way for the construction of high performance SnO₂-based anode materials for potential application in advanced lithium-ion batteries.