Facile synthesis of graphene-clamped nanostructured SnO2 materials for lithium-ion batteries

Graphene-based composite materials have attracted considerable interest due to their exceptional performance in various applications. However, the present synthesis processes, usually via graphene oxide (GO), are still very expensive. Here we propose an easy and affordable strategy based on sulfuric-acid-intercalated GO (SIGO) for the preparation of graphene-clamped nano-SnO2 (GCSnO(2)) with high performance for lithium-ion batteries. SIGO is the direct and readily available intermediate product during the oxidation of graphite in sulfuric acid, but has been overlooked for nearly a century. In the past, SIGO was washed to produce clean GO with great difficulties. An interesting characteristic of SIGO that we have found is its easy expansion and exfoliation to high-quality graphene at very low temperatures (just above 100 degrees C). In this work, GCSnO(2) containing 55 wt% SnO2 nanoparticles (5-10 nm in diameter) has been prepared by the expansion and exfoliation of nano-SnO2 coated SIGO at 300 degrees C in air. The samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The initial reversible charge-discharge capacity of GCSnO(2) was 858 mA h g(-1) at a current density of 200 mA h g(-1) in the potential range between 0.02 and 2.00 V. The capacity decayed to about 600 mA h g(-1) after 10 cycles and then remained almost unchanged; 572 mA h g(-1) remained after the studied 270 cycles. The contribution of SnO2 was estimated to be about 800 mA h g(-1) during cycling, corresponding to the full and stable utilization of the theoretical capacity of SnO2.