▎ 摘　　要

Owing to the discovery of its new reaction mechanism towards lithium, SnO2 has recently gained the attention from scientific field as a promising potential anode material. A theoretical capacity of 1494 mA h g(-1) can be reached, provided that the SnO2 particles are reduced to ultra-small sizes. In addition, two other important aspects, namely cyclic stability and power density, can also be greatly enhanced by applying SnO2 particles with the appropriate dimensions. Therefore, size controlling of SnO2 nanoparticles is critical for their applications in lithium ion batteries (LIBs). In this work, SnO2 nanoparticles with an average diameter of 3 nm are decorated on graphene nanosheets. Owing to the small sizes of SnO2 nanoparticles and the electronic conductive graphene network, an anode consisting of SnO2 and graphene (SnO2/G) delivers a high first reversible capacity of 1239 mA h g(-1) at an initial current density of 0.1 A g(-1), and surprisingly a 574 mA h g(-1) charge capacity under an exceptionally high current density of 10 A g(-1). Meanwhile, superior cyclability is also achieved in view of increasing the reversible capacity up to 1813 mA h g(-1) after over 1000 cycles under a high current density of 2 A g(-1). Such stunning performance is carefully studied with various characterization techniques, including electrochemical measurements, TEM, and ex situ XRD. The high reversible capacity of SnO2/G is attributed to the 3 nm sized SnO2 nanoparticles, which almost doubled the theoretical capacity of the oxide. Additionally, the excellent performance under high current densities is ascribed to the enhanced lithium and electron diffusion, resulting from the significantly shortened lithium diffusion length within each SnO2 particle and the conductive graphene network, respectively. In addition, the prominent increase in reversible capacity upon cycling is explained by the increasing number of active lithium storage sites and polymeric gel-like film formation during the prolonged charge-discharge process.