Carbon-coated SnO2@C with hierarchically porous structures and graphite layers inside for a high-performance lithium-ion battery

A high-performance anode material was prepared from a hierarchically structured activated carbon which contains in situ graphene and nano-graphite. The activated carbon was immersed in a solution of SnCl2 center dot 2H(2)O and subjected to ultrasound. As a result, nanoparticles of SnO2 were uniformly deposited on the surface of the activated carbon. The composite material was then coated with a thin layer of carbon by soaking it in a sucrose solution, followed by carbonization of the adsorbed sucrose at 500 degrees C. The resulting composite showed an outstanding high-rate cycling performance that can deliver an initial discharge capacity of 1417 mAh g(-1) and maintain a discharge capacity of more than 400 mAh g(-1) after 100 cycles at a high current density of 1000 mA g(-1). This outstanding electrochemical performance is likely to be related to a unique combination of the excellent electrical conductivity of the activated carbon with graphite layers formed inside, its hierarchical pore structure which enhances lithium-ion transportation, and the carbon coating which alleviates the effects of volume changes, shortens the distance for Li+ diffusion, facilitates the transmission of electrons, and keeps the structure stable.