Wrapping SnO2 with porosity-tuned graphene as a strategy for high-rate performance in lithium battery anodes

The previous studies on SnO2 as electrode materials convey a message that the inevitable pulverization of SnO2 particles can be resolved by carbon-based materials. Since graphene has also proved effective for the harmful decrepitation of the particles with an advantage of electronic conductivity, wrapping SnO2 by sufficient amount of graphene seems to be an answer to enhancing its cycle life. On the other hand, severe wrapping of SnO2 by graphene is deleterious to its rate capability due to the sluggish motion of Li through the stacked graphene layers. Thus, in order to make graphene sheets favorable for Li-ion diffusion, they were modified to have large porosity with 3-D architectures, by a simple heating-rate control. The porous graphene-wrapped SnO2, having direct diffusion channels for Li+, outperforms the SnO2 with less-porous graphene. Consequently, the excellent performances are fulfilled, showing both stable cyclability (similar to 1100 mAh g(-1) up to 100 cycles) and high rate capability (similar to 690 mAh g(-1) under 3600 mA g(-1)). This strategy using porosity-tuned graphene sheet furnishes a valuable insight into the effective encapsulation of active materials, especially for those undergoing pulverization during cycling. (C) 2015 Elsevier Ltd. All rights reserved.