Graphene-encapsulated porous carbon-ZnO composites as high-performance anode materials for Li-ion batteries

As novel anode materials for lithium-ion batteries (LIBs), ZnO-loaded porous carbons (CMK-3 or CMK-8) are prepared by a two-step method and exhibit better electrochemical properties than pure ZnO particles. ZnO nanoparticles are separated inside the pores of porous carbons, which limit the growth of ZnO crystals and accommodate their volume variation during cycles. Moreover, to further improve their electrochemical performances, these composites are further wrapped by graphene nanosheets through a stepwise heterocoagulation method. Compared to uncoated porous carbon-ZnO, graphene-encapsulated porous carbon-ZnO composites exhibit higher reversible capacities, better cycle performances and rate capabilities. The superior performances of graphene-encapsulated composites may be attributed to graphene encapsulation, which enhances the electrical conductivity of the overall electrode, avoids the aggregation of porous carbon-ZnO particles and even stabilizes the mesostructure of porous carbon during cycles. (C) 2014 Elsevier Ltd. All rights reserved.