Binding of carbon coated nano-silicon in graphene sheets by wet ball-milling and pyrolysis as high performance anodes for lithium-ion batteries

A novel approach has been developed to prepare silicon@carbon/graphene sheets (Si@C/G) composite with a unique structure, in which carbon coated Si nanoparticles are uniformly dispersed in a matrix of graphene sheets, to enhance the cycleability and electronic conductivity of Si-based anodes for Li-ion batteries. In this study, Si nanoparticles and expanded graphite (EG) are treated by combining high-energy wet ball-milling in sucrose solution with subsequent pyrolysis treatment to produce this Si@C/G composite. To achieve better overall electrochemical performance, the carbon content of the composites is also studied systematically. The as-designed Si-30@C-40/G(30) (Si:C:G = 30:40:30, by weight) composite exhibits a high Li-storage capacity of 1259 mAh g(-1) at a current density of 0.2 A g(-1) in the first cycle. Further, a stable cycleability with 99.1/88.2% capacity retention from initial reversible charge capacity can be achieved over 100/300 cycles, showing great promise for batteries applications. This good electrochemical performance can be attributed to the uniform coating and binding effect of pyrolytic carbon as well as the network of graphene sheets, which increase the electronic conductivity and Li+ diffusion in the composite, and effectively accommodated the volume change of Si nanoparticles during the Li+ alloying and dealloying processes. (C) 2016 Elsevier B.V. All rights reserved.