Hierarchic porous graphite/reduced graphene oxide composites generated from semi-coke as high-performance anodes for lithium-ion batteries

Abstract

Graphite has widely been used as anode material for lithium ion batteries, though its electrochemical performances, such as the lithium ion storage capacity and lithiation/delithiation rate capability, are remained to be improved. Herein, porous graphite is fabricated through high temperature graphitization of semi-coke followed by catalytic pore-creation procedure. The as-obtained porous graphite particles were cladded with reduced graphene oxide sheets, which exfoliated with the as-graphitized semi-coke, resulting three-dimensional hierarchic porous graphite/rGO composites. The unique hierarchic porous architecture not only facilitate the transfer of electrons, diffusion of lithium ions and interfacial charge transfer, but can also provide more active sites for lithium ion anchoring, thus improve greatly the overall electrochemical performances of the composites as anode. The composite with appropriate porous graphite to reduced graphene oxide ratio shows a reversible capacity of 460.1 mAh/g at 0.1 A/g and a capacity retention of almost 80% (377.3 mAh/g) at 1 A/g, much better than those of pristine graphite (28% retention), along with excellent cycling stability with >99% capacity retention after 300 cycles. This work may blaze a novel route to convert the low-cost and resourceful coal products to high performance anode materials for lithium-ion batteries and other energy storage systems.