Recently,the Si/graphene hybrid composites have attracted considerable attention due to their potential application for Li-ion batteries.How to effectively anchor Si clusters to graphene substrates to ensure their stability is an important factor to determine their performance for Li-ion batteries.In the present work,we have performed comprehensive density functional theory(DFT)calculations to investigate the geometric structures,stablility,and electronic properties of the deposited Si clusters on defective graphenes as well as their potential applications for Li-ion batteries.The results indicate that the interfacial bonding between these Si clusters with the pristine graphene is quitely weak with a small adsorption energy(<-0.21 eV).Due to the presence of vacancy site,the binding strength of Si clusters on defective graphene is much stronger than that of pristine one,accompanying with a certain amount of charge transfer from Si clusters to graphene substrates.Moreover,the ability of Si/graphene hybrids for Li uptake is studied by calculating the adsorption of Li atoms.We find that both graphenes and Si clusters in the Si/graphene composites preserve their Li uptake ability,indicating that graphenes not only server as buffer materials for accommodating the expansion of Si cluster,but also provide additional intercalation sites for Li.