Research On Interfacial Lithium Storage Mechanism Of Graphene/Metal Sulfides And Oxides

The graphene/metal oxides and layered graphene/metal sulphide composites exhibit excellent electrochemical properties as anode materials for lithium ion battery,due to the synergistic effect between metal sulfide and graphene which is still poorly understood.In this study,Li adsorption and diffusion on MoS₂,SnS₂,Li₂ S,and Li₂ O surface,and at their interfaces with graphene are systematically investigated through first-principles calculations.The analysis of charge density difference,Bader charge,and density of states indicate that the adsorbed Li atoms interact with both the S（O）atoms at metal sulphide（oxides）surfaces and C atoms in graphene,resulting in larger Li adsorption energies at interfaces than on the corresponding surfaces with almost no enhancement of the energy barriers for Li atom diffusion.The enhanced Li adsorption capability at Li₂S/G and Li₂O/G interfaces via interfacial pseudocapacity-like storage mechanism contributes to the extra storage capacity beyond the theoretical capacity of graphene/metal sulphide and oxides composites.Furthermore,through the analysis of the differential charge distribution and Bader charge change of Li₂S/G and Li₂O/G interface with Li adsorbed,the synergistic mechanism between metal sulfide,metal oxides and graphene is revealed.Moreover,band structure analysis shows the electronic conductivity of MoS₂、SnS₂、Li₂S、Li₂O surface is enhanced with the incorporation of graphene.The results are helpful for the design of layered graphene/metal sulfide composites as anode materials for lithium ion batteries.